Novel polyester molding compositions are disclosed which exhibit unexpected water absorption properties. The compositions of the invention include a polyester base resin (which preferably is a linear poly(alkylene) terephthalate, e.g., poly(butylene) terephthalate, or a copolyester elastomer having long chain ester units derived from corresponding long chain glycols of molecular weight 600-6000 and a carbon to oxygen ratio of greater than 2.5), and a copolyester elastomer having a multiplicity of long and short chain ester units, wherein the long chain ester units are derived from corresponding long chain glycols of molecular height 400-3500 and a carbon to oxygen ratio of between about 2.0 to 2.4. Since the polyester molding compositions of this invention exhibit less water absorption, they may satisfactorily be employed to form parts where low swelling is a desireable physical attribute (e.g. as movable parts of a component having critical spatial tolerances).
本发明公开了新型聚酯模塑组合物,它具有意想不到的吸
水性能。本发明的组合物包括聚酯基
树脂(最好是线性聚
对苯二甲酸(烷基)酯,如聚
对苯二甲酸丁二醇酯),或具有从相应长链酯单元衍生而来的长链酯单元的共聚酯弹性体、聚(
丁烯)
对苯二甲酸酯,或具有长链酯单元的共聚聚酯弹性体,长链酯单元来自分子量为 600-6000 的相应长链
乙二醇,碳氧比大于 2.5),以及具有多个长链和短链酯单元的共聚聚酯弹性体,其中长链酯单元来自分子量为 400-3500 的相应长链
乙二醇,碳氧比在约 2.0 至 2.4 之间。由于本发明的聚酯模塑组合物的吸
水性较低,因此可以很好地应用于低膨胀是一种理想物理属性的部件(例如,作为具有关键空间公差的部件的可移动部件)。