| 摘要 |
<p>Vinyl chloride polymers are prepd. by polymerising vinyl chloride, opt. with 25 wt. % further polymerisable unsatd. cpds. (e.g. vinylacetate), in aq. suspension, with oil-soluble, organic radical initiators. Polymerisation takes place in a carboxylic acid medium, at PH 2-6, in the presence of 0.01-1 wt. % (w.r.t. monomer) polyvinyl alcohols contg. 20-30 mol. % residual acetate and/or cellulose ethers as protective colloids. Radical initiators are azo cpds. Polymerisation vessel is kept full, constantly, by feeding with water. Polymers have high bulk density, e.g. 550-700 g/1, and uniform grain structure. Grains are non-porous, vitreous, non-agglomerated and flow well. The grains are suitable for hard-processing, esp. in an extruder.</p> |
