EP0037744B1

EP0037744B1 - Protective clothing for confining toxic compounds using film of highly fluorinated ion exchange polymer

Info

Publication number: EP0037744B1
Application number: EP19810301543
Authority: EP
Inventors: Walther Gustav Grot; Joseph Tracy Rivers; Raimund Heinrich Silva
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1980-04-09
Filing date: 1981-04-08
Publication date: 1984-07-04
Also published as: CA1172920A; DE3164528D1; EP0037744A1

Description

Protective clothing of many types is now well-known for many and varied uses in protecting people from fire and harmful substances, such as suits for industrial workers, flame- and fire-resistant suits for firemen, forest fire fighters, race car drivers and airplane pilots, and suits for use by military personnel. Garments include not only complete, hermetic suits, but also individual garments such as trousers, jackets, gloves, boots, hats, head coverings, masks, etc.
Regulations restricting exposure to hazardous environments of various kinds, such as the Occupational Safety and Health Act, make it increasingly necessary to have better and more effective kinds of protective garments.
Such garments presently available are almost invariably of thick construction and heavy in weight, and are often fabricated at least in part from materials impermeable to water or water vapor, such as natural and synthetic rubbers and elastomers, chlorinated rubbers, etc. In the case of garments impermeable to water vapor, there is considerable discomfort to those wearing them, especially when the garments are of the hermetic variety, because of the entrapment of perspiration and body heat. Entrapment of heat and perspiration results in considerable discomfort of itself, and the heat stress which results from the prevention of loss of heat by the ordinary mechanism of evaporation of perspiration can rapidly reach a dangerous stage of heat prostration for the person wearing the garment.
The invention provides a protective garment characterised by being fabricated at least in part from a composite fabric comprising a component fabric and a continuous film of a highly fluorinated ion exchange polymer having at least as many C-F groups as C-H groups and having sulfonic acid functional groups, there being at least one fluorine atom attached to each carbon atom to which each said functional group is attached, said polymer having an equivalent weight no greater than 2000, all the components of said composite fabric being hydrophilic.
Water vapor can pass through the fabric of the garment, and thereby provide improved comfort for the person wearing the garment. Not only this, but the fabric has also the ability to act as a stable barrier to the passage of most organic substances, including toxic compounds. The protective garment of the invention can protect those exposed to a wide variety of organic or harmful compounds, are thin and light-weight and thus will more readily permit loss of heat by virtue of their light-weight construction.
In EPC Application 81301544.3 (Publication 0037745-A) we describe protective garments fabricated at least in part from a composite fabric containing a continuous film of a highly fluorinated ion exchange polymer having at least one kind of functional group selected from alkali metal salts of, ammonium salts of and amine salts of at least one of sulfonic acid, sulfonamide, monosubstituted sulfonamide, carboxylic acid, carboxamide and monosubstituted carboxamide groups.
In use the protective garment of the invention can prevent the passage of a toxic organophosphorous compound from a second space on the outside of the garment to a first space on the inside of the garment. Thus, in use, (a) water permeates from the first space adjacent a first side of the continuous film of highly fluorinated ion exchange polymer and (b) a toxic organophosphorous compound, said compound having a
moiety wherein R is a C, to C_lo alkyl group, present in said second space (i) permeates only slowly into said film and (ii) that part of said toxic organophosphorous compound which permeates into said film is detoxified by said polymer, whereby said toxic organophosphorous compound is substantially excluded from entering said first space.
The composite fabric from which protective garments of the invention are made contains a continuous film or layer of a highly fluorinated ion exchange polymer having free sulfonic acid functional groups, there being at least one and preferably two fluorine atoms attached to the carbon atom to which the sulfonic group is attached. By "highly fluorinated" is meant that the polymer in ion exchange form has at least as many C-F groups as it has C-H groups.
A film of a highly fluorinated ion exchange polymer having free sulfonic acid groups swells markedly when it absorbs water, and thus may not be a preferred functional group when rejection of certain organic substances by the garment is required. However, the free sulfonic acid groups in such a polymer are easily converted to the alkali metal salt form by an aqueous solution of an alkali metal halide, which salt form swells less. Conversion of the sulfonic acid form to the sodium salt form can gradually occur during wearing of a garment simply from contact with the salt in perspiration. When it is desirable to have a layer in a garment maintained in the sulfonic acid form even after the wearer has perspired, as when there is potential exposure to a nerve gas, two separated layers of the highly fluorinated ion exchange polymer can be used; the inner layer of such polymer can substantially prevent contact of the salt in perspiration with the -S0₃H groups in the second, outer layer of the polymer.
The highly fluorinated ion exchange polymers can be copolymers of fluorinated monomers containing the sulfonic functional group with nonfunctional monomers such as tetrafluoroethylene, trifluoroethylene, vinylidene fluoride, chlorotrifluoroethylene, etc. The polymers are preferably perfluorinated polymers prepared from perfluoro sulfonic monomers and tetrafluoroethylene. Such polymers and their preparation are now well-known in the art, and are described, e.g., in U.S. Patent 3,282,875. Such polymers are unaffected by a large variety of chemicals including typical decontamination systems used after exposure of a protective garment to various toxic and harmful chemicals. Perfluorinated polymers of this type have retained good physical properties after exposure to chlorine gas and strong hot caustic solution within an operating chloralkali cell for times in excess of two years.
So as to have a high moisture permeability which will provide a garment having comfortable wearing properties, the highly fluorinated ion exchange polymer should have an equivalent weight of no greater than 2000, preferably no greater than about 1500. Equivalent weights as low as 1100 and even 1000 provide exceptionally high water vapor transmission rates. The water vapor transmission rates of fabrics containing a layer of such polymer is sufficiently high to permit the loss by permeation of enough perspiration so that a person wearing the garment is substantially more comfortable than he would be if wearing an impermeable garment. However, with increase in equivalent weight, the suppleness of the highly fluorinated ion exchange polymer increases, such polymer is more easily extruded in thinner films, mechanical properties such as flex life improve, and such factors can also be considered when selecting the equivalent weight of the polymer to be used in any particular composite fabric.
The thickness of the layer of highly fluorinated ion exchange polymer is not critical to the permeation rate of water vapor, which is so high that it is almost independent of the thickness of the layer of polymer for the thin films in the range of thickness dealt with herein. In some cases where a garment is to protect the wearer from exposure to a harmful compound, extremely thin layers of the highly fluorinated ion exchange polymer may not be suitable. In those cases where the composite fabric is made by lamination of one or more component fabrics with a preformed film of the highly fluorinated ion exchange polymer or a precursor polymer thereof, the thickness of the film used is generally in the range of about 10 to 125 micrometers (about 0.4 to 5 mils), preferably about 10 to 50 micrometers. In those cases where one step in preparation of the composite fabric is coating a component fabric with a solution of the highly fluorinated ion exchange polymer or a precursor thereof followed by removal of the solvent by drying, composite fabrics containing a thinner layer of highly fluorinated ion exchange polymer, down to about 2.5 micrometers (0.1 mil) thick, and even down to about 1 micrometer (0.04 mil) thick, can be made. For garments intended for protecting the wearer from exposure to a harmful substance, the layer of highly fluorinated ion exchange polymer should be continuous, i.e., it should be substantially free of pinholes, so as to prevent leakage of organic substances to within the garment. A layer of highly fluorinated ion exchange polymer about 12 to 50 micrometers (0.5-2 mil) thick is most preferred.
The highly fluorinated ion exchange polymer should be of high enough molecular weight to be film forming. In order to have adequate toughness to survive conditions of wear without developing leaks which would destroy its integrity, the polymer can be linear, branched or only slightly crosslinked, and is preferably branched. Excessively crosslinked polymer is too brittle for this use.
The component fabrics used in making the composite fabric are many and varied in type. They can be, but are not limited to, cotton, rayon, wool, silk, linen, polyester such as polyethylene terephthalate, polyamides such as polyhexamethylene adipamide, polyhexamethylene decanedicarboxamide, polyhexamethylene dodecanedicarboxamide, polyepsilon-caproamide or the polyamide of bis-para- aminocyclohexylmethane and dodecanedicarboxylic acid, aramids such as poly-meta-phenylene isophthalamide or poly-para-phenylene terephthalamide, polyolefins such as polyethylene, polypropylene or polytetrafluoroethylene, acrylics such as polyacrylonitrile, polybenzimidazoles, polyarylene sulfides, polyarylene-imide-amides, polyphenol-formaldehyde, polyimides, glass, flame- retardant cotton, etc., and blends of two or more of the foregoing. Carbonized cotton, acrylic, etc., fiber or fabric, or other adsorptive materials in any form such as activated carbon, can also be included as components of the composite fabrics. A component fabric can be woven, including, e.g., plain and ripstop weaves, knitted, nonwoven, felted, spunbonded, or poromeric fabric, or a fibrillated film, or a film or extrudate made or treated by any means to make it porous or microporous. In the case of such microporous component, those having a pore size of at least about 0.5 micrometer are preferred. Activated carbon or other adsorptive substances can be incorporated in the composite fabric by distributing it in a thin foamed layer included as one component of the composite fabric, or in any one layer or between two layers of said ion exchange polymer, or in any other suitable manner.
All of the components of the composite fabric of the invention, whether they be fabrics or continuous films, should be hydrophilic in nature. The term "hydrophilic", when used in reference to a film, means that such film will transfer substantial amounts of water through the film by absorbing water on one side where the water vapor concentration is high, and desorbing or evaporating it on the opposite side where the water vapor concentration is low. The term "hydrophilic", when used in reference to a fabric, means that water will spread on the fabric and wick into its porous structure. In the case of those component fabrics listed in the previous paragraph which are not hydrophilic, such as microporous polytetrafluoroethylene fabric, they must be impregnated throughout the structure and on both surfaces with sufficient hydrophilic polymer to render them, in effect, reinforced hydrophilic films; non-hydrophilic materials when so impregnated and coated lose their non-hydrophilic character and behave as hydrophilic components. Films of the highly fluorinated ion exchange polymers referred to hereinabove are hydrophilic, and such polymers are suitable for rendering hydrophilic those component fabrics which would otherwise be non-hydrophilic.
The composite fabric can take any of manifold forms. In addition to the layer of highly fluorinated ion exchange polymer, the composite fabric further comprises at least one layer of component fabric, preferably at least two layers of component fabric which may be the same or different. When the composite fabric contains at least two layers of component fabric, preferably there will be at least one layer of component fabric on each side of the layer of ion exchange polymer so as to provide protection to the latter from mechanical damage. It is further preferred to use as one of the outermost component fabrics a layer of a flame-resistant and/or wear-resistant fabric, and to fabricate the garment with such component fabric being on the outside of the garment.
A preferred embodiment of the composite fabric is that made from only one layer of component fabric in addition to the layer of highly fluorinated ion exchange polymer. Such composite fabric is intended to be used in a protective garment with the layer of highly fluorinated ion exchange polymer on the outside of the garment, and the component fabric side of the composite fabric on the inside of the garment; this orientation of the composite fabric presents a smooth, non-porous, barrier surface against a cloud of toxic gas or liquid droplets, and thereby does not absorb or trap any of the toxic substance in pores or interstices of the composite fabric, thus permitting easy decontamination after exposure to the toxic substance. Garments which are fabricated with a porous or microporous surface toward the outside, once contaminated by entrapment of a toxic substance in the pores, are at least extremely difficult, and often impossible, to decontaminate, and when decontamination is impossible must be carefully disposed of after but a single use. The protective garments of the invention are easily decontaminated, and thus provide for multiple reuse of the garment. With the indicated orientation of the composite fabric, there is the further advantage that the inner layer of hydrophilic component fabric soaks up perspiration and brings it into direct contact with the outer layer of ion exchange polymer. Accordingly, the composite fabric of the invention possesses advantages over known fabrics which have a hydrophobic microporous layer on either side of another component fabric.
It should be noted that there are some situations in which the exposed outer layer of highly fluorinated ion exchange polymer could be damaged, in which case the loss of integrity of the barrier layer of the garment would endanger the person wearing the garment; in those situations, it is advisable that a wear-resistant outergarment be worn over the protective garment to aid in precluding damage to the latter. Such overgarments, following contamination, can either be laundered for reuse, or be of inexpensive, light-weight construction adapted for discarding after exposure to a toxic substance.
The composite fabric can be made from the component fabrics and either a film of highly fluorinated ion exchange polymer or a fabric either melt- or solution-coated with a continuous layer of highly fluorinated ion exchange polymer. The composite fabric is made in some cases by the use of heat and either vacuum or pressure, and in other cases by using suitable adhesives or meltable or soluble polymers to adhere the several components together. In some cases, the highly fluorinated ion exchange polymer is maintained in the form of a melt-fabricable precursor, e.g., with functional groups such as -SO,F, during formation of the composite fabric, and after the composite fabric has been made the melt-fabricable precursor is hydrolyzed or otherwise chemically modified to the ion exchange form defined above. In those cases where a precursor of a highly fluorinated ion exchange polymer having more difficultly hydrolyzable functional groups, such as -SO_zF groups, is used in combination with a component fabric of polyolefin or polyfluorinated polyolefin, hydrolysis can be under any suitable conditions such as those used with hydrolysis bath A in the examples below, but when such a polymer is used in combination with a component fabric of a nylon, cotton, wool or other polymer which may be damaged by vigorous hydrolysis conditions, hydrolysis after fabrication of composite fabric prepared therefrom should be under milder conditions such as with ammonium hydroxide. A highly fluorinated ion exchange polymer having sulfonyl functionality can alternatively be put into the form of the sulfonic acid, sulfonamide or substituted sulfonamide, or an alkali metal, ammonium or amine salt thereof (preferred amines include p-toluidine and triethanolamine) before forming a composite fabric therefrom, and in such cases the composite fabric can be prepared by using a small amount of a highly fluorinated ion exchange polymer having, e.g., -COOCH₃ functional groups as an adhesive bonding agent, which can be hydrolyzed under mild conditions, or by using other types of adhesive such as ethylene/vinyl acetate based hot melt adhesives or two-component epoxy adhesives. Composite fabrics made without an adhesive bonding agent are preferred, inasmuch as most bonding agents interfere with passage of water through the composite fabric, and to the extent used, reduce the active area through which water permeates. If such an adhesive bonding agent is used, a highly fluorinated ion exchange polymer having, e.g., -COOCH₃ functional groups is preferred, as it can be hydrolyzed to -COOH alkali metal salt form which has a high permeability to water; such polymers are known in the art, e.g., in Belgian Patent 866,121. The various salt forms of a functional group can freely be inter- converted from one to another, and to or from the free acid form, in either a component material or a composite fabric, as desired. The composite fabric can be made from the components in some cases in a single operation, and in other cases by a series of sequential steps.
The composite fabrics described above can be used in fabrication of protective garments by techniques known in the art, including sealing of seams and joints by use of radio frequency heating or other known electronic bonding techniques, or by heat and pressure, in some cases with the aid of adhesives or sealants at the seams and joints to prevent leaks at those points. Garments can also be made by sewing, but in cases where a leak-free construction is desired the sewn seams should also contain a sealant or adhesive.
The composite fabrics and garments made therefrom are highly permeable to water vapor. Accordingly, a person wearing such a garment does not suffer heat stress which results from interruption of the usual mechanism of loss of body heat by evaporation of the water of perspiration, and discomfort from the retention of the water of perspiration within the garment is reduced. While the composite fabrics are also permeable to a few low molecular weight organic compounds such as methanol and ethanol, and while the permeation rate for an organic compound depends on the type of compound and its molecular weight, the permeation rates for most organic compounds are extremely low and in the case of many organic compounds the composite fabric is substantially impermeable to the compound. It is believed that the composite fabrics possess barrier properties against a variety of hazardous substances, poisonous compounds, blistering agents, lachrymators, and irritants. As will be seen, the composite fabrics permit the passage of large amounts of water vapor.
The protective garment of this invention is believed to have the ability to protect the wearer against certain toxic organophosphorous compounds that are anticholinesterases and are sometimes referred to as nerve gases, which compounds have the common feature that they contain a
moiety where R is a C, to C₁₀ alkyl group. The essential component of the composite fabric used in making the protective garment, a highly fluorinated polymer having -S0₃H functional groups and at least one fluorine atom attached to each carbon atom to which each -S0₃H group is attached, is a strong acid which is capable of detoxifying such organophosphorus compounds. In the examples, it is demonstrated that highly fluorinated ion exchange polymer is capable of hydrolyzing triethyl phosphate, a compound chosen as a model compound to simulate the toxic organophosphorus compounds. The ability of the highly fluorinated ion exchange polymer to act as a barrier to organophosphorous compounds, and additionally to detoxify that which permeates into the barrier, thus prevents toxic organophosphorus compounds from permeating into the space within a protective garment of the invention.
The composite fabrics have good mechanical properties, such as toughness, strength and flex life. Both the composite fabrics and garments fabricated from them have good storage stability, such that the garments can be retained for long periods before actual use of them.
To further illustrate the innovative aspects of the present invention, the following examples are provided.
In the examples, water permeabilities were measured in accordance with ASTM (American Society for Testing Materials) method E 96-66, using the upright or inverted cup techniques as indicated. Permeabilities to substances other than water were measured by a similar technique, except at uncontrolled, ambient relative humidity.
In Examples 1 and 2 apparatus for continuous preparation of composite fabric was employed which comprised a hollow roll with an internal heater and an internal vacuum source. The hollow roll contained a series of circumferential slots on its surface which allowed the internal vacuum source to draw component materials in the direction of the hollow roll. A curved stationary plate with a radiant heater faced the top surface of the hollow roll with a spacing of about 6 mm (1/4 inch) between their two surfaces.
During a lamination run, porous release paper was used in contacting the hollow roll as a support material to prevent adherence of any component material to the roll surface and to allow vacuum to pull component materials in the direction of the hollow roll. Feed and takeoff means were provided for the component materials and product. In the feed means one idler roll of smaller diameter than the hollow roll was provided for release paper and component materials. The feed and takeoff means were positioned to allow component materials to pass around the hollow roll over a length of about 5/6 of its circumference. A further idler roll was provided for the release paper allowing its separation from the other materials. Takeoff means were provided for the release paper and a composite fabric.

Example 1

A composite fabric was prepared from (1) a piece of component fabric having 27.5 threads/cm (70 threads/in) of 1.5 denier filaments of poly-meta-phenylene isophthalamide in the warp and 19 threads/cm (48 threads/in) of like filaments in the woof in a plain weave, having a weight of 15 mg/cm², about 10 cm by 15 cm, and (2) a piece of film of a copolymer of perfluoro(3,6-dioxa-4-methyl-7- octenesulfonyl fluoride) (referred to herein as PSEPVE) and tetrafluoroethylene (referred to herein as TFE) having an equivalent weight of 1350, the film having a thickness of about 36 micrometers (1.4 mils) and being hydrolyzed on one surface only to a depth of about 15 micrometers (0.6 mil) to the -S0₃K form, the piece of film being slightly larger than the piece of fabric. The lamination was carried out in the apparatus just described, using a web of paper with a window cut in it to carry the components through the apparatus. The piece of fabric was taped into the window, and the piece of film was taped over the fabric. As measured by thermocouples, the hollow roll was heated to 240°C by the internal heaters and the temperature indicated by a thermocouple at the radiant heaters was 360°C. The vacuum in the hollow roll was 0.84 Atmospheres below atmospheric pressure. The line was run at 30 cm/minute (1 ft/min), to provide a dwell time in the heated portion of the apparatus of 1.5 minutes. During lamination, the component cloth contacted the release paper on the heated hollow roll, and the film was placed with its unhydrolyzed side, i.e., the -S0₂F side, against the component fabric.
In the resulting composite fabric, the film was pulled deep into the surface contour of the fabric but not into the interior; the yarn crossover points of the fabric were not bonded together, and the composite fabric had a good hand.
The composite fabric was placed in a solution of 50 volume % methanol and 50 volume % of 28% aqueous ammonium hydroxide at ambient room temperature, about 18°C, for 45 hours, to hydrolyze the remaining -So₂F groups. The composite fabric with sulfonic acid ammonium salt functional groups was then treated for 1 minute with 1 N aqueous hydrochloric acid to put the functional groups into -S0₃H form, and part of that composite fabric was treated with aqueous NACI solution to make the -S0₃Na form. The acid (hydrogen) and sodium salt forms were tested for water vapor permeability by the inverted cup method, with results as shown in Table 1.

Example 2

A composite fabric was prepared from continuous lengths of (1) a component fabric of 40/2 cc yarns of a 50:50 blend of poly-meta-phenylene isophthalamide and poly-para-phenylene terephthalamide staple fibers woven in a 2 by 1 twill as described in Example 2 of U.S. Patent 4,120,914, and (2) a film like that employed in Example 1 above. The lamination was carried out in the same apparatus just described, with the same conditions as in Example 1 except that the vacuum in the hollow roll was 0.675 Atmospheres below atmospheric pressure. As in Example 1, the component cloth contacted the release paper on the heated hollow roll, and the film was placed with its unhydrolyzed side against the component fabric. The composite fabric so made was found to be free of leaks. Half of the composite fabric so made was placed in a solution of 60% by volume of methanol and 40% by volume of 28% aqueous ammonium hydroxide at about 18°C for 65 hours to hydrolyze the remaining -S0₂F groups, washed with water, washed with an aqueous solution containing 2% by wt. acetic acid and 1% by wt. sodium chloride, washed with water, and air dried, the ion exchange groups of the resulting composite fabric being in the Na form. One sample of the resulting composite fabric was placed in boiling water for 30 minutes before testing for water permeability. Another sample of the same composite fabric was soaked in 2N hydrochloric acid to prepare the -S0₃H form, washed with water, soaked in water at 60°C for 20 minutes, and air dried. Samples were tested for water permeability, in all cases by the inverted cup method and with the component fabric side of the composite fabric facing the water in the cup, with the results shown in Table 2.
It should be noted that treatment of a highly fluorinated ion exchange polymer with water at high temperature, such as with boiling water, is known to cause the polymer to swell (see U.S. Patent 3,684,747).

Example 3

A composite fabric was prepared from continuous lengths of (1) a component fabric which was a 22 cut jersey having a weight of 15.6 mg/cm² (4.6 oz/sq yd) knit from 20/1 cc yarn of poly-meta- phenylene isophthalamide, and (2) a film like that employed in Example 1 above. The lamination was carried out with the same apparatus and in the same manner as described in Example 13, and the composite fabric so made was hydrolyzed in the same manner as in Example 2. The resulting hydrolyzed composite fabric felt softer than the composite fabrics of Examples 1 and 2, and had some stretch characteristics. A portion of the composite fabric was converted to hydrogen form by treating with aqueous hydrochloric acid, and another portion was converted to sodium form by treating with aqueous NaCl solution. Permeabilities to water were measured by the inverted cup technique, with the component fabric side of the composite fabric facing the water in the cup, with the results shown in Table 3.

Example 4

A solution of 25 ml of triethyl phosphate, (CH₃CH₂O)3P=O, in 75 ml of water was divided into two equal parts. To one part (A) was added 1.01 g of a PSEPVE/TFE copolymer which had been hydrolyzed to the form having -S0₃H groups, having an equivalent weight of 1100, and in the form of a powder of 60 to 100 mesh. The other part (B) was retained as a control. Each part was separately stirred. Samples (5 ml each) of part A were taken at time intervals (stirring was temporarily stopped to permit the powder to settle when each sample was taken so that it would be free of powder), and the acid formed by hydrolysis was titrated with 0.1 N NaOH solution using phenolphthalein indicator, as summarized in Table 4. Neither of two samples taken from part B, 5 ml after 88 hrs and 25 ml after 136 hrs, required any 0.1 N NaOH for neutralization, thus showing that no hydrolysis occurred in the control part without the ion exchange catalyst.
Based on the assumption that only monobasic hydrolysis of the ester occurred, the overall average rate of hydrolysis for the total 112 hours is about 0.02 meq. of phosphate ester group hydrolyzed per day per gram of ion exchange polymer. The rate for the initial 24 hour period was about 3 times greater.

Example 5

Samples of PSEPVE/TFE film having an equivalent weight of 1075 and thickness of 127 micrometers were hydrolyzed to -S0₃K form with a hydrolysis bath consisting of 15% by wt. potassium hydroxide, 25% by wt. dimethylsulfoxide and 60% by wt. water (referred to herein as hydrolysis bath A), the functional groups in one portion of the film were converted to -S0₃Na form by soaking in a 10% by wt. aqueous solution of NaOH, in another portion of the film to -S0₃Cs form similarly with an aqueous CsOH solution, and in yet another portion of the film to -S0₃H form by treatment with aqueous hydrochloric acid. Permeabilities to various substances were determined as indicated in Table 4 by the inverted cup method.

Example 6

Flame resistance tests

A composite fabric was prepared by heating under pressure a piece, 16 cm in diameter, of a microporous polytetrafluoroethylene cloth having an average pore size of 0.5 micrometers, a porosity of 80%, and a thickness of 25 micrometers (the cloth having a microstructure characterized by nodes interconnected by fibrils, made by high-rate stretching at an elevated temperature of an unsintered, dried paste extrudate of polytetrafluoroethylene, as described in U.S. 3,962,153, and commercially available from W. L. Gore & Associates, Inc., under the trademark (Gore-Tex), and a piece, 10.5 cm in diameter, of a film of a PSEPVE/TFE copolymer having an equivalent weight of 1100 and a thickness of 25 micrometers (1 mil) in a hydraulic press at 240°C for 1 minute and a force of 30,000 kg. The resulting transparent, leak free, composite fabric was treated with hydrolysis bath A at 100°C for 1 hour, to put the functional groups of the copolymer in -S0₃K form, washed and dried, and flame tested. In the flame test, a piece of the composite fabric, 12 cm by 4 cm, was held horizontally by metal clamps in the flame 3 cm above a burning wooden match for 1 5 seconds. The composite fabric did not burn; there was slight charring without destroying the fabric. The behavior was the same when the flame was applied either to the center or to the edge of the film.
In a second test, a piece of composite fabric prepared as described in the previous paragraph, except that the film of PSEPVE/TFE copolymer had an equivalent weight of 1200 and a thickness of 51 micrometers (2 mils), and the components were bonded at 290°C with a force of 18,000 kg, was used. After hydrolysis with hydrolysis bath A as above, it was held vertically, and the flame of a propane torch was applied to the edge of the fabric. The fabric ignited only when the hot, inner, blue cone of the flame impinged on the fabric. The fabric was self-extinguishing, i.e., the fabric stopped burning when the flame was removed.
Although the flame resistance tests were carried out with composite fabrics wherein the functional groups of the copolymer were in the -S0₃K form, the tests are nevertheless indicative of the flame resistance of the composite fabrics where the functional groups are in the -S0₃H form.

Comparative Examples A, B, C and D

In Example A, permeabilities were measured for a film of regenerated cellulose (cellophane) having a thickness of 25 micrometers (1 mil). Although it has a high water vapor permeability, in excess of 10,000 g/m² day, and, by the inverted cup method had a permeability of 36 g/m² day to 2-chloroethyl ether and of 11 g/m² day to n-propyl sulfide, it shatters and tears when mechanically abused and it makes noise when flexed, and was thus considered unsuitable for use as a component of a composite fabric.
In Example B, a chlorinated polyethylene fabric (commercially available under the name "Chloropel") was found to have a permeability of 3000 g/m² day for 2-chloroethyl ether, which is so high as to make it unsuitable as a component of a composite fabric for protective garments. The material was also swollen and delaminated where contacted by 2-chloroethyl ether.
In Example C, a film 127 micrometers thick of a copolymer of ethylene and methacrylic acid having an equivalent weight of 576 was tested for permeability in both the free acid (hydrogen) form and in the sodium salt form. Although the permeability (inverted cup) to 2-chloroethyl ether was considered good, 8.8 g/m² day in the sodium form and 6.2 g/m² day in the hydrogen form, the permeability (inverted cup) to water vapor was 1690 g/m² day in the sodium form and 5 g/m² day in the hydrogen form, these values for water being considered too low to provide the comfort level desired for a protective garment.
In Example D, a membrane comprising a film of a polystyrenesulfonic acid having an ion exchange capacity of 2.7 meq/g of dry resin, backed by a fabric of vinyl chloride/acrylonitrile fibers having a weight of 14 mg/cm² and being 34% by wt. of the membrane, the membrane thickness being 0.6 mm (commercially available from lonics, Inc.) was found to have a permeability (inverted cup) of 19,600 g/m² day for water vapor, and of 1,640 g/m² day for 2-chloroethyl ether.

Industrial applicability

Composite fabrics containing a continuous film of a highly fluorinated ion exchange polymer as defined herein are useful in protective garments such as jackets, trousers, complete suits hermetically sealed, gloves, boots, hats, head coverings, masks, etc. The garments are broadly useful for providing protection to workers in the chemical industry, firemen, forest fire fighters, race car drivers, crop dusters and airplane pilots, and they may have value for defensive use by military personnel. They are believed to provide protection against toxic organophosphorus nerve gases by a dual action of preventing penetration by part of the nerve gas, and of detoxifying that part of the nerve gas which penetrates into the ion exchange barrier layer of the garment. The garments provided herein are technically advanced over those previously known in that they readily permit loss of perspiration and body heat while providing the needed protection. The garments are also waterproof in the sense that gross amounts of liquid will not penetrate the ion exchange film. The water entry pressure of the composite fabric is an order of magnitude above that of ordinary waterproof fabrics. Garments of the composite fabrics are virtually "watertight", yet "breathable". The composite fabrics can also be used for rain or water protection in any kind of rainwear, such as rainsuits, coats, parkas, ponchos, slickers, etc.

Claims

1. A protective garment characterised by being fabricated at least in part from a composite fabric comprising a component fabric and a continuous film of a highly fluorinated ion exchange polymer having at least as many C-F groups as C-H groups and having sulfonic acid functional groups, there being at least one fluorine atom attached to each carbon atom to which each said functional group is attached, said polymer having an equivalent weight no greater than 2000, all the components of said composite fabric being hydrophilic.

2. A protective garment according to claim 1 wherein said polymer is a perfluorinated polymer.

3. A protective garment according to claim 1 or 2 wherein said polymer has an equivalent weight no greater than 1500, and the film is 2.5 to 125 micrometers thick.

4. A protective garment according to claim 3 wherein the film is 10 to 50 micrometers thick.

5. A protective garment according to any one of claims 1 to 4 wherein said component fabric comprises fibers of poly-metaphenylene isophthalamide, poly-para-phenylene terephthalamide or a blend thereof.

6. A protective garment according to any one of claims 1 to 5 wherein said component fabric comprises fibers of polyhexamethylene- adipamide, polyhexamethylene decanedicarboxamide, polyhexamethylene dodecanedicarboxamide, poly-epsilon-caproamide or the polyamide of bis-para- aminocyclohexylmethane and dodecanedicarboxylic acid.

7. A protective garment according to any one of the preceding claims wherein said composite fabric consists of one layer of said continuous film and one layer of component fabric, and said garment is fabricated from said composite fabric so disposed that said film is toward the outside of said garment and said component fabric is toward the inside of said garment.