Method of polymer surface metallization with adhesion pre-treatment

Abstract

A simple, cost-effective, chrome-free, and easy-to-maintain metallization of polymers is disclosed, specifically, an adhesion pre-treatment process before metallization of non-conductive polymers such as polyimides (PI), acrylonitrile-butadiene-styrene copolymer (ABS), its blend with polycarbonate (PC), polypropylene (PP) and, optionally, others to obtain decorative or/and functional metal coatings on polymer parts for various industries. The proposed adhesion pre-treatment process consists of a step of chrome-free and room temperature permanganate etching bath, containing inorganic acids, such as phosphoric acid or/and sulphuric acid, permanganate ions, and additionally two other compounds of copper and ammonium ions, and water, as well as a step of etched surface subsequent treatment in cobalt activation bath with a cobalt ions concentration as low as 0.035 M. The invention allows a surprising double effect, namely, to promote the coating/polymer adhesion allowing utilization of the etching bath at room temperature, and to prolong significantly the service life of the etching bath.

1 . A method of polymer surface metallization, with adhesion pre-treatment of the polymer surface before metallization, comprising steps of:
 (a) a one-step acidic permanganate etching of non-conductive polymer surface, operated at room temperature and utilized in the etching bath containing inorganic acids: phosphoric acid or/and sulphuric acid, permanganate ions, and additionally two other compounds of copper and ammonium ions;   (b) the etched surface is submersed for subsequent activation in a cobalt ions activation bath, followed by the treatment in sulphide containing bath to form a cobalt sulphide layer;   (c) metallizing the polymer surface is performed with a metallizing solution.   
     
     
         2 . The method of  claim 1 , wherein in step (a), the etching solution comprises 0.05-0.2 M potassium permanganate, 0.5-8.0 M copper sulphate, and 0.1-0.5 M ammonium sulphate in 7-12.5 M phosphoric acid. 
     
     
         3 . The method of  claim 1 , wherein in step (a), the etching solution contains 0.05-0.2 M potassium permanganate, 0.5-8.0 M copper sulphate, and 0.1-0.5 M ammonium sulphate in the mixture of 7-12.5 M phosphoric acid and 1-2 M sulphuric acid. 
     
     
         4 . The method of  claim 1 , wherein in step (a), the etching pre-treatment is utilized at room temperature of 18-25° C. for 5-20 minutes. 
     
     
         5 . The method of  claim 1 , wherein in the step (b), the cobalt activation bath comprises (g/l): CoSO 4 *7H 2 O—10 g/l, NH 4 CH 3 COOH—92 g/l, Na 2 B 4 O 7 *10H 2 O—20 g/l, and chelating agent. 
     
     
         6 . The method of  claim 5 , wherein the cobalt activation bath comprises: chelating agent selected from the group of polyhydroxylic compounds having 2-6 hydroxyl groups. 
     
     
         7 . The method of  claim 1 , wherein in step (b), the polymer surface is activated in the cobalt ions activation bath at room temperature of 18-25° C. for 1-3 minutes. 
     
     
         8 . The method of  claim 1 , wherein in step (b), formation of cobalt sulphide layer on polymer surface in sulphide containing bath comprises of 0.064 M Na 2 S. 
     
     
         9 . The method of  claim 1 , wherein in step (b), formation of cobalt sulphide layer on polymer surface is utilized at room temperature of 18-25° C. for 30 seconds. 
     
     
         10 . A polymer product comprising surface metallization, produced by the method of  claim 1 .