Method for producing polyoxymethylene polyoxyalkylene block copolymers
The invention relates to a method for producing a polyoxymethylene polyoxyalkylene block copolymer, said method including the process of reacting a polymer formaldehyde compound with alkylene oxide in the presence of a double metal cyanide (DMC) catalyst and an H-functional starter substance, wherein the theoretical molar mass of the polymer formaldehyde compound is lower than the theoretical molar mass of the H-functional starter substance, and the polymer formaldehyde compound has at least one terminal hydroxyl group, the theoretical molar mass of the H-functional starter substance being at least 500 g/mol. In the method according to the invention, a mixture i) is provided comprising the DMC catalyst and the H-functional starter substance in step (i); the polymer formaldehyde compound is then added to the mixture (i) in step (ii), thereby forming a mixture (ii); and the alkylene oxide is added in step (iii), step (ii) being carried out at the same time as or prior to step (iii).
1. A process for preparing a polyoxymethylene-polyoxyalkylene block copolymer comprising reacting a polymeric formaldehyde compound with an alkylene oxide in the presence of a double metal cyanide (DMC) catalyst and an H-functional starter substance;
wherein the theoretical molar mass of the polymeric formaldehyde compound is less than the theoretical molar mass of the H-functional starter substance;
wherein the polymeric formaldehyde compound has at least one terminal hydroxyl group; and
wherein the theoretical molar mass of the H-functional starter substance is at least 500 g/mol;
the process comprising:
(i) initially charging a mixture i) comprising the DMC catalyst and a polyoxymethylene-polyoxyalkylene block copolymer H-functional starter;
(ii) adding the polymeric formaldehyde compound to mixture i) to form a mixture ii); and
(iii) adding the alkylene oxide;
wherein step (ii) is carried out simultaneously with or prior to step (iii), and wherein the polyoxymethylene-polyoxyalkylene block copolymer H-functional starter has an identical functionality to the polyoxymethylene-polyoxyalkylene block copolymer produced by the process and the number-average molecular weight of the polyoxymethylene-polyoxyalkylene block copolymer H-functional starter diverges from that of the polyoxymethylene-polyoxyalkylene block copolymer produced by the process by up to 10%.
2. The process as claimed in claim 1 , wherein the polyoxymethylene-polyoxyalkylene blockcopolymer has a number-average molecular weight of 1000 g/mol to 10000 g/mol.
3. The process as claimed in claim 1 , wherein the polyoxymethylene-polyoxyalkylene block copolymer H-functional starter is the same as the polyoxymethylene-polyoxyalkylene block copolymer produced by the process.
4. The process as claimed in claim 1 , wherein the polyoxymethylene-polyoxyalkylene block copolymer H-functional starter comprises a reaction product of a polymeric formaldehyde compound with an alkylene oxide in the presence of a DMC catalyst (A).
5. The process as claimed in claim 1 , wherein the DMC catalyst is used in a theoretical amount of 100 to 800 ppm, based on the sum of the masses of the polymeric formaldehyde compound, of the alkylene oxide and of the H-functional starter substance.
6. The process as claimed in claim 4 , wherein the double metal cyanide (DMC) catalyst comprises the double metal cyanide (DMC) catalyst (A) and optionally a double metal cyanide (DMC) catalyst (B), wherein the DMC catalyst (B) is present with the polyoxymethylene-polyoxyalkylene block copolymer H-functional starter.
7. The process as claimed in claim 6 , wherein the mass ratio of the double metal cyanide (DMC) catalyst (A) based on the sum of the masses of double metal cyanide (DMC) catalyst (A) and double metal cyanide (DMC) catalyst (B) is 30% by weight to 90% by weight.
8. The process as claimed in claim 1 , wherein the polymeric formaldehyde compound has 2 hydroxyl groups and 8 to 100 repeating oxymethylene units (n) or 3 hydroxyl groups and 8 to 100 repeating oxymethylene units (n).
9. The process as claimed in claim 1 , wherein step (iii) is carried out at a temperature of 50° C. to 150° C.
10. The process of claim 1 , wherein the mixture i) consists of the DMC catalyst and the polyoxymethylene-polyoxyalkylene block copolymer H-functional starter, and the polymeric formaldehyde is subsequently added to mixture i) to form a mixture ii).