JP2024051311A - Coating composition and coated film - Google Patents

Abstract

To provide a coating composition which enables formation of a coated film that is excellent in brightness feeling, flip-flop property and surface smoothness.SOLUTION: A coating composition contains resin particles (A), transparent beads (B), and a dispersion medium (C) for dispersing the resin particles (A) and the transparent beads (B), wherein the resin particles (A) contain droplet containing an aqueous coating material, and a gelled film covering the surface of the droplet, the aqueous coating material contains an aqueous medium, an aqueous resin (D), and a pigment (E) dispersed in the aqueous medium, a content of the pigment (E) is 14 mass% or more with respect to 100 mass% of the aqueous resin (D), the dispersion medium (C) contains an aqueous medium and an aqueous resin (F), a content of the transparent beads (B) is 20 to 135 mass% with respect to 100 mass% of the aqueous resin (F), and an average particle size of the transparent beads (B) is 10 μm or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a coating composition and a coating film.

Many building surfaces are coated with paint for protective and decorative purposes.
In recent years, there has been a demand for more luxurious designs, and metallic paints that can impart a glittering, lustrous look are particularly popular.

Patent Document 1 discloses a paint composition having resin particles and a dispersion medium for dispersing the resin particles, the resin particles having droplets containing an emulsion paint and a gelled film covering the surface of the droplets, the emulsion paint having a resin emulsion and a pigment dispersed in the resin emulsion, the dispersion medium containing water as a main component, and the pigment having a specific gravity of 2.5 or more.

JP 2021-038275 A

According to the coating composition described in Patent Document 1, even if it contains pigments with high specific gravity such as nickel, stainless steel, and MIO, the pigments are less likely to settle, and a good appearance can be achieved during coating, which makes it possible to form a coating film with a sense of brilliance. However, there are cases where a coating film with a higher brilliance appearance is required.

The present inventor attempted to obtain a coating film appearance with higher brightness by increasing the amount of metallic pigment contained in the resin particles of the coating composition of Patent Document 1. As a result, it was found that although a coating film appearance with higher brightness was obtained, the flip-flop property was deteriorated.
Here, the flip-flop property in the present invention refers to the property that the brightness of the coating film changes depending on the observation angle. The smaller the change in brightness, the more consistent the amount of reflected light that can be sensed (sense of brightness) of the coating film is, even if the observation angle of the coating film is changed, and the better the flip-flop property.

The inventors believed that increasing the metallic pigment content in the resin particles made it easier for the metallic pigment in the coating film before film formation to become oriented parallel to the substrate as it dried, resulting in poor flip-flop properties.
Therefore, when the viscosity of the resin emulsion contained in the resin particles and the viscosity of the paint composition were increased so that the metallic pigment would be randomly oriented relative to the substrate, the flip-flop properties improved but the leveling properties deteriorated. As a result, the coating surface was no longer smooth, and the "smooth, sparkling, metal-like design" was no longer achieved. Even when the coating composition was applied to an uneven substrate, the flip-flop properties improved, but the coating film became uneven, and the "smooth, sparkling, metal-like design" was no longer achieved.

The present invention aims to provide a coating composition capable of forming a coating film having excellent luster, flip-flop properties and surface smoothness, and to provide a coating film having excellent luster, flip-flop properties and surface smoothness.

The present invention has the following aspects.
[1] A coating composition comprising resin particles (A), transparent beads (B), and a dispersion medium (C) for dispersing the resin particles (A) and the transparent beads (B),
The resin particles (A) include droplets containing an aqueous paint and a gelled film covering the surface of the droplets,
The aqueous paint contains an aqueous medium, an aqueous resin (D), and a pigment (E) dispersed in the aqueous medium,
The content of the pigment (E) is 14% by mass or more relative to 100% by mass of the aqueous resin (D),
The dispersion medium (C) contains an aqueous medium and an aqueous resin (F),
The content of the transparent beads (B) is 20 to 135% by mass relative to 100% by mass of the aqueous resin (F),
A coating composition characterized in that the transparent beads (B) have an average particle size of 10 μm or more.
[2] The coating composition according to [1], wherein the pigment (E) is a flat particle.
[3] A coating film formed from the coating composition according to [1] or [2] above.
[4] The coating film according to [3], wherein the value obtained by dividing the average particle size (μm) of the transparent beads (B) by the average film thickness (μm) of the coating film is 0.1 or more.

The present invention provides a coating composition capable of forming a coating film having excellent luster, flip-flop properties and surface smoothness, as well as a coating film having excellent luster, flip-flop properties and surface smoothness.

FIG. 1 is a schematic diagram illustrating a coating composition according to an embodiment. FIG. 2 is a schematic diagram illustrating the resin particle (A) shown in FIG. 1.

Below, a coating composition according to one embodiment of the present invention will be described with reference to Figures 1 and 2. Note that in all of the following drawings, the dimensions and ratios of each component have been appropriately changed to make the drawings easier to understand.

[Paint composition]
FIG. 1 is a schematic diagram illustrating a coating composition 1 according to one embodiment of the present invention.
As shown in FIG. 1, the coating composition 1 has resin particles (A) 10, transparent beads (B) 20, and a dispersion medium (C) 30 in which the resin particles (A) 10 and the transparent beads (B) 20 are dispersed.

<Resin Particles (A)>
FIG. 2 is a schematic diagram illustrating the resin particle (A) 10. As shown in FIG.
As shown in FIG. 2, a resin particle (A) 10 includes a droplet 11 and a gelled film 12 covering the surface of the droplet 11 .
The resin particles (A) in the coating composition 1 may be of one type or two or more types. For example, the coating composition may contain two or more types of resin particles (A) having different color tones.

The average particle size of the resin particles (A) is preferably 0.1 mm to 5 cm, more preferably 0.1 mm to 3 cm, and particularly preferably 0.1 mm to 2 cm. If the average particle size of the resin particles (A) is within the above range, the coating film formed will have excellent design properties. In addition, the workability of painting using an air gun will also be good.
The average particle size of the resin particles (A) is determined by measuring the major axis of 20 randomly selected resin particles (A) with a vernier caliper and calculating the arithmetic mean of the measured values.

(Droplets)
The droplets 11 contain a water-based paint.
The water-based paint contains an aqueous medium, an aqueous resin (D), and a pigment (E) dispersed in the aqueous medium.

"Aqueous medium"
The aqueous medium is a medium consisting of only water, or a medium in which a solvent compatible with water has been added to water. The proportion of water to the total mass of the aqueous medium is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more.
The water that can be used may be ion-exchanged water, tap water, or the like.
Examples of the solvent compatible with water include alcohols such as ethanol and isopropyl alcohol, ethylene glycol, etc. These solvents may be used alone or in combination of two or more kinds.

"Water-based resin (D)"
The aqueous resin (D) is a resin that can be dissolved or dispersed in an aqueous medium. The aqueous resin (D) is preferably a resin that can be dispersed in an aqueous medium (a water-dispersible resin).
There is no particular restriction on the type of the aqueous resin (D) and it can be appropriately selected according to the performance required for the coating composition. As the aqueous resin (D), one that gives good water resistance and weather resistance to the coating film is preferable.
Examples of the type of aqueous resin (D) include acrylic resin, urethane resin, vinyl acetate resin, silicone resin, fluororesin, acrylic urethane resin, acrylic silicone resin, acrylic fluororesin, acrylic polyol resin, acrylic styrene resin, acrylonitrile resin, vinyl chloride resin, epoxy resin, Veova (branched fatty acid vinyl ester), natural rubber, synthetic rubber, and copolymers thereof. These aqueous resins may be used alone or in combination of two or more. Among them, synthetic resins such as acrylic resin, acrylic silicone resin, and acrylic fluororesin are preferred in terms of excellent water resistance and weather resistance.

"Pigment (E)"
The pigment (E) is dispersed within the droplets.
As the pigment (E), a pigment having brilliance such as metallic luster is preferred. Examples of pigments having brilliance include flake-shaped metal pigments such as nickel, stainless steel, and aluminum; calcined mica; and flake-shaped pigments in which glass, mica, and the like are coated with metal oxides such as iron oxide, titanium oxide, and zirconia, or metals such as silver and gold. These may be used alone or in combination of two or more.

The average particle size of the pigment (E) is preferably 0.1 μm or more, more preferably 1 μm or more, in terms of forming a coating film with high brightness. The upper limit of the average particle size of the pigment (E) is sufficient as long as it is within the resin particles (A) and is smaller than the resin particles (A). For example, it is preferably 10 mm or less, more preferably 5 mm or less.
The average particle size of the pigment (E) refers to the volume-based median size (D50), and specifically, is a value measured using a laser diffraction particle size distribution measuring device.

The pigment (E) may have various particle shapes such as spherical particles and flat particles, but flat particles are preferred. When the pigment (E) is a flat particle, the pigment (E) is likely to reflect light when the coating composition is applied, and it is likely to impart a metallic luster to the object to which the coating composition is applied.
In this specification, the term "flat particles" refers to particles having an average aspect ratio of 5 or more.
The aspect ratio is determined from the ratio of the long diameter of a flat particle to the short diameter of the flat particle. The long diameter and short diameter of a flat particle are determined from an electron microscope photograph. When the smallest rectangle circumscribing the flat particle in the electron microscope photograph is assumed, the long side of the rectangle is the long diameter of the flat particle, and the short side of the rectangle is the short diameter.
The average aspect ratio refers to the arithmetic mean of the aspect ratios determined for 20 flat particles seen in one visual field of the above-mentioned electron micrograph.

"Colloid-forming substances"
Water-based paints typically contain colloid-forming substances.
The colloid-forming substance is a substance capable of reacting with a gelling agent to form a gelled film 12. The gelling agent will be described later.

Examples of colloid-forming substances include cellulose derivatives such as hydroxycellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, and ethylcellulose, guar gum, guar gum derivatives, galactomannans such as fenugreek gum, tara gum, locust bean gum, and cassia gum, biogums such as welan gum, gellan gum, and xanthan gum, polysaccharides such as alginic acid, alginic acid derivatives, and starch, alcohols such as polyvinyl alcohol, glycerin, and ethylene glycol, aqueous urethane, polyethyleneimine derivatives, polyvinylvinylidone, polyacrylic acid derivatives, and casein. These colloid-forming substances may be used alone or in combination of two or more. As the colloid-forming substance, guar gum and guar gum derivatives are preferred.
The colloid-forming substance is typically used in the form of an aqueous solution, the concentration of which is, for example, 0.1% by mass to 10% by mass.

(Gelled film)
The gelled film 12 covers the surface of the droplet 11 and defines the outline of the resin particle (A).
The gelled film 12 typically includes a three-dimensional network structure formed by a reaction between a colloid-forming substance contained in the aqueous paint and a gelling agent, resulting in cross-linking. The gelled film 12 has a lower fluidity than the aqueous paint, and contains the droplets 11 inside.

Examples of gelling agents include magnesium montmorillonite clay, sodium pentachlorophenol, borates, aluminum salts, barium salts, calcium salts, magnesium salts, tannic acid, titanium lactate, calcium chloride, etc. Among these, aqueous solutions of borates are preferred. Gelling agents may be used alone or in combination of two or more.

(Optional ingredients)
The resin particles (A) may contain an extender pigment as long as it does not affect the appearance or performance of the coating film.
The term "extender pigment" refers to achromatic pigments used in paints. Examples of the extender pigment include kaolin, barium sulfate, magnesium silicate hydrate, calcium carbonate, etc. The extender pigment may be used alone or in combination of two or more kinds.

The resin particles (A) may contain known additives as necessary. Examples of known additives include emulsifiers, pH adjusters, antifoaming agents, viscosity adjusters, film-forming aids, antifreeze agents, dispersants, wetting agents, penetration aids, preservatives, surface conditioners, ultraviolet absorbers, antioxidants, and heat-shielding agents.

The solid content in the resin particles (A) is preferably 75% by mass or less, more preferably 70% by mass or less, and particularly preferably 65% by mass or less, based on 100% by mass of the resin particles (A).
The solid content of the resin particles (A) is the remainder obtained by removing the aqueous medium from the resin particles (A).

The content of the aqueous resin (D) in the resin particles (A) is preferably 1% by mass or more, more preferably 5% by mass or more, and particularly preferably 10% by mass or more, based on 100% by mass of the resin particles (A). When the content of the aqueous resin (D) is equal to or more than the lower limit, the stability of the droplets tends to be excellent.
The content of the aqueous resin (D) in the resin particles (A) is preferably 70% by mass or less, more preferably 65% by mass or less, and particularly preferably 60% by mass or less, based on 100% by mass of the resin particles (A). When the content of the aqueous resin (D) is equal to or less than the upper limit, the flowability tends to be excellent.
The above upper and lower limits can be combined in any manner.

The content of the pigment (E) in the resin particles (A) is 14% by mass or more, preferably 19% by mass or more, more preferably 23% by mass or more, even more preferably 28% by mass or more, and particularly preferably 33% by mass or more, based on 100% by mass of the aqueous resin (D). When the content of the pigment (E) is equal to or more than the lower limit, a coating film with high brightness can be obtained.
The content of the pigment (E) is preferably 300% by mass or less, more preferably 200% by mass or less, based on 100% by mass of the aqueous resin (D). If the content of the pigment (E) is equal to or less than the upper limit, the capsule structure of the resin particles (A) is less likely to be broken during production or painting, and the coating performance is excellent. In consideration of cost reduction, the content is more preferably 100% by mass or less, even more preferably 80% by mass or less, and particularly preferably 60% by mass or less.
The above upper and lower limits can be combined in any manner.

The volume ratio of pigment (E) to 100 volume percent of the resin solids in resin particles (A) is preferably 5 volume percent or more and 80 volume percent or less. If the volume ratio of pigment (E) is equal to or more than the lower limit, a coating film with high brightness can be obtained. If the volume ratio of pigment (E) is equal to or less than the upper limit, the capsule structure of resin particles (A) is less likely to break during production or painting, and the coating film has excellent performance.

The content of the colloid-forming substance in the resin particles (A) is preferably 0.05 to 5 parts by mass, and more preferably 0.1 to 3.0 parts by mass, per 100 parts by mass of the aqueous resin (D). By keeping the content of the colloid-forming substance within the above range, a stable gelled film can be obtained.

<Transparent beads (B)>
The transparent beads (B) may be either organic or inorganic, as long as they are capable of transmitting light. Examples of organic transparent beads (B) include acrylic resin-based, urethane resin-based, silicone resin-based, and polystyrene resin-based beads. Examples of inorganic transparent beads (B) include glass-based beads. For example, glass beads having a surface coated with a resin or the like may also be used. These transparent beads (B) may be used alone or in combination of two or more types.
The transparent beads (B) may be either colored or colorless, with colorless being preferred.

The refractive index of the transparent beads (B) is preferably at least 1, more preferably at least 1.3, and even more preferably at least 1.45. When the refractive index is at least 1, the brilliance and flip-flop properties of the coating film are more excellent.
The refractive index of the transparent beads (B) is preferably not more than 2, more preferably not more than 1.8, and even more preferably not more than 1.6. When the refractive index is not more than 2, the brilliance and flip-flop properties of the coating film are more excellent.
The above upper and lower limits can be combined in any manner.

The average particle size of the transparent beads (B) is 10 μm or more, preferably 15 μm or more, more preferably 25 μm or more, even more preferably 40 μm or more, and particularly preferably 80 μm or more. If the average particle size of the transparent beads (B) is the lower limit or more, the flip-flop property of the coating film is excellent.
The average particle size of the transparent beads (B) is preferably 400 μm or less, more preferably 350 μm or less, even more preferably 300 μm or less, even more preferably 350 μm or less, and particularly preferably 300 μm or less. If the average particle size of the transparent beads (B) is equal to or less than the upper limit, the surface smoothness of the coating film is more excellent.
The average particle size of the transparent beads (B) refers to the volume-based median size (D50), and specifically, is a value measured using a laser diffraction particle size distribution measuring device.

<Dispersion medium (C)>
The dispersion medium (C) contains an aqueous medium and an aqueous resin (F).

"Aqueous medium"
The aqueous medium in the dispersion medium (C) may be the same as the aqueous medium in the aqueous paint. The aqueous medium in the dispersion medium (C) and the aqueous medium in the aqueous paint may be the same or different.

"Water-based resin (F)"
Examples of the aqueous resin (F) include the same as the aqueous resin (D).
The aqueous resin (F) and the aqueous resin (D) are preferably the same in form and type. As an example, the aqueous resin (F) and the aqueous resin (D) are both acrylic silicone resins that can be dispersed in an aqueous medium.
The aqueous resin (F) and the aqueous resin (D) may be different in type. For example, the aqueous resin (F) is an acrylic silicone resin, and the aqueous resin (D) is an acrylic resin.

"Other ingredients"
The dispersion medium (C) typically contains the above-mentioned gelling agent.
The dispersion medium (C) may contain the above-mentioned colloid-forming substance.
The dispersion medium (C) may contain the above-mentioned pigment (E).
The dispersion medium (C) may contain known additives as necessary. Examples of known additives include those mentioned above.

The content of the aqueous resin (F) in the dispersion medium (C) is preferably 5% by mass or more, more preferably 10% by mass or more, and particularly preferably 15% by mass or more, based on 100% by mass of the dispersion medium (C).
The content of the aqueous resin (F) in the dispersion medium (C) is preferably 90% by mass or less, more preferably 85% by mass or less, and particularly preferably 80% by mass or less, based on 100% by mass of the dispersion medium (C).
When the content of the aqueous resin (F) is equal to or more than the lower limit, the coating film performance such as water resistance tends to be excellent, and when it is equal to or less than the upper limit, the coating composition tends to have excellent storage stability.
The above upper and lower limits can be combined in any manner.

<Content of each ingredient>
In the coating composition, the content of the transparent beads (B) is 20% by mass or more, preferably 25% by mass or more, more preferably 30% by mass or more, and particularly preferably 35% by mass or more, relative to 100% by mass of the aqueous resin (F).
The content of the transparent beads (B) is 135% by mass or less, preferably 130% by mass or less, more preferably 125% by mass or less, and particularly preferably 120% by mass or less, based on 100% by mass of the aqueous resin (F).
By ensuring that the content of the transparent beads (B) is within the above range, a coating film which is smooth, has high brightness and has good flip-flop properties can be formed.
The upper and lower limits can be combined in any desired manner. For example, the content of the transparent beads (B) may be 20 to 135% by mass, 25 to 130% by mass, 30 to 125% by mass, or 35 to 120% by mass, based on 100% by mass of the aqueous resin (F).

The content of the resin particles (A) in the coating composition is preferably 10 mass% or more, more preferably 15 mass% or more, and particularly preferably 20 mass% or more, relative to 100 mass% in total of the resin particles (A) and the dispersion medium (C).
The content of the resin particles (A) is preferably 95% by mass or less, more preferably 90% by mass or less, and particularly preferably 85% by mass or less, based on 100% by mass of the total of the resin particles (A) and the dispersion medium (C).
When the content of the resin particles (A) is within the above range, a coating film having high brightness can be formed.
The upper and lower limits can be combined in any desired manner. For example, the content of the resin particles (A) in the coating composition may be 10 to 95% by mass, 15 to 90% by mass, or 20 to 85% by mass, relative to 100% by mass of the total of the resin particles (A) and the dispersion medium (C).

The content of the dispersion medium (C) in the coating composition is preferably 5% by mass or more, more preferably 10% by mass or more, and particularly preferably 15% by mass or more, relative to 100% by mass of the total of the resin particles (A) and the dispersion medium (C).
The content of the dispersion medium (C) in the coating composition is preferably 90 mass% or less, more preferably 85 mass% or less, and particularly preferably 80 mass% or less, relative to 100 mass% in total of the resin particles (A) and the dispersion medium (C).
By ensuring that the proportion of the dispersion medium (C) in the coating composition is within the above range, a coating film with high brightness can be formed.
The above upper and lower limits can be combined in any manner.

<Method of producing coating composition>
The coating composition described above can be produced, for example, by mixing a dispersion in which resin particles (A) are dispersed in an aqueous medium (hereinafter also referred to as a resin particle (A) dispersion), transparent beads (B), an aqueous resin (F), and, if necessary, a further aqueous medium and other components.

The resin particle (A) dispersion can be produced, for example, by the following production method.
First, the aqueous resin (D), an aqueous medium, and an aqueous solution of a colloid-forming substance are mixed to prepare a mixed liquid (d).
Separately, the pigment (E) is mixed with an aqueous medium and additives such as a dispersant, if necessary, to prepare a mixed liquid (e).
Next, the mixed liquid (d) and the mixed liquid (e) are mixed to prepare the water-based paint (c).
Separately, a gelling agent, an aqueous medium, and, if necessary, a colloid-forming substance and/or additives are mixed to prepare an aqueous solution (f).
Next, the water-based coating material (c) is added to the aqueous solution (f) while stirring the aqueous solution (f) with a disperser.
When the aqueous paint (c) is stirred in the aqueous solution (f), droplets of the aqueous paint (c) are formed, and the colloid-forming substance contained in the droplets reacts with the gelling agent contained in the aqueous solution (f) to crosslink and form a three-dimensional network (gelled film). The aqueous paint (c) is also broken down by stirring while flocculating due to the reaction with the gelling agent. Even during the process of breaking down, the colloid-forming substance and the gelling agent continue to react with each other to form a three-dimensional network (gelled film). This results in resin particles (A) in which the droplets of the aqueous paint (c) are covered with a gelled film.
In this manner, as the colloid-forming substance and the gelling agent react with each other, the aggregates of the water-based paint (c) are broken down into smaller particles, thereby obtaining a resin particle (A) dispersion in which the resin particles (A) are dispersed in the aqueous solution (f).
Two or more types of dispersions of resin particles (A) having different color tones or the like of the resin particles (A) may be prepared and then mixed together.

<Painting method>
The coating composition according to this embodiment is applied onto a substrate and dried to form a coating film.

There are no particular limitations on the substrate, and the coating can be applied to a variety of objects, including ceramic building boards such as ceramic siding boards, flexible boards, calcium silicate boards, gypsum slag barite boards, wood chip cement boards, asbestos cement boards, pulp cement boards, precast concrete boards, lightweight aerated concrete (ALC) boards, and gypsum boards; metal building boards such as aluminum, iron, and stainless steel; mortar, plastic, wood, and paper. In addition, the surfaces of these may have been subjected to a primer treatment using a sealer or primer.

There are no particular limitations on the method for applying the coating composition, and the coating composition can be applied by any known application method, such as with a brush, a trowel, a roller, spray coating, roll coating, or flow coating.
The coating amount of the coating composition can be appropriately selected depending on the average film thickness of the coating film to be formed, but the mass per unit area before drying (wet) is preferably 50 to 1000 g/ ^m2 , more preferably 100 to 800 g/ ^m2 . If the coating amount is equal to or more than the lower limit, the coating film performance such as water resistance, the sense of brilliance, and the flip-flop property tend to be excellent. If the coating amount is equal to or less than the upper limit, problems such as coating film cracking during drying tend not to occur. The upper and lower limits can be combined arbitrarily.
The drying may be performed at room temperature or by heating as long as the aqueous medium can be removed. The drying temperature is, for example, 5 to 90° C. The drying time varies depending on the drying temperature, but is, for example, 5 minutes to 48 hours.
After drying, a top coat may be applied on the formed coating film.

<Coating film>
The average thickness of the coating film formed from the coating composition according to the present embodiment is preferably 100 μm or more, more preferably 120 μm or more, and particularly preferably 140 μm or more. If the average thickness of the coating film is equal to or more than the lower limit, the coating film tends to have excellent coating film performance such as water resistance, brilliance, and flip-flop properties.
The average thickness of the coating film is preferably 600 μm or less, more preferably 550 μm or less, and particularly preferably 500 μm or less. If the average thickness of the coating film is equal to or less than the upper limit, problems such as coating film cracking during drying tend not to occur.
Here, the average film thickness of the coating film is the value after drying, and is the average value of film thicknesses at 20 randomly selected points on the coating film.
The above upper and lower limits can be combined in any manner.

The value obtained by dividing the average particle size (μm) of the transparent beads (B) by the average film thickness (μm) of the coating film (hereinafter referred to as "average particle size/average film thickness") is preferably 0.1 or more, more preferably 0.2 or more. The average particle size of the transparent beads (B)/average film thickness is preferably 3 or less, more preferably 2 or less.
When the average particle size of the transparent beads (B)/average film thickness of the coating film is within the above-mentioned range, a coating film with higher brightness can be obtained.
The reason why a coating film with higher brightness can be obtained is believed to be that when the value of the average particle size of the transparent beads (B)/average film thickness of the coating film is within the above range, light that hits the coating film surface is less likely to be diffusely reflected on the coating film surface and inside the coating film, making it easier to sense reflected light from the pigment (E) inside the coating film.

<Action and effect>
According to the coating composition described above, a coating film having high brightness and excellent flip-flop properties and surface smoothness can be formed.
The reason why the coating film has excellent flip-flop properties is thought to be that the pigment (E) is randomly oriented relative to the substrate when the coating film is made by including transparent beads (B) in the coating composition. It is thought that the random orientation of the pigment (E) makes the direction of the light reflected from the surface of the pigment (E) random, and as a result, it becomes possible to sense the reflected light even when the observation angle is changed. And, it is thought that the fact that it is possible to sense more reflected light in this way makes it appear brighter than the conventional product coating film.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these.
"Parts" means "parts by mass". "%" means "% by mass" unless otherwise specified.

<Materials used>
Resin emulsion: acrylic resin emulsion, Primal AC38, manufactured by Dow Chemical Company, 50% solids.
Colloid-forming material: 4% aqueous solution of a non-ionic guar gum derivative, MEYPRO HPG 8111, manufactured by DuPont.
Pigment 1: FANTASPEARL 1060YR, mica pearl pigment, manufactured by Nihon Koken Kogyo Co., Ltd., average particle size: 23 μm.
Pigment 2: Metashine 1030PS, glass flake pigment, manufactured by Nippon Sheet Glass Co., Ltd., average particle size 25 μm.
Pigment 3: Metashine 2080GP, glass flake pigment, manufactured by Nippon Sheet Glass Co., Ltd., average particle size 80 μm.
Pigment 4: Metashine 5230PS, glass flake pigment, manufactured by Nippon Sheet Glass Co., Ltd., average particle size 230 μm.
Pigment 5: Metashine 5480PS, glass flake pigment, manufactured by Nippon Sheet Glass Co., Ltd., average particle size 480 μm.
Dispersant: Orothan 731, an anionic polymeric dispersant, manufactured by The Dow Chemical Company.
Gelling agent: 5% aqueous solution of ammonium biborate, manufactured by Yoneyama Chemical Industry Co., Ltd.
Extender pigment: 4% aqueous dispersion of hydrated magnesium silicate, talc SSS, manufactured by Nippon Talc Co., Ltd.
CMC-Na: 1% aqueous solution of sodium carboxymethylcellulose, CMC-1170, manufactured by Daicel Chemical Industries, Ltd.

Transparent beads 1: Acrylic beads, GB-05S, manufactured by Aica Kogyo Co., Ltd., average particle size 5 μm.
Transparent beads 2: Acrylic beads, GR-400T, manufactured by Negami Chemical Industries, Ltd., average particle diameter 15 μm.
Transparent beads 3: Acrylic beads, GM-2801, manufactured by Aica Kogyo Co., Ltd., average particle size 28 μm.
Transparent beads 4: Acrylic beads, GM-4003, manufactured by Aica Kogyo Co., Ltd., average particle size 40 μm.
Transparent beads 5: Acrylic beads, GM-9005, manufactured by Aica Kogyo Co., Ltd., average particle size 85 μm.
Transparent beads 6: Acrylic beads, SE-090T, manufactured by Negami Chemical Industries, Ltd., average particle diameter 110 μm.
Transparent beads 7: Acrylic beads, MR-260IBS, manufactured by Soken Chemical & Engineering Co., Ltd., average particle size 260 μm.
Anti-algae agent: HF-260K, manufactured by Nagase ChemteX Corporation, active ingredient 30%.
Antifungal agent: ACTICIDE OTW, manufactured by THOR JAPAN, active ingredient 30%.
Ultraviolet absorber: Tinuvin 400DW, manufactured by BASF JAPAN, active ingredient 40%.
Thickener: Alkali-soluble thickener, SN Thickener 636, manufactured by San Nopco Co., Ltd., active ingredient 30%.

<Production of Resin Particle (A) Dispersions A-1 to A-12>
A mixed liquid (d) was obtained by mixing a resin emulsion and a hydrophilic colloid solution according to the formulation shown in Table 1. Also, a mixed liquid (e) was obtained by mixing water, a pigment, and a dispersant according to the formulation shown in Table 1. Next, the mixed liquid (d) and the mixed liquid (e) were mixed to obtain a water-based paint (c).
Separately, a gelling agent, water, extender pigment and CMC-Na were mixed according to the formulation shown in Table 1 to obtain an aqueous solution (f).
Next, the aqueous coating material (c) was added to the aqueous solution (f) while stirring the aqueous solution (f) with a dissolver (manufactured by Nippon Seiki Seisakusho Co., Ltd., rotation speed 1000 rpm). Stirring was continued until the average particle diameter of the aqueous coating material (c) finely divided by stirring became 0.5 mm to 1 cm, thereby obtaining a dispersion of resin particles (A).
The average particle size of the resin particles (A) was determined by randomly taking out 20 resin particles (A) from the dispersion, measuring the major axis with a vernier caliper, and calculating the arithmetic average of the measured values.
Table 1 shows the content (parts) of resin particles (A) contained in the dispersion, the solid content (parts) of resin particles (A), the content (parts) of aqueous resin (D) in resin particles (A), the proportion (%) of resin particles (A) in 100% dispersion, the proportion (%) of solid content of resin particles (A) in 100% dispersion, the proportion (%) of aqueous resin (D) in 100% resin particles (A), and the content (%) of pigment (E) relative to 100% resin solid content in resin particles (A). Here, the content of resin particles (A) is the total amount of the aqueous paint (c) and the solid content of the gelling agent. The aqueous resin (D) in the resin particles (A) is the solid content of the resin emulsion.

<Examples 1 to 19 and Comparative Examples 1 to 7>
(Production of Coating Composition)
According to the formulations shown in Tables 2 to 4, a resin particle (A) dispersion, a resin emulsion, transparent beads, an anti-algae agent, an anti-fungal agent, an ultraviolet absorber, a thickener, 25% aqueous ammonia, and water were mixed to obtain coating compositions.
Tables 2 to 4 show the resin solids (parts) in the dispersion medium (C), the ratio (%) of the transparent beads (B) relative to 100% of the aqueous resin (F), and the ratio (%) of the resin particles (A) relative to the total of 100% of the resin particles (A) and the dispersion medium (C). Here, the dispersion medium (C) is the remainder excluding the resin particles (A) and the transparent beads. The aqueous resin (F) is the solids of the resin emulsion blended in the production of the coating composition.

(Preparation of painted boards)
The obtained coating composition was spray-coated on the surface of a slate board coated with a gray undercoat so that the coating amount was 400 g/ ^m2 , and the board was dried at room temperature to obtain a coated board having a coating film on the surface.
The cross section of the formed coating film was observed at 10 randomly selected locations on the coating film using a digital microscope (VHX-8000, manufactured by Keyence Corporation) to measure the film thickness, and the average film thickness was calculated by arithmetically averaging the measured values. In addition, the value of the average particle size of the transparent beads (B)/average film thickness was calculated. The results are shown in Tables 2 to 4.

(evaluation)
The coating film of the prepared coated plate was visually observed and evaluated for brightness, flip-flop property, and surface smoothness according to the following criteria. The results are shown in Tables 2 to 4.

Luminance 1: The coating has a very strong luminance (shine).
2: The coating has a strong sense of brilliance (shine).
3: The coating has a sense of brilliance (shine), which is good.
4: The coating film has a sense of brilliance (shine).
5: The coating film has a weak sense of brilliance (shine) and no brilliance is felt.

Flip-flop properties: 1: The brilliance of the coating remains unchanged even when the observation angle is changed, and is very good.
2: The brilliance of the coating film does not change much even when the observation angle is changed, which is good.
3: When the observation angle is changed, the brilliance of the coating film is sometimes strong and sometimes weak, but the difference is small.
4: When the observation angle is changed, the brilliance of the coating film is sometimes strong and sometimes weak, and the difference is very large.

-Surface smoothness ◯: Smooth and good coating appearance.
△: The coating film appears smooth from a distance, but roughness can be seen when viewed up close.
×: There are irregularities and the appearance of the coating film is poor.

The coating films of the coating compositions of Examples 1 to 19 were excellent in lustrous appearance, flip-flop properties and surface smoothness.
On the other hand, the coating film of the paint composition of Comparative Example 1 had a pigment (E) content of less than 14 mass% relative to 100 mass% of the resin solids in the resin particles (A) and did not contain transparent beads (B), and therefore had inferior brightness.
The coating films of the coating compositions of Comparative Examples 2 and 3, which did not contain the transparent beads (B), were inferior in brilliance or flip-flop properties.
The coating film of the coating composition of Comparative Example 4 had poor brilliance because the content of pigment (E) was less than 14% by mass relative to 100% by mass of the resin solids in the resin particles (A).
The coating film of the coating composition of Comparative Example 5 was inferior in brilliance and flip-flop properties because the average particle size of the transparent beads (B) was less than 10 μm.
The coating film of the coating composition of Comparative Example 6 had poor flip-flop properties because the content of transparent beads (B) was less than 20 mass% relative to 100 mass% of the resin solids in the dispersion medium (C).
The coating film of the coating composition of Comparative Example 7 had poor surface smoothness because the content of transparent beads (B) was more than 135 mass% relative to 100 mass% of the resin solids in the dispersion medium (C).

1 Coating composition, 10 Resin particles (A), 11 Droplets, 12 Gelled film, 13 Pigment (E), 20 Transparent beads (B), 30 Dispersion medium (C)

Claims (4)

A coating composition comprising resin particles (A), transparent beads (B), and a dispersion medium (C) for dispersing the resin particles (A) and the transparent beads (B),
The resin particles (A) include droplets containing an aqueous paint and a gelled film covering the surface of the droplets,
The aqueous paint contains an aqueous medium, an aqueous resin (D), and a pigment (E) dispersed in the aqueous medium,
The content of the pigment (E) is 14% by mass or more relative to 100% by mass of the aqueous resin (D),
The dispersion medium (C) contains an aqueous medium and an aqueous resin (F),
The content of the transparent beads (B) is 20 to 135% by mass relative to 100% by mass of the aqueous resin (F),
A coating composition characterized in that the transparent beads (B) have an average particle size of 10 μm or more. The coating composition according to claim 1, wherein the pigment (E) is a flat particle. A coating film formed from the coating composition according to claim 1 or 2. The coating film according to claim 3, wherein the average particle size (μm) of the transparent beads (B) divided by the average film thickness (μm) of the coating film is 0.1 or more.

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