JP2018202827A - Precoated aluminum material and on-vehicle component using the same - Google Patents

Abstract

To provide a precoated aluminum material used for an on-board component housing such as a power control unit (PCU) cover.SOLUTION: The precoated aluminum material is provided that comprises: an aluminum base material; a chemical film formed on the surface of the aluminum base material; and a resin film formed on the chemical film, wherein the resin film includes an epoxy resin as a base resin and a heat dissipating pigment, and an SP value δ (<cal/cm>) of an epoxy resin, a film thickness t (μm) of the resin film and a pts.mass m of the heat dissipating pigment with respect to 100 pts.mass of the epoxy resin satisfy the following expression (1): 6≤{(23.4-δ)×(t)}/(m)≤127 (1).SELECTED DRAWING: None

Description

  The present invention relates to a pre-coated aluminum material used for in-vehicle components such as a cover in a casing of a power control unit (PCU), and an in-vehicle component using the same.

  Aluminum materials are excellent in properties such as light weight, high corrosion resistance, high thermal conductivity, and high recyclability, and are widely used as constituent materials for building materials and electrical products. In such applications, other functions are required without impairing the properties inherent to the aluminum material, and surface-treated products have been put into practical use. Surface treatment methods include anodic oxidation treatment that can improve corrosion resistance and wear resistance, plating treatment that can improve corrosion resistance and adhesion, and corrosion resistance and lubricity. The painting etc. are used. Among them, the coating film formed by painting is mainly composed of a resin, an additive, and the like, and can exhibit various functions by various combinations.

  There are two known processes for coating an aluminum material: a post-coating method in which a coating film is formed after pressing the aluminum material, and a pre-coating method in which a coating film is formed in advance on the aluminum material before pressing. . The pre-coating method has the feature of stability of quality because the thickness of the coating film formed on the aluminum material can be made uniform in addition to the reduction of the total cost and the improvement of the working environment by shortening the process by the user. .

In recent years, as environmental problems become more serious, regulations such as automobile CO ₂ emissions have been greatly strengthened. In order to reduce emissions and improve fuel efficiency, weight reduction of the vehicle body is indispensable, and the use of aluminum materials is increasing. Under such circumstances, Patent Document 1 discloses a technique of processing a pre-coated aluminum material and applying it to an in-vehicle LED illumination heat sink.

Japanese Patent No. 5745674

  Unlike an in-vehicle LED lighting heat sink, an environment in which in-vehicle components such as a power control unit (PCU) cover is mounted uses a chemical having a strong dissolving power. For example, it may be exposed to a 20% aqueous sulfuric acid solution in a high temperature environment. However, the invention disclosed in Patent Document 1 still has a problem that it does not satisfy the chemical resistance required for in-vehicle components.

  The present invention has been completed in order to solve the above-mentioned problems. For example, a pre-coated aluminum material used for in-vehicle components such as a cover in a casing of a power control unit (PCU) and an in-vehicle component using the same are provided. With the goal.

That is, the present invention is the precoated aluminum material according to claim 1, comprising an aluminum base, a chemical conversion film formed on the surface of the aluminum base, and a resin film formed on the chemical conversion film, The resin film includes an epoxy resin as a base resin and a heat-dissipating pigment, the SP value δ (<cal / cm ³ > ^1/2 ) of the epoxy resin, the film thickness t (μm) of the resin film, and the epoxy A pre-coated aluminum material characterized in that a mass part m of the heat dissipating pigment with respect to 100 parts by mass of the resin satisfies the following formula (1).
6 ≦ {(23.4−δ) × (t)} / (m) ≦ 127 (1)

  The present invention provides an in-vehicle component using the precoated aluminum material according to claim 1 in claim 2. Further, according to the present invention, in claim 3, the in-vehicle component is a press-worked product of a pre-coated aluminum material.

  The resin film of the precoated aluminum material according to the present invention maintains a high emissivity by satisfying the above formula (1), that is, a characteristic excellent in heat dissipation, and an affinity and permeability between the resin film and the chemical. These two characteristics are maintained in a good balance, and furthermore, have high temperature and water resistance.

A. Precoat aluminum material The precoat aluminum material which concerns on this invention is equipped with the chemical film formed on the surface of an aluminum base material, and the resin film formed on the said chemical film.

B. Aluminum base material The aluminum base material used in the present invention is appropriately selected for the alloy composition and quality of the aluminum material depending on the mechanical properties and chemical properties required for molding for in-vehicle components. Among them, it is preferable to use 1000 series such as 1100 and 1050, 3000 series such as 3003 or 3004, and 5000 series such as 5052 or 5182. Although the shape of an aluminum base material is not specifically limited, A plate material is used suitably. The thickness in the case of using a plate material is appropriately selected according to the type of the in-vehicle component, and is preferably in the range of 0.1 to 2.0 mm, for example.

C. Chemical conversion film The chemical conversion film used in the present invention may be phosphate chromate, zirconium-based, titanium-based, zinc phosphate, or the like. Among these, it is preferable to use phosphate chromate. Adhesion amount of phosphoric acid chromate is preferably a metal Cr element terms of 5 to 50 mg / ^{m 2,} more preferably 10~45mg / ^{m 2.} If the adhesion amount is less than 5 mg / m ² , the adhesion with the resin film may be reduced. If the adhesion amount is more than 50 mg / m ² , the chemical conversion film cohesively breaks after processing, and the adhesion with the resin film decreases. There is a case.

D. Resin film D-1. Epoxy Resin In the present invention, an epoxy resin that has a low affinity with chemicals and hardly deteriorates even when contacted with chemicals such as strong acids is used as the base resin. In addition, since an epoxy resin is inferior in workability compared with a fluororesin, it is preferable to use the required workability extremely. In addition, unlike a polyester resin, an epoxy resin is difficult to hydrolyze and is therefore suitably used in applications exposed to high temperature and high humidity environments. That is, the epoxy resin has an advantage of being excellent in high temperature water resistance. Furthermore, unlike a fluororesin, an epoxy resin does not have a pressure mark, so that it is not necessary to devise the specifications of the back coating film, and can be manufactured at a low cost.

  In addition, since the emissivity of about 0.5 is achieved by forming a resin film with an epoxy resin without adding a heat dissipating pigment, a certain degree of heat dissipating property is obtained. However, since sufficient heat dissipation cannot be obtained at an emissivity of about 0.5, in the present invention, a heat dissipating pigment is an essential component as described later.

  As the epoxy resin used in the present invention, those which are saturated or unsaturated; cyclic or acyclic; aliphatic, cycloaliphatic, aromatic or heterocyclic can be used. Further, it may have an appropriate substituent, for example, a halogen, a hydroxy group and an ether group.

  Specific examples of the epoxy resin include an epoxy polyether obtained by reacting an epihalohydrin (for example, epichlorohydrin or epibromohydrin) with polyphenol in the presence of an alkali. Examples of polyphenols include resorcinol, catechol, hydroquinone, bis (4-hydroxyphenyl) -2,2-propane (ie, bisphenol A); bis (4-hydroxyphenyl) -1,1-isobutane; 4,4- Dihydroxybenzophenone; bis (4-hydroxyphenyl) -1,1-ethane; and 1,5-hydroxynaphthalene. Most preferred is polyglycidyl ether of bisphenol A.

  Other specific examples of epoxy resins include polyglycidyl ethers of polyhydric alcohols. Examples of such polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, and 1,4-butylene glycol.

  Still another specific example is polyglycidyl ether of polycarboxylic acid. Such compounds include epichlorohydrin or similar epoxy compounds and aliphatic or aromatic polycarboxylic acids such as oxalic acid, succinic acid, glutaric acid, tetraphthalic acid, 2,6-naphthalenedicarboxylic acid and dimerization. Obtained by reaction with linoleic acid.

  Another specific example is one prepared by epoxidation of an olefinically unsaturated alicyclic compound. Such polyepoxides are not phenolic and are obtained by epoxidation of cycloaliphatic olefins, for example by the action of oxygen and certain metal catalysts; by the action of perbenzoic acid; by acid-aldehyde monoperacetic acid or peracetic acid . Examples of such polyepoxides include known epoxy alicyclic ethers or esters.

  Still other specific examples include those having an oxyalkylene group in the epoxy molecule. Still another example is an epoxy novolac resin. Such resins are obtained by reaction of epihalohydrins with condensates of aldehydes and monofunctional or polyfunctional phenols. A typical reaction example is a reaction between epichlorohydrin and a phenol formaldehyde condensate.

  Other examples include acrylic copolymers having copolymerizable glycidyl acrylate or methacrylate units. These acrylic copolymers are prepared by reaction of an alkyl ester of α, β-unsaturated mono- or di-carboxylic acid with either glycidyl acrylate or methacrylate. Other glycidyl-containing copolymerizable monomers such as diglycidyl itaconic acid and diglycidyl maleate may be used. Such a monomer may be copolymerized in the presence of another copolymerizable monomer, for example, a vinyl aromatic compound (for example, styrene or vinyltoluene) or acrylonitrile or methacrylonitrile if necessary.

  Further, a modified epoxy resin may be used. As the modified epoxy resin, a modified epoxy resin obtained by reacting an epoxy resin with phosphoric acid, a low molecular alcohol, or a derivative thereof, or a urethane-modified epoxy resin can be used.

  The above epoxy resin preferably has a glass transition temperature exceeding 40 ° C, more preferably exceeding 50 ° C. When the glass transition temperature is 40 ° C. or lower, chemical resistance may be inferior.

  As the curing agent, it is preferable to use a melamine resin or a blocked isocyanate resin.

D-2. Heat-dissipating pigment As the heat-dissipating pigment used in the present invention, titanium oxide, alumina, carbon black, graphite or the like can be used, but carbon black or graphite is preferably used. Carbon black and graphite do not exist in the state of primary particles in the resin film, but exist in a state where individual particles are aggregated.

  Carbon black is a fine black powder produced by pyrolyzing a hydrocarbon raw material by a channel method, a furnace method, a thermal decomposition method, an acetylene method or the like. The method for producing carbon black used in the present invention is not particularly limited. In the channel method, natural gas is mainly used as a raw material, and this is incompletely burned from a large number of burner chips in a combustion chamber, and carbon black produced by colliding with an iron channel at an appropriate height is attached and captured. It is a way to collect. The furnace method is a method in which a raw material is thermally decomposed in a state where oxygen is insufficient in a furnace lined with refractory bricks. The thermal decomposition method is a method in which the supply of air is completely cut off and heat is supplied from another to perform thermal decomposition. The acetylene method is a method by thermal decomposition of acetylene gas. The average particle size (primary particle size) of carbon black is preferably 105 nm to 200 nm. If the average particle size is less than 105 nm, the concentration of carbon black in the resin film cannot be sufficiently increased, and the heat dissipation may be inferior. On the other hand, when the average particle diameter exceeds 200 nm, not only the heat dissipation effect is saturated but also the cost is increased.

  Graphite is a hexagonal hexagonal plate-like crystal, and the structure is a turtle-shell-like layered substance. In each plane, carbon is connected by strong covalent bonds, and a weak van der is between layers. It is connected by the Waals force. The type of graphite is not particularly limited, and for example, scaly graphite, scaly graphite, granular graphite, earthy graphite and the like are used. The average particle diameter of graphite is preferably 1 μm to 5 μm. The smaller the average particle diameter is, the better the bending workability is. However, if the average particle diameter is less than 1 μm, the effect of the bending workability is saturated and the cost is increased. On the other hand, if the average particle size exceeds 5 μm, bending workability may be inferior.

D-3.6 ≦ (23.4−δ) × (t) / (m) ≦ 127 <Expression (1)>
In the present invention, the SP value δ (<cal / cm ³ > ^1/2 ) of the epoxy resin, the film thickness t (μm) of the resin film, and the mass part m (− of the heat-dissipating pigment with respect to 100 parts by mass of the epoxy resin. ) Must satisfy the above formula (1). Formula (1) preferably satisfies 10 ≦ (23.4−δ) × (t) / (m) ≦ 110, and 15 ≦ (23.4−δ) × (t) / (m) ≦ 100. It is more preferable to satisfy. When (23.4−δ) × (t) / (m) <6, the chemical resistance is poor. On the other hand, (23.4-δ) × (t) / (m)> 127 is inferior in heat dissipation and chemical resistance.

In formula (1), 23.4 (<cal / cm ³ > ^1/2 ) is the SP value of water, and the larger 23.4-δ, the lower the affinity with water. The chemical resistance required for the in-vehicle parts in which the present invention is used is resistance to a sulfuric acid aqueous solution. The lower the affinity with water, the harder the sulfuric acid aqueous solution penetrates into the resin film, and the thicker the resin film thickness is. Since it takes time to reach the aluminum substrate, the chemical resistance is excellent. On the other hand, as the amount of the heat dissipating pigment added, that is, as the mass part m of the heat dissipating pigment with respect to 100 parts by mass of the epoxy resin increases, the non-uniform structure of the resin film increases, and the aqueous sulfuric acid solution permeates through this non-uniform structure. Chemical resistance is poor. On the other hand, since the emissivity of the resin film depends on t and m, in order to satisfy heat dissipation, chemical resistance, and high-temperature water resistance, the formula (1) is satisfied while using an epoxy resin as the base resin. There is a need.

D-3-1. SP value The SP value (solubility parameter) used in the present invention is a measure of solubility. In addition, SP value in case base resin is a 2 or more types of mixture makes SP value the weighted average value of the solubility parameter of each base resin.

The SP value is obtained by weighing 0.5 g of resin in a 100 ml beaker, adding 10 ml of a good solvent (using two kinds of good solvents such as dioxane and acetone) with a whole pipette, stirring and dissolving with a magnetic stirrer, 50 ml of two kinds of poor solvents (for example, n-hexane and ion-exchanged water are used) are added dropwise using a burette, and the point at which turbidity is generated is defined as the dropping amount. The measurement temperature is 20 ° C. The SP value δ is given by the following equations (2) to (4).
δ = {(1/2) (V _m1 · δ _m1 + V _mh · δ _mh )} / {(1/2) (V _ml + V _mh )}
= (V _m1 · δ _m1 + V _mh · δ _mh ) / (V _ml + V _mh ) (2)
Vm = V1V2 / (φ1V2 + φ2V1) (3)
δm = φ1 δ1 + φ2δ2 (4)
V _i : Molecular volume of each solvent (ml / mol), where i is 1 in Formula (3) or
2
φ _i : Volume fraction of each solvent at the cloud point, where i is 1 in the equations (3) and (4)
Or 2
δ _i : SP value of each solvent, where i is 1 or 2 in formula (4)
ml: good solvent mixed system mh: poor solvent mixed system Here, V _{ml and} δ _ml refer to the case where two good solvent mixed systems (for example, 1: dioxane, 2: acetone) are used, and V _mh , Δ _mh refers to a case where two types of poor solvent mixed systems (for example, 1: n-hexane, 2: ion-exchanged water) are used.

  The SP value of the epoxy resin used in the present invention is preferably in the range of 10.7 to 11.2, and more preferably in the range of 10.8 to 11.1.

D-3-2. Film thickness The thickness of the resin film used in the present invention is preferably in the range of 12 μm to 40 μm, and more preferably in the range of 16 μm to 30 μm. If this thickness is less than 12 μm, chemical resistance may be inferior, and if it exceeds 40 μm, workability may be inferior.

D-3-3. Mass part m of heat-dissipating pigment with respect to 100 parts by mass of epoxy resin
The addition amount of the heat dissipating pigment used in the present invention, that is, the heat dissipating pigment mass part (m) with respect to 100 parts by mass of the epoxy resin is preferably 4 to 26 parts by mass, and 6 to 22 parts by mass. More preferred. If it is less than 4 parts by mass, the heat dissipation may be inferior, and if it exceeds 26 parts by mass, a uniform resin film may not be obtained.

E. Manufacturing method As mentioned above, the precoat aluminum material which concerns on this invention forms a chemical conversion film on the surface of an aluminum base material by the spray method or the immersion method. Next, a liquid coating composition for forming a resin film is applied onto the chemical film, and the bark film is formed by baking it. The chemical conversion film and the resin film thereon may be formed on one surface of the aluminum substrate, or may be formed on both surfaces.

E-1. Coating Composition The liquid coating composition for forming a resin film in the present invention is prepared by dissolving or dispersing a coating component in a solvent. The paint component contains an epoxy resin as a base resin and a heat dissipating pigment as essential components, and may further contain an inner wax, a repellency inhibitor, an extender pigment, a dispersion stabilizer, and the like as additives. The solvent is not particularly limited as long as it can dissolve or disperse each paint component. For example, hydrocarbons, alcohols, ketones, esters and the like can be used. In the coating composition, it is preferable to appropriately select the amount of the solvent so that the solid content of the coating material including the coating component is 10 to 60% by mass, preferably 15 to 55% by mass.

E-2. Coating method As a method of applying the coating composition to the surface of the aluminum base material, a roll coating method having excellent film thickness uniformity and good productivity is preferable. In the roll coating method, the coating composition is stored in a pan, the coating composition is scraped from the pan by a pick-up roll, transferred to an applicator roll, and the transferred coating composition is applied to the surface of an aluminum substrate. The aluminum substrate is conveyed using a backup roll. In addition to the roll coat method, it may be applied by a method such as a gravure roll method or a natural coat method, or may be applied by a bar coater.

  The coating composition applied to the aluminum substrate is baked by drying in a hot air dryer. The maximum reached plate temperature in baking is preferably 200 to 310 ° C, more preferably 210 to 300 ° C, and the baking time is preferably 20 to 100 seconds, more preferably 40 to 90 seconds. The heating method used for baking may be infrared heating or high frequency induction heating in addition to the heating method using a hot air dryer.

F. In-vehicle component An in-vehicle component is formed by subjecting the precoated aluminum material according to the present invention to press processing such as punching, bending, and drawing. Such an in-vehicle component is used as a cover for a casing of a power control unit (PCU), for example. The shape and size of the cover are not particularly limited. This cover is joined to a bottom case of a housing made by aluminum die casting using, for example, screwing or an adhesive.

  Examples of the present invention will be described in detail below based on examples of the present invention and comparative examples.

Invention Examples 1-6 and Comparative Examples 1-4
A chemical conversion film and a resin film were formed on the surface of the aluminum base as follows. An aluminum plate (JIS A1050P H24, thickness: 2.0 mm) was degreased with a weak alkaline degreasing solution, and then washed with water. This aluminum plate was subjected to a chemical conversion treatment by immersing it in a commercially available phosphoric acid chromate chemical conversion treatment solution (Nippon Parkerizing, Palcoat 3700) at 50 ° C. for 20 seconds. Then, this was washed with water and dried at room temperature.

  Next, the base resin and the heat-dissipating pigment (carbon black, manufactured by Asahi Carbon Co., Ltd., SB220, average particle size) shown in Table 1 are formed on the chemically treated aluminum plate so that the film thickness after baking and drying is as shown in Table 1. A coating composition in which a diameter of 122 nm) is dispersed in an organic solvent (a mixed solvent of cyclohexanone and toluene) is applied by a bar coater and baked in a hot air dryer at a maximum reached plate temperature of 230 ° C. and a baking time of 60 seconds. A sample was prepared.

  The thickness of the resin film was adjusted by changing the amount of the coating composition to be applied. Moreover, the ratio of the mass part of base resin and a heat-radiating pigment is as showing in Table 1. The total solid content of the base resin and the heat dissipating pigment in the coating composition was 50% by mass.

  About the obtained sample, chemical-resistance, heat dissipation, and high temperature aqueous resistance were evaluated by the method of the below-mentioned. ○ and Δ were accepted, and x was rejected. The results are shown in Table 1.

<Chemical resistance>
The sample was cut into a size of 5 cm × 10 cm, the edge was sealed, immersed in a 20% sulfuric acid aqueous solution and stored at 70 ° C. for 24 hours, and then the appearance of the resin film was visually evaluated according to the following criteria.
○: No change △: Corrosion area ratio exceeds 50% and less than 100% ×: Corrosion area ratio is 50% or less

<Heat dissipation>
The sample was cut into a size of 10 cm × 10 cm, the emissivity was measured at room temperature using an emissometer (DandSAERD: manufactured by Kyoto Electronics Industry Co., Ltd.), and evaluated according to the following criteria.
○: 0.8 or more Δ: 0.7 or more and less than 0.8 ×: less than 0.7

<High temperature water resistance>
The sample was cut into a size of 5 cm × 10 cm, a pressure cooker test was performed, and the appearance was evaluated according to the following criteria. The test time was 120 hours.
○: No peeling of the coating film is observed, and no discoloration is observed.
X: At least one of coating film peeling and discoloration is recognized.

  In Inventive Examples 1 to 6, since the structural requirements of the present invention were satisfied, the chemical resistance, heat dissipation and high temperature water resistance were all acceptable. On the other hand, in Comparative Examples 1-4, any one of chemical resistance, heat dissipation, and high-temperature water resistance was rejected.

  In Comparative Example 1, since (23.4−δ) × (t) / (m) exceeded 127, the heat dissipation performance was rejected.

  In Comparative Example 2, since (23.4−δ) × (t) / (m) was less than 6, chemical resistance was rejected.

  In Comparative Examples 3 and 4, since a resin that is not an epoxy resin was used as the base resin, (23.4-δ) × (t) / (m) was less than 6, and thus the chemical resistance and high-temperature water resistance were poor. Passed.

  The pre-coated aluminum material according to the present invention is suitably used for, for example, a housing cover of a power control unit (PCU) which is an in-vehicle component.

Claims (3)

An epoxy resin comprising an aluminum base material, a chemical conversion film formed on the surface of the aluminum base material, and a resin film formed on the chemical conversion film, wherein the resin film is a base resin And the heat-dissipating pigment, the SP value δ (<cal / cm ³ > ^1/2 ) of the epoxy resin, the film thickness t (μm) of the resin film, and the mass of the heat-dissipating pigment relative to 100 parts by mass of the epoxy resin The pre-coated aluminum material, wherein the part m satisfies the following formula (1).
6 ≦ {(23.4−δ) × (t)} / (m) ≦ 127 (1)   A vehicle-mounted component using the precoated aluminum material according to claim 1.   The in-vehicle component according to claim 2, which is a press-processed product of a pre-coated aluminum material.