Sizing composition and sized fibers with increased hardness

Claim 1

An aqueous sizing composition for glass fibers to produce treated glass fibers having increased hardness and improved integrity with good flow-through and wet-out properties, comprising in weight percent of the aqueous sizing composition: a. about 3 to about 20 weight percent of a substantially noncrystalline liquid epoxy resin in an aqueous dispersion wherein the epoxy resin is in the dispersion in an amount of 50 to 60 percent by weight of the nonvolatiles and has a weight per epoxide of around 500 to 550 and where the dispersion has an average particle size between 1 and 4 microns, b. about 3 to about 15 weight percent of melamine formaldehyde condensate, c. about 1 to about 8 weight percent of a polyamide resin wherein the ratio of amounts of melamine formaldehyde condensate to polyamide resin is in the range of about 2 to about 20 moles of melamine formaldehyde condensate to one mole of polyamide resin and wherein the polyamide resin is reactive with the melamine formaldehyde condensate to form a reaction product; d. about 0.1 to about 2 weight percent of one or more silane coupling agents, e. about 1 to about 12 weight percent of a thermoplastic plasticizing agent selected from the group consisting of vinyl acrylic copolymer and epoxy resin blend, polyurethane, a reaction product of a partial ester of a carboxylic acid and polyepoxy compound, silane polyvinyl acetate copolymer, and plasticized polyvinyl acetate and polyvinylacetate, and f. water in the remaining amount of the composition.