CA1191727A - Soft, strong, absorbent tissue paper and process therefor - Google Patents
Soft, strong, absorbent tissue paper and process thereforInfo
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- CA1191727A CA1191727A CA000412228A CA412228A CA1191727A CA 1191727 A CA1191727 A CA 1191727A CA 000412228 A CA000412228 A CA 000412228A CA 412228 A CA412228 A CA 412228A CA 1191727 A CA1191727 A CA 1191727A
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- web
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Abstract
SOFT, STRONG, ABSORBENT TISSUE
PAPER AND PROCESS THEREFOR
Thomas Ward Osborn III
ABSTRACT OF THE DISCLOSURE
Soft, strong, absorbent tissue paper webs and processes for their manufacture. The webs can be used to form towelling, sanitary tissue, and facial tissue products. The process comprises the steps of forming a papermaking furnish comprising wood pulp fibers and a water-soluble cationic resin, forming an embryonic web from the papermaking furnish as by the use of a Fourdrinier machine, at least partially impregnating the embryonic web with a binder material comprising a polymeric latex having anionic functional groups in the polymer structure, and drying the impregnated embryonic web.
PAPER AND PROCESS THEREFOR
Thomas Ward Osborn III
ABSTRACT OF THE DISCLOSURE
Soft, strong, absorbent tissue paper webs and processes for their manufacture. The webs can be used to form towelling, sanitary tissue, and facial tissue products. The process comprises the steps of forming a papermaking furnish comprising wood pulp fibers and a water-soluble cationic resin, forming an embryonic web from the papermaking furnish as by the use of a Fourdrinier machine, at least partially impregnating the embryonic web with a binder material comprising a polymeric latex having anionic functional groups in the polymer structure, and drying the impregnated embryonic web.
Description
SOFT, STRONG, ABSORBENT TISSUE
PAPER AND PROCESS THEREFOR
Thomas Ward Osborn III
BACKGROUND OF THE II~VENTION
Field of the Invention This invention re.lates to tissue paper webs.
More particularly, it relates to soft, strong, absorbent tissue paper webs which can be used in toweling and sanitary and facial tissue products.
Background Art Paper webs or sheets, sometimes called tissue or paper tissue webs or sheets, find extensive us~
in modern society. Such items as paper towels and facial ~issues are staple items of commerce. It has long been recognized that three important physical attributes of these produets are their softness; their absorbeney, particularly their absorbency for aqueous systems; and their strengkh~
particularly their strength when wet. Research and development efforts have been directed to the improvement of each of these attributes without deleteriously affecting the others as well as to the improvement of two or three attributes simul-taneously.
Softness is the tactile sensation perceived by the consumer as he holds a particular product, rubs it across his skin, or crumples it within his hand. This tactile sensation is a combination of several physical properties. One of the more important physical properties related to softness is generally considered by those skilled in the art to be the stiffness of the sheet of paper ~rom which the product is made.
'72~
Absorbency is the measure of the ability of a product, and of the paper tissue webs from which the product is made, to absorb quantities of liquid, particularly aqueous solutions or dis-persions. Overall absorbency as perceived by thehuman consumer is generally considered to be a combination of the total quantity of liquid a given mass of tissue paper will absorb at saturation as well as the rate at which the mass absorbs the liquid.
Strength is the ability of the product, and its constituent webs, to maintain physical integrity and to resist tearing, bursting, and shredding under use conditions.
One exemplary result of the research directed toward improved paper webs is~described in U.S.
Patent 3,301,746 issued to Sanford and Sisson on January 31, 1967. Despite the high quality of paper webs made by the process described in this patent, and despite the commercial success of products formed from these webs, research efforts directed to finding improved products have con-tinued.
For example, Becker et al. in U.S. Patent 4,158,594 issued January 19, 1979 describe a method they contend will form a strong, soft, fibrous sheet. More specifically, they teach that the strength of a tissue paper web (which may have been softened by the addition of chemical debonding agents) can be enhanced by adhering, during processing, one surface of the web to a creping surface in a fine patterned arrangement by a bonding material, such as an acrylic latex rubber emulsion, a water soluble resin, or an elastomeric bonding material, which has been adhered to one 119~7~ ~
su~face of the web and to the creping surface in the fine patterned arrangement, and creping the web from the creping surface to form a sheet material.
The use of materials such as wet strength resins to enhance the strength of a paper web is widely known. For example, Westfelt described a number of such materials and discussed their chemistry in Cellulose Chemistry And Technology, Volume 13, at pages 813-825 (1979~.
Then, too, Friedman in U.S. Patent 4,277,529 issued July 7, 1981, purports to disclose a bonded, light weight tissue paper having improved strength and excellent softness and absorbency.
The paper is produced by a process which comprises applying a binder containing a cross-linkable ~ latex to the drie~ web.
DISCLOSURE OF THE INVENTION
Summary of the Invention The present invention is a process for pro-ducing tissue paper webs having improved softness, strength, and absorbency and the web so produced.
Briefly, the process comprises the steps of forming a papermaking furnish and making from that furnish a patterned densified fibrous web having a relatively high bulk field of relatively low fiber density and a patterned array of spaced zones of relatively high fiber density at least a sub-stantial proportion of which are at least partially impregnated with binder material. The papermaking furnish comprises an aqueous slurry of papermaking fibers and at least one water-soluble cationic resin. The binder material comprises at least one ~ 7 latex polymer having anionic functional groups in the polymer backbone. The web comprises paper-makîng fibers, cationic resin, and binder.
Accordingly, it is an object of this in-S vention to provide a process for making soft,strong, absorbent tissue paper webs.
It is a further object of this invention to provide soft, strong, absorbent tissue paper sheets.
It is a still further object of this invention to provide soft, strong, absorbent paper towel products.
These and other objects will become readily apparent from a reading of the following detailed description of the invention.
Detailed Description of the Invention Inhile this specification concludes with claims particularly pointing out and distinctly claiming the subject matter regarded as the invention, it is believed that the invention can be better understood from a reading of the fol-lowing detailed description and of the appended examples.
As used herein, the terms "tissue paper web", "paper web", "web", and "paper sheet" all refer to sheets of paper made by a process comprising the steps of forming an aqueous papermaking furnish;
depositing this furnish on a foraminous surface, such as a Fourdrinier wire; and removing the water from the furnish, as by gravity or vacuum-assisted drainage, with or without pressing, and by evapora-tion. As discussed fully hereinafter, the furnish comprises an aqueous slurry of papermaking fibers and at least one water-soluble cationic resin.
Further, the resulting web preferably has a relatively high bulk field of relatively low fiber density and a patterned array of spaced zones of relatively high fiber density at least a S subs~antial proportion of which have been at least partially impregnated with binder material.
The binder material is a latex as described more fully hereinafter. The resulting web exhibits softness, absorbency, and strength greater than that produced by use of the cationic resin alone or by the latex binder material alone. The strength of the resulting web is ~lso greater than that that would be expected from a knowledge of the strength impro~ements provided by the resin alone and the binder material alone.
As used herein, "papermaking furnish" is an aqueous slurry of paper~aking ibers and chemicals as desc~ibed hereinafter.
The firs~ step in the process of this in-vention is the forming of an aqueous papermaking furnish. This furnish comprises papermaking fibers, (hereinafter sometimes reerred to as wood pulp) and at least one water-soluble cationic resin as hereinafter described.
It is anticipated that wood pulp in all its varieties will normally comprise the papermaking fibers used in this invention. However, other cellulosic fibrous pulps, such as cotton liners, bagasse, rayon, etc., can be used and none are disclaimed. Wood pulps useful herein include both sulphite and sulfate pulps as well as mechanical and thermomechanical pulps all well known to B those skilled in the art. Pulps derived from both deciduous and coniferous trees can be used.
Preferably, the papermaking fibers used in this invention comprise Kraft pulp derived from northern softwoods.
The water-soluble cationic resins used in this invention can be of several types. In general, resins which have previously found utility in papermaking as wet strength resins are useful herein. It is to be understood that the cationic resins are water-soluble at the time they are added to the papermaking furnish. It is quite possible, and even to be expected, that subsequent events such as cross-linking will render the resins in-soluble in water. Further, the cationic resins can be soluble only under specific conditions, such as in a limited pH range, and still be water-soluble as that term is used herein. --Of particular utility are the various poly-amide-epichlorohydrin resins. These materials are low molecular weight polymers provided with reactivP
functional groups such as amino, epoxy, and azetidinium groupsO The patent literature is reple~te with descriptions of processes for making such materials. U.S. Patent 3,700,623 issued to Keim on October 24, 1972 and U.S. Patent 3,772,076 issued to Keim on ~ovember 13, 1973 are examples of such paten~s.
Polyamide-epichlorohydrin resins sold under the trademarks"KYmene 557H" and "xymene 2064" by , Hercules Incorporated of Wilmington, Delaware, are particularly useful in this invention. These resins are generally described in the aforementioned patents to Keim.
31'~ 7 Base~activated polyamide-epichlorohydrin resins useful in the present invention are sold under the~santo Res" trademark, such as "santo Res 31, by Monsanto Company, St. Louis, Missouri. These types of materials are generally described in U.S.
Patents 3,855,15~ issued to Petrovich on December 17, 1974; 3,899,388 issued to Petrovich on August 12, 1975; 4,129,528 issued to Petrovich on December 12, 1978; 4,147,586 issued to Petrovich on April 3, 1979; and 4,222,921 issued to Van Een~m on September 16, 1980.
Other water-soluble cationic resins useful herein are the polyacrylamide resins such as those sold under the"Parez"trademark, such as"ParPz 631NC, by American Cyanamid Company of Stanford, Conn. These materials are generally described in ~ U.S. Patents 3,556,932 issued to Coscia et al on January 19, 1971; and 3,5569933 issued to Williams et al on January 19, 1971.
Still other water-soluble cationic resins finding utility in this invention are the urea formaldehyde and melamine formaldehyde resins.
These polyfunctional, reactive polymers have molecular weights on the order of a few thousand.
The more common functional groups include nitrogen containing groups such as amino groups and methylol groups attached to nitrogen.
Although less preferred, polyethylenimine type resins find utility in the present invention.
3~ More complete descriptions of the afore-mentioned water-soluble cationic resins, including their manufacture, can be found in TAPPI monograph P~j .~L'3 ~7'~7 series No. 29, Wet Strength In ~e~ and ~perboard, Technical Association of the Pulp and Paper Industry (New York; 1965) It is anticipated that this invention will find its primary utility in the field of toweling, facial tissue, and similar products requiring wet strength properties. The water-soluble cationic resin has accordingly been described as a wet strength resin. The present invention also finds utility in products such as sanitary tissues where wet strength is not required, but where dry strength is a positive attribute. When use in this type of product is contemplated, the water-soluble cationic resin can be any of the various dry strength resins commonly used in papermaking. For example, products sold under the 'lAccostrengthll trademark by American Cyanamid Company can be used herein. "Accostrength 98" ,T for example, is described , as being a normally water-insoluble polysalt coacervate rendered water-soluble by the inclusion of an ionization suppressor and is useful herein.
~U.S. Patent 3,660,338 issued to Economou on May2, 1972, describes such materials mor ~ully.) These dry strength resins can be used on ~he same basis as the wet strength resins.
The papermaking furnish can be readily formed or prepared by mixing techniques and equipment well known to those skilled in the papermaking art.
In its broadest aspect, the next stage in the process of this invention is the formation of an embryonic web from the papermaking furnish. This embryonic web is then at least partially impregnated with binder material (preferably in discrete, spaced . ~, .
4'7 .
_ 9 _ apart zones) and then dried to form the web of this invention.
It has been surprisin~ly discovered that the following described unique, preferred papermaking process is particularly useful for making a tissue paper web of such strength as to be use~ul in a wide variety of soft, strong, absorbent products.
The tissue paper web in which the present in-vention preferably finds utility is a pattern densified fibrous web having a relatively high bulk field of relatively low fiber density and a patterned array of spaced zones of relatively high fiber density. At least a substantial proportion of the relatively high density spaced zones are at least partially impregnated with binder material.
The high bulk field is preferably substantially uncompacted and devoid of binder material.
- Accordingly, the second step in the preferred embodiment of the process of this invention com-prises the forming from the papermaking furnish a patterned densified embryonic web ha~ing a multi-plicity of discrete zones of relatively high density disposed in a predeiermined pattern array.
The third step of the preferred comprises supporting the embryonic web on an array of spaced supports so that each of a predetermined sub-array of the high density zones is juxtaposed one of a corresponding sub-array of the supports.
The array of spaced supports can be the knuckles of an endless imprinting carrier fabric and the sub-array of such supports can be only t~e top-sur-face-plane knuckles of the fabric in fabrics having both top-surface-plane knuckles and sub-top-surface 7~
knuckles. In fabrics having no sub-top-surface knuckles, the sub-array of supports would, in fact, be the array of supports.
The ourth step of the preferred process is at least partially impregnating at least a substantial proportion of the supported predetermined sub-array of high density zones with a binder material by biasing the predetermined sub-array of supports toward a contacting type impregnating means with the sub-array of the high density zones disposed between ~he sub-array of the supports a~d ~he impregnating means. ~or maximum strengt~, all of the high density zones should be impregnated with binder material. Only a portion of the high density zones need be partially impregnated in webs wherein such partial impregnation provides sufficient strength for their intended use.
Impregnating means such as a full field gravure applicator can be used to impregnate the high density zones of the webs biased against it whereas less-than-full-field gravure applicators can be used to only partially im~regnate all or some of the high density zones o the web, or wholly impregnate only some of the high density zones. The impregnation accomplished in this fourth step must be accomplished before the embryonic web is substantially dried. As used herein, the embryonic web is not substantially dried if it contains at least about 25% moisture.
(Unless otherwise specified, all percentages in this specification are weight percentages.) The la~ices used herein are aqueous emulsions of synthe~ic rubbers or plastics obtained by poly-~ '7~';' meriza~ion, They can be, but need not be, curableas by cross-linking. The polymer struc~ure must contain anionic functional groups which provide an anionic character to the latex. Examples of suitable functional groups include carboxyl, sulfonate, phosphonate and hydroxyl groups. Carboxyl groups are preferred~ These functional groups are sometimes said to be present in the polymer "backbone". Further, the polymer structure can contain more ~han one ~ype of anionic functional group.
Recent developments in latex chemistry have resulted in the creatio~ of latices which are considered to be`cationic, but which contain normally anionic functional g~oups such as carboxyl groups within the polymer structure; such latices are suitable for use in the present invention.
Latices containing functional ~roups as described above can be produced by methods well known to those skilled in the art. For example, acrylic, methacrylic, fumaric or itaconic acid can be reacted with styrene and butadiene ~n con~enticnal processes to form styrene-butadiene rubber ha~ing carboxyl groups in the polymer strueture. Those same acids can be reacted with ac~ylic monomer~
to make acrylic latices having carboxyl functional groups in the polymer structure. ThesP ~inyl acids can also be reacted with Pthylene ~in~l acetate to make functiollal-group containing Latices.
Specific examples of latices useful in the present invention include"Rhoplex TR-520"and "Rhoplex TR-90~", acrylic emulsion polymers made by Rohm and Haas Company of Philadelphia, Pennsylvania. The former is based on ethyl acrylate and the latter on ethyl acrylate and butyl acrylate; Both contain carboxyl groups in the polymer structure. Mixtures of these two latices can also be used.
*Trademark **Trademark '7 Other sui~able latices are the carboxylated styrene/butadiene copolymer supplied under the designation XD~30295. 00 and the carboxylated ctyrene-butadiene-butyl acrylate terpolymer supplied under the designation XD 30221.02 by The Dow Chemical Company of Midland, Michigan.
Mixtures of latices can be used in the present invention.
The latex emulsion preferably has a viscosity of less th2n 100 centipoise, most preferably less than 30 centipoise.
The fifth step of the pref~rred process com-prises drying the embryonic web to fo~m a paper web. Techniques and equipment ~ell known to those skilled in the art can be used in this step. -Further, the process can comprise an optionalstep of subjecting the impregnated zones to addi-tional mechanical pressure or compaction after they are impregnated to increase binder pene-tration and interfiber bonding thereL~.
Still urther, the p~ocess can include an optional and preferred drying step immediately preceding the impregnating s~ep wherein the ~5 embryonic web is dried in the absence of substantial mechanical compression to an average moisture content of from about 25 to about 80% by weight of the embryonic we~. Preferably, this drying step is sufficiently asymmetrical to dry the unsupported portions of the embryonic ~eb substan-tially more than the high density portions.
Preferably, the web is creped, calendered and reeled after being dried to ~urther increase its stretch, bulk and softness, and to control its caliper.
~L~9~727 ~ le amount of binde~ impregnated into the embryonic web is preferably from about 2Z to abou~ 30% by weight of the papermaking fiber although it is not intended to limit the present invention to this range o binder level.
It is to be noted that in this embodiment of the invention, the soft, strong, absorbent tissue paper web of papermaking fibers comprises a multiplicity of relati~ely high density zones impregna~ed with a binder material interposed between and among a plurality of usually vaulted or arcuate shaped relatively low density spa~
portions which are substantially unco~pacted and devoid of binder material. Water-soluble cationic resin is, in general, distributed throughout the web and is present in both the.high denslty and low density zones.
The process for making the pa~tern densified fibrous web described above is described in more detail in European Patent Application 81200093.5 filed on behalf o the inventors P. G. Ayers and J. M. Raley on January 26, 1981 and published~
August 19, 1981, Optionally, the papermaking furnish can comprise materials such as chemical debonders which enhance the softness of the resulting ~issue paper web by reducing the interfibes bonding therein. Of particular use herein is the debonder combination comprising at leas~ one quaternary ammonium compound and at least one nonionic surfactant. The preferred quaternary ammonium compounds are selected rom the group consisting of quaternary ammonium com~ounds having the structure ., .
~3~
CH3 +
CH3 - N - CH3 X , and _ R
quaternary ammonium compounds having the structur~, lo ~ fH3 +
~ H(OCH2CH2~m - I - (CH2CH~O~n X .
R
In the two structures noted above R is an aliphatic hydrocarbon radical selected from the group con-sisting of alkyl having from ~about 12 to about 18 carbon atoms, alkylene having from about 12 to about 18 carbon atoms, coconut and tallow; m and n are both integers each having a value of at least 1; the sum of m and n is from about 2 to about 15;
and X is a halogen.
As used in this context, '~coconut" refers to the alkyl and alkylene moieties derived from coconut oil and from the synthetic mixtures designed to re-semble natural coconut oil. As used in this context, "tallow" refers to the alkyl and alkylene moieties derived from tallow and from the synthetic mixtures designed to resemble natural tallow.
Preferably, the alkyl and alkylene radicals have from about 15 to about 18 carbon atoms.
Alkylenes are ~enerally preferred to alkyls. Coconut is more preferred than the alkyl and alkylene radicals just described.
In the case of the methylpolyoxyethylene quaternary ammonium compounds, the sum of m and n is preferably about 2.
Any of the halide salts can be used. Typically, and preferably, the chloride is used.
Specific examples of quaternary ammonium salts useful in this invention include trimethyloctadecyl-ammonium chloride, trimethylcocoammonium chloride, trimethyltallowammonium chloride, trimethylolelyl-ammoniu~ chloride, methylbis(2-hydroxyethyl)coco-ammonium chloride, methylbis(2-hydroxyethyl)oleyl-ammonium chloride, methylbis(2-hydroxyethyl)octadecyl-ammonium chloride, methylbis(2-hydroxyethyl)tallow-amTnonium chloride, methylpolyoxyethylene(l5)coco-ammonium chloride, and methylpolyoxyethylene(l5)olyl-ammonium chloride.
The most preferred quaternary ammonium com-pound is methylbis(2-hydroxyethyl)cocoammonium chloride.
The quaternary ammonium salt is added to the papermaking furnish at a level of from about 0.5 to about 5.0 grams per kilogram of bone dry papermaking fiber. Preferably 7 it is added at from about 1.0 to about 2.5 grams per kilogram.
Nonionic surfactants useful in the present invention include the ether and ester adducts of ethylene oxide and fatty chemicals. That is to say, the nonionic surfactants useful herein can be described as the ethylene oxide adducts of, re-spectively, fatty alcohols and fatty acids. The fatty moiety of the nonionic surfactant should comprise from about 12 to about 18 carbon atoms.
The ethylene oxide moiety of the nonionic sur factant should comprise from about 2 to about 12 moles ethylene oxide, preferably from about 2 to about 9 moles. Preferably, the fatty moiety is unsaturated. Specific examples of nonionic sur-factants useful in the present invention include polyoxyethylene(2)oleyl ether and polyoxvethylene-~t~
(9)oleyl ester. The former is known in CFTA
nomenclature as Oleth-2, the latter as PEG-9 oleate.
Dieste~s, such as PEG-4 dilaurate (two moles S of lauric acid adducted with 4 moles of ethylene - oxide~, are also useful in the present invention.
The nonionic surfactant is present in the papermaking furnish at a level of from about 0.5 to about 5.0 grams per kilogram bone dry paper-making fiber, preferably from about 1.0 to about
PAPER AND PROCESS THEREFOR
Thomas Ward Osborn III
BACKGROUND OF THE II~VENTION
Field of the Invention This invention re.lates to tissue paper webs.
More particularly, it relates to soft, strong, absorbent tissue paper webs which can be used in toweling and sanitary and facial tissue products.
Background Art Paper webs or sheets, sometimes called tissue or paper tissue webs or sheets, find extensive us~
in modern society. Such items as paper towels and facial ~issues are staple items of commerce. It has long been recognized that three important physical attributes of these produets are their softness; their absorbeney, particularly their absorbency for aqueous systems; and their strengkh~
particularly their strength when wet. Research and development efforts have been directed to the improvement of each of these attributes without deleteriously affecting the others as well as to the improvement of two or three attributes simul-taneously.
Softness is the tactile sensation perceived by the consumer as he holds a particular product, rubs it across his skin, or crumples it within his hand. This tactile sensation is a combination of several physical properties. One of the more important physical properties related to softness is generally considered by those skilled in the art to be the stiffness of the sheet of paper ~rom which the product is made.
'72~
Absorbency is the measure of the ability of a product, and of the paper tissue webs from which the product is made, to absorb quantities of liquid, particularly aqueous solutions or dis-persions. Overall absorbency as perceived by thehuman consumer is generally considered to be a combination of the total quantity of liquid a given mass of tissue paper will absorb at saturation as well as the rate at which the mass absorbs the liquid.
Strength is the ability of the product, and its constituent webs, to maintain physical integrity and to resist tearing, bursting, and shredding under use conditions.
One exemplary result of the research directed toward improved paper webs is~described in U.S.
Patent 3,301,746 issued to Sanford and Sisson on January 31, 1967. Despite the high quality of paper webs made by the process described in this patent, and despite the commercial success of products formed from these webs, research efforts directed to finding improved products have con-tinued.
For example, Becker et al. in U.S. Patent 4,158,594 issued January 19, 1979 describe a method they contend will form a strong, soft, fibrous sheet. More specifically, they teach that the strength of a tissue paper web (which may have been softened by the addition of chemical debonding agents) can be enhanced by adhering, during processing, one surface of the web to a creping surface in a fine patterned arrangement by a bonding material, such as an acrylic latex rubber emulsion, a water soluble resin, or an elastomeric bonding material, which has been adhered to one 119~7~ ~
su~face of the web and to the creping surface in the fine patterned arrangement, and creping the web from the creping surface to form a sheet material.
The use of materials such as wet strength resins to enhance the strength of a paper web is widely known. For example, Westfelt described a number of such materials and discussed their chemistry in Cellulose Chemistry And Technology, Volume 13, at pages 813-825 (1979~.
Then, too, Friedman in U.S. Patent 4,277,529 issued July 7, 1981, purports to disclose a bonded, light weight tissue paper having improved strength and excellent softness and absorbency.
The paper is produced by a process which comprises applying a binder containing a cross-linkable ~ latex to the drie~ web.
DISCLOSURE OF THE INVENTION
Summary of the Invention The present invention is a process for pro-ducing tissue paper webs having improved softness, strength, and absorbency and the web so produced.
Briefly, the process comprises the steps of forming a papermaking furnish and making from that furnish a patterned densified fibrous web having a relatively high bulk field of relatively low fiber density and a patterned array of spaced zones of relatively high fiber density at least a sub-stantial proportion of which are at least partially impregnated with binder material. The papermaking furnish comprises an aqueous slurry of papermaking fibers and at least one water-soluble cationic resin. The binder material comprises at least one ~ 7 latex polymer having anionic functional groups in the polymer backbone. The web comprises paper-makîng fibers, cationic resin, and binder.
Accordingly, it is an object of this in-S vention to provide a process for making soft,strong, absorbent tissue paper webs.
It is a further object of this invention to provide soft, strong, absorbent tissue paper sheets.
It is a still further object of this invention to provide soft, strong, absorbent paper towel products.
These and other objects will become readily apparent from a reading of the following detailed description of the invention.
Detailed Description of the Invention Inhile this specification concludes with claims particularly pointing out and distinctly claiming the subject matter regarded as the invention, it is believed that the invention can be better understood from a reading of the fol-lowing detailed description and of the appended examples.
As used herein, the terms "tissue paper web", "paper web", "web", and "paper sheet" all refer to sheets of paper made by a process comprising the steps of forming an aqueous papermaking furnish;
depositing this furnish on a foraminous surface, such as a Fourdrinier wire; and removing the water from the furnish, as by gravity or vacuum-assisted drainage, with or without pressing, and by evapora-tion. As discussed fully hereinafter, the furnish comprises an aqueous slurry of papermaking fibers and at least one water-soluble cationic resin.
Further, the resulting web preferably has a relatively high bulk field of relatively low fiber density and a patterned array of spaced zones of relatively high fiber density at least a S subs~antial proportion of which have been at least partially impregnated with binder material.
The binder material is a latex as described more fully hereinafter. The resulting web exhibits softness, absorbency, and strength greater than that produced by use of the cationic resin alone or by the latex binder material alone. The strength of the resulting web is ~lso greater than that that would be expected from a knowledge of the strength impro~ements provided by the resin alone and the binder material alone.
As used herein, "papermaking furnish" is an aqueous slurry of paper~aking ibers and chemicals as desc~ibed hereinafter.
The firs~ step in the process of this in-vention is the forming of an aqueous papermaking furnish. This furnish comprises papermaking fibers, (hereinafter sometimes reerred to as wood pulp) and at least one water-soluble cationic resin as hereinafter described.
It is anticipated that wood pulp in all its varieties will normally comprise the papermaking fibers used in this invention. However, other cellulosic fibrous pulps, such as cotton liners, bagasse, rayon, etc., can be used and none are disclaimed. Wood pulps useful herein include both sulphite and sulfate pulps as well as mechanical and thermomechanical pulps all well known to B those skilled in the art. Pulps derived from both deciduous and coniferous trees can be used.
Preferably, the papermaking fibers used in this invention comprise Kraft pulp derived from northern softwoods.
The water-soluble cationic resins used in this invention can be of several types. In general, resins which have previously found utility in papermaking as wet strength resins are useful herein. It is to be understood that the cationic resins are water-soluble at the time they are added to the papermaking furnish. It is quite possible, and even to be expected, that subsequent events such as cross-linking will render the resins in-soluble in water. Further, the cationic resins can be soluble only under specific conditions, such as in a limited pH range, and still be water-soluble as that term is used herein. --Of particular utility are the various poly-amide-epichlorohydrin resins. These materials are low molecular weight polymers provided with reactivP
functional groups such as amino, epoxy, and azetidinium groupsO The patent literature is reple~te with descriptions of processes for making such materials. U.S. Patent 3,700,623 issued to Keim on October 24, 1972 and U.S. Patent 3,772,076 issued to Keim on ~ovember 13, 1973 are examples of such paten~s.
Polyamide-epichlorohydrin resins sold under the trademarks"KYmene 557H" and "xymene 2064" by , Hercules Incorporated of Wilmington, Delaware, are particularly useful in this invention. These resins are generally described in the aforementioned patents to Keim.
31'~ 7 Base~activated polyamide-epichlorohydrin resins useful in the present invention are sold under the~santo Res" trademark, such as "santo Res 31, by Monsanto Company, St. Louis, Missouri. These types of materials are generally described in U.S.
Patents 3,855,15~ issued to Petrovich on December 17, 1974; 3,899,388 issued to Petrovich on August 12, 1975; 4,129,528 issued to Petrovich on December 12, 1978; 4,147,586 issued to Petrovich on April 3, 1979; and 4,222,921 issued to Van Een~m on September 16, 1980.
Other water-soluble cationic resins useful herein are the polyacrylamide resins such as those sold under the"Parez"trademark, such as"ParPz 631NC, by American Cyanamid Company of Stanford, Conn. These materials are generally described in ~ U.S. Patents 3,556,932 issued to Coscia et al on January 19, 1971; and 3,5569933 issued to Williams et al on January 19, 1971.
Still other water-soluble cationic resins finding utility in this invention are the urea formaldehyde and melamine formaldehyde resins.
These polyfunctional, reactive polymers have molecular weights on the order of a few thousand.
The more common functional groups include nitrogen containing groups such as amino groups and methylol groups attached to nitrogen.
Although less preferred, polyethylenimine type resins find utility in the present invention.
3~ More complete descriptions of the afore-mentioned water-soluble cationic resins, including their manufacture, can be found in TAPPI monograph P~j .~L'3 ~7'~7 series No. 29, Wet Strength In ~e~ and ~perboard, Technical Association of the Pulp and Paper Industry (New York; 1965) It is anticipated that this invention will find its primary utility in the field of toweling, facial tissue, and similar products requiring wet strength properties. The water-soluble cationic resin has accordingly been described as a wet strength resin. The present invention also finds utility in products such as sanitary tissues where wet strength is not required, but where dry strength is a positive attribute. When use in this type of product is contemplated, the water-soluble cationic resin can be any of the various dry strength resins commonly used in papermaking. For example, products sold under the 'lAccostrengthll trademark by American Cyanamid Company can be used herein. "Accostrength 98" ,T for example, is described , as being a normally water-insoluble polysalt coacervate rendered water-soluble by the inclusion of an ionization suppressor and is useful herein.
~U.S. Patent 3,660,338 issued to Economou on May2, 1972, describes such materials mor ~ully.) These dry strength resins can be used on ~he same basis as the wet strength resins.
The papermaking furnish can be readily formed or prepared by mixing techniques and equipment well known to those skilled in the papermaking art.
In its broadest aspect, the next stage in the process of this invention is the formation of an embryonic web from the papermaking furnish. This embryonic web is then at least partially impregnated with binder material (preferably in discrete, spaced . ~, .
4'7 .
_ 9 _ apart zones) and then dried to form the web of this invention.
It has been surprisin~ly discovered that the following described unique, preferred papermaking process is particularly useful for making a tissue paper web of such strength as to be use~ul in a wide variety of soft, strong, absorbent products.
The tissue paper web in which the present in-vention preferably finds utility is a pattern densified fibrous web having a relatively high bulk field of relatively low fiber density and a patterned array of spaced zones of relatively high fiber density. At least a substantial proportion of the relatively high density spaced zones are at least partially impregnated with binder material.
The high bulk field is preferably substantially uncompacted and devoid of binder material.
- Accordingly, the second step in the preferred embodiment of the process of this invention com-prises the forming from the papermaking furnish a patterned densified embryonic web ha~ing a multi-plicity of discrete zones of relatively high density disposed in a predeiermined pattern array.
The third step of the preferred comprises supporting the embryonic web on an array of spaced supports so that each of a predetermined sub-array of the high density zones is juxtaposed one of a corresponding sub-array of the supports.
The array of spaced supports can be the knuckles of an endless imprinting carrier fabric and the sub-array of such supports can be only t~e top-sur-face-plane knuckles of the fabric in fabrics having both top-surface-plane knuckles and sub-top-surface 7~
knuckles. In fabrics having no sub-top-surface knuckles, the sub-array of supports would, in fact, be the array of supports.
The ourth step of the preferred process is at least partially impregnating at least a substantial proportion of the supported predetermined sub-array of high density zones with a binder material by biasing the predetermined sub-array of supports toward a contacting type impregnating means with the sub-array of the high density zones disposed between ~he sub-array of the supports a~d ~he impregnating means. ~or maximum strengt~, all of the high density zones should be impregnated with binder material. Only a portion of the high density zones need be partially impregnated in webs wherein such partial impregnation provides sufficient strength for their intended use.
Impregnating means such as a full field gravure applicator can be used to impregnate the high density zones of the webs biased against it whereas less-than-full-field gravure applicators can be used to only partially im~regnate all or some of the high density zones o the web, or wholly impregnate only some of the high density zones. The impregnation accomplished in this fourth step must be accomplished before the embryonic web is substantially dried. As used herein, the embryonic web is not substantially dried if it contains at least about 25% moisture.
(Unless otherwise specified, all percentages in this specification are weight percentages.) The la~ices used herein are aqueous emulsions of synthe~ic rubbers or plastics obtained by poly-~ '7~';' meriza~ion, They can be, but need not be, curableas by cross-linking. The polymer struc~ure must contain anionic functional groups which provide an anionic character to the latex. Examples of suitable functional groups include carboxyl, sulfonate, phosphonate and hydroxyl groups. Carboxyl groups are preferred~ These functional groups are sometimes said to be present in the polymer "backbone". Further, the polymer structure can contain more ~han one ~ype of anionic functional group.
Recent developments in latex chemistry have resulted in the creatio~ of latices which are considered to be`cationic, but which contain normally anionic functional g~oups such as carboxyl groups within the polymer structure; such latices are suitable for use in the present invention.
Latices containing functional ~roups as described above can be produced by methods well known to those skilled in the art. For example, acrylic, methacrylic, fumaric or itaconic acid can be reacted with styrene and butadiene ~n con~enticnal processes to form styrene-butadiene rubber ha~ing carboxyl groups in the polymer strueture. Those same acids can be reacted with ac~ylic monomer~
to make acrylic latices having carboxyl functional groups in the polymer structure. ThesP ~inyl acids can also be reacted with Pthylene ~in~l acetate to make functiollal-group containing Latices.
Specific examples of latices useful in the present invention include"Rhoplex TR-520"and "Rhoplex TR-90~", acrylic emulsion polymers made by Rohm and Haas Company of Philadelphia, Pennsylvania. The former is based on ethyl acrylate and the latter on ethyl acrylate and butyl acrylate; Both contain carboxyl groups in the polymer structure. Mixtures of these two latices can also be used.
*Trademark **Trademark '7 Other sui~able latices are the carboxylated styrene/butadiene copolymer supplied under the designation XD~30295. 00 and the carboxylated ctyrene-butadiene-butyl acrylate terpolymer supplied under the designation XD 30221.02 by The Dow Chemical Company of Midland, Michigan.
Mixtures of latices can be used in the present invention.
The latex emulsion preferably has a viscosity of less th2n 100 centipoise, most preferably less than 30 centipoise.
The fifth step of the pref~rred process com-prises drying the embryonic web to fo~m a paper web. Techniques and equipment ~ell known to those skilled in the art can be used in this step. -Further, the process can comprise an optionalstep of subjecting the impregnated zones to addi-tional mechanical pressure or compaction after they are impregnated to increase binder pene-tration and interfiber bonding thereL~.
Still urther, the p~ocess can include an optional and preferred drying step immediately preceding the impregnating s~ep wherein the ~5 embryonic web is dried in the absence of substantial mechanical compression to an average moisture content of from about 25 to about 80% by weight of the embryonic we~. Preferably, this drying step is sufficiently asymmetrical to dry the unsupported portions of the embryonic ~eb substan-tially more than the high density portions.
Preferably, the web is creped, calendered and reeled after being dried to ~urther increase its stretch, bulk and softness, and to control its caliper.
~L~9~727 ~ le amount of binde~ impregnated into the embryonic web is preferably from about 2Z to abou~ 30% by weight of the papermaking fiber although it is not intended to limit the present invention to this range o binder level.
It is to be noted that in this embodiment of the invention, the soft, strong, absorbent tissue paper web of papermaking fibers comprises a multiplicity of relati~ely high density zones impregna~ed with a binder material interposed between and among a plurality of usually vaulted or arcuate shaped relatively low density spa~
portions which are substantially unco~pacted and devoid of binder material. Water-soluble cationic resin is, in general, distributed throughout the web and is present in both the.high denslty and low density zones.
The process for making the pa~tern densified fibrous web described above is described in more detail in European Patent Application 81200093.5 filed on behalf o the inventors P. G. Ayers and J. M. Raley on January 26, 1981 and published~
August 19, 1981, Optionally, the papermaking furnish can comprise materials such as chemical debonders which enhance the softness of the resulting ~issue paper web by reducing the interfibes bonding therein. Of particular use herein is the debonder combination comprising at leas~ one quaternary ammonium compound and at least one nonionic surfactant. The preferred quaternary ammonium compounds are selected rom the group consisting of quaternary ammonium com~ounds having the structure ., .
~3~
CH3 +
CH3 - N - CH3 X , and _ R
quaternary ammonium compounds having the structur~, lo ~ fH3 +
~ H(OCH2CH2~m - I - (CH2CH~O~n X .
R
In the two structures noted above R is an aliphatic hydrocarbon radical selected from the group con-sisting of alkyl having from ~about 12 to about 18 carbon atoms, alkylene having from about 12 to about 18 carbon atoms, coconut and tallow; m and n are both integers each having a value of at least 1; the sum of m and n is from about 2 to about 15;
and X is a halogen.
As used in this context, '~coconut" refers to the alkyl and alkylene moieties derived from coconut oil and from the synthetic mixtures designed to re-semble natural coconut oil. As used in this context, "tallow" refers to the alkyl and alkylene moieties derived from tallow and from the synthetic mixtures designed to resemble natural tallow.
Preferably, the alkyl and alkylene radicals have from about 15 to about 18 carbon atoms.
Alkylenes are ~enerally preferred to alkyls. Coconut is more preferred than the alkyl and alkylene radicals just described.
In the case of the methylpolyoxyethylene quaternary ammonium compounds, the sum of m and n is preferably about 2.
Any of the halide salts can be used. Typically, and preferably, the chloride is used.
Specific examples of quaternary ammonium salts useful in this invention include trimethyloctadecyl-ammonium chloride, trimethylcocoammonium chloride, trimethyltallowammonium chloride, trimethylolelyl-ammoniu~ chloride, methylbis(2-hydroxyethyl)coco-ammonium chloride, methylbis(2-hydroxyethyl)oleyl-ammonium chloride, methylbis(2-hydroxyethyl)octadecyl-ammonium chloride, methylbis(2-hydroxyethyl)tallow-amTnonium chloride, methylpolyoxyethylene(l5)coco-ammonium chloride, and methylpolyoxyethylene(l5)olyl-ammonium chloride.
The most preferred quaternary ammonium com-pound is methylbis(2-hydroxyethyl)cocoammonium chloride.
The quaternary ammonium salt is added to the papermaking furnish at a level of from about 0.5 to about 5.0 grams per kilogram of bone dry papermaking fiber. Preferably 7 it is added at from about 1.0 to about 2.5 grams per kilogram.
Nonionic surfactants useful in the present invention include the ether and ester adducts of ethylene oxide and fatty chemicals. That is to say, the nonionic surfactants useful herein can be described as the ethylene oxide adducts of, re-spectively, fatty alcohols and fatty acids. The fatty moiety of the nonionic surfactant should comprise from about 12 to about 18 carbon atoms.
The ethylene oxide moiety of the nonionic sur factant should comprise from about 2 to about 12 moles ethylene oxide, preferably from about 2 to about 9 moles. Preferably, the fatty moiety is unsaturated. Specific examples of nonionic sur-factants useful in the present invention include polyoxyethylene(2)oleyl ether and polyoxvethylene-~t~
(9)oleyl ester. The former is known in CFTA
nomenclature as Oleth-2, the latter as PEG-9 oleate.
Dieste~s, such as PEG-4 dilaurate (two moles S of lauric acid adducted with 4 moles of ethylene - oxide~, are also useful in the present invention.
The nonionic surfactant is present in the papermaking furnish at a level of from about 0.5 to about 5.0 grams per kilogram bone dry paper-making fiber, preferably from about 1.0 to about
2.5 grams per kilogram.
Preferably, either the quaternary ammonium compound or the nonionic surfactant contains an unsaturated (alkylene) moiety. More preferably, both contain such an unsaturated (alkylene) moiety.
Other chemicals commonly-used in papermaking can be added to the papermaking furnish so long as ~ they do not significantly and adversely affect the end result of the present invention.
The process of this invention (and, of necessity, the resulting web) has hereinbefore been described in detail in terms of a process which makes a pattern densified fibrous web having a relatively high bulk field of relative low fiber density and a patterned array of spaced zones of relatively high fiber density at least a substantial pro-portion of which are at least partially impreg-nated with binder material. This is the system which is highly preferred and in which the present invention finds greatest utility. It is to be recognized, however, that certain other paper-making process are known to produce webs having binder material impregnated therein, usually in .
some discrete pattern, but wherein the locus of the impregnated zones does not substantially correspond with at least a portion of the locus of zones of relatively high fiber density. The present invention finds utility in such other processes and the webs thereby produced, but such use is no~ preferred.
The tissue paper webs of this invention can be used in any application wh~re soft, absorbent tissue paper webs are required. One partieularly advantageous use of the tissue paper webs of this invention is in paper towel products. For example, two tissue paper webs of this invention can be embossed and adhesively secured together in face-to-face relation (as taught by U.S. Patent
Preferably, either the quaternary ammonium compound or the nonionic surfactant contains an unsaturated (alkylene) moiety. More preferably, both contain such an unsaturated (alkylene) moiety.
Other chemicals commonly-used in papermaking can be added to the papermaking furnish so long as ~ they do not significantly and adversely affect the end result of the present invention.
The process of this invention (and, of necessity, the resulting web) has hereinbefore been described in detail in terms of a process which makes a pattern densified fibrous web having a relatively high bulk field of relative low fiber density and a patterned array of spaced zones of relatively high fiber density at least a substantial pro-portion of which are at least partially impreg-nated with binder material. This is the system which is highly preferred and in which the present invention finds greatest utility. It is to be recognized, however, that certain other paper-making process are known to produce webs having binder material impregnated therein, usually in .
some discrete pattern, but wherein the locus of the impregnated zones does not substantially correspond with at least a portion of the locus of zones of relatively high fiber density. The present invention finds utility in such other processes and the webs thereby produced, but such use is no~ preferred.
The tissue paper webs of this invention can be used in any application wh~re soft, absorbent tissue paper webs are required. One partieularly advantageous use of the tissue paper webs of this invention is in paper towel products. For example, two tissue paper webs of this invention can be embossed and adhesively secured together in face-to-face relation (as taught by U.S. Patent
3,414,459 which issued to Wells on DecembPr 3, 1968) ~o fonn 2-ply paper towels~
As noted hereinbefore, the webs of this invention (and ~he products made from these webs) 20 exhibit greater tensile strength than either webs made with water-soluble cationic resin in the papermaking furnish but without latex bi~des material impregnation or webs made with latex binder material impregnation but withou~ water-soluble cationic resin~ in the papermaking furnish.In fact, the'webs of this invention exhibit greater tensile strength than would be expected from a consideration of the two other webs de-scribed in the immediately preceding sentence.
In addition, the webs of this invention ~and the products formed from them) are soft, absorbent, and exhibit a surprising degree of strength in alkaline, chlorine-containing environments.
In order to better describe the present invention, and not by way of limitation, the t~7 following examples are presented.
EXAMPLE I
A 5% aqueous slurry of unbeaten northern 5 sof~wood Kraft wood pulp fibers was formed in a conventional repulper. Mèthylbis-(2-hydroxyethyl) cocoammonium chloride (as sold under the trademark ~'Ethoquad C-12" by Armak Company of Chicago, Illinois) was added to the pulp slurry at the rate 10 of 2 grams of ~uaternar~ ammonium compound per kilogram of bone dry ~iber. Oleth-2 (as sold under the trademark "Brij 93" by I.C.I. Americas Inc. of Wilmington, Delaware), dissolved in isopropyl alcohol, was added to the fiber slurry lS at a rate of 2 grams of nonionic surfactant per ~ilogram of bone dry fiber. T~e papermaking furnish was completed by the addition of "Kymene 557H" to the aqueous slurry through an inline mixer at a rate of 10 grams of resin per kilogram 20 of bone dry fiber.
This papermaking furnish was then used to make an embryonic web on a pilot scale papermaking machine. Afte~ dilution with water to form a slurry containing approximately~0.12% fiber, the 2~ papermaking furnish was deposited on a Fourdrinier wire of a 4-shed satin weave having about 31 x 24 machine direction (MD) by cross machine direction (CD) filament mesh count per centimeter to form the embryonic web. Water was progressi~ely 30 removed as the embryonic web was being carried through the machine first on the hereinbefore described Fourdrinier wire and after the embryonic web was transferred to an imprinting fabric which B had a 5-shed satin weave of 14 x 13, MD by CD, Z ~
filam~n~ mesh count per centimeter such as de-scribed in U.S. Paten~ 4,191,609 issued to Paul D. Trokhan on March 4, 1980. Dewatering was accomplished by vacuum assisted drainage until the embryonic web had a fiber consistency of abou~ 32~. ~s a result of the transfer from the Fourdrinier wire to the imprinting fabric and the vacuum assisted dewatering, the embryonic web became patterned ' densified when the resulting discrete spaced high density zones we~e juxtaposed the top-surace-plane knuckles of the imprinting ~abric. Vacuum induced differential fluid pressure caused the unsupported por~ions of the embryonic web to be displaced into the interfilamentary ~oids of the imprinting fabric for~ing rela~ ly low density spans between the knuckles. The now patterned -densified em~ryonic web was predried by air blow-through to an ave~age fiber consistency of about 1 65%.
The embryonic web, while still d sposed on the imprintin~ fabric, was carried forward thxvugh a full field pattern pressu~e biased ~ravure impregnating de~ice in such a manner that the relatively high density zones were pressed against the gravure cylinder and thereby impregnated with binder material comprising water based emulsi~
polymer containing ~nionic functional groups i~
the polymer structure. The relatlvely low density ; span zones were not so impregnated.
In this Example 9 the binder material was hereinbefore described TR 5~G latex. In addition to the latex, the binder material contained about *
1O/D Pluronic L-92"ethylene oxide~based nonionic surfactant as made by BASF Wyandotte Corp. of Parsippany, Mew Jersey, abou~ 0.5~/0 ammonium nitrate, trace levels of commercial defoamers"Foammaster 160-L ~s made by the Diamond Shamrock Corp. of Cleveland, Ohio/and"Colloid 694"as made by Colloids Inc. of Newark, New Jersey, and ammonium hydroxide to adjust the pH to 5.0~+ 0.5. Binder material was impregnated into the web at a level of approxi-mately 5% by weight of fiber.
Following impregnation, the web was adheredto *t*he*surface of a Yankee dryer with"Gelvatol 20-90, a polyvinyl alcohol/acetate creping adhesive manufactured by Monsant~ Company. The web was 1~ creped from the surfaoe of the Yankee dryer in a conventional manner by a doct~r blade and was formed into rolls by reeling at 80% of the Yankee ` speed.
Two plys of the web were formed into paper 20~ towel products by laminating them together using polyvinyl alcohol`as the adhesive and the technique described in the ~.S~ -Patent, 3,414,459. The lamin-ate was stored at about 22~C for about six da~s.
Two types of control towels were made by the foregoing process except that in the first case the papermaking furnish did not contain the water-soluble cationic resin and in ~he second case the embryonic webs were not impregnated with binder material.
The paper towel of this invention formed from webs of this invention as made by the process of this invention, when compared to the control paper towels, was found to exhibit wet tensile strength significantly greater than that of either control towel.
*Trademark **Trademark **.*Trademark ****Trademark ~3 ~
EXAMPLE II
. .
The process of Example I ~as repeated except that the papermaking furnish did not contain either the methylbis-~2-hydroxyethyl) cocoammonium chloride or the Oleth-2. Control towels were prepared in a manner analogous to that used to prepare control towels in Example I. Towels prepared from the webs of this invention made according to this Example II exhibited significant strength improvement relative to the control towels. This strength improvement was similar to the strength improvement demonstrated in Example I.
EXAMPLE III .
The process of Example I is repeated except that the water-soluble cationic resin is"Parez 631 N~l-and the hinder material is Dow latex XD-30295.
The binder material contains, in addition to the latex, 1.0% diammonium phosphate and sufficient ammonium hydroxide to adjust the pH of the ~mul-sion to 8.5. The resulting web, is soft, strong, absorbent, and useful in making towels.
, ~!
As noted hereinbefore, the webs of this invention (and ~he products made from these webs) 20 exhibit greater tensile strength than either webs made with water-soluble cationic resin in the papermaking furnish but without latex bi~des material impregnation or webs made with latex binder material impregnation but withou~ water-soluble cationic resin~ in the papermaking furnish.In fact, the'webs of this invention exhibit greater tensile strength than would be expected from a consideration of the two other webs de-scribed in the immediately preceding sentence.
In addition, the webs of this invention ~and the products formed from them) are soft, absorbent, and exhibit a surprising degree of strength in alkaline, chlorine-containing environments.
In order to better describe the present invention, and not by way of limitation, the t~7 following examples are presented.
EXAMPLE I
A 5% aqueous slurry of unbeaten northern 5 sof~wood Kraft wood pulp fibers was formed in a conventional repulper. Mèthylbis-(2-hydroxyethyl) cocoammonium chloride (as sold under the trademark ~'Ethoquad C-12" by Armak Company of Chicago, Illinois) was added to the pulp slurry at the rate 10 of 2 grams of ~uaternar~ ammonium compound per kilogram of bone dry ~iber. Oleth-2 (as sold under the trademark "Brij 93" by I.C.I. Americas Inc. of Wilmington, Delaware), dissolved in isopropyl alcohol, was added to the fiber slurry lS at a rate of 2 grams of nonionic surfactant per ~ilogram of bone dry fiber. T~e papermaking furnish was completed by the addition of "Kymene 557H" to the aqueous slurry through an inline mixer at a rate of 10 grams of resin per kilogram 20 of bone dry fiber.
This papermaking furnish was then used to make an embryonic web on a pilot scale papermaking machine. Afte~ dilution with water to form a slurry containing approximately~0.12% fiber, the 2~ papermaking furnish was deposited on a Fourdrinier wire of a 4-shed satin weave having about 31 x 24 machine direction (MD) by cross machine direction (CD) filament mesh count per centimeter to form the embryonic web. Water was progressi~ely 30 removed as the embryonic web was being carried through the machine first on the hereinbefore described Fourdrinier wire and after the embryonic web was transferred to an imprinting fabric which B had a 5-shed satin weave of 14 x 13, MD by CD, Z ~
filam~n~ mesh count per centimeter such as de-scribed in U.S. Paten~ 4,191,609 issued to Paul D. Trokhan on March 4, 1980. Dewatering was accomplished by vacuum assisted drainage until the embryonic web had a fiber consistency of abou~ 32~. ~s a result of the transfer from the Fourdrinier wire to the imprinting fabric and the vacuum assisted dewatering, the embryonic web became patterned ' densified when the resulting discrete spaced high density zones we~e juxtaposed the top-surace-plane knuckles of the imprinting ~abric. Vacuum induced differential fluid pressure caused the unsupported por~ions of the embryonic web to be displaced into the interfilamentary ~oids of the imprinting fabric for~ing rela~ ly low density spans between the knuckles. The now patterned -densified em~ryonic web was predried by air blow-through to an ave~age fiber consistency of about 1 65%.
The embryonic web, while still d sposed on the imprintin~ fabric, was carried forward thxvugh a full field pattern pressu~e biased ~ravure impregnating de~ice in such a manner that the relatively high density zones were pressed against the gravure cylinder and thereby impregnated with binder material comprising water based emulsi~
polymer containing ~nionic functional groups i~
the polymer structure. The relatlvely low density ; span zones were not so impregnated.
In this Example 9 the binder material was hereinbefore described TR 5~G latex. In addition to the latex, the binder material contained about *
1O/D Pluronic L-92"ethylene oxide~based nonionic surfactant as made by BASF Wyandotte Corp. of Parsippany, Mew Jersey, abou~ 0.5~/0 ammonium nitrate, trace levels of commercial defoamers"Foammaster 160-L ~s made by the Diamond Shamrock Corp. of Cleveland, Ohio/and"Colloid 694"as made by Colloids Inc. of Newark, New Jersey, and ammonium hydroxide to adjust the pH to 5.0~+ 0.5. Binder material was impregnated into the web at a level of approxi-mately 5% by weight of fiber.
Following impregnation, the web was adheredto *t*he*surface of a Yankee dryer with"Gelvatol 20-90, a polyvinyl alcohol/acetate creping adhesive manufactured by Monsant~ Company. The web was 1~ creped from the surfaoe of the Yankee dryer in a conventional manner by a doct~r blade and was formed into rolls by reeling at 80% of the Yankee ` speed.
Two plys of the web were formed into paper 20~ towel products by laminating them together using polyvinyl alcohol`as the adhesive and the technique described in the ~.S~ -Patent, 3,414,459. The lamin-ate was stored at about 22~C for about six da~s.
Two types of control towels were made by the foregoing process except that in the first case the papermaking furnish did not contain the water-soluble cationic resin and in ~he second case the embryonic webs were not impregnated with binder material.
The paper towel of this invention formed from webs of this invention as made by the process of this invention, when compared to the control paper towels, was found to exhibit wet tensile strength significantly greater than that of either control towel.
*Trademark **Trademark **.*Trademark ****Trademark ~3 ~
EXAMPLE II
. .
The process of Example I ~as repeated except that the papermaking furnish did not contain either the methylbis-~2-hydroxyethyl) cocoammonium chloride or the Oleth-2. Control towels were prepared in a manner analogous to that used to prepare control towels in Example I. Towels prepared from the webs of this invention made according to this Example II exhibited significant strength improvement relative to the control towels. This strength improvement was similar to the strength improvement demonstrated in Example I.
EXAMPLE III .
The process of Example I is repeated except that the water-soluble cationic resin is"Parez 631 N~l-and the hinder material is Dow latex XD-30295.
The binder material contains, in addition to the latex, 1.0% diammonium phosphate and sufficient ammonium hydroxide to adjust the pH of the ~mul-sion to 8.5. The resulting web, is soft, strong, absorbent, and useful in making towels.
, ~!
Claims (15)
1. A process for forming a soft, strong, ab-sorbent tissue paper web comprising the steps of (a) forming an aqueous papermaking furnish;
(b) forming from said papermaking furnish a patterned densified embryonic web having a multiplicity of discrete zones of relatively high density disposed in a predetermined pattern array;
(c) supporting said embryonic web on an array of spaced supports so that each of a predetermined sub-array of said high density zones is juxtaposed one of a corresponding sub-array of said supports;
(d) at least partially impregnating at least a substantial proportion of said supported predetermined sub-array of said high density zones with a binder material by biasing said predetermined sub-array of said supports toward a contacting type impregnating means with said sub-array of said high density zones disposed between said sub-array of said supports and said impregnating means; and (e) drying said embryonic web;
wherein said aqueous papermaking furnish comprises papermaking fibers and at least one water-soluble cationic resin and wherein said binder material comprises an aqueous emulsion of at least one polymeric latex wherein the polymer structure of said polymeric latex contains at least one anionic functional group.
(b) forming from said papermaking furnish a patterned densified embryonic web having a multiplicity of discrete zones of relatively high density disposed in a predetermined pattern array;
(c) supporting said embryonic web on an array of spaced supports so that each of a predetermined sub-array of said high density zones is juxtaposed one of a corresponding sub-array of said supports;
(d) at least partially impregnating at least a substantial proportion of said supported predetermined sub-array of said high density zones with a binder material by biasing said predetermined sub-array of said supports toward a contacting type impregnating means with said sub-array of said high density zones disposed between said sub-array of said supports and said impregnating means; and (e) drying said embryonic web;
wherein said aqueous papermaking furnish comprises papermaking fibers and at least one water-soluble cationic resin and wherein said binder material comprises an aqueous emulsion of at least one polymeric latex wherein the polymer structure of said polymeric latex contains at least one anionic functional group.
2. The process of Claim 1 wherein said water-soluble cationic resin is selected from the group consisting of polyamide-epichlorohydrin resins, polyacrylamide resins, melamine formaldehyde resins, melamine formaldehyde resins, urea formaldehyde resins, polyethylenimine type resins, and normally water-insoluble polysalt coacervates rendered water-soluble by the inclusion of an ionization suppressor therein.
3. The process of Claim 2 wherein said anionic functional group is selected from the group consisting of carboxyl, sulfonate, phosphonate, and mixtures thereof.
4. The process of Claim 3 wherein said anionic functional group is carboxyl.
5. The process of Claim 1 wherein said anionic functional group is selected from the group consisting of carboxyl, sulfonate, phosphonate, and mixtures thereof.
6. The process of Claim 5 wherein said anionic functional group is carboxyl.
7. A soft, strong, absorbent tissue paper web comprising papermaking fibers and cationic resin wherein said web comprises a multiplicity of relatively high density zones impregnated with binder material, said high density zones interposed between and among a plurality of arcuate shaped relatively low density span portions which low density span portions are substantially uncompacted and devoid of binder material wherein said binder material comprises a polymeric structure containing at least one anionic functional group.
8 . The soft, strong, absorbent tissue paper web of Claim 7 wherein said anionic functional group is selected from the group consisting of carboxyl, sulfonate, phosphonate, and mixtures thereof .
9. The soft, strong absorbent tissue paper web of Claim 8 wherein said anionic functional group is carboxyl.
10. A process for forming a soft, strong, absorbent tissue paper web comprising the steps of (a) forming an aqueous papermaking furnish, (b) forming from said papermaking furnish an embryonic web;
(c) at least partially impregnating said embryonic web with a binder material; and (d) drying said embryonic web;
wherein said aqueous papermaking furnish comprises papermaking fibers and at least one water-soluble cationic resin and wherein said binder material comprises an aqueous emulsion of at least one polymeric latex wherein the polymer structure of said polymeric latex contains at least one anionic functional group.
(c) at least partially impregnating said embryonic web with a binder material; and (d) drying said embryonic web;
wherein said aqueous papermaking furnish comprises papermaking fibers and at least one water-soluble cationic resin and wherein said binder material comprises an aqueous emulsion of at least one polymeric latex wherein the polymer structure of said polymeric latex contains at least one anionic functional group.
11. The process of Claim 10 wherein said water-soluble cationic resin is selected from the group consisting of polyamide-epichlorohydrin resins, polyacrylamide resins, melamine formaldehyde resins, urea formaldehyde resins, polyethylenimine type resins, and normally water-insoluble polysalt coacervates rendered water-soluble by the inclusion of an ionization suppressor therein.
12 The process of Claim 11 wherein said anionic functional group is selected from the group consisting of carboxyl, sulfonate, phosphonate, and mixtures thereof.
13. The process of Claim 12 wherein said anionic functional group is carboxyl.
14. The process of Claim 10 wherein said anionic functional group is selected from the group consisting of carboxyl, sulfonate, phosphonate, and mixtures thereof.
15. The process of Claim 14 wherein said anionic functional group is carboxyl.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US30657081A | 1981-09-28 | 1981-09-28 | |
| US306,570 | 1981-09-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1191727A true CA1191727A (en) | 1985-08-13 |
Family
ID=23185899
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000412228A Expired CA1191727A (en) | 1981-09-28 | 1982-09-27 | Soft, strong, absorbent tissue paper and process therefor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1191727A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5213588A (en) * | 1992-02-04 | 1993-05-25 | The Procter & Gamble Company | Abrasive wiping articles and a process for preparing such articles |
| US5882743A (en) * | 1997-04-21 | 1999-03-16 | Kimberly-Clark Worldwide, Inc. | Absorbent folded hand towel |
| US6146494A (en) * | 1997-06-12 | 2000-11-14 | The Procter & Gamble Company | Modified cellulosic fibers and fibrous webs containing these fibers |
-
1982
- 1982-09-27 CA CA000412228A patent/CA1191727A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5213588A (en) * | 1992-02-04 | 1993-05-25 | The Procter & Gamble Company | Abrasive wiping articles and a process for preparing such articles |
| US5882743A (en) * | 1997-04-21 | 1999-03-16 | Kimberly-Clark Worldwide, Inc. | Absorbent folded hand towel |
| US6146494A (en) * | 1997-06-12 | 2000-11-14 | The Procter & Gamble Company | Modified cellulosic fibers and fibrous webs containing these fibers |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |