JP7453132B2 - Matte coating composition, coated article, and method for producing coated article - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to matte coating compositions and coated articles, and methods for producing coated articles.

A plurality of coating films having various roles are formed on the surface of a coated object such as a metal base material or a plastic base material. The coating film protects the object to be coated and at the same time imparts design to the object. Patent Documents 1 and 2 disclose coating compositions that exhibit a matte texture.

Special Publication No. 2013-544301 International Publication No. 2016/017778

However, when the coating compositions described in Patent Documents 1 and 2 are used, variations may occur in the gloss of the resulting coating film. In particular, when the shape of the object to be coated is complex, the variation in gloss tends to be large.

An object of the present invention is to provide a matte coating composition that can provide a coating film with small variations in gloss. Another object of the present invention is to provide a coated article having a coating film formed from the above-mentioned coating composition, and a method for producing the same.

The present invention provides the following aspects [1] to [11].
[1]
A matte coating composition comprising a film-forming resin (A), a curing agent (B), a matting agent (C), a viscosity modifier (D) and a non-aqueous solvent (E),
The viscosity modifier (D) includes polymer crosslinked fine particles (D1) and an amide compound (D2),
The polymer crosslinked fine particles (D1) are insoluble in the non-aqueous solvent (E) containing the dissolved film-forming resin (A), and are dispersed in the matte coating composition,
The viscosity η ₁ after 1.5 minutes of coating, measured by a cone-plate viscometer at 20°C and a shear rate of 0.1 s ^-1 (/s), is 26,000 mPa・s or more and 72,000 mPa・s or less A matte paint composition.
[2]
60 degree specular gloss G60 _H of the coating film obtained by applying the matte coating composition on a horizontal surface and curing after 1 minute;
The 60 degree specular gloss G60 _V of the coating film obtained by applying the above-mentioned matte coating composition on a vertical surface and curing it after 7 minutes is as follows:
| _{G60H -G60V} |<10
The matte coating composition according to [1] above, which satisfies the following relationship.

[3]
The content of the polymer crosslinked fine particles (D1) is 0.5 parts by mass or more and 5 parts by mass based on 100 parts by mass of the total solid content of the film-forming resin (A) and the curing agent (B). The matte coating composition according to [1] or [2] above, which is as follows.

[4]
The content of the amide compound (D2) is 0.05 parts by mass or more and 2.0 parts by mass based on 100 parts by mass of the total solid content of the film-forming resin (A) and the curing agent (B). The matte coating composition according to any one of [1] to [3] above, which is as follows.

[5]
The matte coating composition according to any one of [1] to [4] above, wherein the film-forming resin (A) contains a hydroxyl group-containing resin.

[6]
The matte coating composition according to any one of [1] to [5] above, wherein the curing agent (B) contains an isocyanate compound.

[7]
The matte coating composition according to any one of [1] to [6] above, wherein the matting agent (C) contains silica.

[8]
The matte coating composition according to any one of [1] to [7] above, wherein the solid content ratio is 40% by mass or more and 55% by mass or less.

[9]
The matte coating composition according to any one of [1] to [8] above, wherein the viscosity η ₀ measured by the flow cup method at 23° C. is 21 seconds or more and 35 seconds or less.

[10]
The object to be coated,
a colored coating film formed on the object to be coated;
A matte clear coating film formed on the colored coating film,
The coated article, wherein the matte clear coating film is formed from the matte coating composition according to any one of [1] to [9] above.

[11]
a step of coating a colored paint composition on an object to be coated to form an uncured colored paint film;
a step of coating the matte coating composition according to any one of [1] to [9] above on the uncured colored coating film to form an uncured matte clear coating film;
A method for manufacturing a coated article, comprising a curing step of curing the uncured colored coating film and the uncured matte clear coating film.

According to the present invention, a matte coating composition is provided that allows a coating film with small variations in gloss to be obtained. According to the present invention, there is also provided a coated article having a coating film formed from the above-mentioned coating composition, and a method for manufacturing the same.

FIG. 1 is a cross-sectional view schematically showing a coated article according to an embodiment of the present invention. 1 is a flowchart of a method for manufacturing a coated article according to an embodiment of the present invention.

A matte coating composition usually contains a matting agent (typically, silica particles). The matting agent forms minute irregularities on the surface of the paint film, giving it a matte texture. It is thought that the variation in gloss is affected by the difference in the degree of sedimentation of this matting agent. Particularly in the case of objects to be coated that have a complicated three-dimensional shape, such as automobile bumpers, the difference in the degree of settling of the matting agent between coated parts tends to be large. Moreover, in a heating furnace for curing a coating film, the rate of temperature increase of the object to be coated may vary depending on the location. In the case of a coated object having a complicated three-dimensional shape, the variation in temperature increase rate tends to be particularly large. Therefore, there is a difference in the time until hardening, and the difference in the degree of settling of the matting agent becomes even larger.

Therefore, at least two types of viscosity modifiers are used in combination to control the viscosity of the coating composition immediately after coating within a certain range. As a result, differences in the degree of settling of the matting agent caused by differences in the coated area or temperature increase rate are reduced, and variations in gloss are suppressed.

Specifically, polymer crosslinked fine particles (D1) and an amide compound (D2) were used as viscosity modifiers, and a cone-plate type test was carried out under the conditions of 20°C and a shear rate of 0.1 s ^-1 (/sec). The viscosity (hereinafter referred to as coating viscosity) η ₁ measured by a viscometer after 1.5 minutes (1 minute and 30 seconds) of painting is set to 26,000 mPa・s or more and 72,000 mPa・s or less .

When the coating viscosity η ₁ is 26,000 mPa·s or more, excessive flow of the coating film is suppressed, and the matting agent becomes difficult to settle. Therefore, even if the object to be coated has a horizontal and vertical coating surface, or even if there is a difference in the rate of temperature rise of the coating film, the difference in the degree of settling of the matting agent will be small. As a result, variations in gloss are suppressed. In addition, sagging of the paint film is also suppressed. When the coating viscosity η ₁ is 72,000 mPa·s or less, the coating film is leveled and the appearance is improved.

The coating viscosity η ₁ is preferably 26,500 mPa·s or more, more preferably 27,000 mPa·s or more. The coating viscosity η ₁ is preferably 71,000 mPa·s or less, more preferably 70,000 mPa·s or less.

The polymer crosslinked fine particles (D1) are polymeric organic compounds and have a crosslinked structure within the particles. The polymer crosslinked fine particles (D1) are insoluble in the solvent and are uniformly dispersed in the matte coating composition. Therefore, interaction between the particles is difficult, and the viscosity of the matte paint composition (hereinafter referred to as paint viscosity η ₀ ) does not increase significantly. However, when the density of the polymer crosslinked fine particles (D1) in the matte coating composition increases due to volatilization of at least a portion of the solvent, the viscosity of the polymer crosslinked fine particles (D1) decreases due to interactions between the particles. to rise rapidly. That is, the polymer crosslinked fine particles (D1) have the effect of increasing the viscosity (application viscosity) of the matte coating composition after coating, in which at least a portion of the solvent is volatilized. Furthermore, the viscosity of the coating film during the curing process is maintained high by the polymer crosslinked fine particles (D1).

The amide compound (D2) has one or more amide groups in the molecule and easily forms hydrogen bonds within the molecule or with other compounds. Therefore, the amide compound (D2) has the effect of increasing the paint viscosity η ₀ . The amide compound (D2) further contributes to improving the coating viscosity _η1 . In addition, the amide compound (D2) imparts thixotropy to the coating composition.

However, in order to adjust the paint viscosity η ₀ to an appropriate range using only the amide compound (D2), it is necessary to blend the amide compound (D2) in a high proportion. As a result, the proportion of the film-forming resin and curing agent decreases, making it difficult to obtain a high-quality paint film. On the other hand, if only the polymer crosslinked fine particles (D1) are blended, the coating composition will not exhibit sufficient thixotropy, and the matting agent will tend to settle or aggregate. By blending the amide compound (D2) with the polymer crosslinked fine particles (D1) in the matte coating composition, it is possible to obtain a high-quality coating film with less variation in gloss.

According to the matte coating composition according to the present embodiment, variations in gloss on a horizontal painted surface and gloss on a vertical painted surface are suppressed. A matte paint composition was applied on a horizontal surface and cured after 1 minute. 60 degree specular gloss G60 _H of the coating film. A matte paint composition was applied on a vertical surface and cured after 7 minutes. The relationship with the 60 degree specular gloss G60 _V of the coating film is preferably |G60 _H −G60 _V |<10. The 60 degree specular gloss _GH is measured under conditions where gloss tends to be high. On the other hand, the 60 degree specular gloss _GV is measured under conditions where gloss tends to be low. Paint compositions with a difference of less than 10 between 60 degree specular gloss G60 _H and 60 degree specular gloss G60 _V form a coating film with suppressed gloss variation, regardless of the shape of the object to be coated or coating conditions. can do. |G60 _H −G60 _V | is preferably 9 or less, more preferably 8 or less. Typically, the 60 degree specular gloss G60 _H is greater than the 60 degree specular gloss G60 _V.

The 60 degree specular gloss _GH is measured as follows.
First, a paint sample is created. For the coating sample, a matte paint composition was applied using a rotary atomizer (for example, RB-1000 manufactured by ABB) at a temperature of 23°C, a bell rotation speed of 27,000 rpm, and a shaping air of 400 nl (out) and 250 nl (in). , obtained by coating a horizontally installed resin plate (for example, a polypropylene resin plate) under the conditions of a gun speed of 700 mm/sec, a gun pitch of 65 mm, and a separation distance of 17 cm, so that the dry film thickness is 25 μm or more and 30 μm or less. . After painting, the painted sample is left standing at 23° C. for 1 minute while keeping the painted surface horizontal. The coating sample is then heated to 120°C. After the temperature of the coating sample reaches 120° C., it is heated for 20 minutes to cure the coating film. After the obtained cured coating film is allowed to cool to room temperature, the 60 degree specular gloss G60 _H is measured according to JIS Z 8741 specular gloss measurement method.

The coating sample may be a coated object on which a plurality of coating films are formed. In this case, the matte coating composition may be applied onto the uncured coating film.

The 60 degree specular gloss _G60V is measured as follows.
First, a paint sample is created. A paint sample is prepared in the same manner as above. Thereafter, the coating sample is immediately stood vertically and allowed to stand at 23° C. for 7 minutes. Next, the coating sample is heated in the same manner as above to cure the coating film. The 60 degree specular gloss G60 _V of the obtained cured coating film is measured in the same manner as above.

The 60 degree specular gloss G _H and the 60 degree specular gloss G60 _V are not particularly limited, and are appropriately set according to the desired texture and color. The 60 degree specular gloss G _H and the 60 degree specular gloss G60 _V are, for example, about 20% or more and 85% or less.

The coating viscosity η ₁ is measured as follows. The tin plate was coated with a rotary atomizer (for example, RB-1000 manufactured by ABB) at a temperature of 23°C, a bell rotation speed of 27,000 rpm, shaping air of 400 nl (out) and 250 nl (in), and a gun speed of 700 mm/sec. The matte coating composition is electrostatically applied under the conditions of a gun pitch of 65 mm and a separation distance of 17 cm so that the dry film thickness is 25 μm or more and 30 μm or less. Within 1.5 minutes of application, the paint film is scraped from the paint sample and stored in a sealable sample bottle. Within 1 hour after storage, the viscosity of the sample in the sample bottle is measured using a cone-plate viscometer at 20°C and a shear rate of 0.1 s ^-1 (/sec). The application viscosity η ₁ is the average value of the sample viscosities obtained from five different coating samples.

A. Matte coating composition The matte coating composition according to the present embodiment (hereinafter sometimes simply referred to as coating composition) includes a film-forming resin (A), a curing agent (B), a matting agent ( C), a viscosity modifier (D) and a nonaqueous solvent (E). The coating composition may be a two-part type consisting of a solution containing at least the film-forming resin (A) and a solution containing the curing agent (B). These solutions are mixed and used immediately before painting. The matte paint composition according to this embodiment is adjusted to have a viscosity (paint viscosity η ₀ ) suitable for painting.

The method for preparing the coating composition is not particularly limited, and methods known in the art may be used, such as stirring, kneading, or dispersing the above-mentioned materials using a disper, homogenizer, roll, sand grind mill, kneader, etc. can.

During preparation, a varnish containing a film-forming resin (A) and a nonaqueous solvent (E) is prepared, and a curing agent (B), a matting agent (C), and a viscosity modifier (D) are added to this varnish. Additionally, it can be mixed. Thereby, the viscosity modifier (D) can be further uniformly dispersed. Thereafter, a non-aqueous solvent (E) may be further added to adjust the coating viscosity η ₀ . Curing agent (B) may be mixed immediately before use.

The solid content ratio of the coating composition is preferably 40% by mass or more and 55% by mass or less. This makes it easier to adjust the paint viscosity η ₀ and the coating viscosity η ₁ to desired ranges. The solid content ratio of the coating composition is more preferably 44% by mass or more, and even more preferably 47% by mass or more. The solid content ratio of the coating composition is more preferably 53% by mass or less, and even more preferably 52% by mass or less. The solid content of the coating composition is all components excluding diluent components such as the non-aqueous solvent (E).

The coating viscosity η ₀ measured by the flow cup method at 23° C. is preferably 21 seconds or more and 35 seconds or less. When the paint viscosity η ₀ is within the above range, coating can be performed with a high degree of freedom without restrictions on the coating equipment that can be used, coating conditions, etc., and a coating film with no uneven coating can be easily obtained. When the coating composition contains the amide compound (D2) together with the polymer crosslinked fine particles (D1), the coating viscosity η ₀ can be easily adjusted to the above range. In the case of a two-component paint, the paint viscosity η ₀ is measured immediately after mixing the solution containing the film-forming resin (A) and the solution containing the curing agent (B).

The paint viscosity η ₀ is more preferably 22 seconds or more, and even more preferably 23 seconds or more. The paint viscosity η ₀ is more preferably 34 seconds or less, and even more preferably 33 seconds or less. The paint viscosity η ₀ is measured in a No. 4 Ford cup at 23° C. in accordance with “3. Flow cup method” of JIS K5600-2-2:1999. The paint viscosity η ₀ is the average value of the viscosities of five different paint compositions with the same composition.

[Viscosity modifier (D)]
The viscosity modifier (D) contains at least polymer crosslinked fine particles (D1) and an amide compound (D2). By using these two types of viscosity modifiers together, it is possible to increase the coating viscosity while adjusting the viscosity of the coating composition to a range suitable for coating.

The ratio of the polymer crosslinked fine particles (D1) and the amide compound (D2) is appropriately set depending on the coating viscosity η ₀ and the coating viscosity η ₁ . The ratio (=D1/D2) between the polymer crosslinked fine particles (D1) and the amide compound (D2) may be, for example, 1.0 or more, 1.2 or more, or 1.5 or more. It's fine. D1/D2 may be, for example, 20 or less, 15 or less, or 12 or less.

(Polymer crosslinked fine particles (D1))
The polymer crosslinked fine particles (D1) are polymeric compounds containing carbon-carbon bonds in the main chain and have a crosslinked structure within the molecule. The polymer crosslinked fine particles (D1) are insoluble in a non-aqueous solvent (E) (hereinafter sometimes referred to as a resin solution) containing the dissolved film-forming resin (A), and have a particle shape. It can be uniformly dispersed in the coating composition while maintaining its properties. The polymer crosslinked fine particles (D1) are, for example, (meth)acrylic resin.

The polymer crosslinked fine particles (D1) are prepared by polymerizing raw material monomers. The polymerization method is not particularly limited. Among these, emulsion polymerization is preferred. The polymerization may be a one-step polymerization or a multi-step polymerization.

The polymer crosslinked fine particles (D1) are prepared, for example, as follows.
The ethylenically unsaturated monomer (D11) and the crosslinkable monomer (D12) are emulsion polymerized in an aqueous solvent by a known method to obtain an emulsion containing crosslinked fine polymer particles. Thereafter, water contained in the emulsion is removed. Thereby, polymer crosslinked fine particles (D1) are obtained. Removal of water is carried out, for example, by substitution of an aqueous solvent with an organic solvent, azeotropy, centrifugation, filtration, or drying. When replacing the aqueous solvent with an organic solvent, the polymer crosslinked fine particles (D1) are obtained in a state dispersed in the organic solvent.

Emulsion polymerization can be carried out using known emulsifiers and/or dispersants. Among these, emulsifiers having amphoteric ionic groups are preferred, since crosslinked fine polymer particles (D1) with a uniform particle size can be easily obtained. The particle size of the polymer crosslinked fine particles (D1) may affect the paint viscosity and the application viscosity.

A typical example of the ethylenically unsaturated monomer (D11) is an alkyl ester of (meth)acrylic acid. Examples of alkyl esters of (meth)acrylic acid include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and 2-(meth)acrylate. Ethylhexyl is mentioned. These may be used alone or in combination of two or more. In this specification, "(meth)acrylic" is a concept that includes both acrylic and methacrylic.

As the ethylenically unsaturated monomer (D11), other monomers having an ethylenically unsaturated bond that can be copolymerized with the above alkyl ester of acrylic acid or methacrylic acid may be used. Other monomers include, for example, styrene, α-methylstyrene, vinyltoluene, t-butylstyrene, ethylene, propylene, vinyl acetate, vinyl propionate, acrylonitrile, methacrylonitrile, dimethylaminoethyl (meth)acrylate. can be mentioned. These may be used alone or in combination of two or more.

Typically, the crosslinkable monomer (D12) is a monomer (D12a) having two or more radically polymerizable ethylenically unsaturated bonds in the molecule, and a group having mutually reactive groups. A combination of two types of ethylenically unsaturated group-containing monomers (D12b) is mentioned. The monomer (D12a) and the monomer combination (D12b) are used alone or in combination.

Examples of the monomer (D12a) include polymerizable unsaturated monocarboxylic acid esters of polyhydric alcohols, polymerizable unsaturated alcohol esters of polybasic acids, and aromatic compounds having two or more vinyl groups. .

Specifically, the monomer (D12a) includes ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, trimethylolpropane triacrylate, Trimethylolpropane trimethacrylate, 1,4-butanediol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol dimethacrylate, Pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, glycerol dimethacrylate, glycerol diacrylate, glycerol allyloxy dimethacrylate, 1,1,1-trishydroxymethylethane diacrylate, 1,1,1-trishydroxymethylethane triacrylate, 1,1,1-trishydroxymethylethane dimethacrylate, 1,1,1-trishydroxymethylethane trimethacrylate, 1,1,1-trishydroxymethylpropane diacrylate, 1,1,1-trishydroxymethylpropane trimethacrylate Acrylate, 1,1,1-trishydroxymethylpropane dimethacrylate, 1,1,1-trishydroxymethylpropane trimethacrylate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellidate, diallyl terephthalate, diallyl phthalate and Divinylbenzene is mentioned. These may be used alone or in combination of two or more.

Examples of the monomer combination (D12b) include a combination of a glycidyl group-containing ethylenically unsaturated monomer and a carboxyl group-containing ethylenically unsaturated monomer, and a combination of a hydroxyl group-containing ethylenically unsaturated monomer and an isocyanyl group-containing ethylenically unsaturated monomer. A combination with an ethylenically unsaturated monomer containing a nerto group may be mentioned.

Examples of the glycidyl group-containing ethylenically unsaturated monomer include glycidyl methacrylate and glycidyl acrylate. Examples of the carboxyl group-containing ethylenically unsaturated monomer include acrylic acid, methacrylic acid, and crotonic acid. Examples of the hydroxyl group-containing ethylenically unsaturated monomer include 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, allyl alcohol, and methalyl alcohol. Can be mentioned. Examples of the isocyanate group-containing ethylenically unsaturated monomer include vinyl isocyanate and isoprobenyl isocyanate. These may be used alone or in combination of two or more.

As a raw material monomer for the polymer crosslinked fine particles (D1), a monomer (D13) having a functional group capable of reacting with a crosslinking agent may also be used. The monomer (D13) typically includes a carboxyl group-containing monomer, a hydroxyl group-containing monomer, and a nitrogen-containing monomer. Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, allyl alcohol, and methacrylic alcohol. Examples of the nitrogen-containing monomer include acrylic acid amide and methacrylic acid amide. These may be used alone or in combination of two or more.

The polymer crosslinked fine particles (D1) may be prepared by a method other than the above, for example, by dispersion polymerization in a non-aqueous solvent system.

The polymer crosslinked fine particles (D1) may be a commercially available product. Commercially available polymer crosslinked fine particles (D1) include, for example, Setalux 1801 SA-53 and Setalux 1850 SA-50 (manufactured by Allnex).

The polymer crosslinked fine particles (D1) may have a uniform structure or may have a multilayer structure.

The content of the polymer crosslinked fine particles (D1) is based on 100 parts by mass of the total solid content (hereinafter sometimes referred to as resin solid content) of the film-forming resin (A) and the curing agent (B). , preferably 0.5 parts by mass or more and 5 parts by mass or less. This makes it easier to obtain a desired coating viscosity. The content of the polymer crosslinked fine particles (D1) is preferably 1.0 parts by mass or more, more preferably 1.5 parts by mass or more, based on 100 parts by mass of the resin solid content. The content of the polymer crosslinked fine particles (D1) is preferably 4.0 parts by mass or less, more preferably 3 parts by mass or less, based on 100 parts by mass of the resin solid content.

The particle size of the polymer crosslinked fine particles (D1) is not particularly limited. The average particle diameter of the polymer crosslinked fine particles (D1) is, for example, 10 nm or more and 40,000 nm or less. The average particle diameter of the polymer crosslinked fine particles (D1) may be 15 nm or more, and may be 20 nm or more. The average particle diameter of the polymer crosslinked fine particles (D1) may be 5,000 nm or less, 1,000 nm or less, or 500 nm or less. The average particle diameter of the polymer crosslinked fine particles (D1) is the 50% average particle diameter (D50) in a volume-based particle size distribution using a laser diffraction/scattering type particle size distribution measuring device.

(Amide compound (D2))
The amide compound (D2) is a compound having one or more amide groups in the molecule. Among these, the amide compound (D2) preferably contains a fatty acid amide compound.

Examples of fatty acid amide compounds include saturated fatty acid monoamides such as palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide; unsaturated fatty acid amides such as oleic acid amide; methylol stearic acid amide, and methylol behenic acid amide. Methylolamides such as methylene bislauric acid amide, methylene bishydroxystearic acid amide, methylene bis oleic acid amide, ethylene bis isostearic acid amide, hexamethylene bis hydroxystearic acid amide, butylene bis hydroxystearic acid amide, ethylene bis oleic acid Bisamides such as amide, ethylene biserucic acid amide, hexamethylene bis oleic acid amide, m-xylylene bis stearic acid amide; and fatty acid ester amides such as ethanolamine distearate. These may be used alone or in combination of two or more.

Commercially available fatty acid amide compounds include, for example, A670-20M, A650-20X, A603-20X, 603-10X, 6850-20X, 6840-10X, 6820-20M, 6810-20X, 6900-10X, 6900-20XN. , 6900-20X, and 6901-20X (manufactured by Kusumoto Kasei Co., Ltd.). These include fatty acid amide compounds pasted with solvents.

The molecular weight of the amide compound (D2) is not particularly limited. The number average molecular weight (Mn) of the amide compound (D2) is, for example, 1,000 or more and 2,000 or less. This makes it easier to obtain the desired paint viscosity.

The content of the amide compound (D2) is preferably 0.05 parts by mass or more and 2.0 parts by mass or less based on 100 parts by mass of the resin solid content. This makes it easier to obtain a desired coating viscosity. The content of the amide compound (D2) is preferably 0.1 parts by mass or more, more preferably 0.15 parts by mass or more, based on 100 parts by mass of the resin solid content. The content of the amide compound (D2) is preferably 1.8 parts by mass or less, more preferably 1.6 parts by mass or less, based on 100 parts by mass of the resin solid content.

(Other viscosity modifiers)
The coating composition may contain other viscosity modifiers as necessary. Examples of other viscosity modifiers include inorganic viscosity agents, cellulose derivatives, and urethane-associated viscosity agents. These may be used alone or in combination of two or more.

Examples of inorganic viscosity agents include layered silicates (silicate minerals), halogenated minerals, oxide minerals, carbonate minerals, borate minerals, sulfate minerals, molybdate minerals, tungstate minerals, and phosphates. Examples include minerals, arsenate minerals, and vanadate minerals.

Examples of cellulose derivatives include cellulose acetate butyrate, nitrocellulose, cellulose acetate, and cellulose acetate propionate.

The urethane association type viscous agent is not particularly limited. Examples of the urethane-associated viscosity agent include polyurethane viscosity agents having a hydrophobic chain in the molecule and urethane-urea viscosity agents in which at least a portion of the main chain is a hydrophobic urethane chain.

[Coating film-forming resin (A)]
The film-forming resin (A) reacts with the curing agent when heated to form a three-dimensional cured film. At least a portion of the film-forming resin (A) is dissolved in the non-aqueous solvent (E) in the coating composition.

The weight average molecular weight (Mw) of the film-forming resin (A) may be, for example, 4,000 or more and 10,000 or less. Thereby, when the coating composition is applied onto another uncured coating film, generation of a mixed phase can be easily suppressed. In addition, the quick drying properties of the coating composition are improved. Furthermore, the gasohol resistance, weather resistance, and appearance of the resulting coating film are likely to be improved. The Mw of the film-forming resin (A) may be 9,000 or less, 8,000 or less, or 7,000 or less.

The weight average molecular weight can be calculated from a chromatogram measured with a gel permeation chromatography based on the molecular weight of standard polystyrene.

The glass transition temperature (Tg) of the film-forming resin (A) is preferably 10°C or more and 50°C or less. This tends to improve the stain resistance, scratch resistance, and hardness of the resulting coating film. Furthermore, the quick-drying properties of the coating composition also tend to improve. The Tg of the film-forming resin (A) is more preferably 15°C or higher. The Tg of the film-forming resin (A) is more preferably 40°C or lower, particularly preferably 35°C or lower.

Tg is determined by the following method using a differential scanning calorimeter (DSC). A step of raising the temperature from 20°C to 150°C at a temperature increase rate of 10°C/min (step 1), and a step of lowering the temperature from 150°C to -50°C at a cooling rate of 10°C/min after step 1 (step 2), and after step 2, perform the step (step 3) of raising the temperature from -50 °C to 150 °C at a temperature increase rate of 10 °C/min, and calculate the value obtained from the chart at the time of temperature rise in step 3. , Tg.

The solubility parameter (hereinafter referred to as SP value) of the film-forming resin (A) is not particularly limited, as long as at least a part thereof can be dissolved in the non-aqueous solvent (E). The SP value (SP _A ) of the coating film-forming resin (A) may be, for example, 9.0 or more and 11.5 or less. The difference ΔSP between SP _A and the SP value (SP _E ) of the nonaqueous solvent (E) is, for example, 2.0 or less, preferably 1.8 or less. The SP value can be determined by, for example, the literature: SUH, CLARKE, J. P. S. Actual measurements can be made with reference to A-1, 5, 1671-1681 (1967).

The content of the coating film-forming resin (A) is preferably 30% by mass or more and 80% by mass or less based on the solid content of the coating composition, from the viewpoint of the strength of the resulting coating film. The content of the film-forming resin (A) is more preferably 40% by mass or more, particularly preferably 45% by mass or more of the solid content of the coating composition. The content of the film-forming resin (A) is more preferably 70% by mass or less, particularly preferably 65% by mass or less of the solid content of the coating composition.

The film-forming resin (A) is not particularly limited as long as it contains a resin having a functional group capable of reacting with a crosslinking agent, and conventionally known resins are used in clear coatings. Examples of functional groups that can react with the crosslinking agent include hydroxyl groups, cationic functional groups (e.g., amino groups, mono- or di-substituted amino groups, ammonium groups), and anionic functional groups (e.g., carboxyl groups, sulfonic acid groups). group, phosphate group). Among these, resins containing hydroxyl groups are preferred.

The hydroxyl value (OHV) of the hydroxyl group-containing resin is preferably 80 mgKOH/g or more and 220 mgKOH/g or less. This increases the crosslinking density, making it easier to improve weather resistance, water resistance, moisture resistance, and the like. The hydroxyl value of the hydroxyl group-containing resin is more preferably 80 mgKOH/g or more, and even more preferably 110 mgKOH/g or more. The hydroxyl value of the hydroxyl group-containing resin is more preferably 210 mgKOH/g or less, even more preferably 205 mgKOH/g or less, and particularly preferably 180 mgKOH/g or less.

The acid value (AV) of the hydroxyl group-containing resin may be 2 mgKOH/g or more and 30 mgKOH/g or less. This tends to improve the appearance of the resulting coating film. Furthermore, when the coating composition is applied onto another uncured coating film, generation of mixed phases can be easily suppressed. The acid value of the hydroxyl group-containing resin may be 3 mgKOH/g or more. The acid value of the hydroxyl group-containing resin may be 20 mgKOH/g or less, and may be 15 mgKOH/g or less. The hydroxyl value and acid value can be determined by the neutralization titration method using an aqueous potassium hydroxide solution described in JIS K 0070.

The base resin is not particularly limited, and examples thereof include acrylic resins and polyester resins (including alkyd resins; the same applies hereinafter). Preferred film-forming resins (A) include hydroxyl group-containing acrylic resins and hydroxyl group-containing polyester resins.

The film-forming resin (A) may contain both a hydroxyl group-containing acrylic resin and a hydroxyl group-containing polyester resin. In this case, the content of the hydroxyl group-containing acrylic resin is preferably 40% by mass or more, more preferably 50% by mass or more of the resin solid content. The content of the hydroxyl group-containing acrylic resin is preferably 80% by mass or less, more preferably 70% by mass or less of the resin solid content. The content of the hydroxyl group-containing polyester resin is preferably 0.1% by mass or more, more preferably 0.3% by mass or more of the resin solid content. The content of the hydroxyl group-containing polyester resin is preferably 5% by mass or less, more preferably 3% by mass or less of the resin solid content.

The hydroxyl group-containing acrylic resin can be obtained, for example, by polymerizing a hydroxyl group-containing (meth)acrylic monomer and another (meth)acrylic monomer. The (meth)acrylic monomer is at least one of acrylic acid and its esters, and methacrylic acid and its esters.

The (meth)acrylic monomer containing a hydroxyl group is not particularly limited, and examples thereof include hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, Plaxel FM-1 (manufactured by Daicel Chemical Co., Ltd., ε-caprolactone-modified methacrylate) (2-hydroxyethyl acid), polyethylene glycol monoacrylate or monomethacrylate, polypropylene glycol monoacrylate or monomethacrylate. These may be used alone or in combination of two or more.

Other (meth)acrylic monomers are not particularly limited, and include, for example, acid group-containing unsaturated monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and anhydrides thereof; methyl (meth)acrylate; Ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, phenyl (meth)acrylate, Alkyl (meth)acrylates such as benzyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate; acrylonitrile, Examples include nitrile monomers such as methacrylonitrile; acrylamide monomers such as acrylamide, methacrylamide, N-methylolacrylamide, N,N-dimethylacrylamide, and diacetone acrylamide. These may be used alone or in combination of two or more.

The hydroxyl group-containing polyester resin is obtained, for example, by polycondensation (ester reaction) of a polyhydric alcohol and a polybasic acid or anhydride thereof.

Polyhydric alcohols are not particularly limited and include, for example, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 2,3 -Butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, hydrogenated bisphenol A, hydroxyalkylated bisphenol A, 1,4-cyclohexanedimethanol, 2,2-dimethyl- 3-hydroxypropyl-2,2-dimethyl-3-hydroxypropionate, 2,2,4-trimethyl-1,3-pentanediol, N,N-bis-(2-hydroxyethyl)dimethylhydantoin, polytetra Examples include methylene ether glycol, polycaprolactone polyol, glycerin, sorbitol, trimethylolethane, trimethylolpropane, trimethylolbutane, hexanetriol, pentaerythritol, dipentaerythritol, and tris-(hydroxyethyl)isocyanate. These may be used alone or in combination of two or more.

The polybasic acid or its anhydride is not particularly limited, and examples thereof include phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyltetrahydrophthalic acid, and methyltetrahydrophthalic anhydride. Acid, himic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, isophthalic acid, terephthalic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, adipic acid, azelaic acid, sebacin Examples include succinic acid, succinic anhydride, lactic acid, dodecenylsuccinic acid, dodecenylsuccinic anhydride, cyclohexane-1,4-dicarboxylic acid, and endoacid anhydride. These may be used alone or in combination of two or more.

The hydroxyl group-containing polyester resin may be modified with lactone, oil or fatty acid, melamine resin, urethane resin, or the like. The oil or fatty acid is not particularly limited, and examples include oils and fats such as castor oil, dehydrated castor oil, coconut oil, corn oil, cottonseed oil, linseed oil, perilla oil, poppy oil, safflower oil, soybean oil, and tung oil; Examples include fatty acids extracted from fats and oils.

[Curing agent (B)]
The coating composition contains a curing agent (B). This crosslinks the coating film-forming resin and improves the durability of the resulting coating film.

The content of the curing agent (B) is, for example, 20% by mass or more and 50% by mass or less, and preferably 30% by mass or more and 45% by mass or less, based on the resin solid content of the coating composition.

The curing agent (B) is not particularly limited, and is appropriately selected depending on the type of curable functional group that the coating film-forming resin has. Examples of the curing agent (B) include amino resins, isocyanate compounds, epoxy compounds, aziridine compounds, carbodiimide compounds, and oxazoline compounds. These may be used alone or in combination of two or more. Among these, isocyanate compounds are preferred. In particular, by using an isocyanate compound together with a hydroxyl group-containing resin, the adhesion of the coating film is likely to be improved.

The polyisocyanate is not particularly limited as long as it has an average of two or more isocyanate groups in one molecule. Examples of the polyisocyanate include aliphatic diisocyanates such as hexamethylene diisocyanate, pentamethylene diisocyanate, tetramethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic polysaccharides such as isophorone diisocyanate and 4,4'-methylenebis(cyclohexyl isocyanate); Isocyanates: Aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate; Modified products thereof (e.g., urethanates, carbodiimides, uretdiones, uretonimines, biuret forms, isocyanurates, etc.) .

The coating composition may contain other curing agents other than isocyanate compounds, such as amino resins such as melamine resins, guanamine resins, and urea resins. The content of the other curing agent may be, for example, 10% by mass or more and 30% by mass or less of the resin solid content of the coating composition.

[Flatting agent (C)]
The matting agent (C) forms minute irregularities on the surface of the coating film to give the coating film a matte texture.

The average particle diameter of the matting agent (C) is preferably 1 μm or more, more preferably 2 μm or more, particularly preferably 3 μm or more, from the viewpoints of matting ability and storage stability. From the same viewpoint, the average particle diameter of the matting agent (C) is preferably 10 μm or less, more preferably 9 μm or less, and particularly preferably 8 μm or less. The average particle size of the matting agent (C) is the 50% average particle size (D50) in a volume-based particle size distribution using a laser diffraction/scattering type particle size distribution measuring device. D50 is measured after adding the matting agent (C) to a mixed solvent of acetone and isopropyl alcohol and dispersing it using ultrasound for 1 minute to adjust the concentration to a predetermined transmittance range.

The oil absorption amount of the matting agent (C) is preferably 100 mL/100 g or more from the viewpoint of matting ability and the like. From the same viewpoint, the oil absorption amount of the matting agent (C) is preferably 400 mL/100 g or less, more preferably 380 mL/100 g or less, and particularly preferably 360 mL/100 g or less. Oil absorption is measured according to JIS K 5101-13-2:2004.

The content of the matting agent (C) is preferably 3 parts by mass or more and 20 parts by mass or less based on 100 parts by mass of the resin solid content. This makes it easy to obtain the desired matte effect. The content of the matting agent (C) is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, based on 100 parts by mass of the resin solid content. The content of the matting agent (C) is preferably 18 parts by mass or less, more preferably 15 parts by mass or less, based on 100 parts by mass of the resin solid content.

As the matting agent (C), those conventionally known in paints are used. The matting agent may be inorganic fine particles or organic fine particles (hereinafter sometimes referred to as resin beads).

Examples of the inorganic fine particles include silica particles, aluminum oxide particles, titanium dioxide particles, zirconium dioxide particles, zircon particles, tin oxide particles, and magnesium oxide particles. These may be used alone or in combination of two or more.

Among these, silica particles are preferred from the viewpoints of matting ability, storage stability, and the like. The shape of the silica particles is not particularly limited, and may be spherical, hollow, porous, rod-like, plate-like, fibrous, or irregularly shaped.

Commercially available products of silica particles include, for example, the Cylysia series manufactured by Fuji Silicia Co., Ltd. (Silysia 350, Thylysia 430, Thylysia 435, Thylysia 436, Thylysia 450, etc.), Thylysia series (Silysia 100, Thylysia 200, etc.) , Psilohovic 702, Psilohovic 100, 4004, etc.), Cyrosphere series (Silosphere 1504, Cylosphere 1510, etc.), Grace Japan's SYLOID series (Syloid W300, Cyloid W500, etc.), Evonik Degussa Japan Co., Ltd. ACEMATT series (ACEMATT HK460, ACEMATT HK400, ACEMATT OK412, ACEMATT OK520, ACEMATT TS100, ACEMATT 3200, ACEMATT 3300, ACEMATT 3600, etc.), Japanese series NIPGEL series (NIPGEL AZ-200 etc.), NIPSIL series (NIPSIL E-200A, NIPSIL SS-50B, NIPSIL SS-178B, etc.), Mizusawa Chemical Co., Ltd.'s Mizukasil series (Mizukasil P-73, P-526, etc.), Shionogi & Co., Ltd.'s Carplex series (Carplex CS-) E -8), etc.), Aerosil series (AEROSIL 200, AEROSIL R805, AEROSIL R972, etc.), Showa Chemical Industries (Radio Light 100, Radio Right 200, Radio 500, Radio 500, Radio 500, Radio 500, Radio 500, Radio 500 0R, Radio Light 500RS etc.).

The inorganic fine particles may be surface-treated with an organic compound and/or an inorganic compound. Among these, from the viewpoint of storage stability and the like, it is preferable that the inorganic fine particles are surface-treated with an organic compound. Examples of the treatment with an organic compound include polyethylene wax treatment and silane compound treatment. Among these, polyethylene wax treatment is preferred.

Examples of the resin beads include PMMA (polymethyl methacrylate) resin beads, MMA-EGDM (ethylene glycol dimethacrylate) copolymer resin beads, nylon resin beads, and polytetrafluoroethylene resin beads.

Commercially available resin beads include, for example, "Techpolymer Series (trade name)" manufactured by Sekisui Plastics Co., Ltd. and "Dyneon Series (trade name)" manufactured by Sumitomo 3M.

[Non-aqueous solvent (E)]
The nonaqueous solvent (E) is one of the diluent components, and is not particularly limited as long as it can dissolve at least a portion of the film-forming resin (A). The coating composition may contain a diluent component (typically, water) other than the nonaqueous solvent (E).

Examples of nonaqueous solvents include aliphatic or alicyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, cycloheptane, methylcycloheptane, and mineral split; acetone, acetylacetone, methyl ethyl ketone, methyl-i-butyl ketone, and methyl amyl ketone. , cyclohexanone, and other ketone organic solvents; benzene, toluene, ethylbenzene, propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and other aromatic hydrocarbon organic solvents; methyl acetate , ethyl acetate, n-butyl acetate, aluminum acetate and other ester organic solvents; methyl cellosolve, ethyl cellosolve, n-propyl cellosolve, i-propyl cellosolve, n-butyl cellosolve, i-butyl cellosolve, i-amyl cellosolve, phenyl cellosolve , cellosolve-based organic solvents such as benzyl cellosolve; methyl carbitol, ethyl carbitol, n-propyl carbitol, i-propyl carbitol, n-butyl carbitol, i-butyl carbitol, i-amyl carbitol, acetic acid carbitol Carbitol-based organic solvents such as toll, phenyl carbitol, benzyl carbitol; ethylene glycol monoisopropyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-n-butyl ether Ether organic solvents such as butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-n-butyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, dioxane, etc. can be mentioned. These may be used alone or in combination of two or more.

Commercially available aliphatic or alicyclic hydrocarbon solvents include, for example, "Rouse", "Mineral Spirit EC", "Shell Sol 71", "VM&P naphtha", and "Shell TS28 Solvent" (all of which are manufactured by Shell). ], "Isopar C", "Isopar E", "Isopar G", "Isopar H", "Isopar M", "Naphtha No. 3", "Naphtha No. 5", "Naphtha No. 6", "Solvent No. 7" (manufactured by Exxon Chemical Co., Ltd.), "IP Solvent 1016", "IP Solvent 1620", "IP Solvent 2028", "IP Solvent 2835" [manufactured by Idemitsu Kosan Co., Ltd.], "White Sol" [Japan Energy (manufactured by JXTG Energy Corporation), "Mitsubishi Mineral Turpen," "Diamond Solvent," "Pegasol AN-45," and "Pegasol 3040" (all manufactured by JXTG Energy Corporation). Examples of commercially available aromatic hydrocarbon organic solvents include "Solvesso 100" (manufactured by Exxon Chemical Company) and "Solvesso 150" (manufactured by Exxon Chemical Company).

[others]
The coating composition may contain at least one of a colored pigment, a glittering pigment, and an extender pigment within a range that does not impair transparency. Details of each pigment will be described later.

The coating composition may also contain other additives commonly blended in the coating field. Examples of additives include antifoaming agents, ultraviolet absorbers, light stabilizers (for example, hindered amines), antioxidants, surface conditioners, film forming aids, and rust preventives.

B. Painted Article The painted article according to this embodiment includes an object to be painted, a colored coating film formed on the object to be painted, and a matte clear coating film formed on the colored coating film. The matte clear coating film is formed from the above-mentioned matte coating composition. Therefore, the variation in gloss of the coated article is small, and the coated article has an excellent appearance.

[Subject to be coated]
The material of the object to be coated is not particularly limited. Examples of the material of the object to be coated include metal, resin, and glass. The shape of the object to be coated is also not particularly limited. According to the present embodiment, a uniform matte texture can be obtained even for a coated object having a complicated three-dimensional shape.

Examples of metals include iron, copper, aluminum, tin, zinc, and alloys thereof. Specific examples of the metal object to be coated include automobile bodies such as passenger cars, trucks, motorcycles, and buses, and parts for automobile bodies.

The metal object to be coated may be surface-treated. Examples of the surface treatment include phosphate treatment, chromate treatment, zirconium chemical conversion treatment, and complex oxide treatment. The metal object to be coated may be further coated with an electrodeposition paint after the surface treatment. The electrodeposition paint may be of the cationic type or the anionic type.

Examples of the resin include polypropylene resin, polycarbonate resin, urethane resin, polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, and polyamide resin. Specific examples of resin-made objects to be coated include automobile parts such as spoilers, bumpers, mirror covers, grills, and doorknobs.

The object to be coated made of resin is preferably subjected to a degreasing treatment. The resin-made object to be coated may be further coated with a primer paint after being degreased. The primer paint is not particularly limited, and may be appropriately selected depending on the type of paint to be applied above it.

[Colored coating film]
The colored coating film may be one layer, or may be a laminated coating film of two or more layers. The colored coating may be a so-called intermediate coating of one or more layers, a so-called base coating of one or more layers, or a combination thereof.

(Base coating)
The base coating film is formed, for example, from a base coating composition containing a film-forming resin, a curing agent, a viscosity modifier, a diluent component, and a pigment. The base coating composition may contain various of the above-mentioned additives as necessary. The components contained in each base coating may be the same or different.

The base coating composition may be solvent-based or water-based. As the film-forming resin, curing agent, viscosity modifier, and diluent component that are blended into the solvent-based base paint composition, the respective components exemplified as those that are blended into the matte paint composition can be mentioned. . The aqueous base coating composition can include a film-forming resin, a curing agent, and a viscosity modifier prepared for aqueous use, and water as a diluent component.

The thickness of the base coating film is not particularly limited, and is appropriately set depending on the purpose. The thickness per layer of the base coating film may be, for example, 15 μm or more and 50 μm or less. The thickness of each layer of the base coating film is preferably 18 μm or more, more preferably 20 μm or more. The thickness of each layer of the base coating film is preferably 45 μm or less, more preferably 40 μm or less. The thickness of the base coating film is measured using, for example, an electromagnetic film thickness meter. The thickness of the base coating film is the average value of the thickness of the base coating film at five arbitrary points. The thicknesses of other coatings are similarly measured and calculated.

<Pigment>
Examples of pigments include colored pigments, glitter pigments, and extender pigments.

Examples of coloring pigments include azochelate pigments, insoluble azo pigments, condensed azo pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, and dioxane. organic coloring pigments such as quinacridone pigments, isoindolinone pigments, and metal complex pigments; and inorganic coloring pigments such as yellow lead, yellow iron oxide, red iron oxide, carbon black, and titanium dioxide. These may be used alone or in combination of two or more.
Examples of bright pigments include metal pieces (aluminum, chromium, gold, silver, copper, brass, titanium, nickel, nickel chromium, stainless steel, etc.), metal oxide pieces, pearl pigments, and metals coated with metals or metal oxides. glass flakes, silica flakes coated with metal oxides, graphite, holographic pigments and cholesteric liquid crystal polymers. These may be used alone or in combination of two or more.

Extender pigments include, for example, calcium carbonate, barium sulfate, clay, and talc. These may be used alone or in combination of two or more.

The concentration of all pigments, that is, the mass ratio (PWC) of all pigments to 100% by mass of resin solid content of the base coating composition is preferably 0.1% by mass or more and 50% by mass or less. This improves the appearance of the resulting coating film. The PWC of all pigments is more preferably 0.5% by mass or more, particularly preferably 1.0% by mass or more. The PWC of all pigments is more preferably 40% by mass or less, particularly preferably 30% by mass or less.

The PWC of the color pigment and extender pigment is not particularly limited. The PWC of the bright pigment may be, for example, 1% by mass or more and 40% by mass or less. The PWC of the bright pigment is preferably 5% by mass or more. The PWC of the bright pigment is preferably 30% by mass or less.

(Intermediate coating film)
The intermediate coating film is interposed between the object to be coated and the base coating film. The intermediate coating makes the painted surface uniform, making it easier to suppress unevenness in the base coating.

The intermediate coating film is formed, for example, from an intermediate coating composition containing a film-forming resin, a curing agent, a viscosity modifier, a diluent component, and a pigment. The intermediate coating composition may contain various of the above-mentioned additives as necessary.

The intermediate coating composition may be solvent-based or water-based. As the film-forming resin, curing agent, viscosity modifier, diluent component, and pigment, the respective components exemplified as those added to the base coating composition can be mentioned.

The thickness of the intermediate coating film is not particularly limited. In terms of the appearance and chipping resistance of the coated article, the thickness of the intermediate coating film is preferably 5 μm or more and 40 μm or less. The thickness of the intermediate coating film is more preferably 15 μm or more. The thickness of the intermediate coating film is more preferably 30 μm or less.

[Matte clear coating film]
A matte clear coating is formed from the above-described matte coating composition and is usually placed on the outermost side of the coated article. The matte clear coating film suppresses the gloss of the coated article and also prevents pigments and the like contained in the lower layer from falling off and popping out.

The thickness of the matte clear coating film is not particularly limited. From the viewpoint of scratch resistance and appearance, the thickness of the matte clear coating film after drying may be 15 μm or more and 60 μm or less. The thickness of the matte clear coating film is preferably 20 μm or more. The thickness of the matte clear coating film is preferably 40 μm or less.

FIG. 1 is a cross-sectional view schematically showing a coated article according to this embodiment. The coated article 10 includes an object to be coated 11, an intermediate coat film 12 formed on the object to be coated 11, a base coat film 13 formed on the intermediate coat film 12, and a base coat film 13 formed on the base coat film 13. A matte clear coating film 14 is provided.

C. Method for manufacturing coated articles Coated articles are produced by the following steps: coating a colored coating composition on an object to form an uncured colored coating; curing the uncured colored coating; and a colored coating. It is produced by a method comprising the steps of: coating a matte coating composition thereon to form an uncured matte clear coating; and curing the uncured matte clear coating.

The step of forming a colored coating film includes a step of coating an intermediate coating composition on the object to be coated to form an uncured intermediate coating film, a step of curing the uncured intermediate coating film, The method may include a step of applying a base paint composition to form an uncured base paint film, and a step of curing the uncured base paint film.

When the matte clear coating film is formed, the colored coating film may be cured or uncured. In particular, from the viewpoint of productivity, adhesion, and water resistance, it is desirable to laminate each coating film without curing it (so-called wet-on-wet coating) and then simultaneously cure these multiple uncured coating films. is preferred. That is, the coated article includes a step of coating a colored paint composition on an object to be coated to form an uncured colored coating film, and a step of coating a matte coating composition on the uncured colored coating film. It is preferable to manufacture by a method comprising the steps of forming an uncured matte clear coating film, and curing the uncured colored coating film and the uncured matte clear coating film.

FIG. 2 is a flowchart of the method for manufacturing a coated article according to this embodiment. In the illustrated example, the step of forming a colored coating film includes a step (S11) of coating an intermediate coating composition on the object to be coated to form an uncured intermediate coating film; The method includes a step (S12) of coating a base coating composition on the film to form an uncured base coating film. Furthermore, the curing step (S14) includes a step of forming an uncured intermediate coat (S11), a step of forming an uncured base coat (S12), and a step of forming an uncured matte clear coat (S13). will be carried out after.

Each step will be explained in detail below.
(I) Step of forming an uncured intermediate coating film The uncured intermediate coating film is formed by applying the above-mentioned intermediate coating composition to an object to be coated.

The coating method is not particularly limited. Examples of the coating method include air spray coating, airless spray coating, rotary atomization coating, and curtain coating. These methods and electrostatic coating may be combined. Among these, rotary atomization electrostatic coating is preferred from the viewpoint of coating efficiency. Examples of rotary atomization electrostatic coatings include rotary atomization electrostatic coatings commonly known as "micro/microbell", "microbell", "metallic bell", etc. A paint machine is used.

The coating amount of the intermediate coating composition is not particularly limited. The intermediate coating composition is applied, for example, so that the thickness of the intermediate coating film after curing is 5 μm or more and 40 μm or less.

After applying the intermediate coating composition, preliminary drying (also referred to as preheating) may be performed. Thereby, the diluent component contained in the intermediate coating composition is suppressed from bumping during the curing process, and the occurrence of wrinkles is easily suppressed. Furthermore, pre-drying suppresses mixing of the uncured intermediate coating film and the coating composition applied thereon, making it difficult to form a mixed phase. Therefore, the appearance of the obtained coated article is likely to be improved.

Pre-drying conditions are not particularly limited. Pre-drying includes, for example, a method of leaving the product at a temperature of 20° C. or more and 25° C. or less for 15 minutes or more and 30 minutes or less, or a method of heating at a temperature of 50° C. or more and 100° C. or less for 30 seconds or more and 10 minutes or less.

The paint viscosity of the intermediate coating composition is not particularly limited. The paint viscosity of the intermediate coating composition measured by a B-type viscometer at 20° C. is, for example, 500 cps/6 rpm or more and 6,000 cps/6 rpm or less.

The solid content of the intermediate coating composition is not particularly limited. The solid content of the intermediate coating composition is preferably 30% by mass or more and 70% by mass or less. The solid content of the intermediate coating composition is the entire component of the intermediate coating composition excluding diluent components.

(II) Step of forming an uncured base coating film (S12)
An uncured base coating film is formed by coating an object with the above-mentioned base coating composition.

The coating method is not particularly limited. Examples of the coating method include the same coating method as the intermediate coating composition. Among these, rotary atomization electrostatic coating is preferred from the viewpoint of coating efficiency.

The coating amount of the base coating composition is not particularly limited. The base coating composition is applied, for example, so that the thickness of the base coating film after curing is 15 μm or more and 50 μm or less.

After applying the base coating composition, preliminary drying may be performed. The conditions for pre-drying are not particularly limited and may be the same as those for pre-drying the intermediate coating film.

The paint viscosity of the base paint composition is not particularly limited. The paint viscosity of the base paint composition measured by a B-type viscometer at 20° C. is, for example, 500 cps/6 rpm or more and 6,000 cps/6 rpm or less.

The solid content percentage of the base coating composition is not particularly limited. The solid content ratio of the base coating composition is preferably 30% by mass or more and 70% by mass or less. The solid content of the base coating composition is all components of the base coating composition excluding diluent components.

(III) Step of forming an uncured matte clear coating film (S13)
An uncured matte clear coating film is formed by coating the above-mentioned matte coating composition on a colored coating film. Since the matte paint composition contains the amide compound (D2), the paint viscosity η ₀ is appropriately high. Therefore, even if the matte coating composition is applied onto an uncured base coating film, the generation of mixed phases is suppressed.

The coating method is not particularly limited. Examples of the coating method include the same coating method as the intermediate coating composition. Among these, rotary atomization electrostatic coating is preferred from the viewpoint of coating efficiency.

The coating amount of the matte coating composition is not particularly limited. The matte coating composition is applied, for example, so that the thickness of the matte clear coating film after curing is 15 μm or more and 60 μm or less.

After applying the matte coating composition, preliminary drying may be performed. The conditions for pre-drying are not particularly limited and may be the same as those for pre-drying the intermediate coating film.

(IV) Curing step (S14)
Cure each uncured coating. Each coating can be cured by heating. In this step, the intermediate coat, base coat, and matte clear coat are cured all at once.

The heating conditions are appropriately set depending on the composition of each coating composition, the material of the object to be coated, and the like. The heating temperature is, for example, 80°C or higher and 160°C or lower, and may be 100°C or higher and 140°C or lower. The heating time may be appropriately set depending on the heating temperature. When the heating temperature is 100° C. or more and 140° C. or less, the heating time is, for example, 10 minutes or more and 60 minutes or less, and may be 20 minutes or more and 30 minutes or less. Since the matte coating composition contains the polymer crosslinked fine particles (D1), the coating viscosity η ₁ is appropriately high. Therefore, regardless of the curing conditions, the difference in the degree of settling of the matting agent (C) is reduced, and a coating film with suppressed variation in gloss can be obtained.

Examples of the heating device include a drying oven using a heat source such as hot air, electricity, gas, or infrared rays. Further, it is preferable to use a drying oven that uses two or more of these heat sources in combination because the drying time can be shortened.

Hereinafter, the present invention will be explained in more detail using Examples, but the present invention is not limited by the Examples in any way. In the examples, "parts" and "%" are based on mass unless otherwise specified.

[Example 1]
(1) Preparation of matte coating composition Film-forming resin (A), curing agent (B), matting agent (C), viscosity modifier (D) and non-aqueous solvent (E) are shown in Table 1. A matte coating composition was prepared by blending and stirring the composition as described.

Each component listed in Table 1 is as follows.
(A) Film-forming resin (hydroxyl group-containing acrylic resin)
57 parts of butyl acetate was charged into a reaction apparatus equipped with a stirring blade, a thermometer, a dropping device, a temperature control device, a nitrogen gas inlet, and a cooling tube, and the temperature was raised to 120°C under stirring while introducing nitrogen gas. . A mixture consisting of 0.8 parts of methacrylic acid, 26.8 parts of 2-ethylhexyl acrylate, 33.0 parts of methyl methacrylate, 39.4 parts of 2-hydroxyethyl methacrylate, and t-butylperoxy-2- A solution of 7.5 parts of ethyl hexanate dissolved in 5 parts of butyl acetate was added dropwise over 3 hours. After the addition was completed, the mixture was aged for 1 hour. Thereafter, a solution of 0.2 parts of t-butylperoxy-2-ethylhexanate dissolved in 5 parts of butyl acetate was added dropwise to the reactor over 1 hour. The reaction was completed by aging for 2 hours while maintaining the inside of the reactor at 120°C, and a hydroxyl group-containing acrylic resin was obtained. The obtained hydroxyl group-containing acrylic resin had a nonvolatile content of 60%, a weight average molecular weight of 5,500, and a glass transition temperature of 20°C. The hydroxyl value (OHV) was calculated to be 170 from the monomer formulation.

(B) Curing agent B1: Polyisocyanate compound, Desmodur N3900, manufactured by Sumika Covestro Urethane Co., Ltd., NCO/OH = 1.1
B2: Polyisocyanate compound, Desmodur N3400, manufactured by Sumika Covestro Urethane Co., Ltd., NCO/OH = 1.1

(C) Matting agent Silica: Polyethylene wax treated silica, ACEMATT OK520, manufactured by Evonik Degussa Japan, D50 = 6.5 μm

(D) Viscosity modifier (D1) Polymer crosslinked fine particles First, a polyester resin having an amphoteric group was prepared as follows.
134 parts of bishydroxyethyl taurine, 130 parts of neopentyl glycol, 236 parts of azelaic acid, 186 parts of phthalic anhydride, and 27 parts of xylene were added to a 2Q Kolben equipped with a stirrer, a nitrogen inlet tube, a temperature control device, a condenser, and a decanter. I prepared it. The contents were heated to remove water produced by the reaction by azeotroping with xylene. The temperature was raised to 190° C. over about 2 hours from the start of reflux, and stirring and dehydration were continued until the oxidation level of carboxylic acid reached 145. Thereafter, it was cooled to 140°C. While maintaining the temperature at 140° C., 314 parts of “Cardura EIOJ” (manufactured by Shell, persatic acid glycidyl ester) was added dropwise over 30 minutes. Thereafter, stirring was continued for 2 hours to complete the reaction, and a polyester resin having an amphoteric group was obtained. The obtained polyester resin had an acid value of 59, a hydroxyl value of 90, and a number average molecular weight Mn of 1,054.

Separately, 281 parts of deionized water, 30 parts of the polyester resin obtained above, and 3 parts of dimethylethanolamine were charged into a 1 L reaction vessel equipped with a stirrer, a cooler, and a temperature control device. While stirring, the temperature was maintained at 80° C. to dissolve the polyester resin. A solution of 1.0 part of azobiscyanovaleric acid dissolved in 45 parts of deionized water and 0.9 parts of dimethylethanolamine was then added to the reaction vessel. Furthermore, a mixed solution consisting of 30 parts of n-butyl acrylate, 70 parts of styrene, and 60 parts of ethylene glycol dimethacrylate was added dropwise over 60 minutes. Further, a solution of 0.5 part of azobiscyanovaleric acid dissolved in 15 parts of deionized water and 0.4 part of dimethylethanolamine was added. Thereafter, the mixture was stirred at 80° C. for 2 hours to obtain an emulsion with a nonvolatile content of 40% and a particle size of 0.12 μm. This emulsion was spray-dried to obtain polymer crosslinked fine particles (D1).

The obtained polymer crosslinked fine particles (D1) were dispersed in a solvent in which methyl amyl ketone and xylene were mixed at a weight ratio of 1:1 using an ultrasonic disperser to form a dispersion solution of polymer crosslinked particles (heating residue: 40 %) was obtained.

(D2) Amide compound: fatty acid amide compound, Disparon 6901-20X, manufactured by Kusumoto Kasei Co., Ltd.

(E) Non-aqueous solvent diluent solvent T-6110 (manufactured by Nippon Paint Automotive Coatings), SP _E = 9.8

Using the obtained matte coating composition, a coated article was manufactured in the following manner.
(2) Preparation of objects to be coated Two polypropylene substrates were prepared, each wiped with isopropyl alcohol, and then dried with air blow.

(3-1) Formation of uncured intermediate coating film An intermediate coating composition (Nippon Paint Automotive Coatings Co., Ltd. Electrostatically applied water-based intermediate coating WB-1200 (dark gray) manufactured by Co., Ltd. Next, it was preheated at 80° C. for 3 minutes to obtain an uncured intermediate coating film having a thickness of 10 μm after drying.

(4-1) Formation of uncured base paint film A base paint composition (Nippon Paint Automotive Co., Ltd. Aqueous base AR-3020-1 (gray metallic) manufactured by Coatings Co., Ltd. was applied electrostatically. Next, it was preheated at 80° C. for 3 minutes to obtain an uncured base coating film having a thickness of 15 μm after drying.

(5-1) Formation of uncured matte clear coating film The above matte coating composition was statically applied onto each uncured base coating film using a cartridge bell so that the thickness after drying was 25 μm. Electrocoating was performed to obtain an uncured matte clear coating film. In this way, two coating samples having laminated coating films were created.

(6) Curing of the coating film (a) Curing in a horizontal state One of the coated samples was allowed to stand at a temperature of 23°C for 1 minute while keeping the painted surface horizontal, and then heated to 120°C. After the temperature of the coating sample reached 120° C., it was heated for 20 minutes to cure the coating film. A coated article H was thus obtained.

(b) Curing under Vertical Condition The other coated sample was immediately stood vertically, allowed to stand at a temperature of 23°C for 7 minutes, and then heated to 120°C. After the temperature of the coating sample reached 120° C., it was heated for 20 minutes to cure the coating film. A coated article V was thus obtained.

(7) Evaluation The obtained coating composition and coated article were evaluated in the following manner. The results are shown in Table 1.

(60 degree specular gloss G60 _H , G60 _V )
After allowing the obtained coated articles H and V to cool to room temperature, the 60 degree specular gloss was measured using a gloss meter (manufactured by Bic Gardner, AG-4446) in accordance with JIS Z 8741 Specular Gloss - Measurement Method. was measured.

(Variation suppression effect)
A difference between the 60 degree specular gloss G _H and the 60 degree specular gloss G _V of less than 10 was evaluated as good, and a difference of 10 or more was evaluated as poor.

(Paint viscosity η ₀ )
The viscosity of the matte coating composition immediately after preparation was measured using a No. 4 Ford cup at 23° C. in accordance with "3. Flow cup method" of JIS K5600-2-2:1999.

(Coating viscosity η ₁ )
The matte coating composition was electrostatically coated on a tin plate using a rotary atomizer (RB-1000, manufactured by ABB) so that the dry film thickness was 25 μm. Scrape the paint film from the paint sample within 1.5 minutes after painting and store it in a sealable sample bottle. Within 1 hour after storage, at 20°C and at a shear rate of 0.1 s ^-1 (/s). The viscosity of the sample in the sample bottle was measured under the following conditions using a cone plate viscometer (manufactured by TA Instruments, cone plate radius: 40 mm).

[Example 2-5, Comparative Example 1-6]
A film-forming resin (A), a curing agent (B), a matting agent (C), a viscosity modifier (D), and a non-aqueous solvent (E) are blended in the composition shown in Table 1 and stirred. A matte coating composition was prepared.

Coated articles H and V were obtained in the same manner as in Example 1 using the obtained matte coating composition. The coating viscosity of the matte coating composition and the coating articles H and V were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Example 6]
(1) Preparation of matte coating composition Film-forming resin (A), curing agent (B), matting agent (C), viscosity modifier (D) and non-aqueous solvent (E) are shown in Table 2. A matte coating composition was prepared by blending and stirring the composition as described. Each component listed in Table 2 is as described above.

(2) Preparation of objects to be coated Two objects to be coated were obtained in the same manner as in Example 1.

For each object to be coated, create an uncured intermediate coating (3-2), form a base coating (4-2), and form an uncured matte clear coating ( Coated articles H and V were obtained in the same manner as in Example 1, except that 5-2) was performed. The coating viscosity of the matte coating composition and the coating articles H and V were evaluated in the same manner as in Example 1. The results are shown in Table 2.

(3-2) Formation of uncured intermediate coating film An intermediate coating composition (Nippon Paint Automotive Coatings Co., Ltd. A non-electrostatic coating was applied with solvent intermediate coating R-357 (white) manufactured by Co., Ltd. Next, it was preheated at 60° C. for 3 minutes to obtain an uncured intermediate coating film having a thickness of 25 μm after drying.

(4-2) Formation of uncured base paint film A base paint composition (Nippon Paint Automotive Co., Ltd. Aqueous base AR-3020 (mica) manufactured by Coatings Co., Ltd. was applied non-electrostatically. Next, it was preheated at 80° C. for 3 minutes to obtain an uncured base coating film having a thickness of 15 μm after drying.

(5-2) Formation of uncured matte clear coating film The above matte coating composition is uncured onto each uncured base coating film using a cartridge bell so that the thickness after drying is 25 μm. Electrostatic painting was performed to obtain an uncured matte clear coating film. In this way, two coating samples having laminated coating films were created.

[Examples 7 and 8, Comparative Examples 7 and 8]
A film-forming resin (A), a curing agent (B), a matting agent (C), a viscosity modifier (D), and a non-aqueous solvent (E) are blended in the composition shown in Table 2 and stirred. A matte coating composition was prepared.

Coated articles H and V were obtained in the same manner as in Example 6 using the obtained matte coating composition. The coating viscosity of the matte coating composition and the coating articles H and V were evaluated in the same manner as in Example 1. The results are shown in Table 2.

In the coated articles of Examples 1-8, variations in gloss are suppressed. On the other hand, Comparative Examples 1-8 have large variations in gloss.

The matte coating composition of the present invention is particularly suitable for coating automobile bodies and automobile parts.

10 Coated article 11 Coated object 12 Intermediate coating film (colored coating film)
13 Base coating film (colored coating film)
14 Matte clear coating film

Claims (11)

A matte coating composition comprising a film-forming resin (A), a curing agent (B), a matting agent (C), a viscosity modifier (D) and a non-aqueous solvent (E),
The matting agent (C) is inorganic fine particles,
The viscosity modifier (D) includes polymer crosslinked fine particles (D1) and an amide compound (D2),
The polymer crosslinked fine particles (D1) are (meth)acrylic resins that are insoluble in the non-aqueous solvent (E) containing the dissolved film-forming resin (A), and that are insoluble in the matte paint. dispersed in the composition,
The average particle diameter of the polymer crosslinked fine particles (D1) is 20 nm or more and 500 nm or less,
The viscosity η1 after 1.5 minutes of coating, measured by a cone-plate viscometer at 20°C and a shear rate of 0.1 s-1 (/s), is 26,000 mPa-s or more and 72,000 mPa-s or less. A matte paint composition. 60 degree specular gloss G60H of a coating film obtained by applying the matte coating composition on a horizontal surface and curing after 1 minute;
The 60 degree specular gloss G60V of the coating film obtained by applying the matte coating composition on a vertical surface and curing it after 7 minutes is,
|G60H-G60V|<10
The matte coating composition according to claim 1, which satisfies the following relationship. The content of the polymer crosslinked fine particles (D1) is 0.5 parts by mass or more and 5 parts by mass or less based on 100 parts by mass of the total solid content of the film-forming resin (A) and the curing agent (B). The matte coating composition according to claim 1 or 2, which is The content of the amide compound (D2) is 0.05 parts by mass or more and 2.0 parts by mass or less based on 100 parts by mass of the total solid content of the film-forming resin (A) and the curing agent (B). The matte coating composition according to any one of claims 1 to 3, which is The matte coating composition according to any one of claims 1 to 4, wherein the film-forming resin (A) contains a hydroxyl group-containing resin. The matte coating composition according to any one of claims 1 to 5, wherein the curing agent (B) contains an isocyanate compound. The matte coating composition according to any one of claims 1 to 6, wherein the matting agent (C) contains silica. The matte coating composition according to any one of claims 1 to 7, wherein the solid content ratio is 40% by mass or more and 55% by mass or less. The matte coating composition according to any one of claims 1 to 8, which has a viscosity η0 of 21 seconds or more and 35 seconds or less as measured by a flow cup method at 23°C. The object to be coated,
a colored coating film formed on the object to be coated;
A matte clear coating film formed on the colored coating film,
A coated article, wherein the matte clear coating film is formed from the matte coating composition according to any one of claims 1 to 9. a step of coating a colored paint composition on an object to be coated to form an uncured colored paint film;
A step of coating the matte coating composition according to any one of claims 1 to 9 on the uncured colored coating film to form an uncured matte clear coating film;
A method for manufacturing a coated article, comprising a curing step of curing the uncured colored coating film and the uncured matte clear coating film.

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