Stabilized slurries of isoolefin polymers
AssigneeExxon Research & Engineering Co.
InventorsKenneth W. Powers, Ralph H. Schatz
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Abstract
Polymerization slurries of elastomeric isoolefin homopolymers and copolymers, such as butyl rubber, in diluents such as methyl chloride are effectively stabilized against agglomeration of polymer particles through addition of minor proportions of (i) a preformed copolymer stabilizer having both a lyophobic or lyophilic portion, or (ii) an in situ formed stabilizer from a functional lyophilic stabilizer precursor capable of copolymerizing or otherwise chemically bonding with the polymer product. Agglomeration of polymer products is effectively prevented, yielding a number of significant processing advantages. The process is especially adaptable to the production of isobutylene-isoprene butyl rubber.
Claims18
A method of stabilizing a polymerization slurry against agglomeration, said slurry being formed in a cationic Lewis Acid catalyzed polymerization process, and containing as product polymers, polymerized C.sub.4 -C.sub.7 isoolefin homopolymers or butyl rubber copolymers in a polymerization diluent selected from the group consisting of methyl chloride, methylene chloride, vinyl chloride or ethyl chloride diluents, which comprises incorporating into the reaction mixture, said reaction mixture containing monomers, catalyst and diluent, or into the polymerization product slurry about 0.05% to 20% by weight, based upon the weight of product polymers, of a stabilizing agent, said stabilizing agent being a preformed copolymer having a lyophilic, polymerization diluent soluble portion and a lyophobic, polymerization diluent insoluble portion, said lyophobic portion being soluble in or adsorbable by said product polymer and said stabilizing agent being capable of forming an adsorbed solubilized polymer coating around the precipitated isoolefin homopolymer or butyl rubber copolymer to stabilize said slurry.
A method of preparing non-agglomerating homopolymers of C.sub.4 -C.sub.7 isoolefins or butyl rubber copolymers by Lewis Acid cationic polymerization of corresponding monomers at temperatures from about -90.degree. C. to about -20.degree. C. in a polymerization slurry diluent selected from the group consisting of methyl chloride, methylene chloride, vinyl chloride and ethyl chloride diluents in the presence of a stabilizer copolymer, the stabilizer copolymer being a preformed copolymer having a lyophilic diluent soluble portion and a lyophobic diluent insoluble but isoolefin or butyl rubber soluble or adsorbable portion.
Dependencies are inferred from the claim text.