PROCESS FOR METALLIZING NONCONDUCTIVE PLASTIC SURFACES
The present invention relates to a process for metallizing nonconductive plastics using an etching solution free of hexavalent chromium. The etching solution is based on an acidic permanganate solution. 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 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 for permanganate ions, and an acid in a concentration of 0.02-0.6 mol/l based on a monobasic acid.
2 . Process according to claim 1 , wherein process step A) is preceded by performance of the following further process step:
pretreatment step: treating the plastic surface in an aqueous solution comprising at least one glycol compound.
3 . Process according to claim 2 , wherein the at least one glycol compound is selected from compounds of the general formula (I)
wherein
n is an integer from 1 to 4; and
R 1 and R 2 are each independently —H, —CH 3 , —CH 2 —CH 3 , —CH 2 —CH 2 —CH 3 , —CH(CH 3 )—CH 3 , —CH 2 —CH 2 —CH 2 —CH 3 , —CH(CH 3 )—CH 2 —CH 3 , —CH 2 —CH(CH 3 )—CH 3 , —CH 2 —CH 2 —CH 2 —CH 2 —CH 3 , —CH(CH 3 )—CH 2 —CH 2 —CH 3 , —CH 2 —CH(CH 3 )—CH 2 —CH 3 , —CH 2 —CH 2 —CH(CH 3 )—CH 3 , —CH(CH 2 —CH 3 )—CH 2 —CH 3 , —CH 2 —CH(CH 2 —CH 3 )—CH 3 , —CO—CH 3 , —CO—CH 2 —CH 3 , —CO—CH 2 —CH 2 —CH 3 , —CO—CH(CH 3 )—CH 3 , —CO—CH(CH 3 )—CH 2 —CH 3 , —CO—CH 2 —CH(CH 3 )—CH 3 , —CO—CH 2 —CH 2 —CH 2 —CH 3 .
4 . Process according to claim 1 , wherein the source for permanganate ions in the etching solution in process step A) is selected from alkali metal permanganates.
5 . Process according to claim 4 , wherein the alkali metal permanganates are selected from the potassium permanganate and sodium permanganate.
6 . Process according to claim 1 , wherein the source for permanganate ions is present in the etching solution in process step A) in a concentration between 30 g/l-250 g/l.
7 . Process according to claim 1 , wherein the acid comprised in the etching solution in process step A) is an inorganic acid.
8 . Process according to claim 7 , wherein the inorganic acid in the etching solution in process step A) is selected from sulphuric acid, nitric acid and phosphoric acid.
9 . Process according to claim 1 , wherein 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.
10 . Process according to claim 1 , wherein 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 manganese dioxide.
11 . Process according to claim 10 , wherein the reducing agent for manganese dioxide is selected from hydroxylammonium sulphate, hydroxylammonium chloride and hydrogen peroxide.
12 . Process according to claim 1 , wherein 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.
13 . Process according to claim 2 , wherein 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 manganese dioxide.
14 . Process according to claim 2 , wherein 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.
15 . Process according to claim 10 , wherein 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 13 , wherein 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.