Method of increasing grafting efficiency in graft copolymerization

Claim 1

IN A METHOD OF PREPARING A GRAFT COPOLYMER BY POLYMERIZING A FREE RADICAL-POLYMERIZABLE MONOMER OF THE GROUP CONSISTING OF A MONOVINYLIDENE AROMATIC HYDROCARBON,.A CONJUGATED 1,3-DIENE, ACRYLONITRILE, METHACRYLONITRILE, A VINYL HALIDE, A VINYL ESTER OF AN ALKANOIC ACID, AN ALKYL METHACRYLATE, AND MIXTURES THEREOF IN AN AQUEOUS DISPERSION OF A PREFORMED POLYMER CONSISTING ESSENTIALLY OF A CHEMICALLY-COMBINED MONOMER OF THE GROUP CONSISTING OF AN ALPHA-OLEFIN, A MONOVINYLIDENE AROMATIC HYDROCARBON, ACRYLONITRILE, METHACRYLONITIRL,E AN ALKYL METHACRYLATE, AN ALKYL ACRYLATE, A CONJUGATED 1,3-DIENE, AND MIXTURES THEREOF, THE IMPROVEMENT WHICH COMPRISES THE STEPS: (A) FORMING FREE RADICALS ON THE PREFORMED POLYMER CHAIN, PRIOR TO THE ADDITION OF THE FREE RADICAL-POLYMERIZABLE MONOMER, BY CONTACTING A PEROXY FREE RADICAL POLYMERIZATION INITIATOR WITH THE AQUEOUS DISPERSION OF PREFORMED POLYMER IN THE ABSENCE OF OXYGEN AT A TEMPERATURE AT WHICH THE INITIATOR DECOMPOSES TO GENERATE FREE RADICALS, (B) ADDING THE FREE RADICAL-POLYMERIZABLE MONOMER TO THE AQUEOUS DISPERSION AT A TEMPERATURE AT WHICH ANY OF SAID INITIATOR WHICH HAS NOT HAD ITS FREE RADICALGENERATING CAPACITY COMPLETELY CONSUMED IN STEP (A) DOES NOT GENERATE FREE RADICALS, AND (C) CONDUCTING THE GRAFT COPOLYMERIZATION OF THE FREE RADICAL-POLYMERIZABLE MONOMER IN THE ABSENCE OF ANY FREE RADICALS OTHER THAN THOSE WHICH HAVE BEEN FORMED ON THE POLYMER CHAIN IN STEP (A).