Chromium-free plating-on-plastic etch
The present invention relates to a chrome free etch for plating on plastic processes, wherein plastic surfaces are contacted in a first etching step with an etching solution at least comprising Mn(IV)-ions and, in a second etching step, with a solution at least comprising Mn(III)- and Mn(VII)-ions prior to the metal plating step.
1. Process for metallization of plastic surfaces at least comprising the steps of
a) Cleaning,
b) Etching,
c) Rinsing,
d) Activation and
e) Metallization,
characterized in that
etching step b) is a two-stage process, wherein in a first etching step b1) the plastic surfaces are contacted with a first etching solution at least comprising Mn(IV)-ions and, in a second etching step b2), the plastic surfaces are contacted with an etching solution at least comprising Mn(III)- and Mn(VII)-ions;
wherein the concentration of the Mn(IV)-ions in the first etching step b1) is ≥0.5 g/l and ≤15 g/l and the concentration of the Mn(III)- and Mn(VII)-ions in the second etching step b2) is ≥0.05 g/l and ≤20 g/l; and
wherein the Mn(IV)-ion concentration in etching step b1) and the Mn(III)- and Mn(VII)-ion concentration in etching step b2) is adjusted electrochemically by oxidation of solutions at least comprising one or more Mn(II)-salts.
2. Process according to claim 1 , wherein the bath temperature in the first etching step b1) is ≥20° C. and ≤60° C. and bath temperature in the second etching step b2) is ≥30° C. and ≤80° C.
3. Process according to claim 1 , wherein the pH of both etchings solutions in the etching steps b1) and b2) is ≤1.0.
4. Process according to claim 1 , wherein the etching solutions in step b1) and b2) each at least comprise an acid selected from the group consisting of phosphoric acid, sulfuric acid, methanesulfonic acid or combinations thereof.
5. Process according to claim 1 , wherein the bath of etching step b1) further comprises a metal-ion selected from the group consisting of Ag, Bi, Pd, Co or mixtures thereof.
6. Process according to claim 5 , wherein the concentration of the further metal-ion in the bath of etching step b1) is ≥50 mg/l and ≤1000 mg/i.
7. Process according to claim 1 , wherein the density of the etching baths in etching step b1) and b2) is ≥1.5 g/cm 3 and ≤1.8 g/cm 3 .
8. Process according to claim 1 , wherein the overall Mn-concentration of the bath in etching step b1) is ≥3.0 g/l and ≤20.0 g/l and in etching step b2) is ≥0.1 g/l and ≤25.0 g/l.
9. Process according to claim 1 , wherein the Mn(II)-salt in the baths of etching step b1) and b2) is selected from the group consisting of Mn(II)sulfate, Mn(II)methanesulfonate, Mn(II)methanedisulfonate or mixtures thereof.
10. The process according to claim 1 , wherein the first etching solution additionally comprises a stabilizer selected from the group consisting of N′-(2-aminoethyl)ethane-1,2-diamine, dimethyl-bis(oxiran-2-ylmethyl)azanium, hexanedioic acid, chloride or mixtures thereof.
11. The process according to claim 1 , wherein the steps are performed in order.