JP2006265310A - Water-based intermediate coating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based intermediate coating material for automobiles showing reduced generation of volatile organic compounds, excellent in chipping resistance, showing no development of sagging in the coating film and excellent in finished appearance. <P>SOLUTION: The water-based intermediate coating material for automobiles comprises a urethane resin aqueous dispersion (A) having a resin acid value of 2-20 mg KOH/g, a hydroxy group-containing resin (B), and a crosslinking agent (C), wherein the urethane resin aqueous dispersion (A) is prepared by allowing a polyisocyanate to react with a polyol having at least two hydroxy groups in a molecule comprising a polyether polyol, a polyester polyol, a compound having at least one carboxy group and at least two hydroxy groups, and optionally another polyol to obtain a urethane prepolymer, which is neutralized with a neutralizer and then dispersed in an aqueous medium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an aqueous intermediate coating for automobiles having excellent chipping resistance and no sagging in the coating film, and excellent finish, and a method for forming a multilayer coating film using the aqueous intermediate coating for automobiles.

The outer plate portion of an automobile body is usually coated with a multilayer coating composed of an undercoating film, an intermediate coating film and an overcoating film with a cationic electrodeposition coating for the purpose of providing corrosion protection and aesthetics.
Conventional paints mainly use paints that use organic solvents. However, when organic solvents are used, there is always a risk of fire, and the impact on the health of the user has increased. There are concerns about the effects, and there is a need for paints that use safe and harmless solvents.

Furthermore, in the automotive coating field, in order to prevent the above-mentioned chipping and the progression of corrosion due to this, primer coatings such as chemical conversion treatment of base materials, electrodeposition coatings, especially water-based coatings used for intermediate coatings and top coatings Various studies have been conducted.
When the above water-based paint is applied, the impact force is reduced and the coating surface peels off from the metal surface, which causes rusting. There is a need for water-based paints that are free from sagging and have excellent general surface finish.

However, recently, from the viewpoint of energy saving and productivity improvement, the preheating time after painting of the water-based paint and the baking time of the coating film have been shortened. The sagging of the coating film is likely to occur at a site where water is difficult to evaporate, such as the inner plate portion of the door.
Conventionally, there is an invention in which a water-based polyurethane resin is blended with a rust preventive paint (Patent Document 1). Such an aqueous polyurethane has an average molecular weight of 50 to 100,000 and contains two or more active hydrogen atom-containing polyhydroxy compounds or the above polyhydroxy compound and an average molecular weight of 50 to 10
A combination of two or more active hydrogen atom-containing polyvalent amine compounds at 10,000, an organic polyisocyanate, and a polyurethane resin having an active hydrogen atom reactive with an NCO group and a salt-forming group, using a salt-forming agent. It is obtained by mixing and emulsifying in water by a known method. Even when the aqueous dispersion of the water-based polyurethane resin is applied to an aqueous intermediate coating, it has excellent chipping resistance and the coating film does not sag. In addition, a water-based intermediate coating having excellent finish cannot be obtained.

In addition, there is an invention in which the polyurethane resin contains a water-soluble and / or water-dispersible polyurethane resin containing at least one or more carboxyl groups in the molecule and / or at the molecular terminal (Patent Document 2). Even if such a water-dispersible polyurethane resin is simply applied to a water-based intermediate coating, the intended coating film performance of the present application cannot be obtained.
In addition, there is an invention that forms a multilayer coating film excellent in chipping resistance, water resistance, and finish with an aqueous intermediate coating material containing a urethane resin aqueous dispersion (Patent Document 3). The urethane resin aqueous dispersion used for this waterborne intermediate coating has a resin acid value of 2 to 20 mgKOH / g, preferably a solid content of 45% by weight or more and a viscosity of 200 to 3,000 mPa · s (20 ° C.). The water-based paint to which such a urethane resin aqueous dispersion was added was not sufficient in the sagging suppression effect in the coated film.

Therefore, in order to suppress sagging, we attempted to achieve high solid differentiation by adding pigments. However, not only did the structural viscosity (thixotropy) not be obtained and sagging could be suppressed, but the coating flowability after coating decreased and the general surface Caused a decline in finish. In the water-based intermediate coating composition of Patent Document 3, it is difficult to achieve both sagging suppression and general surface finish.
JP-A-62-110984 JP 62-246972 A JP 2004-2729 A

The problem to be solved is to find a water-based intermediate coating material that has no sagging in the coating film and is excellent in finish and general chipping resistance.

As a result of intensive studies, the inventors of the present invention contain an aqueous dispersion (A) of a urethane resin having a specific composition. 4 for 50 seconds (20 ° C.), and with a water-based intermediate coating for automobiles having a thixotropic index in the range of 1.6 to 3.0 measured at 20 ° C. under conditions of 6 rpm and 60 rpm. It has been found that an intermediate coating film having excellent finish and general chipping resistance can be formed, and the present invention has been completed.
That is, the present invention is an aqueous intermediate coating material containing a urethane resin aqueous dispersion (A) having a resin acid value of 2 to 20 mgKOH / g, a hydroxyl group-containing resin (B), and a crosslinking agent (C), and The aqueous intermediate coating material was diluted with water and the Ford Cup No. The water-based intermediate coating material adjusted to 50 seconds (20 ° C.) at 4 has a thixotropic index in the range of 1.6 to 3.0, and the urethane resin aqueous dispersion (A) has at least two molecules per molecule. Polyisocyanate (a) having an isocyanate group, polyether polyol (b ₁ ) which is an alkylene oxide adduct containing a bisphenol A skeleton or hydrogenated bisphenol A skeleton, and a polyester polyol which is a polycondensate of a dicarboxylic acid and a low molecular diol (B ₂ ), having at least two hydroxyl groups in one molecule containing a compound (b ₃ ) having at least one carboxyl group and at least two hydroxyl groups and, if necessary, other polyol (b ₄ ) The urethane prepolymer obtained by reacting the polyol (b) is neutralized with the neutralizing agent (c), Providing automobile aqueous intercoat composition characterized by comprising dispersed in the constant.

The water-based intermediate coating for automobiles of the present invention is a coating containing a urethane resin water dispersion (A) having a specific composition having a resin acid value of 2 to 20 mgKOH / g, and generates sagging, in particular, a keyhole or inner plate of a door. It is possible to obtain a multilayer coating film that suppresses the occurrence of sagging of the threaded portion of the part and ensures the finish of the general surface and further has excellent chipping resistance. Further, the urethane resin aqueous dispersion (A) has a viscosity of 200 to 3,000 mPa · s (20
° C).
In the present invention, by adding the urethane resin aqueous dispersion (A), the thixotropic index of the aqueous intermediate coating at the time of coating measured at 20 ° C. under conditions of 6 rpm and 60 rpm is 1.6-3. By setting it in the range of 0.0, the viscosity can be increased as compared with the conventional coating film.

The aqueous intermediate coating material for automobiles of the present invention contains a urethane resin aqueous dispersion (A) having a specific composition with respect to the total solid content of the resin components. Hereinafter, the waterborne intermediate coating for automobiles will be described in detail.
Urethane resin water dispersion (A):
The urethane resin aqueous dispersion (A) of the present invention comprises a polyisocyanate (a), a polyether polyol (b ₁ ), a polyester polyol (b ₂ ), a compound (b ₃ ), and, if necessary, other polyols ( b ₄ ) is reacted.
The amount of the neutralizing agent (c) is preferably 40% to 120% with respect to the number of moles of carboxyl groups in the urethane prepolymer.
The urethane resin aqueous dispersion (A) of the present invention is obtained by neutralizing a urethane prepolymer with a neutralizing agent (c) and stably dispersing it in an aqueous medium. The urethane prepolymer preferably has an isocyanate terminal. Furthermore, the urethane resin aqueous dispersion (A) preferably has a solid content of 45% by weight or more and a viscosity (note) of 200 to 3,000 mPa · s (20 ° C.).
(Note) Viscosity: Viscosity of the urethane resin water dispersion (A) is adjusted to 45% by weight by dilution with water, and at 20 ° C., a B-type viscometer (manufactured by Tokyo Keiki Co., Ltd., B-type viscosity) Measured using a total, type BM).

Polyisocyanate (a):
The polyisocyanate (a) is a compound having two or more isocyanate groups in one molecule, such as 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, etc.), aliphatic isocyanate having an aromatic ring (xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), etc.), urethanization of the diisocyanate, Carbodiimide, uretdione, burette, and isocyanurate 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). Particularly preferred polyisocyanates include isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI).

Polyol (b):
Examples of the polyol (b) include polyether polyol (b ₁ ) of an alkylene oxide adduct containing a bisphenol A skeleton or a hydrogenated bisphenol A skeleton, and a dicarboxylic acid (for example, adipic acid, sebacic acid, azelaic acid, dimer acid, etc. Aromatic dicarboxylic acids such as aromatic dicarboxylic acids, isophthalic acid, terephthalic acid and orthophthalic acid) and low molecular weight diols (for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6- Polyester polyol (b ₂ ) polycondensed with hexanediol, neopentyl glycol, 3 methyl 1,5-pentanediol, cyclohexanedimethanol, etc.) and hydroxyalkanoic acid (eg 2,2-dimethylolpropionic acid, 2 , 2-Dimethylo A compound (b ₃ ) having at least one carboxyl group and at least two hydroxyl groups of rubutanoic acid, 2,2-dimethylolpentanoic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, etc.) containing as components, if necessary, may contain other polyols (b _4).
In addition, the polyester polyol (b ₂ ) uses at least one aromatic dicarboxylic acid such as isophthalic acid, terephthalic acid, orthophthalic acid, etc. as a constituent component, and the compound (b ₃ ) can be used as a urethane resin. In order to give a resin acid value of 2 to 20 mgKOH / g, preferably 2 to 15 mgKOH / g, it is preferable to use 2,2-dimethylolpropionic acid.

Other polyols (b ₄ ) blended as appropriate include compounds obtained by ring-opening (co) polymerization of cyclic ethers (tetrahydrofuran, etc.) such as alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.) A compound obtained by subjecting polyhydric alcohol such as methylolpropane, glycerin, diglycerin, pentaerythritol, sorbitol and the like to addition polymerization of alkylene oxide, and the like; in addition, it has an ether bond as a repeating unit in the molecule, and one molecule Polyether polyols having two or more hydroxyl groups in them; Polycaprolactone diols obtained by ring-opening polycondensation of ε-caprolactone monomers with diols such as ethylene glycol as initiators; Ester bonds as repeating units in the molecule And One can use a polyester polyol having 2 or more hydroxyl groups in one molecule.

Further, as other polyols (b ₄ ), conjugated diene-based polyols having butadiene, isoprene and the like as repeating units, carbonate-based polyols obtained by polycondensation of low-molecular diols and dialkyl carbonates, hydroxyl-containing polyolefins, and the like are also used. Can do.

The polyol (b) is a compound having a number average molecular weight (Note 1) of 60 to 6,000, preferably 300 to 4,000. Further, the content of the polyether polyol (b ₁ ), the polyester polyol (b ₂ ), the compound (b ₃ ), and the other polyol (b ₄ ) is the same as that of the polyether polyol (b ₁ ) and the polyester polyol (b ₂ ). Polyether polyol (b ₁ ) is 25 to 35% by weight, preferably 27 to 31% by weight, and polyester polyol (b ₂ ) based on the total solid content of compound (b ₃ ) and other polyol (b ₄ ). Is 55 to 73% by weight, preferably 65 to 70% by weight, compound (b ₃ ) is 0.6 to 7% by weight, preferably 1 to 3% by weight, and other polyol (b ₄ ) is 0 to 10% by weight. The range of 0 to 3% by weight is preferable. The weight ratio of the polyether polyol _(b 1) / polyester polyol _(b 2) = it is preferably in the 1 / 4-2 / 1.

(Note 1) Number average molecular weight: Measured in accordance with JIS K0124-83, TSK GEL4000HXL + G3000HXL + G2500HXL + G2000HX
Using L (manufactured by Tosoh Corporation), the flow rate was 1.0 ml / min at 40 ° C., GPC tetrahydrofuran was used as the eluent, and the calculation was performed from the chromatogram obtained with the RI refractometer and the calibration curve of polystyrene.

Neutralizing agent (c):
As the neutralizing agent (c), trialkylamines such as triethylamine, tertiary alkanolamines such as methyldiethanolamine, alkali metal hydroxides such as sodium hydroxide, and the like can be preferably used. Among these neutralizing agents (c), particularly preferably,
Examples include triethylamine and methyldiethanolamine.
As the usage-amount of a neutralizing agent (c), it is the mole of a neutralizing agent (c) with respect to the mole number of the carboxyl group in the urethane prepolymer which reacts a polyisocyanate (a) and a polyol (b). The number is 40% to 120%, preferably 40% to 100%. The urethane resin aqueous dispersion (A) preferably contains a surfactant (d) described below for improving emulsification and water dispersibility.

Surfactant (d):
As the surfactant (d) used in the production of the urethane resin aqueous dispersion (A), an anionic surfactant and a nonionic surfactant can be preferably used. Specific examples include surfactants of higher alcohol-based alkylene oxide adducts.
Urethane resin aqueous dispersion (A) is obtained by reacting polyisocyanate (a) and polyo (b), adding neutralizer (c) and surfactant (d), and then emulsifying and dispersing in water. Obtainable.
In the production, the polyisocyanate (a) is 20 to 40 weights based on the total amount of the solid content of the polyisocyanate (a), polyol (b), neutralizing agent (c) and surfactant (d). %, Polyol (b) is preferably in the range of 60 to 80% by weight, and surfactant (d) is preferably in the range of 0 to 4% by weight. A small amount of the surfactant (d) is preferably added for coating performance (water resistance, etc.).

Furthermore, if necessary, a low molecular weight polyol having a molecular weight of less than 300, a low molecular weight polyamine, or a dihydrazide compound can be used in combination as the chain extender (e).
Examples of the low molecular weight polyol include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3 methyl 1,5-pentanediol, and cyclohexanedi. Bifunctional low molecular weight polyols such as methanol, and polyfunctional low molecular weight polyols such as trimethylolpropane and pentaerythritol can be exemplified.
Examples of the low molecular weight polyamine include ethylenediamine, diethylenetriamine, triethylenepentamine, trimethylenediamine, dipropylenetriamine,
Examples include piperazine and hydroxyaminopropylamine. Examples of the dihydrazide compound include hydrazine and adipic acid dihydrazide. The amount of such chain extender (e) added is an urethane resin aqueous dispersion (A).
The range of 0.1 to 2% by weight is preferable with respect to the total solid content of the components constituting.

The method for producing the urethane resin aqueous dispersion (A) in the present invention is not particularly limited. For example, in the presence or absence of an organic solvent containing no active hydrogen group in the molecule, polyisocyanate ( a), polyether polyol (b ₁ ), polyester polyol (b ₂ ), compound (b ₃ ), and other polyol (b ₄ ) are added as appropriate, and further used for normal urethanization reaction to accelerate the reaction. An amine-based or tin-based catalyst is used, and a urethanization reaction is usually performed at a temperature of 20 ° C. to 150 ° C., preferably 50 ° C. to 120 ° C., to obtain a urethane prepolymer having an isocyanate group at the molecular end.

Next, after adding a neutralizing agent (c) and a surfactant (d) to the obtained urethane prepolymer, it is emulsified and dispersed in water, and the urethane prepolymer is added with water or a chain extender (e). A high molecular weight urethane resin aqueous dispersion (A) can be obtained by reacting an isocyanate group present in the polymer to promote an increase in molecular weight or an internal crosslinking reaction.
The number average molecular weight (see Note 1) of the urethane resin used in the present invention is 2,000 to 5,000,000, preferably 1 from the viewpoint of the chipping resistance of the coating film, the smoothness of the coating surface, and the like.
It is from 30,000 to 3,000,000, more preferably from 30,000 to 1,000,000.

The average particle diameter (Note 2) of the urethane resin aqueous dispersion (A) is 0.02 to 0.4 μm,
Preferably it is 0.08-0.3 micrometer. If the average particle diameter exceeds 0.4 μm, the coating stability and the finish of the coating film are impaired, which is not preferable. On the other hand, the average particle diameter (Note 2) is 0.
When it is less than 02 μm, the viscosity of the urethane resin aqueous dispersion (A) becomes high, and the solid content is 45% by weight or more, and 200 to 3,000 mPa · s cannot be achieved at 20 ° C.
(Note 2) Average particle diameter: The average particle diameter was measured using a light scattering method (Microtrac UPA particle size analyzer, Model No. 9340; manufactured by Nikkiso Co., Ltd.).
In order to achieve the above average particle size range, the resin acid value of the urethane resin is 2 to 20 mgKOH / g, preferably 2 to 15 mgKOH / g, more preferably 5 to 12 mgKOH / g. Thus, a urethane resin aqueous dispersion (A) having a solid content of 45% by weight or more and a viscosity of 200 to 3,000 mPa · s (20 ° C.) can be obtained.

When the solid content of the urethane resin water dispersion (A) is 45% by weight or more and the viscosity is out of 200 to 3,000 mPa · s (20 ° C.), the urethane resin water dispersion (A) is blended in the paint. In some cases, it is difficult to achieve both the suppression of the sagging of the coating film and the finish of the general surface.
The amount of the urethane resin water dispersion (A) added is 0.1 to 70% by weight, preferably 10 to 50% in terms of solid content, based on the total solid content of the resin components constituting the automotive aqueous intermediate coating material. % By weight is good. If the addition amount is less than 0.1% by weight, the effect of improving the sagging property of the coating film is not effective, and if it exceeds 70% by weight, not only the effect of improving the sagging property is small, but also the finishing property is impaired.

Water-based intermediate coating for automobiles Water-based intermediate coating for automobiles includes, in addition to the urethane resin aqueous dispersion (A), hydroxyl-containing resins (B) such as polyester resins and acrylic resins, melamine resins, and blocked polyisocyanate compounds. Contains a crosslinking agent (C).
Hydroxyl-containing resin (B):
The hydroxyl group-containing resin (B) has an acid group such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group in the molecule in order to make the resin water-soluble or water-dispersed by neutralization with a basic compound. In addition, a polyester resin, an acrylic resin, a urethane resin, or the like having a hydroxyl group can be used. For example, a polyester resin has two or more hydroxyl groups in one molecule, and can be prepared by an esterification reaction of a polybasic acid and a polyhydric alcohol.

A polybasic acid is a compound having two or more carboxyl groups in one molecule. For example, terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, diphenylmethane-4,4 ' -Aromatic dicarboxylic acids such as dicarboxylic acids and anhydrides; alicyclic dicarboxylic acids such as hexahydroisophthalic acid, hexahydroterephthalic acid, hexahydrophthalic acid, tetrahydrophthalic acid and anhydrides; adipic acid, sebacic acid, Aliphatic dicarboxylic acids such as suberic acid, succinic acid, glutaric acid, maleic acid, chloromaleic acid, fumaric acid, dodecanedioic acid, pimelic acid, azelaic acid, itaconic acid, citraconic acid, dimer acid and the anhydrides thereof; Lower alkyl such as methyl ester and ethyl ester of dicarboxylic acid Ester; trimellitic acid, trimellitic anhydride, pyromellitic anhydride, pyromellitic acid, trimesic acid, methylcyclohexene tricarboxylic acid, such as tri- or more polybasic acids such as tetrachloro hexene tricarboxylic acid and anhydrides thereof.

A polyhydric alcohol is a compound having two or more hydroxyl groups in one molecule.
Ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butane Diol, 3-methyl-1,2-butanediol, 1,2-
Pentanediol, 1,5-pentanediol, 1,4-pentanediol, 2,4
-Pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 3-methyl-4,5-pentanediol, 2,2,4-trimethyl-1,3 -Dihydric alcohols such as pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, neopentyl glycol, and neopentyl glycol hydroxypivalate A polylactone diol obtained by adding a lactone such as ε-caprolactone to these dihydric alcohols; an ester diol such as bis (hydroxyethyl) terephthalate; an alkylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, Polyether diols such as butylene glycol;

Α-olefin epoxides such as propylene oxide and butylene oxide,
Monoepoxy compounds such as Cardura E10 [manufactured by Shell Chemical Co., Ltd., trade name, glycidyl ester of synthetic hyperbranched saturated fatty acid]; glycerin, trimethylolpropane, trimethylolethane, diglycerin, triglycerin, 1,2,6-hexanetriol , Pentaerythritol, dipentaerythritol, sorbitol, mannitol and other trihydric or higher alcohols; polylactone polyols obtained by adding lactones such as ε-caprolactone to these trihydric or higher alcohols; 1,4-cyclohexanedi Examples include alicyclic polyhydric alcohols such as methanol, tricyclodecane dimethanol, hydrogenated bisphenol A, hydrogenated bisphenol F, hydrogenated bisphenol A, and hydrogenated bisphenol F.

As the hydroxyl group-containing resin (B), a part of hydroxyl groups in the hydroxyl group-containing polyester resin,
A urethane-modified polyester resin obtained by subjecting a partially block polyisocyanate compound to a urethanization reaction can also be used. The hydroxyl group-containing polyester resin has two or more hydroxyl groups in one molecule, and this can be prepared by an esterification reaction between a polybasic acid and a polyhydric alcohol.
The partially blocked polyisocyanate compound is a compound in which a free isocyanate group that is not blocked and a blocked isocyanate group blocked with a blocking agent coexist in one molecule. For example, one of the free isocyanate groups in the polyisocyanate compound. It is obtained by blocking the part with a blocking agent.
The polyisocyanate compound is a compound having two or more free isocyanate groups not blocked in one molecule. Specifically, hexamethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, propylene diisocyanate, butylene diisocyanate,
Aliphatic diisocyanate compounds such as trimethylhexamethylene diisocyanate, dimer acid diisocyanate, and lysine diisocyanate;

Isophorone diisocyanate, methylene bis (cyclohexyl isocyanate),
Cycloaliphatic diisocyanate compounds such as methylcyclohexane diisocyanate, di (isocyanatomethyl) cyclohexane, cyclohexane diisocyanate, cyclopentane diisocyanate;
Xylylene diisocyanate, xylylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, toluidine diisocyanate, diphenyl ether diisocyanate, phenylene diisocyanate, biphenylene diisocyanate, dimethyl-biphenylene diisocyanate, isopropylidenebis (4-phenyl isocyanate), etc. Aromatic diisocyanate compounds;
Polyisocyanate compounds having three or more isocyanate groups in one molecule such as triphenylmethane triisocyanate, triisocyanatobenzene, triisocyanatotoluene, dimethyldiphenylmethanetetraisocyanate; ethylene glycol, propylene glycol, dimethylolpropionic acid A urethanized adduct obtained by reacting a polyisocyanate compound with an excess amount of an isocyanate group to a hydroxyl group of a polyol such as polyalkylene glycol or trimethylolpropane;

Examples thereof include burette type adducts such as hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, and methylene bis (cyclohexyl isocyanate), and isocyanate ring type adducts.
The blocking agent is a compound that blocks a free isocyanate group. When the blocked isocyanate group is heated to, for example, 100 ° C. or higher, preferably 130 ° C. or higher,
The blocking agent is dissociated to regenerate free isocyanate groups, which can be easily reacted with hydroxyl groups.
Examples of the blocking agent include phenols such as phenol and cresol; lactams such as ε-caprolactam and δ-valerolactam; aliphatic alcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, and lauryl alcohol;
Ether alcohols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether; benzyl alcohol; glycolic acid esters such as methyl glycolate and ethyl glycolate; lactic acid, methyl lactate, ethyl lactate, Lactic acid esters such as butyl lactate; Alcohols such as methylol urea and diacetone alcohol; Oximes such as acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime; diethyl malonate,
Active methylenes such as ethyl acetoacetate, methyl acetoacetate, acetylacetone;

Mercaptans such as butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, thiophenol, ethylthiophenol;
Acid amides such as acetanilide, acetanisid, methacrylamide, acetic acid amide, benzamide; imides such as phthalimide, maleic imide; amines such as diphenylamine, phenylnaphthylamine, carbazole, aniline, naphthylamine, butylamine; imidazole, 2-ethyl Imidazoles such as imidazole; Ureas such as urea, thiourea, ethylene urea, diphenylurea; Carbamate esters such as phenyl N-phenylcarbamate; Imines such as ethyleneimine and propyleneimine; Sodium bisulfite, bisulfite Examples thereof include sulfite such as potash.

In preparing the urethane-modified polyester resin, a part of the isocyanate groups in the polyisocyanate compound is blocked with a blocking agent, and one or more free isocyanate groups and blocked blocked isocyanate groups are contained in one molecule. It is preferable to prepare in advance the partially blocked polyisocyanate compound. The reaction between the polyisocyanate compound and the blocking agent can be carried out under known conditions. Further, the ratio of both components is particularly limited as long as the obtained partially blocked polyisocyanate compound has at least one free isocyanate group and one blocked isocyanate group in one molecule. There is no.

A urethane-modified polyester resin is obtained by reacting such a partially-blocked polyisocyanate compound with a part of hydroxyl groups in the hydroxyl group-containing polyester resin. The urethanation reaction between the partially blocked polyisocyanate compound and the hydroxyl group-containing polyester resin can be performed under the conditions of a normal urethanization reaction.
The urethane-modified polyester resin can also be obtained by blocking the remaining isocyanate groups of the product obtained by reacting a part of the hydroxyl groups in the hydroxyl group-containing polyester resin with a part of the isocyanate groups of the unblocked polyisocyanate compound with a blocking agent. Is obtained.
The urethane-modified polyester resin thus obtained has a hydroxyl value of 20 to 200 mg.
KOH / g, especially 40 to 120 mg KOH / g, isocyanate group value of 5 to 120 m
gKOH / g, especially 10 to 50 mgKOH / g, resin acid value of 100 mgKOH / g or less, especially 10 to 60 mgKOH / g, number average molecular weight in the range of 1,000 to 20,000, especially 1,500 to 10,000 Is preferred.

In addition, an alicyclic polybasic acid and / or an alicyclic polyhydric alcohol are essential components, and other polybasic acids and polyester resins containing other polyhydric alcohols may be used as necessary. it can. An alicyclic polybasic acid is a compound having one or more alicyclic structures (mainly 4- to 6-membered rings) and two or more carboxyl groups in one molecule.
Examples include 3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, hexahydrotrimellitic acid, methylhexahydrophthalic acid, and anhydrides thereof. . As other polybasic acids, the same polybasic acids as the polyester resin can be used.
An alicyclic polyhydric alcohol is a compound having one or more alicyclic structures (mainly 4 to 6-membered rings) and two or more hydroxyl groups in one molecule, such as 1,3-cyclohexanedimethanol. 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, hydrogenated bisphenol A, hydrogenated bisphenol F, spiroglycol, dihydroxymethyltricyclodecane, and the like. As other polyhydric alcohols, polyhydric alcohols similar to those of the polyester resin can be used.

The content of the alicyclic polybasic acid and / or alicyclic polyhydric alcohol in the polyester resin is 20 to 70% by weight based on the total solid content of the monomers constituting the polyester resin,
The range of 30 to 60% by weight is preferable.
The weight average molecular weight of the polyester resin obtained by reacting the alicyclic polybasic acid or other polybasic acid and / or the alicyclic polyhydric alcohol or other polyhydric alcohol is 1.0.
00 to 1,000,000, preferably 2,000 to 10,000, hydroxyl value is 3
A range of 0 to 200 mgKOH / g, preferably 50 to 180 mgKOH / g, and a resin acid value of 5 to 100 mgKOH / g, preferably 10 to 60 mgKOH / g are suitable.

In addition, the acrylic resin can be produced by copolymerizing a hydroxyl group-containing monomer and a polymerizable monomer component containing an acrylic monomer under ordinary conditions, and the number average molecular weight is 1,000 to 50,000, particularly 2 The hydroxyl value is preferably 20 to 200 mgKOH / g, particularly 50 to 150 mgKOH / g, and the resin acid value is preferably 3 to 100 mgKOH / g, particularly 20 to 70 mgKOH / g.
A hydroxyl group-containing monomer is a compound having at least one hydroxyl group and one polymerizable unsaturated bond in one molecule. For example, the number of carbon atoms such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, etc. Examples thereof include monoesterified products of 2 to 20 glycols and (meth) acrylic acid.

The acrylic monomer is a monoesterified product of (meth) acrylic acid and a monohydric alcohol having 1 to 22 carbon atoms. For example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl Acrylate, butyl methacrylate, hexyl acrylate, hexyl methacrylate, octyl acrylate, octyl methacrylate, lauryl acrylate, lauryl methacrylate, 2-ethylhexyl acrylate,
Examples include 2-ethylhexyl methacrylate.

Cross-linking agent (C):
As a crosslinking agent (C), a melamine resin, a blocked polyisocyanate compound, etc. are mentioned, It can use by 1 type or in combination of 2 or more types. Examples of the melamine resin include a methylolated amino resin obtained by a reaction between melamine and an aldehyde. Examples of the aldehyde include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like. Moreover, what etherified one part or all part of the methylol group of this methylolated amino resin by monoalcohol can be used as a crosslinking agent (C). Examples of monoalcohols used for etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, 2-ethylbutanol, 2-ethylhexanol and the like.

  Examples of commercially available melamine resins include Cymel 202, Cymel 232, Cymel 235, Cymel 238, Cymel 254, Cymel 266, Cymel 267, Cymel 272, Cymel 285, Cymel 301, Cymel 303, Cymel 325, Cymel 327, Cymel. 350, Cymel 370, Cymel 701, Cymel 703, Cymel 736, Cymel 738, Cymel 771, Cymel 1141, Cymel 1156, Cymel 1158, and the like (manufactured by Nippon Cytec Industries, Inc.), Uban 120, 20HS, 2021, 2028, 2061 ( As mentioned above, it is possible to list those sold under the trade name of Mitsui Chemicals.

The blocked polyisocyanate compound is obtained by blocking an isocyanate group of a polyisocyanate having two or more free isocyanate groups in one molecule with a blocking agent.
Examples of the polyisocyanate compound include hexamethylene diisocyanate,
Aliphatic polyisocyanates such as trimethylhexamethylene diisocyanate, dimer acid diisocyanate, lysine diisocyanate; and burette-type adducts, isocyanurate cycloadducts of these polyisocyanates;
Isophorone diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate), methylcyclohexane-2,4- (or -2,6-) diisocyanate,
1,3- (or 1,4-) di (isocyanatomethyl) cyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-
Alicyclic diisocyanates such as cyclohexane diisocyanate; and burette-type adducts, isocyanurate cycloadducts of these polyisocyanates;

Xylylene diisocyanate, metaxylylene diisocyanate, tetramethyl xylylene diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, 1,4-naphthalene diisocyanate, 4,4'-toluidine diisocyanate, 4 , 4'-diphenyl ether diisocyanate, (m- or p-) phenylene diisocyanate, 4,4
Aromatic diisocyanate compounds such as' -biphenylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, bis (4-isocyanatophenyl) sulfone, isopropylidenebis (4-phenylisocyanate); Burette type adduct of isocyanate, isocyanurate cycloadduct; triphenylmethane-4,4 ′, 4 ″ -triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene , 4,4'-dimethyldiphenylmethane-2,2 ', 5,5'-tetraisocyanate
Polyisocyanates having one or more isocyanate groups; and burette-type adducts, isocyanurate cycloadducts of these polyisocyanates;
A polyisocyanate compound is reacted at an excess ratio of an isocyanate group to a hydroxyl group of a polyol such as ethylene glycol, propylene glycol, 1,4-butylene glycol, dimethylolpropionic acid, polyalkylene glycol, trimethylolpropane, and hexanetriol. And burette type adducts of these polyisocyanates, isocyanurate cyclic adducts, and the like. The blocking agent is for blocking free isocyanate groups.
When heated to 00 ° C. or higher, preferably 130 ° C. or higher, it can easily react with a hydroxyl group.

Examples of the blocking agent include phenols such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and hydroxybenzoic acid methyl; ε-caprolactam, δ-valerolactam, γ -Lactams such as butyrolactam, β-propiolactam; aliphatic alcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, 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, and other ether systems; benzyl alcohol; glycolic acid; methyl glycolate, ethyl glycolate Glycolic acid esters such as butyl glycolate; lactic acid esters such as lactic acid, methyl lactate, ethyl lactate and butyl lactate; alcohols such as methylol urea, methylol melamine, diacetone alcohol, 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate ;

Oxime systems such as formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime;
Active methylenes such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone; butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol Mercaptan series such as ethylthiophenol; Acid amide series such as acetanilide, acetanisidide, acetolide, acrylamide, methacrylamide, acetic acid amide, stearamide, benzamide; Imido series such as succinimide, phthalimide, maleic imide; Diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine Emissions, such as butyl phenylamine amine; imidazole, imidazole and 2-ethylimidazole;
Urea systems such as urea, thiourea, ethylene urea, ethylene thiourea, diphenylurea;
Carbamate esters such as phenyl N-phenylcarbamate; imines such as ethyleneimine and propyleneimine; and sulfites such as sodium bisulfite and potassium bisulfite.

In addition, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-nitro-3,5
Examples include -dimethylpyrazole and 4-bromo-3,5-dimethylpyrazole. Among these, a preferable blocking agent is 3,5-dimethylpyrazole.
In addition, as a blocking agent for blocking the isocyanate group of polyisocyanate,
Examples thereof include hydroxycarboxylic acids having one or more hydroxyl groups and one or more carboxyl groups, such as hydroxypivalic acid and dimethylolpropionic acid.
Here, a blocked polyisocyanate compound imparted with water dispersibility by neutralizing the carboxyl group of the hydroxycarboxylic acids can also be used. As a commercial item, bihydrol VPLS2378 (made by Sumika Bayer Urethane Co., Ltd., a brand name) is mentioned.

The water-based intermediate coating for automobiles according to the present invention includes a color pigment, an extender pigment, a flat pigment (for example, talc, aluminum flakes, mica flakes), a light interference pigment, a dispersant, an anti-settling agent, an organic solvent. , Catalyst for promoting urethanization reaction (eg, organotin compound), catalyst for promoting cross-linking reaction between hydroxyl group and melamine resin (eg, acid catalyst), antifoaming agent, thickener, rust preventive agent, ultraviolet absorber, A surface conditioner or the like can be appropriately blended.
The above-mentioned flat pigment is a pigment having a thin and flat shape like a scale, and when a coating film is formed, it overlaps in a layered manner with other various pigment particles in the coating film. It is considered to have a function of relieving stress and external stress. Specific examples include talc, aluminum flakes, mica flakes, etc. Among them, talc is preferable. As the shape of talc, the thickness is preferably 0.1 to 2 μm, particularly 0.2 to 1.5 μm, and the longitudinal dimension is preferably 1 to 100 μm, particularly 2 to 20 μm.

The amount of the flat pigment added is 0.1 to 100 parts by weight of the solid content of the resin component.
The range is 50 parts by weight, preferably 1 to 20 parts by weight, more preferably 2 to 10 parts by weight. When the amount of the flat pigment exceeds 50 parts by weight, not only the chipping resistance is lowered but also the coating stability is impaired, which is not preferable.

Further, a curing catalyst can be added to accelerate the crosslinking reaction of the coating film. Specifically, tin octylate, dibutyltin di (2-ethylhexanoate), dioctyltin di (2-ethylhexanoate), dioctyltin diacetate, dibutyltin dilaurate, dibutyltin oxide, monobutyltin trioctate, 2 -Lead ethylhexanoate,
Mention may be made of organometallic compounds such as zinc octylate.
Although the usage-amount of a curing catalyst can be selected arbitrarily, the range of 0.01-5 weight% with respect to a resin component, especially 0.05-3 weight% is suitable.
The coating can be performed by a conventionally known method, for example, brush coating, air spray, airless spray, electrostatic coating, and the like.
It is preferably within a range of 100 μm, particularly 15 to 35 μm.

The water-based intermediate coating material for automobiles of the present invention is obtained by converting the water-based intermediate coating material to Ford Cup No. A thixotropic index (Note 3) measured at 20 ° C. under conditions of 6 rpm and 60 rpm with a water-based intermediate coating material prepared by diluting with water so as to be 50 seconds (20 ° C.) in 4 measurements is 1.6. It is suitable to be in the range of -3.0, preferably 1.8-2.8, more preferably 2.0-2.5. In the conventional aqueous intermediate coating material, the thixotropic index value was 1.3 to 1.5, but the viscosity of the coating material was changed by adding the urethane resin aqueous dispersion (A).
(Note 3) Thixotropic index: Thixotropic index is TI.
The value is abbreviated as a value and measured using a B-type viscometer (Tokyo Keiki Co., Ltd., B-type viscometer, type BM) by the rotational viscosity method described in JIS K 5400-4-5-3 (1990) (temperature) It is a value calculated by converting the numerical value obtained by 20 ° C. and rotor rotation speeds of 6 rpm and 60 rpm into mPa · s, and the apparent viscosity mPa · s at 6 rpm / mPa · s at 60 rpm.

The water-based intermediate coating for automobiles of the present invention was applied to an object to be coated at a temperature of 20 ° C. and a relative humidity of 75% so as to have a dry film thickness of 25 μm, and measured with a cone plate viscometer after 1 minute. coating viscosity (Note 4), 10,000～150,000Pa · sec at shear rate 10 sec ^-1, 300 preferably 35,000～80,000Pa · sec, and at a shear rate of 1,000 sec ^-1 The range is 1,000 Pa · sec, preferably 650 to 900 Pa · sec.
From this, the water-based intermediate coating material for automobiles of the present invention can impart viscosity to the coated film after coating, contributes to the suppression of sagging, and is excellent in finish on the general surface. In the case of conventional water-based intermediate coatings for automobiles, under the same measurement conditions, a share rate of 10 seconds- ¹ is 3,000 or more and less than 10,000 Pa · second, and a share rate of 1,000 seconds- ¹ is less than 300 Pa · second. It is.
(Note 4) Viscosity of coating film: As a measuring machine, it can be measured with Rheostress RS150 (manufactured by HAAKE, trade name, cone plate viscometer). The measurement temperature is 25 ° C.
It is a numerical value obtained by reading the coating film viscosity (Pa · sec) when the share rate is continuously changed.

When baking and hardening the water-based intermediate coating material for automobiles of the present invention, the coating film can be heated at 120 to 170 ° C, particularly 130 to 160 ° C for 10 to 40 minutes.
Coating film formation method After the application of the waterborne intermediate coating for automobiles, a multilayer coating film can be formed by a coating film forming method such as the following method (1) to method (4).
As the method (1), the dry film thickness is formed by a method such as airless spraying, air spraying, rotary atomizing coating, etc., on the cured coating film of the water-based intermediate coating material for automobiles of the present invention. 2 coat 2 bake method (2C2B), which is applied at a temperature of about 100 to 180 ° C. and heated for about 10 to 90 minutes as a baking temperature; There is a 2-coat 1-bake method (2C1B) in which a top coat (solid color) is applied repeatedly by wet.

  As a method (2), the dry film thickness is about 10 to 50 μm by a method such as airless spraying, air spraying, rotary atomizing coating, etc., on the cured coating film of the water-based intermediate coating material for automobiles of the present invention. It is applied so that it becomes, and wet-on-wet or cured, and a clear paint is applied so that the film thickness is about 10 to 70 μm in terms of the cured film thickness, and the baking temperature is about 10 at about 60 to 160 ° C. 3 coat 2 bake method (3C2B), 3 coat 3 bake method (3C3B), heated for 90 minutes; and wet base coating of water-based paint on wet coating, airless spray, air spray The film is coated by a method such as rotary atomization coating so that the dry film thickness is about 10 to 50 μm, and is wet-on-wet or cured, and the clear paint has a cured film thickness In was applied to be about 10 to 70 [mu] m, at the baking temperature, 3-coat 1-bake method comprising heating at about 60 to 160 ° C. to about 10 to 90 minutes (3C1B), 3-coat 2-bake method (3C2B);

  As a method (3), the dry film thickness is about 10 to 50 μm by a method such as airless spraying, air spraying, rotary atomizing coating, etc. on the cured coating film of the water-based intermediate coating material for automobiles of the present invention. The first clear paint is applied so that the film thickness is about 10 to 70 μm in the cured film thickness, and is cured by wet on wet or cured. A 4-coat 2-bake method (4C2B) in which the second clear paint is applied to a cured film thickness of about 10-70 μm and heated at a baking temperature of about 60-160 ° C. for about 10-90 minutes. 4 coat 3 bake system (4C3B), 4 coat 4 bake system (4C4B); and

  As a method (4), a dry film thickness is reduced by a method such as airless spraying, air spraying, rotary atomizing coating, and the like on a wet paint film of an aqueous intermediate coating material for automobiles of the present invention in a wet-on-wet manner. Paint to 10-50 μm, wet on wet or cure, apply first clear paint to a cured film thickness of about 10-70 μm, wet on wet, or Cured and coated with a second clear paint so that the film thickness is about 10 to 70 μm, and heated at about 60 to 160 ° C. for about 10 to 90 minutes at a baking temperature for 4 coats and 2 bake system (4C2B), 4 coat 3 bake system (4C3B), etc. are mentioned.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited thereby. “Parts” and “%” indicate “parts by weight” and “% by weight”.
Production Example 1 Urethane resin water dispersion No. 1 Production of 1 Kuraray polyol P-2012 (Note 5) 4 using methyl ethyl ketone as a reaction solvent
8.9 parts, 0.978 parts trimethylolpropane, BPX-11 (Note 11) 24.4
5 parts, dimethylolpropionic acid 2.445 parts, duranate 50MS (Note 14)
23.23 parts were reacted at 70 ° C. using dibutyltin dilaurate as a catalyst to synthesize a urethane prepolymer.

The free isocyanate group of the urethane prepolymer was 1.35%. next,
Neutralization is performed by adding 1.67 parts of triethylamine. After adding 2.0 parts of Emulgen 147 (Note 17) as a surfactant and homogenizing, 120 parts of distilled water are added while stirring at high speed using a homomixer. It was added and emulsified.
Stirring was continued at 30 ° C. until the free isocyanate groups reacted with water and disappeared completely.
Next, methyl ethyl ketone as a reaction solvent was recovered under reduced pressure using an evaporator to obtain a urethane resin aqueous dispersion No. 1 having a solid content of 52.5 wt%, a viscosity of 750 mPa · s, a pH of 8.2, and an average particle size of 0.18 μm. 1 was obtained. The resin acid value of the urethane resin in Production Example 1 was 10 mgKOH / g.

Production Example 2 Urethane resin water dispersion no. Production of 2 Teslak 2477 (Note 6) 44.72 using methyl ethyl ketone as a reaction solvent
Parts, BPX-33 (Note 12) 28.46 parts, dimethylolpropionic acid 2.43
9 parts and 24.39 parts of VESTANAT IPDI (Note 15) were reacted at 70 ° C. using dibutyltin dilaurate as a catalyst to synthesize a urethane prepolymer. The free isocyanate group of the urethane prepolymer was 1.28%.
Next, it neutralizes by adding 1.94 parts of triethylamine, and after adding 2.0 parts of Emulgen 147 (Note 17) as a surfactant and homogenizing it, distilled water is added while stirring at high speed using a homomixer. 120 parts were added and emulsified. Next, an aqueous amine solution prepared by dissolving 0.819 parts of diethylenetriamine in 10 parts of distilled water was added to react with free isocyanate groups at 30 ° C. Next, methyl ethyl ketone, which is a reaction solvent, is recovered under reduced pressure using an evaporator to obtain a solid content of 50.5% by weight and a viscosity of 4
Urethane resin aqueous dispersion No. 50 having a viscosity of 50 mPa · s, pH 8.4, and particle size of 0.25 μm. 2 was obtained. In addition, the resin acid value of the urethane resin in Production Example 2 was 10 mgKOH / g.

Production Example 3 Urethane resin aqueous dispersion no. Production of No. 3 The reaction was carried out under the conditions shown in Production Example 1 except that the raw materials and the charge amounts shown in Table 1 were used. 3 was obtained.
Production Example 4 Urethane resin water dispersion No. 4 Production of No. 4 The reaction was carried out under the conditions shown in Production Example 2 except that the raw materials and preparation amounts shown in Table 1 were used. 4 was obtained.

Production Example 5 Urethane resin water dispersion no. 5 Production of urethane resin No. 5 was carried out under the conditions shown in Production Example 2 except that the raw materials and the charge amounts shown in Table 1 were used. 5 was obtained.
Production Example 6 Urethane resin water dispersion no. Production of No. 6 The reaction was carried out under the conditions shown in Production Example 2 except that the raw materials and preparation amounts shown in Table 1 were used. 6 was obtained.
Production Example 7 Urethane resin water dispersion no. Production of No. 7 The reaction was carried out under the conditions shown in Production Example 2 except that the raw materials and preparation amounts shown in Table 1 were used. 7 was obtained.
Production Example 8 Urethane resin water dispersion no. Production of No. 8 The reaction was carried out under the conditions shown in Production Example 2 except that the raw materials and the charge amounts shown in Table 1 were used. 8 was obtained.
Table 1 shows the raw materials and preparation amounts of Production Example 1 to Production Example 8. In Table 2, urethane resin water dispersion No. 1-No. The property of 8 is shown.

(Note 5) Kuraray polyol P-2012: manufactured by Kuraray Co., Ltd., trade name, polyester resin (adipic acid / isophthalic acid / 3-methyl-1,5-pentanediol), number average molecular weight 2,000, hydroxyl value 56 mgKOH / g
(Note 6) Teslac 2477: manufactured by Hitachi Chemical Co., Ltd., trade name, polyester resin (adipic acid / isophthalic acid / 1,6 hexanediol), number average molecular weight 1,750, hydroxyl value 65 mgKOH / g
(Note 7) Teslac 2450: manufactured by Hitachi Chemical Co., Ltd., trade name, polyester resin (terephthalic acid / isophthalic acid, sebacic acid / 1,4 butanediol), number average molecular weight 2,000, hydroxyl value 56 mgKOH / g
(Note 8) Polylite OD-X-2044: Dainippon Ink and Chemicals, trade name, polyester resin (adipic acid / neopentyl glycol), number average molecular weight 2,000, hydroxyl value 56 mgKOH / g
(Note 9) Nipponran 4040: manufactured by Nippon Polyurethane Co., Ltd., trade name, polyester resin (adipic acid / 1,4 butanediol), number average molecular weight 2,000, hydroxyl value 56 mgKOH / g
(Note 10) NIPPOLAN N-981: manufactured by Nippon Polyurethane Co., Ltd., trade name, 1,6 hexanediol polycarbonate, number average molecular weight 1,000, hydroxyl value 112 mgKOH / g
(Note 11) BPX-11: Asahi Denka Co., Ltd., trade name, bisphenol A propylene oxide adduct (Note 12) BPX-33: Asahi Denka Co., Ltd., trade name, bisphenol A propylene oxide adduct (Note 13) Polyether A: propylene oxide adduct of hydrogenated bisphenol A,
Number average molecular weight 381, hydroxyl value 295 mgKOH / g
(Note 14) Duranate 50MS: Asahi Kasei Chemicals, trade name, isocyanurate form of hexamethylene diisocyanate (Note 15) VESTANIP IPDI: Isophorone diisocyanate (Note 16) Death module W: Sumika Bayer Urethane, trade name, 4 4'-dicyclohexylmethane diisocyanate (Note 17) Emulgen 147: trade name, surfactant, manufactured by Kao Corporation

Production Example 9 Polyester resin solution No. Production of 1 In a four-necked flask equipped with a heating device, a stirring device, a thermometer, a reflux condenser, and a water separator,
1,4-Cyclohexanedicarboxylic acid 61.9 parts Adipic acid 70.1 parts Trimethylolpropane 62.8 parts Neopentylglycol 24.2 parts 1,4-cyclohexanedimethanol 44.6 parts are charged and the contents are charged. After heating from 160 ° C. to 230 ° C. over 3 hours, 230 ° C.
The condensed water produced by holding for 1 hour was distilled off using a rectifying column.
Next, after 15.0 parts of trimellitic anhydride was added to the product, the solvent was removed, neutralized with dimethylethanolamine, mixed with water, and the hydroxyl value was 150 mgKOH.
/ G, resin acid value of 35 mg KOH / g, number average molecular weight of 2,000, polyester resin solution No. 40 having a solid content of 40% by weight. 1 was obtained.

Production Example 10 Acrylic resin solution No. Production Example 1 Thermometer, temperature controller, stirrer, reflux condenser, and dropping device, 300 parts of deionized water in a reaction vessel, 25% rear soap SE-1025 (surfactant, manufactured by Asahi Denka Co., Ltd., (Product name) 4.8 parts was stirred and mixed in a nitrogen stream and heated to 82 ° C. Next, 3 parts of “monomer emulsion (1)” having the following composition and a 1% aqueous solution of sodium persulfate were introduced into a 60-part reaction vessel and kept at 82 ° C. for 20 minutes.

Next, 1% sodium persulfate aqueous solution was added to the remainder of the following “monomer emulsion (1)”.
20 parts were added and added dropwise into the reaction vessel with a metering pump over 4 hours. After completion of the dropwise addition, aging was performed for 2 hours, and 282 parts of a 1% dimethylethanolamine aqueous solution was added, and the mixture was kept at 82 ° C. for 30 minutes. Cool to 30 ° C, filter and discharge with 200 mesh nylon cloth,
Acrylic resin solution No. 1 having a solid content of 40.0% by weight and an average particle size of 0.15 μm at pH 6.5. 1 was obtained.
"Monomer emulsion (1)"
300 parts deionized water
25% SE-1025 43.2 parts
180 parts of styrene
336 parts of n-butyl acrylate
2-hydroxyethyl acrylate 60 parts
Acrylic acid 24 parts

Examples and Comparative Examples Example 1
Urethane resin water dispersion no. 1 (50 parts (solid content)), polyester resin solution No. 1
1 part 10 (solid content), Bihydrol VP LS2378 (note 18) 20 parts (solid content), Cymel 325 (note 19) 20 parts (solid content) were mixed in advance, and MICRO
ACE S-3 (Note 20) 10 parts, JR-806 (Note 21) 65 parts, Carbon MA
-100 (* 22) 0.6 parts, barium sulfate B35 (* 23) 20 parts added, dispersed,
After mixing and adding deionized water, the Ford Cup No. 4 for 50 seconds (20 ° C.). 1 was obtained.

Examples 2-5
In the contents of Table 1, the water-based intermediate coating paints Nos. 2-No. 5 was obtained.

(Note 18) Bihydrol VP LS2378: manufactured by Sumika Bayer Urethane Co., Ltd., trade name, blocked polyisocyanate curing agent, solid content 40% by weight
(Note 19) Cymel 325: manufactured by Nippon Cytec Industries, Ltd., trade name, methyl / butylated melamine resin, solid content 80% by weight
(Note 20) MICRO ACE S-3: Nihon Talc Co., Ltd., trade name, talc (Note 21) JR-806: Teika Co., Ltd., trade name, titanium white (Note 22) Carbon MA-100: Mitsubishi Chemical Corporation Company name, product name, carbon black (Note 23) Barium sulfate B35: Sakai Chemicals, product name, barium sulfate Comparative Examples 1-8
In the contents of Table 2, the water-based intermediate coating paints Nos. 6-No. 13 was obtained.

(Note 24) U-coat UX-8100: Sanyo Chemical Industries, trade name, urethane resin water dispersion (neutralized product of polyisocyanate / polyether polyol carboxylic acid group-containing polyurethane resin), solid content 37% by weight
Preparation of test plate (1) A cold rolled steel plate (70 mm × 150 mm × 0.8 mm) subjected to Palbond # 3020 (manufactured by Nihon Parkerizing Co., Ltd., trade name, zinc phosphate treatment), ELECRON GT-
Electrodeposit 10LF (Kansai Paint Co., Ltd., trade name, cationic electrodeposition paint)
The film was baked and dried at 70 ° C. for 20 minutes to obtain a coating film having a dry film thickness of 20 μm.

On top of that, the aqueous intermediate coating No. obtained in Examples and Comparative Examples was used. 1-No. 10 is 25 μm
It was horizontally painted and baked at 150 ° C. for 20 minutes. Next, 15 μm of Magiclon TB-515 (trade name, acrylic resin / melamine resin-based paint, manufactured by Kansai Paint Co., Ltd.) is applied to the coating surface of the water-based intermediate coating, and left at room temperature for 3 minutes. A clear paint ("Magicron TC-71" manufactured by Kansai Paint Co., Ltd., trade name, acrylic resin / melamine resin system) is applied to the cured coating surface to a film thickness of 35 μm, dried by heating at 140 ° C. for 20 minutes, and a test plate (1 )

Preparation of test plate (2) In preparation of the test plate (1), the test plate (2) was prepared in the same manner as the test plate (1) except that it was heated and dried at 160 ° C. for 20 minutes after the clear paint was applied. Obtained.
Preparation of test plate (3) In the preparation of test plate (1), a cold-rolled steel plate having a 10 mmφ punch hole in the center was used. 1-No. A test plate (3) was obtained in the same manner as the test plate (1) except that 13 was applied vertically. The coating conditions at this time are 25 ° C.
The relative humidity was 80%.

Test results Tables 5 and 6 show the test results of the test plate (1), the test plate (2), and the test plate (3) formed as described above, which were performed according to the following test method.

(Note 25) Thixotropic index (TI value): See (Note 3) (Note 26) Coating film viscosity: See (Note 4) (Note 27) Chipping resistance: US Q -PANEL, Q-G
A test plate is set on the specimen holder of the R gravelometer (chipping test device), and -20
At a temperature of 0.392 MPa (4 kgf / cm2) at a temperature of 7
A granite crushed stone amount of 50 g was sprayed on the coating surface, and the degree of scratches on the coating film was visually observed and evaluated.
◎ indicates that the size of the scratch is small and the coating film of the aqueous intermediate coating (the coating film of the present composition) is exposed. ○ indicates that the size of the scratch is small and the coating film of the aqueous intermediate coating is partially damaged. △ is the extent to which the coating film is exposed, but the size of the scratch is small, but the extent to which the electrodeposition coating surface and the base steel plate are exposed × is the size of the scratch is quite large and the base steel plate is also large Exposed degree (Note 28) Yellowing: The difference (Δb) between the b value of the test plate (1) and the b value of the test plate (2) was evaluated.
○: Δb value is less than 0.9 Δ: Δb value is 0.9 or more and 1.0 or less ×: Δb value exceeds 1.0Δb

(Note 29) Sagging property: The sagging state of the coating film was observed in the coating film around the punch hole of the test plate (3).
○ indicates that there is no problem. Δ indicates that a sagging of the coating film of about 1 mm is observed around the punch hole. × indicates that the sagging of the coating film is 2 mm or more around the punch hole. : Visual appearance of the general surface of the test plate (3) was evaluated.
○ is good in smoothness, gloss, and sharpness △ is either inferior in smoothness, gloss, or sharpness, x is slightly inferior in smoothness, gloss, or sharpness Inferior

The generation of volatile organic compounds (VOC) can be reduced, and a coated article excellent in chipping resistance, sagging property, and finish can be obtained.

Claims (10)

A waterborne intermediate coating composition containing an aqueous urethane resin dispersion (A) having a resin acid value of 2 to 20 mgKOH / g, a hydroxyl group-containing resin (B), and a crosslinking agent (C), and the aqueous intermediate coating composition being water Diluted with Ford Cup No. The water-based intermediate coating material adjusted to 50 seconds (20 ° C.) at 4 has a thixotropic index in the range of 1.6 to 3.0, and the urethane resin aqueous dispersion (A) has at least two molecules per molecule. Polyisocyanate (a) having an isocyanate group, polyether polyol (b ₁ ) which is an alkylene oxide adduct containing a bisphenol A skeleton or hydrogenated bisphenol A skeleton, and a polyester polyol which is a polycondensate of a dicarboxylic acid and a low molecular diol (B ₂ ), having at least two hydroxyl groups in one molecule containing a compound (b ₃ ) having at least one carboxyl group and at least two hydroxyl groups and, if necessary, other polyol (b ₄ ) The urethane prepolymer obtained by reacting the polyol (b) is neutralized with the neutralizing agent (c), Automotive aqueous intercoat composition characterized by comprising dispersed in the constant.   The aqueous intermediate coating material for automobiles according to claim 1, wherein the urethane resin aqueous dispersion (A) contains a surfactant (d). The aqueous intermediate coating material for automobiles according to claim 1 or 2, which contains at least one aromatic dicarboxylic acid selected from orthophthalic acid, isophthalic acid, and terephthalic acid as the dicarboxylic acid constituting the polyester polyol (b ₂ ). The polyether polyol (b ₁ ) is 25 to 35% by weight based on the total solid content of the polyether polyol (b ₁ ), the polyester polyol (b ₂ ), the compound (b ₃ ), and the other polyol (b ₄ ), The polyester polyol (b ₂ ) is 55 to 73% by weight, the compound (b ₃ ) is 0.6 to 7% by weight, and the other polyol (b ₄ ) is 0 to 10% by weight. The water-based intermediate coating material for automobiles according to item 1. Compounds having at least one carboxyl group and at least two hydroxyl groups (b ₃₎ is an automobile aqueous intercoat composition according to claim 1 which is 2,2-dimethylolpropionic acid. The waterborne intermediate coating material for automobiles according to any one of claims 1 to 5, wherein the urethane resin water dispersion (A) has an average particle size of 0.02 to 0.4 µm. The urethane resin aqueous dispersion (A) is contained in an amount of 0.1 to 70% by weight based on 100 parts by weight of the total solid content of the urethane resin aqueous dispersion (A), the hydroxyl group-containing resin (B), and the crosslinking agent (C). The water-based intermediate coating material for automobiles according to any one of claims 1 to 6.   The flat pigment is contained in an amount of 0.1 to 50 parts by weight based on 100 parts by weight of the total solid content of the urethane resin aqueous dispersion (A), the hydroxyl group-containing resin (B) and the crosslinking agent (C). The water-based intermediate coating material for automobiles according to any one of the above. A water-based intermediate coating for automobiles according to any one of claims 1 to 8 is applied onto an object to be coated, and is left uncured or baked and cured, and further includes one or more layers of colored paint and / or clear paint. A method for forming a multi-layer coating film that is applied and heat-cured. When the water-based intermediate coating for automobiles according to claim 9 is applied at a temperature of 20 ° C. and a relative humidity of 75% so as to have a dry film thickness of 25 μm, the coating measured by a cone plate viscometer after 1 minute. film viscosity in the range 10,000～150,000Pa · sec, and at a shear rate of 1,000 sec ^-1 of 300～1,000Pa · sec at shear rate 10 s ^-1, method for forming a multilayer coating film.