| 摘要 |
A process for preparing granular vinyl chloride polymers comprises (1) agitating in a closed reaction vessel a suspension of 100 parts of vinyl chloride in 100 to 400 parts of an aqueous medium containing a suspension stabilizer, (2) introducing 0,005 to 0,100 parts of a preformed dialkyl peroxy dicarbonate and (3) heating the suspension at 100 DEG to 160 DEG F. The dicarbonate is preferably added to the initial monomer charge. Di-C1-6 alkyl peroxy dicarbonates, especially diisopropyl, are preferred and, to avoid the risk of explosion, may be used as a solution in a stabilizing solvent such as xylene or toluene or with other stabilizers, e.g. cyclohexene, naphthalene, phenol or diphenyl ether. The dicarbonate may be used in conjunction with a conventional peroxide catalyst, e.g. lauroyl peroxide, to maintain the polymerization rate towards the end of the reaction. Suspension stabilizers mentioned are gelatin, polyvinyl alcohol and water-soluble cellulose ethers. Buffering agents and anionic or nonionic surface-active agents may be used to modify the physical properties of the products.
|
