JP2004285273A - Cation electrodeposition coating composition superior in throwing power - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cation electrodeposition coating composition having throwing power and stability of a coating compatible with appearance of a coated film obtained. <P>SOLUTION: This cation electrodeposition coating composition comprises a resin composition having a sulfonium group and a propargyl group, in which furthermore, it contains an auxiliary substance for electrolytic active reduction, and standard electrode potential E<SB>S</SB>(V) of sulfur and standard electrode potential E<SB>M</SB>(V) of a metal contained in the auxiliary substance satisfy following inequality (1): ¾ E<SB>M</SB>-E<SB>S</SB>¾≤1.5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００６６】
上記結果から明らかなように、スルホニウム基及びプロパルギル基を有する樹脂と電解活性還元補助剤とを含み、かつ、硫黄の標準電極電位（Ｅ_ｓ（Ｖ））及び電解活性還元補助剤に含有される金属の標準電極電位（Ｅ_Ｍ（Ｖ））が｜Ｅ_Ｍ−Ｅ_Ｓ｜≦１．５で表される関係式を満たすカチオン電着塗料組成物は、塗料安定性及び塗膜外観を低下させることなく、優れた付きまわり性を有することがわかった。
【００６７】
しかしながら、｜Ｅ_Ｍ−Ｅ_Ｓ｜＞１．５である金属を含有する電解活性還元補助剤を含んでいる、あるいは、このような電解活性還元補助剤を含まないカチオン電着塗料組成物は付きまわり性に劣っていることがわかった。
【００６８】
【発明の効果】
本発明のカチオン電着塗料組成物は、スルホニウム基及びプロパルギル基を有するカチオン性樹脂組成物を含み、更に、電解活性還元補助剤を含んでいて、かつ、硫黄の標準電極電位Ｅ_Ｓ（Ｖ）及び上記電解活性還元補助剤に含有される金属の標準電極電位Ｅ_Ｍ（Ｖ）は、｜Ｅ_Ｍ−Ｅ_Ｓ｜≦１．５を満たすものであるので、塗料の安定性及び塗膜外観を低下させることなく、優れた付きまわり性を有する。
本発明のカチオン電着塗料組成物を用いることにより、袋部等の複雑な形状を有する構造物においても均一かつ防錆性に優れた電着塗膜を施すことが可能となる。
【図面の簡単な説明】
【図１】４枚ボックス法によるつきまわり性測定装置の概要を示す図。
【符号の説明】
１．評価板（英字は評価面を表し、カッコ内は、裏面を表す）
２．対極
３．直流電流
４．貫通孔
５．電着塗装槽
６．スターラー
７．電着塗料[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cationic electrodeposition coating composition used as an undercoat for automobiles, and more particularly to a cationic electrodeposition coating composition having excellent throwing power.
[0002]
[Prior art]
The steel sheet for an automobile body is usually coated with an undercoat, a middle coat and a top coat. Here, cationic electrodeposition is performed as the undercoat. This cationic electrodeposition coating can be applied over the details of an automobile body, and is generally performed for the purpose of rust prevention or the like.
[0003]
Therefore, even in the case of an automobile body having a complicated shape, it is required to secure a film thickness of a predetermined value or more in all parts, and therefore, a sufficient throwing power to the paint is required.
[0004]
Conventionally, in order to impart throwing power, a technique of increasing the viscosity of a film deposited by electrodeposition coating has been used. However, in such a method, there is a problem that the viscosity of the resin itself must be increased, the heat flow at the time of heat curing becomes insufficient, and the appearance of the obtained coating film deteriorates.
[0005]
In addition, a method of increasing the deposition rate of a coating film by reducing the amount of hydrating functional groups or the neutralization ratio of the resin has been performed. However, such a method has a problem in that the absolute amount of the hydrating functional group is insufficient, and the stability of the coating material is reduced.
A resin composition for a cationic electrodeposition coating containing an acetylated propargyl group and a sulfonium group is disclosed (for example, see Patent Document 1).
[0006]
[Patent Document 1]
JP-A-2000-38526 (page 2)
[0007]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a cationic electrodeposition coating composition that can achieve both the throwing power, the stability of the coating, and the appearance of the obtained coating film.
[0008]
[Means for Solving the Problems]
The present invention relates to a cationic electrodeposition coating composition containing a cationic resin composition having a sulfonium group and a propargyl group, further comprising an electrolytically active reducing auxiliary, and comprising a standard electrode potential E of sulfur._S(V) and the standard electrode potential E of the metal contained in the electrolytically active reduction aid._M(V) is the following formula (1);
| E_M-E_S| ≦ 1.5 (1)
A cationic electrodeposition coating composition characterized by satisfying the following.
[0009]
The above equation (1) gives | E_M-E_SIt is preferable to satisfy | ≦ 1.0. The electrolytically active reduction aid is preferably 0.1 to 1.0% by mass in terms of metal based on the solid content of the cationic resin composition.
[0010]
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The cationic electrodeposition coating composition of the present invention contains an electrolytically active reducing auxiliary, and has a standard electrode potential E of sulfur._S(V) and the standard electrode potential E of the metal contained in the electrolytically active reduction aid._M(V) is the following formula (1);
| E_M-E_S| ≦ 1.5 (1)
It satisfies. It is considered that the inclusion of the electrolytically active reduction aid containing a metal satisfying the above formula (1) promotes the insulation of the deposited film due to the reduction of sulfur to passivation, and improves the throwing power.
[0011]
Here, the standard electrode potential is an equilibrium potential specific to each element or compound when the reference electrode is defined as a hydrogen electrode (0 V). The standard electrode potential of sulfur (E_S(V)) is -0.476 V (Source: Revised 4th edition, Chemical Handbook Basic Edition II, pages 465 to 468, published September 30, 1993 / edited by The Chemical Society of Japan). The standard electrode potential of this sulfur (E_S(V)), the standard electrode potential (E_MExamples of the metal having (V)) include iron (−0.440 V), copper (+0.153 V), cobalt (−0.277 V), zinc (−0.763 V), and manganese (−1.18 V). Can be mentioned.
[0012]
Where | E_M-E_SWhen |> 1.5, the effect of the present invention becomes insufficient. | E_M-E_S| ≦ 1.0 is more preferable, and | E_M-E_S| ≦ 0.5 is more preferable. Here, from the viewpoint of throwing power, cobalt and zinc are preferable, and considering HAPs, the metal is preferably zinc. Examples of the electrolytically active reduction aid containing a metal satisfying the above formula (1) include carboxylate salts such as cobalt acetate, cobalt lactate, zinc acetate and zinc gluconate.
[0013]
In the cationic electrodeposition coating composition of the present invention, the electrolytically active reducing aid is preferably 0.1 to 1.0% by mass in terms of metal based on the solid content of the cationic resin composition described later. If the amount is less than 0.1% by mass, the effect may be insufficient. If the amount exceeds 1.0% by mass, it is not economical. More preferably, it is 0.1 to 0.7% by mass.
[0014]
The cationic electrodeposition coating composition of the present invention contains a cationic resin composition having a sulfonium group and a propargyl group. The resin constituting the cationic resin composition may have both a sulfonium group and a propargyl group in one molecule, but this is not always necessary. For example, any one of a sulfonium group and a propargyl group in one molecule Or only one of them. In the latter case, the cationic resin composition as a whole has all of these two types of curable functional groups. That is, when the cationic resin composition comprises a resin having a sulfonium group and a propargyl group, a mixture of a resin having only a sulfonium group and a resin having only a propargyl group, or a mixture of all these resins Any of these cases may be used. The cationic resin composition having a sulfonium group and a propargyl group has the meaning described above.
[0015]
The sulfonium group is a hydrating functional group of the cationic resin composition. When a voltage or current exceeding a certain level is applied in the electrodeposition process, the sulfonium group undergoes an electrolytic reduction reaction on the electrode to lose the ionic group and irreversibly become nonconductive. At that time, it is considered that the above-mentioned electrolytically active reduction auxiliary acts to form an electrodeposited film having higher insulating properties.
[0016]
Further, it is considered that an electrode reaction is caused in the electrodeposition coating process, and the generated hydroxide ion is retained by the sulfonium group, so that the electrogenerated base is generated in the electrodeposited film. This electrogenerated base can convert a heat-reactive propargyl group present in the electrodeposited film into an allene bond having a high thermal reactivity.
[0017]
The resin serving as the skeleton of the cationic resin composition is not particularly limited, and for example, an epoxy resin is preferable. As the above-mentioned epoxy resin, those having at least two or more epoxy groups in one molecule are preferable. For example, epibisepoxy resin, a resin obtained by extending the chain thereof with diol, dicarboxylic acid, diamine or the like; epoxidized polybutadiene Novolak phenol type polyepoxy resin; novolak cresol type polyepoxy resin; polyglycidyl acrylate; polyglycidyl ether of aliphatic polyol or polyether polyol; polyepoxy resin such as polyglycidyl ester of polybasic carboxylic acid; it can. Novolak phenol type polyepoxy resin, novolak cresol type polyepoxy resin, and polyglycidyl acrylate are preferred from the viewpoint of easiness of polyfunctionalization for enhancing curability. Note that a part of the epoxy resin may be a monoepoxy resin.
[0018]
The number average molecular weight of the cationic resin composition is not particularly limited, and for example, preferably has a lower limit of 500 and an upper limit of 20,000. If it is less than 500, the coating efficiency at the time of cationic electrodeposition coating may decrease, and if it exceeds 20,000, it may be difficult to form a good coating on the surface of the object to be coated. The number average molecular weight can be set to a preferred molecular weight according to the resin skeleton. For example, in the case of a novolak phenol type polyepoxy resin or a novolak cresol type polyepoxy resin, the lower limit is preferably 700 and the upper limit is preferably 5000. .
[0019]
The content of the sulfonium group of the cationic resin composition is, after satisfying the conditions for the content of the sulfonium group and the propargyl group described below, a lower limit of 5 mmol and an upper limit of 400 mmol per 100 g of the solid content of the cationic resin composition. is there. If it is less than 5 mmol / 100 g, throwing power and curability may be insufficient, and hydration and bath stability may be reduced. If the amount exceeds 400 mmol / 100 g, the deposition of the coating film on the surface of the work may be poor. The content of the sulfonium group can be set to a preferable content according to the resin skeleton. For example, in the case of a novolak phenol type polyepoxy resin or a novolak cresol type polyepoxy resin, the lower limit is 10 mmol / 100 g. Is more preferable. The upper limit is preferably 250 mmol / 100 g, and more preferably 150 mmol / 100 g.
[0020]
The propargyl group of the cationic resin composition acts as a curing functional group in the cationic electrodeposition coating composition of the present invention. Further, for unknown reasons, the coexistence with the sulfonium group can improve the throwing power of the cationic electrodeposition coating composition.
[0021]
The content of the propargyl group of the cationic resin composition, the lower limit of 10 mmol, the upper limit of 495 mmol per 100 g of the solid content of the cationic resin composition, after satisfying the conditions of the content of the sulfonium group and the propargyl group described below. is there. If it is less than 10 mmol / 100 g, the throwing power and curability may be insufficient, and if it exceeds 495 mmol / 100 g, the hydration stability may be poor. The content of the propargyl group can be set to a preferable content according to the resin skeleton. For example, in the case of a novolak phenol type polyepoxy resin or a novolak cresol type polyepoxy resin, the lower limit is 20 mmol / 100 g. Is more preferable. Further, the upper limit is more preferably 395 mmol / 100 g.
[0022]
The total content of sulfonium groups and propargyl groups in the cationic resin composition is preferably an upper limit of 500 mmol per 100 g of the solid content of the cationic resin composition. If it exceeds 500 mmol / 100 g, there is a possibility that a resin may not be actually obtained or a desired performance may not be obtained. The total content of the sulfonium group and the propargyl group of the cationic resin composition can be set to a preferable content according to the resin skeleton, for example, a novolak phenol type polyepoxy resin, a novolak cresol type polyepoxy resin In this case, the upper limit is more preferably 400 mmol / 100 g.
[0023]
The cationic resin composition may further contain a carbon-carbon double bond. Since the carbon-carbon double bond has high reactivity, curability can be improved.
When the cationic resin composition contains a carbon-carbon double bond, the content thereof, after satisfying the condition of the total content of a propargyl group and a carbon-carbon double bond described below, the cationic resin composition It is preferable that the lower limit is 10 mmol and the upper limit is 485 mmol per 100 g of the solid content. If it is less than 10 mmol / 100 g, the effect of improving curability may be insufficient, and if it exceeds 485 mmol / 100 g, hydration stability may be deteriorated. The content of the carbon-carbon double bond can be set to a preferred content according to the resin skeleton, for example, in the case of novolak phenol type polyepoxy resin, novolak cresol type polyepoxy resin, the lower limit Is more preferably 20 mmol / 100 g. Further, the upper limit is more preferably 375 mmol / 100 g.
[0024]
When having a carbon-carbon double bond, the total content of the propargyl group and the carbon-carbon double bond of the cationic resin composition is 80 mmol lower limit and 450 mmol upper limit per 100 g of the solid content of the cationic resin composition. Is preferred. If it is less than 80 mmol, the curability may be insufficient. If the amount exceeds 450 mmol / 100 g, the content of the sulfonium group decreases, and the throwing power may be insufficient. The total content of the propargyl group and the carbon-carbon double bond of the cationic resin composition can be set to a preferable content according to the resin skeleton, for example, novolak phenol type polyepoxy resin, novolac cresol type In the case of a polyepoxy resin, the lower limit is more preferably 100 mmol, and the upper limit is more preferably 395 mmol / 100 g.
[0025]
When the carbon-carbon double bond is contained, the total content of the sulfonium group, propargyl group and carbon-carbon double bond is preferably 500 mmol or less per 100 g of the solid content of the cationic resin composition. . If it exceeds 500 mmol / 100 g, the resin may not be actually obtained or the desired performance may not be obtained. The total content of the sulfonium group, propargyl group and carbon-carbon double bond can be set to a more preferable content depending on the resin skeleton used.For example, novolak phenol type epoxy resin, novolak cresol type epoxy resin In this case, the content is more preferably 400 mmol / 100 g or less.
[0026]
The cationic resin composition contained in the cationic electrodeposition coating composition of the present invention includes, for example, an epoxy resin having at least two epoxy groups in one molecule, a compound having a functional group that reacts with an epoxy group and a compound having a propargyl group. Reacting to obtain an epoxy resin composition having a propargyl group (i), and reacting a sulfide / acid mixture with the remaining epoxy groups in the epoxy resin composition having a propargyl group obtained in step (i). And the step (ii) of introducing a sulfonium group.
[0027]
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, for example, both a functional group that reacts with an epoxy group such as a hydroxyl group and a carboxyl group and a propargyl group. The compound may be contained, and specific examples thereof include propargyl alcohol and propargylic acid. Of these, propargyl alcohol is preferred in terms of availability and ease of reaction.
[0028]
When the cationic resin composition contained in the cationic electrodeposition coating composition of the present invention contains a carbon-carbon double bond, if necessary, in the above-mentioned step (i), a functional group which reacts with an epoxy group is used. A compound having a group and a carbon-carbon double bond (hereinafter, referred to as “compound (B)”) may be used in combination with the compound (A). As the compound (B), for example, a compound containing both a functional group that reacts with an epoxy group such as a hydroxyl group or a carboxyl group and a carbon-carbon double bond may be used. 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 And the like. When the group which 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 mono (meth) acryloyloxyethyl ethyl ester and mono (meth) acryloyloxyethyl phthalate; synthetic unsaturated fatty acids such as oleic acid, linoleic acid and ricinoleic acid; natural unsaturated acids such as linseed oil and soybean oil Saturated fatty acids and the like can be mentioned.
[0029]
In the step (i), the compound (A) is reacted with the epoxy resin having at least two epoxy groups in one molecule to obtain an epoxy resin composition having a propargyl group, or the compound (A) A) and, if necessary, the above compound (B) are reacted to obtain an epoxy resin composition having a propargyl group and a carbon-carbon double bond. In the latter case, in the step (i), the compound (A) and the compound (B) may be used in the reaction after mixing both in advance, or the compound (A) and the compound (A) (B) and may be used separately in the reaction. The functional group that reacts with the epoxy group of the compound (A) and the functional group that reacts with the epoxy group of the compound (B) may be the same or different.
[0030]
In the step (i), when the compound (A) and the compound (B) are reacted, the mixing ratio of the two may be set so as to have a desired functional group content. For example, the above-mentioned propargyl What is necessary is just to set so that it may become content of a group and a carbon-carbon double bond.
[0031]
The reaction conditions in the above step (i) are usually several hours at room temperature or 80 to 140 ° C. In addition, known components necessary for advancing a reaction such as a catalyst and a solvent can be used as necessary. 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 resin composition or analyzing the instrument. The reaction product thus obtained is generally a mixture of an epoxy resin having one or more propargyl groups, or an epoxy resin having one or more propargyl groups and one or more carbon-carbon double bonds. Is a mixture of In this sense, the resin composition having a propargyl group or a propargyl group and a carbon-carbon double bond can be obtained by the step (i).
[0032]
In the step (ii), the sulfonium group is introduced by reacting the sulfide / acid mixture with the remaining epoxy group in the propargyl group-containing epoxy resin composition obtained in the step (i). The sulfonium group can be introduced by reacting a sulfide / acid mixture with an epoxy group to introduce and sulfonate a sulfide, or after introducing a sulfide, further adding an acid or methyl fluoride, methyl chloride, methyl bromide, or the like. The reaction can be carried out by, for example, performing a sulfonium conversion reaction of the introduced sulfide with an alkyl halide or the like and, if necessary, performing anion exchange. From the viewpoint of the availability of reaction raw materials, a method using a sulfide / acid mixture is preferable.
[0033]
The sulfide is not particularly limited, and examples thereof include aliphatic sulfides, mixed aliphatic-aromatic sulfides, aralkyl sulfides, and cyclic sulfides. Specifically, for example, diethyl sulfide, dipropyl sulfide, dibutyl sulfide, dihexyl sulfide, diphenyl sulfide, ethyl phenyl 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.
[0034]
The acid is not particularly limited and includes, 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 and the like. Can be mentioned.
[0035]
The mixing ratio of the sulfide and the acid in the sulfide / acid mixture is generally preferably about 100/40 to 100/100 in terms of molar ratio of sulfide / acid.
[0036]
The reaction of the step (ii) is performed, for example, by mixing the epoxy resin composition having a propargyl group obtained in the step (i) with a predetermined amount of the sulfide set to have the above-mentioned sulfonium group content. And a mixture with the above-mentioned acid and 5 to 10 times the mole of sulfide to be used by mixing with water, and the mixture is usually stirred at 50 to 90 ° C. for several hours. The end point of the reaction may be based on the remaining acid value being 5 or less. Confirmation of sulfonium group introduction in the obtained resin composition can be performed by potentiometric titration.
[0037]
When the sulfonation reaction is performed after the introduction of the sulfide, the reaction can be performed 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.
[0038]
When a part of the propargyl group of the cationic resin composition contained in the cationic electrodeposition coating composition of the present invention is converted into acetylide, the propargyl group-containing epoxy resin composition obtained in the step (i) may be The reaction can be carried out by reacting a metal compound to acetylate some of the propargyl groups in the epoxy resin composition. The metal compound is preferably a transition metal compound that can be converted to acetylide, and examples thereof include a complex or salt of a transition metal such as copper, silver, or barium. Specific examples include copper acetylacetone, copper acetate, silver acetylacetone, silver acetate, silver nitrate, barium acetylacetone, 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, copper acetylacetone is preferable in view of ease of bath management. .
[0039]
The reaction conditions for converting a part of the propargyl group to acetylide are usually several hours at 40 to 70 ° C. The progress of the reaction can be confirmed by coloring of the obtained resin composition, disappearance of methine proton by nuclear magnetic resonance spectrum, and the like. Thus, the reaction time at which the propargyl group in the resin composition is converted into acetylide at a desired ratio is confirmed, and the reaction is terminated. The resulting reaction product is generally a mixture of an epoxy resin in which one or more of the propargyl groups has been acetylated. A sulfonium group can be introduced into the thus obtained epoxy resin composition in which a part of the propargyl group is acetylated by the above step (ii).
[0040]
The step of converting part of the propargyl group of the epoxy resin composition to acetylide and the step (ii) can be performed under the same reaction conditions, so that both steps can be performed simultaneously. A method of performing both steps simultaneously is advantageous because the manufacturing process can be simplified.
[0041]
In this manner, a propargyl group and a sulfonium group, and, if necessary, a carbon-carbon double bond and a cationic resin composition having a propargyl group partially acetylated, while suppressing decomposition of the sulfonium group , Can be manufactured. Note that acetylide has explosive properties in a dry state, but does not pose a safety problem because the acetylide is carried out in an aqueous medium and the target substance can be obtained as an aqueous composition.
[0042]
The cationic electrodeposition coating composition of the present invention contains the above-mentioned cationic resin composition. In the cationic electrodeposition coating composition of the present invention, since the above-mentioned cationic resin composition itself has curability, it is not always necessary to use a curing agent. However, it may be used to further improve the curability. Examples of such a curing agent include compounds having at least one of a propargyl group and a carbon-carbon double bond, such as polyepoxides such as novolak phenol, pentaerythritol tetraglycidyl ether, and propargyl alcohol. And a compound obtained by subjecting a compound having a carbon-carbon double bond such as acrylic acid to an addition reaction.
[0043]
Further, it is not always necessary to use a curing catalyst in the cationic electrodeposition coating composition of the present invention. However, when it is necessary to further improve the curability depending on the curing reaction conditions, a commonly used transition metal compound or the like may be appropriately added as necessary. Such a compound is not particularly limited. For example, a compound in which a ligand such as cyclopentadiene or acetylacetone or a carboxylic acid such as acetic acid is bonded to a transition metal such as nickel, cobalt, manganese, palladium, or rhodium. And the like. The compounding amount of the curing catalyst is preferably 0.1 to 20 mmol per 100 g of the resin solid content in the cationic electrodeposition coating composition.
[0044]
The cationic electrodeposition coating composition of the present invention may contain an amine. The conversion of the sulfonium group to sulfide by electrolytic reduction in the electrodeposition process is increased by the incorporation of the amine. The above-mentioned 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, and examples thereof include alkylamines having 2 to 8 carbon atoms such as monomethylamine, dimethylamine, trimethylamine, triethylamine, propylamine, diisopropylamine, and tributylamine; monoethanolamine; Examples include 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 them, hydroxyamines such as monoethanolamine, diethanolamine, and dimethylethanolamine are preferable because of excellent water dispersion stability.
[0045]
The above amine can be directly blended into the cationic electrodeposition coating composition of the present invention. In conventional neutralized amine-based cationic electrodeposition paints, the addition of free amine will deprive the neutralizing acid in the resin and significantly degrade the stability of the electrodeposition solution, but in the present invention, Such inhibition of bath stability does not occur.
[0046]
The amount of the amine is preferably 0.3 to 25 meq per 100 g of the resin solid content in the cationic electrodeposition coating composition. If it is less than 0.3 meq / 100 g, a sufficient effect on throwing power cannot be obtained, and if it exceeds 25 meq / 100 g, the effect corresponding to the added amount cannot be obtained, which is uneconomical. More preferably, it is 1 to 15 meq / 100 g.
[0047]
The cationic electrodeposition coating composition of the present invention may also contain a resin composition having an aliphatic hydrocarbon group. By blending the resin composition having an aliphatic hydrocarbon group, the impact resistance of the obtained coating film is improved. As the resin composition having the aliphatic hydrocarbon group, a sulfonium group of 5 to 400 mmol per 100 g of solid content of the resin composition, and an aliphatic double chain having an unsaturated double bond having 8 to 24 carbon atoms may be contained. It contains at least one of 10 to 315 mmol of an organic group and a propargyl group having 80 to 135 mmol of a hydrocarbon group and an unsaturated double bond having 3 to 7 carbon atoms at a terminal, and has a sulfonium group and 8 to 24 carbon atoms. The total content of an aliphatic hydrocarbon group which may contain an unsaturated double bond in the chain, an organic group having a terminal of an unsaturated double bond having 3 to 7 carbon atoms, and a propargyl group is a solid content of the resin composition. One having 500 mmol or less per 100 g per minute can be mentioned.
[0048]
When the resin composition having an aliphatic hydrocarbon group is blended with the cationic electrodeposition coating composition, a sulfonium group of 5 to 400 mmol and a carbon number of 8 to 100 g per 100 g of the resin solid content in the cationic electrodeposition coating composition. A total of 10 to 300 mmol of an aliphatic hydrocarbon group which may contain an unsaturated double bond in the chain and a propargyl group and an organic group having an unsaturated double bond having 3 to 7 carbon atoms at a terminal of 24; 485 mmol, and a sulfonium group, an aliphatic hydrocarbon group and a propargyl group which may have an unsaturated double bond having 8 to 24 carbon atoms in the chain, and an unsaturated double bond having 3 to 7 carbon atoms Is at most 500 mmol per 100 g of the cationic electrodeposition coating resin solids, and contains the unsaturated double bond having 8 to 24 carbon atoms in the chain. Content of those aliphatic hydrocarbon group is preferably 3 to 30% by weight of the resin solids of the cationic electrodeposition coating composition.
[0049]
When a resin composition having an aliphatic hydrocarbon group is blended with the cationic electrodeposition coating composition, if the sulfonium group is less than 5 mmol / 100 g, sufficient throwing power and curability can be exhibited. In addition, hydration and bath stability are deteriorated. If it exceeds 400 mmol / 100 g, deposition of the coating film on the surface of the article to be coated will be poor. When the number of the aliphatic hydrocarbon groups having 8 to 24 carbon atoms and which may contain an unsaturated double bond in the chain is less than 80 mmol / 100 g, the improvement in impact resistance is insufficient, and 350 mmol / If it exceeds 100 g, the handleability of the resin composition becomes difficult. When the total of the propargyl group and the organic group having an unsaturated double bond having 3 to 7 carbon atoms at the terminal is less than 10 mmol / 100 g, even when used in combination with another resin or a curing agent, sufficient Curability cannot be exhibited, and if it exceeds 315 mmol / 100 g, the improvement in impact resistance becomes insufficient. A sulfonium group, an aliphatic hydrocarbon group which may contain an unsaturated double bond having 8 to 24 carbon atoms in the chain, a propargyl group, and an organic group having an unsaturated double bond having 3 to 7 carbon atoms at the terminal. The total content is 500 mmol or less per 100 g of the solid content of the resin composition. If it exceeds 500 mmol, the resin may not be actually obtained or the desired performance may not be obtained.
[0050]
The cationic electrodeposition coating composition of the present invention may further contain, if necessary, other components used in ordinary cationic electrodeposition coating compositions. The other components are not particularly limited, and include, for example, pigments, rust preventives, pigment-dispersed resins, surfactants, antioxidants, and additives for paints such as ultraviolet absorbers.
[0051]
The pigment is not particularly limited and includes, for example, coloring pigments such as titanium dioxide, carbon black and red iron oxide; rust-preventive pigments such as basic lead silicate and aluminum phosphomolybdate; and extender pigments such as kaolin, clay and talc. Examples thereof include those generally used for cationic electrodeposition coatings. Specific examples of the rust inhibitor include calcium phosphite, zinc calcium phosphite, calcium-supported silica, calcium-supported zeolite, and the like. The total amount of the pigment and the rust inhibitor is preferably 0 to 50% by mass as a solid content in the cationic electrodeposition coating composition.
[0052]
The pigment dispersion resin is used for stably dispersing the pigment in the cationic electrodeposition coating composition. The pigment-dispersed resin is not particularly limited, and a commonly used pigment-dispersed resin can be used. Further, a pigment dispersion resin containing a sulfonium group and an unsaturated bond in the resin may be used. Pigment dispersion resin containing such a sulfonium group and an unsaturated bond, for example, a hydrophobic epoxy resin obtained by reacting a bisphenol type epoxy resin and a half-blocked isocyanate, or reacting a sulfide compound, or And a method of reacting a sulfide compound with the resin in the presence of a monobasic acid and a hydroxyl group-containing dibasic acid. The non-heavy metal rust inhibitor can also be stably dispersed in the cationic electrodeposition coating composition by the pigment dispersion resin.
[0053]
The curing temperature of the cationic electrodeposition coating composition of the present invention is preferably set to 130 to 220 ° C. When the curing temperature is lower than 130 ° C., the smoothness of the obtained multilayer coating film may be reduced. When the curing temperature is higher than 220 ° C., the physical properties of the obtained multilayer coating film may be reduced, or the appearance of the multilayer coating film obtained by applying the overcoat may be reduced. The setting of the curing temperature can be performed by a method known by those skilled in the art, such as adjusting the types and amounts of the curing functional group, the curing agent and the catalyst.
[0054]
The curing temperature in the present invention refers to a temperature at which a coating film having a gel fraction of 85% is obtained by heating for 30 minutes. The measurement of the gel fraction is performed by a method of calculating from the difference in mass between the test coated plate before and after the test when the test coated plate is immersed in acetone and refluxed for 5 hours.
[0055]
The cationic electrodeposition coating composition of the present invention can be obtained by, for example, mixing the above-mentioned components with the above-mentioned cationic resin composition and dissolving or dispersing in water. When used for cationic electrodeposition coating, it is preferable to prepare a bath solution having a nonvolatile content of 10 to 30%. Further, it is preferable that the content of the propargyl group, the carbon-carbon double bond and the sulfonium group in the cationic electrodeposition coating composition is adjusted so as not to deviate from the range shown for the cationic resin composition. .
[0056]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
Production Example 1 Production of Resin Composition 1
Cresole novolak type epoxy resin having an epoxy equivalent of 201.8 (trade name: Epotote YDCM-703, manufactured by Toto Kasei Co., Ltd.) is added to 3082.5 g, propargyl alcohol 621.3 g and linseed oil fatty acid 535.4 g, and dimethylbenzylamine 9.2 g as a catalyst. Was added to a separable flask equipped with a stirrer, thermometer, nitrogen inlet tube and cooling device, the temperature was raised to 120 ° C., and the mixture was reacted for 2 hours. When the epoxy equivalent reached 1850, 1- (2-hydroxy After adding 311.6 g of ethylthio) -2-propanol, 110 g of glacial acetic acid and 329.9 g of deionized water, the mixture was reacted at 75 ° C. for 6 hours to confirm that the residual acid value was 5 or less. .2 g was added to obtain a target resin composition 1 solution.
[0057]
Production Example 2 Production of Resin Composition 2
660 g of polybutadiene dicarboxylic acid (NISSO PB-C1000, manufactured by Nippon Soda Co., Ltd.) and 60 g of 2-butyne-1,4-diol (manufactured by BASF) were dissolved in 145 g of xylene, and 0.7 g of p-toluenesulfonic acid was added. The mixture was condensed for 7 hours while dehydrating at 150 ° C. When the theoretical amount of water was generated, the solvent was removed under reduced pressure to obtain a resin composition 2 solution having a number average molecular weight of 6070, a glass transition temperature of -21.1 ° C, and a hydroxyl value of 18.5.
[0058]
Example 1
The resin composition 1 solution obtained in Production Example 1 and the resin composition 2 obtained in Production Example 2 were mixed so that the solid content of the resin composition 2 was 17% by mass, and then mixed. After adding deionized water to a solid content of 70% by mass, the mixture was stirred with a high-speed mixer for 1 hour. Further, deionized water was added so that the solid content concentration became 23.5% by mass, and zinc acetate (II) dihydrate was added to 0.6% by mass (based on 100 g of the solid content of the resin composition in terms of metal). , 0.179 g: standard electrode potential -0.763 V), and then N-methylethanolamine was added at 8 meq per 100 g of solid content of the resin composition, followed by stirring. Further, deionized water was added to obtain a cationic electrodeposition coating composition 1 having a solid content concentration of 20% by mass.
[0059]
Example 2
Instead of zinc acetate, cobalt (II) acetate tetrahydrate was added in an amount of 0.6% by mass (0.142 g of cobalt with respect to 100 g of the resin composition in terms of metal: standard electrode potential -0.277 V). Except that, in the same manner as in Example 1, a cationic electrodeposition coating composition 2 having a solid content of 20% by mass was obtained.
[0060]
Comparative Example 1
A cationic electrodeposition coating composition 3 having a solid content of 20% by mass was obtained in the same manner as in Example 1 except that zinc acetate was not used.
[0061]
Comparative Example 2
1.8 mass% of magnesium acetate (II) tetrahydrate in place of zinc acetate (0.204 g in terms of metal, based on 100 g of solid content of the resin composition: standard electrode potential -2.36 V) A cationic electrodeposition coating composition 4 having a solid content of 20% by mass was obtained in the same manner as in Example 1 except for the addition.
[0062]
Evaluation test
<Collapsibility>
The roundness with four boxes was measured by the measuring device shown in FIG. Four liters of the cationic electrodeposition coating compositions 1 to 4 obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were placed in a plastic electrodeposition coating container (100 × 250 × 200 mm), and the mixture was stirred with a magnetic stirrer. Four zinc phosphate-treated steel sheets obtained by treating JIS G 3141 SPCC-SD with Surfdyne SD-500 (a zinc phosphate surface treating agent manufactured by Nippon Paint Co., Ltd.) were used, the distance between the steel sheets was set to 20 mm, and the distance from the counter electrode was 3 mm. An 8mmφ hole was drilled by the first sheet, and an evaluation plate with a box-shaped structure was made so that paint could enter only through this hole, and placed in the above electrodeposition coating container so that the distance to the counter electrode was 150mm. did. The side portions of the evaluation plate having the box-like structure were subjected to an electrical insulation treatment so that no coating was formed on the side portions. The evaluation plate was used as a cathode, and a voltage was applied between the electrode and a counter electrode to perform coating. The coating was performed by increasing the voltage to 200 V in 5 seconds from the start of the application and then maintaining the voltage at 200 V for 175 seconds. The bath temperature at that time was adjusted to 28 ° C. The coated evaluation plate was washed with water and heated at 180 ° C for 20 minutes. After air cooling, the thickness of the A side of the evaluation plate closest to the counter electrode and the thickness of the G side of the evaluation plate farthest from the counter electrode were measured. Then, the throwing power was evaluated based on the G-plane / A-plane ratio (G / A value). The results obtained are shown in Table 1.
[0063]
<Coating appearance>
Examples 1 and 2 and Comparative Examples 1 and 2 were applied to a zinc phosphate-treated steel sheet obtained by treating 70 × 150 mm JIS G 3141 SPCC-SD with Surfdyne SD-500 (a zinc phosphate surface treating agent manufactured by Nippon Paint Co., Ltd.). Each of the cationic electrodeposition coating compositions 1 to 4 obtained in 2 was electrodeposited so as to have a dry film thickness of 15 μm, washed with water, and heated at 180 ° C. for 20 minutes to obtain a test plate. The surface roughness of the obtained test plate was measured using a contact-type surface roughness meter (SJ-201 manufactured by Mitutoyo) under the condition of a center line average roughness (Ra) of a cutoff of 0.8 mm. evaluated. The results obtained are shown in Table 1.
[0064]
<Paint stability>
The cationic electrodeposition coating compositions 1 to 4 obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were placed in a container, and allowed to stand at 40 ° C. ± 1 ° C. with stirring for 30 days. A test plate was prepared in the same manner as described above, and the center line average roughness (Ra) of the coating film was evaluated. The results obtained are shown in Table 1.
[0065]
[Table 1]

[0066]
As is apparent from the above results, the resin containing the sulfonium group- and propargyl group-containing resin and the electrolytically active reducing auxiliary, and the standard electrode potential of sulfur (E_s(V)) and the standard electrode potential (E_M(V)) is | E_M-E_SIt has been found that the cationic electrodeposition coating composition satisfying the relational expression of | ≦ 1.5 has excellent throwing power without lowering the coating stability and the appearance of the coating film.
[0067]
However, | E_M-E_SA cationic electrodeposition coating composition that contains an electroactive reduction aid containing a metal with |> 1.5 or that does not contain such an electroactive reduction aid may have poor throwing power. all right.
[0068]
【The invention's effect】
The cationic electrodeposition coating composition of the present invention contains a cationic resin composition having a sulfonium group and a propargyl group, further contains an electrolytically active reducing auxiliary, and has a standard electrode potential E of sulfur._S(V) and the standard electrode potential E of the metal contained in the electrolytically active reduction aid._M(V) is | E_M-E_SSince it satisfies | ≦ 1.5, it has excellent throwing power without deteriorating the stability of the paint and the appearance of the paint film.
By using the cationic electrodeposition coating composition of the present invention, it is possible to apply an electrodeposition coating film that is uniform and excellent in rust prevention even on a structure having a complicated shape such as a bag portion.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a throwing power measuring device using a four-box method.
[Explanation of symbols]
1. Evaluation board (English letters indicate the evaluation surface, and parentheses indicate the back surface)
2. Opposite pole
3. DC current
4. Through hole
5. Electrodeposition coating tank
6. Stirrer
7. Electrodeposition paint

Claims (3)

A cationic electrodeposition coating composition comprising a cationic resin composition having a sulfonium group and a propargyl group,
Further, it contains an electrolytically active reducing auxiliary,
The standard electrode potential E _S (V) of sulfur and the standard electrode potential E _M (V) of the metal contained in the electrolytically active reducing aid are represented by the following formula (1):
| E _M -E _S | ≦ 1.5 (1)
A cationic electrodeposition coating composition characterized by satisfying the following. The cationic electrodeposition coating composition according to claim 1, wherein the formula (1) satisfies | E _M -E _S | ≦ 1.0. 3. The cationic electrodeposition coating composition according to claim 1, wherein the electroactive reduction aid is 0.1 to 1.0 mass% in terms of metal based on the solid content of the cationic resin composition. 4.

Images