Reagent for removing chromium-free fingerprint-resistant film layer on surface of hot-dip aluminum-zinc steel plate

Abstract

The invention discloses a reagent for removing a chromium-free fingerprint-resistant film layer on the surface of a hot-dip aluminum-zinc steel plate. The reagent mainly solves the problem that the chromium-free fingerprint-resistant film layer on the surface of an existing hot-dip aluminum-zinc steel plate is difficult to remove. According to the technical scheme, the reagent for removing the chromium-free fingerprint-resistant film layer on the surface of the hot-dip aluminum-zinc plated steel plate comprises the following components in percentage by weight: 25%-35% of benzaldehyde, 15%-25% of diethylene glycol monobutyl ether, 5%-10% of trichloromethane, 0.5%-1.0% of ethanol, 5%-8% of OP-10, 10%-15% of potassium fluoride and 20%-30% of water, and the sum of the weight percentages of the components is 100%. The reagent disclosed by the invention is suitable for the chromium-free fingerprint-resistant film layer on the surface of the hot-dip aluminum-zinc steel plate, and the chromium-free fingerprint-resistant film layer takes polyurethane resin, acrylic resin or silane resin as a main body; the reagent is low in volatility and good in using effect.

Description

Technical Field

[0001] The invention relates to a demoulding agent, in particular to an agent for removing a chromium-free fingerprint-resistant film layer on the surface of a hot-dip aluminum-zinc steel plate, and belongs to the technical field of post-processing of hot-dip aluminum-zinc steel plates. Background Art

[0002] Hot-dip aluminum-zinc steel sheets are increasingly used in the fields of construction and home appliances because their corrosion resistance is significantly higher than that of hot-dip galvanized steel sheets. In order to further improve their corrosion resistance, in addition to products used as color steel substrates or automotive panels, the surfaces of hot-dip aluminum-zinc steel sheets that are directly used are generally treated with fingerprint resistance.

[0003] The production process of hot-dip aluminum-zinc fingerprint-resistant sheet is: uncoiling → welding → cleaning → annealing → hot-dip aluminum-zinc → finishing → passivation (including fingerprint resistance) → curling. The fingerprint-resistant liquid is applied to the surface of the hot-dip aluminum-zinc steel sheet by a chemical roller coater and formed into a film after drying. The thickness of the fingerprint-resistant film is only 1μm-2μm. This organic film can effectively isolate oxygen and moisture in the environmental medium. It is widely used in the electronics and electrical industries with excellent fingerprint resistance and corrosion resistance, especially in products such as computers and audio-visual equipment.

[0004] The anti-fingerprint plate is a hot-dip galvanized steel plate directly coated with a material with optical properties similar to those of human fingerprints. It is pre-coated on the surface of the steel plate. Even if fingerprints are attached, the optical reflection difference from the part without fingerprints is very small, which creates fingerprint resistance. This film is not only not easy to produce fingerprints, but more importantly, it provides better corrosion resistance.

[0005] The surface coating of traditional aluminum-zinc-plated steel plates is an inorganic passivation layer with a thickness of tens of nanometers, mainly composed of chromates and silicates. Although it has a low cost, it has low performance and hexavalent chromium pollutes the environment, and has now been basically eliminated.

[0006] The raw materials of existing anti-fingerprint films are all water-based organic resins, and the polymerization method is emulsion polymerization. The anti-fingerprint treatment liquid is generally composed of basic resins, colloidal silica, and corrosion inhibitor additives. Among them, the basic resins include acrylic, epoxy, polyurethane, etc. At present, the low- and medium-end products are mainly silane resins and acrylic ester emulsions, and the high-end products are mainly polyurethane emulsions. Generally, polyurethane has relatively good hardness, lubricity and other properties.

[0007] Alu-zinc substrates are often accompanied by a small number of defects during production, such as zinc slag, zinc spots, zinc ash, etc. These defects have a great impact on the appearance and performance of the galvanized sheet. Chemical, electron microscopy, XPS and other detection methods are required to detect and confirm. Since these defects are all below the fingerprint-resistant film layer, the presence of the film layer affects the detection of defects and must be removed. However, since the film layer is very thin, it is impossible to remove the film by physical methods without damaging the substrate. The aluminum and zinc underneath are amphoteric metals that can be dissolved by acid and alkali, and the film layer cannot be removed by traditional chemical methods.

[0008] A Chinese patent application with application publication number CN108976893A discloses a paint stripper specifically for epoxy paint film on steel surface, and discloses a paint stripper composed of heteropoly acid, imidazole polystyrene, surfactant and nitrate; it is a water-based paint stripper, and the organic matter is kept stable in water by adding surfactant. The paint stripping principle is based on the swelling effect of imidazole polystyrene, and the heteropoly acid reacts with epoxy resin under nitrate catalysis to dissolve the paint film. Since this dissolution reaction is only effective for epoxy resin, the method is only suitable for paint stripping of epoxy paint.

[0009] A Chinese patent application with application publication number CN108299939A discloses a recyclable paint stripper, which is composed of solvent oil, ethylene glycol ethyl ether, dipropylene glycol butyl ether, alcohols, ketones and penetrants; it is an organic paint stripper that uses straight-chain alkanes (solvent oil) and small molecule alcohols, ketones, ethers, etc., based on the principle of like dissolves like, to achieve paint stripping through physical penetration and swelling, and is effective for paints of types such as alkyd resins, epoxy resins, polyester resins and polyurethane resins.

[0010] The fingerprint-resistant film layer is based on polyester resin, polyurethane resin, and silane resin, and adds silane coupling agent, nano-silica, zirconate and titanate to form a spatial network structure. Compared with the traditional straight-chain structure paint film, it has higher density and stronger resistance to swelling effect. The effects of existing paint strippers are not ideal. Summary of the invention

[0011] The purpose of the present invention is to provide a reagent for removing the chrome-free anti-fingerprint film on the surface of a hot-dip aluminum-zinc steel plate, mainly to solve the problem that the chrome-free anti-fingerprint film on the surface of the existing hot-dip aluminum-zinc steel plate is difficult to remove.

[0012] The technical idea of ​​the present invention is to use benzaldehyde, diethylene glycol monobutyl ether and the like to swell various organic resins in the fingerprint-resistant film, and considering the good stability of silane resin and the characteristics of less pores and difficulty in penetration caused by fillers such as nano-silicon dioxide in the film layer, and in view of the strong permeability of chloride ions, chloroform is added to further improve the permeability, and ethanol is added to prevent the decomposition of chloroform; in order to eliminate the filling and spatial network structure formed by silane coupling agent, nano-silicon dioxide, zirconate and titanate, fluoride with strong coordination reaction ability with silicon, titanium and zirconium is added to dissolve titanium dioxide, zirconium dioxide, silicon dioxide and the like in the film layer, and because fluoride is not soluble in organic solvents, a water-based reagent system is constructed by using weakly polar organic matter (referring to benzaldehyde and diethylene glycol monobutyl ether) and adding a surfactant.

[0013] The technical scheme adopted by the present invention is a reagent for removing the chrome-free anti-fingerprint film layer on the surface of a hot-dip aluminum-zinc steel plate, wherein the weight percentage of the components is: benzaldehyde 25%-35%, diethylene glycol monobutyl ether 15%-25%, chloroform 5%-10%, ethanol 0.5%-1.0%, OP-105%-8%, potassium fluoride 10%-15%, water 20%-30%, and the sum of the weight percentages of the components is 100%.

[0014] The chrome-free anti-fingerprint film layer on the surface of the hot-dip aluminum-zinc steel plate of the present invention is a chrome-free anti-fingerprint layer mainly composed of polyurethane resin, acrylic resin or silane resin.

[0015] The reason why the components of the reagent for removing the chromium-free anti-fingerprint film on the surface of the hot-dip aluminum-zinc steel plate of the present invention are limited to the above range is as follows:

[0016] Traditional paint strippers are generally based on the principle of like dissolves like. Small molecules of paint strippers penetrate into the organic paint film, causing the linear molecules in the paint film to swell and separate from the substrate. The main components of aluminum-zinc-plated anti-fingerprint liquid include resin, nano-silicon dioxide and various additives. The resin is mainly acrylic resin, silane resin or polyurethane resin. Common additives include titanates, zirconates, silane coupling agents, etc. The basic film-forming mechanism of the anti-fingerprint film is similar to that of the traditional paint film. After heating, various resin monomers polymerize from small molecules to linear macromolecules with a molecular weight of hundreds of thousands. Since the thickness of the aluminum-zinc-plated anti-fingerprint film layer is about 1μm, which is about one-tenth of the traditional paint film, various additives are added. The added nano-silicon dioxide, silane coupling agent, zirconate and titanate not only fill the gaps in the film layer, making it difficult for organic reagents to penetrate the film layer, but also the additives react with active groups such as hydroxyl, carbon and nitrogen in the organic resin structure to form a three-dimensional spatial network structure. The swelling is prevented. After testing, various types of traditional paint strippers are not ideal when used on aluminum-zinc anti-fingerprint films.

[0017] The invention is based on the traditional paint stripping principle, uses benzaldehyde, diethylene glycol monobutyl ether and other organic resins such as polyurethane resin and acrylic resin in the swelling fingerprint-resistant film, takes into account the good stability of resins such as silane and the characteristics of less pores and difficulty in penetration caused by fillers such as nano silicon dioxide in the film layer, and in view of the strong permeability of chloride ions, chloroform is added to further improve the permeability, and ethanol is added to prevent the decomposition of chloroform. In order to eliminate the filling and spatial network structure formed by silane coupling agent, nano silicon dioxide, zirconate and titanate, fluoride with strong coordination reaction ability with silicon, titanium and zirconium is added to dissolve titanium dioxide, zirconium dioxide, silicon dioxide and the like in the film layer, and because fluoride is not soluble in organic solvents, a water-phase paint stripping agent system is constructed by adopting weak polar organic matter (referring to benzaldehyde and diethylene glycol monobutyl ether) and adding a surfactant.

[0018] 1. Setting of benzaldehyde

[0019] High-grade anti-fingerprint film is generally based on polyurethane. Benzaldehyde has a certain swelling effect on various paint films. Literature has confirmed that it has the best dissolution effect on polyurethane film. Benzaldehyde has a high boiling point (199°C), low toxicity, and little impact on the environment. It can be used as the main body of the reagent. The ratio of benzaldehyde to another main solvent, diethylene glycol monobutyl ether, is 1:1 to 2:1, with good effect. The weight percentage of benzaldehyde in the reagent is 25%-35%.

[0020] 2. Setting of diethylene glycol monobutyl ether

[0021] Most fingerprint-resistant films are acrylic esters. According to the principle of like dissolves like, the best solvents for acrylic polymers are generally various linear ethers, ketones, lipids, etc. However, most of these materials are insoluble in water and cannot be used to construct a water-based system. Diethylene glycol monobutyl ether has a good effect in dissolving acrylic ester materials and is completely miscible with water. It is an indispensable component for constructing a water-based paint stripping system. The weight percentage of diethylene glycol monobutyl ether in the reagent is 15%-25%.

[0022] 3. Settings for chloroform and ethanol

[0023] Chloroform is a very commonly used paint stripper. Chloride has the characteristics of small molecular size and low molecular weight, and can quickly penetrate into the coating, which can soften most types of paint films, especially for chemically stable silane polymers and smaller gaps filled by nano-silicon dioxide, titanates, etc. Chloroform can also work synergistically with other paint strippers, that is, chloroform causes the coating to swell initially, and then other types of paint strippers implement further swelling.

[0024] Chloroform has many disadvantages, such as chloroform itself is toxic, highly volatile (boiling point 61.5℃), and reacts with oxygen in the air under light to gradually generate highly toxic carbonyl chloride (phosgene), which requires the addition of ethanol to inhibit its oxidation reaction. After comprehensive consideration and experiments, it was found that the addition of chloroform at 5%-10% and ethanol at 0.5%-1.0% had a better effect. Ethanol itself has no obvious effect on removing the anti-fingerprint layer, so there is no need to add more ethanol.

[0025] 4. OP-10 settings

[0026] OP-10 is a common surfactant that can increase the solubility of organic matter in water. Among the organic matter in this patent, diethylene glycol monobutyl ether can be miscible with water in any proportion, the solubility of benzaldehyde is relatively large (about 10g), and the solubility of chloroform in water is about 0.8g. Tests show that when 5% OP-10 is added, up to 50% benzaldehyde and 15% chloroform can form a stable mixed solution with 20% water and 15% diethylene glycol monobutyl ether. In addition, OP-10 can change the wettability of the surface, making it easier for the solvent to penetrate into the film layer.

[0027] 5. Setting of Potassium Fluoride

[0028] The main reason why the chrome-free anti-fingerprint film is difficult to remove compared to ordinary paint film is that nano-silicon dioxide, titanate, zirconate, etc. fill the gaps in the film, making it difficult for organic reagents to penetrate. In addition, the added nano-silicon dioxide, zirconate, etc. form a spatial network structure with the resin, making it difficult for swelling to occur; fluoride ions can form soluble coordination compounds (fluorosilicate ions (SiF6)) with silicon, titanium, zirconium, etc. 2- , Fluorozirconate ion (ZrF6) 2- ,fluorotitanate ion ((TiF6) 2- ), release the network structure and dissolve the filler, making it easier for other organic solvents to penetrate and swell the anti-fingerprint film.

[0029] Soluble fluorides include potassium fluoride, sodium fluoride, ammonium fluoride, etc. Among them, sodium fluoride has a low solubility (10g), and ammonium fluoride has poor stability and is easily decomposed into toxic hydrogen fluoride, so both are not suitable for selection. The solubility of potassium fluoride is about 100g, but it is only soluble in water. Therefore, when the water content is controlled at 20%-30%, it is easy to prepare a solution containing 10%-15% potassium fluoride.

[0030] The method for preparing the reagent for removing the chromium-free anti-fingerprint film layer on the surface of the hot-dip aluminum-zinc steel plate comprises the following steps:

[0031] 1) Weigh potassium fluoride and water according to the ratio, dissolve potassium fluoride in water, and stir until the solution is clear to obtain a potassium fluoride solution for later use;

[0032] 2) Weighing benzaldehyde, diethylene glycol monobutyl ether, chloroform, ethanol, and OP-10 respectively according to the proportion, and mixing the above liquids evenly to obtain an organic mixed solution for standby use;

[0033] 3) The potassium fluoride solution and the organic mixed solution are mixed evenly, and stirred until the solution is clear to obtain a finished reagent.

[0034] A method for removing a chromium-free anti-fingerprint film layer on the surface of a hot-dip aluminum-zinc steel plate, using the reagent of the present invention, comprises the following steps:

[0035] 1) Immerse all the hot-dip aluminum-zinc steel sheets with or without chrome anti-fingerprint film in the reagent for 2-8 hours;

[0036] 2) When the anti-fingerprint film layer on the edge of the hot-dip galvanized steel plate has been lifted for 20-30 minutes, remove the hot-dip galvanized steel plate from the reagent;

[0037] 3) Tear off the entire anti-fingerprint film from the edge of the hot-dip galvanized steel plate.

[0038] The reasons for setting the parameters of the above reagent to remove the chrome-free anti-fingerprint film on the surface of the hot-dip aluminum-zinc steel plate are as follows:

[0039] Generally, a beaker is used for the operation. Depending on the needs, a 500mL or 1000mL beaker can be used. The steel plate to be removed from the anti-fingerprint layer is cut into small pieces so that it can be fully immersed in the solution.

[0040] As the temperature rises, the molecular motion intensifies, and the stripping speed will increase. However, considering that the boiling point of chloroform, the key component of the paint stripper, is only 61.5°C, in order to prevent the chloroform from gasifying and polluting the environment after the temperature rises and reduce the concentration of the paint stripper, no heating operation is generally used.

[0041] After about 2 to 8 hours, the fingerprint-resistant film layer is basically separated from the steel plate. Experiments show that when using this paint stripper, the silane film layer has a faster stripping speed, the acrylate film layer has a slower stripping speed, and the polyurethane film layer has the slowest stripping speed; soaking for a longer time has no effect on the stripping effect and the state of the substrate.

[0042] Compared with the middle of the steel plate, the paint stripper can penetrate between the steel plate and the fingerprint-resistant film faster at the edge. Therefore, as the film stripping proceeds, the fingerprint-resistant film layer at the edge of the steel plate will first curl up and separate from the surface of the steel plate. Generally, after about 20min-30min, the bonding force between the film layer in the middle of the steel plate and the steel plate will also weaken. At this time, the steel plate can be taken out of the solution and the entire fingerprint-resistant film layer can be torn off from the edge. The force should not be too large during the operation, and the entire film layer should be completely separated from the steel plate as much as possible.

[0043] Compared with the prior art, the present invention has the following positive effects: 1. The reagent of the present invention is an aqueous reagent, and benzaldehyde is used to achieve the swelling effect of polyurethane and other resins in the fingerprint-resistant film, and diethylene glycol monobutyl ether is used to achieve the swelling effect of acrylic resin in the fingerprint-resistant film, and a surfactant is used to improve stability and permeability; the reagent of the present invention has low volatility and toxicity, is easy to use, has good use effect, and is highly safe; after the aluminum-zinc-plated chrome-free fingerprint-resistant board is immersed in the reagent of the present invention, the entire fingerprint-resistant layer is removed within 2-8 hours, and the surface of the metal substrate is not damaged, which is conducive to the subsequent quality analysis work. 2. The reagent of the present invention is suitable for the chrome-free fingerprint-resistant film layer on the surface of the hot-dip aluminum-zinc steel plate, including a chrome-free fingerprint-resistant layer with polyurethane resin, acrylic resin or silane resin as the main body. 3. The method of the present invention is easy to operate, safe and reliable, has a small reagent consumption, and the aqueous reagent is green and environmentally friendly. DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with Examples 1-3.

[0045] In Example 1, the chrome-free anti-fingerprint film layer on the surface of the hot-dip aluminum-zinc steel plate is a chrome-free anti-fingerprint layer mainly composed of acrylic resin.

[0046] A reagent for removing a chrome-free anti-fingerprint film on the surface of a hot-dip aluminum-zinc steel plate comprises the following components in percentage by weight: 25% benzaldehyde, 20% diethylene glycol monobutyl ether, 10% chloroform, 1% ethanol, 8% OP-10, 15% potassium fluoride and 21% water.

[0047] The method for preparing the reagent for removing the chromium-free anti-fingerprint film layer on the surface of the hot-dip aluminum-zinc steel plate comprises the following steps:

[0048] 1) Weigh potassium fluoride and water according to the ratio, dissolve potassium fluoride in water, and stir until the solution is clear to obtain a potassium fluoride solution for later use;

[0049] 2) Weighing benzaldehyde, diethylene glycol monobutyl ether, chloroform, ethanol, and OP-10 respectively according to the proportion, and mixing the above liquids evenly to obtain an organic mixed solution for standby use;

[0050] 3) The potassium fluoride solution and the organic mixed solution are mixed evenly, and stirred until the solution is clear to obtain a finished reagent.

[0051] The method for removing the chrome-free anti-fingerprint film layer on the surface of the hot-dip aluminum-zinc steel plate by using the above reagent comprises the following steps:

[0052] 1) Cut the hot-dip aluminum-zinc steel sheet with or without a chrome-resistant fingerprint film on the surface into small pieces and immerse all of them in the reagent for 2 hours;

[0053] 2) When the anti-fingerprint film layer on the edge of the hot-dip galvanized steel plate has been lifted for 20 minutes, remove the hot-dip galvanized steel plate from the reagent;

[0054] 3) Tear off the entire anti-fingerprint film from the edge of the hot-dip galvanized steel plate.

[0055] In Example 2, the chrome-free anti-fingerprint film layer on the surface of the hot-dip aluminum-zinc steel plate is a chrome-free anti-fingerprint layer mainly composed of acrylic resin and silane resin.

[0056] A reagent for removing a chrome-free anti-fingerprint film on the surface of a hot-dip aluminum-zinc steel plate comprises the following components in percentage by weight: 30% benzaldehyde, 25% diethylene glycol monobutyl ether, 5% chloroform, 0.5% ethanol, 5% OP-10, 10% potassium fluoride and 24.5% water.

[0057] The method for removing the chrome-free anti-fingerprint film layer on the surface of the hot-dip aluminum-zinc steel plate by using the above reagent comprises the following steps:

[0058] 1) Cut the hot-dip aluminum-zinc steel sheet with or without a chrome-resistant fingerprint film on the surface into small pieces and immerse all of them in the reagent for 3 hours;

[0059] 2) When the anti-fingerprint film layer on the edge of the hot-dip galvanized steel plate has been lifted for 20 minutes, remove the hot-dip galvanized steel plate from the reagent;

[0060] 3) Tear off the entire anti-fingerprint film from the edge of the hot-dip galvanized steel plate.

[0061] Example 3: The chrome-free anti-fingerprint film layer on the surface of the hot-dip aluminum-zinc steel plate is a chrome-free anti-fingerprint layer mainly composed of polyurethane resin.

[0062] The invention discloses a reagent for removing a chrome-free anti-fingerprint film layer on the surface of a hot-dip aluminum-zinc steel plate. The weight percentage of the components thereof is: 35% benzaldehyde, 15% diethylene glycol monobutyl ether, 8% chloroform, 1.0% ethanol, 6% OP-10, 12% potassium fluoride and 23% water.

[0063] The method for removing the chrome-free anti-fingerprint film layer on the surface of the hot-dip aluminum-zinc steel plate by using the above reagent comprises the following steps:

[0064] 1) Cut the hot-dip aluminum-zinc steel sheet with or without a chrome-resistant fingerprint film on the surface into small pieces and immerse all of them in the reagent for 6 hours;

[0065] 2) When the anti-fingerprint film layer on the edge of the hot-dip galvanized steel plate has been lifted for 30 minutes, remove the hot-dip galvanized steel plate from the reagent;

[0066] 3) Tear off the entire anti-fingerprint film from the edge of the hot-dip galvanized steel plate.

[0067] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A reagent for removing the chrome-free anti-fingerprint film on the surface of a hot-dip aluminum-zinc steel plate, characterized in that: The weight percentages of its components are: benzaldehyde 25%-35%, diethylene glycol monobutyl ether 15%-25%, chloroform 5%-10%, ethanol 0.5%-1.0%, OP-105%-8%, potassium fluoride 10%-15%, water 20%-30%, and the sum of the weight percentages of the components is 100%; the chrome-free anti-fingerprint film layer on the surface of the hot-dip aluminum-zinc steel plate is a chrome-free anti-fingerprint layer with polyurethane resin, acrylic resin or silane resin as the main body.

2. The reagent for removing the chromium-free anti-fingerprint film on the surface of the hot-dip aluminum-zinc steel plate according to claim 1, characterized in that: The mass ratio of benzaldehyde to diethylene glycol monobutyl ether in the reagent is 1:1 to 2:

1.

3. A method for preparing a reagent for removing the chromium-free anti-fingerprint film on the surface of a hot-dip aluminum-zinc steel plate according to claim 1, characterized in that: The method comprises the following steps: 1) Weigh potassium fluoride and water according to the ratio, dissolve potassium fluoride in water, and stir until the solution is clear to obtain a potassium fluoride solution for later use; 2) Weighing benzaldehyde, diethylene glycol monobutyl ether, chloroform, ethanol, and OP-10 respectively according to the proportion, and mixing the above liquids evenly to obtain an organic mixed solution for standby use; 3) The potassium fluoride solution and the organic mixed solution are mixed evenly, and stirred until the solution is clear to obtain a finished reagent.

4. A method for removing the chrome-free anti-fingerprint film on the surface of a hot-dip aluminum-zinc steel plate, characterized in that: Using the reagent described in claim 1, the method comprises the following steps: 1) The hot-dip aluminum-zinc steel sheet coated with a chrome-free fingerprint-resistant film layer is completely immersed in the reagent for 2-8 hours; 2) When the anti-fingerprint film layer on the edge of the hot-dip galvanized steel plate has been lifted for 20-30 minutes, remove the hot-dip galvanized steel plate from the reagent; 3) Tear off the entire anti-fingerprint film from the edge of the hot-dip galvanized steel plate.