Method for producing organopolysiloxane

1 . A method for producing an organopolysiloxane having at least one silicon atom-bonded alkoxysilylalkyl group per molecule, the method comprising the following steps:

(i) treating an organopolysiloxane having at least one silicon atom-bonded hydrogen atom per molecule with an alkali salt of carboxylic acid, where the alkali salt of carboxylic acid is present in an amount of from 100 to 1,500 ppm;

(ii) removing the alkali salt from the organopolysiloxane; and

(iii) reacting the organopolysiloxane obtained by step (ii) with an alkenyl group-containing alkoxysilane in the presence of a platinum-based catalyst;

wherein step (i) precedes step (iii).

2 . The method according to claim 1 , wherein the organopolysiloxane in step (i) is represented by the following general formula:

R 1 2 HSiO(R 1 2 SiO) n SiR 1 2 H

wherein each R 1 is the same or different hydrocarbon group with 1 to 12 carbon atoms and is free of an aliphatic unsaturated bond, and “n” is an integer of from 0 to 100.

3 . The method according to claim 1 , wherein the alkali salt in step (i) is selected from the group consisting of sodium salt of acetic acid and sodium salt of propionic acid.

4 . The method according to claim 1 , wherein the alkoxysilane in step (iii) is represented by the following general formula:

R 2 SiR 3 a (OR 4 ) (3-a)

wherein R 2 is an alkenyl group with 2 to 12 carbon atoms, R 3 is a hydrocarbon group with 1 to 12 carbon atoms and is free of an aliphatic unsaturated bond, R 4 is an alkyl group with 1 to 3 carbon atoms, and “a” is 0, 1 or 2.

5 . The method according to claim 1 , wherein the platinum-based catalyst in step (iii) is selected from the group consisting of platinum fine powder, platinum black, platinum supporting silica fine powder, platinum supporting activated carbon, chloroplatinic acid, alcohol-modified chloroplatinic acid, and complexes of chloroplatinic acid with olefins, aldehydes, vinylsiloxanes or acetylene alcohols.

6 . The method according to claim 1 , wherein the platinum-based catalyst in step (iii) is added in an amount such that platinum metal in the catalyst is in a range of from about 1 to about 1,000 ppm in mass unit relative to the total mass of the organopolysiloxane and the alkoxysilane.

7 . The method according to claim 1 , wherein the organopolysiloxane in step (iii) is reacted with the alkenyl group-containing alkoxysilane and an olefin with 4 to 20 carbon atoms simultaneously.

8 . The method according to claim 7 , wherein the olefin is selected from the group consisting of 1-hexene, 1-heptene, 1-octene, and 1-decene.

9 . The method according to claim 1 , further comprising the following step:

(iv) reacting the organopolysiloxane obtained by step (iii) with an olefin with 6 to 20 carbon atoms in the presence of a platinum-based catalyst.

10 . The method according to claim 9 , wherein the olefin is selected from the group consisting of 1-hexene, 1-heptene, 1-octene, and 1-decene.

11 . The method according to claim 9 , wherein step (iv) is carried out at a temperature of from about 30° C. to about 150° C.

12 . The method according to claim 1 , wherein step (iii) is carried out at a temperature of from about 30° C. to about 150° C.

13 . The method according to claim 1 , wherein the alkali salt of carboxylic acid is present in an amount of from 500 to 800 ppm.