JP5657417B2 - Electrodeposition method and electrodeposition apparatus - Google Patents

Description

  The present invention relates to an electrodeposition method and an electrodeposition apparatus.

  2. Description of the Related Art It is widely practiced to produce an electrical device component by applying an insulating paint on the surface of a conductive member such as metal. There are various methods for applying the paint, but when utilizing the fact that the member is conductive, the electrodeposition method is one of the options.

  For example, Patent Document 1 discloses a method for manufacturing a ring-shaped insulating coil plate having a step of forming an insulating coating layer on the surface of a ring-shaped conductive plate having a flat cross-sectional shape and a planar shape having an open portion. An insulating coating layer is disclosed that is formed by electrodeposition of a non-emulsion type cationic electrodeposition coating. An epoxy-based cationic electrodeposition coating is used as a specific coating, and an insulating coating layer having a substantially uniform thickness of 21 to 26 μm is obtained.

  Patent Document 2 discloses a suspension type electrodeposition coating composition containing a block copolymer polyimide having a siloxane bond in the molecular skeleton and an anionic group in the molecule as a resin component.

JP 2008-85077 A WO2008 / 139990 publication

  In the technique disclosed in Patent Document 1, an object to be deposited, which is obtained by cutting a flat plate into a ring shape, is simply immersed in an electrodeposition paint, and an electric current is applied to perform electrodeposition. The electrodeposition method is not devised at all, but it is described that a substantially uniform insulating coating layer is formed on the ring-shaped flat plate. Patent Document 2 describes that an insulating coating layer having an average thickness of 18 to 52 μm is formed on a circular copper wire by electrodeposition.

  The examples of electrodeposition disclosed in the above-mentioned Patent Documents 1 and 2 are those in which electrodeposition coating is performed on a planar object or wire, and for a three-dimensional object to be deposited. There is no disclosure or suggestion about uniform application in either document. Of the three-dimensional object to be deposited, it is considered that the coating thickness at the inner surface side of the concave shape (the shape having wall surfaces in at least three directions) is thinner than the other portions at the boundary between the two wall surfaces. However, techniques for responding to such concerns are not disclosed in Patent Documents 1 and 2.

  The present invention has been made in view of the above points, and the object of the present invention is to provide an electrodeposition method capable of sufficiently applying to the boundary between two wall surfaces on the inner surface side of a recessed shape. It is to provide.

  The electrodeposition method of the present invention is an electrodeposition method in which a paint is applied by electrodeposition to a conductive member having at least a bottom plate portion and two side plate portions extending upward from both ends of the bottom plate portion. A step of preparing an electrodeposition tank, a step of immersing the conductive member and a plurality of counter electrodes in the coating solution of the electrodeposition tank, and the conductive member and the counter electrode Including an application step of applying a paint by passing an electric current therebetween and a step of taking out the conductive member coated with the paint from the coating liquid, and the counter electrode is disposed so as to face the side plate portion And a boundary auxiliary portion arranged at a position closer to the boundary portion between the bottom plate portion and the side plate portion than the main plate portion.

  An electrodeposition apparatus according to the present invention is an electrodeposition apparatus that includes an electrodeposition tank, a plurality of counter electrodes, and a power source, and applies a paint to the conductive member by electrodeposition. The conductive member includes a bottom plate portion and the electrode plate. At least two side plate portions extending upward from both ends of the bottom plate portion, and the counter electrode includes a main plate portion disposed so as to face the side plate portion, the bottom plate portion and the It has a configuration that includes a boundary auxiliary portion disposed at a position close to the boundary portion with the side plate portion.

  Electrodeposition coating is performed on the conductive member having at least the bottom plate portion and the two side plate portions extending upward from both ends of the bottom plate portion using the counter electrode having the above configuration. It is possible to avoid that the coating thickness at the boundary portion becomes too thin as compared with other portions.

3 is a perspective view of a conductive member according to Embodiment 1. FIG. 2 is a perspective view in which counter electrodes are arranged before and after the conductive member according to Embodiment 1. FIG. It is the schematic of an electrodeposition apparatus. It is a figure which shows an example of an internal counter electrode. It is a figure which shows an example of an external counter electrode. 3 is a diagram illustrating a counter electrode according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating an arrangement of counter electrodes according to the first embodiment. It is a figure which shows the electroconductive member and counter electrode which concern on Embodiment 2. FIG. It is a figure which shows the electroconductive member and counter electrode which concern on Embodiment 3. FIG. It is a figure which shows the electroconductive member and counter electrode which concern on Embodiment 4. It is a figure which shows the electroconductive member and counter electrode which concern on Embodiment 5. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following drawings, components having substantially the same function are denoted by the same reference numerals for the sake of brevity.

(Embodiment 1)
<Application target>
In Embodiment 1, electrodeposition coating was performed on the groove-like conductive member 1 shown in FIG. The conductive member 1 has a shape in which two side plate portions 12 a and 12 b extend upward from both ends of the bottom plate portion 11. The bottom plate portion 11 and the side plate portions 12a and 12b are connected at a substantially right angle, and the corner portions forming 90 ° are corner portions 13a and 13b. The conductive member 1 is made by bending a metal plate.

  The material of the conductive member 1 which is a member to be electrodeposited according to the present embodiment is not particularly limited as long as it has conductivity, but from the viewpoint of conductivity, copper, copper alloy, copper grat aluminum, aluminum, zinc Examples thereof include plated iron, silver, gold, nickel, titanium, tungsten, etc. Among them, silver or copper is preferable. Moreover, even if it is an insulating product, the electrodeposition film | membrane by the composition for electrodeposition coating materials of this embodiment can be formed if what carried out the electroconductive process like plating on the surface.

<Electrodeposition paint>
The electrodeposition paint used in this embodiment is a paint described in Patent Document 2. Specifically, this electrodeposition coating composition comprises a block copolymer polyimide having a siloxane bond (—Si—O—) in the molecular skeleton (that is, the main chain of the polyimide) and an anionic group in the molecule. Contains as a resin component.

  Here, the “block copolymerized polyimide” is a tetracarboxylic dianhydride and a diamine that are heated to form an imide oligomer (first stage reaction), and then the same as the tetracarboxylic dianhydride described above. Alternatively, a different tetracarboxylic dianhydride or / and a diamine different from the above diamine is added to react (second stage reaction) to prevent random copolymerization caused by exchange reaction between amic acids. It means a copolymerized polyimide obtained.

  In the block copolymer polyimide containing a siloxane bond in the main chain of the polyimide and having an anionic group in the molecule, the siloxane bond in the main chain is a siloxane bond derived from a tetracarboxylic dianhydride component, or a diamine. Although it may be a siloxane bond derived from a component, it is preferably a siloxane bond derived from a diamine component, and usually a diamine compound having a siloxane bond (-Si-O-) in the molecular skeleton at least at a part of the diamine component. (Hereinafter, it may be referred to as “siloxane bond-containing diamine”) is used.

  The siloxane bond-containing diamine can be used without particular limitation as long as it can be imidized with tetracarboxylic dianhydride. For example, bis (4-aminophenoxy) dimethylsilane, 1,3-bis (4 -Aminophenoxy) -1,1,3,3-tetramethyldisiloxane and the general formula (I):

  (Wherein, each of four R's independently represents an alkyl group, a cycloalkyl group, a phenyl group, or a phenyl group substituted with 1 to 3 alkyl groups or alkoxyl groups, and l and m are each Independently represents an integer of 1 to 4, and n represents an integer of 1 to 20.). The compound represented by the general formula (I) includes a single compound in which n is 1 or 2, and polysiloxane diamine.

  In each of the four Rs in formula (I), the alkyl group and the cycloalkyl group preferably have 1 to 6 carbon atoms, more preferably 1 to 2 carbon atoms. In the phenyl group substituted with 1 to 3 alkyl groups or alkoxyl groups, 1 to 3 alkyl groups or alkoxyl groups may be the same or different when they are 2 or 3 May be. Moreover, as for an alkyl group and an alkoxyl group, C1-C6 is respectively preferable, and 1-2 are more preferable.

  In the compound represented by the general formula (I), four Rs in the formula are preferably an alkyl group (particularly a methyl group) or a phenyl group, and in the formula, l and m are 2 to 3, and n is 5 Polysiloxane diamines in ˜15 are preferred.

  Preferred examples of the polysiloxane diamine include bis (γ-aminopropyl) polydimethylsiloxane (in the formula (I), l and m are 3 and 4 R are methyl groups), bis (γ-amino). Propyl) polydiphenylsiloxane (in the formula (I), l and m are 3, and four R are phenyl groups).

  As the siloxane bond-containing diamine, any one compound may be used alone, or two or more kinds may be used in combination. In addition, a commercial item may be used for this siloxane bond containing diamine, and what is sold from Shin-Etsu Chemical Co., Toray Dow Corning, Chisso can be used as it is. Specifically, KF-8010 (bis (γ-aminopropyl) polydimethylsiloxane: amino group equivalent of about 450), X-22-161A (bis (γ-aminopropyl) polydimethylsiloxane: Shin-Etsu Chemical Co., Ltd .: Amino group equivalent of about 840) and the like, and these are particularly preferable.

  The anionic group is a group that becomes an anion in the solvent (described later) of the electrodeposition composition, and is preferably a carboxyl group or a salt thereof, and / or a sulfonic acid group or a salt thereof. The anionic group may be contained in a siloxane-containing diamine or a tetracarboxylic dianhydride component, but it is preferable to use a diamine having an anionic group as one of the diamine components. Such an anionic group-containing diamine is preferably an aromatic diamine in order to improve the heat resistance of the polyimide, the adhesion to the electrodeposit, and the degree of polymerization. That is, aromatic diaminocarboxylic acid and / or aromatic diaminosulfonic acid is preferable. Examples of the aromatic diaminocarboxylic acid include 3,5-diaminobenzoic acid, 2,4-diaminophenylacetic acid, 2,5-diaminoterephthalic acid, 3,3′-dicarboxy-4,4′-diaminodiphenylmethane, 3,5-diaminoparatoluic acid, 3,5-diamino-2-naphthalenecarboxylic acid, 1,4-diamino-2-naphthalenecarboxylic acid and the like can be mentioned. As aromatic diaminosulfonic acid, 2,5-diamino Examples thereof include benzenesulfonic acid, 4,4′-diamino-2,2′-stilbene disulfonic acid, o-tolidine disulfonic acid, and the like. Among these, 3,5-diaminobenzoic acid is particularly preferable. Such an anionic group-containing aromatic diamine may be used alone or in combination of two or more. When the siloxane bond-containing diamine has an anionic group, the diamine component may be only the siloxane bond-containing diamine.

  As the diamine component, in addition to the above-described siloxane bond-containing diamine and diaminocarboxylic acid, another diamine may be further contained. As such a diamine, an aromatic diamine is usually used in order to improve the heat resistance of the polyimide, the adhesion to the electrodeposit, and the degree of polymerization. Examples of such aromatic diamines include m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 4,4′-diamino-3,3′-dimethyl-1,1′-biphenyl, 4, 4'-diamino-3,3'-dihydroxy-1,1'-biphenyl, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfone, 4,4'-diamino Diphenylsulfone, 4,4′-diaminodiphenyl sulfide, 2,2-bis (4-aminophenyl) propane, 2,2-bis (4-aminophenyl) hexafluoropropane, 1,3-bis (4-aminophenoxy) ) Benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) bif Nyl, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, bis [4- (3-aminophenoxy) Phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, 2,6-diaminopyridine, 2,6-diamino-4-methylpyridine, 4,4 ′-(9-fluorenylidene) dianiline, α, α-bis (4-aminophenyl) -1,3-diisopropylbenzene can be mentioned, among which bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] Sulfone is more preferred.

  In the total diamine component, the proportion of the siloxane bond-containing diamine is preferably 5 to 90 mol%, more preferably 15 to 50 mol%. When the siloxane bond-containing diamine unit is less than 5 mol%, the electrodeposition coating film of polyimide is inferior in elongation, and it becomes difficult to obtain sufficient flexibility, and peeling and cracking are liable to occur. Further, the ratio of the aromatic diaminocarboxylic acid or a salt thereof is preferably 10 to 70 mol% (however, the total of the siloxane bond-containing diamine and the aromatic diaminocarboxylic acid or a salt thereof is 100 mol% or less, Moreover, the 3rd diamine component may be included as above-mentioned.

  On the other hand, as a tetracarboxylic dianhydride component in polyimide, aromatic tetracarboxylic dianhydride is usually used from the viewpoint of heat resistance of polyimide and compatibility of polysiloxane diamine. For example, pyromellitic dianhydride 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride , Bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride Products, 3,3 ′, 4,4′-biphenylsulfone tetracarboxylic dianhydride, etc. Among these, heat resistance of polyimide, adhesion to electrodeposits, polysiloxane diamine 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 3,3 ′, 4,4 ′ from the viewpoint of compatibility and polymerization rate -Benzophenone tetracarboxylic dianhydride and 3,3 ', 4,4'-biphenylsulfone tetracarboxylic dianhydride are particularly preferred. These exemplary tetracarboxylic dianhydrides may be used alone or in combination of two or more.

  The polyimide used as the resin component of the composition is soluble in a water-soluble polar solvent (for example, dissolved in N-methyl-2-pyrrolidone (NMP) at a concentration of 5 wt% or more, preferably 10 wt% or more. It is a block copolymerized polyimide. The block copolymerized polyimide and the production method thereof are already known (for example, described in Patent Documents 8 and 9), and the polyimide used in the present invention is a known method using the diamine component and tetracarboxylic dianhydride. Can be manufactured by application. A water-soluble polar solvent is used for the polymerization reaction. Specifically, N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP) , Γ-butyrolactone (γBL), anisole, tetramethylurea, and sulfolane, and NMP is preferable. In such a water-soluble polar solvent, tetracarboxylic dianhydride and diamine are added in an approximately equimolar amount (preferably in a molar ratio of 1: 0.95 to 1.05) and heated in the presence of a catalyst to perform a dehydration imidization reaction. To produce a polyimide solution directly. The catalyst is a two-component composite catalyst composed of a lactone and a base or a crotonic acid and a base. The lactone is preferably γ-valerolactone, and the base is preferably pyridine or N-methylmorpholine. The mixing ratio of lactone or crotonic acid and the base is 1: 1 to 5 (molar equivalent), preferably 1: 1 to 2. In the presence of water, it acts as an acid-base double salt, exhibits catalytic action, completes imidization, and water comes out of the reaction system (preferably, a polycondensation reaction is performed in the presence of toluene, and water produced is When it is removed from the reaction system together with toluene, the catalytic action is lost. The amount of the catalyst used is usually 1/100 to 1/5 mol, preferably 1/50 to 1/10 mol, relative to tetracarboxylic dianhydride. The mixing ratio (acid / diamine) of tetracarboxylic dianhydride and diamine to be used for the imidization reaction is preferably about 1.05 to 0.95 in terms of molar ratio as described above. The concentration of the acid dianhydride in the entire reaction mixture at the start of the reaction is preferably about 4 to 16% by weight, the concentration of lactone or crotonic acid is preferably about 0.2 to 0.6% by weight, and the concentration of the base Is preferably about 0.3 to 0.9% by weight, and the concentration of toluene is preferably about 6 to 15% by weight. The reaction temperature is preferably 150 ° C to 220 ° C. Moreover, reaction time is not specifically limited, Although it changes with the molecular weight etc. of the polyimide which is going to manufacture, it is about 180 to 900 minutes normally. Moreover, it is preferable to perform reaction under stirring.

  An acid dianhydride and a diamine are heated in a water-soluble polar solvent in the presence of the above-mentioned two-component acid catalyst to form an imide oligomer, and then an acid dianhydride or / and a diamine are added to the second diamine oligomer. A polyimide can be produced by a step reaction. By this method, random copolymerization due to an exchange reaction occurring between amic acids can be prevented. As a result, a block copolymerized polyimide can be produced. The solid concentration at this time is preferably 10 to 40% by weight, more preferably 20 to 30% by weight.

  The polyimide preferably has an inherent logarithmic viscosity (25 ° C.) of 5000 to 50000 mPas, more preferably 5000 to 15000 mPas when 20 wt% NMP solution is used.

  Further, the weight average molecular weight (Mw) of the block copolymerized polyimide used as the resin component is preferably 20,000 to 150,000, particularly preferably 45,000 to 90,000 in terms of polystyrene. When the weight average molecular weight of the polyimide is less than 20,000, the heat resistance of the electrodeposition coating film tends to decrease, the coating film surface becomes rough, and the aesthetics and withstand voltage characteristics tend to decrease. On the other hand, when the weight average molecular weight is larger than 150,000, the polyimide resin has water repellency with respect to water and easily causes gelation in the electrodeposition liquid (paint) manufacturing process.

  Moreover, about a number average molecular weight (Mn), 10,000-70,000 are preferable in polystyrene conversion, More preferably, it is 20,000-40,000. When the number average molecular weight is less than 10,000, the electrodeposition efficiency tends to decrease, and the heat resistance and voltage resistance may decrease. Here, the molecular weight of polyimide is a molecular weight in terms of polystyrene measured by GPC, and is a value measured by using HLC-8220 manufactured by Tosoh Corporation as a GPC device and SCkgel Super-H-RC as a column.

  The electrodeposition paint composition of this embodiment is a suspension type electrodeposition paint. In the present invention, the “suspension type electrodeposition coating composition” is measured by using a particle size analyzer ELS-Z2 (manufactured by Otsuka Electronics Co., Ltd.) with an electrophoretic light scattering method (Laser Doppler method). The suspension-type electrodeposition coating composition in which the particle diameter of the polyimide particles analyzed by the cumulant analysis method is 0.1 to 10 μm and the standard deviation of the particle diameter is 0.1 to 8 μm.

  The intrinsic relative viscosity of the suspension type electrodeposition coating composition of the present embodiment is preferably 5 to 100 mPas. The composition in the above viscosity range is suitable as a composition for electrodeposition coatings that can provide a film thickness of 30 μm or more and a uniform film thickness. The inherent logarithmic viscosity was measured using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.).

  In the electrodeposition coating composition of this embodiment, the average particle size of the particles made of block copolymerized polyimide is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm. When the average particle size is less than 0.1 μm, the Coulomb efficiency is lowered and the withstand voltage performance is lowered due to overvoltage. On the other hand, when the thickness exceeds 5 μm, the coulombic efficiency is controlled and the leakage current is increased due to the increase in particle size, thereby causing a decrease in withstand voltage performance. Therefore, the particle size range in which the control of the coulomb efficiency and the maintenance of the withstand voltage performance are balanced is preferably 0.5 to 5 μm.

Specifically, the above-described electrodeposition coating composition is produced as follows.
First, a post-polymerization composition containing a block copolymerized polyimide obtained through the above polymerization reaction (that is, containing a block copolymerized polyimide and a water-soluble polar solvent, and the content of the block copolymerized polyimide is 15 to 25 wt. % Composition) is heated and melted. The heating temperature here is usually about 50 to 180 ° C., preferably about 60 to 160 ° C. When the heating temperature is less than 50 ° C., the block copolymerized polyimide does not dissolve and tends to be difficult to disperse with other solvents, and when it exceeds 180 ° C., hydrolysis occurs and the molecular weight tends to decrease.

  Next, a basic compound is added to the heated and melted composition and stirred to neutralize the block copolymer polyimide, and then the composition is cooled to 40 ° C. or lower, and the block copolymer polyimide poor solvent and water are further cooled. Is added and mixed and stirred to prepare a suspension.

  In the manufacturing process of such a suspension-type coating composition, when the temperature after cooling of the composition after neutralizing the block copolymerized polyimide exceeds 40 ° C., the polyimide tends to be decomposed by the neutralizing agent. The cooling temperature of the composition is more preferably 30 ° C. or lower. If the cooling temperature of the composition is too low, solidification tends to start again, so the lower limit of the cooling temperature is preferably 20 ° C. or higher.

  The basic compound is not particularly limited as long as it can neutralize the anionic group of the block copolymerized polyimide, but a basic nitrogen-containing compound is preferable, for example, N, N-dimethylaminoethanol, triethylamine, and the like. Primary amines such as triethanolamine, N-dimethylbenzylamine and ammonia, secondary amines and tertiary amines. Also, nitrogen-containing five-membered heterocyclic compounds such as pyrrole, imidazole, oxazole, pyrazole, isoxazole, thiazole, isothiazole, and nitrogen-containing six-membered heterocyclic compounds such as pyridine, pyridazine, pyrimidine, pyrazine, piperidine, piperazine, morpholine, etc. A nitrogen-containing heterocyclic compound is mentioned. In addition, since many aliphatic amines have a strong odor, nitrogen-containing heterocyclic compounds are preferred from the viewpoint of low odor. In consideration of the toxicity of the paint, piperidine, morpholine and the like having low toxicity are preferable among the nitrogen-containing heterocyclic compounds. The amount of the basic compound used is such that the acidic group in the polyimide is stably dissolved or dispersed in the aqueous solution, and is usually about 30 to 200 mol% of the theoretical neutralization amount.

  Examples of the poor solvent for the block copolymer polyimide include alcohols or ketones having a phenyl group, a furfuryl group, or a naphthyl group. Specifically, acetophenone, benzyl alcohol, 4-methylbenzyl alcohol, 4- Examples include methoxybenzyl alcohol, ethylene glycol monophenyl ether, phenoxy-2-ethanol, cinnamyl alcohol, furfuryl alcohol, and naphthyl carbinol. An aliphatic alcohol solvent is preferred because of its low toxicity, and an aliphatic alcohol solvent having an ether group is particularly preferred. Examples of the aliphatic alcohol solvent include 1-propanol, isopropyl alcohol, ethylene glycols, and propylene glycols. Specific examples of ethylene glycols and propylene glycols include dipropylene glycol, tripropylene glycol, ethylene glycol monoethyl ether, propylene glycol monomethyl ether (1-methoxy-2-propanol), propylene glycol methyl ether acetate, and the like. . These poor solvents can use 1 type (s) or 2 or more types.

  The blending amount of the poor solvent is preferably 10 to 40% by weight and more preferably 10 to 30% by weight with respect to the total amount of the composition. The amount of water is preferably 10 to 30% by weight, more preferably 15 to 30% by weight, based on the total amount of the composition.

  In addition to the poor solvent and water of the block copolymer polyimide, an appropriate amount of a water-soluble polar solvent or an oil-soluble solvent may be added for the purpose of adjusting the viscosity and electrical conductivity of the composition. Here, specific examples of the water-soluble polar solvent include the same water-soluble polar solvent used for the polymerization reaction of the block copolymerized polyimide, and examples of the oil-soluble solvent include N-methylpyrrolidone and γ-butyrolactone. Is mentioned. In addition, when adding an oil-soluble solvent, the quantity is 15 weight% or less with respect to the composition whole quantity.

  The solid content concentration of the suspension type electrodeposition coating composition of the present embodiment is preferably 1 to 15% by weight, and more preferably 5 to 10% by weight. The content of the water-soluble polar solvent is preferably 25 to 60% by weight, more preferably 35 to 55% by weight, based on the total amount of the composition.

  The suspension-type electrodeposition coating composition of this embodiment has high electrical conductivity in the process of coating film growth, and high uniformity of film properties on the outer peripheral surface of the member (electrodeposit) even under low current electrodeposition conditions. A polyimide electrodeposition film can be formed. Moreover, since the electrical conductivity in the film growth process of the coating film is high, and the dispersed particles (precipitated particles) of the block copolymerized polyimide are likely to be deposited (attached) on the outer peripheral surface of the member (electrodeposit), A thick electrodeposition film can be formed, and an electrodeposition film having a thickness exceeding 20 μm, which was difficult with a conventional polyimide electrodeposition film, can be formed.

<Electrodeposition method>
In the electrodeposition method of the electrodeposition coating composition of this embodiment, the conductive member (electrodeposit) is immersed in an electrodeposition tank containing the electrodeposition coating composition, and the conductive member is anode. Then, a polyimide coating film may be grown on the conductive member through a current using the counter electrode placed in the electrodeposition bath as a cathode.

  Electrodeposition can be performed by the constant current method or the constant voltage method. For example, in the case of the constant current method, the conditions of current value: 1.0 to 200 mA, DC voltage: 5 to 200 V (preferably 30 to 120 V) are used. Can be mentioned. The electrodeposition time varies depending on the electrodeposition conditions, the thickness of the electrodeposition film to be formed, etc., but is generally selected from the range of 10 to 120 seconds, preferably 30 to 60 seconds. Moreover, the composition temperature at the time of electrodeposition is 10-50 degreeC normally, Preferably it is 10-40 degreeC, More preferably, it is 20-30 degreeC. If the electrodeposition voltage is lower than 5V, it tends to be difficult to form a coating film by electrodeposition. If the electrodeposition voltage is higher than 200V, the generation of oxygen from the coated object becomes intense and it becomes impossible to form a uniform coating film. Also, if the electrodeposition time is shorter than 10 seconds, the coating film is difficult to grow even if the electrodeposition voltage is set high, so pinholes are likely to occur, and the withstand voltage performance of the electrodeposition film tends to decrease. If it exceeds 120 seconds, the thickness of the coating film becomes thicker than necessary, which is not economical. Further, when the composition temperature is lower than 10 ° C., it is difficult to form a coating film by electrodeposition, and when it is higher than 50 ° C., temperature management is required, which increases the production cost.

  The coating film formed by electrodeposition is preferably heat-dried (baked). Baking is performed at 70 to 110 ° C. for 10 to 60 minutes in the first stage, then at 160 to 180 ° C. for 10 to 60 minutes in the second stage and further at 200 to 220 ° C. for 30 to 30 minutes. It is preferable to perform a third stage baking process for 60 minutes. By performing such a three-stage baking process, it is possible to form a sufficiently dried polyimide film that adheres to the electrodeposit (coating product) with high adhesion.

  A polyimide film (electrodeposition film) obtained by heating and drying (baking) an electrodeposition film (coating film) of such an electrodeposition coating composition has extremely high heat resistance (temperature in accordance with JIS-C-3003). The temperature index in the index evaluation method can achieve 180 ° C. (heat resistance category: H), preferably 200 ° C. or more (heat resistance category: C)), and the elongation measured according to JIS-C-2151 The rate is 5% or higher, preferably 8% or higher.

<Examination of counter electrode>
When performing electrodeposition coating on a flat conductive member, if two cathodes, which are counter electrodes, are installed on both sides of the flat conductive member, both sides and the cut surface are cut out. Application is performed so as to obtain a thickness.

  However, there has been little investigation so far regarding a technique for performing electrodeposition coating with a uniform thickness on all surfaces of the groove-like conductive member 1 shown in FIG. In particular, an electrodeposition coating composition containing, as a resin component, a block copolymerized polyimide having a siloxane bond (—Si—O—) in the molecular skeleton (namely, the main chain of the polyimide) and an anionic group in the molecule. Since this is a new type of electrodeposition coating composition, no study has been made on a technique for performing electrodeposition coating with a uniform thickness on the entire surface of a three-dimensional conductive member. If the thickness is not uniform, a pinhole is generated in a portion having a small thickness, and the pressure resistance performance of the portion is significantly deteriorated.

  Then, the counter electrode which can perform electrodeposition coating with uniform thickness on all the surfaces of the groove-shaped electroconductive member 1 was examined.

  First, in the electrodeposition tank filled with the coating liquid, as shown in FIG. 2, the two opposing electrodes 21 and 21 were arranged in parallel at a distance from the entrance / exit of the groove of the conductive member 1. The counter electrode 21 is arranged orthogonal to both the bottom plate portion 11 and the side plate portions 12a and 12b. Moreover, the distance between the counter electrodes 21 and 21 and the conductive member 1 was ensured so as not to disturb the flow of the coating liquid into the groove. Two types of conductive members 1 were prepared, one having R of 0.25 mm and 3 mm between the bottom plate portion 11 and the side plate portions 12a and 12b (corner portions 13a and 13b). As shown in FIG. 3, in the electrodeposition tank 50 filled with the coating liquid 52, the conductive member 1 is used as an anode, the counter electrodes 21 and 21 are used as cathodes, and power is supplied between the two under the conditions of 40V and 40mA. No. 54 was used for electrodeposition by passing an amount of electricity of 1.5C. Thereafter, the electrodeposited conductive member 1 was taken out from the electrodeposition tank 50 and dried.

  The thickness of the coating film applied by electrodeposition to E1 (R of corner portions 13a and 13b is 0.25 mm) and E2 (R of corner portions 13a and 13b is 3 mm) in Table 1 is shown. The corners 13a and 13b are only about 1/6 to 1/3 of the thickness on the inner side. The bottom plate portion 11 and the side plate portions 12a and 12b have substantially the same thickness on the inner surface and the outer surface. Note that the inner thickness of the corner portions 13a and 13b did not change even when R was 0.25 mm or 3 mm.

  From this result, it was decided to make the coating thickness inside the corner portions 13a and 13b equal to the coating thickness at other locations. In addition, about R of corner part 13a, 13b, even if it was 0.25 mm or 3 mm, it was almost the same result, Therefore In the following examination, it was set to R = 3mm.

  First, in addition to the two counter electrodes 21 and 21, the internal counter electrode 22 shown in FIG. The internal counter electrode 22 has a groove shape that is similar to the conductive member 1. It was considered that the uniformity of the coating thickness was improved by arranging the internal counter electrode 22 having a shape similar to that of the conductive member 1 inside the recess of the conductive member 1.

  The internal counter electrode 22 was added to the two counter electrodes 21 and 21, and the electrodeposition was performed under the same conditions as described above. The result is shown as E3 in Table 1. When the counter electrodes 21 and 21 and the internal counter electrode 22 are used in combination, the corner portions 13a and 13b are not changed in thickness compared to the case where only the counter electrodes 21 and 21 are used. The coating thickness on the outside of 13a and 13b, the coating thickness on the outside of the side surface, and the outside of the bottom surface have drastically decreased. Therefore, using only the internal counter electrode 22 shown in FIG. 4 together with the counter electrodes 21 and 21 is not suitable for performing electrodeposition coating with a uniform thickness on the surface of the conductive member 1 of the present embodiment. It was judged.

  From the above results, it was considered that the counter electrode may be placed outside the side surface. Therefore, in addition to the counter electrodes 21 and 21 and the internal counter electrode 22, as shown in FIG. The external counter electrodes 23 and 23 facing the outer surface of 12b are installed, and electrodeposition is performed under the same conditions as described above. The result is shown as E4 in Table 1. When three types of counter electrodes are used in this way, the difference in the coating thickness between the inside and outside of the side surface and the inside and outside of the bottom surface is reduced, but the coating thickness inside the corner portions 13a and 13b does not increase. It was.

  As described above, even when the internal counter electrode 22 having a shape similar to that of the conductive member 1 is used, the coating thickness inside the target corner portions 13a and 13b is increased to substantially the same as the coating thickness of the side surfaces and the bottom surface. It was thought that this could not be done, and we studied to make the coating thickness uniform by another method.

  As a result of various investigations, when the Y-shaped counter electrode 24 shown in FIG. 6 is arranged on the inner side of the conductive member 1, when the coating material of the present embodiment is used, the inside of the corner portions 13a and 13b is applied. It was found that the thickness increased and the overall coating thickness became substantially uniform. The Y-shaped counter electrode 24 includes a main plate portion 24a made of a rectangular plate-shaped metal member, and two branched plate portions (boundaries) extending in a bifurcated manner from one end A that is a bottom side of the main plate portion 24a. Auxiliary section) 24b, 24b, and has a Y-shaped (upside down) shape in a cross section perpendicular to the main plate section 24a.

  The arrangement of the Y-shaped counter electrode 24 on the inner side of the conductive member 1 is such that both surfaces of the main plate portion 24a face (facing) the side plate portions 12a and 12b of the conductive member 1, The two branch plate portions 24b and 24b are arranged so that their tips extend toward the corner portions 13a and 13b, respectively. In such an arrangement, one end A of the main plate portion 24a faces the bottom plate portion 11 of the conductive member 1, and the distance between the one end A and the bottom plate portion 11 is such that the ends of the branch plate portions 24b and 24b and the bottom plate portion. 11 or greater. That is, the tips of the two branch plate portions 24 b and 24 b extending toward the corner portions 13 a and 13 b are arranged closest to the bottom plate portion 11 in the Y-shaped counter electrode 24.

  Electrodeposition coating was performed under the same conditions as described above, using the counter electrode 21 on the outer side and the Y-shaped counter electrode 24 on the inner side. The result is shown as E5 in Table 1. The coating thickness inside the corner portions 13a and 13b became sufficiently large. However, the coating thickness on the outer surface side of the side plate portions 12a and 12b and the outer surface side of the bottom plate portion 11 has been reduced.

  Therefore, in order to increase the coating thickness on the outer surface side, as shown in FIG. 7, in addition to the Y-shaped counter electrode 24, external counter electrodes 23, 23 are further arranged, and electrodeposition coating is performed under the same conditions as described above. Went. The result is shown as E6 in Table 1. Although there is some variation in the coating thickness, the coating thickness inside the corner portions 13a and 13b is sufficiently large and the coating thickness on the outer surface side is not significantly different from the inner surface side.

  Thus, when the external counter electrodes 23, 23 are used in addition to the Y-shaped counter electrode 24, the groove-shaped conductive member 1 has a siloxane bond in the molecular skeleton and an anionic group in the molecule. When electrodeposition is applied using a paint containing the block copolymer polyimide as a resin component, electrodeposition can be applied with a substantially uniform coating thickness on the inner and outer surfaces of the flat portion and the inner and outer surfaces of the corner portion.

  Next, examination was carried out to further increase the coating thickness. When a member subjected to electrodeposition coating is used as a case of an electronic device, high insulation performance is required. Therefore, an insulating coating film having a uniform thickness as a whole and a coating film of about 30 μm is required even at the thinnest part. Because. Therefore, in order to obtain such a coating film, the electrodeposition was performed by increasing the amount of electricity to 3C and changing the other conditions without changing the conditions. When the total application amount is increased, it is considered that the thickness applied to the inside of the corner portions 13a and 13b may change depending on the size of R of the corner portions 13a and 13b. Electrodeposition coating was performed under two conditions of 25 mm and 3 mm. As the counter electrode, a counter electrode 21, a Y-shaped counter electrode 24, and external counter electrodes 23 and 23 were used in combination.

  The results are shown as E7 and E8 in Table 1. In E7 where R = 0.25 mm, the minimum part of the coating thickness is sufficiently thick as 30.26 μm and the insulation performance is high, and the maximum coating thickness is twice the minimum, and the uniformity of the coating thickness is practically sufficient. It is a range. Even in E8 where R = 3 mm, the minimum part of the coating thickness is sufficiently thick as 43.89 μm and the insulation performance is high, and the maximum coating thickness is 1.37 times the minimum, and the uniformity of the coating thickness is practically sufficient It is a range. Both E7 and E8 are sufficiently thick to be applied to the inside of the corner portions 13a and 13b.

(Embodiment 2)
A part of the counter electrode according to the second embodiment is a main plate portion 31 and rod-shaped corner electrodes 32 and 32 which are boundary auxiliary portions as shown in FIG. Other counter electrodes are the same as those in the first embodiment. The main plate portion 31 is a single metal plate, and is placed in parallel with the two side plate portions at an intermediate point between the two side plate portions. The corner electrodes 32 and 32 are placed at the corner portion and extend along the boundary between the bottom plate portion and the side plate portion. The shape / configuration of the conductive member 1, the configuration / conditions of the electrodeposition tank, etc. are substantially the same as in the first embodiment.

  Even if it is a counter electrode like this embodiment, the application | thickness thickness to the corner part of an electroconductive member can be enlarged enough.

(Embodiment 3)
As shown in FIG. 9, a part of the counter electrode according to the third embodiment includes a main plate portion 33a, a boundary auxiliary portion 34a extending from the bottom plate side end B1 of the main plate portion 33a to the corner portion of the conductive member 1, and a main plate portion 33b. And a boundary auxiliary portion 34b extending from the bottom plate side end portion B2 of the main plate portion 33b to the corner portion of the conductive member 1. The pair of counter electrodes have the same shape. Other counter electrodes are the same as those in the first embodiment. The main plate portions 33a and 33b are each a single metal plate and are placed so as to face the two side plate portions, respectively. The boundary auxiliary portions 34a and 34b form a predetermined angle with respect to the main plate portions 33a and 33b. The counter electrode placed inside the conductive member 1 of the present embodiment has a shape in which the main plate portion 24a of the counter electrode of the first embodiment is peeled into two sheets and separated in parallel. The shape / configuration of the conductive member 1, the configuration / conditions of the electrodeposition tank, etc. are substantially the same as in the first embodiment.

  Even if it is a counter electrode like this embodiment, the application | thickness thickness to the corner part of an electroconductive member can be enlarged enough.

(Embodiment 4)
As shown in FIG. 10, a part of the counter electrode according to the fourth embodiment includes a main plate portion 35a, a boundary auxiliary portion 36a extending from the bottom plate side end portion C1 of the main plate portion 35a to the corner portion of the conductive member 1, and a main plate portion 35b. And a boundary auxiliary portion 36b extending from the bottom plate side end portion C2 of the main plate portion 35b to the corner portion of the conductive member 1, and a connecting plate portion 37 for connecting the end portions C1 and C2 of the two main plate portions 35a and 35b. The counter electrode of the present embodiment has a shape in which a connecting plate portion 37 is added to the counter electrode placed inside the conductive member 1 of the third embodiment. The shape / configuration of the conductive member 1, the configuration / conditions of the electrodeposition tank, etc. are substantially the same as in the first embodiment.

  Even if it is a counter electrode like this embodiment, the application | thickness thickness to the corner part of an electroconductive member can be enlarged enough.

(Embodiment 5)
As shown in FIG. 11, the conductive member according to the fifth embodiment is a metal pipe (cylinder) having a rectangular cross section. And the counter electrode 25 arrange | positioned in the cylinder of the electroconductive member 2 has the shape which connected the two Y-shaped counter electrodes 24 of Embodiment 1, and the edge parts on the opposite side to the one end part A. ing. That is, the counter electrode 25 has a shape in which two branched plate portions 25b, 25b,... Extend from the both end portions A, A of the main plate portion 25a to the corner portion of the conductive member 2, respectively. Other configurations and conditions of the counter electrode, the electrodeposition tank, and the like are the same as those in the first embodiment.

  Even in the case of the rectangular cylindrical conductive member 2 as in this embodiment, if the counter electrode 25 as shown in FIG. 11 is used, the coating thickness on the corner portion in the cylinder can be sufficiently increased. .

(Other embodiments)
The above-described embodiments are examples of the present invention, and the present invention is not limited to these examples. The conductive member is not limited to a metal member, and may be a member having conductivity on the surface. The side plate portion of the conductive member of Embodiment 1 does not have to extend vertically from the bottom plate portion. For example, the angle formed by the bottom plate portion and the side plate portion may be 45 ° to 140 °. The side plate portion and the bottom plate portion may be bent or curved. At that time, the sharper the angle formed between the bottom plate portion and the side plate portion, the thinner the inner coating becomes, so the distance between the tip of the branch plate portion and the bottom plate portion must be closer to the acute angle side. . Further, it is preferable that the main plate portions of the branched electrodes are installed at positions as equidistant as possible so that the influence is equal to each side plate. The conductive member of Embodiment 5 does not need to have four angles of 90 °. Furthermore, the electroconductive member of Embodiment 5 should just be a cylinder with a polygonal cross section, and if it is a triangle to an octagonal cylinder, it is preferable.

  As described above, since the electrodeposition method according to the present invention can form a sufficiently thick coating on the inner corner portion, a container that requires high insulation performance, an assembled stator coil, a complicated It is useful as a method for forming an insulating film such as a bus bar having a different shape.

DESCRIPTION OF SYMBOLS 1 Conductive member 2 Conductive member 11 Bottom plate part 12a, 12b Side plate part 21 Counter electrode 23 External counter electrode 24 Y-shaped counter electrode 24a Main plate part 24b Branching plate part (boundary auxiliary part)
25 Counter electrode 25a Main plate portion 25b Branch plate portion 31 Main plate portion 32 Corner electrode (boundary auxiliary portion)
33a, 33b Main plate portions 34a, 34b Boundary auxiliary portions 35a, 35b Main plate portions 36a, 36b Boundary auxiliary portions 37 Connecting plate portions 50 Electrodeposition tank 52 Coating liquid 54 Power source

Claims (6)

An electrodeposition method for applying a paint by electrodeposition to a conductive member having at least a bottom plate portion and two side plate portions extending upward from both ends of the bottom plate portion,
A step of preparing an electrodeposition bath containing a coating liquid;
Immersing the conductive member and a plurality of counter electrodes in the coating solution of the electrodeposition tank;
An application step of applying a paint by passing an electric current between the conductive member and the counter electrode;
Removing the conductive member coated with the paint from the coating liquid;
Including
The counter electrode includes a main plate portion arranged to face the side plate portion, and a boundary auxiliary portion arranged at a position closer to a boundary portion between the bottom plate portion and the side plate portion than the main plate portion. And
The boundary auxiliary part is two branched plate parts extending in two from one end A of the main plate part,
In the application step, the one end portion A of the main plate portion is positioned closest to the bottom plate portion, and both surfaces of the main plate portion are respectively opposed to inner surfaces of the two side plate portions. The branch plate portion extends toward the boundary between the bottom plate portion and the two side plate portions, and the distance between the one end A and the bottom plate portion is greater than the distance between the end of the branch plate portion and the bottom plate portion. towards the distance between has a smaller shape, electrostatic Chakuhoho. An electrodeposition method for applying a paint by electrodeposition to a conductive member having at least a bottom plate portion and two side plate portions extending upward from both ends of the bottom plate portion,
A step of preparing an electrodeposition bath containing a coating liquid;
Immersing the conductive member and a plurality of counter electrodes in the coating solution of the electrodeposition tank;
An application step of applying a paint by passing an electric current between the conductive member and the counter electrode;
Removing the conductive member coated with the paint from the coating liquid;
Including
The counter electrode includes a main plate portion arranged to face the side plate portion, and a boundary auxiliary portion arranged at a position closer to a boundary portion between the bottom plate portion and the side plate portion than the main plate portion. And
The main plate portion exists for each of the two side plate portions,
The boundary auxiliary section extends toward from the bottom end of the plate portion B of the main plate portion in the boundary portion between the side plate portion and the bottom plate, electrostatic Chakuhoho. The electrodeposition method according to claim 2 , further comprising a connecting plate portion that connects the end portions B of the two main plate portions. An electrodeposition apparatus comprising an electrodeposition tank, a plurality of counter electrodes, and a power source, and applying a paint to the conductive member by electrodeposition,
The conductive member includes at least a bottom plate portion and two side plate portions extending upward from both ends of the bottom plate portion,
The counter electrode includes a main plate portion arranged to face the side plate portion, and a boundary auxiliary portion arranged at a position closer to a boundary portion between the bottom plate portion and the side plate portion than the main plate portion. And
The boundary auxiliary part is two branched plate parts extending in two from one end A of the main plate part,
In the coating fabric process, the main with the one end A of the plate portion is placed so that both surfaces of the located closest to the bottom plate portion and the main plate portion is relative respectively to the inner surface of the two side plate portions, the two The branch plate portion extends toward the boundary between the bottom plate portion and the two side plate portions, and the distance between the one end A and the bottom plate portion is greater than the distance between the end of the branch plate portion and the bottom plate portion. An electrodeposition apparatus having a shape with a smaller distance between them. An electrodeposition apparatus comprising an electrodeposition tank, a plurality of counter electrodes, and a power source, and applying a paint to the conductive member by electrodeposition,
The conductive member includes at least a bottom plate portion and two side plate portions extending upward from both ends of the bottom plate portion,
The counter electrode includes a main plate portion arranged to face the side plate portion, and a boundary auxiliary portion arranged at a position closer to a boundary portion between the bottom plate portion and the side plate portion than the main plate portion. And
The main plate portion exists for each of the two side plate portions,
The boundary auxiliary section extends toward from the bottom end of the plate portion B of the main plate portion in the boundary portion between the side plate portion and the bottom plate, electrostatic Chakusochi. An electrodeposition apparatus comprising an electrodeposition tank, a plurality of counter electrodes, and a power source, and applying a paint to the conductive member by electrodeposition,
The conductive member includes at least a bottom plate portion and two side plate portions extending upward from both ends of the bottom plate portion,
The counter electrode includes a main plate portion arranged to face the side plate portion, and a boundary auxiliary portion arranged at a position closer to a boundary portion between the bottom plate portion and the side plate portion than the main plate portion. And
The electrodeposition apparatus further comprising a connecting plate portion that connects the end portions B of the two main plate portions.

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