JP7440767B2 - water-based paint composition - Google Patents

Description

The present invention relates to a water-based coating composition.

BACKGROUND OF THE INVENTION In order to enhance the appearance of buildings such as buildings and residences, a coating film is sometimes applied to the outer walls of buildings.
On the other hand, from the viewpoint of disaster prevention, etc., flame retardancy is sometimes required for the outer walls of buildings, houses, and other structures. When a paint film is provided on such an exterior wall, the paint film is also required to have flame retardancy.

Patent Document 1 describes a coating film structure with excellent flame retardancy and good appearance, which includes an undercoat film containing a flame retardant and a multicolored coating film containing a heat-shielding colored pigment provided thereon. A coating structure is disclosed.

JP2017-205980A

However, the coating structure of Patent Document 1 requires the use of multiple types of paint, and has the disadvantage that the number of coatings is large and the process is complicated.

An object of the present invention is to provide a water-based coating composition that can form a patterned coating film with excellent flame retardancy.

The present invention has the following aspects.
[1] Contains water and gel particles dispersed in the water,
The gel-like particles have droplets containing a resin emulsion and a gelled film covering the surface of the droplets,
A water-based coating composition, wherein 20% by mass or more of 100% by mass of the gel particles contains expanded graphite.
[2] The aqueous coating composition according to [1] above, wherein the proportion of the expanded graphite is 10 to 75 parts by mass with respect to a total of 100 parts by mass of the resin content of the resin emulsion of all the gel particles.

According to the present invention, it is possible to provide a water-based coating composition that can form a patterned coating film with excellent flame retardancy.

[Water-based paint composition]
The water-based coating composition of the present invention includes water and gel particles dispersed in water.
The gel particles have droplets containing a resin emulsion and a gelled film covering the surface of the droplets.
20% by mass or more of 100% by mass of gel particles in the water-based paint composition contains expanded graphite. Hereinafter, gel particles containing expanded graphite will also be referred to as "gel particles (A)."
The water-based paint composition may contain only gel particles (A) as gel particles, and may further contain gel particles that do not contain expanded graphite (hereinafter also referred to as "gel particles (B)"). May contain.
The water-based coating composition may further contain a binder resin, if necessary. Note that since the gel particles function as a binder, the water-based coating composition does not need to contain a binder resin.
The water-based coating composition may further contain other components other than those mentioned above, if necessary.

<Water>
The content of water is preferably 30 to 85% by weight, more preferably 40 to 80% by weight based on 100% by weight of the water-based coating composition.

<Gel-like particles (A)>
The gel particles (A) have droplets containing a resin emulsion and a gelled film covering the surface of the droplets, and contain expanded graphite. Gel particles (A) typically include expanded graphite in droplets.

(droplet)
The droplets contain a resin emulsion.
The droplets typically further include a hydrophilic colloid-forming substance.
In the case of gel particles (A), the droplets typically further include expanded graphite.
The droplet may further contain components other than those mentioned above (hereinafter also referred to as "optional components").

"Resin emulsion"
A resin emulsion includes suspended particles or emulsified particles made of resin as a forming material, and a dispersion medium in which the suspended particles or emulsified particles are dispersed.
Examples of resins for forming suspended particles or emulsified particles include polyvinyl acetate, acrylic resin, polystyrene, acrylonitrile, Beova (branched fatty acid vinyl ester), natural or synthetic rubber, and emulsions of copolymers thereof. . These resins may be used alone or in combination of two or more. Among these, acrylic resin is preferred.
Water is preferred as the dispersion medium for the resin emulsion.
As the resin emulsion, generally commercially available resin emulsions can be used.

"Hydrophilic colloid-forming substance"
The hydrophilic colloid-forming substance is a substance that can react with a gelling agent to form a gelled film. The gelling agent will be described later.
Examples of the hydrophilic colloid-forming substance include aqueous solutions containing cellulose derivatives, polyethylene oxide, polyvinyl alcohol, natural polymers (casein, starch, galactomannone, guar gum, locust bean gum, etc.), and the like. Among these, an aqueous solution of guar gum is preferred. The concentration of the aqueous solution is preferably 0.5 to 5% by weight, more preferably 1.0 to 3% by weight. One type of hydrophilic colloid-forming substance may be used alone, or two or more types may be used in combination.

The content of the hydrophilic colloid-forming substance is preferably 0.05 to 5 parts by weight, more preferably 0.1 to 3.0 parts by weight, based on 100 parts by weight of the resin emulsion. By controlling the content of the hydrophilic colloid-forming substance within the above range, a stable gelled film can be obtained.

"Expanded graphite"
Expanded graphite is also called a graphite intercalation compound, and has the property of expanding when heated.
When the gel particles (A) are exposed to flame after forming a coating film, the expanded graphite contained in the gel particles (A) expands and forms a shell, which has the effect of heat insulation, blocking flammable gas, etc. Suppresses the burning of the paint film and exhibits flame retardant properties.
As the expanded graphite, commonly available commercially available graphite can be used. Examples of commercially available expanded graphite include 955025L manufactured by Ito Graphite Industries, and 160-50 manufactured by NeoGra.
The expanded graphite preferably has an expanded volume of 170 mL/g or more. The upper limit of the expansion volume is, for example, 400 mL/g.
The expansion start temperature of expanded graphite is preferably 200°C or lower. The lower limit of the expansion start temperature is, for example, 160°C.

The content of expanded graphite in the gel-like particles (A) varies depending on the proportion of the gel-like particles (A) in 100% by mass of all gel-like particles, but the content of expanded graphite in the resin emulsion in the gel-like particles (A) It is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, based on 100 parts by mass of the resin content. If the content of expanded graphite is at least the above lower limit, the flame retardance of the coating film will be more excellent.
The content of expanded graphite in the gel-like particles (A) is preferably 75 parts by mass or less, and 70 parts by mass or less, based on 100 parts by mass of the resin content of the resin emulsion in the gel-like particles (A). It is more preferable that there be. If the content of expanded graphite is below the above-mentioned upper limit, the gel particles (A) will not easily collapse.

"Optional ingredients"
The droplets may contain pigments such as coloring pigments and extender pigments within a range that does not impair the effects of the present invention.
In addition to the above, the droplets may contain known additives such as thickeners, dispersants, antifoaming agents, preservatives, leveling agents, etc., as long as they do not impair the effects of the present invention.

When the droplets contain a pigment, the content of the pigment is preferably such that the total amount of the pigment together with the expanded graphite does not exceed the preferable upper limit of the content of the expanded graphite described above. That is, the total content of expanded graphite and pigment is preferably 75 parts by mass or less, more preferably 70 parts by mass or less, based on 100 parts by mass of the resin content of the resin emulsion.

(gel membrane)
The gelled film covers the surface of the droplet and forms the outline of the gelled particle. Since the surface of the droplet is covered with the gel film, the gel particles can be stably dispersed in the dispersion medium.
Examples of the gelled film include those containing a three-dimensional network formed by the reaction and crosslinking of a hydrophilic colloid substance contained in a droplet with a gelling agent. The gelled membrane has lower fluidity than the droplets and contains the droplets inside.

Examples of the gelling agent include magnesium montmorillonite clay, sodium pentachlorophenol, borate, tannic acid, titanium lactate, and calcium chloride. Among these, borates are preferred. One type of gelling agent may be used alone, or two or more types may be used in combination.

The average particle diameter of the gel particles (A) is preferably 5 to 50 mm, more preferably 10 to 40 mm. When the average particle diameter is 5 mm or more, the gel particles are densely present and the flame retardance is good. On the other hand, if the average particle diameter is 50 mm or less, the smoothness of the coating film is good.
The average particle diameter of the gel-like particles is the average value obtained by randomly selecting 20 gel-like particles and measuring their major diameters with a caliper.

<Gel-like particles (B)>
The gel-like particles (B) are the same as the gel-like particles (A) except that they do not contain expanded graphite, and their preferred embodiments are also the same.

The proportion of gel particles (A) is 20% by mass or more out of 100% by mass of all gel particles (total of gel particles (A) and gel particles (B)) in the water-based paint composition. It is preferably 25% by mass or more, and may be 100% by mass. If the proportion of gel particles (A) is 20% by mass or more, sufficient flame retardancy can be imparted to the coating film.

The total content of all gel particles in the water-based paint composition is preferably 30 to 100% by mass, more preferably 40 to 80% by mass, based on 100% by mass of the water-based paint composition. preferable. When the total content of gel particles is 30% by mass or more, the workability of coating the object to be coated with the water-based coating composition is good.

The proportion of expanded graphite is preferably 10 to 75 parts by mass, more preferably 30 to 70 parts by mass, based on the total 100 parts by mass of the resin content of the resin emulsion of all gel particles in the water-based coating composition. preferable. If the content of expanded graphite is at least the lower limit, the flame retardance of the coating film will be better, and if it is at least the upper limit, the content of expanded graphite in the gel particles (A) can be reduced, and the gel The shaped particles (A) do not easily collapse.

<Binder resin>
Examples of the binder resin include polyvinyl acetate, acrylic resin, polystyrene, acrylonitrile, Beova (branched fatty acid vinyl ester), natural or synthetic rubber, and emulsions of copolymers thereof. These resins may be used alone or in combination of two or more. Among these, acrylic resin is preferred.
The binder resin may be blended in the form of a resin emulsion. As the resin emulsion, generally commercially available resin emulsions can be used. Water is preferred as the dispersion medium for the resin emulsion.

The content of the binder resin (in the case of a resin emulsion, in terms of resin content) is preferably 0 to 50 parts by mass, more preferably 0 to 33 parts by mass, based on 100 parts by mass of gel particles. If the content of the binder resin is below the upper limit value, flame retardancy can be easily ensured.

<Other ingredients>
The water-based paint composition may contain an extender pigment. The extender pigment will be described later.
The water-based coating composition may contain a water-soluble polymer compound. The water-soluble polymer compound will be described later.
In addition to the above, the water-based coating composition may contain known additives such as thickeners, dispersants, antifoaming agents, preservatives, leveling agents, etc., as long as they do not impair the effects of the present invention. .

<Method for producing water-based paint composition>
The aqueous coating composition can be prepared, for example, by preparing an aqueous dispersion of gel particles (A), and optionally adding an aqueous dispersion of gel particles (B) to the aqueous dispersion of gel particles (A). It can be manufactured by blending a resin emulsion, optional ingredients, water, etc.

The aqueous dispersion of gel particles (A) can be prepared, for example, by preparing an emulsion paint containing a resin emulsion, a hydrophilic colloid-forming substance, and expanded graphite, and adding the resulting emulsion paint to a gelling agent and water while stirring. It can be prepared by adding it to a dispersion medium containing.

An emulsion paint can be prepared, for example, by adding a hydrophilic colloid-forming substance, expanded graphite, and optional components as necessary to a resin emulsion, and stirring and mixing the mixture.

The dispersion medium includes a gelling agent and water.
The content (solid content) of the gelling agent is preferably 0.05 to 5% by mass, more preferably 0.1 to 3% by mass, based on 100% by mass of the dispersion medium. By controlling the content of the gelling agent within the above range, a stable gelled film can be obtained.
The content of water is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, based on 100% by mass of the dispersion medium.

The dispersion medium may contain an extender pigment, if necessary.
Extender pigments include kaolin, barium sulfate, hydrated magnesium silicate, calcium carbonate, and the like. Among them, hydrous magnesium silicate is preferred. One type of extender pigment may be used alone, or two or more types may be used in combination.
The content (solid content) of the extender pigment is preferably 0.05 to 10% by mass, more preferably 0.1 to 5% by mass, based on 100% by mass of the dispersion medium.

The dispersion medium may contain a water-soluble polymer compound as necessary.
Examples of water-soluble polymer compounds include hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, and the like. Among them, carboxymethylcellulose is preferred. One type of water-soluble polymer compound may be used alone, or two or more types may be used in combination.
The content (solid content) of the water-soluble polymer compound is preferably 0.05 to 3% by mass, more preferably 0.1 to 2% by mass, based on 100% by mass of the dispersion medium.

The dispersion medium can be prepared, for example, by mixing an aqueous solution of a gelling agent, an aqueous dispersion of an extender pigment, and an aqueous solution of a water-soluble polymer compound, and diluting the mixture with water as necessary.
The concentration of the gelling agent in the gelling agent aqueous solution is preferably 0.05 to 10% by mass, more preferably 0.5 to 8% by mass.
The concentration of the extender pigment in the aqueous dispersion of the extender pigment is preferably 0.05 to 20% by mass, more preferably 2 to 10% by mass.
The concentration of the water-soluble polymer compound in the aqueous solution of the water-soluble polymer compound is preferably 0.1 to 5% by mass, more preferably 0.5 to 3% by mass.

When the emulsion paint is stirred in the dispersion medium, droplets of the emulsion paint are formed, and on the surface of the droplets, the hydrophilic colloid-forming substance of the emulsion paint and the gelling agent of the dispersion medium react to form a three-dimensional network structure. It is formed. Further, the droplets of the emulsion paint are aggregated by reaction with the gelling agent, and are then divided into small pieces by stirring. Even in the process of fragmentation, the hydrophilic colloid-forming substance and the gelling agent continuously react to form a three-dimensional network.
The gel-like particles thus obtained contain a large amount of water and are soft particles.

The amount of the emulsion paint to be blended is preferably 100 to 500 parts by weight, more preferably 150 to 400 parts by weight, per 100 parts by weight of the dispersion medium. By setting the amount of the emulsion paint within the above range, gel particles with a uniform shape can be easily obtained.

The stirring method may be a known method, such as stirring with a disperser such as a dissolver.
The average particle diameter of the resulting gel-like particles can be freely controlled by adjusting the viscosity of the emulsion paint or dispersion medium, the rotation speed of the dispersion machine, the stirring time, and the combination and amount of the hydrophilic colloid-forming substance and gelling agent. Generally, increasing the viscosity of an emulsion paint or dispersion medium increases the average particle size, and increasing the rotation speed of the dispersion machine decreases the average particle size.

Aqueous dispersions of two or more types of gel particles (A), each of which emulsion paint contains colored pigments of different tones, may be prepared and then mixed. Thereby, the water-based paint composition can be made into a multi-colored paint composition.

The aqueous dispersion of gel particles (B) can be prepared in the same manner as the aqueous dispersion of gel particles (A), except that the emulsion paint does not contain expanded graphite.
The emulsion paint of gel particles (B) may contain a colored pigment having a different tone from that of the emulsion paint of gel particles (A). Thereby, the water-based paint composition can be made into a multi-colored paint composition.

<Application>
By applying the water-based coating composition of the present invention to the surface of an object to be coated and drying it, a patterned coating film having flame retardancy can be formed.
There is no particular restriction on the object to be coated, and it is possible to coat objects made of various materials such as mortar, concrete, ceramic materials, plastics, metals, and wood.
There are no particular restrictions on the coating method, and any known coating method such as brush, trowel, roller, spray, etc. can be used.
There is no particular restriction on the amount of the water-based coating composition applied, but it is usually preferably 150 to 800 g/m ² . The coating amount is the value before drying.
Drying may be carried out at room temperature or by heating. The drying temperature is, for example, 5 to 80°C. The drying time varies depending on the drying temperature, but is, for example, 5 minutes to 8 hours.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples. In the following, "parts" indicate "parts by mass."

<Preparation of emulsion paint>
(Manufacturing example A-1)
31.7 parts of acrylic resin emulsion (manufactured by DIC Corporation, "Boncourt CF-6140", dispersion medium: water, resin content: 48% by mass) and 28.5 parts of a 1.5% by mass aqueous solution of a nonionic guar rubber derivative. (solid content 0.43 parts) and 10 parts of expanded graphite (manufactured by Ito Graphite Industries Co., Ltd., "955025L", expansion volume: 250 mL/g, expansion start temperature: 160°C) were mixed in a dissolver, and the mixed liquid ( a) was prepared.
A mixed solution (b) was prepared by mixing 1 part of an anionic polymer dispersant (manufactured by Nippon Acrylic Chemical Co., Ltd., "Orothane 731") and 28.8 parts of water.
Mixed solution (b) was added to mixed solution (a) and stirred to obtain emulsion paint A-1.

(Production examples A-2 to A-4)
In the same manner as Production Example A-1, except that part or all of the expanded graphite was changed to a white pigment (titanium oxide, manufactured by Ishihara Sangyo Co., Ltd., "Titanium R930") according to the formulation (parts) shown in Table 1. Emulsion paints A-2, A-3, and A-4 were produced.

<Production of gel-like particle aqueous dispersion>
(Manufacturing example B-1)
25 parts of a 4% by mass aqueous dispersion of hydrated magnesium silicate (1 part by weight), 5 parts by mass of an aqueous solution of ammonium biborate (0.25 parts by mass) and 1% by mass of sodium carboxymethyl cellulose. After adding 25 parts (solid content 0.25 part) and stirring and mixing, 45 parts of water was added to dilute the mixture to obtain a dispersion medium.

60 parts of emulsion paint A-1 was added to 40 parts of the obtained dispersion medium, and the mixture was stirred with a dissolver until the average particle diameter became 30 mm to obtain gel-like particle aqueous dispersion B-1.
Twenty gel particles were randomly selected from gel particle aqueous dispersion B-1, and the average length of the particles was measured using a caliper and was about 30 mm.

(Manufacturing examples B-2 to B-4)
Gel particle aqueous dispersion B-2, B-3, B- 4 was manufactured.

<Manufacture and evaluation of water-based coating composition>
(Examples 1-8, Comparative Examples 1-2)
The gel-like particle aqueous dispersion shown in Table 3 and water or acrylic resin emulsion (manufactured by DIC Corporation, "Boncourt CF-6140", dispersion medium: water, resin content: 48% by mass) in the proportions shown in Table 3. (parts) were mixed to obtain a water-based coating composition.
Table 3 shows the amount (parts) of expanded graphite in the entire gel particles in the water-based paint composition, the amount (parts) of the resin component in the resin emulsion, and the ratio (parts) of expanded graphite to 100 parts by mass of the resin component. show.
A flame retardant test was conducted on the obtained water-based paint composition according to the following procedure. The results are shown in Table 3.

"Flame retardant test"
A water-based coating composition was applied onto a slate board using a roller so that the coating amount (before drying) was 300 g/m ² and dried at 23° C. for 2 weeks to form a coating film.
Then, from a position 5 cm away from the paint film, a burner flame was radiated toward the paint film for 30 seconds to cause it to burn. The state of the flame and smoke during combustion (presence or absence of flame, presence or absence of smoke) was visually confirmed. Regarding smoke, cases where it was visible with a black board as a background were classified as ``slight''.

The coating films of the water-based coating compositions of Examples 1 to 8 had excellent flame retardancy.
On the other hand, the coating film of the aqueous coating composition of Comparative Example 1 in which the gel particles did not contain expanded graphite had poor flame retardancy.
The coating film of the aqueous coating composition of Comparative Example 2 in which the ratio of gel particles containing expanded graphite to 100 mass % of gel particles was 10 mass % was also poor in flame retardancy.

According to the water-based coating composition of the present invention, a patterned coating film with excellent flame retardancy can be formed.
Since a patterned coating film with excellent flame retardancy can be formed using only the water-based coating composition of the present invention, the coating process for forming such a coating film is also simple.

Claims (2)

comprising water and gel-like particles dispersed in the water,
The gel-like particles have droplets containing a resin emulsion and a gelled film covering the surface of the droplets,
A water-based coating composition, wherein 20% by mass or more of 100% by mass of the gel particles contains expanded graphite. The water-based coating composition according to claim 1, wherein the proportion of the expanded graphite is 10 to 75 parts by mass based on a total of 100 parts by mass of the resin content of the resin emulsion of all the gel particles.