Sizing textile with in situ graft polyester

A method of sizing a fibrous synthetic organic yarn to facilitate its construction into a fabric comprising the steps of (a) forming a composite of fiber and size by depositing on the yarn about 3 to about 10 percent by weight based upon the dry weight of the yarn of a solventless size mixture comprising a mixture of

• (I). an unsaturated polyester comprising the reaction product of:
• (a) at least one polycarboxylic acid reactant comprising (1) a dicarboxylic acid reactant selected from the group consisting of dicarboxylic acids, corresponding dicarboxylic anhydrides, dicarboxylic acid esters, and their corresponding acyl halides or (2) a mixture of said dicarboxylic acid reactant with up to 20 mole percent of a polycarboxylic acid reactant having a functionality greater than two based upon 100 mole percent of said dicarboxylic acid reactant and
• (b) at least one polyhydric alcohol reactant comprising (1) a diol or (2) a mixture of a diol and up to 20 mole percent of a polyhydric alcohol having a functionality greater than two based upon 100 mole percent of said polyhydric alcohol, wherein a minor effective proportion of said dicarboxylic acid reactant or polyhydric alcohol reactant is alpha, beta-ethylenically unsaturated and
• (II). at least one monovinyl monomer reactant comprising at least one monovinyl monomer having at least one carboxylic group or a mixture of said vinyl monomer with any monofunctional vinyl monomer and (b) heating, irradiating, or both heating and irradiating said mixture in the presence of an initiator.