JP2022052302A - Coating method and primer - Google Patents

Abstract

To provide a coating method that has superior sagging resistance when coating gelatinous particle inclusion water-based paint under an environment with lower vaporization of moisture and superior water resistance of the formed coated film.SOLUTION: In a coating method where a primer is applied to a substrate, dried to form a primer coated film, a gelatinous particle inclusion water-based paint is applied on the primer coated film then dried, the primer includes an acryl resin having no aqueous medium nor hydroxy group and a hydroxy group inclusion resin, a hydroxy value of the entire the acryl resin and the hydroxy group inclusion resin is 13 to 65 mgKOH/g, a mass ratio represented by the acryl resin/the hydroxy group inclusion resin is 2/8 to 8/2, the gelatinous particle inclusion water-based coating includes a dispersant and at least one color of a gelatinous particle, the gelatinous particle includes an aqueous resin, a hydroxy group inclusion hydrophilic colloid formation material, a hydroxy group inclusion gelatinizer, and at least one type of a gelatinizer selected from a group consisting of gelatinizers that becomes metalhydroxides in water solution.SELECTED DRAWING: None

Description

The present invention relates to a coating method and an undercoat paint.

As a paint used for painting the outer wall of a structure or the like, there is a water-based paint containing gel-like particles of one or more colors (hereinafter, also referred to as “gel-like particle-containing water-based paint”). According to the gel-like particle-containing water-based paint, a coating film having a scattered pattern can be formed by one coating.
The gel-like particle-containing water-based paint is superior to other paints in the design of the coating film to be formed, but is inferior in painting workability and tends to cause dripping during painting. Especially in a low temperature environment or a high humidity environment in winter, the moisture in the coating film does not easily volatilize, so the gel-like particles gradually move downward during the drying of the coating film, resulting in a poor appearance of the coating film. Become. It is considered that one of the factors that cause dripping is that gel-like particles are present in the paint, so that there is a portion in the paint in which the resin is not continuous, and there is no entanglement between the resins in that portion.

In Patent Document 1, a group consisting of an inorganic compound, a fibrous derivative compound, a polyether compound and a polyacrylic acid compound in an aqueous multicolored paint in which at least two colored paint particles are dispersed in a dispersion medium. A water-based multicolored pattern paint containing at least two kinds of viscosity adjusting agents selected from the above is disclosed, and it is said that the paint is less likely to drip by combining a specific viscosity adjusting agent.

Japanese Unexamined Patent Publication No. 2007-262350

However, the water-based multicolored pattern paint of Patent Document 1 does not have sufficient dripping resistance in an environment where moisture in the coating film does not easily volatilize, such as a low temperature environment (for example, 10 ° C. or lower) in winter or a high humidity environment. ..

In order to suppress the dripping of the gel-like particle-containing water-based paint at a high level even in an environment where the water content in the coating film does not easily volatilize, the present inventor precedes the gel-like particle-containing water-based paint and the gel-like particle-containing water-based paint. Various formulations of the undercoat paint to be painted were examined. As a result, it was found that when a hydroxyl group-containing resin was used as the resin for the undercoat paint, the dripping resistance of the gel-like particle-containing water-based paint was improved. However, on the other hand, it was also found that the hydroxyl group-containing resin makes it easier for the undercoat coating film to retain water, and when the coating film is immersed in water for a long time, blistering and poor adhesion occur.
Therefore, when the hydroxyl value of the hydroxyl group-containing resin was lowered for the purpose of improving the water resistance, the result was obtained that the water resistance of the coating film was improved but the sagging resistance was lowered. That is, it was found that there is a trade-off relationship between the dripping resistance of the gel-like particle-containing water-based paint and the water resistance of the coating film.

It is an object of the present invention to provide a coating method and an undercoat paint having excellent dripping resistance during coating of a water-based paint containing gel particles even in an environment where water does not easily volatilize and having good water resistance of the formed coating film. ..

The present invention has the following aspects.
[1] A coating method in which an undercoat paint is applied on a substrate and dried to form an undercoat coating film, and a gel-like particle-containing water-based paint is applied on the undercoat coating film and dried.
The undercoat paint contains an aqueous medium, an acrylic resin having no hydroxyl group dispersed in the aqueous medium, and a hydroxyl group-containing resin dissolved or dispersed in the aqueous medium, and the acrylic resin and the hydroxyl group-containing resin as a whole. The hydroxyl value of the above is 13 to 65 mgKOH / g, and the mass ratio represented by the acrylic resin / the hydroxyl group-containing resin is 2/8 to 8/2.
The gel-like particle-containing water-based paint contains a dispersion medium containing water and gel-like particles of at least one color dispersed in the dispersion medium, and the gel-like particles form a hydrophilic colloid having an aqueous resin and a hydroxyl group. A coating method comprising a substance and at least one gelling agent selected from the group consisting of a gelling agent having a hydroxyl group and a gelling agent that becomes a metal hydroxide in an aqueous solution.
[2] A dispersion medium containing water and gel-like particles of at least one color dispersed in the dispersion medium are contained, and the gel-like particles have an aqueous resin, a hydrophilic colloid-forming substance having a hydroxyl group, and a hydroxyl group. An undercoat paint for a gel-like particle-containing water-based paint containing at least one gelling agent selected from the group consisting of a gelling agent and a gelling agent that becomes a metal hydroxide in an aqueous solution.
It contains an aqueous medium, an acrylic resin having no hydroxyl group dispersed in the aqueous medium, and a hydroxyl group-containing resin dissolved or dispersed in the aqueous medium, and the total hydroxyl value of the acrylic resin and the hydroxyl group-containing resin is 13. An undercoat coating material having a mass ratio of ~ 65 mgKOH / g and represented by the acrylic resin / the hydroxyl group-containing resin of 2/8 to 8/2.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a coating method and an undercoat paint which are excellent in dripping resistance at the time of coating a gel-like particle-containing water-based paint even in an environment where water is hard to volatilize and have good water resistance of the formed coating film.

It is a schematic diagram explaining one Embodiment of the coating method of this invention.

Hereinafter, an embodiment of the coating method of the present invention will be described in detail with reference to the accompanying drawings. The dimensional ratio in FIG. 1 is different from the actual one for convenience of explanation.

As shown in FIG. 1, in the coating method of the present embodiment, first, the undercoat paint is applied on the base material 1 and dried to form the undercoat coating film 3 (step (a)). Next, a gel-like particle-containing water-based paint (hereinafter, also referred to as “paint (G)”) is applied onto the undercoat coating film 3 and dried to form the coating film 5 (step (b)).
The undercoat paint contains an aqueous medium, an acrylic resin having no hydroxyl group dispersed in the aqueous medium, and a hydroxyl group-containing resin dissolved or dispersed in the aqueous medium, and the total hydroxyl value of the acrylic resin and the hydroxyl group-containing resin is 13. It is ~ 65 mgKOH / g, and the mass ratio represented by the acrylic resin / hydroxyl group-containing resin is 2/8 to 8/2.
The paint (G) contains a dispersion medium containing water and gel-like particles of at least one color dispersed in the dispersion medium, and the gel-like particles contain an aqueous resin, a hydrophilic colloid-forming substance having a hydroxyl group, and a hydroxyl group. It contains at least one gelling agent selected from the group consisting of a gelling agent having a gelling agent and a gelling agent that becomes a metal hydroxide in an aqueous solution.
The undercoat paint and the paint (G) will be described in detail later.

<Base material>
The base material 1 is not particularly limited, and for example, ceramic siding board, flexible board, calcium silicate board, gypsum slag bar light board, wood piece cement board, gypsum cement board, pulp cement board, precast concrete board, lightweight bubble concrete (ALC). Examples thereof include ceramic building material boards such as boards and gypsum boards, and metal building material boards such as aluminum, iron and stainless steel.
The surface of the base material 1 may be subjected to a base treatment such as a sealer or a primer.

<Step (a)>
The application method of the undercoat paint is not particularly limited, and can be applied by a known application method such as a brush, a trowel, a roller, a spray coating, a roll coating, and a flow coating.
The amount of the undercoat paint applied is preferably 50 to 1000 g / m ² and more preferably 100 to 800 g / m ² as the mass per unit area before drying (wet). If the coating amount is less than the lower limit, the coating film performance such as water resistance may be insufficient. If the coating amount exceeds the upper limit, problems such as cracking of the coating film may occur during drying.
The drying may be room temperature drying or heat drying 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.

<Step (b)>
The coating method of the paint (G) is not particularly limited, and can be applied by a known coating method such as a brush, a trowel, a roller, a spray coating, a roll coating, and a flow coating.
The amount of the paint (G) applied is preferably 200 to 1200 g / m ² and more preferably 250 to 1000 g / m ² as the mass per unit area before drying (wet). If the coating amount of the paint (G) is less than the lower limit, the coating film performance such as weather resistance and designability may be insufficient. If the coating amount exceeds the above upper limit value, problems such as downward bias of the gel-like particles during painting or drying may occur.
The drying may be room temperature drying or heat drying as long as the dispersion 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 2 weeks.

<Undercoat paint>
The undercoat paint includes an aqueous medium, an acrylic resin having no hydroxyl group (hereinafter, also referred to as “acrylic resin (A)”), and a hydroxyl group-containing resin. The acrylic resin (A) is dispersed in an aqueous medium. The hydroxyl group-containing resin is dissolved or dispersed in an aqueous medium.
If necessary, the undercoat paint may further contain other components other than the aqueous medium, the acrylic resin (A) and the hydroxyl group-containing resin, as long as the effects of the present invention are not impaired. Each component will be described in detail later.

In the undercoat paint, the overall hydroxyl value of the acrylic resin (A) and the hydroxyl group-containing resin is 13 to 65 mgKOH / g, preferably 20 to 60 mgKOH / g, and more preferably 30 to 50 mgKOH / g. When the hydroxyl value is 13 mgKOH / g or more, the dripping resistance of the paint (G) at the time of coating is excellent, and when it is 65 mgKOH / g or less, the water resistance of the undercoat coating film 3 is excellent.
The total hydroxyl value of the acrylic resin (A) and the hydroxyl group-containing resin is the hydroxyl value (mgKOH / g) of each of the acrylic resin (A) and the hydroxyl group-containing resin, and the mass ratio of the acrylic resin (A) and the hydroxyl group-containing resin. It is calculated from.

The mass ratio represented by the acrylic resin (A) / hydroxyl group-containing resin is 2/8 to 8/2, preferably 3/7 to 7/3, and more preferably 4/6 to 6/4. If the mass ratio is 2/8 or more, the undercoat coating film 3 is excellent in water resistance, and if it is 8/2 or less, the paint (G) is excellent in dripping resistance during coating.

The solid content of the undercoat paint is not particularly limited, but is, for example, 30 to 80% by mass.
The solid content means a non-volatile component contained in a coating material that remains after being dried at 125 ° C. for 1 hour, and is measured by the method of JIS K 5601-1-2.

(Aqueous medium)
The aqueous medium is a medium containing only water or a medium obtained by adding a solvent compatible with water to water. The proportion of water in the aqueous medium is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more.
As the water, ion-exchanged water, tap water, or the like can be used.
Examples of the solvent compatible with water include alcohols such as ethanol and isopropyl alcohol, ethylene glycol and the like.

(Acrylic resin (A))
The acrylic resin (A) may be any as long as it does not have a hydroxyl group and can be dispersed in an aqueous medium.
The acrylic resin (A) is typically referred to as at least one monomer selected from the group consisting of (meth) acrylic acid ester and (meth) acrylic acid having no hydroxyl group (hereinafter, also referred to as “acrylic monomer”). ) Includes a polymer having a structural unit based on (hereinafter, also referred to as “acrylic polymer”). Here, "(meth) acrylic acid ester" means at least one of an acrylic acid ester and a methacrylic acid ester. "(Meta) acrylic acid" means at least one of acrylic acid and methacrylic acid.
Hereinafter, the structural unit based on the monomer is also referred to as “monomer unit”.

Examples of the (meth) acrylic acid ester having no hydroxyl group include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic. Alkyl (meth) acrylate, such as isobutyl acid, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, etc. Examples thereof include benzyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate.

The acrylic polymer may have a monomer (hereinafter, also referred to as “non-acrylic monomer”) unit other than the acrylic monomer. Examples of the non-acrylic monomer include olefins such as styrene, vinyl acetate, ethylene and propylene.

It is preferable that at least a part of the acrylic monomer unit is a (meth) acrylic acid ester unit having no hydroxyl group. The (meth) acrylic acid ester unit having no hydroxyl group is preferably an alkyl (meth) acrylic acid unit.

The acrylic resin (A) may be composed of only an acrylic polymer, or may be composed of an acrylic polymer and another polymer. Examples of other polymers include silicone resin, urethane resin, styrene resin, vinyl acetate resin, fluororesin and the like. The acrylic polymer and the other polymer may or may not be chemically bonded.

Examples of the acrylic resin (A) include an acrylic resin composed of only an acrylic polymer, an acrylic silicone resin, an acrylic urethane resin, an acrylic styrene resin, a vinyl acetate-acrylic resin, and an acrylic-fluororesin. These may be used alone or in combination of two or more. Among these, acrylic resin and acrylic silicone resin are preferable in that a coating film having excellent weather resistance and water resistance can be formed.

The hydroxyl value of the acrylic resin (A) is 0 mgKOH / g.

The glass transition temperature of the acrylic resin (A) (hereinafter, also referred to as “Tg”) is preferably 40 ° C. or lower, more preferably 30 ° C. or lower. When the Tg of the acrylic resin (A) is not more than the above upper limit value, the adhesion of the undercoat coating film 3 to the coating film 5 and the base material 1 is more excellent. The lower limit of Tg of the acrylic resin (A) is not particularly limited, but is, for example, −20 ° C.

Tg is a value obtained from the formula of FOX represented by the following formula (i).
1 / (Tg _P +273.15) = Σ [Wi / (Tg _i +273.15)]… ( _i )
In formula (i), Tg _P is the Tg (° C.) of the polymer, _{Wi is the mass fraction of the monomers constituting the polymer, and Tg i is} the Tg (° C.) of the homopolymer of the monomer.
In addition, Tg _i is widely known as a characteristic value of a homopolymer, and for example, the value described in "POLYMER HANDBOOK, THIRD EDITION" or the catalog value of the manufacturer may be used.

The average particle size of the acrylic resin (A) is, for example, 40 to 1000 nm. The average particle size of the acrylic resin (A) is measured by a laser diffraction type particle size distribution measuring device.

(Hydroxy group-containing resin)
The hydroxyl group-containing resin may be any resin (water-soluble resin or water-dispersible resin) that has a hydroxyl group and can be dissolved or dispersed in an aqueous medium.

Examples of the hydroxyl group-containing resin include a hydroxyl group-containing polyester resin, a hydroxyl group-containing silicone-modified polyester resin, a hydroxyl group-containing acrylic resin, a hydroxyl group-containing silicone-modified acrylic resin, a hydroxyl group-containing epoxy resin, a hydroxyl group-containing vinyl resin, and a hydroxyl group-containing fluororesin. .. These resins may be used alone or in combination of two or more.
Of these, a hydroxyl group-containing acrylic resin and a hydroxyl group-containing silicone-modified acrylic resin are preferable because they are excellent in water resistance and durability.

The hydroxyl group-containing acrylic resin typically contains a polymer having a hydroxyl group-containing (meth) acrylic acid ester unit (hereinafter, also referred to as “hydroxyl group-containing acrylic polymer”).
Examples of the hydroxyl group-containing (meth) acrylic acid ester include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) acrylate.

The hydroxyl group-containing acrylic polymer may further have a (meth) acrylic acid ester unit, a (meth) acrylic acid unit, a non-acrylic monomer unit, or the like having no hydroxyl group. Examples of the (meth) acrylic acid ester having no hydroxyl group and the non-acrylic monomer are the same as described above.
The hydroxyl group-containing acrylic polymer preferably has a (meth) acrylic acid ester unit having no hydroxyl group. The (meth) acrylic acid ester unit having no hydroxyl group is preferably an alkyl (meth) acrylic acid unit.

The hydroxyl group-containing acrylic resin may be composed of only a hydroxyl group-containing acrylic polymer, or may be composed of a hydroxyl group-containing acrylic polymer and another hydroxyl group-containing polymer. The hydroxyl group-containing acrylic polymer and the other hydroxyl group-containing polymer may or may not be chemically bonded.

The hydroxyl value of the hydroxyl group-containing resin is preferably 20 to 120 mgKOH / g, more preferably 30 to 100 mgKOH / g, and even more preferably 40 to 90 mgKOH / g. When the hydroxyl value of the hydroxyl group-containing resin is within the above range, the hydroxyl value of the acrylic resin (A) and the hydroxyl group-containing resin as a whole is likely to be within the above range.

The hydroxyl value of the hydroxyl group-containing resin is calculated by the following formula from the monomer composition forming the hydroxyl group-containing resin.
Hydroxy group value (mgKOH / g) = mass fraction of hydroxyl group-containing monomer / molecular weight of hydroxyl group-containing monomer × 56.1 × 1000

The Tg of the hydroxyl group-containing resin is preferably 40 ° C. or lower, more preferably 30 ° C. or lower. When the Tg of the hydroxyl group-containing resin is not more than the above upper limit value, the adhesion of the undercoat coating film 3 to the coating film 5 and the sealer is more excellent. The lower limit of Tg of the hydroxyl group-containing resin is not particularly limited, but is, for example, −20 ° C.

When the hydroxyl group-containing resin is a water-dispersible resin, the average particle size of the hydroxyl group-containing resin is, for example, 40 to 1000 nm. The average particle size of the hydroxyl group-containing resin is measured by a laser diffraction type particle size distribution measuring device.

(Other ingredients)
The undercoat paint may contain known additives, if necessary. Known additives include, for example, emulsifiers, pH regulators, defoamers, viscosity regulators, film-forming aids, antifreeze agents, dispersants, wetting agents, water-soluble resins other than hydroxyl group-containing resins, and penetration aids. , Preservatives, surface conditioners, matting agents, gelling agents, UV absorbers, antioxidants, heat shields and the like.
The undercoat paint may contain a design material. Examples of the design material include colored pigments, extender pigments, luminance pigments, cold water stones, colored stones, colored beads, matte beads, colored resin chips and the like.

(Manufacturing method of undercoat paint)
The undercoat paint can be produced, for example, by mixing an emulsion in which the acrylic resin (A) is dispersed in an aqueous medium (hereinafter, also referred to as “acrylic emulsion (A)”) and a hydroxyl group-containing resin. At this time, other components and a further aqueous medium may be mixed, if necessary. The hydroxyl group-containing resin may be mixed with the acrylic emulsion (A) in the form of a solution in which the hydroxyl group-containing resin is dissolved in an aqueous medium or an emulsion in which the hydroxyl group-containing resin is dispersed in an aqueous medium.

The acrylic emulsion (A) may contain components other than the acrylic resin (A) and an aqueous medium (emulsifier, pH adjuster, etc.).
The solid content of the acrylic emulsion (A) is, for example, 30 to 70% by mass with respect to the total mass of the acrylic emulsion (A).
As the acrylic emulsion (A), a commercially available one may be used, or one manufactured by a known production method may be used. For example, the acrylic emulsion (A) can be produced by polymerizing a monomer mixture containing an acrylic monomer in the presence of an aqueous medium and a radical polymerization initiator. A chain transfer agent may be used during the polymerization. Examples of the polymerization method include an emulsion polymerization method and a suspension polymerization method, and the emulsion polymerization method is preferable.

The solution or emulsion of the hydroxyl group-containing resin may contain components other than the hydroxyl group-containing resin and the aqueous medium (emulsifier, pH adjuster, etc.).
The solid content of the hydroxyl group-containing resin solution or emulsion is, for example, 10 to 60% by mass with respect to the total mass of the hydroxyl group-containing resin solution or emulsion.
As the hydroxyl group-containing resin, a solution or an emulsion thereof, a commercially available product may be used, or a product produced by a known production method may be used. For example, an emulsion of a hydroxyl group-containing acrylic resin can be produced in the same manner as the above acrylic emulsion (A) except that the monomer mixture contains a hydroxyl group-containing (meth) acrylic acid ester.

<Paint (G)>
The paint (G) contains a dispersion medium and gel particles of at least one color.
The paint (G) preferably further contains a binder resin.
The paint (G) may further contain other components (hereinafter, also referred to as “paint (G) optional component”).

(Gel-like particles)
The gel-like particles include an aqueous resin, a hydrophilic colloid-forming substance having a hydroxyl group, and a specific gelling agent.
The gel-like particles may further contain other components (hereinafter, also referred to as "gel-like particles optional component").

The gelling agent typically reacts with and crosslinks the hydrophilic colloid-forming material on the surface of the droplets containing the aqueous resin and the hydrophilic colloid-forming material to form a gelled film containing a three-dimensional network. do. Therefore, the gelled particles typically have droplets containing an aqueous resin and a hydrophilic colloid-forming substance, and a gelled film covering the surface thereof.

The average particle size of the gel-like particles is preferably in the range of 0.1 mm to 5 cm. When the average particle size of the gel-like particles is within the range of 0.1 mm to 5 cm, the design of the coating film 5 is excellent, and the workability of coating with an air gun is also good. When the average particle size of the gel-like particles is less than 0.1 mm, the gel-like particles are visually inconspicuous and it is difficult to obtain an effect on the design. If the size of the gel-like particles exceeds 5 cm, it may cause nozzle clogging during painting work using an air gun.

"Aqueous resin"
The water-based resin is a resin that can be dissolved or dispersed in an water-based medium. As the water-based resin, a resin that can be dispersed in an water-based medium (water-dispersible resin) is preferable.
The type of the aqueous resin is not particularly limited, and can be appropriately selected depending on the compatibility with the hydrophilic colloid-forming substance and the gelling agent and the performance required for the coating film 5. As the water-based resin, those having good water resistance, alkali resistance and weather resistance of the coating film 5 are preferable.
Examples of the types of water-based resins include acrylic resin, urethane resin, vinyl acetate resin, silicone resin, fluororesin, acrylic urethane resin, acrylic silicone resin, acrylic fluororesin, acrylic styrene resin, acrylonitrile resin, vinyl chloride resin, and epoxy resin. , Beova (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 preferable in terms of excellent weather resistance and water resistance.

"Hydrophilic colloid-forming substance"
The hydrophilic colloid-forming substance may have a hydroxyl group and may react with a gelling agent to form a gelled film.
Examples of the hydrophilic colloid-forming substance include cellulose derivatives; polyethylene oxide; polyvinyl alcohol; casein, starch, galactomannan, guar rubber, locust bean gum and other natural polymers. These hydrophilic colloid-forming substances may be used alone or in combination of two or more.

Hydrophilic colloid-forming materials are typically used in the form of aqueous solutions. The concentration of the aqueous solution of the hydrophilic colloid-forming substance is, for example, 0.1% by mass or more and 10% by mass or less.

"Gelling agent"
As described above, the gelling agent reacts with the hydrophilic colloid-forming substance and crosslinks to form a gelled film containing a three-dimensional network structure.
The gelling agent in the coating material (G) is at least one selected from the group consisting of a gelling agent having a hydroxyl group and a gelling agent that becomes a metal hydroxide in an aqueous solution. By including such a gelling agent, a gelled film containing a hydroxyl group is formed.

Examples of the gelling agent having a hydroxyl group include montmorillonite, bentonite, tannic acid and the like.
Examples of the gelling agent that becomes a metal hydroxide in an aqueous solution include borate, aluminum salt, barium salt, calcium salt, magnesium salt and the like.
These gelling agents may be used alone or in combination of two or more.

The gelling agent is typically used in the form of an aqueous solution. The concentration of the gelling agent aqueous solution is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 8% by mass or less. By setting the content of the gelling agent in the gelling agent aqueous solution within the above range, a gelled film can be stably obtained.

"Gel-like particle optional component"
The gel-like particles may contain an extender pigment. The extender pigment is a general term for achromatic pigments used in paints. Examples of the extender pigment include kaolin, barium sulfate, hydrous magnesium silicate, and calcium carbonate. The extender pigment may be used alone or in combination of two or more.
The gelled particles may contain known additives. Known additives include, for example, antifungal agents, antifungal agents, antifoaming agents, viscosity modifiers, film-forming aids, antifreeze agents, wetting agents, water-soluble resins, penetration aids, preservatives, antibacterial agents. , Insecticide, repellent, water repellent, oil repellent, hydrophilic agent, rust preventive, flame retardant, surface conditioner, matting agent, heat shield, ultraviolet absorber, light stabilizer, antioxidant, etc. Can be mentioned.
The paint (G) may contain a design material. Examples of the design material include colored pigments, luminance pigments, aggregates, matte beads, bright materials, colored resin chips and the like.

(Dispersion medium)
The dispersion medium contains water.
Examples of the dispersion medium include those similar to the aqueous medium in the undercoat paint.

(Binder resin)
As the binder resin, an aqueous resin is preferable.
Examples of the water-based resin include those similar to the water-based resin in gel-like particles.
It is preferable that the binder resin and the water-based resin in the gel-like particles have the same form and type. As an example, there is an example in which both the binder resin and the water-based resin in the gel-like particles are acrylic silicone resins that can be dispersed in an water-based medium.
The type of the binder resin and the water-based resin in the gel-like particles may be different. As an example, the binder resin is an acrylic silicone resin, and the aqueous resin in the gel-like particles is an acrylic resin.

(Paint (G) optional component)
The paint (G) may contain the above-mentioned gelling agent.
The paint (G) may contain the above-mentioned hydrophilic colloid-forming substance.
The paint (G) may contain known additives. Known additives include, for example, antifungal agents, antifungal agents, antifoaming agents, viscosity modifiers, film-forming aids, antifreeze agents, wetting agents, water-soluble resins, penetration aids, preservatives, antibacterial agents. , Insecticide, repellent, water repellent, oil repellent, hydrophilic agent, rust preventive, flame retardant, surface conditioner, matting agent, heat shield, ultraviolet absorber, light stabilizer, antioxidant, etc. Can be mentioned.
The paint (G) may contain a design material. Examples of the design material include colored pigments, luminance pigments, aggregates, matte beads, bright materials, colored resin chips and the like.

(Manufacturing method of paint (G))
The paint (G) can be manufactured, for example, by the following manufacturing method.
First, an aqueous resin and an aqueous solution of a hydrophilic colloid-forming substance are mixed to prepare a mixed solution (d). Separately, water and additives such as pigments and dispersants are mixed as needed to prepare a mixed solution (e). Then, the mixed solution (d) and the mixed solution (e) are mixed to prepare an emulsion solution (c).
Separately, an aqueous solution (f) is prepared by mixing a gelling agent, water, and a hydrophilic colloid-forming substance or an additive, if necessary.
Next, the emulsion solution (c) is added to the aqueous solution (f) while stirring the aqueous solution (f) with a disperser.

When the emulsion solution (c) is stirred in the aqueous solution (f), droplets of the emulsion solution (c) are formed, and the hydrophilic colloid-forming substance contained in the droplets and the gel contained in the aqueous solution (f). A three-dimensional network structure (gelled film) is formed by reacting with the agent and cross-linking. Further, the emulsion solution (c) is subdivided by stirring while being aggregated by the reaction with the gelling agent. Even in the process of subdivision, the hydrophilic colloid-forming substance and the gelling agent continuously react to form a three-dimensional network structure (gelled film). As a result, gel-like particles in which the droplets of the emulsion solution (c) are coated with the gelled film are obtained.
In this way, the aggregate of the emulsion solution (c) is subdivided while the hydrophilic colloid-forming substance reacts with the gelling agent, so that the gel-like particles are dispersed in the aqueous solution (f). A liquid is obtained.

The obtained gel-like particle dispersion may be used as it is as the paint (G).
When the paint (G) contains a binder resin, the binder resin may be further added to the gel-like particle dispersion obtained in the above step and stirred.
A plurality of types of gel-like particle dispersions having different color tones of gel-like particles may be prepared and mixed.
Water may be added to the gel-like particle-containing paint for the purpose of adjusting the viscosity or the like.

<Action effect>
In the coating method described above, by applying the paint (G) on the undercoat coating film 3 formed from the undercoat paint, the paint (G) has a dripping resistance at the time of coating and the undercoat is applied. It is possible to achieve both the water resistance of the film 3 at a high level. Regarding the dripping resistance, it is possible to suppress dripping during coating of the paint (G) even in an environment where moisture is hard to volatilize, such as a low temperature environment (for example, 10 ° C. or lower) in winter or a high humidity environment.
The reason for the improvement in dripping resistance is that the undercoat paint contains a hydroxyl group-containing resin, so that hydroxyl groups are present on the surface of the undercoat coating film 3 of the paint (G), and these hydroxyl groups and the gel-like particle-containing water-based paint contain the hydroxyl groups. It is conceivable that an intermolecular force is generated between the existing hydroxyl groups and the paint (G), and the adhesion of the paint (G) to the undercoat coating film 3 is enhanced.
When only a hydroxyl group-containing resin is used as the resin component and the hydroxyl value is 13 mgKOH / g or more, the dripping resistance is improved, but the hydrophilicity of the undercoat film 3 becomes too high, and the water resistance of the undercoat film 3 becomes high. It will be inadequate. By using the hydroxyl group-containing resin and the acrylic resin (A) together in the above mass ratio, water resistance can be ensured even if the hydroxyl value of the entire resin content is 13 mgKOH / g or more, and the dripping resistance and water resistance are high. It is compatible at the level. Although the reason is not clear, the hydrophilic hydroxyl group-containing resin and the particles of the hydrophobic acrylic resin (A) may form the undercoat coating film 3 in a state having a structure like microphase separation. Conceivable.

The coating method of the present invention is not limited to the above-described embodiment. The configurations and combinations thereof in the above-described embodiments are examples, and the configurations can be added, omitted, replaced, and other changes within the scope not deviating from the gist of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. In the following, "part" indicates "parts by mass", and "%" indicates "% by mass".

<Measurement method>
(Glass transition temperature (Tg))
The glass transition temperature (Tg) was calculated from the FOX equation.

(Hydroxy group value (OHV))
The hydroxyl value (OHV) was calculated from the monomer composition used at the time of polymerization by the following formula.
Hydroxy group value (mgKOH / g) = mass fraction of hydroxyl group-containing monomer / molecular weight of hydroxyl group-containing monomer × 56.1 × 1000

[Preparation of paint (G)]
<Manufacturing example 1>
(Preparation of dispersion of gel particles)
The resin and the hydrophilic colloidal solution were mixed according to the formulation shown in Table 1 to obtain a mixed solution (d). Further, water, a pigment and a dispersant were mixed according to the formulation shown in Table 1 to obtain a mixed liquid (e). Then, the mixed solution (d) and the mixed solution (e) were mixed to obtain an emulsion solution (c).
Separately, an aqueous solution (f) was obtained by mixing a gelling agent, water, an extender pigment and CMC-Na according to the formulation shown in Table 1.
Next, the emulsion solution (c) was added while stirring the aqueous solution (f) with a dissolver (manufactured by Nissei Tokyo Office Co., Ltd., rotation speed 1000 rpm). The emulsion solution (c) subdivided by stirring is stirred until the average particle size becomes 0.5 mm to 1 cm, and the dispersion liquid of gel-like particles (gel particle content: 44% with respect to the total mass of the dispersion liquid). ) Was obtained. The average particle size of the gel-like particles was determined by randomly taking out 20 gel-like particles and arithmetically averaging each measured value measured with a nogis for the major axis.

The materials in Table 1 are as follows.
Acrylic resin emulsion: 50% solid content, "Primal AC38" manufactured by Dow Chemical Co., Ltd.
Hydrophilic colloid-forming substance: 4% aqueous solution of nonionic guar rubber derivative, "MEYPRO HPG 8111" manufactured by DuPont.
Pigment: Titanium oxide, "Typake CR95" manufactured by Ishihara Sangyo Co., Ltd.
Dispersant: Anionic polymer dispersant, "Orotan 731" manufactured by Dow Chemical Co., Ltd.
Gelling agent: 5% aqueous solution of ammonium diborate, manufactured by Yoneyama Chemical Industry Co., Ltd.
Constituent pigment: 5% aqueous dispersion of hydrous magnesium silicate, "Talc SSS" manufactured by Japan Talc.
CMC-Na: 1% aqueous solution of sodium carboxymethyl cellulose, "CMC-1170" manufactured by Daicel Chemical Industries, Ltd.

(Preparation of paint (G))
According to the formulation shown in Table 2, the above gel-like particle dispersion, acrylic resin emulsion, algae-proofing agent, fungicide-proofing agent, ultraviolet absorber, thickener, 25% ammonia water and water are mixed to prepare the paint (G). Obtained.

The materials in Table 2 are as follows.
Acrylic resin emulsion: 50% solid content, "Primal AC38" manufactured by Dow Chemical Co., Ltd.
Algae proofing agent: "HF-260K" manufactured by Nagase ChemteX, 30% active ingredient.
Antifungal agent: "ACTICIDE OTW" manufactured by THOR JAPAN, 30% active ingredient.
UV absorber: "Tinuvin 400DW" manufactured by BASF JAPAN, 40% active ingredient.
Thickener: Alkaline-soluble thickener, "SN Thickener 636" manufactured by San Nopco Ltd., 30% active ingredient.

[Preparation of acrylic resin emulsion]
<Manufacturing Example 2-1>
60 parts of deionized water, 6.7 parts of Sannoll NP-2030 (anionic emulsifier manufactured by Lion Co., Ltd., active ingredient 30%) in a polymerization device equipped with a stirrer, a cooler, and a thermometer that can be heated and cooled. Was charged, and nitrogen was blown under the liquid surface at a rate of 40 mL / min for 15 minutes, and then the internal temperature was raised to 80 ° C. with stirring.
In another container, 18 parts of methyl methacrylate, 27 parts of ethyl methacrylate and 55 parts of n-butyl acrylate are mixed, 1 part of α-methylstyrene dimer is mixed, and then 10 parts of Sannol NP-2030 and Leocol TD are mixed. -300 (Nonion-based emulsifier manufactured by Lion Co., Ltd., 100% active ingredient) and 35 parts of deionized water are added, placed in a Waring blender (DYNAMIC CORPORATION OFAMERICA, LB10S type), stirred at 5000 rpm for 10 minutes, and uniformly. A pre-emulsion in an emulsified state (hereinafter, abbreviated as “PE solution”) was prepared and subjected to nitrogen bubbling for 15 minutes.
Five parts of the obtained PE solution was put into a polymerization vessel, heated to 80 ° C., and then a solution in which 0.2 part of sodium persulfate was dissolved in one part of deionized water was put into the polymerization vessel, and the mixture was stirred. It was left for 1 hour.
After 1 hour, the rest of the PE solution and the solution prepared by dissolving 2 parts of sodium persulfate in 10 parts by mass of deionized water were added over 3 hours while maintaining the internal temperature of the polymerization vessel during stirring at 80 ° C. And dropped into the polymerization vessel. After the dropping was completed, the internal temperature was maintained at 80 ° C. for 2 hours to complete the reaction.
After the reaction is completed, the mixture is cooled to room temperature, dimethylethanolamine is added so that the pH of the emulsion becomes 8.5, and deionized water is further added so that the solid content becomes 40% by mass, and the acrylic resin emulsion (E-) is added. 1) was obtained. Table 3 shows the monomer composition and the characteristics (Tg, OHV) of the acrylic resin.

<Manufacturing Examples 2-2-2-5>
Acrylic resin emulsions (E-2) to (E-5) were obtained in the same manner as in Production Example 2-1 except that the monomer composition was changed as shown in Table 3. Table 3 shows the characteristics of the acrylic resin.

The abbreviations in Table 3 indicate the following.
MMA: Methyl methacrylate.
EMA: Ethyl methacrylate.
HEMA: 2-hydroxyethyl methacrylate.
BA: n-butyl acrylate.
2-EHA: 2-ethylhexyl acrylate.
NP-2030: Anionic emulsifier manufactured by Lion Corporation, 30% active ingredient.
TD-300: Nonionic emulsifier manufactured by Lion Corporation, 100% active ingredient.
The amount of emulsifier in Table 3 is the amount of active ingredient.
The acrylic resin of the acrylic resin emulsion (E-1) corresponds to the acrylic resin (A), and the acrylic resins of the acrylic resin emulsions (E-2) to (E-5) correspond to the hydroxyl group-containing resin.

[Examples 1 to 10, Comparative Examples 1 to 5]
<Preparation of undercoat paint>
Each material was mixed and stirred according to the formulations shown in Tables 4 to 5 to prepare an undercoat paint.
Tables 4 to 5 show the ratio of the resin content (mass%) to the total mass of the undercoat paint, the hydroxyl value of the entire resin content, and the mass ratio of the acrylic resin (Ac) having no hydroxyl group to the hydroxyl group-containing resin (AcOH). Ac / AcOH ratio) is shown. Here, the "resin content" refers to the entire acrylic resin having no hydroxyl group and the hydroxyl group-containing resin.
In Tables 4 to 5, the unit of the blending amount of each material is a part. The materials used other than the acrylic resin emulsion are as follows.
Calcium carbonate: "Heavy calcium carbonate" manufactured by Maruo Calcium.
TIM ₂ : "Typake CR95" manufactured by Ishihara Sangyo Co., Ltd.
Blended water: Deionized water.
HEC: Hydroxyethyl cellulose, "QP52000H" manufactured by Dow Chemical Co., Ltd.
Meeting agent: "Coapur 6050" manufactured by Arkema.
Surface conditioner: "BYK-346" manufactured by Big Chemie.
Membrane-forming aid: "Texanol" manufactured by EASTMAN CHEMICAL.

<Evaluation>
(Evaluation of sagging resistance)
The prepared undercoat paint was applied to a slate plate (300 x 15 x 3 mm) that had been previously sealed with an air spray so that the coating amount was 200 g / m ² (wet), and the temperature was 23 ° C and the relative humidity was 50. It was dried for 24 hours under the condition of%. As a result, a coated plate having an undercoat coating film formed on the slate plate was obtained.
Next, the coated plate and the paint (G) prepared in Production Example 1 were placed in an environment of a temperature of 15 ° C. or 5 ° C., and left until the temperature of the coated plate and the paint (G) reached the same temperature as the air temperature.
Next, the coating plate was installed so as to be perpendicular to the floor surface, and the coating material (G) was applied on the undercoat coating film by air spray so that the coating amount was 800 g / m ² (wet). The coated plate was dried for 24 hours in an environment of a temperature of 15 ° C. or 5 ° C. with the coated plate installed vertically. As a result, a test piece in which the undercoat coating film and the coating film were sequentially formed on the slate plate was obtained.
The appearance of the coating film of the obtained test piece was visually observed, and the sagging resistance was evaluated according to the following criteria. The results are shown in Tables 4-5.
"Evaluation criteria for sagging resistance"
〇: No dripping, and the appearance of the coating film is good.
Δ: Some drips are seen.
X: Dripping is observed, and the appearance of the coating film is significantly inferior.

(Evaluation of water resistance)
The prepared undercoat paint was applied to a slate plate (300 x 15 x 3 mm) that had been previously sealed with an air spray so that the coating amount was 200 g / m ² (wet), and the temperature was 23 ° C and the relative humidity was 50. It was dried for 24 hours under the condition of%.
Next, the paint (G) was applied on the formed undercoat film by air spray so that the coating amount was 400 g / m ² (wet), and the temperature was 23 ° C. and the relative humidity was 50%. Allowed to dry for days. As a result, a test piece in which the undercoat coating film and the coating film were sequentially formed on the slate plate was obtained.
The obtained test piece was immersed in water at 23 ° C. for 14 days, pulled up, and then the appearance of the coating film was visually observed, and the water resistance was evaluated according to the following criteria. The results are shown in Tables 4-5.
"Evaluation criteria for water resistance"
〇: The appearance of the coating film is good.
Δ: Partial gloss and whitening are observed.
×: Blisters are recognized.

In Examples 1 to 10, the dripping resistance at the time of coating the paint (G) was excellent in both the environments of the temperature of 15 ° C. and the temperature of 5 ° C. Moreover, the water resistance of the coating film was excellent.
On the other hand, in Comparative Example 1, since the OHV of the entire resin content of the undercoat paint was less than 13 mgKOH / g, the dripping resistance during coating of the paint (G) in an environment of a temperature of 5 ° C. was inferior.
In Comparative Example 2, since the OHV of the entire resin content of the undercoat paint was more than 65 mgKOH / g, the water resistance of the coating film was inferior.
In Comparative Example 3, since the Ac / AcOH ratio of the undercoat paint was more than 8/2 and the amount of the hydroxyl group-containing resin was small, the dripping resistance of the paint (G) at the time of coating in an environment of a temperature of 5 ° C. was inferior.
In Comparative Example 4, the Ac / AcOH ratio of the undercoat paint was less than 2/8 and the amount of the hydroxyl group-containing resin was large, so that the water resistance of the coating film was inferior.
In Comparative Example 5, the OHV of the entire resin content of the undercoat paint was 13 to 65 mgKOH / g, but the acrylic resin having no hydroxyl group was not contained, so that the water resistance of the coating film was inferior.

1 Base material 3 Undercoat coating film 5 Coating film

Claims (2)

A coating method in which an undercoat paint is applied on a base material and dried to form an undercoat coating film, and a gel-like particle-containing water-based paint is applied on the undercoat coating film and dried.
The undercoat paint contains an aqueous medium, an acrylic resin having no hydroxyl group dispersed in the aqueous medium, and a hydroxyl group-containing resin dissolved or dispersed in the aqueous medium, and the acrylic resin and the hydroxyl group-containing resin as a whole. The hydroxyl value of the above is 13 to 65 mgKOH / g, and the mass ratio represented by the acrylic resin / the hydroxyl group-containing resin is 2/8 to 8/2.
The gel-like particle-containing water-based paint contains a dispersion medium containing water and gel-like particles of at least one color dispersed in the dispersion medium, and the gel-like particles form a hydrophilic colloid having an aqueous resin and a hydroxyl group. A coating method comprising a substance and at least one gelling agent selected from the group consisting of a gelling agent having a hydroxyl group and a gelling agent that becomes a metal hydroxide in an aqueous solution. It contains a dispersion medium containing water and gel-like particles of at least one color dispersed in the dispersion medium, and the gel-like particles are an aqueous resin, a hydrophilic colloid-forming substance having a hydroxyl group, and a gelling agent having a hydroxyl group. An undercoat paint for a gel-like particle-containing water-based paint containing at least one gelling agent selected from the group consisting of a gelling agent that becomes a metal hydroxide in an aqueous solution.
It contains an aqueous medium, an acrylic resin having no hydroxyl group dispersed in the aqueous medium, and a hydroxyl group-containing resin dissolved or dispersed in the aqueous medium, and the total hydroxyl value of the acrylic resin and the hydroxyl group-containing resin is 13. An undercoat coating material having a mass ratio of ~ 65 mgKOH / g and represented by the acrylic resin / the hydroxyl group-containing resin of 2/8 to 8/2.

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