Alkoxysilane-terminated prepolymer based on polyether carbonate polyols, for spray foams

1. An alkoxysilane-terminated prepolymer, obtained by reacting at least

A) a polyol,

B) a compound having two or more isocyanate groups, and

C) an alkoxysilane having at least an isocyanate group or an isocyanate-reactive group,

wherein the polyol A) comprises at least a polyethercarbonatepolyol obtained by addition of carbon dioxide and alkylene oxides onto H-functional starter molecules.

2. The alkoxysilane-terminated prepolymer according to claim 1 , wherein the polyethercarbonatepolyol has a number-average molecular weight M n of ≥500 and ≤6000 g/mol.

3. The alkoxysilane-terminated prepolymer according to claim 1 , wherein the polyethercarbonatepolyol has a content of carbonate groups, reckoned as CO 2 , of ≥3 and ≤35 wt. %.

4. The alkoxysilane-terminated prepolymer according to claim 1 , wherein the polyethercarbonatepolyol is obtained by addition of carbon dioxide and alkylene oxides onto H-functional starter molecules while using multimetal cyanide catalysts.

5. The alkoxysilane-terminated prepolymer according to claim 1 , wherein the polyethercarbonatepolyol has ≥2 and ≤4 OH groups.

6. The alkoxysilane-terminated prepolymer according to claim 1 , wherein the proportion of component A) which is attributable to the polyethercarbonatepolyol is ≥50 and ≤100 wt. %.

7. The alkoxysilane-terminated prepolymer according to claim 1 , wherein the alkoxysilane of component C) is an α-alkoxysilane.

8. The alkoxysilane-terminated prepolymer according to claim 1 , wherein component B) is an aliphatic and/or cycloaliphatic compound.

9. The alkoxysilane-terminated prepolymer according to claim 1 , wherein the alkoxysilane-terminated prepolymer is obtained by reaction of at least the alkoxysilane C), comprising isocyanate-reactive groups, with an NCO-terminated polyurethane prepolymer, wherein the NCO-terminated polyurethane prepolymer is obtained by reaction of at least the isocyanate-functional compound B) with the polyol A).

10. A process for preparing the alkoxysilane-terminated prepolymer according to claim 1 comprising the steps of:

reacting the polyol A) with the compound B) to form an NCO- or OH-terminated polyurethane prepolymer, and

reacting the NCO- or OH-terminated polyurethane prepolymer with the alkoxysilane C) to form the alkoxysilane-terminated prepolymer.

11. A composition comprising at least an alkoxysilane-terminated prepolymer i) according to claim 1 and at least one further component.

12. The composition according to claim 11 , wherein the further component is ≥1 and ≤70 wt. % of an alkoxysilane-terminated prepolymer other than i), which comprises a polyetherpolyol and/or a polyesterpolyol having a number-average molecular weight M n of ≥500 and ≤7000 g/mol as polyol component A).

13. The alkoxysilane-terminated prepolymer according to claim 1 , wherein the polyethercarbonatepolyol has a content of carbonate groups, reckoned as CO 2 , of ≥10 and ≤28 wt. %.

14. The alkoxysilane-terminated prepolymer according to claim 13 , wherein the polyethercarbonatepolyol has a number-average molecular weight M n of ≥1000 and ≤3000 g/mol, wherein the polyethercarbonatepolyol has 2 OH groups, wherein the alkoxysilane of component C) is an α-alkoxysilane and wherein component B) is an aliphatic and/or cycloaliphatic compound.