US3054695A - Procedure for producing textiles resistant to chemical warfare liquids - Google Patents

Description

3,054,695 PROCEDURE FOR PRGDUCING TEXTHJE RESET- ANT T CHEMICAL WARFARE LlQUlD Leopold Loeb, Louisville, Ky., and Robert L. Clayton, J12, New Orleans, Stanley P. Kolturn, Metairie, Frederick 5. "Philips, New Gil-leans, Leon Segal, Metairie, and Kazuo H. Tahernura, New Orleans, La, assignors to the United States of America as represented by the decretary of the Army No Drawing. Filed June 24, 1957, Ser. No. 667,717 5 Claims. (Cl. 117-72) (Granted under Title 35, US. Code (E52), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment to us of any royalty thereon.

This invention relates to a process of impregnating textile materials with a composite material which renders them highly resistant to wetting or penetration by chemical Warfare liquids without undesirably altering their hand, feel, or air permeability.

Copending patent application Serial No. 667,719, file'd on even date, describes surface coatings which are resistant to chemical warfare liquids. The present invention provides an improved process of forming such surface coatings on the fibers of a textile material.

Heretofore numerous compositions and treatments for coating the surfaces of textile materials and other permeable materials, to render the materials impermeable to water and similar polar liquids, have been developed. Some of these treatments render the treated materials more permeable to organic solvent soluble materials such as oil and the like, and others render the treated materials impermeable toboth water and oil. However, the more penetrating chemical warfare liquids have a capability of wetting and penetrating that is many times greater than that of either water or oil. Materials capable of resisting penetration by water and oil are often almost instantaneously penetrated by a liquid such as the warfare liquid designated as GB by the Army Chemical Corps i.e. isopropyl methylphosphonofluoridate. The chemical warfare liquids are polar liquids having a low surface tension. They penetrate a cloth composed of a cellulosic textile material in a fraction of a second regardless of the construction or weave of the cloth.

The terms penetration time and wetting time as used in this specification have the following meanings. Penetration time is the time required for the underside of the fabric to show the first traces of penetration by a drop of liquid placed on its upper side. Wetting time is the time required for a drop of the liquid placed upon the fabric to dissipate, i.e., to lose its identity as a drop.

When the surface coatings described in the abovementioned copending application are formed on the surfaces of the fibers of a textile material, the textile materials are generally resistant to Wetting and penetration by liquid GB for at least about 100 seconds, and may be resistant for many hours. Those surface coatings comprise a substantially homogeneous surface coating consisting essentially of a certain type of polymer to which is bonded a Werner-type chromi-nuclear complex in which the acido groups consist essentially of perfluoroalkanoyl groups con- 3,054,695 Patented Sept. 18, 1962 taining at least six carbon atoms. Although those surface coatings can be formed on the surfaces of textile fibers by a basically simple process requiring only two steps and a minimum of control, slight variations in the process of forming them may produce rather widely varying results, and some of the essential reactants have a relatively short working life in the form in which they can be employed.

A primary object of this invention is to provide a substantially foolproof process, adapted for field or plant use, for impregnating a textile fabric with a material that converts the fabric to one which exhibits properties such as hand, feel, air permeability and the like which are substantially as desirable as those of the untreated fabric and will resist wetting and penetration by even the highly active liquid GB for at least about minutes. Another object is to provide a process of bonding Werner-type chromi-nuclear complexes to acid sensitive materials without causing acid induced degradation. A further object is to provide a process of bonding Wernontype chromi-nuolear complexes in which the acido groups consist essentially of periiuoroalkanoyl' groups containing at least six carbon atoms to certain polymeric surface coatings by a bonding process: that enhances the resistance of the resulting composite surface and coating to wetting by polar or non-polar liquids.

In general, in accordance with the present invention, a textile material is rendered highly resistant to wetting and penetration by liquid chemical warfare agents by: impregnating the textile with an inert volatile liquid containing a polymer, of the group consisting of polymethylacrylate, polyethylacrylate, polyvinyl-acetate, and copolymers of acrylonitrile and butadiene containing from about 30 to 60 weight percent of acrylonitrile, to a dry pick-up of from about 25 to 50 Weight percent; drying the impregnated textile at a temperature of from about 20 to 30 centigrade; immersing the dry impregnated textile in and substantially immediately removing it from contact with a liquid composition, which is maintained at a temperature between its freezing point and about 5 C., and which consists essentially of water, from about 0.4 to 3.3 weight percent of a water soluble alleanol, fromabout 0.2 to 1.5 weight percent of a Werner-typcchromi-nuclear complex in which the acido groups consist essentially of perfluoroalk-anoyl groups containing from about 6 to 18 carbon atoms, and suflicient water soluble nitrogen-base to produce a pH of from about 4.8 to 5.5 (substantially immediately); freeing the wet textile of drops of the liquid; and drying the wet textile at a temperature of from about to C. for from about 30 to 90 minutes.

When a textile material is treated in accordance with the present invention the physical structure of the composite material with which the textile is impregnated appears to enhance the capacity of the treated textile to -1 esist wetting and penetration by chemical warfare liquids. While this invention is not premised upon any particular theory or postulated mechanism, it appears that the above combination of steps results in: (1) the formation of a substantially homogeneous layer of a polymeric film which surrounds and draws together at least some bundles of fibers; and (2) the bonding to that film of a substantially monomo-lecular layer of uniformly distributed Werner-type chromi-nuclear complexes arranged so that their perfluoroalkanoyl acido groups extend to form an outer surface layer consisting essentially of chains of carbon atoms surrounded by fluorine atoms. Cotton sateen treated in this manner usually resists wetting and penetration by liquid GB for at least about 1000 seconds and usually exhibits an air permeability equal to or greater than that of the untreated sateen.

Substantially any textile material composed of vegetable, animal, synthetic, or glass fibers can be employed. The employment of fabrics composed essentially of cellulosic textile fibers is preferred. The invention is especially adapted for the treatment of cotton clothing fabrics such as cotton sateen and the like.

The inert volatile liquids containing the polymer can be aqueous dispersions or organic solvent solutions of the specified polymers. The liquids can contain widely varying amounts of polymers. The dispersions or solutions can contain the amounts and types of emulsifying, wetting, and/or dispersing agents that are usually employed in polymer compositions adapted for the production of surface coatings. The polymers can vary widely in molecular Weight or degree of polymerization. The specified proportion of polymer can be applied to the textile in one or a plurality of steps. Illustrative examples of suitable aqueous dispersions which are commercially available include the film-forming dispersions of polyethylacrylate, copolymers of acrylonitrile and butadiene or polyvinylacetate, which are available under the trade names Hycars, Polycos, Rhoplex, Darex, Vinylite dispersions, and Chemigum latices. Suitable organic solvent solutions include solutions of the polymers in the lower alcohols such as methyl, ethyl, and the like alcohols, the lower ketones such as acetone, methyl ethyl ketone, the varnish solvents and the like organic solvents.

The textile materials can be impregnated with the polymer by means of the usual procedures and apparatus for the liquid impregnation of textile materials; employing padders, centrifuges, squeeze rolls, and the like. In the field, the impregnation can be accomplished by a simple hand dipping and squeezing employing a dispersion concentration and a squeezing procedure found by experience to produce the proper polymer pick-u The impregnation of the textile materials to a dry pick-up of resin of from about 25 to 50 weight percent is preferred. The impregnation can be accomplished by one or a plurality of steps. The resin-impregnated textiles can be dried by means of the usual procedures and apparatus for the drying of textile materials, employing temperatures between about to 30 centigrade. In the field, the impregnated textiles can be dried by simply hanging them up in a relatively dry atmosphere.

Werner-type chromi-nuclear complexes in which the acido groups consist essentially of perfluoroalkanoyl groups containing at least six carbon atoms are known compounds. Processes of producing them and bonding them to the surface of a wide variety of materials are described in British Patent No. 712,784, published July 28, 1954. These complexes are also perfluoroalkanoyl analogs of the complexes described in U.S. Patents Nos. 2,373,040, and 2,544,666. They can be produced and applied by procedures analogous to the procedures described in the latter patents. In general, the perfluoroalkanoyl chromi-nuclear complexes can be prepared by effecting contact in solution between the perfluoroalkanoic 'acid and a basic trivalent chromium salt of a monobasic acid, which salt has a basicity of not more than about 50 percent. They can be bonded to the surfaces of materials simply by forming a film of a liquid containing them on the material. The complexes can be dissolved in organic solvents such as isopropanol and the like alcohols. Illustrative examples of acids suitable for employment as the acido groups of the complexes include: perfiuorohexanoic, perfluorooctanoic, perfluorodecanoic, perfluorooctadecanoic and the like acids. The complexes in which the acido groups consist essentially of perfiuoroalkanoyl groups containing from about 8 to 10 carbon atoms are preferred.

The usual compositions for bonding of Werner-type chromi-nuclear complexes consist essentially of rather strongly acidic solutions of the complexes dissolved in a water-diluted organic solvent. Such solutions usually have a pH of from about 1 to 4. Usually, if the pH of such a solution is increased, the complex soon begins to precipitate. Yet, if an acid sensitive material such as a cellulosic textile is contacted with a solution having a pH as low as about 4.0, the textile undergoes noticeable acid degradation during subsequent curing.

We have found that, if a Werner-type chromi-nuclear complex is dissolved in a Water soluble alkanol, and the alkanol solution is cooled, diluted and partially neutralized, to form a solution which, (a) is maintained at a temperature between its freezing point and about 5 C., and (11) consists essentially of water, from about 0.4 to 2.0% by weight of water soluble alkanol, from about 0.2 to 1.0% by Weight of Werner-type chromi-nuclear complex and enough water soluble nitrogen-base to produce a pH of from about 4.8 to 5.5; the solution comprises a composition which is uniquely adapted for bonding the complexes to acid sensitive materials. The Werner-type complexes can be those is which the acido groups consist essentially of the acyl groups of substantially any mono valent carboxylic acid. In contrast to the previously known compositions, these complex-applying compositions are characterized by an acidity not much stronger than that of distilled Water, and a working life of at least 24 hours. In the case of the complexes of the perfluoroalkanoic acids, the use of these complex-applying compositions in the treatment of textile fabrics has the unobvious advantage that in addition to avoiding acidinduced degradation, the liquid repellency is enhanced.

.The same type and amount of complex applied by means of these complex-applying solutions, gives an appreciably greater resistance toward liquid GB and the other chemical warfare liquids than that obtained by applying the complex by means of the previously known compositions, or at room temperature. Illustrative examples of watersoluble alcohols suitable for use in these complex-applying compositions include methyl, ethyl, propyl, isopropyl, isobutyl, and the like alcohols. Illustrative examples of water-soluble bases suitable for employment in these complex-applying compositions include ammonia, monoamines such as ethylamine, polyamines such as hexamethylene tetramine, and the like. The use of isopropanol as the solvent and hexamethylene tetramine as the base, is preferred. These complex-applying compositions can be formed by cooling, diluting, and neutralizing, in the above described manner, the perfluorooctanoic Werner-type chromi-nuclear complexes dissolved to about 30 weight percent complex in isopropanol that are commercially available under the trade name FO-804.

The dried resin-impregnated textile material can be immersed in and substantially immediately removed from the chromi-nuclear complex containing liquid by means of the usual procedures and apparatus for so immersing a textile material in a liquid; using padders, squeeze rolls, centrifuges, and the like adjusted to quickly free the wet textile of liquid. In the field this operation can be accomplished by a simple hand dipping and shaking. The treated textiles can be air dried by means of the usual procedures and apparatus for drying textile materials. The treated textiles are preferably dried by heating them at from about to C. for from about 30 to 90 minutes.

The following examples are illustrative of the details of at least one method of practicing the invention.

Example 1 Swatches of 8.5 oz. carded cotton sateen were impregnated in an aqueous dispersion of a commercially available polyethyl acrylate (Hycar 4501) containing 25% total solids. The impregnated swatches were padded to give 100% wet pick-up and allowed to air dry at room temperature for 6 days. The impregnated sateen was then briefly water washed and allowed to redry. The perfluorooctanoic acid chromi-nuclear complex used for treating the impregnated sateen was prepared as follows: 2.5 grams of a commercially available isopropanol solution (PC-804) containing 30% of the solid complex was diluted with 95 grams of distilled water previously cooled to 5 C. The diluted solution of the complex was partially neutralized by the adidtion of 2.5 grams of a solution of hexamethylene tetramine. The final solution, maintained at 5 C., had a solids content of 0.75% and a pH of 5 .0.

In order to demonstrate the stability of the cooled chromi-nuclear complex solution, swatches of the impregnated sateen, having a resin dry pick-up of 24.8%, were treated in this solution at hourly intervals over a 7 hour period. The treatment consisted of briefly immersing the impregnated sateen in the cooled complex solution and immediately freeing the sateen of excess liquid. The fabric was then cured for one hour at a temperature of 105 C., after which it was briefly washed with a warmed, dilute solution of a synthetic detergent, given a water rinse, then air dried.

Times required for the penetration and wetting of the treated sateen with stabilized liquid GB ranged from 700-2500, and 6000 to 26,000 seconds, respectively. The cooled complex solution appeared to be completely stable toward precipitation during the 7-hour period and the repellency of the treated sateen was independent of the age of the chromi-nuclear complex treating solution.

The treated sateen has a good hand, is not stiff or boardy, and has air permeability equivalent to that of the untreated sateen.

Example 2 Swatches of impregnated sateen containing 24.8% polyethylacrylate (Hycar 4501) were briefly immersed in a cooled solution (4 C.) of the chromi-nuclear complex (PG-804) containing 0.4% solid complex and neutralized with 10% hexamethylene tetramine (HMTA) to a pH of 5.05. After treatment of the first swatch above, the solution was stored for 24 hours at 4 C. and then employed for the treatment of a second swatch of the impregnated sateen. After immersion the treated swatches were processed exactly as described in Example 1. The repellencies of the swatches were evaluated with stabilized BG. The first swatch exhibited penetration and wetting times of 2900 and 29,000 seconds, respectively; where as the swatch treated with the solution aged 24 hours gave values of 2,200 and 10,000 seconds, respectively.

Example 3 Swatches of impregnated sateen containing 24.8% polyethylacrylate (Hycar 4501) were briefly treated in separate portions of perfluorooctanoic acid chromi-nuclear complex solution containing 0.4% solid complex and suflicient 10% HMTA to give a series of solutions ranging in pH from 2.8 to 5.0. After processing of the treated sateen as described in Example 1, it was found that the time required for penetration by liquid stabilized GB increased from 2400 seconds for the fabrics treated at pH 2.8 to 6,550 seconds for the fabric treated at pH of 5.0. The wetting times also increased with increasing pH of the chrome complex treating solution from 18,000 seconds at pH 2.8 to 24,000 seconds at pH 5 .0.

Example 4 A series of swatches of unscoured sateen were impregnated in aqueous dispersions of polyethyl acrylate ranging in total solids concentration from 50 to 5%. After padding to remove excess emulsion and air drying, the impregnated swatches had dry pick-ups ranging from 5.9% to 47.1%. It was found that the original air permeability of the untreated sateen, 12.8 cu. ft./ min./ sq. ft.,

was increased to a maximum value of 21.0 at 29.2% pickup. The impregnated swatches having 5.9 to 47.1% dry pick-up were briefly immersed in a perfluorooctanoic chromi-nuclear complex solution, having a temperature of 5 0., containing 0.4% solid complex and sufficient 10% hexamethylene tetramine to increase the pH to 5.0. After treatment the swatches were processed as described in Example 1. The effect of variation in polyethyl ac rylate pick-up was evaluated from wetting tests with stabihzed liquid GB. The results are summarized in the table below:

Penetration Wetting Dry Pick-Up of Pretreating Polymer Time, Time,

Seconds Seconds The original high air permeability of the impregnated sateen is reduced somewhat by treatment with the chrominuclear complex solution and subsequent processing. However, the air permeability of the final treated sateen is at least as high as that of the original untreated fabric (12.8 cu. ft./min./sq. ft).

Example 5 Unscoured sateen was treated exactly as in Example 1 except that a commercially available polyvinylacetate dispersion (Rhoplex WN75) was employed for the initial impregnation of the sateen and that the air-dry impregnated sateen Was not washed prior to application of the chromi-nuclear complex solution. With a polymer pickup of 37.2% the final treated sateen resisted the penetration of liquid stabilized GB for 300 seconds, and resisted complete wetting for 9500 seconds.

Example 6 Unscoured sateen was treated exactly as in Example 1 except that a laboratory-prepared polymethyl acrylate dispersion was employed for the initial impregnation. The unscoured sateen was impregnated in a 33% dispersion of this polymer and allowed to air dry giving a slightly stiff fabric having 38% dry pick-up. After treatment with aqueous chromi-nuclear complex solution and processing as described in Example 1, the repellency was evaluated with stabilized liquid GB; penetration time 4500 seconds, wetting time 7600 seconds.

Example 7 Unscoured sateen was treated exactly as in Example No. 1 except that a commercially available acrylonitrilebutadiene copolymer emulsion, Hycar 1552, was employed for the initial impregnation. The sateen was impregnated in a 35% aqueous dispersion of the copolymer and allowed to air dry giving a very slightly stiff fabric having a dry pick-up of 40.4%. After treatment with a 1.5% solution of the chromi-nuclear perfluoro octanoic acid complex at a pH of 4.8, the sateen was processed as described in Example N0. 1. The treated sateen resisted penetration by liquid GB for 1300 seconds, and resisted complete wetting for at least 10,000 seconds.

Example 8 Unscoured sateen was treated exactly as in Example 1 except that a 9.7% solution of polyethyl acrylate (Hycar 4501) in acetone was employed for the initial impregnation. The air-dried fabric containing 25.1% dry polymer was treated in a 0.4% chromi-nuclear complex solution at pH of 5.0 and a temperature of 5 C. After processing as in Example 1, the repellency was evaluated with stabilized liquid GB; penetration time, 2500 seconds; Wetting time, 75 seconds.

We claim: 7 V

1. A process of rendering a textile material highly resistant to wetting and penetration by liquid chemical Warfare agents, comprising: impregnating the textile with an inert volatile liquid containing a polymer selected from the group consisting of polymethyl acrylate, polyethyl acrylate, polyvinyl acetate, and copolymers of acrylonitrile and butadiene containing from about 30 to 60 weight per cent of acrylonitrile, to a dry pick-up of from about 25 to 50 weight percent; air drying the impregnated textile at a temperature of from about 20 to 30 centigrade; immersing the dry impregnated textile in and substantially imme diately removing it from contact with a liquid composi tion, which is maintained at a temperature between its freezing point and about C., and which consists essentially of: wtaer, from about 0.4 to 3.3 weight percent of a water soluble alkanol, from about 0.2 to 1.5 weight percent of a Werner-type chrominuclear complex in which the acido groups consist essentially of perfluoroalkanoyl groups containing from about 6 to 18 carbon atoms, and sufiicient water soluble nitrogen-base to produce a pH of from about 4.8 to 5.5; substantially immediately freeing the Wet textile of drops of the liquid; and drying the wet textile at a temperature of from about 90 to 110 C. for from about to 90 minutes.

2. The process of claim 1 in which the polymer with which the textile is impregnated is polyethyl acrylate.

3. The process of claim 1 in which the polymer with which the textile is impregnated is polyvinyl acetate.

4. The process of claim 1 in which the polymer with which the textile is impregnated is polymethyl acrylate.

5. The process of claim 1 in which the polymer with which the textile is impregnated is a copolymer of acrylonitrile and butadiene containing from about 30 to by weight acrylonitrile.

References Cited in the file of this patent UNITED STATES PATENTS 2,552,910 Steinman May 15, 1951 2,611,718 Steinman Sept. 23, 1952 2,693,458 Olson Nov. 2, 1954 2,744,835 Caroselli May 8, 1956 2,745,770 Kingerley May 15, 1956

Claims (1)

1. A PROCESS OF RENDERING A TEXTILE MATERIAL HGIHLY RESISTANT TO WETTING AND PENETRATION BY LIQUID CHEMICAL WARFARE AGENTS, COMPRISING: IMPREGNATING THE TEXTILE WITH AN INERT VOLATILE LIQUID CONTAINING APOLYMER SELECTED FROM THE GROUP CONSISTING OF POLYMETHYL ACRYLATE, POLYETHYL ACRYLATE, POLYVINYL ACETATE, AND COPOLYMERSO ACRYLONITRILE AND BUTADIENE CONTAINING FROM ABOUT 30 TO 60 WEIGHT PERCENT OF ACRYLONITRILE, TO A DRY PICK-UP OF FROM ABOUT 25 TO 50 WEIGHT PERCENT; AIR DRYING THE IMPREGNATED TEXTILE AT A TEMPERATURE OF FROM ABOUT 20 TO 30* CENTIGRADE; IMMERSING THE DRY IMPREGNATED TEXTILE IN AND SUBSTANTIALLY IMMEDIATELY REMOVING IT FROM CONTACT WITH A LIQUID COMPOSITION, WHICH IS MAINTAINED AT A TEMPRATURE BETWEEN ITS FREEZING POINT AND ABOUT 5* C., AND WHICH CONSISTS ESSENTIALLY OF: WATER, FROM ABOUT 0.4 TO 3.3 WEIGHT PERCENT OF A WATER SOLUBLE ALKANOL, FROM ABOUT 0.2 TO 1.5 WEIGHT PERCENT OF A WERNER-TYPE CHROMINUCLEAR COMPLEX IN WHICH THE ACIDO GROUPS CONSIST ESSENTIALLY OF PERFLUOROALKANOYL GROUPS CONTAINING FROM ABOUT 6 TO 18 CARBON ATOMS, AND SUFFICIENT WATER SOLUBLE NITROGEN-BASE TO PRODUCE A PH OF FROM ABOUT 4.8 TO 5.5; SUBSTANTIALLY IMMEDIATELY FREEING THE WET TEXTILE OF DROPS OF THE LIQUID; AND DRYING THE WET TEXTILE AT A TEMPERATURE OF FROM ABOUT 90 TO 110*C. FOR FROM ABOUT 30 TO 90 MINUTES.