Process for the manufacture of shaped structures from acrolein copolymers

摘要

An acrolein copolymer shaped structure, especially a filament or film, is made by spinning or casting an aqueous solution of an adduct of sulphur dioxide with a copolymer of acrolein and an acrylic acid derivative, the copolymer containing 30 to 70% by weight, preferably at least 50% of the acrylic acid derivative, and stretching the spun or cast structure at 50 DEG -200 DEG C. after substantially all the solvent has been removed by evaporation. Specified acrylic acid derivatives include acrylic acid methylester and acrylonitrile, which are preferred, and also alkyl acrylates in general, and acrylic alkylamides, e.g. acrylic acid ethylamide and dimethylamide. The acrolein copolymers may be obtained in known manner by radical-initiated polymerization, preferably by emulsion polymerization in the presence of a redox system, e.g. alkali persulphate/alkali bisulphite, with small additions of activating metal ions, e.g. silver and ferrous ions, and a dispersing agent, e.g. alkyl sulphonates, fatty alcohol sulphates, salts of higher sulphocarboxylic acids or nonionic dispersing agents based on ethylene oxide. A hydrophilic protective colloid may be used in place of the dispersing agent, especially one having no alcoholic hydroxyl groups in the polymer chain, e.g. polyacrylic acid, polyvinyl pyrrolidone, vinyl pyrrolidone-acrylic acid copolymers and high molecular weight polyethylene oxides and water soluble ethylene oxide-propylene oxide copolymers. Preferably, however, the acrolein copolymers are made by the use of a redox system, e.g. that previously mentioned, in a mixture of water and a water-soluble solvent, especially a lower glycol, e.g. ethylene glycol, 1:2 and 1:3 propylene glycols. The solvent mixture consists preferably of 1 part by weight of water to 1,5 to 4,5 parts by weight of organic solvent. The aqueous solution before spinning or casting p preferably contains 3-8% by weight free sulphur dioxide and may also contain 10-20% by weight, calculated on the solid content of the aqueous solution, of a polyglycol ether or up to 10% by weight of a polyalcohol in which the hydroxyl groups are separated by at least four carbon atoms. Spinning or casting is effected in known manner and the solvent is preferably removed at a temperature below 200 DEG C. The shaped structure may then be stretched 200-600%, preferred temperatures being 60 DEG -160 DEG C. for films and 50 DEG -120 DEG C. for filaments.