| 摘要 |
Process for the preparation of vinyl chloride homo- and copolymers in the form of a latex with monodisperse particles and more particularly of a latex with large particles, by aqueous emulsion polymerisation of the corresponding monomer(s) in one or two stages. The first stage is carried out in the absence of surface-active agent and in the presence of at least 0.2 % and preferably of 0.3 to 1 %, by weight relative to the monomer(s), of at least one water-soluble initiator chosen from the group consisting of alkali metal persulphates and ammonium persulphate. The first stage is carried out also in the presence of at least one water-soluble auxiliary compound, a solvent for vinyl chloride, in such quantity that the solubility of vinyl chloride in the aqueous phase at 25 DEG C at atmospheric pressure is at least 1.5 g/l. The process makes it possible to obtain, in one polymerisation stage, vinyl chloride polymers in the form of a latex with monodisperse particles with a mean diameter of between 0.17 and 0.8 mu m and, in two polymerisation stages, vinyl chloride polymers in the form of a latex with monodisperse particles with a mean diameter of between 0.5 and 1.2 mu m. The said latices, whether originating from the first or the second stage, are free from nonspherical particles. |
