Patent GB-923518-A (GB)
Title: Production of filamentary materials of vinyl chloride polymers
IPC: C08L27/06
Filed: 1960-03-28
Abstract: Polyvinyl chloride filaments are produced by dry or wet spinning a dope which has been prepared by mixing the polymer, which has a bulk density of 0,3 to 0,6 gram./cu. cm., a D/D value of 1,08 to 1,27 and a degree of polymerization of 500 to 2500, with a solvent to form a mobile slurry in which the particles of polymer are swollen but not dissolved, and heating the slurry to cause the polymer to dissolve in the solvent.  At most only a short time is allowed to elapse before the dope is spun into filaments.  The P.V.C. may be a homopolymer of vinyl chloride or a copolymer of vinyl chloride with not more than 10% by weight of other unsaturated compounds.  The bulk density of the polymer is the weight in grams of a body of the polymer (the polymer being in particulate form) of known volume, the particulate polymer having been collected in a vessel in the manner specified in Japanese Industrial Standard No. K-6721 of 1955.  The D/D value of the polymer is defined as the ratio of the optical density of the polymer at a wavelength of the polymer of 1426 cm.-1 to the optical density at a wavelength of 1434 cm.-1 and affords a measure of the crystallinity of the polymer.  The bulk density of the polymer, if initially below 0,3, may be raised by one of five methods: (1) Heating the polymer to a temperature between its softening point and its decomposition point.  (2) The above method applied to the polymer after allowing it to absorb a small proportion of a mixture of a solvent and a non-solvent.  (3) The same as method (2) except that the solvent mixture is added during the polymerization of the polymer.  (4) Mixing two or more types of the polymer having different bulk densities in such proportions that the bulk density of the mixture falls within the range 0,3 to 0,6.  (5) The method (4), using in the mixture a small proportion of a P.V.C. prepared by a high temperature process. The solvent used for preparing the slurry is preferably a mixture containing one or more ketones having 3 to 8 carbon atoms in the molecule.  The other component may be an aromatic hydrocarbon, a chlorinated hydrocarbon, an ether derivative of ethylene glycol or an ester of an aliphatic alcohol. The slurry is preferably one in which the P.V.C., solvent, and temperature of formation of the slurry are such that the viscosity of the slurry is 5-200 stokes and particularly 20 to 80 stokes. The slurry preferably contains 20-40% of polymer.  The temperature to which the slurry is heated to dissolve the polymer is generally about 100 DEG -200 DEG C. Filaments are formed from the resulting solution preferably by dry-spinning.  The filaments may be drawn at 95 DEG -115 DEG C. at a draw ratio of 2:1 to 10:1 and thereafter heat set at 70 DEG  to 170 DEG C.  The process of the invention renders it possible to produce filaments having good physical properties and low shrinking tendencies from P.V.C. produced by low temperature polymerization. The examples describe the polymerization of vinyl chloride in bulk, solution and aqueous medium with the aid, as catalysts, of triethyl and tributyl boron, benzoyl peroxide, a mixture of di-tert.butyl peroxide and triethanolamine and ultra-violet light. In one Example (17) the preparation of a copolymer of vinyl chloride and acrylamide is described.  Belgian Specification 569,632 is referred to.