Defoaming agent composition

1. A Gemini-type alkyl-polyoxyalkylene-modified silicone represented by formula (A):

wherein R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are identical to or different from one another, and each may have a halogen atom, a hydroxyl group, an amino group, a thiol group or a hydrosilyl group, representing: an alkyl group that has 1 to 30 carbon atoms; a cycloalkyl group that has 3 to 30 carbon atoms; an aryl group that has 6 to 30 carbon atoms; or an aralkyl group that has 7 to 30 carbon atoms, n represents an integer of 0 to 300, and (B) represents either an identical group or different groups expressed by formula (1):

wherein each of R 7 and X represents a hydrocarbon group that has 1 to 40 carbon atoms and may be substituted by a halogen atom, an alkoxy group, a nitro group, a cyano group or a substituted amino group; R 8 represents a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, a formyl group or an acyl group having 2 to 30 carbon atoms; and a and b represent numbers satisfying 2≦a≦200 and 0≦b≦200, provided that a+b=2 to 200.

2. A method of producing a Gemini-type alkyl-polyoxyalkylene-modified silicone as set forth in claim 1 , comprising:

(1) condensing a mono-endcapped polyoxyalkylene and a hydroxyalkyl carboxylic acid derivative by either

(a) a transesterification reaction between hydroxyl groups of said mono-endcapped polyoxyalkylene and hydroxyalkyl carboxylic acid ester, or

(b) an esterification reaction between hydroxyl groups of said mono-endcapped polyoxyalkylene and carboxyl groups of hydroxyalkyl carboxylic acid; and

(2) reacting a hydroxyalkyl-polyoxyalkylene condensate obtained in said (1) condensing and an organopolysiloxane having a reactive group at both terminals by either

(c) a dehydrocondensation reaction between hydroxyl groups of said hydroxyalkyl -polyoxyalkylene condensate and an organopolysiloxane having a hydrosilyl group at both terminals in the presence of a platinum group metal catalyst or a base catalyst, or

(d) a condensation reaction between hydroxyl groups of said hydroxyalkyl-polyoxyalkylene condensate and an organopolysiloxane having at both terminals a hydrolyzable group directly bonded to a silicon atom in the presence of a condensation catalyst.

3. The method of claim 2 , wherein said hydroxyalkyl carboxylic acid derivative is at least one member selected from the group consisting of a ricinoleic acid, a 12-hydroxystearic acid, a methyl ester of said ricinoleic acid, a methyl ester of said 12-hydroxystearic acid, an ethylester of said ricinoleic acid, an ethylester of said 12-hydroxystearic acid, an n-propylester of said ricinoleic acid, an n-propylester of said 12-hydroxystearic acid, an i-propylester of said ricinoleic acid, an i-propylester of said 12-hydroxystearic acid, a butylester of said ricinoleic acid and a butylester of said 12-hydroxystearic acid.

4. A defoaming agent composition comprising:

(A) a Gemini-type alkyl-polyoxyalkylene-modified silicone in an amount of 1 to 80% by mass and represented by formula (A)

wherein R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are identical to or different from one another, and each may have a halogen atom, a hydroxyl group, an amino group, a thiol group or a hydrosilyl group, representing: an alkyl group that has 1 to 30 carbon atoms; a cycloalkyl group that has 3 to 30 carbon atoms; an aryl group that has 6 to 30 carbon atoms; or an aralkyl group that has 7 to 30 carbon atoms, n represents an integer of 0 to 300, and (B) represents either an identical group or different groups expressed by formula (1):

wherein each of R 7 and X represents a hydrocarbon group that has 1 to 40 carbon atoms and may be substituted by a halogen atom, an alkoxy group, a nitro group, a cyano group or a substituted amino group; R 8 represents a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, a formyl group or an acyl group having 2 to 30 carbon atoms;

and a and b represent numbers satisfying 2≦a≦200 and 0≦b≦200, provided that a+b=2to 200;

(B) a silicone oil compound in an amount of 15 to 60% by mass and containing:

(a) an organopolysiloxane exhibiting a viscosity of 10 to 100,000 mm 2 /s at 25° C. and represented by formula (3)

R 9 c SiO (4-C)/2   (3)

wherein each R 9 independently represents a substituted or an unsubstituted monovalent hydrocarbon group; and c represents a number of 1.9 to 2.2; and

(b) a finely powdered silica in an amount of 0.1 to 30 parts by mass with respect to 100 parts by mass of said component (a), and exhibiting a specific surface area not smaller than 100 m 2 /g by BET method; and

(C) at least one kind of a polyoxyalkylene-modified organopolysiloxane in an amount of 5 to 95% by mass.

5. The defoaming agent composition according claim 4 , further comprising

(D) at least one kind of a polyoxyalkylene polymer in an amount of 5 to 80% by mass.

6. A method of producing a Gemini-type alkyl-polyoxyalkylene-modified silicone represented by formula (A):

wherein R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are identical to or different from one another, and each may have a halogen atom, a hydroxyl group, an amino group, a thiol group or a hydrosilyl group, representing: an alkyl group that has 1 to 30 carbon atoms; a cycloalkyl group that has 3 to 30 carbon atoms; an aryl group that has 6 to 30 carbon atoms; or an aralkyl group that has 7 to 30 carbon atoms, n represents an integer of 0 to 300, and (B) represents either an identical group or different groups expressed by formula (2):

wherein X represents a hydrocarbon group that has 1 to 40 carbon atoms and may be substituted by a halogen atom, an alkoxy group, a nitro group, a cyano group or substituted amino group; R 8 represents a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms, a formyl group or an acyl group having 2 to 30 carbon atoms; and a and b represent numbers satisfying 2≦a≦200 and 0≦b≦200, provided that a+b=2 to 200, the method comprising:

(1) condensing a mono-endcapped polyoxyalkylene and a hydroxyalkyl carboxylic acid derivative by either

(a) a transesterification reaction between hydroxyl groups of said mono-endcapped polyoxyalkylene and hydroxyalkyl carboxylic acid ester, or

(b) an esterification reaction between hydroxyl groups of said mono-endcapped polyoxyalkylene and carboxyl groups of hydroxyalkyl carboxylic acid; and

(2) reacting a hydroxyalkyl-polyoxyalkylene condensate obtained in said (1) condensing and an organopolysiloxane having a reactive group at both terminals by either

(c) a dehydrocondensation reaction between hydroxyl groups of said hydroxyalkyl -polyoxyalkylene condensate and an organopolysiloxane having a hydrosilyl group at both terminals in the presence of a platinum group metal catalyst or a base catalyst, or

(d) a condensation reaction between hydroxyl groups of said hydroxyalkyl-polyoxyalkylene condensate and an organopolysiloxane having at both terminals a hydrolyzable group directly bonded to a silicon atom in the presence of a condensation catalyst.

7. The method of claim 6 , wherein said hydroxyalkyl carboxylic acid derivative is at least one member selected from the group consisting of a ricinoleic acid, a 12-hydroxystearic acid, a methyl ester of said ricinoleic acid, a methyl ester of said 12-hydroxystearic acid, an ethylester of said ricinoleic acid, an ethylester of said 12-hydroxystearic acid, an n-propylester of said ricinoleic acid, an n-propylester of said 12- hydroxystearic acid, an i-propylester of said ricinoleic acid, an i-propylester of said 12-hydroxystearic acid, a butylester of said ricinoleic acid and a butylester of said 12-hydroxystearic acid.