Alkaline cyanide-free zinc-nickel alloy electroplating complexing agent and preparation method thereof

Abstract

The invention belongs to the technical field of electroplating, and particularly relates to an alkaline cyanide-free zinc-nickel alloy electroplating complexing agent and a preparation method thereof.The complexing agent is prepared from, by weight, 10-18 parts of a first complexing agent, 10-12 parts of a second complexing agent and 10-15 parts of hydroxy carboxylic acid; the first complexing agent is a modified aminocarboxylic complexing agent. The electroplating complexing agent disclosed by the invention is extremely high in applicability in an alkaline cyanide-free zinc-nickel alloy electroplating solution and good in complexing effect, and a formed complex is stable in property and has good dispersing performance and covering performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of electroplating, and particularly relates to an alkaline non-cyanide zinc-nickel alloy electroplating complexing agent and a preparation method thereof. Background Art

[0002] In an alkaline zinc-nickel alloy electroplating solution, in addition to the main salts, the selection of electroplating additives has a great influence on the electroplating process effect, and the complexing agent is the key to the success of the electroplating process. A complexing agent is a class of compounds that can form complex ions with metal ions. By complexing with metal ions in the electroplating solution, stable complex ions are formed to prevent the hydrolysis or precipitation of metal ions, and the stability of the electroplating solution can be maintained. Currently, the commonly used complexing agents in electroplating solutions in the prior art include cyanides, hydroxides, citrates, pyrosulfates, etc., and most of them are single or simply combined complexing agents when applied. Although they can also help to form a coating during application, the quality of the coating is not high, and there will also be environmental problems.

[0003] The invention patent with the publication number CN103755738A discloses a complexing agent, a preparation method and an application thereof. The general formula of the complexing agent disclosed in this invention is M x H y P n O 3n+1 R z , where M is any one or more of alkali metal ions and NH 4+ ; R is an acyl group: x, n, and z are all positive integers, y is 0 or a positive integer, and x + y + z = n + 2. The preparation method of the complexing agent is as follows: Mix and react an alkali, carbonate or bicarbonate containing M with phosphoric acid and an acid salt of a monobasic organic acid or polybasic organic acid containing an R group in a molar ratio, and then polymerize the reaction solution in one step at 100 - 800 °C for 0.5 - 10 h to obtain the finished complexing agent; or first dry the above reaction solution, and then polymerize it at 100 - 800 °C for 0.5 - 10 h to obtain the finished complexing agent. This complexing agent does not contain cyanide, and the electroplating solution containing this complexing agent has stable quality, good dispersibility, and a relatively wide process current density range that can be adopted. However, its deep plating performance still needs to be further improved, and the phosphoric acid chain segments on it may also affect the resistance of the plating solution, the current density, and thus the electroplating efficiency. Summary of the Invention

[0004] In order to overcome the deficiencies of the above-mentioned prior art, the present invention discloses an alkaline non-cyanide zinc-nickel alloy electroplating complexing agent and a preparation method thereof. The electroplating complexing agent disclosed in the present invention has extremely strong applicability in an alkaline non-cyanide zinc-nickel alloy electroplating solution, good complexing effect, stable properties of the formed complex, and good dispersion performance and covering performance.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] In the first aspect of the present invention, a cyanide-free zinc-nickel alloy electroplating complexing agent for alkaline is provided. The complexing agent comprises raw materials in the following parts by weight: 10 to 18 parts of a first complexing agent, 10 to 12 parts of a second complexing agent, and 10 to 15 parts of a hydroxycarboxylic acid; the first complexing agent is a modified aminocarboxylic acid complexing agent.

[0007] In some embodiments of the present invention, the preparation steps of the first complexing agent are as follows:

[0008] (1) Mix a polyamine and deionized water, heat to 30 to 45 °C with stirring, then add epichlorohydrin, and heat to 55 to 60 °C, and react for 1 to 3 h to obtain a modified polyamine;

[0009] (2) Mix ethylene glycol diethyl ether diamine tetraacetic acid and glycidyl ether and add them to N,N-dimethylformamide, then add the modified polyamine obtained in step (1), add a catalyst and acetic anhydride, heat to 80 to 100 °C, and react for 6 to 12 h. After washing and drying, the first complexing agent is obtained.

[0010] In some embodiments of the present invention, in step (1), the polyamine is at least one of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0011] Preferably, in step (1), the polyamine is diethylenetriamine.

[0012] In some embodiments of the present invention, in step (1), the mass ratio of the polyamine to epichlorohydrin is 1:(0.7 to 1.1).

[0013] Preferably, in step (1), the mass ratio of the polyamine to epichlorohydrin is 1:0.9.

[0014] In some embodiments of the present invention, in step (2), the glycidyl ether is ethylene glycol diglycidyl ether and / or pentaerythritol tetraglycidyl ether.

[0015] Preferably, in step (2), the glycidyl ether is pentaerythritol tetraglycidyl ether.

[0016] In some embodiments of the present invention, in step (2), the mass ratio of ethylene glycol diethyl ether diamine tetraacetic acid, glycidyl ether, and the modified polyamine obtained in step (1) is 1:(0.8 to 3):(1 to 5).

[0017] Preferably, in step (2), the mass ratio of ethylene glycol diethyl ether diamine tetraacetic acid, glycidyl ether, and the modified polyamine obtained in step (1) is 1:1.9:3.

[0018] First, the present invention modifies polyamine by using epichlorohydrin, and then modifies the main body of the first complexing agent, ethylene glycol diethyl ether diamine tetraacetic acid, together with glycidyl ether through chemical reaction. On the one hand, the polar active groups of the first complexing agent are increased, and on the other hand, the spatial extensibility of the first complexing agent may be further increased by means of polymer segments, jointly increasing the density of the functional groups of the complexing agent, and further increasing its adsorption and complexing sites for metal ions; it also plays a synergistic effect with the second complexing agent to further improve the complexing performance of the complexing agent system.

[0019] In some embodiments of the present invention, the second complexing agent is a mixture of sodium sulfite and polyamine.

[0020] Preferably, the polyamine used in the second complexing agent is at least one of ethylenediamine, diethylenetriamine, and triethylenetetramine.

[0021] More preferably, the polyamine used in the second complexing agent is triethylenetetramine.

[0022] Preferably, the mass ratio of the sodium sulfite to the polyamine is (0.8 - 1.5):2.

[0023] More preferably, the mass ratio of the sodium sulfite to the polyamine is 1.2:2.

[0024] In some embodiments of the present invention, the hydroxycarboxylic acid is at least one of citric acid, tartaric acid, and gluconic acid.

[0025] Preferably, the hydroxycarboxylic acid is citric acid.

[0026] In some embodiments of the present invention, Tween 60 with a mass ratio of 1:(0.5 - 1) to the first complexing agent is further added to the complexing agent.

[0027] Preferably, Tween 60 with a mass ratio of 1:0.7 to the first complexing agent is further added to the complexing agent.

[0028] The applicant has found that adding Tween 60 to the complexing agent system can effectively improve the dispersibility of each component in the system. When it is used in the electroplating solution, it can also maintain the uniform distribution of metal ions in the electroplating solution; at the same time, the applicant has also found that, possibly at a specific ratio, when the first complexing agent forms a stable complex with zinc-nickel metal ions in the electroplating solution, Tween 60 plays a good adsorption role in synergy with it and weakens or even loses the activity of metal ions, while controlling or preventing some possible side reactions in the electroplating solution, assisting the main body of the complexing agent in the system to play a good role in stabilizing metal ions, further improving the stability and uniformity of the electroplating solution, and achieving an unexpected increase in the effect.

[0029] The second aspect of the present invention also provides a preparation method of a complexing agent for alkaline cyanide-free zinc-nickel alloy electroplating, comprising the following steps:

[0030] Mix a first complexing agent, a second complexing agent, and a hydroxycarboxylic acid to obtain a complexing agent for alkaline cyanide-free zinc-nickel alloy electroplating.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The electroplating complexing agent disclosed in the present invention has extremely strong applicability in the alkaline cyanide-free zinc-nickel alloy electroplating solution, with good complexing effect, stable properties of the formed complex, and good dispersion performance and covering performance, making the nickel content of the obtained coating stable, evenly distributed and flat, and suitable for barrel plating and rack plating processes.

[0033] 2. The present invention first modifies polyamine with epichlorohydrin, and then modifies the main body of the first complexing agent, ethylene glycol diethyl ether diamine tetraacetic acid, through chemical reaction and glycidyl ether together. On the one hand, it increases the polar active groups of the first complexing agent, and on the other hand, it further increases the spatial extensibility of the first complexing agent through the polymer segment. The two together increase the density of the functional groups of the complexing agent, thereby increasing its adsorption and complexing sites for metal ions; it also plays a synergistic effect with the second complexing agent to further improve the complexing performance of the complexing agent system.

[0034] 3. Adding Tween 60 to the complexing agent system can effectively improve the dispersibility of each component in the system and maintain the uniform distribution of metal ions in the electroplating solution; at the same time, at a specific ratio, Tween 60 and the first complexing agent play a good adsorption role together and weaken or lose the activity of metal ions. While controlling or preventing some possible side reactions in the electroplating solution, it assists the main body of the complexing agent in the system to play a good role in stabilizing metal ions, further improving the stability and uniformity of the electroplating solution. Specific Embodiments

[0035] The following will illustrate the present invention in conjunction with specific implementation schemes. It should be noted that the following examples and comparative examples are only used to illustrate the present invention, rather than to limit the present invention. Other combinations and various improvements within the concept of the present invention can be made without departing from the main idea or scope of the present invention.

[0036] For the convenience of those skilled in the art to implement the present invention, some of the raw materials and manufacturers in the following embodiments are described as follows.

[0037] Unless otherwise specified, the second complexing agent used in the following embodiments is obtained by mixing sodium sulfite and triethylenetetramine in a mass ratio of 1.2:2; the hydroxycarboxylic acid used is citric acid.

[0038] Preparation Example 1

[0039] The preparation steps of the first complexing agent are as follows:

[0040] (1) Mix 5 g of diethylenetriamine and 20 mL of deionized water, heat to 40 °C with stirring, then add 4.5 g of epichlorohydrin, heat to 57 °C, and react for 2 h to obtain a modified polyamine;

[0041] (2) Mix 5 g of ethylene glycol diethyl ether diamine tetraacetic acid and 9.5 g of pentaerythritol tetraglycidyl ether and add them to 30 mL of N,N-dimethylformamide. Then add 15 g of the modified polyamine obtained in step (1), 2.5 g of pyridine and 5 g of acetic anhydride, heat to 90 °C, and react for 9 h. After washing and drying, the first complexing agent is obtained.

[0042] Preparation Example 2

[0043] The specific preparation steps of the first complexing agent are the same as those in Preparation Example 1, except that the addition amount of epichlorohydrin in step (1) is 6 g.

[0044] Preparation Example 3

[0045] The specific preparation steps of the first complexing agent are the same as those in Preparation Example 1, except that the addition amount of pentaerythritol tetraglycidyl ether in step (2) is 17.5 g.

[0046] Preparation Example 4

[0047] The specific preparation steps of the first complexing agent are the same as those in Preparation Example 1, except that the addition amount of the modified polyamine in step (2) is 25.5 g.

[0048] Example 1

[0049] An alkaline cyanide-free zinc-nickel alloy electroplating complexing agent contains the following raw materials in parts by weight: 14 parts of the first complexing agent, 11 parts of the second complexing agent, and 12.5 parts of hydroxycarboxylic acid.

[0050] The preparation method of the alkaline cyanide-free zinc-nickel alloy electroplating complexing agent in this example includes the following steps:

[0051] Mix the first complexing agent, the second complexing agent, and the hydroxycarboxylic acid to obtain the alkaline cyanide-free zinc-nickel alloy electroplating complexing agent.

[0052] The first complexing agent used in this example is obtained from Preparation Example 1.

[0053] Example 2

[0054] An alkaline cyanide-free zinc-nickel alloy electroplating complexing agent contains the following raw materials in parts by weight: 10 parts of the first complexing agent, 10 parts of the second complexing agent, and 10 parts of hydroxycarboxylic acid.

[0055] In this embodiment, the preparation method of the alkaline cyanide-free zinc-nickel alloy electroplating complexing agent is the same as that in Embodiment 1 in terms of specific implementation.

[0056] The first complexing agent used in this embodiment is obtained from Preparation Example 1.

[0057] Embodiment 3

[0058] An alkaline cyanide-free zinc-nickel alloy electroplating complexing agent contains the following raw materials in parts by weight: 18 parts of the first complexing agent, 12 parts of the second complexing agent, and 15 parts of hydroxycarboxylic acid.

[0059] In this embodiment, the preparation method of the alkaline cyanide-free zinc-nickel alloy electroplating complexing agent is the same as that in Embodiment 1 in terms of specific implementation.

[0060] The first complexing agent used in this embodiment is obtained from Preparation Example 1.

[0061] Embodiment 4

[0062] An alkaline cyanide-free zinc-nickel alloy electroplating complexing agent and its preparation method are the same as those in Embodiment 1 in terms of specific implementation, except that the first complexing agent used in this embodiment is obtained from Preparation Example 2.

[0063] Embodiment 5

[0064] An alkaline cyanide-free zinc-nickel alloy electroplating complexing agent and its preparation method are the same as those in Embodiment 1 in terms of specific implementation, except that the first complexing agent used in this embodiment is obtained from Preparation Example 3.

[0065] Embodiment 6

[0066] An alkaline cyanide-free zinc-nickel alloy electroplating complexing agent and its preparation method are the same as those in Embodiment 1 in terms of specific implementation, except that the first complexing agent used in this embodiment is obtained from Preparation Example 4.

[0067] Embodiment 7

[0068] An alkaline cyanide-free zinc-nickel alloy electroplating complexing agent contains the following raw materials in parts by weight: 14 parts of the first complexing agent, 11 parts of the second complexing agent, 12.5 parts of hydroxycarboxylic acid, and 9.8 parts of Tween 60.

[0069] In this embodiment, the preparation method of the alkaline cyanide-free zinc-nickel alloy electroplating complexing agent includes the following steps:

[0070] Mix the first complexing agent, the second complexing agent, hydroxycarboxylic acid, and Tween 60 to obtain the alkaline cyanide-free zinc-nickel alloy electroplating complexing agent.

[0071] Embodiment 8

[0072] An alkaline cyanide-free zinc-nickel alloy electroplating complexing agent and its preparation method. The specific implementation method is the same as that of Example 7, except that in terms of parts by weight, the addition amount of Tween 60 used in this example is 17 parts.

[0073] Example 9

[0074] An alkaline cyanide-free zinc-nickel alloy electroplating complexing agent and its preparation method. The specific implementation method is the same as that of Example 7, except that in this example, Tween 80 is used to replace Tween 60 in equal amounts.

[0075] Comparative Example 1

[0076] An alkaline cyanide-free zinc-nickel alloy electroplating complexing agent and its preparation method. The specific implementation method is the same as that of Example 1, except that the first complexing agent used is ethylene glycol diethylether diamine tetraacetic acid.

[0077] Performance test:

[0078] In the following tests, the composition and process parameters of the electroplating solution are set as follows: Each liter of electroplating solution contains the following raw materials: ZnO 10 g / L, NiSO4·6H2O 6.5 g / L, sodium hydroxide 120 g / L, the complexing agents prepared in Examples 1 - 9 and Comparative Example 1, 110 mL / L, and the balance is water; The process parameters are set with an iron sheet as the cathode, a tin plate as the anode, a current density of 5 A / dm 2 , a temperature of 25 °C, electroplating for 15 minutes. The following performance tests are carried out on the obtained electroplated layer of the workpiece, and the specific test results are shown in Table 1:

[0079] 1. Dispersion performance test:

[0080] The dispersion performance of each electroplating solution containing the complexing agents prepared in Examples 1 - 9 and Comparative Example 1 is tested and calculated by the bent cathode method.

[0081] 2. Coating thickness test:

[0082] On the electroplated layer of the workpiece, the first point is taken 1 cm from the left edge, and then points are taken every 2 cm in sequence, a total of three points. The coating thickness at different points is measured using the XF-P3 coating thickness gauge of Xifan Instruments, and the ratio of the average value of the coating thickness at the three points to the thickness at the first point is the thickness dispersion. The larger the thickness dispersion value, the more uniform the coating and the higher the flatness of the coating;

[0083] 3. Nickel content test of the coating:

[0084] The nickel content of the electroplated layer of each workpiece is tested using an XDL-B type X-ray fluorescence thickness gauge.

[0085] The test results are shown in Table 1.

[0086] Table 1

[0087] Project Dispersion performance / % Thickness dispersion / % Coating nickel content / wt% Example 1 94.3 70.3 13.54 Example 2 93.7 68.5 13.43 Example 3 93.3 69.1 13.48 Example 4 92.5 66.3 13.23 Example 5 91.8 63.2 13.05 Example 6 91.4 62.6 12.18 Example 7 94.8 72.7 13.59 Example 8 94.5 70.9 13.49 Example 9 94.6 71.5 13.41 Comparative Example 1 78 59.5 12

[0088] From the comparison of the data of Examples 1-3 disclosed in Table 1, it can be seen that the electroplating solution containing the complexing agent of the present invention has excellent dispersion performance, and the obtained coating has a high nickel content and a uniform and flat distribution; from the comparison of Examples 4, 5 and 6 with Example 1, it can be seen that when the addition amounts of epichlorohydrin in step (1), pentaerythritol tetraglycidyl ether in step (2) and modified polyamine in step (2) are changed respectively during the preparation of the first complexing agent, the dispersion ability and covering ability brought by the complexing agent will both decrease, resulting in the comprehensive performance of the coating obtained by the electroplating solution being affected; from the comparison of Example 7 with Example 1, it can be seen that when Tween 60 with a mass ratio of 1:0.7 to the first complexing agent is further added to the complexing agent, the dispersion performance of the electroplating solution is further increased, and due to the possible promotion of the enhanced complexing ability brought by its synergistic effect, the nickel distribution in the coating is more uniform and stable; from the comparison of Example 8 with Example 7, it can be seen that when the mass ratio of Tween 60 to the first complexing agent added to the complexing agent system is changed, the comprehensive performance of the coating will decline to varying degrees; from the comparison of Example 9 with Example 7, it can be seen that when Tween 80 is used to replace Tween 60 in equal amounts, although the dispersion performance of the electroplating solution is not greatly affected, due to the possible decrease or disappearance of the synergistic stabilization effect between it and the complexes in the system, the uniformity of the coating and the nickel content in the coating become worse; from the comparison of Comparative Example 1 with Example 1, it can be seen that when ethylene glycol diethyl ether diamine tetraacetic acid is used as the first complexing agent, due to the possible weakening or disappearance of the synergistic effect of each component in the system, the performance of the coating all declines.

[0089] The above is only a preferred embodiment of the present invention, and it does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the technical content disclosed above within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An alkaline cyanide-free zinc-nickel alloy electroplating complexing agent, characterized in that: The complexing agent comprises the following raw materials in parts by weight: 10 to 18 parts of a first complexing agent, 10 to 12 parts of a second complexing agent, and 10 to 15 parts of hydroxycarboxylic acid; the first complexing agent is a modified aminocarboxylic complexing agent.

2. The alkaline cyanide-free zinc-nickel alloy electroplating complexing agent according to claim 1, characterized in that: The preparation steps of the first complexing agent are as follows: (1) Mix the polyamine and deionized water, raise the temperature to 30-45° C. under stirring, then add epichlorohydrin, raise the temperature to 55-60° C., and react for 1-3 hours to obtain a modified polyamine; (2) Ethylene glycol diethyl ether diamine tetraacetic acid and glycidyl ether are mixed and added to N,N-dimethylformamide, and then the modified polyamine of step (1) is added, a catalyst and acetic anhydride are added, the temperature is raised to 80-100° C., the reaction is carried out for 6-12 hours, and the first complexing agent is obtained after washing and drying.

3. The alkaline cyanide-free zinc-nickel alloy electroplating complexing agent according to claim 2, characterized in that: In step (1), the polyamine is at least one of ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

4. The alkaline cyanide-free zinc-nickel alloy electroplating complexing agent according to claim 2, characterized in that: In step (1), the mass ratio of the polyamine to epichlorohydrin is 1:(0.7-1.1).

5. The alkaline cyanide-free zinc-nickel alloy electroplating complexing agent according to claim 2, characterized in that: In step (2), the glycidyl ether is ethylene glycol diglycidyl ether and / or pentaerythritol tetraglycidyl ether.

6. The alkaline cyanide-free zinc-nickel alloy electroplating complexing agent according to claim 2, characterized in that: In step (2), the mass ratio of ethylene glycol diethyl ether diamine tetraacetic acid, glycidyl ether and the modified polyamine of step (1) is (1-5): (0.8-3):

1.

7. The alkaline cyanide-free zinc-nickel alloy electroplating complexing agent according to claim 1, characterized in that: The second complexing agent is a mixture of sodium sulfite and polyamine.

8. The alkaline cyanide-free zinc-nickel alloy electroplating complexing agent according to claim 1, characterized in that: The hydroxycarboxylic acid is at least one of citric acid, tartaric acid and gluconic acid.

9. The alkaline cyanide-free zinc-nickel alloy electroplating complexing agent according to claim 1, characterized in that: The complexing agent is also added with Tween 60 in a mass ratio of 1: (0.5-1) to the first complexing agent.

10. A method for preparing the alkaline cyanide-free zinc-nickel alloy electroplating complexing agent according to any one of claims 1 to 8, characterized in that: The following steps are involved: The first complexing agent, the second complexing agent and the hydroxycarboxylic acid are mixed to obtain an alkaline cyanide-free zinc-nickel alloy electroplating complexing agent.