Porous polyisocyanate polyaddition products
Process for producing porous polyisocyanate polyaddition products by reacting (a) isocyanates with (b) compounds which are reactive toward isocyanates in the presence of (f) solvent, wherein compounds having a functionality toward isocyanates of at least 6 and a molecular weight of at least 1000 g/mol are used as (b) compounds which are reactive toward isocyanates.
1. A process for producing porous polyisocyanate polyaddition products comprising: reacting isocyanates (a) with compounds reactive toward isocyanates (b) in the presence of solvent inert toward isocyanates (f) and subsequently removing said solvent (f) from the polyurethane, wherein said compounds (b) are hyperbranched, with a degree of branching from 10% to 99.9%, and have a functionality toward isocyanates of at least 6 and a molecular weight of at least 1000 g/mol.
2. The process of claim 1 , wherein said compounds (b) comprise compounds which have a hydroxyl number of at least 100 mg KOH/g.
3. The process of claim 1 , wherein said compounds (b) comprise polyols comprising ester groups.
4. The process of claim 1 , wherein said isocyanates (a) comprise aromatic isocyanates having at least two isocyanate groups.
5. The process of claim 1 , wherein the reaction of isocyanates (a) with compounds (b) is carried out in the presence of a catalyst (d) which activates the isocyanate groups.
6. The process of claim 1 , wherein said isocyanates (a) and said compounds (b) are soluble or dispersible to an extent of at least 1% by weight, based on the total weight of the mixture, at 298 K in said solvent (f) and wherein the reaction of said isocyanates (a) with said compounds (b) results in a gel body in which the proportion of precipitated reaction product is less than 1% by weight, based on the total weight of the mixture.
7. The process of claim 1 , wherein one or more changes of said solvent (f) is carried out after reaction of the reactants.
8. The process of claim 1 , wherein said solvent (f) comprises aliphatic ketones and esters.
9. The process of claim 1 , wherein the proportion by weight of said solvent (f) is in the range of from 50% by weight to 99% by weight, based on the total weight of the components used in the production of the polyurethane foam including the solvent.
10. The process of claim 1 , wherein said solvent (f) is removed after the reaction of said isocyanates (a) with said compounds (b) by selecting a pressure which is less than the critical pressure of said solvent (f) and a temperature which is less than the critical temperature of said solvent (f) during drying.
11. The process of claim 1 , wherein the reaction of said isocyanates (a) with the isocyanate-reactive groups of the compounds (b) and, optionally, with chain extenders and/or crosslinkers (c) is carried out at an index in the range of from 950 to 1050.
12. The process of claim 1 , wherein the degree of branching of said compounds (b) is from 20% to 99%.
13. The process of claim 12 , wherein the degree of branching is from 20% to 95%.
14. The process of claim 13 , wherein the degree of branching is from 20% to 95%.
15. A process for producing a porous polyisocyanate polyaddition product comprising:
reacting isocyanates (a) with compounds reactive toward isocyanates (b) in the presence of solvent inert toward isocyanates (f) and
removing said solvent (f) from the porous polyisocyanate polyaddition product by drying at a pressure which is less than the critical pressure of the solvent (f) and at a temperature which is less than the critical temperature of the solvent (f);
wherein said compounds (b) are hyperbranched, with a degree of branching from 10% to 99.9%.
16. The process of claim 15 , wherein the degree of branching of said compounds (b) is from 20% to 99%.
17. The process of claim 16 , wherein the degree of branching of said compounds (b) is from 20% to 95%.