JPS5949263B2 - Electrodeposition coating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrodeposition coating method using a composition comprising a water-soluble resin and a powdered resin.

More specifically, the medium is a mixture mainly composed of water and a small amount of a water-soluble organic solvent, and a water-soluble acrylic resin having a crosslinkable functional group and an auxiliary crosslinkable functional group having an average particle size of 5 to 50μ are used as a medium. The object of the present invention is to electrodeposit a composition comprising a powdered acrylic resin having the following properties on an object to be coated.

In recent years, in the field of paints, powder paints that do not contain volatile components such as solvents and water-based paints that can be dissolved or dispersed in water have been actively researched or developed from the viewpoint of pollution-free and resource saving.

The use of such powder coatings and water-based coatings is intended to avoid air pollution, water pollution, and the risk of ignition due to harmful solvents.

However, due to reasons such as the expected tightening of legal regulations related to pollution and the future shortage of resources such as solvents, these paints are expected to attract more attention and develop in the future.

In general, conventional powder coating methods include fluidized dipping, electrostatic spraying, and the like.

The disadvantages of powder coatings include the following: First, to briefly explain, the important properties of powder coatings are blocking properties (solidification during storage) and flow properties (smoothness when heated).In general, increasing the glass transition temperature of the resin will cause blocking properties. The properties will be good, but the flow properties will be poor.

Conversely, lowering the glass transition temperature of the resin results in poor blocking properties but good flow properties, which are contradictory properties. Therefore, in order to simultaneously satisfy these various properties, the glass transition temperature range is self-limited and is usually higher than that of conventional solvent-based paints or electrodeposition paints. Flow consistency is somewhat poor.

2) For the curing agent used in powder coatings, from the viewpoint of blocking properties, those that are liquid at room temperature or low-molecular compounds that are sticky cannot be used.

Therefore, the types of curing agents that can be used are also limited. 3)
Generally, in order to lower the curing temperature, it is necessary to heat the resin and the curing agent at a low temperature.

However, kneading at low temperatures has poor working efficiency, and even when applied, it is difficult to obtain a smooth coating film. Furthermore, it is difficult to obtain a smooth coating film simply by mixing the resin (base resin) and curing agent. Furthermore, even if it is applied to form a thin coating film of around 10 μm, a film with good smoothness cannot be obtained. Compositions in which powdered resin is dispersed in water or an organic medium are also known in order to improve the various drawbacks of powder coatings as described above.

After the composition is applied onto the object to be coated by an appropriate method,
If necessary, bake it to form a coating.

As this type of composition and coating method, the following are known, for example. Using a mixed solution of methyl ethyl ketone and trichlorethylene as a dispersant, or a mixed solution prepared by adding carbon tetrachloride to this mixed solution, the nylon powder is split into branches, and the target material is electrodeposition coated (unexamined patent application). (Sho 47-35026).

A method of electrocoating a fine particulate polymer latex obtained by polymerizing monomers in the presence of water and an emulsifier (Japanese Patent Publication No. 48-348
17) etc. are known.

However, in either case, only the powdered resin is electrophoretically electrodeposited. On the other hand, in order to dissolve ordinary water-soluble resins in water, it is necessary to introduce a large amount of hydrophilic groups into the molecule, and the molecular weight cannot be made too high, so it is difficult to apply paints using these resins as a color vehicle. The film had drawbacks such as insufficient coating performance such as water resistance.

However, in order to improve these drawbacks, dispersion-type compositions (Japanese Patent Publication No. 39-25283: 1983-25283), which are a mixture of water-soluble resin and thermoplastic resin fine powder, have been developed. A method using a composition containing a powdered resin of 5 μm or less (Japanese Patent Publication No. 48-21337) is known.

However, both methods have drawbacks, such as the performance of the resulting coating film being insufficient or the powdered resin being precipitated and solidified and not being redispersed. The present invention aims to improve the various drawbacks of the prior art as described above, and provides a coating method that fully utilizes the advantages of powder coatings and water-soluble resin coatings.

That is, the present invention provides a) a medium containing water and a small amount of a hydrophilic organic solvent, and b) a crosslinkable functional group selected from a carboxyl group, a hydroxyl group, and a protoxyisocyanate group. one or more water-soluble acrylic resins dissolved in the medium; and a)) a functional group crosslinkable by heating selected from hydroxyl groups, N-alkoxymethyl groups, epoxy groups, protoxyisocyanate groups, and oxazoline groups; A composition comprising one or more powdered acrylic resins having an auxiliary crosslinking functional group that undergoes a crosslinking reaction with the resin and having an average particle size of 5 to 50μ dispersed in the medium is deposited in an electrodeposition bath. The present invention relates to an electrodeposition coating method, which is characterized by forming a thermally crosslinked reactive film made of the water-soluble resin and a powdered resin on the surface of an object to be coated by electrophoresis.

In other words, the present invention relates to a method of electrophoretically coating a powdered acrylic resin at the same time as a water-soluble acrylic resin. The crosslinkable functional groups form a strong coating film through a crosslinking reaction.

The present invention aims to solve the blocking problem of conventional powder coatings and to obtain a very smooth, thick coating film with excellent performance.

That is, when viewed from the viewpoint of a powder coating, it has the following advantages.

(1) By dispersing the powder coating in water, it becomes difficult to block even if the glass transition temperature of the resin is lower than that of conventional coatings, and the flow properties are also improved.

Furthermore, the flowability can be further improved by adding a water-soluble organic solvent. (2) As a curing agent for powder coatings, water-soluble liquids and sticky low-molecular compounds, which have not been available until now, can also be used.

Therefore, more crosslinking systems can be selected. (
3) Unlike conventional powder coatings, there is no need to uniformly heat-coat the resin and curing agent, and furthermore, a smooth coating film can be obtained by simply heating after electrodeposition coating. (4) A good smooth coating film can be obtained even with a thin film coating of about 10 μm.

In this way, the drawbacks of conventional powder coatings can be improved by simultaneously using a water-soluble coating and electrocoating.

On the other hand, from the viewpoint of conventional electrodeposition coating, (1) the coating film can be thickened by increasing the concentration of coating film forming components in the electrodeposition bath.

(2) Since the concentration of water-soluble resin can be lowered, wastewater treatment becomes easier.

It has the following effects.

Therefore, the various effects of the present invention as described above are achieved by using a specific powdered resin and a small amount of a hydrophilic organic solvent.

The water-soluble acrylic resin used in the present invention does not necessarily have to be water-soluble itself.

That is, what is dissolved in a hydrophilic organic solvent may be soluble in water. However, it is essential to have a crosslinkable functional group. In order to make the resin water-soluble, it is necessary to introduce carboxyl groups into the resin and neutralize it with an amine or an inorganic alkali. The crosslinkable functional group possessed by the water-soluble acrylic resin is selected from carboxyl groups, hydroxyl groups, and pro-isocyanate groups.
Naturally, the water-soluble acrylic resin is also included in the present invention when it has two or more types of crosslinkable functional groups.

In the present invention, the water-soluble acrylic resin may be mixed with a small amount of other water-soluble resins such as a water-soluble melamine resin, a water-soluble alkyd resin, and a water-soluble polybutadiene, if necessary.

The powdered acrylic resin that can be used in the present invention can be obtained by mechanically crushing a solid resin, or by spray-drying a solution resin composition, or by adding it into a poor solvent while stirring, as in conventional powder coatings. It is manufactured by a method such as a method of atomizing the particles using a method such as

In the present invention, the particle size of the powdered acrylic resin is 200μ or less, and the average particle size is 5 to 50μ, preferably 1
It is desirable to use one adjusted to a range of 0 to 30μ in order to obtain a coating film with good smoothness. Furthermore, it has been found that it is suitable to contain 75% or more of the particles having an average particle diameter of preferably 10 to 30 .mu.m.

Regarding the above average particle size, is the particle size of the powdered acrylic resin used 5μ or less? In this case, the powdered acrylic resin dissolves and swells due to the influence of the organic solvent present in the electrodeposition bath, which tends to increase the viscosity of the electrodeposition bath, and the powdered acrylic resin in the electrodeposition bath solidifies and cannot be redispersed. The storage stability of the bath composition becomes extremely poor. On the other hand, if particles with a particle diameter of 200 μm or more are included, flow properties during baking are poor, and the smoothness and other properties of the coating film are significantly reduced.

Further, the powdered acrylic resin of the present invention has an auxiliary crosslinkable functional group.

The auxiliary crosslinkable functional group is a functional group selected from a hydroxyl group, an N-alkoxymethyl group, an epoxy group, a protoxyisocyanate group, and an oxazoline group.

One or more of these may be contained in the powdered acrylic resin.

In the present invention, the auxiliary crosslinkable functional group is one that undergoes a crosslinking reaction with the crosslinkable functional group of the water-soluble acrylic resin when heated.

For example, when the crosslinkable functional group is a hydroxyl group, the auxiliary crosslinkable functional group is selected from an N-alkoxymethyl group or a protoxyisocyanate group, and when the crosslinkable functional group is a carboxyl group, the auxiliary crosslinkable functional group is selected from For example, the auxiliary crosslinkable functional group is an epoxy group or an oxazoline group, and when the crosslinkable functional group is a block isocyanate group, the auxiliary crosslinkable functional group is a hydroxyl group. Furthermore,
When a water-soluble acrylic resin and a powdered acrylic resin are combined, it is also within the technical scope of the present invention to combine one type or two or more of each type.

A method for introducing a functional group or an auxiliary functional group into the powdered resin or water-soluble resin is a copolymerization reaction, broad condensation reaction, or various other chemical reactions.

Reactive comonomers used to introduce functional groups into the acrylic resin used in the present invention include (1) glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether having an epoxy group; (2) acrylic acid, methacrylic acid having a carboxyl group. , crotonic acid, itaconic acid, itaconic acid monoesters, maleic acid, maleic acid monoesters, or acid anhydride maleic acid, itaconic anhydride; (3) Allyl alcohol having a hydroxyl group, 2-hydroxyethyl Adduct of methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, monoaryl ether of polyhydric alcohol, polypropylene glycol monomethacrylate, glycidyl methacrylate and a compound having active hydrogen; (4) N -N-methoxymethyl (meth)acrylamide having an alkoxymethyl group, N-ethoxymethyl (meth)acrylamide, N-n-propoxymethyl (meth)acrylamide, N-isopropoxymethyl (meth)acrylamide, N-n -butoxymethyl(meth)acrylamide, N-Sec-butoxymethyl(meth)acrylamide, N-t-butoxymethyl(
N-alkoxymethylated products of α,β-monoethylenically unsaturated carboxylic acid amides such as meth)acrylamide and N-isobutoxymethyl(meth)acrylamide; or N-methylolated products thereof: (5) Protoxyisocyanate group and (6) 2-isopropenyl-2-toxazoline having an oxazoline group.

These reactive comonomers contain two
It is also possible to introduce more than one type. (The water-soluble acrylic resin and powdered acrylic resin used in the present invention are a combination of a monomer having the above crosslinkable functional group (including an auxiliary crosslinkable functional group) and a copolymerizable monomer as shown below. Specific examples of monomers that can be copolymerized include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate,
n-butyl (meth)acrylate, Sec-butyl (meth)acrylate, t-butyl (meth)acrylate,
Isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (
Alkyl esters of acrylic acid or methacrylic acid such as meth)acrylate, tridecyl(meth)acrylate, stearyl(meth)acrylate; or cyclohexyl(meth)acrylate, phenyl methacrylate, benzyl methacrylate, styrene, vinyltoluene, α-methylstyrene , (meth)acrylonitrile, vinyl acetate, and the like. The above monomers may be used singly or in combination of two or more depending on the purpose and use of the composition. The hydrophilic organic solvent in the present invention refers to one that dissolves in water by 10% or more.

For example, alcohols include isopropyl alcohol, isobutyl alcohol, tert-butyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and diacetone; ketones include acetone and methyl ethyl ketone; ethers include methyl ether, dioxane, and ethylene. Glycol monomethyl ether, ethylene glycol monoethyl ether; in addition to these, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, etc. are used.

These can be used alone or as a mixture of two or more. Furthermore, it is also possible to add a hydrophobic organic solvent if necessary, as long as it is 1% by weight or less of the electrodeposition bath. The electrodeposition bath composition used in the electrodeposition coating method of the present invention is generally used in the following proportions. Coating film-forming solid content mainly composed of water-soluble acrylic resin and powdered acrylic resin 1 to 50% by weight, hydrophilic organic solvent 1 to 10% by weight, and water 50 to 99% by weight.

However, these can be changed depending on the application. The blending ratio of each resin that is a coating film forming component varies depending on the functional group concentration of each resin, but usually 1 to 95 parts by weight of water-soluble acrylic resin, preferably 5 to 70 parts by weight, and 5 to 5 parts by weight of powdered acrylic resin.
It is carried out in an amount of 99 parts by weight, preferably in the range of 30 to 95 parts by weight.

Moreover, in order to obtain a colored coating film, about 2 to 50 parts by weight of pigments, dyes, etc. may be added to 100 parts by weight of the total resin.

The pigment, dye, etc. may be added by kneading and dispersing with either a water-soluble acrylic resin or a powdered acrylic resin, or kneading and dispersing with both resins. Further, the types of pigments used can be different for water-soluble acrylic resin and for powdered acrylic resin. In the present invention, other additives such as a surfactant, a curing agent, and a crosslinking accelerator can be added to the electrodeposition bath or resin.

The electrodeposition coating method uses the bathtub as one electrode and the object to be coated as the other electrode, and applies a rectified current between the electrodes to coat the surface of the object with water-soluble acrylic resin and powdered acrylic resin. Form a film.

In the above, the water-soluble acrylic resin is an anion type resin, and therefore the object to be coated becomes an anode. The powdered acrylic resin is electrophoresed onto the anode along with the water-soluble acrylic resin. The characteristic values of the electrodeposition bath are PH7-10; specific resistance 300-2
000Ω・? ; Non-volatile content (resin + pigment, etc.) is usually used in a range of 1 to 50% by weight. Electrodeposition coating conditions should be set depending on the composition of the electrodeposition bath, but generally the voltage is 50
~300V; Current application time: several seconds to 5 minutes; Bath temperature: 5 to 40°C. The object coated by electrodeposition according to the present invention is then baked at a temperature that causes a crosslinking reaction between the water-soluble acrylic resin and the powdered acrylic resin used.

The baking temperature varies depending on the crosslinking system, but generally a temperature of 120 to 250°C and a time of 10 to 60 minutes are appropriate.
Hereinafter, the present invention will be explained in more detail with reference to Examples.

Note that parts and percentages in the examples represent parts by weight and percentages by weight. Example 1 10% acrylic acid, 10% 2-hydroxyethyl methacrylate, 30V styrene! ), a resin solution consisting of 60 parts of an acrylic resin having carboxyl groups and hydroxyl groups consisting of 20% of ethyl methacrylate and 30% of n-butyl acrylate (Ft) and 40 parts of ethylene glycol monoethyl ether was mixed with dimethyl of 0.75 equivalent of the carboxyl group. A water-soluble acrylic resin solution was prepared by neutralizing it with ethylamine and using hydroxyl groups as crosslinkable functional groups.

The resin solution was diluted with 500 parts of deionized water, and a particle size of 200 mesh pass (average particle size: 20μ) was added, 10% N-n-butoxymethylacrylamide, 40% styrene,
Powdered acrylic resin 63 consisting of 30% n-butyl methacrylate and 20% 2-ethylhexyl acrylate and having an N-alkoxymethyl group as an auxiliary crosslinking functional group
The composition to which 50% was added was used as an electrodeposition bath. Comparative Example 1 An electrodeposition bath was prepared using the same method as in Example 1 without adding powdered acrylic resin.

Comparative Example 2 The powdered acrylic resin in Example 1 had an average particle size of 3 μm.
Other than replacing it with a similar one, the same manufacturer was used.

In the bath compositions of Example 1 and Comparative Examples 1 and 2, cold rolled steel plates (70 x 90 x 0.811) were used as electrodes, and the distance between the electrodes was 10C7n, and the anode to cathode ratio was 1:l under stirring. Electrophoretic coating was performed by applying a rectified current for 2 minutes at a bath temperature of 20°C. The resulting coating film was baked and cured at 200° C. for 30 minutes to finish.

Table 1 shows a comparison of bath properties and coating performance. (1) Film thickness: Measured using an electromagnetic film thickness meter.

(2) Pencil hardness: JIS-K54OO6. According to l4.

(3) Cross-cut test: Cut 100 vertically and horizontally 111 cross-cuts, and show the residue after peeling off the cellophane tape.

(4) Acetone resistance test: Absorbent cotton with a diameter of approximately 1 cm is impregnated with acetone and placed on the coating film.

Constantly soak in acetone at 20°C and observe the state of the coating film, such as dissolution, swelling, and blistering, after 1 hour.

O mark indicates no abnormality, △ mark indicates slightly bad, and X mark indicates very bad. (5) Each electrodeposition solution was placed in a sealed polyethylene container and left to stand at 20°C for one week, and then the redispersibility of the precipitated powdered resin was evaluated based on the following criteria.

The O mark means that redispersion is easy with a stirrer, and the X mark means that redispersion is difficult. In some cases, a cake-like precipitate is formed.

From the above results, it is clear that the coating film obtained by the method of the present invention has superior pencil hardness and acetone resistance compared to Comparative Example 1, and it was also able to obtain a film twice as thick under the same electrodeposition conditions. .

Furthermore, the composition used in the method of the present invention had extremely good storage stability compared to that of Comparative Example 2.

In the composition of Comparative Example 2, the average particle size of the powdered acrylic resin is very small, so it dissolves under the influence of the organic solvent present in the electrodeposition bath, increasing the viscosity of the electrodeposition bath and increasing the viscosity of the electrodeposition bath. Phenomena such as the powdered acrylic resin easily solidified and redispersion was difficult were observed, and the storage stability was extremely poor. Example 2 100 parts of the same water-soluble acrylic resin solution as in Example 1 was diluted with 500 parts of deionized water, and 20
0 mesh pass (average particle size 15 μ) ε - 15% caprolactam-blocked vinyl isocyanate, 30% styrene, 35% n-butyl methacrylate and n
An electrodeposition bath was prepared by adding 60 parts of a powdered acrylic resin containing 20% -butyl acrylate and having a block isocyanate group as an auxiliary crosslinkable functional group.

This electrodeposition bath composition has a pH of 8.2 and a specific resistance of 850Ω/CT.
IL (200C); showed a characteristic value of non-volatile content of 18.0%. Using a cold-rolled steel plate (70 x 90 x 0.8 W!l) as an electrode, the bath temperature was 20°C and the distance between the electrodes was 15 crn while stirring the bath composition. When the anode to cathode ratio was 1:1 and constant pressure electrodeposition was performed at a rectified current of 200 V for 2 minutes, water-soluble acrylic resin and powdered acrylic resin were deposited on the anode. This electrodeposited coating was opaque, but when it was cured by baking at 180° C. for 20 minutes, a transparent continuous coating was obtained. A crosslinked coating film having a film thickness of 11.7μ, which is approximately twice that of Comparative Example 1, and excellent in solvent resistance was obtained. Furthermore, the storage stability was also good. Example 3 Acrylic acid 11 (fl
), 70 parts of an acrylic resin having a carboxyl group consisting of 29% methyl methacrylate, 20% ethyl methacrylate, and 40 (fl) n-butyl acrylate, and 30 parts of ethylene glycol monobutyl ether were added to a resin solution containing 0.8 equivalents of the carboxyl group. was neutralized with triethylamine to prepare a water-soluble acrylic resin solution with carboxyl groups as crosslinkable functional groups.

20 parts of the resin solution diluted with 500 parts of deionized water.
0 mesh pass (average particle size 30μ), 15% 2-isopropenyl-2-oxazoline, 30% styrene, n
An electrodeposition bath was prepared by adding 70 parts of a powdered acrylic resin containing 35% -butyl methacrylate and 20% n-butyl acrylate and having an oxazoline group as an auxiliary crosslinkable functional group. This electrodeposition bath composition exhibited characteristic values of pH 8.6; specific resistance 780 Ω (:IL: non-volatile content 20.4%). While stirring, the bath temperature was 25℃, the electrode distance was 150!n, the anode to cathode ratio was 1:1, and constant pressure electrodeposition was performed at a rectified current and voltage of 170 for 1.5 minutes, and the anode was water-soluble. Acrylic resin and powdered acrylic resin precipitated.The resulting electrodeposited coating was opaque, but
After curing by baking at 0° C. for 30 minutes, a transparent and continuous coating film was obtained. A crosslinked coating film with a film thickness of 27 μm and excellent solvent resistance was obtained. Example 4 60 parts of an acrylic resin having a carboxyl group consisting of 15% methacrylic acid, 25% methyl methacrylate, 20% ethyl methacrylate, and 40% n-butyl acrylate, and 40 parts of ethylene glycol monoethyl ether
A water-soluble acrylic resin solution containing the carboxyl group as a crosslinkable functional group was prepared by neutralizing the resin solution consisting of the above-mentioned carboxyl group with 0.75 equivalent of dimethylethylamine.

The resin solution was diluted with 500 parts of deionized water and mixed with 10% glycidyl methacrylate, 40% styrene, 30(f) n-butyl methacrylate, and 2-ethylhexylate with a particle size of 200 mesh (average particle size 10μ). A composition to which 63 parts of a powdered acrylic resin having an epoxy group consisting of acrylate 20(f) as an auxiliary crosslinking functional group was added was used as an electrodeposition bath. This electrodeposition bath composition has a pH of 8.3;
Specific resistance: 910Ω・CTIL (2'C); Non-volatile content: 18.
It showed a characteristic value of 5%.

Using a cold-rolled steel plate (70 x 150 x 0.8 mm) as an electrode, the bath temperature was 20°C and the distance between the electrodes was 1 while stirring the bath composition.
0 cTn, the anode to cathode ratio was set to 1:1, and electrophoretic coating was performed by applying a rectified current at a voltage of 220 V for 5 minutes.
When the obtained coating film was cured by baking at 200° C. for 30 minutes, a transparent and continuous coating film was obtained. The film thickness was 27μ, and a cured coating film with excellent solvent resistance was obtained. Example
5 10% methacrylic acid, 10% phenol-blocked vinyl isocyanate, 30% styrene, 20% ethyl methacrylate and 300% n-butyl acrylate.
/) A resin solution consisting of 60 parts of an acrylic resin having a carboxyl group and a blocking isocyanate group and 40 parts of ethylene glycol monoethyl ether is neutralized with dimethylethylamine in an amount of 0.75 equivalents of the carboxyl group, and the blocking isocyanate is A water-soluble acrylic resin solution containing a crosslinkable functional group was prepared.

The resin solution was diluted with 500 parts of deionized water and added with 10% 2-hydroxyethyl methacrylate and 40% styrene with a particle size of 200 mesh pass (average particle size 10μ).
, n-butyl methacrylate 30%, and 2-ethylhexyl acrylate 20 (Ffl) 63 parts of a powdered acrylic resin having a hydroxyl group as an auxiliary crosslinking functional group was used as an electrodeposition bath.

This electrodeposition bath composition has a pH of 8.4 and a specific resistance of 930Ω/CT.
n (20°C); showed a characteristic value of non-volatile content of 18.5%.

Using a cold-rolled steel plate (70 x 150 x 0.8 mm) as an electrode, the bath temperature was 20°C and the distance between the electrodes was 1 while stirring the bath composition.
q (1-JMoV!.The anode to cathode ratio was set to 1:1, and a rectified current was applied for 5 minutes at a rope pressure of 220 to perform electrophoretic painting.9
Ta. When the obtained coating film was cured by baking at 180° C. for 30 minutes, a transparent and continuous coating film was obtained. Film thickness is 28
μ, and a cured coating film with excellent solvent resistance was obtained. Example 6 10% itaconic acid, 40% styrene, 20(f) ethyl methacrylate and 30(f) n-octyl acrylate
) A resin solution consisting of 60 parts of acrylic resin having a carboxyl group and 40 parts of ethylene glycol monoethyl ether is neutralized with dimethylethylamine in an amount of 0.75 equivalents of the carboxyl group, and the carboxyl group becomes a crosslinkable functional group. A water-soluble acrylic resin solution was prepared.

The resin solution was diluted with 500 parts of deionized water and mixed with 10% allyl glycidyl ether, 40% styrene, 30% n-butyl methacrylate, and 20% n-octyl acrylate with a particle size of 200 mesh pass (average particle size 20μ). A composition containing 63 parts of a powdered acrylic resin having an epoxy group as an auxiliary crosslinkable functional group was used as an electrodeposition bath.

This electrodeposition bath composition has a pH of 8.5 and a specific resistance of 900Ω. (
20th grade C): showed a characteristic value of non-volatile content of 18.7. Using a cold rolled steel plate (70 x 150 x 0.8 mm) as an electrode,
While stirring the bath composition, the bath temperature was 20°C and the distance between the poles was 10°C.
f! L. Electrophoretic coating was performed by setting the anode to cathode ratio to 1:1 and applying a rectified current at a voltage of 200 V for 2 minutes. When the obtained coating film was cured by baking at 200° C. for 30 minutes, a transparent and continuous coating film was obtained. The film thickness was 19 μm, and a cured coating film with excellent solvent resistance was obtained. Example 7 Acrylic acid 10%, ethylene glycol monomethacrylate 10%, cyclohexyl methacrylate 30%, ethyl methacrylate 20% and t-butyl acrylate 3
A resin solution consisting of 60 parts of acrylic resin having 0% carboxyl group and hydroxyl group and 40 parts of ethylene glycol monoethyl ether was mixed with 0.7% of the carboxyl group.
This was neutralized with 5 equivalents of dimethylethylamine to prepare a water-soluble acrylic resin solution in which hydroxyl groups were used as crosslinkable functional groups.

The resin solution and 6 parts of a water-soluble melamine resin solution (500! methanol solution) were diluted with 500 parts of deionized water, and a particle size of 200 mesh pass (average particle size 20μ) was added.
N-methoxymethylacrylamide 10%, styrene 4
A composition containing 63 parts of a powdered acrylic resin containing an N-alkoxymethyl group as an auxiliary crosslinkable functional group consisting of 0% n-propyl methacrylate, 30% n-propyl methacrylate, and 20% 2-ethylhexyl acrylate was used as an electrodeposition bath. .

This electrodeposition bath composition has a pH of 8. O; Specific resistance 890Q/CT
! L (20'C); Non-volatile content 18.80! ) are shown.

Using a cold rolled steel plate (70 x 150 x 0.8 mm) as an electrode, while stirring the bath composition, the bath temperature was 20'C and the distance between the electrodes was 10 CI! L, the anode to cathode ratio was set to 1:1, and a rectified current was applied at a voltage of 200 V for 3 minutes to perform electrophoretic coating. When the resulting coating film was cured by baking at 180° C. for 30 minutes, a transparent and continuous coating film was obtained. Film thickness is 17
A cured coating film was obtained which was IL and had excellent solvent resistance. Example 8 Methacrylic acid 1001), 2-hydroxyethyl acrylate 1001), styrene 3001), n-propyl methacrylate 20 (:fl), and t-butyl acrylate 30 (acrylic resin having a carboxyl group consisting of Fb and a hydroxyl group 60) A resin solution consisting of 40 parts of ethylene glycol monoethyl ether and 40 parts of ethylene glycol monoethyl ether was neutralized with dimethylamine in an amount of 0.75 equivalents of the carboxyl group to prepare a water-soluble acrylic resin solution having hydroxyl groups as crosslinkable functional groups.

The resin solution was diluted with 500 parts of deionized water, and 10 g of phenol-blocked allyl isocyanate having a particle size of 200 mesh pass (average particle size of 10 It) was added.
A composition containing 63 parts of a powdered acrylic resin containing 40 parts of vinyltoluene, 30 parts of t-butyl methacrylate, and 20 parts of 2-ethylhexyacrylate, which has a block isocyanate group as an auxiliary crosslinkable functional group. The material was used as an electrodeposition bath.

This electrodeposition bath composition has a pH of 8.2; a specific resistance of 900Q・Cf
L (20'C); showed a characteristic value of non-volatile content of 18.5 (fl).

Using a cold-rolled steel plate (70 x 150 x 0.8n) as an electrode, the bath temperature was set to 20 C while stirring the bath composition, and the distance between the electrodes was 1.
Electrophoretic coating was performed by applying a rectified current at a voltage of 200 V for 3 minutes with an anode to cathode ratio of 1:1.

Claims (1)

[Claims] 1 a) A medium containing water and a small amount of hydrophilic organic solvent, b)
One or more water-soluble acrylic resins having a crosslinkable functional group selected from a carboxyl group, a hydroxyl group, and a blocked isocyanate group and dissolved in the medium as a neutralized product of the carboxyl group, and c) a hydroxyl group. , an N-alkoxymethyl group, an epoxy group, a blocked isocyanate group, and an oxazoline group, the particles have an auxiliary crosslinkable functional group that undergoes a crosslinking reaction with a crosslinkable functional group upon heating, and are dispersed in the medium. A composition consisting of one or more types of powdered acrylic resins having a diameter of 5 to 50 μm is used as an electrodeposition bath, and the water-soluble resin and the powdered resin are subjected to a thermal crosslinking reaction on the surface of the coated object by electrophoresis. An electrodeposition coating method characterized by forming a transparent film.