Flame retardant masterbatch composition for foams containing a pH moderator

A process for manufacturing a masterbatch composition suitable for use as a flame retardant in extruded polymer foams, comprising the steps of:

• a) providing a base resin to a mixing device operating at temperature of 150 to 230° C. to form a molten base resin;
• b) contacting the molten base resin in the mixing device with:
• i) acid scavenger comprising an epoxy-based compound;
• ii) antioxidant comprising an alkyl or aryl phosphite;
• iii) water soluble pH moderator;
• and
• iv) flame retardant comprising a non-hexabromocyclododecane (HBCD) polymer or copolymer
• to form a molten flame retardant masterbatch composition;
• and
• c) cooling the molten flame retardant masterbatch composition to form a solid flame retardant masterbatch composition,
• wherein the masterbatch composition has
• (A) 20 to 40 parts by weight of the base resin comprising styrene homopolymer or copolymer;
• (B) 1 to 16 parts by weight of the acid scavenger comprising an epoxy-based compound;
• (C) 2 to 6 parts by weight of the antioxidant comprising an alkyl or aryl phosphite;
• and
• (D) 45 to 60 parts by weight of the flame retardant comprising a non-hexabromocyclododecane (HBCD) brominated polymer or copolymer;
• wherein the amounts of (A), (B), (C), and (D) total 100 parts by weight;
• and
• (E) 0.6 to 10 parts by weight of the water soluble pH moderator, based on 100 parts of (A) base resin plus (E) water soluble pH moderator.