High-electrolyte-resistance trivalent chromium passivation solution for aluminum foil coating and preparation method of high-electrolyte-resistance trivalent chromium passivation solution

Abstract

The invention relates to the technical field of pretreatment of aluminum foil before lithium ion battery soft package aluminum plastic film covering, in particular to a trivalent chromium passivation solution for aluminum foil coating with high electrolyte resistance and a preparation method of the trivalent chromium passivation solution, and the formula of the trivalent chromium passivation solution comprises trivalent chromium salt, hexafluorozirconic acid, a film-forming agent, a film-forming accelerant and deionized water; the weight ratio of the trivalent chromium salt to the hexafluorozirconic acid to the film-forming agent to the film-forming accelerant in each liter of the trivalent chromium passivation solution is (6-10) g: (0.02-0.05) g: (10-15) g: (15-20) g, and the balance is deionized water. The trivalent chromium passivation solution is mainly used for pretreatment of aluminum foil before lithium ion battery soft package aluminum-plastic film lamination, an organic and inorganic composite film is generated on the surface of the aluminum foil through reaction, the bonding strength of aluminum-plastic lamination can be greatly improved, and the trivalent chromium passivation solution has ultrahigh electrolyte resistance.

Description

Technical Field

[0001] The invention relates to the technical field of pretreatment of aluminum foil before lamination of aluminum-plastic film of lithium ion battery soft package, in particular to a trivalent chromium passivation solution for coating aluminum foil with high electrolyte resistance and a preparation method thereof. Background Art

[0002] The composite of aluminum-plastic film for lithium-ion battery soft pack has gone through the following key stages: Initial stage (1991-2000): In 1991, Sony Corporation of Japan launched the first commercial cylindrical lithium-ion battery, marking a revolution in the battery industry. Prior to this, aluminum-plastic film for lithium batteries was mainly monopolized by Showa of Japan, and exports to China were restricted, resulting in high prices. Initial stage of localization (2000-2010): In 2000, China began to come into contact with imported aluminum-plastic films for lithium batteries and realized their high prices and the necessity of localization substitution. Through analysis and comparison, it was found that the structure of imported aluminum-plastic films was similar to the retort-resistant aluminum-plastic composite film materials produced in China at that time, which laid the foundation for subsequent localization substitution; Technological breakthrough and market application stage (2010 to present): Although the structure of domestically produced boiling-resistant aluminum-plastic composite film materials is similar to that of imported aluminum-plastic films, their bonding strength and electrolyte resistance are far inferior to those of imported aluminum-plastic films. After extensive exploration, relevant research institutions and enterprises have found that the key to improving bonding strength and electrolyte resistance lies in the pretreatment of aluminum foil. In addition to cleaning the surface, a conversion film treatment is required. The conversion film is a water-free trivalent chromium passivation agent that is applied to the surface of the aluminum foil with a roller and directly dried to form an organic and inorganic composite film layer. After the pretreatment, the aluminum foil is then laminated with aluminum plastic, which can basically achieve the performance of imported aluminum foils. A breakthrough has been found, and aluminum-plastic films are gradually on the road to localization. Domestic enterprises have gradually narrowed the gap with international standards. However, after investigation, we found that although the localization rate of aluminum-plastic film is gradually increasing, most manufacturers still use Japanese trivalent chromium passivation solution for aluminum foil coating. The passivation solution technology is mainly controlled by Japanese companies. Although there are a few companies in my country conducting research, their performance is far inferior to that of Japan.

[0003] Therefore, in order to correct the above-mentioned defects, we propose a trivalent chromium passivation solution for aluminum foil coating with high electrolyte resistance and a preparation method thereof. Summary of the invention

[0004] The present invention solves the technical problem by providing a trivalent chromium passivation solution for coating aluminum foil with high electrolyte resistance and a preparation method thereof.

[0005] To achieve the above objectives, the first objective of the present invention is to provide a trivalent chromium passivation solution for aluminum foil coating with high electrolyte resistance, the formula of which includes trivalent chromium salt, fluorozirconic acid, film-forming agent, film-forming accelerator and deionized water; The weight ratio of the trivalent chromium salt, fluorozirconic acid, film-forming agent and film-forming accelerator in each liter of trivalent chromium passivation solution is 6-10g: 0.02-0.05g: 10-15g: 15-20g, and the balance is deionized water.

[0006] Furthermore, the trivalent chromium salt is one of chromium acetate C6H9CrO6 or chromium fluoride CrF3.9H2O or a mixture of the two.

[0007] Furthermore, when the chromium acetate C6H9CrO6 or chromium fluoride CrF3.9H2O is mixed, the ratio of the two is 1:1.

[0008] Furthermore, the film-forming agent is a modified water-based acrylic resin.

[0009] Furthermore, the film-forming promoter is one of ethylene glycol monobutyl ether (C6H14O2) or diethylene glycol butyl ether (C8H18O3) or a mixture of the two in any ratio.

[0010] Furthermore, the pH value of the trivalent chromium passivation solution is pH 3.0-3.8, which is adjusted with ammonia water.

[0011] Another object of the present invention is to provide a method for preparing a trivalent chromium passivation solution for aluminum foil coating with high electrolyte resistance. The preparation method comprises the following steps: adding a rated amount of deionized water in proportion, heating to 80 degrees, first adding fluorozirconic acid, stirring evenly, then adding trivalent chromium salt, stirring to fully dissolve it, keeping the temperature at 70-80 degrees for 2 hours, cooling to room temperature, adding a film-forming agent, stirring for 30 minutes, then adding a film-forming promoter, stirring evenly, fixing the volume, and leaving it in a natural state for one day to obtain the water-free trivalent chromium passivation solution for aluminum foil coating.

[0012] Compared with the prior art, the present invention has the following beneficial effects: the trivalent chromium passivation solution in the present invention is mainly used for the pretreatment of aluminum foil before the aluminum-plastic film lamination of the lithium-ion battery soft package, and an organic and inorganic composite film is generated on the surface of the aluminum foil by reaction, which can greatly improve the bonding strength of the aluminum-plastic lamination and has the performance of ultra-high electrolyte resistance, specifically: 1. Significantly improve the bonding strength and electrolyte resistance of aluminum-plastic lamination. The initial bonding strength can reach 15N, and it can still exceed 13N after soaking in electrolyte for 21 days; 2. After coating, it does not need to be washed with water, but can be dried directly. There is no wastewater and VOC emission during the entire use process, which achieves energy saving and environmental protection. It has good environmental benefits; 3. Realizing domestic substitution can save costs for aluminum-plastic film factories, accelerate the localization process of the entire industrial chain, benefit the entire industrial chain, and create good economic and social benefits. DETAILED DESCRIPTION

[0013] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] The present invention provides a technical solution: A trivalent chromium passivation solution for aluminum foil coating with high electrolyte resistance is composed of 6-10 g / L of trivalent chromium salt, 0.02-0.05 g / L of zirconic acid, 10-15 g / L of film former, 15-20 g / L of film accelerator, etc. The trivalent chromium salt is chromium acetate C6H9CrO6 or chromium fluoride CrF3.9H2O, or a mixture of the two in a ratio of 1:1; the film former is a modified water-based acrylic resin; the film accelerator is ethylene glycol monobutyl ether ((C6H14O2) or diethylene glycol butyl ether (C8H18O3) or a mixture of the two in any ratio; the balance is deionized water. The pH value of the passivation solution is pH 3.0-3.8, which is adjusted with ammonia water.

[0015] The preparation method is as follows: Add a rated amount of deionized water in proportion, heat to 80 degrees, add fluorozirconic acid first, stir evenly, then add trivalent chromium salt, stir to fully dissolve, keep warm at 70-80 degrees for 2 hours, cool to room temperature, add film-forming agent, stir for 30 minutes, then add film-forming accelerator, stir evenly, fix volume, and leave it in a natural state for one day to obtain this water-free trivalent chromium passivation solution for aluminum foil coating.

[0016] The treatment process of the present invention generally uses a roller to apply the chemical, and can also be applied by spraying and squeezing. After the coating is completed, it does not need to be washed with water and dried immediately.

[0017] The treatment process is: passivation coating treatment → drying (about 120-150℃).

[0018] The present invention realizes the idea of ​​combining inorganic and organic passivation film layers by adding water-based high molecular polymer materials, and has good film-forming properties and corrosion resistance. It can eventually generate a uniform and dense inorganic-organic composite chemical conversion film layer on the aluminum metal surface. This chemical conversion film layer provides a corrosion-resistant matrix for the entire system, which can significantly improve the adhesion and corrosion resistance of the laminating adhesive, especially the excellent electrolyte resistance performance.

[0019] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A trivalent chromium passivation solution for coating aluminum foil with high electrolyte resistance, characterized in that: Its formula includes trivalent chromium salt, fluorozirconic acid, film former, film-forming accelerator and deionized water; The weight ratio of the trivalent chromium salt, fluorozirconic acid, film-forming agent and film-forming accelerator in each liter of trivalent chromium passivation solution is 6-10g: 0.02-0.05g: 10-15g: 15-20g, and the balance is deionized water.

2. The trivalent chromium passivation solution for coating aluminum foil with high electrolyte resistance according to claim 1, characterized in that: The trivalent chromium salt is one of chromium acetate C6H9CrO6 or chromium fluoride CrF3.9H2O or a mixture of the two.

3. The trivalent chromium passivation solution for coating aluminum foil with high electrolyte resistance according to claim 2, characterized in that: When the chromium acetate C6H9CrO6 or chromium fluoride CrF3.9H2O is mixed, the ratio of the two is 1:

1.

4. The trivalent chromium passivation solution for coating aluminum foil with high electrolyte resistance according to claim 1, characterized in that: The film former is a modified waterborne acrylic resin.

5. The trivalent chromium passivation solution for coating aluminum foil with high electrolyte resistance according to claim 1, characterized in that: The film-forming promoter is one of ethylene glycol monobutyl ether (C6H14O2) or diethylene glycol butyl ether (C8H18O3) or a mixture of the two in any ratio.

6. The trivalent chromium passivation solution for coating aluminum foil with high electrolyte resistance according to any one of claims 1 to 5, characterized in that: The pH value of the trivalent chromium passivation solution is pH 3.0-3.8, which is adjusted with ammonia water.

7. A method for preparing a trivalent chromium passivation solution for coating aluminum foil with high electrolyte resistance as claimed in any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: adding a rated amount of deionized water in proportion, heating to 80 degrees, first adding fluorozirconic acid, stirring evenly, then adding trivalent chromium salt, stirring to fully dissolve it, keeping the temperature at 70-80 degrees for 2 hours, cooling to room temperature, adding a film-forming agent, stirring for 30 minutes, then adding a film-forming accelerator, stirring evenly, fixing the volume, and leaving it in a natural state for one day to obtain the water-free trivalent chromium passivation solution for aluminum foil coating.