POLYURETHANE COATED FIBERS

Abstract: Fibers having thereon the dried residue of an aqueous coating composition having one or more elastomeric, curable polyurethanes, one or more high molecular weight, high boiling point plasticizers and water have good flexibility and do not need to be preheated before incorporation with matrix polymers. The fibers also have greatly improved adhesion to various types of polymers and better resistance to the effects of water. In addition to the above ingredients for the impregnating coating composition, a number of other optional ingredients may be included. Ingredients such as a crosslinking agent present in an amount to at least partially cure the polyurethane, an emulsifier and/or a microcrystalline wax dispersion may be used. Other common fiber treating chemicals may be present also such as anti-static agents, pigments or dyes, silane coupling agents, fire retardants, etc. After the coating of the sized fibers, the coated fibers can be cured at ambient or elevated temperatures.

Description: POLYURETHANE COATED FIBERS gACKgRQWrø OF THE INVENTION Many coatings and treatments for glass and other fibers have been developed over the years for use in varying applications of such fibers, generally for use with polymers where the coated fibers are incorporated into, encapsulated or surrounded by the polymer. Coatings and chemically treated fiber bundles were disclosed in U.S. Patent Noε. 4,663,231; 4,762,750 and 4,762,751, among others. During the step of combining the fibers coated according to the above patents with the polymers as previously mentioned, the coated fibers are generally preheated. This preheating takes time and energy and may also cause the release of volatile materials. It is an object of this invention to provide coated fibers with good flexibility which do not need to be preheated before incorporation with matrix polymers, thereby saving energy and increasing production speed. It is an additional object of this invention to provide coated fibers which have greatly improved adhesion to various types of polymers and better resistance to the effects of water, alkalinity and acidity. SUMMARY OF THE INVENTION The objects of the invention are achieved through the use of high modulus, low elongation fibers, such as glass fibers, having thereon the dried residue of an aqueous chemical coating and impregnating composition having one or more elastomeric, curable polyurethanes, at least 15 weight percent on a non-aqueous basis of one or more high boiling point plasticizers, and water in an effective amount to provide an impregnating coating composition for the fibers. After the coating of the sized fibers, the coated fibers can be cured at ambient or elevated temperatures. Although applicable to other fibers, the invention is primarily useful with glass fibers. Glass fibers are formed, for example, by the method mentioned in U.S. Patent No. 4,762,751. Prior to coating with the impregnating composition, the fibers are treated with an aqueous chemical sizing composition which dries to leave a moisture reduced residue on the fibers. A plurality of fibers are then gathered together constituting a flexible bundle of sized, high modulus, low elongation fibers. In addition to the above ingredients for the impregnating coating composition, a number of other optional ingredients may be included. Ingredients such as a crosslinking agent present in an amount to further cure the polyurethane, an emulsifier and/or a microcrystalline wax dispersion may be used. Other common fiber treating chemicals may be present also such as anti-static agents, pigments or dyes, silane coupling agents, fire retardants, etc. DETAILED DESCRIPTION OF THE INVENTION When the fibers used in the invention are glass fibers they may be those such as "E glass", "S glass", "D glass" or any of the glasses known in the art. The aqueous sizing composition is applied by sprayers, rollers, belts, or the like. Non-starch sizes are preferred and a suitable non-starch aqueous chemical sizing composition for glass fibers is disclosed in U.S. Patent No. 4,390,647. The sized glass fibers are gathered into bundles comprising a plurality of individual fibers, generally from 200 to more than 3000. The bundles are usually wound onto a forming package and the sizing is dried at room temperature or by oven heating. The sized glass fibers generally have between about 0.05 and 5 percent of sizing composition based on the weight of the glass fiber. The aqueous sizing composition has a hydrophilic reducing agent such as a coupling agent and a protectant, where the protectant can be a glass fiber lubricant or a glass fiber film former. Additional ingredients like friction-reducing agents and/or antistatic agents may be present. Any coupling agent, glass fiber lubricant or glass fiber film forming polymer known to those skilled in the art can be used. As an example, the sizing composition and the application of the size and the application of the coating to the sized glass fibers and the 5 types of fibers used can be in accordance with U.S. Patent No. 4,762,751. The largest single component of the aqueous impregnating coating composition, besides water, is a polyurethane polymer. By the use of the term polyurethane, it is meant to include reaction products 10 of organic compounds having at least two active hydrogens and di and/or polyisocyanateε, wherein the resulting polymer is an elastomeric curable polyurethane or polyurethane-urea type polymer. These materials are noncrystalline in the undeformed state and they have a sufficiently high molecular weight to make them elastomeric 15 materials. These materials also have a glass transition temperature of around 0°C or less. Suitable polyurethane polymers are described in U.S. Patent Nos. 4,143,091; 4,208,494; 4,208,495; 4,066,591 and 4,762,751. The preferred polyurethane is that sold as Witcobond® W-290H, which is milky white in appearance, aliphatic in type with a 20 65 percent solids level and with a particle size of around 5 microns, a pH at 25°C (77°F) of 7.5, a viscosity as measured by Brookfield LVF in cpε of 200 and surface tension of 42 dynes/cm. The film properties of the 290H material, when cured with 6.5 parts of epoxy resin dispersion like Witcobond® XW for 100 parts of urethane latex, are: 25 4500 psi tensile strength, 720 percent elongation and moduli of 250 psi at 100%, 540 psi at 300% and 1550 psi at 500%. The amount of polyurethane can range from about 45 to about 80 weight percent of the non-aqueous portion of the impregnating coating composition. One or more softening agents or plasticizers are also 30 present in the aqueous impregnating coating composition. A key feature of the invention is that the plaεticizer should have a high boiling point such that it will not become volatile during the impregnation of the bundles of fiber or during subsequent combination with the polymer composition. High boiling point plasticizers generally have high molecular weights as well. Higher boiling point plasticizers give greater adhesion and less volatility in processing than the medium or low boiling point plasticizers. High boiling point plasticizers means plasticizers with boiling points above 225°C (437°F) at a pressure of 10 millimeters of mercury (mmHg). One such plasticizer is Santicizer® 160 produced by Monsanto Corporation which is a clear oily liquid having a boiling point of 240°C (464 β F) at 10 mmHg a specific gravity of 1.12. Another suitable plasticizer is diiεononyl phthalate (DINP) (sold as PX-109 by Aristech Chemical Corporation) which has a boiling point of 252 β C (486°F) at 5 mmHg, a molecular weight of 418, a pour point of -45°C, a specific gravity of 0.971 at 25°C/25°C, a flash point of 435°F (224°C), a viscosity of 72 cps at 25°C (77 β F) and a refractive index of 1.485 at 25 β C. A particularly suitable plasticizer for use in this invention is mixed normal alkyl trimellitate sold as PX-336 by Aristech Chemical Corp. The common name of PX-336 is 1,2,4-Benzenetricarboxylic acid, mixed hexyl, octyl and decyl ester, and the chemical formula is CgH (C00R)3 where R=Cg,Cg,C^ Q alkyls. The PX-336 material has a boiling point of 275°C at 1 mmHg, a molecular weight of 585, a freeze point of -17°C, a specific gravity of 0.975 at 25°C/25°C, a flash point of 532 β F (278 β C), a viscosity of 103 cps at 25°C and a refractive index of 1.482 at 25°C. Although plasticizers are generally used in amounts of less than 10 weight percent in the compositions of the prior art, an important feature of the present invention is that the plasticizer be present in an amount of at least 15 weight percent. The resulting compositions have excellent adhesion to various polymers although until now it had been believed by those skilled in the art that such amounts of plasticizer would result in a loss of adhesion. The exact amount of plasticizer employed is dependent on the rigidity of the polyurethane used and can range from about 15 to about 40 weight percent of the non-aqueous portion of the impregnating coating composition. An emulsifier may be used with this invention to aid in the 5 emulsification of the plasticizer. Preferred are sorbitan based emulsifiers, examples being polyoxyethylene (4) sorbitan monolaurate and polyoxyethylene (5) sorbitan monolaurate which are produced by ICI America Inc. under the trade names Tween® 21 emulsifier and Tween® 81 emulsifier, respectively. Tween 21 has a flash point of 410°F (210°C) 10 C.O.C. (Cleveland Open Cup), a specific gravity of 1.1 and is a yellow oily liquid. Tween 81 has a flash point of greater than 300°F (149°C) C.O.C, and is also a yellow oily liquid. If used, the emulsifier is generally present in an amount of up to about 20 percent, preferably about 10 weight percent, of the plasticizer. 15 Suitable crosslinking agents which may be used in this invention are described in U.S. Patent Nos. 4,762,750 and 4,762,751 and can range from about 0 to about 10 weight percent of the non-aqueous portion of the impregnating coating composition. Examples of polymeric crosslinking materials include raethylol-containing 20 condensates of phenolic compounds, and polyhydroxyphenolic compounds like resorcinol, urea, melamine, and the like where the methylol results from any methylene donating compound like formaldehyde in its various forms like paraformaldehyde, hexamethylene -tetramine, and furfural and mixtures thereof, and also includes aminoplaεt resins, 25 organic polyisocyanates, and epoxy containing polymerε. A particularly good crosslinking agent which may be used is marketed under the name Witcobond® XW aqueous epoxy emulsion by Witco Chemical Corporation and has an epoxide equivalent weight of 345 to 385, a percent nonvolatiles of 54 to 56 percent, a viscosity in Brookfield at 30 25°C (77 C F) poise of 15 to 70 and an appearance which is a milky white liquid, and has a flashpoint of greater than 93°C (200°F) and a density of 9.1 pounds per gallon at 25°C. One or more waxes may also be included in the practice employed in this invention wherein the wax can be dispersed or emulsified in water with any suitable emulsifier known to those skilled in the art. The wax may be included in the aqueous coating compoεition in a pre-emulsified or pre-dispersed form. The preferred waxes are the microcrystalline wax materials. Examples of microcrystalline waxes include the anionic Polymekon SPPW-40 available from Petrolite Corporation-Bareco Division of Tulsa, Oklahoma which is a hydrocarbon/water dispersion of 40 percent solids. Another material is Mobilcer Q microcrystalline wax from Mobil Corporation which has a solids content of 50.5 weight percent, a melt point of 160°F and an emulsion density of 7.9. Another material is the nonionic Michemlube® 296 from Michelman Inc. The amount of microcrystalline wax can range from about 0 to about 25 weight percent of the non-aqueous portion of the impregnating coating composition. It is preferred to cure the impregnating coating composition at elevated temperatures through an oven in a continuous manner. An example of this proceεs is disclosed in U.S. Patent 5,052,125. Examples of the impregnating coating composition in accordance with this invention are given in the following table in grams: Witcobond® 290H polyurethane PX-336 plasticizer Tween 21® emulsifier Witcobond® XW crosslinker Polymekon SPPW-40 wax Water The above formulations were coated onto a bundle of glasε fibers comprised of individual fibers which had been produced and sized as mentioned above. All of the examples showed an increase in adhesion when compared to fibers produced according to U.S. Patent No. 4,762,751. For instance, the impregnated bundles of glass fibers according to Example B above had properties compared to the impregnated bundles of glasε fibers produced according to U.S. Patent 4,762,751 (USP '751) as follows: Strand Property Tensile strength, lbs. Tensile stiffness, lbs./% Adhesion (compound 1) lbs./in. Adhesion (compound 2) lbs./in. MIT flex, cycles Water .aging; tensile, lbs. Water aging; flex, cycles Humidity aging; tensile, lbs. Humidity aging; flex, cycles Alkali exposure; tensile, lbs. Acid exposure; tensile, lbs. outgassing, % The adhesion was measured using ASTM test method D-1871 with two proprietary PVC compounds supplied by two manufacturers. The MIT flex test was performed according to ASTM test method D-2176 using a 0.06 mil head. The tensile strength was measured using an Instron tensile testing machine with a 500 pound load cell and a rubber covered drum clamp. Outgassing was measured by heating a known weight of the sample in a hot air oven at 250°F (121 β C) for two hours, reweighing and calculating the percentage of volatiles lost from the samples. The alkali resistance was performed by soaking the coated fibers in a 1 normal solution of sodium hydroxide (NaOH) at room temperature (72 β F, 22°C) for 30 minutes, rinsing the strand twice with tap water, drying the strand at 250°F (121°C) for 5 minutes, cooling and then testing the tensile strength as above. The acid resistance was performed by soaking the coated fibers in a 3 normal solution of hydrochloric acid (HC1) at room temperature (72°F, 22°C) for three hours, rinsing the strand twice with tap water, drying the strand at 250 β F (121°C) for 5 minutes, cooling and then testing the tenεile strength as above. The humidity resistance was tested by placing the εtrand in a humidity chamber for 1 month at 120°F (49 β C) and 98 percent relative humidity, cooling to room temperature and then teεting the tensile strength as above. The water aging resistance was tested by soaking the strand in tap water for 1 month at room temperature (72°F, 22 β C) and then drying the strand and testing the tensile strength as above. The bundles of fiberε treated in accordance with this invention showed an increaεe of approximately 35% in adhesion to the PVC compounds, an increase of about 41% in alkali resistance, about 30% in acid resistance and about 41% less outgassing than the USP '751 strand. The bundleε alεo had εignificantly improved flexibility after _water aging and humidity aging when compared to the USP '751 strand.

Claims: I claim: 1. A flexible bundle of sized fibers coated and impregnated with a moisture reduced residue of an aqueous chemical coating composition, where the composition comprises: (A) at least one elastomeric, curable polyurethane; (B) at least one high boiling point plasticizer in an amount of at least 15 weight percent of the non-aqueous portion of the composition; (C) water in an effective amount to provide an impregnating coating composition for the bundle of fiberε. 2. The flexible bundle of sized fibers of claim 1 wherein the aqueous chemical coating composition further comprises a croεεlinking agent present in an amount to at least partially cure said polyurethane. 3. The flexible bundle of sized fibers of claim 1 wherein the aqueous chemical coating composition further comprises a microcrystalline wax dispersion. 4. The flexible bundle of sized fibers of claim 1 wherein the aqueous chemical coating composition further comprises a sorbitan based emulsifier in an amount of 10 weight percent of said plasticizer. 5. The flexible bundle of sized fibers of claim 1 wherein the aqueous chemical coating composition further comprises at least one silane coupling agent. 6. The flexible bundle of sized fiberε of claim 1 wherein the aqueouε chemical coating compoεition further comprises at least one water soluble, dispersible or emulεifiable fire retardant. 7. The flexible bundle of sized fibers of claim 1 wherein the aqueous chemical coating composition further comprises at least one water εoluble, dispersible or emulεifiable dye or pigment. 8. The flexible bundle of sized fibers of claim 1 wherein the aqueous chemical sizing composition includes at leaεt one anti-static agent. 9. The flexible bundle of sized fibers of claim 1 wherein the plasticizer is mixed normal alkyl trimellitate. 10. The flexible bundle of sized fibers of claim 1 wherein the fibers are glasε fiberε. 11. A flexible bundle of sized glaεε fiberε coated and impregnated with a moisture reduced residue of an aqueous chemical coating composition, where the composition comprises: (A) from 45 to 80 weight percent of said coating compoεition on a non-aqueous basis of one or more elastomeric, curable polyurethanes; (B) from 15 to 40 weight percent of said coating composition on a non-aqueouε baεis of one or more high boiling point plasticizers; (C) at least one sorbitan based emulsifier in an amount of 10 weight percent of said plasticizer; (D) at least one microcryεtalline wax dispersion in an amount of said coating composition on a non-aqueous baεiε of 0 to 25 weight percent; (E) at least one crosεlinking agent present in an amount to at least partially cure said polyurethane; (F) water in an effective amount to provide an impregnating coating composition for the bundle of fibers. 12. The flexible bundle of sized fibers of claim 11 wherein the aqueous chemical coating compoεition further compriεeε at leaεt one silane coupling agent. 13. The flexible bundle of εized fibers of claim 11 wherein the aqueous chemical coating compoεition further compriseε at leaεt one water εoluble, dispersible or emulsifiable fire retardant. 14. The flexible bundle of εized fibers of claim 11 wherein the aqueous chemical coating compoεition further comprises at least one water εoluble, dispersible or emulsifiable dye or pigment. 15. The flexible bundle of sized fibers of claim 11 wherein the aqueous chemical sizing composition further comprises includes at least one anti-static agent. 16. The flexible bundle of sized fibers of claim 11 wherein the plasticizer is mixed normal alkyl trimellitate. 17. The flexible bundle of sized fibers of claim 11 wherein the wax is hydrocarbon aliphatic wax in an aqueous medium. 18. The flexible bundle of sized fibers of claim 11 wherein the polyurethane is aliphatic and dispersible, emulsifiable or water soluble. 19. The flexible bundle of sized fibers of claim 11 wherein the fibers are glass fiberε.

Inventors: GIRGIS MIKHAIL M, GIRGIS, MIKHAIL, M.
Applicants: PPG INDUSTRIES INC, PPG INDUSTRIES, INC.
Application year: 1993
Main classification: D02G3
IPC codes: C03C25, C08J5, D02G3, D06M15