Thermoplastic polyurethane resins

A thermoplastic polyurethane resin having a molecular weight larger than 5,000 and comprising a combination of units represented by the following formulas:

• ##STR9## (wherein W is a residue derived by the elimination of the two hydroxyl groups from a long chain diol (A) having a molecular weight in a range of about 500 to 3,000;
• X is a residue derived by the elimination of the two isocyanate groups from an organic isocyanate (C);
• Y is a residue derived by the elimination of the two hydroxyl groups from a short chain triol (D) having a molecular weight in a range lower than about 500;
• Z is a residue derived by the elimination of the two hydroxyl groups from a short chain diol (B) having a molecular weight in a range of about 50 to 500;
• n.sub.1 and n.sub.2 are each a positive integer;
• and
• n.sub.3 is 0 or a positive integer;
• said short chain triol (D) being represented by the formula (II):
• ##STR10## or by the formula (III):
• ##STR11## (wherein R.sub.1 is a group represented by the formula:
• --CH.sub.2).sub.m (OCH.sub.2 CH.sub.2).sub.n
• (where m and n are each an integer from 0 to 6, provided that, when one of m and n is 0, the other is an integer other than 0);
• R.sub.2 is a group represented by the formula:
• --CH.sub.2).sub.p (OCH.sub.2 CH.sub.2).sub.q
• (where p and q are each an integer from 0 to 6, provided that, when one of p and q is 0, the other is an integer other than 0);
• R.sub.3 is a group represented by formula:
• ##STR12## (where r is an integer from 0 to 3) or a group represented by formula:
• ##STR13## (where r has the same meaning as above);
• and R.sub.4 is a group represented by formula:
• --C.sub.s H.sub.2s+l
• (where s is an integer from 0 to 4);
• obtainable by the polyaddition reaction of the long chain diol (A), the organic diisocyanate (C) and the short chain triol (D) and, as desired, the short chain diol (B) in the ratios of:
• b/a.ltoreq.3 (i)
• <
• c/(a+b)<3 (ii) ##EQU4## (wherein a is a molar number of the long chain diol (A);
• b is a molar number of the short chain diol (B);
• c is a molar number of the organic diisocyanate (C);
• and
• d is a molar number of the short chain triol (D)).