Aqueous resin composition and method for manufacturing a coated article

Abstract

An object of the present invention is to provide an aqueous resin composition for improving the matting property and a method for manufacturing a coated article with improved matting property. The aqueous resin composition of the present invention contains a resin emulsion containing resin particles and a wax emulsion containing wax particles. The resin particles contain an ethylenically unsaturated monomer as a constituent unit. The average particle diameter of the resin particles is 25 to 1000 nm, the average particle diameter of the wax particles is 380 to 5000 nm, the particle size distribution (D90 / D10) of the resin particles is 1.01 to 5.00, the melting point of the wax particles is lower than the melting point of the resin particles, and the glass transition temperature of the resin particles is -50 to 100 °C. Here, the melting point of the wax particles is the temperature obtained by differential scanning calorimetry (DSC) for the wax particles, the melting point of the resin particles is the temperature obtained by differential scanning calorimetry (DSC) for the resin particles, and the glass transition temperature of the resin particles is the temperature obtained based on the glass transition temperatures of the respective homopolymers formed only by the monomers constituting the resin particles and the Fox formula.

Description

Technical Field

[0001] The present invention relates to an aqueous resin composition and a method for manufacturing a coated article. Background Art

[0002] In recent years, in coating applications for vehicle interior materials, furniture, etc., users prefer an appearance with a high-class and substantial feeling with suppressed surface gloss. The matting coating agent contains inorganic fillers such as hydrophobic silica and organic fillers such as resin beads as matting agents. The matting coating agent can suppress the gloss of the coating film by the matting agent oozing out onto the coating film to form convex portions. On the other hand, since the matting agent and the coating film are peeled off by friction on the coating film, the weather resistance, stain resistance, matting performance, etc. sometimes decrease.

[0003] Therefore, Patent Document 1 proposes an aqueous coating material that can impart matting properties to a coating film without containing a matting agent in the matting coating agent. For example, Patent Document 1 discloses an aqueous resin composition for a matting coating material, which forms irregularities and has matting properties by using urethane crosslinked particles having different average particle diameters in combination.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2007-308587 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, the prior art described in Patent Document 1 has the following problems: The convex portions formed by the polyurethane crosslinked particles having a large particle diameter are peeled off by friction, and thus sufficient matting properties cannot be obtained.

[0009] An object of the present invention is to provide an aqueous resin composition that improves matting properties and a method for manufacturing a coated article that improves matting properties.

[0010] Means for Solving the Problems

[0011] According to the present invention, there is provided an aqueous resin composition, characterized by containing:

[0012] a resin emulsion containing resin particles and a wax emulsion containing wax particles, wherein the resin particles contain an ethylenically unsaturated monomer as a constituent unit,

[0013] the average particle diameter of the aforementioned resin particles is 25 to 1000 nm,

[0014] the average particle diameter of the aforementioned wax particles is 380 to 5000 nm,

[0015] The particle size distribution (D90 / D10) of the aforementioned resin particles is 1.01 to 5.00,

[0016] The melting point of the aforementioned wax particles is lower than the melting point of the aforementioned resin particles,

[0017] The glass transition temperature of the aforementioned resin particles is -50 to 100 °C,

[0018] Herein, the melting point of the aforementioned wax particles is the temperature obtained by differential scanning calorimetry (DSC) for the aforementioned wax particles,

[0019] The melting point of the aforementioned resin particles is the temperature obtained by differential scanning calorimetry (DSC) for the aforementioned resin particles,

[0020] The glass transition temperature of the aforementioned resin particles is the temperature obtained based on the glass transition temperatures of the respective homopolymers formed separately from the monomers constituting the aforementioned resin particles and the Fox equation.

[0021] Effects of the Invention

[0022] According to the present invention, there can be provided: an aqueous resin composition with improved matting properties, and a method for manufacturing a coated article with improved matting properties. Description of the Drawings

[0023] Figure 1 is a diagram for explaining the mechanism of forming a plurality of recesses on a layer.

[0024] Figure 2 is an SEM image of a layer formed from the aqueous resin composition during drying at room temperature (23 °C).

[0025] Figure 3 is an SEM image of a layer formed from the aqueous resin composition during drying at a high temperature (120 °C). Detailed Description of Embodiments

[0026] Hereinafter, the embodiments will be described in detail. It should be noted that the following embodiments are not limited to the solutions within the scope of the claims, and the combinations of the features described in the embodiments are not all necessary for the solutions. Two or more of the multiple features described in the embodiments can be arbitrarily combined.

[0027] <Aqueous Resin Composition>

[0028] The aqueous resin composition of the present invention contains: a resin emulsion containing resin particles and a wax emulsion containing wax particles, wherein the resin particles contain an ethylenically unsaturated monomer as a constituent unit. The average particle size of the resin particles is 25 to 1000 nm. The average particle size of the wax particles is 380 to 5000 nm.

[0029] The average particle diameter of the resin particles in the aqueous resin composition of one embodiment is 25 to 1000 nm, preferably 50 to 800 nm, more preferably 100 to 600 nm. It should be noted that the average particle diameter represents the average particle diameter (D50), which is measured by the dynamic light scattering method (DLS method).

[0030] Here, the average particle diameter based on the dynamic light scattering method (DLS method) represents the average particle diameter (D50) at which the cumulative value reaches 50% in the volume-based particle size distribution measured by dynamic light scattering. If laser light is irradiated onto particles undergoing Brownian motion in a solution or suspension, the scattered light from the particles will exhibit fluctuations corresponding to the diffusion coefficient. Large particles move slowly, so the fluctuations in the scattered light intensity are slow. On the other hand, small particles move quickly, so the fluctuations in the scattered light intensity change sharply. The dynamic light scattering method detects the fluctuations in the scattered light that reflect this diffusion coefficient and measures the average particle diameter (D50) using the Stokes-Einstein formula or the like.

[0031] The average particle diameter of the wax particles in the aqueous resin composition of one embodiment is 380 to 5000 nm, preferably 400 to 3000 nm, more preferably 500 to 1000 nm. It should be noted that the average particle diameter represents the average particle diameter (D50), which is measured by the dynamic light scattering method (DLS method).

[0032] By containing the resin particles and wax particles within the specified average particle diameter (D50) range, the aqueous resin composition can form a plurality of recesses in the layer of resin particles (hereinafter referred to as the resin particle layer). The matting effect is manifested by forming a plurality of recesses in the resin particle layer.

[0033] Here, regarding the mechanism by which the matting effect is manifested by forming a plurality of recesses on the resin particle layer, Figures 1 to 3 is used for explanation. Figure 1 (a) of is a cross-sectional view of the layer formed from the aqueous resin composition when dried at room temperature (23°C). Figure 1 (b) of is a cross-sectional view of the layer formed from the aqueous resin composition in a state where the wax particles are melted and exist in the form of a thin layer on the surface of the resin particle layer when dried at a temperature above the melting point of the wax (as an example, 120°C). Figure 2 Shows the SEM image of the layer formed from the aqueous resin composition when dried at room temperature (23°C). Figure 3 Shows the SEM image of the layer formed from the aqueous resin composition when dried at a high temperature (120°C).

[0034] Figure 1(a) shows wax particles 100 and a resin particle layer 110. It should be noted that, for ease of illustration, the illustration of each particle of the resin particle layer 110 is omitted. The wax particles 100 are arranged substantially evenly on the resin particle layer 110, or may be arranged unevenly. It should be noted that the wax particles 100 and the resin particle layer 110 respectively correspond to Figure 2 the wax particles 200 and the resin particle layer 210 in the SEM image of Figure 2 . Four wax particles 200 are illustrated in

[0035] Figure 1 (b) shows the recess 120 and the diameter 130 of the upper surface of the recess. The cross-sectional shape of the recess 120 is a shape with a curvature. The resin particle layer 110 has a plurality of recesses 120. The diameter 130 is the diameter of the upper surface of the recess 120 (illustrated by an arrow). By melting the wax particles 100 when heating and drying the aqueous resin composition at a temperature above the melting point of the wax, pores corresponding to the diameter 130 of the wax particles 100 are formed on the resin particle layer 110. Thus, a plurality of recesses 120 can be formed in the resin particle layer 110. It should be noted that the resin particle layer 110 and the recess 120 respectively correspond to Figure 3 the resin particle layer 310 and the recess 320 (hollow portion) in the SEM image of Figure 3 . Two recesses 320 are illustrated in

[0036] Figure 1 In (b), the diameters of the plurality of recesses 120 are the same as the average particle diameter of the wax particles 100, which is 380 - 5000 nm, preferably 400 - 3000 nm, and more preferably 500 - 1000 nm. The diameter of the recess 120 is a value obtained by observing the layer formed from the aqueous resin composition after heating at a temperature above the melting point of the wax using a scanning electron microscope (SEM). When visible light is incident on the surface of the coated article, since the visible light is diffusely reflected within the plurality of recesses 120 on the resin particle layer 110 and the reflected light is reduced, an extinction effect is produced.

[0037] It should be noted that when the diameters of the plurality of recesses 120 are larger than the wavelength range of visible light, 380 - 780 nm, the extinction property is further improved. As described above, since a plurality of recesses 120 are formed in the resin particle layer 110, an extinction effect (for example, low gloss at a 60 - degree specular gloss) is produced on the surface of the coated article coated with the aqueous resin composition of the present invention. According to the aqueous resin composition of the present invention, the extinction property can be improved.

[0038] On the other hand, when the resin particles have an average particle diameter larger or smaller than the specified average particle diameter range, it is impossible to form a plurality of recesses 120 with a diameter of 130 on the resin particle layer 110, so the light extinction property is reduced. In addition, when the wax particles 100 have an average particle diameter larger or smaller than the specified average particle diameter range, it is impossible to form a plurality of recesses 120 with a diameter of 130 on the resin particle layer 110, so the light extinction property is reduced.

[0039] In one embodiment, the aqueous resin composition contains 5 to 200 parts by mass of wax particles (B) relative to 100 parts by mass of resin particles (A). It should be noted that the parts by mass correspond to the amount of the active ingredient described in the examples described later.

[0040] (Resin particles (A))

[0041] The resin particles (A) have a structural unit derived from an ethylenically unsaturated monomer preferably (meth)acrylate. It should be noted that in this specification, the term “(meth)acrylic acid” represents a term including both “acrylic acid” and “methacrylic acid”.

[0042] (Ethylenically unsaturated monomer)

[0043] The resin emulsion (A) contains an ethylenically unsaturated monomer as a constituent unit. The ethylenically unsaturated monomer includes an acrylic monomer, an amide monomer, a styrene monomer, and other ethylenically unsaturated monomers.

[0044] The acrylic monomers include: ethylenically unsaturated carboxylic acid monomers (monomer (a1)), ethylenically unsaturated carboxylic acid alkyl ester monomers (monomer (a2)), ethylenically unsaturated carboxylic acid cycloalkyl ester monomers (monomer (a3)), monoester monomers of ethylenically unsaturated dicarboxylic acids (monomer (a4)), hydroxy-containing ethylenically unsaturated carboxylic acid alkyl ester monomers (monomer (a5)), ethylenically unsaturated carboxylic acid aminoalkyl ester monomers (monomer (a6)), and unsaturated fatty acid glycidyl ester monomers (monomer (a9)).

[0045] The amide monomers include: ethylenically unsaturated carboxylic acid aminoalkylamide monomers (monomer (a7)) and amide group-containing ethylenically unsaturated carboxylic acid monomers (monomer (a8)).

[0046] The styrene monomers include styrene monomers (monomer (a12)).

[0047] The other ethylenically unsaturated monomers include: vinyl cyanide-based monomers (monomer (a10)) and saturated aliphatic carboxylic acid vinyl ester monomers (monomer (11)).

[0048] In one embodiment, the resin particles (A) contain 1 part by mass or more, 1.5 parts by mass or more, or 2 parts by mass or more and 4 parts by mass or less, 3.5 parts by mass or less, or 3 parts by mass or less of the monomer (a1).

[0049] In one embodiment, the resin particles (A) contain 99 parts by mass or less, 98.5 parts by mass or less, or 98 parts by mass or less and 96 parts by mass or more, 96.5 parts by mass or more, or 97 parts by mass or more of the monomer (a2).

[0050] In one embodiment, the resin particles (A) are a copolymer containing the monomer (a1) and the monomer (a2) within the above mass fraction ranges as monomer components. It should be noted that when the resin particles (A) contain the monomer (a12), the monomer (a12) can be contained in an amount of 30 parts by mass or less from the perspective of weather resistance.

[0051] The monomer (a1) is a polymerizable monomer having a carboxyl group, and examples include (meth)acrylic acid, maleic acid, itaconic acid, etc. The monomer (a1) can be used alone or in combination of two or more thereof.

[0052] The monomer (a2) is an alkyl (meth)acrylate having a linear or branched alkyl group with 1 to 18 carbon atoms, and examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, etc. The monomer (a2) can be used alone or in combination of two or more thereof.

[0053] The monomer (a3) is an alkyl (meth)acrylate having a cyclic alkyl group with 1 to 18 carbon atoms, and examples include isobornyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, hydroxymethylcyclohexyl (meth)acrylate, cyclooctyl (meth)acrylate, cyclodecyl (meth)acrylate, and cyclododecyl (meth)acrylate, etc. The monomer (a3) can be used alone or in combination of two or more thereof.

[0054] The monomer (a4) is a polymerizable monomer having a carboxyl group, and examples include ethyl maleate, butyl maleate, ethyl itaconate, and butyl itaconate, etc. The monomer (a4) can be used alone or in combination of two or more thereof.

[0055] The monomer (a5) is a polymerizable monomer having a hydroxyl group, and examples thereof include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and a reaction product of 2-hydroxyethyl (meth)acrylate and ε-caprolactone. The monomer (a5) can be used alone or in combination of two or more of the above.

[0056] The monomer (a6) is a polymerizable monomer having an amino group, and examples thereof include aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and butylaminoethyl (meth)acrylate. The monomer (a6) can be used alone or in combination of two or more of the above.

[0057] The monomer (a7) is an amide-based monomer copolymerizable with (meth)acrylate, and examples thereof include aminoethyl (meth)acrylamide, dimethylaminomethyl (meth)acrylamide, and methylaminopropyl (meth)acrylamide. The monomer (a7) can be used alone or in combination of two or more of the above.

[0058] The monomer (a8) is an amide-based monomer copolymerizable with (meth)acrylate, and examples thereof include acrylamide, methacrylamide, N-hydroxymethylacrylamide, methoxybutylacrylamide, and diacetoneacrylamide. The monomer (a8) can be used alone or in combination of two or more of the above.

[0059] The monomer (a9) is a polymerizable monomer having an epoxy group, and examples thereof include glycidyl acrylate and glycidyl methacrylate. The monomer (a9) can be used alone or in combination of two or more of the above.

[0060] The monomer (a10) is a monomer copolymerizable with (meth)acrylate, and examples thereof include (meth)acrylonitrile and α-chloropropacrylonitrile. The monomer (a10) can be used alone or in combination of two or more of the above.

[0061] The monomer (a11) is a monomer copolymerizable with (meth)acrylate, and examples thereof include vinyl acetate and vinyl propionate. The monomer (a11) can be used alone or in combination of two or more of the above.

[0062] The monomer (a12) is a styrene-based monomer copolymerizable with (meth)acrylate, and examples thereof include styrene, α-methylstyrene, and vinyltoluene. The monomer (a12) can be used alone or in combination of two or more of the above.

[0063] Furthermore, as the monomer contained in the resin particles (A), a monomer capable of crosslinking the resin can be used. Examples of the monomer capable of crosslinking the resin include monomers having two or more polymerizable double bonds, and one of them or a combination of two or more thereof can be used. Examples of the monomer having two or more polymerizable double bonds include (meth)acrylic acid-based monomers having two or more polymerizable double bonds such as ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, allyl (meth)acrylate, and trimethylolpropane tri(meth)acrylate, divinylbenzene, and diallyl phthalate, etc.

[0064] (Particle size distribution (D90 / D10)

[0065] The D90 / D10 of the resin particles (A) is in the range of 1.01 to 5.00, preferably 1.01 to 4.00, and more preferably 1.01 to 3.00. When the D90 / D10 of the resin particles (A) is within the above range, the extinction property is improved because the wax particles (B) are regularly arranged on the resin particle layer.

[0066] The particle size distribution is an index indicating what proportion (relative particle amount with the whole being 100%) of particles of what size (particle diameter) are contained in the sample particle group to be measured. As the reference (dimension) of the particle amount, a volume reference can be used. The particle size distribution data is represented in the form of frequency % or cumulative % (vertical axis) with respect to the particle diameter (horizontal axis). The particle diameter when the cumulative % distribution curve intersects the horizontal axis at 10% is called the 10% particle diameter (D10). In addition, the particle diameter when the cumulative % distribution curve intersects the horizontal axis at 50% is called the 90% particle diameter (D90).

[0067] Here, by using the 10% particle diameter (D10) and the 90% particle diameter (D90) in the particle size distribution to obtain the ratio of D90 to D10, it can be used as an index of the particle size distribution. The closer the value of D90 / D10 is to 1, the sharper the particle size distribution. On the other hand, the larger the value of D90 / D10, the wider the particle size distribution.

[0068] (Glass transition temperature (Tg))

[0069] The glass transition temperature (Tg) of the resin particles (A) is -50 to 100 °C, preferably -30 to 90 °C, and more preferably -10 to 80 °C. The glass transition temperature (Tg) refers to the boundary temperature at which a substance changes from a rubber state to a glass state.

[0070] When the Tg of the resin particles (A) is that of a homopolymer formed from a single monomer, it is a value measured by DSC. In addition, when the resin is a copolymer formed from two or more monomers, the Tg of the resin is a theoretical value calculated by the following formula 1 (Fox equation) using the Tg of the above homopolymer case.

[0071] 1 / Tg = W1 / Tg1 + W2 / Tg2 + … Wn / Tgn (Equation 1)

[0072] In Equation 1, Tg represents the glass transition temperature (unit: K) of each copolymer formed from n monomers (monomers 1 to n). W1, W2, … Wn represent the mass fractions of each monomer (1, 2, … n) relative to the total mass of the n monomers. Tg1, Tg2, … Tgn represent the glass transition temperatures (unit: K) of the homopolymers formed from each monomer (1, 2, … n).

[0073] The Tg of the monomers used in the following-described examples is shown below. The Tg of the copolymer of the resin is calculated using the Tg of each monomer.

[0074] Methyl methacrylate (MMA): 105 °C

[0075] Butyl acrylate (BA): -52 °C

[0076] 2-Ethylhexyl acrylate (2EHA): -70 °C

[0077] Acrylic acid (AAc): 105 °C

[0078] Styrene (ST): 100 °C

[0079] (Core-shell structure)

[0080] The resin particles (A) can have a morphology with a core part and a shell part. When the resin particles (A) have a core-shell structure, the film-forming property, solvent resistance, water resistance, and mechanical stability of the resin particle layer are further improved. The aqueous resin composition can improve the matting property by containing a resin emulsion containing resin particles (A) having a core-shell structure and a wax emulsion containing wax particles (B).

[0081] When the resin particles (A) have a core part and a shell part, they can be particles of a homogeneous structure in which the core part and the shell part are completely compatible and the core part and the shell part cannot be distinguished. In addition, the resin particles (A) can have a core-shell composite structure and a microdomain structure in which the core part and the shell part are not completely compatible and are in a heterogeneous state. In particular, from the viewpoints of the expressiveness, stability, and ease of manufacture of the characteristics of the resin particles (A), the resin particles (A) can be a core-shell composite structure.

[0082] It should be noted that in the core-shell composite structure, the form can be such that the surface of the core part is covered by the shell part. In this case, the surface of the core part can be completely covered by the shell part or incompletely covered. For example, it can be in a form covered in a mesh pattern or a form in which the core part is exposed at multiple places.

[0083] (Wax particles (B))

[0084] The wax used in the wax particles (B) includes natural waxes such as beeswax, carnauba wax, candelilla wax, montan wax, paraffin wax, microcrystalline wax, etc., and synthetic waxes such as amide wax, modified montan wax, polyethylene wax, polypropylene wax, Fischer-Tropsch wax, etc. From the viewpoints of coloring property and melting point, paraffin wax, microcrystalline wax, and polyethylene wax can be used as the wax. It should be noted that the wax can be used alone as 1 type of the above or in combination of 2 types or more.

[0085] (Melting point)

[0086] The melting point of the wax particles (B) is 40 to 150 °C, preferably 50 to 120 °C, more preferably 60 to 100 °C. When the melting point is less than 40 °C, the wax is in a liquid state at room temperature, so the surface of the coated product will have a sticky touch. A coated product refers to a substrate coated with an aqueous resin composition. On the other hand, when the melting point is higher than 150 °C, the wax becomes difficult to melt in the drying process of the aqueous resin composition and cannot form a plurality of recesses on the resin particle layer, so the light extinction property is reduced.

[0087] (Polymerization method of resin particles (A))

[0088] The resin particles (A) are synthesized by solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc. From the viewpoints of ease of adjusting the particle size of the resin particles (A) and productivity, a method of carrying out emulsion polymerization in an aqueous medium can be used. The emulsion polymerization method includes a method of carrying out emulsion polymerization by mixing an aqueous medium, a monomer component, a polymerization initiator, etc. all at once. In addition, the emulsion polymerization method includes a method of carrying out emulsion polymerization using a pre-emulsion containing an aqueous medium and a monomer component, etc.

[0089] (Solvent)

[0090] The aqueous medium includes at least any one of water, deionized water, or a mixture formed by water and water-soluble organic solvents (such as alcohols, ketones, ethers, dimethyl sulfoxide, and dimethylformamide, etc.).

[0091] In one embodiment, relative to 100 parts by mass of the ethylenically unsaturated monomer, the solvent can be contained in an amount of 40 to 900 parts by mass, preferably 70 to 400 parts by mass, more preferably 100 to 230 parts by mass.

[0092] (Other additives)

[0093] Depending on the required properties such as matting properties, the aqueous resin composition may further contain various additives as follows. Additives include, for example, coating aids such as emulsifiers, coagulants, antifreezing agents, curing agents, buffers, neutralizing agents, thickeners, humectants, wetting agents, plasticizers, defoamers, UV absorbers, optical brighteners, light or heat stabilizers, biocides, chelating agents, dispersants, colorants, water repellents, organic or inorganic pigments, extenders, and antioxidants.

[0094] When synthesizing a resin emulsion in an aqueous medium, an emulsifier is used as a surfactant. Emulsifiers include, for example, anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. From the perspective of promoting the synthesis of the resin emulsion, anionic surfactants, nonionic surfactants, and cationic surfactants can be used. The emulsifier can be used alone or in combination of two or more of the above.

[0095] Examples of anionic surfactants include fatty acid salts such as sodium stearate, alkyl sulfates such as sodium lauryl sulfate, polyoxyalkylene alkyl ether sulfates such as polyoxyethylene alkyl ether sodium sulfate, alkyl benzene sulfonates such as sodium dodecyl benzene sulfonate, dialkyl sulfosuccinates, alkyl diphenyl ether disulfonates, and reactive anionic surfactants such as ammonium polyoxyalkylene alkenyl ether sulfate.

[0096] Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether, polyoxyalkylene derivatives such as polyoxyalkylene alkyl ethers, and reactive nonionic surfactants such as polyoxyalkylene alkenyl ethers.

[0097] In one embodiment, the aqueous resin composition may contain an emulsifier in an amount of 0.1 to 20 parts by mass, preferably 0.5 to 10 parts by mass, and more preferably 1 to 5 parts by mass based on 100 parts by mass of the ethylenically unsaturated monomer.

[0098] Thickeners include alkali-soluble thickeners, polyurethane-based associative thickeners, water-soluble polymer-based thickeners, and natural thickeners such as cellulose-based or protein-based thickeners. In one embodiment, the aqueous resin composition may contain a thickener in an amount of 0.1 to 10 parts by mass, preferably 0.3 to 8 parts by mass, and more preferably 0.5 to 6 parts by mass based on 100 parts by mass of the resin emulsion.

[0099] Neutralizing agents include, for example, alkali metal compounds such as sodium hydroxide and potassium hydroxide; alkaline earth metal compounds such as calcium hydroxide and calcium carbonate; and organic amines such as ammonia, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, and diethylenetriamine. The neutralizing agent can be used alone or in combination of two or more thereof.

[0100] When manufacturing a resin emulsion, after obtaining the resin emulsion by polymerizing the monomer components, the resin emulsion can be neutralized using a neutralizing agent. When the resin emulsion has a carboxyl group, the carboxyl group can be neutralized with a basic neutralizing agent. Thereby, the resin emulsion is stabilized.

[0101] Herein, the pH of the resin emulsion is not particularly limited and is 7.0 to 10.0, preferably 7.5 to 9.5, more preferably 8.0 to 9.0. The pH of the resin emulsion is a value measured according to the provisions of JIS K6833-1:2008 and is the value at 25°C.

[0102] In one embodiment, the aqueous resin composition can contain a neutralizing agent in an amount of 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, based on 100 parts by mass of the resin emulsion.

[0103] Wetting agents include organically modified polysiloxanes and the like. In one embodiment, the aqueous resin composition can contain a wetting agent in an amount of 0.1 to 5 parts by mass, preferably 0.5 to 3 parts by mass, more preferably 1 to 2 parts by mass, based on 100 parts by mass of the resin emulsion.

[0104] Defoaming agents include silicone-based defoaming agents and the like. In one embodiment, the aqueous resin composition can contain a defoaming agent in an amount of 0.01 to 1 part by mass, preferably 0.03 to 0.5 part by mass, more preferably 0.05 to 0.1 part by mass, based on 100 parts by mass of the resin emulsion.

[0105] <Coated article and method for manufacturing the same>

[0106] The coated article includes a substrate and a layer of resin particles containing an ethylenically unsaturated monomer as a constituent unit disposed on the substrate. Hereinafter, the substrate and the layer of resin particles will be described.

[0107] (Substrate)

[0108] The substrate is a substrate coated with the aqueous resin composition of the present invention. The substrate can be either an organic material or an inorganic material. Organic materials include plastics, resins, fibers, rubbers, woods, wallpapers, etc. Inorganic materials include glass, ceramics, silica, metals, etc.

[0109] Plastics include, for example, polyesters such as polyethylene terephthalate (PET film), polybutylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer, polystyrene, polycarbonate, polymethylpentene, polysulfone, polyetheretherketone, polyethersulfone, polyphenylene sulfide, polyetherimide, and polyimide, etc.

[0110] Resins include fluororesins, polyamides, acrylic resins, norbornene resins, cycloolefin resins, and triacetyl cellulose (TAC), etc.

[0111] Metals include, for example, ferrous metals such as iron and stainless steel, and non-ferrous metals such as aluminum, magnesium, zinc, and their alloys. Ferrous metals include cold-rolled steel sheets, hot-rolled steel sheets, and stainless steel sheets, etc. Non-ferrous metals include aluminum steel sheets, zinc steel sheets, magnesium alloys, aluminum-zinc alloys, zinc-nickel plated steel sheets, zinc-chromium plated steel sheets, and zinc-magnesium plated steel sheets, etc.

[0112] (Layer of resin particles)

[0113] The layer of resin particles is a coating film obtained by curing and drying the aqueous resin composition of the present invention. The form of the aqueous resin composition is liquid before curing and drying and solid after curing and drying. The coating amount of the aqueous resin composition coated on at least one surface of the substrate can be an amount corresponding to the thickness of the layer of resin particles after drying. The thickness of the layer of resin particles is 0.1 to 300 μm, preferably 0.5 to 200 μm, more preferably 1 to 100 μm.

[0114] Methods for coating the aqueous resin composition on at least one surface of the substrate include, for example, bar coating method, knife coating method, roll coating method, blade coating method, die coating method, gravure coating method, etc. After coating the aqueous resin composition on the substrate by any of the above methods to form a coating film, curing and drying are carried out at 40 to 150 °C, preferably 60 to 140 °C, more preferably 80 to 130 °C. From the perspective of sufficiently melting the wax particles and forming recesses in the resin particle layer, the drying time is 30 to 300 seconds, preferably 40 to 200 seconds, more preferably 50 to 150 seconds.

[0115] The glossiness of the layer of resin particles is measured according to JIS Z8741 using a glossiness meter (manufactured by Konica Minolta, device name: GM-268plus). The glossiness measured at angles of 25°, 60°, and 85° with respect to the surface of the layer is expressed as Gs(25°), Gs(60°), and Gs(85°). In one embodiment, the 60° specular glossiness on the surface of the layer of resin particles is 10% or less.

[0116] As described above, the coated article of the present invention can have a glossiness of Gs(60°) of 10% or less. According to the coated article of the present invention, an excellent matting effect is exhibited on the surface of the resin particle layer.

[0117] <Manufacture of resin emulsion>

[0118] Hereinafter, a manufacturing example of the resin emulsion used in the aqueous resin composition will be described.

[0119] (Production Example 1)

[0120] 265.2 parts by mass of deionized water and 0.4 part by mass (active ingredient: 0.12 part by mass) of polyoxyethylene polycyclic phenyl ether sodium sulfate (trade name: Newcol707SF, manufactured by Nippon Emulsion Co., Ltd., non-volatile component: 30% by mass) as an anionic emulsifier were added to a four-necked detachable flask equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel. While stirring the mixture, the internal temperature of the four-necked detachable flask was raised to 80°C.

[0121] A pre-emulsion to be added to the above mixture was prepared as follows. Based on the compounding ratio of the monomers described in Table 1, 140.0 parts by mass of butyl acrylate (BA), 256.0 parts by mass of methyl methacrylate (MMA), and 4.0 parts by mass of acrylic acid (AAc) of monomer components (total amount: 400.0 parts by mass), 2.0 parts by mass of trimethylolpropane trimethacrylate (trade name: Light Ester TMP, manufactured by Kyoeisha Chemical Co., Ltd., non-volatile component: 100% by mass) as a crosslinking agent, 26.3 parts by mass of Newcol707SF (active ingredient: 7.9 parts by mass) as an anionic emulsifier, and 202.3 parts by mass of deionized water were emulsified in a homodisper to prepare a pre-emulsion.

[0122] Next, while maintaining the internal temperature of the detachable flask at 80°C, the prepared pre-emulsion was uniformly added dropwise to the mixture (deionized water, etc.) in the four-necked detachable flask from the dropping funnel over 3 hours, and at the same time, 100.0 parts by mass (active ingredient: 1 part by mass) of a 1% by mass aqueous ammonium persulfate solution was uniformly added dropwise over 3 hours. After the addition was completed, the mixture was cured at 80°C for 3 hours. After cooling, 2.3 parts by mass of 25% by mass ammonia water was added for neutralization. After adjusting the pH, filtration was performed using a 120-mesh filter cloth to obtain a resin emulsion (A-1). It should be noted that the Tg (theoretical value) of the resin emulsion (A-1) is 29.7°C and the evaporation residue is 40.0 wt% (weight%).

[0123] (Polymerization temperature and polymerization time)

[0124] The polymerization conditions such as the polymerization temperature, polymerization time, polymerization initiator, and emulsifier during the synthesis of the synthetic resin particles (A) can be the same as those of the known emulsion polymerization method.

[0125] For example, the polymerization temperature and polymerization time can be appropriately determined according to the types and amounts of monomers or polymerization initiators, etc. For example, the polymerization temperature is 20 to 100 °C or 40 to 90 °C. The polymerization time is 1 to 15 hours. Furthermore, the method of adding (dropping) the above pre-emulsion into the polymerization initiator can be, for example, a one-time addition method, a continuous addition method, and a multi-stage addition method, etc. In addition, a resin emulsion can be synthesized using an addition method that combines these addition methods.

[0126] (Polymerization initiator)

[0127] Polymerization initiators include, for example, persulfates, organic peroxides, peroxides such as hydrogen peroxide, and azo compounds, etc. The polymerization initiator can be used alone one of the above or in combination of two or more. In addition, one or two or more reducing agents can be used as redox polymerization initiators and polymerization accelerators used in combination with peroxides.

[0128] Persulfates include, for example, potassium persulfate, sodium persulfate, and ammonium persulfate, etc. Organic peroxides include, for example, diacyl peroxides such as benzoyl peroxide and dilauroyl peroxide, dialkyl peroxides such as tert-butyl cumyl peroxide and diisopropylbenzene peroxide, peresters such as tert-butyl laurate peroxide and tert-butyl benzoate peroxide, hydroperoxides such as cumene hydroperoxide and tert-butyl hydroperoxide, etc. Azo compounds include, for example, 2,2'-azobis(2-amidinopropane) dihydrochloride and 4,4'-azobis(4-cyanovaleric acid), etc. Reducing agents include, for example, ascorbic acid and its salts, tartaric acid and its salts, sulfurous acid and its salts, metabisulfurous acid and its salts, thiosulfuric acid and its salts, and iron(II) salts, etc.

[0129] (Polymerization regulator)

[0130] A polymerization regulator is used to adjust the molecular weight of the resin, and it is a known chain transfer agent. Chain transfer agents include, for example, alkyl mercaptans such as hexyl mercaptan, lauryl mercaptan, octyl mercaptan, and n-dodecyl mercaptan or tert-dodecyl mercaptan, etc.

[0131] (Production Examples 2 to 14)

[0132] Table 1 shows the blending ratios of the monomers of the resin emulsions A2 to A14 obtained in Production Examples 2 to 14, respectively. In Production Examples 2 to 14, the same procedures as in Production Example 1 were carried out based on the blending ratios of the monomers in Table 1. Haze (haze (%)) was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., trade name: NDH5000) according to JIS7361-1. Note that the abbreviations of ST to AAC and the Tg of each monomer are shown at the bottom of Table 1.

[0133] [Table 1]

[0134]

[0135] ※Explanation of abbreviations and Tg (°C)

[0136] Methyl methacrylate (MMA): 105 °C

[0137] Butyl acrylate (BA): -52 °C

[0138] 2-Ethylhexyl acrylate (2EHA): -70 °C

[0139] Acrylic acid (AAc): 105 °C

[0140] Styrene (ST): 100 °C

[0141] <Details of the wax emulsion>

[0142] Hereinafter, the details of the wax emulsion used in the aqueous resin composition will be described. Note that since the various waxes described in Table 2 are already in the form of emulsions, the description of the manufacturing method is omitted. The average particle diameters of the three waxes (product names: Saibinol PN-3500, AQUACER 539, CHEMIPEARL W800) in Table 2 are outside the range of 380 to 5000 nm of the average particle diameter of the wax particles (B) defined in the present invention. The above three waxes were used in Comparative Example 1 (PN-3500), Comparative Example 2 (AQUACER 539), and Comparative Example 7 (CHEMIPEARL W800) for comparison with the examples.

[0143] [Table 2]

[0144]

[0145] <Manufacture of the aqueous resin composition>

[0146] (Example 1)

[0147] Based on the raw material compounding amounts recorded in Table 3, 250 parts by mass of the resin emulsion (A-1) prepared in Production Example 1 (active ingredient: 100 parts by mass), 125 parts by mass of a wax emulsion containing wax particles (B) (manufactured by Mitsui Chemicals, Inc., trade name: CHEMIPEARL W900) (active ingredient: 50 parts by mass), 4.3 parts by mass of a thickener (manufactured by ADEKA Corporation, trade name: ADEKA NOL UH-540) (active ingredient: 1.3 parts by mass), 2.9 parts by mass of a thickener (manufactured by Chubu Saiden Co., Ltd., trade name: Vanstar S100) (active ingredient: 0.8 parts by mass), 0.8 parts by mass of a neutralizing agent (25% ammonia water) (active ingredient: 0.2 parts by mass), 0.5 parts by mass of a wetting agent (manufactured by SAN NOPCO Ltd., trade name: SN-WET 125), and 0.1 parts by mass of an antifoaming agent (manufactured by SAN NOPCO Ltd., trade name: NOPTAM 8034-LF) were mixed to obtain a mixture. The mixture was adjusted to a solid content of 20 wt% to obtain an aqueous resin composition (C-1).

[0148] Details of the thickener, wetting agent, and antifoaming agent used above are as follows.

[0149] ADEKA NOL UH-540: A urethane associative thickener, active ingredient 30%

[0150] Vanstar S100: An alkali-soluble thickener, active ingredient 28%

[0151] SN-WET 125: A silicone-based wetting agent, active ingredient 100%

[0152] NOPTAM 8034-LF: A silicone-based antifoaming agent, active ingredient 100%

[0153] (Examples 2 to 9)

[0154] Table 3 shows the raw material compounding amounts of the aqueous resin compositions obtained in Examples 1 to 9. In Examples 2 to 9, the same procedures as in Example 1 were carried out based on the raw material compounding amounts in Table 3, whereby aqueous resin compositions C-1 to C-9 were obtained. It should be noted that A-1 to A-14 represent the resin emulsions obtained in Production Examples 1 to 14, respectively. In addition, the values in the table represent the addition amounts (parts by mass), and the amounts in parentheses represent the active ingredient amounts.

[0155] (Comparative Examples 1 to 9)

[0156] Table 4 shows the raw material compounding amounts of the aqueous resin compositions obtained in Comparative Examples 1 to 9. Based on the raw material compounding amounts in Table 4, Comparative Examples 1 to 9 carried out the same procedures as in Example 1, thereby obtaining aqueous resin compositions C-10 to C-18. Here, Comparative Example 8 and Comparative Example 9 did not contain the wax emulsion containing wax particles (B), and instead of the wax emulsion, they contained a matting agent (manufactured by FujiSilysia chemical Ltd., trade name: SYLYSIA 530, component: powdered silica, average particle size 2.7 μm). It should be noted that A1 to A14 show the resin emulsions obtained in Production Examples 1 to 14. In addition, the values in the table represent the dosage (parts by mass), and the amount in parentheses represents the active ingredient amount.

[0157] [Table 3]

[0158]

[0159] The values are in parts by mass. The amount in parentheses is the active ingredient amount.

[0160] [Table 4]

[0161]

[0162] The values are in parts by mass. The amount in parentheses is the active ingredient amount.

[0163] [Performance Evaluation of Aqueous Resin Composition]

[0164] The following Test Examples 1 to 4 were carried out to evaluate the performance of the aqueous resin composition.

[0165] (Test Example 1 Glossiness Measurement)

[0166] The aqueous resin compositions obtained in Examples 1 to 9 and Comparative Examples 1 to 9 were coated on the surface of a black acrylic plate (length 120 mm × width 100 mm × thickness 2 mm) using a bar coater #10 (4.6 μm / dry). Then, the acrylic plate was dried in an atmosphere at 100 °C for 60 seconds to produce test pieces.

[0167] The glossiness of the above test pieces was measured using a gloss meter (manufactured by Konica Minolta, device name: GM-268plus) (in accordance with JIS Z8741). The glossiness measured at angles of 25°, 60°, and 85° with respect to the surface of the test piece is expressed as Gs(25°), Gs(60°), and Gs(85°). It should be noted that the JIS standard sets the following evaluation criteria for matting properties.

[0168] Glossy: Approximately 90 - 100% with a 60-degree specular gloss meter

[0169] Semi-matte: 30-70% based on 60-degree mirror gloss

[0170] Extinction: less than 30% based on 60-degree mirror gloss

[0171] (Test Example 2 Confirmation of Storage Stability)

[0172] A glass bottle with a cap was filled with an aqueous resin composition and left for one week in an atmosphere of 50° C. After one week, the glass bottle was naturally cooled to room temperature, and the presence or absence of sedimentation (separation degree) of the aqueous resin composition was evaluated based on the following four-level evaluation criteria.

[0173] ◎: No separation or sedimentation.

[0174] ○: There is slight separation and sedimentation, but the original state is restored by just light mixing.

[0175] △: Separated and settled into two layers, but returned to its original state if stirred and mixed.

[0176] ×: Separated and settled into two layers, and did not return to the original state even after stirring and mixing.

[0177] (Test Example 3 Confirmation of Abrasion Resistance)

[0178] The aqueous resin composition obtained in each example was applied to the surface of a 75 μm thick PET film using a bar coater #10 (4.6 μm / dry). The PET film was dried for 60 seconds at 100°C and then naturally cooled for 1 hour in a constant temperature and humidity chamber at 23°C × 50% RH. The PET film was then processed into a size of 250 mm long × 20 mm wide to obtain a test piece.

[0179] The test piece was rubbed 50 times with a load of 200 g using a Gakushin type friction fastness tester (manufactured by Daiei Kagaku Seiki Mfg. Co., Ltd.) After the test, the gloss change, scratches, and peeling of the sample were evaluated based on the following 4-level evaluation criteria.

[0180] ◎: The gloss change before and after the test is less than 5% and there is no obvious scratch or peeling.

[0181] ○: The gloss change rate before and after the test is 5% or more and less than 10%, and there is no significant scratch or peeling.

[0182] △: The gloss change rate before and after the test is 10% or more, or there are scratches or peeling.

[0183] ×: The change in gloss before and after the test is 10% or more and there are scratches and peeling.

[0184] (Test Example 4 Weathering Test)

[0185] Using a bar coater #10 (4.6 μm / dry), coat the surface of a black acrylic plate (120 mm in length × 100 mm in width × 2 mm in thickness) with the aqueous resin compositions obtained in various examples and the like. Dry the black acrylic plate in an atmosphere of 100 °C for 60 seconds to obtain a test piece.

[0186] Use a super accelerated weather resistance tester (manufactured by Iwasaki Electric Co., Ltd., model name: EYE Super UV Tester) to confirm the weather resistance of the test piece. Regarding the test conditions, take 12 hours of 4-hour irradiation (ultraviolet irradiation intensity 90 mW, black panel temperature 63 °C, 70% RH), 4-hour dark (black panel temperature 63 °C, 70% RH), and 4-hour dew condensation (black panel temperature 30 °C, 90% RH) as one cycle, and conduct a total of 10 cycles of tests. After the test, visually observe the cracking, peeling, discoloration, and change in gloss of the coating film of the test piece, and evaluate based on the following evaluation criteria of 4 grades.

[0187] ◎: No significant change compared to before the test.

[0188] ○: Slightly less gloss compared to before the test.

[0189] △: Slightly discolored, cracked, peeled, and less gloss compared to before the test.

[0190] ×: Significantly discolored, cracked, peeled, and less gloss compared to before the test.

[0191] Show the evaluation results of Examples 1 to 9 in Table 5. Show the evaluation results of Comparative Examples 1 to 9 in Table 6.

[0192] [Table 5]

[0193]

[0194] [Table 6]

[0195]

[0196] From the results of Table 5 and Table 6, the following facts were found. It was found that the gloss of Example 1 at all angles was lower than that of Comparative Example 1 (when the average particle size of wax particles (B) was 0.2 μm, less than the specified value). Here, the specified value is 380 - 5000 nm.

[0197] It was found that the gloss of Example 1 at all angles was lower than that of Comparative Example 7 (when the average particle size of wax particles (B) was 8 μm, greater than the specified value). Here, the specified value is 380 - 5000 nm.

[0198] It was found that the glossiness of Example 1 was lower than that of Comparative Example 5 (where the average particle diameter of resin particles (A) was 1150 nm, which was greater than the specified value) at all angles. Here, the specified value was 25 to 1000 nm.

[0199] The reasons why the glossiness of Example 1 was lower than that of Comparative Example 1, Comparative Example 5, and Comparative Example 7 are shown below. It is presumed that this is because by including emulsions of resin particles (A) and wax particles (B) having an average particle diameter (D50) within a specified range in the aqueous resin composition, a plurality of recesses can be formed in the layer of resin particles. In addition, as was found from the comparison results of Example 1 with Comparative Example 1, Comparative Example 5, and Comparative Example 7, it is considered that if neither resin particles (A) nor wax particles (B) have an average particle diameter within the specified average particle diameter (D50) range, a plurality of recesses cannot be formed in the layer of resin particles.

[0200] As described above, the aqueous resin composition of the present invention has a remarkable effect of improving the light extinction property by including a resin emulsion containing resin particles having a specified average particle diameter (D50) and a wax emulsion containing wax particles.

[0201] The present invention is not limited to the above-described embodiments, and various modifications and changes can be made within the scope of the gist of the invention.

Claims

1. An aqueous resin composition, characterized in that it contains: a resin emulsion containing resin particles and a wax emulsion containing wax particles, wherein the resin particles contain an ethylenically unsaturated monomer as a constituent unit, the average particle size of the resin particles is 25 to 1000 nm, the average particle size of the wax particles is 380 to 5000 nm, the particle size distribution of the resin particles, i.e., D90 / D10, is 1.01 to 5.00, the melting point of the wax particles is lower than the melting point of the resin particles, the glass transition temperature of the resin particles is -50 to 100 °C, herein, the melting point of the wax particles is the temperature obtained by differential scanning calorimetry (DSC) for the wax particles, the melting point of the resin particles is the temperature obtained by differential scanning calorimetry (DSC) for the resin particles, the glass transition temperature of the resin particles is the temperature obtained based on the glass transition temperatures of the respective homopolymers formed only from the monomers constituting the resin particles and the Fox formula.

2. The aqueous resin composition according to claim 1, characterized in that relative to 100 parts by mass of the resin particles, 5 to 200 parts by mass of the wax particles are contained.

3. The aqueous resin composition according to claim 1, characterized in that the melting point of the wax particles is 40 to 150 °C.

4. The aqueous resin composition according to claim 1, characterized in that the ethylenically unsaturated monomer contains at least any one of an acrylic monomer, a styrenic monomer, and an amide monomer.

5. The aqueous resin composition according to claim 1, characterized in that the wax particles contain at least any one of paraffin wax, microcrystalline wax, and polyethylene wax.

6. A method for manufacturing a coated article, characterized in that it includes: coating the aqueous resin composition according to claim 1 on a substrate, and heating the substrate coated with the aqueous resin composition at a temperature above the melting point of the wax particles and less than the melting point of the resin particles.

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