US3677810A

US3677810A - Silicone-acrylate soil release treatment for organic textiles

Info

Publication number: US3677810A
Application number: US85702A
Authority: US
Inventors: James K Campbell; Kenneth M Lee
Original assignee: Dow Corning Corp
Current assignee: Dow Silicones Corp
Priority date: 1970-09-03
Filing date: 1970-10-30
Publication date: 1972-07-18
Anticipated expiration: 1989-07-18
Also published as: CH568437B5; US3714287A; BE772087A; DE2144337C3; DE2144337A1; CA953857A; DE2144337B2; GB1367666A; ATA771371A; AT353740B; CH559278A5; CH1284371A4

Abstract

REMOVAL OF STAINS DURING LAUNDERING OF ORGANIC TEXTILES IS FACILITATED AND SUPERIOR HAND IS IMPARTED TO THE FABRIC BY APPLYING THERETO A COMBINATION OF FROM 10 TO 99% BY WEIGHT OF A POLYMETHYLSILOXANE AND FROM 1 TO 90% BY WEIGHT OF A POLYMERIC, UNSATURED, WATER-SOLUBLE CARBOXYLIC ACID. THIS COMBINATION WORKS ESPECIALLY WELL IN COMBINATION WITH AMINOPLAST CREASE RESISTANCE TEXTILE RESINS. A TYPICAL FORMULATION IS 45% BY WEIGHT OF DIHYDROXYL DIMETHYLOLETHYLENE UREA RESIN. 27.5% BY WEIGHT OF A POLYDIMETHYLSILOXANE OF 50,000 CS. VISCOSITY AND 27.5% BY WEIGHT OF POLYMETHACRYLIC ACID.

Description

United States Patent 3,677,810 SILICONE-ACRYLATE SOUL. RELEASE TREAT- MENT FOR ORGANIC TEXTILES James K. Campbell, Midland, and Kenneth M. Lee, Bay City, Mich., assignors to Dow Corning Corporation,

Midland, Mich.

No Drawing. Continuation-impart of application Ser. No. 69,467, Sept. 3, 1970. This application Oct. 30, 1970, Ser. No. 85,702

Int. Cl. C08j 1/40 US. Cl. 117138.8 F 8 Claims ABSTRACT OF THE DISCLOSURE This application is a continuation-in-part of application Ser. No. 69,467, filed Sept. 3, 1970, now abandoned.

The problem with which this invention has to do is that of soil release or stain removal from fabrics during laundering. The term soil release as used herein refers to the phenomenon. This is to be distinguished from dry soiling or dry soil release which is particularly apropos to carpeting and drapes. In the latter, one is primarily concerned with soil build-up while the fabric is in use.

There is considerable debate in the industry as to whether the problem of this invention is due to the lack of removal of the stain by the water detergent mix during laundering or whether the soil or stain is removed and then redeposited during laundering. Applicants are not to be tied to either of these explanations or theories for the operativeness of their invention.

The problem to which this invention relates has become particularly acute with the advent of synthetic fibers such as polyester fibers which are oleophilic in nature and which do not wet well with water. It is also made particuarly acute with the advent of aminoplast crease resistance resins which are applied to various types of fabric in order to prevent wrinkling. In both of these cases, or in a combination thereof, there is considerable difiiculty in removing a stain, particularly oil-based stains from fabrics. Of the fabrics presently on the market the polyester based fabrics pose the worse problem. However, this invention is applicable to all types of organic fabrics such as nylon, acrylic fibers and cellulosic fibers, in general.

It is known particularly from U.S. Pats. 3,236,685 and 3,377,249, that polyacrylic acid polymers can be employed either alone or in conjunction with aminoplast crease resistance resins to enhance the soil release properties of fabrics. It is also known that silicones, in general, increase the soiling of fabrics by oil-based stains. This is shown, for example, in many publications such as one appearing in American Dyestuff Reporter, page 299, May 5, 1958, entitled Wet-soiling Studies on Resin Treated Cotton Fabrics. This article shows that when soft acrylic finishes are placed on fabric the soiling is enhanced. It also shows in FIGS. 2 and 4 that a methylpolysiloxane alone enhances the staining of fabrics by oil based stains and that a combination of a methylpolysiloxane and an acrylate finish is worse than either alone. The article coneludes that once soiled the silicone-acrylate finish on cotton cannot be cleaned and that the soiling is irreversible. This publication is acknowledged and the conclusions concurred in the Textile Research Journal, page 146, February 1963, in an article entitled Some Obersavtions on Wet Soiling of Resin-Treated Cottons. Further statements as to the detrimental aifect of silicones on soiling of textiles are found in the proceedings of the American Association of Textile Chemists and Colorists (AATCC) reported in American Dyestutf Reporter," Oct. 11, 1965, page 37. In discussing the effect of the surface energy of the textile treatment on soiling, the authors came to the conclusion that those materials having low surface energy such as silicones materially enhanced the soiling of the fabric.

In the light of these teachings it is quite obvious why the patentees in the aforementioned patents carefully avoided the mention of any silicone in connection with their soil release treatments.

Applicants have found, however, quite unexpectedly that a combination of the organosiloxanes defined hereinafter and polymeric carboxylic acids as defined hereinafter, produce soil release properties equivalent to or superior to those of the polymeric carboxylic acids alone. It has also been found that the combination of silicones and the polymeric carboxylic acids give far superior hand, particularly in connection with crease resistance resins than do the polymer carboxylic acids alone. The presence of the silicone also greatly enhances the mechanical strength of the fabric which is often badly deteriorated by the use of aminoplast crease resistant resins. For example, the combination of the silicone and polymeric acid when applied in conjunction with the aminoplast resin improves the tear of the fabric by 40% or more and the flex abrasion by from 400 to 500% over the same fabric treated with the aminoplast resin alone.

This invention relates to a mixture of (A) an aminoplast textile resin and in amount sufiicient to increase soil release of an organic fabric to which the mixture is applied, (B) a combination of (1) from 10 to 99% by weight of a polymethylsiloxane containing at least one methyl group per silicon, the remaining substituents on the silicon being substantially all hydrogen or aliphatic hydrocarbon radicals of 1 to 2 carbon atoms and (2) from 1% to by weight of a polymeric, unsaturated, water-soluble carboxylic acid, the proportions of (l) and (2) being based on the combined weights of the two.

This invention also relates to the method of improving soil release of an organic fabric which comprises applying thereto the mixture of (1) and 2) of the preceding paragraph and thereafter drying the coating on the fabric.

The term drying includes curing the coating and merely removing the water or solvent under conditions where no curing occurs.

The types of silicones which are operative herein are dimethylpolysiloxanes, methyl hydrogen polysiloxanes, methylvinylsiloxane and methylethylsiloxane or copolymers of these. Preferably, the siloxaue is a dimethylsiloxane, a methyl hydrogen siloxane or a dimethylsiloxane containing copolymerized therewith a minor amount i.e., 20 mol percent or less of methylvinylsiloxane or methylethylsiloxane. The siloxanes can be endblocked with hydroxyl groups or functional groups such as alkoxy, acetoxy, etc., or they can be endblocked with R SiO units in which R is any hydrocarbon or halohydrocarbon radical. The viscosity of the siloxane is not critical and it can range, for example, from 100 cs. to non-flowing gums.

The polysiloxane can be cured on the fabric or not depending upon the ultimate use of the fabric. If the siloxane is to be cured one can use any of the conventional crosslinkers and catalysts commonly used to cure polysiloxanes. For example, one can cure hydroxyl endblocked polysiloxanes with crosslinkers such as SiH containing siloxanes, alkoxysilanes or alkoxy silicates, acyloxysilanes, ketoxime silanes (i.e. RSi(ON=CR' where R and R are hydrocarbon radicals) and amineoxy silaues using catalysts such as metal salts of carboxylic acids such as dibutyl-tin-diacetate or ferric octoate or alkyl titanates such as tetrabutyl titanate or amines. In addition, one can cure the siloxane via the interaction of SiH with Si alkenyl using such catalysts as chloroplatinic acid. The cure of the siloxane is not to be confused with the cure of the aminoplast resin although the two can be cured simultaneously, if desired.

When cure of the s'iloxane is not desired, the siloxane and polymeric acid are applied to the fabric without a curing catalyst for the siloxane and the coating is heated to remove any solvent or water.

The polymeric carboxylic acids used herein are polymers of unsaturated water-soluble carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, vinylacetic acid or fumaric acid. The polymeric carboxylic acid can be a homopolymer or it can be copolymer of two or more types of such acids. In the case of vinylacetic or fumaric acid it is preferable to prepare a copolymer with either acrylic, methacrylic or itaconic acids. If desired, the polymeric carboxylic acid of this invention can also contain small amounts of other vinylic polymers such as acrylic esters, styrene, vinylchloride, or the like.

The term combination of as used in the claims of this application means that the silicone and the polymeric carboxylic acid can be a copolymer or a mixture. Thus, for example, the polysiloxane can be prepared and then copolymerized with the unsaturated acid by means of standard emulsion polymerization techniques or by means of standard solvent polymerization techniques. In such techniques the preferred catalyst is potassium persulfate. It is also preferable that the siloxane contain alkenyl groups if it is desired to prepare copolymers. However, the present invention operates perfectly well with mere blends of the polymeric carboxylic acid and the siloxane. In these circumstances the polysiloxane is prepared separately from the polymeric carboxylic acid, each being polymerized by conventional techniques. The two polymers are then blended in any convenient fashion. It has been found that this can be done satisfactorily by mixing the two polymers and then passing the mixture through a colloid mill. Preferably, the siloxane will be in the form of a emuls1on.

If desired, the soil release treatment of this invention can be used in conjunction with aminoplast textile resins. These materials are well known articles of commerce. Examples of such resins are urea formaldehyde resins, melamine formaldehyde resins, ethylene urea formaldehyde resins, carbamate formaldehyde resins, amide formaldehyde resins, diurea formaldehyde resins and triazone formaldehyde resins. For a more extensive list of the specific aminoplast resins which are operative herein, one is referred to US. Pat. 3,377,249, columns 5 and 6, which are hereby incorporated in this application by reference.

The aminoplast resin can be cured on the textile by any of the conventional catalysts generally employed in commerce. These can be of the Lewis acid type, of the basic type or any other type desired. For a complete list of such catalysts columns 6 and 7 of the aforesaid patent are hereby incorporated by reference.

Of course, if desired, the aminoplast resin can be cured by other means such as by radiation.

The combination of this invention is applied to the fabric by any conventional means such as by padding, dipping or spraying. The concentration of the treating bath is not critical and can range from 0.1 to 5% or more of the combined weight of the siloxane and polymeric carboxylic acid. The aminoplast resin can be applied to the normal concentration used with the particular type fabric empolyed. When aminoplast resins are used the bath can con- .4 tain conventional amounts of such resins such as from 2 to 30% or more shown in US. Pat. 3,377,249.

The amount of the combination of 1) and (2) on the dry fabric is not critical, nor is the relative amounts of the combination (1) and (2) and the aminoplast resin so long as the aforesaid combination is present in amount suflicient to impart soil release. In general, the wet pick up based on the dry weight of the fabric will run from 50 to of the weight of (1) and (2).

It should be understood that (l), (2) and the aminoplast resin can be applied to the fabric in combination or each ingredient can be applied alone and in any order. Preferably the materials are applied simultaneously.

The soil release properties of this invention are obtained with any organic fabric such as cellulosic fabrics such as cotton, rayon, cellulose acetate or viscose; polyamide fibers such as nylon; polyacrylic fabrics such as polyacrylonitrile and polyester fibers such as those arrived from ethylene glycol and terephthalic acid; protein fibers such as wool and polyvinylic fibers such as those from copolymers of vinyl chloride and vinylidene chloride or polypropylene. It should be understood that blends of any of these types of fibers can be employed, if desired.

The numerical values of soil release shown in the following examples were obtained by the standard of soil release oily stain release AATCC Test Method 1969 which appears in the AATCC Technical Manual, page 223. The test was modified only to the extent that burnt motor oil, Sears chassis grease or salad oil were used in place of Nujol brand mineral oil. Substitution is permitted by the standard test. Briefly in this test the stain remaining on the garment after washing is compared to standards supplied by the American Association of Textile Chemists and Colorists. A rating of 5 indicates excellent stain removal and the standards are graded down through 1 which represents a very poor stain removal.

The following trade names and their definitions appear in the examples infra.

Triton X-l00 is nonyl benzene poly-alkyleneoxide.

Permafresh-183 is dihydroxy dimethylol ethylene urea.

Emulphogen BC-720 is tridecyloxypoly(ethylenoxy) ethanol.

Abex 188 is an anionic surfactant.

In order that those skilled in the art may better understand how the present invention can be practiced, the following examples are given by way of illustration and not by way of limitation. All percents referred to herein are by weight and all viscosities measured at 25 C. unless otherwise specified.

EXAMPLE 1 An emulsion was prepared by polymerizing methacrylic acid with potassium persulfate in an emulsion of a copolymer of 98.5 mol percent dimethylsiloxane and 1.5 mol percent methylvinylsilox-ane in proportions such that the emulsion contain a weight ratio of 50% polysiloxane and 50% polyacrylic acid. The resulting emulsion had a solids content of 13.7%. 26.7 g. of this emulsion was mixed with 44.7 g. of water, .3 g. of Triton X-100, 25 g. of a 45% solids water solution of Permafresh183 and 3.5 g. of a 50% water solution of magnesium chloride. The resulting combination was applied to nylon fabric and cured at 250 F. for 15 minutes. After one wash in accordance with the aforesaid standard test the rating from a Sears chassis grease stain was 5, and from burnt motor oil stand was 5. This indicates excellent removal of the stain in one wash.

EXAMPLE 2 60 g. of methyl hydrogen polysiloxane was mixed with 136 g. of water and emulsified with 4 g. of Emulphogen 130-720. This gave a 30% solids emulsion. 25 g. of this 1 Except In Example 3.

emulsion was mixed with 98.8 g. of polymethacrylic acid water solution containing 7.5 g. of acid.

28.2 g. of the above mixture was mixed with 43 g. of water, .3 g. of Triton X-100, 25 g. of a 45% solution of Permafre'sh-183, and 3.5 g. of a 50% solution of magnesium chloride. The resulting bath was applied to a 5050 blend of polyester-cotton fabric and dried for minutes at 250 F. and then cured for 15 minutes at 250 F. After one wash the rating under the standard test for Sears chassis grease was 5 and for burnt motor oil was 4.

EXAMPLE 3 An emulsion of a copolymer of 98.5 dimethylsiloxane and 1.5 mol percent of methylvinylsiloxane having a concentration of 32% by weight siloxane was prepared. 56.6 g. of this emulsion was mixed with 312 g. of a 7.8% polymethacrylic acid solution. The mixture was put through a colloid mill at a setting of 20 mils followed by 3 passes at a 5 mil setting.

32.4 g. of this mixture was mixed with 38.8 g. of water, 25 g. of a 45% water solution of Permafresh-1 83, .3 g. of Triton X-100 and 3.5 g. of a 50% magnesium chloride solution.

This mixture was applied to a white cloth composed of 5050 polyester-cotton blend and cured at 250 F. for 15 minutes. The fabric was washed and stained in accordance with the aforementioned standard test. However, the stain removal was measured using a photovolt photoelectric cell measuring device which recorded the intensity of light reflected from the sample. The cloth treated with the above mixture was checked against the same untreated unstained cloth, the same untreated stained cloth and the same cloth which was treated with the Permafresh-183 resin only and stained. Each sample was checked after one wash and after 23 washes.

75 g. of 30% solids emulsion of a 25,000 cs. polydimethylsiloxane was mixed with 4 g. Abex 18S surfactant and the mixture warmed to 70 C. 10.5 g. of 2% solution of potassium persulfate was added and then 25 g. of methacrylic acid over a period of 30 minutes. An additional 10.5 g. of 2% potassium persulfate was then added and the emulsion was heated for 30 minutes at 70 C. and then 30 minutes at 85 C. The resulting composition contained 50 weight percent of the combined silicone and polymethacrylic acid.

30.5 g. of the above emulsion was mixed with 45.7 g. of water, .3 g. of Triton X-100, 20 g. of a 45% water solution of Permafresh-183 and 3.5 g. of zinc nitrate solution. The bath contained 4% of the combination of silicone and polymethacrylic acid. The bath was applied to 5050 blend of polyester and cotton and cured 5 minutes at 250 F. and then 15 minutes at 250 F. The fabric was stained with burnt motor oil and upon washing had much better stain removal than an identical fabric treated with a commercial acrylate soil release agent.

EXAMPLE 5 A 31% solids emulsion was made of a 5500 cs. copolymer of 80 mol percent dimethylsiloxane and 20 mol percent methylvinylsiloxane. 79 g. of this emulsion was mixed with 4 g. of Abex 18S and 300 g. of water and heated to 70 C. under nitrogen. 10.5 g. of a 2% potassium persulfate solution was then added, followed by 25 g. of acrylic acid over a 30 minute period. 10.5 additional grams of 2% potassium persulfate were then added and the mixture heated for 30 minutes at 70 C. and then 30' minutes at C.

31 g. of this emulsion was mixed with 45.2 g. of water, 0.3 g. of Triton X100, 20 g. of Permafresh-183 (45% solids) and 3.5 g. of zinc nitrate. This mixture was applied to cotton fabric and cured at 250 F. for 15 minutes. The fabric was stained with burnt motor oil. It was washed in the standard manner and the soil release was better than that with a commercial acrylic soil release coating.

EXAMPLE 6 This example shows use without aminoplast resin. An emulsion was made of a copolymer of 98.5 mol percent dirnethylsiloxane and 1.5 mol percent methylvinylsiloxane using dodecyl benzene sulfonic acid. The solids content was 32.2% by weight. 23.9 g. of this emulsion was blended with 100 g. of 7.7% solution of a polymethacrylic acid.

28.2 g. of this mixture was mixed with 71.5 g. of water and .3 g. of Triton X-100 and the resulting formulation was applied to a 5050 polyester-cotton fabric and dried at 250 F. for 15 minutes.

The test with burnt motor oil showed a soil release of 2 after one wash. The untreated fabric had a rating of 1 after one wash.

EXAMPLE 7 This example shows use of 80% dimethylpolysiloxane and 20% by weight methacrylic acid.

95.7 g. of the silicone emulsion of Example 6 Was mixed with 100 g. of the 7.7 solids polymethacrylic acid solution. 17.8 g. of the resulting mixture was combined with 53.4 g. of water, .3 g. Triton X-100, 25 g. of Permafresh183 (45 solids) and 3.5 g. of MgCl solution (accelerator MX).

A 5050 blend of polyester-cotton fabric was immersed in the composition and put through squeeze rolls at 40 p.s.i. pressure. The fabric was treated 15 minutes at 25 0 F. The soil rating for burnt motor oil was 2 after one wash while the fabric with the Permafresh-183 alone was 1.

EXAMPLE 8 This example shows curing the siloxane. 3 g. of a 35% solids emulsion of a 100,000 cs. hydroxyl endblocked polydimethylsiloxane was mixed with 0.3 g. of methyltrimethoxy silane, 0.3 g. of a 20% solids emulsion of dibutyl-tin-dilaurate, 26.3 g. of a 7.3% solids solution of polymethacrylic acid, and 69.2 g. of water.

This mixture was applied to a 50 50 polyester-cotton fabric and cured 20 minutes at 250 F. The fabric was tested and was found after one Wash to have a stain rating of 2 against burnt motor oil and 3 against salad oil. The untreated fabric gave a rating of 1 for each stain.

EXAMPLE 9 This example also shows curing the siloxane. It further shows that at lower concentrations the polymeric acid improves cleanability with good hand characteristics being obtainable.

Eight compositions (A-H) were prepared and applied to a. white 50-50 polyester-cotton fabric. The fabric samples were dipped into the compositions, nipped between rollers with 40 p.s.i. of pressure, dried, and then oven cured for 15 minutes at 250 F. The fabric samples were then tested for soil release. The compositions employed are set forth below. Compositions A-C and a fabric sample without any composition were included for purposes of comparison.

Composition A consisted essentially of 3 g. of a 35% solids aqueous emulsion of a 100,000 cs. hydroxyl endblocked polydimethylsiloxane, 1 g. of methyltrimethoxysilane, 0.3 g. of a 20% solids aqueous emulsion of dibutyl-tin-dilaurate, 0.1 g. of acetic acid and 95.6 g. of water.

Composition B consisted essentially of 3 g. of a 35% solids aqueous emulsion of a 100,000 cs. hydroxyl endblocked polydimethylsiloxane, 1 g. of methyltrimethoxysilane, 0.3 g. of a 20% solids aqueous emulsion of dibutyltin-dilaurate, 1.3 g. of a 7.7% solids aqueous solution of polymethacrylic acid, and 94.4 g. of water.

Composition C consisted essentially of 3 g. of a 35% solids aqueous emulsion of a 100,000 cs. hydroxyl endblocked polydimethylsiloxane, l g. of methyltrimethoxysilane, 0.3 g. of a 20% solids aqueous emulsion of dibutyltin-dilaurate, 6.5 g. of a 7.7% solids aqueous solution of polymethacrylic acid, and 89.2 g. of water.

Composition D consisted essentially of 3 g. of a 35% solids aqueous emulsion of a 100,000 cs. hydroxyl endblocked polydimethylsiloxane, 1 g. of methyltrimethoxysilane, 0.3 g. of a 20% solids aqueous emulsion of dibutyltin-dilaurate, 13 g. of a 7.7% solids aqueous solution of polymethacrylic acid, and 82.7 g. of water.

Composition E consisted essentially of 3 g. of a 35% solids aqueous emulsion of a 100,000 cs. hydroxyl endblocked polydimethylsiloxane, l g. of methyltrimethoxysilane, 0.3 g. of a 20% solids aqueous emulsion of dibutyltin-dilaurate, 26 g. of a 7.7% solids aqueous solution of polymethacrylic acid, and 69.7% water.

Composition F consisted essentially of 3 g. of a 35 solids aqueous emulsion of a 100,000 cs. hydroxyl endblocked polydimethylsiloxane, 1 g. of methyltrimethoxysilane, 0.3 g. of a 20% solids aqueous emulsion of dibutyltin-dilaurate, 39 g. of a 7.7 solids aqueous solution of polymethacrylic acid, and 56.7% water.

Composition 6 consisted essentially of 3 g. of a 35 solids aqueous emulsion of a 100,000 cs. hydroxyl endblocked polydimethylsiloxane, 1 g. of methyltrimethoxysilane, 0.3 g. of a 20% solids aqueous emulsion of dibutyltin-dilaurate, 65 g. of a 7.7% solids aqueous solution of polymethacrylic acid, and 31.7 g. of water.

Composition H consisted essentially of 3 g. of a 35 solids aqueous emulsion of a 100,000 cs. hydroxyl endblocked polydimethylsiloxane, 1 g. of methyltrirnethoxysilane, 0.3 g. of a 20% solids aqueous emulsion of dibutyltin-dilaurate, 94.8 g. of a 7.7 solids aqueous solution of polymethacrylic acid, and 0.9 g. of water.

The test results appear in the following table.

SOIL RELEASE RATINGS Composition St 1 d lis iic l an A B C D E F G H None t in d 5 5 5 5 5 5 5 5i 5 Uns a e 3 3 3 5 5 5 6 5 4 3 3 4 4 4 4 5 5i 3 1 1 1 2 3 3 4 4 2 1 1 1 1 2 2 3 3 2 E E E G P P P P P E Excellent; G= Good; P =Poor.

That which is claimed is:

1. The method of improving soil release of an organic fabric which comprises applying thereto a soil release effective amount of a combination of (1) from 10 to 99% by weight of a polymethylsiloxane containing at least one methyl group per silicon, the remaining substituents on the silicon being substantially all hydrogen or aliphatic hydrocarbon radicals of 1 to 2 carbon atoms and (2) from 1 to by Weight of a polymeric, unsaturated, Water-soluble carboxylic acid, the proportions of (1) and (2) being based on the combined Weights of (l) and (2) and thereafter drying the coating on the fabric.

2. The method of claim 1 in which the fabric is a polyester fabric, (1) is dimethylpolysiloxane and (2) is polymethacrylic acid.

3. The method of claim 1 in which the fabric is a polyester fabric, (1) is a dimethylpolysiloxane and (2) is polyacrylic acid.

4. The method of claim 1 in which the fabric is also treated with an aminoplast resin.

5. The method of claim 1 in which the fabric is treated with an aminoplast textile resin in combination with the soil release agent.

6. The method of claim 5 in which fabric is a polyester fabric, (1) is polydimethylsiloxane and (2) is polymethacrylic acid. 1;

7. The method of claim 4 in which the fabric is a polyester fabric, (1) is polydimethylsiloxane and (2) is polymethacrylic acid.

8. The method of claim 4 in which the fabric is a blend of polyester fiber and cotton, (1) is polydimethylsiloxane and (2) is polyrnethacrylic acid.

References Cited UNITED STATES PATENTS 9/1957 Dennett 117-161 X 2/1966 Caldwell ....117--138.8

US. Cl. X.R.

1l7--138.8 N, 138.8 UA, 139.4, 139.5 A, 143 A, 145, 161 UA, 161 ZA; 260826