Process for metallizing nonconductive plastic surfaces

Abstract

The present invention relates to a process for metallizing nonconductive plastics using an etching solution free of both trivalent chromium and hexavalent chromium. The etching solution is based on an sulphuric acidic solution containing a source of chlorate ions. After the treatment of the plastics with the etching solution, the plastics are metallized by means of known processes.

1 . Process for metallizing electrically nonconductive plastic surfaces of articles, comprising the process steps of:
 A) etching the plastic surface with an aqueous etching solution;   B) treating the plastic surface with a solution of a metal colloid or of a compound of a metal, the metal being selected from the metals of transition group I of the Periodic Table of the Elements and transition group VIII of the Periodic Table of the Elements, and   C) metallizing the plastic surface with a metallizing solution;   
       characterized in that the etching solution comprises a source of chlorate ions resulting in a concentration of 0.0016 to 0.12 mol/l of chlorate ions and 50-80% v/v sulfuric acid, 
       wherein the etching solution is free of chromium III ions and is free of chromium VI ions. 
     
     
         2 . Process according to  claim 1 , characterized in that the source for chlorate ions in the etching solution in process step A) is selected from sodium and potassium chlorate. 
     
     
         3 . Process according to  claim 1 , characterized in that the chlorate ion concentration ranges between 0.003 and 0.08 mol/l. 
     
     
         4 . Process according to  claim 1 , characterized in that the chlorate ion concentration ranges between 0.01 and 0.06 mol/l. 
     
     
         5 . Process according to  claim 1 , characterized in that the chlorate ion concentration ranges between 0.004 and 0.04 mol/l. 
     
     
         6 . Process according to  claim 1 , characterized in that the sulfuric acid ion concentration ranges between 60 and 70 vol. %. 
     
     
         7 . Process according to  claim 1 , characterized in that the etching solution further comprises a second oxidizing agent in an amount of 2 to 20 g/l with the standard oxidising potential exceeding that of chlorate ions. 
     
     
         8 . Process according to  claim 1 , characterized in that the etching solution further comprises phosphoric acid. 
     
     
         9 . Process according to  claim 8 , characterized in that the phosphoric acid concentration ranges between 10 and 30 vol. %. 
     
     
         10 . Process according to  claim 1 , characterized in that metal in process step B) is palladium. 
     
     
         11 . Process according to  claim 1 , characterized in that the plastic surface has been manufactured from at least one electrically nonconductive plastic and the at least one electrically nonconductive plastic is selected from an acrylonitrile-butadiene-styrene copolymer, a polyamide, a polycarbonate and a mixture of an acrylonitrile-butadiene-styrene copolymer with at least one further polymer. 
     
     
         12 . Process according to  claim 1 , characterized in that the following further process step is performed between process steps A) and B):
 A i) treating the plastic surface in a solution comprising a reducing agent for chlorate ions.   
     
     
         13 . Process according to  claim 12 , characterized in that the reducing agent is selected from hydroxylammonium sulphate, hydroxylammonium chloride and hydrogen peroxide. 
     
     
         14 . Process according to  claim 1 , characterized in that the following further process step is performed between process steps A) and B):
 A i) treating the plastic surface in a solution comprising a neutralizing agent comprising a source of hydroxide ions.   
     
     
         15 . Process according to  claim 1 , characterized in that the following further process steps are performed between process steps B) and C):
 B i) treating the plastic surface in an aqueous acidic solution and   B ii) electrolessly metallizing the plastic surface in a metallizing solution.   
     
     
         16 . Process according to  claim 12 , characterized in that the following further process steps are performed between process steps B) and C):
 B i) treating the plastic surface in an aqueous acidic solution and   B ii) electrolessly metallizing the plastic surface in a metallizing solution.   
     
     
         17 . Process according to  claim 14 , characterized in that the following further process steps are performed between process steps B) and C):
 B i) treating the plastic surface in an aqueous acidic solution and   B ii) electrolessly metallizing the plastic surface in a metallizing solution.   
     
     
         18 . Process according to  claim 14 , characterized in that the following further process step is performed between process steps A) and B):
 A ii) treating the plastic surface in a solution comprising a neutralizing agent comprising a source of hydroxide ions.   
     
     
         19 . Process according to  claim 18 , characterized in that the following further process steps are performed between process steps B) and C):
 B i) treating the plastic surface in an aqueous acidic solution and   B ii) electrolessly metallizing the plastic surface in a metallizing solution.