| 摘要 |
<p>1277409 Suspension polymerization SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ NV 8 Sept 1969 [16 Oct 1968] 49097/68 Heading C3P Polymer beads are manufactured by a process which comprises polymerizing vinyl or substituted vinyl monomers in aqueous suspension containing a difficultly soluble phosphate as suspension stabilizer, at a pH sufficiently high to ensure that at least 90% of the phosphate remains undissolved but is at most pH 6, wherein during at least that part of the polymerization in which it is important to maintain the polymerizable component in stable suspension yet in which the bead size can continue to increase, the said pH is controlled within a range of 1 pH unit by the presence of a buffering agent. Specified monomers are styrene,α-methyl styrene, vinyl toluenes, halo-styrenes, acrylonitrile and alkyl acrylates and methacrylates. The phosphate may be a calcium, strontium or magnesium phosphate, and the buffer a sodium acetate/acetic acid, sodium hydroxide/acetic acid or sodium acetate/hydrochloric acid buffer. Polymerization may be effected in the presence of benzoyl peroxide or t-butyl perbenzoate, optionally with stepwise additions of potassium persulphate; and expanding agents such as pentane may be incorporated during or after polymerization. Examples describe the polymerization of styrene in the presence of calcium phosphate, sodium acetate/hydrochloric acid or sodium hydroxide/potassium phthalate buffers, and benzoyl peroxide optionally with stepwise addition of potassium persulphate.</p> |
