SIZING AGENT FOR REINFORCING FIBERS, AND USE THEREOF

Provided are: a sizing agent for reinforcing fibers, which can simultaneously impart excellent fiber convergence properties in reinforcing fibers used to reinforce a matrix resin, excellent rubfastness, excellent uniformity of adhesion and excellent adhesive properties with a matrix resin; and a synthetic fiber strand and a fiber-reinforced composite material, which use the sizing agent. This sizing agent for reinforcing fibers contains a polyamide (A), a carbodiimide group-containing compound (B) and water (C). The melt viscosity at 150 DEG C of the polyamide (A) is 100-15,000 mPa*s, and thecompound (B) has two or more carbodiimide groups in the molecule. The polyamide (A) is preferably a water-soluble polyamide. 本发明的目的为提供一种强化纤维用上浆剂，其可对用以补强基质树脂的强化纤维同时赋予优异的纤维集束性、优异的耐擦蹭性、优异的均一附着性、及与基质树脂的优异的粘接性，并且还提供使用该强化纤维用上浆剂的合成纤维线束及纤维强化复合材料。一种强化纤维用上浆剂，其含有聚酰胺(A)、含碳二亚胺基的化合物(B)、及水(C)，上述聚酰胺(A)在150℃的熔融粘度为100至15000mPa·s，上述化合物(B)在分子内具有2个以上碳二亚胺基。上述聚酰胺(A)优选为水溶性聚酰胺。