JPS63153297A - Formation of coated film - Google Patents

Abstract

PURPOSE:To improve the edge covering property and resistance to filiform corrosion and chipping of a material to be treated by successively electrodepositing cationic paints respectively contg. pigments of different total oil absorption on the material, heating and curing the paints, and then painting a barrier coat. CONSTITUTION:A cationic electrodeposition paint contg. a resin binder and a pigment, >=5wt% of which has >=100 oil absorption and the total oil absorption of which is controlled to 1,000-10,000 per 100g resin binder, is electrodeposited on the material to be coated. While the paint is not cured, an emulsion-type cationic electrodeposition paint consisting of a resin binder and a pigment having lower total oil absorption than the primer and having <=0.7mA/cm<2> minimum electrolytic current density and >=80% emulsification degree is coated. The successively coated paints are heated and cured, and a barrier coat is painted to form a coated film having 0--75 deg.C static glass transition temp. on the electrodeposited surface. Intermediate coating and final coating are further applied, if necessary.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to improve the corrosion resistance of objects to be coated, especially the edge portions (
This invention relates to a method for forming a composite coating film having excellent corrosion resistance (edge surface) and thread rust resistance, as well as good chipping resistance (impact peeling resistance).

Electrodeposition coating has traditionally been used as an undercoat for automobiles, electrical equipment, etc. Compared to organic solvent-based air spray coatings or electrostatic spray coatings, it has better coverage of the paint on the object being coated and provides a relatively uniform film. It is widely put into practical use because it has the advantage of being able to easily form a thick coating film. In particular, recently, cationic electrodeposition coating forms a coating film with excellent corrosion resistance, and has therefore been replaced by 7-ion electrodeposition coating in fields where corrosion resistance is important, such as automobiles.

However, even when cationic electrodeposition is applied, the formed electrodeposited coating film on the edges of the object undergoes thermal fluidization during heating and hardening, making it impossible to obtain the desired film thickness, resulting in poor coverage of the edges. The drawback is that corrosion resistance is reduced. As a measure to improve such defects, there are examples of using rust-proof steel plates for the object to be coated, and applying repair paint to the edges using a roller or brush using a solvent-based paint with good anti-corrosion properties called Edgecoat, but this is costly. And it is not necessarily satisfactory in terms of productivity.

In addition, as a method for improving the corrosion resistance and thread rust resistance of edge portions, for example, Japanese Patent Publication No. 80-7716 and Japanese Patent Application Laid-Open No. 61-1999
No. 195998, etc., proposes applying multiple electrodeposition paints. However, in the former case, the first layer of electrocoating paint contains conductive powder, which can cause uneven coating and skin irritation, so even if the second layer of electrocoat paint is repeatedly applied, the edges will not remain. The corrosion resistance and smoothness of the coating film were insufficient in areas other than the first electrodeposition coating time.
Because the time is as short as ~2 seconds, it is extremely difficult to accurately control the coating, and its applicability in practical lines is poor.Also, it is possible to electrodeposit in a short time only on the edges of objects with complex shapes. It is actually difficult to form a coating film by painting.
A coating film is formed on areas other than the edge portions, and therefore, the smoothness of the coating film after the second electrodeposition coating is poor.

In addition, when an automobile's exterior panel is electrocoated as described above, and then finished with an intermediate coat and top coat, when it is hit by pebbles, rock salt, etc. thrown up while driving, the paint film is damaged by the energy of the collision. Peeling (so-called “chipping”)
This chipping may vary depending on the impact, such as pebbles, but it often peels off not only the top coat or intermediate coat of the area that has collided, but also the electrodeposited coating, and as a result,
The finished appearance and corrosion resistance will be significantly reduced.

Therefore, the present inventors solved the above-mentioned defects (in particular).

This is the result of intensive research to solve the following problems (edge coverage, thread rust resistance, chipping resistance, etc.).

A specific cationic electrodeposition paint is applied wet-on-wet by electrodeposition, heated and cured, and then a barrier coat is applied to achieve the desired purpose.

This was achieved and the present invention was completed.

That is, the present invention provides a resin binder (A) and at least one
The total amount of pigment (B) and oil amount is 10% of the resin binder (A).
Perform the first cationic electrodeposition coating on the object to be coated using the cationic electrodeposition paint (I), which is formulated so that the concentration is within the range of 1,000 to 10.000 per 0g, and leave it in an uncured state. , which contains a resin binder (C) and a pigment (D) as main components, has a minimum electrodeposition current density of 0.7 mA/cm2 or less and an emulsion degree of 80% by weight or more, and has a total content of pigment (D). An emulsion-type cationic electrodeposition paint (■
) was cationically electrodeposited for the second time, and then both electrodeposited coatings were heated and cured, and then a coating film having a static glass transition temperature of 0 to -75°C was applied to the electrodeposited surface. Eggplant characterized by painting a barrier coat to form a rough coating and applying an intermediate coat and (or) top coat if necessary? In the method of the present invention, a cationic electrodeposition paint containing as an essential component a pigment with an oil absorption of 100 or more is applied as the first layer to form a coating material. The corrosion resistance of the edges was mainly improved, and then an emulsion-type cationic electrodeposition paint having a specific minimum electrodeposition current density was applied as a second layer on the uncured first layer electrodeposition coating. By coating, the coating surface quality8 (especially smoothness) and thread rust resistance of the general areas other than the edge areas, which are disadvantages of the first layer electrodeposited coating, are improved, and the second layer The chipping resistance was improved by applying a barrier coat to the electrodeposited surface.

In the present invention, the cationic electrodeposition paints (I) and (■) to be applied in the first and second times are resin binder components (A) and (C), respectively, which are resins commonly used in electrodeposition paints. Binders, e.g. polyamine resins such as amine-added epoxy resins, e.g. (i) adducts of polyepoxides with primary mono- and polyamines, secondary mono- and polyamines or mixed primary and secondary polyamines (e.g. U.S. Pat. , 984, 299); (ii) 2 having a polyepoxide and a ketiminated primary amino group;
Adducts with marginal and polyamines (see, e.g., U.S. Pat. No. 4,017,438); reactants obtained by etherification of Gin polyepoxides with hydroxy compounds having ketiminated primary amine groups (e.g., When the composite cured coating film formed by the present invention is required to have good weather resistance, resin binder (A) and/or (C) may be used. As such, an amino group-containing or nonionic acrylic resin with excellent weather resistance may be used in combination with the amine-added epoxy resin, and the resin binder (A) and/or (C) may be
The amino group-containing acrylic resin may be used alone.

The above-mentioned amine-added epoxy resin and amine group-containing acrylic resin can be cured using a polyisocyanate compound blocked with alcohol to form an electrodeposited coating.

In addition, amine-added epoxy resins that can be cured without using blocked isocyanate compounds can also be used. For example, resins in which β-hydroxyalkyl carbamate groups are introduced into polyepoxide materials (for example, JP-A-59-155470) ); type of resin that can be cured by transesterification (for example, JP-A-55
-80436) etc. can also be used.

Preparation of a cationic aqueous dispersion using the resin binder described above is usually carried out by neutralizing the resin binder with a water-soluble organic acid such as formic acid, vinegar, or lactic acid. The cationic electrodeposition paint whose main component is the aqueous dispersion thus obtained further contains a pigment, and in the cationic electrodeposition paint (1) used for the first electrodeposition coating, the pigment CB) has an oil absorption of 100%. At least 5% by weight, preferably 10% by weight or more, more preferably 20% by weight of the total amount of the pigment (B), preferably 150 or more pigments.
It is necessary that the content be 95% by weight. The amount of the pigment CB) to be blended with the resin binder (A) is as follows:
) has a total oil absorption of 1.
000-io, ooo, preferably 1,500-9.
000, more preferably within the range of 3.000 to 7.000.

Examples of pigments having an oil absorption of 100 or more that are incorporated into the pigment (B) essential to the above-mentioned cationic electrodeposition paint (I) include silicon dioxide pigments such as anhydrous silicon dioxide and hydrated amorphous silicon dioxide, and carbon pigments. Among them, silicon dioxide pigments are preferred.

Examples of commercially available silicon dioxide pigments with an oil absorption of 100 or more include Nippon Aerosil Co., Ltd.'s product name "Acrylic 200J (oil absorption 143-183)" and Fuji Davison Chemical Co., Ltd.'s product name "Syroid 161J (oil absorption 128).
~135), “Thyroid 244J (oil absorption 270~3
30), "Thyroid 308J (oil absorption amount! 70~2
20), “Thyroid 404J (oil absorption 170-230
), "Thyroid 978J (oil absorption 180-230
), and carbon-based pigments include furnace-type or channel-type carbon black, which is usually used as a black pigment (oil absorption is usually 10
0-130), such as "Carbon BAGJ" manufactured by Columbian Carbon Company, USA.

In the present invention, when the carbon-based pigment is used alone as a pigment with an oil absorption of 10<) or more, the coating workability of the cationic electrodeposition paint (I) is somewhat reduced because this pigment has conductivity. Therefore, it is preferable to use the silicon dioxide pigment in combination with the silicon dioxide pigment.In this case, the combined ratio of the silicon dioxide pigment and the carbon pigment is 9515
-60/40, preferably 90/10 - 70/30.

In addition to the above-mentioned pigments having an oil absorption of 100 or more, pigments to be added to the cationic electrodeposition paint (1) used in the present invention include pigments commonly used in electrodeposition paints, such as red iron and titanium white. Inorganic coloring pigments: Pigments with an oil absorption of less than 100, such as extender pigments such as talc, clay, and calcium carbonate, are mixed with the resin binder (B) of pigment (B).
A) Total oil absorption per 100g is 1,000 to 10.0
They can be used together as long as they fall within the range of 00.

The oil absorption amount of each pigment in the present invention is JISK 51
It is measured by the following method using 01-78 (pigment test method).

Accurately weigh a specified amount of sample to IC) + sg on parchment paper and transfer it to a frosted glass plate. Calculate the amount of boiled linseed oil required from the expected oil absorption of the sample in advance, and add approximately Take 90% of the sample from the microbiulet onto the tip of a spatula, and immediately use this spatula to thoroughly knead the sample on the frosted glass plate with boiled linseed oil for about 5 minutes.

Next, add 1-2 drops of boiled linseed oil to the spatula and mix evenly. The process of adding 1-2 drops of oil to the boiled flax and kneading it is repeated, and the end point is when the whole sample becomes a hard, uniform, putty-like mass for the first time, and the boiled flax has been added to the boiled flax until then. Read the amount of oil to the nearest 0.014.

Next, the oil absorption amount is calculated using the following formula.

Here, A: Oil absorption amount S: Mass of sample (g) L: Amount of boiled linseed oil used (g) Also, the total oil absorption amount is calculated by adding the amount of each pigment (g) to 100 g of resin using the above formula. This value is calculated as the sum of the values obtained by multiplying the oil absorption values of each pigment.

Among the pigments (B) used in the cationic electrodeposition paint (I) of the first layer of Akimoto's Karasu, the amount of pigments with an oil absorption of 100 or more is less than 5% by weight of the total amount of pigments (B). In some cases, the second layer of electrodeposition paint tends to be difficult to deposit.

In addition, in the present invention, if the total oil absorption amount of the pigment (B) in the cationic electrodeposition paint CI) used in the first electrodeposition coating is less than 1,000, If coverage is insufficient and on the other hand exceeds to, ooo, pigment aggregation tends to occur, resulting in problems such as filter clogging and coating surface abnormalities (blur, rough skin) due to pigment agglomerates.

In the present invention, after the first electrodeposition coating is performed,
Although it is not necessarily necessary to wash the electrodeposited coating with water, it is usually preferable to wash it with water (washing with shower water or immersion). Using deionized water or reverse osmosis liquid as the washing water improves the corrosion resistance of the edges. This method is more preferable because it further improves the coating properties and forms an electrodeposited coating film that is substantially free of pinhole defects.

Next, the cationic electrodeposition paint (II) used for the second electrodeposition coating contains a resin binder (C) and a pigment (D) as main components, and has a minimum electrodeposition current density of 0.7 mA. /c
m2 or less, preferably 0,5 mA/cm2 or less,
More preferably, the emulsion degree is 0.3+sA/c- or less, and the degree of emulsion is 80% by weight or more, preferably 85% by weight or more, and still more preferably 90% by weight or more, and the pigment (
There is no particular limitation as long as the total oil absorption per 100 g of the resin binder (C) in D) is smaller than that of the paint (1) used for the first electrodeposition coating, and more preferably less than 1,000. Electrodeposition paints of any composition can be used.

The above-mentioned minimum deposition current density is a value measured by the following method.

A platinum plate with a surface area of 1 am2 and an insulated back surface was used as the object to be coated and a counter electrode, respectively, and placed in an electrodeposition paint bath at a distance of 15 cm so that the two surfaces faced each other. 2
At 8°C, a constant current was applied without stirring, and the time and voltage were recorded.The current density was changed every 0.05 tsA/cm2, and the sudden increase in voltage due to the increase in resistance due to electrodeposition of the paint was measured. The current density that occurs in the vicinity of 3 minutes or more than 3 minutes is defined as the minimum deposition current density.

Furthermore, the degree of emulsion of the cationic electrodeposition paint (II) described above is an index representing the proportion (% by weight) of particles truly suspended as particles in the electrodeposition paint, and is determined by the following procedure. .

First, a clear emulsion with a solid content of 15 to 20% by weight that does not contain pigments or other ingredients, about 35 c.
Put c in a cell and seal it, 28,00 OR,P,M,
Centrifuge the supernatant of the separated sample for 60 minutes at
Pipette the sample and dry it at 120°C for 1 hour to measure the non-volatile content Nl (%).

The cell is then inverted to drain off the supernatant and inverted for an additional 10 minutes to remove the supernatant layer. After homogenizing the remaining sediment layer with a glass rod, 1.5 to 2.0 g was accurately weighed and heated at 120°C.
Dry for 1 hour and measure the non-volatile content N2 (%).

Next, accurately weigh about 2 cc of Clear Emano C John and heat it to 120°C.
Dry for 1 hour and measure the nonvolatile content No. (%).

The degree of emulsification is a value determined by the following formula.

In the present invention, if the minimum deposition current density of the cationic indoor paint (IT) exceeds 0.7 mA/cm2, it becomes difficult to ensure a film thickness that provides smoothness to the coated surface.

In addition, if the degree of emulsion is less than 80% by weight, the second layer of electrodeposition coating will tend to mix with the first layer of electrodeposition coating, resulting in a decrease in edge corrosion resistance and coating surface smoothness. There is.

In the present invention, cationic electrodeposition paint (I) and (I
As the method and apparatus for applying electrodeposition coating to the object using I), any known method and apparatus conventionally employed in cationic electrodeposition coating can be used. It is desirable to use carbon plates as the 7 nodes. The electrodeposition coating conditions that can be used are not particularly limited, but generally bath temperature: 20-30
°C, voltage: 100-400V (preferably 150-35V
0v), current density: 0, 01~3A/d+2, energization time 230 seconds~10 minutes, pole area ratio (A/C): 6/1
~1/6, distance between poles: 10-100cm.

It is desirable to electrodeposit under stirring.

In particular, the first and second electrodeposition coatings in the present invention can be performed by submerging most or all of the object in an electrodeposition paint bath (so-called "total immersion electrodeposition coating"). preferable.

The film thickness (dry state) of the first electrodeposition coating film formed using the above-mentioned electrodeposition coating method is 5 to 30p1, preferably 1
It is within the range of 0 to 251111, and the film thickness (dry state) of the second electrodeposition coating film formed thereon is 5 to 70.
Conveniently, μ is preferably in the range from 10 to 50°.

In the present invention, it is preferable for the second electrodeposition coating to be carried out while the first electrodeposition coating is uncured, from the viewpoint of forming a composite coating film and from the viewpoint of adhesion. As a necessary condition, the first electrodeposition coating film is heated at 120°C for about 1
It is understood that the term "uncured state" in the present invention also includes a semi-cured state. Should.

The electrocoated film formed on the object is about 150 ml after being washed with water.
Hardened by baking at ~180°C. The total electrodeposited coating thickness can be the sum of the above-mentioned first coating thickness and second coating thickness, but from the economic point of view, etc. The deposited film thickness is generally 15 to 80. It is desirable that it be within the range of .

In the present invention, after the electrodeposition paint is repeatedly coated as described above, a barrier coat is further coated.

Although the term "barrier coat" is not commonly used, in the present invention, it is possible to form a coating film that has specific physical properties and achieves the objectives of the present invention such as improved chipping resistance. Possible compositions include water and/or organic solvents as solvents or dispersion media.

The water-based barrier coat to be applied to the above electrodeposition coating is
Specifically, the static glass transition temperature of the formed coating film is O~-75.
An aqueous composition having water as a main solvent or dispersion medium at a temperature of 0.degree. C. is used.

The composition has an aqueous vehicle and water as main components, and can further contain a viscosity imparting agent, an organic solvent 1, a coloring pigment, an extender pigment, an anticorrosive pigment, etc., as necessary.

As the aqueous vehicle, it is preferable to use thermoplastic resins that have excellent adhesion to the above-mentioned electrodeposited coating film and the middle (top) coating film described below, and have a static glass transition temperature within the above range. Things can be mentioned.

・1.Modified polyolefin resin: For example, propylene-ethylene copolymer (in molar ratio, 4
0 to 80: 80 to 20 is preferable) and 1 to 50 parts by weight of chlorinated polyolefin (for example, polypropylene with a chlorination rate of about 1 to 60% by weight), preferably 1 to 2 Oi parts (both of which are based on the copolymer). (per 100 parts by weight); or the above propylene-ethylene copolymer 10
0 parts by weight of maleic acid or maleic anhydride.
Examples include graft polymers in which 1 to 50 parts by weight, preferably 0.3 to 2.0 parts by weight, are graft-polymerized.

The number average molecular weight of these copolymers, chlorinated polyolefins and graft polymers generally ranges from about 5.000 to about 30.
It is preferably within the range of 0.000.

In making the modified polyolefin resin water-based, the propylene-ethylene copolymer can be made water-based by anionic, cationic or nonionic emulsion polymerization, which is known per se. [The chlorinated polyolefin can be water-solubilized or water-dispersed by neutralizing the carboxyl group, and the chlorinated polyolefin can be water-dispersed, for example, in the presence of an emulsifier.

tl/styrene-butadiene copolymer: A copolymer with a styrene content of about 1 to 80% by weight, preferably 10 to 40% by weight, in which styrene and butadiene are used as polymerization regulators, catalysts, soaps, and wood. An aqueous dispersion of the copolymer can be obtained by copolymerizing in the presence of the copolymer.

The polymerization temperature is preferably 100°C or less, and the number average molecular weight of the copolymer is about to, ooo to about 1.000,00
It is preferably within the range of 0.

(2) Butadiene resin: This is an aqueous dispersion composition obtained by polymerizing in the above procedure without using styrene.

- Φ Acrylonitrile-butadiene copolymer: 7 Acrylonitrile content is 1 to 50% by weight.

It is preferably a 10 to 40% by weight copolymer, in which a functional additive such as acrylic acid or methacrylic acid is added to acrylonitrile and butadiene as necessary, and a polymerization catalyst, a molecular weight regulator, a surfactant, etc. The zero polymerization temperature obtained by emulsion polymerization in water in the presence of is preferably 100 ° C or less, and the number molar average molecular weight of the copolymer is within the range of about 10.000 to about 1,000,000. is suitable.

・i-Polybutene: Polybutene is mainly made of isobutylene, mixed with normal butylene if necessary, and is obtained by low-temperature polymerization. In the presence of an emulsifier, heat the polybutene to 50 to 70°C, add water, and stir uniformly and thoroughly. obtained by doing. The number average molecular weight of the resin is preferably within the range of about 1.000 to about 500,000.

■Acrylic resin Niacrylic acid ester and/or methacrylic ugly ester are the main components, and if necessary, acrylic acid, methacrylic acid, functional additives such as droxyethyl acrylate, hydroxypropyl methacrylate, etc.
or) by emulsion polymerizing a vinyl monomer component mixed with other polymerizable unsaturated polymers to form an aqueous dispersion; or by solution polymerizing and then converting it into an aqueous solution or aqueous dispersion. Examples of the acrylic esters include ethyl acrylate, propyl acrylate, n-butyl acrylate, 1so-butyl acrylate, 3-pentyl acrylate, hexyl acrylate, 2-hebutyl acrylate, octyl acrylate, 2-octyl acrylate, nonyl acrylate, lauryl Particularly suitable are acrylate, 2-ethylhexyl acrylate, 2-ethylbutyl acrylate, etc., and examples of methacrylic acid esters include pentyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, tethyl methacrylate, and lauryl methacrylate.

Stearyl methacrylate and the like are particularly preferred.

The static glass transition temperatures of the homopolymers derived from these acrylic esters and methacrylic esters illustrated here are all 0°C or lower, and one or more acrylic monomers selected from these monomers are used. Acid esters and methacrylic esters are suitable as monomers for forming the acrylic resin.

The acrylic resin has a number average molecular weight of about 5,000 to 1.0.
Preferably, it is in the range of 00,000.

(2) In addition to these, natural rubber latex, methyl methacrylate-butadiene copolymer emulsion, polychloroprene emulsion, polyvinylidene chloride emulsion, etc. can also be used as the aqueous vehicle.

The organic solvent-based barrier coat to be applied to the electrodeposited film surface uses an organic solvent as a main solvent or dispersion medium whose static glass transition temperature of the formed film is O to -75°C, specifically an organic solvent and a dispersion medium. The main component is a vehicle component.

Examples of the vehicle component include those exemplified for the aqueous barrier coat described above, and vehicles obtained by removing parent wood groups (or neutralizing groups) from these can also be used.

Suitable organic solvents are those that can dissolve or disperse these vehicles, such as aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, heptane, octane, and decane; and trichumyl. Chlorinated hydrocarbons such as ethylene, perchloroethylene, dichloroethylene, dichloroethane, dichlorobenzene; Ketone solvents such as methyl ethyl ketone and diacet alcohol; Alcohol solvents such as ethanol, propatool, butanol; Methyl cellosolve, butyl cellosolve It is also possible to add cellosolve-based solvents such as cellosolve acetate.

The coating film formed by the barrier coat has a static glass transition temperature (Tg) of 0 to -75°C, preferably -30 to -
It is important that the temperature is 60°C, particularly preferably within the range of -40 to -55°C; if Tg is higher than OoC, the chipping resistance, corrosion resistance, physical performance, etc. of the final composite coating will not be improved; If the temperature is lower than -75°C, the water resistance, adhesion, etc. of the final composite coating will deteriorate, which is not preferable.

In the present invention, if these vehicles themselves have a static glass transition temperature within the above range, they can be used as a barrier coating by themselves, but if the vehicle deviates from the above range or even within the range, the static glass transition temperature cannot be used. When it is desired to finely adjust the target glass transition temperature, a viscous meridian can be added as necessary. The viscosity-imparting agent may be a resin having good compatibility with the vehicle, such as rosin or petroleum resin (
coumaron resin), ester gum, epoxy-modified polybutadiene, low-molecular weight aliphatic epoxy resin, low-molecular weight aliphatic bisphenol type epoxy resin, polyoxytetramethylene glycol, vinyl acetate-modified polyethylene, etc., or emulsified dispersions thereof. The blending amount is 1 to 50 parts per 100 parts by weight of the vehicle (solid content).
It is preferably within the range of parts by weight (as solid content).

Furthermore, extender pigments, coloring pigments, anticorrosion pigments, etc. may be added to the barrier coat. The amount of these pigments is 1 to 100 parts by weight of vehicle (solid content).
It is preferably within the range of 150 parts by weight.

In particular, by incorporating an anti-corrosion pigment into the barrier coat, the anti-corrosion properties can be significantly improved compared to when the anti-corrosion pigment is included in the electrodeposition coating.

Regarding the barrier neat coating film, it is essential that the static glass transition temperature is within the above range. ,000%, especially 300 to 700%, whereby the object of the present invention can be achieved even more markedly.

In the present invention, these barrier coats are applied to the cured electrodeposition coating surface, but the coating method is not limited, and examples include spray coating, spacing coating, dipping coating, melt coating, electrostatic coating, etc. The coating film thickness is preferably 1 to 20 IL, particularly 5 to 1 OJL, based on the dry coating film.

The static glass transition temperature of the formed coating film of the barrier neat used in the present invention was measured using a differential scanning calorimeter (DSC-1 manufactured by Daini Seikokin Co., Ltd.).
The tensile strength elongation rate at break is the value measured using a universal tensile tester with a constant temperature bath (Shimadzu Autograph S-D).
This is the value measured using a mold), and the sample length is 20 mm.
The tensile speed was 20 mm/min. The samples used for these measurements were coated on a tin plate with the barrier coat added to the coating film and heated at 120°C.
After baking for 30 minutes, it was isolated by the mercury amalgam method and used.

Barrier Coat When applying an intermediate coat (or top coat) on the paint surface, it is preferable to bake the barrier coat in advance, but it is also possible to apply the intermediate coat (or top coat) paint wet-on-wet without baking. The baking temperature of the barrier coat is 8.
0-160°C, especially 80-130°C are suitable.

Intermediate paint 2 As a paint to be applied to the barrier coated surface described above, any known intermediate paint with excellent adhesion, smoothness, sharpness, overbake resistance, weatherability, etc. can be used. A specific example is a thermosetting intermediate coating whose main component is a vehicle. These alkyd resins and polyester resins have a hydroxyl value of 60 to 140 and an acid value of 5.
~200, L It is preferable to use unsaturated oil or unsaturated fatty acid as the modified oil, and suitable amino resins include alkyl (1 to 5 carbon atoms) etherified melamine resin, urea resin, benzoguanamine resin, etc. . The blending ratio of these is 65 to 85% of alkyd resin and/or oil-free polyester resin based on solid content weight.
, especially 70-80%, amine resin 35-15%, especially 3
The content is preferably 0 to 20%. Furthermore, S can be reduced by replacing at least a portion of the amino resin with a polyisocyanate compound or a blown polyisocyanate compound.

The form of the intermediate coating is most preferably an organic solution type, but
In the present invention, the hardness (lead ν hardness) of the intermediate coating film is 3B or more (20°C ) is preferably within the range. Furthermore, one extender pigment, one color pigment, and other paint additives can be blended into the intermediate coating paint, if necessary.

In the present invention, the intermediate coating can be applied to the barrier coat surface in the same manner as the barrier coating, and the coating thickness is preferably in the range of 10 to 50 coats even for the cured coating. The curing temperature of the film varies depending on the vehicle components, and when curing by heating, it is 80-170℃, especially 1
It is preferable to heat at a temperature of 20 to 150°C.

Top coat: A paint that is applied to the barrier coated surface or intermediate coated surface, and imparts cosmetic properties to the coated object. Specifically, finished appearance (sharpness, smoothness, gloss, etc.), weatherability (glossy retention, color retention, chalking resistance, etc.), chemical resistance, water resistance, humidity, curing. Known paints that form coating films with excellent properties and the like can be used, such as paints whose main vehicle components are amino-acrylic resins, amino-alkyd resins, amino-polyester resins, etc. . The form of these paints is not particularly limited, and organic solution type, non-aqueous dispersion type, aqueous (dispersion) liquid type, powder type, high solid type, etc. can be used.

Drying and curing of the coating film is carried out by drying at room temperature, heating drying, irradiation with active energy rays, etc. In the present invention,
The coating film formed by these top coats has a lead KF1 hardness of 2B.
It is desirable that the temperature is within the range of ~9H (20°C).

The top coating paints that can be used in the present invention are classified into enamel paints that contain metallic pigments and/or coloring pigments in paints that use the above-mentioned vehicle main component, and clear paints that contain no or little of these pigments. . Coat and bake using these top coats,
Topcoat finishing can be done by methods such as 2 coats 1 bake, 2 coats 2 bakes, 3 coats 1 bake, 3 coats 2 bakes, and 3 coats 3 beta.

The performance of the composite coating film formed by applying two coats of cationic electrodeposition paint to the object to be coated as described above - barrier coating - (intermediate coating) - top coating is determined by the finished appearance (e.g. smoothness, gloss, etc.). It has excellent properties such as sharpness (image clarity, etc.), water resistance, weather resistance, etc., and in particular, chipping resistance, corrosion resistance of steel edges, physical properties, etc. have been significantly improved.

In particular, since the first and second electrodeposition coatings are performed wet-on-wet as described above, the second electrodeposition coating is deposited on the surface of the first electrodeposition coating. A coating film is formed in a multi-layer state with the first electrodeposited layer and the second electrodeposited layer. That is, the first electrodeposited coating containing a highly oil-absorbing pigment covers the edges, and the second electrodeposition coating takes care of the smoothness of the coated surface and the uniformity of the coating. As a result, the multi-layer electrodeposited coating has excellent corrosion resistance at the edges and has an excellent coating surface with no pinhole defects. Furthermore, since a barrier coat is applied to the surface of the electrodeposited film and then an intermediate coat or top coat is applied, the chipping resistance and physical performance of the composite film are significantly improved.

According to the method of the present invention, the corrosion resistance of the edges of the coated material, which was a serious defect of conventional cationic electrodeposition coatings, is significantly improved.
Moreover, it has excellent coating surface smoothness, chipping resistance and good physical properties, making it the most effective coating system for automobile bodies.

The present invention will be specifically explained below with reference to Examples and Comparative Examples. In principle, 0 parts and % mean parts by weight and % by weight.

■ Sample (1) Object to be coated: Bonderite #3004 bent 90' from the center (manufactured by Nippon Barker Rising Co., Ltd.)
SPC mild steel plate (size 3) chemically treated with zinc phosphate
00X90XO, 8ts).

(2) Cationic electrodeposition paint CI) (r-A) Carbon black (12) [40] 3 Graphite [40] 5 Purified clay [43] 15 Thyroid 2
44 (Question 3) [300] 26 Resin: Pigment (solid content weight ratio) = 100:49 Total oil absorption 8,765 (Yo1) Kansai Paint Company Nireclone No. 9000
A corresponding water-soluble epoxy polyamino resin, which is obtained by making an epoxy polyamino resin with a resin base number of 80 solubilized with acetic acid at a neutralization rate of 10.55 (contains a curing agent).

(Thursday 2) Manufactured by Asahi Carbon Co., Ltd., product name “Carbon ASMJ (
Eye) Water-containing amorphous silicon dioxide pigment manufactured by Fuji Davison Co., Ltd. The value in parentheses indicates the oil absorption amount of the pigment. (Similarly below) (I-B) Carbon black (Yo2) 3 Refined clay [43] 10 Thyroid 244 (3rd) 10 Resin: Pigment = lOO: 23 (solid content weight ratio) Total oil amount:
3,550 (t-C) Carbon black (ri) 2 Thyroid 244 (book 3) 15 Resin: Pigment = 100:17 (solid content weight ratio) General oil amount:
4, 580 (Clothing 4) Kansai paint repair using water-soluble epoxy polyamide resin “Nileclone No. 9000J (product name)
Equivalent product A cationic electrodeposition paint made by water-solubilizing an epoxy polyamino resin with a base value of 80 using formic acid with a neutralizing light of 10.55 (contains a curing agent).

(ID) Titanium oxide [22] 20 talc
[43] 5 Purified Clay [
43] 1° Thyroid 244 (
Attack 3) lO Resin: Pigment = 100:45 General oil amount: 4,085 ・ (Attack 5) Kansai Paint using water-soluble epoxy polyamino resin Part name "Nileclone 9400J equivalent product,
An epoxy-based poamino resin with a resin base value of 80 is water-solubilized with hydroxyacetic acid at a neutralization equivalent of 0.6 (contains curing agent).

(I-E) Water-soluble thermosetting epoxy polyamino resin (Ail) 100
(g) Carbon black (zero 2) 2 Titanium white [22] 8 Thyroid 244 (ne 3) 2 General oil amount = 856 (3) Cationic electrodeposition paint (rl) (II-A) Titanium oxide white [22] 10 Refined clay [43] '7 carbon black (gong) l General oil amount: 561 Minimum electrodeposition current density: 0, 25 mA/c + s2 (zero 8
) An epoxy polyamino resin having a resin base value of 80 is water-dispersed with acetic acid at a neutralization equivalent of 0.24, and the degree of emulsion is 90% by weight (contains a curing agent).

(IT-B) Titanium oxide [22] 10 Refined clay [43] 7 Carbon black 30 Total amount of oil: 641 Minimum electrodeposition current density: 0, 20 mA/cm” Epoxy resin containing acrylic resin Kansai Paint replenishment cationic electrodeposition paint using Nireclone #9600J
A corresponding water-soluble acrylic-modified epoxy resin with a resin base value of 45 was water-dispersed with acetic acid at a neutralization equivalent of 0.2, and the degree of emulsion was 92% by weight (contains curing agent).

(II-C) Titanium oxide [22] 20 carbon black [40] 1 Total oil absorption = 480 Electrodeposition current density: 0, 29 iA/ci2 (yo8) An epoxy polyamine resin with a resin base number of 80 was neutralized with hydroxyacetic acid. It was water-dispersed with a total equivalent weight of 0.15, and the degree of emulsion was 95% by weight (contains curing agent).

(TI-D) The epoxy resin of (II-B) above is neutralized with acetic acid and water-dispersed at 5M0-5, and the degree of emulsion is 7.
It was produced in the same manner as (rI-B) except that 5% by weight was used. Deposition current density is 0.91IIA/Cff1
It was 2.

(4) Barrier coat (A) Near-ropyrene-ethylene copolymer (mole ratio, 6
0:40) An organic liquid of a resin graft-polymerized with 11 parts of maleic acid per too many parts by weight (tensile strength elongation at static glass transition temperature of -43°C and 1-20'C: 410%).

(B): Propylene-ethylene copolymer (mole ratio 60:
40) Organic liquid of a composition containing 15 parts by weight of chlorinated polyolefin (chlorination rate 30%) per 100 parts by weight (static glass transition temperature -48°C, tensile strength elongation at -20°C 650) %).

(5) Intermediate paint = 7 Mirak N-2 Sealer (Kansai Paint auxiliary, amino polyester resin intermediate paint) (6) Top coat (A) Near Mirak White (manufactured by Kansai Paint Co., Ltd., amino alkyd resin top coat) , 1 coat 1 bake white paint, pencil hardness H) II Examples and Comparative Examples The above electrodeposition paints (I), (■), barrier coat, intermediate coat paint and top coat paint are shown in Table 1. Painted during the process.

(1) Conditions for the first Kyoryu deposition Coating: Electrodeposition paint (I) was adjusted to 20% solid content with deionized water: A voltage: 150-250V Current application time = 2 minutes Bath temperature: 28℃ Membrane FX: Cationic electrodeposition coating was performed under the conditions of 20 JL (as a dry coating film).

Next, the coated surface was sprayed with deionized water, washed with water, dried at room temperature for 10 minutes, and then the first and second coatings were applied.

(2) 2nd zero electrodeposition coating conditions Electrodeposition paint (TI) was adjusted to a solid content of 20% with deionized water, voltage: 250 to 350V, current application time = 2 minutes, bath temperature: 28℃, film thickness. : Cationic electrodeposition coating was performed under the conditions of 20 to 25 pots (as a dry coating film).

The painted surface is then sprayed with deionized water and washed, and then
The re-electrodeposition coating was cured by baking at 180° C. for 30 minutes.

(3) Barrier coat coating Apply coating on the electrodeposited surface using an air spray machine and heat at 120°C for 30 minutes.
Baked for 0 minutes. The film thickness is 6 cm based on the dry coating.

(4) Both the middle and top coats are spray-painted using an electrostatic coating machine, and the film thickness is 2
Each of the 5 coats and 35 top coats (all based on cured coats) was cured by baking at 140°C for 30 minutes.

Performance test results The test results are also listed in Table 1.

The test method is as follows.

(1) Thread rust resistance ASTM-D2803-69T Thread rust test: 9! Make diagonal X-shaped cuts on the specimen using a 6-edged safety razor according to the standard, and place it in a salt spray tester for 36 hours. Thoroughly wash with deionized water without salt spray, and before the specimen dries, place it in a constant temperature and humidity chamber and maintain the temperature at 50 ± 2°C and humidity at 85 ± 2% RH, and continue the test for 840 hours.

Intermediate checks were made at 240 hours, 480 hours and 720 hours during the test to determine whether yarn rust was occurring.

■=No occurrence Δ: Slight occurrence of thread rust with a length of 3 mm or less ×: A lot of thread rust occurred (2) Edge corrosion resistance The test plates obtained in each of the above painting processes were tested according to JIS Z2371J.
The test was conducted in accordance with the water spray test, and the test continued for a maximum of 840 hours. Intermediate checks were made at 240 hours and 480 hours during the test to determine whether black rust had formed on the bent portions.

0: No abnormality Δ: Slight rust occurrence ×: Significant rust occurs (3) - Crotch corrosion resistance According to JIS Z 2371 salt spray test.

Check for black rust and blistering on the paint film on general parts that do not have cuts or scratches. It lasted up to 2,000 hours.

An intermediate check was performed for 1,000 hours to determine the presence or absence of black rust and blisters.

O: No abnormality Δ: Slight rust (4) #Chipping property: (1) Test equipment: Q-G-R Gravelometer (product of Q Panel Company) (2) Stone to be sprayed: Approximately diameter 15-201/ ■ Crushed stone (3) Capacity of stone to be sprayed: Approximately 500 m1 (4) Air pressure for spraying approximately 4 kg/cm2 (5) Temperature during test:
The test piece was mounted on a test piece holder at about 20°C, and crushed stone grains of about 500 aZ were sprayed onto the test piece using air pressure of about 4 kg/cm2, and the coated surface condition and salt water spray resistance were evaluated.

The condition of the painted surface was visually observed and evaluated using the following criteria. Salt water spray resistance was determined by testing the test piece according to JIS Z2371.
After conducting the salt spray test for 0 hours, adhesive cellophane tape was attached to the painted surface.

It was rapidly peeled off, and the presence or absence of rust from the impact area, peeling of the paint film, and corrosion status were observed.

Δ: Slight unevenness ■ Coated surface condition 0: Only a few scratches due to impact were observed on a portion of the topcoat, and no peeling of the electrodeposited coating was observed.

Δ: Many scratches due to impact were observed on the top coat and intermediate coat, and peeling of the electrodeposition film was also observed here and there.

×: Most of the top coat and intermediate coat peeled off, and the electrodeposited coating on the impact area including the impact area and its surrounding area peeled off.

■ Corrosion resistance ■Almost no secondary rust, corrosion, or peeling of the paint film is observed.

0: Slight peeling of the top coat or intermediate coat is observed.

Δ: Slightly more pot, corrosion, and peeling of the paint film are observed.

×: Significant rust, corrosion, and paint peeling occurred.

(5) Painted surface condition Visual judgment O: Good

Claims (1)

[Claims] Consisting of a resin binder (A) and at least one pigment (B), at least 5% by weight of the pigment (B) has an oil absorption of 1
00 or more, and the total oil absorption amount of the pigment (B) is 1,000 to 10,0 per 100 g of the resin binder (A).
Perform the first cationic electrodeposition coating on the object to be coated using the cationic electrodeposition paint (I) that is formulated to be within the range of 0.00, and then apply the resin binder (C) and The main component is pigment (D), and the minimum electrodeposition current density is 0.7 m.
An emulsion-type cationic electrodeposition paint (II) having A/cm^2 or less and an emulsion degree of 80% by weight or more, and in which the total oil absorption of the pigment (D) is smaller than that in the cationic electrodeposition paint (I). After performing the second cationic electrodeposition coating and then heating and curing both of the above-mentioned layered electrodeposition coatings, a coating film having a static glass transition temperature of 0 to -75°C is formed on the electrodeposition coating surface. A method for forming a paint film, which comprises applying a barrier coat, and further applying an intermediate coat and/or top coat as necessary.