AQUEOUS POLYMER DISPERSIONS MODIFIED WITH SOLVENT-SOFTENED NANOPARTICLES

• US 20090012227A1
• Filed: 03/17/2008
• Published: 01/08/2009
• Est. Priority Date: 03/23/2007
• Status: Active Grant

• Current Assignee: Tremco CPG UK Ltd. (RPM International Incorporated)
• Original Assignee: Tremco Incorporated (RPM International Incorporated)
• Inventors: Galizio, Benjamin, Wang, Ge
• Granted Patent: US 8,729,173 B2
• Time in Patent Office: Days
• US Class Current: 524/501
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C08J 2333/04 esters
• CPC Class Codes: C08J 3/05 from solid polymers
• CPC Class Codes: C08L 2201/00 Properties
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C08L 2666/04 Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
• CPC Class Codes: C09D 133/08 Homopolymers or copolymers of acrylic acid esters
• CPC Class Codes: C09D 201/00 Coating compositions based on unspecified macromolecular compounds

Abstract

The mechanical properties of a polymer protective coating formed from an aqueous dispersion of a polymer having a low glass transition temperature are significantly improved by including in the dispersion solvent softened polymer nanoparticles made from a polymer having a high glass transition temperature.

Claims

1. An aqueous polymer dispersion comprising an aqueous dispersion of primary polymer particles formed from a polymer having a lower glass transition temperature, the aqueous dispersion further containing solvent softened polymer nanoparticles formed from a polymer having a higher glass transition temperature, the higher glass transition temperature being at least 10°

C. greater than the lower glass transition temperature.

2. The aqueous polymer dispersion of claim 1, wherein the aqueous polymer dispersion contains a sufficient quantity of softened polymer nanoparticles so that a protective coating formed by depositing the dispersion on a substrate and drying has better mechanical properties than an otherwise identical protective coating formed from an otherwise identical aqueous polymer dispersion except that the polymer nanoparticles in the dispersion are unsoftened.

3. The aqueous polymer dispersion of claim 1, wherein the higher glass transition temperature is at least 40°

C. greater than the lower glass transition temperature.

4. The aqueous polymer dispersion of claim 1, wherein the softened polymer nanoparticles are softened by contacting an aqueous dispersion of the polymer nanoparticles with an organic solvent.

5. The aqueous polymer dispersion of claim 1, wherein the primary polymer particles are made from a polymer having a glass transition temperature less than 10°

C.

6. The aqueous polymer dispersion of claim 5, wherein the primary polymer particles have an average particle size of about 0.1 to 2μ

, and further wherein polymer nanoparticles, before softening, have an average particle size of 50 nm or less.

7. The aqueous polymer dispersion of claim 1, wherein the aqueous polymer dispersion contains about 0.5 and 40 wt. % softened polymer nanoparticles.

8. The aqueous polymer dispersion of claim 1, wherein polymer nanoparticles are made from an acrylic polymer.

9. The aqueous polymer dispersion of claim 1, wherein the solvent softened polymer nanoparticles are formed by mixing an organic solvent with an aqueous dispersion of the nanoparticles.

10. The aqueous polymer dispersion of claim 9, wherein the mixture of the organic solvent and the aqueous dispersion of the nanoparticles is allowed to soak for 6-20 hours.

19. A polymer protective coating formed by depositing the aqueous polymer dispersion of claim 1 on a substrate and allowing the aqueous polymer dispersion to dry.

11. A process for improving the mechanical properties of a polymer protective coating formed form a primary aqueous dispersion of a polymer having a lower glass transition temperature, the process comprising including in the primary aqueous dispersion solvent softened polymer nanoparticles formed from a polymer having a higher glass transition temperature in an amount sufficient to improve the mechanical propertied of the protective coating, the higher glass transition temperature being at least 10°

C. greater than the lower glass transition temperature.

12. The process of claim 11, wherein up to 10 wt. % solvent softened polymer nanoparticles, based on the other ingredients present, are added to the primary polymer dispersion.

13. The process of claim 12, wherein 0.5 to 40 wt. % solvent softened polymer nanoparticles are added to the primary polymer dispersion.

14. The process of claim 11, wherein the higher glass transition temperature is at least 40°

C. greater than the lower glass transition temperature.

15. The process of claim 11, wherein the primary polymer particles have an average particle size of about 0.1 to 2μ

and further wherein the polymer nanoparticles, before softening, have an average particle size of 50 nm or less.

16. The process of claim 11, wherein the softened polymer nanoparticles have a glass transition temperature of 40°

C. or above, while the primary polymer particles have a glass transition temperature of 10°

C. or below.

17. The process of claim 11, wherein the solvent softened polymer nanoparticles are formed by mixing an organic solvent with an aqueous dispersion of the nanoparticles.

18. The process of claim 17, wherein the mixture of the organic solvent and the aqueous dispersion of the nanoparticles is allowed to soak for 6-20 hours.