High molecular weight linear thermoplastic elastomeric polyurethanes of I.V. 0.9-2 are prepared by reaction in solution. A hydroxyl-terminated prepolymer and a diol chain extender are reacted, in the solvent, with a small excess of diisocyanate, until the --NCO content becomes constant, then a diol chain extender in amount equivalent to the remaining --NCO; reaction is continued, and then terminated after the high I.V. is attained.
This is a continuation, of application Ser. No. 33,886 filed May 1, 1970, now abandoned.
This application is a continuation-in-part of our application Ser. No. 819,337 filed Apr. 26, 1969, now abandoned, whose entire disclosure is incorporated herein by reference.
A solid polyimide composition is described with a softening point reduced to the range of about 50.degree.C to about 150.degree.C to facilitate molding and particularly extrusion. The composition comprises a blend of (a) a selected copolyimide and (b) a dipolar aprotic solvent or phenol having a boiling point .gtoreq.50.degree.C higher than the softening point of the blend but not higher than about 225.degree.C. The copolyimides are those characterized by solubility in organic polar solvents and by thermoplasticity.
