JP5135249B2 - Resin-coated aluminum alloy plate for bottomed cylindrical case for capacitors - Google Patents

Description

  The present invention relates to a resin-coated aluminum alloy plate for a bottomed cylindrical case for a capacitor that is subjected to drawing and ironing.

Conventionally, many aluminum electrolytic capacitors contain a capacitor element impregnated with an electrolytic solution in a bottomed cylindrical case formed by drawing and ironing an aluminum alloy plate and sealing the opening with rubber or the like. Further, the outer peripheral surface was covered with a heat-shrinkable tube such as a vinyl chloride resin or an olefin resin for the purpose of electrical insulation or content display.
In recent years, electronic components have been downsized, and aluminum electrolytic capacitors have also been downsized. In order to reduce the size of aluminum electrolytic capacitors, chip-type capacitors without surface mount leads have been put into practical use. However, with such small aluminum electrolytic capacitors, it is extremely difficult to coat heat-shrinkable tubes. is there.

  Therefore, as a method of omitting the step of covering the heat-shrinkable tube, by laminating a resin film such as polyester or polyamide on an aluminum alloy plate, or forming a resin coating film containing a resin such as a thermosetting resin The coating material is applied to the aluminum alloy plate, and a resin coating film is formed on the surface of the aluminum alloy plate to obtain a resin-coated aluminum alloy plate pre-coated with the resin. A method of drawing and ironing has been proposed (Patent Documents 1 to 3).

  Patent Document 1 discloses a resin film-covered metal plate in which a resin film is coated on at least one surface of a metal plate via an adhesive layer composed of an adhesive, and the adhesive includes a melamine-based curing agent and an isocyanate-based resin. It is composed of at least one selected from among curing agents, the resin film has a crystallinity of 20 to 90%, and the birefringence of the resin film on the surface in contact with the adhesive layer is A resin film-covered metal plate that is less than 0.005 and that is made of a polyester resin having a birefringence of 0.005 or more at a depth of 5 μm from the outermost surface of the resin film is shown. Has been.

  Patent Document 2 discloses a capacitor case material including a base material made of aluminum or an aluminum alloy and a coating film of a wax-containing resin provided on the surface of the base material.

Patent Document 3 discloses a resin-coated aluminum alloy plate in which a chemical coating is provided on an aluminum alloy plate and a resin coating is provided thereon. And at least one selected from the group consisting of acrylic, urethane, and urea, and contains 0.1 to 10 parts by weight of a lubricant with respect to 100 parts by weight of the resin. Shown is a resin-coated aluminum alloy plate for electrical and electronic parts in which the tensile strength of the film is 40 N / mm ² or more, the elongation is 2% or more, and the thickness of the resin coating film is 3 to 10 μm.

  However, although the capacitor case material of Patent Document 2 and the resin-coated aluminum alloy plate for electric and electronic parts of Patent Document 3 are lower in manufacturing cost than the resin film-coated metal plate of Patent Document 1, the diaphragm and ironing are used. Due to poor processability, there is a problem that the resin coating cracks or peels off during processing, or even if the resin coating does not crack or peel off during processing, the resin coating is exposed to high temperature and high humidity. There was a problem that cracking and peeling occurred.

  On the other hand, in order to manufacture the resin film-coated metal plate of Patent Document 1, a process for processing a resin raw material into a film is necessary. Therefore, the capacitor case material of Patent Document 2 and the electric and electronic of Patent Document 3 are used. There was a problem that the manufacturing cost was higher than that of the resin-coated aluminum alloy plate for parts.

  In recent years, in order to reduce the manufacturing cost, the thickness of the resin coating layer of the resin-coated aluminum alloy has been reduced. However, the resin film-coated metal plate of Patent Document 1 cannot be manufactured with a resin film having a thickness of about 6 μm or less, or the manufacturing cost is extremely high even if the thickness is about 6 μm or less. Therefore, the resin film could not be manufactured substantially.

  In contrast, a polyester resin having specific physical properties is combined with an epoxy resin and an amino resin, and a resin coating film is formed using a paint for forming a resin coating film containing them in a specific blending ratio. A resin-coated aluminum alloy plate for ironing has been reported (Patent Document 4). This makes it difficult for the resin coating film to crack or peel during drawing and ironing, and to prevent the resin coating film from cracking or peeling even when exposed to a previously assumed high temperature and humidity environment. .

  However, in recent years, capacitors have become widespread in tropical regions such as Southeast Asia, and will be used in harsher environments than before, so cracking and peeling of resin coatings when exposed to high-temperature and high-humidity environments. The demand for is getting more severe.

JP 2004-122765 A Japanese Patent Laid-Open No. 10-199768 JP 2005-171330 A JP 2007-237542 A

  The present invention has been made in view of such conventional problems, and has good drawing and ironing workability, and the resin coating film does not break during processing, and between the aluminum alloy plate and the resin coating film. An object of the present invention is to provide a resin-coated aluminum alloy plate for a bottomed cylindrical case for a capacitor, which does not cause peeling and does not cause coating film deterioration and corrosion of underlying aluminum even in a harsh environment after processing and molding.

The present invention comprises a substrate made of an aluminum alloy plate, a chemical conversion film formed on the surface of the substrate, and a resin coating film formed on the surface of the chemical conversion film,
The resin coating film has (a) a number average molecular weight of 30,000 to 80,000, and a ratio h ₂ / h of absorbance h ₁ of 830 cm ⁻¹ and absorbance h ₂ of 750 cm ⁻¹ in FT-IR analysis of the coating film. ₁ is an epoxy resin of 0.1 to 10, (b) a polyester resin having a number average molecular weight of 7000 to 30000, a glass transition temperature of −20 ° C. or higher, and (c) an amino resin A cured product of the resin mixture
When the total content of the (a) epoxy resin, the (b) polyester resin, and the (c) amino resin is 100 parts by mass, the resin mixture contains 70 to 98 parts by mass of the (a) epoxy resin. Part (b) 0-20 parts by mass of the polyester resin and (c) 2-20 parts by mass of the amino resin in a resin-coated aluminum alloy plate for a bottomed cylindrical case for a capacitor ( Claim 1).

  The resin-coated aluminum alloy plate for a bottomed cylindrical case for a capacitor (hereinafter referred to as “resin-coated aluminum alloy plate” as appropriate) is a combination of a polyester resin and an amino resin combined with an epoxy resin having the above specific physical properties. It has the resin coating film formed using the resin mixture contained by the mixture ratio. As a result, drawing and ironing workability is good, the resin coating film is not cracked during processing, and no peeling occurs between the aluminum alloy plate and the resin coating film. It can be set as the resin-coated aluminum alloy plate for bottomed cylindrical cases for capacitors in which deterioration and corrosion of base aluminum do not occur.

The resin mixture has (a) a number average molecular weight of 30,000 to 80,000, and a ratio h ₂ / h ₁ of absorbance h ₁ of 830 cm ⁻¹ and absorbance h ₂ of 750 cm ⁻¹ in the FT-IR analysis of the coating film. Contains 0.1 to 10 epoxy resin, (b) a polyester resin having a number average molecular weight of 7000 to 30000, a glass transition temperature of −20 ° C. or higher, and (c) an amino resin. .

  By using the above (a) epoxy resin, the adhesion with the aluminum alloy plate is improved, the coating film is not cracked during the molding process, no peeling occurs between the aluminum alloy plate, and after the molding process, Even in a harsher environment, peeling and alteration of the resin coating film hardly occur, and an effect that the substrate does not corrode can be provided.

Moreover, by using the (b) polyester resin, the elongation of the resin film increases and the blocking performance described later is improved.
Moreover, by using the above (c) amino resin, curing of the resin coating film is promoted, the coating film is difficult to break after processing and molding, and the resin coating film is difficult to soften even in a harsh environment.

  And when the said resin mixture makes the total content of said (a) epoxy resin, said (b) polyester resin, and said (c) amino resin 100 mass parts, said (a) epoxy resin is 70- 98 parts by mass, 0-20 parts by mass of the (b) polyester resin, and 2-20 parts by mass of the (c) amino resin.

  By adjusting to such a blending ratio, the effects obtained from each of the above (a) epoxy resin, (b) polyester resin, and (c) amino resin are adjusted, and good drawing and ironing processability are obtained. Therefore, it is possible to prevent cracking and peeling of the resin coating film during processing, and in particular, it is possible to make it difficult to cause cracking and peeling of the resin coating film when exposed to a high temperature and high humidity environment.

  The resin-coated aluminum alloy plate can satisfactorily adhere the substrate and the resin coating film by interposing the chemical conversion film between the substrate and the resin coating film. It is possible to make it difficult to generate cracks or peeling of the resin coating film exhibiting the above.

Moreover, since the resin-coated aluminum alloy plate for a bottomed cylindrical case for a capacitor according to the present invention is manufactured by forming the resin coating film, the manufacturing cost is lower than that of the capacitor case material of Patent Document 1 described above. The thickness of the resin coating layer can be reduced.
In addition, the resin-coated aluminum alloy plate for a bottomed cylindrical case for a capacitor of the present invention has a squeezing and ironing compared to the capacitor case material of Patent Document 2 and the resin-coated aluminum alloy plate of Electric and Electronic Components of Patent Document 3. During processing, cracking or peeling of the resin coating film hardly occurs, and cracking or peeling of the resin coating film hardly occurs when exposed to a high temperature and high humidity environment.
In addition, the resin-coated aluminum alloy plate for a bottomed cylindrical case for a capacitor according to the present invention is less than the resin-coated aluminum alloy plate for drawing and ironing processing of Patent Document 4, and is deteriorated in a harsh environment after processing and molding. Corrosion of the base aluminum is difficult to occur.

  Thus, according to the present invention, the drawing and ironing workability is good, the resin coating film is not cracked during processing, peeling does not occur between the aluminum alloy plate and the resin coating film, and after processing and molding, It is possible to provide a resin-coated aluminum alloy plate for a bottomed cylindrical case for a capacitor in which coating film deterioration and underlying aluminum corrosion do not occur even in a harsh environment.

  As described above, the resin-coated aluminum alloy plate for a bottomed cylindrical case for a capacitor of the present invention includes a substrate made of an aluminum alloy plate, a chemical conversion film formed on the surface of the substrate, and a surface of the chemical conversion film. And a resin coating film formed on the substrate.

  In the present invention, the aluminum alloy plate is a plate made of either pure aluminum or an aluminum alloy. The aluminum alloy plate is not particularly limited as long as it is an aluminum alloy used for manufacturing a bottomed cylindrical case of an aluminum electrolytic capacitor, and may be appropriately selected depending on the shape of the bottomed cylindrical case. it can.

The chemical conversion film is not particularly limited as long as it is a chemical film that is usually used as a base for coating the substrate with a resin coating film, that is, a base for forming the resin coating film. .
Examples of the chemical conversion film include alkali-chromate-based, chromate-based, phosphate-chromate-based, zinc phosphate-based, non-chromate-based, oxide film-based, and the like. For example, mixed film of aluminum oxide and chromium oxide, mixed film of chromium phosphate and aluminum phosphate, zinc phosphate film, mixed film of aluminum oxide and phosphate ester, chromium oxide and polyacrylic acid Examples thereof include a resin mixed film and an aluminum hydrated oxide film.

  The method for forming the chemical conversion film is not particularly limited as long as it is a method used for forming a chemical conversion film as a base for forming a resin coating film on the aluminum alloy plate. For example, the surface of an aluminum alloy plate obtained by rolling or the like is washed with a neutral detergent, a weakly acidic detergent, a weakly alkaline detergent or a degreasing agent, or etched to obtain aluminum obtained by the above rolling or the like. A method of forming a chemical conversion film on the surface of the aluminum alloy plate by removing oil and fat such as lubricating oil adhering to the surface of the alloy plate and then coating the surface of the obtained degreased aluminum alloy plate Etc.

  As a treatment for forming a chemical conversion film, a chromate chromate treatment in which the degreased aluminum alloy plate is immersed in a treatment solution containing phosphoric acid, chromic anhydride, or hydrogen fluoride, or a compound mainly composed of a zirconium compound or a titanium compound. Examples include a treatment in which the degreased aluminum alloy plate is immersed in a treatment solution containing, and a coating type treatment in which a treatment solution containing an organic resin and a metal salt is applied to the degreased aluminum alloy plate and dried.

The resin coating film has (a) a number average molecular weight of 30,000 to 80,000, and a ratio h ₂ of absorbance h ₁ of 830 cm ⁻¹ and absorbance h ₂ of 750 cm ⁻¹ in FT-IR analysis of the coating film. Epoxy resin having a / h ₁ of 0.1 to 10, (b) a polyester resin having a number average molecular weight of 7000 to 30000 and a glass transition temperature of −20 ° C. or higher, (c) an amino resin, It is the hardened | cured material of the resin mixture containing this.

The (a) epoxy resin is a modified epoxy resin obtained by reacting an epoxy group or a hydroxyl group of a resin having an epoxy group with various modifiers.
Specific examples of the (a) epoxy resin include reacting each modifier with an epoxy group or a hydroxyl group in, for example, a bisphenol type epoxy resin, a novolak type epoxy resin, or a bisphenol type epoxy resin or a novolak type epoxy resin. And modified epoxy resins obtained by the treatment.

  The bisphenol type epoxy resin is a condensate of epichlorohydrin and a bisphenol compound as shown in the following chemical formula (1). In the chemical formula (1), the case where the bisphenol compound is bisphenol A among the condensates of the epichlorohydrin and the bisphenol compound is shown. Bisphenol-type epoxy resins can be produced by, for example, condensing epichlorohydrin and bisphenol compounds up to a high molecular weight in the presence of a catalyst such as an alkali catalyst, if necessary, or epichlorohydrin and bisphenol compounds as needed. A low molecular weight product is obtained by condensation in the presence of a catalyst such as a catalyst, and then the low molecular weight product and a bisphenol compound are subjected to a polyaddition reaction.

  Examples of the bisphenol compound related to the bisphenol type epoxy resin include bis (4-hydroxyphenyl) methane: bisphenol F, 1,1-bis (4-hydroxyphenyl) ethane, and 2,2-bis (4-hydroxyphenyl). Propane: bisphenol A, 2,2-bis (4-hydroxyphenyl) butane: bisphenol B, bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-tert-butylphenyl) -2,2 -Propane, p- (4-hydroxyphenyl) phenol, oxybis (4-hydroxyphenyl), sulfonylbis (4-hydroxyphenyl), 4,4'-dihydroxybenzophenone, bis (2-hydroxynaphthyl) methane and the like. .

The (a) epoxy resin has a number average molecular weight of 30,000 to 80,000.
When an epoxy resin having a number average molecular weight of less than 30,000 is used, there is a problem that the coating film is excessively cured and flexibility is lowered. On the other hand, when an epoxy resin having a number average molecular weight of more than 80000 is used, there is a problem that the coating film is insufficiently cured, the resistance to a harsh environment is lowered, and the coating film is deteriorated or discolored.

Further, the epoxy resin (a), in the FT-IR analysis of the coating film, the absorbance h _1, the ratio h ₂ / h ₁ absorbance h ₂ of 750 cm ^-1 of 830 cm ^-1, is 0.1 to 10 .
The absorption at 830 cm ⁻¹ indicates the absorption of bisphenol A. Further, the absorption at 750 cm ⁻¹ indicates the absorption of bisphenol F.

The bisphenol A is effective in terms of retortability, and the bisphenol F is effective in terms of moldability.
Then, the h ₂ / h ₁ is able to in the case of 0.1 to 10, to satisfy both moldability and retort resistance.
When h ₂ / h ₁ is less than 0.1, coating film cracking occurs in the molding process, and the moldability cannot be ensured. On the other hand, when h ₂ / h ₁ exceeds 10, the coating film deteriorates in a harsh environment, discoloration occurs, and retort properties cannot be ensured.

The (b) polyester resin is an esterified product of a polybasic acid and a polyhydric alcohol.
Examples of the polybasic acid include phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, succinic acid, fumaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, maleic acid, and itacone. Examples thereof include dibasic acids such as acids and dimer acids. The said dibasic acid may be used individually by 1 type, or may be used in combination of 2 or more type.

The polybasic acid may be a combination of the dibasic acid and a tribasic or higher polybasic acid such as trimellitic acid, methylcyclohexeric carboxylic acid, or pyromellitic acid.
Moreover, in addition to the said polybasic acid, the said polyester resin may use together monobasic acids, such as benzoic acid, crotonic acid, and pt-butyl benzoic acid, as needed.

  Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 3-methylpentanediol, 1,4-hexanediol, 1,6-hexanediol, Examples thereof include dihydric alcohols such as cyclohexanedimethanol, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, and bisphenol A propylene oxide adduct. The above dihydric alcohols may be used alone or in combination of two or more.

  The polyhydric alcohol may be a combination of the dihydric alcohol and a trihydric or higher polyhydric alcohol such as glycerin, trimethylolethane, trimethylolpropane, or pentaerythritol.

  The method for producing the polyester resin (b) is not particularly limited. For example, the polybasic acid or a monobasic acid used in combination as necessary and the polyhydric alcohol are publicly known. A method of esterification by a method, or a method of transesterifying the lower alcohol ester of the polybasic acid or the lower alcohol ester of the monobasic acid used in combination as necessary with the polyhydric alcohol by a known method. It is done.

The (b) polyester resin has a number average molecular weight of 7,000 to 30,000.
When a polyester resin having a number average molecular weight of less than 7000 is used, since the elongation of the resin coating film is reduced, there is a problem that the adhesion of the resin coating film is lowered and the resin is easily peeled off. On the other hand, when a polyester resin having a number average molecular weight of more than 30,000 is used, when an organic solvent is used as a solvent for a resin film-forming coating, the polyester resin is difficult to dissolve in the organic solvent. There is a problem that it becomes difficult to form. (B) The number average molecular weight of the polyester resin is preferably 8000 to 20000.

The (b) polyester resin has a glass transition temperature of −20 ° C. or higher.
When a polyester resin having a glass transition temperature of less than −20 ° C. is used, after a resin coating is formed on one side of an aluminum alloy plate, the resulting resin-coated aluminum alloy plate is wound around a coil. There exists a problem that the resin coating film of an alloy plate adheres to the aluminum alloy plate of the non-coating surface which contacts, ie, blocking performance worsens.
The glass transition temperature of said (b) polyester resin becomes like this. Preferably it is -20-80 degreeC, More preferably, it is -10-40 degreeC.

  Here, the blocking performance will be described. The blocking property means that two resin-coated aluminum alloy plates each having a resin coating formed on one side are formed by one resin-coated aluminum alloy plate and the other resin-coated aluminum alloy plate. Adhesion between the resin coating of one resin-coated aluminum alloy plate and the bare surface of the other resin-coated aluminum alloy plate when they are stacked so that they are in contact with the non-formed aluminum alloy plate surface (bearing surface) Refers to the difficulty of sticking. And, the blocking performance of the resin-coated aluminum alloy plate is good when the resin coating film of one resin-coated aluminum alloy plate and the bare surface of the other resin-coated aluminum alloy plate do not stick after overlapping Point to. That the resin-coated aluminum alloy plate has poor blocking performance refers to the case where the resin coating film of one resin-coated aluminum alloy plate and the bare surface of the other resin-coated aluminum alloy plate are adhered after superposition. In the production line, since the production of the resin-coated aluminum alloy plate is usually performed while winding the resin-coated aluminum alloy plate after production on the coil, in the resin-coated aluminum alloy plate produced while winding on the coil, It is essential that the blocking performance is good.

  (C) The amino resin is a methylolated amino resin obtained by an addition condensation reaction of an amino compound having an amino group such as melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, dicyandiamide and the aldehyde, or methylolated amino An alkyl etherified methylolamino resin obtained by etherifying a resin.

  Examples of the aldehyde related to the methylolated amino resin include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. In the alkyl etherified methylol amino resin, the alcohol used for the etherification of the methylolated amino resin is methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, Examples thereof include 2-ethylbutanol and 2-ethylhexanol.

  When the total content of the (a) epoxy resin, the (b) polyester resin, and the (c) amino resin is 100 parts by mass, the resin mixture contains 70 to 98 parts by mass of the (a) epoxy resin. Parts, (b) 0-20 parts by mass of the polyester resin, and (c) 2-20 parts by mass of the amino resin.

  When the content of the (a) epoxy resin is less than 70 parts by mass, the coating film is easily deteriorated when exposed to a high-temperature and high-humidity environment, causing discoloration. On the other hand, when the content of the epoxy resin (a) exceeds 98 parts by mass, the coating film was not sufficiently cured, and the coating film was easily cracked during molding, and was exposed to a high-temperature and high-humidity environment. Sometimes the base aluminum corrodes, causing discoloration. (A) Content of an epoxy resin becomes like this. Preferably it is 80-95 mass parts.

When the total content is 100 parts by mass and the content of the (b) polyester resin exceeds 20 parts by mass, discoloration is likely to occur when exposed to a high-temperature and high-humidity environment.
Moreover, although the said (b) polyester resin does not need to contain, it is preferable to contain 1 mass part or more from the surface of the workability of a resin coating film. (B) The content of the polyester resin is preferably 1 to 10 parts by mass.

  Further, when the content of the (c) amino resin is less than 2 parts by mass, the resin coating film is not sufficiently cured, and the resin coating film is cracked or melted when exposed to a high temperature and high humidity environment. There is a problem. On the other hand, when the content of the (c) amino resin exceeds 20 parts by mass, the coating film is excessively cured and the flexibility is lowered, and the resin coating film is not cracked or peeled during drawing and ironing. There is a problem that arises. The content of the (c) amino resin is preferably 2 to 10 parts by mass.

  Further, the resin-coated aluminum alloy plate for a cylindrical case with a capacitor bottom, when the resin mixture is 100 parts by mass, the resin coating film is further added with 0.1 to 10 parts by mass of polyethylene wax and carnauba wax. It is preferable to contain 1 type (s) or 2 or more types among 0.1-10 mass parts or 0.1-10 mass parts of micro crostalin waxes (Claim 3).

In this case, cracking of the resin coating film during processing can be made less likely to occur while preventing the resin coating film from peeling off.
When the content of each of the above-mentioned waxes is below the lower limit of the above range, a special crack prevention effect may not be sufficiently obtained. On the other hand, when it exceeds the upper limit of the above range, the coating film may be easily peeled off.

In addition, the resin mixture before curing can contain various additives such as a curing accelerator, a pigment, a pigment dispersant, a plasticizer, a colorant, a coating film modifier, and a modifier, if necessary. .
Examples of the curing accelerator include phosphoric acid, sulfonic acid compounds, and amine neutralized products of sulfonic acid compounds.

Examples of the pigment include inorganic pigments such as titanium dioxide, zinc white, barium sulfate, calcium carbonate, talc, silica powder, aerosil, carbon black, aluminum paste, and various organic pigments.
Examples of the coating film preparation agent include a surface smoothing agent that improves the smoothness of the resin coating film, a lubricant, a thixotropic agent, an antifoaming agent, and a surfactant that prevents pinholes and repelling of the resin coating film. Can be mentioned.

  The thickness of the resin coating film is not particularly limited, but is usually 1 to 20 μm, preferably 5 to 10 μm because it is used for manufacturing a bottomed cylindrical case of an aluminum electrolytic capacitor.

  Further, the resin coating of the resin-coated aluminum alloy plate for a bottomed cylindrical case for a capacitor is coated with a paint for forming a resin coating containing the resin mixture on the surface of the chemical coating, and then baked. It is preferable to form by performing (Claim 2).

  In this case, the resin coating film is formed by coating the resin coating film-forming coating material on the surface of the chemical conversion film formed on the surface of the substrate and then baking it. It is formed by evaporating the solvent therein and thermally curing the resin mixture containing the epoxy resin, the polyester resin, and the amino resin.

The paint for forming a resin coating film contains a resin mixture containing the (a) epoxy resin, the (b) polyester resin, and the (c) amino resin. In addition, as described above, the resin coating film-forming coating material may contain various additives such as polyethylene wax, carnauba wax, microclostalline wax, and the same additives as described above. . And the said coating material for resin coating film formation is prepared by mixing the said resin mixture and the said additive contained as needed in a solvent, and making it melt | dissolve or disperse | distribute in this solvent.
It is preferable that content of the said resin mixture in the said coating material for resin film formation, ie, solid content concentration, is 20-60 mass%, More preferably, it is 25-50 mass%.

The solvent used for the resin coating film-forming paint is water or an organic solvent.
The organic solvent is not particularly limited, but is appropriately selected in consideration of the solubility of the resin and the evaporation rate when applied to a metal surface. Specific examples of the organic solvent include xylene, toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, Solvesso # 100, Solvesso # 150, butyl cellosolve, methylpropylene glycol, and methylpropylene glycol. Examples include acetate, methanol, ethanol, butanol, diacetone alcohol, and the like.
Moreover, the said solvent may be used individually by 1 type, or may be used in combination of 2 or more type.
The boiling point of the solvent is preferably 60 to 230 ° C, particularly preferably 80 to 200 ° C.
Further, when water is used as the solvent for the resin coating film-forming paint, the polyester resin is dispersed in the aqueous solvent, but the resin mixture may be difficult to cure.

  The method for coating the resin coating film-forming paint on the surface of the chemical film is not particularly limited, and examples thereof include a bar coating method, a roll coating method, a spray method, and an immersion method.

  After the resin coating film-forming coating is applied to the surface of the chemical conversion film, the substrate on which the resin coating film-forming coating material is applied is heated and baked. If it is the temperature which evaporates and the said resin mixture thermosets, it will not restrict | limit in particular. The said heating temperature is 150-300 degreeC normally, Preferably it is 220-260 degreeC. Moreover, the heating time at the time of the said baking is 30 to 180 second, Preferably it is 40 to 100 second.

Example 1
In this example, 10 types of resin-coated aluminum alloy plates for bottomed cylindrical cases for capacitors (sample E1 to sample E10) are produced as examples of the resin-coated aluminum alloy plates for bottomed cylindrical cases for capacitors of the present invention. As a comparative example, 10 types of resin-coated aluminum alloy plates (sample C1 to sample C10) for a bottomed cylindrical case for a capacitor were produced and evaluated.

Resin-coated aluminum alloy plates (samples E1 to E10) for a bottomed cylindrical case for a capacitor of this example include a substrate made of an aluminum alloy plate, a chemical conversion film formed on the surface of the substrate, and the chemical conversion film It consists of a resin coating formed on the surface,
The resin coating film has (a) a number average molecular weight of 30,000 to 80,000, and a ratio h ₂ / h of absorbance h ₁ of 830 cm ⁻¹ and absorbance h ₂ of 750 cm ⁻¹ in FT-IR analysis of the coating film. ₁ is an epoxy resin of 0.1 to 10, (b) a polyester resin having a number average molecular weight of 7000 to 30000, a glass transition temperature of −20 ° C. or higher, and (c) an amino resin A cured product of the resin mixture
When the total content of the (a) epoxy resin, the (b) polyester resin, and the (c) amino resin is 100 parts by mass, the resin mixture contains 70 to 98 parts by mass of the (a) epoxy resin. Parts, (b) 0-20 parts by mass of the polyester resin, and (c) 2-20 parts by mass of the amino resin.

A method for producing a resin-coated aluminum alloy plate for a bottomed cylindrical case for a capacitor will be described.
First, an aluminum alloy plate made of A3003-H34 having a thickness of 0.26 mm, a width of 200 mm, and a length of 300 mm was prepared.
Moreover, 8 types of epoxy resins AH shown in Table 1 were prepared as an epoxy resin which comprises a resin coating film.
Moreover, five types of polyester resins a to e shown in Table 2 were prepared as polyester resins constituting the resin coating film.
Moreover, Sumimar M-40S (made by Sumitomo Chemical Co., Ltd.) was prepared as an amino resin constituting the resin coating film.

  In addition, the gel permeation chromatography (GPC, polystyrene conversion) was used for the measurement of the number average molecular weight of resin. Further, the glass transition temperature of the resin was measured using a differential scanning calorimeter at a heating rate of 20 ° C./min.

First, the aluminum alloy plate was immersed in a commercially available weak alkaline degreasing agent fine cleaner 4377 (manufactured by Nihon Parkerizing, 10 g / L, 65 ° C.) for 1 minute, washed with water and degreased. Next, degreased aluminum alloy plate was added to a solution of 42 ° C. in a mixed solution of 30 g of Alsurf 401 (manufactured by Nippon Paint Co., Ltd.) and 3 g of Alsurf 41 (manufactured by Nihon Paint Co., Ltd.) to a total volume of 1 liter. By immersing for 20 seconds, a phosphoric acid chromate treatment was performed to obtain an aluminum alloy plate on which a chemical conversion film was formed. At this time, the basis weight of the phosphoric acid chromate treatment was 15 mg / m ^{2 in} terms of chromium.

  Then, the coating material for resin film formation which melt | dissolved the resin mixture which mixed the epoxy resin, the polyester resin, and the amino resin with the compounding quantity shown in Table 3 using xylene as a solvent was obtained. Next, this paint for forming a resin coating film is applied to one surface of an aluminum alloy plate on which a chemical conversion film has been formed by a bar coating method, heated in an electric furnace at 260 ° C. for 1 minute, then removed from the furnace and released. It cooled and obtained the resin-coated aluminum alloy plate (Sample E1-Sample E10, Sample C1-Sample C10). At this time, the number of bars was selected so that the film thickness of the resin coating film after heating was 6 μm.

Next, the obtained resin-coated aluminum alloy plate was subjected to a blocking test, a drawing and ironing test, and a retort test to evaluate the characteristics. The results are shown in Table 4.
<Blocking test>
In the blocking test, 5 pieces of resin-coated aluminum alloy plates were cut into 50 mm × 50 mm, overlapped so that the formation surface of the resin coating and the bare surface overlapped, and a load of 1 kg was applied from above. After being stored in an environment of 50 ° C. and 90% RH for 3 days, adhesion between the plates was observed. When the load was removed, the blocking performance was good if there was no sticking on all five plates, and the blocking performance was poor if even one of them was stuck.

<Drawing and ironing processing test>
In the drawing and ironing test, the resin-coated aluminum alloy plate obtained as described above was cut into a circle having a diameter of 140 mm, and then press oil G-6284M (Nippon Tool Oil) was applied to both sides of the resin-coated aluminum alloy plate. Was applied to the outer surface of the resin coating film, and was drawn and ironed using a drawing and ironing machine to form a cylinder with a diameter of 65 mm and a height of 135 mm. . The ironing rate was 50%.
The molded press oil was degreased by exposure to trichlene vapor for 10 minutes.

  The resin film after drawing and ironing was observed with a microscope with a magnification of 100 times, and evaluation was made on the case where neither cracking nor peeling was observed in the resin film within 5 mm from the end portion. The case where cracks were observed was evaluated as “x (crack)”, and the case where peeling was observed on the resin coating film was evaluated as “x (peel)”. The case where the resin-coated aluminum alloy plate broke during processing was evaluated as “x (break)”. A case where the evaluation is ○ is passed, and a case where the evaluation is × is rejected.

<Retort test>
In the retort test, the pressed product after the drawing and ironing processing test was exposed to water vapor at 121 ° C. for 16 days in a steam kiln. Discoloration of the resin coating after the retort test, and observation with a microscope with a magnification of 100 times, when the resin coating is not observed to pass (evaluation “◯”), discoloration and peeling are observed on the resin coating The case where the expansion of cracks was observed was evaluated as a failure (evaluation “x”).

As is known from Table 4, Sample E1 to Sample E10 as examples showed good results in all items of the blocking test, drawing and ironing test, and retort test.
Thus, according to the present invention, the drawing and ironing workability is good, the resin coating film is not cracked during processing, and no peeling occurs between the aluminum alloy plate and the resin coating film. It can be seen that it is possible to provide a resin-coated aluminum alloy plate for a bottomed cylindrical case for a capacitor that does not cause deterioration of the coating film and corrosion of the underlying aluminum even in a rough environment.

Further, as is known from Table 4, the sample C1 as a comparative example has (a) the number average molecular weight of the epoxy resin is lower than the lower limit of the present invention, and h ₂ / h ₁ is lower than the lower limit of the present invention. Coating film peeling occurred in the drawing and ironing test, and discoloration occurred in the retort test.
Further, in sample C2 as a comparative example, (a) h ₂ / h ₁ of the epoxy resin exceeded the upper limit of the present invention, so that the coating film deteriorated and discoloration occurred in the retort test.

  Sample C3 as a comparative example has (a) the number average molecular weight of the epoxy resin exceeds the upper limit of the present invention, so that the coating film is insufficiently cured and the resistance to harsh environment is reduced. The film deteriorated and discolored.

Sample C4 as a comparative example has (c) the amino resin content exceeding the upper limit of the present invention, so that the flexibility of the coating film is reduced, and in the drawing and ironing test, coating film cracking occurs, and the retort In the test, the aluminum substrate corroded and discolored.
Moreover, since the content of (b) polyester resin exceeded the upper limit of this invention, the sample C5 as a comparative example fell resistance to severe environments, the coating film deteriorated in the retort test, and the discoloration generate | occur | produced.

Samples C6 and C8 as comparative examples have (a) the content of the epoxy resin is lower than the lower limit of the present invention, so that the resistance to harsh environments is reduced, and the coating film is deteriorated and discolored in the retort test. Occurred.
Sample C7 as a comparative example has (a) the content of the epoxy resin exceeds the upper limit of the present invention, and (c) the content of the amino resin is lower than the lower limit of the present invention. Insufficient, the film peeling occurred in the drawing and ironing processing test, the resistance to harsh environment decreased, and the film deteriorated and discolored in the retort test.

Sample C9 as a comparative example has (a) the number average molecular weight of the epoxy resin below the lower limit of the present invention, and (b) the number average molecular weight of the polyester resin exceeds the upper limit of the present invention, and the glass transition point. However, since it is below the lower limit of the present invention, the resin coating film and the opposite bare surface were stuck at the time of coating, and the blocking performance was rejected. In addition, discoloration occurred in the retort test.
Sample C10 as a comparative example is (b) the number average molecular weight of the polyester resin is lower than the lower limit of the present invention, so that the flexibility of the coating film is reduced, and in the drawing and ironing processing test, coating film cracking occurs. In the retort test, the aluminum substrate corroded and discolored.

Claims (3)

A substrate made of an aluminum alloy plate, a chemical conversion film formed on the surface of the substrate, and a resin coating film formed on the surface of the chemical conversion film,
The resin coating film has (a) a number average molecular weight of 30,000 to 80,000, and a ratio h ₂ / h of absorbance h ₁ of 830 cm ⁻¹ and absorbance h ₂ of 750 cm ⁻¹ in FT-IR analysis of the coating film. ₁ is an epoxy resin of 0.1 to 10, (b) a polyester resin having a number average molecular weight of 7000 to 30000, a glass transition temperature of −20 ° C. or higher, and (c) an amino resin A cured product of the resin mixture
When the total content of the (a) epoxy resin, the (b) polyester resin, and the (c) amino resin is 100 parts by mass, the resin mixture contains 70 to 98 parts by mass of the (a) epoxy resin. Part (b) 0-20 parts by mass of the polyester resin, and (c) 2-20 parts by mass of the amino resin.   2. The capacitor according to claim 1, wherein the resin coating film is formed by coating a resin film-forming coating material containing the resin mixture on the surface of the chemical conversion film and then baking the resin coating film. Resin-coated aluminum alloy plate for bottomed cylindrical cases.   In Claim 1 or 2, when the said resin mixture is 100 mass parts, 0.1-10 mass parts of polyethylene waxes, 0.1-10 mass parts of carnauba wax, or micro crostalin is added to the said resin coating film. A resin-coated aluminum alloy plate for a capacitor-bottomed cylindrical case, comprising one or more of 0.1 to 10 parts by mass of wax.