JPH01294895A - Electrodeposition coating method - Google Patents

Abstract

PURPOSE:To form an electrodeposition coating having excellent smoothness and thick even at its edge by dispersing a mixture of an acrylic copolymer and fine pigment particles in water to obtain a cationic electrodeposition coating composition, electrodepositing the composition on a material to be coated, electrodepositing another cationic electrodeposition coating composition, baking, and curing the compositions. CONSTITUTION:An acrylic copolymer (A component) contg. a hydrolyzable alkoxysilane and a cationic group and having generally about 10-100 hydroxyl group value and about 5000-100,000 number average mol.wt. is prepared. Meanwhile, the fine pigment particles (B component) having >=100 oil absorption and <=3.5mum primary particle diameter is prepared. A mixture of the A component and the B component is dispersed in water to cause cross linking in the particles, and a cationic electrodeposition paint composition (I) contg. fine gelled polymer particles contg. fine pigment particles is obtained. The composition is coated with the composition (I) by electrodeposition. The obtained uncured electrodeposition coating film is coated with a cationic electrodeposition paint composition (II) having <=0.7mA/cm<2> minimum electrodeposition and electrodissolution density, and then the compositions are baked and then cured.

Description

[Detailed Description of the Invention] Hair is the best! The present invention relates to a cationic electrodeposition coating method, and more specifically, the present invention relates to a cationic electrodeposition coating method, and more specifically, it applies two coats of electrodeposited coating that has excellent smoothness and is thick even on edges such as corners of cut surfaces, folded corners, and protrusions. The present invention relates to a cationic electrodeposition coating method in which a vine is formed by deposition.

Cationic electrodeposition coating has excellent throwing power and uniformity of film thickness.
It has excellent corrosion resistance on flat surfaces, and is widely used as an undercoat for automobile bodies. However, cationic electrodeposition coatings generally have low melt viscosity and have excellent smoothness, but on the other hand, There is little or no cured coating film formed on the edges, which tends to cause defects such as extremely poor rust prevention at the edges.

In order to improve the rust prevention properties of the edges, for example, anti-rust steel plates are used, or after electrodeposition and baking, anti-corrosion paint is applied to the edges using a roller or spacing. , the cost and number of steps are enormous. In addition, various attempts have been made such as adding a large amount of pigment to the electrodeposition coating or reducing the amount of plasticizing components, but it is difficult to form a thick electrodeposition coating on the edges (hereinafter referred to as ``edge cover''). ) is difficult to achieve at the same time as achieving smoothness of the coating film. Also,
2. Equivalent coating has also been attempted, achieving edge cover by increasing the concentration of electrocoating paint used in the first layer or using pigments with high oil absorption, and achieving smoothness in the second layer. Another method has been proposed, but this method:
Particularly, there is a problem in that poor finishing occurs due to pigment settling in the horizontal portion of the bag structure of the object to be coated.

Therefore, the inventors of the present invention have conducted extensive research with the aim of developing an electrodeposition coating method that has excellent edge coverage and coating surface smoothness, and does not cause poor finish due to pigment sedimentation. In the adhesive coating method, by using a cationic electrodeposition coating composition containing gelled polymer fine particles containing a specific fine particle pigment as the first layer electrodeposition coating, the viscosity of the molten coating film during baking hardening can be reduced. As a result, edge coverage can be sufficiently performed, and a specific cationic electrodeposition paint composition with good thermofluidity is used as the second layer electrodeposition paint, and the first layer and It has been discovered that if the second layer of electrodeposited coating is simultaneously cured by one step by baking, an electrodeposited coating with good coating surface smoothness and finished appearance can be obtained, and the above object can be achieved, and the present invention has been made. completed.

According to the present invention, an acrylic co-1F combination containing a hydrolyzable alkoxysilane group and a cationic group has an oil absorption of 100 or more and a primary particle diameter of 0.5111T1.
A cationic electrodeposition coating composition +11 containing gelled aggregate fine particles containing a fine particle pigment, which is obtained by water-dispersing a mixture with the following fine particle pigment and crosslinking the mixture with the fine particle pigment, is electrodeposited on an object to be coated. A cationic electrodeposition coating composition (Ill) having a minimum electrodeposition current density of 0.7 mA/crn" or less and an emulsion degree of 80% by weight or more is applied onto the cured electrodeposition coating film. An electrodeposition coating method is provided, which comprises baking and curing an uncured electrodeposited multilayer coating film formed by the above method.

In the present invention, the "acrylic copolymer containing a hydrolyzable alkoxysilane group and a cationic group" is used to form the gelling polymer fine particles containing the fine particle pigment contained in the cationic electrodeposition coating composition (1). is a cationic group, especially an acid-neutralized amino group, which is stably dispersed in water as a water-dispersible group, and a silanol group generated by hydrolysis of an alkoxysilane group is dispersed among the silanol groups and even an acrylic group. When a hydroxyl group is present in the copolymer, it is condensed with the hydroxyl group, and together with the fine particle pigment, intraparticle chestnut bridge is performed and gelation occurs.
In the method of the present invention, a cationic electrodeposition coating containing gelling polymer fine particles containing ir+ is formed. It is characterized in that the composition is used as the first layer of electrodeposition paint.

The acrylic copolymer containing a hydrolyzable alkoxysilane group and a cationic group used to form such particulate pigment-containing gelling polymer microparticles generally has a fat vinylic double bond and a hydrolyzable a polymerizable unsaturated vinyl silane monomer containing an alkoxysilane group,
and (b) contains a polymerizable unsaturated monomer containing a vinyl double bond and a cationic group as an essential component, and optionally (c) contains a vinyl double bond and a hydroxyl group. It can be produced by copolymerizing a mixture containing a polymerizable unsaturated monomer and/or (d) a polymerizable unsaturated monomer other than the above.

The vinyl silane monomer of fat described above has the following formula: represents an integer of n
represents an integer from 1 to 8] These are included.

Examples of the vinylsilane monomer represented by the formula fi1 include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris-β-methoxyethoxysilane, etc. Examples of the vinylsilane monomer represented by the formula fi1 include , γ-acryloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, and the like, with γ-methacryloxypropyltrimethoxysilane being preferred.

The stretchable unsaturated monomer containing a vinyl double bond and a cationic group in fb) is a monomer component that introduces a cationic group to impart water dispersibility to the resulting acrylic copolymer. be. Cationic groups include tertiary amino groups, quaternary ammonium bases, tertiary sulfonium bases,
Quaternary phosphonium bases etc. can be used, among which 3
A class amino group is particularly preferred.

Examples of monomers containing a vinylic double bond and a tertiary amino group include dialkylaminoalkyl (meth)acrylates such as dimethylaminopropyl (meth)acrylate and diethylaminoethyl (meth)acrylate (all of these alkyls are preferably Carbon, number of atoms 1 to 6
dialkylaminoalkyl (meth)acrylamides such as dimethylaminopropyl (meth)acrylamide, diethylaminoethyl (meth)acrylamide (all these alkyls are preferably alkyls having 1 to 6 carbon atoms); It will be done.

Examples of polymerizable unsaturated monomers containing a quaternary ammonium base and a vinyl double bond include 3-acrylamido-3-methylbutyltrimethylammonium chloride, 3-methacrylamido-propyltrimethylammonium chloride, and 2-methacryloyloxyethyl. Examples include trimethylammonium chloride.

The polymerizable unsaturated monomer containing a vinyl double bond and a hydroxyl group of the fcl is a monomer component that introduces a hydroxyl group into the acrylic copolymer as necessary, and the hydroxyl group is used to water-disperse the acrylic copolymer. It acts as a hydrophilic group during dispersion and/or as a functional group for a crosslinking reaction within the dispersed particles.

Examples of such unsaturated monomers include 2-hydroxyethyl (
Examples include hydroxyalkyl esters of (meth)acrylic acid such as meth)acrylate and hydroxypropyl (meth)acrylate.

The other polymerizable unsaturated molecules of (di) are the remaining components constituting the acrylic copolymer, and include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl ( Alkyl (C
,~C+s) Ester: Vinyl aromatic monomer such as styrene, α-methylstyrene, vinyltoluene: Does not contain a tertiary amino group (amide derivative of methanoacrylic acid: Normal acrylic resin such as (meth)acrylate trichloride) Known monomers used in the synthesis can be used.
Each may be used alone, or two or more types may be used in combination.

The monomers (a) to (dl are the blending ratios described below: fa) that constitute the acrylic copolymer of the present invention: 1 to 30% by weight, preferably 3 to 20% by weight
Weight% [bl monomer: 5-30% by weight, preferably 5-2
5% by weight fc) Monomer: 0-30% by weight, preferably 5-20
Weight % fd) Monomer 2 10-94% by weight, preferably 35-94% by weight
It is preferable to use it in a range of 82% by weight.

Another method for producing an acrylic copolymer containing a hydrolyzable alkoxysilane group and a cationic group is as follows:
Instead of using the monomer [bl], copolymerization is carried out using a glycidyl group-containing unsaturated vinyl monomer (e.g. glycidyl acrylate, glycidyl methacrylate, etc.), - Once a glycidyl group-containing acrylic copolymer is prepared, A secondary amine or 3
Methods include reacting a tertiary amine salt to introduce a tertiary amino group or quaternary ammonium base, or reacting a secondary sulfide salt or tertiary phosphine salt to introduce a tertiary sulfonium base or a quaternary phosphonium base. It will be done. It is usually preferable to introduce a tertiary amine group.

The copolymerization of the unsaturated monomers fa) to (dl) is carried out using methods known per se for producing acrylic copolymers.
In particular, it can be carried out by solution polymerization. for example,
The reaction can be carried out by continuing the reaction of the monomer mixture described in 2 above in a suitable solvent in the presence of a radical polymerization catalyst at a reaction temperature of usually about 0°C to about 180°C for about 1 to about 20 hours.

As the solvent to be used, it is desirable to use a solvent that dissolves the copolymer to be produced and is miscible with water so that gelation does not occur during the copolymerization reaction.

Examples of such solvents include alcoholic solvents.

Ether alcohol solvents, ether solvents, ketone solvents, ester solvents, etc. can be used.

Further, as the polymerization catalyst, for example, azo compounds, peroxide compounds, sulfides, sulfines, diazo compounds, nitroso compounds, etc. can be used.

In addition, in order to prevent unnecessary granulation of the resulting polymer due to the crosslinking reaction of alkoxysilane during the copolymerization reaction, a dehydrating agent such as dimethoxypropane is added to remove water that becomes a catalyst for the crosslinking reaction. , a polymerization reaction may be performed.

The acrylic copolymer thus obtained generally has a molecular weight of about 10
Amine value of ~100, preferably about 15 to about 80: 0
Hydroxyl value of ~200, preferably about 30 to about 130:
and about 5,000 to about 100,000, preferably about 7
．． It is desirable to have a number average molecular weight of from 0.000 to about 30.000.

When the amine value of the acrylic copolymer is less than 10, the dispersibility in water is generally insufficient and coarse particles are likely to be formed. On the other hand, if the amine value is greater than 100, gelation tends to occur during solution polymerization. Furthermore, when the number average molecular weight of the acrylic copolymer is less than 5.000, water dispersibility often becomes poor or the degree of gelation decreases. On the other hand, the triangular average molecular weight is 100.00
If it is larger than 0, the viscosity of the polymer solution tends to increase and water dispersion becomes difficult.

In the present invention, it is used in combination with the above acrylic copolymer, and the fine particle pigment-containing gelatinized T [the fine particle pigment forming the combined fine particles has an oil absorption of <100 or more, a primary particle diameter of 0
．． Pigments with an oil absorption of 5 μm or less, preferably 100 or more, and a primary particle diameter Q of 1 gm or less can be used, such as silicon dioxide pigments such as anhydrous silicon dioxide and hydrated amorphous silicon dioxide, and carbon-based pigments, which are suitable. is a silicon dioxide pigment.

Commercially available silicon dioxide pigments with an oil absorption of 100 or more include, for example, Nippon Aerosil Co., Ltd.'s product names [Erosil 200J (oil absorption m143-183), "Erosil 3
80'', ``Erosil R-972J (all oil absorption 150-200), Fuji Davison Chemical's product names ``Thyroid 161J (oil absorption 128-160)'', ``Thyroid 244J (oil absorption 270-330), ``Thyroid 308J'' (Oil absorption 170-220), Thyroid 404J (Oil absorption 170-230), Thyroid 978J (Oil absorption 180-230), Tokuyama Soda's product name Keisekifun NJ (Oil absorption 160)
~180), etc. Furnace type or channel carbon black (oil absorption is usually 100 to 160), which is usually used as a black pigment, is used as the six-pronged carbon pigment. Product name [Neo Spectra Mark I1
1. Product name of Sanno Kasei Kogyo Co., Ltd. [Carbon Black 600]
EJ, r carbon black 60013J, etc. can be mentioned.

The primary particle diameter of the fine particle pigment exceeds 0.5 μm,
If the oil absorption h1 of the fine particle pigment is less than 100,
The adsorption effect of the acrylic copolymer on the fine particle pigment becomes insufficient, and the dispersion stability of the fine particle pigment decreases.
This tends to cause a decrease in the finish of the horizontal portion of the object to be coated and a decrease in the edge coverage effect.

In the present invention, a mixture of the acrylic copolymer and the -F fine particle pigment is water-dispersed and particulately crosslinked to obtain a fine pigment-containing gelling polymer fine particle. The method of mixing with fine particle pigments is as follows:
Typically, the following methods (1) to (2) are used.

(2) A method in which fine particle pigments are dispersed in a hydrophilic solvent containing a surfactant for pigment dispersion, and this dispersion is uniformly mixed with an acrylic copolymer.

■A method of mixing and dispersing a pigment-dispersed resin varnish and a fine particle pigment, and uniformly mixing this dispersion with an acrylic copolymer.

■A method of directly mixing and dispersing acrylic copolymer face and fine particle pigment to form a mixture.

In steps (1) to (2) above, mixing and dispersion can be carried out using a conventionally known daysilver, pebble mill, attritor, sand mill, three-roll mill, or the like.

The mixture of the acrylic copolymer and the fine particle pigment obtained by methods such as (1) to (2) above is then dispersed in water and subjected to particulate crosslinking to form gelled polymer fine particles containing the fine particle pigment.

The aqueous dispersion of the acrylic copolymer mixed with the fine particle pigment can be carried out according to a method known per se. Furthermore, when the cationic group is an amino group, the acrylic copolymer containing a hydroxyl group is added to an acid in an amount of about 0.1 to 1 equivalent to the amino group,
For example, this can be carried out by neutralizing with a water-soluble carboxylic acid such as formic acid, acetic acid, lactic acid, or hydroxyacetic acid, and then dispersing with water so that the solid content concentration is about 40% by weight or less.

The thus obtained dispersed particles of the aqueous dispersion of the acrylic copolymer containing fine particles are crosslinked in a particulate manner. Particulate crosslinking is possible to some extent simply by long-term storage of the dispersion, but advantageously the aqueous dispersion is heated to about 50°C.
It is desirable to accelerate the intraparticle crosslinking reaction by heating to a temperature above, or when dispersing the acrylic copolymer in water, tin octylate, zinc octylate, zirconium octylate,
By adding a silanol group condensation catalyst such as dibutyltin laurate and performing water dispersion in the presence of the catalyst, particulate crosslinking can also be performed simultaneously with water dispersion.

The mixing ratio of the above acrylic copolymer and fine particle pigment is:
The solid content ratio is preferably in the range of 1 to 50 parts by weight of the fine particle pigment to 1 part by weight of the acrylic copolymer (1 part by weight, more preferably 5 parts by weight).
More preferably, the amount is in the range of 20 parts by weight.

The gelled polymer microparticle aqueous dispersion thus produced typically has a resin solids content of about 10 to 40% by weight. The particle size of the dispersed particles is generally less than ILLi, preferably 0.
．． O1-0.3 μm, more preferably 0.05-0.2
It is within the range of μm.

The particle size can be adjusted by adjusting the amount of cationic groups in the acrylic copolymer and the type and amount of the fine particle pigment, and a desired range can be easily obtained.

The cationic electrodeposition coating composition +11 that is first coated according to the method of the present invention is the same as that of a normal cationic electrodeposition coating composition, except that it additionally contains the gel specific polymer fine particles containing the specific fine particle pigment described above. It can consist of the following component composition.

Therefore, the above-mentioned cationic electrodeposition paint composition (II) contains, as a resin component, a resin (hereinafter referred to as cationic electrodeposition paint resin) that is usually used in cationic electrodeposition paints in addition to the gelled polymer fine particles. 1) For example, polyamine resins such as amine-added epoxy resins, such as (i) adducts of polyepoxide compounds with primary mono- and polyamines, secondary mono- and polyamines, or 1.2-class mixed polyamines (for example, US patent No. 3.984.299
(see specification): (iil adducts of polyepoxide compounds with secondary mono- and polyamines having ketiminated primary amino groups (for example, U.S. Pat. No. 4.0)
17.438 specification '5); (iH) Reactant obtained by etherification of a polyepoxide compound and a ketiminated hydroxy compound having a primary amino group (for example, see JP-A-59-43013 a) ) etc.

A compound having two or more polyesters in one molecule, which is used in the production of the above polyamine resin, and generally at least two
00, preferably 400-4000. More preferably 8
Those having a number average molecular weight within the range of 00 to 2000 are suitable, and those obtained by the reaction of a polyphenol compound and epichlorohydrin are particularly preferred. Examples of the polyphenol compounds used for forming the polyepoxide compound include bis(4-hydroxyphenyl)-2,2=propane, 4,4'-dihydroxybenzophenone, bis(4-hydroxyphenyl)-1,
l-ethane, bis(4-hydroxyphenyl)-1,
l-isobutane, bis(4-hydroxyLert-butylphenyl)-2,2-propane, bis(2-hydroxynaphthyl)methane, 1,5-dihydroxynaphthalene, bis(2,4-dihydroxyphenyl)methane,
Tetra(4-hydroxyphenyl)-1゜1.2.2-
Ethane, 4.4゛-dihydroxydiphenylsulfone,
Examples include phenol novolak and cresol novolak.

The polyepoxide compound may be one partially reacted with a polyol, polyether polyol, polyester polyol, polyamide amine, polycarboxylic acid, polyisocyanate compound, etc. Furthermore, it may be one that is partially reacted with a polyol, a polyether polyol, a polyester polyol, a polyamide amine, a polycarboxylic acid, a polyisocyanate compound, etc. Furthermore, the polyepoxide compound may be one that is partially reacted with a polyol, a polyether polyol, a polyester polyol, a polyamide amine, a polycarboxylic acid, a polyisocyanate compound, or the like. It may also be something that has been done.

In addition, when good button/I weather resistance is required for the composite cured coating film formed according to the method of the present invention, weather resistance may be added as a resin component other than the above-mentioned fine particle pigment-containing gelling polymer fine particles. It is convenient to use a superior amino group-containing acrylic resin or a nonionic acrylic resin alone or in combination with the amine-added epoxy resin.

The amine-added epoxy resin described above can be cured using a polyisocyanate compound blocked with an alcohol, if necessary.

In addition, amine-added epoxy resins that can be cured without using blocked incyanate compounds can also be used, such as resins in which β-hydroxyalkyl carbamate groups are introduced into polyepoxide materials (for example, JP-A-59-155470). (see Japanese Patent Laid-Open No. 80436/1983): A vine-type resin that is cured by transesterification (for example, see Japanese Patent Application Laid-Open No. 80436/1983) can also be used.

The preparation of the cationic aqueous solution or dispersion of the cationic electrodeposition coating resin described above is usually carried out by neutralizing the resin with a water-soluble organic acid such as formic acid, acetic acid, or lactic acid to make it water-solubilized or water-dispersed. I can do it.

The cationic electrodeposition paint resin solution or aqueous dispersion thus obtained and the aqueous dispersion of the gelling polymer fine particles containing the fine particle pigment are mixed so that the gelling polymer fine particles have a total resin solid content (resin in the gelling polymer fine particles). (including solid content), preferably 1 to 50% by weight, more preferably 5 to 35% of heavy waste
By mixing the cationic electrodeposition coating composition + I), the content of the gelled 1n coalesced fine particles containing the fine particle pigment in the cationic electrodeposition coating composition (1) is reduced to the total resin solid content. If it is less than 11%, the effect of controlling the reduction in the melt viscosity of the electrodeposited coating film during baking is small, and the edge coverage of the electrodeposited film tends to be insufficient, and on the other hand, %, the second
The leveling effect of the coating film of the cationic electrodeposition coating composition (Ill) due to heat flow becomes insufficient, and the smoothness of the electrodeposition coating film tends to be poor.

The cationic electrodeposition paint composition (H further includes conventional paint additives as necessary, such as blue pigments such as titanium white, carbon black, red iron, yellow lead, etc.; extender pigments such as talc, calcium carbonate, mica, Clay, silica, etc.: Pigments such as chromium pigments such as strontium chromate and zinc chromate, and lead pigments such as basic lead silicate and lead chromate can be added to the anti-j+'.

The cationic electrodeposition coating composition fIl can be applied to the surface of a desired substrate by cationic electrodeposition coating. Cationic electrodeposition coating generally has a solid content concentration of approximately 5 to 40% by weight.
This can be carried out using an electrodeposition bath consisting of an electrodeposition coating composition fI) diluted with deionized water or the like so that the cationic composition fI) is diluted with deionized water and further adjusted to have pl+ within the range of 5.5 to 8.0.

Next, according to the method of the present invention, the cationic electrodeposition coating composition (II) to be applied to the uncured electrodeposition coating film of the cationic electrodeposition coating composition fIl described below is The deposition current density is 0.7 mA/c+n2 or less, preferably 0.5 mA/cm" or less, more preferably 0.
, 3 n+A/cm" or less, and the degree of emulsion of the electrodeposition coating resin is 80 ffirit% or more, preferably 85 wt% or more, more preferably 90% by weight or more.
Those within the range of market weight % or higher are used.

Cationic electron used as second layer? 'r Paint composition (
The minimum electrodeposition current density of II l is 0,7 mA/cm2
The larger the size, the less likely it is that electrodeposition will occur.
The film thickness of the second layer tends to decrease (Also, if the degree of emulsion of the electrodeposition paint resin is less than 80% by weight, the paint properties will approach a solution state and the deposited film will become extremely dense, resulting in a decrease in the thickness of the first layer). and the second layer will mix, making it difficult to achieve the intended purpose.

The "minimum deposition current density" in item -F is a value measured by the following method: A platinum plate with a surface area of 10 m2 and an insulated back side is used as the opposite electrode of the object to be coated, and the two surfaces are placed 15 cm apart so that they face each other. placed in an electrodeposition bath at a distance of

At 28°C, a constant current was applied without stirring, and the time and voltage were recorded.
The current density is changed in steps of 0 and 05 mA/cn+2, and the current density when a sudden increase in voltage due to increased resistance due to electrodeposition of paint occurs for 3 minutes or in the vicinity of more than 3 minutes is defined as the minimum electrodeposition current density. do.

Also, the "degree of emulsification" refers to the actual state of particles in the electrodeposition paint! ! This is an index showing the percentage of cloudy particles (weight: 11%), and is determined by the following procedure: First, about 35 cc of a clear emulsion with a solid content of 15 to 20% by market weight is placed in a cell, sealed, and 2 g, 0OOR, P,
Centrifuge for 60 minutes at M. Supernatant 2 of separated sample
cc was taken out with a pipette, dried at 120°C for 1 hour, and the nonvolatile content (N, f%) was measured.

Next, turn the cell upside down and drain off the supernatant.

Invert in river for 10 minutes to remove supernatant layer. After homogenizing the remaining sediment layer with a glass rod, 1.5 to 2.0 g was accurately weighed, dried at 120° C. for 1 hour, and the nonvolatile content (N2f%) was measured.

Next, approximately 2 cc of the clear emulsion was accurately weighed and dried at 120°C for 1 hour to remove the non-volatile content. (%). The degree of emulsification is a value determined by the following formula.

N, (N2-N,) The cationic electrodeposition coating composition + II l has a coating film melting minimum viscosity of 10' to 105 centipoise, preferably 10' to 103 centipoise, at the beginning of curing. Desirable from the viewpoint of improving coating surface smoothness.

The cationic electrodeposition coating composition (II) used as the second layer in the method of the present invention is not particularly limited as long as it satisfies the requirements for the above-mentioned minimum electrodeposition current density and degree of emulsification. The cationic electrodeposition paint resin component may be selected from those described above for the cationic electrodeposition composition fIl used as the first layer. (The resin component may be the same as that in the cationic electrodeposition coating composition M1 as the first layer, or may be a different f-INin).

The minimum electrodeposition current density of the cationic electrodeposition coating composition (II l) to be used can be adjusted by appropriately adjusting the type and amount of the cationizing agent (amino compound) in the base resin component and/or the type and amount of the acid required for neutralization. This can be done empirically (through small-scale experiments) by changing the

Further, the degree of emulsification can also be easily adjusted by the same method as adjusting the minimum electrodeposition current density.

The above cationic electrodeposition paint composition (If l also contains the usual paint additives, for example, carbon black, titanium white, blue pigments such as red iron: clay, talc, calcium carbonate, etc.). Antirust pigments such as strontium dichromate and lead chromate; or other additives may also be added. Other additives include, for example: 1. Dispersion aid (nonionic surfactant): Anti-cissing agents (acrylic resins, fluororesins, silicone resins, etc.): curing accelerators (for example, salts of metals such as lead, bismuth, and tin), and the like.

When using the cationic electrodeposition coating composition (II), it is diluted with deionized water as appropriate to give a solid content concentration of about 5 to about 40.
The weight percent pl+ can be adjusted to be within the range of about 5.5 to about 8.

In the present invention, the method and apparatus for electrocoating the object to be coated using the coating compositions fI) and (II) are methods known per se that have been conventionally used for cationic electrodeposition coating. and equipment can be used. In this case, it is desirable to use the object to be coated as a cathode and to use a carbon plate as an anode. The vine electrodeposition coating conditions to be used are not particularly limited;
0°C), voltage: 100~400V (preferably 2
00-300V), current density +0.01-3A/d,
Electrodeposition is preferably performed under stirring, with current application time: 30 seconds to 10 minutes, electrode area ratio (A/C): 26/1 to .l/6, distance between electrodes: 10 to 100 cm.

The film thickness (dry state) of the first layer of electrodeposition formed using the above-mentioned electrodeposition coating method is 5 to 30 μm, preferably l
The thickness of the second electrodeposition coating film formed thereon (dry state) is 5 to 70 μm.
m, preferably in the range from 10 to 50 μm.

In the present invention, after the first electrodeposition coating, excess electrodeposition paint adhering to the object to be coated is removed by dipping or spraying, followed by washing with reverse osmosis membrane filtrate or deionized water. It is convenient to carry out a second electrodeposition coating. In addition, it is preferable to perform the second electrodeposition coating while the first electrodeposition coating is uncured in order to form a composite coating film and from the viewpoint of adhesion. However, after washing with water, the first electrodeposited coating may be heated for a short time at a temperature of 120°C or less, or heated to the extent that water is removed using hot air. It should be understood that the term "uncured" includes a semi-cured state.

The two-layer electrodeposition coating film formed on the object to be coated is preferably washed with deionized water or reverse osmosis membrane filtrate, and then heated at a temperature equal to or higher than the curing start temperature of the coating composition (+1), preferably 1
Both coatings are cured by heating to 00 to 250°C, more preferably 150 to 200°C.

The electrodeposition coating thickness is generally 15 to 8011 m as the total thickness of the first layer electrodeposition coating thickness and the second layer overlapping coating thickness.
It is desirable that it be within the range of . The electrodeposited coating film formed by hiding can be finished by appropriately applying a top coat as needed.

When the first and second electrodeposition coatings are performed according to the method of the present invention, the second electrodeposition coating is deposited on the surface of the first electrodeposition coating, and the first electrodeposition coating is deposited on the surface of the first electrodeposition coating. A coating film is formed in a multi-layer state of the electrodeposited layer and the second electrodeposited layer. Therefore, if the coating method of the present invention is used, edge coverage can be achieved with the first electrodeposition coating, and the coating surface smoothness and uniform film formation can be achieved with the second electrodeposition coating. can be ensured. As a result, the two-layer coating film has excellent corrosion resistance at the edges, and also has an excellent coating surface condition with no poor finish due to pigment sedimentation or pinhole defects.

According to the electrodeposition coating method of the present invention, conventional ? The corrosion resistance of the edges of the object to be coated, which had been the weak point of IF-adhered coatings, has been significantly improved, and multi-layer coatings with excellent coating surface smoothness can be formed, making it suitable for automobiles, It can be widely applied as an anti-corrosion coating method in a wide range of industrial coating fields, such as electrical machinery 2g and prefabricated steel frames.

The method of the present invention will be explained in more detail below with reference to Examples and Comparative Examples. Hereinafter, "part" and "F%" mean "part by weight" and "% by weight."

Production example of acrylic rt copolymerization Reference example 1 1 equipped with a stirring device, thermometer, cooling tube and heating mantle
320 parts of isopropyl alcohol was placed in a second flask, and the temperature was raised to reflux temperature (approximately 83°C) while stirring. A mixture of the following monomer and polymerization initiator was added dropwise to the mixture at reflux temperature (about 83 to 87°C) over about 2 hours.

Styrene 272 parts N-butyl acrylate 224 parts 2-hydroxyethyl acrylate 80 parts Dimethylaminoethyl methacrylate 144 parts KBM-503*
80 parts azobisisobutyronitrile
24 parts *γ-Methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) Next, after further stirring for 30 minutes, a solution of 8 parts of azobisdimethylvaleronitrile dissolved in 120 parts of isopropyl alcohol was added dropwise over about 1 hour. After stirring for about 1 hour, 320 parts of isopropyl alcohol was added and cooled.

Thus, the solid content is 51%, the amine value is 64, and the hydroxyl value is 48.
An acrylic copolymer face having a number average molecular weight of approximately 20,000 was obtained.

Reference Example 2 An acrylic copolymer face was obtained in the same manner as in Reference Example 1 using the following monomer mixture.

Styrene 304 parts n-butyl methacrylate 2802-hydroxyethyl acrylate 80 dimethylaminopropylacrylamide 56KBM-50380 The obtained acrylic copolymer face had a solid content of 50%, an amine value of 25, a hydroxyl value of 48, and a number average molecular arsenic of about 15. 000
Met.

Reference Example 3 of Manufacturing Fine Pigment Paste 22 Isopropyl alcohol 1260 in a stainless steel round can
and 12.5 parts of a nonionic surfactant EA-152 (manufactured by Dai-Kokai Seiyaku Co., Ltd., solid content 80%) were added thereto, and while stirring with a high-speed disper, 200 parts of Thyroid #244 (product of Nippon Aerosil Co., Ltd.) was gradually added. The mixture was added and mixed uniformly to obtain a paste with a solid content of 14.2%.

Reference Example 4 A mixture of 100 parts of an aqueous acrylic pigment dispersion containing cationic groups with a solid content of 70%, 200 parts of Aerosil 380 (product of Nippon Aerosil Co., Ltd.), and 750 parts of deionized water was heated in a shaker for 0.5 hours. Dispersed solid content 25.7
% paste was obtained.

Example 1 of MA preparation of gelled polymer particles containing microparticle pigment 290 parts of the microparticle pigment paste of Reference Example 3 was added to 480 parts of the acrylic copolymer varnish obtained in Reference Example 1 to 22 flasks with stirring, and the mixture was stirred for about 10 minutes. After mixing until homogeneous, add 4.0 parts of acetic acid and stir at about 30°C for 5 minutes.
662 parts of deionized water was added dropwise over about 30 minutes with strong stirring, the temperature was raised to 75 to 80°C, and stirring was continued for about 3 hours. In this way, a milky-white dispersion of intragranularly crosslinked gelling polymer fine particles containing a fine particle pigment was obtained with a solid content of 20%.

The average particle diameter of these fine particles in ethylene glycol monobutyl ether was 0.10 μm.

Production Example 2 290 parts of the fine particle pigment paste obtained in Reference Example 3 was added to 490 parts of the acrylic copolymer varnish obtained in Reference Example 2 in a 2°C flask with stirring, and after mixing for about 10 minutes until uniform, acetic acid was added. After adding 3.4 parts and stirring at about 30°C for 5 minutes, 653 parts of deionized water was added dropwise over about 30 minutes with strong stirring, the temperature was raised to 50°C, and the mixture was stirred for about 4 hours. In this way, a milky-white dispersion of gelling polymer microparticles containing intraparticle crosslinked microparticle pigments with a solid content of about 20% was obtained, and the average particle size of the microparticles in ethylene glycol butyl ether was 0.20 gm. .

Production Example 3 290 parts of the fine-r-pigment paste obtained in Reference Example 4 was added to 490 parts of the acrylic copolymer varnish obtained in Reference Example 2 in a 2e flask with stirring, and mixed for about 10 minutes until uniform. After that, 4 parts of tin octylate and 3.4 parts of acetic acid were added, and after stirring at room temperature (approximately 30°C) for 5 minutes, 653 parts of deionized water was added and added dropwise under stirring for approximately 30 minutes. Stirring was performed at room temperature (about 30° C.) for about 4 hours. There was thus obtained i') a milky white dispersion of gelling polymer microparticles containing intraparticle crosslinked microparticle pigments, approximately 20% solids. The average particle diameter of these fine particles in ethylene glycol mop der ether was 0.151 part m.

Production Example 4 (for comparison) 1.4 parts of tin octylate and 3.4 parts of acetic acid were added to 490 parts of the acrylic copolymer varnish prepared in Reference Example 2 in 22 flasks.
After stirring at about 30° C. for 5 minutes, 732 parts of deionized water was added dropwise over about 30 minutes with stirring, followed by further stirring at room temperature (about 30° C.) for about 4 hours. Thus, a dispersion of gelled polymer microparticles containing approximately 20% solids of microparticle pigment was obtained. The average particle diameter of these fine particles in ethylene glycol monobutyl ether is 0.15 μm.
Met.

Example of preparation of cationic electrodeposition coating composition fIl Preparation example 1 Clear emulsion for cationic electrodeposition with a solid content of 35% consisting of polyamide-modified epoxy resin and blocked diisocyanate (product name manufactured by Kansai Paint Co., Ltd., Nireclone 9)
450) To 572 parts of Production Example 1, 150 parts of a gelling polymer fine particle dispersion containing fine particle pigments having a solid content of 20% and 139.4 parts of the following pigment paste A having a solid content of 43% were added with stirring, and deionized. Cationic electrodeposition paint (1)-A was diluted with 588.5 parts of water.

Preparation Example 2 In Preparation Example 1, a cationic electrodeposition paint (Tl-B) was prepared using the same method except that 300 parts of the dispersion obtained in Preparation Example 2 was used as the gelled municipal fine particle dispersion containing fine particle pigments. Obtained.

Preparation Example 3 In Preparation Example 1, a cationic electrodeposition paint (t I ) was prepared in the same manner as in Preparation Example 1, except that 200 parts of the 11 loss liquid obtained in Preparation Example 3 was used as the fine particle pigment-containing gel specific polymer fine particle dispersion.
-C was obtained.

Production Example 4 The solid obtained in Production Example 1 was added to 626 parts of a cationic electrodepositing clear emulsion (manufactured by Kansai Paint Co., Ltd., trade name, NILCLON 9600) with a solid content of 32% consisting of polyester-modified epoxy resin, blocked diisocyanate, and nonionic acrylic resin. 200 parts of gelled polymer fine particles containing 20% solids and 139.4 parts of pigment paste A with 43% solids were added with stirring, and 53 parts of deionized water
The mixture was diluted with 4.6 parts to obtain a cationic electrodeposition paint (1).

Preparation Example 5 of Cationic Electron Coating Composition (11) Hydroxyl value 100, amine value (mgKO1l/g solid content)
15 parts of acetic acid was added to 133.3 parts of a 75% solids solution of polyamide-modified epoxy resin No. 50 for neutralization to obtain a neutralized resin solution.

Next, 20 parts of 2-ethylhexyl alcohol diblock of 4.4'-diphenylmethane diisocyanate and 1 part of dibutyltin diacetate were added to 134.8 parts of the above neutralized resin solution, and deionized water was further added while stirring thoroughly. An emulsion with a solid content of 35% was prepared. The degree of emulsification of this emulsion was 93%. The minimum electrodeposition current density was 0.20 mA/crn''. The method was the same as in Preparation Example 1 except that this emulsion was used instead of Nireclone 9450 and the gelled polymer fine particle dispersion was not used. Conducted at 20% solid rate
A cationic electrodeposition paint (H)-E with a pH of 6.7 was prepared.

Creation Example 6 Pigment with a solid content of 43% is added to 626 parts of a clear emulsion for cationic electrodeposition with a solid content of 32% (manufactured by Kansai Paint Co., Ltd., trade name Nileclone No. 9600) consisting of a polyester-modified epoxy resin, blocked diisocyanate, and nonionic acrylic resin. 139.4 parts of paste (A) was added with stirring and diluted with 550 parts of deionized water to obtain cationic electrodeposition paint (II)-F. The minimum electrodeposition current density of this paint was 0.25 mA/crn', and the degree of emulsion was 90%.

Examples 1 to 5 The cationic electrodeposition paints prepared in Preparation Examples 1 to 6 above were applied twice in the combinations shown in Table 1 below and in the steps shown in Table 2 below. ? ¥? A painted board was created.

The coating results and coating performance are shown in Table 3 below.

Table 1 Comparative Example] (Single coat coating method) A cationic electrodeposition paint G was obtained in the same manner as in Preparation Example 1 except that the gelling polymer fine particle dispersion containing fine particle pigments was not blended.

In the process shown in Table 2 for this electrodeposition paint G, the second electrodeposition coating is not performed, and the voltage is set to 250 to 350V and the trace time is 3 minutes under the conditions of the first electrodeposition coating. Other than that, the same process was used to paint and electrodeposit the plate. The coating results and coating performance are shown in Table 3.

Comparative Example 2 (2 same type coating method) 8334.8 parts of pigment paste with a solid content of 43% was added to 572 parts of a cationic electrodepositing clear emulsion (trade name, Nireclone 9450, manufactured by Kansai Paint Co., Ltd.) with a solid content of 35% while stirring. In addition, it was diluted with 814.2 parts of deionized water to obtain a cationic electrodeposition paint H with a high pigment concentration.

This electrodeposition paint 1-1 was used for the first time, electrodeposition paint (1■)-F
was used for the second time, and painted according to the steps shown in Table 2.
A painted board of the same type was created. The coating results and coating performance are shown in Table 3.

Tests for each coating film performance and coating film melt viscosity in Table 3 were conducted based on the test methods described below.

[Test method] *(1) Smoothness of painted surface: Visually evaluate the finish of the electrodeposited surface.

○... Good ■... Good condition △... Slightly poor * (2) Edge coverage: Steel plate with an edge part angle of 45° under the condition that the cured film thickness on the flat part is 20 um. A test plate is prepared by electrodeposition coating and curing under specified baking conditions.

The test plate was set in a straight spray device so that the edge part was vertical, and the corrosion resistance of the edge part was evaluated after 168 hours by a JIS 22371 salt spray test.

0...No rust at all X... Significant rust occurs *(3) Impact resistance.

It is carried out in an atmosphere at 20°C according to JIS K5400-1979 6.13°3B method. Weight 500
g, indicates the maximum height without causing paint film damage under the condition of center of impact tip diameter % inches (cm).

The maximum value was 50 cm.

*(4) ij-1 Chipping property: A thermosetting intermediate coating and top coating were further applied to the baked electrodeposition coated plate, and the following tests were conducted on the heated and cured product.

■Test equipment: Q-G-R Gravelometer (product of Q Panel Company) ■Stones to be sprayed: Crushed stones with a diameter of 15 to 20 m/m ■Capacity of stones to be sprayed: approximately 500 mff ■Shot by air pressure crab 4 kg/c rri''■Temperature during test:
Approximately 20℃ Attach the test piece to the test piece holder and weigh approximately 4 kg/cm''
After spraying approximately 500 mj2 of crushed stone onto the test piece using air pressure, the coating surface condition and salt spray resistance were evaluated. The condition of the painted surface is visually observed and evaluated using the following criteria.

(Evaluation) 0 (Good): Very few scratches due to impact were observed on a part of the top coat, and no scratches or peeling of the electrodeposition coating was observed.

■...Flaws caused by impact are observed on the top coat, intermediate coat, and electrodeposited coating, but no peeling of the electrocoated coating is observed.

△ (slightly poor): There are many scratches on the top coat and intermediate coat due to impact, and there is also some peeling of the electrodeposited coat.

*(5) Secondary adhesion after immersion in hot water: After immersion in water at 40°C for 20 days, JIS K540
0-1979 6.15, make gongs on the coating film, apply adhesive cellophane tape to the surface, and then rapidly peel it off, and then evaluate the coated surface.

0...Good condition with no abnormalities (remaining number 100/100) ■...The edges of the goban are slightly peeled (100
/100) △・・・A part of the gobang eye is peeling (90/100)
*(6) Salt spray resistance: Cross-cut scratches are made on the electrodeposited coating with a knife to reach the substrate, and this is rated at 100 according to JIS 22371.
A 0-hour salt water spray test is conducted, and the extent of rust and blisters from knife scratches is measured.

Book (7) Two-coat weather resistance: On the baked electrodeposited plate, 35μ of amino alkyd resin paint Amirac Clear (manufactured by Kansai Bain Co., Ltd.) was further applied and baked at 140°C for 15 minutes. This coated plate was put on a Sunshine Weatherometer for 20 hours, and then immersed in water at 40℃ for 20 hours.
After soaking for an hour, a cross cut is made in the coating and a peel test is performed using cellophane adhesive tape. This test is repeated to determine the time at which peeling occurs.

*(8) Paint film melt viscosity: The melt viscosity of the electrodeposited film during baking was measured using the rolling ball viscosity measurement method (JIS
- Z-0237) was evaluated based on the thermal fluid appearance of the scratch marks. The numerical value indicates the lowest viscosity (centivoise).

Claims (1)

[Claims] A mixture of an acrylic copolymer containing a hydrolyzable alkoxysilane group and a cationic group and a fine particle pigment having an oil absorption of 100 or more and a primary particle size of 0.5 μm or less is water-dispersed, and cross-linked within the particles. A cationic electrodeposition coating composition containing gelling polymer fine particles containing a fine particle pigment (
The minimum electrodeposition current density is 0.7 mA/cm^2 on the uncured electrodeposited film obtained by electrodepositing I) on the object to be coated.
It is characterized by baking and curing an uncured electrodeposited multilayer coating film formed by electrodepositioning a cationic electrodeposition coating composition (II) having the following properties and an emulsion degree of 80% by weight or more: Electrodeposition coating method.