JP2010143080A - Precoated aluminum sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a precoated aluminum sheet excelling in durability of a coating in a washing process without causing dissolution, stripping, discoloration, sticking, or the like of the coating in a boiling chlorine-based detergent regarding the precoated aluminum plate using thermosetting resin, and combining high moldability and excellent appearance property not inferior to a film laminate material even when drawing is performed. <P>SOLUTION: The precoated aluminum sheet 1 is formed with a precoat film 3 containing base resin 4 crosslinked between molecules, and fine particles 5, on the surface of an aluminum sheet 2. The precoat film 3 has a gel fraction of 50% or more and a surface roughness of 0.25 μm or more in arithmetic-average roughness (Ra). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a precoated aluminum plate made of an aluminum plate, which is mainly used for industrial electronic devices, consumer electronic devices, automobile electrical components and the like.

  Aluminum has various features such as low specific gravity and good thermal conductivity, and is therefore used in various applications. Since this aluminum is excellent in corrosion resistance in a natural environment, there are many cases in which surface treatment for preventing corrosion is not performed, but in recent years, surface treatment for the purpose of imparting functions has been increasingly performed. For example, in applications that require light weight, such as notebook PCs, flat-screen TVs, and car stereos, the use of pre-coated aluminum plates made of aluminum plates and pre-coated with functional films (pre-coated films) is increasing. Yes. The use of a pre-coated aluminum plate has the advantage that it is superior in productivity and cost compared to an after-coating method in which an aluminum plate that has not been surface-treated in advance is individually surface-treated after press molding.

  In addition, the cover of slim type optical disk drive devices mounted on notebook PCs, etc. (1) Lubricity (quick-drying press oil that does not require cleaning in order to reduce the manufacturing cost by omitting the step of cleaning the press oil) (2) Scratch resistance and fingerprint resistance (to improve appearance quality), (3) Conductivity (to ensure antistatic and grounding) Aim) is required. As an example of a pre-coated aluminum plate that satisfies these requirements, for example, in Patent Document 1, a predetermined corrosion-resistant film and a predetermined resin film are formed on at least one surface of an aluminum plate having a predetermined arithmetic average roughness Ra, An aluminum plate for electronic equipment that improves the conductivity by defining the surface resistance value and satisfies the other required performances is disclosed.

  In addition, the inner surface of the cover used in the slot-in type optical disk drive is directly rubbed with the disk when the optical disk is loaded and unloaded. Thus, among the optical disk drives, as an invention assuming application to a slot-in type optical disk drive, for example, in Patent Document 2, a soft bead having a predetermined hardness is added to a precoat film, and the film is cushioned. A pre-coated aluminum metal plate that satisfies the performance of preventing the surface of the optical disc from wrinkling by being held is disclosed.

  Incidentally, housings (covers, etc.) of consumer electronic devices such as optical disk drive devices assumed in Patent Document 1 and Patent Document 2 are formed by forming an aluminum plate into a box shape by bending 90 degrees. I came. The technology for producing box-type housings by bending is to use a coiled plate, continuous molding with progressive molds is possible, and continuous molding technology using quick-drying press oil has been established. Therefore, a cleaning process after press molding is unnecessary, and it can be said that the method is excellent in productivity. However, on the other hand, since the case manufactured by bending always has a gap in the corner of the side wall, the following problems arise when the case needs to be sealed.

  Examples of cases where high sealing performance is required for the casing include, for example, electric components for automobile control installed in harsh environments such as engine rooms (e.g., control devices such as ECUs, batteries for hybrid vehicles and electric vehicles, inverters, etc.) In these cases, if the airtightness inside the housing cannot be maintained, moisture, oils, dust, etc. may enter the housing and cause a failure. Aluminum plate molded products are also used for lithium ion batteries and electrolytic capacitor cases. However, in applications where liquids such as electrolytes are placed inside, as in these cases, in order to prevent liquid leakage, However, the case is required to have high sealing performance. Further, even in consumer electronic devices used in a room such as a home, it is expected that the electromagnetic wave shielding property can be improved by enhancing the sealing property of the cover. As described above, in order to manufacture a case with high hermeticity, a method of forming a box-type case without a gap by drawing rather than bending is advantageous. FIG. 3A is a schematic diagram of a box-shaped housing by bending, and FIG. 3B is a schematic diagram of a box-shaped housing by drawing.

Here, when applying a pre-coated aluminum plate to these cases, it is required that the pre-coated film not only follows the large deformation accompanying the drawing process, but also the pre-coated film. Examples of Patent Document 3 and Patent Document 4 are listed below as documents related to the invention assuming drawing.
As a pre-coated aluminum plate that assumes a large deformation of the pre-coated film associated with the drawing process, for example, Patent Document 3 discloses the gel fraction of the pre-coated film as the intermolecular cross-linked state of the thermosetting resin formed on the surface of the aluminum plate. When the value is compared before and after the heat treatment at 220 ° C., the gel fraction value after the heat treatment is continuously reduced from the value of the gel fraction before the heat treatment, Disclosed is a precoated aluminum plate that satisfies high drawability by controlling so that the decrease from the value of the gel fraction before the heat treatment when the heat treatment is performed for 10 minutes is less than 10%. Has been.

As a technique other than the pre-coated aluminum material mentioned above, a film laminated aluminum plate obtained by laminating a thermoplastic resin film excellent in workability is used in the case of an electrolytic capacitor. The film-laminated aluminum plate has a characteristic that is advantageous for drawing because the resin molecules constituting the film are not cross-linked, and thus the film can be greatly deformed. Some of them have improved durability of cleaning chemicals with chlorinated solvents. For example, Patent Document 4 includes a thermoplastic resin film provided on the surface of an aluminum plate and a thermosetting resin coating layer provided on the surface of the thermoplastic resin film, thereby maintaining moldability. On the other hand, a resin-coated laminated aluminum plate for an electronic component case that prevents the discoloration of the resin coating layer has been disclosed. Further, it is described that a polyamide resin such as nylon or a saturated polyester resin such as PET is used as the thermoplastic resin film.
JP 2003-313684 A (paragraphs 0020-0050) Japanese Patent No. 4134237 (paragraphs 0024 to 0042) JP 2006-305841 A (paragraphs 0024 to 0051) Japanese Patent No. 4003915 (paragraphs 0017 to 0029)

However, the conventional technique has the following problems.
The inventions described in Patent Literature 1 and Patent Literature 2 are inventions that assume an optical disk drive as their application, and as described above, are considered to be inventions that presuppose that the housing is manufactured by bending. In the case of bending, as described above, it is considered that only molding with a quick-drying press oil is assumed. Therefore, it is considered that durability with a boiling chlorine-based cleaning chemical is not considered.

  The invention described in Patent Document 3 assumes drawing. In the drawing process where the deformation amount of the aluminum plate is large, the continuous forming technique using the quick-drying press oil as described in the case of the bending process has not been sufficiently established. Therefore, many methods are still employed in which unnecessary pressing oil and abrasion powder are removed using a cleaning agent after molding using a high-viscosity rust preventive oil or emulsion type wax. In such a method, it is not sufficient that the precoat film satisfies the moldability capable of following a large deformation, and there are problems such as dissolution, peeling, discoloration, and sticking of the film to the chemical used in the cleaning process. The durability of the film in the cleaning process, which does not occur, is essential. Here, in the cleaning process, when performing a harsh cleaning method such as immersing in a boiling liquid of a chlorinated solvent such as trichlene, the technique described in Patent Document 3 dissolves, peels off the film of the molded article, Discoloration, sticking, etc. may occur, causing appearance defects.

  As described in Patent Document 4, a film laminate material made of a thermoplastic resin as a base resin and laminated on the surface of an aluminum plate uses a thermoplastic resin film. Naturally there is a limit. For example, when a polyamide-based thermoplastic resin typified by nylon is used as a base resin, it has good adhesion to an aluminum plate and has excellent moldability. There is a problem that the base resin is easily yellowed or browned. Furthermore, when a saturated polyester-based thermoplastic resin such as PET is used as the base resin, it has good adhesion to the aluminum plate, exhibits excellent moldability, and does not easily discolor the base resin even in high-temperature environments. However, since the base resin is easily hydrolyzed, it tends to be inferior in durability under a high-temperature and humid atmosphere.

  In addition, when a polyolefin resin typified by polyethylene or polypropylene is used as a base resin, the base resin is basically composed only of carbon and hydrogen and does not contain nitrogen or oxygen. Therefore, there is no origin of functional groups and chemical bonds such as hydroxyl groups, carboxyl groups, ester bonds, isocyanate groups, urethane bonds, amino groups, and amide bonds, and the adhesiveness to the aluminum plate is poor.

  Therefore, it is a pre-coated aluminum plate using a thermosetting resin with higher heat resistance and durability than the film laminate material, and it is washed during the process of washing and removing press oil and wear powder etc. in the cleaning agent after press molding. Precoated aluminum with excellent film durability in the cleaning process that can prevent surface abnormalities such as dissolution, peeling, discoloration, and sticking of the precoat film even when cleaning in a high-capacity boiling chlorine-based cleaning agent Development of the board is desired. Furthermore, in addition to the excellent durability of the coating film in the cleaning process, a precoated aluminum plate that has excellent formability in drawing and does not impair the beautiful gloss appearance of the aluminum plate is more desired.

The present invention has been made in view of the above problems, and in a precoated aluminum plate using a thermosetting resin, in a boiling chlorine-based cleaning agent, no dissolution, peeling, discoloration, sticking, etc. of the film occurs. It aims at providing the precoat aluminum plate excellent in the durability of the film | membrane in the washing | cleaning process.
Furthermore, as a more desirable form, pre-coated aluminum that has excellent durability of the film in the cleaning process, and has high formability comparable to that of a film laminate material and excellent appearance properties even when drawn. The purpose is to provide a board.

  A pre-coated aluminum plate according to claim 1 is a pre-coated aluminum plate in which a pre-coated film (hereinafter, referred to as a film as appropriate) including an intermolecular cross-linked base resin and fine particles is formed on the surface of the aluminum plate. The precoat film has a gel fraction of 50% or more and a surface roughness of 0.25 μm or more in terms of arithmetic average roughness (Ra).

  According to such a configuration, when the gel fraction of the precoat film is 50% or more, the crosslink density of the precoat film is increased, and the fine particles added to the precoat film are prevented from falling off during the cleaning process. Can do. In addition, chemical resistance, heat resistance, hydrolysis resistance and the like are improved, and durability of the film in the cleaning process is improved. Furthermore, by adding fine particles, the surface roughness (arithmetic average roughness (Ra)) of the precoat film is controlled, and when the surface roughness Ra is 0.25 μm or more, the surface roughness of the precoat film is reduced. It becomes sufficiently large, and sticking between the films in the boiling chlorine-based cleaning agent is suppressed.

The precoated aluminum plate according to claim 2 is characterized in that the fine particles are inorganic fine particles or crosslinked organic fine particles.
According to such a configuration, the fine particles are not melted by heat when the base resin is subjected to a crosslinking reaction, and the surface roughness Ra of the precoat film can be easily controlled.

The precoated aluminum plate according to a third aspect is characterized in that the fine particles are cross-linked spherical organic fine particles.
According to such a structure, the form of the convex part of a precoat film | membrane becomes smooth and the burden of the metal mold | die for press molding is reduced.

In the precoated aluminum plate according to claim 4, the base resin is a crosslinked polyester resin obtained by crosslinking a polyester resin having a glass transition temperature of 25 to 65 ° C with a melamine curing agent or an isocyanate curing agent. It is characterized by that.
The precoated aluminum plate according to claim 5 is characterized in that the polyester resin has a glass transition temperature of 35 to 60 ° C.
According to such a configuration, the film becomes moderately flexible, and the drawability of the precoated aluminum plate is improved.

The precoated aluminum plate according to claim 6 is characterized in that the surface roughness of the precoated film is an arithmetic average roughness (Ra) of 0.25 to 0.55 μm.
According to such a configuration, the irregular reflection of visible light on the surface of the precoat film is suppressed, and the precoat film is suppressed from being matted. Here, the matte state means that the gloss of the aluminum plate as the material is lost.

According to the invention of claim 1 of the present invention, even when cleaning is performed in a harsh boiling chlorine-based cleaning agent, the film is not dissolved, peeled, discolored, stuck, etc. It is possible to provide a precoated aluminum plate having excellent durability. Thereby, since the manufacturing process which can be selected spreads, the application field of a precoat aluminum plate spreads. In addition, since the basic chemical resistance of the film has been improved, not only the durability of the film in the cleaning process after press molding is improved, but also the solvent resistance and chemical resistance in the actual use environment are improved. .
According to the second aspect of the present invention, the surface roughness Ra of the precoat film can be easily controlled, and a precoat film having a stable surface roughness Ra can be obtained.
According to the invention of claim 3 of the present invention, the burden on the press molding die can be reduced, so that the life of the press molding die can be improved.

According to the inventions according to claims 4 and 5 of the present invention, the flexibility of the precoat film can be appropriately obtained, and the drawability of the precoat aluminum plate can be improved. Therefore, it is possible to provide a precoated aluminum plate that can follow forming with large deformation such as drawing and ironing. As a result, it is possible to provide a casing with excellent hermeticity that is suitable for casings for industrial electronic devices, consumer electronic devices, and automobile electrical components. In addition, it is possible to provide a molded article having excellent heat discoloration resistance and hydrolysis resistance as compared with a film laminated aluminum plate.
According to the invention which concerns on Claim 6 of this invention, it becomes possible to provide the molded article of the beautiful gloss appearance which an aluminum plate has.

Hereinafter, the best mode of the precoated aluminum plate according to the present invention will be specifically described with reference to the drawings as appropriate.
In the drawings to be referred to, FIG. 1 is a partial cross-sectional view schematically showing a configuration of a precoated aluminum plate according to the present invention.

≪Pre-coated aluminum plate≫
As shown in FIG. 1, a precoated aluminum plate 1 has a surface of an aluminum plate 2 on which a precoat film 3 including an intermolecular cross-linked base resin 4 and fine particles 5 is formed. Here, the surface of the aluminum plate 2 means at least one surface of the aluminum plate 2. Each configuration will be described below.

<Aluminum plate>
The aluminum plate 2 referred to in the present invention is made of aluminum or an aluminum alloy, and the aluminum plate (aluminum plate or aluminum alloy plate) 2 used in the present invention is not particularly limited, and may be a product shape or a molding. The method can be selected based on the strength required at the time of use. In general, a non-heat-treatable aluminum plate, that is, a 1000 series industrial pure aluminum plate, a 3000 series Al—Mn alloy plate, and a 5000 series Al—Mg alloy plate can be suitably used. . In particular, when manufacturing a deep container-shaped housing accompanied with ironing, aluminum plates such as A1050, A1100, A3003, A3004, etc. defined in JIS H4000 are recommended. Moreover, when producing a comparatively shallow container-shaped housing | casing, aluminum plates, such as A5052 and A5182, prescribed | regulated to JISH4000 are recommended. Various types of tempering and plate thickness can be selected and used according to the purpose. Further, as will be described later, the aluminum plate 2 may be subjected to reactive base treatment, coating type base treatment, anodizing treatment, electrolytic etching treatment, degreasing treatment, and the like.

<Precoat film>
The precoat film 3 (film 3) includes a base resin 4 and fine particles 5 dispersed in the base resin 4, and is formed on the surface of the aluminum plate 2. This precoat film 3 has a gel fraction of 50% or more and a surface roughness of 0.25 μm or more in terms of arithmetic average roughness (Ra).

[Base resin]
The base resin 4 is a main component of the precoat film 3 and uses a conventionally known intercoat type resin used for a precoat aluminum plate or a precoat steel plate, and has a gel fraction of 50 as described later. The intermolecular cross-linking reaction is performed so as to be at least%.

  There are film laminates that use thermoplastic resins as the base resin as those that do not undergo intermolecular crosslinking by thermosetting reaction, but as described in the above-mentioned prior art, those using thermoplastic resins as the base resin have various points. This creates a practical problem. However, if a resin that performs intermolecular crosslinking by thermosetting reaction or the like is selected as the base resin 4, this resin originally has a functional group for intermolecular crosslinking, and thus has excellent adhesion to the aluminum plate 2. . Moreover, by cross-linking, chemical resistance and heat resistance can be increased, and hydrolysis resistance can be improved.

  The intermolecular cross-linking resin used for the base resin 4 can be selected according to the usage environment and application after pressing. For example, it is desirable to use an epoxy-based resin for the base resin 4 if the hardness and heat resistance of the coating 3 are required. For applications that require weather resistance, antifouling properties, etc., the base resin It is desirable to use a fluorine-based resin for 4. Furthermore, when the product shape is strict and is used after being molded into a complicated shape, it is desirable to use a polyester-based resin that forms a relatively flexible coating 3 as the base resin 4.

  Here, when considering the product shape, as described above, in the case of forming into a box shape by bending, since continuous forming technology using quick-drying press oil has been established, sufficient cleaning If it is not an application that requires a state, a cleaning step after press molding is not necessarily required. In other words, it can be said that the shape of a product formed by using a high-viscosity rust preventive oil or emulsion type wax that needs to be cleaned is often a complicated shape such as a deep drawing shape. Therefore, it is considered that the durability of the coating 3 in the cleaning step in the precoated aluminum plate 1 is combined with a polyester resin capable of obtaining high moldability in a more desirable form.

  As the polyester resin, it is desirable to use a saturated polyester resin obtained by condensation polymerization of a polyhydric alcohol and a polybasic acid. Among these, examples of the polyhydric alcohol include dihydric alcohols such as ethylene glycol, propylene glycol, neopentyl glycol, 1,3-butylene glycol, 1,6-hexanediol, diethylene glycol, glycerin, trimethylolethane, Trihydric alcohols such as methylolpropane, and tetrahydric or higher alcohols can be used. Examples of polybasic acids include dibasic acids such as phthalic anhydride, isophthalic acid, terephthalic acid, adipic acid, and sebacic acid, tribasic acids such as trimellitic anhydride, and tetravalent or higher polybasic acids. A basic acid or the like can be used. These polyhydric alcohols and polybasic acids may be subjected to condensation polymerization by using one kind or two or more kinds at the same time. Moreover, the glass transition temperature of a polyester resin changes by combining these components.

  The glass transition temperature is one of the transition temperatures of the resin. Generally, a resin at a temperature higher than the glass transition temperature is a soft rubber, and a resin at a temperature lower than the glass transition temperature is a hard glass. Therefore, in order for the film 3 to follow a process with large deformation such as deep drawing or ironing, it is theoretically necessary to set the glass transition temperature to the processing temperature or lower. However, in reality, the high molecular structure of macromolecular substances is not uniform, for example, because the molecular weight has a wide range and a branched structure is formed in the molecule. Absent. Therefore, the glass transition temperature is merely a representative value, and the transition gradually occurs in a temperature range having a certain width. In addition, the polyester resin has a relatively high elongation except for a part of the state (a state in which crystallization is promoted in a state of a thermoplastic resin that does not cause a cross-linking reaction) even if it is glassy below the glass transition temperature. Therefore, within a certain range, molding is possible even if a resin having a high glass transition temperature is used as the base resin 4. On the other hand, when the resin having an excessively low glass transition temperature is used as the base resin 4, the coating 3 becomes too soft and wrinkles are likely to enter.

  In this invention, when using a polyester resin for the base resin 4, it is desirable that the glass transition temperature is the range of 25-65 degreeC. If the glass transition temperature is less than 25 ° C., the film 3 becomes too soft and easily wrinkles. On the other hand, if it exceeds 65 ° C., the workability of the precoated aluminum plate 1 is reduced, and the formable shape is limited. The glass transition temperature is more preferably 35 to 60 ° C. By setting the glass transition temperature to 35 ° C. or higher, the flexibility of the film 3 can be made more appropriate, and by setting the glass transition temperature to 60 ° C. or lower, the workability of the precoated aluminum plate 1 can be easily improved. In addition, the glass transition temperature here means what was measured by DSC method.

  Moreover, a crosslinking reaction does not occur only with the polyester resin. In order to cause the crosslinking reaction required in the present invention, a curing agent that reacts with the hydroxyl group or carboxyl group of the polyester resin is added, or a component having the same function as the curing agent is generated in the polyester resin itself. In addition, it is necessary to modify the polyester resin using a chemical reaction. Functional groups that react with these hydroxyl groups and carboxyl groups include isocyanate groups, amino groups, hydroxyl groups, carboxyl groups, etc., and can be easily crosslinked by adding a substance having three or more of these functional groups as a curing agent. It is possible to promote the reaction. Examples of such a curing agent include polyisocyanate compounds, melamine compounds, epoxy compounds, amino compounds, phenol compounds, urea compounds, and the like. In addition, when using polyester-type resin for the base resin 4 by this invention, it is desirable that the hardening | curing agent is a melamine type hardening | curing agent or an isocyanate type hardening | curing agent. These curing agents are advantageous in that they can be easily made into a paint, have both storability at room temperature and immediate reactivity at the baking temperature, and hardly cause discoloration by baking.

[Fine particles]
The fine particles 5 are for controlling the surface roughness Ra of the precoat film 3 in a predetermined manner, and are contained in the base resin 4 of the precoat film 3.
As a method for controlling the surface roughness without containing the fine particles 5 in the precoat film 3, a method of physically roughening the surface by blasting or the like after forming the precoat film, or a roll having unevenness A method of transferring the roughness of the roll by pressing the film onto the surface of the film is conceivable. However, the precoat film whose surface roughness Ra is adjusted by these methods has a problem that the unevenness of the film surface becomes smooth in the cleaning solvent, and the predetermined surface roughness in the precoat film cannot be maintained. As a result, the coating surfaces become smooth, and the coating surfaces tend to stick to each other in the boiling chlorine-based cleaning agent. However, in the precoat film 3 in which the fine particles 5 are contained in the base resin 4, the uneven shape of the film surface does not change before and after the solvent cleaning, and therefore, even in the cleaning process using the boiling chlorine-based cleaning agent, Sticking can be prevented.

  The type, form, size, amount of addition, etc. of the fine particles 5 are not particularly limited as long as the surface roughness Ra of the precoat film 3 can be controlled within a predetermined range by containing the fine particles 5 in the base resin 4. Good. Thereby, sticking of the films 3 in the boiling chlorine-based cleaning agent can be prevented. However, the type of the fine particles 5 is desirably inorganic fine particles or crosslinked organic fine particles. The other fine particles 5 include thermoplastic fine particles that are not cross-linked. However, when thermoplastic fine particles are used, the fine particles 5 are melted by the heat generated when the base resin 4 is subjected to a cross-linking reaction. Is not stable, and it is likely to be difficult to control the surface roughness Ra of the precoat film 3. In the case of inorganic fine particles or crosslinked organic fine particles, the fine particles 5 are not melted by the heat when the base resin 4 of the precoat film 3 is subjected to a crosslinking reaction, so that the precoat film 3 having a stable (uniform) surface roughness Ra is formed. Obtainable.

  When inorganic fine particles are used as the fine particles 5, the convex portions of the precoat film 3 become hard. Therefore, in order to improve the lifetime of the press molding die, it is more desirable that the organic fine particles are cross-linked. Furthermore, it can be said that when the shape of the fine particles 5 is spherical, the shape of the convex portion of the precoat film 3 when viewed microscopically becomes smooth, and therefore the influence on the mold life is small. Therefore, it is more desirable that the fine particles 5 are cross-linked spherical organic fine particles.

  As such crosslinked spherical organic fine particles, for example, crosslinked urethane fine particles, crosslinked acrylic fine particles, silicone fine particles, crosslinked polystyrene fine particles and the like can be suitably used. As an example of the crosslinked urethane fine particles, Daimic Seika's Dymic Beads (registered trademark) (Daiichi Seika), Art Pearl (registered trademark) (Negami Kogyo) and the like can be suitably used. Examples include Tufic (registered trademark) AR (Toyobo), Riosphere (registered trademark) (Toyo Ink), Art Pearl (registered trademark) (Negami Kogyo), Techpolymer (registered trademark) (Sekisui Plastics) Etc.) and silicone powder (Shin-Etsu Chemical), Trefil (registered trademark) (Toray Dow Corning) and the like can be suitably used as examples of silicone fine particles. Non-spherical organic fine particles include, for example, silicone rubber powder (X-52-875 (Shin-Etsu Silicone)), PTFE powder (KT-300M (Kitamura)), cellulose powder (KC Flock (registered trademark) (Nippon Paper Industries). Chemical)), flat polyethylene particles (Sumitomo Seika) and the like. Examples of the inorganic fine particles include nickel powder and talc powder, and examples of the non-crosslinked organic fine particles include thermoplastic urethane beads and polystyrene latex.

  The blending ratio of the fine particles 5 is not particularly limited, but if the ratio of the pre-coated film 3 is less than 1% by mass, it is difficult to make the surface roughness Ra 0.25 μm or more. Then, the surfaces of the precoat film 3 are likely to stick to each other. On the other hand, if it exceeds 50 mass%, it is difficult to fix the fine particles 5 to the base resin 4. Therefore, the blending ratio is desirably 1 to 50% by mass. In addition, it is more desirable that it is 3 to 30% by mass, and it is possible to suppress the appearance of the coating 3 from being matted, and considering that the beautiful gloss appearance of the aluminum plate 2 as a material is not hindered, It is desirable that it is 3-10 mass%.

  The particle diameter of the fine particles 5 is not particularly limited, but considering that the film thickness that can be applied with a general roll coater is approximately 1 to 20 μm, the average particle diameter is less than 1 μm, so Even when the target film thickness is a relatively thin film thickness of 1 μm, it is difficult to make the surface roughness Ra 0.25 μm or more. On the other hand, when the average particle diameter exceeds 50 μm, it is difficult to fix the fine particles 5 to the base resin 4 even when the target film thickness is 20 μm. Therefore, the average particle size is desirably 1 to 50 μm. In addition, it is desirable that the average particle diameter is 1 to 30 μm, considering that the appearance of the film 3 is suppressed to a matte state and considering that the beautiful gloss appearance of the aluminum plate 2 as a material is not disturbed. More desirably, the thickness is 2 to 10 μm. Here, the average particle diameter is the 50% cumulative volume particle diameter measured with a laser diffraction particle size distribution measuring instrument or the like in a state where the fine particles 5 are dispersed in water.

[Gel fraction of precoat film: 50% or more]
In the present invention, the gel fraction of the precoat film 3 is 50% or more. Here, since the precoat film 3 contains the fine particles 5 in addition to the base resin 4 as an essential component, it is difficult to measure the gel fraction of the base resin 4 only in a strict sense. Therefore, in the present invention, the gel fraction of the precoat film 3 is substituted and defined by this gel fraction.
If the gel fraction of the precoat film 3 is 50% or more, the crosslink density of the film 3 is high, and the fine particles 5 added to the precoat film 3 can be prevented from falling off in the washing step. Moreover, the film 3 excellent in chemical resistance, heat resistance and hydrolyzability can be obtained. As a result, dissolution, peeling, discoloration, sticking, etc. of the film 3 in the boiling chlorine-based cleaning agent can be prevented. . In order to improve these effects, the gel fraction is desirably 65% or more. Furthermore, if the gel fraction is 75% or more, chemical resistance, heat resistance, hydrolyzability, durability of the film in the cleaning process, and the like are further increased, which is more desirable. In addition, since it is thought that a gel fraction is so large that it is so preferable, the upper limit of a gel fraction does not need to be prescribed | regulated in particular. Moreover, in order to make a gel fraction 50% or more, it is desirable for the baking temperature at the time of baking a coating film to be about 150-285 degreeC.

  The gel fraction can be measured by a method based on JIS K6796 (however, the extraction solvent is not xylene but 2-butanone). That is, the specimen of the precoated aluminum plate 1 is immersed for 60 minutes in boiled 2-butanone (MEK), and the mass change of the precoated aluminum plate 1 before and after immersion is measured. Thereafter, the mass change of only the precoat film 3 is calculated by measuring the mass of the aluminum plate 2 in which only the precoat film 3 is completely dissolved, and it is assumed that the component that has not eluted into the MEK has undergone a crosslinking reaction. The ratio is calculated as a gel fraction.

[Surface roughness of precoat film]
The surface of the precoat film 3 needs to be formed so that the surface roughness is 0.25 μm or more in terms of arithmetic average roughness (Ra). A feature of the precoated aluminum plate 1 of the present invention is that the precoat film 3 is not dissolved, peeled, discolored, or stuck even in a cleaning process using a boiling chlorine-based cleaning agent. About the adhesion between each other, the surface roughness between the coatings 3 facing each other greatly affects. That is, when the surface roughness Ra is less than 0.25 μm, the surface of the film 3 becomes smooth. Therefore, when the films 3 face each other and are washed with a boiling chlorine-based cleaning agent, a slight tackiness between the films 3 is slight. Begins to occur. Furthermore, when the surface roughness Ra is less than 0.15 μm, the surface of the precoat film 3 becomes smoother. Therefore, when the films 3 face each other and are washed with a boiling chlorine-based cleaning agent, the films 3 are strongly bonded to each other. It sticks. As described above, the adhesion between the coatings 3 in the cleaning process is greatly related to the smoothness of the surface of the precoat coating 3, and the larger the surface roughness Ra, the more the contact between the coating surfaces when viewed microscopically. Since the area is small, the sticking between the coatings 3 is suppressed.

  From the viewpoint of suppressing the sticking between the coatings 3, it is considered that the larger the surface roughness Ra is, the more desirable it is. Therefore, the upper limit value of the surface roughness Ra does not need to be specified. However, when the surface roughness Ra is increased, visible light is likely to be irregularly reflected on the surface of the coating 3, and the surface of the coating 3 has a matte appearance. The surface roughness Ra of the precoat film 3 is 0.55 μm or less in order to suppress the appearance of the film 3 from being matted and to not disturb the beautiful glossy appearance of the aluminum plate 2 as a material. It is desirable that The surface roughness Ra can be controlled by appropriately adjusting the particle diameter, blending ratio, film thickness and the like of the fine particles 5. The surface roughness of the precoat film 3 is measured using, for example, a surface roughness measuring device (Surfcoder SE-30D manufactured by Kosaka Laboratory Ltd.), and the direction of the probe perpendicular to the rolling direction of each aluminum plate 2. And the arithmetic average roughness (Ra) described in JIS B0601 can be measured.

[Others]
The precoat film 3 can contain a colorant and additives imparting various functions without departing from the scope of the present invention.
For example, in order to further improve the moldability, for example, a lubricant such as polyethylene wax, carnauba wax, microcrystalline wax, lanolin, Teflon (registered trademark) wax, silicone wax, graphite lubricant, molybdenum lubricant, etc. 1 type (s) or 2 or more types can be added. In addition, in order to provide conductivity for the purpose of securing the earth required by electronic devices, etc., as the conductive fine particles, for example, metal fine particles including nickel fine particles, metal oxide fine particles, conductive carbon, graphite, etc. 1 type (s) or 2 or more types can be added. Furthermore, when it is desired to improve heat dissipation, one or more heat dissipation additives such as metal oxides such as carbon, graphite, and titanium oxide, and ceramic powder can be added. And when antifouling property is requested | required, you may add a fluorine-type compound and a silicone type compound.
Moreover, as described later, the thickness of the precoat film 3 is preferably 1 to 20 μm from the viewpoint of workability and productivity.

Although the best embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be changed without departing from the scope of the present invention.
For example, a surface treatment film (not shown) may be provided on the surface of the aluminum plate 2 by surface treatment.

<Pretreatment>
The surface of the aluminum plate 2 is preferably subjected to a ground treatment in order to improve the adhesion with the precoat film 3. As a desirable base treatment, a conventionally known reactive type base coat and coating type base coat containing Cr, Zr or Ti can be used. That is, a phosphoric acid chromate film, a chromate chromate film, a zirconium phosphate film, a zirconium oxide film, a titanium phosphate film, a coating type chromate film, a coating type zirconium film, and the like can be used as appropriate. Organic-inorganic hybrid-type ground treatment coatings obtained by combining these coatings with organic components may also be used. In recent years, there has been a tendency to dislike hexavalent chromium from the trend of environmental measures, and phosphate chromate films that do not contain hexavalent chromium, zirconium phosphate films, zirconium oxide films, titanium phosphate films, coated zirconium films, etc. It is desirable to use it.

In the present invention, as the film thickness of the base treatment film, the amount of Cr, Zr or Ti contained in the base treatment film component to the aluminum plate 2 (metal Cr, metal Zr or metal Ti equivalent value) is, for example, Since the conventional fluorescent X-ray method can be used for comparatively simple and quantitative measurement, the quality control of the precoated aluminum plate 1 can be performed without hindering productivity. In addition, as an adhesion amount of a ground-treatment film | membrane, it is desirable that it is 10-50 mg / m < ² > in metal Cr, metal Zr, or metal Ti conversion value. If the adhesion amount is less than 10 mg / m ² , the entire surface of the aluminum plate 2 cannot be uniformly coated, and the corrosion resistance is lowered. Moreover, when it exceeds 50 mg / m < ² >, when the precoat aluminum plate 1 is shape | molded, it will become easy to produce a crack in the membrane | film | coat itself of a surface treatment.

  When productivity is not taken into consideration, a conventionally known process such as an anodizing process or an electrolytic etching process can be performed on the surface of the aluminum plate 2. When these treatments are performed, fine irregularities are formed on the surface of the aluminum plate 2, so that the adhesion of the precoat film 3 is greatly improved.

  Furthermore, when the corrosion resistance is not required so much and a simple method is desired, a method in which only the surface of the aluminum plate 2 is degreased may be used. As a method of degreasing, conventionally known methods such as degreasing with an organic drug, degreasing with a surfactant drug, degreasing with an alkaline drug, degreasing with an acid drug, and the like can be used. However, in the case of organic chemicals and surfactant chemicals, the degreasing ability is slightly inferior, and therefore degreasing with an alkaline chemical or an acid chemical is more productive. The degreasing capacity of alkaline chemicals can be controlled by the main component, concentration, and processing temperature of the alkali used. However, if the degreasing capacity is strengthened, a lot of smut will be generated, and subsequent washing with water will not be performed sufficiently. On the contrary, the adhesion of the precoat film 3 may be lowered. In addition, when a variety containing a large amount of magnesium as an additive element is used for the aluminum plate 2, magnesium may remain on the surface and the adhesion of the precoat film 3 may be reduced with an alkaline chemical. Therefore, in this case, it is desirable to use or use an acid drug.

≪Pre-coated aluminum sheet manufacturing method≫
Next, an example of the manufacturing method of the precoat aluminum plate 1 is demonstrated with reference to FIG. 1 suitably.
The method for producing the precoated aluminum plate 1 is not particularly limited, and a coating material containing a resin, a curing agent, and fine particles 5 as a base resin for the base resin 4 is applied onto the aluminum plate 2 by a conventionally known method. Then, it can be obtained by causing a crosslinking reaction by heating. In addition, in order to make the gel fraction in the film 3 50% or more, it is desirable that the baking temperature when baking the paint is about 150 to 285 ° C.

  Here, the coating may be applied by any means such as a brush, a roll coater, a curtain flow coater, a roller curtain coater, an electrostatic coating machine, a blade coater, or a die coater. At the same time, it is desirable to use a roll coater that is easy to work with. When coating with a roll coater, the film thickness of the precoat film 3 is controlled by appropriately adjusting the conveyance speed of the aluminum plate 2, the rotation direction and rotation speed of the roll, the pressing pressure between the rolls (nip pressure), and the like. In a normal case, the thickness of the coating 3 that can be applied by one application operation is generally 1 to 20 μm. Therefore, the thickness of the precoat film 3 is desirably 1 to 20 μm in consideration of workability and productivity.

  Next, the precoated aluminum plate of the present invention will be specifically described by comparing an example satisfying the requirements of the present invention with a comparative example not satisfying the requirements of the present invention.

[First embodiment]
In the first example, the durability of the film in the cleaning step, which is an essential object of the present invention, was examined for the precoated aluminum plate in the present invention.

In the examination of the pre-coated aluminum plate according to the present invention, the aluminum plate used as a material was a 0.3 mm thick material having an alloy number of A1100-H24. This was degreased with a weak alkaline degreasing agent, and then subjected to a phosphoric acid chromate treatment as a base treatment. The condition of the phosphoric acid chromate treatment was 20 mg / m ² in terms of chromium adhesion. The mechanical properties of the aluminum plate used were a tensile strength of 130 MPa, a proof stress of 120 MPa, and an elongation of 8%. Next, on one side of an aluminum plate that has been subjected to a phosphoric acid chromate treatment, a paint containing various resin-based paints shown in Tables 1 and 2 and fine particles shown in Table 1 is added so that the dry film thickness becomes 6 μm. After coating with a bar coater, a precoat film was formed by baking the paint so that the baking temperature was in the range of 150 to 285 ° C., and used as a test material. In addition, no. No. 20 is coated with a stainless steel surface plate with a surface roughness Ra of about 0.5 μm after the bar coater is painted and baked, and then lightly sandwiched with a hot press heated at 40 ° C. for 10 minutes. The surface roughness of the board was transferred.

  Here, the base resin of the paint shown in Tables 1 and 2 is polyester melamine is a polyester resin blended with a melamine curing agent, polyester isocyanate is a polyester resin blended with an isocyanate curing agent, epoxy Urea is an epoxy resin blended with a urea curing agent, epoxy phenol is an epoxy resin blended with a phenol curing agent, and epoxy acrylic is an intramolecular cross-linked acrylic modified epoxy resin. is there. Further, the glass transition temperatures shown in Tables 1 and 2 are glass transition temperatures in the respective resins.

  For the fine particles shown in Tables 1 and 2, crosslinked acrylic beads and crosslinked urethane beads are crosslinked organic particles, nickel powder and talc powder are inorganic particles, and thermoplastic urethane beads and polystyrene latex are uncrosslinked organic particles. is there. The blending ratio was the mass% of the fine particles in the mass of the dry precoat film including the base resin and the fine particles.

  About the test material manufactured as mentioned above, the gel fraction and surface roughness Ra of the precoat film were measured.

(Measurement of gel fraction)
Using the test material obtained by cutting the test material into 10 cm × 10 cm, the gel fraction of the film was measured. After the test material was dried at 80 ° C. for 60 minutes, the initial mass (a) was measured, and then the test material was immersed in boiled MEK for 60 minutes to elute uncrosslinked components, and then 150 The remaining MEK in the film was dried at 60 ° C. for 60 minutes, and the mass (b) after extraction was measured. Finally, the film was completely dissolved in fuming nitric acid, and the mass (c) of the aluminum plate alone was measured. Here, (a)-(c) is the mass of the original precoat film only, and (b)-(c) can be regarded as the crosslinked film mass, so the gel fraction expressed by the following formula is It represents the degree of crosslinking.
(Gel fraction) = ((b)-(c) / (a)-(c)) × 100 (unit%)

(Measurement of surface roughness Ra)
The surface roughness of the precoat film is measured by using a surface roughness measuring instrument (Surfcoder SE-30D manufactured by Kosaka Laboratory Ltd.) and scanning the probe in a direction perpendicular to the rolling direction of each aluminum plate. The arithmetic average roughness (Ra) described in B0601 was measured.

  Next, the durability of the film in the cleaning process, which is an essential object of the present invention (hereinafter referred to as “cleaning process durability” as appropriate), was examined for the specimen.

(Washing process durability)
Trichrene was used as a chlorine-based cleaning agent and boiled. The coated surfaces of the test materials were sandwiched between clips so as to face each other, dipped in boiling tricyclen for 10 minutes, and then taken out to confirm the appearance. Those having no surface abnormality such as dissolution of the film, peeling of the film, discoloration of the film, and adhesion between the films were judged to have good cleaning process durability (◯) and those having surface abnormality to be defective (×).
These results are shown in Table 1. In Table 1, those not satisfying the configuration of the present invention are underlined, and those not containing fine particles are indicated by “−”.

As shown in Table 1, no. For Nos. 1 to 16, in order to satisfy the configuration of the present invention, surface abnormalities such as dissolution of the film, peeling of the film, discoloration of the film, and adhesion between the films did not occur, and the cleaning process durability was good. .
On the other hand, no. No. 17 contained no fine particles, and the surface roughness did not satisfy the scope of the present invention, so that the films were stuck to each other (denoted as stuck in the table), and the cleaning process durability was poor. No. In No. 18, since the surface roughness did not satisfy the range of the present invention, the films were stuck to each other and the cleaning process durability was poor. No. No. 19, since the gel fraction of the film did not satisfy the scope of the present invention, the films adhered to each other and the color of the film changed to white (denoted as whitening in the table). No. No. 20, although the surface roughness satisfies the scope of the present invention before immersion in boiling trichrene, it does not contain fine particles, so the unevenness of the coating surface becomes smooth during immersion in boiling trichrene, Sticking occurred.

  Thus, if the structure of this invention is satisfy | filled, it turns out that it becomes a precoat aluminum plate excellent in the durability of the film | membrane in the washing | cleaning process.

[Second Embodiment]
In the second example, the drawability and appearance properties were examined in order to investigate a more desirable form of the precoated aluminum plate in the present invention. Since these characteristics are only desirable characteristics for the present invention, even if these characteristics are not satisfied, those satisfying the cleaning process durability of the first embodiment are the minimum of the present invention. The purpose is to reach.
Since the preparation method of the test material, the gel fraction of the precoat film, the measurement of the surface roughness Ra, and the like are the same as in the first embodiment, description thereof is omitted here.

(Drawing formability)
FIG. 2 is a schematic diagram showing a process for producing a bottomed cylindrical container by drawing and ironing a test material. The drawability of the test material was examined by the process shown in FIG. First, after blanking a cylindrical blank, drawing was performed. Next, a 12 mmφ × 15 mmL cylindrical drawn product (intermediate molded product) was obtained by redrawing. The result of evaluating the film state of the intermediate molded product obtained at this time was defined as shallow drawability in Table 2. Next, iron was added to the intermediate molded product so that the reduction rate of the thickness of the cylindrical side wall portion was 20%, trimmed and processed into a cylindrical container shape having a final 10 mmφ × 20 mmL to obtain a final molded product. The result of evaluating the film state of the final molded product obtained at this time was defined as deep drawability in Table 2. The press oil used was an aqueous emulsion wax mainly composed of a fatty acid ester and a surfactant. The processing was performed only at room temperature (35 ° C.).

  The evaluation of the film state is that for the shallow drawability, when the precoat film is not peeled off from the aluminum plate, the shallow drawability is good (◯), and when it is peeled, the shallow drawability is poor (×). Judgment was made regarding the deep drawability, when the precoat film was not peeled off from the aluminum plate, the deep drawability was good (○), and when it was peeled, the deep drawability was judged as poor (×). . And both the shallow drawability and the deep drawability were judged to be good when the precoat film was not peeled off from the aluminum plate. Moreover, although the shallow drawability was good, it was judged that the drawability was slightly inferior for those having poor deep drawability.

(Appearance properties)
The appearance of the precoat film after bar coating and baking was visually observed. When the matte state, unevenness, yellow discoloration, etc. did not occur, the appearance properties were judged as good (◯). In addition, if any of these occurred, it was judged that the appearance properties were slightly inferior, and in Table 2, those with strong matting properties (whether matting was strong or not) Those with slightly strong properties were described as matte Δ, those with unevenness as uneven X, and those with slightly yellow discoloration as yellowing Δ. Here, the appearance property is based on the beautiful gloss appearance of the aluminum plate as a material, and is a standard different from the discoloration of the film in the cleaning process durability.
These results are shown in Table 2. In Table 2, those not satisfying the preferred configuration of the present invention are underlined, and those not containing fine particles are indicated by “−”.

(Drawing formability)
As shown in Table 2, no. Nos. 1 to 7 and 9 to 13 had better drawability because they used more desirable base resins. On the other hand, no. In No. 8, since the glass transition temperature of the polyester resin was too high, the shallow drawability was good, but the deep drawability was poor and the drawability was slightly inferior. No. 14, no. Since No. 15 used an epoxy resin, the shallow drawability was good, but the deep drawability was poor and the drawability was slightly inferior. No. No. 16 used an intramolecular cross-linked acrylic modified epoxy resin, and although the shallow drawability was good, the deep drawability was poor and the drawability was slightly inferior.

(Appearance properties)
As shown in Table 2, no. Nos. 1, 3, 4, 6-9, 12, 14, and 16 had a desirable surface roughness of the film, and more desirable fine particles were used, so that the appearance was good. . On the other hand, no. 2, no. 5, no. 10, no. 11, no. Since the surface roughness of the film 13 was not in a desirable range, the appearance was strong or slightly strong. No. No. 11 used organic fine particles that were not crosslinked as fine particles, so that the surface roughness varied depending on the location, and the appearance was uneven as a whole. In addition, No. No. 15 uses epoxy phenol, but when epoxy phenol is used, yellowing of the film tends to occur. In No. 15, the appearance of the film turned yellow.

  As described above, it can be seen that a more desirable configuration within the range satisfying the configuration of the present invention results in a precoated aluminum plate having excellent formability and appearance properties in addition to excellent durability of the film in the cleaning process. .

  Although no clear data has been obtained at this time, when inorganic fine particles are used as the fine particles, the convex portions of the precoat film become hard, and it is sufficiently expected to reduce the life of the press molding die. Similarly, when the particle shape is spherical, the shape of the convex portion of the precoat film is smooth when viewed microscopically, so there is no irrationality in considering that the influence on the mold life is small.

From the above results, in the precoated aluminum plate, the precoat film formed on the surface of the aluminum plate contains a base resin cross-linked between the molecules and fine particles, and the gel fraction of the precoat film is 50% or more, By using a thermosetting resin, which is the object of the present invention, with a surface roughness Ra of 0.25 μm or more, a precoated aluminum plate excellent in the durability of the film in a cleaning process in a boiling chlorine-based cleaning agent and You can see that you can.
Furthermore, it can be seen that by using a more desirable base resin, it is possible to obtain a precoated aluminum plate having high formability comparable to that of the film laminate material in addition to the achievement of the object. Further, by using more desirable fine particles and setting the surface roughness Ra in a more desirable range, in addition to achieving the above object, a precoated aluminum plate that does not interfere with the beautiful gloss appearance of the aluminum plate that is the material is used. You can see that

  The precoated aluminum plate according to the present invention has been described in detail with reference to the best mode and examples, but the gist of the present invention is not limited to the above-described contents, and the scope of the right is claimed. Must be interpreted based on the description. Needless to say, the contents of the present invention can be modified and changed based on the above description.

It is a fragmentary sectional view which shows typically the structure of the precoat aluminum plate which concerns on this invention. In an Example, it is a schematic diagram which shows the process of producing a bottomed cylindrical container by carrying out drawing processing and ironing of a test material. (A) is a schematic diagram which shows the box-type housing | casing by a bending process, (b) is a schematic diagram which shows the box-type housing | casing by a drawing process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Precoat aluminum plate 2 Aluminum plate 3 Precoat film 4 Base resin 5 Fine particle

Claims (6)

On the surface of the aluminum plate, a precoated aluminum plate in which a precoat film containing a base resin cross-linked between molecules and fine particles is formed,
The precoat film has a gel fraction of 50% or more and a surface roughness of 0.25 μm or more in terms of arithmetic average roughness (Ra).   2. The precoated aluminum plate according to claim 1, wherein the fine particles are inorganic fine particles or crosslinked organic fine particles.   2. The precoated aluminum plate according to claim 1, wherein the fine particles are cross-linked spherical organic fine particles.   The base resin is a crosslinked polyester resin obtained by crosslinking a polyester resin having a glass transition temperature of 25 to 65 ° C with a melamine curing agent or an isocyanate curing agent. Item 4. The precoated aluminum plate according to any one of items 3 to 4.   The precoated aluminum plate according to claim 4, wherein the polyester resin has a glass transition temperature of 35 to 60 ° C.   6. The precoated aluminum plate according to claim 1, wherein the surface roughness of the precoat film is an arithmetic average roughness (Ra) of 0.25 to 0.55 μm. .

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