Environment-friendly cyanide-free zincate zinc plating brightener and preparation method thereof

Abstract

The application relates to an environment-friendly cyanide-free zincate zinc plating brightener and a preparation method thereof, and relates to the technical field of metal surface treatment. The brightener comprises the following components in mass fraction: 10-30 parts of sulfonic acid group modified p-chlorobenzaldehyde acetaldehyde, 10-20 parts of conjugated modified anisaldehyde, 15-40 parts of compound auxiliary brightener, 5-15 parts of isomeric tridecanol polyoxyethylene ether, 3-10 parts of polyethylene glycol, 2-8 parts of walking agent and 30-50 parts of ethylene glycol monobutyl ether. The preparation method comprises the following steps: under the condition of water bath heating, the sulfonic acid group modified p-chlorobenzaldehyde acetaldehyde is added into the ethylene glycol monobutyl ether, after uniform stirring, the conjugated modified anisaldehyde, the isomeric tridecanol polyoxyethylene ether, the polyethylene glycol, the compound auxiliary brightener and the walking agent are sequentially added, stirring is conducted after each component is added, the stirring is continuously conducted by increasing the rotating speed after the components are completely added, and the environment-friendly cyanide-free zincate zinc plating brightener is obtained. The application has the effect of improving the dispersion performance of the brightener, and can effectively improve the uniformity and brightening effect of a plating layer.

Description

Technical Field

[0001] This application relates to the field of metal surface treatment technology, and in particular to an environmentally friendly, cyanide-free zincate zinc plating brightener and its preparation method. Background Technology

[0002] Zinc plating is a crucial metal surface treatment technology, widely used in industries such as automotive, home appliances, and construction to improve product corrosion resistance and aesthetics. Traditional zinc plating processes often employ cyanide-containing solutions. While cyanides possess excellent electrochemical properties, their highly toxic nature poses a serious threat to the environment and workers. In recent years, with increasing environmental awareness and technological advancements, cyanide-free zinc plating technology has gradually become a research hotspot, especially cyanide-free zincate zinc plating technology, which has received widespread attention due to its environmental advantages.

[0003] Currently, cyanide-free zincate zinc plating is mainly achieved by adjusting the composition of the plating bath. Commonly used cyanide-free zincate plating baths typically include zincates, complexing agents, brighteners, and stabilizers. Zincates, as the main salt, provide zinc ions; complexing agents control the release rate of zinc ions and maintain the stability of the plating bath; brighteners improve the gloss and smoothness of the coating; and stabilizers prevent the decomposition and precipitation of the plating bath. In addition, auxiliary components, such as buffers and conductive agents, are often added to further optimize the performance of the plating bath.

[0004] However, existing cyanide-free zincate zinc plating brighteners have some defects. The brighteners are not sufficiently dispersible, and when deposited on complex-shaped workpieces and large-area workpieces, uneven coating thickness will occur, resulting in unstable coating quality. Therefore, improvements are needed. Summary of the Invention

[0005] To improve the dispersibility of brighteners, this application provides an environmentally friendly, cyanide-free zincate zinc plating brightener and its preparation method.

[0006] This application provides an environmentally friendly, cyanide-free zincate zinc plating brightener and its preparation method, which adopts the following technical solution:

[0007] Firstly, this application provides an environmentally friendly, cyanide-free zincate zinc plating brightener, which adopts the following technical solution:

[0008] An environmentally friendly, cyanide-free zincate zinc plating brightener comprises the following components in parts by weight:

[0009] 10-30 parts of sulfonic acid group modified p-chlorobenzyl acetone

[0010] 10-20 parts of conjugated modified anisaldehyde

[0011] 15-40 parts of compound auxiliary brightener

[0012] 5-15 parts of isomeric tridecyl alcohol polyoxyethylene ether

[0013] 3-10 parts of polyethylene glycol

[0014] 2-8 parts of positioning agent

[0015] 30-50 parts of ethylene glycol monobutyl ether.

[0016] Sulfonic acid modification of p-chlorobenzyl acetone introduces sulfonic acid groups, enhancing water solubility and dispersibility. During zinc ion deposition, it regulates the deposition rate and mode, resulting in finer and more uniform zinc coating crystals, thus improving the coating's gloss. Conjugated modification of anisaldehyde, with its conjugated structure capable of absorbing and reflecting specific wavelengths of light, produces a glossy coating surface. During zincate plating, it can adsorb onto the coating surface, synergistically working with sulfonic acid-modified p-chlorobenzyl acetone to regulate the deposition direction and rate of zinc ions, promoting a smoother and brighter coating. The compounded auxiliary brightener, through synergistic effects between components, refines the coating crystals and improves... The brightener enhances the uniformity of the brightening effect and improves the stability of the brightener. Isomeric tridecyl alcohol polyoxyethylene ether reduces the surface tension of the plating bath, promotes the spreading of the brightener and the dispersion of its components, prevents agglomeration and delamination, and improves the uniformity and stability of the brightener. Polyethylene glycol has good hydrophilicity and can interact with other components in the brightener to ensure uniform dispersion in the plating bath, delivering effective components to the surface of the plated parts and synergistically improving the coating quality. The leveling agent effectively improves the dispersion ability of the plating bath, enabling zinc ions to be uniformly deposited on the surface of complex plated parts. It works synergistically with other components to enhance the uniformity and brightening effect of the coating.

[0017] Preferably, the raw materials for preparing the sulfonic acid-modified p-chlorobenzyl acetone include p-chlorobenzyl acetone and chlorosulfonic acid.

[0018] Chlorosulfonic acid introduces sulfonic acid groups onto p-chlorobenzyl acetone. The sulfonic acid groups have strong hydrophilicity and ionization properties, which enhances the solubility of the modified p-chlorobenzyl acetone in the plating bath. At the same time, it can generate electrostatic repulsion or attraction with other charged particles in the plating bath, thereby effectively preventing its own aggregation and improving dispersibility. In the zinc plating process, good dispersibility can ensure that it is evenly distributed throughout the plating bath to regulate the deposition process of zinc ions. During the coating growth, it is adsorbed on the surface and interacts with zinc ions through its special chemical structure, guiding the orderly deposition of zinc ions, reducing defects caused by uneven deposition, and thus improving the uniformity of the coating. This results in a uniform appearance of the coating on a macroscopic scale. This orderly deposition makes the coating crystals more delicate and regular, ultimately effectively improving the brightness of the coating.

[0019] Preferably, the raw materials for preparing the conjugated modified anisaldehyde include anisaldehyde bulk and diethyl malonate.

[0020] The reaction between anisaldehyde and diethyl malonate introduces a conjugated structure, enhancing the compatibility and stability of the conjugated modified anisaldehyde in the brightener system. This conjugated system can generate various interactions such as π-π stacking and hydrogen bonding with metal ions and other organic components in the plating bath, thereby ensuring that the conjugated modified anisaldehyde is uniformly dispersed in the plating bath and avoiding local concentrations that are too high or too low. During zincate plating, the conjugated modified anisaldehyde is uniformly adsorbed on the coating surface. Through synergistic effects with zinc ions and other additives, it guides zinc ions to deposit along a specific direction and rate, effectively reducing defects and irregularities in the coating growth process, resulting in a finer and more uniform coating crystallization, and improving the smoothness and brightness of the coating.

[0021] Preferably, the raw materials for preparing the compound auxiliary brightener include 2-aminobenzamide, cinnamic acid, and modified sodium naphthalenesulfonate.

[0022] 2-Aminobenzamide possesses a nitrogen atom and benzene ring conjugated system, enabling it to generate π-π stacking interactions with the conjugated structure of sulfonic acid-modified p-chlorobenzyl acetone. Simultaneously, 2-aminobenzamide is polar and can interact with the sulfonic acid group. This multi-interaction effectively enhances the dispersibility of the brightener, regulating the zinc ion deposition path during zincate plating and promoting refined coating crystallization. Cinnamic acid can co-adsorb with conjugated modified vanillin on the electrode surface, guiding the orderly deposition of zinc ions. Complementary and synergistic effects with conjugated modified vanillin effectively improve coating smoothness and brightness. Modified sodium naphthalenesulfonate simultaneously promotes the dispersibility of both sulfonic acid-modified p-chlorobenzyl acetone and conjugated modified vanillin, ensuring uniform zinc ion deposition and improving coating uniformity. The combined use of these three components synergistically enhances the brightener's dispersibility, optimizing the zinc ion deposition process from multiple angles during zinc plating, reducing coating defects, and improving coating uniformity, density, and brightness.

[0023] Preferably, the raw materials for preparing the modified sodium naphthalene sulfonate include sodium naphthalene sulfonate bulk, ammonium persulfate, and hexadecyl chloride pyridine.

[0024] Ammonium persulfate can promote the self-polymerization of sodium naphthalene sulfonate and improve its dispersibility through steric hindrance. Chlorohexadecylpyridine grafts quaternary ammonium salt groups onto the surface of sodium naphthalene sulfonate, enhancing its cationicity and improving its adsorption performance in the plating bath. It can effectively adsorb onto the zinc layer surface, and the sulfonic acid group modification of chlorobenzyl acetone and conjugated vanillin can better regulate the deposition behavior of zinc ions, making the coating crystals more fine and uniform, thereby improving the uniformity and brightness of the coating.

[0025] Preferably, the modified sodium naphthalenesulfonate is prepared using the following steps:

[0026] Sodium naphthalene sulfonate was dispersed in water to obtain a sodium naphthalene sulfonate solution. Ammonium persulfate was added to the sodium naphthalene sulfonate solution under stirring. The mixture was heated and stirred to react. After cooling, anhydrous ethanol was poured in to precipitate the precipitate. The precipitate was collected by filtration and washed with anhydrous ethanol. The washed precipitate was then dried under vacuum to obtain polynaphthalene sulfonate.

[0027] The prepared sodium naphthalene sulfonate was dispersed in N,N-dimethylformamide to obtain a sodium naphthalene sulfonate solution. Chlorohexadecylpyridine was added to the sodium naphthalene sulfonate solution, and the mixture was heated and stirred to react. After cooling, ice water was added to precipitate the product, which was then washed with ice water and dried under vacuum to obtain modified sodium naphthalene sulfonate.

[0028] Preferably, the mass ratio of sodium naphthalenesulfonate bulk, ammonium persulfate and hexadecyl pyridine chloride is 1:0.05:(0.02-0.08).

[0029] The modified sodium naphthalene sulfonate prepared according to the above steps and mass ratio has good performance and can effectively improve the dispersibility of brightener, thereby improving the quality and brightness of the coating.

[0030] Preferably, the positional agent comprises carboxyethyl isothiourea chloride, sodium hydroxymethylsulfonate, and 2-mercaptobenzimidazole.

[0031] Carboxyethyl isothiourea chloride can ionize into charged groups in the plating bath. By changing the electric field distribution, it guides zinc ions to migrate to the low current density region of the workpiece, thereby improving the dispersion ability of the plating bath and ensuring uniform deposition of the coating on the complex-shaped workpiece. Sodium hydroxymethylsulfonate has good water solubility and coordination ability. It can form a weak coordination complex with zinc ions. During the electroplating process, it changes the deposition potential of zinc ions, further promoting the uniform deposition of zinc ions in all parts of the workpiece. This is beneficial to improving the deep plating capability and enabling good coatings to be obtained even in the depressions and pores of the workpiece. The heterocyclic structure of 2-mercaptobenzimidazole enables it to adsorb onto the coating surface, providing specific active sites for zinc ion deposition. It works synergistically with carboxyethyl isothiourea chloride to enhance the regulation of the electric field distribution, causing zinc ions to migrate to various parts of the coated part and further improving the dispersion ability of the plating solution. At the same time, its adsorption properties help stabilize the weak coordination complex formed between sodium hydroxymethylsulfonate and zinc ions, optimize the regulation effect of zinc ion deposition potential, promote the uniform and orderly deposition of zinc ions on the coating surface, reduce defects caused by uneven deposition, and jointly improve the density and smoothness of the coating.

[0032] Preferably, the mass ratio of carboxyethyl isothiourea chloride, sodium hydroxymethylsulfonate, and 2-mercaptobenzimidazole is (0.02-0.05):1:0.5.

[0033] The leveling agent formulated according to the above mass ratio can effectively improve the uniformity and brightness of the coating.

[0034] Secondly, this application provides a method for preparing an environmentally friendly, cyanide-free zincate zinc plating brightener, using the following technical solution:

[0035] A method for preparing an environmentally friendly, cyanide-free zincate zinc plating brightener includes the following steps:

[0036] Sulfonic acid-modified p-chlorobenzyl acetone was added to ethylene glycol monobutyl ether under water bath heating conditions. After stirring evenly, conjugated modified anisaldehyde, isomeric tridecanol polyoxyethylene ether, polyethylene glycol, compound auxiliary brightener and positioner were added in sequence. Stirring was performed after each addition. After the addition was completed, the speed was increased and stirring was continued to obtain an environmentally friendly cyanide-free zincate zinc plating brightener.

[0037] The environmentally friendly, cyanide-free zincate zinc plating brightener prepared according to the above steps has good dispersibility and can be evenly distributed in the plating solution, effectively improving the uniformity and density of the coating, and the coating has a good bright effect.

[0038] In summary, this application includes at least one of the following beneficial technical effects:

[0039] 1. Sulfonic acid group modification of p-chlorobenzyl acetone enhances water solubility and dispersibility. During zinc ion deposition, it regulates the deposition rate and mode, resulting in finer and more uniform crystallization of the zinc coating, thereby improving the coating's gloss. Conjugated modification of anisaldehyde, with its conjugated structure capable of absorbing and reflecting specific wavelengths of light, produces a glossy coating surface. During zincate plating, it can adsorb onto the coating surface and synergistically work with sulfonic acid group-modified p-chlorobenzyl acetone to regulate the deposition direction and rate of zinc ions, promoting a smoother and brighter coating. The compounded auxiliary brightener, through synergistic effects between components, refines the coating crystallization. The brightener improves the uniformity of the brightening effect and enhances the stability of the brightener. Isomeric tridecyl alcohol polyoxyethylene ether reduces the surface tension of the plating bath, promotes the spreading of the brightener and the dispersion between components, prevents agglomeration and stratification, and improves the uniformity and stability of the brightener. Polyethylene glycol has good hydrophilicity and can interact with other components in the brightener to ensure uniform dispersion in the plating bath, delivering effective components to the surface of the plated parts and synergistically improving the coating quality. The leveling agent effectively improves the dispersion ability of the plating bath, enabling zinc ions to be uniformly deposited on the surface of complex plated parts, and works synergistically with other components to enhance the uniformity and brightening effect of the coating.

[0040] 2. In the compounded auxiliary brightener, 2-aminobenzamide possesses a nitrogen atom-benzene ring conjugated system, which can generate π-π stacking interactions with the conjugated structure of sulfonic acid-modified p-chlorobenzyl acetone. Simultaneously, 2-aminobenzamide is polar and can interact with the sulfonic acid group. This multi-interaction effectively improves the dispersibility of the brightener, regulating the zinc ion deposition path during zincate plating and promoting finer coating crystals. Cinnamic acid can co-adsorb with conjugated modified vanillin on the electrode surface, guiding... The orderly deposition of zinc ions, complementing and synergistically working with conjugated modified vanillin, effectively improves the smoothness and brightness of the coating. Modified sodium naphthalene sulfonate can simultaneously promote the dispersion of sulfonic acid-modified chlorobenzyl acetone and conjugated modified vanillin, enabling uniform deposition of zinc ions and improving the uniformity of the coating. When these three are combined, they synergistically enhance each other, further improving the dispersibility of the brightener. During zinc plating, the zinc ion deposition process can be optimized from multiple angles, reducing coating defects and improving the uniformity, density, and brightness of the coating.

[0041] 3. Carboxyethyl isothiourea chloride can ionize into charged groups in the plating bath. By changing the electric field distribution, it guides zinc ions to migrate to areas of low current density on the workpiece, thereby improving the dispersion ability of the plating bath and ensuring uniform deposition of the coating on complex-shaped workpieces. Sodium hydroxymethylsulfonate has good water solubility and coordination ability. It can form weak coordination complexes with zinc ions. During the electroplating process, it changes the deposition potential of zinc ions, further promoting uniform deposition of zinc ions in all parts of the workpiece. This is beneficial for improving the deep plating capability and ensuring a good coating even in the depressions and pores of the workpiece. The heterocyclic structure of 2-mercaptobenzimidazole enables it to adsorb onto the coating surface, providing specific active sites for zinc ion deposition. Synergistically, it works with carboxyethyl isothiourea chloride to enhance the regulation of the electric field distribution, causing zinc ions to migrate to various parts of the coated component and further improving the dispersion ability of the plating solution. Simultaneously, its adsorption properties help stabilize the weakly coordinated complex formed between sodium hydroxymethylsulfonate and zinc ions, optimizing the regulation of the zinc ion deposition potential, promoting uniform and orderly deposition of zinc ions on the coating surface, reducing defects caused by uneven deposition, and jointly improving the density and smoothness of the coating. Detailed Implementation

[0042] This application discloses an environmentally friendly, cyanide-free zincate zinc plating brightener and its preparation method. Unless otherwise specified, all raw materials used in this application are commercially available. The following examples provide further detailed description of this application:

[0043] Raw material description: p-Chlorobenzide acetone (CAS No.: 122-57-6), chlorosulfonic acid (CAS No.: 7790-94-5), anisaldehyde (CAS No.: 123-11-5), diethyl malonate (CAS No.: 105-53-3), sodium ethoxide (CAS No.: 141-52-6), sodium naphthalenesulfonate (CAS No.: 1321-69-3), ammonium persulfate (CAS No.: 7727-54-0), hexadecyl pyridine chloride (CAS No.: 6004-24-6), ethylene glycol monobutyl ether (CA S No.: 111-76-2), Isotridecyl alcohol polyoxyethylene ether (CAS No.: 9043-30-5), polyethylene glycol PEG-400 (CAS No.: 25322-68-3), 2-aminobenzamide (CAS No.: 88-68-6), cinnamic acid (CAS No.: 140-10-3), carboxyethyl isothiourea chloride (CAS No.: 5425-78-5), sodium hydroxymethylsulfonate (CAS No.: 870-72-4), 2-mercaptobenzimidazole (CAS No.: 583-39-1).

[0044] Example 1

[0045] Preparation of sulfonic acid-modified p-chlorobenzyl acetone

[0046] 35g of p-chlorobenzyl acetone was placed in an ice-water bath and stirred at 100 rpm. 25g of chlorosulfonic acid was added over 1 hour. After the addition was complete, the temperature was raised to 40°C and the mixture was stirred at 200 rpm for 3 hours. After the reaction was completed, the solution was poured into ice water and stirred at 200 rpm. After the solid precipitated, the solid was collected by filtration and recrystallized with anhydrous ethanol to obtain sulfonic acid-modified p-chlorobenzyl acetone.

[0047] Preparation of conjugated modified anisaldehyde

[0048] 20g of anisaldehyde and 23.5g of diethyl malonate were dispersed in 100mL of anhydrous ethanol and stirred at 200rpm until fully dissolved to obtain a modified solution. 10g of sodium ethoxide was added to the modified solution, and the mixture was heated to 80℃ and stirred at 200rpm for 4h. After cooling to below 30℃, the modified solution was poured into ice water, and the pH was adjusted to 4 with hydrochloric acid to precipitate the product. The precipitate was collected by filtration, washed with deionized water, and dried under vacuum at 60℃ to obtain conjugated modified anisaldehyde.

[0049] Preparation of modified sodium naphthalenesulfonate

[0050] 46.73 g of sodium naphthalene sulfonate was dispersed in 500 mL of deionized water to obtain a sodium naphthalene sulfonate solution. 2.34 g of ammonium persulfate was added to the sodium naphthalene sulfonate solution under stirring at 200 rpm. The mixture was heated to 80 °C and stirred at 200 rpm for 4 h. After cooling to 30 °C, anhydrous ethanol was added to precipitate the product. The precipitate was collected by filtration and washed with anhydrous ethanol. The washed precipitate was then vacuum dried at 60 °C to obtain polynaphthalene sulfonate.

[0051] The prepared sodium naphthalene sulfonate was dispersed in 500 mL of N,N-dimethylformamide to obtain a sodium naphthalene sulfonate solution. 0.93 g of hexadecyl chloropyridine was added to the sodium naphthalene sulfonate solution, the temperature was raised to 100 °C, and the mixture was stirred at 300 rpm for 4 h. After cooling to 30 °C, ice water was added to precipitate the product. The product was washed with ice water and dried under vacuum at 60 °C to obtain modified sodium naphthalene sulfonate.

[0052] Preparation of environmentally friendly, cyanide-free zincate zinc plating brightener

[0053] In a 40℃ water bath, 10g of sulfonic acid-modified p-chlorobenzyl acetone was added to 30g of ethylene glycol monobutyl ether. After stirring evenly at 200rpm, 10g of conjugated modified anisaldehyde, 5g of isomeric tridecyl alcohol polyoxyethylene ether, 3g of polyethylene glycol, 15g of compound auxiliary brightener, and 2g of position agent were added sequentially. The mass ratio of 2-aminobenzamide, cinnamic acid, and modified sodium naphthalene sulfonate in the compound auxiliary brightener was 1:1.5:2, and the mass ratio of carboxyethyl isothiourea chloride, sodium hydroxymethyl sulfonate, and 2-mercaptobenzimidazole in the position agent was 0.02:1:0.5. After each component was added, the mixture was stirred at 200rpm for 10min. After all the components were added, the stirring speed was increased to 300rpm, and stirring was continued for 1h to obtain an environmentally friendly cyanide-free zincate zinc plating brightener.

[0054] Example 2

[0055] Preparation of sulfonic acid-modified p-chlorobenzyl acetone

[0056] 35g of p-chlorobenzyl acetone was placed in an ice-water bath and stirred at 100 rpm. 25g of chlorosulfonic acid was added over 1 hour. After the addition was complete, the temperature was raised to 40°C and the mixture was stirred at 200 rpm for 3 hours. After the reaction was completed, the solution was poured into ice water and stirred at 200 rpm. After the solid precipitated, the solid was collected by filtration and recrystallized with anhydrous ethanol to obtain sulfonic acid-modified p-chlorobenzyl acetone.

[0057] Preparation of conjugated modified anisaldehyde

[0058] 20g of anisaldehyde and 23.5g of diethyl malonate were dispersed in 100mL of anhydrous ethanol and stirred at 200rpm until fully dissolved to obtain a modified solution. 10g of sodium ethoxide was added to the modified solution, and the mixture was heated to 80℃ and stirred at 200rpm for 4h. After cooling to below 30℃, the modified solution was poured into ice water, and the pH was adjusted to 4 with hydrochloric acid to precipitate the product. The precipitate was collected by filtration, washed with deionized water, and dried under vacuum at 60℃ to obtain conjugated modified anisaldehyde.

[0059] Preparation of modified sodium naphthalenesulfonate

[0060] 44.25 g of sodium naphthalene sulfonate was dispersed in 500 mL of deionized water to obtain a sodium naphthalene sulfonate solution. 2.21 g of ammonium persulfate was added to the sodium naphthalene sulfonate solution under stirring at 200 rpm. The mixture was heated to 80 °C and stirred at 200 rpm for 4 h. After cooling to 30 °C, anhydrous ethanol was added to precipitate the product. The precipitate was collected by filtration and washed with anhydrous ethanol. The washed precipitate was then vacuum dried at 60 °C to obtain sodium polynaphthalene sulfonate.

[0061] The prepared sodium naphthalene sulfonate was dispersed in 500 mL of N,N-dimethylformamide to obtain a sodium naphthalene sulfonate solution. 3.54 g of hexadecyl chloropyridine was added to the sodium naphthalene sulfonate solution, the temperature was raised to 100 °C, and the mixture was stirred at 300 rpm for 4 h. After cooling to 30 °C, ice water was added to precipitate the product. The product was washed with ice water and dried under vacuum at 60 °C to obtain modified sodium naphthalene sulfonate.

[0062] Preparation of environmentally friendly, cyanide-free zincate zinc plating brightener

[0063] Under a 40℃ water bath, 30g of sulfonic acid-modified p-chlorobenzyl acetone was added to 50g of ethylene glycol monobutyl ether. After stirring evenly at 200rpm, 20g of conjugated modified anisaldehyde, 15g of isomeric tridecyl alcohol polyoxyethylene ether, 10g of polyethylene glycol, 40g of compound auxiliary brightener, and 8g of position agent were added sequentially. The mass ratio of 2-aminobenzamide, cinnamic acid, and modified sodium naphthalene sulfonate in the compound auxiliary brightener was 1:1.5:2, and the mass ratio of carboxyethyl isothiourea chloride, sodium hydroxymethyl sulfonate, and 2-mercaptobenzimidazole in the position agent was 0.05:1:0.5. After each component was added, the mixture was stirred at 200rpm for 10min. After all the components were added, the stirring speed was increased to 300rpm, and stirring was continued for 1h to obtain an environmentally friendly cyanide-free zincate zinc plating brightener.

[0064] Example 3

[0065] Preparation of sulfonic acid-modified p-chlorobenzyl acetone

[0066] 35g of p-chlorobenzyl acetone was placed in an ice-water bath and stirred at 100 rpm. 25g of chlorosulfonic acid was added over 1 hour. After the addition was complete, the temperature was raised to 40°C and the mixture was stirred at 200 rpm for 3 hours. After the reaction was completed, the solution was poured into ice water and stirred at 200 rpm. After the solid precipitated, the solid was collected by filtration and recrystallized with anhydrous ethanol to obtain sulfonic acid-modified p-chlorobenzyl acetone.

[0067] Preparation of conjugated modified anisaldehyde

[0068] 20g of anisaldehyde and 23.5g of diethyl malonate were dispersed in 100mL of anhydrous ethanol and stirred at 200rpm until fully dissolved to obtain a modified solution. 10g of sodium ethoxide was added to the modified solution, and the mixture was heated to 80℃ and stirred at 200rpm for 4h. After cooling to below 30℃, the modified solution was poured into ice water, and the pH was adjusted to 4 with hydrochloric acid to precipitate the product. The precipitate was collected by filtration, washed with deionized water, and dried under vacuum at 60℃ to obtain conjugated modified anisaldehyde.

[0069] Preparation of modified sodium naphthalenesulfonate

[0070] 45.46 g of sodium naphthalene sulfonate was dispersed in 500 mL of deionized water to obtain a sodium naphthalene sulfonate solution. 2.27 g of ammonium persulfate was added to the sodium naphthalene sulfonate solution under stirring at 200 rpm. The mixture was heated to 80 °C and stirred at 200 rpm for 4 h. After cooling to 30 °C, anhydrous ethanol was added to precipitate the product. The precipitate was collected by filtration and washed with anhydrous ethanol. The washed precipitate was then vacuum dried at 60 °C to obtain sodium polynaphthalene sulfonate.

[0071] The prepared sodium naphthalene sulfonate was dispersed in 500 mL of N,N-dimethylformamide to obtain a sodium naphthalene sulfonate solution. 2.27 g of hexadecyl chloropyridine was added to the sodium naphthalene sulfonate solution, the temperature was raised to 100 °C, and the mixture was stirred at 300 rpm for 4 h. After cooling to 30 °C, ice water was added to precipitate the product. The product was washed with ice water and dried under vacuum at 60 °C to obtain modified sodium naphthalene sulfonate.

[0072] Preparation of environmentally friendly, cyanide-free zincate zinc plating brightener

[0073] Under a 40℃ water bath, 20g of sulfonic acid-modified p-chlorobenzyl acetone was added to 40g of ethylene glycol monobutyl ether. After stirring evenly at 200rpm, 15g of conjugated modified anisaldehyde, 10g of isomeric tridecyl alcohol polyoxyethylene ether, 6.5g of polyethylene glycol, 22.5g of compound auxiliary brightener, and 5g of position agent were added sequentially. The mass ratio of 2-aminobenzamide, cinnamic acid, and modified sodium naphthalene sulfonate in the compound auxiliary brightener was 1:1.5:2. The mass ratio of carboxyethyl isothiourea chloride, sodium hydroxymethyl sulfonate, and 2-mercaptobenzimidazole in the position agent was 0.035:1:0.5. After each component was added, the mixture was stirred at 200rpm for 10min. After all the components were added, the stirring speed was increased to 300rpm and stirring was continued for 1h to obtain an environmentally friendly cyanide-free zincate zinc plating brightener.

[0074] Example 4

[0075] Example 4 is based on Example 3. The only difference between Example 4 and Example 3 is that in Example 4, the modified sodium naphthalene sulfonate does not contain chlorohexadecylpyridine, the amount of sodium naphthalene sulfonate is 47.62g, and the amount of ammonium persulfate is 2.38g.

[0076] Example 5

[0077] Example 5 is based on Example 3. The only difference between Example 5 and Example 3 is that in Example 5, the amount of sodium naphthalenesulfonate is 42.73g, the amount of ammonium persulfate is 2.14g, and the amount of hexadecyl chloropyridine is 5.13g.

[0078] Example 6

[0079] Example 6 is based on Example 3. The only difference between Example 6 and Example 3 is that in Example 6, the modified sodium naphthalene sulfonate is replaced with sodium naphthalene sulfonate.

[0080] Example 7

[0081] Example 7 is based on Example 3. The only difference between Example 7 and Example 3 is that cinnamic acid is not added in Example 7.

[0082] Example 8

[0083] Example 8 is based on Example 3. The only difference between Example 8 and Example 3 is that 2-aminobenzamide and cinnamic acid are not added in Example 8.

[0084] Example 9

[0085] Example 9 is based on Example 3. The only difference between Example 9 and Example 3 is that the mass ratio of carboxyethyl isothiourea chloride, sodium hydroxymethylsulfonate and 2-mercaptobenzimidazole in Example 9 is 0.01:1:0.5.

[0086] Example 10

[0087] Example 10 is based on Example 3. The only difference between Example 10 and Example 3 is that in Example 10, the mass ratio of carboxyethyl isothiourea chloride, sodium hydroxymethylsulfonate and 2-mercaptobenzimidazole is 0.07:1:0.5.

[0088] Example 11

[0089] Example 11 is based on Example 3. The only difference between Example 11 and Example 3 is that sodium hydroxymethylsulfonate and 2-mercaptobenzimidazole are not added to the leveling agent in Example 11.

[0090] Comparative Example 1

[0091] Comparative Example 1 is based on Example 3. The only difference between Comparative Example 1 and Example 3 is that the sulfonic acid-modified p-chlorobenzyl acetone is replaced with p-chlorobenzyl acetone in Comparative Example 1.

[0092] Comparative Example 2

[0093] Comparative Example 2 is based on Example 3. The only difference between Comparative Example 2 and Example 3 is that the conjugated modified anisaldehyde is replaced with anisaldehyde in Comparative Example 2.

[0094] Brightener performance test: A 10cm*10cm*0.5mm iron sheet was selected as the item to be electroplated. It was degreased with alkaline solution, rinsed with hot water and deionized water, and then dried to obtain a pre-treated iron sheet for later use. A Hull cell experiment was conducted. The pre-treated iron sheet was electroplated in a 250mL Hull cell. The plating solution contained 220g / L potassium chloride, 65g / L zinc chloride, 30g / L boric acid, and 1mL / L of the sample. The electroplating temperature was 25℃, and the current density was 1A / dm³. 2 Electroplating was performed for 15 minutes. The thickness of the coating was measured at the two endpoints (referred to as the first and third points) and the center point (referred to as the second point) on the diagonal of each sample. The coating thickness was calculated and the results were recorded in Table 1. Under the illumination of a 50W fluorescent lamp, the appearance of the electroplated iron sheet was observed at a distance of 40cm from the fluorescent lamp and the results were recorded in Table 1.

[0095] Table 1. Test results of brightener dispersibility and brightening effect

[0096]

[0097] As shown in Table 1, the thickness difference between the three sites in Examples 1-3 is less than 0.27 μm, and the coating is smooth and has high gloss, thus demonstrating that the brightener prepared in this application has good dispersibility and brightening effect.

[0098] As shown in Table 1, the only difference between Examples 4 and 5 and Example 3 is that: in Example 4, no hexadecylpyridine chloroform was added to the modified sodium naphthalene sulfonate; in Example 5, the mass ratio of sodium naphthalene sulfonate, ammonium persulfate, and hexadecylpyridine chloroform was 1:0.05:0.12. Compared with Example 3, the uniformity of the coating thickness in Examples 4 and 5 decreased. This is because without the addition of hexadecylpyridine chloroform, the dispersibility and adsorption of the modified sodium naphthalene sulfonate decreased, the auxiliary effect on the main brightener was weakened, the dispersibility of the brightener decreased, and the uniformity of the coating decreased. Adding excessive hexadecylpyridine chloroform would affect the water solubility and dispersibility of the modified sodium naphthalene sulfonate due to the excessive hydrophobic hexadecyl group, and the dispersibility of the brightener would also be affected.

[0099] As shown in Table 1, the differences between Examples 6, 7, and 8 and Example 3 are only as follows: in Example 6, modified sodium naphthalene sulfonate was replaced with sodium naphthalene sulfonate; in Example 7, cinnamic acid was not added; and in Example 8, 2-aminobenzamide and cinnamic acid were not added. Compared with Example 3, Examples 6, 7, and 8 showed a decrease in the uniformity of the coating thickness and a deterioration in the brightening effect. This is because sodium naphthalene sulfonate lacked modification treatment, resulting in a decrease in dispersibility and adsorption performance. Furthermore, reducing the types of auxiliary brighteners reduced the synergistic effect between components, further decreasing the performance of the brighteners, thereby reducing the dispersibility and brightening effect, and decreasing the uniformity of the coating.

[0100] As shown in Table 1, the only difference between Examples 9, 10, and 11 and Example 3 is that the mass ratio of the components was changed in Examples 9 and 10, and sodium hydroxymethylsulfonate and 2-mercaptobenzimidazole were not added in Example 11. Compared with Example 3, the uniformity of the coating decreased and the bright effect deteriorated in Examples 9, 10, and 11. This is because changing the component ratio will affect the synergistic effect between the leveling agents, and reducing the components will further weaken the synergistic effect between the components, thereby affecting the dispersion performance and reducing the uniformity and bright effect of the coating.

[0101] As shown in Table 1, the only difference between Comparative Examples 1 and 2 and Example 3 is that in Comparative Example 1, the sulfonic acid-modified p-chlorobenzyl acetone was replaced with p-chlorobenzyl acetone, and in Comparative Example 2, the conjugated modified anisaldehyde was replaced with anisaldehyde. Compared with Example 3, the uniformity and brightness of the coating in Comparative Examples 1 and 2 decreased significantly. This is because the main brightener lacked modification treatment, its dispersibility decreased significantly, and its concentration in the plating solution was locally too high or too low, which affected the deposition and growth of zinc ions, reduced the uniformity of the coating, and worsened the brightness.

[0102] This specific embodiment is merely an explanation of this application and is not intended to limit it. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this application. The technical scope of this application is not limited to the contents of the specification but must be determined according to the scope of the claims.

Claims

1. An environmentally friendly, cyanide-free zincate zinc plating brightener, characterized in that: The components include the following parts by mass: 10-30 parts of sulfonic acid group modified p-chlorobenzyl acetone 10-20 parts of conjugated modified anisaldehyde 15-40 parts of compound auxiliary brightener 5-15 parts of isomeric tridecyl alcohol polyoxyethylene ether 3-10 parts of polyethylene glycol 2-8 parts of positioning agent 30-50 parts of ethylene glycol monobutyl ether; The raw materials for preparing the conjugated modified anisaldehyde include anisaldehyde bulk and diethyl malonate. The raw materials for preparing the compound auxiliary brightener include 2-aminobenzamide, cinnamic acid, and modified sodium naphthalenesulfonate; The positional agent is composed of carboxyethyl isothiourea chloride, sodium hydroxymethylsulfonate, and 2-mercaptobenzimidazole in a mass ratio of (0.02-0.05):1:0.

5. The raw materials for preparing the modified sodium naphthalene sulfonate include sodium naphthalene sulfonate bulk, ammonium persulfate, and hexadecyl chloride pyridine.

2. The environmentally friendly, cyanide-free zincate zinc plating brightener according to claim 1, characterized in that: The raw materials for preparing the sulfonic acid-modified p-chlorobenzyl acetone include p-chlorobenzyl acetone and chlorosulfonic acid.

3. The environmentally friendly, cyanide-free zincate zinc plating brightener according to claim 1, characterized in that: The modified sodium naphthalenesulfonate is prepared using the following steps: Sodium naphthalene sulfonate was dispersed in water to obtain a sodium naphthalene sulfonate solution. Ammonium persulfate was added to the sodium naphthalene sulfonate solution under stirring. The mixture was heated and stirred to react. After cooling, anhydrous ethanol was poured in to precipitate the precipitate. The precipitate was collected by filtration and washed with anhydrous ethanol. The washed precipitate was then dried under vacuum to obtain polynaphthalene sulfonate. The prepared sodium naphthalene sulfonate was dispersed in N,N-dimethylformamide to obtain a sodium naphthalene sulfonate solution. Chlorohexadecylpyridine was added to the sodium naphthalene sulfonate solution, and the mixture was heated and stirred to react. After cooling, ice water was added to precipitate the product, which was then washed with ice water and dried under vacuum to obtain modified sodium naphthalene sulfonate.

4. The environmentally friendly, cyanide-free zincate zinc plating brightener according to claim 3, characterized in that: The mass ratio of sodium naphthalenesulfonate, ammonium persulfate, and hexadecyl pyridine chloride is 1:0.05:(0.02-0.08).

5. A method for preparing an environmentally friendly, cyanide-free zincate zinc plating brightener as described in any one of claims 1-4, characterized in that: Includes the following steps: Sulfonic acid-modified p-chlorobenzyl acetone was added to ethylene glycol monobutyl ether under water bath heating conditions. After stirring evenly, conjugated modified anisaldehyde, isomeric tridecanol polyoxyethylene ether, polyethylene glycol, compound auxiliary brightener and positioner were added in sequence. Stirring was performed after each addition. After the addition was completed, the speed was increased and stirring was continued to obtain an environmentally friendly cyanide-free zincate zinc plating brightener.

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