Process for metallization of an article having a plastic surface avoiding the metallization of the rack which fixes the article within the plating bath

Abstract

The invention refers to a process for metallization of an article having a plastic surface avoiding the metallization of the rack which fixes the article within the plating bath.

Claims

1. A process for metallization of an article having a plastic surface comprising the steps of: a) fastening the article to a rack; b) etching the plastic surface with an aqueous etching solution free of Cr.sup.6+, c) treating the etched plastic surface with a reducing agent; and d) metalizing the treated plastic surface; wherein, after step c) or during step c), the plastic surface of the article and the rack are treated with an aqueous acidic rack conditioning solution which comprises water, at least one organosulfur compound, and at least one inorganic acid at a temperature from 25 C. to 70 C.

2. The process according to claim 1, wherein the at least one organosulfur compound is an organosulfur compound containing bivalent sulphur.

3. The process according to claim 2, wherein the organosulfur compound is represented by the formula RSH, wherein R represents an organic group.

4. The process according to claim 2, wherein the organosulfur compound is selected from the group consisting of dithiocarbamates, 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 3-mercaptopropansulfonic acid sodium salt, thioglycolic acid, 3-(benzothiazolyl-2-mercapto)propyl sulfonic acid sodium salt, and mixtures thereof.

5. The process according to claim 1, wherein the at least one inorganic acid in the rack conditioning solution is selected from the group consisting of hydrochloric acid, sulphuric acid, phosphoric acid, and mixtures thereof.

6. The process according to claim 5, wherein the at least one inorganic acid is hydrochloric acid wherein the concentration of the hydrochloric acid in the rack conditioning solution is from 0.01 to 2 mol/L.

7. The process according to claim 1, wherein the reducing agent is added as a separate step by treating the rack with an aqueous reducing solution or the treatment is simultaneous to the treatment with the rack conditioning solution by adding the reducing agent to the rack conditioning solution.

8. The process according to claim 1, wherein the reducing agent is suitable to chemically reduce manganese compounds.

9. The process according to claim 8, wherein the reducing agent is selected from the group consisting of compounds having a hydroxylamine group, ascorbic acid, hydrazine, thiosulfate salts, and mixtures thereof.

10. The process according to claim 1, wherein the rack conditioning solution further comprises at least one thickening agent.

11. The process according to claim 10, wherein the at least one thickening agent is selected from the group consisting of polyvinyl alcohol, PEG, sodium alginate, polysaccharides, agarose, carboxymethylcellulose, and mixtures thereof.

12. The process according to claim 1, wherein the aqueous rack conditioning solution and/or an aqueous reducing solution comprising the reducing agent has a temperature of 25 to 70 C.; and/or the plastic surface is treated with the aqueous rack conditioning solution and/or aqueous reducing solution for 0.1 to 15 min.

13. The process according to claim 1, wherein the etching solution comprises KMnO.sub.4 and phosphoric acid.

14. The process according to claim 1, wherein the plastic surface of the article at least partially comprises or consists of a plastic selected from the group consisting of acrylonitrile-butadiene-styrene, acrylonitrile-butadiene-styrene blends, polypropylene and mixtures thereof.

15. The process according to claim 1, wherein the rack does not comprise a plastic surface identical to the plastic surface of the article.

16. The process according to claim 1, wherein, before step b), the plastic surface is cleaned with a cleaning solution.

17. The process according to claim 1, wherein, after any one or all of steps a) to d) and the treatment with the rack conditioning solution the plastic surface is rinsed with water.

18. The process according to claim 1, wherein the metalizing of the treated plastic surface comprises at least one of the steps of: i) treating the plastic surface with an aqueous acidic catalyst solution; ii) treating the plastic surface with an aqueous acidic accelerator solution; and iii) treating the plastic surface with an aqueous alkaline solution for electroless deposition of a metal; and electrolytically depositing a metal on the surface having electroless-deposited metal.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

(1) FIG. 1 depicts the results of Examples 1-10.

(2) FIG. 2 depicts the results of Examples 11-14.

(3) FIG. 3 depicts the results of Examples 15-17.

(4) FIG. 4 depicts the SEM pictures obtained on the ABS and PVC surfaces immediately after rinse of the reduction step (Example 15).

(5) FIG. 5 depicts the SEM pictures obtained on the ABS and PVC surfaces immediately after rinse of the reduction/rack conditioning step (Example 16).

(6) FIG. 6 depicts the SEM pictures obtained on the ABS and PVC surfaces immediately after rinse of the reduction/rack conditioning step (Example 17).

DETAILED DESCRIPTION OF THE INVENTION

(7) With reference to the following examples, the subject-matter according to the invention is intended to be explained in more detail without wishing to restrict said subject-matter to the specific embodiments shown here.

(8) The Solutions Used in the Successive Examples have the Following Composition:

(9) Cleaning: SILKEN CLEANER 201 (Coventya), 40 mL/L in water, 3 min at 45 C.; Swelling: SILKEN CLEANER 202 (Coventya), 140 mL/L in water, 3 min at 45 C.; Rack conditioning: 0.1 mol/L phosphoric acid, 0.1 g/L carboxymethyl-cellulose, 0.2 g/L 2-mercaptobenzothiazole, 3 min at 45 C.; Etching: SILKEN BOND ETCH PART A (Coventya) 12 mL/L (0.3 g/L KMnO.sub.4), H.sub.3PO.sub.4 620 mL/L, SILKEN BOND ETCH PART C (Coventya) (STABILIZER) 340 mL/L, 12 min at 65 C.; Reduction: 12 g/L hydroxylamine sulfate, 1.2 mol/L hydrochloric acid, 3 min at 55 C.; Reduction/Rack Conditioning: 6 g/L Hydroxylamine sulfate, 0.2 mol/L hydrochloric acid, 0.1 g/L carboxymethylcellulose, 0.2 g/L 2-mercapto-benzothiazole, 3 min at 55 C.; Conditioner: SILKEN BOND CONDITIONER (Coventya) 10 mL/L, 1 min 25 C.; Catalyst: SILKEN CATALYST 501 (Coventya) 10 mL/L (40 ppm colloidal Pd), 250 mL/L HCl 32%, 3 min 30 C.; Accelerator: SILKEN ACCELERATOR (Coventya) 601 50 g/L, 25 mL/L sulfuric acid 96%, 2 min 40 C.; Electroless dep.: Electroless Nickel as process SILKEN METAL 706 (Coventya) with ammonia (Ni 3 g/L hypophosphite 18 g/L), 10 min at 28 C.; Electrolytic dep.: Cu/Ni/Cr deposition solution.

(10) The sequence of use of said compositions is shown in FIGS. 1, 2 and 3. Rinses steps in water are always present between each steps. An X indicates that a treatment with the indicated solution has been performed whereas a blank box indicates that no treatment with the indicated solution has been performed.

Example 1Treatment of an article with ABS surface and a rack with PVC surface with a Sequence comprising a reducing step followed by a mix reducing/rack conditioning step

(11) The articles having a surface comprising or consisting of ABS are panels molded in ABS Novodur P2MC. The racks used for fixing the articles to be metalized have a PVC surface.

(12) The result of the experiment is shown in FIG. 1. In fact, the metallization of the article with the ABS surface was 100% whereas the metallization of the rack with the PVC surface (fixing the article with the ABS surface in each solution) was 0% regardless.

Example 2Treatment of an Article with ABS Surface and a Rack with PVC Surface with a Sequence Comprising Only a Mix Reducing/Rack Conditioning Step

(13) The articles having a surface comprising or consisting of ABS are panels molded in ABS Novodur P2MC. The racks used for fixing the articles to be metalized have a PVC surface.

(14) The result of the experiment is shown in FIG. 1. In fact, the metallization of the article with the ABS surface was 100% whereas the metallization of the rack with the PVC surface (fixing the article with the ABS surface in each solution) was 0%.

Example 3Treatment of an Article with ABS Surface and a Rack with PVC Surface with a Sequence Comprising Separately a Reducing Step and a Rack Conditioning Step

(15) The articles having a surface comprising or consisting of ABS are panels molded in ABS Novodur P2MC. The racks used for fixing the articles to be metalized have a PVC surface.

(16) The result of the experiment is shown in FIG. 1. In fact, the metallization of the article with the ABS surface was 100% whereas the metallization of the rack with the PVC surface (fixing the article with the ABS surface in each solution) was 0%.

(17) In all these examples (1, 2 and 3), whether the reduction solution and rack conditioning solution were used separately or a combined reduction/rack conditioning solution was used, the PVC metallization is prevented.

Example 4Treatment of an Article with ABS Surface and a Rack with PVC Surface with a Sequence without Rack Conditioning Step

(18) The articles having a surface comprising or consisting of ABS are panels molded in ABS Novodur P2MC. The racks used for fixing the articles to be metalized have a PVC surface.

(19) The result of the experiment is shown in FIG. 1. In fact, the metallization of the article with ABS surface was 100% and also the metallization of the rack with PVC surface (fixing the article with the ABS surface in each solution) was 100%.

Example 5Treatment of an Article with ABS Surface and a Rack with PVC Surface with a Sequence where the Rack Conditioning Step is Before the Etching Step

(20) The articles having a surface comprising or consisting of ABS are panels molded in ABS Novodur P2MC. The racks used for fixing the articles to be metalized have a PVC surface.

(21) The result of the experiment is shown in FIG. 1. In fact, the metallization of the article with ABS surface was 100% and also the metallization of the rack with PVC surface (fixing the article with the ABS surface in each solution) was 100%.

(22) The results of the examples 4 and 5 allow the conclusion that the treatment of the articles with ABS surface with the rack conditioning solution does not prevent metallization of their ABS surface whereas the metallization of the PVC surface of the racks is effectively prevented. However, prevention of the PVC surface metallization is only observed if the treatment with the rack conditioning solution is performed after the etching step and not if it is performed before the etching step.

Example 6Treatment of an Article with ABS/PC Surface and a Rack with PVC Surface with a Sequence Comprising a Reducing Step Followed by a Mix Reducing/Rack Conditioning Step

(23) The articles having a surface comprising or consisting of ABS/PC are panels molded in ABS/PC BAYBLEND T45. The racks used for fixing the articles to be metalized have a PVC surface.

(24) The result of the experiment is shown in FIG. 1. In fact, the metallization of the article with ABS/PC surface was 100% whereas the metallization of the PVC surface of the rack (fixing the article with the ABS/PC surface in each solution) was 0%.

Example 7Treatment of an Article with ABS/PC Surface and a Rack with PVC Surface with a Sequence Comprising Only a Mix Reducing/Rack Conditioning Step

(25) The articles having a surface comprising or consisting of ABS/PC are panels molded in ABS/PC BAYBLEND T45. The racks used for fixing the articles to be metalized have a PVC surface.

(26) The result of the experiment is shown in FIG. 1. In fact, the metallization of the article with the ABS/PC surface was 100% whereas the metallization of the rack with the PVC surface (fixing the article with the ABS/PC surface in each solution) was 0% regardless.

Example 8Treatment of an Article with ABS/PC Surface and a Rack with PVC Surface with a Sequence Comprising Separately a Reducing Step and a Rack Conditioning Step

(27) The articles having a surface comprising or consisting of ABS/PC are panels molded in ABS/PC BAYBLEND T45. The racks used for fixing the articles to be metalized have a PVC surface.

(28) The result of the experiment is shown in FIG. 1. In fact, the metallization of the article with the ABS/PC surface was 100% whereas the metallization of the rack with the PVC surface (fixing the article with the ABS/PC surface in each solution) was 0%.

(29) In the examples 6, 7 and 8, whether the reduction solution and rack conditioning solution were used separately or a combined reduction/rack conditioning solution was used, the PVC metallization is prevented.

Example 9Treatment of an Article with ABS/PC Surface and a Rack with PVC Surface with a Sequence without Rack Conditioning Step

(30) The articles having a surface comprising or consisting of ABS/PC are panels molded in ABS/PC BAYBLEND T45. The racks used for fixing the articles to be metalized have a PVC surface.

(31) The result of the experiment is shown in FIG. 1. In fact, the metallization of the plastic article with ABS/PC surface was 100% and also the metallization of the rack with PVC surface (fixing the article with the ABS/PC surface in each solution) was 100%.

Example 10Treatment of an Article with ABS/PC Surface and a Rack with PVC Surface with a Sequence where the Rack Conditioning Step is Before the Etching Step

(32) The articles having a surface comprising or consisting of ABS/PC are panels molded in ABS/PC BAYBLEND T45. The racks used for fixing the articles to be metalized have a PVC surface.

(33) The result of the experiment is shown in FIG. 1. In fact, the metallization of the article with ABS/PC surface was 100% and also the metallization of the rack with PVC surface (fixing the article with the ABS/PC surface in each solution) was 100%.

(34) The results of the example 9 and 10 allow the conclusion that the treatment of the articles with ABS/PC surface with the rack conditioning solution does not prevent metallization of their ABS/PC surface whereas the metallization of the PVC surface of the racks is effectively prevented. Again, prevention of rack metallization is only observed if the treatment with the rack conditioning solution is performed after the etching step and not if it is performed before the etching step.

Example 11Treatment of Article with an ABS and PC Surface (Bi-Component Articles) and a Rack with PVC Surface

(35) The article to be metalized has two different plastic surfaces i.e. is a bi-component plastic article comprising ABS on one part of its surface and PC on another part of its surface (ABS-PC bi-component). Said article is specifically common in the automotive market. The racks used for fixing the article to be metalized have a PVC surface.

(36) The result of the experiment is shown in FIG. 2. In fact, the metallization of the ABS-PC bi-component article was 100% at the ABS surface and 0% at the PC surface. The metallization of the PVC surface of the rack (fixing the bi-component articles in each solution) was 0%.

Example 12Treatment of Article with an ABS and PC Surface (Bi-Component Articles) and a Rack with PVC Surface without Rack Conditioning Step

(37) The article to be metalized has two different plastic surfaces i.e. is a bi-component plastic article comprising ABS on one part of its surface and PC on another part of its surface (ABS-PC bi-component). Said article is specifically common in the automotive market. The racks used for fixing the article to be metalized have a PVC surface.

(38) The result of the experiment is shown in FIG. 2. In fact, the metallization of the ABS surface of the bi-component article was 100% and also the metallization of the PC surface of the bi-component article was 100%. The metallization of the PVC surface of the rack (fixing the bi-component articles in each solution) was 100% as well.

(39) The results of the examples 11 and 12 allow the conclusion that the treatment of the bi-component article with the rack conditioning solution does not prevent metallization of the ABS surface of the bi-component article whereas the metallization of the PC surface of the bi-component article is effectively prevented (=selective metallization of ABS surface compared to PC surface). In addition, the metallization of the PVC surface of the rack is effectively prevented (=selective metallization of ABS surface compared to PVC surface). This allows the conclusion that the treatment of article with the rack conditioning solution after the etching step provokes a very selective metallization of surfaces comprising or consisting of ABS compared to other types of plastic surfaces (e.g. PC and PVC surfaces).

Example 13Treatment of an Article with an ABS and PCTA Surface (Bi-Component Articles) and a Rack with PVC Surface

(40) The article to be metalized has two different plastic surfaces i.e. is a bi-component plastic article comprising ABS on one part of its surface and PCTA on another part on its surface (ABS-PCTA bi-component). Said article is specifically common in the perfume taps market. The racks used for fixing the article to be metalized have a PVC surface.

(41) The result of the experiment is shown in FIG. 2. In fact, the metallization of the ABS-PCTA bi-component article was 100% at the ABS surface and 0% at the PCTA surface. The metallization of the PVC surface of the rack (fixing the bi-component article in each solution) was 0%.

Example 14Treatment of an Article with an ABS and PCTA Surface (Bi-Component Articles) and a Rack with PVC Surface without Rack Conditioning Step

(42) The article to be metalized has two different plastic surfaces i.e. is a bi-component plastic article comprising ABS on one part of its surface and PCTA on another part on its surface (ABS-PCTA bi-component). Said article is specifically common in the perfume taps market. The racks used for fixing the article to be metalized have a PVC surface.

(43) The result of the experiment is shown in FIG. 2. In fact, the metallization of the ABS surface of the bi-component plastic article was 100% and also the metallization of the PCTA surface of the bi-component plastic article was 100%. The metallization of the PVC surface of the rack (fixing the bi-component articles in each solution) was 100% as well.

(44) The results of the examples 13 and 14 allow the conclusion that the treatment of the bi-component article with the rack conditioning solution does not prevent metallization of the ABS surface of the bi-component plastic article whereas the metallization of the PCTA surface of the bi-component plastic article is effectively prevented (=selective metallization of ABS surfaces compared to PCTA surfaces). In addition, the metallization of the PVC surface of the rack is effectively prevented (=selective metallization of ABS surfaces compared to PVC surfaces). This allows the conclusion that the treatment of plastic articles with the rack conditioning solution after the etching step provokes a very selective metallization of surfaces comprising or consisting of ABS compared to other types of plastic surfaces (e.g. PCTA and PVC surfaces).

Example 15Measurement by EDX and SEM Images of the ABS and PVC Surface after Treatment without Rack Conditioning

(45) The articles having a surface comprising or consisting of ABS are panels molded in ABS Novodur P2MC. The racks used for fixing the articles to be metalized have a PVC surface.

(46) The result of the experiment is shown in FIG. 3, example 15. In fact, the metallization of the article with ABS surface was 100% and also the metallization of the rack with PVC surface (fixing the article with the ABS surface in each solution) was 100%.

(47) From the EDX measurement made on the ABS and PVC surface immediately after rinse of the reduction step, only traces of sulfur element is detected both on the ABS surface and on the PVC surface due probably to pollution or background noise of the EDX measurement.

(48) From the SEM pictures made on the ABS and PVC surface immediately after rinse of the reduction step, FIG. 4, example 15, a normal attack of the ABS surface can be observed by the creation of a porosity adapted to the metal anchoring. And nothing relevant is observed on the PVC surface meaning no crystal formation or modification of the PVC surface.

Example 16Measurement by EDX and SEM Images of the ABS and PVC Surface after Treatment with Rack Conditioning without Thickening Agent

(49) The articles having a surface comprising or consisting of ABS are panels molded in ABS Novodur P2MC. The racks used for fixing the articles to be metalized have a PVC surface.

(50) The result of the experiment is shown in FIG. 3, example 16. In fact, the metallization of the article with the ABS surface was 100% whereas the metallization of the rack with the PVC surface (fixing the article with the ABS surface in each solution) was 20% regardless.

(51) From the EDX measurement made on the ABS and PVC surface immediately after rinse of the reduction/rack conditioning step, a sulfur content is increased about 2 times on the PVC surface compared to ABS surface. The sulfur content on the ABS surface remained substantially unchanged in comparison to the example 15.

(52) From the SEM pictures made on the ABS and PVC surface immediately after rinse of the reduction/rack conditioning step, FIG. 5, example 16, a normal attack of the ABS surface can be observed by the creation of a porosity adapted to the metal anchoring. And nothing relevant is observed on the PVC surface meaning no crystal formation or modification of the PVC surface. But the content of sulfur present on the surface is able to limit the initiation of the electroless deposit.

Example 17Measurement by EDX and SEM Images of the ABS and PVC Surface after Treatment with Rack Conditioning Containing the Thickening Agent

(53) The articles having a surface comprising or consisting of ABS are panels molded in ABS Novodur P2MC. The racks used for fixing the articles to be metalized have a PVC surface.

(54) The result of the experiment is shown in FIG. 3, example 17. In fact, the metallization of the article with the ABS surface was 100% whereas the metallization of the rack with the PVC surface (fixing the article with the ABS surface in each solution) was 0%.

(55) From the EDX measurement made on the ABS and PVC surface immediately after the rinse of the reduction/rack conditioning step, the sulfur content is highly increased on the PVC surface by the addition of the thickening agent in the rack conditioning step, when on the ABS surface, the sulfur content remained substantially unchanged in comparison to the examples 15 and 16.

(56) From the SEM pictures made on the ABS and PVC surface immediately after the rinse of the reduction/rack conditioning step, FIG. 6, example 17, a normal attack of the ABS surface can be observed by the creation of a porosity adapted to the metal anchoring. The presence of crystal formation is observed on the entire PVC surface linked to the sulfur content strongly increased thanks to the thickening agent. This crystal formation is not observed on the ABS surface.