PROCESS FOR THE PREPARATION OF POLYISOCYANATES AND USE THEREOF

1 . A process for isocyanate modification which comprises reacting

a) at least one organic isocyanate having an NCO functionality greater than or equal to 1,

b) a catalyst comprising at least one phosphonium salt comprising at least one cycloalkyl substituent bonded directly to a P atom of a phosphonium cation,

c) optionally a solvent, and

d) optionally additives.

2 . The process according to claim 1 , wherein the phosphonium salt comprises a cation corresponding to the formula I:

wherein R 1 to R 4 independently of one another represent organic radicals selected from the group consisting of C 1 - to C 20 -alkyl, C 3 - to C 20 -cycloalkyl, C 7 - to C 20 -aralkyl, and C 6 - to C 20 -aryl, which are optionally branched, substituted, or a combination thereof, and wherein at least one of the radicals R 1 to R 4 represents a C 3 - to C 20 -cycloalkyl radical which is optionally branched, substituted, or a combination thereof, and a carbon atom of the cycloalkyl ring is bonded directly to the P atom.

3 . The process according to claim 2 , wherein R 1 to R 4 independently of one another represent organic radicals selected from the group consisting of C 1 - to C 20 -alkyl which is optionally branched, cyclopentyl, and cyclohexyl which is optionally substituted, and

wherein at least two of the radicals R 1 to R 4 represent an optionally substituted cyclopentyl, cyclohexyl radical, or combinations thereof which are each bonded directly to the P atom via a ring carbon atom.

4 . The process according to claim 2 , wherein the phosphonium cation of the formula (I) has a counter-ion X − wherein X − is selected from the group consisting of fluoride (F − ) and a di- or poly-(hydrogen)fluoride ([F − ×(HF) m ], wherein in represents whole or fractional numbers from 0.001 to 20.

5 . The process according to claim 1 , wherein the at least one organic isocyanate is selected from the group consisting of aliphatic di- or poly-isocyanates, cycloaliphatic di- or poly-isocyanates, araliphatic di- or poly-isocyanates, and mixtures thereof, and wherein the at least one organic isocyanate has a functionality greater than or equal to 2.

6 . The process according to claim 1 , wherein the reaction is carried out at a temperature from 0 to 250° C.

7 . The process according to any claim 1 , further comprising terminating the reaction when from 5 to 80% of the at least one organic isocyanate has been converted.

8 . The process according to claim 1 , further comprising separating the unconverted isocyanates from the reaction mixture.

9 . A modified isocyanate produced by the process according to claim 1 .

10 . A catalyst for isocyanate modification comprising at least one phosphonium salt comprising at least one cycloalkyl substituent bonded directly to a P atom of a phosphonium cation.

11 . The catalyst according to claim 10 , wherein the phosphonium salt comprises a cation corresponding to the formula I:

wherein R 1 to R 4 independently of one another represent organic radicals selected from the group consisting of C 1 - to C 20 -alkyl, C 3 - to C 20 -cycloalkyl, C 7 - to C 20 -aralkyl, and C 6 - to C 20 -aryl, which are optionally branched, substituted, or a combination thereof, and wherein at least one of the radicals R 1 to R 4 represents a C 3 - to C 20 -cycloalkyl radical which is optionally branched, substituted, or a combination thereof, and a carbon atom of the cycloalkyl ring is bonded directly to the P atom.

12 . The catalyst according to claim 11 , wherein R 1 to R 4 independently of one another represent organic radicals selected from the group consisting of C 1 - to C 20 -alkyl which is optionally branched, cyclopentyl, and cyclohexyl which is optionally substituted, and

wherein at least two of the radicals R 1 to R 4 represent an optionally substituted cyclopentyl, cyclohexyl radical, or combinations thereof which are each bonded directly to the P atom via a ring carbon atom.

13 . The catalyst according to claim 11 , wherein the phosphonium cation of the formula (I) has a counter-ion X − wherein X − is selected from the group consisting of fluoride (F − ) and a di- or poly-(hydrogen)fluoride ([F − ×(HF) m ], wherein m represents whole or fractional numbers from 0.001 to 20.