JP7080849B2 - Cationic electrodeposition coating film forming method - Google Patents

Description

The present invention relates to a method for forming a cationic electrodeposition coating film. More specifically, the present invention relates to a method for producing a cured coating film of a composition for cationic electrodeposition coating on a metal substrate.

Cathodic electrodeposition coating is performed by immersing the object to be coated in the cationic electrodeposition coating material as a cathode and applying a voltage. A steel sheet occupies most of the object to be coated with cationic electrodeposition coating, and generally, electrodeposition coating is performed on the surface-treated material.

Electrodeposition coating can be applied to details even if the object to be coated has a complicated shape, and can be applied automatically and continuously, so it has a large and complicated shape such as an automobile body. However, it is widely used as an undercoat coating method for objects to be coated that require high rust resistance. While the surface of the member after undercoating is required to be smooth, since multiple members after painting are often fastened with bolts or the like, slippage does not occur between the members at the time of fastening, and the member may be firmly fixed. It is especially important in terms of workability and quality of the final product.

As a conventional technique for improving the bolt fastening property of a member, for example, a method of providing an abrasive holding layer containing an abrasive between the members (for example, Patent Document 1) is known. However, in this method, the steps of forming the abrasive holding layer on either one of the members to be fastened are increased.

In another method, the coefficient of friction is composed of a water-based urethane resin emulsion and an aqueous liquid containing an olefin / unsaturated carboxylic acid copolymer emulsion or a urethane-modified polyolefin emulsion with respect to a bolt for fastening an electrodeposited member. A method of applying a stabilizer to stabilize the friction coefficient of the bolt surface (for example, Patent Document 2) and a cationic electrodeposition coating composition containing a fluorine-containing polymer improve the slipperiness of the screw surface and tighten it. (For example, Patent Document 3) is known. However, these methods focus on screws such as bolts, and do not suppress slipping as the performance of the coating film itself.

Further, as a conventional technique for defining the friction coefficient of the surface of the electrodeposited coating film, a cationic electrodeposition coating composition containing fluororesin fine particles (for example, Patent Document 4) and an anion electrodeposition composition containing polytetrafluoroethylene particles are used. A thing (for example, Patent Document 5) is known.

However, in the methods of Patent Documents 4 and 5, an intermediate coating film and / or a topcoat coating composed of a base coat coating film, a clear coating film, and the like are applied onto the electrodeposition coating film (undercoat film) formed by the electrodeposition coating. When a film or the like is formed and used for an automobile body or its parts, it is not possible to secure the adhesion between the electrodeposition coating film and the coating film formed on the electrodeposition coating film.

Japanese Unexamined Patent Publication No. 2006-22948 Japanese Unexamined Patent Publication No. 2006-206682 Japanese Unexamined Patent Publication No. 2006-199948 Japanese Unexamined Patent Publication No. 2004-277565 Japanese Unexamined Patent Publication No. 2013-142111

However, an object of the present invention is to provide a method for forming a cured coating film having good smoothness and excellent slip resistance without any defects caused by the prior art.

As a result of diligent research, the present inventors have found that the above problems can be solved by the following cationic electrodeposition coating film forming method.

That is, the above-mentioned subject of the present invention is a method for forming a cationic electrodeposition coating film using a cationic electrodeposition coating composition, wherein the cationic electrodeposition coating composition is used.
(A) Amine-modified epoxy resin,
(B) Blocked isocyanate compound,
(C) Pigments and (d) Surface conditioners,
Contains,
(D) The solubility parameter (SP value) of the surface conditioner is 9.0 or more, and the solubility parameter (SP value) is 9.0 or more.
(D) The content of the surface conditioner with respect to the total mass of the cationic electrodeposition coating composition is in the range of 0.1% by mass to 0.3% by mass.
The solution is solved by a method for forming a cationic electrodeposition coating film, characterized in that the static friction coefficient of the surface of the baking hardened coating film obtained from the cationic electrodeposition coating composition is 0.1 or more.

By the cationic electrodeposition coating film forming method of the present invention, a cured coating film having a surface having excellent smoothness and slip resistance can be produced.

FIG. 1 is an explanatory diagram (cross-sectional view) of an evaluation sample used for a slip resistance evaluation test and a measurement method in Examples and Comparative Examples. FIG. 2 is a front view of the constituent members of the evaluation sample shown in FIG.

The cationic electrodeposition coating composition used in the present invention contains (a) an amine-modified epoxy resin, (b) a blocked isocyanate compound, (c) a pigment, and (d) a surface conditioner.

In the above cationic electrodeposition coating composition, (d) a surface conditioner having a solubility parameter (SP value) of 9.0 or more is used, and (d) a cationic electrodeposition coating composition of the surface conditioner. The content with respect to the total mass of the substance is in the range of 0.1% by mass to 0.3% by mass.

The object to be coated by electrodeposition coating with the cationic electrodeposition coating composition is cured by baking, but the static friction coefficient of the surface of the cured coating film of the present invention obtained from the above cationic electrodeposition coating composition is preferably 0.1 or more. Is 0.12 or more, particularly preferably 0.14.

If the static friction coefficient of the cured coating film of the electrodeposition coating composition exceeds 0.5, the appearance may be poor.

The cured coating film obtained by the present invention having the above structure has not only the corrosion resistance and smoothness required for the undercoat layer, but also the surface of the cured coating film has excellent slip resistance. That is, the cured coating film is not slippery even during assembly work such as fastening with bolts or the like by superimposing the cured coating film on each other or with other members, and the workability is improved, and the final having these coating films. There is no looseness in the product, and the accuracy and quality of the product are improved.

Further, the cured coating film obtained by the present invention has a good appearance because the surface can be obtained smoothly, and even when a top coat layer or the like is laminated on the upper portion to form a multi-coat coating film, the film formation is affected. It is also excellent in adhesion to the upper layer without giving.

Hereinafter, the components of the cationic electrodeposition coating composition used in the present invention will be described.

[Component (a) Amine-modified epoxy resin]
As the substrate resin of the cationic electrodeposition coating composition, (a) an amine-modified epoxy resin is used.

(A) As the epoxy resin used for the amine-modified epoxy resin, all low molecular weight and high molecular weight compounds can be used as long as they have more than one glycidyl group per molecule on average. In particular, polyglycidyl ethers having two or more glycidyl groups are preferred.

The epoxy equivalent of the (a) amine-modified epoxy resin used in the present invention is preferably about 500 to 1000, particularly preferably about 700 to 900. By setting the epoxy equivalent in the above range, the emulsifying property becomes good and a stable emulsion can be obtained.

Examples of the above-mentioned polyglycidyl ether include polyphenol polyglycidyl ether.

The polyphenols used as raw materials include bisphenol A (2,2-bis (4-hydroxyphenyl) propane), bisphenol E (1,1-bis (4-hydroxyphenyl) ethane), and bisphenol F (bis (4-hydroxy)). Bisphenols such as phenyl) methane), 2,2-bis (4-hydroxy-3-t-butylphenyl) propane, and naphthalenes such as 1,5-dihydroxy-3-naphthalene can be used.

Further, as the raw material of (a) the amine-modified epoxy resin, polyglycidyl ether obtained from a cyclic polyol other than the above can also be used. Examples of such cyclic polyols include alicyclic polyols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, and 1,2-bis (hydroxymethyl) cyclohexane, hydrogenated bisphenol A, and the like. Bisphenol F can be mentioned.

The polyglycidyl ether may be obtained by reacting a monophenol compound with a linear polyol polyglycidyl ether such as polyethylene glycol, polypropylene glycol or the like, for example, a polyalkylene glycol having C2-C4 alkylene glycol as a repeating unit. Examples thereof include the obtained polyglycidyl ether, the polyglycidyl ether of a phenolic novolak resin or a similar polyphenol resin, and the polyglycidyl ether obtained by reacting an epoxy compound with a butadiene-acrylonitrile copolymer having a carboxyl terminal group.

(A) In the production of the amine-modified epoxy resin, as the amine to be reacted with the polyglycidyl ether, a primary or secondary monoamine or these polyamines can be used.

Examples of the primary monoamine include C1-C6 alkylamines such as methylamine, ethylamine, propylamine and butylamine, and C1-C6 alkanolamines such as ethanolamine. Examples of the secondary monoamines include dimethylamine, diethylamine and dipropylamine. , DiC1-C6 alkylamines containing methylbutylamines, and diC1-C6 alkanolamines containing diethanolamines; C1-C6 alkyls C1-C6 alkanolamines.

Further, examples of the polyamine include diC1-C6 alkylamino C1-C6 alkylamines such as dimethylaminoethylamine and diethylaminopropylamine.

(A) Specific examples of the amine-modified epoxy resin to be noted include
(I) Adduct of polyglycidyl ether and primary mono or polyamine, secondary mono or polyamine, or 1, 2 mixed mono or polyamine, or (ii) polyglycidyl ether and ketiminated primary amine. Examples include an adduct with a polyamine having a group.

(A) As the amine-modified epoxy resin, either one of the above (i) or (ii) may be used, or both of them may be used.

Of the above, in the present invention, an adduct of a polyglycidyl ether having a bisphenol skeleton or the like and a polyamine having a ketiminated primary amine group is preferably used.

Examples of the polyamine having a ketiminated primary amino group include N-methylaminopropylamine and a reaction product of diethylenetriamine and methyl isobutyl ketone.

Further, the cationic electrodeposition coating composition used in the present invention includes, as long as it is a resin having a functional group that reacts with an isocyanate group, in addition to (a) an amine-modified epoxy resin, an acrylic type, an alkyd type, a polybutadiene type, and the like. Any resin such as polyester can be used in combination, and two or more kinds may be used in combination.

(A) The ratio of the amine-modified epoxy resin used (resin solid content) is preferably 40 to 90% by mass, particularly 50 to 80% by mass, based on the total resin solid content of the cationic electrodeposition coating composition. By blending (a) an amine-modified epoxy resin in this range, a cured coating film having excellent rust resistance can be obtained.

[Component (b) Blocked Isocyanate Compound]
The cationic electrodeposition coating composition contains (b) a blocked isocyanate compound.

It is a blocked isocyanate curing type electrodeposition coating composition, which contains a resin having a cationic charge and a blocked isocyanate, and is electrodeposited using the charge of the resin, and the blocking agent of the blocked isocyanate is dissociated when the coating film is cured. , A urethane-type cationic electrodeposition coating material that cures by reacting with active hydrogen in a coating composition, for example, (a) active hydrogen such as a hydroxyl group in an amine-modified epoxy resin.

The (b) blocked isocyanate compound may be, for example, a self-crosslinking type contained in the molecule of (a) an amine-modified epoxy resin, or an external cross-linking type contained outside the (a) amine-modified epoxy resin.

When producing either a self-crosslinked type or an externally crosslinked type blocked isocyanate compound, the following isocyanates and blocking agents are used.

Examples of the polyisocyanate compound include tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, p-phenylenedi isocyanate, 3,3'-dimethylbiphenyl 4,4'-diisocyanate, 1,5-naphthalenedi isocyanate and the like. Aromatic diisocyanate,
Aliphatic diisocyanates such as tetramethylene diisocyanate, 1,6-hexane diisocyanate, and lysine diisocyanate,
Alicyclic diisocyanates such as 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, norbornane diisocyanate,
Examples thereof include polymer-like isocyanates such as polymethylene polyphenyl polyisocyanate.

The above-mentioned polyisocyanate compound has, for example, ethylene glycol, propylene glycol, tetramethylene glycol, trimethylolpropane, polyethylene glycol, polypropylene glycol, polycaprolactone so as to retain isocyanates (preferably two or more) at the ends of molecules. , Polyethylene polyols and other polyols, carboxylic acids such as adipic acid, phthalic acid, azelaic acid, sebacic acid and maleic acid, or those further reacted with both of the above polyols and carboxylic acids.

(B) As an example of a blocking agent that can be used for producing a blocked polyisocyanate compound,
i) Phenols such as phenol, cresol, xylenol, nitrophenol, chlorophenol, ethylphenol, t-butylphenol, hydroxybenzoic acid, esters of these acids, or 2,5-di-t-butyl-4-hydroxytoluene;
ii) Lactam, eg, ε-caprolactam, δ-valerolactam, γ-butyrolactam, or β-propiolactam;
iii) Active methylene compounds such as diethyl malonate, dimethyl malonate, acetoacetate ethyl ester, acetoacetate methyl ester, or acetylacetone;
iv) Alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, n-amyl alcohol, t-amyl alcohol, lauryl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether. , Ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, methoxymethanol, glycolic acid, glycolic acid ester, lactic acid, lactic acid ester, methylol urea, methylol melamine, diacetone alcohol, ethylene chlorohydrin, Ethylene bromhydrin, 1,3-dichloro-2-propanol, 1,4-cyclohexyldimethanol, or acetocyanhydrin;
v) Mercaptan, such as butyl mercaptan, hexyl mercaptan, t-butyl mercaptan, t-dodecyl mercaptan, 2-merkaprobenzothiazole, thiophenol, methylthiophenol, or ethylthiophenol;
vi) Acid amides such as acetanilide, acetanilidein amide, acrylamide, methacrylic amide, acetate amide, stearic acid amide, or benzamide;
vii) Imide, such as succinimide, phthalimide, or maleimide;
viii) Amines such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, or butylphenylamine;
ix) imidazole, eg imidazole, or 2-ethylimidazole; x) ureas, eg urea, thiourea, ethyleneurea, ethylenethiourea, or 1,3-diphenylurea;
xi) Carbamate, eg N-phenylcarbamide acid phenyl ester, or 2-oxazolidone;
xi) imine, eg ethylene imine;
xiii) Oxime, such as acetone oxime, formaldoxime, acetatoaldoxime, acetone oxime, methyl ethyl ketoxime, diisobutylketoxime, diacetylmonoxim, benzophenoxime, or chlorohexanoxime;
xiv) Salts of sulfur-containing acids, such as sodium bisulfite, or potassium bisulfite;
xv) Hydroxamic acid ester, eg, benzylmethacrylohydroxamate (BMH), or allylmethacrylohydroxamate;
xvi) Substituted pyrazole, imidazole, or triazole;
xvii) 1,2-polyols such as ethylene glycol, propylene glycol, 1,2-butanediol;
xviii) 2-hydroxyesters such as 2-hydroxyethyl acrylates, 2-hydroxyethyl methacrylate;
xix) A mixture of two or more kinds of blocking agents according to any one of the above (i) to (xviii).

In the present invention, a blocking agent that dissociates by heating at 100 to 200 ° C. is preferably used.

It is possible to use a dissociation catalyst for promoting the dissociation of the blocking agent of the blocked polyisocyanate compound. As the dissociation catalyst, organic tin compounds such as dibutyltin dilaurate, dibutyltin oxide and dioctyltin, amines such as N-methylmorpholine, and metal salts such as zinc, cobalt, bismuth and zirconium can be used. The concentration of the catalyst is generally 0.1 to 5% by mass with respect to the total resin solid content of the cationic electrodeposition coating composition.

The externally crosslinked type (b) blocked isocyanate compound is preferably used in a state where all free isocyanate groups are blocked.

Further, when (b) a self-crosslinking type having a blocked isocyanate in the amine-modified epoxy resin is used as the (b) blocked isocyanate, this can be produced by a known method. For example, the blocked isocyanate is introduced into the amine-modified epoxy resin by (a) a method of reacting the free isocyanate in the partially blocked polyisocyanate compound with the active hydrogen in the amine-modified epoxy resin. Will be done.

When only the externally crosslinked type (b) blocked isocyanate compound is used, the usage ratio (resin solid content) is 10 to 50% by mass, particularly 20 to 50% by mass, based on the total resin solid content of the cationic electrodeposition coating composition. It is preferably 40% by mass. It is also possible to appropriately use the externally crosslinked type (b) blocked isocyanate compound and the self-crosslinked type (b) blocked isocyanate compound in combination. By blending (b) the blocked isocyanate compound in this range, a cured coating film having excellent toughness can be obtained.

[(C) Pigment]
The cationic electrodeposition coating composition used in the present invention contains (c) a pigment.

The pigment (c) is not particularly limited as long as it is a pigment usually used in electrodeposition paints, and can be blended by appropriately selecting a pigment in consideration of desired color and surface characteristics. Examples of such pigments include coloring pigments such as titanium oxide, red iron oxide, carbon black, and iron yellow oxide; extender pigments such as clay, talc, mica, and calcium carbonate; zinc phosphate molybdate, aluminum phosphate, and aluminum polyphosphate. Anti-rust pigments and the like can be mentioned.

In the cationic electrodeposition coating composition used in the present invention, a pigment dispersion resin can be used for the purpose of (c) improving the dispersion state of the pigment in the cationic electrodeposition coating composition. The pigment dispersion resin is not limited, and a known pigment dispersion resin used for the same purpose, for example, a resin having a cation charge can be used, but a resin having improved dispersibility of the pigment is preferable, for example. Epoxy quaternary ammonium type, tertiary amine type, and acrylic quaternary ammonium type resins are suitable.

It is also possible to use (a) an amine-modified epoxy resin as the pigment dispersion resin. The (a) amine-modified epoxy resin used alone as the substrate resin and the (a) amine-modified epoxy resin as the pigment dispersion resin may be different types of resins, but for ease of work and compatibility. In consideration, it is also possible to use resins prepared from the same material. In this case, the pigment dispersion resin is used by making the epoxy equivalent of the (a) amine-modified epoxy resin for the pigment dispersion resin smaller than the epoxy equivalent of the (a) amine-modified epoxy resin used alone as the substrate resin. Consideration to improve the dispersibility of the pigment is also effective. When (a) an amine-modified epoxy resin is used as the pigment dispersion resin, the amount used thereof is taken into consideration as a part of the amount of (a) amine-modified epoxy resin used.

(C) The pigment is added in the range of 0.1 to 20% by mass, particularly 1 to 10% by mass, based on the total mass of the cationic electrodeposition coating composition. As a result, the desired rust preventive property is exhibited while maintaining good coating film physical properties such as adhesion to the object to be coated and coating property of the cationic electrodeposition coating composition.

[(D) Surface conditioner]
In the cationic electrodeposition coating composition used in the present invention, (d) a surface conditioner having a solubility parameter (SP value) of 9.0 or more is used as an essential component. (D) The reason why the surface conditioner is indispensable is that by blending it, not only the smoothness is increased as a leveling agent for the coating film, but also the decrease in the static friction coefficient of the coating film is suppressed and the resistance of the coating film is reduced. It is to develop slipperiness.

In the prior art, the surface conditioner blended in the paint tends to be oriented toward the surface of the coating film and improve the smoothness of the surface, but at the same time, the slip resistance of the surface tends to be deteriorated. As the adjusting agent, a compound whose compatibility with the epoxy resin is adjusted and which does not deteriorate the slip resistance is used.

(D) As the surface conditioner, an acrylic type, vinyl ether type, silicon type, butadiene type surface conditioner, or a mixture thereof or the like is used. Of these, an acrylic type, for example, a surface conditioner of a (meth) acrylic acid copolymer is preferably used.

(D) Since the solubility parameter (SP value) of the surface conditioner is 9.0 or more, the compatibility with the epoxy resin is adjusted, and both surface leveling and slip resistance can be achieved. (D) The more preferable range of the solubility parameter (SP value) of the component is 9.2 to 10.5, and the more preferable range is 9.5 to 10.2. (D) Examples of the surface conditioner include Polyflow WS (trade name, manufactured by Kyoeisha Chemical Co., Ltd., SP value: 10.2), Polyflow No. 85 (trade name, manufactured by Kyoeisha Chemical Co., Ltd., SP value: 9.5), Polyflow No. 7 (trade name, manufactured by Kyoeisha Chemical Co., Ltd., SP value: 9.3), Polyflow No. 90 (trade name, manufactured by Kyoeisha Chemical Co., Ltd., SP value: 9.6), Polyflow No. 36 (trade name, manufactured by Kyoeisha Chemical Co., Ltd., SP value: 9.5) and the like can be mentioned.

(D) One type of surface adjusting agent may be used, or two or more types may be used in combination, and the content thereof is 0.1% by mass to 0.3% by mass with respect to the total mass of the cationic electrodeposition coating composition. It is said to be% by mass.

(D) When the content of the surface conditioner is less than 0.1% by mass, the effect on the surface leveling property is insufficient, and when it exceeds 0.3% by mass, the slip resistance may be deteriorated. be. (D) A more preferable range of the content of the surface conditioner is 0.12 to 0.28% by mass in the coating composition, and a more preferable range is 0.15 to 0.25% by mass in the coating composition. be.

[Measurement method of solubility parameter (SP value)]
The solubility parameter (SP value) of the (d) surface conditioner used in the present invention is measured as follows based on the so-called dakuten titration method.

First, 0.5 g of an additive sample is collected in a transparent glass beaker, 24.5 g of tetrahydrofuran is added, and the mixture is completely dissolved. Then, normal hexane is added dropwise with stirring to cause normal hexane when cloudiness begins. The mass w1 (g) is measured.
Next, the distilled water mass w2 (g) is measured in the same manner except that distilled water is used instead of normal hexane. Both w1 and w2 were measured at 20 ° C., the solvent mole numbers n1 and n2 were obtained from the obtained masses w1 and w2 (g), respectively, and the solubility parameter (SP value) D was determined by the following formula (1). calculate.

D = ((Vmix1) ^1/2 x Dmix1 + (Vmix2) ^1/2 x Dmix2) / ((Vmix1) ^1/2 + (Vmix2) ^1/2 ). .. .. .. .. (1)
Vmix1 and Vmix2 in the above formula (1) are represented by the following formulas (2) and (3).

Vmix1 = Vm1 × Vm0 / ((1-f1) × Vm1 + f1 × Vm0). .. .. .. (2)
Vmix2 = Vm2 × Vm0 / ((1-f2) × Vm2 + f2 × Vm0). .. .. .. (3)
Dmix1 (in the case of normal hexane) and Dmix2 (in the case of distilled water) in the above formula (1) are represented by the following formulas (4) and (6).

For normal hexane:
Dmix1 = f1 × d1 + (1-f1) × d0. .. .. .. .. (4)
In the formula (4), f1 is represented by the following formula (5).

f1 = n1 × Vm1 / (n1 × Vm1 + n0 × Vm0). .. .. .. .. .. (5)
For distilled water:
Dmix2 = f2 × d2 + (1-f2) × d0. .. .. .. .. (6)
In the formula (6), f2 is represented by the following formula (7).

f2 = n2 × Vm2 / (n2 × Vm2 + n0 × Vm0). .. .. .. .. .. (7)

The definitions of the symbols used in the above equations (2) to (7) are as follows.

f: Volume fraction at the dakuten (normal hexane f1, distilled water f2)
d: Solvent solubility parameter (SP value)
(Tetrahydrofuran d0, normal hexane d1, distilled water d2)
n: Number of moles of solvent (tetrahydrofuran n0, normal hexane n1, distilled water n2)
Vm: Molar volume of solvent (tetrahydrofuran Vm0, normal hexane Vm1, distilled water Vm2)
Here, the solubility parameters (SP values) of each solvent (d0, d1, d2 in the above formulas (4) and (6)) used the literature values. [Reference: C.I. M. Hansen, K. et al. Skaarup, J. et al. Paint Technology, 38,511 (1967)]

[Measurement method of static friction coefficient]
In the present invention, the static friction coefficient of the cured coating film is measured according to ASTM D1894 (friction test between a plastic film and a sheet) using the equipment described below.

Further, the cationic electrodeposition coating composition used in the present invention comprises an additive for preventing craters, a thermosetting reaction diluent, a pigment dispersant, a photoprotective agent, for example, a UV absorber and a reversible radical trapping agent (HALS). , Antioxidants, organic solvents, wetting agents, emulsifiers, polymerization inhibitors, corrosion inhibitors, easy-flowing aids, desiccants, killing agents and the like can be contained in an effective amount. However, the fluororesin fine particles are not contained because the adhesion between the electrodeposition coating film formed and the coating film formed on the electrodeposition coating film cannot be ensured.

In the production of the cationic electrodeposition coating composition used in the present invention, the pigment is usually pulverized to a desired size using a ball mill, a bead mill, a sand mill, a super mill, a continuous disperser, or the like, and if necessary, described above. It is preferable to first produce a pigment paste by sufficiently wetting and kneading the dispersion together with the pigment dispersion resin and the pigment dispersant.

Further, it is mixed with (a) an amine-modified epoxy resin, (b) a blocked polyisocyanate compound, and necessary additives. When the obtained mixture is hydrated, an amount of water sufficient to form a continuous water phase is blended, and an aqueous solution or an aqueous emulsion is produced using a stirrer, an emulsifying device or the like. An additive-free electrodeposition coating composition can be obtained by adding a pigment or pigment paste prepared in advance to the aqueous solution or aqueous emulsion thus obtained. In addition, (c) a pigment or a pigment paste can be added at the time of mixing (a) an amine-modified epoxy resin and (b) a blocked polyisocyanate compound. In either case, it is preferred that the pigment be uniformly dispersed in the mixture.

Subsequently, (d) a surface conditioner having a solubility parameter (SP value) of 9.0 or more is added to and mixed with the above aqueous solution or aqueous emulsion to obtain a cationic electrodeposition coating composition.

The cationic electrodeposition coating composition used in the present invention generally has a coating solid content of 5 to 35% by mass and a pH of 5.0 to 6.5 by adding an aqueous medium such as water, if necessary. Adjust so as to perform electrodeposition coating. As the coating conditions, for example, it is preferable to perform coating so that the coating temperature is 25 to 35 ° C., the voltage is 40 to 400V, and the film thickness of the cured coating film is in the range of 10 to 40 μm. Further, the baking temperature at the time of curing the coating film is preferably in the range of 100 to 200 ° C.

The cationic electrodeposition coating composition used in the present invention comprises a desired conductive substrate (object to be coated) such as cold-rolled steel, hot-rolled steel, aluminum, magnesium, magnesium alloy, etc., depending on the required quality. The metal base material is subjected to surface treatment, for example, zinc phosphate treatment, iron phosphate treatment, chromate treatment, zircon-based treatment, organic film treatment, etc., as necessary, and then electrodeposition is conventionally used. Used by the painting method.

In the present invention, it is particularly essential that the static friction coefficient of the surface of the electrodeposition coating film / cured coating film after baking is 0.1 or more. If the coefficient of static friction on the surface of the electrodeposited coating film / cured coating film after baking is less than 0.1, slippage will occur when bolting to such a cured coating film, resulting in insufficient slip resistance. You can say that. That is, the above-mentioned coefficient of friction is required in order to firmly fasten bolts with good workability and prevent loosening over a long period of time. A more preferable range of the static friction coefficient of the surface of the electrodeposition coating film / cured coating film after baking is 0.12 to 0.5, and a more preferable range is 0.14 to 0.3.

The cured coating film obtained by the present invention has corrosion resistance (rust resistance) similar to or higher than that of conventional products by being used as an undercoat layer of the above-mentioned metal base material for vehicles such as automobile bodies and parts thereof. Can be given. The cured coating film of the present invention is used as an undercoat layer, and if necessary, an intermediate coating film and / or a topcoat coating film composed of a base coat coating film, a clear coating film, or the like is formed on the coating film. It can also be a multi-coat coating system.

The cationic electrodeposition coating film of the present invention has excellent smoothness after curing, excellent slip resistance, and good adhesion to other coating films provided on the electrodeposition coating film.

Next, the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples. In the following Examples , Reference Examples and Comparative Examples, all the descriptions relating to "parts" and "%" mean "parts by mass" or "% by mass" unless otherwise specified.

[Production example of cationic electrodeposition coating composition]
Production Example 1 Production of Resin for Dispersing Pigment In a reactor equipped with a stirrer, a reflux cooler, an internal thermometer and an inert gas supply pipe, 2598 parts of bisphenol-A-diglycidyl ether having an epoxy equivalent of 188, bisphenol A787 Epoxy resin A having an epoxy equivalent of 856 was produced by reacting 603 parts of dodecylphenol and 206 parts of butyl glycol in the presence of 4 parts of triphenylphosphine at 130 ° C. Next, while cooling, 849 parts of butyl glycol and 1534 parts of polypropylene glycol diglycidyl ether (DER732, trade name, manufactured by Dow Chemical) were added to 3988 parts of the epoxy resin A, and 2- (2-amino) was added at 90 ° C. Ethoxy) 266 parts of ethanol and 212 parts of N, N-dimethylaminopropylamine were added and reacted. After 2 hours, after the viscosity became constant, the mixture was diluted with 1512 parts of butyl glycol, neutralized with 201 parts of glacial acetic acid, and further added with 1228 parts of deionized water to prepare a pigment dispersion resin having a solid content of 60%. ..

Production Example 2 Production of Block Polyisocyanate Compound Polymethylenepolyphenylpolyisocyanate (Luprant, trade name, manufactured by BASF) 10552 in a reactor equipped with a stirrer, a reflux cooler, an internal temperature controller and an inert gas supply pipe. The part was charged under a nitrogen atmosphere. 18 parts of dibutyl tin dilaurate was added to this reactor, and 9448 parts of butyl diglycol was added dropwise little by little while cooling occasionally so that the reaction temperature did not exceed 60 ° C. After completion of the addition, the temperature of the reaction mixture was kept at 60 ° C. for another 60 minutes and dissolved in 7768 parts of methyl isobutyl ketone. Then, 933 parts of trimethylolpropane was added to the product at a predetermined rate so that the temperature did not exceed 100 ° C. After the addition was completed, the reaction was further carried out for 60 minutes, and it was confirmed that no free NCO group was detected. The mixture of the polyisocyanate compound thus obtained was cooled to 65 ° C., and 965 parts of n-butanol and 267 parts of methyl isobutyl ketone (diluent) were added at the same time to obtain a blocked polyisocyanate compound having a solid content of 70%. Got

Production Example 3 Production of ketimine In a reactor equipped with a stirrer, a reflux condenser, an internal thermometer and an inert gas supply tube, 180 parts of diethylenetriamine and 350 parts of methylisobutylketone are mixed and then heated to reflux at 130 to 150 ° C. Was performed to remove the generated water. When the distilling of the produced water stopped at 150 ° C., the mixture was cooled to obtain 467 parts of ketimine.

Production Example 4 Production of Amine-Modified Epoxy Resin A In a reactor equipped with a stirrer, a reflux cooler, an internal thermometer and an inert gas supply pipe, 6150 parts of bisphenol-A-diglycidyl ether having an epoxy equivalent of 188 is bisphenol A1400. It was heated to 125 ° C. under a nitrogen atmosphere with parts, 335 parts of dodecylphenol, 470 parts of p-cresol and 441 parts of xylene, and then cooled for 10 minutes. The mixture was then heated to 130 ° C. and 23 parts of N, N'-dimethylbenzylamine was added. The reaction mixture was maintained at this temperature until the epoxy equivalent reached 880. Additive 90 parts of the additive polyether (K-2000, trade name, manufactured by BYK Chemie) was added, maintained at 100 ° C., and after 30 minutes, 211 parts of butyl alcohol and 1210 parts of isobutanol were added. Immediately after this, a mixture of 467 parts of ketimine and 450 parts of methylethanolamine obtained in Production Example 3 was added, and the temperature of the reactor was adjusted to 100 ° C. Further, after 30 minutes, the temperature of the reaction mixture was raised to 105 ° C., and then 80 parts of N, N'-dimethylaminopropylamine was added. After 75 minutes of adding the amine, 903 parts of a propylene glycol compound (Plastilit 3060, trade name, manufactured by BASF) was added, diluted with 725 parts of propylene glycol phenyl ether and cooled to obtain an amine-modified epoxy resin A having a solid content of 80%. rice field.

Production Example 5 Production of Pigment Paste Using the pigment dispersion resin obtained in Production Example 1, each compounding component is sufficiently mixed in the mass ratio shown in Table 1, and then the particle size of the pigment is evaluated by a grain gauge using a ball mill. A pigment paste having a solid content of 58.1% was obtained by dispersing in JISK5600-2-5) so as to be 10 μm or less. As the grain gauge, a grind meter manufactured by Toyo Seiki Seisakusho Co., Ltd. was used.

Production Example 6 Production of Emulsion A 9949 parts of the amine-modified epoxy resin A obtained in Production Example 4 and 4872 parts of the blocked polyisocyanate compound obtained in Production Example 2 are mixed, and 424 parts of 88% lactic acid is removed with stirring. A mixed solution with 7061 parts of ionized water was added dropwise. Next, 12600 parts of deionized water was added dropwise over 30 minutes to obtain an emulsion having a solid content of 32%.

Production Example 7 Production of Additive-Free Electroplated Paint Composition 471 parts of the emulsion obtained in Production Example 6 was added to a container in which 453 parts of deionized water was previously charged. Subsequently, under stirring, 76 parts of the pigment paste obtained in Production Example 5 was added and mixed to obtain an additive-free electrodeposition coating composition having a solid content of 20%.

[Example 1]
Polyflow WS (trade name, manufactured by Kyoeisha Chemical Co., Ltd.) was added to the additive-free electrodeposition coating composition obtained in Production Example 7 so that the content of the coating composition with respect to the total mass was 0.15% by mass. A cationic electrodeposition coating composition was produced by adding and mixing the mixture.

[Examples 2 to 4 , reference examples, comparative examples 1 to 4]
By the same materials and methods as in Example 1 except that the surface conditioner shown in Table 2 was used at the content shown in the same table, the cation electric currents of Examples 2 to 4 , Reference Examples, and Comparative Examples 1 to 4 were used. A coating composition was produced. The content of the surface conditioner in each Example and Comparative Example indicates the content (% by mass) of the surface conditioner in the total mass of the cationic electrodeposition coating composition.

In the present invention, the total mass means the mass including all volatile components such as water and solvent.

(Measurement and evaluation method of cationic electrodeposition coating film)
By the method described below, the static friction coefficient of the above Examples , Reference Examples and Comparative Examples was measured and the slip resistance was evaluated. The results obtained are shown in Table 2.

(1) Measurement method of static friction coefficient [Preparation of sample for evaluation]
The cationic electrodeposition coating composition obtained in the above Examples , Reference Examples and Comparative Examples is applied to a cold-rolled steel sheet for automobiles treated with zinc phosphate (PBL-3020, trade name, manufactured by Nippon Parker Rising Co., Ltd.). Electrodeposition coating was performed under the conditions of a temperature of 30 ° C., a voltage of 200 V, and an electrodeposition time of 3 minutes. After washing with water, it was baked at 170 ° C. for 20 minutes to obtain a coating film having a dry film thickness of 15 μm.

[Measurement of static friction coefficient]
The static friction coefficient of the surface of the cured product of the cationic electrodeposition coating composition according to each example , reference example and comparative example was measured using a surface tester (tribo gear type HEIDON14FW (trade name), manufactured by Shinto Kagaku Co., Ltd.). It was measured. The above-mentioned surface tester has a SUS304 stainless steel ball having a radius of 4 mm at the tip of the tester, and the ball is slid on the surface of each cured coating film by 10 mm at a load of 500 g and a speed of 40 mm / min. As a result, the static friction coefficient of the cured coating film was measured.

(2) Sliding resistance evaluation method The sample and evaluation method used for slip resistance evaluation will be described with reference to FIGS. 1 and 2.

[Creating a sample for evaluation]
The slip resistance evaluation sample 1 shown in FIG. 1 has a plate body 2 shown in FIG. 2 (a) and a plate body 3 shown in FIG. 2 (b) as main members. As shown in FIG. 2A, the plate body 2 is made of a square steel material (40 mm × 150 mm × 10 mm) as the base material 2a, and has a hole 2b having a diameter of 20 mmφ on one end side thereof. The base material 2a is subjected to surface treatment by zinc phosphate treatment with PBL-3020 (trade name, manufactured by Nippon Parker Rising Co., Ltd.), and then by the cationic electrodeposition coating composition obtained by the above Examples , Reference Examples and Comparative Examples. The paint was electrodeposited under the conditions of a paint temperature of 30 ° C., a voltage of 200 V, and an electrodeposition time of 3 minutes. The base material 2a after electrodeposition coating is a plate body 2 having a coating film 2c having a dry film thickness of 15 μm on the entire surface by baking at 170 ° C. for 20 minutes after washing with water. Similarly, the plate body 3 shown in FIG. 2B is composed of a square steel material 3 (40x150x10 mm) as the base material 3a, and has a hole 3b having a diameter of 13 mmφ on one end side thereof. The base material 3a is subjected to zinc phosphate treatment, electrodeposition coating, washing with water and baking by the same material and method as the above base material 2a, and has a coating film 3c having a dry film thickness of 15 μm on the entire surface. There is.

As shown in FIG. 1, the evaluation sample 1 is configured by arranging one plate 2 so that the two plates 3 sandwich the holes 2b and 3b of the respective plates so as to overlap each other. To. Here, the two plate bodies 3 are arranged so as to overlap each other from the hole 3a to the opposite end (the other end) 3d. On the other hand, in the plate body 2, the end portion (the other end portion) 2d having no hole 2a does not overlap with the other end portion 3a of the plate body 3, and is opposite to the plate body 3 with respect to the holes 2a and 3a. Arranged so as to extend in the direction. The plate bodies 2 and 3 thus arranged are fixed to the three plate bodies 2 and 3 with an axial force of 20 KN by passing the M12 bolt 4 through the holes 2b and 3b and using the nut 5. did. This was used as the evaluation sample 1.

[Slip resistance evaluation]
The other end 3d of the plate 3 in the evaluation sample 1 was fixed by being brought into close contact with a horizontal table (not shown). In this state (initial state), the bolt 4 is located above the hole 2b, and the lower part of the hole 2b is a cavity.

A load was applied to the plate 2 by pulling it at 10 mm / min in the arrow D direction (upper in the vertical direction) shown in FIG. 1 using a slip resistance tester (universal tensile tester, manufactured by Shimadzu Corporation). When the joint surface of the plates 2 and 3 slips, that is, the relationship between the bolt 4 and the hole 2b in the sample 1 changes from the initial state, and the cavity of the hole 2b without the bolt 4 is relatively upward. The point at which the movement started was measured as the time when the slip occurred. The tensile load at the time of slippage displayed by the above testing machine was read and evaluated according to the following criteria.

OK: Slip occurs only when the tensile load is 3.0 KN or more NG: Slip occurs when the tensile load is less than 3.0 KN

The surface conditioners in Table 2 are as follows.

Surface conditioner A: Polyflow WS (trade name, manufactured by Kyoeisha Chemical Co., Ltd.)
Surface Conditioning Agent B: Polyflow No. 85 (Product name, manufactured by Kyoeisha Chemical Co., Ltd.) Surface conditioner C: Polyflow No. 7 (Product name, manufactured by Kyoeisha Chemical Co., Ltd.)
Surface conditioner D: Floren AC326F (trade name, manufactured by Kyoeisha Chemical Co., Ltd.)

The present invention is not limited to the configuration and examples of the above-described embodiment, and various modifications can be made within the scope of the gist of the invention.

For example, regarding the cationic electrodeposition coating composition used in the present invention, in the above description, it has been described that (a) an amine-modified epoxy resin is used as a substrate resin, but in addition to (a) an amine-modified epoxy resin, the present invention It is also possible to use other known resins in combination as long as the effect of the above is not impaired.

Further, in the above embodiment, it has been explained by using an example of bolt fastening that a member having a cured coating film has excellent slip resistance, but according to the coating film forming method of the present invention, bolt fastening can be performed. Not limited to this, the surfaces of the cured coating film have the advantage of not causing unnecessary displacement in other fastenings or assembly of members that should maintain a contact state, and thus are effectively used in various assembly.

1 Sample for slip resistance evaluation 2 Plate 3 Plate 4 Bolt 5 Nut

Claims (6)

A method for forming a cationic electrodeposition coating film using a cationic electrodeposition coating composition, wherein the cationic electrodeposition coating composition is used.
(A) Amine-modified epoxy resin (excluding amine-modified epoxy resin obtained by reacting a hydroxyl group of a bisphenol-type epoxy resin with a cyclic ester compound) ,
(B) Blocked isocyanate compound,
(C) Pigments and (d) Acrylic surface conditioners,
Contains,
The solubility parameter (SP value) of the acrylic surface conditioner (d) is 9.5 to 10.2.
The content of the acrylic surface conditioner (d) with respect to the total mass of the cationic electrodeposition coating composition is in the range of 0.1% by mass to 0.3% by mass.
A method for forming a cationic electrodeposition coating film, wherein the static friction coefficient of the surface of the baking hardened coating film obtained from the cationic electrodeposition coating composition is 0.1 or more. The method for forming a cationic electrodeposition coating film according to claim 1, wherein the content of the acrylic surface conditioner (d) is 0.12 to 0.28% by mass with respect to the total mass of the cationic electrodeposition coating composition. .. The (a) amine-modified epoxy resin is
(I) Adduct of polyglycidyl ether and primary mono or polyamine, secondary mono or polyamine, or 1, 2 mixed mono or polyamine, or (ii) polyglycidyl ether and ketiminated primary amine. The method for forming a cationic electrodeposition coating film according to claim 1 or 2, which is an adduct with a polyamine having a group. The (b) blocked isocyanate compound is composed of only an externally crosslinked type blocked isocyanate compound, and its usage ratio (resin solid content) is 10 to 50% by mass with respect to the total resin solid content of the cationic electrodeposition coating composition. The method for forming a cationic electrodeposition coating film according to any one of claims 1 to 3. Further described in any one of 1 to 4, wherein a pigment dispersion resin is used, and the pigment dispersion resin and the amine-modified epoxy resin (a) are amine-modified epoxy resins prepared from the same material. Method for forming a cationic electrodeposition coating film. The cationic electrodeposition coating film formation according to any one of claims 1 to 5, wherein the (d) acrylic surface conditioner is a surface conditioner of a (meth) acrylic acid copolymer. Method.

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