JP2009263491A - Cationic electrodeposition coating composition, coating film-forming method and coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a cationic electrodeposition coating composition having a high heat conductivity of an obtained cured film. <P>SOLUTION: The cationic electrodeposition coating composition comprises a diamond powder and an epoxy resin, and the volume average particle diameter of the diamond powder is in the range of 0.1-1.5 μm. The epoxy resin has a sulfonium group and a propargyl group and at least one skeleton selected from the group consisting of a novolak cresol type skeleton and a novolak phenol type skeleton. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cationic electrodeposition coating composition, a method for forming a coating film using the cationic electrodeposition coating composition, and a coating film obtained by the method.

  The electrodeposition coating method can evenly coat even a workpiece having a complicated shape, and can be applied automatically and continuously. Therefore, the electrodeposition coating method has a large and complicated shape and is highly resistant. It is widely used as an undercoating method for objects that require rust. Moreover, since the use efficiency of the paint is extremely high as compared with other coating methods, it is economical and widely used as an industrial coating method.

  As such an electrodeposition coating method, a method is known in which a cationic electrodeposition coating composition containing an epoxy resin having a specific structure is used so that the bath stability is excellent and the curability of the resulting cured film can be increased. (For example, refer to Patent Document 1).

  By the way, since the calorific value of these devices has increased in recent years in the electrical and electronic field, the cationic electrodeposition coating composition capable of forming a coating film excellent in thermal conductivity has been demanded. ing.

On the other hand, a thermosetting adhesive composition containing an epoxy resin and diamond powder as a heat conductive ceramic powder is known (see, for example, Patent Document 2). However, this is used as a sealing agent for electronic circuits, and cannot be applied uniformly to an object having a complicated shape.
International Publication No. 98/03595 pamphlet (released January 29, 1998) Japanese translation of PCT publication No. 2002-512278 (published on April 23, 2002)

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a cationic electrodeposition coating composition having high thermal conductivity of the obtained cured film, and a coating using the cationic electrodeposition coating composition. It is to realize a film forming method and a coating film obtained by the method.

  The present inventor has intensively studied to solve the above problems. Specifically, the present inventor studied the dispersion and mixing of diamond powder in an epoxy resin, which was conventionally considered difficult due to the hardness of diamond.

  As a result, surprisingly, the inclusion of diamond powder having a specific particle size in a specific epoxy resin increases the thermal conductivity of the cured film formed from the resulting cationic electrodeposition coating composition. As a result, the present invention has been completed.

  Furthermore, by making the concentration of the diamond powder within a specific concentration range, in addition to increasing the thermal conductivity of the resulting cured film, it is excellent in bath stability, and the insulation and curability of the resulting cured film. It was also found that a cationic electrodeposition coating composition having a high value can be realized.

  That is, the cationic electrodeposition coating composition according to the present invention is a cationic electrodeposition coating composition containing diamond powder and an epoxy resin in order to solve the above problems, and the volume average particle diameter of the diamond powder is 0. The epoxy resin has a sulfonium group and a propargyl group, and the epoxy resin is at least selected from the group consisting of a novolac cresol type skeleton and a novolak phenol type skeleton. It is characterized by having one skeleton.

  According to the said structure, since the diamond powder which has the said predetermined particle diameter is uniformly disperse | distributed and contained in a predetermined epoxy resin, the coating film after electrodeposition coating is excellent in thermal conductivity. Therefore, it is possible to provide a cationic electrodeposition coating composition in which the obtained cured film has high thermal conductivity.

  In the cationic electrodeposition coating composition according to the present invention, the content of the diamond powder is preferably in the range of 0.5% by mass or more and 50% by mass or less.

  According to the said structure, in addition to the heat conductivity of the obtained cured film being high, it can provide the cationic electrodeposition coating composition which is excellent in bath stability, and the insulation property and sclerosis | hardenability of the obtained cured film are high. There is a further effect.

  In the cationic electrodeposition coating composition according to the present invention, the content of the diamond powder is preferably in the range of 10% by mass to 40% by mass.

  According to the said structure, the heat conductivity of the obtained cured film is high, it is excellent in bath stability more, and it can be provided that the cationic electrodeposition coating material composition whose insulation property and sclerosis | hardenability of the obtained cured film are higher can be provided. There is a further effect.

  In order to solve the above problems, the method for forming a coating film according to the present invention includes a step of forming an electrodeposition coating film by electrodeposition coating using the cationic electrodeposition coating composition according to the present invention. It is characterized by.

  According to the said method, since the cationic electrodeposition coating composition which concerns on the said invention is used, there exists an effect that a coating film with high heat conductivity can be formed.

  In order to solve the above-mentioned problems, the coating film according to the present invention is obtained by the forming method according to the present invention.

  According to the said structure, there exists an effect that a coating film with high heat conductivity can be provided.

  As described above, the cationic electrodeposition coating composition according to the present invention is a cationic electrodeposition coating composition containing diamond powder and an epoxy resin, and the volume average particle diameter of the diamond powder is 0.1 μm or more. The epoxy resin has a sulfonium group and a propargyl group, and the epoxy resin has at least one skeleton selected from the group consisting of a novolac cresol skeleton and a novolak phenol skeleton. It is characterized by that.

  For this reason, it is effective in the ability to provide the cationic electrodeposition coating composition with high heat conductivity of the cured film obtained.

  As described above, the method for forming a coating film according to the present invention includes a step of forming an electrodeposition coating film by electrodeposition coating using the cationic electrodeposition coating composition according to the present invention. Yes.

  For this reason, there exists an effect that a coating film with high heat conductivity can be formed.

  As described above, the coating film according to the present invention is obtained by the forming method according to the present invention.

  For this reason, there exists an effect that the coating film with high heat conductivity can be provided.

  An embodiment of the present invention will be described as follows.

  In the present specification, “A to B” indicating a range means A or more and B or less. Further, various physical properties listed in the present specification mean values measured by the methods described in the examples described later unless otherwise specified.

  The cationic electrodeposition coating composition according to the present embodiment contains diamond powder and an epoxy resin.

(I) Epoxy Resin The epoxy resin has a sulfonium group and a propargyl group, and has at least one skeleton selected from the group consisting of a novolak cresol skeleton and a novolac phenol skeleton.

  The epoxy resin may have both a sulfonium group and a propargyl group in one molecule, but it is not always necessary. For example, the epoxy resin has only one of a sulfonium group or a propargyl group in one molecule. It may be. In the latter case, the resin composition as a whole only needs to have all of these two types of curable functional groups.

  The sulfonium group is a hydrated functional group in the cationic resin composition. When a voltage or current of a certain level or higher is applied in the electrodeposition process, the sulfonium group undergoes an electrolytic reduction reaction on the electrode, and the ionic group disappears and becomes irreversibly nonconductive. It is considered that the cationic electrodeposition coating composition can exhibit a high throwing power due to this.

  Further, in the electrodeposition step, an electrode reaction is caused, and it is considered that an electrogenerated base is generated in the cationic electrodeposition coating composition by retaining the generated hydroxide ions in the sulfonium group. This electrogenerated base can convert a propargyl group present in the cationic electrodeposition coating composition that is less reactive by heating to an allene bond that is more reactive by heating.

  As the epoxy resin, a polyfunctional group for enhancing curability is easy, and thus a novolak phenol type polyepoxy having at least one skeleton selected from the group consisting of a novolak cresol type skeleton and a novolak phenol type skeleton. Resin and / or novolac cresol type polyepoxy resin is used.

  The number average molecular weight of the epoxy resin is preferably a lower limit of 700 and an upper limit of 5,000.

  The content of the sulfonium group in the epoxy resin is a lower limit of 5 millimoles and an upper limit of 400 millimoles per 100 g of the solid content of the epoxy resin after satisfying the conditions for the content of sulfonium groups and propargyl groups described later. If it is 5 mmol / 100 g or more, throwing power and curability can be sufficiently exhibited, and it is excellent in hydration property and bath stability. If it is 400 mmol / 100g or less, the precipitation of the resin layer to to-be-coated object will become more favorable.

  The lower limit per 100 g of the solid content of the epoxy resin is more preferably 5 mmol, and even more preferably 10 mmol. Further, the upper limit is more preferably 250 mmol, and even more preferably 150 mmol.

  The propargyl group of the epoxy resin functions as a curing functional group in the cationic electrodeposition coating composition. Although the reason is unknown, the throwing power of the cationic electrodeposition coating composition can be further improved by coexisting with the sulfonium group.

  The propargyl group content of the epoxy resin is a lower limit of 10 mmol and an upper limit of 495 mmol per 100 g of the solid content of the epoxy resin after satisfying the conditions for the content of sulfonium group and propargyl group described later. If it is 10 mmol / 100 g or more, throwing power and curability can be sufficiently exhibited, and if it is 495 mmol / 100 g or less, it is more excellent in hydration stability. The lower limit per 100 g of the solid content of the epoxy resin is more preferably 20 mmol, and the upper limit is further preferably 395 mmol.

  In addition, the “content of propargyl group” in the present specification means a value calculated from the charged amount of each raw material when producing an epoxy resin.

  The total content of the sulfonium group and propargyl group of the epoxy resin is preferably 500 mmol or less per 100 g of the solid content of the epoxy resin. If it is 500 millimoles / 100 g or less, a resin for a cationic electrodeposition coating material that provides a coating film excellent in thermal conductivity can be obtained more stably. The total content of the sulfonium group and propargyl group of the epoxy resin is more preferably 400 mmol or less per 100 g of the solid content of the epoxy resin.

  A part of the propargyl group in the epoxy resin may be acetylated. Acetylide is a salt-like metal acetylenide. The content of propargyl group to be acetylated in the epoxy resin is preferably a lower limit of 0.1 mmol and an upper limit of 40 mmol per 100 g of the solid content of the epoxy resin. If it is 0.1 mmol or more, the effect by acetylide formation will be fully exhibited, and if it is 40 mmol or less, acetylide formation can be performed stably. This content can set a more preferable range depending on the metal to be used.

  The metal contained in the acetylated propargyl group is not particularly limited as long as it exhibits a catalytic action, and examples thereof include transition metals such as copper, silver, and barium. In these, if environmental compatibility is considered, copper and silver are preferable, and copper is more preferable from availability.

  When copper is used, the content of propargyl group to be acetylated in the epoxy resin is more preferably 0.1 to 20 mmol per 100 g of the solid content of the epoxy resin.

  A curing catalyst can be introduced into the resin by acetylating a part of the propargyl group in the epoxy resin. In this way, in general, it is not necessary to use an organic transition metal complex that is difficult to dissolve or disperse in an organic solvent or water, and even a transition metal can be easily acetylated and introduced. Even metal compounds can be used freely. Further, as in the case of using a transition metal organic acid salt, it can be avoided that the organic acid salt is present as an anion in the electrodeposition bath, and further, the metal ion is not removed by ultrafiltration. Easy management and electrodeposition coating design.

  Moreover, the said epoxy resin may contain the carbon-carbon double bond. Since the said carbon-carbon double bond has high reactivity, it can improve sclerosis | hardenability more.

  The content of the carbon-carbon double bond satisfies the conditions for the content of the propargyl group and carbon-carbon double bond described below, and the lower limit is 10 mmol and the upper limit is 485 mmol per 100 g of the solid content of the epoxy resin. preferable. If it is 10 mmol / 100 g or more, sufficient curability can be exhibited by addition, and if it is 485 mmol / 100 g or less, the hydration stability becomes better.

  The content of the carbon-carbon double bond is more preferably a lower limit of 20 mmol and an upper limit of 375 mmol per 100 g of the solid content of the epoxy resin.

  When the carbon-carbon double bond is contained, the total content of the propargyl group and the carbon-carbon double bond may be in the range of a lower limit of 80 mmol and an upper limit of 450 mmol per 100 g of the solid content of the epoxy resin. preferable. If it is 80 mmol / 100g or more, curability will become more favorable, and if it is 450 mmol / 100g or less, throwing power will become more favorable.

  The total content of the propargyl group and the carbon-carbon double bond is more preferably a lower limit of 100 mmol and an upper limit of 395 mmol per 100 g of the solid content of the epoxy resin.

  Moreover, when it contains the said carbon-carbon double bond, it is preferable that the total content of the said sulfonium group, a propargyl group, and a carbon-carbon double bond is 500 millimoles or less per 100g of solid content of an epoxy resin. If it is 500 mmol / 100 g or less, a resin having the intended performance can be obtained stably.

  The total content of the sulfonium group, propargyl group and carbon-carbon double bond is more preferably 400 mmol or less per 100 g of the solid content of the epoxy resin.

  The said epoxy resin can be manufactured by the method described in the Japanese translations of PCT publication No. 2005-538872, for example. Specifically, the step of obtaining an epoxy resin having a propargyl group by reacting an epoxy resin having at least two epoxy groups in one molecule with a compound having a functional group that reacts with the epoxy group and a propargyl group (i) And the step (ii) of introducing a sulfonium group by reacting a sulfide / acid mixture with the remaining epoxy group in the epoxy resin having a propargyl group obtained in step (i). .

  Examples of the compound having a functional group that reacts with the epoxy group and a propargyl group (hereinafter referred to as “compound (A)”) include both a functional group that reacts with an epoxy group such as a hydroxyl group and a carboxyl group and a propargyl group. Examples of such compounds include propargyl alcohol and propargylic acid. Of these, propargyl alcohol is preferred because of its availability and ease of reaction.

  When the epoxy resin has a carbon-carbon double bond, a compound having a functional group that reacts with the epoxy group and a carbon-carbon double bond (hereinafter referred to as “compound (B)” in the step (i). May be used in combination with the compound (A).

  As said compound (B), the compound which contains both the functional group and carbon-carbon double bond which react with epoxy groups, such as a hydroxyl group and a carboxyl group, is mentioned, for example.

  Specifically, when the group that reacts with the epoxy group is a hydroxyl group, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, allyl alcohol, methacryl alcohol Etc.

  When the group that reacts with the epoxy group is a carboxyl group, acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, phthalic acid, itaconic acid; maleic acid ethyl ester, fumaric acid ethyl ester, itaconic acid ethyl ester, succinic acid Half-esters such as acid mono (meth) acryloyloxyethyl ester and phthalic acid mono (meth) acryloyloxyethyl ester; synthetic unsaturated fatty acids such as oleic acid, linoleic acid and ricinoleic acid; natural unnatural such as linseed oil and soybean oil Saturated fatty acid etc. are mentioned.

  In the step (i), the compound (A) is reacted with an epoxy resin having at least two epoxy groups in one molecule to obtain an epoxy resin having a propargyl group, or the compound (A). And, if necessary, the compound (B) is reacted to obtain an epoxy resin having a propargyl group and a carbon-carbon double bond.

  In this latter case, in the step (i), the compound (A) and the compound (B) may be used in the reaction after they are mixed in advance, or the compound (A) and the compound may be used. (B) may be used separately in the reaction.

  In addition, the functional group which reacts with the epoxy group which the said compound (A) has, and the functional group which reacts with the epoxy group which the said compound (B) have may be the same, or may differ.

  In the step (i), the mixing ratio of the compound (A) and the compound (B) when they are reacted may be set so as to have a desired functional group content. For example, the propargyl described above is used. What is necessary is just to set so that it may become content of group and a carbon-carbon double bond.

  The reaction conditions in the above step (i) are usually several hours at room temperature or 80 to 140 ° C. Moreover, the well-known component required in order to advance reaction, such as a catalyst and a solvent, can be used as needed.

  The completion of the reaction can be confirmed by measuring the epoxy equivalent, and the introduced functional group can be confirmed by measuring the nonvolatile content of the obtained reaction product or by instrumental analysis.

  The reaction product thus obtained is generally a mixture of epoxy resins having one or more propargyl groups, or an epoxy resin having one or more propargyl groups and one or more carbon-carbon double bonds. It is a mixture of That is, the epoxy resin which has a propargyl group or a propargyl group, and a carbon-carbon double bond is obtained by the said process (i).

  In the step (ii), a sulfonium group is introduced by reacting a sulfide / acid mixture with the remaining epoxy group in the epoxy resin having a propargyl group obtained in the step (i).

  The introduction of the sulfonium group can be carried out by reacting a sulfide / acid mixture with an epoxy group to introduce the sulfide and sulfonium, or after introducing the sulfide, an acid or methyl fluoride, methyl chloride, methyl bromide, etc. It is possible to carry out the sulfoniumation reaction of the introduced sulfide with an alkyl halide or the like, and an anion exchange if necessary. From the viewpoint of easy availability of reaction raw materials, a method using a sulfide / acid mixture is preferred.

  The sulfide is not particularly limited, and examples thereof include aliphatic sulfide, mixed aliphatic-aromatic sulfide, aralkyl sulfide, and cyclic sulfide. Specifically, for example, diethyl sulfide, dipropyl sulfide, dibutyl sulfide, dihexyl sulfide, diphenyl sulfide, ethylphenyl sulfide, tetramethylene sulfide, pentamethylene sulfide, thiodiethanol, thiodipropanol, thiodibutanol, 1- (2 -Hydroxyethylthio) -2-propanol, 1- (2-hydroxyethylthio) -2-butanol, 1- (2-hydroxyethylthio) -3-butoxy-1-propanol and the like.

  The acid is not particularly limited, and for example, formic acid, acetic acid, lactic acid, propionic acid, boric acid, butyric acid, dimethylolpropionic acid, hydrochloric acid, sulfuric acid, phosphoric acid, N-acetylglycine, N-acetyl-β-alanine, etc. Is mentioned.

  In general, the mixing ratio of the sulfide and the acid in the sulfide / acid mixture is preferably about sulfide / acid = 100/40 to 100/100 in terms of molar ratio.

  The reaction of the step (ii) includes, for example, an epoxy resin having a propargyl group obtained in the step (i), a predetermined amount of the sulfide set to have the sulfonium group content, and the above The mixture with the acid can be mixed with 5 to 10 moles of water of the sulfide used and usually stirred at 50 to 90 ° C. for several hours. The end point of the reaction may be a measure that the residual acid value is 5 or less. Confirmation of sulfonium group introduction in the obtained resin can be performed by potentiometric titration.

  Even when the sulfoniumation reaction is carried out after the introduction of the sulfide, it can be carried out according to the above. As described above, by introducing the sulfonium group after the introduction of the propargyl group, decomposition of the sulfonium group due to heating can be prevented.

  When part of the propargyl group of the epoxy resin is acetylated, a part of the propargyl in the epoxy resin is reacted with the epoxy resin having the propargyl group obtained in the step (i). This can be done by the step of acetylating the group.

  The metal compound is preferably a transition metal compound that can be converted into an acetylide, and examples thereof include a complex or salt of a transition metal such as copper, silver, or barium. Specific examples include acetylacetone copper, copper acetate, silver acetylacetone, silver acetate, silver nitrate, acetylacetone barium, and barium acetate. Among these, a copper or silver compound is preferable from the viewpoint of environmental compatibility, and a copper compound is more preferable from the viewpoint of availability. For example, acetylacetone copper is preferable in view of ease of bath management. .

  The reaction conditions for acetylating a part of the propargyl group are usually several hours at 40 to 70 ° C. The progress of the reaction can be confirmed by coloration of the obtained cationic resin composition, disappearance of methine protons by a nuclear magnetic resonance spectrum, or the like. In this way, the reaction is completed after confirming the reaction time point at which the propargyl group in the epoxy resin is acetylated in a desired ratio.

  The resulting reaction product is generally a mixture of epoxy resins in which one or more of the propargyl groups are acetylated. A sulfonium group can be introduced into the epoxy resin obtained by acetylating a part of the propargyl group thus obtained by the above step (ii).

  In addition, since the reaction conditions can be set in common in the process of acetylating a part of propargyl group which an epoxy resin has, and the said process (ii), it is also possible to perform both processes simultaneously. The method of performing both steps simultaneously is advantageous because the manufacturing process can be simplified.

  In this manner, an epoxy resin having a propargyl group and a sulfonium group, and if necessary, a carbon-carbon double bond and a part of the propargyl group acetylated is produced while suppressing the decomposition of the sulfonium group. be able to.

(II) Diamond powder The volume average particle diameter of the diamond powder is in the range of 0.1 to 1.5 μm, preferably in the range of 0.2 to 1.0 μm, and more preferably 0.3 μm. It is in the range of 1.0 μm or less.

  When the volume average particle diameter is less than 0.1 μm, the heat conduction effect of the diamond powder becomes insufficient, and the heat conductivity of the cured film becomes insufficient. On the other hand, when the volume average particle diameter exceeds 1.5 μm, the dispersion stability of the diamond powder is reduced, or the diamond powder is not fully contained in the cured film to be obtained, and the film protrudes, so that a uniform cured film is obtained. It becomes difficult to form.

  The shape of the diamond used in the present embodiment is not particularly limited, and examples thereof include a spherical shape, an ellipsoid, and a blocky shape (lump shape).

  As the diamond powder, commercially available diamond powder can be used, and for example, GMM series (trade name) sold by Diamond Innovation can be used.

(III) Cationic electrodeposition coating composition The content of the diamond powder in the cationic electrodeposition coating composition is not particularly limited, but is preferably in the range of 0.5 mass% to 50 mass%. More preferably, it exists in the range of 5 mass% or more and 50 mass% or less. If the content of the diamond powder is within the above range, in addition to the high thermal conductivity of the resulting cured film, the cationic electrodeposition coating composition is excellent in bath stability and has high insulation and curability of the resulting cured film. A composition can be provided. The content of the diamond powder is more preferably in the range of 10% by mass to 40% by mass.

  The content of the epoxy resin in the cationic electrodeposition coating composition is preferably in the range of 50% by mass to 99.5% by mass.

  Since the cationic electrodeposition coating composition contains the above-described epoxy resin, the cationic resin composition itself is curable. For this reason, in the said cationic electrodeposition coating composition, use of a hardening | curing agent is not necessarily required, but you may use for the further improvement of sclerosis | hardenability.

  Examples of such a curing agent include a compound having a plurality of at least one of a propargyl group and a carbon-carbon double bond, for example, polyepoxide such as novolac phenol, pentaerythritol tetraglycidyl ether, propargyl alcohol, etc. And compounds obtained by addition reaction of a compound having a propargyl group or a compound having a carbon-carbon double bond such as acrylic acid.

  Moreover, it is not always necessary to use a curing catalyst in the cationic electrodeposition coating composition. However, when it is necessary to further improve the curability depending on the curing reaction conditions, a transition metal compound or the like that is usually used may be added as necessary.

  The compound that can be used as such a curing catalyst is not particularly limited. For example, a transition metal such as nickel, cobalt, manganese, palladium, rhodium, a ligand such as cyclopentadiene or acetylacetone, acetic acid, or the like. The thing etc. which carboxylic acid etc. couple | bonded are mentioned. The blending amount of the curing catalyst is preferably a lower limit of 0.1 mmol and an upper limit of 20 mmol per 100 g of resin solid content in the cationic electrodeposition coating composition.

  An amine can be blended in the cationic electrodeposition coating composition. By blending the amine, the conversion rate of sulfonium groups to sulfides by electrolytic reduction in the electrodeposition process is increased. The amine is not particularly limited, and examples thereof include amine compounds such as primary to tertiary monofunctional and polyfunctional aliphatic amines, alicyclic amines, and aromatic amines.

  Among these, water-soluble or water-dispersible ones are preferable, for example, monoalkylamine, dimethylamine, trimethylamine, triethylamine, propylamine, diisopropylamine, tributylamine and other alkylamines having 2 to 8 carbon atoms; monoethanolamine , Dimethanolamine, methylethanolamine, dimethylethanolamine, cyclohexylamine, morpholine, N-methylmorpholine, pyridine, pyrazine, piperidine, imidazoline, imidazole and the like. These may be used alone or in combination of two or more. Among these, hydroxyamines such as monoethanolamine, diethanolamine, and dimethylethanolamine are preferable because of excellent water dispersion stability.

  The amine can be directly blended into the cationic electrodeposition coating composition.

  The lower limit of 0.3 meq and the upper limit of 25 meq are preferable for the compounding amount of the amine per 100 g of resin solid content in the cationic electrodeposition coating composition. If it is 0.3 meq / 100 g or more, a sufficient effect on throwing power is obtained, and if it is 25 meq / 100 g or less, an effect according to the amount added can be obtained, which is economical. The lower limit is more preferably 1 meq / 100 g, and the upper limit is more preferably 15 meq / 100 g.

  The cationic electrodeposition coating composition can be blended with a resin composition having an aliphatic hydrocarbon group. By blending the resin composition having an aliphatic hydrocarbon group, the impact resistance of the cured coating film is improved.

  The resin composition having an aliphatic hydrocarbon group includes (i) a sulfonium group of 5 to 400 mmol and an unsaturated double bond of 8 to 24 carbon atoms in the chain per 100 g of the solid content of the resin composition. An aliphatic hydrocarbon group that may be 80 to 135 mmol, an organic group having an unsaturated double bond having 3 to 7 carbon atoms, and at least one kind of propargyl group of 10 to 315 mmol, and , (Ii) having a sulfonium group, an aliphatic hydrocarbon group which may contain an unsaturated double bond having 8 to 24 carbon atoms in the chain, and an unsaturated double bond having 3 to 7 carbon atoms at the end The total content of the organic group and the propargyl group is 500 mmol or less per 100 g of the solid content of the resin composition.

  When the resin composition having an aliphatic hydrocarbon group is blended with the cationic electrodeposition coating composition, (i) 5 to 400 mmol of sulfonium groups per 100 g of resin solid content in the cationic electrodeposition coating composition And 10 to 300 mmol of an aliphatic hydrocarbon group which may contain an unsaturated double bond of 8 to 24 carbon atoms in the chain, a propargyl group and an unsaturated double bond of 3 to 7 carbon atoms as a terminal. (Ii) a sulfonium group and an aliphatic hydrocarbon group that may contain an unsaturated double bond having 8 to 24 carbon atoms in the chain; The total content of propargyl group and organic group having an unsaturated double bond having 3 to 7 carbon atoms at the end is 500 mmol or less per 100 g of resin solid content in the cationic electrodeposition coating composition, (iii) 8 to 8 carbon atoms Content of 4 unsaturated double bond and optionally containing in the chain aliphatic hydrocarbon group is preferably 3 to 30% by weight of the resin solids of the cationic electrodeposition coating composition.

  When blending the resin composition having an aliphatic hydrocarbon group to the cationic electrodeposition coating composition, if the sulfonium group is 5 mmol or more per 100 g of the solid content of the cationic electrodeposition coating composition, The throwing power and curability can be sufficiently exhibited, and it is excellent in hydration property and bath stability. If it is 400 millimoles or less per 100g of solid content of the said cationic electrodeposition coating composition, precipitation to a to-be-coated object will become more favorable.

  Moreover, if the aliphatic hydrocarbon group that may contain an unsaturated double bond having 8 to 24 carbon atoms in the chain is 80 mmol or more per 100 g of the solid content of the cationic electrodeposition coating composition, If the impact property is improved more favorably and is 350 mmol or less per 100 g of the solid content of the cationic electrodeposition coating composition, the handleability of the resin composition becomes easy.

  If the sum of the propargyl group and the organic group having an unsaturated double bond having 3 to 7 carbon atoms is 10 mmol or more per 100 g of the solid content of the cationic electrodeposition coating composition, sufficient curability is exhibited. If the cation electrodeposition coating composition has a solid content of 315 mmol or less per 100 g of solid content, the impact resistance is improved more favorably.

  It has a sulfonium group, an aliphatic hydrocarbon group that may contain an unsaturated double bond of 8 to 24 carbon atoms in the chain, a propargyl group, and an unsaturated double bond of 3 to 7 carbon atoms at the end. The total content with the organic group is 500 mmol or less per 100 g of the solid content of the cationic resin composition. If it is 500 millimoles or less, the resin of the target performance can be obtained stably.

  The cationic electrodeposition coating composition can be obtained, for example, by mixing the above-described components with the cationic resin composition as necessary, and dissolving or dispersing in water. When used in the electrodeposition step, it is preferably prepared so that the non-volatile content is a bath liquid having a lower limit of 10% by mass and an upper limit of 30% by mass. Moreover, it is preferable to prepare so that content of a propargyl group, a carbon-carbon double bond, and a sulfonium group in a cationic electrodeposition coating composition may not deviate from the range mentioned above.

  In the present embodiment, in order to disperse the diamond powder in the epoxy resin, it is not a mixed dispersion by a normal disperser such as a sand grinder mill, but a method in which the diamond and the dispersion medium are dispersed by collision is used. it can.

  The cationic electrodeposition coating composition according to the present embodiment has high diamond dispersion stability even when it contains diamond at a high concentration. This is because the cationic electrodeposition coating composition according to the present embodiment includes an epoxy resin having a predetermined structure as described above. Specifically, due to the high affinity between the diamond-constituting carbon and the aromatic ring structure in the novolak cresol type skeleton and the novolak phenol type skeleton in the epoxy resin, the hydrophobic interaction (Van der Waals force) It is estimated that the dispersibility is increasing.

(IV) Formation method of cationic electrodeposition coating film The coating film according to the present embodiment is formed according to the method described in International Publication No. 98/03595 pamphlet using the above-described electrodeposition coating composition. Can do.

  Specifically, in the method for forming a cationic electrodeposition coating film according to the present embodiment, the object to be coated immersed in the above-mentioned electrodeposition coating composition is used as a cathode, and a voltage is applied between the counter electrode and the above-mentioned electrode coating composition. It consists of an electrodeposition process for forming a film made of an electrodeposition coating composition on the surface of an object to be coated, and a heating process for obtaining a cured film by heating the film obtained in the electrodeposition process.

  As said coating object, it is a base material which shows the electroconductivity which can perform an electrodeposition process, and if it is a plate shape or a film form, it will not specifically limit, For example, iron, copper, aluminum, gold | metal | money, Examples thereof include metal molded products such as silver, nickel, tin, zinc, titanium, tungsten and the like, and plates and molded articles made of alloys containing these metals.

  Although the density | concentration of the said electrodeposition coating composition is not specifically limited, From a viewpoint of performing electrodeposition coating favorably, it is preferable to prepare so that a non volatile matter may be 15-25 mass%.

  The magnitude of the applied voltage is determined by the electric resistance value of the normally applied film, and a DC voltage of generally 5 to 500 V, more preferably 50 to 350 V is applied.

  The bath liquid temperature at the time of applying the voltage is appropriately set within a range of 0 to 100 ° C. because bath stability can be maintained even when the electrodeposition coating composition according to the present embodiment is at a high temperature. be able to. In consideration of the mechanical stability and thermal stability of the electrodeposition coating composition, and the reactivity of the cured functional group, 5 to 50 ° C is more preferable, and 15 to 35 ° C is still more preferable.

  The processing time of the electrodeposition process is generally set so that the total voltage application time, which is the sum of the time until the voltage is increased to the predetermined applied voltage and the time held at the predetermined voltage, is 0.5 to 30 minutes. Preferably, it is 1 to 10 minutes. If the time is 0.5 minutes or longer, a sufficient amount of chemical species activated by the electrode reaction is generated, and the curability of the coating can be improved. On the other hand, power consumption can be suppressed if the time is 30 minutes or less.

  The article to be coated may be sent to the heating process as it is after the electrodeposition process, or may be sent to the heating process after washing the surface with water to remove unnecessary water-soluble substances.

  The washing with water is preferably performed with pure water, and after the washing, the article to be coated is preferably left at room temperature for about 10 minutes.

  The heating step is performed in a heating furnace such as an electric drying furnace or a gas drying furnace. It is preferable to bake the coating object at 100 to 240 ° C., preferably 140 to 200 ° C., for 5 to 60 minutes, preferably 10 to 30 minutes.

(V) Coating film The coating film which concerns on this Embodiment is obtained by the formation method mentioned above.

  Since the coating film according to the present embodiment is obtained by the above-described forming method, diamond is uniformly dispersed in the coating film, and the smoothness when the film thickness is 20 μm is, for example, Ra = 0. 2 to 0.4 μm.

  Moreover, since the coating film which concerns on this Embodiment is obtained by the formation method mentioned above, a heat conductivity coefficient is about 0.20-0.35 W / m * K and a withstand voltage is about 1.5-2. It can be 5 kV.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to a following example.

(Thermal conductivity)
A cured coating film having a thermal conductivity coefficient κ and a known film thickness d was formed on a substrate having a thickness d ′ having a known thermal conductivity coefficient κ ′. For a measurement sample having a total film thickness of d ₀ (d ₀ = d ′ + d) and a heat conduction coefficient of κ ₀ , the temperature difference ΔT that has become a steady state and becomes constant after giving a constant amount of heat q. Measure and
q / 2 = κ ₀ · ΔT / d ₀
After obtaining κ ₀ from
d ₀ / κ ₀ = d / κ + d ′ / κ ′
From which κ was calculated.

  In addition, when the film thickness of the hardened coating film was thin, in order to make the error as small as possible, a measurement sample was obtained by stacking several to ten measurement samples. When stacking a plurality of such measurement samples, it is necessary to perform operations such as decompression so that air does not enter between the measurement samples (so that an air layer is not formed), and the measurement samples must be brought into close contact with each other. is there.

[Volume average particle diameter of diamond powder]
The volume average particle diameter of the diamond powder was measured by a laser diffraction / scattering method. As a measuring instrument, a particle size distribution measuring device (trade name: MICROTRACK-X100, manufactured by Nikkiso Co., Ltd.) was used.

[Number average molecular weight of epoxy resin]
The number average molecular weight of the epoxy resin was determined by measurement (polystyrene conversion) by gel permeation chromatography (GPC).

[Content of sulfonium group]
The sulfonium group content was determined by potentiometric titration using a potentiometer.

[Content of carbon-carbon double bond]
The content of carbon-carbon double bonds was determined by iodine value titration.

[Amine content]
The amine content was determined by potentiometric titration using a potentiometer.

[Example 1]
A novolak cresol type epoxy resin having an epoxy equivalent of 200.4 (trade name: Epototo YDCN-701, manufactured by Tohto Kasei Co., Ltd.), 13.5 g of propargyl alcohol and 0.2 g of dimethylbenzylamine were added to a stirrer, a thermometer, and a nitrogen introduction tube. In addition to the separable flask equipped with a reflux condenser, the temperature was raised to 105 ° C. and reacted for 1 hour to obtain a propargyl alcohol group and an epoxy resin having an epoxy equivalent of 445.

  To this, 50.6 g of linoleic acid and 0.1 g of additional dimethylbenzylamine were added, and the reaction was continued at the same temperature for 3 hours, containing a propargyl alcohol group and a long-chain unsaturated fatty acid residue, and an epoxy equivalent An epoxy resin having 2100 was obtained.

  To this was added 10.6 g of 1- (2-hydroxyethylthio) -2,3-propanediol, 4.7 g of glacial acetic acid, and 7.0 g of deionized water, and the mixture was allowed to react for 6 hours while keeping at 75 ° C. After confirming that the acid value is 5 or less, cation electrodeposition is finally obtained with diamond powder (trade name: “GMM-0-1”, manufactured by Diamond Innovations, volume average particle size: 0.5 μm). It added so that content in a coating composition might be 20 mass%, and was fully stirred and mixed. Furthermore, 60.8 g of deionized water was added to prepare a cationic electrodeposition coating composition.

  In the obtained cationic electrodeposition coating composition, the content (sulfonium value) of the sulfonium group in the epoxy resin solid content was 23.1 mmol / 100 g.

  Subsequently, using the cationic electrodeposition coating composition, electrodeposition coating was performed using the article to be coated as a cathode and the stainless steel plate as an anode.

  The object to be coated was lifted from the electrodeposition bath, washed with water, and cured by heating at a temperature of 190 ° C. for 25 minutes to obtain a coating film having a thickness of 20 μm. Various measurement results of the obtained coating film are shown in Table 1. In addition, the measurement of the thermal conductivity was repeated by stacking about 10 coating films and then reducing the pressure to make it a close contact.

[Example 2]
The same operation as in Example 1 was performed except that the diamond powder used was diamond powder (trade name: “GMM-0-2”, manufactured by Diamond Innovations, volume average particle diameter: 1.0 μm), and the film thickness was 20 μm. Coating film was obtained. Various measurement results of the obtained coating film are shown in Table 1.

Example 3
The same operation as in Example 1 was performed except that the diamond powder used was diamond powder (trade name: “GMM-0-0.5”, manufactured by Diamond Innovations, volume average particle diameter: 0.25 μm), and the film A coating film having a thickness of 20 μm was obtained. Various measurement results of the obtained coating film are shown in Table 1.

Example 4
Except that the content of diamond powder in the cationic electrodeposition coating composition was 10% by mass, the same operation as in Example 1 was performed to obtain a coating film having a thickness of 20 μm. Various measurement results of the obtained coating film are shown in Table 1.

Example 5
Except that the content of diamond powder in the cationic electrodeposition coating composition was 40% by mass, the same operation as in Example 1 was performed to obtain a coating film having a thickness of 20 μm. Various measurement results of the obtained coating film are shown in Table 1.

Example 6
Except that the content of diamond powder in the cationic electrodeposition coating composition was 60% by mass, the same operation as in Example 1 was performed to obtain a coating film having a thickness of 20 μm. Various measurement results of the obtained coating film are shown in Table 1.

[Comparative Example 1]
Except that diamond powder was not added to the cationic electrodeposition coating composition, the same operation as in Example 1 was performed to obtain a coating film having a thickness of 20 μm. Various measurement results of the obtained coating film are shown in Table 1.

[Comparative Example 2]
The same operation as in Example 1 was performed except that the diamond powder to be used was diamond powder (trade name: “GMM-2-4”, manufactured by Diamond Innovations, volume average particle diameter: 3 μm). A membrane was obtained. Various measurement results of the obtained coating film are shown in Table 1.

[Comparative Example 3]
The same operation as in Example 1 was performed except that the diamond powder to be used was diamond powder (trade name: “GMM-4-6”, manufactured by Diamond Innovations, volume average particle diameter: 5 μm). A membrane was obtained. Various measurement results of the obtained coating film are shown in Table 1.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The cationic electrodeposition coating composition of the present invention can form a coating film having high insulation and chemical resistance as well as excellent thermal conductivity. For this reason, it can apply suitably for uses, such as insulating films, such as an electrical and electronic component.

Claims (5)

It is a cationic electrodeposition coating composition containing diamond powder and an epoxy resin,
The volume average particle diameter of the diamond powder is in the range of 0.1 μm to 1.5 μm,
The epoxy resin has a sulfonium group and a propargyl group,
The cationic epoxy coating composition, wherein the epoxy resin has at least one skeleton selected from the group consisting of a novolak cresol skeleton and a novolak phenol skeleton.   2. The cationic electrodeposition coating composition according to claim 1, wherein the content of the diamond powder is in the range of 0.5 mass% to 50 mass%.   2. The cationic electrodeposition coating composition according to claim 1, wherein the content of the diamond powder is in the range of 10 mass% to 40 mass%.   A method for forming a coating film comprising a step of forming an electrodeposition coating film by performing cationic electrodeposition coating using the cationic electrodeposition coating composition according to any one of claims 1 to 3.   A coating film obtained by the forming method according to claim 4.