Polyamide-based powder and its use for obtaining an antibacterial coating

Abstract

The present invention relates to the use of a powder for coating articles, this powder comprising, by weight, 99.8 to 97% of at least one polyamide and 0.2 to 3% of a soluble ceramic in which silver ions are encapsulated. This powder may be prepared by simple dry-blending of the constituents. The invention also relates to this powder. The ceramic protects the Ag ions from the temperature during application and use of the product, from UV radiation and from other components present in the formulation. It is the presence of moisture on the surface of the coating, needed for bacterial growth, which causes silver ions to be released and therefore the bacteria to be eliminated. This composition contains an inorganic biocide using silver ions as sole active metal species. This powder paint has the advantage of being able to be applied at temperatures above 300° C. without any undesirable discoloration problems and without the use of zinc compounds. The side reactions caused by the silver species are therefore avoided by the choice of an encapsulation in a soluble ceramic which effectively protects the Ag+ metal ions from the temperature and UV light, but also from the other compounds of the formulation.

Description

[0001] This application claims benefit, under U.S.C. §119(a) of French National Application Number 03.14305, filed Dec. 5, 2003; and also claims benefit, under U.S.C. § 119(e) of U.S. provisional application 60 / 540,482, filed Jan. 30, 2004.FIELD OF THE INVENTION [0002] The present invention relates to a polyamide-based powder and its use for coating articles. It is useful in processes for covering an article with a film formed from the melting of a thin layer of powder deposited beforehand on the article. More precisely, the powder of the invention is a blend of polyamide on the one hand, and silver ions encapsulated in a soluble ceramic on the other. BACKGROUND OF THE INVENTION [0003] Currently, there are several industrial methods for covering an article by the melting of a polymer. [0004] The first method is electrostatic powder coating, which consists in charging the powder with static electricity and bringing it into contact with the article to be covered, connected to zero pot...

AI Technical Summary

Benefits of technology

[0016] This powder may be prepared by simple dry blending of the constituents.

[0018] The ceramic protects the Ag ions from the temperature during application and use of the product, from UV radiation and from the other components present in the formulation. It is the presence of moisture on the surface of the coating, necessary for bacteria to grow, which releases silver ions and therefore eliminates the bacteria.

[0033] The invention described above has many advantages. The polyamide powder paint composition applied to a metal surface, either by electrostatic powder coating or by fluidized-bed dip coating or by not spraying, gives it lasting antibacterial properties. This composition contains an inorganic biocide using silver ions as the only metallic species. This powder paint has the advantage of being able to be applied at temperatures above 300° C. without undesirable discoloration problems and without the use of zinc compounds. The side reactions caused by the silver species are therefore avoided by choosing an encapsulation in a soluble ceramic that effectively protects the silver ions from temperature and UV light, but also the other components of the formulation.

Problems solved by technology

However, experience shows that repeated cleaning does not prevent many infections in hospitals.

Their inferior thermal stability at 300° C. prevents them from withstanding the very severe conditions associated with the processing of polyamides.

In addition, since their activity is obtained by migration of the biocide through the polymer, this rapidly decreases over time.

However, since silver ions are very reactive, this type of biocide may easily interact with the polymers to which they have been added and also with the additives and fillers possibly contained in these polymers, and cause discoloration problems.

In the case of polyamide-based powder paints, the processing temperatures, especially when they are applied by dipping, make the choice of biocide very difficult.

Most inorganic compounds (silver-exchanged zeolites or silver-exchanged zirconium phosphates, for example) result in substantial and undesirable colour changes on the surface.