percent by weight or rubber of sodium lauryl sulfate are charged to a reactor and heated under nitrogen and with agitation to about 60 u00b0 c an aqueous solution of 1 0 parts of sodium formaldehyde sulfoxylate and a small quantity of chelated iron is added before graft monomer addition to this latex is continuously added over a one hour period a first monomer composition of 100 parts acrylonitrile 200 parts styrene 100 parts methyl methacrylate and 4 parts ethylene glycol dimethacrylate during monomer addition 1 part of potassium persulfate in aqueous solution is charged to the reactor stirring is continued during the addition of the first monomer composition and is continued for an additional period of one hour thereafter then 0 8 part of sodium formaldehyde sulfoxylate and 0 8 part of potassium persulfate in aqueous solution is added to the latex and a second monomer composition of 130 parts acrylonitrile 70 parts styrene and 2 parts tert dodecyl mercaptan is continuously added to the reactor over a one half hour period towards the end of the second monomer composition addition a solution of 11 parts sodium lauryl sulfate is charged to the reactor and agitation and heating are continued for about 30 minutes the latex is then cooled to 25 u00b0 c and 5.