Improved graft polymerization process

Abstract

Abstract A graft polymerization process comprises prepolymerizing with agitation a feed mixture comprising a monovinyl aromatic compound and a synthetic or natural rubber dissolved therein until substantially all of the rubber phase is out of solution and the rubber particles have an average size of less than 10 microns, and then subjecting the resulting reaction product mixture to further polymerization to obtain a higher level of conversion to polymeric material. Monovinyl aromatic compounds specified are styrene, a -methyl styrene, vinyl toluene, vinyl xylene, vinyl ethyl benzene, vinyl chlorobenzene, and mixtures thereof. The rubber is dissolved in the monovinyl aromatic compound and prepolymerized in bulk using heat or oil-soluble organic peroxides as reaction initiators. The prepolymerized mixture is then either suspended in an aqueous solution containing a suspending agent such as hydroxyethyl cellulose and further polymerized with the addition of an organic peroxide catalyst, or suspended in an inert organic solvent such as ethyl benzene and further polymerized at a higher temperature. A number of other suspending agents and solvents are listed. The usual additives such as lubricants, antioxidants, chain regulators and inert fillers may be incorporated in the prepolymerization reaction mixture. The prepolymerization is effected under high shear conditions.

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