Method for producing a polyoxyalkylene polyester polyol
The invention relates to a method for producing a polyoxyalkylene polyester polyol by reacting a polyoxyalkylene polyol with a lactone in the presence of a Brønsted acid catalyst, wherein the catalyst has a pKa value of 1 or less; the number-average molar mass of the polyoxyalkylene polyol is ≥1000 g/mol, preferably ≥1500 g/mol, particularly preferably ≥2000 g/mol; and in the lactone a CH2 group is bonded to the ring oxygen. The invention further relates to polyoxyalkylene polyester polyols obtainable using the method according to the invention, and to a method for producing polyurethanes by reacting the polyoxyalkylene polyester polyols according to the invention with polyisocyanates.
1. A process for preparing a polyoxyalkylene polyester polyol comprising reacting a polyoxyalkylene polyol with a lactone comprising beta-propiolactone in the presence of a Brønsted-acidic catalyst;
wherein the catalyst has a pKa of 1 or less; and
wherein the number-average molar mass of the polyoxyalkylene polyol is ≥1000 g/mol;
wherein the polyoxyalkylene polyol has a proportion of secondary OH end groups of at least 75%, based on the sum total of primary and secondary OH end groups, as determined by means of 1H NMR spectroscopy; and
wherein the polyoxyalkylene polyester polyol has a proportion of primary OH end groups of at least 80%, based on the sum total of primary and secondary OH end groups, as determined by means of 1H or 13C NMR spectroscopy.
2. The process as claimed in claim 1 , wherein the molar ratio of lactone to the hydroxyl end groups of the polyoxyalkylene polyol is 1:1 to 20:1.
3. The process as claimed in claim 1 , wherein the Brønsted-acidic catalyst comprises trifluoromethanesulfonic acid, perchloric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, methanesulfonic acid, trichloroacetic acid, trifluoroacetic acid, or a mixture thereof.
4. The process as claimed in claim 1 , wherein the Brønsted-acidic catalyst is used in an amount of 0.001 mol % to 0.5 mol %, based on the amount of lactone.
5. The process as claimed in claim 1 , wherein the polyoxyalkylene polyol comprises a polyether polyol and/or polyether carbonate polyol.
6. The process as claimed in claim 5 , wherein the polyoxyalkylene polyol comprises a polyether polyol prepared by reaction of an H-functional starter substance with alkylene oxide in the presence of a double metal cyanide catalyst.
7. The process as claimed in claim 5 , wherein the polyoxyalkylene polyol comprises a polyether carbonate polyol prepared by reaction of an H-functional starter substance with alkylene oxide and carbon dioxide in the presence of a double metal cyanide catalyst.
8. The process as claimed in claim 6 , wherein the alkylene oxide is ethylene oxide and/or propylene oxide.
9. The process as claimed in claim 8 , wherein the proportion by weight of propylene oxide is 80% by weight to 100% by weight based on the sum total of the masses of propylene oxide and of ethylene oxide metered in.
10. The process as claimed in claim 1 , wherein the process is performed without addition of a solvent.
11. The process as claimed in claim 2 , wherein the molar ratio of lactone to the hydroxyl end groups of the polyoxyalkylene polyol is 2:1 to 6:1 and the Brønsted-acidic catalyst is used in an amount of 0.005 mol % to 0.3 mol %, based on the amount of lactone.
12. The process as claim in claim 11 , wherein the Brønsted-acidic catalyst comprises trifluoromethanesulfonic acid.