Chemical removal of residual monomer from polyvinyl chloride latices and slurries

Abstract

Air quality standards are becoming increasingly stringent. Stripping and gas purging of the latex are no longer adequate to reduce dryer emissions of unreacted monomer below proposed limits. New technology has been developed in which the monomer is chemically removed from the latex before the drying step to reduce monomer emissions from the dryer and to lower monomer content in the product (1). Ozonation of vinyl latex is an effective technique because of its rapid reaction with double bonds. The short half life of ozone will result in no contamination of the product by unreacted ozone. Ozonation byproducts from the reaction with vinyl chloride are nontoxic and nonpolluting. Because the ozonation reaction is specific for double bonds, the polymer structure is left intact without affecting resin physical properties.

Selective and Quantitative Oxidation of Xanthate End-Groups of RAFT Poly(n-butyl acrylate) Latexes by Ozonolysis

“…Its reactivity on the CS bound is similar to the one observed on the CC . This also means that such a reagent oxidizes the unreacted monomer in the latex, which is interesting for industrial purposes where the reached concentration of residual monomer must be as low as possible.…”

“…The ozone molecule can be considered a 1,3-dipolar compound and is known to present a high reactivity toward olefi nic derivatives. [ 25 ] Its reactivity on the C S bound is similar to the one observed on the C C. [ 21,26 ] This also means that such a reagent oxidizes the unreacted monomer in the latex, [ 27 ] which is interesting for industrial purposes where the reached concentration of residual monomer must be as low as possible.…”