US2923641A

US2923641A - Composition and method for impregnation of sheet materials with synthetic resin latices utilizing coagulants of water-soluble amine or quaternary ammonium salts

Info

Publication number: US2923641A
Application number: US502220A
Authority: US
Inventors: Jr George Leonard Graf
Original assignee: Celastic Corp
Current assignee: Celastic Corp
Priority date: 1955-04-18
Filing date: 1955-04-18
Publication date: 1960-02-02
Anticipated expiration: 1977-02-02
Also published as: FR70714E; GB830335A

Description

United States Patent COMPOSITION AND METHOD FOR INIPREGNA- TION OF SHEET MATERIALS WITH SYNTHETIC RESIN LATICES UTILIZING COAGULANTS 0F WATER-SOLUBLE AMINE OR QUATERNARY AMMONIUM SALTS George Leonard Graf, Jr., Wilmington, Del., assignor to The Celastic Corporation, Arlington, N..I., a corporation of Delaware No Drawing. Application April 18, 1955 Serial No. 502,220

9 Claims. (Cl. 11765) This invention relates to a method for stiflening a fibrous sheet material, and more particularly, it relates to a method of preparing shoe stiifeners by treating a sheet material with a synthetic resin latex.

High quality shoe stifleners in the past have been made by impregnating a flannel sheet material with finely divided particles of cellulose nitrate. After drying, this product was stored until ready for use, at which time the impregnated flannel was dipped into a solvent for the cellulose nitrate, applied to the appropriate shoe part and allowed to dry to a stiffened condition.

It is also known that sheet materials such as flannel may be impregnated by dipping the flannel into an aqueous dispersion of synthetic resin, such as a synthetic rubber latex. However, inv all the known processes there are operating difliculties which arise because of the tendency of such a latex to deposit in a dense impervious form. As a result of such a formation, the porosity of the impregnated material is low and the ability of the material to absorb solvents is poor. The low porosity and poor solvent absorption prevents the achievement of the greatest stiffness for a given composition of impregnated fabric. Therefore to obtain a desired stiffness, according to known processes, heavier flannels or other supporting materials, must be impregnated with a greater amount of resin, and such procedures are commercially unattractive.

In copending application, Serial No. 445,183, filed by G. L. Graf, Jr., on July 22, 1954, now Patent No. 2,760,884, there is described and claimeda process for impregnating a flannel fabric with an aqueous latex containing vinyl polymer particles, a non-ionic thermosensitive dispersing agent and a polyvalent metal salt coagulant. After the impregnated sheet is stripped of excess liquid, it is heated to. cause the dispersing agent to insolubilize allowing the coagulant to become effective in agglomerating the polymeric particles. The impregnated material is then dried, forming a flexible material which may at any later time be stiffened by applying to the material a volatile liquid capable of dissolving the polymeric particles. The process of the present invention is an improvement on that of the aboveidentified copending application in that certain organic coagulants are employed in place of the polyvalent metal salts. These organic coagulants are volatile, much less corrosive than metal salts, may provide fungicidal properties, and are therefore, more desirable components in the preparation of shoe stiifeners.

It is an object of this invention to provide a novel process for impregnating fabric with a synthetic resin latex in a single impregnating step. It is another object of this invention to provide an improved method for preparing shoe stiffening materials. Other objects will be apparent to those skilled in the art.

The above objects are accomplished in accordance with the process of this invention by impregnating a fibrous sheet material with an aqueous latex containing 20% to 60% by weight of vinyl polymer particles and, based on the weight of vinyl polymer particles, 0.5% to 5% of a non-ionic dispersing agent which is soluble in water at room temperature and becomes substantially insoluble in water at temperatures from about 40 C. to about 100 C., and 0.5% to 15% of a water-soluble latex coagulant selected from the group consisting of amine salts and quaternary ammonium salts. After stripping the impregnated sheet material of excess liquid, the sheet material is heated to a temperature above from about 40 C. to about 100 C., causing the dispersing agent to insolubilize and allowing the coagulant to cause the resin particles to form small agglomerates dispersed throughout the sheet material, which as a result of this treatment has a non-tacky, but somewhat moist surface. The remaining moisture is then removed by drying the sheet material by any known means. At any later time the dry impregnated sheet material may be treated with a volatile solvent for the resin agglomerates, the sheet may then be formed into the desired shape, and dried by evaporating the solvent. Upon evaporation of the solvent, the sheet material stiifens.

In the preferred embodiment of this invention an impregnating medium is prepartd by mixing'at room temperature, 3 parts by weight of an aqueous polystyrene latex containing about 50% solids, 1 part of an aqueous latex of a copolymer of styrene and butadiene (in theapproximate proportion of parts styrene to 20 parts butadiene) containing about 45% solids, and about 3% by weight of resin solids of dodecylphenyl polyglycol ether as' a dispersing agent. After the dispersing agent has dissolved, 0.5% to 15% by Weight of resin solids of an amine salt or a quaternary ammonium salt, in the form of an aqueous solution, is added slowly and accompanied with suflicient agitation to prevent localized coagulation. It may also be desirable in some embodiments of this invention to add 20% to 50% by weight of resin solids of a filler material, such as calcium carbonate. If the latex is acid, the pH of the mixture is then adjusted to the range of 6.0 to 7.0 by adding about 1% by weight of resin solids of calcium carbonate, and water is added to' provide a latex containing about 40% solids.

The desired sheet material is then dipped into th above mixture and stripped between rolls to give a loading of at least 50% by weight of impregnating solids. The impregnated sheet material is then heated to about C. or more'by direct contact with steam. During this period the synthetic resin particles in the impregnated sheet material agglomerate to the desired size and are dispersed evenly throughout the sheet material. The agglomerationo'ccurs because the heat causes the ,dis persing agent (dodecylphenyl polyglycol ether in this case) 'to become insolubilized, thus removing the substance which inhibits the coagulation of the resin particles. The material is then dried to remove the remaining moisture. It is desirable if sufficient heat is applied to. cause any excess coagulant to volatilize and thus be removed-from the material. After this treatment the impregnated sheet material is dry and flexible, easy to handle, and capable of being stored over long periods without using special precautions and without fear of chemical change in the sheet material.

When this impregnated material is ready for useas a stiffener, it is blanked into the desired shape, treated The following examples are given to illustrate various embodiments of this invention. Parts and percentages are by weight unless otherwise specified.

Example 1.A latex blend was prepared by mixing 3 parts of a polystyrene aqueous latex containing 50% resin solids and 1 part of aqueous latex of a copolymer of styrene and butadiene in the proportions of 80/20, this latex contained 45% resin solids. To this latex blend there was added, based on the weight of resin solids, 4% of dodecylphenyl polyglycol ether, 1% of dodecylamine acetate, and 1% of calcium carbonate. The entire latex was then diluted with sufficient water until the resin solids amounted to 40% of the weight of the latex.

This latex mixture was used to impregnate pieces of cotton flannel having a twill weave and a thickness caliper of 0.033 inch to 0.039 inch and a weight per square yard of 0.35 to 0.38 pound. A piece of this flannel measuring 10 x 15 inches was impregnated by dipping the flannel into the above latex mixture followed bystri'pping thewet material between rolls placed 0.050 inch apart. The impregnated fabric was then placed in a chamber filled with steam at 95 C. to 100 C. in such a manner that both sides of the fabric were exposed to the steam. After the fabric had been in the steam chamher for 1 minute it was removed and placed in a circulating air oven at 110 C. for 1 /2 hours. Or" the total weight of the impregnated fabric, 71.7% by weight was resin. This figure is called the percent resin loading hereinafter.

This impregnated fabric was then tested for solvent absorption and stiffness by dipping it into a solvent comprising a mixture of 90% by weight of toluene and 10% by weight of a commercial petroleum naphtha fraction boiling in the range of 100 to 167 C. The material was found to have absorbed 83.7% by weight of solvent, based on the dry weight of the impregnated fabric before solvent treatment.

This material, treated with solvent, was then laminated into a simulated shoe toe portion comprising, in the order named, shoe leather, doubler cloth, stiflener, and liner cloth. The resin migration as observed from the liner cloth was very good and there was no indication of spotty adhesion. The adhesion between the liner and the stiffener, between the stiffener and the doubler, and between the doubler and the leather, was good.

The laminate was then cut into strips measuring 1 x 3 inches, and one of these strips was tested according to The Standard Method of Testing for Stiffness in Flexure in Plastics ASTM D747-50 (adopted 1950). The stiffness values for this laminate was 100,000 pounds per square inch. From the data obtained from the ASTM test there was calculated a value called rigidity which wasindependent of the leather thickness. This value is the inch-pounds of work requiredto deflect a one inch wide specimen with a lever arm of two inches through a deflection angle of 30. The total distance throughwhich the free end of the specimen moved was one inch. Thus the value of rigidity is reported in terms of inchpounds of work per inch of deflection. The rigidity of this laminate was found to be 5 inch-pounds per inch of deflection.

The impregnated material of this example Was laminated into a simulated shoe toe and tested for compression number according to American Standards Association Bulletin on Mens Safety Shoes No. 241.1-1944. The compression number was found to be 61.

Example 2.A latex blend was prepared in allrespect's similar to Example 1 except that the coagulant was 2 by weight of the resin solids of alkylaryl pyridinium chloride (instead of 1% of dodecylamine acetate). Laminates and simulated shoe toes were prepared 'from this material as described in Example 1. Resin loading of the material was 715% and solvent absorption was 88.4%. The laminate exhibited a stiifness of 130,000 psi. and a rigidity of 6.8 inch-pounds per 4 inch of deflection. The simulated shoe toes had a compression number of 65.

Example 3.A latex mixture was prepared in the same manner as described in Example 1 with the exception that the coagulant was 5.5% by weight of resin solids of cetyl dimethylbenzyl ammonium chloride (instead of 1% of dodecylamine acetate). Laminates and simulated shoetoes were prepared in the manner de scribed in Example 1. Resin loading. of :the material Was 71.3% and solvent absorption was 87.0%. The laminate exhibited a stiffness of 95,000 p.sli. and a rigidity of 7.2 inch-pounds per inch of deflection. The simulated shoe toes had a compression number of 80.

Any of several kinds of synthetic resins having electronegative properties may be used as the major ingredient in the impregnating latex, although the vinyl resins are preferred, such as polystyrene, polymethyl styrene, polyvinyl halides, polyvinylidene halides, polyacrylates, polyacrylonitrile, and polyalkylacrylates. It is desirable in many instances to employ a plasticized resin, such as a mixture of polystyrene and a copolymer of high styrene content and low butadiene content, the copolymer acting as a plasticizer and thereby causing the polystyrene to be less brittle although retaining its stiffness. Other known plasticizers such as organic esters, and other nonvolatile, non hardening liquids may be incorporated with the base resin to reduce brittleness in the same manner as the styrene/butadiene copolymer is used above. Polymers of styrene or of vinyl halides are particularly desirable because of their availability and low cost.

Many varieties of resins and combinations of polymers have been found to be useful in this process. One useful group of resins is a copolymer of styrene/butadiene containing 4% to 20% by weight of butadiene. A preferred formulation is a mixture of 3 parts polystyrene with 1 part of an /20 copolymer of styrene/butadiene, which mixture has a total composition of styrene and 5% butadiene. The proportions of polystyrene and the styrene/butadiene copolymer can be varied within the general range of 4-20% by weight of butadiene in the total mixture to produce slightly stiffer and harder compositions as the butadiene proportion is reduced and softer more elastic compositions as the butadiene proportion is increased. The same'varietyof compositions can be obtained by mixing well-known plasticizers with polystyrene or other hard plastic materials, particularly the vinyl polymers such as vinyl halide, vinylidene halide, alkyl acrylate's, and other resins known to those skilled in the art.

The latex used as a starting material in the prepara tion of the'impregnating bath of this invention is a colloidal dispersion of one or more of the above resins in an aqueous medium. Preferably, the dispersion contains from about 40% to about 60-% resin solids, while the remainder is essentially all water. These dispersions or latices are available commercially on the open market in concentrations of40% to 60% solids, or they may be prepared by known methods, such as dispersion polymerization. The latex of resin and water constitutes the largest portion of the impregnating mixture of this in vention and the additives described below constitute less than about 15% of the total weight of the impregnating mixture, although there are some embodiments of this inventionwherein a large amount of filler is employed. After all additives are incorporated into the latex, it may then be diluted if desired, and in any case will contain about 20% to 60% resin solids in the final form as an impregnating bath,

Dispersing agents are required additives to the latex utilized in this invention so as to stabilize the latex against premature coagulation. The dispersing agent is non-ionic and must be .one which is soluble in the latex medium at room temperature and increasingly insoluble at higher temperatures. The solubility of these substances should to such that it is soluble in water at some temperature from about room temperature (20 C.) to about 40 C. and that the substance is insoluble in water at some temperature from about 40 C. to about 100 vC. Of course,

the solubility of chemical substances normally changes rather slowly with temperature and itis not intended to limit this invention to those dispersingja'gen'ts which are completely solubleat room temperature and completely insoluble at 40 C., but rather to include those non-ionic dispersing agents which can be dissolved in an aqueous medium at room temperatures or thereabout andwhich have inverse solubility characteristics and'will therefore become insoluble as the temperature is increasedup to about l C. The solubility requirement of the dispersing agents used in this invention is such that the impregnating latex may be prepared at ordinary temperatures (20 C. to 40 C.) and the dispersing agent will be soluble and thus prevent any gross coagulation, or premature agglomeration of the latex but as the temperature is raised to some convenient point. (40 C. to 100 C.) the dispersing agent becomes insoluble and allows agglomeration to occur. The preferred compounds which function as non-ionic dispersing agents and have inverse solubility characteristics include the polyglycol ethers such as octylphenyl polyglycol ether, dodecylphenyl' polyglycol ether, and ethers formed as the con densation product of ethylene oxide and rosin. The alkylphenyl polyglycol ethers are preferred in this invention.

The amount of dispersing agent employed is at least about 0.5%, and normally not more than by weight of the resin solids present in the latex. If the liquid latex constitutes about to-about 60% resin solids, then the dispersing agent will be present from about 0.1% to about 3.0% by weight of the total latex. Great.-

er amounts than 5% by weight of the resin solids may be used without affecting the process other than increasing the costs involved. Generally, about 3% of dispersing agent is recommended for the preferred embodiments of this invention. since this amount effectively inhibits coagulation or agglomeration of the latex at room temperature as well as reducing the surface tension of the latex liquid and thus permit rapid penetration of the latex into the sheet material. Coagulants which may be employed in the process of this invention are Water-soluble compounds selected from the group consisting of amine salts and quaternary ammonium salts. These salts may be chlorides, nitrates, sulfates, acetates, etc. of alkyl amines, aryl amines, and quaternary ammonium bases, unsubstituted or substituted with alkylor aryl groups. Examples of these various salts include, but are not limited to, decylaminesulfate, dodecylarnine acetate, octadecylamine acetate, alkylaryl pyridinium chloride, cetyldimethylbenzyl ammonium chloride, dimethyldidodecyl ammonium acetate, and stearyl trimethyl ammonium nitrate. The quaternary ammonium salts are preferred because of their better solujbility characteristics. The amount of coagulant required will vary slightly with the chemical nature of the coagulant salt, the type and amount 'of resin employed, and other reaction conditions, Approximately 05% of the coagulant, based on the weight of the resin solids present in the latex is sufficieut to accomplish the desired amount of agglomeration, although for a speedier reaction about 1%5% is normally employed. There may be other variables of this process which will affect the amount of coagulant required to achieve the most efiicient operation; these variables including the temperature employed to insolubilize the dispersing agent, the chemical nature of the impregnating medium, and otherfactors known'to those skilled in the art. f

The coagulant salts of this invention are capable of causing the colloidal resin particles in the latex to change into a dense curdlike mass it there is no protective effect of a dispersing agent. A change'into such a dense curdlikemass is referred to herein as coagulation? In theprocess of this invention the colloidal resin particles of the latex are protected from the action of the coagulant salt by the presence of a dispersing agent which gradually becomes insoluble as the temperature of the latex is raised. As the dispersing agent becomes insoluble the resin particles form small clusters of the original colloidal particles and these clusters deposit in the impregnated material in the form of a porous mass as distinguished from the coagulated, dense curdlike mass referred to above. The formation of the porous clusters is referred to herein as agglomeration.

The material which is to be stiffened may, in general, be any fibrous'sheet material such as any of the varieties of fabrics, textiles, felted materials, mats, p'apers,'or the like. The sheet material may be made of natural or synthetic fibers or a mixture of the two. In the case of shoe stifieners the material commonly employed is a cotton flannel, although non-woven sheet material or even paper may be used in some cases.-

Filler materials may be incorporated into the impregnating medium of this invention to serve several useful purposes. For example, the filler may be used to reduce the cost of the materials used in the impregnating bath. The use of a filler in many instances causes the impregnated material to be more porous and therefore to be able to absorb more solvent and achieve a greater stiffness. In some cases, the use of a filler enhances the adhesiveness of the impregnated material to an adjacent laminating layer. Some filler materials serve many purposes in addition to their diluent effect, for example, they may act as a buffering agent as will be explained later, they may improve fire resistance, improve adhesiveness and solvent absorption and other uses apparent to those skilled in theart. Inthe manufacture of shoe parts using the impregnated shoe stiffener of this invention it has been found that the incorporation of filler materials permits the shoe stiffener to be handled easily when it is wet with solvent and ready to be incorporated into the shoe partand, furthermore, after the shoe part has been assembled there is less likelihood that resin solids will migrate from the shoe stiffener and cause visible spotting on the leather surfaces of the shoes. Filler materials which may be used include water soluble salts such as calcium carbonate and calcium sulfate, infusorial earths, bentonite clays, and other inert materials known to those skilled in the art. The amount of filler materials which may be used may be as much as about by weight of the resin solids present and a range of values of about 20% to 50% is preferable for most embodiments of this invention.

Thickeners have utility in this invention when it is desired to regulate the amount of resin solids that may be put into a fabric by impregnation, when frothing of the impregnating medium is desirable, and when fillers and other. ingredients of the latex have a tendency to settle out. Thickcners which have been used successfully include methyl cellulose and methyl carboxy cellulose. Other equally useful thickeners are well known to those skilled in the art.

In the preparation of high quality shoe stifieners and in certain other embodiments of this invention it is highly desirable to maintain the pH of the impregnating latex at substantial neutrality so that there will be no injury to the supporting fibrous sheet material due to acidic attack. Latices containing a mixture of polystyrene and a copolymer of styrene/buta-diene, a dispersing agent, a filler such as calcium carbonate, and one of the coagulant salts described above normally are substantially neutral in pH vvalues. However, if for some reason the latex is acid, it is preferable to add an alkalizing material to adjust the pH to a value of 6.0 to 7.0. Any of a large variety of -salts-may 'be added to the latex to perform the buffering function, such as the alkali metal and alkaline earth metal carbonates, bicarbonates and hydroxides. Calcium car- 7 bonate has been found to be desirable for this purpose, and approm'mately 1% by weight of the resin solids is sufiicient to raise the pH to 6.0 or'7.0. It is also possible to utilize hydroxides, such as calcium hydroxide, in very small amounts to adjust the pH to the desired level of 6.0 to 7.0. 1

As a final step in the preparation of the impregnating latex, water may be added to form the desired concentration of resin solids, which for most embodiments of this invention will be from about 20% to about 60% by weight of solids. For the preparation of most shoe stiffeners, a concentration of about 40% solids has been found to be preferable.

Because of the sensitivity of synthetic resin latices toward coagulation, it is recommended that the impregnating composition be prepared by mixing the ingredients in a specific order; namely, that the resin latex and the dispersing agent be thoroughly mixed before adding the coagulant. Furthermore, it is helpful to add the coagua lant slowly, and in a diluted condition, to the latex while the latex is being agitated. Such precautions as these assist in preventing any localized coagulation of the resin solids in the latex.

In the process of preparing a stiffened material such as a shoe stiffener, cotton flannel or other supporting sheet material is dipped, sprayed, covered, or otherwise treated with the impregnating latex, which is prepared according to the above description.

The excess liquid is removed from the wet impregnated material by a suitable means such as coacting stripping rolls, a wiper knife, or the like. Such an operation is capable of loading the supporting material to the desired amount of about 50% or more by weight of impregnating solids if the original impregnating latex contains about 40% solids. Some shoe stifleners are prepared with much less than 50% resin solids and this process is capable of preparing such shoe stiffeners by loading the material with less than 50% solids. The stripped, impregnated material is then heated to cause agglomeration of the resin solids and to evaporate the remaining water from the material. Any method of heating may be utilized although it has been found that the most desirable results are obtained if the material is heated in a humid atmosphere, for example, 95 C. by contact with steam at about 95 C. to about 120 C. The steam treatment is followed by drying to produce a dry, impregnated material having better solvent absorption characteristics, and thereby, a greater stiffness, than can be produced by using other methods. In some cases it may be desirable to subject the dried impregnated sheet material to the action of calendering rolls to produce an accurate caliper thickness in the material.

The dried impregnated material, by the above treatment, contains small agglomerates of resin particles uni formly dispersed throughout the sheet material. As such this material may be stored if desired, or it may be used in the production of a stiffened article of manufacture, such as a box toe or counter in a shoe, a laminate with other materials, shaped molds, and other similar objects. The stiliening process is accomplished by treating the dry, impregnated material with a solvent for the resin, forming the solvent-treated material into the desired shape and allowing the solvent to evaporate leaving a stiif, self-supporting, article. The solvent for the polystyrene resin may be methyl ethyl ketone, toluene, or mixtures of these materials, and the solvent for the polyvinyl chloride resin may be methyl ethyl ketone, cyclohexanone, or mixtures of these materials with each other or with diluents. Other solvents for these and other operable resins are known to those skilled in the art.

The process of this invention is particularly useful in the preparation of shoe stiffening materials such as box toe or shoe counters and it also finds a wide variety of uses in the preparation of impregnated materials which are used to stiffen or otherwise strengthen materials with which it is laminated. The impregnated material of this invention may be used to repair sheet metal articles such as roof gutters; downspouts, fenders and bodies of automobiles. This material also finds use in covering the decks and hulls of small boats, in the preparation of artificial limbs, in the manufacture of mannikins, and various display devices and in any of a variety of laminating applications.

I claim:

1. A process for preparing sheet materials capable of being stiffened comp-rising preparing an aqueous latex consisting essentially of 1) 20% to 60% by weight of a vinyl polymer, (2) 0.5% to 5% by weight of said vinyl polymer of a non-ionic dispersing agent which is soluble 'in Water at some temperature from about room temperature to about 40 C. and is substantially insoluble in water at some temperature from about 40 C. to about 100 C., and (3) from about 0.5% to about 15% by Weight of said vinyl polymer of a water-soluble salt from the group consisting of amine salts and quaternary ammonium salts; impregnating a fibrous sheet material with said aqueous latex, removing excess latex from said sheet material, heating said sheet material at a temperature of 40 C. to 100 C. until the liquid latex particles agglomerate, and thereafter drying the sheet material.

2. The process of claim 1 in which the heating of said sheet material at a temperature of 40 C. to 100 C. is accomplished in a humid atmosphere.

3. A process for preparing sheet materials capable of being stiffened comprising preparing an aqueous latex consisting essentially of (l) 20% to 60% by weight of a mixture of a major portion of polystyrene and a minor portion of a copolymer of styrene/butadiene, (2)-0.5% to 5% by weight of said mixture of a non-ionic dispersing agent which is soluble inwater at some temperature from about room temperature to about 40 C., and insoluble in water at some temperature from about 40- C. to 100 C., and (3) from about 0.5% to about 15% by Weight of said vinyl polymer of a Water-soluble salt from the group consisting of amine salts and quaternary ammonium salts; impregnating a fibrous sheet material with said aqueous .latex, removing excess latex from said sheet material, impregnating a fibrous sheet material with said aqueous latex, removing excess latex from said sheet material, heating said sheet material to a temperature of at least 95 C. by direct contact with steam until the liquid latex particles agglomerate, and thereafter drying the sheet material.

4. The process of claim 3 in which the weight ratio of said major portion to said minor portion is about 3:1 and said copolymer contains styrene and butadiene in the weight ratio of about :20.

5. The process for preparing a shoe stiffener comprising preparing an aqueous latex consisting essentially of (1) 30% to 50% by weight of resin solids comprising 3 parts by Weight of polystyrene and 1 part by weight of an 80/20 copolymer of styrene/butadiene, (2) 0.5% to 5% by weight of said resin solids of an alkyl phenyl polyglycol ether dispersing agent, (3) about l%5% of a water-soluble quaternary ammonium salt; impregnating a cotton flannel sheet material with said aqueous latex, removing excess latex from said sheet material until at least 50% of the weight of the impregnated sheet material comprises latex solids, heating said sheet material to a temperature of C. to C. in a humid atmosphere until the liquid latex particles agglomerate, removing the remaining moisture in said sheet material, and recovering a dry, flexible, impregnated flannel sheet material capable of being stiffened by subjecting it to the action of a solvent for said resin solids.

6. The process for preparing a shoe stiffener comprising preparing an aqueous latex consisting essentially of (l) 30% to 50% by weight of resin solids comprising 3 parts by weight of polystyrene and 1 part by weight of an 80/20 copolymer of styrene/butadiene, (2) 0.5

to by weight of said resin solids of an alkyl phenyl polyglycol ether dispersing agent, (3) about 1%-5% of a water-soluble quaternary ammonium salt, and (4) 20% to 50% by weight of said resin solids of calcium carbonate, impregnating a cotton flannel sheet material with said aqueous latex, removing excess latex from said sheet material until at least 50% of the weight of the impregnated sheet material comprises latex solids, agglomerating the liquid latex particles in the resulting sheet material by heating said sheet material to a temperature of 95 C. to 120 C. by direct contact with steam, removing the remaining moisture in said sheet material, and recovering a dry, flexible, impregnated flannel sheet material capable of being stiffened by subjecting it to the action of a solvent for said resin solids.

7. The process for preparing a shoe stiffener comprising preparing an aqueous latex consisting essentially of (1) 30% to 50% by Weight of resin' solids comprising 3 parts by weight of polystyrene and 1 part by Weight of an 80/20 copolymer of styrene/butadiene, (2) 0.5% to 5% by weight of said resin solids of an 'alkylphenyl polyglycol ether dispersing agent, (3) about 1%-5% of a water-soluble amine salt, and (4) 20% of said resin solids of calcium carbonate, impregnating a cotton flannel sheet material with said aqueous latex, removing excess latex from said sheet material until at least 50% of the weight of the impregnated sheet material comprises latex solids, agglomerating the liquid latex particles in the resulting sheet material by heating said sheet material to a temperature of 95 C. to 120 C. by direct contact with steam, removing the remaining moisture in said sheet material, and recovering a dry, flexible, impregnated flannel sheet material capable of being stiffened by subjecting it to the action of a solvent for said resin solids.

8. A liquid composition consisting essentially of (1) to 50% by Weight 20% to 60% by weight of a vinyl polymer, (2) 0.5% to 5.0% by weight of said vinyl polymer of a non-ionic dispersing agent which is soluble in water at some temperature from about room temperature to about C. and is insoluble in water at some temperature from about 40 C. to about 100 C., (3) 0.5% to 15% by weight of said vinyl polymer of a water-soluble salt from the group consisting of amine salts and quaternary ammonium salts, and (4) sufficient water such'that the sum of all components equals 100%.

9. A liquid composition consisting essentially of (l) 20% to by weight of colloidal resinous particles comprising polymeric styrene and polymeric butadiene in the proportions of 4% to 20% by weight of polymeric butadiene and 96% to by weight of polymeric styrene, (2) 0.5% to 5.0% by weight of said resinous particles of an alkylphenyl polyglycol ether dispersing agent, (3) about 1% to 5% by weight of said resinous particles of a Water-soluble quaternary ammonium salt, (4) 20% to 50% by weight of said resinous particles of calcium carbonate, and (5) suflicient water such that the sum of all components equals 100%.

References Cited in the file of this patent UNITED STATES PATENTS 2,040,320 Lovell May 12, 1936 2,444,801 Arundale July 6, 1948 2,618,796 Brophy Nov. 25, 1952 2,629,877 Carnes Jan. 27, 1953 2,635,055 Figdor Apr. 14, 1953 2,639,240 Ehle May 19, 1953 2,692,245 Groves Oct. 19, 1954 2,760,884 Graf Aug. 28, 1956 OTHER REFERENCES Whitby: Synthetic Rubber, Sept. 15, 1954.

Claims

1. A PROCESS FOR PREPARING SHEET MATERIALS CAPABLE OF BEING STIFFENED COMPRISING PREPARING AN AQUEOUS LATEX CONSISTING ESSENTIALLY OF (1) 20% TO 60% BY WEIGHT OF A VINYL POLYMER, (2) 0.5% TO 5% BY WEIGHT OF SAID VINYL POLYMER OF A NON-IONIC DISPERSING AGENT WHICH IS SOLUBLE IN WATER AT SOME TEMPERATURE FROM ABOUT ROOM TEMPERATURE TO ABOUT 40*C. AND IS SUBSTANTIALLY INSOLUBLE IN WATER AT SOME TEMPERATURE FROM ABOUT 40*C. TO ABOUT 100*C., AND (3) FROM ABOUT 0.5% TO ABOUT 15% BY WEIGHT OF SAID VINYL POLYMER OF A WATER-SOLUBLE SALT FROM THE GROUP CONSISTING OF AMINE SALTS AND QUATERNARY AMMONIUM SALTS, IMPREGNATING A FIBROUS SHEET MATERIAL WITH SAID AQUEOUS LATEX, REMOVING EXCESS LATEX FROM SAID SHEET MATERIAL, HEATING SAID SHEET MATERIAL AT A TEMPERATURE OF 40*C. TO 100*C. UNTIL THE LIQUID LATEX PARTICLES AGGLOMERATE, AND THEREAFTER DRYING THE SHEET MATERIAL.