POLYACRYLONITRILES OF LOW MOLECULAR WEIGHT AND A PROCESS FOR THEIR PRODUCTION

摘要

1429138 Low molecular weight acrylonitrile polymers BAYER AG 16 April 1974 [13 April 1973] 16435/74 Heading C3P The invention comprises low molecular weight acrylonitrile polymers comprising at least 80 wt. per cent acrylonitrile units, having a number average molecular weight of 4500 to 20,000, a molecular weight inconsistency of 1À0 to 2À7, and a K-value of 35-65 (measured at 25‹ C. as a 0À5 wt. per cent solution in dimethyl formamide. The polymers may be produced by precipitation polymerization of the required monomer(s), in a continuous or semi-continuous fashion in a dilute aqueous solution at a pH of 1À5 to 4À0 and in the presence of a colourless complex former to remove heavy metal traces, the concentration of acrylonitrile monomer in the aqueous solution being 0À1 to 1À5% and the initiator being 6-55 wt. per cent (based on the monomer(s)) of a water-soluble redox system. Molecular weight inconsistency is defined by the formula where U is the inconsistency and Mv and Mn are the viscosimetric and osmometric molecular weights respectively. The colourless complex former may be a polyphosphate, ethylene diamine tetraacetic acid, nitrilotriacetic acid, tartaric acid, boric acid or sodium fluoride, all of which are well known. The use of a very dilute solution of acrylonitrile in water as the polymerization system, apparently determines the formation of the low molecular weight polymer. The novel polymers may be blended with a polymer comprising at least 80 wt. per cent acrylonitrile units but having a K-value (determined as above) of at least 75. Such blends are fibre forming.