GB2076844A - Aqueous sizing composition comprising vinyl acetate/acrylic copolymer, and sized glass fibers - Google Patents

Abstract

The invention concerns an improved aqueous size composition for treating glass fibers during forming to produce glass fiber strands having improved wet-out, mold conformity, and wet-through when used in gun roving application. The improved size composition substitutes an externally plasticizable vinylacetate-acrylate copolymer and external plasticizer for the same amount of polyvinylacetate homopolymer in a previously described sizing composition. The composition also contains a fatty acid (amide) lubricant, gamma (ethylene diamine) propyl trialkoxy silane, and a methacrylato chromic halide. The pH of the sizing composition is adjusted to be between 6.1 and 6.5, and the solids content between 7.0 and 7.5 weight percent.

Description

SPECIFICATION Aqueous sizing composition comprising polyvinyl acetate/acrylic copolymer, and sized glass fibers The present invention is directed to an improvement in a sizing composition for treating glass fibres, wherein the composition is comprised of an aqueous mixture of at least a polyvinyl acetate film-former, a fatty acid lubricant, methacrylato chromic halide, and gamma(ethylene diamine)-propyltralkoxy silane.

Glass fibers in the form of continuous strand, chopped strand, roving, mats and woven cloth have been utilized for many years in the preparation of thermosetting polyester resin glass fiber reinforced articles.

There are numerous methods used to mold and fabricate glass fibre reinforced plastics. One method is the spray-up process. In this process a spray gun and a glass fiber roving chopper are combined, and the resin and chopped roving are sprayed simultaneously on the mold. The resin-impregnated fibers are then compacted with a roller, brush or squeegee and allowed to cure. This process is especially useful for molding large shapes, short production runs, prototypes and for on-sight fabrication. This process is used in the production of such glass fiber reinforced articles as boats, trailers, reefer liner equipment, coffins, swimming pools, missile parts and vending machine parts.

Glass fibers utilized in the spray-up molding process should possess the potential for good adhesion with the resin, which they are to reinforce; and should possess good wet-out characteristics; and should be capable of readily mixing with the resins used in the spray gun type applicator; and should possess good lay-down characteristics when sprayed on the mold. The application of a satisfactory forming size on the surface of the glass fibers utilized in preparing the glass fiber roving for use in the spray-up process is fundamental to supplying glass fiber roving having the aforementioned characteristics.

It was recently suggested in U.S. Patent 3,933,711 (Motsinger et al) to have an aqueous forming size for use on glass fibers to produce spray-up gun roving that is comprised of an aqueous mixture of a polyvinyl acetate film-fomer, a fatty acid lubricant, methacrylato chromic chloride, and gamma (ethylene diamine) propyltrialkoxysilane. The sizing mixture contained between 7 and 7.5 percent by weight solids and had a pH in the range of 6.1 to 6.5.

According to the present invention there is provided an improved forming size glass fibers for use in the spray-up process of molding glass fiber reinforced polymeric aticles. The aqueous forming size provides sized glass fibers having improved wet-out properties without trapping air, good mold conformity, and good resin wet-through. The improved aqueous forming size for glass fibers of the present invention is comprised of an externally plasticizable polyvinyl acetate-acrylic copolymer and external plasticizer instead of a polyvinyl acetate homopolymer. The aqueous forming size also contains one or more lubricants, e.g.

cationic amidated polyamine, fatty acid lubricant; methacrylato chromichalide, e.g. methacrylato chromic chloride; and gamma(ethylene diamine)propyltrialkoxysilane. The sizing mixture is provided with sufficient quantities of ingredients to provide a formulation which results in an aqueous mixture having between 7 and 7.5 percent by weight solids. Also, the pH of the aqueous mixture is adjusted to be between 6.1 and 6.5.

The externally plasticizable polyvinyl acetate-acrylic copolymer generally has from 1 to about 20 parts of acrylic units to 100 parts of vinyl acetate units. Generally, the external plasticizers that can be used with the acetate-acrylate copolymer are those that are non-reactive and compatible with the acetate-acrylate copolymer. The amount of external plasticizer used is generally in the range of about 5 to about 55 percent by weight of the acetate-acrylate copolymer. The combined amount of the acetate-acrylate copolymer and external plasticizer used in the forming size composition is in the range of about 70 to about 90 percent by weight of the non-aqueous components of the aqueous forming size composition.

The aqueous forming size composition does not require any other components in addition to those mentioned above and water and a small amount of acid for the pH adjustment in order to accomplish the objects of the present invention. Although not required, small amounts of additional additives, for example film-former modifiers, lubricants, coupling agents, stabilizers, anti-foaming agents and the like that are known to those skilled in the art may be added to the forming size. These additional additives are those that are compatible with the sizing composition and do not adversely affect the basic characteristics of the sizing composition.

The process of the present invention involves applying the improved forming size to glass fibers during their formation. The treated glass fibers are produced into one or more strands. The strands produced find particular utility when formed into roving and used to produce a paticularly effective gun roving product with improved properties of wet-out, mold conformity, and resin wet-through.

The forming size of the present invention is based on the discovery of improvements resulting from the substitution of an externally plasticizable polyvinylacetate-acrvlate copolymer and external plasticizer for the same amount of polyvinylacetate homopolymer in a particular forming size composition. The forming size is one that usually has an aqueous mixture of polyvinyl acetate homopolymer, fatty acid lubricant, methacrylate chromic chloride and gamma (ethylene diamine) propyl alkoxy silane and that has a pH between 6.1 and 6.5.

The improvements resulting from the substitution are improved wet-out of treated glass fiber strand, good mold conformity of the treated strand and good resin wet-through of the treated glass fiber strand.

The polyvinyl acetate/acrylic copolymer can be formed by any process known to those skilled in the art.

The copolymer is generally formed by aqueous emulsion polymerization of ethylenic monomers such as various acrylates, which are esters of acrylic or methacrylic acid, e.g. methyl methacrylate, methyl acrylate, ethyl methacrylate; and vinyl acetate. Because of the process of producing the copolymer, the copolymer may include certain small amounts of various polymerization additives, e.g. stabilizers and surfactants.

These small amounts of additives do not adversely affect the forming size composition. The copolymer may be the commercially available copolymers that are generally available as aqueous emulsions having around 30 to 55 percent solids. To these copolymer products, the external plasticizer may be added in the necessary amounts. It is particularly advantageous to use commercially available copolymer and plasticizer mixtures.

Nonexclusive examples of the copolymer/plasticizer mixture that can be used include: the acetate/acrylate copolymer-plasticizer product available from National Starch and Chemical Corporation, under the trade designation RESYN 25-1052, and the acetate/acrylate copolymer-plasticizer product available from H. B.

Fuller Company, Minneapolis, Minnesota under the trade designation "PN-3086C." The amount of the copolymer alone is in the range of about 45 to about 85 weight percent of the non-aqueous components of the forming size composition.

The external plasticizer that can be used in the aqueous forming size of the present invention can be selected from fugitive plasticizers or permanent plasticizers. It is preferred to use the permanent type plasticizers, non-exclusive examples of which include: phthalates, such as dibutyl phthalate, dioctyl phthalate and diioctyl phthalate; phosphates, such as tricresyi phosphate; and polyester plasticizers.

The amount of the external plasticizer used is in the range of about 3 to about 50 weight percent of the non-aqueous components of the forming size composition. The combined amount of the polyvinylacetateacrylic copolymer and external plasticizer is in the range of about 70 to about 90 percent by weight based on the total weight of the components other than water in the sizing composition.

The other components of the forming size composition are a fatty acid lubricant and possibly a cationic amidated polyamine lubricant, methacrylato chromic halide, e.g. methacrylate chromic chloride, and gamma (ethylene diamine) propyl trialkoxy silane which are more fully described in U.S. Patent 3,993,711 (motsinger et al) which is commonly assigned and hereby incorporated by reference. Also more fully described in U.S. patent 3,993,711 are the total solids, pH adjustment and preparation of the forming size composition.

In the preferred embodiment of the present invention the polyvinyl acetate/acrylic copolymer is the product available from National Starch and Chemical Corporation under the trademark RESYN 25-1052C which already contains the external plasticizer dibutyl phthalate. The RESYN 25-1052C is a polyvinyl acetate/acrylic copolymer emulsion having 55 percent solids and a pH of around 4.5 with a viscosity of 125 centipoise and an average particle size of 1 micron and a particle charge that is nonionic. The latex density of 72"F. (22"C) of the emulsion in pounds per gallon is 9.1, The polyvinyl acetate-acrylate copolymer and plasticizer mixture is combined with water in a mixing tank with agitation.To this mixture there is added the gamma (ethylene diamine) propyl trimethoxy silane which has preferably been premixed with cold water. After mixing these ingredients the Werner-type coupling agent is added slowly to the mix tank. After mixing the coupling agent into the mix tank, the glass fibre lubricants are added. The-mixture is diluted to final volume with water. The mixture is checked for its pH characteristic and sufficient acetic acid is added to control the pH between 6.1 and 6.5.

In the preferred embodiment of the aqueous forming size of the present invention, the polyvinyl acetate/acrylic copolymer is present along with the plasticizer in an amount in the range of about 70 to about 90 percent by weight based on the total weight of the size solution solids. In an alternative embodiment where the plasticizer is not in admixture with commercially available copolymer, the amount of dibutyl phthalate present in the aqueous forming size is preferably in the range of about 5 to about 30 weight percent based on the total weight of the size solution solids. The amounts of the fatty acid lubricant, methacrylato chromic chloride, and gamma (ethylene diamine) propyltrimethoxysilane are the same as those discussed in U.S. Patent 3,933,711, except for the amount of fatty acid lubricant that is used which is preferably about 0.1 to about 5 weight percent solids.

In addition to the above ingredients, the preferred embodiment includes several additional ingredients such as an anti-foaming agent such as SAG sold by Dow Chemical Company in an amount sufficient to control foaming, and a cationic lubricant emulsifier such as PELARGONIC acid amide of tetraethylene pentamine available from Imperial Chemical Industries and used in an amount of about 0.5 to 5 weight percent of the non-aqueous sizing composition. This latter material may be any cationic fatty acid amidated polyamine lubricant.

After the sizing composition is used to treat the glass fibers, the treated fibers are gathered into one or more strands and wound into a package. A plurality of the packages are dried in an oven for a period of around 11 hours at about 100 C. to 1400C. A plurality of dried packages can be placed on an appropriate balloon creel and wound on a roving winder to provide a glass fiber roving product having the dried residue of the aqueous forming size composition placed on the fibers during forming. The dried residue represents a coating of between 1.25 and 1.55 percent by weight of the bare glass. Roving produced by fibers sized with the quantity of sizing composition of the present invention have been found particularly effective in producing spray-up glass fiber reinforced polymeric products. The polymeric material may be thermoplastic orthermosetting polyesters or vinylesters.

The following example illustrates a typical preparation of the forming size of the present invention.

Example I Polyvinyl acetate/acrylate copolymer (RESYN 78-3802 without plasticizer) 4,653.5 grams Dibutyl phthalate (Plasticizer) 1,000 grams Gamma(ethylene diamine)propyltrimethoxysilane in methanol (40% volume by weight) Z-6026 236 grams Werner complex of methacrylic acid chromic chloride (VOLAN) 345 grams Pelargonic acid amide of tetraethylene pentamine (C-185A) 113.5 grams Fatty acid amide lubricant (Emery 6717) 10 grams SAG (anti-foaming agent) 20 milliliters Acetic acid amount necessary to control pH at 6.3 In the above formulation the copolymer is present in an amount of 75.2 weight percent based on the solids of the composition and the dibutyl phthalate is present in an amount of 15.7 weight percent. The silane is present in an amount of 3.7 weight percent and the Werner complex is present in an amount of 5.4 weight percent.The cationic lubricant emulsifier "C-185A" is present in an amount of 1.8 weight percent while the cationic fatty acid amide is present in an amount of about 0.16 weight percent.

The size preparation listed above is prepared by mixing the polyvinyl acetate/acrylic copolymer with the plasticizer, dibutyl phthalate, with about 35 percent of total water to be used in preparing the final size solution in the desired volume. The gamma(ethylene diamine)propyltrimethoxysilane is then mixed with a small quantity of cold water and added to the mixing tank foilowed by the addition of the Werner coupling agent. The cationic fatty acid amide and the pelargonic acid amide of tetraethylene pentamine are mixed in hot water and added to the size ingredients during continuous mixing. The mixing tank is then diluted to the final volume of 10 gallons. The pH is then measured and acetic acid is added in sufficient quantities to control the pH preferably in the range of 6.3 + 0.2.It is preferred that the pH of the final size be maintained at 6.3 although the general range for the pH can be from about 6.1 to about 6.5.

After mixing the forming size for Example I, it is applied to the individual glass fibers during their formation in a manner similar to that discussed in U.S. Patent 3,933,711.

In general, the amounts of the ingredients in the size formulation can be in the general ranges of: polyvinyl acetate/acrylic copolymer about 45 to about 85 percent by weight plasticizer about 5 to about 55 percent by weight gamma(ethylene diamine)propyltrialkoxy- about 2 to about 6 silane percent by weight solids methacrylic acid chromic halide about 2 to about6 coupling agent percent by weight solids fatty acid amide lubricant about 0.1 to about7 percent by weight based on solids cationic lubricant about 2 to about 6 percent by weight solids acetic acid sufficient to bring the pH of the forming size in the range of 6.1 to about 6.5 and the aque - ous sizing composition having 7.0 to about 7.5 percent by weight solids Glass fibers treated with the sizing composition of Example I showed improved wet-out without trapping air and excellent mold conformity and superb resin wet-through.

Claims (17)

1. An aqueous sizing composition for glass fiber strand whose ingredients other than water comprise: about 45 to about 85 percent by weight based on the total weight of the size solution solids of an externally plasticizable polyvinyl acetate/acrylic copolymer film-former; about 5 to about 55 weight percent based on solids of a compatible external plasticizer; about 0.1 to about 7 percent based on solids of a fatty acid amide lubricant; about 3 to about 6 percent by weight solids gamma(ethylene diamine)propyltrialkoxysilane; and about 2 to about 6 percent by weight methacrylic acid chromic halide coupling agent; said sizing composition having been adjusted to a pH of about 6.1 to about 6.5 and said composition having about 7.0 to about 7.5 percent byweightsolids.

2. An aqueous sizing composition as claimed in claim 1, wherein the alkoxysilane is gamma(ethylene diamine) propytrimethoxysilane.

3. An aqueous sizing composition as claimed in claim 2, wherein the gamma(ethyiene-diamine) propyltrimethoxysilane is present in an amount between 4 to 5 percent based on the size ingredients exclusive of water.

4. An aqueous size composition as claimed in any of claims 1 to 3, wherein the polyvinyl acetate/acrylic copolymer and plasticizer are incorporated into the sizing composition as a mixture in an amount of about 70 to about 90 weight percent of the non-aqueous sizing composition.

5. An aqueous sizing composition as claimed in any of claims 1 to 4, wherein the plasticizer is bibutyl phthalate.

6. An aqueous sizing composition as claimed in any of claims 1 to 5, wherein the polyvinyl-acetateacrylic copolymer has about 5 to about 20 parts of acrylic units to 100 parts of vinyl acetate.

7. An aqueous sizing composition as claimed in any of claims 1 to 6, wherein the polyvinylacetateacrylic-copolymer is selected from polyvinylacetate-acrylic copolymer, polyvinylacetate methacrylate copolymer, polyvinyl acetate methyl methacrylate copolymer, polyvinyl acetate methacrylate copolymer and polyvinyl-acetate-ethyl-methacrylate copolymer.

8. An aqueous sizing composition as claimed in any of claims 1 to 7, which includes a cationic lubricant emulsifier.

9. An aqueous sizing composition as claimed in claim 8, wherein the cationic lubricant emulsifier is pelargonic acid amide of tetraethylene pentamine.

10. An aqueous sizing composition as claimed in any of claims 1 to 9, which includes an antifoaming agent.

11. An aqueous sizing composition as claimed in any of claims 1 to 10, wherein the pH is adjusted with acetic acid to be within a range of about 6.2 to about 6.4.

12. An aqueous sizing composition as claimed in claim 1 and substantially as hereinbefore described with reference to the Example.

13. Sized glass fibers treated with an aqueous sizing composition as claimed in any of claims 1 to 12.

14. Sized glass fibers as claimed in claim 13 and substantially as hereinbefore described with reference to the Example.

15. Polymeric material reinforced with the sized glass fibers as claimed in claim 13 or claim 14.

16. A method of producing sized glass fiber strands, which comprises applying to glass fibers during their formation an aqueous sizing composition as claimed in any of claims 1 to 12, and gathering the treated fibers into one or more strands.

17. A method of producing sized glass fiber strands, which comprises: drawing glass fibers at a high rate of speed from molten cones of glass located at the tips of small orifices in a bushing; treated the glass fibers with an aqueous sizing composition whose ingredients other than water comprise 45 to 85 percent by weight based on the non-aqueous components of the sizing composition of a polyvinylacetate-acrylate copolymer, film-former, 5 to 55 percent by weight based on the weight of the acetate-acrylate copolymer of an external plasticizer, 0.1 to 7 percent by weight solids of fatty acid amide lubricant, 0.5 to 5 percent by weight solids of cationic amidated polyamine lubricant, 3 to 6 percent by weight solids gamma-ethylene diamine propyl trialkoxy silane, and 2 to 6 percent by weight solids methacrylic acid chromic halide coupling agent, where said composition is adjusted to a pH of about 6.2 to 6.4 and has a solids content of 7.0 to 7.5 percent by weight; gathering the treated fibers into one or more strands, and winding the strands into a package.

17. A method of producing sized glass fiber strands, which comprises: drawing glass fibers at a high rate of speed from moiten cones of glass located at the tips of small orifices in a bushing; treated the glass fibers with an aqueous sizing composition whose ingredients other than water comprise 45 to 85 percent by weight based on the total weight of the size solution solids of a polyvinylacetate-acrylate copolymer, film-former, 5 to 55 percent by weight based on solids of an external plasticizer, 0.1 to 7 percent by weight solids of fatty acid amide lubricant, 0.5 to 5 percent by weight solids of cationic amidated polyamine lubricant, 3 to 6 percent by weight solids gamma-ethylene diamine propyl trialkoxy silane, and 2 to 6 percent by weight solids methacrylic acid chromic halide coupling agent, where said composition is adjusted to a pH of about

6.2 and 6.4 and has a solids content of 7.0 to 7.5 percent by weight; gathering the treated fibers into one or more strands, and winding the strands into a package.

New claims or amendments to claims filed on 16/6/81 New or amended claims: Claims 1,14 & 17

1. An aqueous sizing composition for glass fiber strand whose ingredients other than water comprise: about 45 to about 85 percent by weight based on the non-aqueous components of the sizing composition of an externally plasticizable polyvinyl acetate/acrylic copolymer film-former; about 5 to about 55 weight percent based on the weight of the acetate-acrylate copolymer of a compatible external plasticizer; about 0.1 to 7 percent based on solids of a fatty acid amide lubricant; about 3 to about 6 percent by weight solids gamma (ethylene diamine) propyltrialkoxysilane; and about 2 to about 6 percent by weight methacrylic acid chromic halide coupling agent; said sizing composition having been adjusted to a pH of about 6.1 to about

6.5 and said composition having about 7.0 to about 7.5 percent by weight solids.

14. Sized glass fibers as claimed in claim 13 and substantially as hereinbefore described with reference to the Example.