Polysiloxanes and their preparation
View Patent ↗An amino-functional polysiloxane is prepared by reacting an aminosilane (A) which contains an aminoalkyl group and at least one alkoxy group bonded to Si with a carboxylic acid and a silanol-functional polysiloxane (B). The aminosilane (A) is partially converted into its carboxylate salt which acts as a catalyst for the siloxane condensation polymerization reaction between (A) and (B).
1. An amino-functional polysiloxane of the formula
wherein A and A′ are each independently a linear or branched alkylene group having 1 to 6 carbon atoms;
q=0-4;
R is selected from the group consisting of hydrogen, an alkyl group, and a hydroxyalkyl group having 1 to 4 carbon atoms;
Y is an alkyl or aryl group;
Z and Z′, which can be the same or different, are each an optionally substituted alkyl or aryl group;
X is hydrogen or an aliphatic group optionally containing one or more ether linkages, with the proviso that at least one X is an aliphatic group having 8 to 30 carbon atoms;
m=4-100; and
n is 1-1000.
2. An amino-functional polysiloxane according to claim 1 wherein 0.2-25% of the amino groups are in carboxylate salt form.
3. A process for the preparation of an amino-functional polysiloxane comprising reacting an aminosilane (A) which contains an aminoalkyl group and at least one alkoxy group bonded to Si with a carboxylic acid (C), a silanol-functional polysiloxane (B) and an aliphatic alcohol having 8 to 30 carbon atoms, the amount of carboxylic acid (C) being such that the molar ratio of carboxylic acid groups of (C) to amino groups of aminosilane (A) is less than 1:1 and the amount of silanol-functional polysiloxane (B) being such that the molar ratio of silanol groups of (B) to Si-bonded alkoxy groups of aminosilane (A) is greater than 1:1 , whereby the aminosilane (A) is partially converted into its carboxylate salt which acts as a catalyst for the siloxane condensation polymerization reaction between (A) and (B).
4. A process according to claim 3 , wherein the aminosilane (A) has the formula
wherein A and A′ are each independently a linear or branched alkylene group having 1 to 6 carbon atoms; q=0-4; R is selected from the group consisting of hydrogen, an alkyl group, and a hydroxyalkyl group having 1 to 4 carbon atoms; R′ is selected from the group consisting of an alkyl group and an alkoxyalkyl group having 1 to 6 carbon atoms; and Y and Y′ are each independently selected from the group consisting of a group OR′, substituted alkyl groups, substituted aryl groups, unsubstituted alkyl groups, and unsubstituted aryl groups.
5. A process according to claim 4 , wherein the group Y of aminosilane (A) is an unsubstituted alkyl group and the group Y′ is of the formula —OR′.
6. A process according to claim 4 wherein the linkages A and A′ of aminosilane (A) are each independently a linear or branched alkylene group having 2 to 4 carbon atoms; q=1; and R is hydrogen.
7. A process according to claim 5 wherein the silanol-functional polysiloxane (B) is a linear hydroxyl endblocked polydimethylsiloxane of degree of polymerisation 4-1000.
8. A process according to claim 3 wherein the silanol-functional polysiloxane (B) is a linear hydroxyl endblocked polydiorganosiloxane containing methyl groups and 2-30 carbon atoms containing groups selected from the group consisting of alkyl groups, alkenyl groups, aryl groups, and aralkyl groups.
9. A process according to claim 3 wherein the carboxylic acid (C) is substituted by an electron-withdrawing moiety.
10. A process according to claim 9 wherein the carboxylic acid (C) is selected from the group consisting of lactic acid and fluoroalkanoic acids.
11. A process according to claim 3 wherein the carboxylic acid is an aliphatic carboxylic acid having 6 to 20 carbon atoms.
12. A process according to claim 3 wherein the amount of carboxylic acid (C) is such that the molar ratio of carboxylic acid groups of (C) to amino groups of aminosilane (A) is 0.002-0.25:1.
13. A process according to claim 3 wherein the amount of silanol-functional polysiloxane (B) is such that the molar ratio of silanol groups of (B) to Si-bonded alkoxy groups of aminosilane (A) is 1.2-2.0:1.
14. A process according to claim 3 wherein an alcohol is co-reacted with the aminosilane (A), carboxylic acid and silanol-functional polysiloxane (B).
15. A process according to claim 14 wherein the alcohol is selected from the group consisting of an ether alcohol and hydroxy-terminated polyether.
16. A process according to claim 3 wherein the carboxylic acid (C) is selected from the group consisting of an alkanoic acid having 1 to 3 carbon atoms and a hydroxy-substituted carboxylic acid and the alcohol is selected from the group consisting of a linear alkanols having 2 to 4 carbon atoms and branched alkanols having 2 to 4 carbon atoms.
17. A process according to claim 3 wherein the condensation reaction between (A) and (B) is carried out at a temperature in the range 60-140° C.
18. A process according to claim 3 wherein a material selected from the group consisting of water and an alcohol endblocker is added to the reagents after a desired reaction time in order to quench reaction.
19. A process for the preparation of an amino-functional polysiloxane comprising reacting an aminosilane (A) which contains an aminoalkyl group and at least one alkoxy group bonded to Si with a carboxylic acid (C) and a silanol-functional polysiloxane (B), the amount of carboxylic acid (C) being such that the molar ratio of carboxylic acid groups of (C) to amino groups of aminosilane (A) is less than 1:1 and the amount of silanol-functional polysiloxane (B) being such that the molar ratio of silanol groups of (B) to Si-bonded alkoxy groups of aminosilane (A) is greater than 1:1, whereby the aminosilane (A) is partially converted into its carboxylate salt which acts as a catalyst for the siloxane condensation polymerization reaction between (A) and (B), wherein a non-reactive polysiloxane having a viscosity of less than 375 mPas is added to the reagents and reaction is continued in the non-reactive polysiloxane as diluent, thereby forming a solution of amino-functional polysiloxane in the non-reactive polysiloxane.
20. A process according to claim 19 in which the non-reactive polysiloxane is a cyclic polysiloxane having at least 5 silicon atoms.
21. A process according to claim 19 in which the non-reactive polysiloxane is a trimethylsilyl-terminated polydimethylsiloxane.
22. A process for the preparation of an amino-functional polysiloxane comprising reacting an aminosilane (A) which contains an aminoalkyl group and at least one alkoxy group bonded to Si with a carboxylic acid (C) and a silanol-functional polysiloxane (B), the amount of carboxylic acid (C) being such that the molar ratio of carboxylic acid groups of (C) to amino groups of aminosilane (A) is less than 1:1 and the amount of silanol-functional polysiloxane (B) being such that the molar ratio of silanol groups of (B) to Si-bonded alkoxy groups of aminosilane (A) is greater than 1:1, whereby the aminosilane (A) is partially converted into its carboxylate salt which acts as a catalyst for the siloxane condensation polymerization reaction between (A) and (B), wherein the aminosilane (A), the carboxylic acid and the silanol-functional polysiloxane (B) are mixed with a surfactant and water to form an emulsion, and the condensation reaction between (A) and (B) is carried out in the emulsion, thereby forming an emulsion of an amino-functional polysiloxane.
23. A process according to claim 22 wherein the aminosilane (A), carboxylic acid, silanol-functional polysiloxane (B), surfactant and water are mixed to form an emulsion at a temperature below 50° C. and the emulsion is heated to a temperature in the range 60-140° C. to effect the condensation reaction.