PROCESS FOR METALLIZING PLASTIC SURFACES

Abstract

The invention relates to a process for coating plastic surfaces with metals, especially plastic surfaces composed of acrylonitrile/butadiene/styrene copolymers (ABS) and composed of mixtures of these copolymers with other plastics (ABS blends), using an etch solution (composition C) comprising at least one ionic liquid IL, wherein the process comprises the treating of the plastic surface after the etching with an aqueous rinse solution RS while applying ultrasound.

Claims

1. A process for coating a plastic surface with at least one metal, the process comprising: a) pretreating the plastic surface with a composition, comprising more than 50% by weight of an ionic liquid, wherein the ionic liquid is a salt which is liquid at 100 C., 1 bar; b) primary treating the plastic surface from a) with an aqueous rinse solution while applying ultrasound; c) secondary treating the plastic surface from b) with an activator composition, comprising an ionogenic activator, a colloidal activator or both of the ionogenic and the colloidal activator; d) tertiary treating the plastic surface from c) with an accelerator composition, comprising an acid, a reducing agent, or both of the acid and the reducing agent; e) chemically depositing a metal layer, by treating the plastic: surface from d) with a first coating composition, comprising a metal salt and a reducing agent; f) electrochemically coating the plastic surface from e) with at least one additional metal layer, by electrochemically treating the plastic surface from step e) with at least one second coating composition, comprising a metal compound. wherein the plastic surface is a plastic comprising a polyimide, a polystyrene, a copolymer of styrene selected from a styrene/acrylonitrile copolymer, an acrylic ester/styrene/acrylonitrile copolymer and an acrylonitrile/butadiene/styrene copolymer, or a mixture thereof and/or a multicomponent plastic comprising the plastic.

2. (canceled)

3. The process according to claim 1, wherein the ionic liquid is at least one salt having a cation selected from the group consisting of an imidazolium cation, a pyridinium cation, a pyrazolium cation and an alkylammonium cation.

4. The process according to claim 1, wherein the ionic liquid is a salt having an alkylammonium cation of formula (I): ##STR00009## wherein R is an unbranched and unsubstituted C.sub.1-C.sub.18-alkyl, CH.sub.3O(CH.sub.2CH.sub.2O).sub.pCH.sub.2CH.sub.2 or CH.sub.3CH.sub.2O(CH.sub.2CH.sub.2O).sub.pCH.sub.2CH.sub.2 with p=0 to 3; R.sup.1, R.sup.2 and R.sup.3 are each independently: a hydrogen atom, unsubstituted C.sub.1-C.sub.18-alkyl, 2-hydroxyethyl, 2-cyanoethyl, 2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(n-butoxycarbonyl)ethyl, chlorine, CH.sub.3O(CH.sub.2CH.sub.2O).sub.pCH.sub.2CH.sub.2 or CH.sub.3CH.sub.2O(CH.sub.2CH.sub.2O)CH.sub.2CH.sub.2 with p=0 to 3, or two adjacent R.sup.1, R.sup.2 and R.sup.3 radicals together with a nitrogen atom in formula (I) form a saturated unsubstituted five- to seven-membered ring; X is an anion; and n is 1, 2 or 3.

5. The process according to claim 1, wherein the ionic liquid is methyltri(1-butyl)ammonium methylsulfate.

6. The process according to claim 1, wherein the ionic liquid comprises a first ionic liquid and a second ionic liquid, the first ionic liquid comprises, as a cation, at least one an alkylammonium cation, and the second ionic liquid comprises, as a cation, an aromatic heterocycle having a delocalized cationic charge and a nitrogen atom.

7. The process according to claim 1, wherein the ionic liquid is at least one selected from the group consisting of methyltri(1-butyl)ammonium methylsulfate. 1-ethyl-3-methylimidazolium methylsulfate, 1-ethyl-3-methylimidazolium ethylsulfate, 1-ethyl-3-methylimidazolium hydrogensulfate, -ethyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium methanesulfonate and 1-ethyl-3-methylimidazolium diethylphosphate.

8. The process according to claim 1, wherein the composition comprises 1% to 30% by weight, based on an overall composition, of at least one solvent selected from the group consisting of water, propylene carbonate, polyethylene glycols, diacetin, triacetin, ethylene glycol, diethylene glycol, triethylene glycol and tetraethylene glycol.

9. The process according to claim 1, wherein the composition comprises, based on an overall composition: 49% to 94% by weight of a first ionic liquid, which comprises an alkylammonium cation; 5% to 50% by weight of a second ionic liquid comprising, as a cation, an aromatic heterocycle having a delocalized cationic charge and a nitrogen atom; and 1% to 30% by weight of at least one solvent selected from the group consisting of water, propylene carbonate, polyethylene glycols, diacetin, triacetin, ethylene glycol, diethylene triethylene glycol and tetraethylene glycol.

10. (canceled)

11. The process according to claim 1, wherein the metal is at least one selected from nickel, aluminium, copper, chromium, tin, zinc and an alloy thereof.

12. The process according to claim 1, wherein the plastic surface is a plastic comprising an acrylonitrile/butadiene/styrene copolymer, and the pretreating is carried out at a temperature in the range from 50 to 60 C. and over a period of 5 to 15 min.

13. The process according to claim 1, wherein the prim, treating in b) is carried out by dipping the plastic surface from a) into an ultrasound bath comprising the aqueous rinse solution at a power in the range from 40 to 60 watts/L, over a period of 1 to 30 min and at a temperature of 40 to 60 C., and wherein the aqueous rinse solution comprises at least 85% by weigh of water.

14. The process according to claim 1, wherein b) comprises: b1) treating the plastic surface from a) with a first aqueous rinse solution, by spraying the plastic surface with the first aqueous rinse solution or dipping the plastic surface into the first aqueous rinse solution; and b2) treating the plastic surface from b1) with a second aqueous rinse solution while applying ultrasound.

15. The process according to claim 1, wherein the electrochemical coating in step f) comprises: f1) electrochemically coating the plastic surface from e) with a layer consisting essentially of copper, nickel, or both of the copper and the nickel, by treating the plastic surface from e) with a third coating, composition, comprising a copper compound, a nickel compound, or both of the copper compound and the nickel compound; and f2) electrochemically coating the plastic surface from f1) with a layer consisting essentially of chromium, by (eating the surface from f1) with a fourth coating composition, comprising a chromium compound.

16. The process according to claim 1, wherein the plastic surface is a plastic consisting of a polyamide, a polystyrene, a copolymer of styrene selected from a styrene/acrylonitrile copolymer, an acrylic ester/styrene/acrylonitrile copolymer and an acrylonitrile/butadiene/styrene copolymer, or a mixture thereof and/or a multicomponent plastic comprising the plastic.

17. The process according to claim 12, wherein the plastic surface is a plastic consisting of an acrylonitrile/butadiene/styrene copolymer.

Description

DESCRIPTION OF THE FIGURE

[0303] The electron micrographs in FIG. 1 show ABS surfaces which have been obtained according to comparative example C1 (with a simple rinse step) (upper image) and ABS surfaces which have been obtained according to inventive example I1 with ultrasound treatment according to the invention (lower image). In examples C1 and I1, an etchant composed of MTBS:EMIM-OAc (95:5) was used. The ABS surfaces were etched at 70 C. for 10 min.

[0304] FIG. 2 shows one possible configuration of steps a) and b) of the invention. The labels here have the following meanings: [0305] (I) pretreatment bath (step a) [0306] (II) collecting vessel of the spray apparatus (step b1) [0307] (III) spray nozzles (step b1) [0308] (IV) ultrasound rinse bath (step b2) [0309] (V), (VI) filters [0310] (1) onward route of the molding to (II) [0311] (2) onward route of the molding to (IV) [0312] (3) removal of the spray solution, first spray solution [0313] (4) removal of the ultrasound bath rinse solution, second rinse solution [0314] (5) onward route of the cleaned rinse solutions [0315] (5.1), (5.2) recycling of the cleaned rinse solution to (II)/(IV) [0316] (6.1), (6.2) discharge of the plastic removed [0317] (7) discharge of a portion of the cleaned rinse solution

[0318] FIG. 2 shows one embodiment of process steps a), b1) and b2). The molding is immersed into the treatment bath (I) comprising at least one ionic liquid IL (step a). When the molding is moved onward via (1) to the spray step (spray apparatus consisting of (II) and (III)), a portion of the ionic liquid and partly dissolved plastic particles on the surface of the molding are entrained therewith. In the spray apparatus (collecting vessel (II) and spray nozzles (III)), adhering composition C is rinsed off the molding by spraying the molding with the first rinse solution RS (step b1). The spent rinse solution is collected in the collecting vessel and conducted via (3) to the filter (VI). When the molding is moved onward via (2) to the ultrasound rinse bath (IV) comprising the second rinse solution RS (step b2)), a portion of the ionic liquid and of the first rinse solution and partly dissolved plastic particles on the surface of the molding are again entrained therewith. The molding is immersed into the ultrasound bath, removed from the bath after the dwell time and sent to the further process steps. In the ultrasound bath (IV), in a continuous manner, the second rinse solution is removed from the bath via (4) and fed to the filter (V). In addition, there is a feed of cleaned rinse solution via (5), (5.1) and (5.2) to (II) and (IV). In the filters (V) and (VI), the polymer is filtered out of the spent rinse solutions and discharged. The cleaned rinse solutions are recycled via (5) to the process; a portion is discharged via (7).

[0319] The invention is illustrated in detail by the examples which follow.

EXAMPLE 1

[0320] 1.1 General Test Method for Examination of Etching Action

[0321] A plaque of dimensions 60302 mm of ABS (acrylonitrile/butadiene/styrene terpolymer Terluran GP 35 from Styrolution) is immersed at 70 C. into 2 L of stirred ionic liquid (composition C) for 10 minutes. After the etching has ended, the substrate is rinsed with water. In the inventive example, the plaque is subsequently treated in an ultrasound water bath.

[0322] The etching action is checked by means of SEM analysis and shows new structuring of the surface (see FIG. 1).

[0323] 1.2 Comparison of the Etching Outcome With and Without an Ultrasound Rinse Step

[0324] The etching steps were conducted as described above on ABS test plaques, using an etch solution composed of methyltri(1-butyl)ammonium methylsulfate (MTBS) and 1-ethyl-3-methylimidazolium acetate (EMI M-OAc) in an MTBS/EMIM weight ratio of 95:5.

[0325] After the etching step (step a)), the ABS test plaques were either immersed into a water bath at 50 C. for 10 min (C1) or treated with ultrasound (6 L of water, 280 W, corresponding to about 50 W/L, at 35 kHz) at 50 C. for 10 min (II).

[0326] The SEM images in FIG. 1 show the ABS surfaces which have been obtained according to comparative example C1 (with a simple rinse step) (upper image) and the ABS surfaces which have been obtained according to inventive example 11 with ultrasound treatment according to the invention (lower image).

[0327] In the SEM images, it is apparent that the ultrasound rinsing step gave much better removal of partly dissolved plastic particles which were partly dissolved by the etch solution. In the SEM image C1 without ultrasound treatment, voluminous porous plastic residues are clearly apparent. In the SEM image II with ultrasound treatment, such residues are entirely absent. The SEM image with ultrasound treatment shows a homogeneously etched ABS surface having a morphology of particularly good suitability for conduction of subsequent metallization steps.

EXAMPLE 2

Variation of Etch Conditions

[0328] ABS test plaques were treated by the general test method described above for examination of etching action.

[0329] The etch solution (composition C) used in all cases was a mixture of methyltri(1-butyl)ammonium methylsulfate (MTBS), 1-ethyl-3-methylimidazolium ethylsulfate (EMI M-EtSO.sub.4) and propylene carbonate (PC) in an MTBS/EMIM-ETSO.sub.4/PC weight ratio of 80:10:10. Various etch conditions (temperature and time) as described in table 2 below were established.

[0330] The etching action was checked by means of SEM analysis and shows new structuring of the surface.

[0331] After the etching and rinsing, the test plaques were metallized. For this purpose, the following treatment steps were conducted: [0332] Treatment with activator composition A.fwdarw.treatment with accelerator composition B.fwdarw.chemical electroless deposition of nickel using the coating composition M1.fwdarw.electrodeposition of copper using the coating composition M.

[0333] The following products were used: [0334] Activator composition A Activator U from HSO or Surtec 961 Pd from Surtec [0335] Accelerator composition B HSO Accelerator from HSO or Surtec 961 A from Surtec [0336] Coating composition M1 Electroless Nickel 601KB from HSO or Surtec 3/11D from Surtec [0337] Coating composition M Copper HD 500 from HSO or Surtec 867 from Surtec

[0338] The quality of the metal coating is determined with the aid of what is called the cross-cut test according to ISO 2409:2007. The results are summarized in table 1.

TABLE-US-00001 TABLE 1 Etch conditions (step a)) Experiment Temperature Treatment time No. [ C.] [min] Cross-cut test P1 45 15 inadequate adhesion P2 50 5 adhesion P3 50 7 adhesion P4 50 10 adhesion P5 65 5 inadequate adhesion P6 65 7 inadequate adhesion

[0339] It is found that, by means of a treatment of the ABS surface in step a) at a temperature of 45 C., even with an etch time of 15 min, it is not possible to obtain homogeneous structuring of the surface (P1). When the etch temperature is too low and/or the treatment time is too short, the surface is insufficiently roughened. The nucleation necessary for the metallization in the subsequent step is inadequate. It is not possible to produce a layer between the plastic surface and metal layers that has adequate adhesion (insufficient push-button effect).

[0340] At a higher etch temperature of 65 C. and/or with an excessively long etch time, the plastic surface is attacked excessively (P5 and P6), meaning that the surface is too fissured and exhibits inhomogeneous structuring.

[0341] A particularly advantageous and homogeneous surface structuring of the ABS surface was obtained in this example at a temperature in the range from 50 to 60 C., more preferably 50 to 55 C., and with a duration of 5 to 15 min (see P2 to P4). In the case of optimal etch parameters, the depressions (also called caverns) necessary for the push-button effect are formed, and the subsequent metal layers have good adhesion. The optimal etch conditions, such as time and temperature, may vary according to the type of plastic, geometry, injection molding parameters or age of the substrate.