Process for preparing polydimethylsiloxanes on sulphonic acid cation exchange resins
View Patent ↗The invention relates to a process for the targeted reorganization of polydimethylsiloxanes over sulphonic acid-containing cation exchange resins which have water contents of 8 to 25% by weight, and polydimethylsiloxanes thus prepared and the use thereof.
1. A composition containing different polydimethylsiloxanes of formula (1)
having a chain length N=n+2, wherein the sum of polydimethylsiloxanes with N=6 and N=7 is ≧20% by weight, and the sum of polydimethylsiloxanes having a boiling point lower than the boiling point of a polydimethylsiloxane with N=6 is less than 5% by weight, wherein said % by weight is based on the mass of the polydimethylsiloxanes of formula (1).
2. The composition according to claim 1 , wherein the sum of polydimethylsiloxanes with N=6 to N=12 is 20 to 58% by weight, based on the mass of the polydimethylsiloxanes of formula (1).
3. The composition according to claim 1 , wherein the sum of polydimethylsiloxanes with N≧13 is <7% by weight, based on the mass of the polydimethylsiloxanes of formula (1).
4. The composition according to claim 1 , wherein the composition contains 20 to 58% by weight of polydimethylsiloxanes having a chain length N of 6 to 12, and 7% by weight of polydimethylsiloxanes having a chain length N of ≧13.
5. The composition according to claim 1 , wherein the composition contains 20 to 35% by weight of polydimethylsiloxanes having a chain length N of 6 and 7, 3 to 23% by weight of polydimethylsiloxanes having a chain length N of 8 to 12, and ≦7% by weight of polydimethylsiloxanes having a chain length N of ≧13.
6. The composition according to claim 1 , wherein a mass ratio Q of the polydimethylsiloxane with N=6 or 7 to the polydimethylsiloxane with N=13 to 18 is from 4 to 60.
7. The composition according to claim 1 , wherein the composition contains less than 1% by weight of compounds having a boiling point lower than the boiling point of a polydimethylsiloxane of the formula (1) with N=6, wherein said % by weight is based on the mass of the polydimethylsiloxanes of formula (1).
8. A method of forming a polyurethane foam comprising adding a composition according to claim 1 to a reaction mixture comprising polyurethane foam reactants.