PROCESS FOR PREPARING A CURED COMPOSITE MATERIAL FOR USE IN A CURED PRODUCT AND TELECOMMUNICATION DE

专利摘要:
a process for preparing a cured composite material for use in a telecommunication device and cured product a process for preparing a cured composite material useful for radio frequency filter applications comprising the steps of: (a) providing a curable thermosetting epoxy resin composition comprising (i ) at least one epoxy resin; (ii) at least one healer; (iii) at least one hardener; and (iv) at least one charge; (b) curing the curable thermosetting epoxy resin composition from step (a) to form a cured composite; wherein the thermosetting epoxy resin composition curable in response to cure provides a cured composite product with a balance of properties comprising tg, thermal expansion coefficient, thermal conductivity, flame resistance, tensile strength, and having a density less than 2, 7 g/cm3; and (c) coating at least a portion of the surface of the cured composite from step (b) with an electrically conductive metallic layer to form a metallized coating over at least a portion of the surface of the cured composite. the cured composite material can be useful as a radiofrequency cavity filter body housing for radiofrequency filter applications.
公开号:BR112014014990B1
申请号:R112014014990-9
申请日:2012-12-04
公开日:2021-06-15
发明作者:Mohamed Esseghir；William J. Harris；Chester J. Kmiec；Robert F. Eaton；Lin Fu；Martin W. Bayes；Bret P. Neese
申请人:Rohm And Haas Electronic Materials Llc；Dow Global Technologies Llc；
IPC主号:

专利说明:

field of invention
[0001] The present invention relates to a metallized epoxy resin composite and a process for preparing the metallized epoxy resin composite that can be useful in various applications, for example, in the preparation of tower communication equipment components. cell phone such as radio frequency filters. Historic
[0002] It is expected that the demand for bandwidth will increase annually around the world to support new services and the increasing number of users thus shifting wireless systems to higher frequency bands. There is a trend in the industry to move electronics from a base station to the top of a cellular tower from such a base station (ie, tower top electronics). It is expensive to install and maintain antennas and remote radio inputs on cellular antennas. Therefore there is a need for a light weight infrastructure and associated equipment.
[0003] A radio frequency (RF) filter is a key component in a remote radio input (RRH) device. RF filters are used to eliminate signals of certain frequencies. Such filters are commonly used as subsystems for duplexers and diplexers to combine or separate multiple frequency bands. RF filters play an important role in minimizing interference between systems operating in different bands.
[0004] An RF cavity filter is a commonly used RF filter. A common practice for manufacturing these filters of various designs and physical geometries is to press-cast aluminum into a desired machine or structure in the final geometry of a press-cast precast. An example of an RF filter is shown and described in U.S. Patent No. 7,847,658 incorporated herein by reference. It is known that current die cast aluminum technology consumes a lot of energy (eg, about 7500 BTU/inch3 as disclosed in "Reaction Injection Molding", Walter E. Becker, Ed., Van Nostrand-Reinhold, New York, 1979, pp. 316). In addition, the aluminum density of pressure-cast aluminum filters is about 2.7 g/cm3 and one-piece fabrication requires time-consuming post-machining due to the complex geometry of the cavity duplexer filter requiring machining with a tool. matrix with finite service life and intensive work.
[0005] In addition, due to increasing miniaturization and the need to reduce the weight of top components of a cell tower infrastructure and its subcomponents, it is also desired to manufacture lighter weight filters (nowadays the weight of cell tower filters). aluminum depending on design generally ranges from a few kilograms to as high as 15 kg or more) while still maintaining acceptable coefficient of thermal expansion (CTE) and performance close to that of the material in use.
[0006] A first critical parameter for RF cavity filter performance is the cavity dimensional stability of the RF cavity filter under external conditions (eg from about -50°C to about 85°C). A high CTE filter housing material is less desirable compared to a low CTE filter housing material because with temperature fluctuations in the environment surrounding the filter body housing, the higher CTE material can have greater changes in the shape and size of the cavities in the body housing sufficient to change the filtering frequency of the RF cavity filter from its target value. A second important requirement for RF filter performance is the quality of electrolytic deposition of metal (copper or silver) on the surface of the filter body housing material. RF waves operate primarily on the surface of the electroplated metal layer within the coating depth. Therefore, any defects in the electroplated silver or copper layer would cause interference with RF waves and would destroy or detrimentally affect RF filtering performance. A third critical requirement for RF cavity filter performance is thermal dissipation. Since RF cavity filter comprises heat generating electronics, heat build-up can increase the overall temperature of the device, which in turn can affect the long-term reliability and dimensional stability of the device.
[0007] U.S. Patent No. 7,847,658 discloses low thermal expansion and light weight polymer foams for radio frequency filtration applications; this patent requires the use of a polymer foam and a metal-coated filler.
[0008] A thermoplastic polymer ULTEM® 3452 (45% mineral-filled polyetherimide and fiberglass) was previously proposed for use in the fabrication of radio frequency systems (RFS). The glass transition temperature of ULTEM® 3452 is 217°C, and CTE of ULTEM® 3452 is anisotropic in nature. The anisotropic nature of the ULTEM® 3452 material should present challenges when used in RF cavity filter applications when the material can undergo non-linear deformation under operating temperature conditions (eg, -50°C to about 85°C). Non-linear changes in dimensions in all directions will make it very difficult to fine-tune the filter for proper operation.
[0009] In addition to RF cavity filter articles, other devices that use die cast aluminum or extruded aluminum for their fabrication is a heat sink device for a remote radio input. A typical heatsink for a remote radio input is illustrated, for example, on the following internet site: http://www.ejlwireless.com/pdf/ Huawei%20RRU3804%20DNA- I%2020%20TOC.pdf. The current material for the heat sink is aluminum cast or extruded with a copper heat sink.
[0010] Yet another device that is made of solid aluminum and that would be a desirable candidate for weight reduction may be an enclosure that is used to enclose and protect electronic components. For example, a known enclosure is an enclosure using a 40W model 9341 RRH remote radio input, commercially obtainable from Alcatel-Lucent. Generally, because of the size of the aluminum casing alone, the aluminum casing is a heavy piece. Some of the requirements for an enclosure to be functional include the following: the enclosure must (1) have good enough mechanical properties to withstand a drop test; (2) provide good heat dissipation from internal electronics; (3) have good weather resistance properties for long service life; (4) provide good UV resistance; and (5) provide good flame resistance. Invention Summary
[0011] An embodiment of the present invention relates to a process for preparing a cured epoxy composite material useful in various applications such as applications in radio frequency filters including the following steps: (a) providing a curable thermosetting epoxy resin composition comprising (I) at least one epoxy resin; (II) at least one curing agent; (III) at least one hardener; and(IV) at least one charge; (b) curing the curable thermosetting epoxy resin composition from step (a) to form a cured composite; wherein the thermosetting epoxy resin composition curable in response to cure provides a cured composite product with a balance of properties comprising Tg, thermal expansion coefficient, thermal conductivity, flame resistance, tensile strength, and having a density less than 2, 7 g/cm3; and (c) coating at least a portion of the cured composite from step (b) with an electrically conductive metallic layer to form a metallized coating over at least a portion of the surface of the cured composite.
[0012] Another embodiment of the present invention relates to a cured epoxy composite material useful in various applications such as a radio frequency filter application, a heat sink application, an enclosure or a combination thereof for telecommunication applications in top of tower.
[0013] Yet another embodiment of the present invention relates to a radio frequency filter, a heat sink, or an enclosure made of the above cured epoxy composite material.
[0014] Yet another embodiment of the present invention relates to a process for manufacturing the radio frequency filter, heat sink, casing above. Brief description of the figures
[0015] For the purpose of illustrating the present invention, the drawings show a form of the present invention which is currently preferred. However, it should be understood that the present invention is not limited to the embodiments shown in the drawings.
[0016] Figure 1 is a graphic illustration of the dimensional change compared to ambient before temperature cycling measured by thermomechanical analysis at 25°C in response to the heating portion of 10 consecutive temperature cycles from -50°C to 100°C at -50°C; and
[0017] Figure 2 is a graphic illustration of the dimensional change compared to ambient before temperature cycling measured by thermomechanical analysis at 65°C in response to the heating portion of 10 consecutive temperature cycles from -50°C to 100°C at -50°C. Detailed description of the invention
[0018] The test methods described here refer to the latest test methods as of the priority date of this document when no date is indicated with the test method number. Test method references contain both a reference to the testing society and the test method number. The following are the test method and identifier abbreviations applied here: ASTM refers to ASTM International, and ISO refers to International Organization for Standards.
[0019] “And/or” means “and, or as an alternative”. All numerical ranges include endpoints unless otherwise noted.
[0020] In its broadest scope, the present invention includes curing a curable epoxy resin composition to form a cured epoxy composite, wherein the curable epoxy resin composition comprises (a) at least one epoxy resin; (b) at least one curing agent such as, for example, an amphiphilic polyether block copolymer, carboxyl terminated butadiene/acrylonitrile elastomer, or a core-film rubber; (c) at least one hardener; and (d) at least one charge; and wherein the cured epoxy composite prepared from the curable composition can be metallized such that the final product metallized composite can be used in various applications including, for example, radio frequency filters, heat sinks, or electronics housings.
[0021] The epoxy resin composition or formulation of the present invention in response to cure provides a cured product with a balance of properties comprising glass transition temperature, thermal expansion coefficient, tensile strength, thermal conductivity, and density.
[0022] Furthermore, the cured product of the present invention comprises a high glass transition epoxy composite which can be metallized without adversely affecting the properties of the metallized coating and the properties of the epoxy composite.
[0023] An embodiment of the present invention includes a high Tg epoxy composite material useful for radio frequency cavity filter applications. Some of the unique properties and advantages of the epoxy resin composition of the present invention (discussed in more detail below) include, for example, where the epoxy resin composition has controllable full viscosity to facilitate processing before curing.
[0024] Some of the unique properties and advantages of the epoxy composite material of the present invention (discussed in more detail below) include, for example, where the epoxy resin composition has an improved glass transition temperature, density, CTE, thermal conductivity, and /or tensile strength; wherein the epoxy composite exhibits no cracking and no leftovers which provide an indication of the machinability of the composite and an improvement in the composite's surface smoothness; and the epoxy composite being capable of being coated with metal.
[0025] Additionally, the present invention uses liquid epoxy resins (LER) and provides a thermosetting charged system that, prior to curing, has lower processing viscosity as well as lower processing temperature during filling of an RF filter mold when compares with viscous particulates or thermoplastic polymers with known fibrous fillers.
[0026] The thermosetting or curable resin composition of the present invention useful for radio frequency filter applications may include one or more epoxy resins. Epoxy resins useful in the present invention can be selected from any epoxy resin known in the art; and can include conventional and commercially obtainable epoxy resins, which can be used alone or in combinations of two or more. For example, a broad enumeration of epoxy resins useful in the curable composition of the present invention includes epoxides described in Pham et al., Epoxy Resins in the Kirk-Othmer Encyclopedia of Chemical Technology; John Wiley & Sons, Inc.: December 4, 2004 and references therein; in Lee et al., Handbook of Epoxy Resins, McGraw-Hill Book Company, New York, 1967, Chapter 2, pages 257-307 and references therein; in May, C.A. Ed. Epoxy Resins: Chemistry and Technology, Marcel Dekker Inc., New York, 1988 and references therein; and U.S. Patent No. 3,117,099, all of which are incorporated herein by reference.
[0027] In the selection of epoxy resins for the compositions disclosed herein, one should not only consider the fine product properties, but should also consider viscosity and other properties that can influence the processing of the resin composition. In one embodiment, particularly suitable epoxy resins useful in the present invention are based on reaction products of polyhydric alcohols, polyglycols, phenols, cycloaliphatic carboxylic acids, aromatic amines, or aminophenols with epichlorohydrin. Other suitable epoxy resins useful for the compositions disclosed herein include reaction products of epichlorohydrin with o-cresol and if epichlorohydrin with phenolic novolacs. In another embodiment, the epoxy resin useful in the present invention for preparing the epoxy resin composition may be selected from commercially obtainable products, such as, for example, DER® 330, DER® 331, DER® 332, DER® 324, DER® 352, DER® 354, DER® 383, DER® 542, DER® 560, DER® 736, DER® 732, DEN® 425, DEN® 431, DEN® 438, or mixtures thereof. D.E.R resins are commercially obtainable from The Dow Chemical Company.
[0028] Few non-limiting embodiments of epoxy resin useful as a compound in the curable epoxy resin formulation of the present invention may include, for example, diglycidyl ether of bisphenol A, diglycidyl ether of tetrabromo bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of resorcinol, triglycidyl ethers of para-aminophenols, epoxy novolacs, divinylarene dioxides, or mixtures thereof.
[0029] Examples of preferred embodiments of the epoxy resin include diglycidyl ether of bisphenol A, diglycidyl ether of tetrabromo bisphenol A, or a mixture of diglycidyl ether of bisphenol A and diglycidyl ether of tetrabromo bisphenol A. Oligomers may also be useful in the present invention. of the above epoxy resins. Examples of another preferred embodiment of the epoxy resin may be a mixture of bisphenol A diglycidyl ether, bisphenol A tetrabromo diglycidyl ether, and a diglycidyl ether prepared by reacting poly(propylene glycol) and epichlorohydrin. In one embodiment, the curable epoxy resin composition may be useful, for example, for radio frequency filter applications.
[0030] In general, at least one of the epoxy resins used in the composition of the present invention has a viscosity between about 1 mPa-s and about 100,000 mPa-s in an embodiment, between about 5 mPa-s and about 50,000 mPa -s in another embodiment, between about 10 mPa-s and about 25,000 mPa-s in yet another embodiment, and between about 10 mPa-s and about 10,000 mPa-s in yet another embodiment at room temperature (about 20°C to 25°C).
[0031] The concentration of the epoxy resin used in the curable composition of the present invention may depend on the hardener used with the epoxy resin. Generally the concentration of epoxy resin can range from about 2 percent by weight (% by weight) to about 60% by weight in one embodiment, from about 4% by weight to about 46% by weight in another embodiment, of about 5% by weight to about 37% by weight in yet another embodiment, from about 5% by weight to about 30% by weight in yet another embodiment, from about 7% by weight to about 30% in weight in yet another embodiment, from about 10% by weight to about 25% by weight in yet another embodiment, from about 12% by weight to about 23% by weight in another embodiment, and from about 13% in another embodiment. weight to about 20% by weight in yet another embodiment, based on the total weight of the composition.
[0032] When using a mixture of two or more epoxy resins in the composition of the present invention, for example, a first epoxy resin and a second epoxy resin, the first resin can be between about 1% by weight and 99% by weight of the total epoxy used, with the second epoxy resin, and any other additional epoxy resin used in the composition of the present invention, adding up to 100% of the total epoxy required. For example, a mixture of epoxy resins used in the composition of the present invention in one embodiment may include a mixture of tetrabromo bisphenol A diglycidyl ether as a first epoxy and a bisphenol A diglycidyl ether as the second epoxy.
[0033] Generally, in an embodiment the amount of diglycidyl ether of tetrabromo bisphenol A may be at least 20% by weight of the total epoxy used in the composition, at least 35% by weight of the total epoxy used in the composition in another composition, at least 50% by weight of the total epoxy used in the composition in yet another composition, and at least 55% by weight of the total epoxy used in the composition in yet another embodiment. In the above epoxy resin blend, generally the amount of bisphenol A diglycidyl ether may be at least 80% by weight of the total epoxy used in the composition in one embodiment, at least 65% by weight of the total epoxy used in the composition in another embodiment, at least 50% by weight of the total epoxy used in the composition in yet another embodiment, and at least 45% by weight of the total epoxy used in the composition in yet another embodiment.
[0034] The use of a curing agent in the curable resin composition of the present invention typically leads to an increase in toughness when the curable composition is cured to form the cured epoxy composite material characterized by a variety of methods including intensity factor critical stress, K1c, following ASTM test method D 5045-99, as well as % elongation increase at break following ASTM test method D 638. In addition to the improved toughness of the curable resin composition of the present invention, a curing agent can be added to the curable resin composition to maintain a high Tg of the cured composite without any decrease in Tg or only a nominal decrease in Tg (e.g., less than about 15% decrease and more preferably less than about 7.5% decrease in Tg for higher Tg transition if the composition of the present invention exhibits more than one Tg). The curing agent can also lead to crack reduction and/or burr reduction when drilling holes, threading holes, or machining the cured epoxy composite material from the curable resin composition of the present invention. In a preferred embodiment, the epoxy composite product of the present invention can be drilled or threaded without substantial cracking or chipping.
[0035] Typically, the curing agent is an organic polymer additive that separates from phase in a cured epoxy resin. The curing agent useful in the present invention may include, for example, block copolymers, amphiphilic block copolymers, acrylic block copolymers, carboxyl terminated butadiene/acrylonitrile rubber (CTBN), core-film rubbers (CSR), copolymers of linear polybutadiene/polyacrylonitrile, oligomeric polysiloxanes, silicone polyethers, organic polysiloxane resins, or mixtures thereof. Other curing agents useful in the present invention may include carboxyl-terminated polybutadiene, polysulfide-based curing agents, amine-terminated butadiene/nitrile rubbers, polythioethers, or mixtures thereof. The use and function of healing agents is described, for example, in the Handbook of Epoxy Resins and Epoxy Resins: Chemistry and Technology mentioned above. In addition, suitable curing agents for use in the present invention are described, for example, in US Patent Nos. 5,262,507, 7,087,304, and 7,037,958, and in US Patent Application Publication Nos. 20050031870 and 20060205856, all of which are incorporated herein by reference. Amphiphilic block copolymers useful as curing agents are disclosed herein, for example, in WO 2006/052725, WO 2006/052726, WO 2006/052727, WO 2006/052729, WO 2006/052730, WO 2005/097893, in US patents Nos. 6,887,574 and 7,923,073, and US Patent Application Publication No. 20040247881, all of which are incorporated herein by reference.
[0036] An embodiment of the curing agent useful in the present invention may include, for example, an amphiphilic polyether block copolymer, a core-film rubber, carboxyl terminated butadiene/acrylonitrile elastomer, and/or rubbery/insoluble additives . For example, the amphiphilic polyether block copolymer useful in the present invention may include FORTEGRA™ 100 which is a polyol derivative commercially obtainable from The Dow Chemical Company. For example, the core-film rubber useful in the present invention can include FORTEGRA™ 301 in which the core-film rubber can be formulated in bisphenol A diglycidyl ether which is commercially available from The Dow Chemical Company. For example, the carboxyl terminated butadiene/acrylonitrile elastomer useful in the present invention may include FORTEGRA™ 201 which contains a bisphenol A diglycidyl ether adduct and carboxyl terminated butadiene/acrylonitrile elastomer and is commercially available from The Dow Chemical Company.
[0037] The amphiphilic polyether block copolymer useful in the present invention may include one or more polyether block copolymers comprising at least one epoxy-miscible polyether block segment derived from an alkylene oxide such as ethylene oxide (EO) and at least one epoxy-immiscible polyether block segment derived from an alkylene oxide such as, for example, 1,2-epoxy-butane commonly known as butylene oxide (BO). The immiscible block segment may also comprise mixtures of C3 or higher analog monomers that are copolymerized together to provide the immiscible block segment.
[0038] Examples of epoxy resin miscible polyether block segment include a poly(ethylene oxide) block, a poly(propylene oxide) block, a poly(ethylene oxide-co-propylene oxide) block , a poly(ethylene oxide-random-propylene oxide) block, or mixtures thereof. Preferably, the epoxy resin miscible polyether block segment useful in the present invention may be a poly(ethylene oxide) block.
[0039] Examples of the epoxy resin immiscible polyether block segment include a poly(butylene oxide) block, a poly(hexylene oxide) block derived from 1,2-epoxy-hexane, a poly(oxide block) of dodecylene) derived from 1,2-epoxy-dodecane, or mixtures thereof. Preferably, the resin-immiscible polyether block segment useful in the present invention may be a poly(butylene oxide) block.
[0040] Amphiphilic polyether block copolymers that may be employed in the practice of the present invention include, for example, but not limited to, diblock copolymer, a linear triblock, linear tetrablock, other multiblock structures, a block structure branched, or a star block structure.
[0041] Preferred examples of suitable block copolymers useful in the present invention include amphiphilic polyether diblock copolymers such as, for example, poly(ethylene oxide)-b-poly(butylene oxide) (PEO-PBO) or copolymers in amphiphilic polyether triblocks such as, for example, poly(ethylene oxide)-b-poly(butylene oxide)-b-poly(ethylene oxide) (PEO-PBO-PEO).
[0042] The concentration of the curing agent used in the curable compositions described herein may depend on a variety of factors including the equivalent weight of the polymers, filler supply, and the desired properties of the product made with the curable composition. In general, the curing agent can be used in an amount sufficient to provide sufficient toughness of the resulting composite to allow screw holes in the composite without cracking or chipping of the composite. For example, the amount of curing agent can generally range from about 0.1% by weight to about 30% by weight in one embodiment, from about 0.25% by weight to about 10% by weight in another embodiment of from about 0.5% by weight to about 7% by weight in yet another embodiment, and from about 1% by weight to about 5% by weight in yet another embodiment, based on the total weight of the curable composition.
Above and below the aforementioned concentrations of curing agent, the high Tg and improved toughness of the resulting cured epoxy resin composite prepared with the curable composition of the present invention may not occur; that is, for example, the advantages of reduced cracking and/or reduced chipping when drilling holes/paths, threading holes/paths, or machining of the cured epoxy composite material prepared with the curable resin composition of the present invention may not come true.
[0044] The hardener also referred to as cross-linking agent) useful in the present invention can be any compound having an active group being reactive with the epoxy group of the epoxy resin. The chemistry of such crosslinking agents is described, for example, in the Handbook of Epoxy Resins and in Epoxy Resins: Chemistry and Technology mentioned above. The curing agent useful in the present invention includes nitrogen containing compounds such as amines and their derivatives; oxygen containing compounds such as carboxylic acids, carboxylic acid terminated polyesters, anhydrides, phenol formaldehyde resins, amino formaldehyde resins, phenol novolacs, bisphenol A and cresol, phenolic terminated epoxy resins; sulfur-containing compounds such as polysulfides, polymercaptans; and catalytic curing agents such as tertiary amines, Lewis acids, Lewis bases and combinations of two or more of the above curing agents.
[0045] Generally, the hardener useful in the present invention can be selected, for example, but not limited to, dicyandiamide, substituted guanidines, phenolic compounds, amino compounds, benzoxazine, anhydrides, starch amines, polyamides, polyamines, aromatic amines, carbodiimides , polyesters, polyisocyanates, polymercaptans, urea-formaldehyde and melamine-formaldehyde resins, diamino diphenyl sulfone and its isomers, amino benzoate, various acid anhydrides, phenol novolac resins and cresol-novolac resins, and mixtures thereof.
[0046] In one embodiment, at least one hardener can include one or more aliphatic amines such as ethanolamine, ethylenediamine, diethylenetriamine (DETA), triethylenetetraamine (TETA), 1-(o-tolyl)-biguanide, dicyandiamide, polyols terminated with amine, aromatic amines such as methylene-dianiline (MDA), toluenediamine (TDA), diethyl-toluenediamine (DETDA), diamino-diphenyl-sulfone (DADS), one or more of polyphenols such as bisphenol A, bisphenol F, 1.1 - bis(4-hydroxy phenyl)-ethane, hydroquinone, resorcinol, catechol, tetrabromo-bisphenol A, novolacs such as phenol novolac, bisphenol A novolac, hydroquinone novolac, resorcinol novolac, naphthol novolac, one or more of mercaptans such as polymers of mercaptan terminated polysulfides, CAPCURE hardeners (Cognis trade name), one or more of anhydrides such as phthalic anhydride, trimellitic anhydride, nadic anhydride, methyl tetrahydrophthalic anhydride, methyl hexahydrophthalic anhydride; and mixtures thereof.
[0047] In general, the curing agent useful for the curable epoxy resin composition of the present invention may comprise a liquid cyclic anhydride curing agent selected from one or more cyclic anhydride curing agents known in the art. Cyclic anhydride curing agents useful in the present invention may also contain limited amounts of carboxylic acid functionalities which can also function as a curing agent.
[0048] In one embodiment, the anhydride curing agent useful in the present invention may include, for example, cyclic anhydrides of aromatic, aliphatic, cycloaliphatic, and heterocyclic polycarbonic acids that may or may not be substituted with alkyl, alkenyl, or halogen groups. Examples of anhydride curing agents include phthalic anhydride, tetrachlorophthalic anhydride, tetrahydrophthalic anhydride, methyl tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, methyl nadic anhydride, succinic anhydride, dodecenyl succinic anhydride, glutaric anhydride, male anhydride isatoic anhydride, tetracarboxylic benzophenone anhydride, and mixtures thereof. The anhydride curing agents described in U.S. Patent No. 6,852,415, incorporated herein by reference, can also be used.
[0049] As an illustration of an embodiment of the present invention, methyl nadic anhydride can be used as the cyclic anhydride curing agent in the composition of the present invention. Methyl nadic anhydride is a liquid cyclic anhydride hardener that has particularly desirable attributes for the formulations of the present invention such as being a liquid at room temperature, and having a viscosity of less than about 300 mPa-s at 25°C. The use of methyl nadic anhydride in the hardener for the formulation of the present invention can also advantageously provide filler wettability and facilitate filler adhesion on cured epoxy resins. The use of methyl nadic anhydride in the hardener for the formulation of the present invention may also advantageously provide other uses such as generally resulting in low exothermic behavior during curing and low shrinkage during curing of the formulation of the present invention. Additionally, the use of methyl nadic anhydride in the hardener of the present invention can generally lead to an increase in the Tg of the cured product of the present invention when compared to other liquid anhydride hardeners.
[0050] In one embodiment, the hardener used in the composition of the present invention may comprise methyl tetrahydrophthalic anhydride (MTHPA), alone, or in combination with methyl nadic anhydride (NMA).
Generally, the amount of curing agent used in the present invention can range from about 0.5% by weight to about 50% by weight, from about 1.5% by weight to about 42% by weight in another embodiment; from about 2.5% by weight to about 34% by weight in yet another embodiment; from about 2.6% by weight to about 32% by weight in yet another embodiment, from about 7% by weight to about 35% by weight in yet another embodiment, from about 10% by weight to about 30% by weight in yet another embodiment, from about 12% by weight to about 25% by weight in yet another embodiment, and from about 14% by weight to about 23% by weight in yet another embodiment, based in the total weight of the composition. Preferred embodiments of the curing agents may include, for example, anhydride curing agents and active hydrogen curing agents. Above and below the aforementioned concentrations of curing agent, the high Tg and improved mechanical properties of the resulting cured epoxy resin composite prepared with the curable composition of the present invention may not occur.
[0052] The curable epoxy resin composition of the present invention includes at least one filler. The mechanical or thermomechanical performance (ie, such as storage modulus, tensile strength, thermal conductivity, and thermal expansion coefficient when measured at a temperature representative of typical operating temperatures of internal or external telecommunications equipment) of the cured charge material may be improved by incorporating charge into the curable composition. The use of fillers in the curable composition can also provide other advantages such as reduced shrinkage during curing of the formulation as well as other attributes such as reduced water absorption, reduced environmental aging, and other attributes in a cured formulation as known in the art. Furthermore, the use of fillers in the curable composition can further improve other advantages such as improved flame retardancy (FR).
[0053] The payload in the curable composition of the present invention may include, for example, one or more loads with treated surface to improve interaction between polymer and load, one or more loads with untreated surface, electrically and/or thermally conductive loads, one or more non-conductive charges, and mixtures thereof. For example, charges falling within the following classes can be used in the present invention: metal particles, nanoparticles, metal oxides, metal nitrides, metal carbides, metal hydroxides, metal carbonates, metal sulfates, natural and synthetic minerals mainly silicates, and silicates of aluminum; and mixtures thereof.
[0054] Specific examples of the payloads in the present invention may include, quartz, silica, silicon oxide, fused silica, fused quartz, natural silica, synthetic silica, natural aluminum oxide, synthetic aluminum oxide, aluminum hydroxide, hydroxide oxide of aluminum, magnesium hydroxide, boron nitride, lithium aluminum silicate, zinc oxide, aluminum nitride, mullite, wollastonite, talc, mica, kaolin, bentonite, boehmite, xnolit, andalusite, zeolite, dolomite, vermiculite, muscovite , nephelite, albite, microline, slate, powdered aluminum, silver, graphite, synthetic graphite, natural graphite, amorphous graphite, flake graphite, graphite vein, expandable/intumescent graphite, antimony oxides, borates (including zinc borates and sodium borates), molybdates (including calcium molybdate and zinc molybdate), stannates (including zinc stannate), phosphinates (including aluminum phosphinate, aluminum phosphinite), ammonium polyphosphate, polyphosphine melamine act, melamine salts, zinc sulfide, red phosphorus, layered clays (including montmorillonite and hectorite), gold, carbon, single or multiwall carbon nanotubes, graphene, powdered glass, fiberglass, cloth of glass, glass sheets, carbon fibers, other organic and inorganic particulate fillers or mixtures thereof. The filler can be added to the curable composition in the final state of load or the filler can be formed on site.
[0055] In an embodiment of the present invention, at least one of the fillers used in the present invention comprises a surface treated filler either prior to incorporation into the curable composition or at the site during the composition of the formulation. Examples of various filler surface treatments include fatty acids, silane coupling agents, titanates, zirconates, aluminates, or silazanes.
[0056] In an embodiment of the present invention, for example, the filler can be surface treated with silane, often referred to as silanized, and the functionality or modification of the resulting filler can be such that the filler is compatible with, or may react as part of, the epoxy curing process. In another embodiment, fillers can be treated with silane coupling or sizing agents. In general, the silane coupling agent contains at least one alkoxy group to facilitate surface treatment and optionally bind to the inorganic filler. In yet another embodiment, the silane coupling agent may contain groups including, for example, epoxy, amine, hydroxyl, carboxyl, vinyl, allyl, hydrosilyl (i.e. -SH), or other functionalities that may react with the epoxy formulation. or be compatible or miscible with the epoxy formulation.
Examples of fillers treated with the silane coupling agent include 3-glycidoxy-propyl-trimethoxysilane which is commercially available from Dow Corning Corporation under the tradename Silane Z-6040 Dow Corning; or epoxy-silane treated quartz and fused quartz commercially obtainable from Quarzwerke under the trade name SILBOND with different grades described as 126 EST, W6 EST, W12 EST, 1000 EST, 600 EST, FW 61 EST, FW 12 EST, FW 100 EST , FW 300 EST, FW 600 EST and 800 EST.
[0058] As mentioned above, the component filler used in the formulation of the present invention may be a combination of fillers that may or may not individually be surface treated. In an embodiment in which the filler comprises epoxy silane treated quartz or fused quartz, for example, the epoxy silane treated quartz or fused quartz may be 100% of the filler used in the composition of the present invention; or else one or more different fillers may be used in combination with the epoxy-silane treated quartz.
[0059] The payload material in the present invention can include fillers with morphologies such as platelets, fibers, spheres, granules, needles, which can be crystalline, semi-crystalline or amorphous, or any combination thereof. These fillers with different size distributions and different shapes can be combined to have a synergistic effect on the viscosity of the curable composition; and on the coefficient of thermal expansion (CTE), modulus, strength, and/or thermal or heat conductivity of the cured composition.
[0060] The particle size of the filler material can generally vary from nanoparticle to conventional microparticle. In general, the particle size of the filler material of the present invention, when used in granular form, has an average particle size, often referred to as d50%, sufficient to promote an acceptable processing viscosity balance prior to hardening and to promote a balance of acceptable thermomechanical properties after curing. For example, the average particle size, d50%, for granular filler may generally be in the range from about 0.0005 µm to about 500 µm in one embodiment, from about 0.1 µm to about 100 µm in another incorporation, from about 1 µm to about 50 µm in another embodiment, from about 3 µm to about 40 µm in yet another embodiment, and from about 12 µm to about 25 µm in yet another embodiment.
[0061] The filler or blend of fillers used in the present invention may optionally have a thermal conductivity greater than that of an uncharged cured epoxy resin which may be greater than about 0.2 W/mK measured at 25°C. In the present invention, heat dissipation of an RF filter is required using conventional industrial methods; and therefore, the thermal conductivity of the payload in the present invention can generally be greater (>) than about 0.5 W/mK in one embodiment, and greater than about 2 W/mK in another embodiment. As an illustrative embodiment, the thermal conductivity of the charge can be from about 0.2 W/mK to about 4000 W/mK; from about 0.2 W/mK to about 1000 W/mK in another embodiment; from about 0.2 W/mK to about 600 W/mK in yet another embodiment; from about 0.2 W/mK to about 500 W/mK in yet another embodiment; from about 0.2 W/mK to about 200 W/mK in yet another embodiment, and from about 0.2 W/mK to about 100 W/mK in yet another embodiment.
[0062] Generally, the thermal conductivity of the cured epoxy composite prepared with the curable composition may be greater than about 0.20 W/mK in one embodiment, greater than about 0.5 W/mK in another embodiment, greater than about of 0.75 W/mK in yet another development, and greater than about 1.0 W/mK in yet another development. As an illustrative embodiment, the thermal conductivity of the cured epoxy composite can be from about 0.20 W/mK to about 300 W/mK in an embodiment, from about 0.35 W/mK to about 300 W/mK in another embodiment, from about 0.35 W/mK to about 250 W/mK in yet another embodiment; from about 0.35 W/mK to about 50 W/mK in yet another embodiment; from about 0.7 W/mK to about 10 W/mK in yet another embodiment; and from about 0.90 W/mK to about 5 W/mK in yet another embodiment.
[0063] Supplies of payloads in the present invention may vary and depend on the type of payload used. Generally, the concentration of total charge present in the curable composition of the present invention can be from more than about 35% by weight to about 90% by weight in an embodiment, from more than about 40% by weight to about 90% in weight in another embodiment, from more than about 45% by weight to about 80% by weight in yet another embodiment, from about 55% by weight to about 75% by weight in yet another embodiment, from about 60% in weight to about 75% by weight in yet another embodiment, and from about 60% by weight to about 70% by weight in yet another embodiment, based on the weight of the total composition. Below a filler supply of 35% by weight, the composition containing such a filler supply can be expected to result in a composite having higher CTE which deviates from the desired low CTE of the present invention; and above a 90% by weight filler supply no additional advantage can be seen in the composite of the present invention over CTE.
[0064] In a preferred embodiment and in order to approximate the CTE of metallic aluminum, such as using a quartz charge, fused quartz charge, or a mixture of quartz charge and fused quartz charge, the charge supply may generally be greater than about 45% by weight. In addition to the choice of base resin used and a composition leading to a high Tg, the loading level of the composition can be a significant factor in achieving a low CTE of the resulting composite prepared with the composition.
[0065] The curable resin composition of the present invention may optionally include at least one catalyst to facilitate the reaction of the epoxy resin with the curing agent. The use and function of catalysts is described, for example, in Handbook of Epoxy Resins and Epoxy Resins: Chemistry and Technology mentioned above. The catalyst, useful as an optional component in the composition of the present invention, may include catalysts well known in the art, such as, for example, catalyst compounds containing portions of amine, phosphine, heterocyclic nitrogen, ammonium, phosphonium, arsonium, sulphonium, and any combination of them. Some non-limiting examples of the catalyst of the present invention may include, for example, ethyl triphenyl phosphonium; benzyl trimethyl ammonium chloride; triflates and heterocyclic nitrogen containing catalysts including those that are not complex described in U.S. Patent No. 4,925,601, incorporated herein by reference; imidazoles, triethylamine; and any combination thereof.
[0066] For example, the catalyst may include tertiary amines such as triethylamine, tripropylamine, tributylamine, benzyl-dimethylamine, and mixtures thereof; imidazoles such as 2-methyl-imidazole, 1-methyl-imidazole, 2-ethyl-4-imidazole, and mixtures thereof; organic phosphines; acid salts; organic metal salts; cationic photoinitiators such as diaryl iodonium salts including IRGACURE™ 250 obtainable from Ciba-Geigy or triaryl sulfonic salts such as CYRACURE™ 6992 obtainable from The Dow Chemical Company; and mixtures thereof.
[0067] In another embodiment, one can use a "superacid" catalyst in a formulation where the reagents contain epoxy groups and potentially other reagents that contain hydroxyl groups. The catalyst acts as a "hardener". The system can be a 2-part system where the catalyst is, for example, added to hydroxy compounds, where the catalyst is inactive or reacts slowly at ambient temperatures, or where the catalyst is, for example, "locked" at ambient temperatures and is “unlocked” when heated. Unblocking can be exemplified, for example, using diethyl ammonium triflate which is, for example, non-reactive as a salt, but active when amine volatilizes. A blocked non-volatile catalyst can be, for example, a sulfonic hexafluoroantimonate, with a third chain attached to the sulfur. Glycidyl epoxies such as, for example, D.E.R. 332, an epoxy resin having an EEW of 171 and commercially available from The Dow Chemical Company, would add "tenacity" (e.g., dart drop impact, no cracking) to the composite prepared with the formulation. A cycloaliphatic epoxy would raise the Tg and reduce the formulation viscosity.
[0068] You can add the curing catalyst in the component epoxy resin and/or in the component hardener; or alternatively, one can mix the curing catalyst into the curable composition.
[0069] The concentration of the curing catalyst used in the present invention can be less than 3% by weight. Generally, the curing catalyst can be present in the curable composition at a concentration of from about 0.005% by weight to about 3% by weight in an embodiment; from about 0.025% by weight to about 2% by weight in another embodiment; from about 0.01% by weight to about 1.5% by weight in yet another embodiment; from about 0.1% by weight to about 1.0% by weight in yet another embodiment; and from about 0.2% by weight to about 0.8% by weight in yet another embodiment, based on the total weight of the curable composition. The use of lower concentrations of catalyst typically does not provide a sufficient catalytic effect, resulting in very low reactivity of the curable composition. Using higher concentrations of catalyst results in very high reactivity of the curable composition.
[0070] The curable resin composition of the present invention may optionally include at least one flame retardant (FR) component to provide flame retardancy to the cured composite product prepared with the curable resin composition of the present invention. The FR component useful in preparing the composition is as an optional component of the present invention and may include, for example, one or more reactive and non-reactive flame retardant ingredients or compounds known in the art to provide flame retardancy. In the curable resin composition one or more halogen-containing compounds such as bromine-containing compounds, or non-halogen-containing compounds such as phosphorus-containing compounds can be used. Advantageously, some combinations of two or more of the above flame retardant compounds can function synergistically to provide flame retardancy.
[0071] As used herein, "reactive flame retardant compounds" includes flame retardant compounds that are capable of chemically bonding to a cured epoxy resin and/or hardener; and can become part of a crosslinked epoxy network. As used herein, "non-reactive flame retardant compounds" include flame retardant compounds useful as additives which are capable of dissolving or partially dissolving in a crosslinked epoxy network or capable of being phased out of a crosslinked epoxy network or are effectively a charge on a crosslinked epoxy net.
[0072] The flame retardant (RF) components used in the present invention may be present in the curable resin composition in a concentration that provides a balance of properties for the resulting composite prepared with the curable composition of the present invention, such as, for example, thermal, mechanical, and thermomechanical properties of the composite. For example, the concentration of one RF component, or mixture of two or more RF components, may generally be sufficient to allow, in an embodiment, the composite to meet at least a V-2 rating determined by UL 94 testing; in another embodiment at least a V-1 rating determined by UL 94 testing; and in yet another embodiment, at least a V-0 rating determined by UL 94 testing.
[0073] The flame retardants useful in the present invention can function in different modes (such as endothermic degradation, thermal shielding [e.g., carbon residue formation], rapid cooling via gas phase radicals, gas phase dilution, and the like) or in multiple modes such as in one or more of the aforementioned modes; and it is often desirable to use two different flame retardants in a composition such that the two different flame retardants function in different ways and/or such that the two different flame retardants combined work synergistically.
[0074] Some non-limiting examples of FR compounds that can be used in the curable epoxy resin formulations of the present invention may include aluminum hydroxide, magnesium hydroxide, antimony oxide, red phosphorus, ammonium polyphosphate, zinc borate, molybdate zinc, tetrabromo-bisphenol A diglycidyl ether and its oligomers, triglycidyl phosphate, 2-(6-oxide-6H-dibenzo[c,e][1,2]oxa-phosphorin-6-yl)1,4-benzenediol (DOPO-HQ), 9,10-dihydro-9-oxa-phospha-phenanthrene-10-oxide (DOPO) and its derivatives, phosphorus-amidates, 5,5-dimethyl-[1,3,2]dioxa-phosphinane -2-oxide (DDPO) and its derivatives, dimethyl phosphite and other organic phosphates, diethyl phosphinic acid and other organic phosphinic acids, ethyl phosphonic acid and other organic phosphonic acids, tris(4-hydroxy phenyl)phosphine oxide and other oxides of organic phosphine, bis(2-hydroxy phenyl)phenyl phosphinate and other organic phosphinates, melamine polyphosphate, aluminum diethyl phosphinate and other phosphinates metallic ones, triphenyl phosphate, resorcinol bis(diphenyl phosphate), bisphenol A diphenyl phosphate and other organic phosphates, other organic phosphonates and oligomers thereof, and mixtures thereof.
[0075] Other examples of suitable flame retardants useful in the present invention and their classes can be found, for example, in a monograph entitled "Flame Retardants - 101 Basic Dynamics - Past Efforts Create Future Opportunities", presented at the Fire Retardant Chemicals Association, Baltimore Marriot Inner Harbor Hotel, Baltimore MD, March 24-27, 1996; Materials 2010, 3, 4300-4327; U.S. Patent No. 6,645,631; WO 2004118604; and WO 2008144252, all of which are incorporated herein by reference.
[0076] An example of a flame retardant compound useful in the present invention may include tetrabromo-bisphenol A diglycidyl ether, aluminum hydroxide, aluminum diethyl phosphinate, ammonium polyphosphate, or mixtures thereof. The concentration of RF compound present in the curable composition may depend on the specific RF compound used and the end use application in which the curable composition can be used. However, such compositions can be determined by the qualified technician.
[0077] Other optional components that may be useful in the present invention include conventional components commonly used in resin formulations. For example, an assortment of optional additives that may be added to the reactive curable epoxy resin composition of the present invention may include, other resins, stabilizers, plasticizers, catalyst deactivators, dyes, pigments, thixotropic agents, photoinitiators, latent catalysts, inhibitors, solvents, surfactants, flow-controlling agents, thinners, flexibilizing agents, processing aids, dispersing/wetting agents, air release agents, reactive thinners (low viscosity monoepoxy or polyepoxy materials that aid processing as described in the books that describe above-mentioned epoxy resins), other curing agents not mentioned above, other halogen-containing flame retardants, other halogen-free flame retardants, other synergists to improve flame-quenching performance, adhesion promoters such as organosilanes modified (epoxidized, methacryl, amino), acetyl acetonates, or sulfur-containing molecules; wetting and dispersing aids such as modified organosilanes, BYK 900 series and BYK W-9010, fluorocarbons, air release additives such as BYK-A 530, BYK-A 525, BYK-A 555, BYK-A 560; surface modifiers such as slip and gloss additives (a number of which are obtained from Byk-Chemie), or mixtures thereof.
[0078] The amount of optional additives used in the present invention may be such that (I) the Tg of the resulting cured composite may be greater than or equal to 100°C in one embodiment, or greater than or equal to 130°C in another embodiment; and (II) the CTE of the resulting cured composite may be less than or equal to 80 ppm/°C in one embodiment, or less than or equal to 50 ppm/°C in another embodiment, or less than or equal to 40 ppm/°C in yet another incorporation. For example, the concentration of optional additives used in the present invention can generally range from 0% by weight to about 10% by weight in one embodiment, from about 0.01% by weight to about 5% by weight in another embodiment, of from about 0.1% by weight to about 2.5% by weight in yet another embodiment, and from about 0.5% by weight to about 1.0% by weight in yet another embodiment, based on weight of all components of the composition.
[0079] The process for preparing the epoxy resin composition useful for the manufacture of RF filters includes mixing (I) at least one epoxy resin; (II) at least one curing agent (tenacity); (III) at least one hardener; (IV) at least one charge; and (V) optionally, at least one cure catalyst. For example, the curable epoxy resin composition of the present invention can be prepared, for example, by mixing in a container the epoxy resin, a curing agent, a hardener, a filler, an optional curing catalyst, and any other desirable optional additives; and then allowing the components to combine into an epoxy resin composition. Any of the aforementioned optional assorted formulation additives, for example, an inert organic solvent or gas release agent, can also be added to the composition during mixing or prior to mixing to form the composition.
[0080] For example, the curable epoxy resin composition of the present invention can be obtained by mixing with or without vacuum in a PD Ross mixer (Charles Ross), a FlackTek speed mixer or other mixer known in the art that moistens the charge with and dispenses evenly the above IV resin components. The aforementioned elements can generally be added in any sequence, in various combinations, and at various addition times as is convenient and desired. For example, to extend shelf life, the optional curing catalyst can be added late or at a later time during mixing and optional degassing, but before pouring the composition. Any of the aforementioned optional assorted formulation additives, for example an additional epoxy resin, can also be added to the composition during mixing or prior to mixing to form the composition.
[0081] In one embodiment, one or more of the above components (I)-(V) of the formulation can be premixed. For example, the catalyst can be pre-mixed in the hardener and then the pre-mixed components can be added to the formulation. In another embodiment, components (I) and (II) are pre-mixed.
[0082] For the formulations of the present invention, degassing the formulation is an option for the present invention and can be achieved via methods known in the art. Typically, degassing can be performed by applying a vacuum in some mixing apparatus for the formulation, including the individual components as well as mixtures of individual components, or by applying a suitable vacuum directly to the mold. The range of vacuums, vacuum ramps and steps, and the timing of vacuum application to effectively degas a formulation before melting and curing depends on a variety of factors known in the art such as, for example, temperature, viscosity of the formulation, formulation mass, geometry of the degassing vessel and its mixing quality and the like. In general, it is desirable to apply a vacuum at some point during mixing of resin components (I)-(V) and the vacuum can be set here, for example, to something less than atmospheric pressure.
[0083] Degassing can occur in the same device and/or container, or in separate devices and/or containers that can be used to mix or initially maintain any of the components (I)-(V) as well as optional additives. Mixing or stirring can be performed normally when degassing. Any vacuum can be applied, but the degassing rate improves when smaller vacuums are applied. Degassing can be performed at less than about 300 millibar in one incorporation, less than about 100 millibar in another incorporation, less than about 50 millibar in yet another incorporation, and less than about 20 millibar in yet another incorporation. As an illustrative embodiment, degassing can be performed in a vacuum of from about 0.1 millibar to about 900 millibar. Generally, it is preferred to have some lower vacuum limit applied for both economic considerations and the desire to minimize volatilization of a component which depends on the component and the temperature of the component. It is preferred to use some vacuum greater than about 0.5 millibar in degassing and more preferably to use a vacuum greater than about 1 millibar.
[0084] All components of the epoxy resin composition are typically mixed and dispersed; and optionally degassed at a temperature which permits the preparation of an effective curable epoxy resin composition such that when cured provides a cured product having the desired balance of properties required for use in, for example, RF filter applications. Generally, the temperature during mixing of all components can be from about 10°C to about 110°C in one embodiment, from about 20°C to about 90°C in another embodiment, and about 40°C to about 80°C in yet another embodiment. Lower mixing temperatures help minimize the reaction of the epoxy resin with the hardener to maximize formulation storage time, but higher short-term mixing temperatures can lower formulation viscosity and facilitate mixing, degassing, and formulation transfer prior to be healed.
[0085] In general, the viscosity of curable epoxy resin composition at the transfer or pour temperature into a mold or shape can be any viscosity value at which the formulation flows. For example, the complex viscosity of the complete formulation at the temperature at which the formulation is transferred or poured may be less than about 200,000 mPa-s at 80°C in one embodiment, less than about 100,000 mPa-s in another embodiment, less than around 50,000 mPa-s in yet another development, and less than around 25,000 mPa-s in yet another development. In yet another embodiment, the viscosity of the complete epoxy resin formulation can range from about 200 mPa-s to about 25,000 mPa-s.
[0086] As a general illustrative embodiment of the present invention, the complex viscosity of the epoxy resin composition of the present invention, prior to curing, which is useful in preparing the epoxy composite may generally be, for example, about 500 mPa -s to around 200,000 mPa-s in one development, from around 1,000 mPa-s to around 100,000 mPa-s in another development, and from around 2,000 mPa-s to around 25,000 mPa-s in yet another development, measured by 80°C.
[0087] In general, it is desired that the complete curable epoxy resin formulation or composition of the present invention be mixed, degassed, and transferred to be cured to the mold, shape or apparatus in which the formulation will generally be used in less than about 2 days in one embodiment, less than about 1 day in another embodiment, and less than about 12 hours in yet another embodiment, when kept at room temperature (about 25°C) to about 60°C. As a general illustrative embodiment of the present invention, the formulation will generally be used, for example, from about 0.02 hr to about 2 days. However, in another preferred embodiment, the complete, degassed formulation has transfer initiated immediately, rather than storing it, to be cured in the mold, or specific form in which the RF material will generally be used.
[0088] As is known in the art, the storage time (or shelf life) of a complete formulation may depend not only on the temperature at which the formulation is kept, but also on the amount and type of catalyst that can be included in the formulation. with lower catalyst concentration typically extending the shelf life of the formulation. For extended shelf life, the blended compound formulation can typically be stored at temperatures below room temperature to maximize shelf life and optionally without containing the catalyst. Acceptable temperature ranges for storage include, for example, from about -100°C to about 25°C in one embodiment, from about -70°C to about 10°C in another embodiment, and from about -50 °C to about 0 °C in yet another embodiment. As an illustration of an embodiment, the storage temperature can be about -40°C.
[0089] Curing of the heat-set composition can be performed at a predetermined temperature and for a predetermined period of time and in a series of temperature ramps and temperature steps sufficient to cure the composition. The cure of the formulation may depend on the hardeners used in the formulation as well as the optional catalyst and its amounts as well as other additives. It is hypothesized to use more than one temperature step in curing the formulation in which some of the steps only partially cure or gel the formulation to facilitate the development of properties of the fully cured formulation. It is thought that such a step-temperature process serves to better control the homogeneity, shrinkage, and stresses that occur during the curing of the formulations of the present invention and can lead to a material of more consistent or better mechanical performance for RF filters, heat, or boxes. Whatever the cure profile, it is generally recognized by those skilled in the art that the final cure temperature should generally exceed the glass transition temperature, Tg, of a fully cured epoxy/hardener system. After curing or post-curing the composition, the process may include controlled cooling which may include one or multiple temperature ramps and temperature steps to minimize stress development and possible defects in the cured material.
[0090] In one embodiment, a partially cured thermosetting resin composition (stage B) of the present invention may first be produced followed by complete curing of the composition (stage C). Curing can be performed via thermal cure. For example, the cure temperature or series of one or more cure steps for the formulation may generally be from about 10°C to about 300°C in one embodiment, from about 10°C to about 250°C in another incorporation, from about 25°C to about 250°C in yet another embodiment, from about 30°C to 225°C in yet another embodiment, from about 50°C to about 200°C in yet another embodiment , and from about 50°C to about 120°C in yet another embodiment.
[0091] The cure time can be chosen depending on the size and shape of the substrate. Generally, the cure time can be between about 1 minute and about 96 hours in one embodiment, between about 5 minutes and about 72 hours in another embodiment, between about 10 minutes and about 48 hours in yet another embodiment, between about 20 minutes and about 24 hours in yet another embodiment, and between about 1 minute and about 4 hours in yet another embodiment. Below a time period of about 1 minute the time may be too short to ensure sufficient reaction under conventional processing conditions; and above about 96 hours, the time may be too long to be practical or economical. The size and shape of the cured epoxy formulation as well as the components of the epoxy formulation play an important role in the curing profiles used known to those skilled in the art. Below a time period of about 1 minute the time may be too short to ensure sufficient reaction under conventional processing conditions; and above about 72 hours, the time may be too long to be practical or economical.
[0092] In stage C, in one incorporation, it generally reacted more than about 70% molar of the thermoset resin portions, reacted more than about 80% molar of the thermoset portions in another incorporation, and reacted more than about 90% molar of the thermoset portions in another merger.
[0093] In an embodiment, it is advantageous to gel or partially cure the composition in one or more steps or temperature ramps. For example, one can use a first step or temperature ramp from about 10°C to about 250°C; and thereafter, at least one heating/cure step or ramp from about 120°C to about 300°C can be used. In another embodiment of a curing process of at least two stages, the composition curing stage may include, for example, a first stage of curing at a temperature of from about 70°C to about 120°C, and a second step of cures at a temperature of about 130°C to about 160°C. In yet another embodiment, a third stage of curing may be used after performing the above first and second stages, the third stage temperature being from about 175°C to about 250°C. In any of the steps/ramps described above, the heating time at the desired temperature can be from about 1 minute to about 96 hours.
[0094] In yet another embodiment, an initial gel time to "green cure" (incomplete) may be from about 12 minutes to about 78 minutes at about 100°C to about 120°C. In a subsequent step, curing can continue in about 2 hours to about 4 hours at about 140°C to about 160°C; and optionally in about 8 hours at a temperature greater than about 200°C, for example, for cycloaliphatic and epoxy novolac systems.
[0095] If the formulation or composition is cured too quickly or at a temperature too high for a particular temperature step or ramp then it may more likely result in decreased performance of the cured material as well as the device in which the cured material will be used. Decreased performance can give rise to, but is not limited to, defects in the resulting cured composition which can lead to decreased performance or failure in the formulation or in the device in which the formulation is used. If the formulation is cured too slowly, it can give rise to decreased performance or failure in performance of the formulation; or the device in which the composition is used may have a substantive non-uniform distribution of charge(s) which may adversely affect the performance of the device. Examples of such defects include cracks, blisters, substantive non-uniform distribution of charge(s), and the like.
[0096] Processes for fabricating parts using the epoxy resin formulations of the present invention, that is, for curing the curable composition of the present invention, include, but are not limited to, for example, vacuum casting, liquid injection molding (LIM), reactive injection molding (RIM), resin transfer molding (RTM), automatic pressure gelation (APG), and the like.
[0097] An embodiment of the RF filter body manufacturing process includes one where the filter can be molded and cured using the proposed epoxy compositions to be close to the final geometry, requiring only some additional machining and surface treatment to result in a semi-finished product ready for metallic coating followed by installation of other parts and accessories and then final adjustment. Another embodiment of the RF filter body manufacturing process includes one where the proposed epoxy resin composition of the present invention can be molded and cured into blocks of desired dimensions, then the final geometry of the molded and cured blocks can be machined to target parts semifinals to be followed by the same steps described above. In either of the above two embodiments, the RF filter body can be fabricated by including a plurality of holes to secure a cover plate by screws and seal interior electronics such as resonators and component connectors with screws. In one embodiment, the holes can be molded during the fabrication of the RF filter body, eliminating the need to drill holes after molding. In another embodiment, the RF filter body can be molded using insert molding technology that includes, for example, threaded inserts molded into the body, eliminating the need for drilling and clearing post mold holes.
[0098] The thermoset product of the present invention (ie, crosslinked epoxy composite prepared with the formulation of the present invention) shows several desirable properties. For example, the present invention provides a thermoset system that is preferably isotropic in terms of mechanical properties and/or coefficient of thermal expansion as opposed to thermoplastic polymers with known charges. Dimensional stability and isotropicity are two desirable properties in certain applications such as RF filters because the filter signal regulation depends on the characteristic stability.
[0099] With reference to a device, "dimensional stability" here means thermal dimensional stability at the operating temperature of the device indicated by the coefficient of thermal expansion (CTE) of the material in the device.
[0100] As used herein, the term "isotropicity" means an average orientation property value that is substantially the same measurement in the x, y, and z direction of measurement. The x, y, and z directions of measurements are generally within limits of about 60% of each other in one embodiment, within limits of about 75% of each other in another embodiment, and within limits of about 90% of each other. others in yet another incorporation.
[0101] In another embodiment, "isotropicity" here means, when heated within the limits of the operating temperature range, dimensional change defined by the CTE of the material is substantially similar in all dimensions. Here, "substantially similar" means a CTE change that may be generally less than about 60% in a less than about 50% incorporation in another incorporation, less than about 40% in yet another incorporation, less than about 30% in yet another incorporation , less than about 25% in yet another merger, and less than about 10% in yet another merger. In yet another preferred embodiment, the CTE change can be essentially zero.
[0102] An illustrative embodiment and advantage of the present invention includes, for example, where the glass transition temperature (Tg) of the epoxy composite can generally be greater than about 100°C. For example, the cured epoxy resin product of the present invention can generally have a Tg of about 100°C to about 300°C in one embodiment; from about 120°C to about 250°C in another embodiment; from about 130°C to about 200°C in yet another embodiment; from about 135°C to about 180°C in yet another embodiment; and from about 140°C to about 170°C in yet another embodiment, measured by differential scanning calorimetry.
[0103] One can measure the Tg using a differential scanning calorimeter (DSC) scanning at 10°C/min from near room temperature (0 to 25°C) at some temperature higher than the Tg, for example, at a temperature of about 250°C with a first heating cycle, a cooling cycle, and a second heating cycle. The Tg can be determined from the middle height of the 2nd order transition of the second heating cycle. The Tg of the cured material of the present invention is the Tg of the continuous phase epoxy/hardener; and if the curing agent (tenacity) is in a phase separate from the continuous epoxy/hardener phase, the Tg will be the largest 2nd order transition associated with the component epoxy/hardener.
[0104] Another illustrative embodiment and advantage of the present invention may be that where the density of the epoxy composite is less than 2.7 g/cm3 (which is the density of aluminum, the incumbent metal). For example, the density of the epoxy composite of the present invention can generally be less than about 2.5 g/cm3 in one embodiment; less than about 2.3 g/cm3 in another embodiment; and less than about 2.2 g/cm3 in yet another embodiment, for light weight against incumbent metal technology. In other examples, the density of the epoxy composite of the present invention can be from about 1.2 g/cm3 to about 2.7 g/cm3 in one embodiment; from about 1.2 g/cm3 to about 2.5 g/cm3 in another embodiment; from about 1.2 g/cm3 to about 2.2 g/cm3 in yet another embodiment, from about 1.4 g/cm3 to about 2.1 g/cm3 in yet another embodiment, from about 1 from about 1.6 g/cm3 to about 2.0 g/cm3 in yet another embodiment, from about 1.8 g/cm3 to about 2.0 g/cm3 in yet another embodiment, and from about 1.7 g µg/cm3 to about 1.9 g/cm3 in yet another embodiment as measured by ASTM D-792.
[0105] An object of the present invention is to provide an epoxy resin composite that is substantially lighter than aluminum. With reference to the epoxy resin composite of the present invention, "substantially lighter" here means at least about 10% lighter than aluminum in one embodiment, at least about 20% lighter than aluminum in another embodiment, at least about 30% lighter than aluminum in yet another embodiment, at least about 40% lighter than aluminum in yet another embodiment, and at least about 50% lighter than aluminum in yet another embodiment. In another embodiment, the epoxy resin composite of the present invention can be about 10% to about 50% lighter than aluminum.
[0106] Yet another illustrative embodiment and advantage of the present invention may be where the CTE of the epoxy composite may be generally less than about 80 ppm/°C in an embodiment, from about 0 ppm/°C to about 50 ppm /°C in another embodiment, from about 10 ppm/°C to about 50 ppm/°C in yet another embodiment, and from about 20 ppm/°C to about 45 ppm/°C in yet another embodiment throughout. the usage temperature range of about -50°C to about 85°C, where the CTE must be consistent with the temperature range. The CTE value of the thermoset device reflects the isotropic nature of the compound.
[0107] In yet another illustrative embodiment and advantage of the present invention may be where the tensile strength of the epoxy composite can generally be greater than or equal to 35 MPa. For example, the tensile strength can be from about 35 MPa to about 250 MPa in one embodiment, from about 50 MPa to about 250 MPa in another embodiment, from about 55 MPa to about 125 MPa in yet another embodiment, from about 65 MPa to about 125 MPa in yet another embodiment, and from about 75 MPa to about 100 MPa in yet another embodiment, as measured by ASTM D-638, Type 1 drawbar.
[0108] In another embodiment of the present invention, the fracture toughness of the epoxy composite can be measured in terms of the critical stress intensity factor, K1c, following the test method in ASTM D 5045-99. For example, the fracture toughness of the epoxy composite of the present invention can generally be a K1c greater than about 0.6 MPa-m0.5 in one embodiment; greater than about 1.0 MPa-m0.5 in another incorporation; and greater than about 1.5 MPa-m0.5 in another embodiment. In an illustrative embodiment, the fracture toughness of the epoxy composite of the present invention can generally be a K1c greater than about 0.6 MPa-m0.5 to about 10 MPa-m0.5, and from about 1.0 MPa -m0.5 to about 5 MPa-m0.5 in another embodiment.
[0109] No crack or burr of the epoxy composite provides an indication of the composite's machinability when it is drilled or threaded (including tap screws), but also the material's ability to produce high quality machined surfaces illustrated by surface smoothness as well as thread strength when threaded holes are drilled in the composite. This can be measured, for example, by torque to failure when threaded screws are inserted and tightened to thread failure in threaded holes. Such attributes are another illustration of the advantages of the present invention.
[0110] The desired application in the present invention requires good surface properties for the electrodeposition step, as well as overall geometric requirements, and any significant defect, such as large pores, would compromise the usefulness of the material. It is well known that polymer sponging either via gas injection, or on-site gas generation, especially when it comes to cell size control can be a delicate process. Therefore, eliminating the foaming step would be desirable to obtain both good surface quality for metal cladding and simplified manufacturing process. In the case of syntactic foams, where lighter weight hollow particles such as glass microspheres are incorporated in the epoxy formulation, generally tensile and flexural strengths show a decreasing trend with the introduction of microspheres when compared to unfilled resins as described, for example, in Update on Syntactic Foams; B. John and C.P. Reghunadhan Nair; pp. 23-29; RAPRA Publishing, incorporated herein by reference.
[0111] In addition, the epoxy composite of the present invention can be coated with metal. The ability to metal coat a polymer composite is one of the key features useful for RF cavity filter applications in accordance with the present invention. "Ability to coat with metal" is defined herein as the ability to deposit a layer of metal such as copper, silver or gold onto the polymer composite via various electrodeposition techniques and the coating would result in acceptable adhesion of the metal layer to the composite of polymer measured by an exfoliation force. The total required thickness of metallic layers will vary depending on the specific application, but will typically be in the range of about 0.25 microns (μm) to about 50μm in an embodiment; from about 1 µm to about 20 µm in another embodiment; from about 0.25 µm to about 10 µm in yet another embodiment; and from about 0.25 µm to about 2.5 µm in yet another embodiment. In general, the tack strength in terms of the peel strength of the metallic layer of the polymer composite can be greater than about 0.17 N/mm (1.0 lb/inch) in one incorporation, greater than 0.26 N/mm (1.5 lb/inch) in another incorporation, greater than or equal to 0.35 N/mm (2.0 lb/inch) in yet another incorporation. As an illustration of another embodiment, the peel strength can be from about 0.17 N/mm (1.0 lb/inch) to about 1.75 N/mm (10 lb/inch). ASTM B-533 test method can be used as the standard test method for peel resistance of metal electrocoated plastic.
[0112] The above properties are advantageous to ensure (1) the dimensional stability of the filter made with the curable composition of the present invention when the filter is in operational conditions measured, for example, by CTE; (2) the ease and robustness of the process for the compositions; and (3) the filter's overall thermomechanical performance under operating conditions.
[0113] In an embodiment, since the curable composition of the present invention can be cured to form the cured epoxy resin composite, optionally, said cured epoxy resin composite can still be processed, for example, by machining and/or preparation of the surface of the resulting cured composite.
[0114] In another embodiment, the present invention also relates to a process to metallize the cured composite described above. For example, a copper electroplating process can be performed on epoxy composite materials of the present invention and a high quality copper plating layer can be achieved. Here, a high-quality plating layer with reference to an electro-coated composite substrate means that the exfoliation strength of the substrate's copper layer is, for example, greater than about 0.35 N/mm (2 lbs/inch) . The high-quality plating layer also means that the electro-coating layer is stable over an outdoor temperature range. One method to ensure that the electrocoat on the composite substrate is of high quality might be, for example, to heat the electrocoated filter to about 160°C for about 30 minutes; thereafter, the resulting heated item can be quickly cooled in water. The resulting high quality cooled item does not show any signs of blistering or loss of metallic flakes that can be quickly removed from the substrate. For example, an assessment of the ability to remove the electrocoat substrate from the substrate can be done (I) manually using the hands to remove stray metallic flakes or (II) applying moderate force to the electrocoated substrate with an object.
[0115] The metallization process of the present invention can be performed by initially processing a substrate part through an appropriate pre-treatment process, followed by electrodeposition of a thin layer (for example, from about 0.25 μm to about 2 .5 μm) of metal such as copper or nickel. For example, in an incorporation, a copper layer can be electrocoated on the composite, the layer being 1 μm thick. Electrocoating can proceed up to a thickness of up to about 20 μm; and thereafter, another layer of metal such as silver can optionally be applied to the desired thickness of the layer such as, for example, about 1 µm. In another embodiment, multiple layers can be used or, in a preferred embodiment, a single layer of metallic electrocoat can be used.
[0116] For example, additional metallic layers can be conveniently applied over an initial plating layer using electrolytic coating techniques or other metallic coating techniques such as deposition without electrolysis or dip deposition. Typically, electrolytic processes are used to add thicker layers as these processes are fast. In an incorporation where an additional copper layer is desired, the layer can be added using a process without electrolysis (although the deposition rate for the higher thickness may be lower). For an incorporation where a final silver layer is desired, the thickness can be small, and therefore deposition without electrolysis or by immersion can also be used.
[0117] Appropriate pretreatment methods include, but are not limited to, chemical blasting with acid/base treatments and physical grinding (eg sandblasting).
[0118] For the epoxy composite material of the present invention, a preferred embodiment of the pretreatment method may be a chemical pickling method, based on an initial conditioning step in an alkaline solution containing solvent, followed by treatment with an alkaline solution hot containing permanganate ions. Residues from the permanganate pickling step are then removed in a neutralizing bath containing an acidic solution of a hydroxylamine.
[0119] In one embodiment, the curable epoxy resin and composite formulation of the present invention can be used to manufacture radio frequency filters. Radio frequency filters are incorporated, for example, into tower-top electronics such as wireless filter applications. Radio frequency filters, their characteristics, their manufacture, their machining, and their overall production are described, for example, in U.S. Patent Nos. 7,847,658 and 8,072,298, which are incorporated herein by reference.
[0120] For example, the radio frequency filter includes a housing housing with other components known in the art to provide a functional radio frequency cavity filter. For example, the body housing may further include a cover plate attached to the body housing that encloses resonant cavities of the body housing. Those skilled in the art are familiar with other components the body housing may have to facilitate the operation of the RF filter.
[0121] In general, the process used to manufacture the radiofrequency filter includes, for example, a process step of forming a radiofrequency filter body housing with the curable thermosetting epoxy resin composition of the present invention, the composition of A curable thermosetting epoxy resin comprises (I) at least one epoxy resin; (II) at least one curing agent; (III) at least one hardener; and (IV) at least one filler, the filler material being uniformly distributed and randomly oriented throughout the epoxy resin polymer.
[0122] In an embodiment, the liquid curable epoxy resin composition can be placed in a cavity matrix or mold and then cured by a casting process. The curable epoxy resin composition can then be polymerized after closing and heating the mold. Those skilled in the art are familiar with other casting or molding processes, such as reaction or transfer molding processes, that can be used. For example, the curable epoxy resin composition can be heated to an elevated temperature to melt the composition and then the composition can be transferred to a heated mold where the mixture reacts to form a thermoset product.
[0123] In another embodiment, molding the body housing may include a step of machining a block of the product cured epoxy resin composite into a desired shape of the body housing. Machining is desired when the polymer composition can be molded into a shape that is not the same as the intended shape of the body housing. When machining the cured epoxy resin composite product into its intended shape, the cavity matrix can be block-shaped, or the curable epoxy resin composition can be extruded from the matrix as a block-shaped component. The product cured epoxy resin composite block can be machined using machining devices known in the art. Other embodiments for molding the cured product are disclosed, for example, in U.S. Patent No. 7,847,658, which is incorporated herein by reference.
[0124] In an embodiment, the process of coating the body housing with an electroconductive material may include depositing successive metallic layers (eg, copper and silver) onto the copper housing. Coating processes with or without electrolysis, or a combination of both, can be used to coat a portion of the surface of the body housing or the entire surface of the body housing with such electroconductive materials.
[0125] In another embodiment, some of the components in the curable composition may be precoated with a metal to improve the initiation of electrodeposition. For example, a copper layer can be deposited on at least some of the filler material particles or fibers mixed with the polymer via chemical vapor deposition. The skilled technician is familiar with other coating processes. To coat the body housing other conventional techniques such as spraying or painting can also be used.
[0126] Other steps to complete fabrication of the body housing may include securing a plate over the body housing such that the body housing cavities are enclosed by the plate and walls of the body housing. Attaching the plate can include threading, nailing or anchoring the plate to the body housing, or adhesively bonding the plate to the body housing. Fabrication of the body housing may include attaching adjustment bars to the plate or body housing, for example, by screwing in, or otherwise adjustably securing the adjustment bars to the plate or body housing.
[0127] Those skilled in the art are familiar with other steps in the manufacture of the RF filter, which may depend on the particular configuration of the device in which the RF filter will be used. For example, where the apparatus is a wireless transmission system, the method of the present invention may include the step of affixing the radio frequency filter body housing to a mobile base station antenna mast.
[0128] The following examples and comparative examples further illustrate the present invention in detail, but will not be construed to limit its scope.
[0129] The terms and designations used in the Examples include, for example, the following: D.E.N. 425 is an epoxy resin having an EEW of 172, and is commercially available from The Dow Chemical Company; D.E.R. 332 is an epoxy resin having an EEW of 171 and is commercially available from The Dow Chemical Company; D.E.R. 542 is an epoxy resin having an EEW of 332 and is commercially available from The Dow Chemical Company; "NMA" means methyl nadic anhydride, and is commercially available from Polysciences; "ECA 100" means epoxy curing agent 100, and is commercially available from Dixie Chemical, and ECA 100 generally comprises greater than 80% methyl tetrahydrophthalic anhydride and greater than 10% tetrahydrophthalic anhydride; "1MI" means 1-methyl-imidazole, and is commercially available from Aldrich Chemical; SILBOND® FW12EST is an epoxy silane treated quartz with a d50% bead size of 17 μm and is commercially obtainable from Quarzwerke; SILBOND® 126EST is an epoxy silane treated quartz with a d50% bead size of 22 μm and is commercially obtainable from Quarzwerke; HYMOD® SB432 SE is a proprietary surface treated aluminum hydroxide commercially available from J.M. Huber Corporation; KEMGARD® 911C is a zinc molybdate/magnesium silicate complex obtainable from J.M. Huber Corporation; EXOLIT AP 422 is an ammonium polyphosphate with an average particle size of 15 µm commercially obtainable from Clariant; EXOLIT OP1230 is a phosphinate with an average particle size ranging between 20 and 40 µm commercially obtainable from Clariant; BYK-A 525 is a polyether modified methyl alkyl polysiloxane copolymer solution as an air release additive and BYK-W 9010 is a wetting/dispersing additive and both are commercially obtainable from BYK Additives & Instruments, a member of ALTANA; FORTEGRA™ 100 epoxy toughening agent (F100) is a toughening agent, and is commercially available from The Dow Chemical Company; FORTEGRA™ 201 (F201) hardened epoxy resin is an elastomer-modified epoxy functional adduct formed by the reaction of a liquid bisphenol A epoxy resin and a carboxyl-terminated butadiene/acrylonitrile elastomer with an elastomer content of 40% by weight and is commercially available from The Dow Chemical Company; FORTEGRA™ 301 hardened epoxy resin (F301) is a dispersion of core-film rubber particles (CSR) preformed in a liquid bisphenol A epoxy resin containing 15% by weight of CSR and is commercially available from The Dow Chemical Company.
[0130] In the examples, the following standardized analytical methods and equipment are used: Glass transition temperature measurements (Tg)
[0131] A portion of the cured epoxy formulation is placed in a differential scanning calorimeter (DSC) with heating and cooling at 10°C/minute in a first heating scan of 0°C to 200°C or 250°C for a second heating sweep from 0°C to 200°C or 250°C. Tg is reported as the average height value of the 2nd order transition in the second heat sweep from 0°C to 200°C or 250°C. Tensile Strength Property Measures
[0132] Tensile property measurements (tensile strength and % elongation at break) are performed on the epoxy formulation cured to ASTM D638 using a Type 1 drawbar and 0.2 inch strain rate /minute. Thermal conductivity measurements
[0133] Thermal conductivity measurements are performed on the cured epoxy resin formulation according to ISO 22007-2 (the transient plane heat source [hot disk] method). Generally speaking, thermal conductivity of charges is measured and reported in the technique.
[0134] The coefficient of thermal expansion (CTE) is measured using a thermomechanical analyzer (TMA 2940 from TA Instruments). An expansion profile is generated using a heating rate of 5°C/minute, and CTE is calculated as the slope of the expansion profile curve as follows: CTE= ΔL/ (ΔT x L) where ΔL is a change in sample length (μim), L is the original sample length (m) and ΔT is the change in temperature (°C). The temperature range in which the slope is measured is 20°C to 60°C on the second heating. This particular temperature range was selected because it is the most common operating temperature range of a global range of -50°C to 100°C. Density/Relative Density Measurements
[0135] Density/relative density is measured using the method in distilled water (120 mL) containing ALCONOX® detergent (0.84 g) where the solution relative density is 0.9975 according to ASTM D792. of epoxy formulation
[0136] Complex viscosity is obtained as a function of temperature using an ARES G2 rheometer equipped with a fixed accessory of parallel plates. The plate diameter is 50 mm operating in fluid mode at shear rates of 10 s-1 and a temperature ramp of 5°C/minute starting at 40°C. Flame Retardance Test
[0137] Flame retardancy is tested in accordance with Underwriters Laboratories Inc. standard UL 94 for safety "Tests for Flammability of Plastics Materials for Parts in Devices and Appliances". Electroplating Thermal Shock Test
[0138] The epoxy samples are coated with a layer of non-electrolytic copper and a specimen is placed in an oven at 140°C for 30 minutes, then removed and rapidly cooled in water. The specimens are observed for any exfoliation or delamination of the copper coating of the epoxy. Long-term thermal cycling test of the coating
[0139] The epoxy samples are coated with a layer of non-electrolytic copper and a specimen is placed at a cycling temperature in a humidity chamber of -30°C to 85°C at a relative humidity of 85% for 35 days. After aging, the specimens are observed for any exfoliation or delamination of the copper coating of the epoxy.Examples 1-18 and Comparative Examples A and B
[0140] Tables I-III show examples of epoxy composite compositions of the present invention and comparative examples. The mixing, pouring and curing processes for epoxy composite compositions are generally carried out as described below. General procedure
[0141] The indispensable load sample is dried in an oven overnight at a temperature of approximately 70°C. Epoxy resin which typically contains FORTEGRA™ toughening agents and anhydride hardeners are separately preheated to a temperature of approximately 60°C. The designated amount of heated epoxy resin, heated anhydride hardeners, optional BYK-A 525 and/or BYK W9010, and 1-methyl-imidazole which are vortexed manually prior to addition of filler is loaded by weight into a wide mouth plastic container. heated which may include FR additives. Thereafter, the container contents are mixed in a SPEEDMIXER™ from FlackTek with multiple cycles of approximately 1-2 minutes duration from about 800 to about 2000 rpm.
[0142] The mixed formulation is loaded into a resin reservoir of approximately 500 to 1000 mL at controlled temperature with an overhead stirrer using a glass stirring shaft and containing a Teflon® blade along with a vacuum pump and a vacuum controller for degassing. A degassing profile is run between about 55°C and about 75°C with the following representative stages: 5 minutes, 80 rpm, 100 Torr; 5 minutes, 80 rpm, 50 Torr; 5 minutes, 80 rpm, 20 Torr with N2 stop at approximately 760 Torr; 5 minutes, 80 rpm, 20 Torr with N2 stop at approximately 760 Torr; 3 minutes, 80 rpm, 20 Torr; 5 minutes, 120 rpm, 10 Torr; 5 minutes, 180 rpm, 10 Torr; 5 minutes, 80 rpm, 20 Torr; and 5 minutes, 80 rpm, 30 Torr. Depending on the size of the formulation to be degassed times at higher vacuums may optionally be increased as well as the use of a higher vacuum of 5 Torr when desired.
[0143] The heated degassed mixture is brought to atmospheric pressure and poured into the heated molding assembly described below. For the specific mold described below, some amount between about 350 g and 450 g is poured into the open side of the mold. The filled mold is placed by standing vertically in an oven at 80°C for about 16 hours with the temperature subsequently raised and held at a final temperature ranging from about 175°C to about 225°C for a total of 4 hours; and then cooled slowly to room temperature (about 25°C). (Formulations containing DER 542 and EXOLIT OP 1230 have a final cure temperature of approximately 200°C; formulations containing EXOLIT AP422 have a final cure temperature of approximately 185°C; formulations containing HYMOD SB432E have a final cure temperature of approximately 175 °C). Molding set
[0144] On two metal plates of approximately 355 mm2 with angled cuts on one edge it is attached to each DUOFOIL™ (~330 mm x 355 mm x approximately 0.38 mm). A U-bar spacer approximately 3.05 mm thick and silicone rubber tubing with approximately 3.175 mm ID x approximately 4.75 mm OD (used as a gasket) is placed between the plates and the mold is kept closed with C-clamps. The mold is preheated in an oven to 65°C before use. The same molding process can be adapted for leaks with smaller metal plates as well as using thicker U-spacer bars with a proper fit on the silicone rubber tubing that acts as a gasket.



Example 19
[0145] In this example, a formulation of the present invention (formulation of Example 1) is cured to form an epoxy composite and then the epoxy composite is electrocoated with a copper layer according to a general electrodeposition procedure and described in Table IV as follows. General Electrodeposition Procedure
[0146] The process used to electrocoat the epoxy resin composite substrate of the present invention can include a variety of techniques to make the surface receptive to the application of metallization. Typically, epoxy substrates can be metallized by a process that first involves exposure, sequentially to a composition containing materials, increasing the degree of attack in a subsequent pickling step, then a pickling step and then a step that substantially removes residue from the pickling step.
[0147] The first step, often referred to as "solvent swelling", employs a "sweller" which may include materials such as solvents and/or alkaline materials such as alkali metal hydroxides. The second step, often referred to as the "degreasing" step (from the common use of this process step to remove residual epoxy materials from copper surfaces, for example, during the fabrication of printed circuit boards), employs an "oxidizer" which may include strong oxidizing components capable of epoxy pickling, such as alkaline permanganate solutions. The third step contains “neutralizing” materials capable of neutralizing residues of the oxidizing material, for example, in the case of permanganate, compositions such as acidic solutions containing hydrogen peroxide, or hydroxylamines. For epoxy materials that are particularly chemically resistant these three steps can be repeated one or more times to increase the degree of pickling in order to increase the adhesion of subsequently applied metallizations.
[0148] In the examples of the present invention, an epoxy resin composite substrate is electrocoated using a series of first, second and third steps as described above. Typically, the swelling, oxidizing and neutralizing materials are applied to the substrate at a certain temperature and for a predetermined period of time followed by a rinsing step in between these three chemical application steps (eg Steps 1-3). These three-step sets are performed in sequence for any desired number of repetitions, for example, three times (Steps 1-9) as shown in Table IV.
[0149] After the pickling steps, a catalytic material (most commonly a colloidal tin and palladium material) can be applied to the substrate surface. Prior to application of the catalytic material, the surface may advantageously be treated in a solution containing one or more additives which promote subsequent adsorption of the colloidal material. Furthermore, immediately before the part is introduced into the catalytic solution, it is common practice to immerse the part in a solution containing a similar mixture of components present in the composition containing colloid with the exception of the colloidal material itself, in order to increase the bath life of the solution containing colloid.
[0150] In the examples of the present invention, after pickling, the epoxy resin composite substrate is subjected to a conditioning step (Step 10), a micro pickling step (Step 11), and a pre-immersion step ( Step 12) before using a catalyst (Step 13) as described above. These treatment steps are carried out at a certain temperature and for a predetermined period of time followed by a rinsing step between these application steps (eg Steps 10-13) as shown in Table IV.
[0151] After treatment in a catalytic composition, the substrate or part can be treated with a so-called acceleration composition or, as shown in Table IV, introduced directly into a plating bath without electrolysis (Step 14) designed to operate without any intermediate steps between the catalyst bath and the metallization without electrolysis. A number of different electrolysis-free plating compositions can be used to apply an initial sticky plating layer that is sufficiently thick and durable to allow subsequent application of a thicker metallic layer, either without electrolysis or, as shown in Table IV, by electrolytic deposition (Step 14) (due to the highest rate typically attainable by electrolytic processes).
[0152] After metallization without electrolysis (Step 14), the part can be dried (Step 15) and then the part can be baked (Step 16) in order to improve the adhesion of the metallization. The cooking step can be performed at temperatures ranging from 80°C to 150°C in time intervals from 0 minutes to 200 minutes. The benefits of the baking step may depend on the specific composition of the material to be metallized.
[0153] After an acid immersion step (Step 17) and an electroplating step (Step 18) according to the process sequence described in Table IV, the electrogalvanized deposit, which is uniform and shows excellent smoothness and adhesion to substrate, is tested for adhesion strength, for example, using the general procedure described in ASTM B-533, except that a test sample width of 1 cm is used. Forces measured for the 1 cm test width can then be converted to pound/inch (lb/in) units using the appropriate numerical conversion factor. Measured force values are between about 2.0 lb/in and about 2.4 lb/in.
[0154] In the examples of the present invention, the resulting electrocoated composite has a flat and smooth of an electrocoated copper layer and may contain an additional electroplated silver layer. Peel strength measurements on the copper electrocoated epoxy composite were performed in accordance with ASTM B-533 except that a test sample width of 1 cm is used.
Example 20 and Comparative Example CRF Filter Prototype Fabrication and Testing Procedures
[0155] Two prototype RF filter boxes (Example 20 and Comparative Example C) are prepared as follows.
[0156] The composition of Example 1 was molded into a block and subsequently machined into an open rectangular box approximately 58 mm long x 35 mm wide x 29 mm deep with a wall thickness of approximately 2 mm (this Example 20 of the present invention). A cover plate of the composition of Example 1 was also molded in such a way that the cover fits with a cover to the box and is securely fastened with screws. The case and cover plate were coated with a non-electrolyzing copper coating under a silver coating to create an electroconductive surface.
[0157] An Al or Al alloy box and cover plate of similar size were also coated as a comparative example (Comparative Example C). Both coated housings (Example 19 and Comparative Example C) were used to manufacture RF filter devices containing a single resonator and two connectors.
[0158] The two prototypes above, Example 20 and Comparative Example C, were tested using a vector network analyzer and temperature chamber, and Table V describes the test results. The prototype of the present invention (Example 20) exhibited an advantage over the comparative prototype (Comparative Example C) in terms of insertion loss and charge quality fact at room temperature (about 25°C). The prototypes were also heated to 65°C, and the prototype of the present invention (Example 20) exhibited less frequency variation than the comparative prototype (Comparative Example C) determined by visual observation.

权利要求:
Claims (14)
[0001]
1. A process for preparing a cured composite material for use in a telecommunication device, characterized in that it comprises the steps of: (a) providing a curable thermosetting epoxy resin composition comprising: (i) at least one epoxy resin; (ii) at least one curing agent comprising an amphiphilic polyether block copolymer, a rubber core-film, a carboxyl terminated butadiene/acrylonitrile elastomer, or mixtures thereof; (iii) at least one hardener; and (iv) at least one filler; (b) curing the curable thermosetting epoxy resin composition from step (a) to form a cured composite; wherein the thermosetting epoxy resin composition curable in response to cure provides a cured composite product with a balance of properties comprising Tg, thermal expansion coefficient, thermal conductivity, flame resistance, tensile strength, and having a density less than 2, 7 g/cm3; and (c) coating at least a portion of the surface of the cured composite from step (b) with an electrically conductive metallic layer to form a metallized coating over at least a portion of the surface of the cured composite.
[0002]
2. Process according to claim 1, characterized in that the curing agent comprises an amphiphilic polyether block copolymer containing at least one epoxy resin miscible block segment and at least one epoxy resin immiscible block segment; wherein the miscible block segment comprises at least one polyether structure; and wherein the immiscible block segment comprises at least one polyether structure.
[0003]
3. Process according to claim 1, characterized in that the curable thermosetting epoxy resin composition includes a flame retardant reagent compound or a flame retardant additive.
[0004]
4. Process according to claim 1, characterized in that the curable thermosetting epoxy resin composition has a complex viscosity at 80°C of less than 200,000 mPas.
[0005]
5. Process according to claim 1 characterized in that the thermosetting epoxy resin composition curable in response to cure provides a cured product with a balance of properties comprising a glass transition temperature of 100°C to 300°C; a thermal expansion coefficient of 0 ppm/°C to 80 ppm/°C at a temperature of -50°C to 80°C; a tensile strength of 35 MPa to 250 MPa; a thermal conductivity of 0.2 W/m-K to 300 W/m-K; and a density of 1.2 g/cm3 to 2.7 g/cm3 as measured by ASTM D-792.
[0006]
6. Process according to claim 1, characterized in that the curable thermosetting epoxy resin composition includes a filler, and the filler comprises a thermally conductive filler.
[0007]
7. Process according to claim 1, characterized in that the composition of curable thermosetting epoxy resin includes a filler, and the filler comprises a quartz treated with epoxy-silane.
[0008]
8. Process according to claim 7, characterized in that the concentration of the charge varies from more than 35 percent by weight to 90 percent by weight.
[0009]
9. Cured product, formed from the composition of curable thermosetting epoxy resin, obtained by the process defined in claim 1, characterized in that it presents a balance of properties comprising a glass transition temperature from 100°C to 300°C; a thermal expansion coefficient of 0 ppm/°C to 80 ppm/°C at a temperature of -50°C to 80°C; a tensile strength of 35 MPa to 250 MPa; a thermal conductivity of 0.2 W/m-K to 300 W/m-K; and a density of 1.2 g/cm3 to 2.7 g/cm3 as measured by ASTM D792.
[0010]
10. The cured product according to claim 9, characterized in that the cured product includes a metallic coating over at least a portion of the surface of the cured product.
[0011]
11. Cured product, according to claim 9, characterized in that it comprises a metallized composite material.
[0012]
12. Cured product, according to claim 9, characterized in that it comprises a radio frequency cavity filter, a heat sink, or a housing for electronic components.
[0013]
13. Cured product, according to claim 9, characterized in that it comprises a heat sink.
[0014]
14. Cured product, according to claim 9, characterized in that it comprises a casing for electronic components.

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CN103827038B|2016-05-11|Molybdenum compound powder, prepreg and plywood

---

TWI673310B|2019-10-01|Toughening masterblends

---

KR20100116636A|2010-11-01|Halogen-free benzoxazine based curable compositions for high tg applications

---

CN106103532A|2016-11-09|Novel novolac hardeners containing alkoxysilyl and preparation method thereof, the compositions containing sclerosing agent, hardening product and application thereof

---

US20140316068A1|2014-10-23|Bimodal toughening agents for thermosettable epoxy resin compositions

---

Liu et al.2022|Flame-Retardant multifunctional epoxy resin with high performances

---

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---

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---

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---

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同族专利:

---

公开号 | 公开日

---

CN104159968B|2016-11-02|

---

WO2013095908A2|2013-06-27|

---

JP2015505333A|2015-02-19|

---

KR101976890B1|2019-05-09|

---

WO2013095908A3|2013-11-28|

---

JP6199889B2|2017-09-20|

---

EP2794757A2|2014-10-29|

---

US20150299457A1|2015-10-22|

---

CA2858840C|2020-09-29|

---

CA2858840A1|2013-06-27|

---

KR20140104041A|2014-08-27|

---

MX2014007667A|2014-12-05|

---

EP2794757B1|2019-05-15|

---

MX365593B|2019-06-07|

---

TW201341441A|2013-10-16|

---

CN104159968A|2014-11-19|

---

BR112014014990A2|2017-06-13|

引用文献:

---

公开号 | 申请日 | 公开日 | 申请人 | 专利标题

---

---

GB1051391A|1959-12-24|

---

US3702783A|1970-09-04|1972-11-14|Robert C Hartlein|Epoxy silane coupling agents|

---

US4925901A|1988-02-12|1990-05-15|The Dow Chemical Company|Latent, curable, catalyzed mixtures of epoxy-containing and phenolic hydroxyl-containing compounds|

---

US5262507A|1990-09-11|1993-11-16|Dow Corning Corporation|High modulus silicones as toughening agents for epoxy resins|

---

US5367956A|1992-02-07|1994-11-29|Fogle, Jr.; Homer W.|Hermetically-sealed electrically-absorptive low-pass radio frequency filters and electro-magnetically lossy ceramic materials for said filters|

---

US5928767A|1995-06-07|1999-07-27|Dexter Corporation|Conductive film composite|

---

JP5485487B2|1999-12-13|2014-05-07|ダウグローバルテクノロジーズエルエルシー|Flame retardant phosphorus element-containing epoxy resin composition|

---

EP1453364A4|2001-07-18|2007-01-17|Ajinomoto Kk|Film for circuit board|

---

US6632860B1|2001-08-24|2003-10-14|Texas Research International, Inc.|Coating with primer and topcoat both containing polysulfide, epoxy resin and rubber toughener|

---

AT277103T|2002-01-28|2004-10-15|Abb Research Ltd|POWDERING COMPOSITION BASED ON DUROPLASTIC EPOXY RESINS|

---

JP2004051973A|2002-05-30|2004-02-19|Sekisui Chem Co Ltd|Method for roughening resin sheet|

---

JP2004022685A|2002-06-14|2004-01-22|Mitsui Chemicals Inc|Radio wave absorption cap|

---

US7087304B1|2003-02-19|2006-08-08|Henkel Corporation|Polysulfide-based toughening agents, compositions containing same and methods for the use thereof|

---

CN1239587C|2003-04-03|2006-02-01|中国石油化工股份有限公司|Composite powder, its preparation method and application|

---

US6887574B2|2003-06-06|2005-05-03|Dow Global Technologies Inc.|Curable flame retardant epoxy compositions|

---

KR101228245B1|2004-04-02|2013-01-30|리전츠 오브 더 유니버시티 오브 미네소타|Amphiphilic block copolymer-toughened thermoset resins|

---

CN1960997B|2004-05-28|2014-05-07|陶氏环球技术有限责任公司|Phosphorus-containing compounds useful for making halogen-free, ignition-resistant polymers|

---

BRPI0516698A|2004-11-10|2008-09-16|Dow Global Technologies Inc|curable epoxy resin composition, process for preparing a curable composite epoxy resin|

---

MX2007005597A|2004-11-10|2007-05-23|Dow Global Technologies Inc|Amphiphilic block copolymer-toughened epoxy resins and electrical laminates made therefrom.|

---

RU2389743C2|2004-11-10|2010-05-20|Дау Глобал Текнолоджиз Инк.|Epoxide resins hardened by amphiphilic bloc-copolymers, and powder coatings made from said epoxide resins|

---

MX2007005599A|2004-11-10|2007-05-23|Dow Global Technologies Inc|Amphiphilic block copolymer-modified epoxy resins and adhesives made therefrom.|

---

ES2339370T3|2004-11-10|2010-05-19|Dow Global Technologies Inc.|EPOXIDIC RESINS STRENGTHENED WITH COPOLIMEROS OF AMPHIFILIC BLOCKS AND COATINGS WITH HIGH CONTENT IN SOLID CURED TO ENVIRONMENTAL TEMPERATURE OBTAINED FROM THEM.|

---

US20060205856A1|2004-12-22|2006-09-14|Williamson David T|Compositions of polyesters and sepiolite-type clays|

---

KR20090113169A|2006-11-13|2009-10-29|주식회사 케이엠더블유|Radio frequency filter|

---

AT458769T|2007-04-03|2010-03-15|Abb Research Ltd|HARDENABLE EPOXY RESIN COMPOSITION|

---

EP2147034B1|2007-05-09|2014-12-17|Dow Global Technologies LLC|Epoxy thermoset compositions comprising excess epoxy resin and process for the preparation thereof|

---

WO2008144252A1|2007-05-16|2008-11-27|Dow Global Technologies Inc.|Flame retardant composition|

---

BRPI0813201A2|2007-08-02|2014-12-23|Dow Global Technologies Inc|"CURABLE COMPOSITION, COMPOSITE AND METHOD FOR FORMING A COMPOSITE"|

---

CN101910230A|2007-10-26|2010-12-08|陶氏环球技术公司|Epoxy resin composition containing isocyanurates for use in electrical laminates|

---

US7847658B2|2008-06-04|2010-12-07|Alcatel-Lucent Usa Inc.|Light-weight low-thermal-expansion polymer foam for radiofrequency filtering applications|

---

US8722798B2|2009-03-09|2014-05-13|Leiming Ji|Thermosettable composition containing a combination of an amphiphilic block copolymer and a polyol and a thermoset product therefrom|WO2014028338A1|2012-08-13|2014-02-20|Henkel Corporation|Liquid compression molding encapsulants|

---

MX344525B|2012-09-27|2016-12-19|Dow Global Technologies Llc|Metallized optical fiber.|

---

WO2014062903A1|2012-10-19|2014-04-24|Dow Global Technologies Llc|Polymer particle dispersions with polyols|

---

EP2935464B1|2012-12-20|2017-08-16|Dow Global Technologies LLC|Polymer composite components for wireless-communication towers|

---

KR101617387B1|2013-02-26|2016-05-02|주식회사 엘지화학|Coating composition and plastic film prepared therefrom|

---

WO2016029450A1|2014-08-29|2016-03-03|Blue Cube Ip Llc|Halogen-free epoxy formulations|

---

EP3218433A1|2014-11-11|2017-09-20|Dow Global Technologies LLC|Adhesive composition with glass spheres|

---

CN107257829A|2015-02-27|2017-10-17|J.M.休伯有限公司|Paste compound for fire-retardant and hydrophobic coating|

---

US11104108B2|2015-04-08|2021-08-31|Amogreentech Co., Ltd.|Heat dissipating coating composition and heat dissipating unit formed using same|

---

CN105061999A|2015-08-06|2015-11-18|殷姝媛|High-thermal conductivity high-molecular composite material|

---

CN106916268B|2015-12-25|2019-06-14|广东生益科技股份有限公司|A kind of anhydride-modified linear phenolic resin, Preparation method and use|

---

CN105924945A|2016-05-09|2016-09-07|李红玉|Composition for 3D printing and preparing method thereof|

---

CN105820509A|2016-05-09|2016-08-03|李红玉|Polymer material used for 3D printing and preparing method thereof|

---

US20200181779A1|2016-06-24|2020-06-11|Dow Global Technologies Llc|Metalized polyurethane composite and process of preparing the same|

---

CN107266861A|2017-07-19|2017-10-20|冯苇荣|Epoxy resin functional graphene integration filtering IC and preparation method thereof|

---

JP2021512990A|2018-02-12|2021-05-20|スリーエム イノベイティブ プロパティズ カンパニー|Curable compositions, articles manufactured from them, and methods and uses thereof.|

---

CN108424618B|2018-03-19|2021-04-09|江苏兴盛化工有限公司|Graphene/epoxy resin composite material and preparation method thereof|

---

CN111087758A|2018-10-24|2020-05-01|深圳市群达汽车系统有限公司|Preparation method of novel PDCPD rapid forming die|

---

CN109694680B|2018-12-26|2021-08-20|河南工业大学|Epoxy resin adhesive for repairing building cracks and preparation method thereof|

---

CN110041659B|2019-04-10|2021-09-28|黑龙江省科学院高技术研究院|Preparation method of expanded graphite-epoxy resin-organic silicon resin pressure-resistant composite material|

---

CN111909485A|2019-05-10|2020-11-10|南通联鑫新材料科技有限公司|Epoxy resin composite board and preparation method thereof|

---

CN110564183A|2019-08-22|2019-12-13|魏军刚|graphene-coated mica material and preparation method and application thereof|

---

CN111909600B|2020-08-06|2021-11-12|广东创辉鑫材科技股份有限公司|Manufacturing method of high-thermal-conductivity resin for metal substrate|

法律状态:
2018-03-27| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|

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2019-10-22| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2020-09-08| B06A| Notification to applicant to reply to the report for non-patentability or inadequacy of the application [chapter 6.1 patent gazette]|

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2021-03-23| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2021-06-01| B350| Update of information on the portal [chapter 15.35 patent gazette]|

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2021-06-15| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 04/12/2012, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

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申请号 | 申请日 | 专利标题

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US201161577918P| true| 2011-12-20|2011-12-20|

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US61/577,918|2011-12-20|

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PCT/US2012/067714|WO2013095908A2|2011-12-20|2012-12-04|Epoxy resin composites|

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