This invention relates to polyamide elastomer having high flexibility and high heat resistance in addition to good physical characteristics of the known polyamide elastomers.
It is well known that polyamide elastomers comprising hard segments derived from polyamide and soft segments derived from polyethers has good physical characteristics such as high impact-recovery resilience, and low temperature flexibility. For instance, U.S. Pat. No. 4,331,786 describes polyether-ester-amide block copolymer.
However, the known polyamide elastomers having hard segments of polyamide and soft segment of polyether has disadvantageous characteristics such as low heat resistance and noticeable yellowing.
Japanese Patent Provisional Publication 8-134210 describes polyamide elastomer comprising hard segments derived from aromatic amides and soft segments derived from aliphatic polyesters, aliphatic polycarbonates, aliphatic polyether carbonate, or polyorganosiloxane and having a weight average molecular weight of 30,000 to 1,000,000.
It is an object of the invention to provide a polyamide elastomer having high flexibility and high heat resistance in addition to good physical characteristics of the known polyamide elastomers.
The present invention resides in polyamide elastomer comprising units derived from polyamide-forming monomers having no divalent aromatic group, units derived from polycarbonate diols, and units derived from dicarboxylic acids.
The invention further resides in polyamide elastomer comprising units derived from aliphatic polyamides having a carboxylic acid group at each end thereof, and units derived from polycarbonate diols.
The invention furthermore resides in polyamide elastomer comprising aliphatic polyamide units in an amount of 15 to 95 weight %, polycarbonate diol units, and dicarboxylic acid units.