Abstract: A polyimide copolymer containing a block polyimide polymer component composed of a rigid aromatic diamine compound and an aromatic tetracarboxylic acid compound and a random polyimide copolymer component composed of a flexible aromatic diamine compound and at least two types of aromatic tetracarboxylic acid compounds is prepared by a two-stage polymerization process. Resin molded products prepared from the polyimide copolymer have high modulus, low thermal expansion and low water absorption and can be used as TAB base films that require higher processability and precision.

Abstract: A durable dry-spun, polyurethane fiber exhibits a small angle X-ray scattering pattern that forms a layer line scattering image or an eyebrow-shaped four dot scattering image. The fiber is particularly useful in pantyhose, undergarments and the like.