阅读说明：本技术 一种高分散性碱性无氰镀锌光亮剂及其制备方法和应用 (High-dispersity alkaline cyanide-free zinc plating brightener and preparation method and application thereof ) 是由 蒋晟 吕明威 吕志 于 2019-11-21 设计创作，主要内容包括：本发明公开了一种高分散性碱性无氰镀锌光亮剂及其制备方法和应用,属于表面处理电镀锌领域。该制备方法包括以下步骤：将摩尔比为1～3：1～3的5-氨基-8-羟基喹啉和水杨醛溶解在能与水互溶的有机溶剂中,加入少量的多聚甲醛作为催化剂,升温至80～90℃,回流反应4～5h；反应完成后,加入氢氧化钠溶液,升温至40～50℃,滴加丙磺酸内酯,加完后,升温至90～105℃反应充分,即得到碱性无氰镀锌光亮剂；其中,丙磺酸内酯与5-氨基-8-羟基喹啉的摩尔比为1.0-1.3:1。由本发明制备的光亮剂配制成的镀液的电流密度范围为0.5～11A/dm<Sup>2</Sup>,通过电流为2A时,电流效率≥80％,分散能力达到88％左右,具有良好的应用前景。(The invention discloses a high-dispersity alkaline cyanide-free galvanizing brightener and a preparation method and application thereof, and belongs to the field of surface treatment galvanizing. The preparation method comprises the following steps: and (3) mixing the raw materials in a molar ratio of 1-3: dissolving 1-3 parts of 5-amino-8-hydroxyquinoline and salicylaldehyde in an organic solvent which can be mutually dissolved with water, adding a small amount of paraformaldehyde as a catalyst, heating to 80-90 ℃, and carrying out reflux reaction for 4-5 hours; after the reaction is finished, adding a sodium hydroxide solution, heating to 40-50 ℃, dropwise adding propane sultone, heating to 90-105 ℃ after the addition is finished, and fully reacting to obtain the alkaline cyanide-free zinc plating brightener; wherein the molar ratio of the propane sultone to the 5-amino-8-hydroxyquinoline is 1.0-1.3: 1. The current density range of the plating solution prepared from the brightener prepared by the method is 0.5-11A/dm 2 When the passing current is 2A, the current efficiency is more than or equal to 80 percent, the dispersion capacity reaches about 88 percent, and the method has good application prospect.)

1. A preparation method of a high-dispersity alkaline cyanide-free galvanizing brightener is characterized by comprising the following steps:

and (3) mixing the raw materials in a molar ratio of 1-3: dissolving 1-3 parts of 5-amino-8-hydroxyquinoline and salicylaldehyde in an organic solvent which can be mutually dissolved with water, adding a small amount of paraformaldehyde as a catalyst, heating to 80-90 ℃, and carrying out reflux reaction for 4-5 hours; after the reaction is finished, adding a sodium hydroxide solution, heating to 40-50 ℃, dropwise adding propane sultone, heating to 90-105 ℃ after the addition is finished, and fully reacting to obtain the alkaline cyanide-free zinc plating brightener;

the molar ratio of the propane sultone to the 5-amino-8-hydroxyquinoline is 1.0-1.3: 1;

after the sodium hydroxide solution is added, the concentration of NaOH in the reaction solution is 1-2N.

2. The method for preparing the highly dispersible basic cyanide-free zinc plating brightener as set forth in claim 1, wherein: the concentration of 5-amino-8-hydroxyquinoline in the organic solvent is 1-3 mol, and the concentration of salicylaldehyde is 1-3 mol.

3. The method for preparing a highly dispersible basic cyanide-free zinc plating brightener as set forth in claim 1 or 2, characterized in that: the molar ratio of the 5-amino-8-hydroxyquinoline to the salicylaldehyde in the organic solvent is 1: 1.

4. The method for preparing the highly dispersible basic cyanide-free zinc plating brightener as set forth in claim 1, wherein: the organic solvent which can be mutually dissolved with water is one or more of methanol, ethanol, acetone, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and ethylene glycol monobutyl ether.

5. The method for preparing the highly dispersible basic cyanide-free zinc plating brightener as set forth in claim 1, wherein: the addition amount of the paraformaldehyde is 0.03 wt% of the total amount of the reaction substrate.

6. The method for preparing the highly dispersible basic cyanide-free zinc plating brightener as set forth in claim 1, wherein: the mol ratio of the dropwise added propane sultone to the 5-amino-8-hydroxyquinoline is 1: 1.

7. The method for preparing the highly dispersible basic cyanide-free zinc plating brightener as set forth in claim 1, wherein: the concentration of the added sodium hydroxide solution is 3N, and the addition amount is equal to the volume of the organic solvent which can be mutually dissolved with water.

8. An alkaline cyanide-free zinc plating brightener, characterized by being prepared by the preparation method of the high-dispersibility alkaline cyanide-free zinc plating brightener as claimed in any one of claims 1 to 7.

9. A bath formulated from the alkaline cyanide-free zinc plating brightener of claim 8, characterized in that: the concentrations of the components in the plating solution are as follows:

Technical Field

The invention relates to the field of alkaline cyanide-free electrogalvanizing surface treatment by taking ZnO and NaOH as raw materials, in particular to a high-dispersity alkaline cyanide-free galvanizing brightener and a preparation method and application thereof.

Background

The traditional alkaline zinc plating mainly adopts cyanide zinc plating, and the cyanide electroplating process always occupies the important position of the alkaline zinc plating process due to the advantages of wide process range, high impurity tolerance and the like, particularly in national defense and military industrial products. In the cyanide galvanizing process, cyanide is very critical, zinc ions and cyanide form zinc cyanide complex ions, the discharge of the zinc ions at a cathode is inhibited by the existence of the complex ions, cathode polarization is improved, and therefore the effect of refining crystallization is achieved.

In the beginning of the nineties of the last century, the cyanide galvanizing process is required to be eliminated gradually along with the promotion of clean production in China, so that the alkaline cyanide-free galvanizing process is produced at the same time, has the characteristics of simple plating solution components, easy wastewater treatment, low toxicity, no corrosion and the like, and rapidly occupies a leading position. However, alkaline non-cyanide galvanization also has the defects of narrow current density range, low current efficiency, poor deep galvanization capability of dispersing capability, high carbon content and high brittleness of a plating layer and the like. At present, the alkaline cyanide-free zinc plating brightener mainly comprises a primary brightener, a secondary brightener and an auxiliary brightener, wherein the primary brightener mainly comprises a condensation polymerization reaction product of aliphatic amine and epoxy chloropropane and a carbamidine cationic polymer, the secondary brightener mainly comprises benzyl pyridine carboxylic acid humate and a derivative of aromatic aldehyde, the two brighteners cannot form a complex with zinc ions or zincate ions, but the reduction potential of the brighteners is slightly more positive than that of the zincate, so that the discharge of the zinc ions is inhibited to achieve the effect of fine crystallization; the auxiliary brightening agent is mostly wetting agent and organic complexing agent, such as EDTA and its sodium salt, nitrilotriacetic acid, triethanolamine, sodium gluconate, etc. Although some defects of alkaline cyanide-free zinc plating are compensated to a certain extent by using a large amount of complexing agent, the problems that waste water is difficult to treat, a plating layer is easy to discolor and impurities are accumulated and the like are brought about, so that the application of the plating layer is limited to a certain extent.

Chinese patent publication No. CN103255449A discloses a high-dispersibility alkaline zinc plating additive, which comprises 120g/L of DPE-III, 40g/L of benzyl nicotinic acid salt, 20g/L of imidazole propoxy condensate, 80g/L of polyamine sulfone derivative, 8g/L of imidazole cation quaternary ammonium salt, 2g/L of 2-mercaptothiazoline and EDTA-2Na2g/L of component A and 125g/L of urea amine cation quaternary ammonium salt, wherein the dispersing capacity of the plating solution can reach 81.81 percent; chinese patent CN107513732A discloses a cyanide-free alkaline zinc plating dispersant, which is composed of sodium bis-phenylsulfonylimide, triethanolamine and 2-ethylhexyl sodium sulfate, the cylinder opening amount is 12-15 mL/L, a zinc coating with uniform and consistent thickness in a high-low current region can be obtained, and the problems of low current efficiency, poor covering power and dispersing performance and the like of alkaline cyanide-free zinc plating exist.

Disclosure of Invention

In order to overcome the problems of narrow current density range, low current efficiency, poor covering power and dispersing performance and the like of the conventional alkaline cyanide-free galvanizing, the invention provides a high-dispersity alkaline cyanide-free galvanizing brightener and a preparation method thereof, which can avoid adding a complexing agent into an alkaline cyanide-free galvanizing additive.

The technical scheme provided by the invention is as follows:

a preparation method of a high-dispersity alkaline cyanide-free galvanizing brightener comprises the following steps:

and (3) mixing the raw materials in a molar ratio of 1-3: dissolving 1-3 parts of 5-amino-8-hydroxyquinoline and salicylaldehyde in an organic solvent which can be mutually dissolved with water, adding a small amount of paraformaldehyde as a catalyst, heating to 80-90 ℃, and carrying out reflux reaction for 4-5 hours; after the reaction is finished, adding a sodium hydroxide solution, heating to 40-50 ℃, dropwise adding propane sultone, heating to 90-105 ℃ after the addition is finished, and fully reacting to obtain the alkaline cyanide-free zinc plating brightener;

the mol ratio of the propane sultone to the 5-amino-8-hydroxyquinoline is 1.0-1.3: 1;

after the sodium hydroxide solution is added, the concentration of NaOH in the reaction solution is 1-2N.

On the basis of the technical scheme, the concentration of 5-amino-8-hydroxyquinoline in the organic solvent is 1-3 mol, and the concentration of salicylaldehyde is 1-3 mol.

On the basis of the technical scheme, the molar ratio of the 5-amino-8-hydroxyquinoline to the salicylaldehyde in the organic solvent is 1: 1.

On the basis of the technical scheme, the organic solvent capable of being mutually soluble with water is one or more of methanol, ethanol, acetone, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and ethylene glycol monobutyl ether.

On the basis of the technical scheme, the addition amount of the paraformaldehyde is 0.03 wt% of the total amount of the reaction substrate.

On the basis of the technical scheme, the molar ratio of the dropwise added propane sultone to the 5-amino-8-hydroxyquinoline is 1: 1.

On the basis of the technical scheme, the concentration of the added sodium hydroxide solution is 3N, and the addition amount of the sodium hydroxide solution is equal to the volume of the organic solvent which can be mutually dissolved with water.

The invention also provides the alkaline cyanide-free galvanizing brightener prepared by the preparation method.

The invention also provides a plating solution prepared from the alkaline cyanide-free zinc plating brightener, wherein the concentration of each component in the plating solution is as follows:

the principle of the invention is as follows:

in alkaline cyanide-free zinc plating systems, Zn is predominantly present in the form [ Zn (OH) ]₄]^2-The method is stable in plating solution, the discharging process is carried out in two steps, larger energy is needed, the equilibrium potential of the method is more negative than that of hydrogen evolution reaction, and the hydrogen evolution reaction is firstly carried out when the electroplating is started, so the current efficiency of alkaline zincate galvanizing is not high; the brightener synthesized by the invention has the main structure of substituted aromatic alkane, has high chemical stability, can selectively form a ligand with zinc ions or zincate ions under an alkaline condition, is hardly interfered by other impurity metal ions, and forms a zinc ion complex in a plating solution, wherein the instability constant K of the complex is 1.1 multiplied by 10 measured by an equimolar method^-18K instability with zinc tetracyanide complex is 1.3X 10^-17Very close to the zinc can effectively control the zinc coordination after the electroplating is startedThe discharge speed of the zinc increases the cathode polarization potential of the zinc in the electrodeposition process of the zinc, thereby obtaining compact and fine crystal grains. Meanwhile, the structure is reformed by sulfoalkylation, so that the ligand shows surface activity, the conductivity of the plating solution is increased, and the using current density of the plating solution is expanded to a low region; as can be seen from the cathode polarization curve, the plating solution using the brightener of the invention has the advantages of obviously negative shift of cathode potential, obviously increased cathode polarization and better polarization behavior than other plating solutions, which indicates that the plating layer using the brightener of the invention has finer crystallization.

Compared with the prior art, the invention has the following advantages and beneficial effects:

the brightener prepared by the method has less hydrogen evolution amount, wide current density range and higher current efficiency than common alkaline cyanide-free zinc plating, and the current efficiency is 0.5-11A/dm²The current density range of the alloy can obtain a white and bright uniform coating, the brightener has a stable structure and is not easy to decompose, the coating has high purity, low carbon content and good toughness, when the passing current is 2A, the current efficiency is more than or equal to 80 percent, and the dispersing capacity reaches about 88 percent.

Drawings

Fig. 1 is an SEM image of a zinc coating layer without additives;

FIG. 2 is an SEM image of a DPE-III + BPC-48 zinc coating;

FIG. 3 is an SEM image of a zinc coating layer using the brightener of the present invention.

Detailed Description

The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The reagents and raw materials used are commercially available unless otherwise specified. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.