Water-based glossy coating compositions and coated panels

Abstract

A water-based glossy coating composition and a coated panel are provided, which can express a metallic design and suppress coating defects. The water-based glossy coating composition comprises a cellulose ester derivative, cellulose nanofibers, and flake-like pigments, wherein the amount of solid components in the water-based glossy coating composition is 0.1% by mass or more and 12% by mass or less. The coated panel has a coated object and a glossy coating film formed from the above-mentioned water-based glossy coating composition.

Description

Technical Field

[0001] This invention relates to water-based glossy coating compositions and coated panels. Background Technology

[0002] In recent years, coatings capable of imparting a metallic sheen to the exterior of automobiles have been proposed. For example, Patent Document 1 discloses a glossy coating capable of forming a coating with excellent metallic or pearlescent sheen.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2021 / 002196 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, if the coating described in Patent Document 1 is used, the coating film is prone to defects such as borders and orange peel, which reduces design flexibility. The objective of this invention is to provide a glossy water-based glossy coating composition and a coated panel that can express a metallic style while suppressing coating defects.

[0008] Methods for solving problems

[0009] To address the aforementioned issues, the present invention provides the following approach.

[0010] [1] A water-based glossy coating composition comprising cellulose ester derivatives, cellulose nanofibers, and flake-like pigments.

[0011] The amount of solid components contained in the aforementioned water-based glossy coating composition is 0.1% by mass or more and 12% by mass or less.

[0012] [2] According to the water-based glossy coating composition described in [1] above, wherein the content of the aforementioned cellulose nanofibers C N The content of the aforementioned cellulose ester derivatives C E The ratio C N / C E It is above 0.03 and below 1.0.

[0013] [3] According to the waterborne glossy coating composition described in [1] or [2] above, wherein the aforementioned cellulose ester derivative is a condensation reaction product of an oxyacid having a hydrocarbon group having 1 to 20 carbon atoms and cellulose.

[0014] [4] The waterborne glossy coating composition according to any one of [1] to [3] above, wherein the acid value of the aforementioned cellulose ester derivative is 20 mg KOH / g or more.

[0015] [5] The water-based glossy coating composition according to any one of [1] to [4] above, wherein the content of the aforementioned cellulose nanofibers C N The content is 0.03% by mass or more and 1% by mass or less of the aforementioned water-based glossy coating composition.

[0016] [6] The waterborne glossy coating composition according to any one of [1] to [5] above, wherein the content of the aforementioned flake pigment is 0.1% by mass or more and 1.5% by mass or less of the aforementioned waterborne glossy coating composition.

[0017] [7] The waterborne glossy coating composition according to any one of [1] to [6] above, wherein the content of the aforementioned flake pigment is 3% by mass or more and 50% by mass or less of all solid components of the aforementioned waterborne glossy coating composition.

[0018] [8] The water-based glossy coating composition according to any one of [1] to [7] above, wherein the aforementioned flake pigment comprises aluminum particles,

[0019] The aforementioned water-based glossy coating composition also contains compounds containing phosphate groups.

[0020] [9] According to the above [8] waterborne glossy coating composition, wherein the aforementioned phosphate-containing compound comprises at least one of an alkyl phosphate having an alkyl group having 4 to 30 carbon atoms and a phosphate-containing polymer having a phosphate group value of 5 mg KOH / g or more and 300 mg KOH / g or less.

[0021]

[10] According to the above-described [8] or [9] waterborne glossy coating composition, wherein the content of the aforementioned compound containing phosphate groups is 0.1% by mass or more and 15% by mass or less of all solid components of the aforementioned waterborne glossy coating composition.

[0022]

[11] A coated panel having a coating material and a glossy coating film,

[0023] The aforementioned glossy coating is formed from any of the water-based glossy coating compositions described in any one of [1] to

[10] .

[0024]

[12] According to the coated plate described in

[11] above, the dry film thickness of the aforementioned glossy coating is less than 5 μm.

[0025] Invention Effects

[0026] According to the present invention, a water-based glossy coating composition and coated panel are provided that can express a metallic design and suppress coating defects. Attached Figure Description

[0027] Figure 1 This is a front view of the coated panel produced in Example 1.

[0028] Figure 2 This is a front view of the painted panel produced in Comparative Example 1. Detailed Implementation

[0029] To enhance the metallic effect of the design, it is required that the flake-like pigments be arranged parallel to the surface of the glossy coating. Therefore, the paint (glossy coating) that forms the glossy film should have a low solids content. Consequently, cellulose nanofibers (hereinafter sometimes simply referred to as CNF) are typically blended in to adjust the viscosity to a usable consistency for coating purposes. CNF can increase the viscosity of the coating in small amounts. Furthermore, CNF is used to suppress the sedimentation of the flake-like pigments.

[0030] CNF can cause excessive aggregation of solid components in coatings. Therefore, during the application and drying process of coatings containing CNF, coating film aggregation sometimes occurs, resulting in coating defects known as orange peel or edge formation.

[0031] It has been established that blending cellulose ester derivatives with CNF can suppress coating defects. Because cellulose ester derivatives tend to concentrate on the coating surface, the surface viscosity of glossy coatings increases. As a result, the movement of glossy coatings, and consequently multilayer coatings, is suppressed, making the aforementioned coating defects less likely to occur. Furthermore, cellulose ester derivatives improve the alignment of flake pigments, thus further enhancing design flexibility.

[0032] [Water-based gloss coating composition]

[0033] Waterborne glossy coating compositions (hereinafter sometimes simply referred to as glossy coatings) comprise cellulose ester derivatives, cellulose nanofibers, and flake pigments. Glossy coatings may, as needed, include various additives such as surface conditioners. In cases where the flake pigments contain aluminum particles, the glossy coating preferably also contains compounds containing phosphate groups. Glossy coatings are prepared by diluting a mixture of the above components with an aqueous solvent.

[0034] The amount of solid components (solid component content) in the glossy coating is 0.1% by mass or more and 12% by mass or less. This allows the flake-like pigments to easily align at a high density along the coated surface. The solid component content of the glossy coating is preferably 0.5% by mass or more, more preferably 1% by mass or more, and particularly preferably 1.5% by mass or more. The solid component content of the glossy coating is preferably 10% by mass or less, more preferably 8% by mass or less, and particularly preferably 5% by mass or less. The solid component of the glossy coating comprises all components remaining after removing the aqueous solvent from the glossy coating.

[0035] There is no particular limitation on the viscosity of glossy coatings. From the viewpoint of easily suppressing the disordered arrangement of flake pigments, the viscosity of glossy coatings measured by a type B viscometer at 20°C is preferably 20 cps / 6 rpm or higher and 2,000 cps / 6 rpm or lower.

[0036] (cellulose nanofibers)

[0037] Cellulose nanofibers (CNFs), as defined in ISO TS 20477, are obtained by mechanically defibrating plant raw materials. CNFs are substances containing crystalline, quasi-crystalline, or amorphous cellulose microfibers (single nanofibers), either individually or longitudinally torn, entangled, or aggregates of these materials with a mesh-like structure. CNFs also include substances referred to as cellulose nanofibers, fibrillated cellulose, nanocellulose crystals, etc. Common plant raw materials include wood. Other examples include bamboo, rice straw, wheat straw, rice husks, herbs (such as Miscanthus sinensis), and seaweed. As described later, CNFs, for example, have an aspect ratio of 10 or higher and are fibrous. Therefore, CNFs disperse in a mesh-like structure in glossy coatings, increasing the viscosity of the coating.

[0038] Before mechanical defiberization, the plant raw material is usually chemically treated. The shape of the plant raw material does not change due to chemical treatment; it remains fibrous. Anionic groups such as carboxyl, phosphate, phosphite, carboxymethyl, and sulfonyl groups are introduced into the resulting CNF through chemical treatment. Examples of chemical treatments include, for instance, the TEMPO oxidation method (introducing carboxyl groups by oxidation with 2,2,6,6-tetramethylpiperidin-1-oxy (TEMPO)), the phosphorylation method (introducing phosphate groups), the phosphite esterification method (introducing phosphite groups), the carboxymethylation method (introducing carboxymethyl groups), and the sulfonation method (introducing sulfonyl groups). The characteristics of the resulting CNF may vary depending on the type of chemical treatment. In this embodiment, CNFs subjected to any chemical treatment can be used.

[0039] From the viewpoint of excellent transparency, CNF treated by TEMPO oxidation (hereinafter referred to as TEMPO-oxidized CNF) is preferred. CNF treated by TEMPO oxidation after acid treatment is particularly preferred. The acid treatment is carried out under conditions, for example, a pH of 2 to 6 and a temperature of 30°C or higher and 120°C or lower. The acid can be an inorganic acid or an organic acid.

[0040] The amount of carboxyl groups in TEMPO oxidized CNF is, for example, 0.5 mmol / g or more and 2.5 mmol / g or less relative to absolute dry mass. The aforementioned amount of carboxyl groups can be 1.0 mmol / g or more, particularly preferably 1.3 mmol / g or more. The aforementioned amount of carboxyl groups can be 2.0 mmol / g or less, or 1.6 mmol / g or less.

[0041] The amount of carboxyl groups was calculated, for example, by the following method: 0.1 M hydrochloric acid aqueous solution was added to 60 mL of 0.5% by mass CNF slurry to adjust the pH to 2.5. Next, 0.05 N sodium hydroxide aqueous solution was added dropwise to the slurry, and the conductivity was measured until the pH reached 11. The amount of sodium hydroxide consumed (a) during the weak acid neutralization phase, in which the conductivity changed slowly, was determined. The amount of carboxyl groups was calculated based on this amount of sodium hydroxide (a) and the following formula.

[0042] Carboxyl group content [mmol / g TEMPO oxidized CNF] = a[mL] × 0.05 / mass of TEMPO oxidized CNF [g]

[0043] From the viewpoint of preventing the sedimentation of flake-like pigments, the average fiber width of CNF is, for example, 1 nm or more and 300 nm or less. The average fiber width of CNF can be 2 nm or more, or 3 nm or more. From the viewpoint of transparency, the average fiber width of CNF can be 200 nm or less, 100 nm or less, or 90 nm or less.

[0044] From the viewpoint of preventing the sedimentation of flake-like pigments, the average fiber length of CNF can be, for example, 0.1 μm or more and 200 μm or less. The average fiber length of CNF can be 0.5 μm or more, 1 μm or more, or 2 μm or more. From the viewpoint of transparency, the average fiber length of CNF can be 100 μm or less, or 90 μm or less.

[0045] The aspect ratio of CNF can be, for example, 10 or more and 2,000 or less. The aspect ratio of CNF can be 20 or more, 25 or more, or 100 or more. The aspect ratio of CNF can be 2,000 or less, 1,000 or less, or 500 or less.

[0046] Average fiber width and average fiber length can be calculated by measuring the fiber diameter and fiber length of a sufficient number of fibers using atomic force microscopy (AFM) or transmission electron microscopy (TEM) and then averaging them. The aspect ratio is the value obtained by dividing the average fiber length by the average fiber width (average fiber length / average fiber width).

[0047] CNF content C NPreferably, it is 0.03% by mass or more of the glossy coating. This makes it easier to exhibit the effects achieved by CNF. (Content C) N Preferably, it is 1.0% by mass or less of the glossy coating. This easily suppresses the occurrence of coating defects. Content C N More preferably, it is 0.06% by mass or more of the glossy coating, and particularly preferably 0.1% by mass or more. Content C N More preferably, the content of the glossy coating is 0.6% by mass or less, and particularly preferably 0.3% by mass or less. In one embodiment, the content C N It is 0.03% by mass and less than 1.0% by mass of the glossy coating.

[0048] (cellulose ester derivatives)

[0049] Cellulose ester derivatives are oxyacids (representatively carboxylic acids) and cellulose (C6H4O2). 10 O5) n The condensation reaction products of cellulose esters. In cellulose ester derivatives, the hydroxyl groups of cellulose are esterified, thus controlling the balance between hydrophilicity and hydrophobicity. Consequently, the aspect ratio of cellulose ester derivatives is smaller than that of CNF, for example, less than 10. Therefore, cellulose ester derivatives exhibit different behavior from CNF in glossy coatings or films.

[0050] The oxyacid (in other words, the group that forms an ester bond with the hydroxyl group of cellulose) preferably has a hydrocarbon group having 1 to 20 carbon atoms. The general structure of cellulose ester derivatives is shown in the following formula.

[0051] [Chemistry 1]

[0052]

[0053] In the formula, R is independently hydrogen (H) or acyl group (-C(=O)-R). 1 ), hydrocarbon group (-R) 1 ), carboxyalkyl (-R) 2 (COOH), at least one of which is an acyl group. Multiple R 1 and R 2 They can be the same or different.

[0054] R 1 For example, a hydrocarbon group with 1 to 20 carbon atoms. The hydrocarbon group can be aliphatic, chain-like, or cyclic, and may also have an aromatic ring. Among them, R... 1 Preferably, it is a chain or branched aliphatic hydrocarbon group with 2 to 10 carbon atoms, or more specifically 2 to 4 carbon atoms.

[0055] R 2 For example, alkylene groups having 1 to 20 carbon atoms. Alkylene groups can be chain-like, branched, or cyclic. Wherein, R...2 Preferably, it is a chain or branched alkylene group having 2 to 10 carbon atoms, or more specifically 2 to 4 carbon atoms.

[0056] The acid value of the cellulose ester derivative is preferably 20 mg KOH / g or higher. This allows the cellulose ester derivative to exist stably in water-based coatings and easily exert its effects. More preferably, the acid value of the cellulose ester derivative is 40 mg KOH / g or higher. The acid value of the cellulose ester derivative can be 150 mg KOH / g or lower.

[0057] As cellulose ester derivatives, specifically, examples include cellulose acetate, cellulose triacetate, cellulose acetate phthalate, cellulose acetate butyrate, cellulose butyrate, cellulose tributyrate, cellulose propionate, cellulose tripropionate, cellulose acetate propionate, carboxymethyl cellulose acetate, carboxymethyl cellulose acetate propionate, carboxymethyl cellulose acetate butyrate, cellulose acetate butyrate succinate, and cellulose propionate butyrate. They can be used individually or in combination of two or more. Carboxymethyl cellulose acetate butyrate is preferred.

[0058] The content of cellulose ester derivatives is preferably set based on the CNF content. The content of cellulose nanofibers (C) N Content of cellulose ester derivatives C E The ratio C N / C E Preferably, it is 0.03 or higher. This makes it easier to exhibit the effects achieved by CNF, namely, preventing viscosity increases and the sedimentation of flake pigments. Ratio C N / C E More preferably, it is 1.0 or less. This makes it easier to exhibit the effects of cellulose ester derivatives, namely, suppressing the occurrence of coating defects. Ratio C N / C E Further preferably, it is 0.06 or higher, and particularly preferably 0.1 or higher. Ratio C N / C E More preferably, it is 0.6 or less, and particularly preferably 0.3 or less. In one embodiment, the ratio C N / C E It is between 0.03 and 1.0. The content is calculated based on the solid content.

[0059] (Scale-like pigment)

[0060] There are no particular limitations on the aspect ratio of flake-shaped pigments as long as they reflect light. From the viewpoint that it is easier to enhance the metallic texture, the aspect ratio of flake-shaped pigments is preferably 2 or higher. The aspect ratio is the ratio of the major diameter of one principal surface of the flake-shaped pigment to the distance (thickness) between the two principal surfaces of the flake-shaped pigment: major diameter / thickness. The aspect ratio of flake-shaped pigments can be 10 or higher and 1000 or lower.

[0061] The major diameter of the flake-like pigment is not particularly limited. For example, the major diameter of the flake-like pigment can be 1 μm or more and 80 μm or less. The major diameter of the flake-like pigment can be 3 μm or more. The major diameter of the flake-like pigment can be 50 μm or less. The above-mentioned major diameters are calculated by observing the coating film formed by the glossy paint (glossy coating film) from its normal direction using an electron microscope. In the field of view, image processing software is used to binarize the area corresponding to the flake-like pigment and the other areas. Then, 20 flake-like pigments are randomly selected, and their longest diameters are measured. The average of these measurements is the major diameter of the flake-like pigment.

[0062] The thickness of the flake-like pigment is not particularly limited. For example, the thickness of the flake-like pigment can be 0.02 μm or more and 0.18 μm or less. The thickness can also be 0.15 μm or less. These thicknesses can be calculated by observing the cross-section of the glossy coating using an electron microscope. In the field of view, image processing software is used to binarize the area corresponding to the flake-like pigment and the other areas. Then, 20 flake-like pigments are randomly selected, and the length of their thickest portion is measured for each. The average of these measurements is the thickness of the flake-like pigment.

[0063] There is no particular limitation on the average particle size of flake-like pigments. From the viewpoint that a metallic texture can be easily enhanced, the average particle size of flake-like pigments can be 2 μm or more and 50 μm or less. The average particle size of flake-like pigments can be 5 μm or more. The average particle size of flake-like pigments can be 35 μm or less. The average particle size refers to the volume average particle size D50. The volume average particle size D50 can be measured using a laser Doppler particle size analyzer (e.g., Nikkiso's "MICROTRAC UPA150").

[0064] From a design perspective, the content of the flake-like pigment is preferably 0.1% by mass or more of the glossy coating. From the same perspective, the content of the flake-like pigment is preferably 1.5% by mass or less of the glossy coating. More preferably, the content of the flake-like pigment is 0.15% by mass or more of the glossy coating, and particularly preferably 0.2% by mass or more. More preferably, the content of the flake-like pigment is 1% by mass or less, and particularly preferably 0.8% by mass or less. In one embodiment, the content of the flake-like pigment is 0.1% by mass or more and 1.5% by mass or less. In particular, if the content of cellulose nanofibers C... NIf the content of glossy coating is 0.03% to 1% by mass and the content of flake pigment is 0.1% to 1.5% by mass, the designability can be further improved.

[0065] From a design perspective, the content of flake pigments can be 3% or more by mass, 5% or more by mass, or 7% or more by mass of the total solid components of the glossy coating. The content of flake pigments can be, for example, less than 50% by mass of the total solid components of the glossy coating, less than 20% by mass, or less than 10% by mass. In one embodiment, the content of flake pigments is 3% or more and less than 50% by mass of the total solid components of the glossy coating.

[0066] There are no particular limitations on flake-shaped pigments. Examples of flake-shaped pigments include metal particles, metal-coated mica, metal-coated glass particles, and graphite. Specifically, examples of metal particles include particles of aluminum, copper, zinc, iron, iron phosphide, nickel, tin, aluminum oxide, and alloys containing them. They can be used alone or in combination of two or more. Flake-shaped pigments can be used for coloring. From the viewpoint that a metallic texture is easily enhanced, aluminum particles are preferred.

[0067] (Compounds containing phosphate groups)

[0068] Glossy coatings may further contain compounds containing phosphate groups. Especially in cases where the flake pigment contains aluminum particles, glossy coatings preferably contain compounds containing phosphate groups. Using compounds containing phosphate groups improves the dispersibility of aluminum particles in water-based coatings, thereby facilitating their alignment.

[0069] The content of the compound containing phosphate groups is not particularly limited. Preferably, the content of the compound containing phosphate groups is 0.1% by mass or more, more preferably 1% by mass or more, of the total solid components of the glossy coating. Preferably, the content of the compound containing phosphate groups is 15% by mass or less, more preferably 12% by mass or less, of the total solid components of the glossy coating. In one embodiment, the content of the compound containing phosphate groups is 0.1% by mass or more and 15% by mass or less of the total solid components of the glossy coating.

[0070] Compounds containing phosphate groups only need to have a phosphate group (-P (=O) OR) 2 (R is independently hydrogen or hydrocarbon group) There is no particular limitation. Compounds containing phosphate groups are, for example, at least one of alkyl phosphate esters having alkyl groups having 4 to 30 carbon atoms and polymers containing phosphate groups with a phosphate group value of 5 mg KOH / g or more and 300 mg KOH / g or less.

[0071] Alkyl phosphate esters

[0072] Alkyl phosphates have alkyl groups having 4 to 30 carbon atoms. Examples of alkyl phosphates include monoalkyl phosphates, dialkyl phosphates, and mixtures thereof. In dialkyl phosphates, the two alkyl groups may be the same or different. Dialkyl phosphates preferably have two identical alkyl groups.

[0073] Examples of alkyl groups with 4 to 30 carbon atoms include butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, octadecyl, nonadecanyl, eicosyl, dodecyl, tetradecyl, hexadecyl, and octadecyl. Alkyl groups can be linear or branched.

[0074] Examples of alkyl phosphate esters include, for instance, butyl phosphate (a mixture of monobutyl phosphate and dibutyl phosphate), 2-ethylhexyl phosphate (a mixture of mono-2-ethylhexyl phosphate and di-2-ethylhexyl phosphate), isodecanyl phosphate (a mixture of monoisodecyl phosphate and diisodecyl phosphate), dilauryl phosphate, lauryl phosphate (a mixture of monolauryl phosphate and dilauryl phosphate), tridecyl phosphate (a mixture of monotetrate phosphate and ditetrate phosphate), monostearyl phosphate, distearyl phosphate, stearyl phosphate (a mixture of monostearyl phosphate and distearyl phosphate), isostearyl phosphate (a mixture of monoisostearyl phosphate and diisostearyl phosphate), oleyl phosphate (a mixture of monooleyl phosphate and dioleyl phosphate), and docosyl phosphate (a mixture of monodocosyl phosphate and di(docosyl) phosphate).

[0075] <Polymers containing phosphate groups>

[0076] Polymers containing phosphate groups have a phosphate group value of 5 mg KOH / g or more and 300 mg KOH / g or less. When the phosphate group value is within this range, water resistance and adhesion are easily improved together. Preferably, the phosphate group value of the polymer containing phosphate groups is 10 mg KOH / g or more, more preferably 50 mg KOH / g or more. Preferably, the phosphate group value of the polymer containing phosphate groups is 250 mg KOH / g or less, more preferably 150 mg KOH / g or less. In one embodiment, the polymer containing phosphate groups has a phosphate group value of 50 mg KOH / g or more and 300 mg KOH / g or less.

[0077] The phosphate value is calculated according to the JIS K56012-1 method for determining acid value. Specifically, the acid value is the number of mg of potassium hydroxide (KOH) required to neutralize the free acid in 1g of the nonvolatile matter of the product.

[0078] The number average molecular weight of polymers containing phosphate groups is, for example, 1,000 or more and 50,000 or less. The number average molecular weight of polymers containing phosphate groups is preferably 3,000 or more, more preferably 5,000 or more. The number average molecular weight of polymers containing phosphate groups is preferably 30,000 or less, more preferably 20,000 or less.

[0079] Examples of polymers containing phosphate groups include acrylic resins, polyester resins, polyether resins, and epoxy resins, with phosphate group values ​​of 5 mg KOH / g or more and 300 mg KOH / g or less. These can be used individually or in combination of two or more. From the viewpoint of water resistance, acrylic resins containing phosphate groups are preferred. Acrylic resins containing phosphate groups are obtained, for example, by polymerizing α,β-ene unsaturated monomers containing phosphate groups or by copolymerizing such monomers with other α,β-ene unsaturated monomers that do not contain phosphate groups.

[0080] (Water-based solvent)

[0081] As a water-based solvent, various types of water can be listed, such as pure water, ion-exchanged water, tap water, and industrial water. There is no particular limitation on the amount of water-based solvent; it is set such that the solid content of the glossy coating is 0.1% by mass or more and 12% by mass or less.

[0082] Glossy coatings can contain both aqueous and organic solvents. Examples of organic solvents include alkyl (or aromatic) alcohols such as n-butanol, n-hexanol, 2-ethylhexanol (2EHOH), lauryl alcohol, phenol methanol, and methylphenylmethanol; cellosols such as ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylhexyl ether, and ethylene glycol monobutyl ether (butyl cellosol); phenols such as p-tert-butylphenol and cresol; and oximes such as dimethyl ketoxime, methyl ethyl ketoxime, methyl isobutyl ketoxime, methyl pentyl ketoxime, and cyclohexanone oxime. Alkyl alcohols and cellosols are preferred.

[0083] (Surface Conditioner)

[0084] Glossy coatings can contain surface modifiers. This allows for control of the surface tension of the glossy coating, making it easier for flake-like pigments to align parallel to the glossy film. Furthermore, it improves the wettability of the uncured colored film of the glossy coating and enhances interlayer adhesion.

[0085] The surface modifier is not particularly limited. Examples of surface modifiers include silicone-based, acrylic-based, vinyl-based, and fluorine-based surface modifiers. They can be used alone or in combination of two or more. From the viewpoints of design and water resistance, silicone-based surface modifiers are preferred. Examples of silicone-based surface modifiers include polydimethylsiloxane and modified silicones obtained by modifying it. Examples of modified silicones include polyether modifiers, acrylic modifiers, and polyester modifiers.

[0086] Commercially available surface conditioners include, for example, the BYK series (manufactured by Bickchem), the Tego series (manufactured by Evonick), the Granoel series, the Polyflo series (all manufactured by Kyoei Chemical Co., Ltd.), and the Disparon series (manufactured by Kusumoto Chemical Co., Ltd.).

[0087] The amount of surface modifier is not particularly limited. Preferably, the amount of surface modifier is 0.1% by mass or more of the glossy coating, more preferably 0.15% by mass or more. Preferably, the amount of surface modifier is 10% by mass or less of the glossy coating, more preferably 5% by mass or less, and particularly preferably 2% by mass or less.

[0088] (Resin film formation)

[0089] Glossy coatings may contain film-forming resins. From a design perspective, it is desirable to have a low content of film-forming resins. The content of film-forming resins in glossy coatings is preferably 10% by mass or less, more preferably 5% by mass or less, and can be 0% by mass.

[0090] Examples of film-forming resins include acrylic resins, polyester resins, epoxy resins, and urethane resins. Film-forming resins may comprise resins containing curable functional groups and corresponding curing agents. Specifically, examples include hydroxyl-containing resins and combinations of at least one selected from amino resins (melamine resins), urea resins, polyisocyanate compounds, epoxy-containing compounds, carboxyl-containing compounds, carbodiimide-containing compounds, hydrazide-containing compounds, and urea-amino-containing compounds. Polyisocyanate compounds comprise end-capped polyisocyanate compounds obtained by end-capping isocyanate groups with an end-capping agent. They may be used alone or in combination of two or more.

[0091] (Other adhesives)

[0092] The glossy coating may include adhesives other than cellulose ester derivatives and CNFs, to the extent that it does not impair the effects of this embodiment. Examples of such adhesives include hydrophobic associative adhesives, polycarboxylic acid adhesives, amide-based adhesives, inorganic mineral-based adhesives, silica-based micropowders, barium sulfate micropowders, polyamide-based adhesives, organic resin microparticle adhesives, diurea-based adhesives, and cellulose ethers. One of these can be used alone, or two or more can be used in combination.

[0093] Examples of hydrophobic associative adhesives include, for example, polyacrylic acid adhesives copolymerized with hydrophobic monomers, polyurethane adhesives (urethane associative thickeners) having hydrophobic chains in their molecules, urethane-urea adhesives whose main chain is at least partly composed of hydrophobic urethane chains, and amide-urea adhesives whose main chain is at least partly composed of hydrophobic amide chains. Examples of cellulose ethers include, for example, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, and hydroxypropyl methyl cellulose.

[0094] (Other pigments)

[0095] Glossy coatings may contain pigments other than flake pigments, depending on their opacity and other properties. Examples of other pigments include, for instance, anti-rust pigments, coloring pigments, and extender pigments. From the viewpoint of the arrangement of flake pigments, the content of other pigments is preferably 10% by mass or less, more preferably 5% by mass or less, of the total of all flake pigments and other pigments.

[0096] Organic pigments, such as azo chelate pigments, insoluble azo pigments, condensed azo pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, phthalocyanine pigments, indigo pigments, perylene ketone pigments, perylene pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments, and metal complex pigments, are examples of organic pigments. Inorganic pigments, such as chrome yellow, yellow iron oxide, iron oxide red, carbon black, and titanium dioxide, are examples of inorganic pigments. Extender pigments, such as calcium carbonate, barium sulfate, clay, and talc, are also examples. These can be used individually or in combination of two or more.

[0097] (other)

[0098] In addition to glossy coatings, various additives may be included as needed. Examples of additives include, for instance, UV absorbers, light stabilizers, antioxidants, defoamers, dispersants, and anti-pinhole agents.

[0099] [Painted Panel]

[0100] The coated panel described in this embodiment includes a coated object and a glossy coating film. The glossy coating film is formed from the above-described water-based glossy paint composition.

[0101] (The object being coated)

[0102] There are no particular limitations on the material of the object to be coated. Examples of materials that can be coated include metal, resin, and glass. There are also no particular limitations on the shape of the object to be coated. Examples of objects that can be coated include the body of automobiles such as cars, trucks, motorcycles, and buses, and parts for automobile bodies.

[0103] Examples of metals include iron, copper, aluminum, tin, zinc, or their alloys. Metallic substrates can undergo surface treatment. Examples of surface treatments include phosphate treatment, chromate treatment, zirconium formation treatment, and composite oxide treatment. After surface treatment, metallic substrates can be further coated with electrodeposited coatings. Electrodeposited coatings can be cationic or anionic.

[0104] Examples of resins include polypropylene resin, polycarbonate resin, urethane resin, polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, and polyamide resin. The resin-based coating is preferably degreased. After degreasing, the resin-based coating can be further coated with a primer. The primer is not particularly limited, as long as it is appropriately selected based on the type of coating to be applied.

[0105] (Glossy coating)

[0106] Glossy coatings impart a metallic texture to the coated object. The thickness of the glossy coating is, for example, 0.05 μm or more and 5 μm or less. This facilitates the arrangement of flake-like pigments, making it easier to achieve a superior metallic design. The thickness of the glossy coating can be less than 1.0 μm, less than 0.8 μm, or less than 0.7 μm. The thickness of the glossy coating can also be greater than 0.1 μm or greater than 0.3 μm.

[0107] (Colored coating)

[0108] The desired coating is a colored coating film. This colored coating film is positioned between the substrate and the glossy coating film, or is configured to cover the glossy coating film. The colored coating film masks the texture and color of the substrate, imparting the desired hue to the coated panel.

[0109] A colored coating film is formed by a colored paint. The colored paint contains, for example, a hydroxyl-containing resin, a curing agent, and a coloring pigment. The colored paint is prepared by diluting a mixture of the above components with an aqueous solvent or an organic solvent. The colored paint can be a one-component paint, a two-component paint, or a multi-component paint.

[0110] There is no particular limitation on the thickness of the colored coating. From the viewpoint of opacity, the thickness of the colored coating can be 5 μm or more and 50 μm or less. The thickness of the colored coating can be 10 μm or more and 20 μm or more. The thickness of the colored coating can be 45 μm or less and 40 μm or less.

[0111] (Transparent coating)

[0112] The desired coating is a transparent film that covers the glossy coating. The transparent film protects the glossy coating. There are no particular limitations on the transparent film; existing known transparent coatings can be used. The transparent coating can be a powder, water-based, or solvent-based. The transparent coating can be a one-component coating, a two-component coating, or a multi-component coating. The transparent coating can contain pigments to the extent that it does not impair transparency.

[0113] There is no particular limitation on the thickness of the transparent coating. From the viewpoint of facilitating improved appearance, the thickness of the transparent coating can be 10 μm or more but less than 50 μm. The thickness of the transparent coating can be 15 μm or more. From the viewpoint of not compromising whiteness and the metallic texture, the thickness of the transparent coating can be less than 40 μm.

[0114] [Manufacturing method of coated panels]

[0115] Coated panels can be obtained, for example, by a process of applying a glossy coating to a substrate to form an uncured glossy coating film, and a process of curing the uncured glossy coating film.

[0116] A coated panel having a colored coating, a glossy coating, and a clear coating in sequence is preferably manufactured by the following method. That is, the coated panel can be manufactured by a method comprising the following steps: applying a colored coating to a substrate to form an uncured colored coating; applying a glossy coating to the uncured colored coating to form an uncured glossy coating; applying a clear coating to the uncured glossy coating to form an uncured clear coating; and curing the uncured colored coating, the uncured glossy coating, and the uncured clear coating to obtain a multilayer coating.

[0117] (Painting method)

[0118] There are no particular limitations on the coating method for each type of paint. Examples of coating methods include air spray coating, airless spray coating, rotary atomization coating, and curtain coating. These methods can be combined with electrostatic coating. Among these, from the viewpoint of coating efficiency, rotary atomization electrostatic coating is preferred. Rotary atomization electrostatic coating can be performed using rotary atomization electrostatic coating machines, such as those commonly known as "micromicrobeal (μμbeal)," "microbeal (μbeal)," or "metalicbeal."

[0119] After each coat of paint is applied, pre-drying (also known as preheating) can be performed. This prevents sudden boiling of the solvent in the coating film during the curing process, thus reducing the likelihood of wrinkles. Furthermore, pre-drying inhibits the mixing of uncured coating layers, making it less likely for a mixed phase to form. Therefore, the appearance of the resulting coated panel is generally improved.

[0120] There are no particular limitations on the pre-drying conditions. Examples of pre-drying methods include placing the product at a temperature of 20°C or higher and 25°C or lower for 15 to 30 minutes, or heating it at a temperature of 50°C or higher and 100°C or lower for 30 to 10 minutes.

[0121] (Curing)

[0122] Each coating film can be cured by heating. The heating conditions are appropriately set according to the composition of each coating film. The heating temperature is, for example, 70°C or higher and 150°C or lower, or 80°C or higher and 140°C or lower. The heating time is, for example, 10 minutes or higher and 40 minutes or lower, or 20 minutes or higher and 30 minutes or lower. Examples of heating devices include drying ovens such as hot air furnaces, electric furnaces, and infrared induction heating ovens.

[0123] Example

[0124] The present invention is illustrated below with examples and comparative examples. However, the invention is not limited to these examples. It should be noted that "parts" and "%" are based on mass. The mixing amounts listed in the table are solid content amounts.

[0125] [Example 1]

[0126] The following procedures were followed to produce a glossy coating and a coated panel with multiple layers. The resulting glossy coating and coated panel were then evaluated. The results are shown in Table 1. Figure 1 A front view photograph of the coated panel produced in Example 1 is shown.

[0127] (I) Preparation of the coating material

[0128] As the substrate, a zinc phosphate treated steel sheet with a cured electrodeposited coating is prepared. The cured electrodeposited coating is formed by electrodepositing a cationic electrodeposited coating composition "Powernix" manufactured by Nippon Paint Co., Ltd. onto the zinc phosphate treated steel sheet with a dry film thickness of 20 μm, followed by heating at 160°C for 30 minutes.

[0129] (II) Preparation of coatings

[0130] (II-1) Preparation of Coloring Coatings

[0131] 130.5 parts of a white pigment dispersion paste, 73.9 parts (30 parts by weight of resin solids) of an acrylic resin emulsion containing hydroxyl groups, 60 parts (30 parts by weight of resin solids) of a polyester resin containing hydroxyl groups, 100 parts (20 parts by weight of resin solids) of a polyurethane resin containing hydroxyl groups (manufactured by PAINTAUTOMOTIVE COATINGS, Japan), and 22.2 parts of CYMEL327 (melamine resin manufactured by Allnex) as a curing agent were mixed. Then, 40 parts of deionized water were added to the mixture, and mixing was further performed. Next, 3.3 parts of Viscalex HV-30 (polycarboxylic acid adhesive manufactured by BASF, with 30% non-volatile components) as a viscous agent were added to the mixture, and mixing and stirring were performed further to obtain a colored coating.

[0132] (Preparation of white pigment dispersion paste)

[0133] 4.5 parts of Disperbyk190 (manufactured by Big Keme Co., Ltd., a nonionic / anionic dispersant), 0.5 parts of BYK-011 (manufactured by Big Keme Co., Ltd.) as an antifoaming agent, 22.9 parts of ion-exchanged water, and 72.1 parts of titanium dioxide were premixed. Then, glass beads were added to the paint mixer and mixed at room temperature until the secondary particle size of titanium dioxide reached less than 5 μm to obtain a pigment dispersion paste.

[0134] (Manufacturing of acrylic resin emulsions containing hydroxyl groups)

[0135] 445 parts water and 5 parts Newcol 293 (manufactured by Nippon Emulsifier Co., Ltd.) were added to a typical reaction vessel for manufacturing acrylic resin emulsions, equipped with a stirrer, thermometer, dropping funnel, reflux condenser, and nitrogen inlet pipe, and the mixture was heated to 75°C while stirring. Using a homogenizer, a mixture containing 145 parts methyl methacrylate, 50 parts styrene, 220 parts ethyl acrylate, 70 parts 2-hydroxyethyl methacrylate, and 15 parts methacrylic acid, 240 parts water, and 30 parts Newcol 293 (manufactured by Nippon Emulsifier Co., Ltd.) was emulsified to obtain a monomer pre-emulsion. The monomer pre-emulsion was added dropwise over 3 hours while stirring the mixture in the reaction vessel. Simultaneously with the addition of the monomer preemulsion, an aqueous solution obtained by dissolving 1 part of APS (ammonium persulfate) as a polymerization initiator in 50 parts of water was added dropwise until the addition of the monomer preemulsion to the reaction vessel was completed. After the addition of the monomer preemulsion was completed, the reaction was continued at 80°C for 1 hour. After cooling the reactants, an aqueous solution obtained by dissolving 2 parts of dimethylaminoethanol in 20 parts of water was added to the reaction vessel to obtain a hydroxyl-containing acrylic resin emulsion with a solid content of 40.6% by mass.

[0136] (Manufacturing of polyester resins containing hydroxyl groups)

[0137] 25.6 parts isophthalic acid, 22.8 parts phthalic anhydride, 5.6 parts adipic acid, 19.3 parts trimethylolpropane, 26.7 parts neopentyl glycol, 17.5 parts ε-caprolactone, and 0.1 parts dibutyltin oxide were added to a reactor, and the mixture was stirred while the temperature was raised to 170°C. The reactants were then heated to 220°C over 3 hours, and water generated by the condensation reaction was removed until the acid value reached 8. Next, 7.9 parts trimellitic anhydride were added to the reactor, and the mixture was reacted at 150°C for 1 hour to obtain a polyester resin with an acid value of 40. The polyester resin was then cooled to 100°C, and 11.2 parts butyl solvent were added, followed by stirring until homogeneous. The polyester resin was then cooled to 60°C, and 98.8 parts deionized water and 5.9 parts dimethylethanolamine were added. This yielded a hydroxyl-containing polyester resin with a solid content of 50% by mass.

[0138] (II-2) Preparation of glossy coatings

[0139] A glossy coating was prepared according to the components and mixing ratios shown in Table 1. The viscosity of the glossy coating, measured using a Type B viscometer (Toki Sangyo Co., Ltd., model: TVB10, single-cylinder rotary viscometer) at a coating temperature of 20°C and 60 rpm, was 400 mPa·s, and the solid content was approximately 4.1% by mass.

[0140] The phosphate-containing polymers (phosphate-containing compounds) and hydroxyl-containing acrylic resin emulsions (film-forming resins) listed in Table 1 are manufactured as follows. CYMEL327 (manufactured by Allnex, curing agent) is used as the melamine resin (film-forming resin). The solids ratio of the hydroxyl-containing acrylic resin emulsion to the melamine resin (hydroxyl-containing acrylic resin emulsion / melamine resin) is 7 / 3.

[0141] (Manufacturing of polymers containing phosphate groups)

[0142] 40 parts by weight of ethoxypropanol were added to a reaction vessel, and at 120°C for 3 hours, the following components were added dropwise: 4 parts by weight of styrene, 35.96 parts by weight of n-butyl acrylate, 18.45 parts by weight of ethylhexyl methacrylate, 13.92 parts by weight of 2-hydroxyethyl methacrylate, 7.67 parts by weight of methacrylic acid, and acetyl phosphate hexa(oxypropene) monomethacrylate. A monomer solution (121.7 parts by weight) of 20 parts by weight of Monometrastone (manufactured by Unichemicol Co., Ltd., "Hosmer PP"), 20 parts by weight of ethoxypropanol, and 1.7 parts by weight of azobisisobutyronitrile was prepared and stirred continuously at the same temperature for 1 hour to obtain a liquid containing a polymer with phosphate groups (an acrylic resin containing phosphate groups) (non-volatile component: 63% by weight). The obtained polymer containing phosphate groups had a number average molecular weight of 6,000, a phosphate group value of 55 mg KOH / g, and a hydroxyl group value of 60 mg KOH / g.

[0143] (Manufacturing of acrylic resin emulsions containing hydroxyl groups)

[0144] Add 330g of deionized water to the reaction vessel and heat to 80°C while mixing and stirring under a nitrogen atmosphere. Then, over 15 minutes, simultaneously add dropwise a monomer emulsion comprising 11.25 parts acrylic acid, 139 parts n-butyl acrylate, 75 parts methyl methacrylate, 187 parts n-butyl methacrylate, 75 parts 2-ethylhexyl methacrylate, 150 parts 2-hydroxyethyl methacrylate, 112 parts styrene, 11.2 parts ciocalcol 20 (n-dodecyl mercaptan, manufactured by Kao Corporation, 100% active ingredient), 74.3 parts retimul PD-104 (emulsifier, manufactured by Kao Corporation, 20% active ingredient), and 300 parts deionized water, along with a 30% initiator solution comprising 2.63 parts ammonium persulfate and 90 parts deionized water. After the addition is complete, allow the mixture to mature at the same temperature for 15 minutes. Then, the remaining monomer emulsion and initiator solution were simultaneously added dropwise to the reaction vessel over 180 minutes. After the addition was completed, the mixture was allowed to mature at the same temperature for 1 hour. Next, it was cooled to 40°C and filtered through a 200-mesh filter to obtain a hydroxyl-containing acrylic resin emulsion with an average particle size of 200 nm, a non-volatile content of 49%, a solid content acid value of 15 mg KOH / g, and a hydroxyl value of 85 mg KOH / g.

[0145] (II-3) Preparation of transparent coating

[0146] As a transparent coating, PU Eccell O-2100 (a two-component transparent coating manufactured by Nippon Paint Co., Ltd.) is prepared.

[0147] (III) Formation process of uncured colored coating film

[0148] Using a montage, a coloring paint is applied to the object to be coated.

[0149] (IV) Formation process of uncured glossy coating

[0150] Using a montage, a glossy coating is applied to an uncured colored film.

[0151] (V) Formation process of uncured transparent coating film

[0152] Using a micro-micro coating, apply a transparent coating onto an uncured glossy film.

[0153] (VI) Curing process

[0154] After the transparent coating formation step (V), the plate is heated at 140°C for 20 minutes to obtain a coated plate with multiple coatings. The thickness of the colored coating is 30 μm. The thickness of the glossy coating is 0.5 μm. The thickness of the transparent coating is 30 μm.

[0155] [Examples 2-8, Comparative Examples 1-5]

[0156] Glossy coatings were prepared according to the components and mixing ratios shown in Table 1. Otherwise, the same procedures as in Example 1 were followed to prepare coated panels with multiple layers of coating, and the results were evaluated. The results are shown in Table 1. Figure 2 A front photograph of the painted panel produced in Comparative Example 1 is shown.

[0157] [evaluate]

[0158] (1) Appearance

[0159] Visually inspect the coated panels to comprehensively evaluate for border defects, cracks, runs, and the presence or absence of orange peel. The evaluation criteria are as follows.

[0160] Good: No defects were observed.

[0161] Yes: Only orange peel can be identified.

[0162] Undesirable: At least one of the following defects is observed: bordering, cracking, and dripping.

[0163] (2) Design

[0164] Using a multi-angle spectrophotometer MA-68 (manufactured by X-Rite), the spectrophotometric reflectance was measured at an angle of 15 degrees relative to normal reflection, when light was incident from a 45-degree angle relative to the multilayer coating. Then, L was calculated from the spectrophotometric reflectance. * a * b * Color system (CIE 1976L) * a * b * luminance L in color space * (L value). The higher the L value, the better the metallic effect. The calculated L value is evaluated according to the following criteria. The L value of the substrate before applying the gloss coating is 90 after the cured colored film has formed.

[0165] Good: 100 or above

[0166] Acceptable: 85 and above but less than 100

[0167] Not good: less than 85

[0168] (3) Settling properties

[0169] The glossy coating was placed in a sealed glass container and left to stand at 20°C for 10 days. The condition of the coating was then visually evaluated. The evaluation criteria are as follows.

[0170] Good: No sedimentation of flaky pigments was observed.

[0171] It is permissible that: after the paint has been left to stand for 7 days, the sedimentation of flaky pigments was observed.

[0172] Undesirable: Settling of flaky pigments was observed after the paint had been left to stand for up to one day.

[0173] The components used in the examples and comparative examples are shown below.

[0174] (Scale-like pigment)

[0175] Aluminum granules: Trade name SB-10, manufactured by Asahi Kasei Corporation, thickness 0.06μm, average particle size 10μm

[0176] Metallic-coated mica: Xirallic T60-10WNT Crystal Silver, manufactured by Merck Co., Ltd., with an average particle size of 17μm.

[0177] (cellulose nanofibers)

[0178] TEMPO oxidized CNF, average fiber width 2-4 nm, carboxyl content 1.4 mmol / g

[0179] (cellulose ester derivatives)

[0180] Carboxymethyl cellulose acetate butyrate (CAB), trade name: Solus 3050, acid value: 50 mg KOH / g, manufactured by Eastman Chemical Company.

[0181] (Other adhesives)

[0182] Adhesive 1: Hydrophobic associative adhesive, Adekano UH540 (manufactured by ADEKA Corporation, urethane associative thickener)

[0183] Adhesive 2: Polycarboxylic acid type adhesive, SN Sickner 640 (manufactured by Sunopco Co., Ltd., polycarboxylic acid adhesive)

[0184] Adhesive 3: Amide adhesive, Disparon 6700 (manufactured by Kusumoto Chemical Co., Ltd., polyamide adhesive)

[0185] Adhesive 4: Inorganic mineral adhesive, LAPONITE RD (manufactured by BYK, sodium magnesium lithium silicate)

[0186]

[0187] Industrial utilization

[0188] The waterborne glossy coating composition of the present invention can produce coatings with no coating defects and a metallic design, and is therefore particularly suitable for coating the exterior panels of automobile bodies.

[0189] This application claims priority based on Japanese Patent Application No. 2021-106997 filed on June 28, 2021, the entire contents of which are incorporated herein by reference.

Claims

1. An aqueous glossy coating composition comprising a cellulose ester derivative, cellulose nanofiber, and a flaky pigment, the amount of the solid component contained in the aqueous glossy coating composition is 0.1 mass% or more and 12 mass% or less, The content C of the cellulose nanofiber N The content C of the cellulose ester derivative E The ratio C of the content C of the cellulose ester derivative N / C E is 0.03 or more and 0.6 or less.

2. The aqueous, glossy coating composition according to claim 1, wherein, the cellulose ester derivative is a condensate of an oxygen-containing acid having a hydrocarbon group with a carbon number of 1 to 20 and cellulose.

3. The aqueous, glossy coating composition according to claim 1 or 2, wherein, the acid value of the cellulose ester derivative is 20 mgKOH / g or more.

4. The aqueous, glossy coating composition according to any one of claims 1 to 3, wherein, The content C of the cellulose nanofiber N is 0.03 mass% or more and 1 mass% or less of the water-based glossy coating composition.

5. The aqueous, glossy coating composition according to any one of claims 1 to 4, wherein, the content of the flaky pigment is 0.1 mass% or more and 1.5 mass% or less of the aqueous glossy coating composition.

6. The aqueous, glossy coating composition according to any one of claims 1 to 5, wherein, the content of the flaky pigment is 3 mass% or more and 50 mass% or less of the total solid component of the aqueous glossy coating composition.

7. The aqueous, glossy coating composition according to any one of claims 1 to 6, wherein, the flaky pigment comprises aluminum particles, the aqueous glossy coating composition further comprises a compound containing a phosphoric acid group.

8. The aqueous, glossy coating composition according to claim 7, wherein, the compound containing a phosphoric acid group comprises at least one of a phosphoric acid alkyl ester having an alkyl group with a carbon number of 4 to 30 and a polymer containing a phosphoric acid group having a phosphoric acid group value of 5 mgKOH / g or more and 300 mgKOH / g or less.

9. The aqueous, glossy coating composition according to claim 7 or 8, wherein, the content of the compound containing a phosphoric acid group is 0.1 mass% or more and 15 mass% or less of the total solid component of the aqueous glossy coating composition.

10. A coated board provided with a coated object and a glossy coating film, the glossy coating film is formed from the aqueous glossy coating composition according to any one of claims 1 to 9.

11. The coated sheet according to claim 10, wherein, the dry film thickness of the glossy coating film is 5 μm or less.

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