Compositions for use with fabrics

Abstract: A novel antiwicking composition is provided for which comprises a fluorinated ethylene/propylene copolymer, a polymeric fluoroaliphatic ester, a liquid carrier, and a dispersant. Preferably, the novel antiwicking compositions also comprise a wetting/saturating agent. A method for imparting antiwicking properties to a fabric also is provided for, which method comprises applying the novel antiwicking compositions to the fabric.

Description: This invention is related to antiwicking compositions suitable for application to fabrics. More particularly, it is directed to antiwicking compositions suitable for the treatment of fabric used in the manufacture of protective clothing. Protective clothing is necessary in handling and cleaning up hazardous chemicals. One type of material commonly used in such protective clothing comprises a chemical barrier, such as polytetrafluoroethylene (PTFE) film, carried on both sides of a fabric substrate. In handling chemicals or cleaning up spills, a person typically encounters a variety of tools and other objects with sharp or protruding edges, and protective clothing must be capable of withstanding considerable wear and tear and fairly rough use. Unfortunately, many chemical barriers can be punctured under such conditions. Moreover, many chemical barriers are inherently inflexible, and may split during fabrication or wear of protective clothing. If the exterior chemical barrier film is punctured, the fabric substrate of such composite material may be capable of preventing the puncture of the interior barrier film, and thus, of preserving the structural integrity of the barrier and the protective clothing as a whole. Chemicals may not be able to pass through the material as a whole; however, if the outer chemical barrier is split or punctured, chemicals can penetrate into the fabric substrate and many chemicals will tend to wick through the fabric substrate and contaminate areas removed from the point of penetration. When the garment is repaired, large portions of the composite material must be replaced, thereby increasing repair costs and unnecessarily compromising the structural integrity of the garment. Compositions for preventing the wicking of liquids through a fabric, per se , are known, and they are based on a variety of chemical compounds. Many conventional antiwicking agents, however, are not universal in their action. For example, silicone-based antiwicking agents resist wicking of aqueous solutions, but not wicking of organic solvents. Other antiwicking agents suffer the additional defect of having to be applied in amounts that create unacceptable stiffness in the fabric. The subject invention, therefore, is directed to novel antiwicking compositions which impart to a fabric more universal resistance to wicking and which do not appreciably decrease the flexibility of the fabric. The subject invention is further directed to methods for imparting to a fabric more universal resistance to wicking whereby the flexibility of the fabric is not appreciably decreased. The subject invention is also directed to flexible fabrics which are more universally resistant to wicking. Accordingly the subject invention provides for a novel antiwicking composition, which composition comprises a fluorinated ethylene/propylene copolymer, a polymeric fluoroaliphatic ester, a carrier which includes a liquid capable of carrying a fluorinated ethylene/propylene copolymer or a polymeric fluoroaliphatic ester into the fabric, and a dispersant. The subject invention further provides for a method for imparting antiwicking properties to a fabric, which method comprises applying the novel antiwicking compositions to the fabric. Additionally, the subject invention provides for fabrics having antiwicking properties, which nonwicking fabrics comprise fabrics treated with the novel antiwicking compositions. The subject invention is predicated on the unexpected observation that fluorinated ethylene/propylene copolymers and polymeric fluoroaliphatic esters together may be applied successfully to a fabric without appreciably decreasing the flexibility of the fabric, and that when a mixture of those components are so applied, more universal antiwicking properties are imparted to the fabric as compared to those imparted by conventional antiwicking agents. A carrier which includes a liquid capable of carrying a fluorinated ethylene/propylene copolymer or a polymeric fluoroaliphatic ester into the fabric and a dispersant, and preferably, a wetting/saturating agent are provided to facilitate the application of the fluorocarbon chemical and fluorocarbon polymer to the fabric. The fluorinated ethylene/propylene copolymer (FEP) component includes any of the well-known and conventional copolymers of tetrafluoroethylene and hexafluoropropylene. The FEP component, along with the polymeric fluoroaliphatic ester (PFE), are the primary components of the composition which remain in the fabric after drying, the other components being volatized in large part during the application process. Although the structure of the treated fabric is not completely understood, it is presently believed that the FEP, along with the PFE, substantially impregnate and coat the fibers of the fabric, thereby imparting antiwicking properties to the fabric. They are also resistant to a wide variety of chemicals, and thus, ensure that the antiwicking properties of the fabric will persist for longer periods of time, despite chemical contamination of the fabric. In general, the FEP may comprise from 2.0 to 8.0 wt%, and preferably from 3.5 to 6.5 wt% of the antiwicking composition. In greater amounts, the FEP may tend to coat on the surface of the fabric or tend to form a film through the fabric, thereby decreasing the fabric's flexibility. If too little FEP is used, inadequate antiwicking properties may be imparted. The amount of FEP, as discussed in greater detail below, also should be coordinated with the amount of PFE comprised by the antiwicking composition. As noted above in discussing the FEP component, the PFE component cooperates with the FEP to impart more universal antiwicking properties. The PFE should be applied in amounts sufficient to impart the desired antiwicking properties, but not in amounts which will unnecessarily stiffen the fabric or will tend to fill in or close its pores. Accordingly, the PFE may comprise from 1.0 to 6.0 wt%, and preferably from 3.5 to 5.0 wt% of the composition. Furthermore, the FEP and PFE preferably should be used in combined amounts of from 3.0 to 13.0 wt%, preferably 4.0 to 8.0 wt% of the composition. The carrier should be selected and included in amounts sufficient to enable the FEP and PFE to be carried into the fabric in a reproducible manner. Such carriers may be selected from a variety of organic and inorganic liquids well-known to be useful for such purposes, but for safety, environmental, and economic reasons, water, and in particular, distilled or deionized water, is the carrier of choice. The dispersant should be selected and included in amounts sufficient to provide a stable, uniform dispersion and, thereby, to ensure uniform, complete, and reproducible application of the FEP and PFE to the fabric. Accordingly, suitable dispersants may be selected from a variety of conventional anionic and non-ionic dispersants, including those selected from the group consisting of poly(acrylic) acid and its derivatives, e.g. , sodium polyacrylate and ammonium polyacrylate, cellulose and its derivatives, e.g. , methyl cellulose, carboxymethyl cellulose, and hydroxyethyl cellulose, and mixtures thereof. Such dispersants are available commercially, including Acrysol R GS sodium polyacrylate, available from Rohm & Haas Company, Philadelphia, Pennsylvania; and Cellosize R hydroxyethyl cellulose, available from Union Carbide Corporation, Danbury, Connecticut. The optimum amount of dispersant used will vary somewhat depending on the choice of the dispersant and other components. Sufficient amounts should be used to ensure a stable, uniform dispersion, but beyond that, no useful purpose is served and the cost is increased unnecessarily. Accordingly, the dispersant typically will comprise from 0.5 to 1.5 wt%, and preferably from 0.75 to 1.25 wt% of the composition. The antiwicking compositions of the subject invention preferably comprise a wetting/saturating agent which facilitates preparation of the composition and permits the composition to be sufficiently retained in, to contact, and to saturate, as opposed to flowing through, the fabric. It thereby aids in ensuring a uniform, complete, and reproducible application of the novel antiwicking composition to the fabric. Such wetting/saturating agents may be selected from conventional anionic or non-ionic wetting agents, with the non-ionic wetting agents, such as water-soluble alcohols, e.g. , isopropyl alcohol, being somewhat preferred. While compounds having both saturant and wetting properties preferably are selected, compounds having only a saturant or wetting activity may be used in combination with other such compounds. Typically, if necessary, the wetting/saturating agent will comprise from 0.1 to 1.5 wt%, preferably from 0.5 to 1.25 wt%, of the antiwicking composition. Although most dispersants will also contribute to wetting/saturation, depending on the choice of dispersants and other components of the composition and the fabric to be treated, below such amounts it may be more difficult to prepare the composition or to saturate the fabric during application. While not necessarily deleterious, amounts greater than those specified generally do not provide any further benefits, but simply increase the cost of the composition. Preferably, the antiwicking compositions are prepared from FEP and PFE dispersions. Suitable dispersions are available commercially, e.g. , Teflon R FEP fluorocarbon polymer dispersions available from DuPont de Nemours, E.I. & Co., Inc., Wilmington, Delaware; Neoflon™ FEP fluorocarbon polymer dispersions, available from Daikin Koygo Yodogawa, Osaka, Japan; and PFE dispersions from 3M Company, St. Paul, Minnesota. The two dispersions then are mixed, along with the other components. Typically, commercially available dispersions will be in a more concentrated form than is preferred, e.g. , from 30 to 60 wt% solids, and thus, they should be diluted before or after mixing. It also should be noted that commercially available dispersions necessarily contain dispersants, usually a mixture of anionic and non-ionic dispersants, and thus it may not be necessary to add additional dispersants. Similarly, as noted above, the dispersants may provide sufficient wetting/saturation and it may not be necessary to add additional agents for that purpose. If additional dispersants and/or wetting agents are desired, however, they preferably are diluted somewhat in the carrier prior to admixture with the other components. The novel antiwicking compositions, in general, may be applied to any knit, woven or non-woven fabric. Although the amounts of the antiwicking compositions applied to a fabric may vary according to the particular fabric chosen or according to the desired degree of antiwicking properties or flexibility, the antiwicking compositions typically are applied in amounts ranging from 50.86 to 169.6 gram/meter² (1.5 to 5.0 ounce/yard²), preferably from 67.8 to 135.6 gram/meter² (2.0 to 4.0 ounce/yard²) add-on weight. They may be applied to the fabric by methods well-known for applying conventional antiwicking agents, e.g. , saturating the fabric, squeezing out the excess, and drying the saturated fabric. Drying typically will be conducted at elevated temperatures, e.g. , from 274 to 288°C (525 to 550°F), and preferably is accompanied by the application of pressure, e.g. , calendaring the treated fabric. Because of the more universal antiwicking properties of the novel antiwicking compositions, they preferably are applied to fabric to be used in composite material for protective clothing used in handling and cleaning up chemicals. Accordingly, such fabric materials are composed of a variety of natural and synthetic fibers, including metal, polyamide, aromatic, aramid, carbon, glass, graphite, ceramic, potassium, titanate, and blends thereof. Polyaramide and polyamide fabrics are especially preferred. Such fabrics, and a preferred composite structure into which they are incorporated, are described in greater detail in U.S. patent application Serial No. 130,742 of J. G. Adiletta, filed on December 9, 1987, and entitled "Chemically Resistant Composite Structures and Garments Produced Therefrom". A preferred composite structure of the above referenced application generally comprises a fabric substrate and thermally bonded on both sides thereof a coated, universally chemically resistant film, which coated film comprises a PTFE film having a thermoplastic flouropolymer coating on both sides or only on its inner side. The fabric substrate may comprise any knit, woven, or non-woven fabric material which is generally suitable for use as clothing and which presents a reasonably flat contact area for bonding. Such fabric material also should be dimensionally stable and otherwise capable of withstanding the temperatures encountered in thermally-melt-bonding the coated film to the fabric substrate. Those temperatures will vary according to the thermoplastic fluoropolymers selected for the coated film, but in general will be higher than about 288°C (550°F). Accordingly, such fabric materials are composed of a variety of natural and synthetic fibers, including metal, polyamide, aromatic aramid, carbon, glass, graphite, ceramic, potassium titanate, and blends thereof. In general, the fabric substrate will have a thickness of from 0.025 to 0.508 cm (from 0.010 to 0.200 inch), preferably from 0.127 to 0.152 cm (from 0.050 to 0.060 inch), and a weight of from 67.8 to 339.1 gram/meter² (from 2.0 to 10.0 ounce/yard²), preferably from 101.7 to 135.6 grams/meter² (from about 3.0 to about 4.0 ounce/yard²). While suitable fabric substrate material may be manufactured by methods well known in the art, they also are available commercially from a variety of manufacturers. Woven fabric is preferred because of its relatively greater strength and flexibility as compared to non-woven fabric material. For this reason, polyaramide and polyamide fabrics, and blends thereof, are especially preferred. Those fabrics are tough and durable, and are extremely resistant to tearing and puncturing, especially on an equivalent weight and weave basis. Accordingly, even when the outer coated film layer is penetrated, a polyaramide or polyamide fabric substrate is much more capable of preventing puncturing or tearing of the inside coated film and, thus, of preserving a leak-proof, impermeable chemical barrier. Polyaramide and polyamide fabrics also impart a degree of thermal insulation against the heat generated by fires which may be encountered in chemical accidents. Further, they are flame-resistant and themselves are somewhat chemically inert. It has been found that a less expensive, spun-laced Nomex R /Kevlar R polyaramide blend fabric provides adequate strength and flexibility while providing a better bonding surface, and accordingly, such fabrics are especially preferred. Those fabrics are preferred also because they have a high voids volume which also acts as thermal insulation. The coated, universally chemically resistant film may comprise a PTFE film having a thermoplastic fluoropolymer coating on both sides or only on its inner side. Alternatively, the composite structure may comprise separate, pre-formed PTFE and thermoplastic polymer films. The PTFE films may be composed primarily of PTFE. PTFE films substantially free of additional components are especially preferred. The thermoplastic fluoropolymer coatings employed bind the coated film to the fabric substrate and assist in maintaining the integrity of the barrier in the seam area. The inner coating of thermoplastic fluoropolymer may be thermally-melt-bonded directly to the fabric substrate, and thereby bind the PTFE film securely to the fabric substrate without the use of adhesives. The outer coating of thermoplastic flouropolymer enables more efficient filling of the seam holes in sewn seams. The composite structure may preferably be formed by thermally-melt-bonding pre-formed coated films to each side of the fabric substrate. The fabric substrate is preferably pre-treated with an antiwicking composition. The composite structures may be used to fabricate articles of protective clothing. Because the composite structures have increased strength and flexibility, they may be joined by a variety of seams, especially when the coated film comprises an outer coating. Where increased strength is important, sewn seams are preferred. The invention will be described further by reference to the following example. It is not intended to limit the scope of the invention; rather, it is presented merely to facilitate the practice of the invention by those of ordinary skill in the art. Example 1 Repellency-wicking may be measured by a standard industry test in which a drop of a challenge fluid is placed on a test sample and the diameter of the drop, if it remains in tact, is measured after fixed time intervals. A spun-laced Nomex R /Kevlar R polyaramid blend fabric, Product No. E-89, available from Du Pont, untreated and treated with two antiwicking compositions, is evaluated uunder such procedures. The first antiwicking composition comprises a Teflon R FEP-120 dispersion, available from DuPont and containing about 5-7 wt% mixed anionic and non-ionic dispersants/wetting agents, which is diluted with deionized water to reduce the FEP content to about 5 wt%. The second antiwicking composition comprises a diluted mixture of FC-824 PFE dispersion, available from 3-M Company, and FEP-120 dispersion. More particularly, it comprises 5 wt% PFE, 5 wt% FEP, 1wt% isopropyl alcohol, and the balance deionized water. The results of such evaluation will be as set forth below in Table I: Sample Challenge Fluid Initial Drop Size (mm) Drop Size After 1 minute (mm) Drop Size After 10 minutes(mm) Untreated fabric water 5.0 6.0 7.0 Untreated fabric kerosene wets wets wets Untreated fabric alcohol wets wets wets Fabric Treated with Comp. No. 1 water 5.0 5.0 5.0 Fabric Treated with Comp. No. 1 kerosene 4.5 5.0 5.0 Fabric Treated with Comp. No. 1 alcohol 3.0 wets wets Fabric Treated with Comp. No. 2 water 5.0 5.0 6.0 Fabric Treated with Comp. No. 1 kerosene 4.0 4.0 4.0 Fabric Treated with Comp. No. 2 alcohol 2.5 3.0 8.0 Such results will show the more universal resistance to wicking exhibited by fabrics treated with the novel antiwicking compositions as compared to untreated fabrics and those treated with other compositions.

Claims: An antiwicking composition, which composition comprises a fluorinated ethylene/propylene copolymer, a polymeric fluoroaliphatic ester, a carrier which includes a liquid capable of carrying a fluorinated ethylene/propylene copolymer or a polymeric fluoroaliphatic ester into the fabric, and a dispersant. The antiwicking composition of claim 1, wherein said composition comprises a wetting/saturating agent. The antiwicking composition of claim 1, wherein said composition comprises from 2.0 to 8.0 wt% fluorinated ethylene/propylene copolymer, from 1.0 to 6.0 wt% polymeric fluoroaliphatic ester, and from 0.5 to 1.5 wt% dispersant. The antiwicking composition of claim 2, wherein said composition comprises from 2.0 to 8.0 wt% fluorinated ethylene/propylene copolymer, from 1.0 to 6.0 wt% polymeric fluoroaliphatic ester, from 0.5 to 1.5 wt% dispersant, and from 0.1 to 1.5 wt% wetting/saturating agent. The antiwicking composition of claim 1, wherein said composition comprises from 3.5 to 6.5 wt% fluorinated ethylene/propylene copolymer, from 3.5 to 5.0 wt% polymeric fluoroaliphatic ester, and from 0.75 to 1.25 wt% dispersant. The antiwicking composition of claim 2, wherein said composition comprises from 3.5 to 6.5 wt% fluorinated ethylene/propylene copolymer, from 3.5 to 5.0 wt% polymeric fluoroaliphatic ester, from 0.75 to 1.25 wt% dispersant, and from 0.5 to 1.25 wt% wetting/saturating agent. A method for imparting antiwicking properties to a fabric, which method comprises applying the antiwicking composition of any one of claims 1-6 to the fabric. A fabric having antiwicking properties, which nonwicking fabric comprises a fabric treated with the antiwicking composition of any one of claims 1 to 6. The nonwicking fabric of claim 8, wherein said fabric comprises a fabric selected from the group consisting of polyaramid and polyimide fabrics, and blends thereof.

Inventors: ADILETTA JOSEPH G, ADILETTA, JOSEPH G.
Applicants: PALL CORP, PALL CORPORATION
Application year: 1988
Main classification: D06M15
IPC codes: D06M15, D06M101