The Dow Chemical Company

Gerald A Garcia

Chung P Park

Roby G Watson

A low density foam having a density less than 15 pounds per cubic foot (240 kg/m.sup.3) is formed from an amorphous polyethylene terephthalate polymer. An expandable resin composition is also disclosed, comprising an amorphous polyethylene terephthalate polymer and a blowing agent mixture comprising a low permeability blowing agent and a high solubility blowing agent. Unexpanded and partially expanded foam particles, impregnated with the blowing agent mixture are disclosed. Numerous methods are disclosed for producing lightweight foams from amorphous polyethylene terephthalate polymers. One such method utilizes an Accumulating Extrusion Expansion System which avoids problems experienced with the prior art when attempting to extrusion expand polyesters.

Amorphous polyester foam

Disclosed is a process for making a thermoplastic polymer foam structure with a blowing agent having water. The process comprises in sequence: a) melting the polymer to form a polymer melt; b) incorporating a brominated aliphatic fire retardant into the polymer melt; c) incorporating and mixing a first blowing agent into the polymer melt to form a first foamable gel; d) cooling the first foamable gel to a suitable foaming temperature; e) incorporating and mixing a second blowing agent comprising water into the cooled first foamable gel to form a second foamable gel; f) optionally further cooling the second foamable gel to a suitable foaming temperature; and g) extruding the second foamable gel through an extrusion die to form a foam structure. Incorporating of the water blowing agent downstream in the process after the foamable gel has been cooled reduces or minimizes process corrosion problems. Further disclosed is an apparatus for making the foam structure.

Process and apparatus for making a thermoplstic foam structure employing

A steam expandable alkenyl aromatic polymer composition and methods of preparation are provided. The composition is mixed with a volatile blowing agent containing, as a primary blowing agent, dichlorodifluoromethane and as a secondary blowing agent, a halogenated hydrocarbon, a hydrocarbon, or an aliphatic alcohol containing from 1 to 4 carbon atoms, the secondary blowing agent having a normal atmospherpic boiling point of from about 0.degree. to about 100.degree. C. The composition may be expanded by steam immediately after extrusion foaming or may be expanded after aging of the composition which has been impregnated with volatile blowing agent.

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Newark, OH, United States of America

Gerald A Garcia