Synthetic fiber first processing agent, synthetic fiber processing agent, aqueous solution preparation method, synthetic fiber processing method, synthetic fibers, short fibers, spun yard and non-woven fabric

Abstract

The present invention addresses the problem of providing a synthetic fiber first processing agent which improves storage stability. This synthetic fiber first processing agent contains a phosphate compound (A), a solvent (S) and an optional non-ionic surfactant (C), said agent being characterized in that the content ratio of the phosphate compound (A) to the non-ionic surfactant (C) is within a prescribed range, and by being used in conjunction with a synthetic fiber second processing agent which contains a non-ionic surfactant (E). The phosphate compound (A) contains a prescribed organic phosphate ester compound, and the proton NMR integration ratio attributable to an inorganic phosphate compound during proton NMR measurement when performing an alkali over-neutralization preprocessing is set to a prescribed range. The solvent (S) has a boiling point no higher than 105° C. at atmospheric pressure. The non-ionic surfactant (C) has a (poly)oxyalkylene structure in the molecule thereof.