JP2007290271A - Surface-treated aluminium material, its manufacturing process, resin coating aluminium material using the same, and its manufacturing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-treated aluminium material excellent in adhesion property and corrosion resistance, and a resin coating aluminium material excellent in adhesion property and corrosion resistance using this. <P>SOLUTION: The surface-treated aluminium material comprises a matrix including aluminium or an aluminium alloy, an aluminium oxidized film formed on the surface of the matrix, and an organic compound film formed on the surface of the aluminium oxidized film, wherein the aluminium oxidized film has a thickness of 15 nm or less, wherein the formed amount of the organic compound film is 1 to 50 mg/m<SP>2</SP>in terms of carbon, and wherein the organic compound has one functional group or more selected from the group consisting of (a) two hydroxyl groups or more, (b) two carboxyl groups or more, and (c) one hydroxyl group or more and one carboxyl group or more. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface-treated aluminum material having an aluminum oxide film and an organic compound film on at least one surface of an aluminum substrate, a resin-coated aluminum material having a resin-coated film on the surface-treated aluminum material, and methods for producing the same About. This resin-coated aluminum material is excellent in adhesion and corrosion resistance.

  In recent years, aluminum alloy plates have been widely adopted as resin coatings for food containers, furniture, and building materials. This is because aluminum is more recyclable than other metal materials and has excellent workability and aesthetics.

  Conventionally, phosphoric acid chromate treatment or chromate chromate treatment has been used as a base surface treatment method for a resin-coated aluminum material. The chromate conversion coating formed by these chromate surface treatment agents is excellent in corrosion resistance of the coating alone, and also has excellent characteristics of adhesion and corrosion resistance after various resin coatings are applied. However, in recent years, from the viewpoint of environmental protection, chromium-containing wastewater during chromate treatment leads to environmental pollution, and wastewater treatment also has a disadvantage that requires cost. In recent years, it has become necessary to abolish the use of chromate-based treatment agents because valent chromium is harmful to the human body.

Therefore, a treatment agent not containing hexavalent chromium is desired, and various studies have been conducted so far. For example, Patent Document 1 describes a method of treating with a treatment liquid containing zirconium, titanium, or a mixture thereof, phosphate, and fluoride. Patent Document 2 discloses a treatment liquid containing a phosphate having a pH of 2 to 4 containing a phosphate ion and a zirconium compound, and an oxidizing agent of 500 ppm or less and 2000 ppm or less containing at least one of hydrofluoric acid or fluoride as fluorine. There has been proposed a surface treatment method using the above.
U.S. Pat. No. 4,148,670 JP 7-48677 A

  By the treatment using such a non-chromate treatment solution, a composite chemical conversion film mainly composed of zirconium oxide is formed on the surface of the aluminum substrate. However, in the non-chromate treatment method, the reaction between oxygen in the atmosphere and the top surface of the conversion coating during the process of storing the aluminum oxide formed on the top surface of the conversion coating at the same time as the formation of the conversion coating or the aluminum substrate subjected to the conversion treatment. The aluminum oxide grown by this forms a weak boundary layer. Such a weak boundary layer has a drawback that it can be used only for limited applications as compared with the conventional chromate treatment method because it affects the lowering of the adhesion of the resin coating film.

  As a method of forming a resin coating film using a thermoplastic resin or the like, a method of thermally bonding a thermoplastic resin film is generally used. The method using a thermoplastic resin film does not require a drying and baking step performed in the case of coating, can be resin-coated only by thermal bonding, and is continuous along the surface direction of the thermoplastic film. Therefore, it has been widely adopted because it has advantages such as the uniformity of the resin coating film thickness.

However, when the thermoplastic resin film is directly thermocompression bonded onto the aluminum chemical conversion film, the resulting adhesive strength generally decreases. In view of this, a method of performing thermal bonding by applying a coating called an adhesion primer on either the upper part of the chemical conversion film or the bonding surface of the thermoplastic resin film is employed. For example, in Patent Document 3, a thermosetting powder coating is applied on a metal plate, and a polyethylene terephthalate film is laminated and pressure-bonded at a temperature not lower than the melting point of the coating and not higher than a curing start temperature, and thereafter, not lower than a curing start temperature of the coating And a method for producing a thermoplastic resin-coated metal sheet by heating to a temperature below the melting point of polyethylene terephthalate.
Japanese Patent Laid-Open No. 1-154746

  By forming such an adhesion primer layer, even when an aluminum oxide layer that is a weak boundary layer is formed on the outermost surface of the chemical conversion film, a resin-coated aluminum material having excellent adhesion to a thermoplastic resin is provided. can do. However, in the laminated structure of the chemical conversion film / thermosetting adhesive primer layer / thermoplastic resin film, although the interface breakdown between the adhesive primer layer and the thermoplastic resin film can be suppressed, the interface breakdown between the chemical conversion film and the adhesive primer layer, It has often been confirmed that adhesive failure occurs due to cohesive failure of the adhesive primer layer itself.

  The present invention has been made to solve the above problems, and without performing chemical conversion treatment and adhesion primer coating treatment, a surface-treated aluminum material having excellent adhesion and corrosion resistance with a resin coating film, and An object of the present invention is to provide a resin-coated aluminum material provided with a resin-coated film. Another object of the present invention is to provide a surface-treated aluminum material having the above excellent characteristics and a method for producing a resin-coated aluminum material using the same.

  As a result of studying the above problems, the present inventors have found that the decrease in the adhesion and corrosion resistance between the aluminum substrate and the resin coating film is caused by the aluminum oxide formed on the outermost surface of the chemical conversion film during the chemical conversion treatment. I found out. Therefore, as a result of intensive studies based on such findings, it is possible to suppress the growth of aluminum oxide by treating at least one surface of the aluminum substrate with a tannin aqueous solution and providing a tannin film, and as an organic functional group on the tannin film. The surface-treated aluminum material with excellent adhesion and corrosion resistance to the resin coating film, without the chemical conversion treatment or the adhesion primer coating treatment, was found that the bonding with the resin coating film was strengthened by the hydroxyl group contained A resin-coated aluminum material using the same is provided.

The present invention comprises a base material made of aluminum or an aluminum alloy according to claim 1, an aluminum oxide film formed on the surface of the base material, and an organic compound film formed on the surface of the aluminum oxide film,
The aluminum oxide film has a thickness of 15 nm or less;
The amount of the organic compound film formed is 1 to 50 mg / m ² in terms of carbon, and the organic compound is (a) two or more hydroxyl groups; (b) two or more carboxyl groups; or (c) 1 A surface-treated aluminum material having one or more functional groups selected from the group (a) to (c) consisting of one or more hydroxyl groups and one or more carboxyl groups. In claim 2, the organic compound is tannin.

  The resin-coated aluminum material according to claim 3, further comprising a resin coating film formed from a paint or a resin film on the organic compound film of the surface-treated aluminum material according to claim 1 or 2. It was.

The present invention according to claim 4, wherein at least one surface of a substrate made of aluminum or an aluminum alloy is washed with an alkaline aqueous solution;
Washing the washing surface of the alkaline aqueous solution with an acidic aqueous solution;
Treating the washed surface of the acidic aqueous solution with an organic compound solution,
The thickness of the aluminum oxide film formed on the substrate surface after the washing step with the acidic aqueous solution is 15 nm or less,
An organic compound film is formed on the aluminum oxide film by the treatment step with the organic compound solution, and the amount of the organic compound film formed is 1 to 50 mg / m ² in terms of carbon. A manufacturing method was adopted. In claim 5, the organic compound is tannin.

  The present invention according to claim 6, further comprising the step of coating a resin coating film formed from a paint or a resin film on the organic compound film after the treatment step with the organic compound solution in claim 4 or 5. It was set as the manufacturing method of the characteristic resin-coated aluminum material.

  Surface-treated aluminum material having high adhesion and high corrosion resistance of the resin coating film, and resin-coated aluminum using the same, without performing conventional chromate-based or non-chromate-based chemical conversion treatment, or further forming an adhesive primer layer Material can be provided.

A. Inhibition of aluminum oxide Conventionally, when the surface of a base material made of aluminum or an aluminum alloy (hereinafter referred to as “aluminum base material”) is subjected to a zirconium phosphate nonchromate treatment, the structure of the chemical conversion film formed is In addition, an aluminum oxide film made of aluminum fluoride, oxide, oxyhydroxide, etc. exists at the interface between the aluminum base and the chemical conversion film, and zirconium phosphate, hydroxide, oxide and their A model has been proposed in which a chemical conversion film composed of a hydrate or the like is formed.

  As a result of detailed elemental analysis in a depth direction of a chemical conversion film formed by a conventional method, a so-called depth profile, the present inventors used an analytical instrument based on Auger electron spectroscopic analysis and secondary ion mass spectrometry. The main component of the aluminum oxide film has a so-called gradient structure in which the element concentration does not take a uniform structure in the depth direction or a layered structure made of several substances, and the element concentration continuously changes in the depth direction. I confirmed.

  That is, the surface of the aluminum base material subjected to the chemical conversion treatment has an aluminum oxide film component that increases as the chemical film component (the zirconium and phosphorus film components) increases in the surface layer direction from the aluminum base material body, and further the surface layer. As it goes in the direction, it has an inclined structure in which the aluminum oxide film component shows a maximum value and then decreases as the aluminum base material component decreases. Moreover, it was confirmed that the aluminum oxide film component remains with the zirconium and phosphorus film components on the outermost surface of the chemical conversion film.

  Moreover, the aluminum oxide which exists in the chemical conversion film surface layer influences adhesiveness with a resin coating film, and corrosion resistance, and these performances deteriorate, so that there are many amounts of aluminum oxide. Therefore, in order to obtain a chemical conversion film having good coating performance, the formation of aluminum oxide on the outermost surface of the chemical conversion film must be suppressed. The present inventors tried various chemical film formations by strictly controlling the chemical conversion treatment conditions or the concentration of the chemical conversion liquid composition, etc., but obtaining a good chemical conversion film in which the formation of aluminum oxide was suppressed. Was difficult.

  The inventors of the present invention first cleaned the surface of the aluminum substrate with an alkaline aqueous solution, then washed with an acidic aqueous solution, then treated with an organic compound solution without performing a chemical conversion treatment to provide an organic compound film, and a resin thereon It has been found that by applying the coating, a resin-coated aluminum material having excellent adhesion and corrosion resistance can be obtained in a state in which the generation of aluminum oxide serving as a weak boundary layer is suppressed.

B. Surface-treated aluminum material The surface-treated aluminum material according to the present invention is prepared by washing the surface of an aluminum substrate with an alkaline aqueous solution, then washing with an acidic aqueous solution, and then treating with an organic compound solution to form an organic compound film. Is done. As shown in FIG. 1, the surface-treated aluminum material 1 according to the present invention is schematically formed on an aluminum base film surface 2 by such cleaning with an alkaline aqueous solution and subsequent cleaning with an acidic aqueous solution. Is formed, and the organic compound film 4 is formed on the aluminum oxide film 3 by further treatment with an organic compound solution.

B-1. Aluminum substrate The aluminum substrate is made of aluminum or an aluminum alloy, and an Al-Mn JIS 3000 alloy, an Al-Mg JIS 5000 alloy, or the like is preferably used.

B-2. Washing with an alkaline aqueous solution The aluminum substrate is first washed with an alkaline aqueous solution. Cleaning with an alkaline aqueous solution is performed for the purpose of removing contaminants such as wear and rolling oil adhering to the surface of the aluminum substrate. As a cleaning method, alkali cleaning conventionally used in alkali cleaning treatment of metals such as an aluminum substrate can be performed. An alkaline cleaner is usually used as the alkaline cleaning liquid. It does not specifically limit as an alkaline cleaner, For example, what is used for normal alkali cleaning can be used. Examples thereof include Surf Cleaner EC370, EC371, 420N-2 manufactured by Nippon Paint, and FC4498-SK3 manufactured by Nippon Parkerizing.

  The conditions for washing with the alkaline aqueous solution are not particularly limited, and conditions that can efficiently remove contaminants may be selected. Since contaminants are removed by a weak etching action on the surface of the aluminum base material, the treatment can usually be performed in a shorter time as the cleaning temperature and concentration are higher. If the alkaline cleaning is not sufficient, contaminants on the surface of the aluminum substrate remain even after the treatment, and the hydrophilicity of the surface of the aluminum substrate cannot be secured. It will be limited. In addition, when washing with an alkaline aqueous solution, for example, at a high temperature, a high concentration, and for a long time, contaminants on the surface of the aluminum substrate are well removed, but the surface of the aluminum substrate is whitened by the etching action, It is not preferable from the viewpoint of appearance quality. In the washing with an alkaline aqueous solution, treatment conditions of 2 to 20 seconds are usually used at a temperature of 40 to 70 ° C. using an alkaline aqueous solution of 0.5 to 5% by weight.

B-3. Washing with an acidic aqueous solution Following washing with an alkaline aqueous solution, washing with an acidic aqueous solution is performed. The purpose of the cleaning with the acidic aqueous solution is to remove magnesium oxide called smut concentrated on the surface of the aluminum base during the cleaning with the alkaline aqueous solution and the aluminum oxide that grows simultaneously with the etching. Also in the cleaning method using an acidic aqueous solution, conventional acidic cleaning used for acidic cleaning treatment of metals such as an aluminum base can be performed. It is preferable to use commercially available sulfuric acid, nitric acid or the like for the acidic aqueous solution. Also in the cleaning with an acidic aqueous solution, the higher the cleaning temperature and concentration, the shorter the processing time becomes possible. When washing with an acidic aqueous solution is not sufficient, smut and aluminum oxide on the surface of the aluminum substrate remain even after the treatment, which adversely affects the processability with the organic compound solution in the next step. In the removal of smut and aluminum oxide, when an acidic aqueous solution having a concentration of about 2% by weight is used, the treatment is performed at a temperature of 40 to 60 ° C. for 3 to 10 seconds.

  The aluminum oxide film on the surface of the aluminum substrate after washing with an acidic aqueous solution needs to be 15 nm or less. When the aluminum oxide film has a thickness of 15 nm or less, good hydrophilicity can be ensured, and the treatment with the organic compound solution in the next step is easily and uniformly performed. Moreover, since the hydrogen bond between the aluminum base material and the phenolic hydroxyl group of the organic compound is formed well, strong adhesion can be obtained between the aluminum base material and the organic compound film.

  On the other hand, if the aluminum oxide film after treatment with an acidic aqueous solution exceeds 15 nm, sufficient hydrophilicity cannot be obtained, and coating unevenness tends to occur during treatment with an organic compound solution. Furthermore, since the hydrogen bond between the aluminum substrate and the organic compound film is inhibited by the aluminum oxide film, the adhesion between the aluminum substrate and the organic compound film is inferior. If the adhesion between the aluminum substrate and the organic compound film is inferior, interfacial peeling is likely to occur between them, and sufficient resin coating adhesion and corrosion resistance cannot be obtained.

The thickness of the aluminum oxide film defined in the present invention refers to the intersection of the Al depth direction profile and the oxygen depth direction profile in the depth profile of Auger electron spectroscopy analysis, and the intersection position from the outermost surface. Expressed as distance.
For example, measurement of the depth profile of Al, oxygen (O), and Mg when an aluminum substrate (JIS-A5482 alloy) is treated with an aqueous alkaline solution and then treated with a 2% by weight sulfuric acid aqueous solution at 30 ° C. for 1 second. An example is shown in FIG. In this case, the thickness of the aluminum oxide film is 68 nm. Measurement of depth profile of Al, oxygen (O) and Mg when aluminum substrate (JIS-A3004 alloy) is treated with alkaline aqueous solution and then treated with 2 wt% sulfuric acid aqueous solution at 50 ° C for 3 seconds An example is shown in FIG. In this case, the aluminum oxide film thickness is 6 nm.

  It is preferable to use a spray method for the washing treatment with the alkaline aqueous solution and the washing treatment with the acidic aqueous solution. Furthermore, after washing the alkaline aqueous solution and after washing the acidic aqueous solution, it is preferable to perform a water washing treatment in order to remove the alkaline aqueous solution and acidic aqueous solution remaining on the surface of the aluminum substrate.

B-4. Organic Compound Film By forming a predetermined organic compound film on the surface of the aluminum oxide film, the adhesion and corrosion resistance of the resin coating film can be improved. Such organic compounds comprise the group (a) two or more hydroxyl groups; (b) two or more carboxyl groups; or (c) one or more hydroxyl groups and one or more carboxyl groups; ) To (c) having one or more functional groups. Hydroxyl groups and carboxyl groups provide adhesion to the resin coating film by dehydration condensation with the hydroxyl groups of the aluminum oxide film and by forming hydrogen bonds with the hydroxyl groups of the resin coating film. Is done. Furthermore, since the hydration reaction starting from the hydroxyl group on the surface of the aluminum oxide film is suppressed by the hydroxyl group or carboxyl group, corrosion resistance is also imparted.

  Such organic compounds include those having two or more hydroxyl groups as functional groups, such as alditols represented by glycerin, erythritol, pentitol, hexitol, catechol, orcin, pyrogallol, inositol and the like. Can be mentioned.

  Further, such organic compounds include those having two or more carboxyl groups as functional groups, such as malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, glutaconic acid, adipic acid, and phthalic acid. And aconitic acid.

  Further, such organic compounds include those having one or more of both a carboxyl group and a hydroxyl group as functional groups, for example, glyceric acid, lactic acid, malic acid, tartaric acid, alabonic acid, citric acid, salicylic acid. , Hydroxycinnamic acid, gallic acid, ellagic acid, mandelic acid, tropic acid, atropic acid, ferulic acid, shikimic acid and the like, and aldonic acids represented by mannonic acid, gluconic acid, galactonic acid, mannal acid, Also included are aldaric acids represented by glucaric acid and galactaric acid.

  Further, such an organic compound has two or more carboxyl groups as functional groups, two or more carboxyl groups, or one or more each of both carboxyl groups and hydroxyl groups. Further, those having an amino group are also included, and examples thereof include aminohydroxycinnamic acid, amino acids represented by serine, threonine, tyrosine, aspartic acid, glutamic acid and the like.

  A film formed by these organic compounds has two or more hydroxyl groups as structural functional groups, two or more carboxyl groups, or a component containing at least one hydroxyl group and one carboxyl group. Therefore, a strong composite film with the aluminum oxide film is formed based on the chemical bond formed by the dehydration condensation reaction between the functional groups by heating according to the constituent elements.

The organic compound film is formed by applying the organic compound solution to the surface of the aluminum oxide film. The coating amount of the organic compound solution is such that the formation amount of the organic compound layer after drying is 1 to 50 mg / m ^{2 in} terms of carbon, that is, the amount of carbon existing in the organic compound layer after drying. With such a coating amount, a film with good uniformity is formed. Furthermore, by setting it as such application quantity, even if the unevenness | corrugation exists in the aluminum base-material surface by a rolling mark etc., favorable adhesiveness and corrosion resistance are exhibited stably.

When the amount of the organic compound layer formed is less than 1 mg / m ² , it is not possible to form an organic compound film that covers the entire surface of the aluminum substrate after the acidic cleaning. In such a case, aluminum oxide grows by reaction between the surface of the aluminum substrate and oxygen in the atmosphere at a place not covered with the organic compound film, and the resin coating film by the subsequent resin coating Adhesion and corrosion resistance will be poor.

On the other hand, when the amount of the organic compound layer formed exceeds 50 mg / m ² , the aluminum substrate surface can be completely covered with the organic compound film, so that the growth of aluminum oxide as a weak boundary layer is suppressed. it can. However, when the amount of the organic compound film is increased, cohesive failure occurs inside the organic compound film, leading to a decrease in adhesion and corrosion resistance.

  The organic compound solution to be applied is prepared at a concentration suitable for application by dissolving or dispersing the organic compound in water or a solvent such as a polar or nonpolar organic solvent. As the solvent, water is preferably used. The coating method is not particularly limited, and a roll coating method, a spray coating method, a bar coating method, a dip coating method, or the like is used. After coating, the film is dried at a temperature of 30 to 200 ° C, preferably 50 to 180 ° C. The drying time is appropriately selected according to the drying temperature and the like. That is, it is desirable to shorten the drying time when the drying temperature is high, and lengthen the drying time when the drying temperature is low. However, drying at a high temperature for a long time causes cracks in the aluminum oxide film, leading to a decrease in adhesion and corrosion resistance. Therefore, drying at a low temperature for a short time is preferable. For example, when the drying temperature is 60 ° C., the drying time is preferably 40 seconds, and when 150 ° C., it is preferably 15 seconds. By this drying treatment, the bond between the aluminum oxide film layer and the organic compound film can be strengthened by a dehydration condensation reaction between the hydroxyl group of the aluminum oxide film and the hydroxyl group or carboxyl group contained as a functional group in the organic compound. Moreover, the bond between organic compounds can be strengthened.

B-5. Tannin film As the organic compound, tannin having many hydroxyl groups and carboxyl groups in the molecule is preferably used. By applying the tannin solution to the surface of the aluminum oxide film, a surface-treated aluminum material with even better adhesion to the resin coating film and corrosion resistance can be obtained. In particular, the adhesion of a resin coating film formed from an epoxy-based aqueous paint or a polyethylene terephthalate film is improved by the tannin film.

  Tannin, also called tannic acid, is a general term for aromatic compounds having a complex structure having a large number of phenolic hydroxyl groups widely distributed in the plant kingdom. The tannin may be hydrolyzable tannin or condensed tannin. There are various types of tannins, including hameli tannin, oyster tannin, chatannin, pentaploid tannin (tannic acid), gallic tannin, milobala tannin, dibidi tannin, argarovira tannin, valonia tannin, catechin tannin and the like. The tannin may be a tannin degradation product obtained by decomposing tannin present in a plant by hydrolysis or the like.

  Since the tannic acid illustrated in FIG. 4 contains many hydroxyl groups, the film formed of tannic acid efficiently forms a stable film with cohesiveness or associability, and contributes to the improvement of corrosion resistance. Furthermore, gallotannin, the main component of tannin, contains organic functional groups that react with the hydroxyl groups of the aluminum oxide film, and also organic functional groups that bind to the resin coating film in a well-balanced manner. The adhesion is improved. Thus, the tannin film is particularly excellent as an organic compound film excellent in corrosion resistance and adhesion.

  As the tannin, commercially available products such as tannic acid extract A, B tannic acid, N tannic acid, and purified tannic acid manufactured by Dainippon Pharmaceutical Co., Ltd. can be used. The said tannin may be used independently and may mix and use 2 or more types.

  Tannin preferably has a number average molecular weight of 200 or more. When a tannin degradation product is used as tannin, since the decomposition proceeds too much and the molecular weight is a low molecular weight compound of less than 200, since it does not have properties as tannin, the adhesion of the resin coating film is not improved. .

The tannin film is formed by applying a spray method, a roll coat method, a bar coat method, a dip coat method or the like using a tannin solution. The tannin solution is preferably used as an aqueous solution. In addition, the concentration of the tannin aqueous solution can be appropriately selected according to the application method, whereby a desired film formation amount can be obtained. That is, the formation amount of the tannin film needs to be 3 to ²⁰ mg / m ^{2 in} terms of carbon, and the concentration and application method of the tannin aqueous solution are selected according to the target formation amount of the tannin film. Therefore, there is no need to restrict the application conditions such as concentration and application method in detail. Here, if the formation amount of the tannin film is less than 3 mg / m ² , it is not possible to form a film that covers the entire surface of the aluminum substrate after the acid cleaning. On the other hand, if it exceeds 20 mg / m ² , the amount of film formation becomes too large and cohesive failure occurs inside the film. The amount of tannin film formed can be measured by a total organic carbon analyzer.

  In the treatment step with the tannin solution, since the deposition property of the film is not affected by the temperature, the tannin solution is not particularly required to adjust the treatment temperature. However, in order to facilitate drying after the treatment, the tannin solution is 20 to 60 ° C. It is preferable to set the degree. Moreover, when processing the said tannin solution by a spray method, the processing time of the said tannin solution is 1 to 10 seconds, More preferably, it is 2 to 6 seconds. This is because if it is less than 1 second, the amount of film formed is not sufficient even when the concentration of the tannin solution is high, and the adhesion and corrosion resistance are reduced due to the formation of a uniform film. On the other hand, even if a treatment exceeding 10 seconds is performed, the amount of film formation does not increase and the production efficiency is lowered. After the tannin solution treatment by the spray treatment method, the excessive solution on the surface is removed using a rubber roll or the like. This is because when an excessive solution remains on the surface of the aluminum substrate and a local liquid pool exists, poor appearance and poor adhesion are caused.

  Moreover, after processing an aluminum base material with a tannin solution, it must dry without performing water washing. If washed with water, the tannin is washed away and the desired amount of film cannot be obtained. After the treatment with the tannin solution, it is necessary to carry out a drying treatment. As a drying method, heat drying is preferable, and for example, oven drying or hot air drying is used.

  The drying temperature after processing with a tannin solution is 40-200 degreeC as an aluminum base material temperature, Preferably it is 60-180 degreeC. The drying time can be appropriately selected depending on the drying method and the drying temperature, but the tannin needs to be completely dried after the drying step. By drying tannin on the surface of the aluminum substrate, an associative film of tannin is formed, and the hydrogen bonding reaction between the aluminum substrate and the phenolic hydroxyl group is promoted, so a strong adhesion layer can be obtained. It becomes. When the upper limit of the drying temperature is up to 200 ° C., the associative film of tannin will not be altered by heat, but the strength of the aluminum substrate itself may be lowered, so sufficient care is required for temperature control. is there.

C. Resin-Coated Aluminum Material As shown in FIG. 5, the resin-coated aluminum material 5 according to the present invention is typically an aluminum oxide film 3 on the aluminum base 2 and an organic film formed on the aluminum oxide film. In the surface-treated aluminum material 1 including the compound film 4, the organic compound film 4 is coated with a resin coating film 6 formed from a resin paint or a resin coating film 6 formed from a resin film.

C-1. In general, it is preferable to use a resin having a polar functional group in the molecule for the paint and the resin film . The paint using a resin having a polar functional group exhibits excellent adhesion because it forms a hydrogen bond with a hydroxyl group or a carboxyl group contained in an organic compound such as tannin present on the surface of the aluminum substrate. As such paints, thermoplastic acrylic resin paints, thermosetting acrylic resin paints, epoxy resin paints, polyurethane resin paints, polyester resin paints, polyamide resin paints, and the like are used.

  Moreover, as a coating method of the resin paint, a roll coater method, an electrodeposition coating method, a spray coating method, or the like can be used. Furthermore, if necessary, multilayer coating can be applied by undercoating, intermediate coating, top coating, and the like. The applied resin paint is baked at 150 to 300 ° C. for 10 to 60 seconds to form a resin coating film.

  In addition, any resin film that exhibits thermal adhesiveness to an aluminum substrate may be used, and a resin film having various characteristics can be selected according to various characteristics required for the resin-coated aluminum material. It is. Examples of such resin films include polyethylene terephthalate, polyethylene naphthalate, nylon 6, nylon 11, polycarbonate, polyarylate, and the like.

  The thermocompression bonding of the resin film to the aluminum base material after the tannin film is formed can be performed by heating the aluminum base material by high frequency induction heating or direct flame heating, or pressing the film on the surface of the aluminum base material by extrusion coating. A heat bonding method is used. These methods are all conventional methods, and can be appropriately selected according to the purpose, application, and the like. The resin film is pressure-bonded or bonded onto the organic compound layer at 150 to 300 ° C. In addition, an organic compound film such as a tannin film is formed on the surface of the aluminum substrate, and since this film makes a strong adhesion to the resin film, it adheres to the surface of the resin film or the aluminum chemical treatment material as before. There is no need to provide a primer.

  The resin-coated aluminum material produced in this manner is excellent in the adhesion of the resin-coated film and excellent in corrosion resistance even after molding such as press molding.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to the example as described below.

Examples 1-10 and Comparative Examples 1-6
JIS-A5482 alloy and JIS-A3004 alloy were used as the aluminum substrate, and casting, processing and tempering were performed as follows. The A5482 alloy was cast by a DC casting method, subjected to hot rolling after homogenization, and annealed, and then cold rolled to a plate thickness of 0.25 mm. Then, finish annealing was performed by a conventional method in a continuous annealing furnace or a batch annealing furnace. A3004 alloy was also cast by a DC casting method, hot-rolled after homogenization treatment, and annealed and then cold-rolled to a thickness of 0.30 mm.

The above alloy plate is etched for 10 seconds at 60 ° C. using a 2 wt% aqueous alkali solution of Surf Cleaner 420N-2 manufactured by Nippon Paint Co., Ltd., washed with water, and under various conditions using a 2 wt% aqueous sulfuric acid solution. Smut processing was performed. Next, a bar coating treatment with a # 8 bar coater was performed using a 1% by weight tannic acid aqueous solution, followed by drying at 80 ° C. for 1 minute. In this way, a sample of the surface-treated aluminum material was produced.
On the other hand, in order to compare with the conventional phosphoric acid chromate treatment or zirconium phosphate-based non-chromate treated material, samples were prepared by performing these chemical conversion treatments, washing with water and drying.

  In order to evaluate adhesion and corrosion resistance with the resin coating film, a thermoplastic polyethylene terephthalate resin film made by Teijin DuPont with a film thickness of 15 μm was thermocompression bonded at 250 ° C. to the surface of each sample, and the resin-coated aluminum material Was made. Table 1 shows the acid cleaning conditions with the sulfuric acid aqueous solution and the amount of tannin film formed.

  The amount of tannin film formed was determined in terms of carbon as the amount of carbon present in the tannin film. The amount of carbon was measured with a total organic carbon analyzer (manufactured by Shimadzu Corporation, TOC-VCPH type).

  Table 2 shows the evaluation results of the film thickness of the aluminum oxide film of the surface-treated aluminum material sample, and the adhesion and corrosion resistance of the resin-coated aluminum material. In addition, the measuring method of the film thickness of an aluminum oxide film, the evaluation method of the adhesiveness and corrosion resistance of a resin-coated aluminum material, and these evaluation criteria are shown below.

Measurement of film thickness of aluminum oxide film The depth profile of Al and oxygen (O) on the surface of the sample after treatment with an acidic aqueous solution was measured by Auger electron spectroscopy to obtain the intersection on the graph of both profiles. The depth from the surface was taken as the film thickness of the aluminum oxide film.

Peel adhesion of resin-coated aluminum material As shown in FIG. In FIG. 6, after the cut of the solid line L1 is provided from the resin coating film surface side to the test piece 5 of the resin-coated aluminum material in which the resin coating film is formed only on one surface by the hand press machine, Pulled by a tensile tester in the direction of the surface where the resin coating is not formed and so that both end portions E, E of the incision are directed toward the surface where the resin coating is applied, and the fracture portion indicated by the dotted line L2 in the figure Is formed. Although the resin coating having the solid line L3 as an end portion remains in the fractured portion, the maximum width H of the residual resin coating was measured, and the width was evaluated according to the following criteria. ◎ and ○ were accepted, and x was rejected.

A: Width H is less than 0.4 mm O: Width H is 0.4 mm or more and less than 0.7 mm X: Width H is 0.7 mm or more

Corrosion resistance of resin-coated aluminum material Scratches reaching the aluminum substrate using a cutter were placed in a resin-coated aluminum material sample, and immersed in a mixed aqueous solution of 0.5 wt% sodium chloride and 1 wt% citric acid at 70 ° C for 72 hours. The peel width of the resin coating due to corrosion at the scratch was measured, and the width was evaluated according to the following criteria. ◎ and ○ were accepted, and x was rejected.

A: Peeling width is less than 0.3 mm B: Peeling width is 0.3 mm or more and less than 0.5 mm X: Peeling width is 0.5 mm or more

As shown in Table 1, in Examples 1 to 10, the amount of tannin film formed was in the range of 4 to 18 mg / m ^{2 in} terms of carbon and achieved 3 to ²⁰ mg / m ² . Further, as shown in Table 2, in these examples, the aluminum oxide film thickness after smut treatment with an acidic aqueous solution was 15 nm, and it was confirmed that both the adhesion and the corrosion resistance of the resin coating film showed good results.

  On the other hand, in Comparative Examples 1 to 3, cleaning with an acidic aqueous solution is insufficient, so that an aluminum oxide film of 15 nm or more remains on the aluminum substrate surface. Therefore, despite the formation amount of the tannin film being in the proper range, either or both of the adhesion and the corrosion resistance of the resin coating film were inferior.

In Comparative Example 4, although the aluminum oxide was successfully removed, the amount of tannin film formed was as large as 30 mg / m ^{2 in} terms of carbon, resulting in poor corrosion resistance. In Comparative Examples 5 and 6 that were subjected to the conventional phosphoric acid chromate treatment or zirconium phosphate nonchromate treatment, the adhesion primer treatment was not performed, so that satisfactory adhesion and corrosion resistance could not be obtained.

As described above, in the present invention, contaminants are first removed with an alkaline aqueous solution, then subjected to a smut treatment with an acidic aqueous solution so that the aluminum oxide film thickness after the treatment is 15 nm or less, and further converted into carbon by organic compound solution treatment. By providing an organic compound film having a concentration of 1 to 50 mg / m ² , high corrosion resistance and high adhesion were maintained without performing conventional chromate-based and non-chromate-based chemical conversion treatments, and even adhesive primer layer formation treatments. A surface-treated aluminum material is obtained, and a resin-coated aluminum material having the same effect can be obtained by further providing a resin-coated film on the organic compound film.

It is sectional drawing of the surface treatment aluminum material which concerns on this invention. It is a graph which shows the depth profile by Auger electron spectroscopy analysis for calculating | requiring the aluminum oxide film thickness of the surface treatment aluminum material which concerns on this invention. It is a graph which shows the depth profile by Auger electron spectroscopy analysis for calculating | requiring the aluminum oxide film thickness of the surface treatment aluminum material which concerns on this invention. It is a figure which shows the structural formula of the tannic acid which forms the tannin film of the surface treatment aluminum material which concerns on this invention. It is sectional drawing of the resin-coated aluminum material which concerns on this invention. It is explanatory drawing of the peeling adhesiveness measurement of a resin-coated aluminum material.

Explanation of symbols

1 Surface treatment aluminum material 2 Aluminum base material 3 Aluminum oxide film 4 Organic compound film 5 Resin-coated aluminum material, sample piece L1 Cutting depth D Cutting edge Part E ... Both ends of the cut H ... Maximum width of the remaining resin coating film

Claims (6)

A base material made of aluminum or an aluminum alloy, an aluminum oxide film formed on the surface of the base material, and an organic compound film formed on the surface of the aluminum oxide film,
The aluminum oxide film has a thickness of 15 nm or less;
The amount of the organic compound film formed is 1 to 50 mg / m ² in terms of carbon, and the organic compound is (a) two or more hydroxyl groups; (b) two or more carboxyl groups; or (c) 1 A surface-treated aluminum material having one or more functional groups selected from the group (a) to (c) consisting of one or more hydroxyl groups and one or more carboxyl groups.   The surface-treated aluminum material according to claim 1, wherein the organic compound is tannin.   A resin-coated aluminum material comprising a resin coating film formed from a paint or a resin film on the organic compound film of the surface-treated aluminum material according to claim 1. Washing at least one surface of a base material made of aluminum or an aluminum alloy with an alkaline aqueous solution;
Washing the washing surface of the alkaline aqueous solution with an acidic aqueous solution;
Treating the washed surface of the acidic aqueous solution with an organic compound solution,
The thickness of the aluminum oxide film formed on the substrate surface after the washing step with the acidic aqueous solution is 15 nm or less,
An organic compound film is formed on the aluminum oxide film by the treatment step with the organic compound solution, and the amount of the organic compound film formed is 1 to 50 mg / m ² in terms of carbon. Production method.   The method for producing a surface-treated aluminum material according to claim 4, wherein the organic compound is tannin.   6. The resin-coated aluminum material according to claim 4, further comprising a step of coating a resin coating film formed from a paint or a resin film on the organic compound film after the treatment step with the organic compound solution in claim 4 or 5. Production method.