Low modulus structural foam

Claim 2

A formable low-modulus thermoplastic composition which comprises: (a) a low-modulus poletherester copolymer wherein the ether linkage are present as high molecular weight polyalkylene ether units derived from long chaim polyalkylene ether glycols, and (b) an effective amount of a chemical blowing agent selected from the group consisting of citric acid, and a mixture of citric acid and sodium bicarbonate, sufficient to achieved the desired weight reduction in the resultant foamed composition.

Claim 3

The composition of claim 1 wherein the chemical blowing agent is citric acid.

Claim 4

The composition of claim 1 wherein the chemical blowing agent is a mixture of citric acid and soduim bicarbonate.

Claim 5

The composition of claim 1 wherein the low-modulus thermoplastic polymer is a polyetherester copolymer consisting essentially of a multiplicity of recurring intralinear long-chain and short-chain ester units connected head-to-tail through ester linkages, said long-chain ester units being represented by the following structure: ##STR5## and said short-chain ester units being represented by the following structure: ##STR6## wherein G is a divalent radical remaining after removal of terminal hydroxy groups from poly(alkylene oxide) glycols having a carbon-to-oxygen ratio of about 2.0-4.3 and a molecular weig.ht between about 400 and 6000; R is a divalent radical remaining after removal of carboxyl groups from one or more dicarboxylic acids having a molecular weight less than about 300; and D is a divalent radical remaining after removal of hydroxyl groups from one or more saturated and/or unsaturated, low molecular weight diols having a molecular weight less than about 250 with the provisions that the short-chain ester units constitute about 15-95% by weight, preferably 25-90% by weight, of the copolyetherester and, ergo, the long-chain ester units constitute about 5-85% by weight, preferably 10-75% by weight of the copolyetherester.

Claim 6

The composition of claim 4 wherein the copolyetherester is derived from butanediol, poly(tetramethylene oxide) glycol and dimethyl terephthalate.

Claim 7

The composition of claim 4 wherein the copolyetherester is derived from butanediol, hexanediol, poly(tetramethylene oxide) glycol and dimethyl terephthalate.

Claim 8

The composition of claim 4 wherein the copolyetherester is derived from butanediol, butene-diol, poly(tetramethylene oxide) glycol and dimethyl terephthalate.

Claim 9

The foamable composition of claim 1 wherein the amount of blowing agent used is from about 0.01 to about 1.5 parts by weight per 100 parts by weight of polymer.

Claim 10

The foamable composition of claim 1 wherein the amount of blowing agent used is from about 0.1 to about 0.8 parts by weight per 100 parts by weight polymer.

Claim 11

The foamable low-modulus thermoplastic compostion of claim 1 which further comprises one or more high-molecular weight thermoplastic polymers selected from the group consisting essentially of polyesters, polycarbonates, polyolefins, styrenic resins and copolymers thereof.

Claim 12

The composition of claim 10 wherein the high-molecular weight thermoplastic polymer is a polyester represented by the formula ##STR7## wherein n is an integer of from about 2 to about 10.

Claim 13

The composition of claim 11 wherein the polyester is poly(butylene terephthalate).

Claim 14

The composition of claim 1 which further comprises a nucleating amount of a filler or reinforcing agent selected from the group consisting essentially of mica, clay, glass, talc, foamed silica and mixtures thereof.

Claim 15

The composition of claim 13 wherein the filler and/or reinforcing agents are present in an amount up to about 50% by weight based on the total composition.

Claim 16

The composition of claim 1 which further comprises a flame retarding amount of a flame retardant.