Stabilizing Additives For Thermochromic Pigments

Abstract

A microencapsulation process is improved by adding a stabilizing agent that contains one or more catalytic organo-metal oxide materials, such as metal soaps. This functions as a crosslinker by causing unsaturated bonds in the microcapsule walls to react, thereby stabilizing the microcapsules against the effects of additives to coatings that, otherwise, degrade the functionality of thermochromic or photochromic materials at the microcapsule core.

Claims

1-37. (canceled)

38. A slurry comprising: a photochromic or thermochromic material encapsulated within a microcapsule; a solvent-based vehicle; and a stabilizing agent comprising a metallocene catalyst or transition metal bonded to at least one organic moiety through an oxygen linkage; wherein said stabilizing agent is effective to stabilize said photochromic or thermochromic material encapsulated within said microcapsule against deleterious effects of said solvent-based vehicle.

39. The slurry of claim 38, wherein said transition metal comprises zirconium.

40. The slurry of claim 39, wherein said zirconium comprises zirconium 2-ethylhexanoate.

41. The slurry of claim 38, wherein said microcapsule is cured.

42. The slurry of claim 38, wherein said stabilizing agent protects a color activation temperature of said photochromic or thermochromic material encapsulated within said microcapsule in said solvent-based vehicle.

43. The slurry of claim 38, wherein a cured coating comprising said thermochromic material encapsulated within said microcapsule, said solvent-based vehicle, and said stabilizing agent does not show a temperature repression for full color development.

44. The slurry of claim 38, wherein said solvent-based vehicle comprises a polymer.

45. The slurry of claim 44, wherein said polymer is formulated for application as an external coating on metal.

46. The slurry of claim 45, wherein said metal comprises coiled aluminum stock.

47. The slurry of claim 45, wherein said metal is intended to form a beverage can.

48. The slurry of claim 38, wherein said solvent-based vehicle comprises at least one polar solvent.

49. A slurry comprising: a photochromic or thermochromic material encapsulated within a microcapsule; a solvent-based vehicle; and a stabilizing agent comprising a melamine resin; wherein said stabilizing agent is effective to stabilize said photochromic or thermochromic material encapsulated within said microcapsule against deleterious effects of said solvent-based vehicle.

50. The slurry of claim 49, wherein said microcapsule is cured.

51. The slurry of claim 49, wherein said stabilizing agent protects a color activation temperature of said photochromic or thermochromic material encapsulated within said microcapsule in said solvent-based vehicle.

52. The slurry of claim 49, wherein a cured coating comprising said thermochromic material encapsulated within said microcapsule, said solvent-based vehicle, and said stabilizing agent does not show a temperature repression for full color development.

53. The slurry of claim 49, wherein said solvent-based vehicle comprises a polymer.

54. The slurry of claim 53, wherein said polymer is formulated for application as an external coating on metal.

55. The slurry of claim 54, wherein said metal comprises coiled aluminum stock.

56. The slurry of claim 54, wherein said metal is intended to form a beverage can.

57. The slurry of claim 49, wherein said solvent-based vehicle comprises at least one polar solvent.

Description

DETAILED DESCRIPTION

[0012] The following embodiments teach by way of example and not by limitation.

EXAMPLE

[0013] Thermochromic microcapsules are incorporated into a solvent based high molecular weight epoxy coating where the solvent package contains polar solvents such as methyl isobutyl ketone, 2-butoxy ethanol, and n-butanol for example. The coating is then cured at a temperature above 200 C. for a duration of 10 seconds to 30 seconds. In the absence of the stabilizing agent, the temperature profile of the thermochromic system is significantly repressed so that the full color development cannot be attained unless the coated sample is subjected to sub-zero temperatures for a period of time. By the addition of stabilizing additives such as a melamine resin (Cymel 303), metallic salts (zirconium ethyl hexanoate), and other agents which can accelerate crosslinking in the resin system surrounding the microcapsules, the microcapsule wall becomes more stable thus protecting the internal thermochromic properties. The effect is that the cured coating does not show a temperature repression for the full color development, even in the presence of the strongly polar solvents which are known to be harmful to the thermochromic properties of microcapsules. The effect of the stabilizing additive can be significant at concentrations of 0.5-15% by weight of the thermochromic coating.