Creping process on a felt with prolonged production cycle and improved drying

专利摘要:

公开号:ES2627204T9
申请号:ES08743496.5T
申请日:2008-02-20
公开日:2018-02-21
发明作者:Hung Liang Chou；Mark S. Hunter；Kang Chang Yeh
申请人:GPCP IP Holdings LLC；
IPC主号:

专利说明:

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DESCRIPTION
Creping process on a felt with prolonged production cycle and improved drying Technical field
The present invention relates to an improved creping process on a felt for manufacturing absorbent sheets, such as tissue paper or towels. Addition of adhesives to and on a Yankee dryer cylinder is performed at relatively low levels, providing prolonged production cycles between separations of the excess coating of a Yankee dryer cylinder. A heated support cylinder dries the continuous sheet before transferring it to the Yankee dryer reducing the load on it (see WO-A-2007001837).
Background
Creping has been used on a felt in relation to papermaking processes that include mechanical or compactor wear of the continuous sheet of paper as a means of influencing the properties of the product. See U.S. Patents Nos. 4,689,119 and 4,551,199 issued to Weldon, 4,849,054 and 4,834,838 to Klovak and 6,287,426 to Edwards et al. Although in many ways these processes have more potential than conventional papermaking processes in terms of energy consumption and the ability to use recycled fibers, the operation of creping processes on a felt has been hindered by the difficulty of effectively transferring to a dryer. a continuous sheet of paper of high or intermediate consistency. See also U.S. Patent No. 6,350,349 issued to Hermans et al., Which describes wet transferring a continuous sheet of paper from a rotating transfer surface to a felt. Other United States patents related to creping on a felt include the following: 4,834,838, 4,482,429, 4,445,638 and 4,440,597 issued to Wells et al.
More recently, creping processes have been developed on a felt at high speed, as seen in document US-A-2005217814 (US application serial number 10 / 679,862, filed on October 6, 2003, entitled "Fabric - Create Process for Making Absorbent Sheet ”)
The level of adhesion of the continuous sheet of paper to a Yankee dryer cylinder is important because it refers to the transfer of the continuous sheet from a creping felt to the dryer cylinder as well as to the control of the continuous sheet between the dryer and the mandrel on which rolls up a paper reel. Continuous sheets that adhere insufficiently can form blisters or, worse, detach from a drying cylinder and cause a fire in the hood.
In addition, wet tack is critical in creping processes on a felt when insufficient wet tack can cause a transfer failure from a creping felt to a drying cylinder and remains embedded in the felt causing stops and loss of material and Energy.
Furthermore, the level of adhesion of the continuous sheet of paper to the dryer is important because it is related to the drying of the continuous sheet. High levels of adhesion reduce the impedance to heat transfer and cause faster drying of the continuous sheet, allowing a more efficient operation of energy and higher speed, provided that excessive accumulation of adhesive is avoided. However, it should be noted that some accumulation is desirable since the adhesion of the sheet to the dryer occurs mainly by means of creping adhesive deposited in previous passes. The thickness of a coating layer in a Yankee dryer cylinder tends to increase over time, insulating a continuous wet sheet from the Yankee surface to the continuous sheet. In other words, the accumulation of adhesive coating on the surface of the Yankee dryer reduces heat transfer from the surface of the Yankee dryer. To maintain the same level of moisture in the finished product, the temperature of the Yankee dryer hood (and the energy supply to the continuous sheet) is increased accordingly. After a production interval of two hours or so, the temperature of the hood reaches its upper limit and it is necessary to remove the coating layer to reduce the temperature of the hood to a normal operating window. Typically a new cleaning scraper is used to remove the accumulation of old coating.
However, the separation of the coating causes problems of transfer of the sheet in the pressure roller due to the formation of blisters and flotation of the edges. More details can be found in document US-A-2007204966 (provisional US patent application pending processing serial number 60 / 779,614, entitled "Method of Controlling Adhesive Build-Up on a Yankee Dryer", filed on 6 March 2006). Another method of manufacturing a creped absorbent cellulosic sheet on a felt is described, for example, in WO 2007 / 001837A2. This document describes that a continuous sheet is transferred from a creping felt to the surface of a heating cylinder of a Yankee dryer. Then, the dry continuous sheet is separated from the heating cylinder and wound.
The absorbent sheet treated creped on a felt has a length of curvature in the longitudinal direction of approximately 3.5 cm or more, as well as an absorbency of approximately 3 g / g or more. Preferably the sheet is produced without drying with hot air circulation through it or without dry creping and is a low dust product that is especially suitable for automatic towel dispensers.
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Even if the separation operation is performed efficiently, downtimes significantly reduce production.
Initially, the operation of creping processes on a felt at high speed was based, in part, on the belief that the wet tack required for effective transfer from a creping felt to a Yankee dryer cylinder was best achieved with relatively sheets moist and with relatively high levels of creping adhesive, especially with a hygroscopic rewetting adhesive, such as a polyvinyl alcohol resin.
Surprisingly it has been found, in accordance with the present invention, that low levels of creping adhesive are advantageously employed in a Yankee dryer cylinder in a production process with a heated cylinder upstream of the Yankee dryer.
Summary of the Invention
In order to solve the aforementioned problems, the present invention provides a method for manufacturing an absorbent cellulosic sheet creped on a felt and having the characteristics described in claim 1. Other preferred embodiments of said method are defined in the dependent claims.
Adhesive is added to a Ynkee dryer cylinder at relatively low levels and the speed of the Yankee dryer hood temperature increase is maintained below approximately 0.55 ° C / min (1 ° F / min) for the production campaign to manufacture the creped sheet on a felt. Substantial productivity increases, 20% and more are obtained in a commercial papermaking machine, keeping the addition of adhesive low while transferring the sheet to a Yankee dryer.
The process of the present invention provides a pre-dried sheet to a transfer zone located between a creping felt and a Yankee dryer cylinder by means of wet pressing and heating of the continuous sheet before transferring it to the Yankee dryer to dry it further. The process of the invention includes compacting a paper pulp suspension to form a continuous cellulosic sheet and simultaneously applying the continuous sheet to a heated rotating support cylinder. From the support cylinder, the continuous sheet is creped on a felt at a consistency of about 30 to about 60% with a structured creping felt so that the continuous sheet is creped from the surface of the support cylinder and transferred to the felt of curly A composition of a resinous adhesive is applied to the surface of the heated dryer cylinder of the Yankee dryer; Advantageously, this composition is added at a dose of less than 20 mg / m2 of the surface of the drying cylinder so that a coating of the resinous adhesive is formed. The Yankee dryer can have a drying hood with a characteristic operating temperature limit of approximately 454 ° C (850 ° F) or more or less. The continuous sheet is transferred from the creping felt to the surface of the heated drying cylinder of the Yankee dryer and is adhered to the drying cylinder by the coating of the resinous adhesive, after which the continuous sheet dries on the surface of the drying cylinder. The dry continuous sheet is separated from the surface of the drying cylinder, for example, by peeling or creping. Since the adhesive tends to accumulate on the Yankee dryer cylinder, it is cleaned periodically when the characteristic operating temperature limit of the Yankee dryer hood is reached. The composition of the adhesive and the paste suspension are selected and the process parameters are controlled so that a production interval between successive separations of adhesive coatings of the Yankee dryer cylinder has a duration of at least four hours and preferably 5 hours or more
The advantages of the present invention therefore include greater drying capacity and prolonged production cycles, the combination of which significantly increases the amount of production that can be achieved in a papermaking machine.
Greater dryness of the continuous sheet can be achieved before transferring it to the Yankee dryer, for example, by heating the support roller and increasing the pressure in the transfer line to the support roller. When the continuous sheet has a higher solids content, it brings less water to the Yankee dryer. Without pretending to be limited by any particular theory, it is believed that the adhesion to the Yankee dryer is improved because the coating is more concentrated, that is, less diluted by water under conventional conditions. This provides the opportunity to reduce the adhesive added during the process and provides longer production cycles. To increase the dryness of the continuous sheet before the Yankee dryer, it can also be pressed with a shoe press during compacting wear. For example, the load of the shoe press on transfer to the support cylinder can be set at 129.5 kg / cm (725 PLI) and the water vapor pressure contributed to the support cylinder at approximately 6.55-6 , 89 bars (95-100 psig). This produces a relatively high dryness of the continuous sheet before transferring it to the Yankee dryer on the tangency line. The coating added in the Yankee dryer cylinder can be reduced to approximately 15 mg / m2 of the dryer cylinder surface or less and the coating separation cycle can easily be extended to 5 hours or more by making the aforementioned process modifications. A production interval between successive coating separations of 8-10 hours is desirable.
It has been found that the pre-packaged paper fibers provide higher processing speeds and further lengthen the production interval between necessary separation operations. Without pretending to be bound
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By no particular theory, possible explanations include less ionic and less fine wastes that may interfere with adhesion to the Yankee dryer cylinder. It is also believed that the pre-drying of the pulp produces hysteresis of drying in the pulp allowing a more efficient drying of the pulp suspension, thus reducing processing times. That is, it is believed that "disintegrated pastes, with a dryness of less than about 80%, contain relatively large amounts of water firmly bonded in the fibers, which requires more heat to separate it than in the case of commercial pre-dried pasta.
An appropriate selection of the coating composition also facilitates the practice of the process of the invention. A preferred coating composition includes polyvinyl alcohol (PVOH) resin, polyamidoamine adhesive resin and a creping modifier. Preferred coating compositions provide good transfer of the continuous sheet with rapid recovery of the coating after a change of the scraper and allows the coating to be reduced to 15 mg / m2 of dryer surface or less during continuous operation of the machine. paper making Preferably, the coating composition is stable at a temperature of at least about 148.9 ° C (300 ° F) so that this temperature can be maintained during a production campaign.
A synergistic effect was obtained when the aforementioned aspects of the invention were used during the tests. The speed of the machine was increased by 14.2% in the manufacture of towels and the total production was increased by 20% due to the shorter coating recovery time and the longer coating / separation cycle. These advantages of the present invention are appreciated by reference to Figures 1-5, which present operational data of the same papermaking machine operating under the different conditions indicated in the figures. Figure 1 is a graph of the Yankee dryer bell temperature as a function of time for a commercial papermaking machine operating with a hood temperature limit of 454.4 ° C (850 ° F). It is seen that the operation of the machine is kept below
of the hood's temperature limit of 5-6 hours when an adhesive added at a dose of 10 is used
mg / m When the operating temperature limit is reached, the Yankee coating is separated and the operation is continued. When the same papermaking machine operates under similar conditions with double dosing of adhesive, it is seen in Figure 2 that the Yankee coating must be separated every 3 hours or so.
Also, according to the invention, the energy consumption in the Yankee hood is reduced as seen in Figures 3-5. Figure 3 is a graph of gas consumption in the Yankee hood as a function of time for the same papermaking machine and the same production tests discussed above in relation to Figure 1. Figure 3 shows that consumption of energy in the Yankee hood starts at approximately 2110 MJ / ton (2 MMBtu / ton) after separating a coating from the Yankee dryer and increases to approximately 4220 KJ / ton (4 MMBtu / ton) over a period of 5-6 hours . It should also be noted that the energy consumption in the hood is kept below 3165 MJ / ton (3 MMBtu / ton) of continuous leaf produced in 1-2 hours.
Figure 4 is a graph of the energy consumption in the Yankee dryer hood as a function of time for the same papermaking machine operating with a larger dose of added adhesive and a wetter continuous sheet provided to the Yankee dryer. Here it is seen that the energy consumption in the Yankee dryer hood starts between 2638 and 3165 MJ / ton (2.5-3 MMBtu / ton) and increases to approximately 4220 MJ / ton (4 MMBtu / ton) by 2, 5 hours or so. It should be noted that, in Figure 4, the energy consumption in the hood exceeds 3165 KJ / ton (3 MMBtu / ton) of continuous leaf produced almost immediately when the production interval begins. Since the Yankee dryer hood requires a relatively high quality energy source, natural gas, the process of the present invention is much more preferred since water vapor produced with any fuel, including recycled fuels, is used and can be obtained easily in production plants to heat the continuous sheet before transferring it to a Yankee dryer.
Figure 5 is a similar graph for the same papermaking machine operating with an added adhesive dose of 20 mg / m2, with a dried sheet that was used in the tests of Figure 4 (which has a dryness of the sheet in the transfer to the Yankee dryer similar to figure 1). Here it is seen that although there is a benefit of drying the sheet before transferring it to the Yankee dryer, the results are not nearly as good as in the cases where less added adhesive is used.
Details included with respect to Figures 1-5 are described below.
Brief description of the drawings
The invention is described in detail with reference to the drawings, in which equal numbers designate similar parts and in which:
Figure 1 is a graph of temperatures of the Yankee dryer inlet jet as a function of the operating time of a high speed machine for making crepe paper on a felt, in which the continuous sheet was dried in the cylinder creping with high pressure water vapor and the Yankee dryer operated with little adhesive added in accordance with the present invention;
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Figure 2 is a graph of temperatures of the inlet jet to the Yankee dryer hood as a function of time during operation of a high speed machine for making crepe paper on a felt, in which the continuous sheet was steam dried of high-pressure water in the creping cylinder and the Yankee dryer operated twice as much adhesive as compared to the process in Figure 1;
Figure 3 is a graph of gas consumption in the Yankee dryer hood as a function of time for the process of Figure 1;
Figure 4 is a graph of gas consumption in the Yankee dryer hood as a function of time for a process that used twice as much adhesive as in the process of Figure 1 and in which the steam support cylinder was supplied of water at low pressure;
Figure 5 is a graph of gas consumption in the Yankee dryer hood as a function of time for a process that used twice as much adhesive as in the process of Figure 1 and in which the steam support cylinder was provided of high pressure water as in figure 1;
Figure 6 is a schematic diagram of a first papermaking machine, convenient for carrying out the process of the present invention, and
Figure 7 is a schematic diagram of a second papermaking machine, convenient for carrying out the present invention.
Detailed description
The invention is described in detail below with reference to various embodiments and numerous examples. This discussion is for illustrative purposes only.
Here, the terminology used has the meaning consistent with the example definitions specified immediately after; mg refers to milligrams and m2 refers to square meters, MM refers to million, BTU refers to British thermal units, psgi refers to gauge pressure, etc.
The “added” dose of creping adhesive is calculated by dividing the adhesive application dose (mg / min) by the surface of the drying cylinder through which the continuous sheet passes under an injection of a spray applicator (m2 / min). Most preferably, the resin adhesive composition includes a polyvinyl alcohol resin, a polyamidoamine epichlorohydrin resin and a creping modifier. The dose of adhesive added is calculated based on the content of solids or active ingredients, that is, regardless of the water content. Commercial components can be purchased dried or in suspension form and diluted with water to the desired concentration. Likewise, the percentage by weight of the various components of the adhesive resin or of the coating composition was calculated on a dry basis.
Throughout this specification and in the claims, when a nascent continuous sheet is mentioned having an apparently random distribution of fiber orientation, it refers to the distribution of fiber orientation that originates when known forming techniques are used. to deposit a paste suspension on the formation cloth. When examined under a microscope, the fibers appear to be randomly oriented even when, depending on the jet at the speed of the fabric, they may have a significant tendency to be oriented in the longitudinal direction, causing the tensile strength of the Continuous sheet in the longitudinal direction is greater than the tensile strength in the transverse direction.
Unless otherwise specified, "grammage" refers to the weight of a ream of 278.7 square meters (3000 square feet) of product. Consistency refers to the percentage of solids of a nascent continuous sheet calculated, for example, on a dry basis. "Air dry" means that it includes residual moisture, conventionally up to about 10% moisture in the case of pulp and up to about 6% in the case of paper. A nascent continuous leaf that has 50% water and 50% air dry pasta has a consistency of 50%. 95% air dry pasta has a consistency of 85% or more.
The characteristic operating limit of the temperature of a drying hood refers to the maximum temperature of the inlet jet to the Yankee dryer hood, measured in the humid part of the hood, unless otherwise indicated. This may be a limit of the equipment or it may be imposed by operational considerations in the humid part of the hood, for example, so that the product does not burn. Likewise, the Yankee dryer hood temperature and the characteristic operating temperature depend on the temperature of the jet in the humid part of the hood.
Here, the term "compactly degassing the continuous sheet or pulp suspension" refers to mechanically degassing by wet pressing on a stripper felt, for example, in some embodiments using mechanical pressure applied continuously to the surface of the sheet. continues, as in the tangency zone between a press roller and a pressure shoe, in which the continuous sheet is in contact with a felt of the papermaking machine. The term "compact degassing" is used to differentiate processes in which the initial degassing of the continuous sheet is mainly performed by thermal means such as
the case, for example, in United States patents numbers 4,529,480 granted to Trokhan and 5,607,551 granted to Farrington et al. Therefore, compactly stripping a continuous sheet refers, for example, to removing water from a nascent continuous sheet that has a consistency of less than 30% or so by pressure application and / or increasing the consistency of the continuous sheet by approximately 15% or more per 5 pressure application.
The term "cellulosic", "cellulosic sheet" and the like includes any product that incorporates paper fibers as a major constituent. "Paper fibers" include cellulosic fibers of virgin pastes or recycled (secondary) pastes or mixtures of fibers comprising cellulosic fibers. Fibers suitable for manufacturing the continuous sheets of this invention include: fibers from non-woody species, such as cotton fibers or cotton derivatives, abaca, kenaf, sabai grass, flax, esparto, straw, jute, hemp, bagasse, milkweed fibers and pineapple leaf fibers; and fibers from woody species, such as coniferous and leafy, including fibers of coniferous species, such as kraft fibers from northern and southern conifers (United States); fibers from leafy species, such as eucalyptus, maple, birch, poplar, etc. Paper fibers can be released from their source material by any one of a series of bleaching processes familiar to those skilled in the art, including processes to soda, sulfate, bisulphite, polysulfide, etc. If desired, the paste can be bleached by chemical means, including the use of chlorine, chlorine dioxide, oxygen, alkaline peroxides, etc. The products of the present invention may comprise a mixture of conventional fibers (derived from virgin pastes or recycled pastes) and tubular fibers rich in lignin and of high unit weight, such as bleached chemical-thermomechanical paste (BCTMP). "Paste suspension" and similar terms refer to aqueous compositions that include paper fibers, optionally wet strength resins, glues etc. To make paper.
In accordance with the present invention, it has been found that pre-cooked pastes are preferred over disintegrated pastes. When pre-dried pastes are mentioned, this term refers to pastes that have a dryness of at least 80%, that is, they have been dried to a consistency of at least 72% before using them in the pulp suspension contributed to the process. . The “air dry” paste is calculated by the following formula: Consistency 90 x 100%. Commercial pastes having a dry air content of at least 90% or 95% are preferred and can be leafy kraft pastes, coniferous kraft pastes, etc., such as kraft fibers from the North or South of the United States. Convenient pre-packaged commercial pastes may have a GE whiteness of at least 80, 85 or 90; In many cases, convenient pastes can have a GE whiteness between about 85 and 30 95. In some preferred cases, at least 60% of pre-dried pulp is used while in others it is used for
at least 75% pre-dried pasta or more. Recycled paste can be used, as desired.
Creped on a felt and similar terms refer to a felt or tape that has a convenient structure for carrying out the process of the present invention and is preferably permeable enough so that the continuous sheet can be dried while on the creping felt. In cases where the continuous sheet is transferred to another felt or surface (other than creping felt) to dry it, the creping felt may have a lower permeability.
When it is mentioned that an adhesive coating or composition is durable at a specific temperature, it means that the coating or composition does not harden and can be rewetted after it has been heated to that temperature.
40 M / min refers to meters per minute while m / s refers to meters per second.
GE whiteness is measured in accordance with TAPPI T 452 om-02. The TAPPI 452 standard incorporates 45 ° illumination and 0 ° observation geometry.
MD means longitudinal direction and CD means transverse direction.
Tangency parameters include, but are not limited to, tangency pressure, tangency length, hardness of the support roller, felt approach angle, felt removal angle, uniformity and delta velocity between tangency surfaces.
Tangency width means the length over which the tangency surfaces are in contact.
"Wet sticky" generally refers to the ability of an adhesive coating present on a drying cylinder to adhere a continuous wet sheet to the cylinder in order to dry the continuous sheet.
50 "Creping ratio on a felt" is an expression of the velocity differential between the creping felt and the forming fabric and is typically calculated as the ratio of the speed of the continuous sheet immediately before the creping felt and the velocity immediately after creping felt, the formation fabric and the transfer surface at the same speed typically functioning, although not necessarily:
Crepe ratio on a felt = transfer cylinder speed / crepe felt speed
55 The creping on a felt can also be expressed as a percentage calculated as:
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Crepe on a felt (%) = [Crepe ratio on a felt - 1] x 100%
A continuous sheet creped from a transfer cylinder with a surface speed of 228.6 m / min (750 ft / min) to a felt with a speed of 152.4 m / min (500 ft / min) has a ratio of creping of 1.5 and a creping on the felt of 50%. For mandrel creping, the mandrel creping ratio is calculated as the speed of the Yankee dryer cylinder divided by the mandrel speed. To express the mandrel creping as a percentage, 1 is subtracted from the creping ratio in the winder and the result is multiplied by 100%.
The total creping ratio is calculated as the ratio of the velocity of the forming fabric to the mandrel speed and the percentage of total creping is:
Total creping (%) = [Total creping ratio - 1] x 100%
A process with a formation web speed of 609.6 m / min (2000 ft / min) and a mandrel speed of 304.8 m / min (1000 ft / min) has a total creping ratio of 2 and a total creping of 100%.
It is considered a “detached” product of the Yankee dryer cylinder when it has been separated without substantial creping in the coil, under tension. Typically, a detached product has less than 1% creping in the coil.
"Production interval" refers to a period of operation that is stable or almost stable during which absorbent sheet is being produced for consumption between successive cleaning or separation operations, for example, when the material is typically recycled to the process. Preferably, the paper production is maintained at a constant speed ± 20% of the target speed during the production interval.
PLI or pli means force (pounds) per linear inch.
Pusey and Jones (P&J) hardness (indentation) is measured in accordance with ASTM D 531 and refers to the indentation number (sample and standard conditions).
Delta velocity means a difference in linear velocity.
The resin adhesive coating composition used to secure the continuous sheet to the Yankee dryer cylinder is preferably a hygroscopic, rewettable and substantially non-crosslinking composition. Typically, the resin adhesive coating composition includes one or more adhesive resins, a modifier and one or more additives. Examples of adhesive compositions are those that include polyvinyl alcohol and polyamidoamine-epichlorohydrin resins (PAE resins) of the general class described in U.S. Patent No. 4,528,316 issued to Soerens et al. See also U.S. Patent Nos. 5,660,687 and 5,833,806, both granted to Allen et al.
Polyamide adhesive resins for use in the present invention may include polyamide-epihalohydrin resins, such as polyamidoamine-epichlorohydrin (PAE) resins of the same general type employed as wet strength resins. PAE resins are described, for example, in "Wet-Strenght Resins and Their Applications" by H. Epsy, Chapter 2, entitled Alkaline-Curing Polymeric Amine-Epicholorohydrin Resins. PAE resins suitable for use in accordance with the present invention include a water soluble polymer product of the reaction of an epihalohydrin, preferably epichlorohydrin, and a water soluble polyamide having secondary amino groups derived from a polyalkylene polyamine and a dibasic carboxylic acid saturated aliphatic containing about 3 to about 10 carbon atoms. A suitable PAE resin may be one based on diethylenetriamine (DETA), glutaric and / or adipic acid and epichlorohydrin.
PAE resin compositions for use in accordance with the present invention can be obtained from Process Applications Ltd., Washington Crossing, PA, and from Hercules Corporation, Wilmington, Delaware. A particularly convenient PAE creping adhesive resin composition that is useful in connection with the present invention is Ultracrepe® HP. Commercial PAE resin compositions may include other components, such as crosslinking agents, additives, byproducts, etc.
The creping adhesive also preferably includes a semicrystalline polymer that forms a film. The semicrystalline polymers that form a film for use in the present invention can be selected, for example, from hemicellulose and carboxymethylcellulose and. most preferably, they include polyvinyl alcohol (PVOH). The polyvinyl alcohols used in the creping adhesive can have an average molecular weight of about 13,000 to about 124,000 Da.
Polyvinyl alcohol (PVOH) resins may be resins based on vinyl acetate homopolymers or vinyl acetate copolymers with any convenient comonomer and / or mixtures thereof. The PVOH resins used in the present invention are predominantly based (more than 75 mol%) on vinyl acetate monomer that is subsequently polymerized and hydrolyzed to polyvinyl alcohol. In general, the resins are resins of 99 mol% or more of vinyl acetate. If used, the comonomers may be present in amounts of about 0.1 to 25 mol% with vinyl acetate and include acrylic comonomers, such as AMPS or salts thereof. Other convenient comonomers include glycol comonomers, comonomers of
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versate, comonomers of maleic or lactic acid, comonomers of itaconic acid, etc. Also useful may be vinyl versatate which includes alkyl groups (veova). See Finch et al., Ed. Polyvinil Alcohol Developments (Wiley, 1992), pages 84 et seq. The comonomers may be grafted or copolymerized with vinyl acetate as part of the main structure. Likewise, if desired, homopolymers can be mixed with copolymers.
In general, a polyvinyl acetate in an alcohol solution can be converted into polyvinyl alcohol, that is, the -0COCH3 groups are replaced by -OH groups by "hydrolysis", also called "alcoholysis". The degree of hydrolysis refers to the mole percent of the vinyl acetate monomer in the resin that has been hydrolyzed. The methods of producing polyvinyl acetate polymers and copolymers (vinyl alcohol) are well known to those skilled in the art. U.S. Patents Nos. 1,971,951 and 2,109,883, as well as various references in the literature, describe these types of polymers and their preparation. Among the references in the bibliography can be cited "Vinyl Polymerization", Volume 1, Part 1, of Ham, published by Marcel Dekker Inc. (1967) t "Preparative Methods of Polymer Chemistry", by Sorenson and Campbell, published by Interscience Publishers Inc., New York (1961).
Poly (vinyl alcohols) for use in accordance with the present invention include those obtainable from Monsanto Chemical Co. and Celanese Chemical. Suitable polyvinyl alcohols from Monsanto Chemical Co. include Gelvatoles such as, but not limited to, Gelvatol 1-90, Gelvatol 3-60, Gelvatol 20-30, Gelvatol 1-30, Gelvatol 20-90 and Gelvatol 20-60- With respect to the Gelvatoles, the first number indicates the percentage of residual poly (vinyl acetate) and the next number multiplied by 1000 gives the number corresponding to the average molecular weight. In general, polyvinyl alcohol resins or PVOH resins consist mainly of repeating units of hydrolyzed polyvinyl acetate (more than 50 mol%) but may include monomers other than polyvinyl acetate in amounts of up to about 10 mol% or so in typical commercial resins.
Listed below are Celanese Chemical polyvinyl alcohol products for use in creping adhesive (formerly Airvol products of Air Products until October 2000):
Table 1
Poly (vinyl alcohol) for creping adhesive
 Kind  Hydrolysis (%) Viscosity1 (cp) pH Volatile (maximum) (%) Ash (maximum) 3 (%)
 Superhydrolyzed
 Celvol® 125  99.3+ 28-32 5.5-7.5 5 1.2
 Celvol® 165  99.3+ 62-72 5.5-7.5 5 1.2
 Fully hydrolyzed
 Celvol® 103  98.0-98.8 3.5-4.5 5.0-7.0 5 1.2
 Celvol® 305  98.0-98.8 4.5-5.5 5.0-7.0 5 1.2
 Celvol® 107  98.0-98.8 5.5-6.6 5.0-7.0 5 1.2
 Celvol® 310  98.0-98.8 9.0-11.0 5.0-7.0 5 1.2
 Celvol® 325  98.0-98.8 28.0-32.0 5.0-7.0 5 1.2
 Celvol® 350  98.0-98.8 62-72 5.0-7.0 5 1.2
 Intermediate hydrolyzate
 Celvol® 418  91.0-93.0 14.5-19.5 4.5-7.0 5 0.9
 Celvol® 425  95.5-96.5 27-31 4.5-6.5 5 0.9
 Partially hydrolyzed
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 Kind  Hydrolysis (%) Viscosity1 (cp) pH Volatile (maximum) (%) Ash (maximum) 3 (%)
 Celvol® 502  87.0-89.0 3.0-3.7 4.5-6.5 5 0.9
 Celvol® 203  87.0-89.0 3.5-4.5 4.5-6.5 5 0.9
 Celvol® 205  87.0-89.0 5.2-6.2 4.5-6.5 5 0.7
 Celvol® 513  86.0-89.0 13-15 4.5-6.5 5 0.7
 Celvol® 523  87.0-89.0 23-27 4.0-6.0 5 0.5
 Celvol® 540  87.0-89.0 45-55 4.0-6.0 5 0.5
(1) 4% aqueous solution; 20 ° C
The creping modifiers that can be used include quaternary ammonium complexes, polyethylene glycols, etc. The modifiers include those obtainable from Goldschmidt Corporatio, Essen (Germany), or from Process Applications Ltd., Washington Crossing, PA. Goldschmidt creping modifiers include, but are not limited to, Varisoft® 222LM, Varisoft® 222, Varisoft® 110, Varisoft® 222LT, Varisoft® 110DEG and Varisoft® 238. A particularly suitable modifier is Ultra FDA GB, available from Process Applications Ltd.
Preferred resin adhesive coating compositions used in connection with the present invention include a polyvinyl alcohol resin, a PAE resin and a modifier. A suitable PAE resin may be one based on glutaric acid and DETA having a weight average molecular weight (GPC) of 150,000 or more, while the creping modifier may include imidazolinium salts and polyethylene glycols as major components. The resin adhesive resin composition may conveniently include less than 75% by weight of a polyvinyl alcohol resin, conveniently between about 40% and 80% by weight of the resin adhesive coating composition. In some preferred embodiments, the resinous adhesive coating composition includes less than 60% by weight of polyvinyl alcohol resin and, in some embodiments, less than 50% by weight of polyvinyl alcohol resin. Partially hydrolyzed polyvinyl alcohol of relatively high viscosity can be used.
The resin adhesive coating composition also conveniently includes a major portion of polyvinyl alcohol and about 5% to about 35% by weight of a polyamidoamine composition, such as the commercially available compositions mentioned above. Thus, suitable resin adhesive compositions include at least 10-30% by weight of a polyamidoamine composition, such as Ultracrepe® HT, as well as about 2.5 to about 20% or about 30% by weight of a modifier, such as Ultra FDA GB, the rest being Celvaol® 523 polyvinyl alcohol.
In relation to the present invention, an absorbent paper is manufactured by dispersing paper fibers to form an aqueous suspension (suspension) and depositing this aqueous suspension on the forming mesh of a papermaking machine. Any convenient training scheme can be used. For example, an extensive, but not limiting, relationship of trainers includes, in addition to trainers of the Fourdrinier type of machine, a growing former, a two-wrapping fabric C, a two-wrapping machine S, or a forming with head roller. The forming fabric can be any perforated fabric, including single layer fabrics, two layer fabrics, three layer fabrics, photopolymer fabrics, etc. A non-exhaustive list of prior art documents relating to training fabrics includes U.S. Patents Nos. 4,157,276, 4,605,585, 4,161,195, 3,545,705, 3,549,742, 3,858,623, 4,041,989 , 4,071,050, 4,112,982, 4,149,571, 4,182,381, 4,184,519, 4,314,589, 4,359,069, 4,376,455, 4,379,735, 4,453,573, 4,564,052,
4,592,395, 4,611,639, 4,640,741, 4,709,732, 4,759,391, 4,759,976, 4,942,077, 4,967,085, 4,998,568, 5,016,678,
5,054,525, 5,066,532, 5,098,519, 5,103,874, 5,114,777, 5,167,261, 5,199,261, 5,199,467, 5,211,815, 5,219,004,
5,245,025, 5,277,761, 5,328,565 and 5,379,808. A formation fabric particularly useful in the present invention is
Voith 2164 training fabric, manufactured by Voith Fabrics Corporation, Shreveport, LA.
The pulp suspension may contain chemical additives to alter physical properties of the paper produced. These chemical additives are well known to those skilled in the art and can be used in the form of any known combination. These additives may be surface modifiers, softeners, glidants, resistance adjuvants, latices, opacity agents, optical brighteners, dyes, pigments, sizing agents, barrier chemicals, retention aids, insolubilization agents, crosslinking agents organic or inorganic or combinations of these additives, optionally comprising these chemical additives polyols, PPG esters, PEG esters, phospholipids, surfactants, polyamines, HMCP (hydrophobically modified cationic polymers), HMAP (hydrophobically modified anionic polymers), etc.
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The paste can be mixed with resistance adjusting agents, such as wet strength agents, dry strength agents, softeners / softeners, etc. Convenient wet strength agents are well known to those skilled in the art. An extensive, but not limiting, relationship of useful resistance adjuvants includes urea-formaldehyde resins, melanin-formaldehyde resins, glyoxylated polyacrylamide resins, polyamide-epichlorohydrin resins, etc. Thermostable polyacrylamides are produced by reacting acrylamide with diallyl dimethyl ammonium chloride (DADMAC) to produce a cationic polyacrylamide copolymer, which is finally reacted with glyoxal to produce polyacrylamide, a cationic wet strength cross-linking resin. These materials are generally described. in U.S. Patent Nos. 3,556,932 issued to Coscia et al. and 3,556,933 granted to Williams et al. Resins of this type are commercially available under the trade name of Parez 631NC, from Bayer Corporation. Different molar ratios of acrylamide / DADMAC / glyoxal can be used to produce crosslinking resins, which are useful as wet strength agents. In addition, glyoxal can be substituted by other dialdehydes to produce thermosetting wet strength resins. Of particular utility as wet strength resins are polyamide-epichlorohydrin resins, examples of which are Kymene 557LX and Kymene 557H, marketed by Hercules Incorporated, Wilmington, Delawaew, and Amres®, of Georgia-Pacific Resins Inc. these resins and processes for manufacturing them in United States patents numbers 3,700,623 and 3,772,076. An extensive description of polymeric amines-epihalohydrin resins is given in Wet Strenght Resins and Their Application, Chapter 2, Alkaline-Curing Polymeric Amine-Epicholorohydrin, by Espy (L. Chan editor, 1994). A reasonably comprehensive relationship of wet strength resins is described in Westfelt, Cellulose Chemistry and Technology, volume 13, page 813, 1979.
Also suitable agents of temporary wet strength can be included, particularly in applications where disposable towels with permanent wet strength resins should be avoided. A comprehensive, but not exhaustive list of useful agents of temporary wet strength include aliphatic and aromatic aldehydes, including glyoxal, malonic dialdehyde, succinic dialdehyde, glutaraldehyde and dialdehyde starches, as well as substituted or reacted starches, disaccharides, polysaccharides, chitosan or others polymeric reaction products of monomers or polymers having aldehyde groups and, optionally, nitrogen groups. Representative nitrogen polymers that can conveniently react with monomers or polymers containing aldehydes, include vinyl amides, acrylamides and related nitrogen polymers. These polymers impart a positive charge to the reaction product containing aldehydes. In addition, other commercially available agents of temporary wet strength can be used, such as Parez 745, manufactured by Bayer, together with those described, for example, in U.S. Patent No. 4,605,702.
The temporary wet strength resin can be any one of a variety of water soluble organic polymers containing aldehyde units and cationic units, used to increase the dry and wet strength of the paper. These resins are described in U.S. Patent Nos. 4,675,394, 5,240,562, 5,138,002, 5,085,736, 4,981,557, 5,008,344, 4,603,176, 4,983,748, 4,866,151, 4,804. 769 and 5,217,576. Modified starches marketed under the trade names CO-BOND 1000 and CO-BON® 1000 Plus may be used by National Starch and Chemical Company, Bridgewater, N.J. Before use, the water-soluble cationic aldehyde polymer can be prepared by preheating an aqueous suspension of approximately 5% solids maintained at a temperature of approximately 115.6 ° C (240 ° F) and at a pH of approximately 2.7 for approximately 3.5 minutes Finally, the suspension can be cooled and diluted by adding water to produce a mixture of approximately 1.0% solids to less than approximately 54.4 ° C (130 ° F).
Other temporary wet strength agents, also available from National Starch and Chemical Company, are marketed under the trade names CO-BOND® 1600 and CO-BOND® 2300. These starches are supplied in the form of colloidal aqueous dispersions and do not require preheating before of using them
Temporary wet strength agents, such as glyoxylated polyacrylamide, can be used. Temporary wet strength agents such as glyoxylated polyacrylamide resins are produced by reacting acrylamide with diallyldimethylammonium chloride. (DADMAC) to produce a cationic polyacrylamide copolymer, which finally reacts with glyoxal to produce glyoxylated polyacrylamide, a cationic cross-linking resin, of temporary or semi-permanent wet strength. These materials are generally described in U.S. Patent Nos. 3,556,932 issued to Coscia et al. and 3,556,933 granted to Williams et al. Resins of this type are commercially available under the trade names of PAREZ 631NC, from Bayer Industries. Different molar ratios of acrylamide / DADMAC / glyoxal can be used to produce crosslinking resins, which are useful as wet strength agents. In addition, glyoxal can be substituted for other dialdehydes to produce wet strength characteristics.
Convenient wet strength agents include starch, guar gum, polyacrylamides, carboxymethyl cellulose, etc. Of particular utility is carboxymethyl cellulose, of which an example is marketed by Hercules Incorporated, Wilmington, Delaware, under the trade name of Hercules CMC. According to one embodiment, the pulp may contain about 0 to about 7.5 kg of dry strength agent per ton of pulp (0 to about 15 lb / ton). According to another embodiment, the pulp may contain about 0.5 to about 2.5 kg of dry strength agent per ton of pulp (1 to about 5 lb / ton).
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Likewise, suitable sliders are well known to those skilled in the art. The softeners or softeners can be incorporated into the paste or sprayed on the continuous sheet of paper after its formation. The present invention can also be used with softening materials including, but not limited to, the class of amidoamine salts derived from amines partially neutralized by an acid. Such materials are described in U.S. Patent No. 4,720,383. Evans, Chemistry and Industry, July 5, 1969, pages 893-903; Egan, J. Am. Oil Chemist's Soc., Volume 55 (1978), pages 118-121; and Trivedi et al., J. Am. Oil Chemist’s Soc., June 1981, pages 754-756, frequently indicate that softening agents can be purchased commercially only in the form of complex mixtures and not as individual compounds. Although the following discussion will focus on the predominant species, it should be understood that in practice commercially available mixtures are generally used.
Quasoft 202-JR is a convenient softening material, which can be obtained by renting a condensation product of oleic acid and diethylenetriamine. Synthesis conditions using an alkylating agent deficit (eg, diethyl sulfate) and only one alkylation stage, followed by pH adjustment to protonate the non-alkylated species, give rise to a mixture consisting of cationic ethylated species and species cationic non-ethylated. A minor proportion (for example, about 10%) of the resulting amidoamine is cycled to imidazoline compounds. Since only the imidazoline portions of these materials are quaternary ammonium compounds, the compositions as a whole are pH sensitive. Therefore, in the practice of the present invention with this class of chemicals, the pH in the machine head box will be approximately 6 to 8, more preferably 6 to 7 and most preferably 6.5 to 7.
Also suitable are quaternary ammonium compounds, such as quaternary dialkydimethylammonium salts, particularly when the alkyl groups contain about 10 to 24 carbon atoms. These compounds have the advantage of being relatively insensitive to pH.
Biodegradable softening agents can be used. Representative biodegradable cationic softening / softening agents are described in U.S. Patent Nos. 5,312,522, 5,415,737, 5,262,007, 5,264,082 and 5,223,096. The compounds are biodegradable diesters of quaternary ammonium compounds, quaternized amines esters and esters based on biodegradable vegetable oils functionalized with quaternary ammonium chloride and dierucyldimethylammonium chloride and are representative biodegradable softening agents.
In some embodiments, a particularly preferred sliding composition includes a quaternary amine component as well as a non-ionic surfactant.
Typically the nascent continuous sheet of paper is torn down on a felt from the papermaking machine. Any convenient felt can be used. For example, felts may have two-layer fabrics, three-layer fabrics or stratified fabrics. Preferred felts are those with the stratified fabric design. A wet press felt that may be particularly useful in the present invention is Vector 3, manufactured by Voith Fabric. Background documents regarding press felts include U.S. Patents Nos. 5,657,797, 5,368,696, 4,973,512, 5,023,132, 5,225,269, 5,182,164, 5,372,876 and 5,618,612. Likewise, a differential pressing felt such as that described in United States Patent No. 4,533,437 issued to Curran et al.
Convenient creped or textured felts include single-layer or multi-layer felts or composite structures, preferably open mesh. The construction of the felt per se is less important than the topography of the creping surface in the tangency line of creping rollers as will be discussed in more detail below. In some products, long knuckles in the longitudinal direction with slightly smaller knuckles in the transverse direction are generally preferred. Felts must have at least one of the following characteristics: (1) on the face of the creping felt that is in contact with the continuous wet sheet of paper ("upper" side) the number of threads per centimeter in the longitudinal direction ( MD) is 25.4 to 508 (10 to 200 threads per inch (mesh)) and the number of threads per centimeter in the transverse direction (CD) is also 25.4 to 508 (10 to 200 threads per inch (count) ); (2) typically the diameter of the wires is less than 0.127 cm (0.050 in); (3) on the upper face, the distance between the highest point of the knuckles in the longitudinal direction and the highest point of the knuckles in the transverse direction is approximately 0.0025 to approximately 0.051 or 0.076 cm (0.001 to approximately 0 , 02 or 0.03 in); (4) between these levels there may be knuckles formed by threads in the longitudinal direction or in the transverse direction that give the topography of a three-dimensional mountain / valley appearance that is imparted to the continuous sheet of paper; (5) the felt may be oriented in any possible way to achieve the desired effect on the product and the desired properties on the product; long warp knuckles may be on the upper face to increase edges in the product in the longitudinal direction or long knuckles may be on the upper face if more edges in the longitudinal direction are desired to influence creping characteristics when transferred the blade continues from the support cylinder to the creping felt; and (6) the felt can be manufactured to present certain geometric structures that are pleasing to the eye, which are repeated between every 2 to 50 warp threads. A preferred felt is W013, a multilayer felt manufactured by Albany International. Such felts are formed from monofilament polymer fibers having diameters that typically range from about 0.25 to about 1 mm. Such felts are formed from monofilament polymer fibers having diameters that typically range from about 10 to
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approximately 100 mm This felt can be used to produce an absorbent cellulosic continuous sheet having variable local weight and comprising a reticule of paper fibers provided with (i) a plurality of regions enriched with relatively high local weight fibers, which extend in the transverse direction. (CD), interconnected by (ii) a plurality of elongated densified regions of compressed paper fibers, the elongated densified regions having a relatively low local molecular weight and generally oriented along the longitudinal direction (MD) of the continuous sheet. The elongated densified regions are further characterized by an MD / CD orientation ratio of at least 1.5. Typically, the MD / CD orientation ratios of the densified regions are greater than 2 or greater than 3, generally between about 2 and 10. In most cases the fiber-enriched regions have a skewed orientation along the direction. Transversal of the continuous sheet and the densified regions of relatively low weight extend in the longitudinal direction and also have a biased orientation of the fibers along the transverse direction of the continuous sheet. This product is also described in the United States patent application pending processing serial number 60 / 808,863 entitled "Fabric Creped Absorbent Sheet with Variable Local Basis Weight", filed on May 26, 2006 (file number 20179; GP- 06-11).
The creping felt may be of the class described in U.S. Patent No. 5,607,551 issued to Farrington et al., Columns 7-8, as well as the felts described in U.S. Patent Nos. 4,239,065 issued to Trochen and 3,974,025 granted to Ayers. Such felts may have from about 50.1 to about 152.4 meshes per centimeter (20 to about 60 meshes per inch) and are formed from monofilament polymer fibers having diameters that typically range from about 0.020 to about 0.064 cm (0.008 to about 0.025 inches). The weft and warp monofilaments can have, but not necessarily, the same diameter.
In some cases the filaments are woven and complementary in a sinuous manner in at least the Z direction (the thickness of the felt) to provide a first group or set of coplanar crosses in the plane of the upper surface of both sets of filaments; and a second predetermined group or set of crosses below the upper surface The assemblies are intermingled so that portions of the crossings of the upper surface plane define a set of cavities similar to wicker baskets on the upper surface of the felt, cavities that they are arranged to the triplet in the longitudinal direction (MD) and in the transverse direction (CD) and, whereby each cavity covers at least one cross-linking below the upper surface. The cavities are discretely and perimetrically enclosed in the plan view by an alignment similar to posts comprising portions of a plurality of the crossings of the plane of the upper surface. The felt loop may comprise thermoset monofilaments of thermoplastic material; the upper surfaces of the coplanar intersections of the plane of the upper surface may be flat monoplanar surfaces. Specific embodiments of the invention include plain ligaments as well as hybrid ligaments of three or more puffs, and mesh counts of about 4 x 4 to about 47 x 47 per centimeter (10 x 10 to about 120 x 120 filaments per inch). Although the preferred range of mesh counts is about 9 x 8 to about 22 x 19 per centimeter (18 x 16 to about 55 x 48 filaments per inch).
Instead of a printing felt, if desired, a felt felt can be used as a creping felt. Suitable felts are described in U.S. Patent Nos. 5,449,026 (woven style) and 5,690,149 (wire style superimposed in the longitudinal direction) granted to Lee, as well as U.S. Patent No. 4,490 .925 granted to Smith (spiral style).
If a Fourdrinier machine or other type of forming machine is used, the nascent continuous sheet can be conditioned with suction boxes and a stream of water vapor until it reaches a convenient solids content to transfer it to a stripper felt. The nascent continuous sheet can also be transferred to the felt with the help of vacuum. In a growing formator, no vacuum help is needed because the nascent continuous sheet is formed between the forming cloth and the felt.
Fig. 6 is a schematic diagram of a papermaking machine 10 having a conventional two-fabric forming section 12, a felt path 14, a shoe press section 16, a creping felt 18 and a Yankee dryer 20, convenient for carrying out the present invention. The forming section 12 includes a pair of forming fabrics 22, 24 supported by a plurality of rollers 26, 28, 30, 32, 34, 36 and a forming roller 38. An inlet box 40 provides an aqueous pulp suspension leaving it in the form of a jet in the longitudinal direction to the tangency line 42 between the forming roller 38 and the roller 26 and the fabrics. The aqueous pulp suspension forms a nascent continuous sheet 44 which drains onto the fabrics with the aid of vacuum, for example, by means of the suction box 46.
The nascent continuous sheet advances towards the felt 48 which is supported by a plurality of rollers 50, 52, 54, 55 and the felt contacts a shoe press roller 56 having a shoe 62. When the continuous sheet is transferred to the felt It has a low consistency. The transfer can be aided by aspiration; for example, the roller 50 may be an aspirating roller, if so desired, or a pickup or vacuum shoe, as is well known in the art. When the continuous sheet reaches the shoe press roller it can have a consistency of 10-25%, preferably 20 to 25% or so when it enters the tangency line 58 between the shoe press roller 56 and the transfer roller 60. The transfer or support roller 60 is heated with steam of
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Water. It has been found that increasing the pressure of the water vapor provided to the roller 60 helps lengthen the time between the desired separation of the excess adhesive in the Yankee 20 dryer cylinder. The convenient pressure of the water vapor can be approximately 6.55 bar. (95 psig) or so, taking into account that roller 60 is a pumped roller and roller 70 has a negative pumped to engage so that the contact area between the rollers is influenced by the pressure existing in roller 60. Thus, care must be taken to maintain the coupling contact between the rollers 60, 70 when a high pressure is used.
Instead of a shoe press roller, roller 56 may be a conventional aspirating press roller. If a shoe press is used, it is desirable and preferred that the roller 54 be an effective vacuum roller to remove water from the felt before it is in the contact area of the shoe press since the water in the pulp suspension It will be pressed on the felt in the contact area of the shoe press. In any case, using a vacuum roller 54, it is typically desirable to ensure that the continuous sheet remains in contact with the felt during the change of direction, as those skilled in the art can see from the diagram.
The continuous sheet 44 is wet pressed on the felt on the tangency line 58 with the aid of the pressure shoe 62. The continuous sheet thus drains compactly at 58, typically increasing the consistency 15 or more points at this stage of the process. The configuration shown in 58 is generally called a shoe press; in relation to the present invention, the cylinder 60 functions as a transfer cylinder that operates by transporting the continuous sheet 44 at high speed, typically at 304.8-1828.8 m / min (1000 ft / min - 6000 ft / min), towards the creping felt.
The cylinder 60 has a smooth surface 64, which may be provided with adhesive (the same as the creping adhesive using in the Yankee dryer cylinder) and / or release agents if necessary. The continuous sheet 44 adheres to the transfer surface 64 of the cylinder 60 which rotates at a high angular velocity when the continuous sheet advances in the longitudinal direction indicated by arrows 66. On the cylinder, the continuous sheet 44 has an apparent fiber distribution generally random,
Direction 66 is called the longitudinal direction (MD) of the continuous sheet as well as of the papermaking machine 10, while the transverse direction (CD) is the direction in the plane of the continuous sheet perpendicular to the longitudinal direction MD.
Continuous sheet 44 enters the tangency line 58 typically at a consistency of 10-25% or so and drips and dries to consistencies of about 25 to about 70 during the time it is transferred to creping felt 18, such as It is shown in the diagram.
The felt 18 is supported by a plurality of rollers 68, 70, 72 and the contact press roller 74 and forms a contact area 76 creping on the felt with the transfer cylinder 60, as shown.
The creping felt defines a creping contact area in the distance or width in which the creping felt 18 is adapted to contact the roller 60; that is, it applies significant pressure to the continuous sheet against the transfer cylinder. For this purpose, the support roller (or creping) 70 can be provided with a deformable soft surface that will increase the width of the creping area and the creping angle on the felt between the felt and the continuous sheet and can be used as Roller 70 the contact point or a roller of the shoe press to increase effective contact with the continuous sheet in the contact area 76 of creping on the high impact felt when the continuous sheet 44 is transferred to the felt 18 and advances in the longitudinal direction.
The creping contact area 76 extends across the width of the felt creping zone from about 0.3175 cm to about 5.08 cm (1/8 in to about 2 in), typically from 1.27 cm to 5, 08 cm (0.5 in to 2 in). In a creping felt with 32 filaments per centimeter in the transverse direction, the continuous sheet 44 will find about 4 to about 64 warp filaments in the contact area.
The pressure in the contact zone 76, that is, the load between the support roller 70 and the transfer roller 60 is conveniently 3.6-35.7 kg per linear centimeter (20-200 pounds per linear inch (PLI) ), preferably 7.1-12.5 kg per linear centimeter (40-70 pounds per linear inch (PLI)).
After creping on the felt, the sheet continues to advance along the longitudinal direction 66 where it is wet pressed on the cylinder 80 of the Yankee dryer in the contact zone 82. Optionally, vacuum is applied to the continuous sheet by means of a suction box 45.
Transfer in contact zone 82 occurs at a consistency of the continuous sheet generally from about 25 to about 70%. To these consistencies, it is difficult to adhere the continuous sheet to the surface 84 of the cylinder 80 firm enough to completely separate the continuous sheet from the felt. This aspect of the process is important, particularly when it is desired to use a high speed drying hood.
The use of particular adhesives helps to adhere a moderately moist continuous sheet (25-70% consistency) to the Yankee dryer sufficiently to allow high speed system operation and
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drying and subsequent detachment of the Yankee dryer from the continuous sheet by a high velocity blast air jet. In this respect, if necessary, an adhesive composition of polyvinyl alcohol / polyamidoamine is applied to the surface 86, preferably in a proportion less than about 20 mg / m2 of continuous sheet. One or more spray jets can be used.
The continuous sheet is dried on the Yankee 80 dryer cylinder, which is a heated and high-speed air cylinder in the hood 88 of the Yankee dryer. The hood 88 can operate at variable temperature. During operation, the temperature can be monitored at the wet end A of the hood (or at or near the point where the continuous wet sheet enters) and at the dry end B of the hood (or at or near the point by which leaves the continuous wet sheet) using an infrared detector or any other convenient means, if desired. When the cylinder rotates, the continuous blade 44 detaches from the cylinder at 89 and is wound around the mandrel 90. The mandrel 90 can rotate at 1.52-9.14 m / min, preferably 3.05-6.1 m / min (5-30 ft / min, preferably 10-20 ft / min), faster than the Yankee dryer cylinder in steady state when the line speed is, for example, 640.08 m / min (2100 ft / min) A creping scraper C and a cleaning scraper D mounted for intermittent coupling are normally used to control accumulation. When the accumulated adhesive is separated from the cylinder 80 of the Yankee dryer, the continuous sheet is segregated from the product in the mandrel 90, being preferably fed to a 100-percent drop to be recycled to the production process.
Instead of being detached from cylinder 80 at 89 during steady-state operation as shown, the continuous sheet can be creped into dryer cylinder 80 using a creping scraper, such as creping scraper C, if so desired.
In Figure 7, another papermaking machine 10 is shown schematically that can be used in connection with the present invention. The papermaking machine 10 is a three-felt loop machine, which has a forming section 12 generally referred to in the increasing forming technique. The forming section 12 includes a forming wire 22 supported by a plurality of rollers, such as rollers 32, 35. The forming section also includes a forming roller 38 that still supports paper felt 48 so that the continuous sheet 44 it is formed directly on the felt 48 The path 14 of the felt extends to a section of shoe presses 16 in which the continuous wet sheet is deposited on a transfer roller 60 as described above. Then, the continuous sheet 44 is creped on a felt in the tangency line between the rollers 60, 70 before being deposited on the Yankee dryer 20 in another press tangency line 82. Optionally vacuum is applied by the suction layer 45 when The continuous sheet is in the felt to conform the continuous sheet to the textured felt. The input box 40 and the shoe press 62 function as indicated above in relation to Figure 1. In some embodiments, the system includes a return vacuum roller 54; however, the three-loop system can be configured in various ways in which a return roller is not necessary.
Between the Yankee dryer and the mandrel 90 there is a Measurex® control instrument to measure consistency and weight to provide data for feedback control of the papermaking machine. Other details can also be seen in the following pending applications: United States patent application serial number 11 / 151,761, filed on June 14, 2005, entitled "High Solids Fabric Crepe Process for Producing Absorbent Sheet with In -Fabric Drying ”(file 12633; GP-03-35); US patent application serial number 11 / 402,609, filed on April 12, 2006, entitled "Multy-Ply Paper Towel With Absorbent Core" (file number 12601; GP-04-11); US patent application serial number 11 / 451,112, filed on June 12, 2006, entitled "Fabric-Creped Sheet for Dispensers" (file 20195; GP-06-12); provisional US patent application serial number 60 / 808,863, filed on May 26, 2006, entitled "Fabric-creped Absorbent Sheet with Variable Local Basus Weight" (file number 20179; GP-06-11); and United States patent application serial number 10 / 679,862, filed on October 6, 2003, entitled "Fabric-crepe Process for Making Absorbent Sheet" (file number 12389; GP-02-12), applications that describe details particular of papermaking machines, such as creping techniques, equipment and properties; US Patent Application Serial Number 11 / 108,375, filed on April 18, 2005, entitled "Fabric-crepe / Draw Process for Producing Absorbent Sheet" (file 12389P1; GP-02-12-1) also provides more information about processing and composition; US patent application serial number 11 / 108,458, filed on April 18, 2005, entitled "Fabric-crepe and In Fabric Drying Process for Producing Absorbent Sheet" (file number 12611P1; GP-03-33-1 ); and U.S. Patent Application Serial Number 11 / 104,014, filed on April 12, 2005, entitled "Wet-Pressed Tissue and Towel Products With Elevated CD Stretch and Low Tensile Ratios Made With a High Solids Fabric-crepe Process ”(File 12636; GP-04-5); They provide more variation for component selection and processing techniques. Another United States patent application, pending processing, pending processing, serial number 11 / 451,111, filed on June 12, 2006, entitled "Method of Making Fabric-creped Sheet for Dispensers" (file number 20079; Gyp -05-10) provides information on drying and other convenient manufacturing techniques.
Preferably, the methodology employed includes: a) compactly degassing a pulp suspension to form a nascent continuous sheet having an apparently random distribution of paper fibers; b) apply the continuous degassed sheet having an apparently random distribution of fibers to a transferable transfer surface that moves at a first speed; and c) creping on a felt the continuous sheet
from the transfer surface at a consistency of about 30% to about 60%, the creping stage being performed under pressure on the defined tangency line between the creping surface and the creping felt, in which the felt moves to a second speed slower than the speed of said transfer surface, the felt structure being selected, parameters of the tangency line, delta velocity 5 and consistency of the continuous sheet so that the continuous sheet is creped from the transfer surface and it is redistributed on the creping felt to form a continuous sheet with an optionally extensible lattice having a plurality of interconnected regions of different local weights that include at least (i) a plurality of regions enriched in interconnected high local graft fibers by means of (ii) a plurality of optionally elongated densified regions of fi Compressed paper bins, the densified regions 10 having a relatively low local weight and preferably being oriented generally along the longitudinal direction (MD) of the continuous sheet. In a preferred embodiment, elongated densified regions are further characterized by an MD / CD aspect ratio of at least 1.5.
Various characteristics and operational parameters of the present invention are summarized in the following table 2.
Table 2
15 Operating characteristics
 Operational characteristic  Typical range (s) Preferred range (s)
 Adhesive composition added to Yankee dryer cylinder (mg / m2)  5-25; 5-50; <20 <15; <10, 5-15
 Production interval between successive Yankee dryer cylinder liner separations (hours)  5-15> 8
 Average temperature of the air jet inlet to the Yankee dryer hood  <454.4 (<850) 315.6-426.7 (600-800)
 (° C (° F))    optionally up to 454.4 (850)
 Duration temperature limit of the coating composition  115.6-148.9 (240-300) 148.9 (300)
 (° C (° F))
 Final dryness of the continuous sheet  90-99> 95; > 92.5
 (%)
 Creped on felt  2-50 2-20
 (%)
 Creped on the mandrel  0-25 2-15; 2.5-20
 (%)
 Pressing the shoe press to the support roller (kg / cm (PLI))  89.3-144 (500-800)> 107.1 (> 600) 120.5-139.5 (675-775)> 116.1 (> 650)
 Saturated water vapor pressure contributed to the support roller  3.44-10.34 (50-150); > 4.14 (> 60); > 5.17 (> 75); > 6.21 (> 90);
 (bars (psig))  5.51-10.34 (80-150) 6.21-7.59 (90-110)
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 Operational characteristic  Typical range (s) Preferred range (s)
 Saturated water vapor pressure contributed to the Yankee dryer cylinder  5.17-10.34 (75-150) 6.21-8.62 (90-125)
 (bars (psig))
 Production speed  > 609.6 (2000)> 685.8 (2250)
 (m / min (ft / min))    > 762 (2500)
EXAMPLES
Using a papermaking machine of the kind shown in Figures 6 and 7, a series of absorbent base sheet manufacturing tests were performed on a commercial papermaking machine. Typical conditions appear in Table 2 above. Creping adhesive compositions that included commercial compositions of polyamidoamine resins, a commercial polyvinyl alcohol resin and commercial creping modifier compositions were used. Typical compositions of creping resins included 60-70% by weight of polyvinyl alcohol (PVOH), 25-35% by weight of polyaminoamide-epichlorohydrin resin (PAE) and 5-20% by weight of modifier of curly The composition of the selected resin must be effective in transferring the continuous sheet from the creping felt to the Yankee dryer cylinder at the addition levels used. The most outstanding features and results are presented in Figures 1-5.
Figure 1 is a graph of the temperature of the hood as a function of time for three production intervals in a commercial papermaking machine. The machine operated at 746.8 m / min (2450 ft / min) with a dose of creping adhesive added to the Yankee dryer of 10 mg / m2. During these tests 60 relatively high pressure saturated steam (approximately 6.55 bar) (approximately 95 psig) was supplied to the support cylinder to dry the continuous sheet before transferring it to the Yankee dryer. During the various production campaigns shown in Figure 1, it was found that the rate of increase in the temperature of the hood remained relatively low, approximately 0.28 ° C / min (0.5 ° F / min). This allowed the machine to run for six hours or so until the operating temperature limit of the Yankee dryer, approximately 454 ° C (850 ° F), was reached.
Figure 2 is a graph of the temperature of the hood as a function of time for several production intervals on the same machine operating at a slightly lower speed and with a slightly higher dose of adhesive coating added in the Yankee dryer (20 mg / m2) Figure 2 shows that the rate of temperature increase over time is much greater than that seen in Figure 1. The temperature was increased in the various production tests by approximately 0.55 ° C / min (1 ° F / min) and more during the various production intervals shown in Figure 2. In these tests, high pressure steam (6.55 bar) (95 psig) was supplied to the support cylinder 60 and it was possible that the machine will run for three hours or more when said additional heating was provided upstream of the support cylinder, that is, prior to transfer to the Yankee dryer. However, comparing Figures 1 and 2 shows that much better results are achieved with a lower dose of creping adhesive added in the Yankee dryer.
This last point is further illustrated in Figure 3, which is a graph of gas consumption per ton (MMBtu) in the Yankee dryer hood as a function of time for the production tests discussed above in relation to Figure 1. In the Figure 3 shows that gas consumption per ton is quite low at the beginning of a production interval, approximately 2110 MJ / ton (2 MMBtu / ton). In addition, gas consumption per ton in the Yankee dryer hood remains below 3165 MJ / ton (3 MMBtu / ton) for prolonged periods of time during a production interval, generally more than an hour and up to an hour and a half. or two hours in some cases.
Figure 4 is a graph similar to Figure 3, in which the papermaking machine operated at a slightly lower production rate with a dose of creping adhesive coating added in the Yankee dryer of 20 mg / m2. During the tests illustrated in Figure 4, 60 lower pressure steam, approximately 3.79 bar (55 psig), was supplied to the support cylinder. Figure 4 shows that the energy consumption in the Yankee dryer hood is much higher at the start of a production test, typically about 3165 MJ / ton (3 MMBtu / ton) and increases quite rapidly.
Figure 5 is a graph of the gas consumption in the Yankee dryer hood per ton at a production rate similar to that of Figure 4, in which the coating on the Yankee dryer at 20 mg / m2 was also applied. The production tests in Figure 5 differ from those in Figure 4 in that high pressure water vapor of approximately 6.55 bar (approximately 95 psig) was supplied to the heated support cylinder, rather than water vapor of low pressure, approximately 3.79 bar (55 psig). Figure 5 shows that the high pressure of the water vapor or the additional drying before the transfer to the Yankee dryer caused a consumption
minor initial gas in the Yankee dryer hood. Typically, the production tests in Figure 5 initially consumed less than 2638 MJ of energy / ton (2.5 MMBtu / ton) in the hood at the start of a production test. Although Figure 5 shows substantially better results than those of Figure 4, a comparison of Figure 3 with Figure 5 reveals that decreasing the dose of adhesive added in the Yankee dryer 5 and increasing the drying before transfer of the continuous sheet remarkably better results are obtained at the Yankee dryer cylinder.
Although the invention has been described in detail, various mosifications will be apparent to those skilled in the art. In view of the previous discussion, relevant knowledge in the art and references, including the pending processing requests mentioned above in relation to the Background and Detailed Description, further description is deemed unnecessary.

权利要求:
Claims (19)
[1]
5
10
fifteen
twenty
25
30
35
40
Four. Five
1. A method of manufacturing an absorbent cellulosic sheet (44) creped on a felt, comprising
(a) compactly degassing a pulp suspension to form a continuous cellulosic sheet and simultaneously applying the continuous sheet to a heated rotating support cylinder (60);
(b) creping on a felt the continuous sheet from the surface (64) of the heated support cylinder, at a consistency of about 30% to about 60%, using a structured creping felt (18), producing the creping stage under pressure on a creping tangency line (76) defined between the surface (64) of the support cylinder and the creping felt (18), in which the felt travels at a second speed slower than the speed of the surface (64) of said support cylinder, the felt structure being selected, parameters of the tangency line, delta velocity and consistency of the continuous sheet so that the continuous sheet is creped from the surface (64) of the support cylinder and it is transferred to the creping felt (18);
(c) providing a resinous adhesive coating composition to a surface (86) of a heated dryer cylinder (80) of a Yankee dryer (20) so that a resinous adhesive coating is formed, also having the Yankee dryer (20) ) a hood (88) of the dryer with a characteristic operating temperature limit;
(d) transfer the continuous sheet from the creping felt (18) to the surface (86) of the heated dryer cylinder (80) of the Yankee dryer (20) so that the continuous sheet adheres to the dryer cylinder (80) by the resinous adhesive coating;
(e) drying the continuous sheet on the surface of the dryer cylinder (80);
(f) separating the dry continuous sheet from the surface (86) of the drying cylinder; characterized by
(g) periodically separating at least a portion of the resin adhesive coating from the surface (86) of the drying cylinder when the characteristic operating limit of the drying hood temperature (88) of the Yankee dryer (20) is reached;
wherein the composition of the pulp suspension and resinous adhesive coating is selected and the heating of the support cylinder (60) and the drying cylinder (80) is controlled so that a production interval between successive coating separations of The adhesive of the drying cylinder (80) has a duration of at least 4 hours and during which production interval a predetermined target speed of dry leaf production is satisfied.
[2]
2. The method according to claim 1, wherein the added dose of the resinous adhesive coating composition is less than 20 mg / m2 of surface area (86) of the drying cylinder.
[3]
3. The method according to claim 1, wherein the hood (88) of the dryer is configured to provide the continuous sheet on the Yankee dryer cylinder (80) with a drying energy in the form of a hot air stream, having the hood (88) a characteristic operating temperature and a characteristic limit of the operating temperature, and in which the production interval is further characterized in that the average speed of increase of the operating temperature characteristic of the dryer hood in the entire range of Production is less than 0.55 ° C / min (1 ° F / min).
[4]
4. The method according to claim 1, further comprising steps (a) to (g):
(i) preparing an aqueous paper pulp suspension that includes pulp comprising pre-dried paper fibers, which have been dried to at least 80% air-dried pulp before preparing the aqueous suspension;
(ii) deposit the pulp suspension on a perforated support (24, 48).
[5]
5. The method according to claim 2, wherein the production interval between successive adhesive coating separations of the drying cylinder (80) is at least about 7 hours.
[6]
6. The method according to claim 2, wherein the production interval between successive adhesive coating separations of the drying cylinder (80) is at least about 10 hours.
[7]
7. The method according to claim 2, wherein the continuous dry sheet is detached from the surface (86) of the drying cylinder.
[8]
8. The method according to claim 2, wherein the dry sheet production is substantially constant during a production interval between successive adhesive coating separations of the drying cylinder (80).
[9]
9. The method according to claim 3, wherein the average rate of increase of the operating temperature characteristic of the hood (88) of the dryer in the entire production range is less than 0.41 ° C / min
(0.75 ° F / min).
[10]
10. The method according to claim 3, wherein the average rate of increase of the operating temperature characteristic of the hood (88) of the dryer over the entire production range is less than 0.28 ° C / min (0 , 5 ° F / min).
The method according to claim 3, wherein the hood (88) of the energy dryer is provided
drying at a rate less than 3165 MJ / ton (3 MMBtu / ton) for a duration of at least 30 minutes during the production interval.
[12]
12. The method according to claim 3, wherein drying hood is provided to the dryer hood (88) at a rate less than 3165 MJ / ton (3 MMBtu / ton) for a duration of at least 60 minutes
15 during the production interval.
[13]
13. The method according to claim 3, wherein the resin adhesive coating composition provided to the dryer cylinder (80) includes a polyvinyl alcohol resin and a polyamidoamine resin.
[14]
14. The method according to claim 13, wherein the composition of resinous adhesive coating provided to the dryer cylinder includes less than 65% by weight of polyvinyl alcohol resin.
The method according to claim 4, wherein the paste of the aqueous suspension comprises at least
minus 60% by weight of previously dried fibers or in which the paste of the aqueous suspension comprises at least 75% by weight of previously dried fibers.
HOOD TEMPERATURE T (° C)
FIG. one
TEMPERATURES OF THE YANKEE HOOD ENTRANCE JET Depending on the time
DRYER SPEED YANKEE 745 MflMIH (2450ft / min) COVER DOSE ADDED
10mg / m2 (INVENTION)
image 1

HOOD TEMPERATURE ° F TO
FIG. 2
image2
2
10 12 U 1G 18
500-
4

GAS CONSUMPTION PER TONS MMBTU (MJ)
Fifi 3
[4]
4.5- r
Í47 ^ 0)
4- ■■
[4220J
[3]
3.5-
nm
3-- I3UG5)
[2]
2.5 *
mm
2- ■
[2110)
1.5 *
[1583)
1- ■
11055)
0.5-4527.5)
OH ------- t ------- r ------ i --------- 1 -------'-------- r ------'--------- r ------ 1 --------- r ------ * -------- t ------ * --------- r ------> --------- r ------ * -------- -r-
2 4 G 0 10 12 H IB IB
image3

GAS CONSUMPTION BY TON ADA MMBTU (MJ)
fig. 4
image4

GAS CONSUMPTION PER TONS MMBTU (MJ)
Fifi 5
[4]
4.5-
um
(4K0Í
[3]
3.5-
Í3G93]
3-
0165)
[2]
2.5- (2G3GI
■
[2110)
1.5- {1583!
ll
11055 0.5-- 5 7 5] O1
image5
>. IB. III .11
3 li 10min
3h 10min
2h 50min 2h SOmin
t --------'-------- 1 --------'-------- 1 --------'---- ---- 1 -------- 1 -------- 1 --------'-------- r -------- 1 -------- r ~
6 0 10 12 H 1G IB

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同族专利:

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公开号 | 公开日

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HUE032606T4|2018-05-28|

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LT2132380T|2017-07-25|

---

ES2627204T3|2017-07-27|

---

CA2678879C|2015-11-24|

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US7608164B2|2009-10-27|

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EP2132380B9|2017-11-08|

---

SI2132380T1|2017-07-31|

---

HRP20170779T1|2017-10-20|

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CA2678879A1|2008-09-04|

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PL2132380T3|2017-09-29|

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EP2132380B1|2017-04-26|

---

PT2132380T|2017-06-07|

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CY1118942T1|2018-01-10|

---

WO2008106344A1|2008-09-04|

---

DK2132380T5|2018-02-05|

---

DK2132380T3|2017-06-06|

---

HUE032606T2|2017-10-30|

---

US20080264589A1|2008-10-30|

---

EP2132380A1|2009-12-16|

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法律状态:

优先权:

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申请号 | 申请日 | 专利标题

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US90378907P| true| 2007-02-27|2007-02-27|

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