JPH02279774A - Cationic electrodeposition coating - Google Patents

Abstract

PURPOSE:To perform the subject coating which can decrease heating loss and form a coating with improved corrosion resistance and low-temp. curing properties by using an electrodeposition coating compsn. wherein a resin with a specified number of specified groups is an essential component. CONSTITUTION:Electrodeposition coating is performed by using an electrodeposition coating compsn. contg. a resin with a tert. amino group and 0.6 or more, on average per molecule, 3-alkoxyalkyl-3-(meth)acryloyl-ureido group of formula I (wherein R<1> is H or CH; R<2> is a 1 to 4C alkylene; R<3> is a 1 to 10C alkyl) and a number-average mol.wt. of 800 to 50,000 and becoming water-soluble or water-dispersible by neutralization as an essential component and using a material to be coated as a cathode. By said method, it is possible to decrease especially heating loss on baking and to form a coating with improved corrosion resistance and low temp. curing properties. Said resin is obtd. by introducing an adduct prepd. by reacting part of the isocyanate groups of the polyisocyanate with N-alkoxyalkyl(meth)acrylamide of formula II (R<1>, R<2> and R<3> is as defined above) into a resin contg. a tert. amino group and hydroxyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a new cationic electrodeposition coating method, and more specifically, it is capable of reducing heating loss during baking, and improving corrosion resistance and low-temperature curing properties. The present invention relates to a cationic electrodeposition coating method capable of forming a coated film.

Conventional techniques and their problems Conventionally, cationic electrodeposition coating compositions have been prepared by combining a synthetic resin having a hydroxyl group or an amino group with a crosslinking agent, such as a combination of an epoxy-polyamine resin having a hydroxyl group and a blocked polyisocyanate as a crosslinking agent. compositions (for example, see JP-A-54-93024), compositions that combine synthetic resins having active hydrogen and crosslinking agents capable of transesterification (see, for example, JP-A-54-93024)
For example, see Japanese Patent Application Laid-Open No. 55-80436).

However, in electrodeposition coating compositions using blocked polyisocyanates, the blocking agent dissociates from the polyisocyanate during heat curing and evaporates into the air, so the blocking agent not only does not contribute to coating film formation, but also causes environmental pollution. Another problem is that in electrodeposition coating compositions using crosslinking agents capable of transesterification, the acid concentration increases due to hydrolysis of the crosslinking agent, resulting in a decrease in crosslinking and curability.

In addition, a synthetic resin having a polymerizable unsaturated group and α.

An electrodeposition coating composition in combination with a blocked polyisocyanate using an alcohol containing a β-ethylenically unsaturated double bond as a blocking agent (for example, JP-A-59-122564
Since the block polyisocyanate has an ester bond, the block polyisocyanate has disadvantages in that the acid concentration tends to increase due to hydrolysis of the crosslinking agent and it tends to form a crystal structure. In addition, alcohol containing α, β-ethylenically unsaturated double bonds dissociated from the block polyisocyanate by heating remains in the coating film, increasing the hydroxyl group concentration, resulting in poor coating performance such as corrosion resistance. Ta.

On the other hand, a self-curing binder component for electrodeposition coatings employs a crosslinking method in which α,β-ethylenically unsaturated double bonds are contained as functional groups in the resin and the resin is thermally polymerized (Japanese Patent Application Laid-Open No. 53-1999). -84035 Publication) or α,β-ethylenically unsaturated double bonds are preliminarily added with an amino compound,
Electrodeposition coating method using a binder component that uses a crosslinking method in which α,β-ethylenically unsaturated double bonds, which are generated by the release of amino compounds from this adduct by baking, are reacted with a resin having active hydrogen groups. (Unexamined Japanese Patent Publication No. 55-3
1889) etc. are publicly known. However, since the former binder component is a polymerization reaction between α and β-ethylenically unsaturated double bonds, high temperature baking (approximately 180°C or higher) is required, and hardening is inhibited by oxygen, resulting in insufficient hardening of the coated surface. On the other hand, the latter binder component has disadvantages in that the cured film tends to discolor and the amino compound evaporates from the coating during the curing process, which is unfavorable from a safety and health standpoint.

Means for Solving the Problems For this reason, the present inventors have developed a cationic compound that can reduce the loss on heating and thus cause almost no environmental problems, and can form a coating film with improved water resistance, corrosion resistance, and low-temperature curability. As a result of intensive research aimed at providing a mold electrodeposition coating method,
Surprisingly has an alkoxyalkyl group (meth)
Cation type 1! is produced using an electrodeposition coating composition containing as an essential component a resin having a specific number of 3-alkoxyalkyl-3-(meth)acryloyl-ureido groups obtained from the reaction of an acrylamide compound and an isocyanate group. The present inventors have discovered that by coating, it is possible to reduce the loss on heating and form a coating film with improved corrosion resistance and low-temperature curability, and have thus arrived at the present invention.

Thus, according to the present invention, a tertiary amino group and an average of 0.6 or more per molecule of the general formula % [wherein R1 is a hydrogen atom or a methyl group, and R2 is an alkylene group having 1 to 4 carbon atoms] , R3 each represents an alkyl group having 1 to 10 carbon atoms. ], has a number average molecular weight of 800 to 50,000, and becomes water-soluble or water-dispersible upon neutralization (hereinafter referred to as " A cationic electrodeposition coating method is provided, which is characterized in that electrodeposition is carried out using an electrodeposition coating composition containing as an essential component an object to be coated as a cathode, further comprising: A hydroxyl group-containing resin containing 1.4 or more primary or secondary hydroxyl groups per molecule and having a number average molecular weight of 600 to 50,000 (hereinafter abbreviated as "resin B"), and a resin of the general formula (I ) 3-alkoxyalkyl-3-
The average number of (meth)acryloyl-ureido groups is 1 per molecule.
or more, and a number average molecular weight of 400 to 30,000 (hereinafter abbreviated as "resin C"), which neutralizes one or both of the resins in the mixture. Using an electrodeposition coating composition containing as an essential component the mixture containing a sufficient amount of tertiary amino groups so that the mixture becomes water-soluble or water-dispersible, an electrodeposition is applied using the coated object as a cathode. A cationic electrodeposition coating method is provided, which is characterized by coating.

The group represented by the general formula (, I) in the present invention (hereinafter,
It is abbreviated as [ureido group of formula (I)]. ) is a polyfunctional group having both an α,β-ethylenically unsaturated double bond that can be added to a hydroxyl group and an alkoxy group that can also be ether exchanged or self-condensed with a hydroxyl group.

First, resin A in the method of the present invention will be explained.

Resin A is a self-crosslinking resin containing a tertiary amino group and an average of 0.6 or more ureido groups of formula (I) per molecule. From the viewpoint of curability, resin A should have an average of 2 or more groups per molecule of the group represented by formula (I) and the primary or secondary hydroxyl group that may be included as necessary. More preferred.

Resin A is, for example, a part of isocyanate groups in polyisocyanate, expressed by the general formula % () [wherein R1, R2 and R3 are as described above]. ] N-alkoxyalkyl (meth)acrylamide (
Hereinafter, it will be abbreviated as "compound of formula (II)". ) (hereinafter abbreviated as "adduct a") into a resin containing a tertiary amino group and a hydroxyl group. The introduction can be carried out by a urethanization reaction between the remaining isocyanate groups in the adduct a and the hydroxyl groups in the resin.

As the polyisocyanate used in the production of adduct a, any type of polyisocyanate such as aliphatic, alicyclic, aromatic, etc. can be used, and representative examples include 2.4-
and 2,6-tolylene diisocyanate, m-xylylene diisocyanate, methylcyclohexane-2,4-
Polyisocyanate compounds such as diisocyanate, 1,3-isocyanate methylcyclohexane, isophorone diisocyanate, diphenylmethane-4,4'-diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, polymethylene polyphenyl polyisocyanate, and these Examples include polyisocyanates obtained by reacting an excess amount of a polyisocyanate compound with a low-molecular active hydrogen-containing compound such as ethylene glycol, propylene glycol, trimethylolpropane, hexanetriol, or castor oil. Two or more types can be used in combination.

In the compound of formula (II) used for the production of adduct a,
R2 may be linear or branched as long as it is an alkylene group having 1 to 4 carbon atoms, such as methylene group, ethylene group, n-propylene group, n-butylene group, etc. R3 is an alkyl group having 10 or less carbon atoms, more preferably an alkyl group having 4 or less carbon atoms, and may be linear or branched, such as a methyl group, an ethyl group,
Examples include n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, n-hexyl group, 2-ethylhexyl group, n-decyl group, and the like.

Representative examples of the compound of formula (II) include N-n-butoxymethyl (meth)acrylamide, N-1so-butoxymethyl (meth)acrylamide, N-methoxymethylacrylamide, etc., which may be used alone or in combination. The above can be used in combination.

The reaction between the polyisocyanate and the compound of formula (n) is a reaction between the isocyanate group and the NH group in the compound of formula (II), and is usually carried out using an isocyanate addition catalyst and radical polymerization in an inert organic solvent. Reaction temperature in the presence of an inhibitor from 80°C to 150°C, preferably from 100°C to 120°C
This can be achieved by reacting for 5 to 30 hours.

The blending ratio of the polyisocyanate used in this reaction and the compound of formula (n) is preferably such that the number of isocyanate groups remaining after the reaction in the polyisocyanate is 1 or less per molecule in terms of chemical theory. .

The inert organic solvent that may be used in the above reaction is inert to isocyanates, and polyisocyanates,
A compound capable of dissolving or dispersing the compound of formula (If) and the reaction product of both is used.

Typical examples include aromatic hydrocarbons such as xylene and toluene, ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and acetone, ethers without hydroxyl groups such as ethyl alcohol dimethyl ether and diethylene glycol dimethyl nityl, dioxane, etc. Examples include cyclic ethers.

The isocyanate addition catalyst used in the above reaction is typically an organic lead compound such as lead octylate or lead acetate;
Organozinc compounds such as zinc naphthenate, organomanganese compounds such as manganese acetate, organotin compounds such as dibutyltin dilaurate and dibutyltin diacetate, organometallic compounds such as organosodium compounds such as sodium oxalate, triethylamine, tri-n-butylamine, pyridine. Examples include tertiary amines such as, quaternary ammonium organic acid salts such as cetyltrimethylammonium bromide and tetraethylammonium bromide, and alkali metal compounds such as sodium hydroxide and potassium hydroxide.

A larger amount of this isocyanate addition catalyst is required than in the case of a normal reaction between a hydroxyl group and an isocyanate group. For example, when dibutyltin dilaurate is used as an addition catalyst, the reaction between a hydroxyl group and an isocyanate group is It is usually about 5°Oppm, but in the reaction of polyisocyanate and the compound of formula (If), it is about 500ppm.
About 0 ppm to 50,000 ppm is required, and the amount of firefly required is 10 to 100 times the amount used in a normal reaction between a hydroxyl group and an isocyanate group.

In addition, as the radical polymerization inhibitor that can be used in the above reaction, those that suppress the radical polymerization reaction due to heat are used, and typical examples include parabenzoquinone, methoxyphenol, 2,6- or 2,5-dichloro-p- benzoquinone, diphenylvicrylhydrazyl, hydroquinone,
Examples include tert-butyl-hydroquinone, methylhydroquinone, phenothiazine, N,N'-di-2-naphthyl-P-phenylenediamine, and these radical polymerization inhibitors have a content of 1000 to 50000 ppm (7)
It is preferable to use the range.

The adduct a obtained by the reaction of the above polyisocyanate with the compound of formula (II) is further subjected to a urethanization reaction with a resin containing a tertiary amino group and a hydroxyl group. Any known resin may be used without any particular restriction as long as it has a tertiary amino group and an average of 2 or more, preferably 2 to 200, hydroxyl groups in one molecule and has a number average molecular weight of 600 to 50,000. I can do it.

Specific examples of the resin containing a tertiary amino group and a hydroxyl group include acrylic polyols, polyester polyols, polyether polyols, alkyds, caprolactone polyols, which have a tertiary amino group and a hydroxyl group in the above range; Examples include epoxy type and urethane polyol type.

These resins containing a tertiary amino group and a hydroxyl group include, for example, polycaprolactone diol, which is a reaction product of a diol such as ethylene glycol and ε-caprolactone, polypropylene glycol, polytetramethylene glycol, dimer acid polyamide, carboxyl It may be modified with a modifier such as a terminal acrylonitrile-butadiene copolymer, an adduct of acrylic acid or methacrylic acid, and ε-caprolactone.

The urethanization reaction between the adduct a and the resin containing a tertiary amino group and a hydroxyl group is usually carried out in an inert organic solvent in the presence of an isocyanate addition catalyst and a radical polymerization inhibitor at a reaction temperature of 0°C to This can be achieved by heating at 150°C for about 1 to 30 hours.

The blending ratio of adduct a and the resin containing tertiary amino groups and hydroxyl groups used in this reaction is not particularly limited as long as all the isocyanate groups in adduct a react with the resin, but usually The ratio of the former/latter is preferably in the range of 0.5/99.5 to 90/10, more preferably in the range of 10/90 to 70/30 in terms of resin solid content weight ratio.

The inert organic solvent that can be used in the urethanization reaction is inert to the incyanate group and is suitable for the adduct a1.
A material capable of dissolving or dispersing the above resin and the reaction product of both is used. Representative examples include those exemplified as inert solvents that can be used for the reaction of the polyisocyanate and the compound of formula (II).

Furthermore, as the isocyanate addition catalyst and radical polymerization inhibitor that can be used in the above reaction, catalysts and inhibitors that can be used in the reaction between the polyisocyanate and the compound of formula (n), respectively, can be used.

The amount of the isocyanate addition catalyst used is usually preferably about 1/10 to 1/100 of the amount used in the reaction of the polyisocyanate and the compound of formula (II).

Resin A can be obtained as described above, but the amount of tertiary amino groups in resin A should be such that resin A itself can be made water-soluble or water-dispersible by neutralization (usually 0.4 ~2.1 mol/kg resin 1. Preferably 0.5-1.7 mol/kg
A range of resins. Further, resin A has an average of 0.6 or more ureido groups of formula (I) per molecule, and preferably the total of primary or secondary hydroxyl groups and ureido groups of formula (I) is 1 molecule. It is desirable that the average number of pieces per serving is two or more. Furthermore, the ratio of the number of ureido groups in formula (I) to primary or secondary hydroxyl groups is ureido group/hydroxyl group in formula (I) = 110.
From the viewpoint of curability, it is desirable that the ratio is in the range of 1/3 to 1/3, more preferably 110.3 to 1/2. If the number of ureido groups of formula (I) is less than 0.6 on average per molecule, self-crosslinking properties will not be sufficient.

In addition, resin A has a number average molecular ff1800 to 50000,
Preferably, it needs to be 1000 to 30000, and those with a number average molecular weight of less than 800 are difficult to synthesize.
On the other hand, if it exceeds 50,000, good coating surface smoothness cannot be obtained.

Next, resin B in the method of the present invention will be explained.

Resin B has about 1.4 to 430 primary or secondary hydroxyl groups per molecule, and has a number average molecular weight of 600 to 50,000.
It is a hydroxyl group-containing resin. Resin B is used in combination with resin C, but resin B may or may not contain a ureido group of formula (I), and from the viewpoint of curability, it may contain a primary or secondary hydroxyl group and a ureido group of formula (I). ) and ureido groups is preferably about 2 to 200 on average per molecule.

When resin B does not have the ureido group of formula (I), it is desirable to have 2 or more hydroxyl groups, preferably 2 to 200, and known resins can be used as such resins. . Specifically, examples of the hydroxyl group-containing resin include acrylic polyols, polyester polyols, polyether polyols, alkyds, caprolactone polyols, epoxy and urethane polyols. These hydroxyl group-containing resins include, for example, polycaprolactone diol, which is a reaction product of a diol such as ethylene glycol and ε-caprolactone;
It may be modified with a modifier such as polypropylene glycol, polytetramethylene glycol, dimer acid polyamide, carboxyl-terminated acrylonitrile-butadiene copolymer, or an adduct of acrylic acid or methacrylic acid with ε-caprolactone. Further, the resin may or may not have a tertiary amino group that can be made water-soluble or water-dispersible by neutralization.

When resin B contains the ureido group of formula (I), for example, the resin having two or more hydroxyl groups and the adduct a are combined with the adduct a, tertiary amino group and hydroxyl group in the production of resin A. The reaction may be carried out under the same conditions as in the reaction with a resin containing.

Resin B has a number average molecular weight ff of 1,600 to 50,000, preferably 1,000 to 30,000, and a number average molecular weight of 60
If it is less than 0, the corrosion resistance will not be sufficient, while if it exceeds 50,000, the smoothness of the painted surface will be poor.

Next, resin C used in combination with resin B in the method of the present invention will be explained.

Resin C is a resin having a number average molecular weight of 400 to 30,000 and containing on average one or more ureido groups of formula (I) per molecule, for example, an equivalent adduct of a compound of formula (n) and a mono- or polyisocyanate. , a reaction product between the adduct a and a compound or resin containing a hydroxyl group, and the like.

Examples of the mono- or polyisocyanates include benzene, 1-(1-isocyanato-1-methylethyl')
Examples include -4-(1-methylethynyl), the polyisocyanates exemplified above, and compounds having one or more isocyanate groups in the molecule obtained by partially blocking the polyisocyanates with a blocking agent such as alcohol. Further, the compound or resin containing a hydroxyl group that forms a reaction product with the adduct a is one containing about 1 to about 80, preferably about 2 to 40, hydroxyl groups in the compound or resin, such as Hydroxyl groups shown as ethylene glycol, propylene glycol, trimethylolpropane, hexanetriol, castor oil and resin B are
Examples include resins having more than one.

The adduct of the compound of formula (n) and a mono- or polyisocyanate can be produced under the same reaction conditions as in the production of the adduct a. In addition, the reaction product of adduct a and a compound or resin containing a hydroxyl group is produced by the same reaction as in the reaction of adduct a with a resin containing a tertiary amino group and a hydroxyl group in the production of resin A. It can be done under certain conditions.

Among the resins A, B, and C obtained as described above and above, resin A has self-crosslinking property and can be used alone, but resin B does not have self-crosslinking property or has no self-crosslinking property. Since it is sufficient, it is necessary to use it together with resin C.

The mixing ratio of resin B and resin C may be selected as appropriate;
Preferably, the ratio of the sum of the number of ureido groups of formula (I) in resin B and resin C to the number of primary or secondary hydroxyl groups in resin B and resin C is ureido group of formula (I) / Hydroxyl group = 11
0.02 to 1/3, more preferably 110.3 to 1/2
From the viewpoint of curability, it is desirable that the amount is within this range. Also,
The blending ratio of resin B and resin C is usually resin solid content ii
The total ratio of resin B/resin C-9515 to 30/70 is preferably used in the range of 90/10 to 60/40. Furthermore, when Resin B and Resin C are used together, one or both of these resins may be neutralized with sufficient additives to make the mixture of these resins water-soluble or water-dispersible. It is desirable to contain a certain amount of tertiary amino groups. In this case, the amount of tertiary amino group is usually 0.4 to 2.1 mol/kg resin, preferably 0.5 to 1.7 mol per 1 kg of mixed resin solid content of resin B and resin C. /kg resin.

The resin thus obtained or the mixture of resin B and resin C can be made into an electrodeposition coating composition by neutralization and dilution with water. Resin components such as; curing catalyst; coloring pigments, extender pigments,
Pigments such as antirust pigments; dyes; paint additives such as pigment dispersants, leveling agents, antifoaming agents, and anti-sagging agents; solvents, etc. may be blended.

The neutralizing agent used to neutralize the tertiary amino groups in the mixed system of A resin or B resin and C resin includes organic acids such as formic acid, acetic acid, propionic acid, and lactic acid, as well as hydrochloric acid, sulfuric acid, phosphoric acid, etc. The neutralization equivalent of these acids may be determined as appropriate depending on the case, but it is usually 0.2 to 1.2 equivalents, preferably 0.3 to 1.0 equivalents. It is within the range of neutralization.

Examples of resin components that may be blended as necessary include crosslinking agents such as block polyisocyanate resins and melamine resins, and resins for modification or pigment dispersion such as acrylic resins, polyester resins, and epoxy resins. It can be used in an amount of less than 50% by weight in all resin components.

The above-mentioned curing catalysts include metal hydroxides, gold scrap organic acid salts, quaternary ammonium bases, quaternary phosphonium bases, tertiary
Examples include at least one basic compound selected from class sulfonium bases, organic acid salts of these onium bases, and alkali metal alkoxides. Examples of metal hydroxides include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, and alkaline earth metal hydroxides such as calcium hydroxide, magnesium hydroxide, and barium hydroxide. . In addition to the above, other metal hydroxides such as nickel hydroxide, copper hydroxide, molybdenum hydroxide, lead hydroxide, iron hydroxide, chromium hydroxide, manganese hydroxide, tin hydroxide, cobalt hydroxide, etc. can be mentioned.

As the above quaternary ammonium base, quaternary phosphonium base and tertiary sulfonium base, those represented by the following general formula can be used.

[In each formula, Rb1RoSRa and R8 are preferably hydrogen or an organic group having 1 to 14 carbon atoms, and at least one of Rb1RoSRd and R is the same or different, and at least one of Rb1RoSRd and R is a group having 1 to 14 carbon atoms. An organic group is preferred. Further, R and R1 or Rb1Ro and Rd may be combined with b c to form a heterocycle together with the nitrogen atom, phosphorus atom, or sulfur atom to which they are bonded. ] Rb, Ro, R, and R8 preferably have 1 to 1 carbon atoms
As the organic group 4, the same organic groups having 1 to 14 carbon atoms as exemplified as R1, Ro and R4 of the onium organic acid salt in the resin can be used. In addition, when Rb and R1 or Rb5Ro and Rd together form a heterocycle formed with the nitrogen atom, phosphorus atom, or sulfur atom to which they are bonded, the cations include, for example, the following: Can give examples.

The organic acid salts of the metal hydroxides and the onium bases used as curing catalysts in the method of the present invention include octenoic acid, naphthenic acid, abietic acid, acetic acid, formic acid, and propionic acid. , trimethylacetic acid, acrylic acid, methacrylic acid, lactic acid, hydroxyacetic acid,
It can be obtained by neutralization with an organic acid such as crotonic acid, chloroacetic acid, monomethyl maleate, monoethyl fumarate, monomethyl itaconate. Further, representative examples of alkali metal alkoxides include sodium ethoxide, sodium methoxide, potassium methoxide, potassium ethoxide, and the like.

Among the above, it is preferable to use metal hydroxides and metal organic acid salts because they form films with excellent low-temperature hardening properties and high-temperature water resistance. Especially preferred are acid salts.

The mixing ratio of the curing catalyst is approximately 20 parts by weight or less, preferably in the range of 0.1 to 10 parts by weight, based on 100 parts by weight of the resin solid content.

In the present invention, pigments, dyes, various paint additives, and solvents that may be incorporated into the electrodeposition paint composition are usually:
Those used in the field of paints can be used, but from the viewpoint of bath stability, it is preferable that the amount of pigments be 50% by weight or less based on the total solid content. Among these, typical examples of solvents include alcohols such as isopropanol, butanol, 2-ethylhexyl alcohol, and benzyl alcohol, monoalkyl ethers of ethylene glycol such as octoxyethanol, and propylene glycol. Monoalkyl ethers, monoalkyl ethers of diethylene glycol, monoalkyl ethers of dipropylene glycol, dialkyl ethers of ethylene glycol, dialkyl ethers of diethylene glycol and dipropylene glycol, and aromatic, aliphatic, and alicyclic hydrocarbons,
Examples include ketones and cyclic ethers such as dioxane.

In the method of the present invention, the solid content of the electrodeposition coating composition is generally about 1 to 30%, preferably 13 to 2%.
Electrodeposition coating is performed using a 5% by weight electrodeposition bath and the object to be coated as a cathode. The object to be coated must be conductive, and a constant voltage of usually about 10 to 500 V, preferably 50 to 350 V, is usually applied for a period of about 30 seconds to 10 minutes between the object to be coated and the counter electrode. method, the so-called slow start method in which the voltage is started from Ov and gradually increased to a constant voltage and electrodeposition is performed for a predetermined period of time, the constant current method in which a constant current is applied instead of applying a constant voltage, or a combination of these. Electrodeposition coating can be suitably performed depending on the mode and the like. The coating thickness can be adjusted from a thin film of about 5 microns to a thick film of about 50 to 80 microns by adjusting the electrodeposition conditions.

After electrodeposition coating, the object to be coated is pulled up from the electrodeposition bath, washed with water, and then baked, but this electrodeposition film has good low-temperature curing properties,
A temperature of 60°C or higher, preferably about 80°C to 200°C,
More preferably at a temperature of 120 to 170°C, preferably 5
It can be cured by heating for at least 10 minutes, preferably about 10 to 60 minutes, and the loss on heating during baking is small, and the cured coating film has excellent corrosion resistance.

Actions and Effects of the Invention Although the curing mechanism of the coating film obtained by the method of the present invention is not clear, changes in the infrared absorption spectrum due to heating indicate the disappearance of unsaturated groups and changes in ether bonds, and the formation of isocyanate groups. The addition reaction of a hydroxyl group to a polymerizable unsaturated group, the ether exchange reaction between an alkoxy group and a hydroxyl group of an alkoxyalkyl group, and the alkoxyalkyl group are effective because of the fact that no It can be assumed that a dealcoholization condensation reaction between the two is occurring.

The resin which is an essential component of the electrodeposition coating composition used in the method of the present invention is a 3-alkoxy resin having two functional groups: an α,β-ethylenically unsaturated double bond and an alkoxyalkyl group bonded to an amide. It has an alkyl-3-(meth)acryloyl-ureido group as a reactive group, and the ureido bond of this ureido group is stable and does not dissociate to produce free incyanate even when heated during curing. Since no reaction occurs, the loss on heating is small, so there are almost no environmental problems, and corrosion resistance is improved due to improved adhesion to the substrate due to mononoid bonding, which is also thought to be due to the above reaction mechanism. However, it improves low temperature curability.

EXAMPLES Next, the present invention will be explained in more detail with reference to production examples, working examples, and comparative examples.

Hereinafter, "part" and "%" mean "part by weight" and "% by weight", respectively.

Production Example 1 of a resin containing a tertiary amino group and a hydroxyl group Bisphenol A diglycidyl ether (
760 parts of epoxy (epoxy equivalent: about 190, molecular weight: 380), 228 parts of bisphenol A, and 0.35 parts of dimethylbenzylamine were charged, and the mixture was reacted at 120°C under nitrogen gas blowing until the epoxy equivalent was 490. Next, 303 parts of methyl isobutyl ketone, 1 part of jetanolamine
, 68 parts and N,N,N'-trihydroxy-1,2
-Diaminoethane (57.6 parts) was added and reacted at 80°C for 8 hours to obtain a resin solution (1). The resulting resin had an average of 4.
It had 1 primary hydroxyl group/molecule and an average of 4.0 secondary hydroxyl groups/molecule.

Production Example 2 In a flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a reflux condenser, butyl glycidyl ether-modified bisphenol A diglycidyl ether (rXB manufactured by Ciba Geigy) was added.
-4122J, 470 parts of epoxy equivalent (390), 270 parts of bisphenol A, and 0.3 parts of dimethylbenzylamine were charged, and the mixture was reacted at 160°C under nitrogen gas blowing until the epoxy group disappeared. Then bisphenol A diglycidyl ether (epoxy equivalent 190,
Add 603 parts of molecular weight (approximately 380) and 0.2 parts of dimethylbenzylamine and react at 130°C until the epoxy equivalent becomes 650 or less.
92 parts, jetanolamine 168 parts and N, N, N'
-1-lihydroxy-1,2-diaminoethane 57.6
of the mixture was added, and the mixture was reacted at 80° C. for 8 hours to obtain a resin solution (2).

Production Example 3 Bisphenol A diglycidyl ether (
Epoxy equivalent 190, molecular weight approximately 380) 760 parts, bisphenol A 114 parts and dimethylbenzylamine 0. 3 parts were charged and reacted at 130° C. under nitrogen gas blowing until the epoxy equivalent reached 290. Then ε
- Add 680 parts of caprolactone and 0.2 parts of tetrabutoxy titanate, react at 170°C, perform time-lapse sampling, and trace unreacted ε-caprolact II by infrared absorption spectroscopy, and the reaction rate is 98% or more. At that point, 114 parts of bisphenol A and 0.04 parts of dimethylbenzylamine were added, and the epoxy equivalent was 830 at 150°C.
After confirming the end point, 473 parts of methyl isobutyl ketone, 168 parts of jetanolamine and N, N, N
'Trich droxy-1,2-diaminoethane 57゜6
of the mixture was added, and the mixture was reacted at 80° C. for 8 hours to obtain a resin solution (3).

Production Example 4 Diethylene glycol dimethyl ether 5 was added to a flask equipped with a stirrer, thermometer, nitrogen inlet tube, and reflux condenser.
00 parts and heated at 110°C under nitrogen gas blowing to 2-
A mixed solution of 300 parts of hydroxyethyl methacrylate, 157 parts of N,N-dimethylaminoethyl methacrylate, 300 parts of styrene, 243 parts of n-diptylacrylate, and 20 parts of benzoyl peroxide was added dropwise over 3 hours. Next, the resin solution (4
) was obtained.

Production Example 5 of Hydroxyl Group-Containing Resin In a flask equipped with a stirrer, thermometer, nitrogen inlet tube, and reflux condenser, diethylene glycol dimethyl ether 5
00 parts and heated at 110°C under nitrogen gas blowing to 2-
300 parts of hydroxyethyl methacrylate, 3 parts of styrene
A mixed solution of 90 parts of n-butyl acrylate, 310 parts of n-butyl acrylate, and 20 parts of benzoyl peroxide was added dropwise over 3 hours.

The mixture was then aged at 110° C. for 4 hours to obtain a resin solution (5).

Production of adduct a Production example 6 In a flask equipped with a stirrer, thermometer and reflux condenser,
250 parts of diphenylmethane diisocyanate, 2.6-
4.9 parts of cycloparabenzoquinone and 4.9 parts of dibutyltin dilaurate were charged, and after heating to 120°C, N-
235.5 parts of n-butoxymethylacrylamide was added dropwise to react while maintaining the temperature at 120°C, and when the NC0 value reached 43, 44.1 parts of methyl isobutyl ketone was added to obtain an adduct a-1 solution.

Production Examples 7 to 12 Solutions of adducts a-2 to a-7 were obtained in the same manner as in Production Example 6, except for using the formulations shown in Table 1.

Production Example 13 of Adduct b-1 A solution of adduct b-1 was obtained in the same manner as in Production Example 6 except that the formulations shown in Table 1 were used. Adduct b-1 is the formula (1)
It had 2.0 ureido groups/molecule.

Production Example 14 In a flask equipped with a stirrer, thermometer and reflux condenser,
666 parts of isophorone diisocyanate, 11.4 parts of parabenzoquinone, and 11.4 parts of dibutyltin dilaurate were charged, and while the temperature was raised and maintained at 120°C, 471 parts of N-n-butoxymethylacrylamide was added dropwise to react with N.
When the C0 value reached 110, 134 parts of trimethylolpropane was added and the mixture was reacted at 120°C. When the NC0 value became 0, 295 parts of methyl isobutyl ketone was added to obtain an adduct b-2 solution.

Adduct b-2 had 3.0 ureido groups of formula (1)/molecule on average.

Production of resin solution BC for comparison Production Example 15 500 parts of methyl ethyl ketone was charged into a flask equipped with a stirrer, a thermometer, a nitrogen inlet pipe, and a reflux condenser, and the mixture was heated to N-n at 80°C under nitrogen gas blowing. A mixed solution of 1000 parts of -butoxymethylacrylamide and 20 parts of azobisdimethylvaleronitrile was added dropwise over 3 hours. Then, the mixture was aged at 80°C for 4 hours to obtain resin solution BC-1.

Production of isocyanate group-containing adduct (for comparative example) AC solution Production Example 16 In a flask equipped with a stirrer, thermometer and reflux condenser,
After charging 174 parts of tolylene diisocyanate and raising the temperature to 70°C, 90 parts of ethylene glycol monoethyl ether was added dropwise while maintaining the temperature at 70°C, and when the N00 value reached 159, 29.3 parts of methyl isobutyl ketone was added.
1 part was added to obtain an adduct ac-1 solution.

Production Example 17 In a flask equipped with a stirrer, thermometer and reflux condenser,
174 parts of tolylene diisocyanate and 0.15 parts of parabenzoquinone were charged, the temperature was raised to 70°C, and 116 parts of 2-hydroxyethyl acrylate was added dropwise while maintaining the temperature at 70°C to react, and the N00 value became 145. At this point, 32.1 parts of methyl isobutyl ketone was added to form the adduct ac
-2 solution was obtained.

Production Example 18 In a flask equipped with a stirrer, thermometer and reflux condenser,
174 parts of tolylene diisocyanate, 2.6 parts of parabenzoquinone, and 2.6 parts of dibutyltin dilaurate were charged, the temperature was raised to 120°C, and 85 parts of methacrylamide was added dropwise to react while maintaining the temperature at 120°C. Crystallization occurred and the reaction could not proceed. Moreover, even if tetrahydrofuran was added to this reaction product, it could not be dissolved.

Production Example 19 In a flask equipped with a stirrer, thermometer and reflux condenser,
1517 parts of resin solution (1) and 34 parts of methyl ethyl ketone
After charging 7 parts and raising the temperature to 70°C, adduct a-1 solution 1
350 parts were added dropwise over 90 minutes while keeping the temperature at 70°C, and the mixture was allowed to react at 70°C. After sampling over time and confirming that there was no unreacted NGO by infrared absorption spectroscopy, 24 parts of ethylene glycol monobutyl ether was added. In addition, a ureido group-containing resin A-1 solution was obtained. The obtained resin has an average of 3.75 ureido groups of formula (I) and 2.85 primary or secondary hydroxyl groups in one molecule, and also has a tertiary amino group in the resin. 0.9 per kg solid content
I had one.

Production Examples 20 to 31 The same procedures as Production Example 19 were carried out except that the formulations shown in Table 2 were used, and ureido group-containing resin A-2 to A-11 solutions and comparative resin AC-1 to AC-2 solutions were prepared. Obtained.

Example 1 10 parts of the resin A-1 solution obtained in Production Example 18, 1.0 part of carbon black, 15 parts of talc, 3 parts of ethylene glycol monoethyl ether, 0.7 part of acetic acid, and 17.3 parts of deionized water. 48% of the mixture in a pebble ball mill.
After time dispersion, a pigment paste with bulges of 10 microns or less was obtained.

Next, 1 part of cobalt acetate and 1.4 parts of acetic acid were added to 123 parts of the resin A-1 solution and stirred uniformly. Then, 507 parts of deionized water was gradually added while stirring to obtain an aqueous clear liquid. Add 47 parts of the above pigment paste to this aqueous clear liquid,
Stable water-based paints were prepared by uniform stirring (Table 3).

Cationic electrodeposition was performed using this aqueous paint as an electrodeposition bath at a bath temperature of 28° C. and a zinc phosphate-treated plate was used as a cathode to give a dry film thickness of 20 microns, followed by washing with water and baking hardening under predetermined conditions. The baking conditions were 140°C for 30 minutes and 160°C for 30 minutes. Table 4 shows the coating performance of the baked painted board obtained.

Examples 2 to 11 Baked coated plates were obtained in the same manner as in Example 1, except that the formulations shown in Table 3 were used. Table 4 shows the coating film performance of the coated board.

Example 12 1517 parts of the resin solution (1) obtained in Production Example 1, 1253 parts of the adduct b-1 solution obtained in Production Example 13, and 329 parts of ethylene glycol dimethyl ether were placed in a flask equipped with a stirrer, thermometer, and reflux condenser. After mixing at 70° C. for 60 minutes, 23 parts of propylene glycol monomethyl ether was added and mixed uniformly to obtain a mixed resin solution M-1.

A baked painted board was obtained in the same manner as in Example 1 except that mixed resin solution M-1 was used and the formulation shown in Table 3 was used. Table 4 shows the coating film performance of the coated board.

Example 13 In a flask equipped with a stirrer, a thermometer, and a reflux condenser, 1517 parts of the resin solution (1) obtained in Production Example 1, 1011 parts of the adduct b-2 solution obtained in Production Example 14, and 162 parts of ethylene glycol dimethyl ether were added. and mixed at 70° C. for 60 minutes to obtain a mixed resin solution M-2.

A baked painted board was obtained in the same manner as in Example 1, except that mixed resin solution M-2 was used and the formulation shown in Table 3 was used. Table 4 shows the coating film performance of the painted board.

Comparative Examples 1 and 2 A clear paint was prepared in the same manner as in Example 1, except that the formulations shown in Table 3 were used, and a baked-on coated board was obtained. Table 4 shows the coating film performance of the baked painted board.

Comparative Example 3 A flask equipped with a stirrer, a thermometer, and a reflux condenser was charged with 1,517 parts of the resin solution (1) and 66 parts of the resin solution BC-1 obtained in Production Example 15, and mixed at 70°C for 60 minutes. A mixed resin solution MC-1 was obtained. Using the obtained mixed resin solution MC-1, the same procedure as in Example 1 was carried out except that the formulations shown in Table 3 were used to obtain a baked painted board. Table 4 shows the coating film performance of the baked painted board.

Table (continued) The tests in Table 4 were conducted according to the following method.

(*1) Gel fraction: The free coating film was immersed in acetone at about 57°C (under reflux) for 4 hours to perform extraction.

(*2) Heat aging: After painting and before baking, the solvent was removed from the coating film under reduced pressure at 80° C. until the weight became constant, and then baked at a predetermined temperature for 30 minutes, and determined by the following formula.

(*3) Salt spray resistance: cross-cut the coating film with a knife to reach the substrate, and then apply JIs Z2
A salt spray test was conducted using No. 371, and the time at which the maximum blistering width or creep width on one side of the crosscut reached 3 mm was recorded.

Claims (4)

[Claims] (1) General formula with a tertiary amino group and an average of 0.6 or more per molecule ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) [In the formula, R^1 is a hydrogen atom or a methyl group, R^ 2 is an alkylene group having 1 to 4 carbon atoms, and R^3 is an alkylene group having 1 to 10 carbon atoms.
represents an alkyl group. ] has a 3-alkoxyalkyl-3-(meth)acryloyl-ureido group, and has a number average molecular weight of 800 to 50,000,
A cationic electrodeposition coating method, which comprises using an electrodeposition coating composition containing as an essential component a resin that becomes water-soluble or water-dispersible upon neutralization, and carrying out electrodeposition coating using the object to be coated as a cathode. (2) The water-soluble or water-dispersible resin has a primary or secondary hydroxyl group as required, and the primary or secondary hydroxyl group and the group represented by the general formula (I) Total is 1
2. The cationic electrodeposition coating method according to claim 1, wherein the number of particles per molecule is two or more on average. (3) There are hydroxyl group-containing resins that have 1 to 4 or more primary or secondary hydroxyl groups per molecule and a number average molecular weight of 600 to 50,000, and general formulas ▲ mathematical formulas, chemical formulas, tables, etc. ▼ (I) [In the formula, R^1 is a hydrogen atom or a methyl group, R^2 is an alkylene group having 1 to 4 carbon atoms, and R^3 is an alkylene group having 1 to 10 carbon atoms.
represents an alkyl group. ] A mixture with a resin having an average of one or more 3-alkoxyalkyl-3-(meth)acryloyl-ureido groups per molecule and having a number average molecular weight of 400 to 30,000; An electrodeposition paint containing as an essential component a mixture in which one or both of the resins contains a sufficient amount of tertiary amino groups to make the mixture water-soluble or water-dispersible by neutralization. A cationic electrodeposition coating method characterized by using a composition and performing electrodeposition coating on an object to be coated as a cathode. (4) The hydroxyl group-containing resin has the general formula (I) as necessary.
contains a group represented by the formula (I), and the total of the primary or secondary hydroxyl group and the group represented by the general formula (I) is 1
4. The cationic electrodeposition coating method according to claim 3, wherein the number of particles per molecule is two or more on average.