Use of surfactants for improving the compatibility of inorganic pigments in aqueous coating compositions

• US 6,638,998 B2
• Filed: 04/18/2001
• Issued: 10/28/2003
• Est. Priority Date: 04/18/2001
• Status: Expired due to Term

• Current Assignee: BASF AG (BASF SE)
• Original Assignee: BASF AG (BASF SE)
• Inventors: Zhao, Cheng-Le, Dittrich, Uwe
• Primary Examiner(s): NILAND, PATRICK DENNIS
• Application Number:
  US09/837,034
• Publication Number:
  US 20030022970A1
• Time in Patent Office: 923 Days
• Field of Search: 524/127, 524/141
• US Class Current: 524/127
• CPC Class Codes: C09D 5/027 Dispersing agents anti-settling agents C09D7/45

Abstract

The present invention is an aqueous coating composition and method of preparing same that uses certain polyoxyalkylene phosphate surfactants to increase the compatibility of inorganic pigments such as TiO₂ with latex polymer binders to reduce the clustering of the inorganic pigment particles in the aqueous coating composition. The aqueous coating composition of the invention includes at least one polyoxyalkylene phosphate surfactant having the following structure:

wherein m is 1 or 2, n is an integer from 1 to 100, R¹ is C1-C5 alkyl, O—R² is an alkylphenol residue wherein R² has the structure C₆H₄—C_pH_2p+1 or O—R² is a linear or branched alkyl alcohol residue wherein R² has the structure C_pH_2p+1, and p is an integer from 1 to 30. The aqueous composition further includes at least one latex polymer, at least one inorganic pigment and water.

Claims

1. A aqueous coating composition, comprising:

(a) at least one polyoxyalkylene phosphate surfactant having the following structure;

wherein m is 1 or 2, n is an integer from 1 to 100, R¹ is C1-C5 alkyl, O—

R² is an alkylphenol residue wherein R² has the structure C₆H₄—

C_pH_2p+1 or O—

R² is a linear or branched alkyl alcohol residue wherein R² has the structure C_pH_2p+1, and p is an integer from 1 to 30, with the proviso that R¹ is not only C2 alkyl and that R¹ is not only C2 alkyl and C3 alkyl;

(b) at least one latex polymer;

(c) at least one inorganic pigment; and

(d) water.

2. The composition according to claim 1, wherein R¹ is selected from the group consisting of C1 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, and combinations thereof.

3. The composition according to claim 1, wherein n is from 2 to 30.

4. The composition according to claim 1, wherein n is from 3 to 15.

5. The composition according to claim 1, wherein p is an integer from 8 to 18.

6. The composition according to claim 1 further comprising a polyoxyethylene surfactant having the following structure:

wherein m is 1 or 2, n is an integer from 1 to 100, and O—

R² is an alkylphenol residue wherein R² has the structure C₆H₄—

C_pH_2p+1 or O—

R² is a linear or branched alkyl alcohol residue wherein R² has the structure C_pH_2p+1, and p is an integer from 1 to 30.

7. The composition according to claim 6, wherein the the polyoxyethylene surfactant has the following structure:

wherein m is 1 or 2, n is an integer from 2 to 30, and O—

R is at least one of i) an alkylphenol residue wherein R has the structure C₆H₄—

C_pH_2p+1 and p is an integer from 8 to 18, and ii) an alkyl alcohol residue wherein R has the structure C_pH_2p+1 and p is an integer from 8 to 18.

8. The composition according to claim 1, wherein R² is nonylphenyl or tridecyl.

9. The composition according to claim 1, wherein the inorganic pigment is selected from the group consisting of TiO₂, clay, CaCO₃, talc, barytes, zinc oxide and zinc sulfite.

10. The composition according to claim 1, wherein the inorganic pigment includes TiO₂.

11. The composition according to claim 1, wherein the surfactant is incorporated in the latex.

12. The composition according to claim 1, wherein the at least one latex polymer is selected from the group consisting of pure acrylics, styrene acrylics, vinyl acrylics and acrylated ethylene vinyl acetate copolymers.

13. The composition according to claim 1, wherein the at least one latex polymer includes a pure acrylic.

14. The composition according to claim 13, wherein the at least one latex polymer is derived from at least one acrylic monomer selected from the group consisting of acrylic acid, acrylic acid esters, methacrylic acids, and methacrylic acid esters.

15. The composition according to claim 14, wherein the at least one latex polymer is further derived from one or more monomers selected from the group consisting of styrene, α

-methyl styrene, vinyl chloride, acrylonitrile, methacrylonitrile, ureido methacrylate, vinyl acetate, itaconic acid, crotonic acid, maleic acid, fumaric acid, ethylene, and C4-C8 conjugated dienes.

16. The composition according to claim 1, further comprising at least one anti-freezing agent.

17. The composition according to claim 1, further comprising one or more additives selected from the group consisting of plasticizers, drying retarders, dispersants, surfactants or wetting agents, rheology modifiers, defoamers, thickeners, coalescing agents, biocides, mildewcides, colorants, waxes, perfumes and co-solvents.

18. The composition according to claim 1, wherein the latex polymer is a butyl acrylate/methyl methacrylate copolymer.

19. A method of preparing a aqueous coating composition, comprising the step of:

mixing at least one polyoxyalkylene phosphate surfactant having the following structure;

wherein m is 1 or 2, n is an integer from 1 to 100, R¹ is C1-C5 alkyl, O—

R² is an alkylphenol residue wherein R² has the structure C₆H₄—

C_pH_2p+1 or O—

R² is a linear or branched alkyl alcohol residue wherein R² has the structure C_pH_2p+1, and p is an integer from 1 to 30, with the proviso that R¹ is not only C2 alkyl and that R¹ is not only C2 alkyl and C3 alkyl;

at least one latex polymer; and

at least one inorganic pigment.

20. The method according to claim 19, wherein said mixing step comprises mixing at least one inorganic pigment in slurry form.

21. The method according to claim 20, wherein said mixing step comprises blending the surfactant with the at least one inorganic pigment in slurry form prior to mixing the surfactant and at least one inorganic pigment with the at least one latex polymer.

22. The method according to claim 19, wherein said mixing step comprises mixing at least one surfactant wherein R¹ is selected from the group consisting of C1 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, and combinations thereof.

23. The method according to claim 19, wherein said mixing step comprises mixing at least one surfactant wherein n is from 2 to 30.

24. The method according to claim 19, wherein said mixing step comprises mixing at least one surfactant wherein n is from 3 to 15.

25. The method according to claim 19, wherein said mixing step comprises mixing at least one surfactant wherein p is an integer from 8 to 18.

26. The method according to claim 19, wherein said mixing step further comprises mixing at least one polyoxyethylene surfactant having the following structure:

where m is 1 or 2, n is an integer from 1 to 100, and O—

R² is an alkylphenol residue wherein R² has the structure C₆H₄—

C_pH_2p+1 or O—

R² is a linear or branched alkyl alcohol residue wherein R² has the structure C_pH_2p+1, and p is an integer from 1 to 30.

27. The method according to claim 26, wherein the polyoxyethylene surfactant has the following structure:

where m is 1 or 2, n is an integer from 2 to 30, and O—

R is at least one of i) an alkylphenol residue wherein R has the structure C₆H₄—

C_pH_2p+1 and p is an integer from 8 to 18, and ii) is an alkyl alcohol residue wherein R has the structure C_pH_2p+1 and p is an integer from 8 to 18.

28. The method according to claim 19, wherein said mixing step comprises mixing at least one surfactant wherein R² is nonylphenyl or tridecyl.

29. The method according to claim 19, wherein said mixing step comprises mixing at least one inorganic pigment wherein the inorganic pigment is selected from the group consisting of TiO₂, clay, CaCO₃, talc, barytes, zinc oxide and zinc sulfite.

30. The method according to claim 19, wherein the inorganic pigment includes TiO₂.

31. The method according to claim 19, wherein said mixing step comprises mixing at least one latex polymer selected from the group consisting of pure acrylics, styrene acrylics, vinyl acrylics and acrylated ethylene vinyl acetate copolymers.

32. The method according to claim 19, wherein the at least one latex polymer includes a pure acrylic.

33. The method according to claim 19, wherein the at least one latex polymer is derived from at least one acrylic monomer selected from the group consisting of acrylic acid, acrylic acid esters, methacrylic acids, and methacrylic acid esters.

34. The method according to claim 33, wherein the at least one latex polymer is further derived from one or more monomers selected from the group consisting of styrene, α

-methyl styrene, vinyl chloride, acrylonitrile, methacrylonitrile, ureido methacrylate, vinyl acetate, itaconic acid, crotonic acid, maleic acid, fumaric acid, ethylene, and C4-C8 conjugated dienes.

35. The method according to claim 19, wherein said mixing step comprises further mixing at least one anti-freezing agent.

36. The method according to claim 19, wherein said mixing step comprises further mixing at least one additive selected from the group consisting of plasticizers, drying retarders, dispersants, surfactants or wetting agents, rheology modifiers, defoamers, thickeners, coalescing agents, biocides, mildewcides, colorants, waxes, perfumes and co-solvents.

37. The method according to claim 19, further comprising the step of preparing the polymer latex binder using emulsion polymerization by feeding monomers to a reactor in the presence of at least one initiator and the at least one surfactant and polymerizing the monomers to produce the latex binder, wherein said mixing step comprises mixing the at least one inorganic pigment with the resulting latex binder to prepare the aqueous coating composition.

38. The method according to claim 37, wherein said step of preparing the polymer latex binder comprises:

preparing an initiator solution comprising the initiator;

preparing a monomer pre-emulsion comprising monomers and the surfactant;

adding the initiator solution to a reactor; and

adding the monomer pre-emulsion to the reactor.

39. The method according to claim 38, wherein at least a portion of said initiator solution is added to the reactor prior to adding the monomer pre-emulsion.

40. The method according to claim 38, further comprising the step of adding a seed latex to the reactor prior to adding the initiator and adding the monomer pre-emulsion.

41. The method according to claim 38, further comprising the step of chemically stripping the latex binder by adding a peroxide and a reducing agent to the latex binder thereby decreasing the residual monomer content of the latex binder.

42. The method according to claim 38, wherein said preparing step comprises feeding monomers to a reactor comprising at least one acrylic monomer selected from the group consisting of acrylic acid, acrylic acid esters, methacrylic acids, and methacrylic acid esters.

43. The method according to claim 39, wherein said preparing step comprises feeding monomers to a reactor further comprising one or more monomers selected from the group consisting of styrene, α

-methyl styrene, vinyl chloride, acrylonitrile, methacrylonitrile, ureido methacrylate, vinyl acetate, itaconic acid, crotonic acid, maleic acid, fumaric acid, ethylene, and C4-C8 conjugated dienes.

44. In a method for limiting the clustering of TiO₂ particles in a aqueous coating composition comprising a polymer latex and water, the improvement comprising adding at least one polyoxyalkylene phosphate surfactant having the following structure:

wherein m is 1 or 2, n is an integer from 1 to 100, R¹ is C1-C5 alkyl, O—

R² is an alkylphenol residue wherein R² has the structure —

C₆H₄—

C_pH_2p+1 or O—

R² is a linear or branched alkyl alcohol residue wherein R² has the structure —

C_pH_2p+1 and p is an integer from 1 to 30, with the proviso that R¹ is not only C2 alkyl and that R¹ is not only C2 alkyl and C3 alkyl, to the aqueous coating composition.