MXPA01001744A - New fabric coating compositions providing excellent resistance to seam combing, particularly for use on automotive airbag fabrics - Google Patents

Abstract

This invention relates to a new adhesive coating composition, particularly for use on airbag fabrics, which is composed of a crosslinked blend of a polyalkyl- or polyphenylsiloxane with vinyl functionality and a copolymer of ethylene and methyl acrylate. This coating provides excellent adhesive properties to the coated fabric, in that it restricts the movement, when put under stress, of the yarns constructing that fabric, which are situated adjacent to seams in the fabric. This reduces the effect known in the trade as combing. Fabric treated with this material in the manner described herein, requires a marked increase in the amount of force required for this yarn movement. This distortion of the fabric can be detrimental in an automotive airbag, in that, it may result in the loss of inflating air, and under extreme conditions may result in a seam failure.

Description

COMPOSITIONS FOR COATING NOVELTY FABRICS THAT PROVIDE EXCELLENT RESISTANCE TO HAIRSTYLE SEWING. PARTICULARLY FOR USE IN AUTOMOTIVE AIR BAGS Technical Field This invention relates to a novel adhesive coating composition, particularly for use in air bag fabrics, which are composed of a combination interlaced with polyalkyl or polyphenylsiloxane with vinyl functionality and a copolymer of ethylene and methyl acrylate. This coating provides excellent adhesive properties to the coated fabric, since it restricts the movement when placed under tension of the threads that make up that fabric, which are located adjacent to the fabric. seams on fabrics. This reduces the effect known in the trade as hairstyle. The fabric treated with this material in the manner described herein requires an increase in the amount of force required for the movement of this yarn. This distortion of the fabric can be harmful in a car airbag, since can result in inflation air loss and under extreme conditions can result in seam failure.

Background Art Air bags for automotive vehicles are known and have been used for a substantial period. Those Devices are installed in the driver's and car's passenger's way, and in the event of a collision, they are quickly inflated with gas, to act as a barrier between the driver or passenger and the steering wheel or dashboard of the automobile. 5 Coatings have been applied to fabrics, intended for use in automotive air bags, to resist undesirable permeation of air through the fabric and, to a lesser degree, to protect the fabric from the detriment of the hot gases used for inflate the bags. Polychloroprene was the polymer of choice in the first developments of this product, although the desire to decrease the folded size of the finished air bag, and the tendency of the polychloroprene to degrade, with exposure to heat, to release the hydrochloric acid components (potentially degrading this way the fabric component as well as releasing hazardous chemicals) has led to the almost complete acceptance of silicone (polydimethylsiloxane or similar materials) as the most suitable coating. In the search for the most compact folded size possible, the polymer coating levels have been reduced from approximately 84.75 grams / m2 of fabric, up to levels that approximate 16.95 grams / m2. Current developments in airbags, particularly the most recent designs that are being placed on the sides of the passenger compartment, have introduced the requirement that the bags maintain the pressure longer during use. This, and the evolution of the lower levels of silicone polymer coating, have begun to highlight the effect that, when a sewn seam is placed under tension, a silicone coating that naturally lubricates can allow the threads starting from which is made the fabric move. This displacement can lead to escape of the inflation gas through the new pores formed from the moving threads or, in drastic cases, it can cause the seam to fail. Since the airbag must maintain its integrity during In the event of a collision event, in order to sufficiently protect the driver or the passenger, there is a need to provide coatings that provide effective permeability characteristics and sufficient restriction of yarn displacement for the airbag to function properly, if and whenever necessary. Therefore, there is a need for a coating of one layer, effective in cost which provides low permeability, resistance to yarn displacement and resistance to aging through extended storage periods. It is therefore an object of the invention to provide a Adhesive coating composition for cloth substrates, which provides substantial tendency reduction of the yarns, located at cutting edges or seams in the fabric, to the displacement when placed under tension. It is a further object of the invention to provide a formulation of easy handling and simple processing to a highly effective cost for use as a coating adhesive on fabric surfaces. Yet another object of the invention is to provide a highly effective coating for air bag fabrics, bags and cushions, which substantially reduces the chances of an airbag failure due to broken or torn seams during inflation initiated by an event. of collision.

Description of the Invention The coating of the invention (which can be used on any fabric substrate) provides said improvement. This coating is comprised of a vinyl functionalized polysiloxane polymer, combined with a copolymer containing ethylene (in combination with a substituent having a polar nature) the complete system which is cured with an agent capable of crosslinking both polymers. More specifically, the material of the invention is comprised of a polyalkyl or a polyphenylsiloxane, combined with a copolymer of ethylene and, as a preferred non-limiting substituent, methyl acrylate or a copolymer of ethylene and, as another preferred substituent non-limiting, vinyl acetate and cured with a peroxide. It has been found that the ethylene-methyl acrylate copolymer provides the most desired adhesive qualities upon incorporation with the vinyl-containing polysiloxane, while retaining the other properties required for an air bag fabric.

Preferably, the coating is produced by combining, in solution, 50-95 parts in the polysiloxane polymer, 5-50 parts of the ethylene-containing copolymer, and 2-10 parts of an organic peroxide curing agent. The siloxane component can be comprised of a polyalkylsiloxane, a polyarylsiloxane or a copolymer of both, each containing at least one vinyl functionality to allow adequate entanglement. Specifically, the preferred polyalkylsiloxane is a vinyl-containing polydimethylsiloxane and the preferred polyarylsiloxane is a vinyl-containing polyphenylsiloxane, any of these materials may contain common undescribed materials for the formation of compounds of commercial materials of this type. The ethylene-containing copolymer can be a copolymer comprised of 60-85 percent by weight of ethylene and 15-40 percent by weight of methyl acrylate, preferably 65-75 percent by weight of ethylene and 25-35 percent by weight of acrylate of methyl, and more preferably a distribution of about 66-67 to about 33-34 of the two components. It may also be a copolymer containing ethylene comprised of 20-60 percent by weight of ethylene and 40-80 percent by weight of vinyl acetate, preferably from about 25-50 percent by weight of ethylene and from about 50-75 percent by weight. by weight of vinyl acetate, and more preferably from about 40 to about 60 weight percent of those two components. The preferred curing agent is an acyl peroxide, typically, but not limited to, benzoyl peroxide. Other well-known curing agents can also be implemented either as a supplement or as a substitute for the preferred peroxide. Also, a solvent is preferably present to effect adequate and complete mixing of the components of the preferred coating composition. More preferably, said solvent is organic and volatile (i.e., it readily evaporates at a relatively low temperature); more preferably said solvent is toluene or a volatile liquid of similar type. The coating may have silane coupling agents of the well-known commercial type to improve the adhesion of silicone-containing coatings for fabric (such as trimethoxysilanes, only as a broad example). It may also contain pigments or dyes, (for identification or for aesthetic reasons); inert ingredients (such as calcium carbonate or other materials classified as fillers (to reduce cost without also reducing the desired performance of the coating of the invention as applied to the objective fabric; flame retardants; and necessary processing aids) to process the composition and make it suitable for use as an air bag cover This coating composition of the invention can be applied to any type of fabric substrate to reduce seam tearing and crumbling at the edges of the fabric. _ * __ £. < 1i ÍtM tflß * -t-? ^? ~ cut. Therefore, any type of fabric can be used in conjunction with the coating of the invention, including those comprising natural fibers, such as cotton, ramie, mannose hemp, wool and the like; synthetic fibers, such as polyester, 5 polyamide, regenerated cellulose and the like; and inorganic fibers, such as glass, boron-derived fibers and the like. In addition, the objective fabrics can be woven, knitted, non-woven and the like. Preferably, the objective fabric substrate comprises synthetic fibers, preferably polyesters and polyamides, and an air bag fabric is preferable. If an air bag fabric is desired, any standard low permeability air bag fabric construction can be used as the objective air bag fabric with the composition of the invention. However, preferably the objective air bag fabric within this invention is a smooth woven fabric, formed from yarns comprising polyamine or polyester fibers. Said thread preferably has a linear density of about 210 denier to about 630 denier. Such yarns are preferably formed from multiple filaments, wherein the filaments have linear densities of about 6 denier per filament or less and more preferably about 4 denier per filament or less. Such substrate fabrics are preferably woven using fluid jet weaving machines as described in US Patent Nos. 5,503,197 and 5,421,378 for Bower et al. & MÍ ¡¡¡¡^^^^^^^ rt ^ A ^^^ _ ^^^ a ^^^ _ J_jf * - __i? l _____ i? ¡? '. i'iiiiín 1 _ ^ -?. ^; i - ^ _____ s ___ ¡__? _______ (incorporated herein by reference). The fabric substrate with the applied coating will be referred to hereinafter as an air bag base fabric. In accordance with the potentially preferred practices of the present invention, a toluene dispersion comprised of -30 percent non-volatile materials, is made from the materials described above. The potentially preferred dispersion comprises 65 phr of the vinyl functional polysiloxane, available under the tradename Silastic® HS-30 from Dow Corning silicone rubber (which is considered to have offices in Midland, Michigan), 35 phr of the ethylene-acrylate copolymer of methyl, available under the trade name Vamac D® from DuPont Polymers (which is considered to have offices in Wilmington, Delaware), 5 phr of benzoyl peroxide and 1 phr of 3-methacryloxypropyltrimethoxysilane available under the trade name Silane Z-603® by Dow Corning. Once the formation of the compound is complete, the formulation is preferably scraped over the base fabric of the air bag, the solvent (eg, toluene) is subsequently removed by evaporation by placing the bag base fabric. of treated air in an oven at 60-90 ° C and the resulting coated air bag base fabric is then cured in an oven at 150-200 ° C to form a thin coating. Scratch coating, in this sense, includes, and is not limited to, knife coating methods, in particular, knife on roller, knife on opening, knife on board, floating knife and knife on foam pad, to mention a few. types of methods. Since the coating composition exhibits excellent adhesive properties, generally only one coating pass, it is necessary to provide a low permeability, stable and effective coating on the target fabric surface. The final dry weight of the coating is preferably about 67.8 grams / m2, and more preferably 33.90 grams / m2 or less, the resulting base cloth is also substantially permeable to air, when measured in accordance with the ASTM D737 test, "Air Permeability of Textile Fabrics'7 As previously indicated, the substrate fabric is preferably a woven nylon material, In the most preferred embodiment, each fabric of substrate will be formed from fibers of nylon 6.6. It has been found that such polyamide materials exhibit a particularly suitable adhesion when used in combination with the coating according to the invention.

BEST MODE FOR CARRYING OUT THE INVENTION 20 To further describe the present invention, the following non-limiting examples are set forth. The examples are provided for the sole purpose of illustrating the preferred embodiments of the invention and are not to be construed as limiting the scope of the invention in any way. tm ^ m? if ^^^ Example 1 A coating dispersion was prepared using the following components, where all proportions are in parts: Component Proportion Toluene 392 parts Silica rubber SilasticO HS-30 65 parts Copolymer Vamac DO 35 parts Trihydrate of alumina 5 parts Silane Z-6030O 1 part Inorganic pigment 1 part Benzoyl peroxide 5 parts Calcium oxide filler 5 parts This material was coated on a 420 denier nylon 6,6 cloth substrate, using a knife coater, dried for two minutes at 90 ° C, and cured for 7 minutes at 170 ° C. the weight of the dry coating was 33.90 grams / m2. The air permeability measured at 124 Pa was essentially zero cfm per 0.092 m2 of fabric (as tested in accordance with Method ASTM D737) the force required to remove a fixed number of wires adjacent to a cutting edge, tested in accordance with the method published by TRW Occupant Restraint Systems in TRW TP 9904 0180 (Comb Stripping Resistance) was 58.89 kg.

Example 2 A coating dispersion was prepared using the following components, where all proportions are in parts: Component Proportion Toluene 392 parts Silica rubber SilasticO HS-30 70 parts Copolymer Levapren 400O 35 parts Alumina trihydrate 5 parts Silane Z-6030O 1 part Inorganic pigment 1 part Benzoyl peroxide 5 parts Calcium oxide filler 5 parts This material was coated on a 6,6 nylon denier substrate of 420 denier, using a knife coater, drying for two minutes at 90 ° C , and cured for seven minutes at 170 ° C.

The dry coat weight was 33.90 grams / m2. The air permeability measured at 124 Pa was essentially zero cfm per 0.092 m2 of fabric (as tested in accordance with Method ASTM D737). The force required to remove a fixed number of wires adjacent to a cutting edge, tested according to the method published by TRW Occupant Restraint Systems on TRW TP 9904 0180 (Comb Stripping Resistance) was 42.58 kg. Levapren 400O is a copolymer, understood to contain 60 percent by weight of ethylene and 40 percent by weight of vinyl acetate. It was obtained from _- < _ £. • _.

Bayer Fibers, Organics and Rubber Division, which has commercial offices in Akron, Ohio.

Example 3 (Comparative) A typical silicone coating dispersion was prepared using the following components, wherein all proportions are in parts: Component Proportion Toluene 336 parts Silica rubber SilasticO HS-30 100 parts Silane Z-6030O 1 part Inorganic pigment 1 part Benzoyl peroxide 5 parts Calcium oxide filler 5 parts This material was coated on a 420 denier nylon 6,6 cloth substrate, using a knife coater, dried for two minutes at 90 ° C, and cured for 7 minutes at 170 ° C. The weight of the dry coating was 30.51 grams / m2. The air permeability measured at 124 Pa was essentially zero cfm per 0.092 m2 of fabric (as tested in accordance with Method ASTM D737). The force required to remove a fixed number of yarns adjacent to a cutting edge, tested according to the method published by TRW Occupant Restraint Systems on TRW TP 9904 0180 (Comb Stripping Resistance) was 27.18 kg.

Obviously, the addition of the ethylene-containing copolymer provided a marked increase in strength for the fabric while not resulting in appreciable loss in low air permeability. There are, of course, many alternative embodiments and modifications of the present invention that are intended to be included within the spirit and scope of the following claims. k

Claims (20)

1. CLAIMS 1. A coating composition comprising a polysiloxane entangled with a copolymer containing ethylene. The coating composition according to claim 1, characterized in that the polysiloxane comprises at least one vinyl functional group and is selected from the group consisting of vinyl containing vinyl and polyarylsiloxane containing vinyl and the ethylene-containing copolymer containing polyalkylsiloxane. it is selected from the group consisting of ethylene-methyl acrylate and ethylene-vinyl acetate. 3. The coating composition according to claim 2, characterized in that the polysiloxane is a polyalkylsiloxane and the copolymer containing ethylene is ethylene-methyl acrylate. 4. The coating composition according to claim 3, characterized in that the polyalkylsiloxane is polydimethylsiloxane. 5. The coating composition according to claim 2, characterized in that the polysiloxane is a polyalkylsiloxane and the ethylene-containing copolymer is ethylene-vinyl acetate. 6. The coating composition according to claim 5, characterized in that the polyalkylsiloxane is polydimethylsiloxane. The coating composition according to claim 2, characterized in that it comprises from about 50-95 parts of the polysiloxane polymer and 5-50 parts of the ethylene-containing copolymer. 8. The coating composition according to claim 3, characterized in that the ethylene-methyl acrylate comprises from about 60-85 percent by weight of ethylene and from about 15-40 percent by weight of methyl acrylate. 9. The coating composition according to claim 5, characterized in that the ethylene-vinyl acetate comprises from about 20-60 weight percent of ethylene and from about 40-80 weight percent of vinyl acetate. 10. A fabric substrate coated with the composition according to claim 1. 11. A fabric substrate coated with the composition according to claim 2. 12. A fabric substrate coated with the composition according to claim 3. 13. A fabric substrate coated with the composition according to claim 5. 14. A fabric substrate coated with the composition according to claim 8. 15. A fabric substrate coated with the composition in accordance with claim 1. 9. 16. The fabric substrate according to claim 10, characterized in that the fabric is an air bag fabric. A method for producing the coating composition according to claim 2 comprising the steps of (a) mixing the polysiloxane, the ethylene-containing copolymer, optionally an organic silane, optionally components selected from the group consisting of fillers , pigments, processing aids and mixtures thereof, a solvent and a curing agent; (b) applying the resulting mixture to the surface of a cloth substrate; (c) heating the fabric substrate to a temperature sufficient to evaporate the solvent from the fabric substrate surface; and (d) heating the resulting treated fabric substrate to a temperature sufficient to effect entanglement of the polysiloxane and the ethylene-containing copolymer on the substrate surface of the fabric. 18. The method according to claim 17, characterized in that the polysiloxane is polyalkylsiloxane; the ethylene-containing copolymer is ethylene-methyl acrylate; the curing agent is a peroxide; the solvent is an organic volatile solvent; the cloth substrate is an air bag fabric; the heating temperature of step "c" is from about 60 to about 90 ° C; and the heating temperature of step "d" is from about 150 to about 200 ° C. 19. The method according to claim 17 characterized in that the polysiloxane is polyalkylsiloxane; the ethylene-containing copolymer is ethylene-vinyl acetate; the curing agent is a peroxide; the solvent is an organic volatile solvent; the cloth substrate is an air bag fabric; the heating temperature of step "c" is from about 60 to about 90 ° C; and the heating temperature of step "d" is from about 150 to about 200 ° C. 20. A fabric substrate treated with the composition produced by the method of claim 17.