Herstellung von Fasern, Faeden oder Filmen aus thermoplastischen Mischpolymeren

Artificial filaments and films are produced by forming an aqueous dispersion of at least 20% by weight of thermoplastic organic polymeric material, the dispersed polymer particles having p an average size below about 2 microns and being formed by emulsion polymerization using an acid-sensitive emulsifier and a free radical polymerization initiator and the pH of the dispersion being at least 7, extruding the dispersion into an aqueous coagulating bath having a pH of not over 4,1, and preferably below 1, removing the filaments or films thereby formed from the bath, heating the filaments or films to dry them and bring them to such a temperature above their apparent second order transition temperature as to cause the particles to coalesce, and then stretching the filaments or films. The polymeric material consists of one or more thermoplastic copolymers each of which meets the following requirements. (1) It consists of units corresponding to monomers containing a single CH2 = C < group, there being present at least 5% by weight of two different types of units of which one type contains groups having atoms other than carbon and hydrogen. (2) It consists of predominantly linear molecules which are capable of orientation and have a number average molecular weight of 20,000 to 1,000,000 or more as determined by osmosis. (3) It has an apparent second order transition temperature between 30 DEG C. and 150 DEG C. as determined by a described method. (4) It is capable of being formed by emulsion polymerization to give an aqueous dispersion in which the copolymer particles have an average size below about 2 microns. The monomers may be esters, ethers, amides, nitriles or cyclic compounds having a single CH2 = C < group, the preferred esters, nitriles and amides being of the acrylic type. Thus there may be used esters of acrylic or methacrylic acid with aliphatic, cycloaliphatic, aryl, aryl-aliphatic or heterocyclic alcohols free of polymerizable unsaturated linkages. There may also be used as one of the co-monomers esters of itaconic acid with alcohols of the above types. Vinyl esters of monocarboxylic acids can be used but are less desirable. Amides of acrylic and methacrylic acids having an N-substituent and reactivity towards stabilizing agents are also suitable. Vinyl ethers containing alcohol residues of the kinds specified above, vinyl chloride, vinylidene chloride, styrene and vinyltoluene may also be used. Copolymers containing a major proportion of acrylonitri