JP2003268315A - Leadless cationic electrodeposition paint composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leadless cationic electrodeposition paint composition excellent in a surface smoothing effect in the formation of an anticorrosive paint film by electrodeposition coating. <P>SOLUTION: The leadless cationic electrodeposition paint composition contains porous silica particles having a pore volume of 0.44-1.8 ml/g and an average particle diameter of 10 μm or less; the above silica particles have the porosity, an oil absorption of 300 ml/100 g or less and a pore volume of 0.44-1.81 ml/g; and the electrodeposition paint composition comprises the above silica particles, a cationic epoxy resin, its hardener and a pigment. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead-free cationic electrodeposition coating composition containing a rust preventive pigment exhibiting a surface smoothing effect when forming a coating film by an electrodeposition coating method. Further, the present invention relates to a lead-free cationic electrodeposition coating composition which is excellent in storage stability of the pigment-dispersed paste.

[0002]

2. Description of the Related Art In electrodeposition coating, even an article to be coated having a complicated shape can be coated in detail, and automatic and continuous coating can be performed. It has a complicated shape and is widely used as an undercoating method for objects to be coated that require high rust prevention. Further, compared with other coating methods, the use efficiency of the paint is extremely high, which is economical and is widely used as an industrial coating method. Cationic electrodeposition coating is performed by immersing an object to be coated as a cathode during the cationic electrodeposition coating and applying a voltage.

Hitherto, in order to impart corrosion resistance to the electrodeposition coating composition, a corrosion resistance imparting agent containing lead has been added. recent years,
Since lead has an adverse effect on the environment, it is required to reduce the amount used, and so-called lead-free cationic electrodeposition coatings that do not contain such a corrosion resistance-imparting agent containing lead are being mainly used.

The properties required for the coating film obtained by the cationic electrodeposition coating film are that the coating film is smooth and has no surface defects such as pits and dents called cratering, It has high adhesion and does not adversely affect smoothness and gloss. A defective coating called cissing is considered to be caused by volatile components or oils on the coating surface or in the coating film, and they may be caused by bumping during baking or by forming through holes in the coating film when it volatilizes. ing.

In order to avoid the cissing phenomenon, a method of preventing the volatile component or oil which causes the cissing phenomenon from entering the coating film or the inside thereof, or modifying the coating material itself by the materials or additives to be incorporated into the coating material Can be considered. However, it is not possible to avoid the entry or mixing of the causative substance because various processes are required before coating, or because the coated product has a complicated shape and the oil content is unavoidable. is there. Therefore, mainly the improvement of the material of the paint itself,
Additives are being studied.

JP-A-64-62496, JP-A-6-62
4-62497, and JP-A-64-66278.
Japanese Patent Laid-Open Publication No. 2003-242242 discloses that cationic electrodeposition paint has an oil absorption of 100 ml / 1.
It is disclosed that a specific amount of pigment of 00 g or more is mixed. A silicon dioxide pigment is described as an example of the pigment having an oil absorption of 100 ml / 100 g or more. However, this paint is intended to improve the corrosion resistance of the edge portion (end surface), and is not intended to avoid coating film defects such as cissing.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides a lead-free cationic electrodeposition coating composition having an excellent surface smoothing effect in the formation of a rust preventive coating film by electrodeposition coating. To provide.

[0008]

According to the present invention, the average particle size is 10 μm, which is porous and has a pore volume of 0.44 to 1.8 ml / g.
The present invention provides a lead-free cationic electrodeposition coating composition containing the following silica particles, which achieves the above object.

The silica particles have an oil absorption of 300 ml.
It is preferably / 100 g or less.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Generally, a cationic electrodeposition coating composition contains a cationic epoxy resin and a curing agent for the resin as basic components, and further contains pigments and additives and is dispersed in an aqueous medium. . The cationic electrodeposition paint used in the present invention needs to be "lead-free". "Lead-free" means substantially free of lead compounds or lead ions, and means free of lead in an amount that adversely affects the environment. Specifically, it means that the concentration of the lead compound in the cationic electrodeposition bath is not more than 100 ppm, preferably not more than 50 ppm.

The lead-free cationic electrodeposition coating composition of the present invention is characterized by containing specific silica particles as described above. The silica particles are porous and their pore volume is 0.
It is 44 to 1.8 ml / g, preferably 0.8 to 1.6 ml / g. If it is less than 0.44 ml / g, it has a drawback that its effect is small, and if it is less, it becomes more remarkable. When it exceeds 1.6 ml / g, it has a defect of poor dispersion stability, and when it is more than that, dispersion becomes more impossible. Here, the pore volume means the pore volume of the porous portion. The pore volume is measured by the mercury porosimetry method. The mercury porosimetry method is a method in which mercury is injected into the pores of powder and the pressure required for the porosity and the amount of mercury injected are measured to measure the specific surface area and pore distribution. These can be measured using a mercury penetration type pore distribution measuring device.

The silica particles have an average particle size of 10 μm or less, preferably 5 to 0.1 μm. If it is smaller than 0.1 μm, the dispersion stability is poor. 10μ
If it exceeds m, the corrosion resistance decreases. Here, the "average particle size" is generally used to represent the particle size of the particles (whether the particle size is coarse or fine), the median diameter equivalent to 50% by weight, the arithmetic average diameter, the surface area average diameter, Volume area average diameter and the like are used. The average particle diameter shown in this specification is shown by the value measured by the laser method. The laser method is a method of measuring the average particle size, particle size distribution, etc. by dispersing particles in a solvent, applying a laser beam to the dispersion solvent, and capturing and calculating the scattered light obtained.

Generally, silica refers to a solid substance containing silicon dioxide as a main component, but the silica particles of the present invention are porous as described above and have a pore volume of 0.44 to 1.8 ml / g.
The average particle size must be 10 μm or less. The silica particles having such characteristics are special and different from commonly known silica gel and natural silica particles (for example, extender pigments such as kaolin). The silica particles used in the present invention can be obtained by mixing a sodium silicate and an acid using a so-called wet method. Specific silica particles used in the present invention include Sylysia commercially available from Fuji Silysia Chemical Ltd.

In the present invention, since the silica particles are porous, a large amount of silicate ions are eluted from the silica particles into the electrodeposition coating composition, and a large amount of silicate ions are present, resulting in a high smoothness of the coating film. Therefore, it is considered to prevent the coating film defect called cissing, but at present it has not been confirmed. It is also considered that the addition of silica particles changes the rheology at the time of baking due to, for example, a thickening effect, and enhances the smoothness of the coating film, and as a result, it is possible to prevent coating film defects.

The silica particles used in the present invention also have an oil absorption of 350 ml / 100 g or less, preferably 220 to 50 ml / 1.
00 g, more preferably 170-50 ml / 100 g. When the oil absorption is low, the water dispersibility is improved and the storage stability is improved. Here, the oil absorption amount means JIS K5101-91.
(Pigment test method) The value of the oil absorption amount depends on the characteristics of the substance constituting the pigment, the size of the particles, and the like. Generally, the smaller the pigment particles, the larger the oil absorption value. As a method for reducing the oil absorption value of small particles, coating of particles (for example, organic coating with wax) is currently known. It was also found that addition of silica particles improves water traceability. Here, "improvement in water traceability" means that the trace residue due to water on the coating film surface is reduced.

The silica particles used in the present invention can be considered to be a solid substance which constitutes a part of the pigment described later. In that case, it can be considered that some of the pigments described below can be replaced with the silica particles of the present invention. Therefore, the blending amount of the above silica is preferably 1 to 90% by weight, more preferably 3 to 50% by weight, and particularly preferably 5 to 25% by weight based on the pigment. If it is added in an amount of more than 90%, the coating film hiding property is deteriorated. On the contrary, if the addition amount is less than 1% by weight, the effect due to the addition of silica particles (prevention of coating film defects) becomes insufficient. It is possible to consider the silica particles of the present invention as an additive without considering them as a part of the pigment. In that case, the amount of the silica particles to be incorporated in the electrodeposition coating composition is 0.1 parts by weight relative to 100 parts by weight of the coating solid content.
2 to 150 parts by weight, preferably 0.5 to 20 parts by weight, more preferably 1 to 7 parts by weight. The drawbacks when the addition amount is large and when the addition amount is small are the same as in the case where it is considered as a part of the pigment. However, when it is considered as an additive, the amount of the pigment added is inevitably small.

As described above, the lead-free cationic electrodeposition coating composition of the present invention contains, in addition to the specific silica particles, a cationic epoxy resin, a curing agent and, if necessary, a pigment or an additive. Hereinafter, each component will be described.

Cationic Epoxy Resin The cationic epoxy resin used in the present invention includes amine-modified epoxy resin. This cationic epoxy resin is disclosed in JP-A Nos. 54-4978 and 56-3.
Known resins such as those described in No. 4186 may be used.

The cationic epoxy resin is typically a
All of the epoxy rings of the bisphenol type epoxy resin are opened with an active hydrogen compound capable of introducing a cationic group, or
Alternatively, some of the epoxy rings are opened with another active hydrogen compound, and the remaining epoxy rings are opened with an active hydrogen compound capable of introducing a cationic group.

A typical example of the bisphenol type epoxy resin is a bisphenol A type or bisphenol F type epoxy resin. As the former commercial product, Epicoat 828
(Yukaka Shell Epoxy Co., epoxy equivalent 180 to 19
0), Epicoat 1001 (the same, epoxy equivalent 450-
500), Epicoat 1010 (the same, epoxy equivalent 30
00 to 4000), and the latter commercially available products include Epicoat 807, (the same, epoxy equivalent 170).

Japanese Patent Laid-Open No. 5-306327, No. 0004
An oxazolidone ring-containing epoxy resin as described in the formula of the paragraph, Chemical formula 3 may be used as the cationic epoxy resin. This is because a coating film having excellent heat resistance and corrosion resistance can be obtained.

As a method for introducing an oxazolidone ring into an epoxy resin, for example, a blocked polyisocyanate blocked with a lower alcohol such as methanol and a polyepoxide are heated and kept in the presence of a basic catalyst to produce a lower alcohol produced as a by-product. Obtained by distilling from the system.

A particularly preferred epoxy resin is an oxazolidone ring-containing epoxy resin. This is because a coating film having excellent heat resistance and corrosion resistance as well as impact resistance can be obtained.

It is known that an epoxy resin containing an oxazolidone ring can be obtained by reacting a bifunctional epoxy resin with a diisocyanate blocked with a monoalcohol (that is, bisurethane). Specific examples and production methods of this oxazolidone ring-containing epoxy resin are described in, for example, JP-A No. 2000-128959, paragraphs 0012 to 0.
047 paragraph.

These epoxy resins may be modified with suitable resins such as polyester polyols, polyether polyols, and monofunctional alkylphenols. Further, the epoxy resin can be chain-extended by utilizing the reaction between the epoxy group and the diol or dicarboxylic acid.

These epoxy resins have a content of 0.3-
It is desirable to perform ring opening with an active hydrogen compound so that the amine equivalent is 4.0 meq / g, more preferably 5 to 50% of the primary amino group is occupied.

Examples of the active hydrogen compound capable of introducing a cationic group include acid salts of primary amine, secondary amine and tertiary amine,
There are sulfide and acid mixtures. In order to prepare the primary, secondary or / and tertiary amino group-containing epoxy resin of the present invention, an acid salt of a primary amine, a secondary amine or a tertiary amine is used as an active hydrogen compound capable of introducing a cationic group. To use.

Specific examples include butylamine, octylamine, diethylamine, dibutylamine, methylbutylamine, monoethanolamine, diethanolamine, N-methylethanolamine, triethylamine hydrochloride, N, N-dimethylethanolamine acetate, diethyl disulfide. Besides acetic acid mixture, there are secondary amines obtained by blocking primary amines such as aminoethylethanolamine ketimine and diethylenetriamine diketimine. A plurality of amines may be used in combination.

Curing Agent The curing agent used in the present invention is preferably a blocked polyisocyanate obtained by blocking polyisocyanate with a blocking agent, wherein the polyisocyanate has two or more isocyanate groups in one molecule. Refers to a compound. Examples of the polyisocyanate include aliphatic series,
It may be any one of an alicyclic type, an aromatic type, an aromatic-aliphatic type and the like.

Specific examples of polyisocyanates include aromatic diisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), p-phenylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate (HDI), 2,2. Aliphatic diisocyanates having 3 to 12 carbon atoms such as 1,4-trimethylhexane diisocyanate and lysine diisocyanate; 1,4-cyclohexane diisocyanate (CDI), isophorone diisocyanate (IPDI), 4,4′-dicyclohexylmethane diisocyanate (water MDI), methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, and 1,3
-Diisocyanatomethylcyclohexane (hydrogenated XD
I), hydrogenated TDI, 2,5- or 2,6-bis (isocyanatomethyl) -bicyclo [2.2.1] heptane (also called norbornane diisocyanate) and the like having 5 to 18 carbon atoms. Alicyclic diisocyanates having an aromatic ring such as xylylene diisocyanate (XDI) and tetramethyl xylylene diisocyanate (TMXDI); modified products of these diisocyanates (urethanes, carbodiimides, uretdiones, uretoimines, Viewlet and /
Or isocyanurate modified product); and the like. These can be used alone or in combination of two or more kinds.

Polyisocyanate is added to ethylene glycol, propylene glycol, trimethylol propane,
Polyhydric alcohols such as hexanetriol and NCO / O
An adduct or prepolymer obtained by reacting at an H ratio of 2 or more may also be used as a curing agent.

The polyisocyanate is preferably an aliphatic polyisocyanate or an alicyclic polyisocyanate. This is because the formed coating film has excellent weather resistance.

Preferred examples of the aliphatic polyisocyanate or the alicyclic polyisocyanate include hexamethylene diisocyanate, hydrogenated TDI, hydrogenated MDI and hydrogenated XD.
I, IPDI, norbornane diisocyanate, their dimers (biuret), trimers (isocyanurate)
Etc.

The blocking agent is a compound which is added to a polyisocyanate group and is stable at room temperature, but can regenerate a free isocyanate group when heated above the dissociation temperature.

As the blocking agent, low temperature curing (160 ° C.)
If desired), lactam blocking agents such as ε-caprolactam, δ-valerolactam, γ-butyrolactam and β-propiolactam, and formaldoxime, acetoaldoxime, acetoxime, methylethylketoxime, diacetylmonooxime. It is preferable to use an oxime-based blocking agent such as cyclohexane oxime.

The binder containing the cationic epoxy resin and the curing agent is generally 2% of the total solid content of the electrodeposition coating composition.
It is contained in the electrodeposition coating composition in an amount of 5 to 85% by weight, preferably 40 to 70% by weight.

Pigment The electrodeposition coating composition generally contains a pigment as a colorant. The electrodeposition coating composition of the present invention also contains a pigment usually used. Examples of such pigments are color pigments such as titanium white, carbon black and red iron oxide;
Extenders such as kaolin, talc, aluminum silicate, calcium carbonate, mica and clay; zinc phosphate, iron phosphate, aluminum phosphate, calcium phosphate, zinc phosphite, zinc cyanide, zinc oxide, aluminum tripolyphosphate, Examples thereof include rust preventive pigments such as zinc molybdate, aluminum molybdate, calcium molybdate, aluminum phosphomolybdate, and aluminum zinc phosphomolybdate.

The pigment is generally contained in the electrodeposition coating composition in an amount of 1 to 35% by weight, preferably 10 to 30% by weight based on the total solids of the electrodeposition coating composition. As aforementioned,
The specific silica particles used in the present invention can be considered as a part of the pigment as a solid component, and in that case, a part of the blending amount of the above pigment is made the silica particles. If you consider silica particles as an additive, the amount of pigment blended will decrease,
0.01 to 15% by weight of the coating solid content, preferably 0.2 to
It becomes 2% by weight.

However, since the electrodeposition coating material of the present invention is lead-free, a corrosion resistance-imparting agent containing lead, for example, basic lead silicate,
Lead-based rust preventive pigments such as basic lead sulfate, red lead, and cyanamide lead are not used, or even if they are used, the diluted paint (state added to the electrodeposition bath) has a lead ion concentration of 100 ppm.
It should be used in the following amounts: A high lead ion concentration may not only be harmful to the environment, but also reduce smoothness.

Pigment Dispersion Paste When a pigment is used as a component of an electrodeposition coating composition, the pigment is dispersed in an aqueous medium in advance at a high concentration together with a resin generally called a pigment dispersion resin to form a paste. This is because the pigment is in powder form, and it is difficult to disperse it in one step in a low-concentration uniform state used in the electrodeposition coating composition. Generally, such a paste is called a pigment dispersion paste.

The pigment dispersion paste is prepared by dispersing a pigment together with a pigment dispersion resin in an aqueous medium. In the present invention,
It is preferable that the silica particles are also made into a dispersion paste together with the pigment. As the pigment-dispersing resin, a cationic or nonionic low-molecular-weight surfactant or a cationic polymer such as a modified epoxy resin having a quaternary ammonium group and / or a tertiary sulfonium group is generally used. As the aqueous medium, ion-exchanged water, water containing a small amount of alcohol, or the like is used. Generally, the solid content ratio of the pigment dispersion resin and the pigment is 1:10.
Used in a ratio of ~ 1: 1.

Electrodeposition Coating Composition The electrodeposition coating composition of the present invention comprises a cationic epoxy resin,
It is prepared by dispersing a pigment dispersion paste containing a curing agent and silica particles in an aqueous medium. Moreover, a neutralizing agent is usually contained in the aqueous medium in order to improve the dispersibility of the cationic epoxy resin. The neutralizing agent is an inorganic or organic acid such as hydrochloric acid, nitric acid, phosphoric acid, formic acid, acetic acid, lactic acid. The amount is at least 20%, preferably 3
It is an amount that achieves a neutralization rate of 0 to 60%.

The amount of the curing agent is such that it reacts with the active hydrogen-containing functional groups such as primary, secondary or / and tertiary amino groups and hydroxyl groups in the cationic epoxy resin during curing to give a good cured coating film. Generally 90/10 to 50/50, preferably 80/20 to 65, expressed as the solids weight ratio of the cationic epoxy resin to the curing agent.
The range is / 35.

The electrodeposition paint is dibutyltin dilaurate,
It may include tin compounds such as dibutyltin oxide, and conventional urethane cleavage catalysts. Since it contains substantially no lead, its amount is preferably 0.1 to 5% by weight of the blocked polyisocyanate compound.

The electrodeposition coating composition can contain conventional coating additives such as water-miscible organic solvents, surfactants, antioxidants, UV absorbers, and pigments.

The electrodeposition coating composition of the present invention is electrodeposition coated on an object to be coated by a method well known to those skilled in the art to form a cured coating film. The object to be coated in the case of performing electrodeposition coating using this cationic electrodeposition coating composition is preferably a conductor which has been subjected to surface treatment such as zinc phosphate treatment by a dipping or spraying method in advance, The surface treatment may not be performed. The conductor is not particularly limited as long as it can serve as a cathode during electrodeposition coating, and a metal base material is preferable.

Examples of such metal base materials include steel sheets such as cold rolled steel sheets and zinc-nickel steel sheets. Further, such a steel plate may be a structure that is used for a specific purpose, such as the automobile body described above. The structure refers to a structure formed by molding the above metal material into an uneven shape so as to be used for automobiles and other purposes. Particularly when used for automobiles, the article to be coated is preferably a structure using a zinc-nickel steel plate from the viewpoint of corrosion resistance.

The conditions under which electrodeposition is carried out are generally the same as those used for other types of electrodeposition coating. The applied voltage may vary widely and may range from 1 volt to hundreds of volts. Current density is usually about 10 amps / m ^{2 to} 160
Ampere / m ² , which tends to decrease during electrodeposition.

After the electrodeposition, the coating is baked at an elevated temperature by a conventional method, for example, in a baking oven, a baking oven or an infrared heat lamp. The baking temperature may vary, but is usually about 1
It is 40 ° C to 180 ° C.

[0050]

Effects of the Invention By adding silica particles having a specific shape to the lead-free cationic electrodeposition coating composition, it is possible to impart a surface smoothing effect and rust preventive property, and further improve water traceability. Furthermore, the silica particles of a specific form have an oil absorption of 3
By using less than 00 ml / 100 g, the storage stability of the pigment dispersion paste is improved.

[0051]

EXAMPLES The following Preparations and Examples are given by way of illustration only and not limitation. In these, "parts" and "%" are based on weight unless otherwise specified.

Production Example 1 (Cationic Epoxy Resin Combination)
Adult) stirrer, condenser, nitrogen inlet tube, a bisphenol A type epoxy resin in a flask fitted with a thermometer and a dropping funnel (epoxy equivalent 188) 752.0 parts methanol 7
7.0 parts, methyl isobutyl ketone 200.3 parts and dibutyl tin dilaurate 0.3 part were charged and stirred at room temperature to form a uniform solution, and 2,4- / 2,6-tolylene diisocyanate 80/20 (mass ratio). 5 parts of 174.2 parts of the mixture
If added dropwise over 0 minutes, the temperature inside the system will rise to 70 ° C due to heat generation.
Reached IR spectrum is based on isocyanate 2
It showed the appearance of absorption of 1730 cm ^-1 based on the carbonyl group of disappearance and urethane absorption of 280 cm ^-1.

After adding 2.7 parts of N, N-dimethylbenzylamine, the temperature inside the system was raised to 120 ° C., and by-product methanol was distilled off using a decanter until the epoxy equivalent reached 463. I went. The IR spectrum showed the disappearance of the absorption at 1730 cm ^{-1 due} to the carbonyl group of the urethane and the appearance of the absorption at 1750 cm ^{-1 due} to the carbonyl group of the oxazolidone ring.

158.3 parts of octyl acid and 83.3 parts of methyl isobutyl ketone were added and the reaction was carried out while maintaining the temperature of 125 ° C. until the epoxy equivalent reached 1146. The system was cooled until the temperature reached 110 ° C., and 47.2 parts of aminoethylethanolamine ketimine (79% by mass methyl isobutyl ketone solution), diethanolamine 42.0 parts, N-methylethanolamine 30.0 parts and After adding 17.3 parts of methyl isobutyl ketone, it heated up and made it react at 120 degreeC for 2 hours. Thus, an amino group-containing epoxy resin having a nonvolatile content of 80% was obtained.

Production Example 2 (Compound of polyisocyanate curing agent)
In a flask equipped with a stirrer, a cooler, a nitrogen introducing tube, a thermometer and a dropping funnel, 199 parts of hexamethylene diisocyanate isocyanurate type trimer (Coronate HX, manufactured by Nippon Polyurethane Co.) and methyl isobutyl ketone 122.8. Parts and dibutyltin dilaurate 0.2
Parts were weighed and heated to 50 ° C. Methyl ethyl ketoxime 87 while cooling from the outside and maintaining the temperature at 50 ° C
Parts were added dropwise over 2 hours. After the dropping was completed, the temperature was raised to 70 ° C., and the reaction was carried out until the isocyanate group disappeared by IR analysis while maintaining this temperature to obtain an aliphatic block polyisocyanate curing agent.

Production Example 3 (Production of Pigment Dispersion Resin) A reaction vessel equipped with a stirrer, a cooling pipe, a nitrogen introducing pipe and a thermometer was charged with isophorone diisocyanate (hereinafter, IP).
222.0 parts of DI) was added and diluted with 39.1 parts of MIBK, and then 0.2 parts of dibutyl tin laurate was added. Then, after raising the temperature to 50 ° C., 131.5 parts of 2-ethylhexanol was added dropwise over 2 hours in a dry nitrogen atmosphere while stirring. The reaction temperature was maintained at 50 ° C. by cooling as appropriate. As a result, 2-ethylhexanol half-blocked IPDI was obtained.

Then, 376.0 parts of Epicoat 828 (bisphenol A type epoxy resin manufactured by Yuka Shell Epoxy Co., epoxy equivalent 182 to 194), bisphenol A
114.0 parts and 29.2 parts of octylic acid were mixed with a stirrer,
The reaction vessel was equipped with a cooling tube, a nitrogen introducing tube and a thermometer. The reaction mixture was heated to 130 ° C. in a nitrogen atmosphere, 0.15 parts of dimethylbenzylamine was added, and the mixture was reacted at 170 ° C. for 1 hour under an exothermic reaction.
A bisphenol A type epoxy resin having an epoxy equivalent of 649 was obtained.

Then, after cooling to 140 ° C., the 2-ethylhexanol half-blocked IPD prepared above was prepared.
I396.8 parts were added, and the mixture was kept at 140 ° C. for 1 hour for reaction. Then, 323.2 parts of ethylene glycol monobutyl ether was added for dilution, and the reaction mixture was diluted with 1 part.
Cooled to 00 ° C. Then, 78.3% of the methyl isobutyl monoketimine compound of aminoethyl ethanolamine
188.8 parts of MIBK solution was added.

After the mixture was kept at 110 ° C. for 1 hour, it was cooled to 90 ° C., 360.0 parts of ion-exchanged water was added, and stirring was continued for another 30 minutes to remove the ketiminated portion in the epoxy resin. Converted to primary amino group.
After removing excess water and MIBK from this mixture under reduced pressure, ethylene glycol monobutyl ether 588.1
It was diluted with 1 part to obtain a resin for pigment dispersion having a primary amino group. (Resin solid content 50%)

Production Example 4 (Production of Pigment Dispersion Paste) In a sand grind mill, 60 parts of the pigment dispersion resin obtained in Production Example 3 in solid content, 2.0 parts of carbon black, and 100 parts of the pigments shown in Table 1 were used. 0.0 parts, titanium dioxide 80.0
Parts, 18.0 parts of aluminum phosphomolybdate and 221.7 parts of ion-exchanged water were added and dispersed until the particle size became 10 μm or less, to obtain pigment dispersion pastes A to D.

[Table 1] ^* Silica particles: Silysia manufactured by Fuji Silysia Chemical Ltd.

[0061] Example 1 cationic epoxy resin of Preparation 1 and Preparation Example 2 blocked polyisocyanate curing agent solids blending ratio of 75:25
After uniform mixing with, ethylene glycol mono-2-ethylhexyl ether was added so as to be 3% based on the solid content. 90% acetic acid was added to this and the neutralization rate was 43.0.
It was neutralized so that the concentration became%, and ion-exchanged water was further added to slowly dilute. MIBK was removed by reducing the pressure so that the solid content became 36.0% to obtain a main emulsion. Pigment dispersion paste A541.7 parts obtained according to Preparation Example 4 (formulation 1 in Table 1) using 150.0 parts of this main emulsion and the pigment dispersion resin obtained according to Preparation Example 3 was replaced with 1949.3 parts of ion-exchanged water and dibutyltin. A cationic electrodeposition coating composition having a solid content of 20.0% was prepared by mixing with 9.0 parts of oxide. The content of silica particles was 3% (solid content ratio).

Example 2 A cationic electrodeposition coating composition was prepared in the same manner as in Example 1 except that paste B was used instead of pigment dispersion paste A.

Comparative Example 1 A cationic electrodeposition coating composition was prepared in the same manner as in Example 1 except that paste C was used instead of pigment dispersion paste A.

Comparative Example 2 A cationic electrodeposition coating composition was prepared in the same manner as in Example 1 except that paste D was used instead of pigment dispersion paste A.

Evaluation (1) Evaluation of cissing resistance (mixing cissing property) 10 ppm of rust preventive machine oil (Knox Frust 320 Parker Kosan Co., Ltd.) was mixed with the obtained electrodeposition coating composition and continuously stirred for 48 hours. Then, a test piece having a size of 7 × 15 cm was placed vertically and electrodeposited so that the dry coating film had a thickness of 20 μm to obtain a wet film. Wash this wet film with water and
After leaving it for 0 minutes, it was baked at 160 ° C. for 10 minutes. The surface of the coating film after baking was visually observed, the number of cissing was counted, and evaluated according to the following evaluation criteria.

Evaluation criteria If the number of cissing is 5 or less

(2) Anti-repellency evaluation (boiling oil repellency) The obtained electrodeposition coating composition was electrodeposited so that a dry coating film of 20 μm was obtained to obtain a test piece of 7 × 15 cm having a wet film. . The wet film was washed with water, left for 30 minutes, and then 0.2 ml of rust-preventing machine oil (Knox Frust 320 Parker Kosan Co., Ltd.) was scattered and adhered during the baking process. After cooling, the coating film surface was visually observed, the number of cissing was counted, and evaluated according to the following evaluation criteria.

Evaluation criteria If the number of cissing is 100 or less

(3) Evaluation of Water Traceability The obtained electrodeposition coating composition was electrodeposited so as to obtain a dry coating film of 20 μm to obtain a test piece of 7 × 15 cm having a wet film. The wet film was washed with water and left for 30 minutes, then the test piece was leveled and 0.2 ml of pure water was placed on the wet film. 160 ℃, keeping the horizontal state
The surface of the coating film after baking for 10 minutes was visually observed and evaluated according to the following evaluation criteria.

Evaluation Criteria ○: Water marks remain, but the marks cannot be seen by applying the intermediate coating. ×: Water marks remain, and the water marks are still visible even when the intermediate coating is applied.

(4) Evaluation of Storage Stability The pigment-dispersed pastes A to D obtained above were stored at 40 ° C. for 1 hour.
After leaving for one day, a change in viscosity was confirmed.

Evaluation criteria ◯: Change in viscosity 10 kU or less ×: Change in viscosity 10 kU or more

The evaluation results are shown in Tables 2 and 3.

[Table 2]

[0074]

[Table 3]

Claims (3)

[Claims] 1. A porous material having a pore volume of 0.44 to 1.
A lead-free cationic electrodeposition coating composition containing silica particles having an average particle size of 10 μm or less, which is 8 ml / g. 2. The oil absorption of the silica particles is 300 ml / 10.
The lead-free cationic electrodeposition coating composition according to claim 1, which is 0 g or less. 3. A lead-free cationic electrodeposition coating composition containing a cationic epoxy resin, a curing agent therefor and a pigment, which is more porous and has a pore volume of 0.44 to 1.8 ml / g.
And a lead-free cationic electrodeposition coating composition containing silica particles having an average particle diameter of 10 μm or less.