Surface anti-oxidation process of aluminum mold and aluminum mold obtained

Abstract

The present invention relates to C23C22 / 34, and more particularly to a surface anti-oxidation process for an aluminum mold and the resulting aluminum mold. The process comprises the following steps: 1) degreasing and deoiling the aluminum mold, then washing it in clean water and drying it with nitrogen; 2) immersing the aluminum mold in an aqueous solution of a passivating solution for passivation; and 3) rinsing the immersed mold with clean water and drying it with nitrogen.

Description

Technical Field

[0001] The present invention relates to C23C22 / 34, and in particular to a surface anti-oxidation process of an aluminum mold and the prepared aluminum mold. Background Art

[0002] Aluminum, with its excellent corrosion resistance, weldability, high strength, and lightweight properties, is widely used in various technical fields. Generally, aluminum forms a thin oxide film under the action of oxygen. However, this oxide film on the surface of aluminum does not truly protect the aluminum surface, so further surface treatment is necessary.

[0003] Patent CN102965654A - A highly salt spray-resistant aluminum passivator and its preparation method treats aluminum with an aqueous solution prepared from fluorine-containing zirconate, 5% sulfuric acid, sodium hydroxide, fluoride salt, nitrate and nickel salt, so that the aluminum passivator has extremely strong salt spray corrosion resistance, as well as adhesion and impact performance.

[0004] Patent CN105349988A - An antibacterial and mildew-proof aluminum alloy chromium-free passivator and its preparation method. The passivator is prepared by the mutual coordination of substances such as fluorotitanic acid, fluorozirconic acid, borax, sodium fluoride, etc., which can effectively prevent aluminum alloy from mildew and has high toughness and adhesion.

[0005] However, there is little research on the surface micromorphology of aluminum materials in the existing technology. Since aluminum materials are often formed by press molding, pitting is easily generated on the surface of the aluminum materials during the early press molding process, resulting in a high scrap rate and increased economic costs. Summary of the Invention

[0006] In order to solve the above technical problems, the first aspect of the present invention provides a surface anti-oxidation process for an aluminum mold, comprising the following steps:

[0007] 1) The aluminum mold is degreased and deoiled, then washed in clean water and dried with nitrogen;

[0008] 2) Immersing the aluminum mold in an aqueous solution of a passivation solution for passivation treatment;

[0009] 3) Use clean water to clean the soaked mold and blow it dry.

[0010] Preferably, the passivation solution comprises a passivation composition and a film-forming aid, wherein the mass ratio of the passivation composition to the film-forming aid is 1:(2.5-10).

[0011] Preferably, the passivation solution further comprises organosilicon and acidic substances.

[0012] Preferably, the mass ratio of the organosilicon to the passivation composition is (10-15): (2.5-5).

[0013] Preferably, the acidic substance accounts for 15-25% of the total mass of the passivation composition.

[0014] Preferably, the passivation composition includes a fluorine-containing compound and a nitrate.

[0015] Preferably, the fluorine-containing compound is selected from at least one of sodium fluoride, potassium fluoride, nickel fluoride, fluorotitanic acid, fluorozirconic acid, sodium fluorotitanate, sodium fluorozirconate, lithium hexafluorophosphate, and lithium hexafluorostannate.

[0016] More preferably, the fluorine-containing compound includes fluorotitanic acid and fluorozirconic acid.

[0017] More preferably, the mass ratio of the fluorotitanic acid, fluorozirconic acid and nitrate is 1:(0.3-0.8):(1.5-3).

[0018] Preferably, the nitrate is selected from at least one of sodium nitrate, potassium nitrate, lithium nitrate, iron nitrate, cerium nitrate, neodymium nitrate, and titanium nitrate.

[0019] Further preferably, the nitrate comprises cerium nitrate.

[0020] During experiments, the applicant discovered that using a silicate passivation solution containing fluorotitanic acid, fluorozirconic acid, and cerium nitrate can improve the corrosion resistance of aluminum molds and reduce surface oxidation. The applicant speculates that the reason for this is that the silicate solution can form a film on the surface of the aluminum mold, but the pH value of the silicate passivation solution is unstable and easily forms a gel during use. By using a weight ratio of fluorotitanic acid, fluorozirconic acid, and cerium nitrate of 1:(0.3-0.8):(1.5-3), the pH stability of the silicate passivation solution can be improved. The resulting silicate passivation film can form a physical barrier for the aluminum, preventing oxygen from reacting with the aluminum surface. It also has a certain degree of hydrophobicity, preventing water vapor from adhering to the aluminum surface and causing long-term bacterial growth. Furthermore, the introduction of cerium metal ions inhibits the cathodic and anodic reactions during the corrosion process, preventing oxidation reactions on the aluminum surface that affect the appearance of the aluminum mold.

[0021] Preferably, the film-forming aid includes epoxy resin and / or silica sol.

[0022] More preferably, the film-forming aid includes epoxy resin and silica sol.

[0023] Preferably, the viscosity of the epoxy resin at 25° C. is 10,000-15,000 mPas.

[0024] Preferably, the epoxy equivalent weight of the epoxy resin is 184-195 g / mol.

[0025] Preferably, the epoxy resin is selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, glycidyl ether epoxy resin, and glycidyl ester epoxy resin.

[0026] More preferably, the epoxy resin comprises bisphenol A epoxy resin.

[0027] Preferably, the mass fraction of silica in the silica sol is 29-31 wt%.

[0028] Preferably, the particle size of the silica sol is 20-40 nm.

[0029] During the experiment, the applicant discovered that the synergistic effect of bisphenol A epoxy resin and silica sol can form a dense protective film on the surface of the aluminum mold, improving the adhesion between the aluminum mold and the protective film. The possible reasons are speculated to be: the acidic salt ion solution has poor film-forming properties on the aluminum surface. The introduction of bisphenol A epoxy resin and silica sol can effectively improve the uniformity and hydrophobicity of the film layer, increasing the density of the film layer. The silica sol and vinyltrimethoxysilane work synergistically, combining Si-O-Si bonds with Si-O bonds, enhancing the adhesion of the film layer to the aluminum. The bisphenol A epoxy resin with a viscosity of 12000mPas and an epoxy equivalent weight of 184-195g / mol can synergize with the silica sol to increase the connection between the metal ions in the passivation solution and enhance the density of the protective film. In addition, the silicate passivation solution can form a cross-linked interpenetrating network structure with the magnesium oxide and silica in the 6061 aluminum mold, further improving the adhesion between the protective film and the aluminum mold.

[0030] Preferably, the weight ratio of the epoxy resin to the silica sol is 1:(2.5-4.6).

[0031] The applicant further discovered that a weight ratio of bisphenol A epoxy resin to silica sol of 1:(2.5-4.6) can make film formation on the surface of aluminum molds easier. It is speculated that the possible reason is that exceeding the preferred weight ratio range will reduce the wetting properties of the passivation solution and reduce the surface activity of the aluminum material, which is not conducive to surface film formation.

[0032] Preferably, the organosilicon includes at least one of aminosilane, sulfur silane, epoxy silane, vinyl siloxane, methacryloxy silane, and isocyanate silane.

[0033] More preferably, the organosilicon includes vinyl siloxane.

[0034] Preferably, the vinylsiloxane is at least one selected from vinyltrimethoxysilane, vinyltriethoxysilane, alkenyltri(β-methoxyethoxy)silane, and vinyltri(trimethylsiloxy)silane.

[0035] More preferably, the vinyl siloxane includes vinyltrimethoxysilane.

[0036] Preferably, the acidic substance is selected from at least one of acetic acid, oxalic acid, tartaric acid, citric acid, malic acid, and succinic acid.

[0037] Further preferably, the acidic substance includes citric acid.

[0038] Preferably, the preparation method of the aqueous solution of the passivation solution comprises the following steps: mixing the organosilicon and water evenly, hydrolyzing the mixture at 75-85° C. for 3-5 hours, then sequentially adding an acidic substance and a passivation composition and stirring evenly, and finally adding a film-forming aid and stirring evenly.

[0039] Preferably, the pH of the passivation solution is 2-3.

[0040] Preferably, the weight ratio of the passivation solution to water in the aqueous solution of the passivation solution is (0.8-1.2):15.

[0041] Preferably, the passivation treatment specifically includes the following steps: soaking the aluminum mold in an aqueous solution of the passivation solution at 18-30° C. for 5-10 minutes, or at 1-15° C. for 15-30 minutes, and then taking it out.

[0042] During the experiment, the applicant found that the thickness of the passivation protective film formed by immersing the aluminum mold in the aqueous solution of the passivation solution at 18-30°C for 5-10 minutes or at 1-15°C for 15-30 minutes was suitable and the flatness was high. The possible reason is that when the passivation temperature is low, the passivation reaction is slow, the film-forming efficiency is low, and the passivation protective film formed is thin. It is necessary to extend the reaction time to increase the thickness of the film layer. When the immersion time exceeds 15-30 minutes, the thickness of the film layer does not increase significantly, and the improvement of the corrosion resistance effect is not significant. Therefore, the reaction time of 15-30 minutes is selected. When the passivation temperature is 18-30°C, the passivation reaction rate is improved, and a dense and uniform passivation protective film can be formed in a short time. However, beyond the preferred temperature range, the rate of the passivation reaction will continue to increase. The passivation reaction rate is too fast, resulting in a loose passivation protective film that is easy to fall off on the surface of the aluminum mold, and the film layer is uneven, which is prone to cracks in the protective film. Moreover, when the reaction temperature is high, the rate of formation of the passivation film accelerates, and the rate of dissolution of the passivation film also accelerates. When the passivation temperature exceeds the preferred reaction temperature, the dissolution rate of the passivation film is greater than the rate of formation of the passivation film. As the passivation time increases, the thickness of the passivation film decreases instead of increases, eventually leading to the shedding of the passivation protective film.

[0043] Preferably, the aluminum mold is a 6061 aluminum mold.

[0044] A second aspect of the present invention provides an aluminum mold, which is manufactured according to the above-mentioned surface anti-oxidation process for an aluminum mold.

[0045] Beneficial effects:

[0046] 1) The present invention provides a surface anti-oxidation process for aluminum molds. By limiting the passivation agent raw materials and reaction conditions of each step of the surface anti-oxidation process for aluminum molds, the surface of the aluminum mold obtained by the treatment is free of pitting, is not easily adsorbed by impurities, has a better surface morphology, and has high gloss. At the same time, the passivation film has high adhesion to the aluminum mold and good corrosion resistance.

[0047] 2) The present invention uses fluorotitanic acid, fluorozirconic acid, and cerium nitrate as a passivation composition, and limits their weight ratio to 1: (0.3-0.8): (1.5-3) to form a physical isolation layer on the surface of the aluminum mold, thereby improving the anti-corrosion effect of the aluminum mold and preventing oxidation of the aluminum mold surface and the formation of pitting.

[0048] 3) The present invention utilizes bisphenol A epoxy resin and silica sol to synergistically form a dense protective film on the surface of the aluminum mold, thereby enhancing the adhesion between the aluminum mold and the protective film. In particular, when the bisphenol A epoxy resin has a heated viscosity of 12,000 mPas and an epoxy equivalent weight of 184-195 g / mol, the denseness of the protective film is further enhanced, giving the aluminum mold higher corrosion resistance. The present invention further discovered that a weight ratio of bisphenol A epoxy resin to silica sol of 1:2.5-4.6 can effectively control the surface properties of the aluminum mold, making it easier to form a protective film on the aluminum mold surface.

[0049] 4) The present invention also limits the reaction conditions of step 2), by soaking at 18-30°C for 5-10 minutes, or soaking at 1-15°C for 15-30 minutes, to control the passivation reaction rate, avoid the occurrence of film cracks, and ensure that the protective film formed on the surface of the aluminum mold has a moderate thickness and a smooth surface.

[0050] 5) The surface anti-oxidation process of the aluminum mold provided by the present invention can reduce pitting on the surface of the aluminum mold, improve the surface performance of the aluminum mold, reduce the adsorption rate of packaging materials, materials to be cut, and impurities, and avoid the influence of electrostatic adsorption on the processing technology of packaging materials. DETAILED DESCRIPTION

[0051] Example

[0052] Example 1

[0053] A surface anti-oxidation process for an aluminum mold comprises the following steps:

[0054] 1) Degrease and deoil the aluminum mold, then rinse it in clean water and blow dry it with nitrogen;

[0055] 2) Soak the aluminum mold in the passivation solution at 25°C for 8 minutes and then remove it;

[0056] 3) Use clean water to clean the soaked mold and blow it dry.

[0057] The weight ratio of the passivation solution to water in the aqueous solution of the passivation solution is 1:15.

[0058] The passivation solution includes a passivation composition and a film-forming aid. The passivation solution also includes organosilicon and an acidic substance. The mass ratio of the passivation composition to the film-forming aid is 1g:6g. The mass ratio of the organosilicon to the passivation composition is 12:4. The acidic substance accounts for 20% of the total mass of the passivation composition.

[0059] The passivation composition includes a fluorine-containing compound and a nitrate. The fluorine-containing compound includes fluorotitanic acid and fluorozirconic acid. The nitrate includes cerium nitrate. The mass ratio of the fluorotitanic acid, fluorozirconic acid, and nitrate is 1:0.5:2.5.

[0060] The film-forming aid comprises epoxy resin and silica sol, wherein the weight ratio of the epoxy resin to the silica sol is 1:3.

[0061] The epoxy resin includes bisphenol A epoxy resin, has a viscosity of 12000 mPa·s at 25° C., and an epoxy equivalent weight of 184-195 g / mol, and is purchased from Jinan Quanxing New Materials Co., Ltd., model: Phoenix 618 epoxy resin.

[0062] The silica sol has a mass fraction of 29-31 wt % of silica and a particle size of 20-40 nm. It is purchased from Linyi Kehan ​​Silicon Products Co., Ltd., model: KHAS-3030.

[0063] The organosilicon includes vinyl siloxane, and the vinyl siloxane includes vinyl trimethoxy silane.

[0064] The acidic substance includes citric acid.

[0065] The pH of the passivation solution is 2.5.

[0066] The preparation method of the aqueous solution of the passivation solution comprises the following steps: mixing organic silicon and water evenly, hydrolyzing at 80° C. for 4 hours, then sequentially adding an acidic substance and a passivation composition and stirring evenly, and finally adding a film-forming aid and stirring evenly.

[0067] The aluminum mold is a 6061 aluminum mold.

[0068] An aluminum mold is made according to the surface anti-oxidation process of the aluminum mold described above.

[0069] Example 2

[0070] A surface anti-oxidation process for an aluminum mold, the specific implementation method is the same as that of Example 1, except that the surface anti-oxidation process for an aluminum mold includes the following steps:

[0071] 1) Degrease and deoil the aluminum mold, then rinse it in clean water and blow dry it with nitrogen;

[0072] 2) Soak the aluminum mold in an aqueous solution of the passivation solution at 10°C for 20 minutes and then remove it;

[0073] 3) Use clean water to clean the soaked mold and blow it dry.

[0074] Example 3

[0075] A surface anti-oxidation process for an aluminum mold, the specific implementation method is the same as that of Example 1, except that the weight ratio of the epoxy resin to the silica sol is 1:2.5.

[0076] Comparative Example 1

[0077] A surface anti-oxidation process for an aluminum mold, the specific implementation method is the same as that of Example 1, except that the epoxy resin includes bisphenol A epoxy resin, has a viscosity of 19000-24000 mPa·s at 25°C, and an epoxy equivalent weight of 205-225 g / mol, purchased from Changsha Fudakang Chemical Materials Co., Ltd., model: CYD-128S.

[0078] Comparative Example 2

[0079] A surface anti-oxidation process for an aluminum mold, the specific implementation method is the same as that of Example 1, except that the mass ratio of fluorotitanic acid, fluorozirconic acid and nitrate is 1:0.5:1.

[0080] Performance Testing

[0081] 1. Surface performance of aluminum molds: The sample is anodized and the surface morphology of the sample after treatment is observed using a scanning electron microscope. If there are grain depressions, it means there are pits and the test fails; if not, the test passes.

[0082] 2. Adhesion test: Adhesion test shall be carried out in accordance with GB / T 9286-1998 “Scratch test for paint and varnish films”.

[0083] Table 1 Performance test results

[0084]

[0085]

Claims

1. A surface anti-oxidation process for an aluminum mold, characterized in that: The following steps are involved: 1) The aluminum mold is degreased and deoiled, then washed in clean water and dried with nitrogen; 2) Immersing the aluminum mold in an aqueous solution of a passivation solution for passivation treatment; 3) Rinse the soaked mold with clean water and blow dry. The passivation solution comprises a passivation composition, a film-forming aid, organic silicon and an acidic substance; The passivation composition comprises fluorotitanic acid, fluorozirconic acid and cerium nitrate in a mass ratio of 1:(0.3-0.8):(1.5-3); The film-forming aid comprises epoxy resin and silica sol in a weight ratio of 1:(2.5-4.6); The passivation treatment specifically includes the following steps: immersing the aluminum mold in an aqueous solution of the passivation solution at 1-15° C. for 15-30 minutes, and then taking it out.

2. The surface anti-oxidation process of an aluminum mold according to claim 1, characterized in that: The epoxy resin is selected from at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, glycidyl ether epoxy resin, and glycidyl ester epoxy resin.

3. The surface anti-oxidation process of an aluminum mold according to claim 1, characterized in that: The organic silicon is selected from at least one of aminosilane, sulfur silane, epoxy silane, vinyl siloxane, methacryloxy silane and isocyanate silane.

4. An aluminum mold, characterized in that: It is made by the surface anti-oxidation process of an aluminum mold according to any one of claims 1 to 3.

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