JPH0348271B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for forming a film with excellent hydrophilicity, corrosion resistance, and plastic workability on the surface of aluminum and aluminum-containing materials (hereinafter simply referred to as "aluminum materials"). The present invention relates to a hydrophilic corrosion-resistant film-forming agent. [Conventional technology and problems] Aluminum materials are widely used for various purposes, but
Depending on the application, it is desired that the surface be so-called hydrophilic, meaning that it can be easily wetted by water. That is,
For example, in the case of heat exchangers, as performance increases and miniaturization progresses, attempts are being made to improve heat transfer performance by narrowing the fin spacing. However, in a heat exchanger, heat is exchanged with the atmosphere on the fin surface, and moisture in the atmosphere condenses on the fin surface. However, if the fin spacing is narrowed to, for example, 3 to 4 mm or less, Condensed water forms so-called bridges between the fins, which increases ventilation resistance and causes noise generation and a reduction in energy consumption efficiency. Therefore, attempts have been made to impart hydrophilicity to the fin surface to prevent the formation of bridges. In addition to heat exchangers, it is also used when you want to prevent dew condensation on the surface of aluminum materials in a humid atmosphere, when you want to prevent fogging on the surface of aluminum materials that require gloss, or when you want to increase the wettability of water and remove water from the surface of aluminum materials. In cases where it is desired to increase the amount of evaporation of aluminum, a hydrophilic film is formed on the surface of the aluminum material. As a means of imparting hydrophilicity, methods are taken depending on the aluminum material used, but a method of applying a treatment agent that imparts hydrophilicity is known. Additives such as silica powder and surfactants are known, but it is necessary to add a large amount of silica powder, which reduces the density of the inorganic film and reduces the corrosion resistance of the film. If the concentration of hexavalent chromium ions is increased to compensate, 6
Problems such as chromium ion leaching, dies wearing out when performing die molding after film formation, or surfactants leaching over time and deteriorating hydrophilicity. or,
If the hydrophilicity is increased, there are problems such as lowering the corrosion resistance of the aluminum material depending on the usage environment and deterioration of the hydrophilicity over time. )
is desired. [Means and effects for solving the problem] The present inventors have conducted repeated research in order to obtain a film-forming agent that can form a film that not only provides good hydrophilicity and corrosion resistance but also has excellent plastic workability. As a result, we have discovered that the object can be achieved by appropriately blending a chromium compound, fluoride, ion exchange resin, and acrylic acid polymer, and have accomplished the present invention. That is, in the present invention, a hexavalent chromium compound is added in an amount of 0.05 to 2 g/3 in terms of CrO ₃ in an aqueous solution.
1 to 18 g of chromium compounds in terms of _CrO3 ,
This is a hydrophilic corrosion-resistant film-forming agent for aluminum materials, which contains 0.1 to 5 g of fluoride as F ^- , 1 to 100 g of ion exchange resin powder as solid content, and 1 to 20 g of acrylic acid polymer as solid content. Examples of the aluminum material in the present invention include:
Examples include formed materials such as plates and extruded materials made of aluminum and its alloys, aluminum-coated steel materials (plated materials, clad materials, etc.), and products with specific shapes and assemblies such as heat exchangers. . Examples of the source of the trivalent chromium compound constituting the film forming agent of the present invention include chromium hydroxide,
Inorganic acid salts such as chromium nitrate, chromium fluoride, chromium phosphate, chromium sulfate, organic acid salts such as chromium acetate, chromium maleate, etc. can generally be used as a source of hexavalent chromium compounds. is a chromate, such as chromium trioxide, ammonium chromate, potassium chromate, sodium chromate, lithium chromate, or ammonium dichromate, potassium dichromate, sodium dichromate, lithium dichromate. Dichromates such as dichromates may be commonly used. In addition to adding trivalent chromium in the form of a compound as described above, a hexavalent chromium compound such as chromium trioxide is used, and a portion of this is added in formalin, formalin, etc.
It is also possible to mix trivalent compounds by reducing them with an organic reducing agent such as phenol or polyhydric alcohol, and compared to the case of mixing trivalent chromium compounds and hexavalent compounds, trivalent chromium It is preferable to use it on the low concentration side. Therefore, the hexavalent chromium compound in the film forming agent is added in the range of 0.05 to 2 g/in terms of _CrO3 , and if the amount added is less than 0.05 g/,
The corrosion resistance effect was not sufficient, and the crosslinking reaction of the acrylic acid polymer was not carried out to a sufficiently satisfactory extent.
In this case, hexavalent chromium is likely to be eluted from the film, causing a pollution problem, and as a result, the corrosion resistance of the film is reduced. The trivalent chromium compound is used to compensate for the decrease in the effectiveness of chromium due to the restriction on the amount of hexavalent chromium compound used, and is added in a range of 1 to 18 g/in terms of _CrO3 . The purpose of the project cannot be fully achieved. It should be noted that if the total amount of chromium exceeds 20 g/min, the surface of the aluminum material will be colored, the chromium will be locally concentrated, the film will become non-uniform, and it is also economically disadvantageous. Thus, the chromium compound acts on the surface of the aluminum material in cooperation with the fluoride to form an inorganic layer with high corrosion resistance, and also crosslinks the acrylic acid polymer to make it insolubilized. Next, examples of fluorides include fluoric acid,
Silicon fluoride, boron fluoride, titanium fluoride, zirconium fluoride, zinc fluoride, etc. are mentioned, and such soluble fluoride is expressed as fluorine ion (F ^- ) in an amount of 0.1 to 5 g/, preferably 0.7
Add in a range of ~3.5g/. If F ^- is less than 0.1g/, good corrosion resistance of the inorganic layer, which is mainly composed of reaction products between aluminum material and chromium compound, cannot be obtained, and if it is more than 5g/, the elution of aluminum material becomes noticeable and the film becomes dense. The film-forming agent bath is difficult to control. Thus, the fluoride acts cooperatively with the chromium compound to form an inorganic layer with corrosion resistance and good plastic workability on the aluminum surface. Next, ion exchange resins include compounds that have hydrophilic atomic groups and can act as water-insoluble surfactants, and are commercially available as ion exchange resin particles and ion exchange resin membranes. It can be appropriately selected from resins, and has a total ion exchange capacity of 0.5 [mg equivalent/g-DryR] or more, more preferably 1 [mg equivalent/g-Dry-R].
The above are appropriate. That is, for example,
Condensation type ion exchange resins include phenolsulfonic acid type, ethyleneimine-epichlorohydrin type, epoxy type, etc. Polymerized type ion exchange resins include styrene-divinylbenzene type, vinyl-divinylbenzene type, methacrylic acid-divinylbenzene type. Cation exchange resins are available with hydrophilic groups such as sulfonic acid groups, phosphonic acid groups, phosphinic acid groups, quaternary ammonium, or primary or tertiary amines. Alternatively, it is commercially available as an anion exchange resin, and an appropriate one can be selected from these and used. In addition, amphoteric ion exchange resins such as strongly basic anion exchange resins polymerized with acrylic acid, or fluorine resins into which hydrophilic atomic groups are introduced are also commercially available, and any of these can be used. Among these ion exchange resins, cation exchange resins are preferred because they have excellent hydrophilicity, and sulfonic acid type strongly acidic cation exchange resins are most suitable. In addition, the ion exchange resin is not limited to one type, but can be used in appropriate proportions depending on the desired degree of hydrophilicity, such as strong acidic and weakly acidic cation exchange resins or strongly basic and weakly basic anion exchange resins. Two or more types can be used in combination. Furthermore, not only new products but also recycled products that have been used in other processes can be used in the same way. Therefore, ion exchange resin is used as a powder with a particle size that corresponds to the desired film thickness. If it is difficult to obtain particles of such a particle size, it may be finely ground using a grinder.In order to obtain uniform hydrophilicity, the solid content should be 1-100g/, preferably 3-60
If the amount is less than 1 g/g, it is difficult to obtain uniform hydrophilicity, and if it is more than 100 g/, it is difficult to obtain uniform hydrophilicity.
Repeated swelling of the ion exchange resin reduces the adhesion and water resistance of the film. Therefore, the ion exchange resin acts as a water-insoluble surfactant, and also gives the film hydrophilicity that does not change over time and plastic workability that does not cause die wear when plastic working aluminum materials. be. Next, as the acrylic acid polymer, water-soluble or water-dispersible polyacrylic acid or polyacrylic ester (hereinafter referred to as resin) is used,
For example, acrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, maleic acid A compound obtained by polymerization or copolymerization of compounds such as , itaconic acid, etc. is used. Note that water-soluble resins undergo a chelate reaction with divalent or higher metal species (chromium ions in the present invention) coexisting in the film-forming agent during a relatively low-temperature, short-time heat treatment process, resulting in water-insoluble resins. The average molecular weight of water-soluble resins is preferably 10,000 to 300,000. Examples of such resins include Primal A-1, A-3, and A-5 (trade name). , ROHM &
(manufactured by Haas) are commercially available. For water-dispersed emulsion type resins, the upper limit of the molecular weight is not limited to this. Further, the acid value of the resin should be determined in relation to the molecular weight, but it is preferably 5 or more, and if it is less than this, high temperature and long-term treatment will be required, which is economically disadvantageous. However, the amount of resin added is 1 to 20 in terms of solid content.
g/, preferably in the range of 4 to 14 g/; below 1 g/and above 20 g/, the film tends to become uneven depending on the area, and the adhesion and corrosion resistance of the film also lacks uniformity. , the stability of the film former is also reduced. Further, when using an emulsion type resin, the amount is preferably 10 g/or less in view of the stability of the emulsion. In addition, the insolubilization of the water-soluble resin in the present invention is
As mentioned above, this is due to the formation of poorly soluble organic chromate compounds through a crosslinking reaction with coexisting chromium compounds, and the amount of chromium required for crosslinking is
() It is sufficient to add 0.2% or more, and the amount of the resin can be changed substantially arbitrarily as long as the content of the chromium compound of the present invention is met. Furthermore, it is also possible to improve the corrosion resistance of the film by adding a thermosetting water-soluble resin. The film forming agent of the present invention is prepared by blending these compounds within the above-mentioned range, and is
It is about 1.5 to 3. If desired, it is possible to add surfactants such as α-olefin sulfonate, sodium alkylnaphthalene sulfonate, etc. at a rate of about 0.5 to 1 g/as an initial hydrophilicity improver; acids, metaphosphoric acid, phosphorous acid, etc.
Addition of 0.1 to ₅₀ g of PO ^3-4 increases the uniform application of the film and further improves the long-term stability of hydrophilicity, so it can be used depending on the application method. In addition, silica powder such as silica sol or fumed silica can be used as a thickener for the film forming agent, a dispersant for ion exchange resins, or a hydrophilicity imparting aid.
There is no problem in adding about 0.5 to 4 g/approximately, or blending the total amount of additives such as antifungal agents and slip agents that are added to ordinary paints to about 0.01 to 0.5 g/approximately. As a method for preparing the film forming agent of the present invention, for example, a bath A in which ion exchange resin powder is uniformly dispersed in a resin liquid and a bath B in which a chromium compound and a fluoride are mixed and dissolved in water are separately prepared. A method in which both baths are prepared in advance or immediately before use and mixed together. Or A' bath in which ion exchange resin powder is uniformly dispersed in the resin liquid and trivalent chromium liquid is added;
A method in which fluoride and hexavalent chromium are mixed and prepared in bath B' immediately before use. or,
Mix all compounds immediately before use. Furthermore, any suitable method may be used, such as a method in which baths A and B or baths A' and B' are separately applied onto the surface of the aluminum material and mixed on the surface of the aluminum material. However, the film-forming agent of the present invention, like the conventional processing agents, requires complicated roll coating, spraying, etc. methods for forming materials with simple shapes such as continuous plates and extruded materials. In the case of a product having a specific shape, it can be applied to the aluminum surface by an appropriate method depending on the shape of the aluminum material, such as brushing, dipping, or spraying. That is, a film forming agent prepared to have a composition suitable for these application means is applied at a liquid temperature of 20 to 40°C in an application amount of 0.1 to 5 g/m ^{2 .}
(dry film standard), then apply to
Heat treatment is performed at 250℃ for 10 seconds to 30 minutes to dry and bake the film. Note that if the film forming agent of the present invention is applied to the aluminum material while still retaining residual heat after rolling, extrusion, or other heat treatment, the subsequent heating and fixing process of the film can be omitted. You can use the residual heat. Furthermore, before the film is insolubilized, the film thickness can be increased by repeatedly applying the film forming agent of the present invention many times. Furthermore, coating can be applied not only after forming the aluminum material, but also because the resulting film has excellent press formability, so it can also be applied after forming the film.For example, it can be applied during press punching, etc. Secondary effects such as reducing die wear may also occur. The film obtained by applying the film-forming agent in this way consists of a lower layer consisting of an inorganic layer containing a chromium compound and highly corrosion resistant, and a resin layer mainly composed of an ion exchange resin that is highly hydrophilic and suppresses the elution of chromium compounds. It has a two-layer structure with an upper layer. This is thought to be the reason why the treatment agent permanently exhibited far superior hydrophilicity and corrosion resistance compared to conventional treatment agents. [Effects of the Invention] The present invention has a chromium compound, a fluoride, an ion exchange resin, and an acrylic acid polymer as constituent components,
Since we have blended a predetermined amount of each of these, when applied to the surface of an aluminum material, normal coating operations can be performed, and a film with little deterioration over time and excellent hydrophilicity and corrosion resistance can be formed. The resulting film has at least a two-layer structure, and the outer layer is a resin layer, so it has excellent processability after forming the film, and does not cause wear of processing dies or cracks in the film itself. Excellent effects are recognized, such as being able to prevent the elution of hexavalent chromium in the film. Next, examples of the present invention will be described. Example 1 (1) Preparation of hydrophilic corrosion-resistant film forming agent Water was added to a 20% by weight aqueous solution of polyacrylic acid (trade name Schurimar AC10H, manufactured by Nippon Pure Chemical Industries, Ltd.) so that the concentration of polyacrylic acid was 16 g/ml. After that, a sulfonic acid polyethylene cation exchange resin (trade name: Amberlite IR-120, manufactured by Rohm & Haas), which had been ground and dried to have an average particle size of 1 μm, was added at a rate of 16 g/ml and uniformly dispersed. solution (A bath) and chromium sulfate (Cr ₂
(SO ₄ ) ₃・5H ₂ O) 19.3 g/, chromium trioxide (CrO ₃ ) 1.5 g/, hydrofluoric acid (46% HF) 2.1 g/
An aqueous solution (bath B) was prepared in advance, and when used, the same amounts of bath A and bath B were mixed together. (2) Film formation and press processing As the aluminum material, after degreasing and cleaning a 0.15 mm thick AA3102 aluminum alloy coil material with a weak alkaline cleaning solution, it was coated as described in the previous section (1) using a roll coating method.
^A film-forming agent prepared by
Heat treatment at 150℃ for 20 minutes to make the film insoluble.
fixed. Next, using the obtained coil material, a cross fin material for a heat exchanger was manufactured by press punching and press ironing. (3) Evaluation test (a) Test method and evaluation of hydrophilicity and corrosion resistance (a) Test method of hydrophilicity (i) Initial performance: After immersing in deionized water, take it out and leave it for 30 seconds. It was measured. (ii) Long-term durability: relative humidity 95%, temperature 50℃
The wetted area ratio was measured after being left in the atmosphere for 500 hours. (b) Corrosion resistance test method (i) Salt spray: The corrosion area rate was measured after 1000 hours based on the salt spray method according to JISZ2371 (1955). (ii) Acetic acid salt spray: The corrosion area rate was measured after 100 hours based on the Aluminum Surface Treatment Technology Research Association test standard ARS2132. (c) Evaluation The measurement results of the above test are shown in the attached table, and it can be seen that the film treatment agent of the present invention exhibits hydrophilicity equivalent to that of conventional treatment agents, and its corrosion resistance is significantly superior. Recognize. (b) Evaluation of press formability The processing die used to process the coil material treated with the film-forming agent of the present invention was processed at least 10 times as much as the treatment used for the comparative material treated with the conventional treatment agent. It was confirmed that the product could be used without any trouble even after reaching a certain amount, and that a film with a small amount of die wear could be obtained. This is also proven in the pressure ball abrasion test. Example 2 (1) Preparation of hydrophilic corrosion-resistant film forming agent Chromium acetate (Cr ₂ (C ₂ H ₃ O) ₆・2H ₂ O)
g/, chromium trioxide (CrO ₃ ) 1.42g/
, an aqueous solution (A bath) containing 1 g of hydrofluoric acid (46% HF) and 1 g of orthophosphoric acid (100% H ₃ PO ₄ ), and an acrylic acid polymer.
A 25% by weight aqueous solution (trade name: Primer A-1, manufactured by Rohm & Haas) was diluted with water to give an acrylic acid polymer concentration of 15.4 g/cm, and then a sulfonic acid type ion exchange resin with an average particle size of 0.5 to 1 μm was prepared. (Product name: R-120B, manufactured by Organo) in solid content.
An aqueous solution (bath B) was prepared in advance by mixing and uniformly dispersing 50 g of each, and equal amounts of each were mixed before use. (2) Formation of film and press processing Thickness of aluminum material treated with Triclean degreasing
It was coated on a 0.12 mm AA1050 alloy aluminum plate using a roll coater in the same manner as in Example 1,
Similarly, the film was made insoluble and fixed to form a film with a thickness of 1 μm. Then, press working was performed in the same manner as in Example 1. (3) Evaluation test The same test method as in Example 1 was conducted. These results are shown in the table below, and the corrosion resistance is significantly superior to that of conventional treatment agents, and the plastic workability shows no trouble at all even when the throughput is more than 10 times that of conventional treatment agents. Ta. Comparative example Commercially available acrylic resin paint (trade name Watersol 727, manufactured by Dainippon Ink Co., Ltd.), melamine resin paint (trade name Watersol S695, manufactured by Dainippon Ink Co., Ltd.), and colloidal silica (trade name Snotex, manufactured by Nissan Chemical Co., Ltd.) A mixture of 48 parts, 12 parts, and 40 parts of solids was prepared, and the same tests were conducted by coating, fixing by baking, and pressing under the same conditions as in the example. Ta. The results are shown in the attached table. 【table】

Claims (1)

[Claims] 1 In an aqueous solution, add 0.05 to 2 g of a hexavalent chromium compound (calculated as CrO _{3 )} and a trivalent chromium compound
1 to 18g/ in terms of _CrO3 , fluoride as ^F-
A hydrophilic corrosion-resistant film forming agent for aluminum material, characterized in that it contains 0.1 to 5 g/solid content of ion exchange resin powder, and 1 to 100 g/solid content of acrylic acid polymer.