FREMGANGSMAATE FOR I NOEDSFALL AA STOPPE POLYMERISERINGSREAKSJONEN VED SUSPENSJONSPOLYMERISERING AV VINYLKLORID

1303908 Controlling vinyl chloride polymerization SHINETSU CHEMICAL CO 10 June 1971 [11 June 1970] 19972/71 Heading C3P The rate at which vinyl chloride polymerizes in aqueous suspension in the presence of a catalyst and either a suspending agent or a dispersing agent is controlled by condensing gaseous monomer issuing from the polymerization medium while concurrently adding a polymerization inhibitor to the medium, whereby the condensed monomer absorbs the inhibitor, the condensed monomer and inhibitor are absorbed by suspending particles, and then the absorbed monomer vaporizes thereby agitating the medium and ensuring that the inhibitor is uniformly distributed throughout the medium. The agitation of the medium may be enhanced by introduction of an inert gas, e.g. nitrogen. The process is used to rapidly reduce the rate of polymerization in emergency, e.g. loss of electrical power. Suitable components of the reaction are:-suspending agents: partially saponified polyvinyl acetate, cellulose ether or gelatine; dispersing agents: CaCO 3 , MgCO 3 , BaSO 4 , Al 2 O 3 or TiO 2 ; catalysts: lauroyl peroxide, benzoyl peroxide, isopropyl peroxydicarbonate, acetyl cyclohexylsulphonyl peroxide, azobisisobutyronitrile or azobisdimethylvaleronitrile; inhibitors: hydroquinone, methyl hydroquinone, nitrobenzene, bisphenol or tertiary butyl catechol.