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CN-121992388-A - Organic-inorganic composite alkaline passivator for galvanized sheet and preparation method thereof

CN121992388ACN 121992388 ACN121992388 ACN 121992388ACN-121992388-A

Abstract

The invention relates to the technical field of passivating agents, in particular to an organic-inorganic composite alkaline passivating agent for a galvanized sheet and a preparation method thereof. The organic-inorganic composite alkaline passivator for the galvanized sheet comprises, by mass, 20-40% of resin emulsion, 0.5-3% of carbodiimide, 3-8% of silica sol, 0.2-0.8% of titanyl sulfate, 0.1-0.4% of complexing agent, 0.5-2% of functional auxiliary agent and the balance of deionized water, wherein the resin emulsion contains 30-40% of epoxy modified polyurethane by mass. The invention realizes excellent corrosion resistance through the special synergistic effect of organic film formation, chemical crosslinking and active corrosion inhibition, and has the core that the three components are indispensable and epoxy modification is indispensable, so that the passivating agent has excellent yellowing performance and corrosion resistance.

Inventors

  • LI YUCAI
  • ZHAN HONG
  • Zhu Zhewen
  • LUO XIAOFENG
  • LU BIAO

Assignees

  • 武汉迪赛环保新材料股份有限公司

Dates

Publication Date
20260508
Application Date
20260210

Claims (10)

  1. 1. The organic-inorganic composite alkaline passivator for the galvanized sheet is characterized by comprising, by mass, 20-40% of resin emulsion, 0.5-3% of carbodiimide, 3-8% of silica sol, 0.2-0.8% of titanyl sulfate, 0.1-0.4% of complexing agent, 0.5-2% of functional auxiliary agent and the balance of deionized water; the resin emulsion contains 30-40% of epoxy modified polyurethane by mass percent.
  2. 2. The organic-inorganic composite alkaline passivator according to claim 1, wherein the preparation method of the resin emulsion comprises the steps of adding epoxy resin into polyurethane prepolymer, heating to 85-95 ℃, stirring to react to obtain an epoxy modified polyurethane intermediate, cooling the intermediate to 40-50 ℃, adding triethylamine to neutralize to pH 7.5-9.5, neutralizing to 80-90%, stirring, slowly dripping deionized water, and emulsifying and dispersing to obtain the aqueous anionic polyurethane dispersion, namely the resin emulsion.
  3. 3. The organic-inorganic composite alkaline passivator according to claim 2, wherein the epoxy resin is added in an amount of 10-20% of the mass of the polyurethane prepolymer, the temperature is raised to 85-95 ℃, the stirring reaction is carried out for 1.5-2.5h, and the disappearance of-NCO characteristic peaks is monitored by infrared spectrum during the stirring reaction, so as to obtain the epoxy modified polyurethane intermediate.
  4. 4. The organic-inorganic composite alkaline passivator according to claim 2, wherein the polyester polyol with the number average molecular weight of 1000-2000 and diisocyanate are mixed according to the molar ratio of-NCO/-OH of 1.2-1.5, and an organic bismuth catalyst accounting for 0.1-0.3% of the total system mass is added for thermal insulation reaction for 2-3 hours at 70-80 ℃ to obtain the polyurethane prepolymer.
  5. 5. The organic-inorganic composite alkaline deactivation agent according to claim 4, wherein said polyester polyol is one or both of adipic acid polyester diol and polycaprolactone diol, and said diisocyanate is selected from isophorone diisocyanate, hexamethylene diisocyanate and toluene diisocyanate.
  6. 6. The organic-inorganic composite alkaline passivation agent of claim 2, wherein the epoxy resin has an epoxy value of 0.4-0.6eq/100g.
  7. 7. The organic-inorganic composite alkaline passivation agent according to claim 1, wherein the silica sol contains 20-30% of solid content, 8-10 of pH value and 10-30nm of silica particle size.
  8. 8. The organic-inorganic composite alkaline passivation agent of claim 1, wherein the complexing agent is selected from citric acid, oxalic acid, or EDTA.
  9. 9. The organic-inorganic composite alkaline passivation agent of claim 1, wherein the functional auxiliary agent comprises a leveling agent and an antifoaming agent.
  10. 10. A method for preparing the organic-inorganic composite alkaline passivation agent according to any one of claims 1 to 9, comprising the steps of: stirring the resin emulsion and deionized water, adding carbodiimide, and continuing stirring until the solution is uniformly dispersed to obtain a precursor solution; Dissolving a complexing agent in ionized water, adding titanyl sulfate, dispersing uniformly to obtain a titanium-containing complex solution, and regulating the pH value to 7-8 by ammonia water to obtain a solution containing a complex; And sequentially stirring and adding silica sol, a solution containing the complex and a functional auxiliary agent into the precursor liquid to obtain the passivating agent.

Description

Organic-inorganic composite alkaline passivator for galvanized sheet and preparation method thereof Technical Field The invention relates to the technical field of passivating agents, in particular to an organic-inorganic composite alkaline passivating agent for a galvanized sheet and a preparation method thereof. Background Metallic materials (especially steel, galvanized parts and zinc-aluminum-magnesium alloy coating materials) are easy to corrode and fail in the environments of atmosphere, ocean, soil and the like, and huge economic loss is brought to industrial production. The galvanization is used as a main stream anti-corrosion means, and the subsequent passivation is a key link for inhibiting the generation of white rust and improving the protective performance. The traditional passivation process mainly uses a chromate system, has the advantages of simple operation, low cost, excellent corrosion resistance of a passivation film and the like, but hexavalent chromium, trivalent chromium and other components have strong toxicity and carcinogenicity, seriously pollute the environment and harm the health of human bodies, cannot meet the environmental protection regulation requirements of European Union RoHS and the like, and needs to develop chromium-free substitution technology. In recent years, students at home and abroad focus on the research and development of low-toxicity/non-toxic chromium-free passivating agents, and various systems such as titanium salt, molybdate, phytic acid, rare earth salt and the like are formed, but the problems of insufficient corrosion resistance, poor stability and the like of the technologies generally exist, and large-scale industrial application cannot be realized. It is worth noting that the existing chromium-free passivation technology mostly adopts an acidic system, and the acidic environment is easy to cause the dissolution of a zinc oxide film generated on the surface of metal, which is a core symptom that the protective performance is poor. In contrast, a zinc oxide or aluminum oxide passivation film which is more compact and complete and has stronger chemical stability can be formed under the alkaline condition, the treatment process is mild, and the method is more suitable for the fields of food processing, medical appliances and the like with severe requirements on environmental protection. The related patent of the existing alkaline passivating agent has been primarily explored, for example, chinese patent publication No. CN105755456B discloses an alkaline passivating solution with pH=10-12, which consists of alkaline substances (25-65 g/L), fluoride (5-10 g/L), sulfate (10-15 g/L) and hydrogen peroxide (15-25 mL/L), so that the environment-friendly design without chromium and heavy metals is realized, the passivating solution has good stability and simple preparation process, the patent publication No. CN102753728B provides an alkaline passivating zinc surface composition containing ferric ions, phosphate ions and complexing agents, and the patent publication No. CN107002247A discloses a cerium-based alkaline coating composition for metal surface pretreatment. However, the prior alkaline passivation technology still has obvious defects that part of the formula contains heavy metal oxysalt and phosphate, and the environmental protection is not enough. Disclosure of Invention The invention aims at providing an organic-inorganic composite alkaline passivator for a galvanized plate and a preparation method thereof, aiming at the defects of the prior art. The first aim of the invention is to provide an organic-inorganic composite alkaline passivator for galvanized plates, which comprises, by mass, 20-40% of resin emulsion, 0.5-3% of carbodiimide, 3-8% of silica sol, 0.2-0.8% of titanyl sulfate, 0.1-0.4% of complexing agent, 0.5-2% of functional auxiliary agent and the balance of deionized water; the resin emulsion contains 30-40% of epoxy modified polyurethane by mass percent. The preparation method of the resin emulsion comprises the steps of adding epoxy resin into polyurethane prepolymer, heating to 85-95 ℃, stirring and reacting to obtain an epoxy modified polyurethane intermediate, cooling the intermediate to 40-50 ℃, adding triethylamine to neutralize to pH value of 7.5-9.5, neutralizing to 80-90%, stirring, slowly dripping deionized water, emulsifying and dispersing to obtain the aqueous anionic polyurethane dispersion, namely the resin emulsion. Further, the addition amount of the epoxy resin is 10-20% of the mass of the polyurethane prepolymer, the temperature is raised to 85-95 ℃, the reaction is stirred for 1.5-2.5h, and the disappearance of the-NCO characteristic peak is monitored by infrared spectrum during the reaction, so that the epoxy modified polyurethane intermediate is obtained. Further, the polyester polyol with the number average molecular weight of 1000-2000 and diisocyanate are mixed according to the mol ratio of-NCO/-OH of 1.2-1.5, and