JP2023067964A - Multi-component type aqueous primer composition and coating method - Google Patents

Abstract

To provide a multi-component type aqueous primer composition and a coating method which enable formation of a coating film excellent in adhesion, especially, water-resistant adhesion.SOLUTION: A multi-component type aqueous primer composition contains a main agent component (I), and a curing agent component (II), wherein the main agent component (I) contains a hydroxyl group-containing acrylic resin (A) having a hydroxyl value of 15-180 mgKOH/g and a glass transition temperature of 30-70°C, and a pigment (B), the curing agent component (II) contains a polyisocyanate compound (C) having an isocyanate group content of 10 mass% or more, the main agent (I) and/or the curing agent component (II) contain a silane coupling agent (D), and a content of the component (D) is within the range of 0.01-10 mass% on the basis of the mass of the curing agent component (II).SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a multi-component water-based undercoat composition which can form a coating film excellent in adhesion, particularly water-resistant adhesion, and which is useful as a primer surfacer in the field of automobile repair.

Conventionally, undercoat paints (primer surfacers) in the field of automotive refinishing have focused on performance such as quick-drying, adhesion, water resistance, and polishing workability. is the mainstream. However, in recent years, from the viewpoint of environmental conservation, there has been a shift from organic solvent-based paints to water-based paints, and various water-based undercoat paints for automobile repair have been proposed. For example, Patent Document 1 discloses an epoxy/amine-based two-component water-based primer surfacer, and Patent Document 2 describes an epoxy-based one-component water-based coating composition. Moreover, in Patent Document 3, a water-based two-liquid type urethane paint is being studied. However, for example, when repairing the outer panel of an automobile, there are cases where the base material (steel plate) part that is partially exposed by polishing is painted. is undercoated with the paints of the inventions of Patent Documents 1 to 3, and then repaired with a repair coating composition. In some cases, water adhesion resistance and finish were insufficient.

JP-A-10-60369 JP-A-7-258596 Japanese Patent Application Laid-Open No. 2001-262053

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a multi-component water-based base coating composition capable of forming a coating film having excellent adhesion, particularly water adhesion resistance. .

Under such circumstances, the present inventors conducted extensive research and found that the main agent component (I) contains an acrylic resin having a specific hydroxyl value and glass transition temperature, and the curing agent component (II) contains a specific isocyanate group. The above problems are solved by using a multi-component water-based undercoat paint composition containing a polyisocyanate compound of a specific amount, and the main component (I) and/or the curing agent component (II) containing a specific amount of a silane coupling agent. I found what I can do.

The present invention provides a multi-component waterborne basecoat composition as shown in the following sections:
Section 1. A multi-component water-based undercoat composition comprising a main component (I) and a curing agent component (II),
The main ingredient component (I) contains a hydroxyl group-containing acrylic resin (A) having a hydroxyl value in the range of 15 to 180 mgKOH/g and a glass transition temperature in the range of 30 to 70°C, and a pigment (B),
The curing agent component (II) contains a polyisocyanate compound (C) having an isocyanate group content of 10% by mass or more, and the main agent (I) and/or the curing agent (II) component contains a silane coupling agent (D). , A multi-component water-based undercoat composition in which the content of component (D) is in the range of 0.01 to 10% by mass based on the mass of component (II) of the curing agent.

Section 2. The pigment (B) contains at least one extender pigment selected from calcium carbonate, clay, talc, mica, baryta, and silica, and the content thereof is based on 100 parts by mass of the resin solid content contained in the main component. Item 1. The multi-component water-based undercoat composition according to Item 1, which contains 30 to 350 parts by mass.

Item 3. Item 3. The multi-component water-based undercoat composition according to Item 1 or Item 2, wherein the curing agent component (II) contains a water-soluble solvent (E) having no hydroxyl group.

Section 4. The hydroxyl group-containing acrylic resin (A) contains 3 to 45% by mass of the hydroxyl group-containing polymerizable unsaturated monomer (a) based on the total amount of copolymerization components, and the glass transition temperature of the homopolymer is 30 ° C. or higher. 4. The multi-component aqueous multi-component type according to any one of Items 1 to 3, wherein 40 to 85% by mass of the unsaturated monomer (b) and 0 to 25% by mass of the other polymerizable unsaturated monomer (c) are copolymerized components. Primer paint composition.

Item 5. 5. A multi-component aqueous solution according to any one of items 1 to 4, wherein the main ingredient component (I) further comprises a resin (H) having a glass transition temperature of -10°C or higher and lower than 30°C and/or a viscosity modifier. Primer paint composition.

Item 6. A multi-component system in which a water-based diluent component (III) is further combined with the main agent component (I) and the curing agent component (II), wherein the diluent component (III) is 6. The multi-component water-based undercoat composition according to any one of Items 1 to 5, which contains a silicone-based surface control agent (F).

Item 7. Item 7. The multi-component water-based base coating composition according to Item 6, wherein the diluent component (III) further contains an inorganic viscosity modifier (G).

Item 8. Item 8. A coating method, comprising coating an object to be coated with the multi-component water-based undercoat paint composition according to any one of Items 1 to 7.

By using the multi-component water-based undercoat paint composition of the present invention, it is possible to form a paint film which is excellent in adhesion, particularly water-resistant adhesion, and in which the finish after topcoating is excellent.

The water-based undercoat composition of the present invention is a multi-component water-based undercoat composition comprising a main component (I), a curing agent component (II), and optionally a diluent component (III). . They will be described in order below.

<Main component (I)>
In the present invention, the main component (I) comprises a hydroxyl group-containing acrylic resin (A) and a pigment (B) having a hydroxyl value in the range of 15 to 180 mgKOH/g and a glass transition temperature in the range of 30 to 70°C. characterized by comprising

(A) Hydroxyl-containing acrylic resin In the present invention, the hydroxyl-containing acrylic resin (A) contained in the main ingredient component (I) is a component that becomes a polyurethane film-forming component together with the polyisocyanate compound (B) described later, and has a hydroxyl value of It is a resin having a range of 15 to 180 mgKOH/g and a glass transition temperature of 30 to 70°C.

In particular, the hydroxyl value of the hydroxyl-containing acrylic resin (A) is preferably 30 to 160 mgKOH/g, more preferably 50 to 140 mgKOH/g, from the viewpoint of hardening the resulting coating film and achieving both polishability and water-resistant adhesion of the coating film. Anything within the range of is suitable.

In addition, the glass transition temperature (hereinafter sometimes abbreviated as Tg) of the hydroxyl-containing acrylic resin (A) is in the range of 30 to 70° C., which makes the resulting coating film hard and improves the polishability and adhesion of the coating film. From the viewpoint of compatibility, a temperature within the range of 40 to 68°C, more preferably 45 to 65°C is suitable.

In addition, in this specification, the glass transition temperature (Tg) of the hydroxyl group-containing acrylic resin is a value calculated by the following formula.

1/Tg(K)= _W1 / _T1 + _W2 / _T2 +... _Wn / _Tn
Tg (°C) = Tg (K) - 273
In the formula, W ₁ , _{W 2} , _{. .} . Wn are the mass fractions of each monomer,
is the glass transition temperature Tg (K) of the homopolymer of each monomer. The glass transition temperature of the homopolymer of each monomer is described in POLYMER HANDBOOK Fourth Edition, J. Am. Brandrup, E. h. Immergut, E.; A. Grulke (1999), and the glass transition temperature of a monomer not described in the literature is the static Let it be the glass transition temperature.

In this specification, the static glass transition temperature of a resin is measured, for example, by taking a sample in a measuring cup, vacuuming the sample to completely remove the solvent, and measuring the differential scanning calorimeter "DSC-50Q type" (manufactured by Shimadzu Corporation, product name), the change in the amount of heat is measured in the range of -100 ° C to 150 ° C at a heating rate of 3 ° C / min, and the first baseline change point on the low temperature side is the static glass transition temperature. , can be measured.

The hydroxyl-containing acrylic resin (A) is, for example, a copolymer of a hydroxyl-containing polymerizable unsaturated monomer (a) and another polymerizable unsaturated monomer copolymerizable with the hydroxyl-containing polymerizable unsaturated monomer. be able to.

The hydroxyl group-containing polymerizable unsaturated monomer (a) is a compound having one or more hydroxyl groups and one or more polymerizable unsaturated bonds in one molecule, specifically, for example, 2-hydroxyethyl (meth)acrylate , 2-Hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate and other (meth)acrylic acid monoesters with dihydric alcohols having 2 to 8 carbon atoms; ε-caprolactone modified product of the monoesterified product of the (meth)acrylic acid and a dihydric alcohol having 2 to 8 carbon atoms; N-hydroxymethyl (meth)acrylamide; allyl alcohol; Examples include (meth)acrylates having an ethylene chain. Among them, 2-hydroxyethyl methacrylate and/or 2-hydroxypropyl methacrylate are preferred from the standpoint of abrasiveness and reactivity with a curing agent, which will be described later.

Other polymerizable unsaturated monomers copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate; propyl (meth) acrylate, n-butyl (meth) ) acrylate, isobutyl (meth) acrylate, tertiary butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, etc. Linear or branched alkyl (meth)acrylate; cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate Alicyclic alkyl (meth)acrylates such as acrylates, adamantyl (meth)acrylate and tricyclodecenyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; styrene, α-methylstyrene, vinyltoluene Aromatic ring-containing polymerizable unsaturated monomers such as; alkoxyalkyl (meth)acrylates such as 2-methoxyethyl (meth)acrylate and 2-ethoxyethyl (meth)acrylate; perfluoroalkyl (meth)acrylates; Nitrogen-containing polymerizable unsaturated compounds such as (meth)acrylamide, N,N-dialkylaminoalkyl (meth)acrylates such as N,N-diethylaminoethyl (meth)acrylate, adducts of glycidyl (meth)acrylate and amine compounds Monomer; allyl (meth) acrylate, ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, trimethylolpropane tri (Meth)acrylates, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tetra( meth)acrylate, glycerol di(meth)acrylate, 1,1,1-trishydroxymethylethane di(meth)acrylate, 1,1,1-trishydroxymethylethane tri(meth)acrylate, 1,1,1-tris Polymerizable unsaturated monomers having at least two polymerizable unsaturated groups in one molecule such as hydroxymethylpropane tri(meth)acrylate; (meth)acrylic acid, maleic acid, crotonic acid, 2-carboxyethyl (meth) Carboxyl group-containing polymerizable unsaturated monomers such as acrylate; carbonyl group-containing polymerizable unsaturated monomers such as acetoacetoxyethyl (meth)acrylate and diacetone (meth)acrylamide; glycidyl (meth)acrylate, 2-methylglycidyl (meth) Epoxy group-containing acrylates, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, 3,4-epoxycyclohexylpropyl (meth)acrylate, 4-hydroxybutyl acrylate glycidyl ether, etc. Polymerizable unsaturated monomers; isocyanato group-containing polymerizable unsaturated monomers such as isocyanatoethyl (meth)acrylate; Saturated monomers; oxidatively curable group-containing polymerizable unsaturated monomers such as dicyclopentenyloxyethyl (meth)acrylate, dicyclopentenyloxypropyl (meth)acrylate, dicyclopentenyl (meth)acrylate, etc., which are respectively They can be used singly or in combination of two or more.

In the present specification, "(meth)acrylate" is "acrylate or methacrylate", "(meth)acrylic acid" is "acrylic acid or methacrylic acid", (meth)acryloyl is "acryloyl or methacryloyl", "(meth)acrylamide " means "methacrylamide or acrylamide", and "(meth)acrylonitrile" means "acrylonitrile or methacrylonitrile".

Among the other polymerizable unsaturated monomers, in order to make the glass transition temperature of the hydroxyl group-containing acrylic resin (A) within the above range and from the viewpoint of the polishability and water resistance of the resulting coating film, the glass transition temperature of the homopolymer is preferably 30° C. or higher as part of the copolymerization component.

Specific examples of the monomer (b) having a homopolymer Tg of 30° C. or higher include styrene [100], methyl methacrylate [105], tertiary butyl methacrylate [107], neopentyl glycol diacrylate [117], 3-methyl-1,5-pentanediol diacrylate [105], 1,6-hexanediol diacrylate [105], isobornyl acrylate [94], tripropylene glycol diacrylate [90], 1,9- nan diacrylate [68], cyclohexyl methacrylate [66], ethyl methacrylate [65], benzyl methacrylate [54], isobutyl methacrylate [53], tertiary butyl acrylate [43], stearyl acrylate [38], cetyl acrylate (alias; hexadecyl acrylate) [35], neopentyl glycol dimethacrylate [33], etc. (However, functional group-containing polymerizable polymers such as carboxyl groups, epoxy groups, alkoxysilyl groups, isocyanato groups and oxidative curing groups) excluding saturated monomers and the hydroxyl group-containing polymerizable unsaturated monomers (a)). The above [ ] indicates the glass transition temperature [° C.] of the homopolymer of each monomer.

Among the above, at least one monomer selected from a group of monomers having a homopolymer Tg of preferably 40 to 130° C., more preferably 50 to 120° C., from the standpoint of polishing properties of the coating film. It is particularly preferred to use

The content of each copolymer component in the hydroxyl-containing acrylic resin (A) can be appropriately adjusted so as to be within the range of the hydroxyl value and glass transition temperature of the acrylic resin, but the polishability and water resistance of the resulting coating film are 3 to 45% by mass, preferably 5 to 40% by mass of the hydroxyl group-containing polymerizable unsaturated monomer (a) based on the total amount of copolymerization components, the glass transition temperature of the homopolymer is 30 ° C. or higher. Polymerizable unsaturated monomer (b) 40 to 85 mass%, preferably 45 to 80 mass%, and other polymerizable unsaturated monomer (c) 0 to 25 mass%, 0 to 20 mass% as copolymer components preferably.

The monomer (b) having a Tg of the homopolymer of 30° C. or higher can be used alone or in combination. ) is suitably in the range of 1 to 95% by mass, more preferably 5 to 95% by mass.

The hydroxyl group-containing acrylic resin (A) is preferably a particulate aqueous dispersion (also referred to as an emulsion).

As a technique for dispersing the hydroxyl group-containing acrylic resin in water, for example, part or all of the anionic groups such as carboxyl groups contained in the acrylic resin produced by solution polymerization in an organic solvent are neutralized with a basic compound. or by adding and dispersing the acrylic resin in an aqueous medium containing a basic compound, or emulsifying the polymerizable unsaturated monomer component using a polymerization initiator in the presence of an emulsifier. A method of polymerization and the like can be mentioned.

Examples of emulsifiers used in emulsion polymerization include anionic surfactants and nonionic surfactants, and examples of polymerization initiators include persulfates and peroxides.

In the present invention, the hydroxyl group-containing acrylic resin (A) is an aqueous dispersion of an acrylic resin having a core-shell structure obtained by copolymerizing polymerizable unsaturated monomer components having different compositions in multiple stages. is more preferable from the viewpoint of excellent storage stability of the main component (I).

In the case of producing the aqueous dispersion of the acrylic resin having the core-shell type structure, for example, a mixture of the monomer component (X) forming the core portion is emulsion-polymerized using a polymerization initiator in the presence of an emulsifier. After obtaining an aqueous dispersion of the copolymer, a mixture of the monomer component (Y) forming the shell portion is added to the aqueous dispersion, and emulsion polymerization is performed using a polymerization initiator. be able to.

Specifically, the monomers for the core portion and the shell portion can be appropriately selected from the items listed in the section on the hydroxyl group-containing unsaturated monomer and other polymerizable unsaturated monomers copolymerizable with the monomer. The polymerizable unsaturated monomer component (X) forming the part preferably contains an epoxy group-containing polymerizable unsaturated monomer as at least a part of the component, and the polymerizable unsaturated monomer component (X) forming the shell part ( Y) preferably contains a carboxyl group-containing polymerizable unsaturated monomer as at least part of its components. The epoxy group-containing polymerizable unsaturated monomer contained in the monomer component (X) forming the core portion is reacted with the carboxyl group contained in the polymerizable unsaturated monomer component (Y) to obtain the polymerizable unsaturated monomer component (X ) and a copolymer of the polymerizable unsaturated monomer component (Y) to further improve the water dispersion stability of the water dispersion of the hydroxyl group-containing acrylic resin (A). is.

In the hydroxyl group-containing acrylic resin (A), the use ratio of the epoxy group-containing polymerizable unsaturated monomer in the polymerizable unsaturated monomer component (X) can be appropriately adjusted as long as it is within the scope of the present invention. It can range from 0.1 to 40% by weight, preferably from 0.5 to 25% by weight, based on the total amount of unsaturated monomer component (X).

Further, the proportion of the carboxyl group-containing polymerizable unsaturated monomer used in the polymerizable unsaturated monomer component (Y) is 5 to 60% by mass, preferably 10%, based on the total amount of the polymerizable unsaturated monomer component (Y). It can be in the range of -50% by weight.

Further, in these polymerizable unsaturated monomer components (X) and (Y), the ratio of carboxyl groups contained in the polymerizable unsaturated monomer component (Y) to 1 mol of epoxy groups contained in the polymerizable unsaturated monomer component (X) is The amount is adjusted to be in the range of 3 to 30 mol, particularly 6 to 20 mol, which is suitable from the viewpoint of the storage stability of the hydroxyl group-containing acrylic resin (A) and the finish and polishability. .

The proportion of the polymerizable unsaturated monomer component (X) forming the core portion and the monomer component (Y) forming the shell portion is from 60/40 in mass ratio of monomer component (X)/monomer component (Y). A ratio of 95/5, particularly 70/30 to 90/10 is suitable from the viewpoint of water dispersion stability and finish of the hydroxyl group-containing acrylic resin (A).

When the hydroxyl group-containing acrylic resin (A) is an aqueous dispersion, the average particle size of the dispersed resin is appropriately in the range of 0.05 to 1.0 μm, preferably 0.08 to 0.8 μm.

In this specification, the average particle size is measured by Coulter Counter N4 (trade name, manufactured by Beckman Coulter, Inc., particle size distribution measuring device). 20°C).

From the standpoint of the dispersion stability of the hydroxyl group-containing acrylic resin (A), the resin solid content of the hydroxyl group-containing acrylic resin (A) is preferably about 35 to 65% by mass.

Here, the resin solid content in this specification is a value calculated by taking about 2.0 g of a sample in an aluminum foil cup with a diameter of about 5 cm and measuring the residue (g) after heating at 110 ° C. for 1 hour. is.

(B) Pigment As the pigment (B) contained in the main ingredient component (I) in the present invention, conventionally known pigments can be used, for example, colored pigments such as titanium white, carbon black, red iron oxide; fine aluminum powder; metallic pigments; extender pigments such as calcium carbonate, clay, talc, mica, barita, silica, alumina white, etc.; rust preventive pigments such as aluminum tripolyphosphate, aluminum phosphomolybdate, and zinc phosphate; They can be used alone or in combination of two or more depending on the desired color and coating performance.

The content of the pigment (B) is preferably 100 to 500 parts by mass, preferably 120 to 400 parts by mass, per 100 parts by mass of the resin solid content contained in the main component (I).

Among the above pigments, at least one selected from calcium carbonate, clay, talc, mica, barita and silica as an extender pigment from the viewpoint of cost, film-forming properties, polishability, and the balance between finish properties and coating film performance after topcoating. Seeds are preferred, particularly at least one selected from calcium carbonate, talc and baryta, more particularly talc and/or baryta.

Among the pigments, the content of the extender pigment is preferably 30 to 350 parts by mass based on 100 parts by mass of the resin solid content contained in the main ingredient component (I), from the viewpoint of the balance between the polishing property and the coating film performance. is preferably contained within the range of 100 to 340 parts by mass.

The average particle size of the pigment (B) is suitably in the range of 0.001 to 100 μm, preferably 0.05 to 50 μm, from the viewpoint of finish.

The average particle size of the pigment in the present invention is the value of the median size (d50) of the volume-based particle size distribution measured by the laser diffraction scattering method using a Microtrac particle size distribution analyzer MT3300 (trade name, manufactured by Nikkiso Co., Ltd.).

The main ingredient component (I) includes a resin other than the hydroxyl group-containing acrylic resin (A), a viscosity modifier, a pigment dispersant, an ultraviolet absorber, a light stabilizer, polymer fine particles, a dispersing aid, a preservative, an antifoaming agent, and a curing agent. Other ingredients such as paint additives commonly used in the preparation of aqueous paints, such as catalysts, organic solvents, neutralizers, etc., may also be included.

In the present invention, the main ingredient component (I) is, in addition to the hydroxyl group-containing acrylic resin (A), a resin (H) having a glass transition temperature of -10°C or higher and lower than 30°C, particularly in the range of -5 to 10°C. / Or it is preferable to contain a viscosity modifier. As a result, the finish of the topcoat may be improved without impairing the weather resistance and water resistance of the coating film formed from the water-based undercoat paint composition. The glass transition temperature of the resin (H) is a value calculated by the formula described in the section of the glass transition temperature (Tg) of the hydroxyl group-containing acrylic resin (A).

As the resin (H), considering the point of cross-linking with the curing agent (II) component described later, a resin containing a hydroxyl group is preferable. resins containing both hydroxyl groups and acid groups are preferred.

The hydroxyl value of resin (H) is preferably 5 to 150 mgKOH/g, particularly 20 to 120 mgKOH/g, and the acid value is preferably 10 to 120 mgKOH/g, particularly 30 to 70 mgKOH/g.

The type of resin (H) is not particularly limited, but acrylic resins and polyester resins are suitable from the viewpoint of water resistance and topcoat finish.

As a method for producing the resin (H), a known method can be adopted, but in the case of an acrylic resin, it can be produced by the same method as for the hydroxyl group-containing acrylic resin (A).

When the main ingredient component (I) contains the resin (H), the content of the resin solids contained in the main ingredient component (I) is Based on 100 parts by weight per minute, it is preferably 40 parts by weight or less, preferably in the range of 5 to 25 parts by weight.

As the viscosity modifier, those known as viscosity modifiers for paints can be used. Alkali-swelling polyacrylic acid-based viscosity modifiers and the like are included. Further, an inorganic viscosity modifier (G), which will be described later, can also be included in the main component (I). These viscosity modifiers may be used singly or in combination of two or more.

When the inorganic viscosity modifier (G) is used, it may be mixed with the pigment (B) component in advance and blended as a paste, or may be added later.

The content of the viscosity modifier, which is optionally blended with the main ingredient component (I), is 100 parts by mass of the resin solid content contained in the main ingredient component (I), from the viewpoint of the balance between polishing properties and coating performance. 0.5 to 10 parts by mass, preferably 1 to 5 parts by mass.

<Curing agent component (II)>
The curing agent component (II) used in the present invention is characterized by containing a polyisocyanate compound (C) having an isocyanate group content within a specific range.

(C) Polyisocyanate compound The polyisocyanate compound (C) contained in the curing agent component (II) used in the present invention has an isocyanate group content of 10% by mass or more.

In particular, the isocyanate group content of the polyisocyanate compound (C) is preferably 12 to 25% by mass, more preferably 18 to 25% by mass, from the viewpoint of water adhesion resistance.

Here, in the present specification, the isocyanate group content is the amount of isocyanate groups contained in the compound expressed as a mass fraction. The amount of isocyanate groups can be measured according to JIS K 1603-1 (2007). Specifically, it is a value obtained by adding an excess amount of dibutylamine to a sample and allowing it to sufficiently react, and then back-titrating the unreacted dibutylamine with a hydrochloric acid standard solution.

The polyisocyanate compound is a compound having two or more free isocyanate groups in one molecule, and those conventionally used in the production of polyurethane can be used. For example, aliphatic diisocyanates such as tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate and lysine diisocyanate; alicyclic diisocyanates such as 4,4′-methylenebis(cyclohexyl isocyanate) and isophorone diisocyanate; xylylene diisocyanate , tolylene diisocyanate, diphenylmethane diisocyanate, polyphenylmethane diisocyanate (hereinafter referred to as polymeric MDI) and other aromatic diisocyanates; can be used as Among these, it is particularly preferred that at least part of the components thereof are aliphatic diisocyanates, alicyclic diisocyanates and derivatives thereof, particularly hexamethylene diisocyanate (HMDI) and hexamethylene diisocyanate (HMDI). derivatives, isophorone diisocyanate (IPDI), derivatives of isophorone diisocyanate (IPDI), and the like are preferably used.

In the present invention, the polyisocyanate compound (C) may be a hydrophilized polyisocyanate compound obtained by introducing a hydrophilic group into the polyisocyanate compound, or a polyisocyanate compound dispersed in water using a surfactant. It is preferable to use a polyisocyanate compound for water-based coatings such as a water-dispersible polyisocyanate compound that can be used.

Examples of the hydrophilic polyisocyanate compound include a polyether-modified polyisocyanate compound into which a polyether skeleton is introduced and an anionic group-containing polyisocyanate compound. Examples of polyether-modified polyisocyanate compounds include compounds obtained by reacting a polyisocyanate compound with a hydrophilic polyether alcohol such as a monoalcohol such as polyoxyethylene. Examples of the anionic group-containing polyisocyanate compound include compounds obtained by reacting an active hydrogen group-containing compound having an anionic group with an isocyanate group of a polyisocyanate compound. The active hydrogen group-containing compound having an anionic group is not particularly limited, and examples thereof include compounds having one anionic group and at least one active hydrogen group. Specifically, it includes a compound having an anionic group such as a carboxyl group, a sulfonic acid group, a phosphoric acid group, or a betaine structure-containing group in one molecule and having an active hydrogen group capable of reacting with an isocyanate group. Hydrophilicity can be imparted to the polyisocyanate compound by reacting the compound with the polyisocyanate compound. The active hydrogen group is a functional group capable of reacting with an isocyanate group, and examples thereof include a hydroxyl group and an amino group.

Active hydrogen group-containing compounds having a carboxyl group include, for example, 2,2-dimethylolacetic acid, 2,2-dimethylollactic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and dimethylolheptanoic acid. , dimethylolnonanoic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid; 1-carboxy-1,5-pentylenediamine, dihydroxybenzoic acid, 3,5-diaminobenzoic acid diaminocarboxylic acids such as , lysine and arginine; and half ester compounds of polyoxypropylene triol and maleic anhydride or phthalic anhydride.

Active hydrogen group-containing compounds having a sulfonic acid group include, for example, N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, 1,3-phenylenediamine-4,6-disulfonic acid, diaminobutane sulfonic acid, 3,6-diamino-2-toluenesulfonic acid, 2,4-diamino-5-toluenesulfonic acid, 2-(cyclohexylamino)-ethanesulfonic acid, 3-(cyclohexylamino)-propanesulfonic acid, etc. mentioned.

Examples of active hydrogen group-containing compounds having a phosphate group include 2,3-dihydroxypropylphenyl phosphate.

Active hydrogen group-containing compounds having betaine structure-containing groups include, for example, sulfobetaine group-containing compounds obtained by reacting tertiary amines such as N-methyldiethanolamine with 1,3-propanesultone.

These active hydrogen group-containing compounds having an anionic group may be, for example, modified alkylene oxides to which alkylene oxides such as ethylene oxide and propylene oxide are added.

Among the hydrophilic polyisocyanate compounds, anionic group-containing polyisocyanate compounds are preferable from the viewpoint of the smoothness of the resulting coating film, and the anionic group is a polyisocyanate compound having a sulfonic acid group and/or a phosphoric acid group. is particularly preferred.

Examples of the water-dispersible polyisocyanate compound include those obtained by self-emulsifying polyisocyanate, those forcibly dispersed using a stirrer or the like, and those dispersed using a surfactant. The surfactant used for obtaining the water-dispersible polyisocyanate compound is preferably an anionic surfactant and/or a nonionic surfactant, more preferably an anionic surfactant.

In addition to the hydrophilic polyisocyanate compound and/or the water-dispersible polyisocyanate compound, the curing agent component (II) may also contain a hydrophobic polyisocyanate compound in combination. As such a hydrophobic polyisocyanate compound, those commonly used in solvent-based coating compositions can be used.

The content of the polyisocyanate compound (C) contained in the curing agent component (II) is in the range of 10 to 99.9% by mass, preferably 30 to 80% by mass, based on the mass of the curing agent component (II). can be adjusted to

(D) Silane coupling agent In the main agent component (I) and/or the curing agent component (II) used in the present invention, the silane coupling agent (D) is 0 based on the mass of the curing agent component (II). It is contained within the range of 0.01 to 10% by mass.

In particular, the content of the silane coupling agent (D) is in the range of 0.01 to 10% by mass based on the mass of the curing agent component (II), and the water adhesion resistance and adhesion of the resulting film to the steel plate From the point of view of improving properties, it is preferably in the range of 0.05 to 8% by mass, more preferably 0.1 to 6% by mass.

The type of silane coupling agent is not particularly limited, but examples include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxy Propylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)methyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)methyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane , 2-(3,4-epoxycyclohexyl) methyldimethoxysilane and other epoxy group-containing silane coupling agents; 3-(2-aminoethyl) aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2 ( Amino group-containing silane coupling agents such as aminoethyl)3-aminopropyltrimethoxysilane and N-2 (aminoethyl)3-aminopropylmethyldimethoxysilane; mercapto group-containing silane coupling agents such as 3-mercaptopropyltrimethoxysilane; Agent; vinyl group-containing silane coupling agent such as vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(methoxyethoxy)silane; 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxy Examples thereof include silane, (meth)acryloyl group-containing silane coupling agents such as 3-(meth)acryloyloxypropyldimethoxymethylsilane, and the like. Among them, an epoxy group-containing silane coupling agent is particularly preferred.

From the viewpoint of storage stability, the silane coupling agent (D) is preferably contained in the curing agent component (II).

The curing agent component (II) may be diluted with an organic solvent, and may also include ultraviolet absorbers, light stabilizers, polymer fine particles, dispersing aids, preservatives, antifoaming agents, curing catalysts, medium Other ingredients such as paint additives commonly used in the preparation of water-based paints, such as admixtures and dehydrating agents, may also be included.

(E) Water-soluble solvent As the organic solvent for diluting the curing agent (II), since it may react with the polyisocyanate compound (C) described above, it is preferable to appropriately select a water-soluble solvent that does not have a hydroxyl group. However, for example, acetate-based, ketone-based, ester-based, ether-based, and glycol ether-based water-soluble solvents can be used.

Acetates include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol mono-n-butyl ether acetate (also known as n-butyl cellosolve acetate), diethylene glycol monoethyl ether acetate, diethylene glycol mono-n-butyl ether acetate, 3 -Methoxybutyl acetate, propylene glycol monomethyl ether acetate (alias: methoxypropyl acetate) and the like.

Examples of ketone-based solvents include acetone, methyl ethyl ketone, methyl amyl ketone, methyl isobutyl ketone, and the like.

Examples of esters include ethyl acetate (alias: ethyl acetate), butyl acetate (alias: butyl acetate), isobutyl acetate (alias: isobutyl acetate), methyl benzoate (alias: methyl benzoate), ethyl ethoxypropionate, and propionate. Examples include ethyl acetate and methyl propionate.

Ether-based hydrocarbons include tetrahydrofuran, dioxane, dimethoxyethane, aromatic hydrocarbons, and aliphatic hydrocarbons.

Glycol ethers include ethylene glycol diethers such as ethylene glycol dimethyl ether and ethylene glycol diethyl ether; Ether; triethylene glycol diether such as triethylene glycol dimethyl ether and triethylene glycol divinyl ether; tetraethylene glycol diether such as tetraethylene glycol diethyl ether; propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl Ethers, propylene glycol diethers such as propylene glycol diisopropyl ether, propylene glycol di-n-butyl ether, propylene glycol diisobutyl ether, propylene glycol diallyl ether, propylene glycol diphenyl ether; dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, and dipropylene glycol Dipropylene glycol diethers such as di-n-butyl ether, dipropylene glycol diisobutyl ether, dipropylene glycol allyl ether; tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, and tripropylene glycol di-n-butyl ether, tripropylene glycol diisobutyl ethers, tripropylene glycol diethers such as tripropylene glycol diallyl ether; butylene glycol diethers such as butylene glycol dimethyl ether, butylene glycol diethyl ether, and butylene glycol di-n-butyl ether; 2-butoxyethyldiethoxyethyl ether; 2-butoxyethyltriethoxyether, 2-butoxyethyltetraethoxyethylether and the like.

Of the organic solvents, at least one selected from hydroxyl-free acetate-based water-soluble solvents and hydroxyl-free glycol ether-based water-soluble solvents is preferable.

When the above organic solvent is contained, the content is adjusted to 10% by mass or more, particularly preferably within the range of 20 to 65% by mass, based on the mass of the curing agent component (II). It is particularly preferable from the viewpoint of miscibility with C), that is, finishing property.

The above organic solvents can be used in appropriate combination according to the purpose of adjusting the viscosity, adjusting the coatability, and the like.

The amount of the curing agent component (II) used is such that the equivalent ratio (NCO/OH) between the hydroxyl group contained in the main component and the isocyanate group contained in the curing agent (II) is usually in the range of 0.05 to 3.0. It is preferably adjusted to be within 0.8 to 2.5 from the viewpoint of water adhesion resistance of the coating film.

<Diluent Component (III)>
The water-based undercoat paint composition of the present invention may contain a water-based diluent (III) from the viewpoint of improving coating workability.

The diluent component (III) contains water as a main component, and also includes ultraviolet absorbers, light stabilizers, polymer fine particles, preservatives, antifoaming agents, curing catalysts, organic solvents, viscosity modifiers, surface modifiers, and the like. Other ingredients such as paint additives commonly used in the preparation of water-based paints may also be included.

By containing the silicone-based surface modifier (F) as the surface modifier, when it is used as an undercoat paint composition, the wettability to the base and the leveling of the paint composition are adjusted to improve the finish and the coating film. It is preferable because it can improve the physical properties and can be expected to suppress foaming and defoam.

Examples of the silicone-based surface conditioner (F) include organopolysiloxanes such as dimethylpolysiloxane, modified silicones obtained by modifying organopolysiloxanes, and the like. Specific examples of modified silicone include alkyl-modified polysiloxane, phenyl-modified polysiloxane, and polyether-modified polysiloxane. These can be used individually or in combination of 2 or more types.

Specifically, for example, dimethylpolysiloxane; methylphenylpolysiloxane; polyether-modified polydimethylsiloxane, polyether-modified siloxane such as polyether-modified dimethylpolysiloxane; polyester-modified dimethylpolysiloxane; alkylsiloxane, etc.; polymethylalkylsiloxane; aralkyl-modified polymethylalkylsiloxane; polyether-modified acrylic group-containing polydimethylsiloxane; polyester-modified acrylic group-containing polydimethylsiloxane; Among them, polyether-modified siloxane is preferred.

The weight average molecular weight of the polyether-modified siloxane is preferably in the range of 400-3,000, more preferably in the range of 500-2,000. The weight average molecular weight is a value in terms of polystyrene measured by gel permeation chromatography (GPC).

Commercially available products can be used as the polyether-modified siloxane, and specific examples include BYK-345, BYK-347, BYK-348, BYK-349, BYK-UV3500, BYK-3510, BYK-3530, and BYK-3570. (above, product names, manufactured by Vic Chemie Japan), TEGO Wet 245, TEGO Wet 250, TEGO Wet 260, TEGO Wet 270, TEGO Wet 280 (above, product names, manufactured by Evonik Degussa), etc. can be mentioned.

Surface conditioners other than those described above include silicone-based, acetylene-based, acrylic-based, fluorine-based, and vinyl-based agents other than the polyether-modified siloxane.

When the silicone-based surface conditioner (F) is contained, the content is in the range of 0.01 to 10% by mass, preferably 0.3 to 2.0% by mass, based on the mass of the diluent component (III). is preferable from the viewpoint of improving the wettability and finish of the water-based undercoat composition.

In particular, as a viscosity modifier, it is preferable to contain an inorganic viscosity modifier (G) from the viewpoint of storage stability.

As the inorganic viscosity modifier (G), those known in the art can be used without limitation. Any processed product may be used. Specific examples include montmorillonite, beidellite, nontronite, saponite, hectorite, stevensite, mica and bentonite. These may be diluted with a diluent medium such as an organic solvent or water.

"Bentone 27", "Bentone 34", "Bentone 38", "Bentone SD-1", "Bentone SD-2", "Bentone SD-3", "Bentone 52", "Bentone 57" ( All of the above are manufactured by Rheox, trade names), "Tixogel VP", "Tixogel TE", "Tixogel UN", "Tixogel EZ100", "Tixogel MP100", "Tixogel MP250" (all of these are manufactured by Sud Chemical, products name), “Claytone 40”, “Claytone 34”, “Claytone HT”, “Claytone APA”, “Claytone AF”, “Claytone HY” (all of these are manufactured by Southern Clay Products, trade names), “Aerosil RX200” , “Aerosil R812”, “Aerosil R805”, “Aerosil RY200”, “Aerosil R202” (all of these are manufactured by Nippon Aerosil Co., Ltd., product names), “Laponite RD”, “Laponite RDS” (product names, BYK Chemie company).

When the diluent component (III) contains the inorganic viscosity modifier (G), its content is preferably 0.1 to 3.0% by mass based on the mass of the diluent component (III). is preferably in the range of 0.3 to 2.0% by mass from the viewpoint of the finish of the water-based undercoat composition.

When the diluent component (III) is used, the amount used is preferably 30 to 400 parts by mass based on 100 parts by mass of the resin solid content contained in the main component (I) from the viewpoint of coating workability and finish. can be in the range of 50 to 150 parts by weight.

The water-based undercoat paint composition of the present invention comprises a base component (I) containing the hydroxyl group-containing acrylic resin (A) and the pigment (B), a curing agent component (II), and optionally a diluent component (III). It is a multi-component water-based base coat composition containing these and can be easily adjusted by mixing them immediately before use.

A coated article having a cured coating film on the object to be coated can be obtained by applying the aqueous undercoat composition of the present invention thus obtained onto the object to be coated and curing the composition.

The water absorption rate of the coating film obtained from the water-based base coating composition of the present invention can be less than 10%, preferably in the range of 0.1 to less than 10% from the viewpoint of water adhesion resistance. especially desirable.

In this specification, the water absorption of the coating film is measured as follows.

A sample is uniformly coated on a polypropylene plate (300×100×5 mm) so that the dry film thickness becomes 40 μm, and forcedly dried at 60° C. for 30 minutes to obtain a coating film. After that, a free coating film was cut from the coating film in a 3 cm square at an arbitrary location except for a range of 1 cm from the end, immersed in deionized water at 20 ° C. for 24 hours, and then wiped off water droplets on the surface. Weigh quickly and measure the water absorption according to the following formula.

Water absorption (%) = [(B - A) / A] x 100
However, A: mass (g) of free coating film before immersion in water B: mass (g) of free coating film after immersion in water.

The substrate to be coated with the water-based base coating composition of the present invention is not limited, but examples thereof include substrates made of metals, plastics, etc. Specific examples include automobiles, motorcycles, trucks, and the like. It is suitably applied to coating of vehicles and parts such as construction machines and trains, or repair coating.

<Repair painting method>
Although the water-based undercoat paint composition of the present invention is not particularly limited, it can be suitably used, for example, in the repair coating method described below.

In the damaged part of the painted body,
(1) a step of applying the multi-component water-based undercoat paint composition of the present invention to form a surface treatment layer;
(2) a step of drying and polishing the formed base treatment layer;
(3) A step of applying a repair colored base coat paint composition to the ground surface treatment layer to form a coating film can be included.

(1) Step of forming a surface treatment layer The water-based undercoat paint composition of the present invention is first subjected to cleaning, sanding with sandpaper, etc., in advance, centering on the damaged part of the coated body and its surroundings, and if necessary, applying putty. After putty filling with the composition, the aqueous basecoat composition of the present invention can be applied as a primer/surfacer. The composition of the present invention can be applied using a conventionally known method such as spray coating. When the putty is applied, it is preferable to dry it and then polish the surface of the putty.

(2) The step of drying and polishing the base treatment layer Examples of methods for drying the water-based undercoat paint composition of the present invention include normal temperature drying and forced drying, and this drying step hardens to the inside of the coating film. can be done. In the case of normal temperature drying, specifically, it is left at room temperature (for example, 5 to less than 40 ° C.) for 5 hours or more, or in the case of forced drying, 40 to 120 ° C. for 5 to 60 minutes, preferably 20 to It can be dried by heating for 40 minutes. In the case of the forced drying, the film may be set (still) at room temperature for 2 to 30 minutes before heat curing from the viewpoint of finish. For drying, for example, a blower or the like may be used.

The film thickness of the water-based undercoat composition (primer/surfacer) to be obtained is preferably 8 to 500 μm, more preferably 10 to 150 μm, in terms of dry film thickness in consideration of subsequent polishing.

As a method of polishing, for example, water-resistant paper, sandpaper, or the like can be used. Further, water sanding may be performed using waterproof paper, or polishing may be performed sequentially with a compound for rough polishing and a compound for finish polishing.

(3) Step of forming a colored base coating film In order to form a colored base coating film, for example, a colored base coating composition can be used.

As top coating compositions such as colored base coating compositions and clear coating compositions, conventionally known compositions can be used without particular limitation. etc., as a main component, block polyisocyanate, polyisocyanate, melamine resin or epoxy resin as a curing agent, or lacquer paint containing cellulose acetate butyrate-modified acrylic resin as a main component can be suitably used. Furthermore, paint additives such as pigments, cellulose derivatives, additive resins, ultraviolet absorbers, light stabilizers, surface conditioners and curing catalysts may be contained as necessary. The form of the topcoat composition may be organic solvent-based, water-based, powder, or the like.

Since the aqueous undercoat paint composition of the present invention is excellent in coating workability and topcoat suitability, after applying the undercoat paint composition, the topcoat paint composition is applied only with a colored base paint. It can be painted with a single coat or can be overcoated with a two coat finish using a pigmented base coat and a clear coat. In particular, by coating a water-based paint or a high solids type paint as a topcoat paint composition on the paint film layer obtained from the water-based undercoat paint composition of the present invention, an all-water-based paint system or an environmentally friendly paint system can be obtained. It can be a coating system, and it is possible to maintain the appearance of the substrate surface for a long period of time while giving consideration to odor, the human body, and the environment.

As the topcoat paint composition for repair that can be recoated, the above-mentioned paints known per se can be used, and water-based or high solid content type paint compositions are preferable, and these are suitable for the surface of the substrate. Depending on the type, coating environment, etc., each may be used alone or in combination of two or more.

Specifically, it is preferable to use a colored base coating composition for repair that contains a pigment as at least a part of its components from the viewpoint of the substrate hiding property and finish, and the colored base coating composition for repair is water-soluble. A colored aqueous base coat paint composition containing a resin and/or a water-dispersible resin, a coloring pigment and/or a luster pigment is preferred.

Moreover, after applying the colored water-based base coat paint composition for repair, the top clear may be applied.

When the paint of the present invention is used for repair painting of automobiles, etc., after forming a colored base paint film on the paint film obtained from the water-based undercoat paint composition, or if necessary, a top clear paint film is formed. Polishing may be performed at any time after polishing.

As described above, the coating film obtained by coating using the multi-component water-based undercoat paint composition of the present invention has excellent adhesion, especially water-resistant adhesion, and the topcoat finish after topcoat is also good. can form a thin film.

The present invention will be described in more detail below with reference to examples. "Parts" and "%" indicate "mass parts" and "mass%" unless otherwise specified.

(Production Example 1) Production of hydroxyl group-containing acrylic resin 300 parts of deionized water and 1 part of sodium dodecylbenzenesulfonate were charged into a 2-liter glass reaction vessel equipped with a stirrer, thermometer, and cooling tube, and the air inside was removed. After purging with nitrogen, the internal temperature was raised to 82° C. with stirring to dissolve. In a separate vessel, 320 parts of deionized water, 40 parts of sodium dodecylbenzenesulfonate and 2 parts of ammonium persulfate were added and stirred well. A monomer mixture consisting of 152 parts of butyl methacrylate, 192 parts of 2-hydroxyethyl methacrylate and 32 parts of acrylic acid was added and stirred to form an emulsion, which was continuously added dropwise over 4 hours to the previous reactor.
After completion of the dropwise addition, the mixture was further stirred at 82° C. for 2 hours and then cooled to 40° C. to obtain an aqueous dispersion of hydroxyl group-containing acrylic resin (A-1) having an average particle size of 150 nm and a solid content of 50%. The hydroxyl group-containing acrylic resin had a hydroxyl value of 103 mgKOH/g and a glass transition temperature of 62°C.

(Production Example 2) Production of hydroxyl group-containing acrylic resin 300 parts of deionized water and 1 part of sodium dodecylbenzenesulfonate were charged into a 2-liter glass reaction vessel equipped with a stirrer, thermometer, and cooling tube, and the air inside was removed. After purging with nitrogen, the internal temperature was raised to 82° C. with stirring to dissolve. 320 parts of deionized water, 20 parts of sodium dodecylbenzenesulfonate, and 1 part of ammonium persulfate were added to a separate container and stirred well. A monomer mixture consisting of 120 parts of butyl methacrylate, 152 parts of 2-hydroxyethyl methacrylate and 8 parts of glycidyl methacrylate was added and stirred to form an emulsion, which was continuously added dropwise over 2 hours to the reaction vessel.
After completion of the dropwise addition, after aging at the same temperature for 30 minutes, 160 parts of deionized water, 20 parts of sodium dodecylbenzenesulfonate and 1 part of ammonium persulfate were added in a separate container and thoroughly stirred. , n-butyl methacrylate 32 parts, 2-hydroxyethyl methacrylate 40 parts and acrylic acid 32 parts.
After completion of dropping, the mixture was aged at the same temperature for 2 hours and then cooled to 40° C. to obtain an aqueous dispersion of hydroxyl group-containing acrylic resin (A-2) having an average particle diameter of 150 nm and a solid content of 50%. The hydroxyl group-containing acrylic resin had a hydroxyl value of 103 mgKOH/g and a glass transition temperature of 62°C.

(Production Examples 3 to 5) Production of hydroxyl-containing acrylic resin -5) was obtained. Table 1 also shows the hydroxyl value and glass transition temperature of the acrylic resin.

(Production Example 6) Production of Curing Agent Component A commercially available polyisocyanate compound No. 2 having an isocyanate group content of 21%. 68 parts of silane coupling agent No. 1 (solid content: 100%); As No. 1, 2 parts of 3-glycidoxypropyltrimethoxysilane and 30 parts of dipropylene glycol dimethyl ether (a water-soluble solvent having no hydroxyl group) were added and stirred for 30 minutes to obtain a curing agent having a solid content of 70% (B- 1) was produced.
(Production Examples 7 to 14) Production of Curing Agent Component In Production Example 6, the curing agent ( B-2) to (B-9) were obtained. Table 2 shows the formulations of Production Examples 6 to 14.

Polyisocyanate compound No. in the table. 1-3 and *1-3 refer to the following.

Polyisocyanate compound no. 1: A commercially available polyisocyanate compound having an isocyanate group content of 21% (a hexamethylene diisocyanate compound having a sulfonic acid group in the molecule).

Polyisocyanate compound no. 2: A commercially available polyisocyanate compound having an isocyanate group content of 14% (a hexamethylene diisocyanate compound having a sulfonic acid group in the molecule).

Polyisocyanate compound no. 3: A commercially available polyisocyanate compound having an isocyanate group content of 8% (a hexamethylene diisocyanate compound having a sulfonic acid group in the molecule).

(*1) Silane coupling agent No. 1:3-glycidoxypropyltrimethoxysilane,
(*2) Silane coupling agent No. 2: 2-(3,4-epoxycyclohexyl)methyltrimethoxysilane,
(*3) Silane coupling agent No. 3: 3-mercaptopropyltrimethoxysilane.

(Production Example 15) Production of pigment paste To 100 parts of deionized water, 50 parts of titanium white ("JR-701", trade name, manufactured by Tayca), carbon black ("MA-7", trade name, Mitsubishi Chemical) ) 2 parts, 200 parts of calcium carbonate as an extender pigment ("Tancal 200", trade name, manufactured by Adachi Lime Industry Co., Ltd.), 30 parts of antirust pigment ("Ruston RP" trade name, manufactured by Daiichi Sangyo Kagaku Kogyo Co., Ltd.) and 5 parts of a dispersing agent (“DISPERBYK-187” trade name, manufactured by BYK-Chemie) were added, stirred and mixed with a disper for 15 minutes, and further dispersed with a sand mill for 30 minutes. The resulting pigment paste P1 had a grain gauge of 40 μm or less.

(Production Example 16) Production of Pigment Paste In Production Example 15, the extender pigment "Tancal 200" was mixed with barita ("Barium Sulfate 100", trade name, manufactured by Sakai Chemical Industry Co., Ltd., precipitated barium sulfate, average particle size 8 μm). Pigment paste P2 was obtained in the same manner except that The resulting pigment paste had a particle gauge of 40 μm or less.

(Production Example 17) Production of Pigment Paste A pigment paste is produced in the same manner as in Production Example 15, except that talc ("Talc SSS", manufactured by Nippon Talc Co., Ltd., average particle size: 12.0 μm) is used instead of the extender pigment "Tancal 200". P3 was obtained. The resulting pigment paste had a particle gauge of 40 μm or less.

(Production Example 18) Production of Pigment Paste Pigment paste P4 was obtained in the same manner as in Production Example 15, except that titanium white (“JR-701”) was used instead of “Tancal 200” of the extender pigment. The resulting pigment paste had a particle gauge of 40 μm or less.

(Production Example 19) Production of Pigment Paste Pigment paste P5 was prepared in the same manner as in Production Example 15, except that the extender pigment "Tancal 200" was changed to clay ("NN Kaolin Clay", trade name, manufactured by Takehara Chemical Industry Co., Ltd.). Obtained. The resulting pigment paste had a particle gauge of 40 μm or less.

(Production Example 20) Production of Pigment Paste In Production Example 15, 200 parts of the extender pigment "Tancal 200" was replaced with 100 parts of "Tancal 200", silica ("CM Silica Flower M", trade name, manufactured by Takeori Kogyosho Co., Ltd.). A pigment paste P6 was obtained in the same manner except that 50 parts of the pigment and 50 parts of mica ("SYA-21R", trade name, manufactured by Yamaguchi Mica Co., Ltd.) were used. The resulting pigment paste had a particle gauge of 50 μm or less.

(Production Example 21) Production of diluent To 99 parts of deionized water, a silicone-based surface conditioner ("BYK-348", trade name, manufactured by BYK Chemie, polyether-modified siloxane, weight average molecular weight 1,500) , solid content 100% by mass) and 0.5 part of an inorganic viscosity modifier (“LAPONITE RD” trade name, manufactured by BYK-Chemie, synthetic layered silicate) are added, and stirring is continued for 10 minutes. to make a diluent.

(Examples 1 to 18 and Comparative Examples 1 to 6)
200 parts by mass (solid content: 100 parts by mass) of each acrylic resin obtained in the above production example and 30 parts by mass of propylene glycol mono-n-propyl ether (*4) were stirred for 30 minutes with the formulation shown in Table 3, and then The pigment paste was added and stirring continued for an additional hour. A preservative (*5) and an antifoaming agent (*6) were added in this order, and after adjusting the pH of the paint to 8.0 with triethylamine, stirring was continued for an additional hour to prepare each main component. .

The main agent component prepared as described above and the curing agent component obtained in the production example were mixed by hand stirring in the types and amounts (NCO/OH equivalent ratio = 1.5) shown in Tables 3 to 5, and the above prepared A diluent component was added in the amounts shown in Tables 3 to 5, and the mixture was further stirred to prepare each aqueous base coating composition.

* in Tables 3 to 5 indicates the following.

(*4) organic solvent: propylene glycol mono-n-propyl ether,
(*5) Antiseptic: “Delltop 33”, trade name, manufactured by Takeda Pharmaceutical Company, Ltd.,
(*6) Antifoaming agent: "BYK-024", trade name, manufactured by BYK-Chemie, a water-based silicone antifoaming agent.

(*7) Other resin (H) No. 1: acrylic resin, water-soluble hydroxyl-containing acrylic resin (methyl methacrylate/2-hydroxyethyl methacrylate/n-butyl acrylate/acrylic acid), glass transition temperature (Tg) = 5 ° C., hydroxyl value = 52 mgKOH/g, acid 50 mg KOH/g, 50% resin solids.

(*8) Other resin (H) No. 2: Polyester resin, water-soluble polyester resin, (1,6-hexanediol/neopentyl glycol/hexahydrophthalic anhydride/adipic acid system) static glass transition temperature (Tg) = 5°C, hydroxyl value = 50 mgKOH/g, Acid value 30 mgKOH/g, resin solid content 40%, mixed solvent of propylene glycol mono-n-propyl ether and deionized water.

(*9) Viscosity modifier: "SN Thickener 612", trade name, manufactured by San Nopco, urethane associative viscosity modifier, resin solid content 40%,
(*10) Viscosity modifier: "ACRYSOL ASE-60", trade name, manufactured by Dow Chemical Co., alkali-swelling polyacrylic acid-based viscosity modifier, resin solid content 28%.

(Preparation of test plate)
A 70×150×0.8 mm electrodeposition coated plate coated with an epoxy resin electrodeposition paint was polished with #240 paper, and each water-based undercoat composition was applied as a primer surfacer onto the coated plate where the steel plate was partially exposed. , dried at 60°C for 30 minutes, and water-polished with #400 paper. On top of this, "Retan WB Eco EV 202 Sunmetallic" (manufactured by Kansai Paint Co., Ltd., colored base coat paint for water-based repair) was spray-coated to a dry film thickness of 15 μm, allowed to stand for 10 minutes, and then heated at 60° C. for 10 minutes. After forced drying, "Retan PG Eco HS (High Solid) Clear (Q)" (manufactured by Kansai Paint Co., Ltd., urethane curing type, eco-friendly clear paint) was spray-painted so that the dry film thickness was 50 μm. C. for 20 minutes to obtain each test plate. Each test coated plate thus obtained was subjected to the following performance test.

The water absorption of the coating films obtained from each of the waterborne undercoat paint compositions of Examples 1 to 18 is all less than 10%, and the water absorption of the coating films obtained from each of the waterborne undercoat paint compositions of Comparative Examples 1 to 6 is All were 10% or more. The results are shown in Tables 3-5.

(performance test)
Test item 1: Adhesion 100 squares of 2 mm x 2 mm are made on the coated surface of each test plate according to JIS K 5600-5-6 (1990), an adhesive tape is attached to the surface, and it is rapidly peeled off. The residual state of the cross-cut coating film after the coating was examined, and the adhesion was evaluated according to the following criteria.

S: Remaining number/Total number = 100/100 with no edge chipping A: Remaining number/Total number = 100/100 with edge chipping B: Remaining number/Total number = 99 to 90/100 C: remaining number/total number=89 or less/100.

Test item 2: Water resistance Each test coated plate was immersed in a constant temperature water bath at 40°C for 10 days, taken out, and left to stand for 1 hour.

S: no abnormality,
A: A very small amount, although there are glossiness, blisters, and cracks, but at a level that is not a problem for practical use.
B: Partially glossy, blistered, and cracked,
C: Glossy spots, blisters, and cracks are present on the entire surface.

Test item 3: Water adhesion resistance Each test coated plate was immersed in a constant temperature water bath at 40°C for 10 days and then taken out. The post-coating surface was evaluated.

S: no peeling,
A: There is partial peeling,
B: There is peeling on the entire surface,
C: There is peeling at the time of cross cutting.

Test Item 4: Abrasiveness After coating each primer surfacer, it was evaluated by the presence or absence of clogging of the paper when it was water-polished with #400 paper.

S: good without clogging;
A: Although there is a very small amount of clogging, there is no problem in practical use,
B: Slight clogging,
C: There is clogging.

Test Item 5: Solvent Resistance After the primer surfacer coating, 0.5 ml of xylol was dropped on the coated surface, left to stand for 10 minutes, and then the xylol was wiped off to evaluate the softened state of the coating film.

S: no abnormality,
A: Very little softening,
B: slightly softened,
C: Remarkably softened.

Test item 6: Topcoat finish The finish of each test coated plate was visually observed.

S: very good,
A: A very small amount of Chijimi is generated, but there is no problem in practical use.
B: Chijimi occurs partially,
C: Chijimi occurs on the entire surface.

Claims (8)

A multi-component water-based undercoat composition comprising a main component (I) and a curing agent component (II),
The main ingredient component (I) contains a hydroxyl group-containing acrylic resin (A) having a hydroxyl value in the range of 15 to 180 mgKOH/g and a glass transition temperature in the range of 30 to 70° C. and a pigment (B),
The curing agent component (II) contains a polyisocyanate compound (C) having an isocyanate group content of 10% by mass or more, and the main agent (I) and/or the curing agent (II) component contains a silane coupling agent (D). , A multi-component water-based undercoat composition in which the content of component (D) is in the range of 0.01 to 10% by mass based on the mass of curing agent component (II). The pigment (B) contains at least one type of extender pigment selected from calcium carbonate, clay, talc, mica, baryta and silica, and the content thereof is contained in the main component (I). Resin solid content 100 The multi-component water-based undercoat composition according to claim 1, which is 30 to 350 parts by mass based on the parts by mass. 3. The multi-component water-based undercoat composition according to claim 1, wherein said curing agent component (II) contains a water-soluble solvent (E) having no hydroxyl group. The hydroxyl group-containing acrylic resin (A) contains 3 to 45% by mass of the hydroxyl group-containing polymerizable unsaturated monomer (a) based on the total amount of copolymerization components, and the glass transition temperature of the homopolymer is 30 ° C. or higher. 40 to 85% by mass of the unsaturated monomer (b) and 0 to 25% by mass of the other polymerizable unsaturated monomer (c) are copolymerized components of the multicomponent type according to any one of claims 1 to 3. Aqueous primer composition. 5. The multi-component type according to any one of claims 1 to 4, wherein the main component (I) further contains a resin (H) having a glass transition temperature of -10 ° C. or higher and lower than 30 ° C. and / or a viscosity modifier. Aqueous base coat composition. A multi-component system in which a water-based diluent component (III) is further combined with the main agent component (I) and the curing agent component (II), wherein the diluent component (III) is 6. The multi-component water-based undercoat composition according to any one of claims 1 to 5, further comprising a silicone-based surface control agent (F). 7. The multi-component water-based base coating composition according to claim 6, wherein said diluent component (III) further contains an inorganic viscosity modifier (G). A coating method comprising coating an object to be coated with the multi-component water-based undercoat composition according to any one of claims 1 to 7.