Chain extender for increasing speed for spinning fine-denier filaments in a Nisshinbo dry process

The invention relates to a chain extender, in particular to a chain extender for increasing speed for spinning fine-denier filaments in a Nisshinbo dry process. The chain extender comprises the following components: ethylenediamine and 1,2-diaminopropane, wherein the weight ratio of ethylenediamine to 1,2-diaminopropane is 3.8-4.0:1. The chain extender for increasing the speed for spinning the fine-denier filaments in the Nisshinbo dry process is a two-component chain extender, so that the flexicity of the chain extender is reduced through adjusting the ratio range of the chain extender, the polymerization reaction speed is slowed, the reaction is moderate, and the homogeneity of the prepared spinning dope is guaranteed.