JP2997562B2 - Cationic electrodeposition paint and coating film forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cationic electrodeposition coating composition capable of forming a cationic electrodeposition coating film having excellent rust prevention and adhesion to metals, and a method of forming the coating film.

[0002]

2. Description of the Related Art Conventionally, cationic electrodeposition paints have excellent coating efficiency and form a uniform coating film with good throwing power on materials such as complex metal products or parts. Widespread. However, conventional cationic electrodeposition paints, when using a material that has been subjected to a sufficient surface treatment such as zinc phosphate, can form a coating film with good adhesion and rust prevention to a substrate, Cathodic electrodeposition coating with excellent adhesion to the substrate and excellent rust prevention for those that are not sufficiently surface-treated, are not evenly surface-treated, or are not surface-treated. It was difficult to form a film.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a paint and a paint film which can provide a paint film having excellent performance such as adhesion and rust prevention even on a metal substrate which has not been subjected to surface treatment. The purpose is to develop a forming method.

[0004]

[Means for Solving the Problems] The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have found that the conventional cationic electrodeposition paints have A method of electrodepositing a metal-containing paint and an acidic aqueous liquid containing the metal, which is carried out earlier than the electrodeposition of the paint, followed by electrodeposition coating of a conventional cationic electrodeposition paint, recoating and heating. Thus, the present invention can provide a coating film having excellent adhesion to a metal substrate and excellent rust resistance, and completed the present invention.

That is, the present invention relates to a cationic electrodeposition coating composition comprising:
At the time of cationic electrodeposition coating, the electrodeposition is performed earlier than the electrodeposition of the cationic electrodeposition coating, and at least one or more metals selected from water-soluble metals, metal compounds and salts thereof at a pH of less than 7.0. Metals and metal compounds which dissolve in water at a pH of less than 7.0 as a first step in a cationic electrodeposition coating containing metals (hereinafter, may be abbreviated as "Invention 1") and a coating object as a first step. Electrodeposition of an acidic aqueous liquid containing at least one metal selected from salts to deposit the metals, followed by application and application of a cationic electrodeposition coating as a second step, followed by heating Method for forming coating film of paint (hereinafter, may be abbreviated as "invention 2").
About.

First, Invention 1 will be described below. The cationic electrodeposition paint used in the present invention 1 is a blocked isocyanate-curable cationic electrodeposition paint containing a cationic resin and a blocked polyisocyanate compound as a curable resin component, a resin containing a hydroxyl group and a cationic group, and an alicyclic skeleton ( And / or) an epoxy hydroxyl group-curable cationic electrodeposition coating composition containing, as a curable resin component, an epoxy resin having an average of two or more epoxy group-containing functional groups in which an epoxy group is bonded to a bridged cyclic skeleton. It can be suitably used.

[0007] The curable resin component used in the above-mentioned blocked isocyanate-curable electrodeposition paint will be described below.

The cationic resin is a cationic resin that can be cured with isocyanate, and any of conventionally known resins such as epoxy resin, acrylic resin, polybutadiene, and alkyd resin can be used. From the side, it is an amine-added epoxy resin.

As the amine-added epoxy resin, a conventionally known adduct of, for example, an adduct of a polyepoxide compound (I) with a primary mono- and polyamine, a secondary mono- and polyamine, or a mixed primary and secondary polyamine (for example, US (II) Japanese Patent No. 3,984,299); (II) a polyepoxide compound and a ketiminated 2-amino group having a primary amino group;
Adducts with primary mono- and polyamines (see, for example, U.S. Pat. No. 4,017,438); (III) obtained by etherification of a polyepoxide compound with a ketiminated hydroxy compound having a primary amino group. Reactants (for example, see JP-A-59-43013) can be mentioned.

The amine-added epoxy resin may be of a type having a blocked isocyanate group in the resin molecule and self-crosslinking without the need for a crosslinking agent,
In addition, the resin may not be a blocked isocyanate group, and may be an externally crosslinked type containing a blocked isocyanate compound as a crosslinking agent in the resin composition.

The polyepoxide compound used for producing the above amine-added epoxy resin is a compound having two or more epoxy groups in one molecule.
0, preferably 400 to 4,000, more preferably 8
Those having a number average molecular weight in the range of 00 to 2,000 are suitable, and those obtained by reacting a polyphenol compound with epichlorohydrin are particularly preferable.

The polyphenol compound which can be used for forming the polyepoxide compound includes, for example, bis (4
-Hydroxyphenyl) -2,2-propane, 4,4-
Dihydroxybenzophenone, bis (4-hydroxyphenyl) -1,1-ethane, bis- (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-tert-butyl-phenyl) -2,2-propane ,
Bis (2-hydroxynaphthyl) methane, 1,5-dihydroxynaphthalene, bis (2,4-dihydroxyphenyl) methane, tetra (4-hydroxyphenyl)-
Examples thereof include 1,1,2,2-ethane, 4,4-dihydroxydiphenylsulfone, phenol novolak, and cresol novolak.

The polyepoxide compound may be partially reacted with a polyol, a polyether polyol, a polyester polyol, a polyamidoamine, a polycarboxylic acid, a polyisocyanate compound, or the like. Further, ε-caprolactone, an acrylic monomer, etc. May be obtained by graft polymerization.

The blocked isocyanate compound used to introduce a blocked isocyanate group into a resin molecule or used as an external crosslinking agent is a stoichiometric amount of a polyisocyanate compound and an isocyanate blocking agent (eg, an alcohol compound, an oxime compound, Phenolic compounds). As the polyisocyanate compound, for example, tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, bis (isocyanate methyl)
Aromatic, cycloaliphatic, and aliphatic polyisocyanate compounds such as cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, and isophorone diisocyanate, and excess amounts of these polyisocyanate compounds include ethylene glycol, propylene glycol, and trimethylolpropane. And isocyanate-terminated compounds obtained by reacting a low-molecular-weight active hydrogen-containing compound such as hexanetriol and castor oil.

Further, as the acrylic resin,
For example, aminoethyl (meth) acrylate, N, N-
An aminoalkyl ester of (meth) acrylic acid such as dimethylaminoethyl (meth) acrylate is used as an essential component, and methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, propyl (meth) acrylate, 2-ethylhexyl C _1-12 alkyl esters of (meth) acrylic acid such as (meth) acrylate; (meth) acrylates such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate
C _1-4 hydroxyalkyl esters of acrylic acid; glycidyl (meth) acrylate; (meth) acrylic acid; styrene and its derivatives (eg, α-methylstyrene);
Α, β- such as (meth) acrylonitrile and butadiene
Those obtained by (co) polymerization according to a conventional method using an ethylenically unsaturated monomer as necessary can be mentioned.

In the curable resin composition used in the present invention, it is preferable to use an alkyltin ester compound of an aromatic carboxylic acid as a dissociation catalyst. The compound is of a liquid type that can be uniformly mixed in the cationic resin component or in the mixing varnish during water-solubilization and does not cause abnormalities in the stability of the coating and the state of the coated surface.

As such an alkyltin ester compound of an aromatic carboxylic acid, any alkyltin aromatic carboxylic acid ester can be used without any particular limitation. The alkyltin alkyl group preferably has 10 or less carbon atoms. As the aromatic carboxylic acid, benzoic acid and substituted benzoic acid are preferred. Representative examples of the alkyltin ester compound of an aromatic carboxylic acid include dioctyltin benzoateoxy, dibutyltin benzoateoxy, dioctyltin dibezoate, dibutyltin dibenzoate, and the like.

The amount of the liquid tin catalyst to be used can be selected according to the performance required for the electrodeposition coating composition. Generally, the amount of the liquid tin catalyst is based on 100 parts by weight of the resin solid content in the electrodeposition coating composition. It is in the range of 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight.

The curable resin component used in the epoxy hydroxyl group-curable cationic electrodeposition paint is disclosed in JP-A-2-25587.
The same resin composition for a cationic electrodeposition coating as described in JP-A No. 4 can be suitably used.

The one described in the publication is a resin (A) containing a hydroxyl group and a cationic group and an epoxy group-containing functional group in which an epoxy group is bonded to an alicyclic skeleton and / or a bridged alicyclic skeleton. And an epoxy resin (B) having an average of 2 or more per molecule as a main resin component. The outline of the publication is described below.

The resin (A) containing a hydroxyl group and a cationic group contains a sufficient number of cations containing a hydroxyl group capable of reacting with the epoxy group of the component (B) and forming a stable aqueous dispersion. Any resin having a functional group is included. The following are examples of the resin (A). (I) a reaction product obtained by reacting a polyepoxy resin with a cationizing agent; (ii) a polycondensate of a polycarboxylic acid and a polyamine (see U.S. Pat. No. 2,450,940). (Iii) a polyisocyanate or a polyadduct of a polyol and a mono- or polyamine protonated with an acid; (iv) a copolymer of a hydroxyl- and amino-containing acrylic or vinyl-based monomer with an acid (Japanese Patent Publication No. 45-12395, Japanese Patent Publication No. 45-12396)
(V) a product obtained by protonating an adduct of a polycarboxylic acid resin and an alkyleneimine with an acid (US Pat. No. 3,403,
No. 088); and the like.

The epoxy resin (B) is a curing agent for forming a crosslinked and cured coating film mainly by an etherification reaction or the like with the base resin (A) as described above. It has two or more, preferably three or more functional groups on average per molecule.

That is, the epoxy group-containing functional group in the curing resin (B) comprises an alicyclic skeleton and / or a bridged alicyclic skeleton and an epoxy group.
It contains a 10 to 10-membered, preferably 5 to 6-membered saturated carbocyclic ring or a condensed ring obtained by condensing two or more such rings, and the bridged alicyclic skeleton has the above-mentioned cyclic or polycyclic ring. A linear or branched C _1-6 (preferably C _1-4 ) alkylene group between two constituting carbon atoms [eg, -CH _2- , -CH
_{2 CH 2 -, - CH (} CH 3) -, - CH 2 (CH 3)
_{CH 2 -, - C (CH} 3) 2 -, - CH (C 2 H 5) C
H ₂ — etc.) (endmethylene, endethylene, etc.).

On the other hand, an epoxy group

Embedded image Is that one of the carbon atoms in the epoxy group is directly bonded to a ring carbon atom in the alicyclic skeleton or the bridged alicyclic skeleton, or two carbon atoms of the epoxy group are It is one having two adjacent carbon atoms constituting a ring in the formula skeleton or bridged alicyclic skeleton in common.

An epoxy resin having two or more such epoxy group-containing functional groups in one molecule [curing resin (B)]
Are disclosed, for example, in JP-B-56-8016 and JP-A-57-8016.
No. 47365, JP-A-60-166675,
JP-A-63-221121, JP-A-63-234
No. 028, etc., and those known per se can be used.

The metal used in the present invention 1 is a metal which dissolves in water at a pH of less than 7.0 at which the electrodeposition is performed earlier than the electrodeposition of the cationic electrodeposition coating at the time of cationic electrodeposition coating.
Metal compounds and salts thereof. Further, the salt may be in any form such as a single salt, a double salt and a chain salt.

As the metals, those which improve the curability of the electrodeposition coating film or the adhesion to metal materials are preferably used. Such metals include copper, nickel, zinc,
Metals such as lead, cobalt, chromium, aluminum, manganese, zirconium, tin, iron, lead-tin, copper-tin and lead monoxide, lead oxide, zinc oxide, chromic anhydride, cuprous oxide, and copper oxide Metal oxides such as copper, stannous oxide, ferrous oxide, and nickel oxide; and ferrous hydroxide, ferric hydroxide, cuprous hydroxide, cupric hydroxide, and nickel hydroxide;
Metal hydroxides such as chromium hydroxide and metal salts such as zinc ammonium chloride, aluminum potassium sulfate, cobalt ammonium sulfate, potassium stannate, ferrous ammonium sulfate, nickel ammonium sulfate and basic nickel carbonate are included.

The metals can be added in an amount of about 0.1 to 10 parts by weight, preferably about 0.5 to 5 parts by weight, based on 100 parts by weight of the resin for cationic electrodeposition coating. If the amount is out of the above range, it is difficult to obtain a coating film having excellent rust prevention, adhesion and finish.

In order to incorporate metals into the cationic electrodeposition paint, for example, a metal powder is directly mixed into the cationic electrodeposition paint, or a solution in which the metals are dissolved in an acid is added into the cationic electrodeposition paint. It can be implemented by doing. Examples of the acid preferably include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, sulfonic acid, and carbonic acid, and organic acids such as formic acid, acetic acid, and sulfamic acid.

In the present invention 1, it is important that the rate of electrodeposition of the metal compounded in the cationic electrodeposition paint is faster than the electrodeposition rate of the cationic electrodeposition paint. Is equal to or slower than the electrodeposition rate of the cationic electrodeposition paint, metals are not deposited on the interface between the surface of the object to be coated and the cationic electrodeposition paint deposition coating film, and a coating film having excellent anticorrosion properties and adhesion is obtained. Can not do. Also, the metals have a pH
Those which are soluble in water with a water content of less than 7.0 are selected. However, when those which do not satisfy the above conditions are used, paint stability (such as sedimentation) is deteriorated, and metals which are dense on the surface of the object to be coated are used. There is a drawback that the precipitation of is not performed.

The paint of the present invention 1 includes a color pigment, an extender pigment,
Anticorrosion pigments, polymer fine particles (for example, JP-A-2-47173)
JP, JP-A-2-47107, Japanese Patent Application No. 1-19
No. 7929), and other additives for paints and the like can be added as required.

The method of forming a cationic electrodeposition coating film using the coating material of the present invention 1 may be performed, for example, by coating the coating material with a concentration (solid content of 5 to 4).
0 wt%, preferably 10 to 25 wt%) pH 5.0
8 Preferably, a bath paint in the range of 5.5 to 7 is prepared. Then, using the bath paint, a voltage is applied between the two electrodes using the object to be coated as a cathode and the carbon plate as an anode, and a cation is applied to the surface of the object to be coated. It can be carried out by forming an electrodeposited coating film, subsequently lifting the coated product from the bath, washing with water and heating. The type of the object to be coated is not particularly limited, but a metal (for example, a steel plate, an iron plate, or the like) material that is particularly treated to significantly improve rust resistance by using the paint of the present invention is preferable. The voltage applied between the two electrodes is about 5 to 30 V, preferably about 10 to 20 V (about 30 seconds or more, preferably about 10 to 20 V) in order to preferentially deposit metals in the cationic electrodeposition paint on the surface of the workpiece. (At least 60 seconds), followed by a voltage at which the cationic resin precipitates, generally about 50-500 V, preferably about 100-300 V (about 1-5 minutes, preferably about 2-4 minutes).
Minutes). Washing can be performed with tap water, deionized water, ultrafiltrate, RO permeate, or the like. Heating after washing with water is usually about 70 to 250 ° C., preferably about 1 to about 250 ° C.
About 20 to 180 ° C. for about 10 to 40 minutes, preferably about 20 to 180 ° C.
~ 30 minutes. The thickness of the film after heating is not particularly limited, but about 5 to 200 μm is considered to be sufficient.

Next, invention 2 will be described below. In the second aspect of the present invention, it is preferable to use a treated metal material in the same manner as in the first aspect of the present invention, as an object to be electrodeposited with the acidic aqueous liquid as the first step.

The acidic aqueous liquid used in the first stage is prepared by dissolving metals in an acid and water (if necessary, a water-soluble organic solvent), and has a pH of less than 7.0, preferably a pH of 5 to 7. Acidic aqueous liquids can be used. As the metals and acids, those similar to those described in Invention 1 can be mentioned.

The content of metals in the acidic aqueous liquid is not particularly limited, but is generally in the range of about 0.05 to 10% by weight.

As a method for electrodepositing an acidic aqueous liquid on the object to be coated, for example, using the acidic aqueous liquid as a bath liquid,
It can be carried out by applying a voltage between both electrodes using the object to be coated as a cathode and the carbon plate as an anode. The applied voltage can be appropriately set according to the required amount of deposited metals. In addition, the amount of metals deposited on the surface of the object to be coated can be appropriately selected according to the required performance, but it is generally considered that it is sufficient if the amount can be detected by an X-ray microanalyzer.

Next, the object to be coated on which the metals obtained by the method of the first step are deposited is subjected to electrodeposition coating in a cationic electrodeposition coating bath using the object as a second step. It is. As the electrodeposition paint, the same electrodeposition paint containing no metals can be used. The electrodeposition coating conditions are the same as the conventional conditions, for example, bath concentration (solid content 5 to 40% by weight), bath pH
5.0-8.0, voltage about 50-500V, conduction time about 1
５5 minutes. In addition, the first stage and the second stage
It is desirable to wash with water between the steps.

The coated product obtained by the second stage method is preferably heated after washing with water. Heating is usually about 70
~ 250 ° C, preferably about 120 ~ 180 ° C for about 10 ~
It can be performed for 40 minutes, preferably for about 20 to 30 minutes. The thickness of the film after heating is not particularly limited, but may be about 5
It is considered that about 200 μm is sufficient.

[0039]

The coating film formed by the paint and coating method of the present invention exhibits excellent adhesion to metal substrates and excellent rust prevention. It is not clear why the excellent effects of the adhesion and rust prevention are exhibited, but the metals deposited on the interface between the metal base and the cationic electrodeposition coating film are adsorbed (or bonded) to the metal base and the metal surface It is presumed that the rust-preventing property of the cation-electrodeposited film itself was improved and the cation-electrodeposited film acted as a curing agent or a curing catalyst to improve the adhesion of the cation-electrodeposited film to a metal substrate and the rust-preventive property.

[0040]

Embodiments will be described below with reference to embodiments.

Production Example of Cationic Electrodeposition Paint 1900 g of a bisphenol A type epoxy resin having an epoxy equivalent of 950 (trade name “Epicoat 1004”, manufactured by Shell Chemical Co., Ltd.) was dissolved in 993 g of butyl cellosolve, and 210 g of diethanolamine was heated at 80 to 100 ° C. After the dropwise addition, the mixture was kept at 100 ° C. for 2 hours to obtain a hydroxyl group-containing cationic resin solution having a solid content of 68% by weight, a primary hydroxyl group equivalent of 528 and an amine value of 53. EHPE3150 [Epoxy equivalent: 175 to 195, manufactured by Daicel Chemical Industries, Ltd.] 3
2.6 g and 8.2 g of propylene glycol monomethyl ether were dissolved by heating at 100 ° C., and the solid content was 80% by weight.
40.8 g of an epoxy resin solution having an epoxy equivalent of 190 was obtained. The number average molecular weight of the resin was about 1,500. 7 g of the above hydroxyl group-containing cationic resin solution, 3 g of ostix lead, 19 g of titanium oxide, 5 g of purified clay, 1 g of carbon black, 0.25 g of acetic acid, and 37.7 g of deionized water were dispersed in a pebble mill to obtain a pigment having a solid content of 43% by weight. A paste was obtained. The above hydroxyl group-containing cationic resin solution 10
3 g, 37 g of an epoxy resin solution and a neutralized mixture with acetic acid were stirred with a dissolver while stirring 358 of deionized water.
g was gradually added to obtain a cationic electrodeposition paint having a solid content of 20% by weight.

Example 1 Lead monoxide (3PbO: H ₂ O) 100 g of crystal water was mixed with formic acid 2
An acidic aqueous solution (pH 5.6) dissolved in 0 g and 3000 g of deionized water was obtained. Next, 300 g of the acidic aqueous liquid was gradually added while stirring 3200 g of the cationic electrodeposition paint having a solid content of 20% by a dissolver to obtain a cationic electrodeposition paint of Example 1.

COMPARATIVE EXAMPLE In Example 1, the solid content was 20% without mixing the acidic aqueous liquid.
% By weight of the cationic electrodeposition coating was used as a comparative example.

Table 1 shows the results of Examples and Comparative Examples.

Preparation of Test Plate Coating Condition A: The paints of Examples and Comparative Examples were placed in an electrodeposition tank provided with an anode plate, and then the objects to be coated (cathode, untreated steel plate) were immersed in the paint. After electrodeposition coating was performed under the electrodeposition conditions shown in Table 1, washing with water and heating (180 ° C. for 30 minutes) were performed. Coating condition B: The acidic aqueous liquid of Example 1 (solid content: 3% by weight) was put in an electrodeposition tank provided with an anode plate, and then the object to be coated (cathode, untreated steel plate) was immersed in the liquid. After performing the first electrodeposition coating under the conditions described in -1 and washing with water, a cationic electrodeposition paint having a solid content of 20% by weight and containing no acidic aqueous liquid was placed in an electrodeposition tank provided with a separate anode plate. A second electrodeposition coating was carried out in the bath paint under the conditions shown in Table 1, washed with water and heated (180 ° C. for 30 minutes).

The test results are shown in Table 1. In the examples, the cured coating thickness of the metal-free cationic electrodeposition paint was about 30 to 40 μm.

[0047]

[Table 1] * 1 Corrosion resistance: 4% in 50% sodium chloride aqueous solution at 50 ° C
The test plate was immersed for 80 hours. After immersion, leave the test plate at room temperature to dry, then press the cellophane tape firmly against the surface of the test plate (the anode plate at the time of electrodeposition coating), then rapidly separate the cellophane tape from the test plate surface, and the coating remains on the test plate The area was evaluated according to the following criteria. ◎: 95% or more, ：: 94 to 9
0%, Δ: 89 to 70%, ×: 69% or less

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-279773 (JP, A) JP-A-63-268776 (JP, A) JP-A-60-28468 (JP, A) JP-A-59-1988 142267 (JP, A) JP-A-63-101466 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 5/44 C09D 7/12 C25D 13/10

Claims (2)

(57) [Claims] 1. A metal or metal compound which dissolves in water at a pH of less than 7.0, in which the electrodeposition is carried out earlier than the electrodeposition of the cationic electrodeposition paint in the cationic electrodeposition paint. And at least one metal selected from salts thereof. 2. The coating material has a pH of 7.0 as a first step.
An acidic aqueous liquid containing at least one or more metals selected from metals, metal compounds and salts thereof which are soluble in water at a concentration less than or equal to one another is electrodeposited and the metals are deposited. A method for forming a coating film of a cationic electrodeposition paint, which comprises applying a paint, applying the paint again, and then heating.