Process For Making and Using Foam Control Compositions

• US 20090306282A1
• Filed: 05/17/2007
• Published: 12/10/2009
• Est. Priority Date: 05/31/2006
• Status: Active Grant

• Current Assignee: Dow Silicones Corporation (Dow, Inc.)
• Original Assignee: Dow, Inc.
• Inventors: Hilberer, Alain, Navet, Emilie, Vermeire, Laurent
• Granted Patent: US 8,053,480 B2
• Time in Patent Office: Days
• US Class Current: 524/588
• CPC Class Codes: B01D 19/04 by addition of chemical substances
• CPC Class Codes: B01D 19/0409 compounds containing Si-atoms
• CPC Class Codes: D21C 11/00 Regeneration of pulp liquors or effluent waste waters
• CPC Class Codes: D21H 21/12 Defoamers

Abstract

A process for making a foam control composition comprising a cross-linked polyorganosiloxane in which is dispersed a filler, with hydrophobic surface, comprising step (A) mixing (i) a finely divided filler, (ii) a polyorganosiloxane having on at least two reactive substituents, for example on average two reactive substituents, and (iii) a polyorganosiloxane having at least three reactive substituents, capable of addition reaction via hydrosilylation; (B) hydrosilylation reaction of components (ii) and (iii) until the mixture at least partially gels, followed by applying shearing forces to this at least partially gelled mixture. Optionally step (A) comprises a diluent or solvent and after step (B) an emulsification step is carried out to make the foam control composition into an O/W emulsion. Also a process for controlling foam in an aqueous environment by using a foam control composition according to the invention, selected from inks, coatings, paints, detergents, black liquor of from those encountered during pulp and paper manufacture, waste water treatment, textile dyeing processes or the scrubbing of natural gas.

Claims

1. A process for making a foam control composition comprising a branched or cross-linked polyorganosiloxane material in which is dispersed a finely divided filler, whose surface is hydrophobic, which comprises the steps of

A) mixing, before step (B), (i) a finely divided filler, (ii) a polyorganosiloxane having at least two reactive substituents capable of addition reaction with component (iii) via hydrosilylationQ and (iii) a polyorganosiloxane having at least three reactive substituents, capable of addition reaction with component (ii) via hydrosilylation;

B) followed by causing hydrosilylation reaction of components (ii) and (iii) in the presence of a transition metal catalyst

wherein the hydrosilylation reaction is conducted until the reaction mixture at least partially gels, and shearing forces are applied to this at least partially gelled reaction mixture.

2. A process according to claim 1, wherein the finely divided filler (i) is a silica with a surface area as measured by BET of at least 50m²/g, selected from precipitated silica and gel formation silica with a particle size of from 0.5 to 2 μ

m.

3. A process according to claim 1, wherein component (i) is added in an amount of from 2 to 15% by weight, component (ii) in an amount of from 80 to 92% by weight! and component (iii) in an amount of from 0.1 to 5% by weight based on the total weight of components (i), (ii) and (iii), and the amount of transition metal catalyst is in the range of providing 0.1 to 1000 parts per million of the metal by weight based on the combined weight of components (ii) and (iii).

4. A process according to claim 1, wherein component (ii) and component (iii) have reactive substituents selected from silicon bonded hydrogen atoms and silicon-bonded aliphatically unsaturated hydrocarbon groups, where the unsaturation is between the terminal carbon atoms of the group.

5. A process according to claim 1, wherein component (ii) is a linear polyorganosiloxane material with the reactive groups situated on the terminal silicon atoms thereof.

6. A process according to claim 4, wherein the aliphatically unsaturated hydrocarbon is a vinyl or allyl group.

7. A process according to claim 1, wherein component (iii) is selected from cyclic, linear, branched or resinous polyorganosiloxanes or a mixture including two or more of such polyorganosiloxanes, whereof the viscosity is lower than that of component (ii).

8. A process according to claim 7, wherein the resinous polyorganosiloxane for use as component (iii) has a molecular weight of no more than 15,000, has from 3 to 10 silicon-bonded reactive groups per molecule, with each being substituted on a different silicon atom.

9. A process according to claim 1, wherein the ratio of reactive groups in components (ii) and (iii) is such that on average from 3/1 to ⅓

SiH groups are used for every silicon bonded aliphatically unsaturated hydrocarbon group.

10. A process according to claim 1, wherein the foam control composition has a viscosity of from 20,000 to 100,000 mPa·

s measured at 25°

C.

11. A process according to claim 1, which also comprises in step (A) from 50 to 80% by weight of a polydiorganosiloxane as a solvent or diluent having a viscosity from 500 to 12,500 mPa·

s at 25°

C., based on the total weight of the foam control composition.

12. A process according to claim 1, wherein the foam control composition has a viscosity in the range from 40,000 to 75,000 mPa·

s at 25°

C.

13. A process according to claim 1 wherein after step (B), the foam control composition is emulsified as an oil-in-water emulsion.

14. A process according to claim 13, wherein a silicone resin having monofunctional and tetrafunctional units is added in amounts of up to 5% by weight of the total weight of the foam control composition.

15. A process for controlling foam in an aqueous environment by using a foam control composition according to claim 1, the aqueous environment being selected from inks, coatings, paints, detergents, black liquor of from those encountered during pulp and paper manufacture, waste water treatment, textile dyeing processes or the scrubbing of natural gas.

16. A process according to claim 15, where the aqueous environment has a pH of less than 3 or more than 12.

17. A process according to claim 1, wherein the shearing forces are applied to the foam control composition comprising the at least partially gelled reaction mixture through a step selected from stirring of the mixture, passing the mixture through a homogenizer, and passing the mixture through a mixer to improve its flowability.

18. A process according to claim 17, wherein the flowability of the at least partially gelled reaction mixture resulting from step (B) is improved by dispersing, redispersing or liquefying the mixture through application of the shearing forces.

19. A process according to claim 1, wherein the application of the shearing forces is applied prior to use of the foam control composition as a neat material or prior to further manipulation of the mixture resulting from step (B) to provide it in an emulsion form.

20. A process according to claim 5, wherein the aliphatically unsaturated hydrocarbon is a vinyl or allyl group.