breathable film formed from renewable polyester

专利摘要:
BREATHABLE FILM FORMED FROM RENEWABLE POLYESTER. Presentation of a breathable film that contains a renewable rigid polyester and presents a structure with empty areas. To obtain such a structure, the thermoplastic compound containing the renewable polyester and the polymeric curing additive is extruded onto a surface to form a precursor material for the film, where the curing additive can be dispersed as discrete physical domains within a continuous matrix. renewable polyester. The precursor film is then stretched or pulled at a temperature below the glass transition temperature of the polyester (i.e. "cold drawn"). Without the intention of limiting by theory, these inventors believe that the deformation force and the stretching tension of the traction process causes the disintegration of the renewable polyester matrix, in the areas adjacent to the discrete domains. This creates a network of empty areas in positions adjacent to the discrete domains.
公开号:BR112014019432B1
申请号:R112014019432-7
申请日:2013-01-28
公开日:2020-12-22
发明作者:Ryan J. Mceneany；Neil T. Scholl；Vasily A. Topolkaraev；Tom Eby
申请人:Kimberly-Clark Worldwide, Inc；
IPC主号:

专利说明:

History of the invention
[001] Disposable absorbent products (for example, diapers, feminine hygiene products, incontinence products, etc.) are subjected to one or more liquid substances, such as water, urine, menstrual flows or blood, during use. Many commercialized diapers allow water vapor to pass through the diaper towards the environment, in order to decrease the amount of moisture held against the skin and reduce the chance of causing irritation and diaper rash due to overhydration. To allow the passage of steam through the diaper and towards the environment while containing the liquid, an external "breathable" cover is usually used, formed by a laminated non-woven blanket for a film. Conventional films employ filler particles that cause a series of micropores to develop in the film when it is stretched. Examples of such filler particles include inorganic particles such as calcium carbonate, clay, titanium dioxide, diatomite and other similar particles. To achieve the desired breathability, these films will typically contain about 45% to about 65% of filler particles. The micropores that are created by the filler particles form what is commonly called "tortuous paths" through the film. The liquid in contact with one side of the film cannot find a direct passage through it. Instead, a network of microporous channels in the film prevent the passage of liquids, but allow gases and water vapors to pass through.
[002] A deficiency of these microporous films is that they are generally formed by polyolefins (for example, LPEBD), which are not renewable. Unfortunately, the use of renewable polymers in these films is problematic due to the difficulty involved in the thermal processing of these polymers. Renewable polyesters, for example, have a high glass transition temperature and usually demonstrate very high rigidity and tension modulus, while having a low malleability / elongation at break. As an example, polylactic acid has a glass transition temperature of about 59 ° C and a stress modulus of about 2 GPa or more. However, the stress elongation (at break) for PLA materials is only about 5%. This high modulus and low elongation significantly limits the use of such polymers in the film, where a good balance between stiffness and elongation of the material is required. In addition to these problems, polylactic acid, for example, is also too rigid for applications that require flexible films that do not make noise and it tends to exhibit performance problems during use, causing noisy rustling in female products for adults.
[003] Thus, there is a need for breathable films that can be formed by renewable polyester compounds and still be able to exhibit good mechanical properties. Summary of the invention
[004] In accordance with an embodiment of the present invention, a breathable film is disclosed that has a water vapor transmission rate of about 500 g / m2 / 24 hours or more. The film comprises a thermoplastic compound that includes at least one renewable rigid polyester, with a glass transition temperature of about 0 ° C or more, and at least one polymeric curing additive. The thermoplastic compound has a morphology in which several discrete and empty primary domains are dispersed within a continuous phase, with the domains containing the polymeric curing additive and with the continuous phase containing the renewable polyester. The average percentage volume of the compound that is occupied by the voids is about 20% to about 80% per cubic centimeter.
[005] In accordance with another embodiment of the present invention, an absorbent product is disclosed which comprises a breathable and generally liquid-impermeable film, which comprises a thermoplastic compound as described herein.
[006] In accordance with another embodiment of the present invention, a method for forming a breathable film is disclosed. The method comprises forming a mixture containing a renewable rigid polyester and a polymeric curing additive, wherein the renewable rigid polyester has a glass transition temperature of about 0 ° C or more; extruding the mixture onto the surface to form a precursor material for the film; and stretching the precursor material of the film to a temperature below the glass transition temperature of the renewable polyester, so as to form a breathable film that contains a variety of void areas.
[007] Other features and aspects of the present invention are discussed in more detail below. Brief description of the illustrations
[008] A complete and clarifying description of the present invention, including its best mode, directed to people with technical knowledge in the field, is demonstrated in more detail in the rest of the specification, which makes reference to the attached figures in which:
[009] Fig. 1 is a schematic illustration of an embodiment of the film formation of the present invention;
[010] Fig. 2 is a SEM photomicrograph of a sample from example 2 before cold drawing; and
[011] Fig. 3 is a SEM photomicrograph of a sample from example 2 before cold drawing.
[012] The repeated use of reference characters in this specification and in the drawings presented, aims to represent resources or elements similar, or analogous, of the present invention. Detailed Description of Representative Forms of Realization
[013] Detailed references will be made to various configurations of the invention, with one or more examples described below. Each example is provided for the purpose of explaining the invention, and not as a limitation on it. Indeed, it will be apparent to those skilled in the art that various modifications and variations can be made to the present invention, without departing from the scope or spirit of the invention. For example, the features illustrated or described as part of a configuration can be used in another configuration, to obtain a third configuration. Thus, it is intended that the present invention covers modifications and variations that are within the scope of the attached claims and their equivalents.
[014] In general, the present invention is directed to a breathable film formed from a thermoplastic compound, which contains a renewable rigid polyester and has a structure with empty areas. To obtain such a structure, the thermoplastic compound containing the renewable polyester and the polymeric curing additive is extruded onto a surface to form a precursor material for the film, where the curing additive can be dispersed as discrete physical domains within a continuous matrix. renewable polyester. The precursor film is then stretched or pulled at a temperature below the glass transition temperature of the polyester (ie "cold drawn"). Without the intention of being limited by theory, the present inventors believe that the deformation force and the stretching tension of the stretching process causes the disintegration of the renewable polyester matrix, in the areas adjacent to the discrete domains. This creates a network of empty areas in positions adjacent to the discrete domains.
[015] The average percentage volume occupied by the empty spaces within a given volume unit of the thermoplastic compound is relatively high, such as from about 20% to about 80% per cm3, in some embodiments from about 30% to about 70%, and in some embodiments, from about 40% to about 60% per cubic centimeter of the compound. This high volume of empty spaces can significantly increase the water vapor transmission rate (“TTVA”) of the film, which is the rate at which water vapor penetrates the material, as measured in units of grams per square meter for 24 hours (g / m2 / 24 h). For example, the film may exhibit a TTVA of about 500 grams / m2-24 hours or more, in some embodiments about 1,000 grams / m2-24 hours or more, in some embodiments about 2,000 grams / m2 -24 hours or more, and in other embodiments, from about 3,000 to about 15,000 grams / m2- 24 hours. The high volume of empty spaces can also decrease the density of the film. For example, the film may have a density of about 1.4 grams per cubic centimeter ("g / cm3") or less, in some embodiments about 1.1 g / cm3 or less, in some embodiments from about 0.4 g / cm3 to about 1.0 g / cm3 and, in some embodiments, from about 0.5 g / cm3 to about 0.95 g / cm3.
[016] Various embodiments of the present invention will now be described in more detail.
[017] I. Thermoplastic compound
[018] A. Renewable polyester
[019] Renewable polyesters typically make up about 70% by weight to about 99% by weight, in some embodiments, about 75% to about 98% by weight and, in other embodiments, around 80% to about 95% by weight of the thermoplastic compound. Various renewable polyesters can normally be used in the thermoplastic compound, such as aliphatic polyesters such as polycaprolactone, polyesteramides, polylactic acid (PLA) and their copolymers, polyglycolic acid, polyalkylene carbonates (for example, polyethylene carbonate), poly-3-hydroxybutyrate (PHB), poly-3-hydroxyvalerate (PHV), poly-3-hydroxybutyrate-co-4-hydroxybutyrate, copolymers of poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV), poly-3-hydroxybutyrate-co- 3-hydroxyhexanoate, poly-3-hydroxybutyrate-co-3-hydroxyoctanoate, poly-3-hydroxybutyrate-co-3-hydroxidecanoic, poly-3-hydroxybutyrate-co-3-hydroxyoctadecanoate, and aliphatic polymers based on succinate (for example , polybutylene succinate, polybutylene succinate adipate, polyethylene succinate, etc.); aliphatic-aromatic copolyesters (for example, polybutylene adipate terephthalate, polyethylene adipate terephthalate, polyethylene adipate isophthalate, polybutylene adipate isophthalate, etc.); aromatic polyesters (for example, polyethylene terephthalate, polybutylene terephthalate, etc.); and so on.
[020] Typically, the thermoplastic compound contains at least one renewable polyester, which is rigid in nature and thus has a relatively high glass transition temperature. For example, the glass transition temperature ("Tg") can be about 0 ° C or more, in some embodiments from about 5 ° C to about 100 ° C, in some embodiments of about 30 ° C to about 80 ° C, and in some embodiments, from about 50 ° C to about 75 ° C. Renewable polyester can also have a melting temperature of about 140 ° C to about 260 ° C, in some embodiments, from about 150 ° C to about 250 ° C and, in other embodiments, from about 160 ° C to about 220 ° C. The melting temperature can be determined using differential scanning calorimetry (“DSC”) in accordance with ASTM D-3417. The glass transition temperature can be determined by dynamic mechanical analysis in accordance with ASTM E1640-09.
[021] An especially suitable rigid polyester is polylactic acid, which can be derived from monomeric units of any lactic acid isomer, such as levorotatory lactic acid (“L-lactic acid”), dextrorotatory lactic acid (“D-lactic acid”) , meso-lactic acid or combinations of these. Monomeric units can also be formed by anhydrides of any isomer of lactic acid, including L-lactide, D-lactide, meso-lactide or combinations thereof. Cyclic dimers of these lactic acids and / or lactides can also be used. Any known polymerization method, such as polycondensation or ring opening polymerization, can be used to polymerize lactic acid. A small amount of a chain extender agent (for example, a diisocyanate compound, an epoxy compound or an anhydride acid) can also be employed. The polylactic acid can be a homopolymer or a copolymer, such as one that contains monomeric units derived from L-lactic acid and monomeric units derived from D-lactic acid. Although not required, the content ratio of one of the monomeric units derived from L-lactic acid and the monomeric unit derived from D-lactic acid is preferably about 85% per mol or more, in some embodiments about 90% per mol or more and, in other embodiments, about 95% per mol or more. Various polylactic acids, each with a different ratio between the monomeric unit derived from L-lactic acid and the monomeric unit derived from D-lactic acid, can be mixed in any random percentage. Obviously, polylactic acid can be mixed with other types of polymers (for example, polyolefins, polyesters, etc.).
[022] In a specific embodiment, polylactic acid has the following general structure:

[023] A specific example of a suitable polylactic acid polymer that can be used in the present invention, is marketed by Biomer, Inc. of Krailling, Germany) under the name BIOMER ™ L9000. Other suitable polylactic acid polymers are marketed by Natureworks LLC of Minnetonka, Minnesota (NATUREWORKS®) or Mitsui Chemical (LACEA ™). Other suitable polylactic acids can be described in U.S. Patent No. 4,797,468; 5,470,944; 5,770,682; 5,821,327; 5,880,254; and 6,326,458, which are incorporated herein in their entirety, as a reference, for all purposes.
[024] Polylactic acid typically has an average molecular weight in number ("Mn") ranging from about 40,000 to about 160,000 grams per mole, in some embodiments from about 50,000 to about 140,000 grams per mole and , in other embodiments, from about 80,000 to about 120,000 grams per mol. Likewise, the polymer usually also has an average molecular weight by weight ("Mn") ranging from about 80,000 to about 200,000 grams per mol, in some embodiments from about 100,000 to about 180,000 grams per mol and, in other embodiments, from about 110,000 to about 160,000 grams per mol. The relationship between the average molecular weight by weight and the average molecular weight in number (“Mw / Mn”), that is, the “polydispersity index”, is also relatively low. For example, the polydispersity index usually ranges from about 1.0 to about 3.0, in some embodiments from about 1.1 to about 2.0, and, in other embodiments, from about from 1.2 to about 1.8. The weight and average molecular weight numbers of the weight can be determined by methods known to those skilled in the art.
[025] Polylactic acid may also have an apparent viscosity of about 50 to about 600 pascal seconds (Pa-s), in some embodiments from about 100 to about 500 Pa ^ s, in some embodiments , and about 200 to about 400 Pa ^ s, as determined at a temperature of 190 ° C and a shear rate of 1,000 sec-1. The melt index of polylactic acid (on a dry basis) can also vary from about 0.1 to about 40 grams for 10 minutes, in some embodiments from about 0.5 to about 20 grams for 10 minutes and , in some embodiments, from about 5 to about 15 grams for 10 minutes, determined at a load of 2,160 grams and at 190 ° C.
[026] Some types of pure polyester (for example, polylactic acid) can absorb water from an environment so that it has a moisture content of about 500 to 600 parts per million (“ppm”), or even higher, based on in the dry weight of the initial polylactic acid. The moisture content can be determined in several ways as is known in the art, in accordance with ASTM D 7191- 05, as described below. Since the presence of water during melt processing can hydrolytically degrade the polyester and reduce its molecular weight, it is sometimes better to dry the polyester before mixing it. In most embodiments, for example, it is best for renewable polyester to have a moisture content of about 300 parts per million ("ppm") or less, in some embodiments about 200 ppm or less, in some embodiments of about 1 to about 100 ppm before mixing with the curing additive. Drying of the polyester can take place, for example, at a temperature of about 50 ° C to about 100 ° C, and in some embodiments, from about 70 ° C to about 80 ° C.
[027] B. Polymeric hardening additive
[028] As indicated above, the thermoplastic compound of the present invention also contains a polymeric curing additive. Due to its polymeric nature, the curing additive has a relatively high molecular weight that can help to improve the melting capacity and stability of the thermoplastic compound. Although not required, the polymeric curing additive can be immiscible with renewable polyester. In this way, the curing additive can be better spread as discrete phase domains within a continuous phase of the renewable polyester. The discrete domains are able to absorb energies resulting from an external force, which increases the stiffness and the total resistance of the resulting material. The domains have a variety of different shapes, such as elliptical, spherical, cylindrical, etc. In one embodiment, the domains are quite elliptical in shape. The physical dimension of an individual domain is usually small enough to minimize the propagation of cracks in the polymeric material, by applying an external stress, but large enough to initiate a microscopic plastic deformation and allow shear zones in the inclusion of particles or around them.
[029] Although the polymers may be immiscible, the curing additive can still be selected having a solubility parameter that is relatively similar to that of renewable polyester. This can improve the interfacial compatibility and physical interaction of the discrete and continuous phase boundaries and thus reduce the likelihood of the compound breaking. For this, the ratio of the renewable polyester solubility parameter to the hardening additive parameter is normally from about 0.5 to about 1.5, and in some embodiments, from about 0.8 to about 1.2. For example, the polymeric curing additive may have a solubility parameter of about 15 to about 30 MJoules1 / 2 / m3 / 2, and in some embodiments, from about 18 to about 22 MJoules1 / 2 / m3 / 2, while polylactic acid may have a solubility parameter of about 20.5 MJoules1 / 2 / m3 / 2. The term “solubility parameter” as used here, refers to the “Hildebrand Solubility Parameter”, which is the square root of the density of cohesive energy, calculated using the following equation: δ = y ((Δfi „- flT ) / Vm) where:
[030] Δ Hv = heat of vaporization
[031] R = Universal gas constant
[032] T = Temperature
[033] Vm = Molar volume
[034] Hildebrand's solubility parameters for many polymers are also found in Wyeych's Solubility Handbook of Plastics (2004), which is incorporated here as a reference.
[035] The polymeric curing additive can also have a fluidity index (or viscosity) to ensure that the resulting discrete domains and voids can be maintained properly. For example, if the curing rate of the curing additive is too high, it tends to flow and disperse uncontrollably during the continuous phase. This results in lamellar or plaque-like domains that are difficult to maintain and are likely to rupture prematurely. On the other hand, if the flow rate of the curing additive is too low, it will tend to agglutinate and form very large elliptical domains, which are difficult to disperse during mixing. This can cause an uneven distribution of the curing additive throughout the continuous phase. Accordingly, the present inventors have found that the ratio of the curing index of the curing additive to the flow rate of the renewable polyester is normally from about 0.2 to about 8, in some embodiments of about 0 , 5 to about 6 and, in other embodiments, from about 1 to about 5. The curing additive can, for example, have a melt index of 0.1 to about 250 grams for 10 minutes, in some embodiments from about 0.5 to about 200 grams for 10 minutes and, in other embodiments, from about 5 to about 150 grams for 10 minutes, determined at a load of 2,160 grams and 190 ° C.
[036] In addition to the properties noted above, the mechanical characteristics of the polymeric curing additive can also be selected to achieve the desired increase in stiffness. For example, when a mixture of the renewable polyester and the curing additive is applied with an external force, shear flow and / or plastic flow zones can be initiated in and around the discrete phase domains as a result of concentrations of stress arising from a difference in the modulus of elasticity of the curing additive and in renewable polyester. Higher concentrations of stress promote a more intense localized plastic flow in the domains, allowing them to undergo considerable elongation when subjected to stress. These elongated domains allow the compound to behave more flexibly and softly than rigid polyester resin. To improve stress concentrations, the hardening additive is selected in a way that it has a relatively low Young's modulus of elasticity compared to renewable polyester. For example, the ratio of the modulus of elasticity of the renewable polyester to that of the curing additive is usually about 1 to about 250, in some embodiments from about 2 to about 100, and in other embodiments, from about 2 to about 50. The modulus of elasticity of the curing additive can, for example, vary from about 2 to about 500 megapascals (MPa), in some embodiments from about 5 to about 300 MPa and, in other embodiments, from about 10 to about 200 MPa. In contrast, the modulus of elasticity of polylactic acid is usually about 800 MPa to about 2000 MPa.
[037] In order to provide the desired increase in stiffness, the polymeric curing additive may also exhibit an elongation at break (ie, the percentage of elongation of the polymer at its pour point) greater than renewable polyester. For example, the polymeric curing additive of the present invention may exhibit an elongation at break of about 50% or more, in some embodiments of about 100% or more, in some embodiments of about 100% to about 2,000% and, in other embodiments, from about 250% to about 1,500%.
[038] Although a wide variety of polymeric additives with the properties identified above can be employed, especially suitable examples of such polymers may include, for example, polyolefins (for example, polyethylene, polypropylene, polybutylene, etc.); styrenic copolymers (for example, styrene-butadiene-styrene, styrene-isoprene-styrene, styrene-ethylene-propylene-styrene, styrene-ethylene-butadiene-styrene, etc.); polytetrafluoroethylenes; polyesters (for example, recycled polyester, polyethylene terephthalate, etc.); polyvinyl acetates (for example, poly (ethylene vinyl acetate), polyvinyl chloride acetate, etc.); polyvinyl alcohols (for example, polyvinyl alcohol, poly (ethylene vinyl alcohol), etc.); polyvinyl butyral; acrylic resins (for example, polyacrylate, polymethylacrylate, polymethylmethacrylate, etc.); polyamides (for example, nylon); polyvinyl chlorides; polyvinylidene chlorides; polystyrenes, polyurethanes; etc. Suitable polyolefins may, for example, include ethylene polymers (for example, low density polyethylene (“PE-LD”), high density polyethylene (“HDPE”), linear low density polyethylene (“PELBD”), etc. .), propylene homopolymers (for example, syndiotactic, atactic, isotactic, etc.), propylene copolymers and so on.
[039] In a given embodiment, the polymer is a propylene polymer such as homopolypropylene or a propylene copolymer. The propylene polymer can, for example, be formed from an isotactic polypropylene homopolymer or a copolymer containing an amount equal to or less than about 10% by weight of another monomer, that is, at least about 90% by weight of propylene. Such polymers can have a melting point of about 160 ° C to about 170 ° C.
[040] In yet another embodiment, the polyolefin can be a copolymer of ethylene or propylene with another α-olefin, such as C3-C20 α-olefin or C3-C12 α-olefin. Specific examples of suitable α-olefins are 1-butene; 3-methyl-1-butene; 3,3-dimethyl-1-butene; 1-pentene; 1-pentene with one or more methyl, ethyl or propyl substituents; 1-hexene with one or more methyl, ethyl or propyl substituents; 1-heptene with one or more methyl, ethyl or propyl substituents; 1-octene with one or more methyl, ethyl or propyl substituents; 1-nonene with one or more methyl, ethyl or propyl substituents; 1-decene substituted by ethyl, methyl or dimethyl; 1-dodecene; and styrene. The especially desired alpha olefin comonomers are 1-butene, 1-hexene and 1-octene. The ethylene or propylene content of these copolymers can vary from about 60% to about 99% per mol, in some embodiments from about 80% to about 98.5% per mol and, in other embodiments, from about 87% to about 97.5% per mol. The content of α-olefin can vary from about 1% to about 40% per mole, in some embodiments, from about 1.5% to about 15% per mole, and in other forms of from about 2.5% to about 13% per mol.
[041] Examples of olefin copolymers for use in the present invention include ethylene-based copolymers, marketed under the name EXACT ™, from ExxonMobil Chemical Company of Houston, Texas. Other suitable ethylene copolymers are marketed under the name ENGAGE ™, AFFINITY ™, DOWLEX ™ (PELBD) and ATTANE ™ (PEUBD) from Dow Chemical Company of Midland, Michigan. Other suitable ethylene polymers are described in U.S. Patent No. 4,937,299 to Ewen et al .; 5,218,071 to Tsutsui et al .; 5,272,236 to Lai, et al .; and 5,278,272 to Lai, et al., which are included in their entirety in this document, by reference, for all purposes. Propylene copolymers are marketed under the name VISTAMAXX ™ from ExxonMobil Chemical Co. of Houston, Texas; FINA ™ (eg 8573) from Atofina Chemicals of Feluy, Belgium; TAFMER ™ marketed by Mitsui Petrochemical Industries; and VERSIFY ™, marketed by Dow Chemical Co. of Midland, Michigan. Other examples of suitable propylene polymers are described in U.S. Patent No. 6,500,500 to Datta, et al .; 5,539,056 to Yang, et al .; and 5,596,052 to Resconi, et al., which are included in their entirety in this document, by reference, for all purposes.
[042] A wide variety of known techniques can be employed to form olefin copolymers. For example, olefin polymers can be formed using a free radical or a coordinating catalyst (for example, Ziegler-Natta). Preferably, the olefin polymer should be formed by a single site coordination catalyst, such as a metallocene catalyst. This catalyst system produces ethylene copolymers, in which the comonomer is randomly distributed within a molecular chain and uniformly distributed among the different molecular weight fractions. Metallocene-catalyzed polyolefins are described, for example, in U.S. Patent No. 5,571,619 to McAlpin et al .; 5,322,728 for Davis et al .; 5,472,775 to Obijeski et al .; 5,272,236 to Lai et al .; and 6,090,325 for Wheat, et al., which are included in their entirety in this document, by reference, for all purposes. Examples of metallocene catalysts include bis (n-butylcyclopentadienyl) titanium dichloride, bis (n-butylcyclopentadienyl) zirconium dichloride, bis (cyclopentadienyl) scandium chloride, bis (indenyl) zirconium dichloride, methyl (dichloride) bis (methylene chloride) dichloride , bis (methylcyclopentadienyl) zirconium dichloride, cobaltocene, cyclopentadienyltitanium trichloride, ferrocene, hafnocene dichloride, isopropyl dichloride (cyclopentadienyl, -1- flourenyl) zirconium, molybdenum dichloride, dichloride, niquel, nickel zirconocene chloride hydride, zirconocene dichloride and so on. Polymers created using the metallocene catalyst usually have a narrow molecular mass range. For example, metallocene-catalyzed polymers may have polydispersity numbers (Mw / Mn) below 4, controlled short chain branch distribution and controlled isotacticity.
[043] Regardless of the materials used, the relative percentage of the polymeric curing additive in the thermoplastic compound is selected in order to achieve the desired properties without considerably affecting the resulting compound's ability to renew. For example, the curing additive is normally employed in the amount of about 1% to about 30% by weight, in some embodiments, from about 2% to about 25% by weight and, in other embodiments, from about 5% to about 20% by weight of the thermoplastic compounds, based on the weight of the renewable polyesters employed in the compound. The concentration of the curing additive in the entire thermoplastic compound can also form from about 0.1% to about 30% by weight, in some embodiments, from about 0.5% to about 25% by weight and , in other embodiments, from about 1% to about 20% by weight.
[044] C. Interphasic modifier
[045] An interphase modifier can also be used in the thermoplastic compound to reduce the degree of friction and connectivity between the hardening additive and the renewable polyester and thus increase the degree and uniformity of the peel. be distributed in a very homogeneous form throughout the compound. The modifier is generally in liquid or semi-solid form at room temperature (for example, 25 ° C), so that it has a relatively low viscosity, allowing it to be more easily incorporated into the thermoplastic compound and migrated to the polymer surfaces. In this regard, the kinematic viscosity of the interphasic modifier is normally about 0.7 to about 200 centistokes ("cs"), in some embodiments from about 1 to about 100 cs and, in other embodiments , from about 1.5 to about 80 dogs, determined at 40 ° C. In addition, the interphasic modifier is also normally hydrophobic, so that it has an affinity with the polymeric curing additive, resulting in a change in the interfacial tension between the renewable polyester and the curing additive. By reducing the physical forces at the interfaces between the polyester and the curing additive, it is believed that the hydrophobic and low-viscosity nature of the modifier can help facilitate the detachment of the polyester matrix at a reduced external stress. As used here, the term "hydrophobic" usually refers to material that has a contact angle of water and air of about 40 ° or more and, in some cases, about 60 ° or more. In contrast, the term "hydrophilic" usually refers to material that has a contact angle of water and air less than about 40 °. A suitable test for measuring the contact angle is ASTM D5725-99 (2008).
[046] Some suitable, low-viscosity hydrophobic interphase modifiers are, for example, silicones, silicone-polyether copolymers, aliphatic polyesters, aromatic polyesters, alkylene glycols (eg ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene polypropylene glycol, polybutylene glycol, etc.), alkanes diols, (for example, Propane-1,3-diol, 2,2-dimethyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1, 5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,6 hexanediol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3 - cyclobutanediol, etc.), amine oxides (eg octyldimethylamine oxide), fatty acid esters, etc. A particularly suitable interphase modifier is polyester polyol, such as those marketed under the trade name PLURIOL® WI by BASF Corp. Another particularly suitable modifier is the partially renewable ester, such as the one marketed under the name HALLGREEN® IM by Hallstar.
[047] Although the actual amount may vary, the interphasic modifier is usually employed in the amount of about 0.1% to about 20% by weight, in some embodiments, from about 0.5% to about 15% by weight and, in other embodiments, from about 1% to about 10% by weight of the thermoplastic compounds, based on the weight of the renewable polyesters employed in the compound. The concentration of interphasic modifiers in the entire thermoplastic compound can likewise comprise from about 0.05% to about 20% by weight, in some embodiments from about 0.1% to about 15% in weight and, in other embodiments, from about 0.5% to about 10% by weight.
[048] When the quantities observed above are used, the interphasic modifier will have a characteristic that allows it to migrate quickly to the interfacial surface of the polymers and facilitate the detachment without damaging the melting properties of the thermoplastic compound. For example, the interphasic modifier does not normally have a plasticizing effect on the polymer by reducing its glass transition temperature. In contrast, the present inventors have found that the glass transition temperature of the thermoplastic compound can be the same as that of the initial renewable polyester. In this regard, the ratio of the glass transition temperature of the compound to that of the polyester is normally about 0.7 to about 1.3, in some forms and carrying out from about 0.8 to about 1.2 and , in other embodiments, from about 0.9 to about 1.1. The thermoplastic compound can, for example, have a glass transition temperature of about 35 ° C to about 80 ° C, in some embodiments of about 40 ° C to about 80 ° C and, in other forms of from about 50 ° C to about 65 ° C. The fluidity index of the thermoplastic compound can also be similar to that of renewable polyester. For example, the fluidity index of the compound (on a dry basis) can be about 0.1 to about 70 grams for 10 minutes, in some embodiments from about 0.5 to about 50 ranges for 10 minutes and, in other embodiments, from about 5 to about 25 grams for 10 minutes, determined at a load of 2,160 grams and at a temperature of 190 ° C.
[049] D. Compatibilizer
[050] As indicated above, the polymeric curing additive is normally selected so that it has a solubility parameter relatively close to that of renewable polyester. Among other things, this can improve phase compatibility and increase the overall distribution of discrete domains within the continuous phase. However, in some embodiments, a compatibilizer can be used to further improve the compatibility between the renewable polyester and the polymeric curing additive. This may be desirable especially when the polymeric curing additive has a polar part, such as polyurethanes, acrylic resins, etc. When used, compatibilizers generally form about 0.5% to about 20% by weight, in some embodiments, about 1 to about 15% by weight and, in other embodiments, from about 1, 5% by weight to about 10% by weight of the thermoplastic compound. An example of a suitable compatibilizer is the functionalized polyolefin. The polar component can, for example, be provided by one or more functional groups, and the non-polar component can be provided by an olefin. The olefin component of the compatibilizer can normally be formed from any branched or linear α-olefin monomer, oligomer or polymer (including copolymers) derived from an olefin monomer, as described above.
[051] The compatibilizer functional group can be any group that provides a polar segment to the molecule. Especially suitable functional groups are maleic anhydride, maleic acid, fumaric acid, maleimide, maleic acid hydrazide, a reaction product of maleic anhydride and diamine, methylnadic anhydride, dichloromaleic anhydride, maleic acid amide, etc. Maleic anhydride modified polyolefins are especially suitable for use in the present invention. These modified polyolefins are usually formed by grafting maleic anhydride into a material of the polymeric structure. These maleated polyolefins are marketed by EI du Pont de Nemours and Company under the name of FUSABOND®, as the P series (chemically modified polypropylene), E series (chemically modified polyethylene), C series (chemically modified satin vinyl foam), A series (chemically modified ethylene acrylate copolymers or terpolymers), or the N series (chemically modified ethylene-propylene diene monomer ("EPDM") or ethylene-octene). As an alternative, maleated polyolefins are also marketed by Chemtura Corp. under the name of Polybond® and by the Eastman Chemical Company under the name of Eastman G series.
[052] In certain embodiments, the compatibilizer can also be reactive. An example of such a reactive compatibilizer is the polyepoxide modifier that contains, on average, at least two axirane rings per molecule. Without the intention of being limited by theory, it is believed that these polyepoxide molecules can induce a reaction of the renewable polyester under certain conditions, thus improving its melting capacity without greatly reducing the glass transition temperature. The reaction may involve chain extension, side chain branching, grafting, copolymer formation, etc. Chain extension, for example, can occur through a variety of different reactive pathways. For example, the modifier can allow a nucleophilic reaction for ring opening through a renewable polyester carboxyl end group (esterification) or through a hydroxyl group (etherification). Reactions on the oxazoline side can occur to form ester-amide parts. Through these reactions, the molecular weight of the renewable polyester can be increased to combat the degradation often seen during the fusion process. Although it is desirable to induce a reaction with the renewable polyester as described above, the present inventors have found that too much reaction can cause crosslinking between the polyester structures. If this crosslinking is allowed to proceed to a considerable extent, the resulting polymer mixture may become brittle and difficult to mold into a film format, with the desired strength and elongation properties.
[053] In this sense, the present inventors have found that polyepoxide modifiers with a relatively low epoxy resource are especially effective, which can be quantified by their "epoxy equivalent weight". The epoxy equivalent weight reflects the amount of resin that contains a molecule in an epoxy group, and can be calculated by dividing the average molecular weight in number of the modifier by the number of epoxy groups in the molecule. The polyepoxide modifier of the present invention usually has an average molecular weight in number ranging from about 7,500 to about 250,000 grams per mole; in some embodiments, from about 15,000 to about 150,000 grams per mole, and in other embodiments, from about 20,000 to about 100,000 grams per mole, with a polydispersity index ranging from 2.5 to 7 The polyepoxide modifier may contain less than 50, in some embodiments, from 5 to 45 and, in other embodiments, from 15 to 40 epoxy groups. In turn, the epoxy equivalent weight can be less than about 15,000 grams per mol; in some embodiments, from about 200 to about 10,000 grams per mole, and in other embodiments, from about 500 to about 7,000 grams per mole.
[054] The polyepoxide can be a linear or branched homopolymer or copolymer (for example, random, graft, block, etc.) containing terminal epoxy groups, skeletal oxirane units and / or pendant epoxy groups. The monomers used to form these polyepoxides may vary. In a specific embodiment, for example, the polyepoxide modifier contains at least one epoxy-functional monomeric (meta) acrylic component. As used here, the term “(meta) acrylic” includes acrylic and methacrylic monomers, as well as salts or esters thereof, such as acrylate and methacrylate monomers. For example, suitable epoxy-functional (meta) acrylic monomers can include, but are not limited to, those containing 1,2-epoxy groups, such as glycidyl acrylate and glycidyl methacrylate. Other suitable epoxy-functional monomers include allyl glycidyl ether, glycidyl ethacrylate and glycidyl itoconate.
[055] Poliepoxide normally has a relatively high molecular mass, as indicated above, so it can not only result in the extension of the renewable polyester chain, but also help to achieve the desired blend morphology. Thus, the resulting flow rate of the polymer can thus vary from about 10 to about 200 grams for 10 minutes; in some embodiments, from about 40 to about 150 grams for 10 minutes and, in other embodiments, from about 60 to about 120 grams for 10 minutes, determined at a load of 2160 grams and at a temperature 190 ° C.
[056] If desired, other monomers can also be used in the polyepoxide to help achieve the desired molecular mass. Such monomers may vary and include, for example, ester monomers, (meta) acrylic monomers, olefin monomers, amide monomers, etc. In a particular embodiment, for example, the polyepoxide modifier includes at least one linear or branched α-olefin monomer, such as those with 2 to 20 carbon atoms and, preferably, with 2 to 8 carbon atoms. Specific examples are ethylene, propylene, 1-butene; 3-methyl-1-butene; 3,3-dimethyl-1-butene; 1-pentene; 1-pentene with one or more methyl, ethyl or propyl substituents; 1-hexene with one or more methyl, ethyl or propyl substituents; 1- heptene with one or more methyl, ethyl or propyl substituents; 1-octene with one or more methyl, ethyl or propyl substituents; 1-nonene with one or more methyl, ethyl or propyl substituents; 1-decene substituted by ethyl, methyl or dimethyl; 1-dodecene; and styrene. The α-olefin comonomers specifically desired are ethylene and propylene.
[057] Another suitable monomer may include an (meta) acrylic monomer that is not epoxy-functional. Examples of such (meta) acrylic monomers can be methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, s-butyl acrylate, i-butyl acrylate, t-acrylate - butyl, n-amyl acrylate, i-amyl acrylate, isobornyl acrylate, n-hexyl acrylate, 2-ethylbutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-decyl acrylate, acrylate methylcyclohexyl, cyclopentyl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, i-propyl methacrylate, methacrylate, methacrylate, methacrylate of n-amyl, n-hexyl methacrylate, i-amyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, 2-ethylbutyl methacrylate, methylcyclohexyl methacrylate, cinnamyl methacrylate, methacrylate methacrylate , cyclopentyl methacrylate, 2-ethoxyethyl methacrylate, methacrylate isobornyl, etc., as well as combinations thereof.
[058] In a particularly desirable embodiment of the present invention, the polyepoxide modifier is a terpolymer formed from an epoxy-functional monomeric (meta) acrylic component, an alphaolefin monomeric component and a non-epoxy acrylic monomeric (meta) component -functional. For example, the polyepoxide modifier can be poly (ethylene-co-methyl acrylate-co-glycidyl methacrylate), with the following structure:
where x, y and z are 1 or greater.
[059] The epoxy-functional monomer can be formed into a polymer using several known techniques. For example, a monomer containing polar functional groups can be grafted onto a polymer structure to form a grafted copolymer. Such grafting techniques are well known in the art and are described, for example, in U.S. Patent No. 5,179,164, which is incorporated herein in its entirety, by reference, for all purposes. In other embodiments, a monomer containing epoxy-functional groups can be copolymerized with a monomer to form a random block or copolymer using known free radical polymerization techniques, such as high pressure reactions, Ziegler-catalytic reaction systems Natta, single site catalytic reaction systems (eg metallocene), etc.
[060] The relative part of the monomeric components can be selected in order to achieve a balance between epoxy reactivity and fluidity index. More specifically, high levels of epoxy monomer can result in a good reactivity with the renewable polyester, but a very high content can reduce the flow rate in such a way that the polyepoxide modifier will negatively affect the melt resistance of the polymer mixture. Thus, in most embodiments, epoxy-functional (meta) acrylic monomers form about 1% to about 25% by weight, in some embodiments, from about 2% to about 20% by weight and , in other embodiments, from about 4% to about 15% by weight of the copolymer. Alphaolefin monomers can also comprise from about 55% to about 95% by weight; in some embodiments; from about 60% to about 90% by weight and; in other embodiments; from about 65% to about 85% by weight of the copolymer. When used, other monomeric components (for example, non-epoxy-functional (meta) acrylic monomers) can make up from about 5% to about 35% by weight, in some embodiments, from about 8% to about 30% % by weight and, in other embodiments, from about 10% to about 25% by weight of the copolymer. A specific example of a suitable polyepoxide modifier that can be used in this invention is marketed by Arkema under the name of LOTADER® AX8950 or AX8900. LOTADER® AX8950, for example, has a melt index of 70 to 100 g / 10 min and has a 7% to 11% by weight glycidyl methacrylate monomer content, a 13% methyl acrylate monomer content at 17% by weight, and an ethylene monomer content of 72% to 80% by weight.
[061] In addition to controlling the type and relative content of the monomers used to form the polyepoxide modifier, the overall mass percentage can also be controlled in order to achieve the desired benefits. For example, if the level of modification is very low, the desired increase in melt strength and mechanical properties may not be achieved. The present inventors have also found, however, that if the level of modification is too high, the ability to form the film may be restricted due to strong molecular interactions (eg, crosslinking) and physical network formation by epoxy-functional groups. Thus, the polyepoxide modifier is normally employed in an amount of about 0.05% to about 10% by weight, in some embodiments, from about 0.1% to about 8% by weight, in other forms of from about 0.5% to about 5% by weight and, in other embodiments, from about 1% to about 3% by weight, based on the weight of the renewable polyesters employed in the compound. The polyepoxide modifier can also comprise from about 0.05% to about 10% by weight, in some embodiments, from about 0.05% to about 8% by weight, in other embodiments, from about 0.1% to about 5% by weight and, in other embodiments, from about 0.5% to about 3% by weight, based on the total weight of the compound.
[062] In addition to polyepoxides, other reactive compatibilizers can also be employed in the present invention, such as polymers functionalized with oxazoline, polymers functionalized with cyanide, etc. When used, these reactive compatibilizers can be used within the concentrations indicated above for the polyepoxide modifier. In a specific embodiment, an oxazoline-grafted polyolefin, that is, a polyolefin grafted with a monomer containing an oxazoline ring, can be employed. Oxazoline may include 2-oxazolines, such as 2-vinyl-2-oxazoline (for example, 2-isopropenyl-2-oxazoline), 2-fatty acid-alkyl-2-oxazoline (for example, obtained from oleic acid ethanolamine, linoleic acid, palmitoleic acid, gadoleic acid, erucic acid and / or arachidonic acid) and combinations thereof. In another embodiment, oxazoline can be selected from ricinoloxazoline maleinate, undecyl-2-oxazoline, soy-2-oxazoline, castor-2-oxazoline and combinations thereof, for example. In yet another embodiment, oxazoline is selected from 2-isopropenyl-2-oxazoline, 2-isopropenyl-4,4-dimethyl-2-oxazoline and combinations thereof.
[063] E. Other Components
[064] An exclusive aspect of the present invention is that the film can be formed with a volume of voids and relatively high breathability without the need for filler particles, such as those described above, which are normally necessary to form microporous films. This can provide several benefits, including a possible reduction in costs and manufacturing complexity. In fact, the thermoplastic compound and / or one or more layers of the film (e.g., base layer) may normally contain no filler particles (e.g., inorganic filler particles). For example, filler particles may be present in an amount of no more than about 10% by weight, in some embodiments no more than about 5% by weight and, in other embodiments, no more than about 1% by weight of the thermoplastic compound. However, in some embodiments, higher amounts of filler particles can be employed in the thermoplastic compound, if desired.
[065] In addition to achieving a high degree of breathability without conventional filler particles, the present inventors have also discovered that good mechanical properties can be provided without the need for various conventional additives such as plasticizers (for example, solid or semi-polyethylene glycol) -solid). In fact, the thermoplastic compound may not normally contain plasticizers. For example, plasticizers can be present in an amount of no more than about 1% by weight, in some embodiments no more than about 0.5% by weight and, in other embodiments, about 0.001 % to about 0.2% by weight of the thermoplastic compound. Obviously, a wide variety of ingredients can be used in the compound for several different reasons. For example, materials that can be used include, without limitation, catalysts, antioxidants, stabilizers, surfactants, waxes, solid solvents, fillers, nucleating agents (eg calcium carbonate, etc.), particulates and other materials added to in order to improve the processing capacity of the thermoplastic compound.
[066] II. Mixture
[067] Raw materials (eg, renewable polyester, curing additive and other optional components) can be mixed using a variety of known techniques. In one embodiment, for example, the raw materials can be supplied separately or as a combination. For example, raw materials can first be mixed dry in order to form an essentially homogeneous dry mixture. Raw materials can also be supplied simultaneously or sequentially to a melt processing device that mixes materials dispersively. They can be used batch and / or continuous melt processing techniques. For example, a mixer / kneader, Banbury mixer, Farrel continuous mixer, single screw extruders, double screw extruders, laminators, etc. can be used to mix and process the fusion materials. Especially suitable fusion processing devices may be a co-rotating twin screw extruder (for example, the ZSK-30 extruder marketed by Werner & Pfleiderer Corporation of Ramsey, New Jersey or a Thermo Prism ™ USALAB 16 extruder , marketed by Thermo Electron Corp., Stone, England). These extruders can include supply and ventilation ports and provide a high intensity distributive and dispersive mixture. For example, the raw materials can be introduced in the same ports, or in different ports, of the twin screw extruder, and mixed by melting to form a very homogeneous molten mixture. If desired, other additives can also be injected into the molten polymer and / or introduced separately into the extruder at a different point along its length. Alternatively, the additives can be pre-mixed with the renewable polyester and / or with the hardening.
[068] Regardless of the specific processing technique chosen, the raw materials are mixed under sufficient shear / pressure and heat to ensure sufficient dispersion, but not so high as to negatively reduce the size of the discrete domains, making them incapable to achieve the desired firmness and elongation. For example, mixing normally takes place at a temperature of about 180 ° C to about 260 ° C; in some embodiments, from about 185 ° C to about 250 ° C and, in other embodiments, from about 190 ° C to about 240 ° C. Likewise, the apparent shear rate during the melting process can vary from about 10 seconds-1 to about 3000 seconds-1, in some embodiments, from about 50 seconds-1 to about 2,000 seconds- 1 and, in other embodiments, from about 100 seconds-1 to about 1,200 seconds-1. The apparent shear rate is equal to 4Q / πR3, where Q is the volumetric flow rate (“m3 / s”) of the polymer melt and R is the radius (“m”) of the capillary (for example, extrusion) through which the molten polymer flows. Obviously, other variables, such as the residence time during the melting process, which is inversely proportional to the transfer rate, can also be controlled in order to achieve the desired degree of homogeneity.
[069] To achieve the desired shear conditions (eg rate, residence time, shear rate, melt processing temperature, etc.), the speed of the extruder rotations can be selected with a certain interval. Generally, an increase in the temperature of the product is observed with increasing speed of rotation due to the additional input of mechanical energy into the system. For example, the speed of rotation can vary from about 50 to about 500 revolutions per minute (“rpm”), in some configurations, from about 70 to about 300 rpm and, in other configurations, from about 100 to about 200 rpm. This can result in a temperature high enough to disperse the curing additive without adversely affecting the size of the resulting domains. The melt shear rate and, in turn, the degree to which the polymers are dispersed, can also be increased during the use of one or more distributive and / or dispersive mixing elements within the extruder mixing section. Among the single-thread distributive mixers are, for example, the Saxon, Dulmage, Cavity Transfer, etc. In the same way, suitable dispersive mixers may include bubble ring, Leroy / Maddock, CRD, etc. As is known in the art, mixing can be further enhanced by using pins in the cylinder that create a bend by reorienting the polymer melt, such as those used in Buss Kneader extruders, Cavity Transfer mixers and Vortex Intermeshing Pin (VIP) mixers.
[070] III. Film construction
[071] As indicated above, the film of the present invention is generally formed by a cold stretch of the precursor material of the film containing the renewable rigid polyester, the polymeric curing additive and other optional components. Any known technique can be used to form a precursor film from the mixed compound, including blowing, melting, flat mold extrusion, etc. In a given embodiment, the film can be formed by a blowing process in which a gas (for example, air) is used to expand a bubble of the extruded polymer mixture by means of an annular mold. The bubble is then undone and collected in the form of a flat film. The processes for producing blown films are described, for example, in U.S. Patent No. 3,354,506 to Raley; 3,650,649 for Schippers; and 3,801,429 to Schrenk et al., as well as U.S. patent application publications No. 2005/0245162 to McCormack, et al. and 2003/0068951 to Boggs, et al. In yet another embodiment, however, the film is formed using a melting technique.
[072] With respect to Fig. 1, for example, an embodiment of a method for forming a molten film is shown. In this embodiment, the raw materials (not shown) are supplied to extruder 80 and then melted on a molding roll 90 to form a single layer precursor film 10a.If a multilayer film is to be produced, the various layers are co-extruded together on the melting roll 90. The melting roll 90 can optionally be supplied with relief elements to transmit a pattern to the film. Typically, the mold roll 90 is maintained at a temperature sufficient to solidify and cool the sheet 10a as it is formed, such as from about 20 to 60 ° C. If desired, a vacuum box can be positioned adjacent to the mold roll 90 to help keep the precursor film 10a close to the surface of the roll 90. In addition, air knives or electrostatic tweezers can help to force the precursor film 10a against the surface of the fusion roller 90 as it moves around a rotating roller. Air knives are devices known in the art that direct an air jet at a very high flow rate, in order to fix the edges of the film.
[073] Regardless of the specific nature of the precursor material, a network structure of empty spaces is introduced by stretching the material to a temperature below the glass transition temperature of the renewable polyester. Stretching can occur in the longitudinal direction (for example, machine direction), transverse direction (for example, machine cross direction), or a combination of them. The degree of stretching is generally selected in the present invention to ensure that the desired network of voids is achieved, but not in such a way that the mechanical properties of the resulting material are negatively impacted. In this regard, the precursor material is normally stretched (for example, in the machine direction) at a stretch rate of about 1.1 to about 3.0, in some embodiments of about 1.2 to about of 2.0 and, in other embodiments, from about 1.3 to about 1.8. The “stretch rate” is determined by dividing the length of the stretched material by its length before stretching. The stretch rate can also vary to help achieve the desired properties, for example, the variation of about 5% to about 1,000% per minute of deformation, in some embodiments from about 20% to about from 500% per minute of deformation and, in other embodiments, from about 25% to about 200% per minute of deformation. The precursor material is generally maintained at a temperature below the glass transition temperature of the renewable polyester during stretching. Among other things, this helps to ensure that the polyester chains are not altered in such a way that the web of voids becomes unstable. Usually, the precursor material is stretched at a temperature of at least about 10 ° C, in some embodiments of at least about 20 ° C and, in other embodiments of at least about 30 ° C. ° C below the glass transition temperature. For example, the precursor material can be stretched at a temperature of about 0 ° C to about 50 ° C, in some embodiments of about 15 ° C to about 40 ° C and, in other embodiments, from about 20 ° C to about 30 ° C. If desired, the precursor material can be stretched without the application of external heat (for example, heated rollers).
[074] Although not required, the precursor material can be stretched on the line without having to remove it for separate processing. Various stretching techniques can be employed, such as stretching the tension frame, biaxial stretching, multi-axial stretching, profile stretching, cold air stretching, vacuum stretching, etc. For example, the precursor material of the film can be stretched by rollers rotating at different speeds of rotation, so that the sheet is stretched at the desired stretching rate in the longitudinal direction (machine direction). The uniaxially arranged film can also be arranged in the transverse direction of the machine to form a “biaxially arranged” film. For example, the film can be attached to its side edges by chain clamps and transported to a tensioning furnace. In the tensioning furnace, the film can be reheated and pulled in the transversal direction of the machine at a desired stretching rate, by chain clamps spaced on its forward path.
[075] With reference again to Fig. 1, for example, a specific method for forming uniaxially stretched film is shown. As illustrated, the precursor film 10a is directed to a film orientation unit 100 or machine-oriented guide ("OSM"), such as those marketed by Marshall and Willams, Co. of Providence, Rhode Island. The OSM has a variety of stretch rollers (such as 5 to 8), which progressively stretch and thin the film in the machine direction, which is the direction the film travels through the process as shown in Fig. 1. Although the OSM 100 is illustrated with eight rolls, it should be understood that the number of rolls can be greater or less, depending on the desired stretch level and the degree of stretching between each roll. The film can be stretched in discrete single or multiple stretch operations. It should be noted that some of the cylinders in an OSM apparatus may not be operating at higher progressive speeds. The faster progressive speeds of the adjacent cylinders in the OSM act to stretch the film 10a. The rate at which the stretch rollers rotate determines the amount of stretch of the film and its total weight. To “cold stretch” the film, in the manner described above, it is generally preferable that the cylinders of the OSM 100 are not heated. However, if desired, one or more cylinders can be slightly heated to facilitate the stretching process, as long as the film temperature remains below the ranges noted above. Once formed, the resulting film 10b can then be rolled up and stored in a take-up cylinder 60. Although not shown here, several additional steps of possible processing and / or finishing known in the art, such as cutting, treating, perforating, printing images or laminating the films with other layers (for example, non-woven blanket materials), can be carried out without departing from the spirit and scope of the invention.
[076] Cold drawing in the manner described above generally results in the formation of empty spaces that have an axial dimension in the direction of the stretching (for example, longitudinal or in the machine direction) relatively small. For example, in one embodiment, the axial dimension of the voids can be about 5 micrometers or less, in some embodiments about 2 micrometers or less and, in other embodiments, from about 25 nanometers to about 1 micrometer. In certain cases, voids can be “micro-voids” in the sense that at least one dimension of these voids is about 1 micrometer or more in size. For example, these micro-voids may have a dimension in a direction orthogonal to the axial dimension (i.e., machine's cross-sectional direction) of about 1 micrometer or more, in some embodiments about 1.5 micrometers or more and, in other embodiments, from about 2 micrometers to about 5 micrometers. This can result in an aspect ratio of the micro-voids (the ratio of the axial dimension to the orthogonal dimension to the axial dimension) of about 0.1 to about 1, in some embodiments of about 0.2 to about 0.9 and, in other embodiments, about 0.3 to about 0.8. Likewise, “nano-voids” can also be present, alone or in conjunction with micro-voids. Each dimension of nano-voids is generally less than about 1 micrometer and, in some embodiments, about 25 to about 500 nanometers.
[077] In addition to forming a void network as described above, stretching can also significantly increase the axial dimension of the primary domains, so that they have a generally elongated and linear shape. For example, elongated domains can have an axial dimension of about 10% or more, in some embodiments from about 20% to about 500% and, in some embodiments, from about 50% to about 250% larger than the axial dimension of the domains before stretching. The axial dimension after stretching can, for example, vary from about 1 μm to about 400 μm, in some embodiments from about 5 μm to about 200 μm and, in some embodiments, from about 10 μm to about 150 μm. Domains can be relatively thin and thus have a small dimension in a direction orthogonal to the axial dimension (ie, transversal dimension). For example, the cross-sectional dimension can be from about 0.02 to about 75 micrometers, in some embodiments from about 0.1 to about 40 micrometers and, in other embodiments, from about 0.4 about 20 micrometers. This can result in an aspect ratio of the domains (the ratio of the axial dimension to the orthogonal dimension to the axial dimension) from about 2 to about 150, in some embodiments from about 3 to about 100, and in other embodiments, from about 4 to about 50.
[078] The present inventors have also discovered that voids can be distributed quite evenly throughout the compound. For example, voids can be distributed in columns oriented in a direction normally perpendicular to the direction in which the tension is applied. These columns can generally be parallel to each other over the entire width of the compound. Without the intention of imposing theoretical limitations, it is believed that the presence of this system of homogeneously distributed voids may result in a significant dissipation of energy under load and a significantly greater stretching tension.
[079] The film of the present invention can be monolayer or multilayer. Multilayer films can be prepared by coextrusion of layers, coextrusion coating or any other conventional layering process. For example, the film can contain two (2) to fifteen (15) layers and, in some embodiments, from three (3) to twelve (12) layers. These multilayer films contain at least one base layer and at least one additional layer (for example, surface layer), but can contain as many layers as desired. For example, multilayer films can be formed by base layers and one or more surface layers, where the base layer is formed by the thermoplastic compound of the present invention. In most embodiments, the surface layers are formed by a thermoplastic compound as described above. It should be understood, however, that other polymers can also be used in the surface layers, such as polyolefin polymers (for example, linear low density polyethylene (PELBD) or polypropylene).
[080] The film thickness of the present invention can be relatively small to increase flexibility. For example, the film may be about 1 to about 200 micrometers thick, in some forms about 2 to about 150 micrometers, in some forms about 5 to about 100 micrometers and in some ways other forms of performance, from about 10 to about 60 micrometers. Despite the low thickness, the film of the present invention is, however, capable of maintaining good mechanical properties during use. For example, the film is relatively malleable. A parameter indicative of the malleability of the film is the percentage of its elongation at its breaking point, as determined by the strain strain curve, in accordance with ASTM D638-10 at 23 ° C. For example, the percentage of elongation at the break of the film in the machine direction (“longitudinal or MD”) can be about 10% or more, in some embodiments about 50% or more, in some embodiments about 80% or more and, in other embodiments, from about 100% to about 600%. Likewise, the percentage of elongation at the break of the film in the transverse direction (“CD”) can be about 15% or more, in some embodiments about 40% or more, in some embodiments about 70 % or more and, in other embodiments, from about 100% to about 400%. Another parameter indicative of malleability is the tension module of the film, which is equal to the ratio of the tensile stress to the strain strain, and is determined from the slope of a stress-strain curve. For example, the film typically exhibits an MD and / or CD tension module of about 2,500 megapascals (“MPa”) or less, in some embodiments about 2,200 MPa or less and, in other embodiments, about from 500 MPa to about 2,000 MPa. The voltage module can be determined in accordance with ASTM D638-10 at 23 ° C.
[081] Although the film is malleable, it can also be relatively strong. A parameter indicative of the relative strength of the film is its maximum stress resistance, which is equal to the maximum stress obtained in a stress-strain curve, as obtained according to the STM D638-10 standard. For example, the film of the present invention may exhibit a peak MD and / or CD voltage of about 5 to about 65 MPa, in some embodiments of about 10 to about 60 MPa, and in other embodiments , from about 20 MPa to about 55 MPa. The film may also exhibit an MD and / or CD voltage drop of about 5 to about 60 MPa, in some embodiments from about 10 to about 50 MPa and, in some embodiments, from about 20 MPa to about 45 MPa. The peak voltage and the breaking voltage can be determined in accordance with ASTM D638-10 at 23 ° C.
[082] If desired, the film of the present invention can be subjected to one or more extra productive steps, before and / or after cold drawing. Examples of such processes include, for example, groove roller stretching, perforation, embossing, coating, etc. The film can also have its surface treated with any of the known techniques to improve its properties. For example, high-energy beams (for example, plasma, x-ray, electron beam, etc.) can be used to remove or reduce any surface layer that forms on the film, to change polarity, porosity, topography of the surface, etc. If desired, these treatment surfaces can be used alternatively before and / or after cold drawing the film.
[083] The film can also be laminated with one or more non-woven blankets, to reduce the coefficient of friction and improve the tactile feel of fabric on the compound's surface. Examples of polymers for use in forming nonwoven blanket coatings can include, for example, polyolefins, for example, polyethylene, polypropylene, polybutylene, etc .; polytetrafluoroethylene; polyesters, for example, polyethylene terephthalate and so on; polyvinyl acetate; polyvinyl acetate chloride; polyvinyl butyral; acrylic resins, for example, polyacrylate, polymethylacrylate, polymethylmethacrylate, and so on; polyamides, for example, nylon; polyvinyl chloride; polyvinylidene chloride; polystyrene; polyvinyl alcohol; polyurethanes; polylactic acid; its copolymers; and so on. If desired, renewable polymers, such as those described above, can also be used. Synthetic or natural polymers can also be used, including, but not limited to, cellulose esters; cellulose ethers; cellulose nitrates; cellulose acetates; cellulose butyrate acetates; ethyl cellulose; regenerated celluloses like viscose, rayon and so on. It should be noted that polymers can also contain other additives, such as processing aids or treatment compounds to impart the desired properties to the fibers, residual amounts of solvents, pigments or dyes, and so on.
[084] Single-component and / or multi-component fibers can be used to form the lining of the nonwoven mat. Mono-component fibers are generally formed by a polymer or a mixture of polymers extruded from a single extruder. Multi-component fibers are generally formed by two or more polymers (for example, bicomponent fibers) extruded from separate extruders.The polymers can be organized in distinct zones positioned constantly along the transversal direction of the fibers. The components can be arranged in any desired configuration, such as core coating, tile, pie, island in the sea, three islands, porthole, or various other forms of organization known in the area. Multicomponent fibers with various irregular shapes can also be formed.
[085] Fibers of any desired length can be used, such as cut fibers, continuous fibers, etc. In a given embodiment, for example, the cut fibers can be used with a length in the range of about 1 to about 150 millimeters, in some forms of carrying out from about 5 to about 50 millimeters, in some forms of carrying out about from 10 to about 40 millimeters and, in other ways, from about 10 to about 25 millimeters. Although not necessary, carding techniques can be employed to form fibrous layers with cut fibers, as is well known in the art. For example, fibers can be transformed into carded blankets by placing bales of fibers in a picker that separates them. Then the fibers are sent through a combing or carding unit, which separates and aligns the fibers towards the machine, to form a fibrous nonwoven blanket oriented in the machine direction. The carded blanket can then be joined using known techniques to form a nonwoven carded fixed blanket.
[086] If desired, the lining of the nonwoven web used to form the nonwoven compound can have a multilayer structure. Suitable multilayer materials can be, for example, heat-sealed / meltblown / heat-welded laminates (SMS) and heat-welded / meltblown laminates (SM) Another example of a multilayer structure is the thermal welded blanket produced in a multi-rotary table machine in which the rotary table deposits fibers on the layer of fibers deposited in a previous rotation of the table. This individual heat-sealed blanket can also be understood as a multilayer structure. In this case, the various layers of fibers deposited on the non-woven blanket may be the same, or may differ in weight and / or composition, type, size, level of friezes and / or in the shape of the fibers produced. As another example, a single non-woven web can be provided, such as two or more layers produced individually from a heat-sealed web, a carded web, etc., which have been joined to form the non-web web. These individually produced layers may differ in terms of production method, weight, composition and fibers, as mentioned above. A nonwoven blanket covering can also contain an additional fibrous component that is considered a compound. For example, a non-woven blanket can be entangled with another fibrous component using a variety of entanglement techniques known in the art (for example, hydraulic, air, mechanical, etc.). In one embodiment, the non-woven blanket is entangled entirely with cellulose fibers using hydraulic entanglement. A typical hydraulic entanglement process uses high pressure water jet streams to entangle the fibers and form a highly entangled consolidated fibrous structure, for example, a non-woven blanket. The fibrous component of the compound can contain any desired amount of the resulting substrate.
[087] The weight of non-woven blanket coverings can generally vary, from about 5 grams per square meter (“g / m2”) to 120 g / m2 and, in some embodiments, around 8 g / m2 m2 to about 70 g / m2 and, in other embodiments, from 10 g / m2 to 35 g / m2. When using multiple coatings of non-woven blankets, these materials can have the same weights or different weights.
[088] IV. applications
[089] The film of the present invention can be used in a wide variety of applications, such as packaging films, individual wrap, packaging pouch or a pouch for the disposal of a variety of products such as food, paper (for example, fabrics , cleaning wipes, paper towels, etc.), absorbent products, barrier films, filter media, nanoporous membranes, etc. Various suitable configurations of packaging, wraps, or bags for absorbent products are disclosed, for example, in U.S. Patent No. 6,716,203 to Sorebo, et al. and 6,380,445 to Moder, et al., as well as U.S. patent application publications No. 2003/0116462 to Sorebo, et al.
[090] The film can also be used in other applications. For example, the film can be used in an absorbent product. An "absorbent product" generally refers to any article capable of absorbing water and other fluids. Examples of absorbent articles are, but are not limited to: absorbent articles for personal care, such as diapers, training diapers, absorbent panties, incontinence products, feminine hygiene products (for example, sanitary wipes, menstrual pads, etc.), bathing suits, baby wipes, and so on; medical absorbent articles, such as clothing, fenestration materials, bed linings, dressings, absorbent surgical drapes and medical wipes; paper towels for heavy cleaning in kitchens, articles of clothing, and so on. Several examples of such absorbent products have been described in U.S. Patent No. 5,649,916 to DiPalma, et al .; 6,110,158 for Kielpikowski; 6,663,611 to Blaney, et al. Other suitable products have also been described in U.S. Patent Application Publication No. 2004/0060112 A1 to Fell et al., As well as U.S. Patent No. 4,886,512 to Damico et al .; 5,558,659 to Sherrod et al .; 6,888,044 to Fell et al .; and 6,511,465 for Freiburger et al. The materials and processes suitable for forming such products are well known to those skilled in the art.
[091] Therefore, a particular embodiment of an absorbent product that can employ the film of the present invention, will now be described in more detail. For example, an absorbent product may include a main body portion containing an upper sheet, an outer cover or bottom sheet, an absorbent core positioned between the bottom sheet and the top sheet and two flaps extending on each longitudinal side of the main body portion. The top sheet defines a surface of the absorbent product, facing the body. The absorbent core is positioned inwardly from the outer perimeter of the absorbent product, and includes a side facing the body, positioned adjacent to the top sheet, and a surface facing the clothing, positioned adjacent to the bottom sheet. In a particular embodiment of the present invention, the backsheet is a film formed by a thermoplastic compound of the present invention and is generally impermeable to liquid and, optionally, vapor permeable. The film used to form the backsheet can also be laminated with one or more nonwoven blanket coatings as described above.
[092] The top sheet is generally designed to be in contact with the user's body and is liquid permeable. The top sheet can surround the absorbent core in order to completely cover the absorbent product. Alternatively, the top sheet and the backsheet can extend beyond the absorbent core and join peripherally, in whole or in part, using known techniques. Normally, the top and bottom sheets are joined using adhesives, ultrasound, or any other joining method known in the art. The top sheet is hygienic, clean in appearance and relatively opaque to hide body discharges collected and absorbed by the absorbent core. The top sheet also exhibits good penetration and rewetting characteristics, allowing discharges to penetrate quickly through the top sheet and forward to the absorbent core, but not allowing body fluid to return through the top sheet and contact the skin. of user. For example, some suitable materials that can be used for the topsheet include non-woven materials, perforated thermoplastic films or a combination thereof. A non-woven fabric made of polyester, polyethylene, polypropylene, bicomponent, nylon, rayon or fiber may be used similar. For example, there is a preference for a uniform, white, heat-sealed material as the color exhibits good properties to disguise the periods that pass through it. U.S. patents 4,801,494 to Datta, et al. and 4,908,026 to Sukiennik, et al. present several other cover materials that can be used in the present invention.
[093] The top sheet may also contain a variety of openings formed through it, to allow the body fluid to reach the absorbent core more quickly. The openings can be arranged evenly or randomly throughout the top sheet or they can be arranged only in the narrow longitudinal strip positioned along the longitudinal axis of the absorbent product. The openings allow the rapid penetration of body fluids into the absorbent core. The size, shape, diameter and number of openings can vary to meet the specific needs of each person.
[094] The absorbent product may also contain an absorbent core positioned between the top sheet and the bottom sheet. The absorbent core can be formed by a single absorbent member or by a compound containing different and separate absorbent members. It is to be understood, however, that any number of absorbent members can be used in the present invention. For example, in one embodiment, the absorbent core may contain an absorption member positioned between the topsheet and a transfer delay member. The absorption member can be made of a material capable of rapidly transferring, in the z direction, the body fluid received by the topsheet. The absorption member can, in general, have any desired shape and / or size. In one embodiment, the absorber member has a rectangular shape, with a length equal to or less than the total length of the absorbent product, and a width less than the width of the absorbent product. For example, a length between 150 mm and about 300 mm, and a width between 10 mm and about 60 mm can be used.
[095] A variety of different materials can be used for the absorption member, in order to perform the functions described above. The material can be synthetic, cellulose or a combination of both. For example, cellulose fabrics formed by airflow may be suitable for use on the absorption member. The cellulose fabric formed by airflow can have a weight ranging from about 10 grams per square meter (g / m2) to about 300 g / m2 and, in some embodiments, between about 100 g / m2 at about 250 g / m2. In one embodiment, the cellulose fabric formed by airflow has a weight of about 200 g / m2. Airflow fabric can be made of hardwood and / or softwood fibers. The air flow tissue has a fine pore structure and provides excellent evaporation capacity, especially for menstruation.
[096] If desired, the transfer delay member can be positioned vertically below the absorption member. The transfer delay member can contain less hydrophilic material than the other absorbent members and can, in general, be characterized as quite hydrophobic. For example, the transfer delay member may be a fibrous, non-woven mat composed of a relatively hydrophobic material, such as polypropylene, polyethylene, polyester or the like, and may also be composed of a mixture of these materials. An example of suitable material for the transfer delay member is a heat-sealed blanket made up of multi-polyester polypropylene fibers. of transversal shape and that can be of hollow or solid structures. Normally, the wefts are joined, for example, by thermal bonding, above 3% to about 30% of the web area. Other examples of suitable materials that can be used on the transfer delay member are described in U.S. Patent No. 4,798,603 to Meyer, et al. and 5,248,309 for Serbiak, et al. To adjust performance, the transfer delay member can also be treated with a selected amount of surfactant, to increase its initial water absorption capacity.
[097] The transfer delay member can, in general, have any size, such as an approximate size of 150 mm to about 300 mm. Normally, the length of the transfer delay member is almost equal to the length of the absorbent product. The transfer delay member may also be equal in width to the absorption member, but is generally wider. For example, the width of the transfer delay member can be between about 50 mm to about 75 mm, and especially about 48 mm. The transfer delay member normally weighs less than other absorbent members. For example, the weight of the transfer delay member is usually less than 150 grams per square meter (g / m2) and, in some embodiments, between about 10 g / m2 to about 100 g / m2. In a specific embodiment, the transfer delay member is formed by a heat-sealed blanket with a weight of about 30 g / m2. In addition to the aforementioned members, the absorbent core may also include a composite absorbent member, such as a shaped material. In that case, fluids can be absorbed from the transfer delay member to the composite absorbent member. The composite absorbent member may be formed separately from the absorption member and / or the transfer delay member, or may be formed simultaneously with them. In one embodiment, for example, the composite absorbent member may be formed in the transfer delay member or in the absorption member, which acts as a carrier during the shaped process described above.
[098] Although various configurations of an absorbent product have been described above, it should be understood that other configurations are also included in the scope of the present invention. In addition, the present invention is in no way limited to the bottom sheets, and the film of the present invention can be incorporated into a variety of compounds other than an absorbent product. For example, a non-stick liner of an absorbent product can include the film of the present invention.
[099] The present invention can be better understood by referring to the following examples. Testing methods
[100] Flow rate:
[101] The fluidity index (“MFR”) is the mass of a polymer (in grams) forced through the hole of an extrusion rheometer (0.0825 inch diameter) when subjected to a load of 2,160 grams for 10 minutes, usually at 190 ° C or 230 ° C. Unless otherwise indicated, the flow rate is measured according to the ASTM D1239 test method, with a plastomer by Tinius Olsen extrusion.
[102] Thermal properties:
[103] The glass transition temperature (Tg) can be determined by dynamic mechanical analysis (DMA) in accordance with ASTM E1640-09. TA Instruments A Q800 can be used. Experimental runs can be performed on voltage / voltage geometry, in a temperature range mode in the range of -120 ° C to 150 ° C with a heating rate of 3 ° C / min. The frequency of the voltage amplitude can be kept constant (2 Hz) during the test. Three (3) independent samples can be tested to obtain an average glass transition temperature, which is defined by a peak value of the tan δ curve, where tan δ is defined as the ratio of the loss module to the storage module. (tan δ = E ”/ E ').
[104] The melting temperature can be determined using differential scanning calorimetry-DSC. The differential scanning calorimetry equipment can be a DSC Q100 Differential Scanning Calorimeter, equipped with a liquid nitrogen cooling accessory and UNIVERSAL ANALYSIS 2000 analysis software (version 4.6.6), both marketed by TA Instruments Inc. of New Castle, Delaware. To avoid direct handling of the samples, tweezers and other tools are used. The samples are placed on an aluminum plate and weighed to the nearest 0.01 milligrams on an analytical balance. A lid is placed over the material sample on the plate. Usually, the resin grains are placed directly on the weighing pan.
[105] The differential scanning calorimetry equipment is calibrated using an Indian metal standard and a base correction is made, as described in the equipment's operating manual. A sample of the material is placed in the test chamber of the differential scanning calorimetry equipment to be tested, and an empty plate is used as a reference. All tests are performed with a nitrogen discharge of 55 cubic centimeters per minute (industrial scale) in the test chamber. For resin grain samples, the heating and cooling program is a 2-cycle test, which started with chamber equilibration at -30 °° C, followed by a first heating period to a rate of 10 ° C per minute to a temperature of 200 ° C, followed by a sample equilibrium at 200 ° C for 3 minutes, followed by a first cooling period of 10 ° C per minute to a temperature of - 30 ° C, followed by the sample equilibrium at -30 ° C for 3 minutes, and then a second heating period, at a rate of 10 ° C per minute to a temperature of 200 ° C. All tests are carried out with the discharge of 55 cubic centimeters of nitrogen per minute (industrial scale) in the test chamber.
[106] The results are evaluated by the UNIVERSAL ANALYSIS 2000 analysis software, which identified and quantified the glass transition temperature (Tg) of the inflection, the endothermic and exothermic peaks and the areas under the peaks in the DSC traces. The glass transition temperature is identified as the region of the drawn line where there was a clear change in the slope, and the melting temperature is determined by using an automatic inflection calculation.
[107] Voltage properties
[108] Films were tested for stress properties (maximum stress, modulus, breakage deformation and energy per break volume) on an MTS Synergie 200 stress frame. The test was performed in accordance with ASTM D638-10 (at about 23 ° C). Samples of dog bone shaped films with a central width of 3.0 mm were cut prior to testing. The dog bone film samples were held in place by means of fasteners on the MTS Synergie 200 device with a length of the part to be measured 18.0 mm. The film samples were stretched at a 5.0 "min traction speed until breakage occurred. Five samples of each film were tested in the machine (MD) and crosswise (CD) directions. A computer program was used called TestWorks 4 to collect data during the test and generate a stress versus strain curve, from which various properties were determined, including modulus, maximum stress, elongation and energy to break.
[109] Expansion ratio, density and percentage of empty volume.
[110] To determine the expansion ratio, density and percentage of empty volume, the width (Wi) and thickness (Ti) of the specimen were initially measured before cold drawing. The length (Li) before stretching was also determined by measuring the distance between two marks on the specimen's surface. Consequently, the specimen was cold drawn to begin emptying. The width (Wf), thickness (Tf) and length (Lf) of the specimen were then measured to the nearest 0.01 mm using a Digimatic Caliper caliper (Mitutoyo Corporation). The volume (Vi) before cold drawing was calculated by Wi x Ti x Li = Vi. The volume (Vf) after cold drawing was calculated by Wf x Tf x Lf = Vf. The expansion rate (Φ) was calculated by Φ = Vf / Vi; density (Pf) was calculated by: Pf = Pi / Φ, where Pi is the density of the precursor material; and the percentage of empty volume (% Vv) was calculated by:% Vv = (1 - 1 / Φ) x 100.
[111] Moisture content
[112] The moisture content can be determined using the Arizona Instruments Computrac Vapor Pro moisture analyzer (Model No. 3100), in accordance with ASTM D 7191-05, incorporated here, in full, by reference for all purposes. The test temperature (§X2.1.2) can be 130 ° C, the sample size (§X2.1.1) can be 2 to 4 grams, and the emptying time of the bottle (§X2.1.4) can be 30 seconds. In addition, the closure criterion (§X2.1.3) can be defined as a “prediction” mode, which means that the test is ended when the internally programmed criterion (which mathematically calculates the moisture content at the end point) is reached.
[113] Water vapor transmission rate (“TTVA”)
[114] The test used to determine the TTVA of a material may vary based on the nature of the material. A technique for measuring the value of TTVA involves using a test precedence standardized by INDA (Association of the Nonwoven Fabric Industry), number IST-70.4-99, called "STANDARD TEST METHOD FOR WATER STEAM TRANSMISSION RATE BY PLASTIC AND NON WOVEN FILM USING A PROTECTIVE FILM AND STEAM PRESSURE SENSOR ", which is incorporated here in its entirety, by reference. The INDA test precedence is summarized as follows. A dry chamber is separated from a wet chamber of known temperature and humidity by a permanent protective film and the sample material to be tested. The purpose of the protective film is to define a definite air gap and to calm or calm the air in the air gap while it is characterized. The dry chamber, the protective film and the wet chamber form a diffuser cell, in which the test film is sealed. The sample holder is known as the Permatran-W model 100K manufactured by Mocon / Modem Controls, Inc., Minneapolis, Minnesota. A first TTVA test of the protective film and air gap is carried out between the evaporator assembly, generating 100% relative humidity. The water vapor diffuses through the air gap and the protective film and then mixes with the dry gas flow, proportional to the water vapor concentration. The electrical signal is routed to a computer for processing. The computer calculates the transmission rate of the air gap and the protective film and stores the value for later use.
[115] The transmission rate of the protective film and air gap is stored in the computer as CalC. The sample material is then sealed in the test cell. Again, the water vapor diffuses through the air gap into the protective film and the test material, and then mixes with the dry gas stream that sweeps the test material. Also, again, the mixture is conducted to the steam sensor. The computer then calculates the transmission rate for the combination of air gap, protective film and test material. This information is then used to calculate the transmission rate at which moisture is transmitted by the test material according to the equation: TR- Test material = TR Test material, protective film, loose - TR 1 protective film, loose
[116] The water vapor transmission rate ("TTVA") is then calculated as follows:
on what,
[117] F = the flow of water vapor in cm3 per minute;
[118] psat (T) = the density of water in saturated air at temperature T;
[119] RH = the relative humidity at specific locations in the cell;
[120] A = the transverse area of the cell; and
[121] Psat (T) = the saturated steam pressure of water vapor at temperature T. EXAMPLE 1
[122] Films formed from 100% polylactic acid (PLA) were formed as a control by extruding PLA 6201D (Natureworks®, 10 g / 10 min melt index at 190 ° C) onto a film. The grains were transferred in large volume to a Rheomix 252 signal screw extruder with an L: D ratio of 25: 1 heated to a temperature of about 208 ° C in which the molten PLA exits through a molten film Haake mold of 6 inches, and is stretched through a Haake tensioner drum to a film thickness ranging from 41.9 μm to 48.3 μm. EXAMPLE 2
[123] The possibility of forming films was demonstrated from a mixture of 85.3% by weight of polylactic acid (PLA 6201D, Natureworks®), 9.5% by weight of a curing additive and 1.4% of a polyepoxide modifier, and 3.8% by weight of an internal interfacial modifier (MII). The hardening additive was VISTAMAXX ™ 2120 (ExxonMobil), which is a polyolefin copolymer / elastomer with a melt index of 29 g / 10 min (190 ° C, 2,160 g) and a density of 0.866 g / cm3. The polyepoxide modifier was poly (ethylene-co-methyl acrylate-co-glycidyl methacrylate) (Lotader® AX8950, Arkema), with a melt index of 70-100 g / 10 min (190 ° C / 2,160 g), a glycidyl methacrylate content of 7% to 11% by weight, a methyl acrylate content of 13% to 17% by weight, and an ethylene content of 72% to 80% by weight. The MMI was BASF's PLURIOL® WI285 Lubricant Basestock. The polymers were introduced into a co-rotating twin screw extruder (ZSK-30, diameter 30 mm, length 1,328 mm) for compounds manufactured by Werner and Pfleiderer Corporation, of Ramsey, New Jersey. The extruder had 14 zones, numbered sequentially from 1 to 14, from the feed funnel to the die. The first zone of barrel # 1 received the resins through the gravimetric feeder, at a total yield of 15 pounds per hour. PLURIOL® WI-285 was added via the injection pump into zone no. 2 of the barrel at a feed rate of 0.6 lbs / h. The die used to extrude the resin had 3 die openings (6 millimeters in diameter) separated by 4 millimeters. After formation, the extruded resin was cooled on a conveyor belt cooled by a fan and transformed into grains by a Conair granulator. The screw speed of the extruder was 200 revolutions per minute (“rpm”). The grains were introduced in large volume into a Rheomix 252 signal screw extruder with an L / D ratio of 25: 1, heated to a temperature of about 212 ° C where the melted mixture came out through a fused film Haake matrix. 6 inches, and was stretched to a film thickness ranging from 39.4 μm to 50.8 μm by means of a Haake tensioning drum. The film was cold drawn in the machine direction to a 160% longitudinal strain at a tensile rate of 50 mm per min (strain rate of 67% per min) using the MTS Synergie 200 tension frame with fasteners at a useful length of 75 mm.
[124] SEM photomicrographs were taken from example 2 before and after cold drawing. The results are illustrated in Figs. 2 to 3. As shown, the PLA matrix in example 2 underwent decomposition, which resulted in the formation of many empty areas in the film. EXAMPLE 3
[125] The films were formed as described in example 2, unless the film was also stretched across the machine to a 100% strain, at a tensile rate of 50 mm by me (100% strain rate by min) with fasteners at a useful length of 50 mm.
[126] Various properties of the films of examples 1 to 3 were tested as described above. The results are shown in tables 1 and 2. Table 1: Film properties

Table 2: Tension properties

[127] Although the invention has been described in detail with respect to its specific configurations, it would be good for experts in the field, after obtaining an understanding of the above, to be able to easily conceive changes, variations and equivalents to such configurations. Therefore, the scope of the present invention must be assessed as that of the appended claims and their equivalents.

权利要求:
Claims (15)
[0001]
1. Breathable film with a water vapor transmission rate of 500 g / m2 / 24 hours or more, and preferably 2,000 g / m2 / 24 hours or more, the film being characterized by the fact that it comprises a thermoplastic compound that contains: at least one renewable rigid polyester with a glass transition temperature of 0 ° C or higher, and preferably from 50 ° C to 75 ° C; and at least one polymeric curing additive that includes a polyolefin, at least one interphasic modifier, wherein the interphasic modifier is a silicone copolymer, silicone-polyether, aliphatic polyester, aromatic polyester, alkylene glycol, alkane diol, amine oxide, ester of fatty acid or a combination thereof, and at least one polyepoxide compatibilizer containing, on average, at least two oxirane rings per molecule; where the thermoplastic compound has a morphology in which several discrete and empty primary domains are dispersed within a continuous phase, with the domains containing the polymeric hardening additive and with the continuous phase containing the renewable polyester, where the average percentage volume of the compound , which is occupied by voids, is 20% to 80% per cubic centimeter, and preferably 40% to 60% per cubic centimeter, in which the water vapor transmission rate is determined according to the standardized test by INDA IST-70.4-99.
[0002]
2. Breathable film according to claim 1, characterized by the fact that the thermoplastic compound is free of non-organic filler particles.
[0003]
Breathable film according to claim 1 or 2, characterized by the fact that the void ratio is 0.1 to 1, and preferably the voids have a longitudinal dimension of 2 micrometers or less, and a transverse dimension from 2 micrometers to 5 micrometers.
[0004]
4. Breathable film according to any one of the preceding claims, characterized by the fact that the thermoplastic compound has a density of 1.4 grams per cubic centimeter, or less.
[0005]
5. Breathable film according to any one of the preceding claims, characterized by the fact that the renewable polyester is a polylactic acid or a polyethylene terephthalate.
[0006]
6. Breathable film according to any one of the preceding claims, characterized by the fact that the ratio between the renewable polyester solubility parameter and the polymeric curing additive solubility parameter is 0.5 to 1.5, the ratio between the flow rate of the renewable polyester and the flow rate of the polymeric curing additive is 0.2 to 8, and the ratio between the Young's modulus of the renewable polyester and the Young's modulus of the curing additive polymeric is 2 to 500.
[0007]
Breathable film according to any one of the preceding claims, characterized in that the polymeric curing additive contains a propylene homopolymer, alphaolefin / propylene copolymer, ethylene / alphaolefin copolymer, or a combination thereof.
[0008]
8. Breathable film according to any one of the preceding claims, characterized by the fact that the interphasic modifier has a kinematic viscosity of 0.7 to 200 centistokes, determined at a temperature of 40 ° C.
[0009]
Breathable film according to any one of the preceding claims, characterized by the fact that the interphasic modifier is hydrophobic.
[0010]
10. Breathable film according to any one of the preceding claims, characterized by the fact that the polymeric curing additive constitutes 1% by weight to 30% by weight, based on the weight of the renewable polyester, and the interphasic modifier constitutes 0 , 1% by weight to 20% by weight based on the weight of the renewable polyester.
[0011]
11. Breathable film according to any one of the preceding claims, characterized by the fact that polepoxide compatibilizer contains an epoxy-functional acrylic monomeric (meta) component.
[0012]
12. Breathable film according to any one of the preceding claims, characterized by the fact that the renewable polyester makes up 70% or more of the weight of the thermoplastic compound.
[0013]
13. Film according to any one of the preceding claims, characterized by the fact that the film is a multilayer film and contains a basic layer and at least one additional layer, where the basic layer contains the thermoplastic compound.
[0014]
14. Absorbent product characterized by the fact that it comprises the film as defined in any one of the preceding claims, the product further comprising an absorbent core positioned between the liquid impermeable film and a liquid permeable layer, in which the film is preferably bonded to a nonwoven weft material.
[0015]
15. Method for forming a breathable film, characterized by the fact that it comprises: the formation of a mixture containing a renewable rigid polyester, such as polylactic acid, a polymeric hardening additive, which includes a polyolefin, at least one interphasic modifier, in that the interphasic modifier is a silicone copolymer, silicone-polyether, aliphatic polyester, aromatic polyester, alkylene glycol, alkane diol, amine oxide, fatty acid ester or a combination thereof, and at least one polypoxide compatibilizer containing, on average, at least two oxirane rings per molecule; where the renewable rigid polyester has a glass transition temperature of 0 ° C or higher; extruding the mixture onto a surface to form a precursor material for the film; e stretch the precursor material of the film to a temperature below the glass transition temperature of the renewable polyester, preferably at a temperature at least 10 ° C below the glass transition temperature of the renewable polyester, to form a breathable film containing several empty areas.

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MX2014009536A|2014-09-04|

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KR20200032755A|2020-03-26|

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AU2013217365B2|2016-03-31|

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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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2020-03-31| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2020-09-29| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2020-12-22| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 28/01/2013, 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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US13/370,943|US20130210621A1|2012-02-10|2012-02-10|Breathable Film Formed from a Renewable Polyester|

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US13/370,943|2012-02-10|

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PCT/IB2013/050732|WO2013118022A1|2012-02-10|2013-01-28|Breathable film formed from a renewable polyester|

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