| 摘要 |
Particulate thermoplastic polymers of ethylenically unsaturated monomers are rendered readily dispersible and non-swelling in the cold in solvents by heating the polymer at such a temperature and for such a time that a layer of degraded polymer is produced at the surface only of the particles. The heating may be effected by suspending the particulate polymer in a non-solvent liquid such as water or ethylene glycol, and heating the liquid or blowing a current of steam through it, or by suspending the particles in a stream of hot gas, e.g. nitrogen, at 120 DEG C. Specified polymers are polyvinyl chloride, polyacrylonitrile, and copolymers of acrylonitrile with vinylpyridine or ethyl acrylate. Solutions formed by heating dispersions of the polymers in organic solvents are used in the manufacture of fibres and films. Specifications 712,568 and 735,183 are referred to. |
