Grafting vinyl monomers onto a diene polymer backbone with a divinylbenzene cross-linking agent present

Claim 1

IN A PROCESS FOR PREPARING A GRAFT COPOLYMER BY (1) FORMING AN AQUEOUS DISPERSION OF RUBBERY POLYMER BY POLYMERIZING A FIRST MONOMER CHARGE COMPRISING AN ALIPHATIC CONJUGATED 1,3-DIENE IN AN AQUEOUS EMULSION IN THE PRESENCE OF A CROSS-LINKING AGENT, AND (2) SUBSEQUENTLY POLYMERIZING IN THE PRESENCE OF SAID AQUEOUS DISPERSION OF RUBBERY POLYMER A SECOND MONOMER CHARGE CONSISTING ESSENTIALLY OF 20-100% BY WEIGHT OF A MONOVINYLIDENE AROMATIC HYDROCARBON, UP TO 80% BY WEIGHT OF AN ACRYLIC COMPOUND OF THE GROUP CONSISTING OF ACRYLONITRILE, METHACRYLONITRILE, A C1-C4 ALKYL ACRYLATE, A C1-C4 ALKYLK METHACRYLATE, AND MIXTURES THEREOF, AND UP TO 20% BY WEIGHT OF OTHER COPOLYMERIZABLE ETHYLENICALLY-UNSATURATED COMPOUNDS; THE IMPROVEMENT WHICH COMPRISES CONDUCTING THE POLYMERIZATION OF THE FIRST MONOMER CHARGE IN THE ABSENCE OF THE CROSS-LINKING AGENT UNDER AGITATION CONDITIONS OF A NET HORSEPOWER OF ABOUT 0.0001-0.0004 HP/GALLON OF REACTION MIXTURE UNTIL THE STAGE OF ABOUT 30-60% CONVERSION TO POLYMER, THEN ADDING THE CROSS-LINKING AGENT, AND CONTINUING THE POLYMERIZATION UNDER AGITATION CONDITIONS OF A NET HORSEPOWER OF ABOUT 0.0001-0.0004 HP/GALLON OF REACTION MIXTURE.