Foamable thermoplastic polymers and a method for foaming
AssigneeThe Dow Chemical Company
InventorsTu-Anh Pham, Gerald M. Lancaster
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Abstract
Foamed products are prepared by subjecting a crosslinked polymer such as an ethylene-carbon monoxide copolymer susceptible to heating by high frequency electromagnetic radiation such as microwave or radio frequency which has been imbibed or impregnated with a suitable mechanical or physical blowing agent such as a halogenated hydrocarbon to sufficient high frequency electromagnetic radiation to cause foaming of the polymer.
Claims32
A polymer composition which when subjected to high frequency electromagnetic radiation produces a foamed polymer, which polymer composition comprises
- (1) from about 10 to about 100 percent by weight based upon the combined weight of components (1) and (2) of at least one thermoplastic polymer which is heatable when subjected to high frequency electromagnetic radiation, which polymer contains in its backbone, some carbon atoms which have attached thereto a member selected from the group consisting of .dbd.O, --Cl, --OH, --OCH.sub.3, --OC.sub.2 H.sub.5, --O--CO--CH.sub.3, and --O--CO--C.sub.2 H.sub.5 ;
- which groups are present in an amount to render the polymer heatable by high frequency electromagnetic radiation;
- (2) from about zero to about 90 percent by weight based upon the combined weight of components (1) and (2) of at least one polymer which is not heatable when subjected to high frequency electromagnetic radiation:
- and wherein each of the polymer compositions (1) and (2) has been imbibed or impregnated with a suitable mechanical or physical foaming or blowing agent in an amount which causes expansion of the imbibed or impregnated polymer when subjected to a sufficient amount of electro-magnetic radiation to cause foaming of the imbibed or impregnated polymer composition.
A method for forming a shaped object from a thermoplastic polymer foam which process comprises
- (a) foaming or expanding by high frequency electromagnetic radiation or by conventional means individual thermoplastic beads or pellets which have been imbibed with a mechanical or physical foaming or blowing agent:
- and
- (b) placing the expanded beads or pellets in a suitable mold having the desired shape and subjecting the thus filled mold to high frequency electromagnetic radiation thereby causing the beads or pellets to fuse together;
- thereby forming a foamed object of the desired shape.
Dependencies are inferred from the claim text.