METALLIZATION INHIBITOR FOR RACKS EMPLOYED IN GALVANIC TREATMENTS

Abstract

The metallization of a metallic rack employed in galvanic metallization processes of plastic material items, coated by immersion in PVC Plastisol, is inhibited thanks to the fact that PVC Plastisol is mixed with a C8-C18 thiol selected from octyl mercaptan, nonyl mercaptan, decyl mercaptan, n-octadecyl-3-mercaptopropionate, isooctyl-3-mercaptopropionate, n-octyl-mercaptopropionate, dodecyl-3-mercaptopropionate, tridecyl-3-mercaptopropionate, palmityl mercaptan, bis-phenyl-1,4-thiol.

Claims

1. A method for inhibiting metallization of a metallic rack employed in galvanic metallization processes of plastic material items, wherein the rack designed to bear the plastic material item is coated by immersion in PVC Plastisol, wherein the PVC Plastisol is mixed with a C8-C18 thiol selected from octyl mercaptan, nonyl mercaptan, decyl mercaptan, n-octadecyl-3-mercaptopropionate, isooctyl-3-mercaptopropionate, n-octyl-mercaptopropionate, dodecyl-3-mercaptopropionate, tridecyl-3-mercaptopropionate, palmityl mercaptan, bis-phenyl-1,4-thiol, and wherein the metallic rack is treated by a chromium (VI)-free etching solution.

2. The method according to claim 1, wherein the amount of C8-C18 thiol is comprised between 0.1% and 5% by weight of PVC Plastisol.

3. A metallization inhibitor for metallic racks employed in galvanic metallization of plastic material items and coated by PVC Plastisol, wherein the inhibitor consists of a C8-C18 thiol selected from octyl mercaptan, nonyl mercaptan, decyl mercaptan, n-octadecyl-3-mercaptopropionate, isooctyl-3-mercaptopropionate, n-octyl-mercaptopropionate, dodecyl-3-mercaptopropionate, tridecyl-3-mercaptopropionate, palmityl mercaptan, bis-phenyl-1,4-thiol mixed with PVC Plastisol before racks coating.

4. The metallization inhibitor according to claim 3, wherein the thiol is n octadecyl-3-mercaptopropionate in an amount comprised between 0.5 and 5% by weight of PVC Plastisol.

5. The metallization inhibitor according to claim 3, wherein the thiol is dodecyl-3-mercaptopropionate in an amount comprised between 0.5 and 5% by weight of PVC Plastisol.

6. A metallic rack coated by PVC Plastisol and employed in galvanic metallization processes of plastic material items, whose metallization is inhibited by the method according to claim 1.

7. A metallic rack coated by PVC Plastisol mixed with a metallization inhibitor according to claim 3.

8. The metallization inhibitor of claim 3 wherein the thiol is n-octadecyl-3-mercaptopropionate in an amount comprised between 1 and 5% by weight of PVC Plastisol.

9. The metallization inhibitor according to claim 3, wherein the thiol is dodecyl-3-mercaptopropionate in an amount comprised between 1 and 5% by weight of PVC Plastisol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0024] In accordance with the invention, the metallic frames used for metallization treatments and galvanic etching of plastic material items are in turn inhibited from metallization through their plasticization by immersion in a PVC Plastisol containing from 0.1% to 5% by weight of a C8-C18 thiol as identified above.

[0025] Preferably, the amount of thiol is between 0.5 and 5% and more preferably between 1 and 5%, and more conveniently the thiol consists in n-octadecyl-3-mercaptopropionate.

[0026] The composition thus obtained can further include, in the generic formulation of the PVC plastisol used for the plasticization of galvanic frames, the following components: [0027] Plasticizers 25-40% by weight: acetyl tributyl citrate ATBC, di octyl adipate DOA, di iso-nonyl phthalate DINP, Alkylsulphonic phenyl ester MESAMOLL, epoxidized soybean oil ESBO [0028] PVC resin: 45-60% by weight (Polyvinyl chloride emulsion and/or microsuspension K70-K80) [0029] MINERAL FILLERS: 2-5% by weight (Calcium Carbonate, Calcium Oxide) [0030] THICKENERS 1-5% by weight (Pyrogenic Silica, Calcium Sulphonate) [0031] STABILIZERS 1-5% by weight (Calcium/Zinc Complex Salt)

[0032] The frames coated in this way completely effectively inhibit their metallization during the electroplating processes also, and particularly, with etching solutions free of carcinogenic substances such as chromium (VI).

[0033] The following examples are provided in a purely indicative and not limitative way.

EXAMPLE 1 (COMPARATIVE)

Metallization of Frame Coated by PVC Plastisol, Treated by a Chromium (VI)-Free Mn (III)-Based Etching Solution

[0034] A chromoplating frame coated by a PVC plastisol coating with an ABS test panel hooked was immersed in a cleaning solution then in a mordanting (“etching”) solution based on Manganese (III) ions at a temperature of 40° C.

[0035] Subsequently, the frame was subjected to the process of galvanic electrodeposition of the metallic coating (rinsing in water, activation of the surface by palladium solution, chemically-obtained deposition of a thin layer of metal, electrodeposition of metals on the metallized plastic material substrate)

[0036] At the end of the treatment there was a complete coating of the ABS panel but also of more than 80% of the frame. The solution used for etching did not inhibit the metallic coating of the frame.

EXAMPLE 2 (COMPARATIVE)

Metallization of Frame Coated by PVC Plastisol, Treated by a Chromium (VI)-Free Permanganate-Based Etching Solution

[0037] A chromoplating frame coated by a PVC plastisol coating with an ABS test panel hooked was immersed in a cleaning solution then in a mordanting (“etching”) solution based on Permanganate and sulphuric acid at a temperature of 65° C.

[0038] Subsequently, the frame was subjected to the same galvanic electrodeposition process described in the comparative example 1.

[0039] At the end of the treatment there was a complete coating of the ABS panel but also of more than 50% of the frame. Also in this case the solution used for the etching did not inhibit the metallic coating of the frame.

EXAMPLE 3 (COMPARATIVE)

Metallization of Frame Coated by PVC Plastisol with Addition of XyleneThiol Inhibitor, Treated by a Chromium (VI)-Free Mn (III)-Based Etching Solution

[0040] A PVC plastisol was prepared with the addition of 3% by weight (5% to the resin) of XyleneThiol as a metallization inhibitor. This modified plastisol was used to coat a chromoplating frame with an ABS test panel hooked, which was then subjected to the same process used in the comparative example 1.

[0041] At the end of the treatment there was a complete coating of the ABS panel but also of more than 70% of the frame. The solution used for etching and the PVC coating modified in this way did not inhibit the metallic coating of the frame.

EXAMPLE 4 (COMPARATIVE)

Metallization of Frame Coated by PVC Plastisol with Addition of XyleneThiol Inhibitor, Treated by a Chromium (VI)-Free Permanganate-Based Etching Solution

[0042] A PVC plastisol was prepared with the addition of 3% by weight (5% to the resin) of XyleneThiol as a metallization inhibitor. This modified plastisol was used to coat a chromoplating frame with an ABS test panel hooked, which was then subjected to the same process used in the comparative example 2.

[0043] At the end of the treatment there was a complete coating of the ABS panel but also of more than 60% of the frame. Also in this case the solution used for etching and the PVC coating modified in this way did not inhibit the metallic coating of the frame.

EXAMPLE 5

Use of a Frame Coated by PVC Plastisol with the Addition of an Inhibitor Treated by a Chromium (VI)-Free Mn (III)-Based Etching Solution

[0044] A PVC plastisol was prepared with the addition of 3% by weight of dodecyl-3-mercaptopropionate as a metallization inhibitor. This modified plastisol was used to coat a chromoplating frame with an ABS test panel hooked, which was then subjected to the same process used in the comparative example 1.

[0045] In this case there was no metallic coating on the frame, while the ABS panel was completely coated.

[0046] This test was repeated 10 times changing only the ABS panel and all the tests confirmed the positive results.

EXAMPLE 6

Use of a Frame Coated by PVC Plastisol with the Addition of an Inhibitor Treated by a Chromium (VI)-Free Mn (III)-Based Etching Solution

[0047] A PVC plastisol was prepared with the addition of 2% by weight of n-octadecyl-3-mercaptopropionate as a metallization inhibitor. This modified plastisol was used to coat a chromoplating frame with an ABS test panel hooked, which was then subjected to the same process used in the comparative example 1.

[0048] In this case there was no metallic coating on the frame, while the ABS panel was completely coated.

[0049] This test was repeated 20 times changing only the ABS panel and all the tests confirmed the positive results.

EXAMPLE 7

Use of a Frame Coated by PVC Plastisol with the Addition of an Inhibitor Treated by a Chromium (VI)-Free Permanganate-Based Etching Solution

[0050] A PVC plastisol was prepared with the addition of 2% by weight of n-octadecyl-3-mercaptopropionate as a metallization inhibitor. This modified plastisol was used to coat a chromoplating frame with an ABS test panel hooked, which was then subjected to the same process used in the comparative example 2.

[0051] In this case there was no metallic coating on the frame, while the ABS panel was completely coated.

[0052] This test was repeated 20 times changing only the ABS panel and all the tests confirmed the positive results.