Process for the preparation of polyurethane solutions based on siliconpolycarbonate diols

A polyurethane solution prepared by a process comprising:

• (a) reacting a polycarbonate siloxane diol prepared by reaction of a carbonate source, such as a dialkylcarbonate, such as diethylcarbonate, or an alkylene dicarbonate with a bis(hydroxyalkyl)(tetramethyldisolaxane), such as BHTD, in the presence of an initiator catalyst;
• with a diisocyanate, such as MDI to form a prepolymer;
• (b) chain extending the prepolymer by reaction with an alkylene diol, such as BDO to yield a polyurethane;
• (c) adding dimethylacetamide to the stirred, heated mixture (such as at about 75-85° C.) to yield about a 15-50 wt-% solution, such as a 17-30 wt-% of said polyurethane;
• and
• (d) cooling the solution to about 20-30° C.