JP2005232397A - Cationic electrodeposition coating and method for forming coated film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cationic electrodeposition coating capable of forming a coating film excellent in chipping resistance, corrosion-preventing property and finishing property. <P>SOLUTION: This cationic electrodeposition coating is provided by containing (A) 1-40 pts. wt. water dispersion of a urethane resin having 2,000-12,000 number-average molecular weight and obtained by reacting (a) a polyisocyanate, (b) a polyol and (c) a diol having a tertiary amino group in its molecule, in its solid portion, based on 100 pts. wt. total of the solid portions of a base material resin and curing agent, and preferably, ≥50 wt. % of the polyol (b) is a polyester polyol and/or polyether polyol. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cationic electrodeposition coating material capable of forming a coating film excellent in chipping resistance, corrosion resistance, and finish, and a coating film forming method using the cationic electrodeposition coating material.

In recent years, in the automotive industry field, there has been an increasing demand for durability improvement in corrosive environments (for example, rock salt spraying on roads in cold regions). Instead, a galvanized steel sheet having excellent rust prevention properties is used.
On the other hand, there is a problem that the coating film applied to the outer plate of the vehicle body causes a so-called “chipping” in which rock salt particles, pebbles and the like which are lifted during running collide with the coating film surface and the coating film peels off.

Especially in low-temperature environments such as in cold regions, the coating film becomes hard and loses elasticity, so the collision can hardly be alleviated, and impact is directly applied to the steel sheet, between the steel sheet and the chemical conversion coating on the surface, There is an urgent need to examine chipping countermeasures in a low-temperature environment because peeling easily occurs between galvanized layers.
As a countermeasure against this, for example, in Japanese Patent Application Laid-Open No. 62-65765, a chipping sealer for forming a coating film having a low static glass transition temperature is applied to an object after electrodeposition coating, and then a normal intermediate coating or top coating is applied. A painting method for painting is disclosed [Patent Document 1].

The coating film thickness of this chipping sealer is preferably in the range of 3 to 10 μm. Below this, the effect of chipping resistance cannot be expected so much, and beyond this, the finish quality after top coating tends to decrease.
However, it is difficult to control the film thickness of such a thin film with a spray coating method that is usually used. In addition, introducing a step of applying a chipping sealer into the coating process is a retrograde process from the viewpoint of saving processes, and is not economically preferable.

  On the other hand, a urethane elastomer and a curing agent having a molecular weight of 1,000 to 10,000 having a blocked isocyanate group in a cationic water-dispersible resin as a film imparting flexibility to improve chipping resistance [Patent Document 2] describes a cationic electrodeposition paint obtained by blending the above. However, this paint has a drawback that the compatibility between the water-dispersible resin and the urethane elastomer is poor, and therefore the chipping resistance and rust resistance of the coating film are still insufficient.

  Japanese Patent Application Laid-Open No. 63-89578 [Patent Document 3] discloses that a coating film is provided with flexibility, impact resistance, and the like, and includes a cationic property containing an amine-epoxy resin adduct and a urethane resin adduct. Electrodeposition coating compositions are known. However, even if what is specifically disclosed as a urethane resin adduct to be blended in the coating composition is simply blended in the cationic electrodeposition coating, it is insufficient for improving the chipping resistance.

  In addition, a high molecular weight polyurethane having a number average molecular weight of at least 15,000, which is compatible with the electrodeposition resin, is added to the coating film for improving chipping resistance and rust prevention. There is an electrodeposition coating composition comprising [Patent Document 4]. However, since the polyurethane has a high molecular weight, there is a problem that water dispersion stability, bath paint stability when blended in a cationic electrodeposition paint, coating surface smoothness and the like are lowered.

In addition, an electrodeposition coating composition comprising a particle A containing a resin a having a solubility parameter of δa, a resin b having a solubility parameter of δb, and a particle B containing a curing agent, wherein (δb−δa)
Is a film obtained by forming a film only from the particles A, with a dynamic glass transition temperature of the particles A being −110 to 10 ° C., a dynamic glass transition temperature of the particles B being 60 to 150 ° C. There is an invention aimed at improving the chipping resistance with an elongation percentage of 200% or more [Patent Document 5].

Patent Document 5 obtains a coating film excellent in corrosion resistance and chipping resistance by separating particles A and B in an electrodeposition coating film, but contains two types of particles having no compatibility. When the resin a has a low molecular weight, it is necessary to contain a curing agent.
JP-A-62-65765 JP 55-52359 A JP 63-89578 A Japanese Patent Laid-Open No. 7-150079 JP 2002-129105 A

  The problems to be solved are obtained by a cationic electrodeposition coating material capable of forming a coating film excellent in chipping resistance, corrosion resistance and coating film smoothness, a coating film forming method for coating the cationic electrodeposition coating material, and the method. It is to provide a painted article.

As a result of intensive studies to solve the above problems, it has been found that it can be solved by a cationic electrodeposition paint containing a specific urethane resin aqueous dispersion (A), and the present invention has been completed.
That is, the present invention
1. Number average molecular weight obtained by reacting polyisocyanate (a), polyol (b) and diol (c) having a tertiary amino group in the molecule with respect to 100 parts by weight of the solid content of the base resin and the curing agent. A cationic electrodeposition coating containing 1 to 40 parts by weight of a solid dispersion of an aqueous dispersion (A) of urethane resin having a molecular weight of 2,000 to 12,000,
2. The cationic electrodeposition coating according to 1, wherein 50% by weight or more of the polyol (b) is a polyester polyol and / or a polyether polyol,

3. The cationic electrodeposition coating composition according to item 1 or 2, wherein the urethane resin has a hydroxyl value of 25 to 60 mgKOH / g,
4). The cationic electrodeposition coating material according to any one of items 1 to 3, wherein the amine value of the urethane resin is 20 to 60 mgKOH / g,
5). The cationic electrodeposition coating material according to any one of items 1 to 4, wherein the urethane resin has an average particle size of 0.01 to 0.3 µm,
6). A method for forming a coating film, which is obtained by applying the cationic electrodeposition coating composition according to any one of items 1 to 5 to an object to be coated,
A coated article obtained by the method according to 7.6,
About.

The coated article obtained by applying the cationic electrodeposition coating composition of the present invention is excellent in chipping resistance, corrosion resistance and finish. The reason why the above-mentioned coating film characteristics can be obtained by containing the urethane resin water dispersion (A) is that the urethane resin water dispersion (A) is a low molecular resin dispersion having a cationic group and a hydroxyl group. Therefore, 1. 1. Easy transfer to coating during electrodeposition coating. 2. Good heat flow during baking and excellent finish. For example, it can be uniformly dispersed in the electrodeposition coating film, and the hydroxyl group of the urethane resin aqueous dispersion (A) can crosslink with the curing agent in the electrodeposition coating material to form a tougher coating film.

  From these facts, an effect can be seen in chipping resistance with a small addition amount without impairing the corrosion resistance and finish.

The present invention is a cationic electrodeposition coating composition containing 1 to 40 parts by weight of a specific urethane resin aqueous dispersion (A) as a solid content with respect to 100 parts by weight of the total solid content of a base resin and a curing agent. Details will be described below.
Urethane resin water dispersion (A):
The urethane resin dispersion (A) used in the present invention has a number average molecular weight of 2,000 obtained by reacting a polyisocyanate (a), a polyol (b), and a diol (c) having a tertiary amino group. An aqueous dispersion in which ~ 12,000 polyurethane resin is dispersed in water.

The polyisocyanate (a) that can be used for this is a compound having two or more isocyanate groups in one molecule, for example, aromatic isocyanate (tolylene diisocyanate (TDI), 4,4′- Diphenylmethane diisocyanate (MDI),
Naphthalene diisocyanate, etc.), aliphatic isocyanate (hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexamethylene diisocyanate, etc.), alicyclic isocyanate (1,4-cyclohexane diisocyanate, isophorone diisocyanate (IPDI), 4,4 '-Dicyclohexylmethane diisocyanate (hydrogenated MDI)), aliphatic isocyanate having an aromatic ring (xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI)), urethanization of the above diisocyanates, carbodiimide, uretdione, burette, isocyania Nurate modified products can be used. Among these polyisocyanates, preferred are hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4′-diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), 4,4′-dicyclohexylmethane diisocyanate ( Hydrogenated MDI).

As the polyol (b), one having two or more hydroxyl groups in the molecule and having a number average molecular weight of 300 to 5,000, preferably 400 to 4,000 can be suitably used. Further, the urethane resin dispersion used in the present invention has a polyol content of 50% by weight or more, more preferably 7%.
A urethane resin aqueous dispersion using 0 to 100% by weight of polyether polyol and / or polyester polyol is particularly preferable.

Specific examples of polyether polyols include those obtained by ring-opening (co) polymerization of alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.), cyclic ethers (tetrahydrofuran, etc.), trimethylolpropane, glycerin, di- Examples include polyhydric alcohols such as glycerin, pentaerythritol, and sorbitol, which are addition-polymerized with alkylene oxide, and bisphenol A alkylene oxide adducts. Any compound having an ether bond as a unit and having two or more hydroxyl groups in one molecule can be suitably used.

Specific examples of polyester polyols include aliphatic dicarboxylic acids (adipic acid, sebacic acid, azelaic acid, dimer acid, etc.) and / or aromatic dicarboxylic acids (isophthalic acid, terephthalic acid, orthophthalic acid, etc.) and low molecular weight diols (ethylene Glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3methyl 1,5-pentanediol, cyclohexanedimethanol, etc.) , And polycaprolactone diol obtained by ring-opening polycondensation of ε-caprolactone monomer can be exemplified, but it has an ester bond as a repeating unit in the molecule without being particular about these, and 2 in one molecule. Any compound having at least one hydroxyl group is preferred Can be used.

One or more of these polyols can be used in a proportion of 50% by weight or more of the polyol (b). A conjugated diene-based polyol having butadiene, isoprene and the like as a repeating unit at a ratio of 50% by weight or less, a carbonate-based polyol obtained by polycondensation of a low-molecular diol and a dialkyl carbonate, a hydroxyl group-containing polyolefin, and the like can be used. .

  Specific examples of the diol (c) having a tertiary amino group include a compound having a compound having an active hydrogen group capable of reacting with one or more tertiary amino groups and two or more isocyanate groups in one molecule. In the polyurethane resin aqueous dispersion (A), a component used for introducing a cationic hydrophilic group for imparting cationic electrodeposition is exemplified. Specific examples thereof include N-methyldiethanolamine, N-butyl. Diethanolamine, N-oleyldiethanolamine, N-cyclohexyldiethanolamine, N-methyldiisopropanolamine, N-cyclohexyldiisopropanolamine, N, N-dihydroxyethylaniline, N, N-dihydroxyethyltoluidine, N, N-dihydroxypropylnaphthylamine, And ethyl alkanolamines Oxyalkylenated alkanolamines such as obtained by adding a small amount of alkylene oxide such as oxide or propylene oxide. Of these, preferred are N-methyldiethanolamine, N-butyldiethanolamine and N-oleyldiethanolamine.

  The amount of the diol (c) having a tertiary amino group is 20 to 60 mgKOH / g, preferably 22 to 36 mgKOH / g in the urethane resin aqueous dispersion (A) as an amine value based on the tertiary amino group. is there. If it is less than 20 mgKOH / g, it may be difficult to obtain a stable aqueous dispersion for use in cationic electrodeposition coatings. If it exceeds 60 mgKOH / g, the hydrophilicity of the polymer will increase, and the water resistance of the coating film may decrease.

The urethane resin aqueous dispersion (A) can be obtained by reacting the above-mentioned polyisocyanate (a), polyol (b) and diol (c) components. If necessary, the low molecular weight polyol (with a molecular weight of less than 300 below) ( d) A polymerization terminator (e) can be used in combination.
Examples of low molecular weight polyols (d) include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3 methyl 1,5-pentanediol. And bifunctional low molecular weight polyols such as cyclohexanedimethanol, and polyfunctional low molecular weight polyols such as trimethylolpropane and pentaerythritol.

The polymerization terminator (e) can be used to adjust the molecular weight of the urethane resin aqueous dispersion (A) within the above range, and is a compound having at least one active hydrogen capable of reacting with an isocyanate group in one molecule. It is.
Specifically, for example, low molecular monoalcohol (methanol, ethanol, isopropanol, butanol, cyclohexanol, etc.); monovalent alkyl monoamine (mono- and di-ethylamine, mono- and dibutylamine, etc.); primary or Examples include alkanol monoamines having a secondary amino group (such as mono- and di-ethanolamine).

The polymerization terminator (e) is an isocyanate terminal having a molecular weight more suitable for the equivalent ratio of the polyisocyanate (a) and the alcohol component (that is, polyol (b), diol (c) and low molecular weight polyol (d)). An amount sufficient to block the isocyanate groups of the prepolymer can be added.
The preferred number average molecular weight (Note 1) of the urethane resin used in the present invention is 2,000 to 12,000, preferably 4,000, from the viewpoints of chipping resistance, smoothness of the coating surface, and the like.
It is suitable that it is ˜12,000, more preferably 5,000 to 10,000.
(Note 1) Number average molecular weight: Measured according to JISK0124-83, using TSK GEL4000H _XL + G3000H _XL + G2500H _XL + G2000H _XL (manufactured by Toyo Soda Co., Ltd.) as the separation column at a flow rate of 1.0 ml / min, eluent In addition, GPC tetrahydrofuran was used to calculate from the chromatogram obtained with the RI refractometer and the calibration curve of polystyrene.

The urethane resin aqueous dispersion (A) used in the present invention has a hydroxyl group, and the urethane resin molecule preferably has a hydroxyl value of 25 to 60 mgKOH / g, preferably 28 to 45 mgKOH / g as a hydroxyl value. . Hydroxyl groups present in the molecules are involved in the crosslinking reaction of the coating film, and as a result, the urethane resin and the base resin are present in the coating film in a bonded form via a curing agent.
Therefore, although the number average molecular weight of the urethane resin is as low as 2,000 to 12,000, a cationic electrodeposition coating film excellent in chipping resistance and corrosion resistance can be formed.

In addition, as a method of introducing a hydroxyl group into the molecule of the urethane resin, (1). When polymerizing the urethane resin, the raw material is used in a quantity relationship of [isocyanate group equivalent] <[polyol hydroxyl equivalent]. A method in which the terminal is a hydroxyl group.
(2). As the polymerization terminator (e), an alkanol monoamine having a primary or secondary amino group (mono- and di-ethanolamine, etc.) is used to block the isocyanate group of the isocyanate-terminated prepolymer and simultaneously introduce a hydroxyl group. Method.

(3) A method of introducing a hydroxyl group into a side chain inside the molecule by reacting the isocyanate-terminated prepolymer with a diamine (f) having a hydroxyl group (for example, hydroxyethylaminopropylamine). Etc., but is not limited by the introduction method.
Urethane resin aqueous dispersion (A ) Is not particularly limited, and examples thereof include the methods exemplified below.

  (1) In the presence of an organic solvent that does not contain an active hydrogen group in the molecule (for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dioxane, N-methylpyrrolidone, toluene, xylene, and a mixture of two or more thereof). Or in the absence of a solvent, the polyisocyanate (a), the polyol (b), a diol (c) having a tertiary amino group, and optionally a low molecular weight polyol (d), a polymerization terminator (e) and / Or a method of urethanizing a diamine (f) having a hydroxyl group by a one-shot method.

  (2). The polyisocyanate (a), the polyol (b) and the diol (c) having a tertiary amino group in the presence or absence of an organic solvent containing no active hydrogen group in the molecule; A method of completing a reaction by adding a polymerization terminator (d) and / or a diamine (f) having a hydroxyl group to a urethane prepolymer having a terminal NCO group by reacting with a low molecular weight polyol (d) as required. . The polyurethane-forming reaction is usually performed at a temperature of 20 ° C. to 150 ° C., preferably 50 ° C. to 120 ° C. (in the case of reaction with polyamine, it is usually 80 ° C. or less, preferably 0 ° C. to 70 ° C. Done).

In order to promote the above reaction, an amine-based or tin-based catalyst used in a normal urethanization reaction may be used. After neutralizing the tertiary amino group introduced into the urethane resin using a monovalent organic acid (formic acid, acetic acid, etc.) or inorganic acid (hydrochloric acid, sulfuric acid, etc.) as necessary. A water dispersion of urethane resin having an average particle size (Note 2) of 0.01 to 0.3 μm, preferably 0.04 to 0.28 μm, and more preferably 0.05 to 0.25 μm by dispersing in water. (A) can be obtained. When dispersed in water, a nonionic surfactant or a cationic surfactant can be used in combination as necessary.
(Note 2) Average particle size: The average particle size was measured using a light scattering method (Microtrac UPA particle size analyzer, Model No. 9340; manufactured by Nikkiso Co., Ltd.).

Next, the base resin and the curing agent of the cationic electrodeposition paint obtained by blending the urethane resin aqueous dispersion (A) will be described.
Base resin: As the base resin, for example, (1) reaction product of epoxy resin and cationizing agent; (2) polycondensate of polycarboxylic acid and polyamine (see US Pat. No. 2,450,940) is acid. (3) polyisocyanate compound and polyaddition product of polyol and mono- or polyamine protonated with acid; (4) hydroxyl group- and amino group-containing acrylic or vinyl monomer. Copolymers protonated with acid (see Japanese Patent Publication Nos. 45-12395 and 45-12396); (5) Protonation of an adduct of polycarboxylic acid resin and alkyleneimine with acid (See U.S. Pat. No. 3,403,088).

Among these, a base resin obtained by reacting a cationizing agent with an epoxy resin by reaction of a polyphenol compound and epichlorohydrin, which is included in the above (1), is preferable because it has excellent corrosion resistance.
As said epoxy resin, it has 2 or more of epoxy groups in 1 molecule, and a number average molecular weight is 200 or more, Preferably it is 400-4,000, Epoxy equivalent is 190-2,000, Suitably 400- One thousand known per se can be used. Examples of the polyphenol compound used for preparing the epoxy resin include 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-hydroxybutyl) methane, 1,5 -Dihydroxynaphthalene, bis (2,4-dihydroxyphenyl) methane, tetra (4-hydroxyphenyl) -1,1,2,2-ethane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy Examples thereof include diphenylsulfone, phenol novolak, cresol novolak and the like. Examples of such epoxy resins include those modified with polyhydric alcohols, polyether polyols, polyester polyols, polyamidoamines, polycarboxylic acids, polyisocyanate compounds, and those graft-polymerized with acrylic monomers. Is also included.

As the cationizing agent, for example, amine compounds such as primary amines, secondary amines, tertiary amines, polyamines, and the like can be used. A cationic group-containing resin can be obtained by introducing a cationic group such as an amino group, a tertiary amino group, or a quaternary ammonium base.
The introduction of a hydroxyl group into a cationic group-containing resin includes the reaction with an alkanolamine as a cationizing agent, the reaction with a ring-opened product of caprolactone and polyol which may be introduced into the epoxy resin, Secondary secondary hydroxyl groups that are inherently included can be mentioned. Of these, primary hydroxyl groups introduced by reaction with alkanolamine as a cationizing agent are preferred because of excellent crosslinking reactivity with block polyisocyanate compounds. Examples of such alkanolamines include monoethanolamine, n-propanolamine, isopropanolamine, diethanolamine, din-propanolamine, diisopropanolamine, N-methylethanolamine, N-ethylethanolamine, Examples thereof include triethanolamine, N, N-dimethylethanolamine, N-methyldiethanolamine, N, N-diethylethanolamine and N-ethyldiethanolamine.

Curing agent: The blocked polyisocyanate used as a curing agent is an addition reaction product of approximately a stoichiometric amount of polyisocyanate compound and blocking agent.
Examples of the polyisocyanate compound used here include aromatics and fats such as tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, bis (isocyanate methyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, and isophorone diisocyanate. Terminal isocyanates obtained by reacting aliphatic or alicyclic polyisocyanate compounds, and low-molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, trimethylolpropane, hexanetriol, castor oil and the like in excess of these isocyanate compounds Examples thereof include compounds.

  On the other hand, the blocking agent is added and blocked to the isocyanate group of the polyisocyanate compound, and the blocked polyisocyanate compound produced by the addition is stable at room temperature, but the baking temperature of the coating film (usually about 100 to When heated to about 200 ° C., it is desirable that the blocking agent dissociates and free isocyanate groups can be regenerated.

  Examples of the blocking agent that satisfies such requirements include lactam compounds such as ε-caprolactam and γ-butyrolactam; oxime compounds such as methyl ethyl ketoxime and cyclohexanone oxime; phenols such as phenol, para-t-butylphenol, and cresol. Compounds; aliphatic alcohols such as n-butanol and 2-ethylhexanol; aromatic alkyl alcohols such as phenyl carbinol and methyl phenyl carbinol; ether alcohol compounds such as ethylene glycol monobutyl ether.

The blending ratio of the base resin and the curing agent is generally 55 to 90% by weight, preferably 60 to 85% by weight, and more preferably 60 to 80% by weight based on the total solid weight of these two components. , And the curing agent can generally be in the range of 10 to 45 wt%, preferably 15 to 40 wt%, more preferably 20 to 40 wt%.
The cationic electrodeposition paint containing the base resin, the curing agent, and the urethane resin aqueous dispersion (A) is, for example, sufficiently mixed with the base resin and the curing agent, and then neutralized with a water-soluble organic carboxylic acid. It can be prepared by adding the urethane resin aqueous dispersion (A) to a water-soluble or water-dispersed medium.

As the organic carboxylic acid for neutralization, acetic acid, formic acid or a mixture thereof is suitable, and by using these acids, finish properties, throwing power, low temperature curability, paint stability of the coating composition to be formed Improves.
The cationic electrodeposition paint of the present invention can optionally contain a tin compound as a curing catalyst. Examples of the tin compound include organic tin compounds such as dibutyltin oxide and dioctyltin oxide; dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dioctyltin benzoateoxy, dibutyltin benzoateoxy, dioctyltin dibenzoate, dibutyl Examples thereof include aliphatic or aromatic carboxylates of dialkyl tin such as tin dibenzoate. Among these, dialkyl tin aromatic carboxylates are preferred from the viewpoint of low-temperature curability.

The content of these tin compounds in the coating composition of the present invention is not strictly defined and can be varied over a wide range according to the performance required for the cationic electrodeposition coating. It is suitable that the tin content per 100 parts by weight of the resin solid content is in the range of 0.01 to 8 parts by weight, preferably 0.05 to 5.0 parts by weight.
The cationic electrodeposition paint can contain zinc phosphate, zinc molybdate, zinc oxide, zinc phosphomolybdate, aluminum tripolyphosphate, bismuth oxide, bismuth hydroxide, and the like as a rust inhibitor. Furthermore, paint additives such as a color pigment, an extender pigment, an organic solvent, a pigment dispersant, and a surface conditioner can be blended as necessary.

  The cationic electrodeposition coating can be applied to a desired substrate surface. The electrodeposition coating is generally diluted with deionized water or the like so that the solid content concentration is about 5.0 to about 40% by weight, preferably 15 to 25% by weight, and further the pH is 5.5 to 9. The electrodeposition bath comprising the coating composition of the present invention adjusted within the range can be usually adjusted to a bath temperature of about 15 to about 35 ° C. and under a load voltage of 100 to 400V.

  The film thickness of the electrodeposition coating film formed using the coating composition of the present invention is not particularly limited, but is generally 10 to 40 μm, particularly 15 to 35 μm based on the cured coating film. Within the range is preferable. The baking temperature of the coating film is generally about 120 to about 200 ° C., preferably about 140 to about 180 ° C. on the surface of the coating, and the baking time is about 5 to 60 minutes, preferably It can be about 10 to 30 minutes.

  The cationic electrodeposition paint of the present invention forms a cured coating film excellent in chipping resistance, corrosion resistance, and finish. For example, in addition to automobile bodies and automobile parts, construction and architectural fields, etc. It is also useful as an undercoat paint.

  Hereinafter, the present invention will be described in more detail with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited thereto. In each example, “part” represents part by weight, and “%” represents% by weight.

Production Example 1
Urethane resin water dispersion no. Production of 1 Polyisocyanate (a): 249.4 parts of isophorone diisocyanate, polyol (b): 513.8 parts of polypropylene glycol (number average molecular weight 2,000), and 171.3 parts of polybutylene adipate (number average molecular weight 2, 000),
A diol having a tertiary amino group (c): 60.2 parts of methyldiethanolamine and a low molecular weight polyol (d): 5.3 parts of trimethylolpropane are dissolved in 400 parts of methyl isobutyl ketone to carry out a urethanization reaction. A urethane prepolymer containing 1.8% of isocyanate groups per resin solid content was obtained.

To the obtained prepolymer, 45.0 parts of diethanolamine was added to block the isocyanate group, and a hydroxyl group was introduced into the molecule. After cooling, neutralized with 30.6 parts of acetic acid, dispersed in water, and distilled off the methyl isobutyl ketone under reduced pressure to obtain an average particle size of 0.08 μm, a hydroxyl value of 46 mg KOH / g, an amine value of 28 mg KOH / g, a number Urethane resin water dispersion No. 5 having an average molecular weight of 5,900 and a solid content of 35% by weight. 1 was obtained.

Production Example 2
Urethane resin water dispersion no. Production of 2 Polyisocyanate (a): 200.0 parts of tolylene diisocyanate,
Polyol (b): 285.7 parts of polybutadiene polyol (poly BD R-15HT manufactured by Idemitsu Petrochemical, number average molecular weight 1,200), and polyester of 3-methyl-1,5-pentanediol and adipic acid (number average) Molecular weight 1,000) 428.6 parts,
A diol having a tertiary amino group (c): 71.4 parts of methyldiethanolamine and a low molecular weight polyol (d): 14.3 parts of trimethylolpropane are dissolved in 800 parts of methyl isobutyl ketone to perform a urethanization reaction. A urethane polymer having a terminal hydroxyl group was obtained. After neutralizing with 29.0 parts of acetic acid, it was dispersed in water, and methyl isobutyl ketone was distilled off under reduced pressure to obtain an average particle size of 0.10 μm, a hydroxyl value of 37 mgKOH / g, and an amine value of 34 mgK.
Urethane resin aqueous dispersion No. OH / g, number average molecular weight 4,050, solid content 30% by weight. 2 was obtained.

Production Example 3
Urethane resin water dispersion no. 3. Preparation of 3 To 500 parts of methyl isobutyl ketone, polyisocyanate (a): 382.6 parts of isophorone diisocyanate, polyol (b): 510.2 parts of polytetramethylene glycol (number average molecular weight 1,000), low molecular weight polyol (d ): 20.4 parts of trimethylolpropane, diol having a tertiary amino group (c): 63.8 parts of methyldiethanolamine were dissolved and urethanized, cooled, and diamine having a hydroxyl group (f): 23.0 parts of hydroxyaminopropylamine was added to obtain a urethane prepolymer containing 2.0% of isocyanate groups per resin solid content.

To the obtained prepolymer, 25.0 parts of diethanolamine and 30.8 parts of dibutylamine were added to block the isocyanate group and introduce a hydroxyl group into the molecule. After cooling, the mixture was neutralized with 29.2 parts of acetic acid, dispersed in water, and the methyl isobutyl ketone was distilled off under reduced pressure to obtain an average particle size of 0.08 μm, a hydroxyl value of 35 mgKOH / g, an amine value of 30 mgKOH / g, a number Urethane resin aqueous dispersion No. 1 having an average molecular weight of 6,500 and a solid content of 30% by weight. 3 was obtained.

Production Example 4
Urethane resin water dispersion no. 4 (for comparative example)
Sanixdiol PL-2100 (trade name, polyethylene-propylene (block) ether glycol, number average molecular weight 2477, manufactured by Sanyo Chemical Industries, Ltd.) 479.2 parts, neopentyl glycol 39.74 parts, hexamethylene diisocyanate 158.3 And 75 parts of methyl isobutyl ketone were charged into a reaction vessel, and the reaction system was purged with nitrogen gas. Then, the mixture was reacted with stirring at 110 ° C. for 3 hours, and then the reaction product was cooled to 60 ° C. .78 parts and 225 parts of methyl isobutyl ketone were added, and further reacted at 90 ° C. for 4 hours to synthesize a urethane prepolymer solution having a residual NCO group content of 1.30%.

After cooling this urethane prepolymer solution to 40 ° C., 22.9 parts of isophorone diamine, 2.44 parts of monoethanolamine, a mixture of methyl isobutyl ketone and isopropanol were added and reacted for 1 hour to chain extension until there were no remaining NCO groups. After the reaction, a polyurethane resin solution was obtained.
Next, 500 parts of the above polyurethane resin solution was charged into a four-necked glass reaction vessel, 41.3 parts of 10% acetic acid was added and stirred for 30 minutes, and then 465 parts of deionized water was added for about 15 minutes while stirring vigorously. Then, methyl isobutyl ketone and isopropanol are distilled off under reduced pressure to obtain a solid content of about 35%, an average particle size of 0.15 μm, and an amine value of 15.4 mgKOH.
/ G, urethane resin water dispersion No. having a number average molecular weight of about 35,000 and a solid content of 40.0% by weight. 4 was obtained.

Production Example 5
Urethane resin water dispersion no. 5 (for comparative example)
458.0 parts of polytetramethylene ether glycol (number average molecular weight 3,065), 41.42 parts of neopentyl glycol, 175.8 parts of hexamethylene diisocyanate and 75 parts of methyl isobutyl ketone are charged into a reaction vessel, and the reaction system is filled with nitrogen. After gas replacement, the reaction was carried out at 110 ° C. for 3 hours with stirring, then the reaction product was cooled to 60 ° C., 23.76 parts of N-methyldiethanolamine and 225 parts of methyl isobutyl ketone were added, and further at 90 ° C. for 3 hours By reacting, a urethane prepolymer solution having a residual NCO group content of 2.51% was synthesized.

After cooling this urethane prepolymer solution to 40 ° C., a mixture of 61.5 parts of 4,4′-diaminodicyclohexylmethane, 620 parts of methyl isobutyl ketone and 185 parts of isopropanol is added and reacted for 1 hour until there are no remaining NCO groups. After performing the elongation reaction, next, 500 parts of the above polyurethane resin solution was charged into a four-necked glass reaction vessel, and 41.3 parts of 10% acetic acid was added and stirred for 30 minutes, followed by deionization with vigorous stirring. 465 parts of water was added dropwise over about 15 minutes to emulsify, and methyl isobutyl ketone and isopropanol were distilled off under reduced pressure to obtain a solid content of about 35%, an average particle size of 0.15 μm, an amine value of 16.0 mgKOH / g,
A urethane resin aqueous dispersion No. 1 having a number average molecular weight of about 113,000 and a solid content of 40.0%. 5 was obtained.

Production Example 6
Manufacture of base resin Add 390 g of bisphenol A and 0.2 g of dimethylbenzylamine to 1010 g of amino group-containing epoxy resin Epicoat 828EL (manufactured by Yuka Shell Co., Ltd., trade name, epoxy resin), and react at 130 ° C. until an epoxy equivalent of 800 is reached. It was. Next, 160 g of diethanolamine and 65 g of a diethylenetriamine ketiminate were added and reacted at 120 ° C. for 4 hours. Then, 355 g of ethylene glycol monobutyl ether was added to obtain a base resin having an amine value of 67 mgKOH / g and a solid content of 80%.

Production Example 7
Production of Curing Agent In a reaction vessel, 250 parts of diphenylmethane-4,4′-diisocyanate and 25 parts of methyl isobutyl ketone were added and heated to 70 ° C. In this, 15 parts of 2,2-dimethylolbutanoic acid was gradually added, and then 118 parts of ethylene glycol monobutyl ether was added dropwise, reacted at 70 ° C. for 1 hour, cooled to 60 ° C., 188 parts of 4-pentanediol were added. While maintaining this temperature, sampling was performed over time, and it was confirmed by infrared absorption spectrum measurement that there was no absorption of unreacted isocyanate groups, and a curing agent having a solid content of 80% was obtained.

Production Example 8
Production of emulsion 87.5 parts of 80% base resin obtained in Production Example 6 (solid content 70 parts), 80% curing agent obtained in Production Example 7 33.3 parts (solid content 30 parts), 10 15 parts of acetic acid was blended and stirred uniformly, and then 158 parts of deionized water was added dropwise over about 15 minutes with vigorous stirring to obtain an emulsion having a solid content of 34%.

Production Example 9
Manufacture of pigment dispersion paste 5.83 parts of quaternary chlorinated epoxy resin 60% (solid content 3.5), titanium white 10 parts, carbon black 0.3 parts, bismuth hydroxide 2.0 parts, organotin compound 1 11.4 parts of deionized water was added to the part, and stirred sufficiently to obtain a pigment dispersion paste having a solid content of 55.0%.

Example 1
Cationic electrodeposition paint No. Production of 1 Into 294 parts of emulsion obtained in Production Example 8 (100 parts of solid content), 30.5 parts of pigment dispersion paste obtained in Production Example 9 (solid content of 16.8 parts), and solid content obtained in Production Example 1 35% urethane resin water dispersion No. No. 1 was added 28.5 parts (solid content 10 parts) and deionized water 281 parts. 1 was obtained.

Example 2
Cationic electrodeposition paint No. 2 In Example 1, urethane resin aqueous dispersion No. 2 was prepared. 1 is a urethane resin aqueous dispersion No. 1 having a solid content of 30%. 2 Change to 33.3 parts (10 parts solids), adjust with deionized water, 20% solids
Cationic electrodeposition paint No. 2 was obtained.

Example 3
Cationic electrodeposition paint No. 3 In Example 1, urethane resin aqueous dispersion No. 3 was prepared. 1 is a urethane resin aqueous dispersion No. 1 having a solid content of 30%. 3 Change to 33.3 parts (10 parts solids), adjust with deionized water, 20% solids
Cationic electrodeposition paint No. 3 was obtained.

Comparative Example 1
In Example 1, urethane resin water dispersion No. No. 1 is a urethane resin water dispersion No. 1 having a solid content of 40.0% by weight. 4 Change to 25 parts (solid content 10 parts), adjust with deionized water, solid content 2
0% cationic electrodeposition paint No. 4 was obtained.

Comparative Examples 2-4
In the content of Table 1, the cationic electrodeposition paint No. 5-No. 7 was obtained.

(Note 3) Superflex E-4000: manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name, nonionic urethane resin aqueous dispersion, average particle size 0.28 μm, hydroxyl value 0 mgKOH / g, amine value 0 mgKOH / g, number average Molecular weight 100,000 or more, solid content 45% by weight
Coating test: 0.8 × 150 × 70 mm cold-rolled steel plate and galvanized steel plate obtained by chemical conversion treatment with Palbond # 3020 (manufactured by Nihon Parkerizing Co., Ltd., trade name, zinc phosphate treatment agent) are obtained in the above examples and comparative examples. Electrodeposition coating obtained by immersing each cation electrodeposition paint and using this as a cathode for electrodeposition coating was baked at 170 ° C. for 20 minutes using an electrodeposition hot air dryer, and a dry film thickness of 20 μm was tested. I got a plate.

  Table 2 shows the results of the test plate. The test conditions were as follows.

(Note 4) Corrosion protection: An electrodeposited coating plate coated with each cationic electrodeposition coating on a cold-rolled steel sheet is cross-cut with a knife so as to reach the substrate, and this is applied according to JISZ-2371. The salt spray resistance test was conducted for 840 hours, and the following criteria were evaluated by the rust and blister width from the knife scratch.
○: The maximum width of rust and blisters is less than 3 mm from the cut part (one side)
Δ: Maximum width of rust and blisters is less than 3 to 4 mm from cut (one side)
X: The maximum width of rust and blisters is 4 mm or more from the cut part (Note 5) Finishing property: The surface roughness of the electrodeposition coating film of each electrodeposition coating plate coated with each cationic electrodeposition coating on a cold rolled steel sheet Ra value (Cut Off) (product name, surface roughness meter, manufactured by MITSUTOYO)
0.8 mm) was measured.

○: Ra = 0.20 μm or less Δ: Ra = 0.20 to 0.25 μm
×: Ra exceeds 0.30 μm (Note 6) Chipping resistance:
WP-300T (trade name, waterborne intermediate coating) manufactured by Kansai Paint Co., Ltd. is applied to an electrodeposition coating plate obtained by coating each cation electrodeposition coating on a galvanized steel sheet, and baked at 150 ° C. for 30 minutes to form an intermediate coating film. Obtained.

Further, neoamylac 6000 white (trade name, white alkyd-type top coat paint manufactured by Kansai Paint Co., Ltd.) was applied on the coating film to a thickness of 35 μm, and heated at 140 ° C. for 30 minutes to obtain a multilayer coating film.
Next, a test plate was placed on a specimen holder of a stepping stone testing machine JA-400 (chipping test apparatus) manufactured by Suga Test Instruments Co., Ltd., and compressed air of 0.392 MPa (4 kgf / cm ² ) at −20 ° C. Then, 50 g of granite crushed stone of size 7 was sprayed on the coating surface, and the degree of scratches on the coating film was observed and evaluated visually.

◎: Scratch level is quite small and intermediate coating film is slightly exposed ○: Scratch level is small and intermediate coating film is exposed △: Scratch size is small, but base steel sheet X: The size of the scratch is quite large and the base steel plate is also exposed. (Note 7) Paint stability: After stirring the paint at 30 ° C for 1 month, it is filtered through a 500 mesh wire mesh. The amount of residue was evaluated.

○: Filtration residue amount less than 10 mg / L Δ: Filtration residue amount of 10 mg / L or more and less than 20 mg / L
×: Filtration residue amount 20 mg / L or more

The present invention is a cationic electrodeposition coating material that can form a coating film excellent in chipping resistance, corrosion resistance, and finish.

Claims (7)

  Number average molecular weight obtained by reacting polyisocyanate (a), polyol (b) and diol (c) having a tertiary amino group in the molecule with respect to 100 parts by weight of the solid content of the base resin and the curing agent. A cationic electrodeposition paint containing 1 to 40 parts by weight of a solid dispersion of an aqueous dispersion (A) of urethane resin having a weight of 2,000 to 12,000. The cationic electrodeposition paint according to claim 1, wherein 50% by weight or more of the polyol (b) is a polyester polyol and / or a polyether polyol.   The cationic electrodeposition coating composition according to claim 1 or 2, wherein the urethane resin has a hydroxyl value of 25 to 60 mgKOH / g.   The cationic electrodeposition paint according to any one of claims 1 to 3, wherein the urethane resin has an amine value of 20 to 60 mgKOH / g.   The cationic electrodeposition paint according to any one of claims 1 to 4, wherein the urethane resin has an average particle size of 0.01 to 0.3 µm. The coating-film formation method formed by apply | coating the cationic electrodeposition coating material of any one of Claims 1-5 to to-be-coated material. A coated article obtained by the method according to claim 6.