CN101736327A - Palladium-free plastic chemical plating method for generating reductant film - Google Patents

Abstract

The invention discloses a palladium-free plastic chemical plating method for forming a reducing agent film. The reducing agent film is firstly reduced to form a reducing agent film, and then the nickel in the waste liquid is reduced. The method of the invention has low cost, firm plating layer and simple process flow , can be applicable to the palladium-free activation method of different plastic substrates; a kind of composite activation solution that the inventive method uses, its cost will be lower than the palladium chloride activation solution that adopts at present greatly, and the brightness of final plastic electroless plating, combining Power and other performance is excellent.

Description

A kind of palladium-free plastic electroless plating method that generates reducing agent film

technical field

The invention relates to a plastic chemical plating method, in particular to a palladium-free plastic chemical plating method for generating a reducing agent film.

Background technique

The wide application of plastics has brought great convenience to people's lives. However, due to the poor wear resistance, non-conductivity and easy deformation of plastics, their applications have been limited. In order to meet the requirements of plastic properties in special cases , using the chemical plating method, a layer of metal is plated on the plastic surface to improve the performance and processing characteristics of the plastic, so that the application range of the plastic is wider. There are many methods for the metallization of the plastic surface, and the most commonly used method at present is chemical plating.

The general process of electroless plating on plastics is: substrate degreasing - roughening - sensitization - activation - degumming - chemical plating. The first few steps are the surface treatment before electroless plating, which is required by the particularity of the plastic substrate (such as non-conductive, non-catalytic activity on the surface, poor bonding with the plating, etc.). The activation process is a very critical step. The quality of the activation effect is directly related to whether the electroless plating can be carried out, whether the coating is uniform, and whether the bonding force between the coating and the substrate is up to standard. The so-called activation is to form a layer of discontinuous, uniformly distributed metal particles with catalytic activity on the surface of the substrate, thereby inducing subsequent electroless plating.

Electroless plating first started with electroless nickel plating. Electroless nickel plating on non-conductors generally requires a layer of electroless plating catalyst to be formed on the substrate. The traditional process uses PdCl ₂ -SnCl ₂ activation-sensitization method. The process of this process is complicated, and the PdCl2 used is expensive and toxic, so its application is limited to a certain extent. In order to save precious metals and reduce production costs, scientific research workers have invested a lot of energy in the research of non-precious metal activation solutions, and have achieved certain results, and many patent documents have been issued, but the application of palladium-free activation processes in industrial production still exists. There are many problems, such as the activation effect is generally not as good as that of precious metals, and the required activation temperature is higher and the time is longer. So far, no non-precious metal activation process has been applied to industrial production on a large scale.

The palladium activation method in the electroless plating activation process was applied earlier, and the process is very mature, and has played a very important role in the electroless plating industry. However, compared with the expensive palladium activation method, the palladium-free activation process has low cost and less pollution, but there are still many problems, such as: some activation effects are not as good as palladium, and cannot meet industrial needs; some processes are too complicated and industrial production is not feasible. high. The basic principle of palladium-free activation is to generate a nickel catalytic layer on the plastic substrate, and use the self-catalytic ability of nickel to realize electroless plating. Japan firstly reported that an activation solution containing chitosan or its extensions was coated on the surface of a non-conductive material, and the activation center was formed on the collective surface by utilizing the chelation of chitosan to metal palladium. At present, the main process of palladium-free activation solution is to form a nickel ion film on the surface of the plastic collective, and then put the collective into the reducing agent. Such as Chinese patent application CN101067206A a kind of ABS plastic surface without palladium activation treatment new process and Chinese patent application CN101381865A: a kind of plastic substrate surface of sodium carboxymethylcellulose chelation adsorption nickel without palladium activation method, its basic principle is all like this, It's just that the chelating agent is different and some processes are different.

At present, there are three patents and patent application documents that disclose the palladium-free activation process, which are respectively the chemical nickel plating on plastic surface without palladium activation formula and process (CN1772950C), a new process for ABS plastic surface palladium-free activation treatment (CN101067206A), a A palladium-free activation method on the surface of a plastic substrate on which carboxymethylcellulose sodium chelates and adsorbs nickel (CN101381865A). The comparisons are described below.

Patent CN1772950C is that when activating, put the plastic substrate into the nickel acetate alcohol solution, then pour the sodium borohydride alcohol solution into the nickel acetate alcohol solution for activation, and age it for a certain period of time. The active nickel is prepared by sodium borohydride reduction at room temperature, and the activation method of replacing palladium with nickel has the advantage of low temperature. But there is certain deficiency in this invention aspect the reuse of activation solution.

Both patent applications CN101067206A and CN101381865A first form a nickel ion film on the surface of the plastic substrate, and this method effectively solves the solution reuse problem of the patent CN1772950C. However, on the whole, the nickel-ion membrane method is somewhat complicated. In the patent application CN101067206A, a complex polymer film-forming agent must first be configured to form a film, then nickel ions are adsorbed, and finally reduced, with drying and other operations in between, which is a bit complicated. The patent application of CN101381865A effectively realizes film formation and nickel ion adsorption at the same time, reducing the operation steps, but it needs to be dried for 30 minutes to 60 minutes.

Contents of the invention

The purpose of the present invention is to overcome the defective of prior art, provide a kind of method of the palladium-free plastic electroless plating that generates reductant film, utilize reduction film-forming agent to generate reductant film first, then the nickel in waste liquid is reduced, the present invention The method is low in cost, the coating is firm, and the process flow is simple, and it is applicable to palladium-free activation methods for different plastic substrates; the cost of a composite activation solution used in the method of the present invention is much lower than that of the palladium chloride activation solution currently used. At the same time, the brightness and binding force of the final plastic electroless plating are excellent.

The object of the invention is achieved through the following technical solutions:

A method for generating the palladium-free plastic electroless plating of reducing agent film, comprises the following steps:

(1) Dry the plastic substrate that has undergone chemical degreasing and roughening treatment, put it into the reducing film-forming agent, and let it stand for 15s to 30s, and a liquid film is formed on the surface of the plastic substrate;

(2) Air-drying of the substrate: air-drying the above-mentioned film-forming plastic substrate until a solid film is formed on the surface of the plastic substrate;

(3) Generate activation center: put the air-dried plastic substrate into the electroless plating waste solution, and react for 5-10s;

(4) Electroless plating: the plastic substrate obtained in step (3) is taken out and cleaned, and then put into the plating solution for plating.

Described chemical degreasing, coarsening and electroless plating can be selected from the commonly used process conditions in the technical field, preferably the following conditions:

The chemical degreasing is to put the plastic base material into a mixed solution of sodium carbonate and trisodium phosphate at a temperature of 50-70° C. The mass volume concentration is 25g/L.

The roughening is to put the plastic base material after chemical degreasing into the mixed solution of chromic anhydride and concentrated sulfuric acid at a temperature of 65-70°C and soak for 10 minutes, wherein the mass volume concentration of chromic anhydride is 200g/L, The volume concentration is 8000mL/L.

The electroless plating is to put the treated plastic substrate into a plating solution with a temperature of 65-72°C and a pH of 5 for plating, wherein the formulation of the plating solution is: nickel sulfate 30g/L, sodium hypophosphite 27g/L, Sodium citrate 20g/L, lactic acid 9g/L, sodium dodecylbenzenesulfonate 0.0025g/L.

The reduction film-forming agent is prepared according to the following steps:

(1) methanol and ethanol are mixed into a solvent in a volume ratio of 1:1 to 7:3;

(2) Add sodium hydroxide, stir to make it dissolve;

(3) added biphenyl, silane coupling agent and sodium borohydride, stirred slowly to dissolve it,

The ratio of the amount of the above substances added to the volume of the solvent is sodium hydroxide: 10g/L~20g/L, biphenyl: 2g/L~5g/L, silane coupling agent: 5mL/L~8mL/L, sodium borohydride : 15～25g/L.

The weight-to-volume ratio of the nickel compound in the electroless plating waste solution is more than or equal to 3g/L.

The silane coupling agent includes silane coupling agent KH-560.

Advantage and beneficial effect that the present invention has with respect to prior art:

1. No palladium process. As a rare precious metal, palladium itself determines the limitations of the palladium activation method to a large extent due to its own characteristics. Palladium activation first greatly increases the cost of electroless plating. Although palladium chloride has a long service life, its high cost inevitably increases the process cost; secondly, the palladium activation method consumes a large amount of rare metal palladium .

2. Simplifies the process flow of plastic electroless plating and greatly reduces the process cost. The plastic electroless plating process commonly used at present is degreasing-coarsening-sensitization-activation-degelling-electroless plating. This process has high stability but is relatively complicated. The method of the invention does not need sensitization and degumming, and does not need any expensive equipment.

3. Use electroless plating waste solution for corresponding activation. The plastic products whose surface is coated with reducing agent need not be put into the plating solution, which may cause unstable factors to the plating solution. We only need to put the sample into the waste liquid that still contains nickel ions, and a layer of nickel metal particles can be well reduced on the plastic surface.

4. Normal temperature operation. The whole activation process of the present invention is realized at normal temperature, which is simple and easy to implement.

5. The activation time is short. The entire activation process of the present invention can be completed in a relatively short period of time, and the key is that the natural air-drying speed is fast.

Description of drawings

Fig. 1 is the whole technological process of plastic chemical plating of the present invention (wherein dotted line square frame is activation process);

Fig. 2 is the surface metallographic micrograph * 800 of embodiment 1 plastics;

Fig. 3 is the surface metallographic micrograph of embodiment 2 plastics × 800

Detailed ways

Notch test:

Carve 10 vertical and horizontal grids with a distance of 1 mm on the surface of the sample to form a staggered grid, pull it up once with 3M strong adhesive tape, and observe under a 5x magnifying glass. If the coating has no peeling or blistering, it is considered qualified.

High-temperature shock method to test the bonding force of the coating:

The method was proposed by the Association of Plastic Electroplaters in West Germany: keep warm in hot water at 80±5°C for 1 hour, take it out and soak it in cold water at 5±5°C for 30s within 30 seconds, and then switch to high temperature Insulate in hot water for 1 hour, after three cycles, if the coating has no bubbles, peeling, wrinkling and other defects, it is considered qualified.

Brightness test:

Visual Judgment Standard

Level 1 (mirror bright): The surface of the coating is as bright as a mirror, and the facial features and eyebrows can be clearly seen.

The surface of the secondary (bright) coating is bright, and the facial features can be seen, but the eyebrows are somewhat blurred

Level 3 (semi-bright): The surface of the coating is slightly bright, and the facial features cannot be seen clearly.

Level 4 (dull): The surface of the coating is dull, and no facial features can be seen.

Surface Microstructure:

The microscopic morphology of the coating surface was observed with a metallographic microscope with a magnification of ×800.

Example 1

Soak the ABS plastic substrate in a mixed solution of sodium carbonate and trisodium phosphate at a temperature of 50°C for 2 minutes to remove oil, wherein the mass volume concentration of sodium carbonate is 25g/L, and the mass volume concentration of trisodium phosphate is 25g /L; then soak the plastic base material after chemical degreasing in a mixed solution of chromic anhydride and concentrated sulfuric acid at a temperature of 65°C for 10 minutes to roughen, wherein the mass volume concentration of chromic anhydride is 200g/L, concentrated sulfuric acid The volume concentration is 8000mL/L; put the degreasing and roughened ABS plastic substrate into the reducing film-forming agent for 15s, and the reducing film-forming agent is formed by mixing methanol and ethanol at a volume ratio of 7:3 To the solvent, add 20g/L of sodium hydroxide, 5g/L of degrading agent biphenyl, 25g/L of sodium borohydride and 5mL/L of silane coupling agent KH-560 in proportion to the volume of the solvent. The plastic substrate was formed into a film in the reducing film former for 15 seconds, and then air-dried naturally for 10 minutes. Then immerse it in the electroless plating waste solution containing NiSO ₄ 5g/L for 5s, take it out, wash it and throw it into the plating solution for plating for 8min. The brightness of the obtained coating is second grade, and through metallographic microscopic observation (see Figure 1), the coating is smooth, compact and excellent in binding force.

Example 2

Soak the ABS plastic substrate in a mixed solution of sodium carbonate and trisodium phosphate at a temperature of 70°C for 5 minutes to remove oil, wherein the mass volume concentration of sodium carbonate is 25g/L, and the mass volume concentration of trisodium phosphate is 25g /L; then soak the plastic base material after chemical degreasing in a mixed solution of chromic anhydride and concentrated sulfuric acid at a temperature of 70°C for 10 minutes to roughen, wherein the mass volume concentration of chromic anhydride is 200g/L, concentrated sulfuric acid The volume concentration is 8000mL/L; put the degreasing and roughened ABS plastic substrate into the reducing film-forming agent for 30s. To the solvent, add 10g/L of sodium hydroxide, 2g/L of degrading agent biphenyl, 15g/L of sodium borohydride and 5mL/L of silane coupling agent KH-560 in proportion to the volume of the solvent. The film-forming time of the base material in the reduced film-forming agent was 30s, and then air-dried for 10 minutes. Then immerse it in the electroless plating waste solution containing NiSO ₄ 5g/L for 10s, take it out, wash it and throw it into the plating solution for plating for 8min. The brightness of the obtained coating is two grades, which is better than that of Example 1. Through metallographic microscopic observation (see Figure 2), the coating is smooth, compact and excellent in binding force.

Example 3

Soak the ABS plastic substrate in a mixed solution of sodium carbonate and trisodium phosphate at a temperature of 70°C for 5 minutes to remove oil, wherein the mass volume concentration of sodium carbonate is 25g/L, and the mass volume concentration of trisodium phosphate is 25g /L; then soak the plastic base material after chemical degreasing in a mixed solution of chromic anhydride and concentrated sulfuric acid at a temperature of 70°C for 10 minutes to roughen, wherein the mass volume concentration of chromic anhydride is 200g/L, concentrated sulfuric acid The volume concentration is 8000mL/L; put the degreasing and roughened ABS plastic substrate into the reducing film-forming agent for 20s, and the reducing film-forming agent is prepared by mixing methanol and ethanol at a volume ratio of 1:1. In the solvent, add sodium hydroxide, 2g/L degrading agent biphenyl, 20g/L sodium borohydride and silane coupling agent KH-5605mL/L in proportion to solvent volume. The film-forming time of the substrate in the reducing film-forming agent was 20s, and then air-dried for 10 minutes. Then immerse it in the electroless plating waste solution containing NiSO ₄ 5g/L for 10s, take it out, wash it and throw it into the plating solution for plating for 8min. The luminance of the obtained coating is second grade, and through metallographic microscopic observation, the coating is flat, densely bonded and excellent in bonding force.

Example 4

Soak the ABS plastic substrate in a mixed solution of sodium carbonate and trisodium phosphate at a temperature of 60°C for 3 minutes to remove oil, wherein the mass volume concentration of sodium carbonate is 25g/L, and the mass volume concentration of trisodium phosphate is 25g /L; then soak the plastic base material after chemical degreasing in a mixed solution of chromic anhydride and concentrated sulfuric acid at a temperature of 70°C for 10 minutes to roughen, wherein the mass volume concentration of chromic anhydride is 200g/L, concentrated sulfuric acid The volume concentration is 8000mL/L; put the degreasing and roughened ABS plastic substrate into the reducing film-forming agent for 15s, and the reducing film-forming agent is formed by mixing methanol and ethanol at a volume ratio of 7:3 To the solvent, add 20g/L of sodium hydroxide, 5g/L of degrading agent biphenyl, 25g/L of sodium borohydride and 5mL/L of silane coupling agent KH-560 in proportion to the volume of the solvent. The base material was formed into a film in the reduced film former for 15 seconds, and then air-dried for 10 minutes. Then immerse it in the electroless plating waste solution containing NiSO ₄ 5g/L for 5s, take it out, wash it and throw it into the plating solution for plating for 8min. The brightness of the obtained coating is second grade, and through metallographic microscopic observation (see Figure 1), the coating is smooth, compact and excellent in binding force. The luminance of the obtained coating is three grades, and through metallographic microscopic observation, the coating is flat, densely bonded, and has good bonding force.

Example 5

Change the plastic substrate, soak the PVC plastic substrate in a mixed solution of sodium carbonate and trisodium phosphate at a temperature of 50°C for 2 minutes to remove oil, wherein the mass volume concentration of sodium carbonate is 25g/L, and that of trisodium phosphate The mass volume concentration is 25g/L; then put the plastic base material after chemical degreasing into the mixed solution of chromic anhydride and concentrated sulfuric acid at a temperature of 65°C for 10 minutes to roughen, and the mass volume concentration of chromic anhydride is 200g /L, the volume concentration of concentrated sulfuric acid is 8000mL/L; Put the ABS plastic base material that has been degreased and roughened into the reducing film-forming agent for 15s. : 3 mixed into the solvent, adding the ratio of the volume of the solvent to be 20g/L sodium hydroxide, 3g/L degrading agent biphenyl, 25g/L sodium borohydride and 8mL/L silane coupling agent KH -560. The base material was formed into a film in the reduced film former for 15 seconds, and then air-dried for 10 minutes. Then immerse it in the electroless plating waste solution containing NiSO ₄ 5g/L for 6s, take it out, wash it, put it into the plating solution and apply plating for 8min. The luminance of the obtained coating is three grades, and through metallographic microscopic observation, the coating is flat, densely bonded, and has good bonding force.

Claims (4)

1. a method for generating the palladium-free plastic electroless plating of reducing agent film, is characterized in that comprising the following steps: (1) Dry the plastic base material that has undergone chemical degreasing and roughening treatment, put it into the reducing film-forming agent, and let it stand for 15 to 30 seconds, and a liquid film is formed on the surface of the plastic base material; (2) Air-drying of the substrate: air-drying the above-mentioned film-forming plastic substrate until a solid film is formed on the surface of the plastic substrate; (3) Generate activation center: put the air-dried plastic base material into the electroless plating waste solution, and react for 5-10 seconds; (4) Electroless plating: take out and clean the reacted plastic substrate, and then put it into the plating solution for plating. 2. method according to claim 1, it is characterized in that described reducing film-forming agent is prepared according to the following steps: (1) methanol and ethanol are mixed into a solvent in a volume ratio of 1:1 to 7:3; (2) Add sodium hydroxide, stir to make it dissolve; (3) added biphenyl, silane coupling agent and sodium borohydride, stirred slowly to dissolve it, The ratio of the amount of the above substances added to the volume of the solvent is sodium hydroxide: 10g/L~20g/L, biphenyl: 2g/L~5g/L, silane coupling agent: 5mL/L~8mL/L, sodium borohydride : 15～25g/L. 3. The method according to claim 2, characterized in that the silane coupling agent comprises silane coupling agent KH-560. 4. The method according to claim 1, characterized in that the concentration of the nickel compound in the electroless plating waste solution is greater than or equal to 3g/L.

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