JP2013239550A - Aluminum resin covering material for capacitor case, capacitor case arranged by use thereof, capacitor with capacitor case, and method for manufacturing aluminum resin covering material for capacitor case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an aluminum resin covering material for a capacitor case which is superior in formability, coating film adhesion, insulating property, resistance to high-temperature water and chemical resistance, and further excellent in safety and environment; a manufacturing method thereof; a capacitor case arranged by use thereof; and a capacitor with such a capacitor case.SOLUTION: Provided is an aluminum resin covering material for a capacitor case which comprises: an aluminum base material; and a finished coating film which is formed on at least one surface of the aluminum base material without providing a chemical coating there. The finished coating film includes a polyacrylamide-based resin and glyoxal. The weight ratio of the polyacrylamide-based resin to the glyoxal is 100:100-250, and the finished coating film has a thickness of 1-20 μm. Also, a method for manufacturing the aluminum resin covering material, a capacitor case arranged by use thereof, and a capacitor with the capacitor case are provided.

Description

  The present invention uses an aluminum resin coating material for a capacitor case, which is excellent in moldability, coating film adhesion, insulation, high-temperature water resistance and chemical resistance, and also excellent in safety and environmental performance, and the aluminum resin coating material. The present invention relates to a capacitor case, a capacitor using the capacitor case, and a method of manufacturing the aluminum resin coating material for the capacitor case.

  Recently, a resin-coated aluminum alloy plate material that does not require an insulating resin coating after molding has been used as a capacitor case material. This capacitor case is typically cylindrical and has various height / diameter ratios. In order to form the aluminum alloy sheet into a cylindrical shape, a forming process is performed under severe conditions combining deep drawing and ironing. For this reason, when a general resin-coated aluminum alloy plate material used for building materials or the like is applied to the capacitor case material, cracks or peeling occurs in the resin layer, and sufficient insulation cannot be obtained. In particular, this tendency is remarkable in molding of a case having a large height / diameter ratio.

Patent Document 1 discloses a resin-coated aluminum material that is used for a capacitor case or the like and has excellent moldability, heat discoloration resistance, and high temperature and high humidity durability. This is because a nonporous anodic oxide film having a porosity of 5% or less is formed on the surface of pure aluminum or an aluminum alloy, and an epoxy resin having a number average molecular weight of 2,000 to 100,000 is formed on the upper layer via a silane coupling agent. It has a coated structure. The film thickness of the nonporous anodic oxide film is 30 to 200 nm, the coating amount of the silane coupling agent on the nonporous anodic oxide film is 0.5 to 10 mg / m ² , and the number of the epoxy resins It is described that the average molecular weight is preferably 5000 to 80000 and the coating thickness is preferably 1 to 20 μm.

  In Patent Document 2, (A) a film-forming resin composition containing a hydroxyl group-containing resin and a blocked isocyanate curing agent, (B) an inorganic compound surface-treated with a nitrogen-containing compound having an aldehyde compound adsorption ability, and (C) The titanium phosphate compound is contained in a proportion of 0.1 to 10 parts by weight of component (B) and 0.1 to 10 parts by weight of component (C) with respect to 100 parts by weight of component (A). A thermosetting coating composition for pre-coating and a pre-coated metal plate obtained by coating it on a metal plate are disclosed. Furthermore, as the hydroxyl group-containing resin contained in the component (A), a hydroxyl group-containing polyester resin having a hydroxyl value of 5 to 200 mg KOH / g and a number average molecular weight of 1,000 to 20,000 is described.

  However, the resin-coated aluminum coating materials of Patent Documents 1 and 2 are excellent in moldability because an epoxy resin or polyester resin is formed on the outermost surface, but are used in press molding after processing. A cleaning liquid is required to remove the pressed oil. When the cleaning liquid for this purpose remains, there is a problem that it reacts with the electrolytic solution in the capacitor case, the coating film is denatured and dissolved, and the reliability of the capacitor itself is impaired.

  In recent years, due to global environmental problems, there has been a movement to abolish the use of treatment liquids containing chromium components, and surface treatments that do not use chromium components have also been developed. However, in the treatment method using a non-chromate treatment solution that does not contain a chromium component, the aluminum oxide formed inside or on the outermost surface of the chemical conversion film at the same time as the formation of the chemical conversion film affects the decrease in adhesion to paints and films. Sometimes. For this reason, there is a drawback that it can be used only for specific purposes. Furthermore, it is pointed out that non-chromate treatment is expensive and expensive.

  Patent Document 3 discloses that a polyamide resin film is directly coated on the surface of an aluminum material without forming a chemical conversion film. However, since the film adhesion is inferior to that of the material on which the chemical conversion film is formed, it has been difficult to apply the capacitor case material.

JP 2010-125722 A JP 2007-204579 A Japanese Patent Laid-Open No. 10-303085

  The purpose of the present invention is excellent moldability that can be molded into a severe capacitor case, adhesion between the aluminum substrate and the finished coating film, and excellent insulation, high temperature water resistance, and chemical resistance after molding. Furthermore, since no chromate-based chemical conversion film is used, the environmentally friendly and excellent safety of the aluminum resin coating material for the capacitor case, the capacitor case using the aluminum resin coating material, the capacitor using the capacitor case, and An object of the present invention is to provide a method for producing an aluminum resin coating material for a capacitor case.

  The present invention is the aluminum resin coating material according to claim 1, comprising an aluminum base material and a finish coating film formed without providing a chemical conversion coating on at least one surface of the aluminum base material. The polyacrylamide resin and glyoxal are included, and the weight ratio of the polyacrylamide resin to glyoxal is polyacrylamide tree: glyoxal = 100: 100 to 250, and has a thickness of 1 to 20 μm. It was set as the aluminum resin coating material for capacitor cases.

  The present invention provides a capacitor case according to claim 2, wherein the aluminum resin coating material according to claim 1 is used. Furthermore, the present invention provides a capacitor according to claim 3, wherein the capacitor case according to claim 2 is used.

  The present invention according to claim 4, wherein an alkaline degreasing solution having a pH of 8 to 14 and a temperature of 40 to 80 ° C. is sprayed on the aluminum substrate for 1 to 120 seconds, or the aluminum substrate is sprayed on the alkaline degreasing solution for 1 to 120 seconds. A degreasing step for degreasing the aluminum substrate by dipping; a water washing step for washing the degreased aluminum substrate; and a polyacrylamide resin and glyoxal on at least one surface of the washed aluminum substrate; An application step of applying a coating composition in which the weight ratio of the polyacrylamide resin to glyoxal is polyacrylamide tree: glyoxal = 100: 100 to 250; and the temperature of the aluminum substrate coated with the coating composition is 180 to 300 Bake at 120 ° C. for 1 to 120 seconds to form a finished film with a thickness of 1 to 20 μm And as the manufacturing method of the aluminum resin coating material for capacitor case which comprises a; and finishing coating film forming step.

  The present invention according to claim 5 is the invention according to claim 5, wherein the acid treatment solution is sprayed for 1 to 120 seconds at a pH of 1 to 5 and a temperature of 5 to 60 ° C. for 1 to 120 seconds between the water washing step and the coating step. An acid cleaning step for acid cleaning the aluminum base material by immersing the aluminum base material in the acidic treatment liquid for 1 to 120 seconds; and a water washing step for water cleaning the acid cleaned aluminum base material. .

  According to a sixth aspect of the present invention, the degreasing step of degreasing the aluminum base and the rinsing step of rinsing the degreased aluminum base are repeated twice or more in the fourth or fifth aspect.

  The aluminum resin coating material for a capacitor case according to the present invention does not form a chemical conversion film, and has a high deep-drawing formability required for the capacitor case, adhesion between the aluminum substrate and the finished coating film, insulation after molding, High-temperature water resistance that can withstand harsh environments, and excellent chemical resistance that does not denature even when a cleaning solution or electrolyte is attached. Furthermore, since a chromate-based chemical conversion film is not used, the environment is excellent and the safety is also excellent. In addition, the capacitor case using this, as well as the capacitor using this capacitor case, similarly has excellent moldability, coating film adhesion, insulation, high temperature water resistance and chemical resistance, and good safety. Has environmental properties. Moreover, the aluminum resin coating material for capacitor cases according to the present invention can be manufactured easily and with good reproducibility.

1. Aluminum resin coating material for capacitor case The aluminum resin coating material for capacitor case according to the present invention includes a base material made of pure aluminum or an aluminum alloy, and a finished coating film formed without providing a chemical conversion film on at least one surface of the base material. With.

1-1. Aluminum substrate The aluminum substrate used in the present invention is a substrate made of pure aluminum or an aluminum alloy. Pure aluminum means 99 mass% or more of aluminum. As the aluminum alloy, A1100, A1200, A3003, A3004, A5052, A6063 and the like are preferably used. As for the tempering, Al material such as O material, H14, 24, and 36 material such as T6 material that has been subjected to age hardening treatment can be used as appropriate in accordance with molding. Moreover, although it does not specifically limit to the thickness of an aluminum base material, the thing about 0.1-1.2 mm thick is used suitably. Hereinafter, pure aluminum and an aluminum alloy are simply referred to as “aluminum”. In addition, metals other than aluminum can also be used for a base material.

1-2. Finished coating In the present invention, the finished coating is formed without providing a chemical conversion coating on at least one surface of the aluminum substrate. Because it does not use a chemical film containing a chromium component, it does not pollute the global environment and is excellent in safety. In addition, by using a finish coating film with an appropriate weight ratio of polyacrylamide resin and glyoxal, excellent moldability, coating film adhesion, insulation, high temperature water resistance and chemical resistance even in the absence of chemical conversion film Sex is obtained.

(I) Polyacrylamide resins In polyacrylamide resins, functional groups such as amino groups are bonded to aluminum oxides and hydrates existing on the surface of the aluminum substrate, and strong covalent bonds are formed between them. Is formed. In this way, the strong coating film adhesion between the finished coating film and the aluminum base material follows the deformation of the material even under severe molding conditions such as a capacitor case, resulting in excellent moldability and coating adhesion. It is done.

  As the polyacrylamide resin, a generally manufactured polyacrylamide resin may be used. Specifically, a resin mainly composed of a monomer having a polymerizable unsaturated double bond selected from acrylamide monomers such as acrylamide, methacrylamide, N-methylol acrylamide, diacetone acrylamide and the like can be given.

  The polyacrylamide resin used in the present invention may be a homopolymer of an acrylamide monomer or a copolymer of an acrylamide monomer and another copolymerizable monomer having a plurality of amide groups. Can do. For example, the proportion of the acrylamide monomer is preferably copolymerized at 30 parts by weight or more, more preferably 50 parts by weight or more, and even more preferably 80 parts by weight or more. Most preferred are homopolymers of acrylamide monomers. In the present invention, when a polyacrylamide copolymer is used, it is necessary to adjust the blending amount of glyoxal according to the content of the polyacrylamide resin in the copolymer.

  Examples of the monomer or oligomer that can be used for the copolymerization include alkyl (meth) acrylate, hydroxyalkyl (meth) acrylate, glycerin (meth) acrylate, ethylene glycol mono (meth) acrylate, caprolactone-modified hydroxyethyl (meth) acrylate, and epoxy. (Meth) acrylate, vinyl pyrrolidone, styrene, vinyl toluene, methyl styrene, allyl alcohol, alkyl vinyl ether, ethylene, propylene, butadiene, isoprene, α-olefin, acrylonitrile and the like.

  Of the above polyacrylamide resins, homopolymer polyacrylamide resins having many amide bonds in the molecule are preferred. Further, the weight average molecular weight of the polyacrylamide resin is preferably 10,000 to 10,000,000, and more preferably 500,000 to 3,000,000.

  The aluminum resin coating material for a capacitor case according to the present invention is immersed and washed in an organic solvent or a chemical in a cleaning process for removing press oil after molding, and the electrolytic solution contained in the capacitor case adheres to the case. Therefore, it is necessary to impart resistance to organic solvents and chemicals. In addition, since the capacitor itself is mounted on automobiles, home appliances, etc., it is exposed to a severe environment and the function of the capacitor must be maintained, so that the coating film itself needs to have environmental resistance. When a coating film is formed only with the above polyacrylamide resin, a part of the polyacrylamide resin is hydrolyzed in a high temperature and high humidity environment, thereby impairing the function of the capacitor. Therefore, it is necessary to add a predetermined amount of glyoxal described below according to the weight ratio of the polyacrylamide resin.

(Ii) Glyoxal As described above, the inventors of the present invention are excellent in addition to the moldability, coating film adhesion, and insulation of the polyacrylamide resin by containing a specific ratio of glyoxal to the polyacrylamide resin. It has been found that it is possible to further impart high chemical resistance and high-temperature water resistance.

  The reason for the effect of including the polyacrylamide resin and glyoxal is not clear, but it is considered that glyoxal has a function as a cross-linking agent that bonds polyacrylamide molecules to each other. That is, it is considered that a solid three-dimensional network structure in which polyacrylamide molecules are cross-linked by glyoxal is formed by setting the content of the polyacrylamide resin and glyoxal to the blending ratio of the present invention. Thereby, the chemical resistance and high-temperature water resistance of the finished coating film are improved, and it is considered that adhesion at the interface between the finished coating film and the aluminum substrate not treated with the chromium component is imparted.

  The blending ratio of the polyacrylamide resin and glyoxal is 100 to 250 parts by weight of glyoxal with respect to 100 parts by weight of the polyacrylamide resin, thereby improving chemical resistance and high-temperature water resistance. The mixing ratio of glyoxal with respect to 100 parts by weight of the polyacrylamide resin is preferably 125 to 200 parts by weight, and more preferably 150 to 175 parts by weight. When the mixing ratio of the glyoxal is less than 100 parts by weight, the amount of glyoxal for bonding the polyacrylamide molecules is insufficient, and sufficient coating adhesion, chemical resistance and high-temperature water resistance cannot be obtained in the finished coating film. On the other hand, if the mixing ratio of the glyoxal exceeds 250 parts by weight, the desired moldability cannot be obtained and it becomes uneconomical.

(Iii) Additives In the finished coating film, if necessary, rust preventives such as tannic acid, gallic acid, phytic acid, and phosphinic acid; leveling agents such as alkyl esters of polyalcohol; range that does not impair compatibility Additives such as a colorant such as a phthalocyanine compound, a surfactant such as an alkyl sulfate ester salt and an alkyl sulfosuccinate salt, and the like can be added.

2. Manufacturing method of aluminum resin coating material for capacitor case The manufacturing method of an aluminum resin coating material for a capacitor case according to the present invention includes a degreasing step of degreasing an aluminum base material; a water washing step of washing the degreased aluminum base material with water; An application step of applying a coating composition containing a polyacrylamide resin and glyoxal to at least one surface of an aluminum substrate; and a finish coating film that forms a final coating film by baking the aluminum substrate coated with the coating composition The aluminum base material surface to which the coating composition is applied is not treated with a treatment liquid containing a chromium component. And between the water washing process and the application | coating process, the acid washing process which acid-washes an aluminum base material; The water-washing process which water-washes the acid-washed aluminum base material may be further provided. Furthermore, you may repeat the degreasing process of degreasing an aluminum base material; and the water-washing process of washing the degreased aluminum base material twice or more.

2-1. Degreasing process In this invention, before apply | coating a coating composition to an aluminum base material, a degreasing process is performed to an aluminum base material. Thereby, even if it does not process with the process liquid containing a chromium component, the aluminum resin coating material excellent in the moldability and adhesiveness is obtained. Oil, grease, mineral oil, rolling oil, cutting oil, and other oily substances adhering to the surface of the aluminum base during the manufacturing process; impurities such as carbon seizing on the surface of the aluminum base during rolling and molding; Non-adherent materials such as fine aluminum powder adhering to the surface at the time of production may adversely affect the coating process of the coating composition and the finish coating film forming process, which are subsequent processes. Therefore, it is necessary to remove these stains, impurities and non-adhering materials by degreasing the aluminum base material. In the degreasing step, the aluminum substrate is sprayed with a degreasing solution, or the aluminum substrate is immersed in the degreasing solution. As the degreasing liquid, an alkaline degreasing liquid, an acidic degreasing liquid, a neutral degreasing liquid, a solvent degreasing liquid, or the like is used, and degreasing with an alkaline degreasing liquid excellent in oil removal performance and economy is preferable.

(I) Alkaline degreasing liquid An alkaline degreasing liquid is a liquid in which an alkali component is dissolved or dispersed in a solvent. The alkaline component has a function of saponifying a fatty acid which is one of the soil components and solubilizing it in a degreasing solution. Furthermore, the alkali component also has an action of etching the surface of the aluminum substrate. Due to the etching action of the alkali component, the solid matter adhering to the surface of the aluminum base material is detached together with a part of the base material, and the above-mentioned dirt, impurities and adhering matter are peeled off from the surface by foaming of hydrogen gas generated during the etching. Let Such an action of the alkali component cleans the surface of the aluminum substrate.

  As an alkaline component of the alkaline degreasing solution, a general alkaline degreasing agent such as an alkali metal salt or an ammonium salt is used. For example, strong basic compounds such as sodium hydroxide and potassium hydroxide; weak basic compounds such as sodium carbonate, sodium hydrogen carbonate, sodium silicate, sodium phosphate, sodium borate and the like. In order to adjust the pH of the alkaline degreasing solution, these alkali components are preferably used alone or in combination of two or more. As the alkali component, it is preferable to use sodium hydroxide, sodium carbonate, or sodium phosphate alone, and it is more preferable to use a mixture of two or more thereof. The content of the alkali component in the alkaline degreasing solution is 0.05 to 10 wt%, preferably 0.5 to 5 wt%. As the solvent for the alkaline degreasing solution, water, glycols and the like are used. In the present invention, it is particularly preferable to use water.

  An additive may be added to the alkaline degreasing solution. Examples of the additive include a surfactant for emulsifying oil adhering to the surface of the aluminum substrate, preventing re-adhesion, and promoting water wettability of the aluminum substrate. Examples of the surfactant include a cationic surfactant, an anionic surfactant, a nonionic (nonionic) surfactant, and an amphoteric surfactant, but are not particularly limited.

  Examples of the cationic surfactant include alkylamine salts such as octadecylamine acetate; quaternary ammonium salts such as alkyltrimethylammonium salts; and the like. Examples of the anionic surfactant include higher fatty acid salts such as sodium stearate and potassium oleate; alkyl sulfate esters such as sodium lauryl sulfate; alkyl benzene sulfonates such as sodium dodecylbenzene sulfonate; and the like. Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether; polyoxyethylene fatty acid esters such as polyethylene glycol monolaurate; and the like. Examples of the amphoteric surfactant include alkylbetaines such as amidopropyl betaine laurate. The above surfactants can be used alone or in combination of two or more. Among these surfactants, it is preferable to use a nonionic surfactant that is hardly affected by the pH of the alkaline degreasing solution or metal ions. In addition, it is preferable that content of surfactant in an alkaline degreasing liquid shall be 0.01-2 wt%.

As another additive, a chelating agent may be used in order to promote the removal of the cation component in the alkaline degreasing liquid and the dissolution of aluminum mixed in the liquid. Such a chelating agent is not limited as long as it can chelate aluminum ions or the like in the liquid, but it is an aminocarboxylic acid type chelating agent such as ethylenediaminetetraacetic acid (EDTA, hydroxyethylethylenediaminetriacetic acid). Carboxylic acid type chelating agents such as citric acid and gluconic acid are preferred, and these chelating agents can be used alone or in combination of two or more. The content of the agent is preferably 0.01 to 2 wt%.
An antifoaming agent such as a silicone oil emulsion; a solvent such as ethylene glycol; an antibacterial agent; a pH adjusting agent;

(Ii) Degreasing treatment The pH of the alkaline degreasing solution is adjusted to 8-14. By adjusting to such a pH range, etching of the aluminum base material and removal of oil on the surface are effectively performed. When the pH is less than 8, the degreasing property is inferior, and oil and the like remain on the surface of the aluminum base, so that the moldability and coating film adhesion at the time of processing are lowered. On the other hand, if the pH exceeds 14, it is not industrially stable, the amount of aluminum material dissolved is increased, and the surface becomes unstable. The preferable pH range of the alkaline degreasing solution is 10 to 14, and is more excellent in degreasing properties than pH 8 or more and less than 10. The pH adjustment of the alkaline degreasing solution can be achieved by dissolving or dispersing an alkaline component such as sodium hydroxide, sodium carbonate, sodium hydrogen carbonate or the like in a solvent such as water so as to have a predetermined concentration. The predetermined concentration needs to be set as appropriate depending on the type of the alkali component, the temperature of the degreasing solution, the solvent, and the like. For example, as the alkali component, a mixture of sodium carbonate and sodium hydroxide (sodium carbonate: sodium hydroxide by weight ratio = 4). 1), the pH can be adjusted to about 13 by setting the mixture concentration in the alkaline degreasing solution to 2 wt%.

  The temperature of the alkaline degreasing solution is adjusted to 40 to 80 ° C. By increasing the temperature of the degreasing liquid, the viscosity of oil and the like adhering to the surface of the aluminum base material is lowered, and solubilization in the degreasing liquid is promoted. Furthermore, the etching action on the aluminum substrate is improved, and the surface deposits can be easily removed. When the temperature of the alkaline degreasing solution is less than 40 ° C., the above effect cannot be obtained sufficiently and the degreasing property becomes insufficient. Further, it takes a long time for the degreasing treatment. On the other hand, when the temperature of the alkaline degreasing liquid exceeds 80 ° C., aluminum hydroxide and the like are easily generated, and a residue such as aluminum hydroxide adheres to the surface of the aluminum base material etched by the alkali component. As a result, the adhesion of the finished coating film is lowered, and the workability is also lowered due to the high temperature.

  As a degreasing treatment method, a spray method in which an alkaline degreasing solution is sprayed on an aluminum substrate, an immersion method in which an aluminum substrate is immersed in an alkaline degreasing solution, an aluminum substrate is immersed in an alkaline degreasing solution, and an ultrasonic wave is applied thereto. An ultrasonic method that radiates the light can be used. The dipping method and the spray method are preferable because they are excellent in degreasing properties on the surface of the aluminum base material and economically excellent. Among these, the spray method is more preferable than the dipping method because it is more excellent in degreasing properties and quickness. The ultrasonic method is particularly excellent in degreasing properties, but is inferior to the immersion method and the spray method in terms of complication of the apparatus and an increase in operation cost. In any process, the processing time is 1 to 120 seconds. When the treatment time is less than 1 second, sufficient degreasing properties cannot be obtained, and when it exceeds 120 seconds, the degreasing effect is saturated and further effects cannot be obtained, and it is not preferable from the viewpoint of productivity.

2-2. Water washing step Following the degreasing step with an alkaline degreasing solution, the aluminum substrate is subjected to a water washing step. By the water washing treatment, the alkaline degreasing liquid component existing in the vicinity of the surface of the aluminum base material is removed, and the pH in the vicinity of the surface can be rapidly lowered to the neutral region. As a result, it is possible to quickly remove the aluminum ions dissolved in the high pH alkaline degreasing solution from the surface of the aluminum base material without causing precipitation as aluminum hydrated oxide. For example, when the pH drop on the surface of the aluminum substrate becomes slow as in the case of wet treatment under high humidity, the aluminum ions dissolved in the alkaline degreasing solution are converted into aluminum hydrated oxide as the aluminum substrate surface. Deposited in the next step. In addition, dirt, impurities, non-adhering matters, and the like of the oily substance peeled from the aluminum base material surface are quickly removed from the vicinity of the aluminum base material surface by the water washing treatment.

  The washing time is appropriately set, but is preferably 2 seconds or longer. When the washing time is less than 2 seconds, the surfactant contained in the alkaline degreasing solution remains without being removed, and the acid washing solution or coating composition used in the acid washing or coating composition coating step is used. There is a risk of contamination. In order to remove the surfactant more reliably, it is more preferable that the washing time is 4 seconds or more. The upper limit of the washing time is not particularly limited, but is preferably 30 seconds or less. When the washing time exceeds 30 seconds, it is not preferable from the viewpoint of productivity.

  The washing temperature is preferably in the range of 0 to 60 ° C. If the washing temperature exceeds 60 ° C., pseudoboehmite-like aluminum hydrated oxide is generated and the appearance of the aluminum surface is impaired. In addition, the equipment cost is increased to make the apparatus compatible with high temperatures. On the other hand, if the washing temperature is less than 0 ° C., sufficient washing treatment cannot be performed because the treatment liquid freezes. Further, when a small amount of aluminum ions remain in the vicinity of the aluminum substrate surface, at such a low temperature, the aluminum ions are precipitated on the surface of the aluminum substrate as an aluminum hydrated oxide and mixed into the next step.

  As water used for the water washing treatment, pure water such as distilled water, ion exchange water, and reverse osmosis water is preferably used, but soft water or industrial water having an electric conductivity of 20 μS / cm or less can also be used.

  As the water washing treatment method, the same method as the degreasing treatment method can be used. That is, a spray method in which water is sprayed on an aluminum substrate, an immersion method in which an aluminum substrate is immersed in water, an ultrasonic method in which an aluminum substrate is immersed in water and an ultrasonic wave is emitted thereto, and the like can be used. The dipping method and the spray method are preferable because they are excellent in water washability on the surface of the aluminum base material and are economically excellent. Among these, the spray method is more preferable than the dipping method because it is more excellent in washing performance and quickness. The ultrasonic method is particularly excellent in water washability, but is inferior to the immersion method and the spray method in terms of complication of the apparatus and an increase in operation cost.

  In addition, you may repeat this cycle 2 times or more by making the said degreasing process and the water washing process into 1 cycle. This makes it possible to more completely remove dirt, impurities and non-sticking materials remaining on the surface of the aluminum substrate.

2-3. Acid Washing Step Following the water washing step, it is preferable to provide an acid washing step in which the aluminum substrate is acid washed with an acidic treatment liquid. Alkali insoluble residues such as oxides and hydroxides of aluminum and smuts (Mg (OH) ₂ ) that were formed on the surface of the aluminum substrate in the degreasing process with an alkaline degreasing solution and could not be removed in the water washing process were formed. Adversely affects the properties and adhesion. Therefore, by removing these oxide films and impurities by acid cleaning treatment, it is possible to add excellent high formability to the aluminum substrate.

(I) Acid treatment liquid The acid treatment liquid used in the acid washing step is a liquid obtained by dissolving or dispersing an acid component in a solvent. An acid and an acid salt are used as the acid component. Examples of the acid include sulfuric acid, nitric acid, phosphoric acid and the like. Examples of the acid salt include ammonium chloride and sodium hydrogen sulfate. In order to adjust the pH of the acidic treatment liquid, it is preferable to use these acid components alone or in combination of two or more. From the viewpoints of workability and stability of the treatment liquid, it is preferable to use sulfuric acid and nitric acid alone as the acid component, or a mixture thereof. Content of the said acid component in an acidic process liquid is 0.5-50 wt%, Preferably it is 3-30 wt%. In addition, water, glycols and the like are used as the solvent for the acidic treatment liquid, but water is preferably used.

  An additive may be added to the acidic treatment liquid. By adding a pickling aid containing an acid fluoride, the oxide film can be strongly removed. Moreover, in order to suppress precipitation of the ionized metal which exists in an acidic processing liquid, you may add chelating agents, such as phosphoric acid and EDTA. Further, a nonionic surfactant such as polyoxyethylene lauryl ether may be added as a pickling accelerator. Further, in order to prevent excessive dissolution of the aluminum substrate, a nitrogen-based pickling inhibitor such as pyridine or a sulfide-based pickling inhibitor such as butyl mercaptan may be added.

(Ii) Acid cleaning treatment The pH of the acid treatment solution is adjusted to 1-5. By setting it as such a pH range, the dissolution of the oxide film of an aluminum material and the removal of the surface smut are performed effectively. When concentrated sulfuric acid having a pH of less than 1 is used, the oxide film of the aluminum base material does not dissolve, and the load on the equipment increases, which is not preferable. On the other hand, when the pH exceeds 5, the removability of the oxide film and smut becomes insufficient, and the adhesiveness and the like of the finished coating film decrease when severe molding is performed. The pH adjustment of the acidic treatment liquid can be achieved by dissolving or dispersing acid components such as sulfuric acid and nitric acid in a solvent such as water so as to have a predetermined concentration. The predetermined concentration needs to be appropriately set depending on the type of the acid component, the temperature of the acidic treatment liquid, the solvent, etc. For example, the pH can be reduced to about 1 by using a 10 wt% sulfuric acid aqueous solution as the acid component.

  The temperature of the acidic treatment liquid is adjusted to 5 to 60 ° C. If the temperature of the acidic treatment liquid is less than 5 ° C., the above effect cannot be obtained sufficiently. On the other hand, when the temperature of the acidic treatment liquid exceeds 60 ° C., not only the surface of the aluminum substrate is etched excessively, the adhesion of the finished coating film is lowered, but also the workability is lowered due to the high temperature.

  As the acid cleaning treatment method, a spray method of spraying an acidic treatment liquid onto an aluminum substrate, an immersion method of immersing an aluminum substrate in an acidic treatment solution, and immersing an aluminum substrate in an acidic treatment solution and emitting ultrasonic waves thereto. An ultrasonic method can be used. The dipping method and the spray method are preferable because they are excellent in acid washability on the surface of the aluminum base material and economically. Among these, the spray method is more preferable than the dipping method because it is more excellent in acid cleaning properties and quickness. The ultrasonic method is particularly excellent in the acid cleaning property, but is inferior to the immersion method and the spray method in terms of the complexity of the apparatus and the increase in operation cost. In any process, the processing time is 1 to 120 seconds. If the treatment time is less than 1 second, sufficient acid washability cannot be obtained. On the other hand, if it exceeds 120 seconds, excessive dissolution of the aluminum base material occurs, which is not preferable from the viewpoint of productivity.

2-4. Water washing step Following the acid washing step with the acidic treatment liquid, it is preferable to subject the aluminum substrate to a water washing step. The acid component of the acid treatment liquid used in the acid cleaning process may be brought into the coating process of the coating composition in the next process and mixed into the finished coating film, resulting in a decrease in the repelling property and adhesion of the finished coating film. Because.

  The washing time is appropriately set, but is preferably 2 seconds or longer, and more preferably 4 seconds or longer. If the washing time is less than 2 seconds, the acid washing treatment liquid adhering to the surface of the aluminum base material cannot be sufficiently replaced, and the remaining acid washing treatment liquid is mixed in the coating process, resulting in gelation of the paint. May end up. The upper limit of the washing time is not particularly limited, but is preferably 30 seconds or less. When the washing time exceeds 30 seconds, it is not preferable from the viewpoint of productivity.

  The washing temperature is preferably in the range of 0 to 60 ° C. If the washing temperature exceeds 60 ° C., pseudoboehmite-like aluminum hydrated oxide is generated and the appearance of the aluminum surface is impaired. In addition, the equipment cost is increased to make the apparatus compatible with high temperatures. On the other hand, if the washing temperature is less than 0 ° C., sufficient washing treatment may not be performed because the treatment liquid freezes.

  As water used for the water washing treatment, pure water such as distilled water, ion exchange water, and reverse osmosis water is preferably used, but soft water or industrial water having an electric conductivity of 20 μS / cm or less can also be used.

  As the water washing treatment method, the same method as the degreasing treatment method can be used. That is, a spray method in which water is sprayed on an aluminum substrate, an immersion method in which an aluminum substrate is immersed in water, an ultrasonic method in which an aluminum substrate is immersed in water and an ultrasonic wave is emitted thereto, and the like can be used. The dipping method and the spray method are preferable because they are excellent in water washability on the surface of the aluminum base material and are economically excellent. Among these, the spray method is more preferable than the dipping method because it is more excellent in washing performance and quickness. The ultrasonic method is particularly excellent in water washability, but is inferior to the immersion method and the spray method in terms of complication of the apparatus and an increase in operation cost.

  In addition, you may repeat this cycle 2 times or more by making the said acid washing process and the subsequent water washing process into 1 cycle. This makes it possible to more completely remove dirt, impurities and non-sticking materials remaining on the surface of the aluminum substrate.

2-5. Coating composition application process Finish coating film on at least one surface of an aluminum base material that has undergone a water washing process after a degreasing process, or an acid base washing process after the water washing process and a further water washing process. A liquid coating composition for coating is applied (painted).

  Such a coating composition is prepared by dissolving or dispersing a polyacrylamide resin and glyoxal in a solvent. The content ratio of the polyacrylamide resin and glyoxal is a weight ratio of polyacrylamide resin: glyoxal = 100: 100 to 250. The total concentration of the polyacrylamide resin and glyoxal in the coating composition is preferably 1 to 30 wt% in consideration of the viscosity of the coating composition that is easy to apply. Moreover, you may contain the appropriate quantity of the said additive.

  The solvent to be used is not particularly limited as long as each component can be dissolved or dispersed. For example, aqueous solvents such as water; ketone solvents such as acetone; alcohol solvents such as ethanol; ethylene glycol alkyl ether solvents such as ethylene glycol monoethyl ether; diethylene glycol alkyl ether solvents such as diethylene glycol monobutyl ether; propylene glycol monomethyl And propylene glycol alkyl ether solvents such as ether; and esterified products of a series of glycol alkyl ether solvents such as ethylene glycol monoethyl ether acetate; among them, aqueous solvents are preferable, and water is particularly preferable.

  The coating composition is applied by a roll coater method, roll squeeze method, chemicoater method, air knife method, dipping method, spray method, electrostatic coating method, etc. However, a roll coater method is preferable. As the roll coater method, a gravure roll method with easy coating amount management, a natural coating method suitable for thick coating, a reverse coating method suitable for giving an aesthetic appearance to the coated surface, and the like can be employed. Moreover, a general heating method, a dielectric heating method, etc. are used for drying of a coating film.

2-6. Finishing coating film forming step Baking in the finishing coating film forming step is performed under the conditions that the baking temperature (the surface temperature of the reached plate) is 180 to 300 ° C and the baking time is 1 to 120 seconds. When the baking temperature in the finish coating film formation is less than 180 ° C. or the baking time is less than 1 second, the coating film is not sufficiently formed and the coating film adhesion is lowered. When the baking temperature exceeds 300 ° C. or the baking time exceeds 120 seconds, the finished coating film is denatured, and the strength and elongation of the coating film are remarkably reduced, and good moldability cannot be obtained.

The finished coating thickness should be 1 to 20 μm, preferably 5 to 15 μm. If the coating thickness is less than 1 μm, the desired insulation cannot be obtained, and if it exceeds 20 μm, the moldability, coating adhesion, insulation after processing, high-temperature water resistance, and chemical resistance are saturated and further improvement is achieved. It becomes uneconomical.
In addition, the said finish coating film is formed in the at least one surface of an aluminum base material. That is, the finished coating film may be formed only on one surface of the aluminum base material, or may be formed on both surfaces.

3. Capacitor Case The capacitor case according to the present invention is manufactured by subjecting the aluminum resin coating material for a capacitor case manufactured as described above to a plurality of molding steps. These molding processes include processes such as slitting after applying press molding oil to the surface of the aluminum resin coating material, and processes such as deep drawing. Through these molding steps, a capacitor case having a desired shape is produced.

4). Capacitor The capacitor according to the present invention is not particularly limited. For example, in a capacitor case manufactured as described above, a sheet of paper impregnated with an electrolyte solution is sandwiched and an aluminum foil with terminals attached thereto is accommodated, and a sealing rubber is inserted into the case opening The aluminum electrolytic capacitor is manufactured by caulking the lower part of the case.

  Hereinafter, preferred embodiments of the present invention will be specifically described based on the present invention examples and comparative examples, but the present invention is not limited thereto.

Invention Examples 1-32 and Comparative Examples 1-20
As the aluminum base material, 1100-H24 material having a thickness of 0.300 mm was used. As shown in Tables 1 to 7, the present invention examples 1 to 11 and comparative examples 1 to 20 are subjected to a degreasing process and a water washing process, and in the present invention examples 12 to 32, the acid washing process is further performed. A water washing step was performed. Table 8 shows the degreasing liquids A to I used in the degreasing process and the acid treatment liquids X to Z used in the acid cleaning process.

  Thus, the coating composition containing the resin component described in Tables 1-7 and the reaction component which reacts with this was apply | coated to the aluminum base material pretreated by the roll coater method. In addition, water was used as the solvent of the coating composition, and the total concentration of the resin component and the reaction component in the coating composition was appropriately selected within the range of 10 to 15 wt%.

  The polyacrylamide A used for the resin is a polyacrylamide homopolymer, the weight average molecular weight is 1,000,000, and the polyacrylamide B is a polyacrylic acid Na-acrylamide copolymer, and its weight average. The molecular weight was 200,000. For the measurement of the weight average molecular weight of these resins, gel permeation chromatography (GPC, polystyrene conversion) was used.

  Thus, the aluminum base material which apply | coated the coating composition is baked on the conditions shown in Tables 1-7 (attainment plate surface temperature (PMT), baking time), and the aluminum of the thickness shown in Tables 1-7 A sample of the resin coating material was prepared.

  About the aluminum resin coating material sample, the moldability, coating film adhesion, insulation, high temperature water resistance and chemical resistance were evaluated by the methods described below. The results are also shown in Tables 1-7.

(Formability A)
The aluminum resin coating material sample was molded into a capacitor case with a drawing ratio of 2.0 with the finished coating film side of the aluminum resin coating material sample as the outer surface by a five-stage drawing ironing method, and the finished coating film surface was visually observed and evaluated. In the molding, a volatile press oil having a kinematic viscosity of 1.6 mm ² / s was used.
(Formability B)
In order to evaluate even more severe formability, the same squeezing iron forming method and volatile press oil as formability A were used, the draw ratio was changed to 2.2, and a capacitor case was formed. Observed and evaluated.

In formability A and B, it evaluated based on the following evaluation criteria, (double-circle) and (circle) were set as the pass, and (triangle | delta) and x were set as disqualified.
(Double-circle): There is no change in the state of the surface of a finishing coating film before and behind shaping | molding.
○: The surface of the finished coating film after molding is slightly rough and cannot be confirmed by visual observation. However, when enlarged with a microscope, minute cracks can be confirmed on the surface of the finished coating film.
(Triangle | delta): The finished coating film surface after shaping | molding is rough, and a crack can be confirmed on the finishing coating film surface by visual observation.
X: The surface of the finished coating film after molding is rough, and further streaks are observed, and cracks can be confirmed on the finished coating film surface by visual observation.

(Coating adhesion A)
A tape peeling test was performed on the side wall portion of the capacitor case evaluated by the moldability A, and the peeling state of the finished coating film was evaluated.
(Coating adhesion B)
A tape peeling test was performed on the side wall portion of the capacitor case evaluated by the moldability B, and the peeling state of the finished coating film was evaluated.

In coating film adhesion A and B, it evaluated based on the following evaluation criteria, (circle) was set as the pass and x was set as the disqualification.
○: No peeling of the finished coating film was confirmed.
X: Peeling of the finished coating film was confirmed.

(Insulation)
In the insulation test, the surface resistance of the finished coating film of the aluminum resin coating material sample was measured according to JIS K 6911. Insulation was evaluated based on the following evaluation criteria, and ◎ and ○ were accepted and Δ and × were rejected.
A: Surface resistance of finished coating ≧ 10 ¹⁴ Ω
○: 10 ¹⁴ Ω> Surface coating surface resistance ≧ 10 ¹⁰ Ω
Δ: 10 ¹⁰ Ω> Surface resistance of finished coating ≧ 10 ⁶ Ω
×: 10 ⁶ Ω> surface resistance of the finished coating film

(High temperature water resistance)
In the high temperature water resistance test, the aluminum resin coating material sample was exposed to water vapor at 121 ° C. for 5 days. The discolored state of the finished coating film surface after the test was visually observed. The high temperature water resistance was evaluated on the basis of the following evaluation criteria, and ○ was accepted and Δ and × were rejected.
○: No discoloration was observed on the entire surface of the finished coating film.
Δ: Discoloration was confirmed on the entire surface of the finished coating film.
X: The finished coating film was dissolved and peeled off, and the coating film was not confirmed.

(chemical resistance)
In the chemical resistance test, the aluminum resin coating material sample was immersed in a γ-butyrolactone solution used as an electrolyte at 20 ° C. for 1 hour, and the state of dissolution and discoloration on the surface of the finished coating film was visually observed. Chemical resistance was evaluated based on the following evaluation criteria, and ◎ and ○ were accepted, and Δ and × were rejected.
A: Dissolution and discoloration were not confirmed on the entire surface of the finished coating film.
○: Dissolution is not confirmed on the entire surface of the finished coating film, and discoloration is confirmed in part, but it can withstand use as a product.
Δ: Dissolution was not confirmed on the entire surface of the finished coating film, but discoloration was confirmed on the entire surface.
X: Dissolution and discoloration were confirmed on the entire surface of the finished coating film.

  As shown in Tables 1 to 7, all of the inventive examples 1 to 32 passed the moldability (A and B), the film adhesion (A and B), the insulating property, the high-temperature water resistance, and the chemical resistance. It was. Further, in Examples 1 to 4 and 6 to 32 of the present invention, the moldability A for severe processing was excellent. Furthermore, in the inventive examples 12-14, 18-22, 25, 26, 28, 29, 31, 32, the moldability B in more severe processing was also excellent.

On the other hand, in Comparative Example 1, the degreasing treatment was carried out, but the finish coating film was not formed, so that the insulating property was not acceptable.
In Comparative Example 2, since polyacrylic acid was used as a resin component and glyoxal as a reaction component was not used, the evaluation excluding the insulating property was unacceptable.
In Comparative Example 3, since an epoxy resin was used as a resin component and glyoxal as a reaction component was not used, chemical resistance was unacceptable.
In Comparative Example 4, since a polyester resin was used as a resin component and glyoxal as a reaction component was not used, the high-temperature water resistance and chemical resistance were unacceptable.
Moreover, in Comparative Example 5, since polyamide resin was used as a resin component and glyoxal as a reaction component was not used, moldability B, coating film adhesion B, high-temperature water resistance and chemical resistance were unacceptable.
In Comparative Example 6, since the reaction component, glyoxal, was not contained, the insulating property, high-temperature water resistance and chemical resistance were unacceptable.
In Comparative Example 7, since the isocyanate was used instead of the reaction component glyoxal, the chemical resistance was unacceptable.
In Comparative Example 8, since the blending amount of glyoxal as a reaction component was small, coating film adhesion A and B, high temperature water resistance, and chemical resistance were unacceptable.
In Comparative Example 9, since the compounding amount of glyoxal which is a reaction component was large, the moldability B was unacceptable.
In Comparative Example 10, since the degreasing process was not performed, the coating film adhesion B was unacceptable.
In Comparative Example 11, since the degreasing liquid used in the degreasing step was an acid, the coating film adhesion B was unacceptable.
In Comparative Example 12, since the degreasing liquid used in the degreasing step was a hydrocarbon-based cleaning agent, the coating film adhesion B was unacceptable.
In Comparative Example 13, since water was used for the degreasing liquid used in the degreasing step, the coating film adhesion B was unacceptable.
In Comparative Example 14, since the treatment temperature was as low as 20 ° C. in the degreasing step, the coating film adhesion B was not acceptable.
In Comparative Example 15, since the treatment time was as short as 0.5 seconds in the degreasing step, the coating film adhesion B was unacceptable.
In Comparative Example 16, since the baking temperature was as low as 160 ° C., the coating film adhesion B was unacceptable.
In Comparative Example 17, since the baking temperature was as high as 320 ° C., the moldability A and B were unacceptable.
In Comparative Example 18, since the baking time was as short as 0.5 seconds, the coating film adhesion B and the chemical resistance were unacceptable.
In Comparative Example 19, since the baking time was as long as 150 seconds, the moldability A and B was unacceptable.
In Comparative Example 20, since the film thickness of the finished coating film was as thin as 0.5 μm, the insulating property was unacceptable.

  According to the present invention, high deep-drawing formability, adhesion between the aluminum base material and the finished coating film, insulation after molding, high-temperature water resistance that can withstand harsh environments, and non-denaturing even if a cleaning solution or electrolyte is attached There is provided an aluminum resin coating material for a capacitor case which has excellent chemical resistance and is excellent in environmental performance and safety because it does not use a chemical film containing a chromium component. In addition, the capacitor case using this, as well as the capacitor using this capacitor case, similarly has excellent moldability, coating film adhesion, insulation, high temperature water resistance and chemical resistance, and good safety. Has environmental properties. Furthermore, the manufacturing method which can manufacture the said aluminum resin coating | covering material for capacitor cases easily and with sufficient reproducibility is also provided.

Claims (6)

  An aluminum resin coating material comprising: an aluminum base material; and a finish coating film formed without providing a chemical conversion film on at least one surface of the aluminum base material, wherein the finish coating film comprises a polyacrylamide resin and glyoxal. And a weight ratio of the polyacrylamide resin and glyoxal is polyacrylamide resin: glyoxal = 100: 100 to 250, and has a thickness of 1 to 20 μm. .   A capacitor case using the aluminum resin coating material according to claim 1.   A capacitor using the capacitor case according to claim 2.   The aluminum substrate is sprayed with an alkaline degreasing solution having a pH of 8 to 14 at a temperature of 40 to 80 ° C. for 1 to 120 seconds, or the aluminum substrate is immersed in the alkaline degreasing solution for 1 to 120 seconds. A degreasing step for degreasing the material; a water washing step for washing the degreased aluminum substrate; and a polyacrylamide resin and glyoxal on at least one surface of the water-washed aluminum substrate, the polyacrylamide resin and glyoxal An application step of applying a coating composition having a weight ratio of polyacrylamide resin: glyoxal = 100: 100 to 250; and baking an aluminum substrate coated with the coating composition at a temperature of 180 to 300 ° C. for 1 to 120 seconds. A finishing coating film forming step for forming a finishing coating film having a thickness of 1 to 20 μm; Method for producing an aluminum resin coating material for capacitor case, which comprises.   Between the water washing step and the coating step, the aluminum substrate is sprayed with an acidic treatment solution at a pH of 1 to 5 at a temperature of 5 to 60 ° C. for 1 to 120 seconds, or the aluminum substrate is applied to the acidic treatment solution for 1 to 120. The aluminum resin coating material for a capacitor case according to claim 4, further comprising: an acid cleaning step of acid cleaning the aluminum base material by dipping for 2 seconds; and a water cleaning step of water cleaning the acid cleaned aluminum base material. Production method.   The manufacturing method of the aluminum resin coating material for capacitor cases of Claim 4 or 5 which repeats the degreasing process of degreasing the said aluminum base material; and the water washing process of washing the degreased aluminum base material with water twice or more.