Verfahren zur Herstellung von ausgerichteten Kunststoffprodukten

1,136,928. Acrylonitrile polymer films. STANDARD OIL CO. 24 Dec., 1965 [28 Dec., 1964], No. 54800/65. Heading B5B. [Also in Division C3] A process for preparing a biaxially oriented polymer film comprises forming a film from a solution in a polar solvent or mixture of polar solvents of a polymer composed primarily of at least one alpha, beta-olefinically unsaturated nitrile, stretching the film at an elevated temperature in a longitudinal and a transverse direction and drying the film at an elevated temperature while it is retained in its biaxially stretched condition. Preferably the alpha, beta-olefinically unsaturated nitrile is acrylonitrile or methacrylonitrile. Polymers most useful in the present invention are those resulting from the polymerization of at least one alpha, beta-mono-olefinically unsaturated nitrile monomer having three or four carbon atoms and a terminal CH 2 = C = group. From 5-15% by weight of the alpha, beta-monoolefinically unsaturated nitrile may be replaced with one or more polymerizable monoalkenyl monomers copolymerizable therewith, e.g. acrylate esters, methacrylate esters, vinyl esters, vinyl aromatics, vinyl amides, vinyl halides, vinylidene chloride, vinylidene fluoride, dichlorodifluoroethylene and tetrafluoroethylene, and olefines. Many such compounds are listed. Specified alpha, beta-mono-olefinically unsaturated nitrile monomers include in addition to acrylonitrile and methacrylonitrile, alphachloroacrylonitrile, crotononitrile, vinylidene cyanide, cinnamonitrile and atroponitrile. Polymer solutions suitable for casting or otherwise forming films may be prepared by dissolving from 10-75% by weight of the polymers in one or a combination of volatile polar solvents, e.g. dimethylformamide, dimethyl thioformamide, N - methyl - beta - cyano - ethyl formamide, alpha-cyano acetamide, N-methyl pyrrolidone, gamma - butyrolactone, ethylene carbonate, tetramethyl oxamide, epsiloncyanolactone, 1,3,3,5 - tetracyanopentane, dimethyl cyanamide, dimethyl methoxy acetamide, N-formyl morpholine, N-formyl hexamethylene imine, dimethyl sulphoxide, propiolactone, N,N-dimethyl acetamide, dimethyl sulphone, tetramethylene cyclic sulphone, ethylene cyanohydrin, nitromethane, acetonitrile, malononitrile, tris - dimethylamino phosphine oxide or N,N1-tetramethylmethane phosphonamide. Solvents used in examples include a 90/10 by weight mixture of dimethyl formamide and ethylene carbonate; dimethyl formamide; and methyl ethyl ketone. In a preferre