Process for preparation of spinnable solutions of acrylonitrile polymers or copolymers having a high-acrylonitrile content

摘要

Spinnable solutions of polyacrylonitrile, or of copolymers containing over 85% by weight of acrylonitrile, are produced by polymerization of the monomer(s) in dimethyl formamide in at least two sequential stages, in the first of which the polymerization is carried out at 60 DEG to 65 DEG C. until reaching not less than 30% and not more than 40% conversion of the monomer(s), while in the second stage or the following stages the polymerization is carried on under controlled temperature conditions until reaching a higher conversion, the amount of dimethyl formamide and catalyst required to attain said higher conversion being divided into as many fractions as there are stages and one of said fractions being individually added at the beginning of each stage. The final conversion attained is desirably in the range 70 to 80%. The temperature conditions may be controlled by carrying out the process under sub-atmospheric pressure, in which case the polymerization is terminated by increasing the pressure and distilling off unreacted monomer(s). In the examples, the polymerization is carried out in two stages. In Examples 1 and 3 copolymers of acrylonitrile, sodium allyl sulphonate and methyl methacrylate are prepared and in Example 2 a copolymer of acrylonitrile, sodium allyl sulphonate and ethyl acrylate. Lauroyl peroxide is used as catalyst and thiourea dioxide is present in the reaction solutions of Examples 1 and 2.