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.

1 . A powder composition for coating articles 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.  
     
     
         2 . The powder composition according to  claim 1 , in which the polyamide is chosen from PA-11 and PA-12.  
     
     
         3 . The powder composition according to  claim 1 , in which the powder comprises, by weight, 99.5 to 99% of at least one polyamide and 0.5 to 1% of a soluble ceramic in which silver ions are encapsulated.  
     
     
         4 . The powder composition according to  claim 1 , in which the proportion of silver ions in the ceramic is between 1 and 10% by weight.  
     
     
         5 . The powder composition according to  claim 4 , in which the proportion of silver ions in the ceramic is between 3 and 6% by weight.  
     
     
         6 . Method of covering an article with a film formed from the melting of a thin layer of powder, comprising: 
 a) charging a 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 to form an electrified powder by any means;    b) bringing the article and powder into contact with each other, the article being connected to zero potential or a potential sufficient to cover it with powder; and    c) placing the powder-covered article in an oven at a temperature high enough to melt the thin layer of powder to obtain a coating film.    
     
     
         7 . Method of covering an article with a film formed from the melting of a thin layer of powder comprising: 
 a) placing the powder in fluidized bed form, wherein the powder comprises 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;    b) heating the article to be covered to a temperature high enough for the powder to melt on contact with it;    c) dipping the article into the fluidized bed for a time long enough for it to be covered with powder; and    d) withdrawing the article from the fluidized bed.    
     
     
         8 . Method of covering an article with a film formed from the melting of a thin layer of powder comprising: 
 a) heating the article to be covered to a temperature high enough for the powder to melt on contact with it; and    b) spraying the powder onto the article so that it is covered with powder, wherein said powder comprises 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.    
     
     
         9 . Articles having an antibacterial coating, obtained by the use of the powder according to  claim 1.