Method of forming and sizing glass fibers

In the process for producing precision wound packages of glass fiber strands comprising drawing glass fibers from molten cones of glass in a bushing, applying aqueous sizing composition to said fibers during formation, drying the sized glass fibers in an oven, to obtain fibers having a moisture content of 8 percent by weight or less, gathering the fibers into a strand or strands, collecting the stand or strands into a precision wound package of strand or roving, and drying the precision wound packages to reduce further the moisture content, the improvement comprising applying to said fibers an aqueous sizing composition to obtain glass fibers having a moisture content of 8 percent by weight or less without drying the glass fibers before they are gathered and collected into precision wound packages and to reduce the time or temperature conditions of drying the packages, wherein the aqueous sizing composition, comprises in percent by weight based on the total weight of the sizing composition:

• 3.4 to 11.5 of phenolic epoxy resin,
• 0.56 to 1.9 of the reaction product of a partial ester of a polycarboxylic acid containing one or more unesterified carboxyl groups with a compound containing more than one epoxy group,
• 1.04 to 3.6 of non-ionic surface active agents, about 0.5 to about 3.5 of one or more organosilane coupling agents,
• up to 5.76 of polyvinylpyrrolidone, and the remainder of the aqueous composition being an amount of water to give a total solids content in the range of about 9 to about 30 weight percent.