PROCESS FOR PRETREATMENT OF PLASTIC SURFACES FOR METALLIZATION

Abstract

The invention relates to a process for coating plastics or plastic surfaces with metals, especially plastics composed of acrylonitrile/butadiene/styrene copolymers (ABS) and composed of mixtures of these copolymers with other plastics (e.g. ABS blends), wherein the process comprises the pretreatment of the plastic surfaces with a composition C (etch solution) comprising at least two different ionic liquids IL1 and IL2.

Claims

1: A process for coating plastic with one or more metals, comprising: a) pretreating the plastic with a composition C comprising at least two different ionic liquids IL1 and IL2, the first ionic liquid IL1 comprising, as cation, at least one alkylammonium cation and the second ionic liquid IL2 comprising, as cation, at least one aromatic heterocycle having a delocalized cationic charge and comprising at least one nitrogen atom; b) treating the plastic from a) with an activator composition A comprising at least one ionogenic and/or colloidal activator; c) treating the plastic from b) with an accelerator composition B comprising an acid and/or a reducing agent; d) chemically depositing a metal layer, by treating the plastic from c) with a coating composition M1 comprising at least one metal salt and at least one reducing agent; e) electrochemically coating the plastic from d) with at least one further metal layer, by electrochemically treating the plastic from d) with at least one coating composition M comprising at least one metal compound, wherein the at least one ionic liquid IL1 comprises an alkylammonium cation of formula (I) ##STR00007## 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).sub.pCH.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 the nitrogen atom in formula (I) are a saturated unsubstituted five- to seven-membered ring; X is an anion; and n is 1, 2 or 3; wherein the ionic liquid IL2 comprises, as cation, at least one cation selected from the group consisting of pyridinium cations, pyridazinium cations, pyrimidinium cations, pyrazinium cations, imidazolium cations, pyrazolium cations, thiazolium cations and triazolium cations, and wherein the composition comprises the at least two different ionic liquids IL1 and IL2 in a mass ratio of IL1 to IL2 in the range from 3 to 18.

2: The process according to claim 1, wherein the ionic liquids IL1 and IL2 are each a salt which is liquid at 100 C., 1 bar.

3: The process according to claim 1, wherein the second ionic liquid IL2 comprises, as cation, exactly one imidazolium cation.

4: The process according to claim 1, wherein the composition C comprises as the first ionic liquid IL1 methyltri(1-butyl)ammonium methylsulfate (MTBS) and as the second ionic liquid IL2 a compound selected from the group consisting of 1-ethyl-3-methylimidazolium methylsulfate, 1-ethyl-3-methylimidazolium ethylsulfate, 1-ethyl-3-methylimidazolium hydrogensulfate, 1-ethyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium methanesulfonate and 1-ethyl-3-methylimidazolium diethylphosphate.

5: The process according to claim 1, wherein the composition C comprises 50% e to 95% by weight, based on the overall composition C, of the at least one ionic liquid IL1; 5% to 50% by weight, based on the overall composition C, of the at least one ionic liquid IL2; and 0% to 45% by weight, based on the overall composition C, of at least one solvent S.

6: The process according to claim 1, wherein the composition C comprises 49% to 94% by weight, based on the overall composition C, of the at least one ionic liquid IL1; 5% to 50% by weight, based on the overall composition C, of the at least one ionic liquid IL2; and 1% to 30% by weight, based on the overall composition C, of at least one solvent S selected from the group consisting of water, propylene carbonate, polyethylene glycols, diacetin, triacetin, ethylene glycol, diethylene glycol triethylene glycol and tetraethylene glycol.

7: The process according to claim 1, wherein the plastic comprises one or more polyamides, polystyrenes or copolymers of styrene selected from styrene/acrylonitrile copolymers SAN, acrylic ester/styrene/acrylonitrile copolymers ASA and acrylonitrile/butadiene/styrene copolymers ABS, or blends and/or multicomponent plastics comprising at least two of the plastics mentioned.

8: The process according to claim 1, wherein the plastic comprises acrylonitrile/butadiene/styrene copolymer ABS or a blend and/or multicomponent plastic comprising ABS.

9: The process according to claim 1, wherein the metals comprise at least one metal selected from the group consisting of nickel, aluminium, copper, chromium, tin, zinc and alloys thereof.

10: The process according to claim 1, wherein the electrochemical coating in e) comprises: e1) electrochemically coating the plastic from d) with a layer consisting essentially of copper and/or nickel, by treating the plastic from d) with a coating composition M2 comprising at least one copper compound and/or at least one nickel compound; and e2) electrochemically coating the plastic from e1) with a layer consisting essentially of chromium, by treating the plastic from e1) with a coating composition M3 comprising at least one chromium compound.

11: A composition C for pretreatment of plastic surfaces, comprising at least two different ionic liquids IL1 and IL2, the first ionic liquid IL1 comprising, as cation, at least one alkylammonium cation and the second ionic liquid IL2 comprising, as cation, at least one aromatic heterocycle having a delocalized cationic charge and comprising at least one nitrogen atom, wherein the composition C comprises 49% to 94% by weight, based on the overall composition C, of the at least one ionic liquid IL1; 5% to 50% by weight, based on the overall composition C, of the at least one ionic liquid IL2; 1% to 30% by weight, based on the overall composition C, of at least one solvent S selected from the group consisting of water, propylene carbonate, polyethylene glycols, diacetin, triacetin, ethylene glycol, diethylene glycol, triethylene glycol and tetraethylene glycol; wherein the at least one ionic liquid IL1 comprises an alkylammonium cation of formula (I) ##STR00008## wherein R is an unbranched and unsubstituted C.sub.1-C.sub.18-alkyl, CH.sub.3O(CH.sub.2CH.sub.2).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).sub.pCH.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 the nitrogen atom in formula (I) are a saturated unsubstituted five- to seven-membered ring; X is an anion; and n is 1, 2 or 3; wherein the ionic liquid IL2 comprises, as cation, at least one cation selected from the group consisting of pyridinium cations, pyridazinium cations, pyrimidinium cations, pyrazinium cations, imidazolium cations, pyrazolium cations, thiazolium cations and triazolium cations, and wherein the composition comprises the at least two different ionic liquids IL1 and IL2 in a mass ratio of IL1 to IL2 in the range from 3 to 18.

12. (canceled)

Description

EXAMPLES

Example 1

[0309] 1.1 General Test Method for Examination of Etching Action

[0310] a) Etching of ABS

[0311] A plaque of dimensions 60302 mm made from ABS (Terluran GP 35 from Styrolution), for preliminary cleaning, is dipped into 60 mL of ethanol at room temperature for 2 minutes. Subsequently, the plaque is dipped into 2 L of stirred ionic liquid at 50 C. for 5 minutes. After etching has ended, the substrate is rinsed with water, cleaned in an ultrasound bath at 50 C. in water for 10 min and, to remove the last residues of the etch solution, rinsed under flowing water (distilled water) at room temperature for 1 minute. The etching action of the etch solutions (compositions C) is checked by means of SEM analysis and shows new structuring of the surface.

[0312] The ionic liquids used were the following compositions:

TABLE-US-00001 C1 methyltri(1-butyl)ammonium methylsulfate (MTBS) C2 mixture of methyltri(1-butyl)ammonium methylsulfate (MTBS) and 1-ethyl-3-methylimidazolium ethylsulfate (EMIM-EtSO.sub.4) in a ratio of 90:10

[0313] FIG. 1 shows the ABS surface prior to etching. FIG. 2 shows the ABS surface after the treatment with composition C2.

[0314] The above-described etching process was repeated on plaques of the ABS polymer NovodurP2MC from Styrolution. FIG. 3 shows the ABS surface after the treatment with composition C2.

[0315] b) Metallization

[0316] After the etching and rinsing, the test plaques were metallized. For this purpose, the following treatment steps were conducted:

[0317] 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.

[0318] The following products were used:

TABLE-US-00002 Activator composition A Activator U from HSO or Surtec 961 Pd from Surtec Accelerator composition B HSO Accelerator from HSO or Surtec 961 A from Surtec Coating composition M1 Electroless Nickel 601KB from HSO or Surtec 3/11D from Surtec Coating composition M Copper HD 500 from HSO or Surtec 867 from Surtec

[0319] The quality of the metal coating is determined with the aid of what is called the cross-cut test according to ISO 2409:2007.

[0320] It was found that the metal layers which were obtained using the composition C1 (with pure MTBS) have inadequate adhesion. The metal layers which were obtained using the composition C2 (MTBS/EMIN) exhibit good adhesion.

Example 2Addition of a Solvent

[0321] a) Viscosity

[0322] Various mixtures of the ionic liquids in various organic solvents were prepared by intimately mixing the components. The mixtures comprised one or more of the following components:

TABLE-US-00003 MTBS methyltri(1-butyl)ammonium methylsulfate EMIM-EtSO.sub.4 1-ethyl-3-methylimidazolium ethylsulfate PEG 200 polyethylene glycol (molecular weight 200) PC propylene carbonate (4-methyl-1,3-dioxolan-2-one)

[0323] The dynamic viscosity of the mixtures (compositions C) was measured by means of rotary viscometry to DIN 53019 at 60 C. or at 23 C. as indicated in Table 1. The compositions of the mixtures and the viscosities measured are compiled in table 1 below.

TABLE-US-00004 TABLE 1 Mixtures of IL and IL/solvent Experiment Viscosity no. Components Weight ratio [mPa*s] 1 MTBS solid 2 MTBS/EMIM-EtSO 85:15 260 (60 C.) 3 MTBS/PEG 200 80:20 80 (60 C.) 4 MTBS/EMIM-EtSO/PC 80:10:10 233 (60 C.) 5 MTBS/EMIM-EtSO/PC 75:10:15 312 (23 C.) 6 MTBS/EMIM-EtSO/PC 75:5:20 185 (23 C.)

[0324] Through the addition of a second selected ionic liquid IL2, for example EMIM, it is possible to distinctly lower the viscosity of MTBS. It was additionally found that the viscosity of the mixture of two ionic liquids IL1 and IL2 used with preference can be distinctly lowered by the addition of a suitable solvent, for example propylene carbonate.

[0325] Although the mixture according to experiment no. 3 has the lowest viscosity, it exhibits shortcomings in relation to the stability of the treated plastics.

[0326] b) Entrainment Losses

[0327] The entrainment of the etch compositions (etch solutions) owing to adhesion on the plastic surface was studied as described hereinafter:

[0328] An ABS plastic specimen (plastic plaque of dimensions 60302 mm) was dipped vertically into the various etch compositions Z according to table 2 and etched under the conditions specified. Thereafter, the plaque was removed and allowed to drip for 5 seconds. The amount of adhering etch composition is determined by gravimetric means and reported in g per m.sup.2 of plastic surface area.

TABLE-US-00005 TABLE 2 Entrainment owing to adhesion of the etch compositions C Entrainment after Experiment Weight Etch dripping no. Components C ratio conditions [g/m2] 6 MTBS/EMIM- 90:10 60 C., 10 354 EtSO4 min 7 MTBS/EMIM- 80:10:10 50 C., 7 min 187 EtSO/PC

[0329] The etch conditions have to be selected differently, since a different etch finish on the surface would otherwise arise given the different composition of the etchant.

[0330] A lower viscosity has a distinct influence on the unfavorable entrainment of etch composition and the associated loss of ionic liquid. The viscosity can be regarded as an important factor for the adhesion of the etch solutions on the plastic surface. Lowering the viscosity of the etchant can significantly reduce the entrainment of etch composition C.

[0331] The results of the crosscut test after the metallization described in 1 b showed that the addition of the solvent, for example propylene carbonate, did not have any adverse effect on the bond strength of the subsequent coatings.