Flame retardant resinous compositions and process

A resinous, flame-retardant composition comprising (i) 40-66 wt. % alkenyl aromatic resin, (ii) 9-33 wt. % ammonium polyphosphate, (iii) 14-40 wt. % starch, and (iv) at least one additive selected from the group consisting of lubricants, flow promoters, plasticizers, antistatic agents, mold release agents, impact modifiers, stabilizers, color stabilizers, heat stabilizers, light stabilizers, antioxidants, anti-drip agents, UV screeners, UV absorbers, metal stearates, adjunct flame retardants, rubbery additives, adjunct copolymers comprising structural units derived from maleic anhydride, acrylic acid or methacrylic acid, and mixtures thereof, wherein ammonium polyphosphate and starch are present in a weight % ratio in a range of 1:2 to 2:1 effective to provide molded articles exhibiting at least V-1 flame rating as determined according to the UL-94 protocol.

An extrusion process for preparing a resinous, flame-retardant composition comprising (i) 40-66 wt. % alkenyl aromatic resin, (ii) 9-33 wt. % ammonium polyphosphate, (iii) 14-40 wt. % starch, and (iv) at least one additive selected from the group consisting of lubricants, flow promoters, plasticizers, antistatic agents, mold release agents, impact modifiers, stabilizers, color stabilizers, heat stabilizers, light stabilizers, antioxidants, anti-drip agents, UV screeners, UV absorbers, metal stearates, adjunct flame retardants, rubbery additives, adjunct copolymers comprising structural units derived from maleic anhydride, acrylic acid or methacrylic acid, and mixtures thereof, wherein ammonium polyphosphate and starch are present in a weight % ratio in a range of 1:2 to 2:1 effective to provide molded articles exhibiting at least V-1 flame rating as determined according to the UL-94 protocol, which process comprises the step of adding at least a portion of the ammonium polyphosphate to the extruder down-stream from the alkenyl aromatic resin and the starch.