JP5207613B2 - Water-based paint - Google Patents

Description

  The present invention relates to a water-based paint having stable film forming performance.

Conventionally, in the paint field, solvent-based paints that use organic solvents such as aromatic hydrocarbons have been the mainstream, but in recent years, water is used as a medium from the standpoint of environmental issues, resource saving, occupational safety and health, etc. Switching to water-based paint is progressing.
Synthetic resin emulsions are often used as binders in water-based paints. In general, a synthetic resin emulsion forms a continuous film by fusing emulsion particles together with volatilization of water as a medium. Therefore, in order to ensure the film-forming property, it is necessary to set the Tg of the synthetic resin emulsion to be somewhat low. However, if the Tg is lowered, the formed coating film tends to exhibit adhesiveness, and dirt is also attached. It becomes easy.
For such a problem, in a water-based paint, as a technique for achieving both film-forming properties and adhesion resistance (contamination resistance), it is possible to use a multilayer structure emulsion composed of a high Tg shell portion and a low Tg core portion. Known (Patent Document 1, etc.). A high boiling point solvent is generally used as a film-forming aid in a paint containing such a multilayer structure type emulsion. Patent Document 1 describes the use of a high-boiling solvent such as 2,2,4-trimethyl 1,3-pentanediol monoisobutyrate as a film-forming aid.
However, water-based paints composed of such components may lack film-forming stability depending on the environmental conditions at the time of application. In particular, when forming a coating film under high humidity, it tends to be difficult to ensure film-forming stability.

JP 2000-104010 A

  The present invention has been made in view of the above-described problems, and an object of the present invention is to improve the film-forming stability of an aqueous paint using a multilayer structure emulsion as a binder.

  As a result of intensive studies to achieve the above object, the present inventor conceived of using a specific hydrophilic solvent and a hydrophobic solvent in combination in a water-based paint having a multilayer structure emulsion as a binder. It came to complete.

  That is, the present invention has the following characteristics.

1. Each of the core part and the shell part comprises a polymer of a monomer group containing at least one or more (meth) acrylic acid alkyl esters,
The (meth) acrylic acid alkyl ester having an alkyl group having 4 or more carbon atoms and having a homopolymer having a glass transition temperature (hereinafter referred to as “Tg”) of −30 ° C. or less has a core portion rather than a shell portion. Is set to be high,
A multilayer structure type synthetic resin emulsion (A) having a Tg of -80 to 20 ° C. in the core part, a Tg of 0 to 100 ° C. in the shell part, and a Tg of the shell part higher than the Tg of the core part,
An essential component is a hydrophilic solvent (B) having a solubility in water of 10 g / 100 g or more and a boiling point of 200 ° C. or more, and a hydrophobic solvent (C) having a solubility in water of less than 10 g / 100 g and a boiling point of 200 ° C. or more,
The hydrophilic solvent (B) and the hydrophobic solvent (C) are contained in a total of 1 to 50 parts by weight per 100 parts by weight of the solid content of the multilayer structure type synthetic resin emulsion (A), and the hydrophilic solvent ( B) and the weight ratio of the hydrophobic solvent (C) is 95: 5 to 5: 95 der is, water-based paint which is characterized in that the coating and drying at 5 to 40 ° C..
2. The multilayer structure type synthetic resin emulsion (A) contains 50% by weight or more of a shell part in the resin solid content, and Tg of the core part is 40 ° C. or more lower than Tg of the shell part. The water-based paint described.
3. The multilayer structured synthetic resin emulsion (A) has an average particle size of 120 nm or less. Or 2. The water-based paint described.
4). The coating and drying are performed at a relative humidity of 80% or more. ~ 3. The water-based paint according to any one of the above.

  The water-based paint of the present invention can exhibit stable performance in film-forming properties while ensuring physical properties such as adhesion resistance and stain resistance. In particular, even when coating is performed in a high humidity environment, sufficient film-forming properties can be exhibited.

  Hereinafter, the best mode for carrying out the present invention will be described.

  The multilayer structure type synthetic resin emulsion (A) in the present invention (hereinafter referred to as “component (A)”) has a core part and a shell part, and each of the core part and the shell part is at least one (meta). ) It consists of a polymer of a monomer group containing an acrylic acid alkyl ester. Such (meth) acrylic acid alkyl ester is the main component of the resin skeleton. In the present invention, the acrylic acid alkyl ester and the methacrylic acid alkyl ester are collectively referred to as (meth) acrylic acid alkyl ester.

  Specific examples of the (meth) acrylic acid alkyl ester include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-amyl ( (Meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate, Examples include cyclohexyl (meth) acrylate, phenyl (meth) acrylate, and benzyl (meth) acrylate. These can be used alone or in combination of two or more.

  The (A) component of the present invention is a (meth) acrylic acid having such a (meth) acrylic acid alkyl ester having an alkyl group having 4 or more carbon atoms and a Tg of the homopolymer of -30 ° C. or lower. The alkyl ester (a) (hereinafter referred to as “component (a)”) is an essential component. Examples of the component (a) include n-butyl acrylate (homopolymer Tg: -54 ° C), 2-ethylhexyl acrylate (homopolymer Tg: -85 ° C), dodecyl methacrylate (homopolymer Tg: -65 ° C), and the like. Can be mentioned. The component ratio of the component (a) may be set so as to be higher in the core portion than in the shell portion, and the shell portion may not include the component (a).

  In the component (A), the Tg of the core part is set to −80 to 20 ° C., the Tg of the shell part is set to 0 to 100 ° C., and the Tg of the shell part is set to be higher than the Tg of the core part. In the present invention, the above-described component (a) is used as the component constituting the component (A), and the Tg of each layer is set under such conditions, thereby making the film-forming property and the anti-adhesion property compatible to some extent. Is possible. The resin solid content of component (A) contains 50% by weight or more (preferably 60% by weight or more, more preferably 70% by weight or more) of the shell part, and Tg of the core part is 40 ° C. or more (preferably Tg of the shell part) If it is set to be low, it is more preferable in terms of both film-forming properties and adhesion resistance. In addition, Tg of (A) component can be calculated | required with the formula of Fox.

  The component ratio of the (meth) acrylic acid alkyl ester in the monomer group constituting the component (A) is usually 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more. Although an upper limit is not specifically limited, Usually, it is 99.8 weight% or less, Preferably it is 99.5 weight% or less, More preferably, it is 99 weight% or less. If the constituent ratio of the (meth) acrylic acid alkyl ester is within such a range, good physical properties in terms of weather resistance, water resistance, chemical resistance and the like can be ensured.

The component (A) may contain a polymerizable monomer other than the above as a constituent component as necessary. Examples of such polymerizable monomers include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, and maleic acid; N-methylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and dimethylaminoethyl. Amino group-containing monomers such as vinyl ether; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; vinyl ester monomers such as vinyl acetate and vinyl propionate; nitrile groups such as acrylonitrile and methacrylonitrile Containing monomers: aromatic monomers such as styrene, 2-methylstyrene, vinyltoluene, t-butylstyrene, chlorostyrene, vinylanisole, vinylnaphthalene, divinylbenzene; acrylamide Amide group-containing monomers such as methacrylamide, maleic acid amide, N-methylol (meth) acrylamide; Epoxy group-containing monomers such as glycidyl (meth) acrylate, diglycidyl (meth) acrylate, allyl glycidyl ether; acrolein, diacetone (meth) Carbonyl group-containing monomers such as acrylamide, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone; alkoxysilyl group-containing monomers such as vinyltrimethoxysilane, vinyltriethoxysilane, and γ- (meth) acryloyloxypropyltrimethoxysilane; Vinylidene halide monomers such as vinylidene and vinylidene fluoride; other ethylene, propylene, isoprene, butadiene, vinyl pyrrolidone, vinyl chloride, vinyl ether, Examples include vinyl ketone, vinyl amide, and chloroprene.
The composition ratio of the polymerizable monomer in the monomer group is usually 50% by weight or less, preferably 40% by weight or less, more preferably 30% by weight or less.

(A) component can be manufactured by carrying out emulsion polymerization of the monomer group which mixed the said polymerizable monomer suitably. A known method may be adopted as the polymerization method. In the polymerization, an initiator, a polymerization inhibitor, a polymerization inhibitor, a buffering agent, a chain transfer agent and the like can be appropriately used.
The average particle diameter of the component (A) is not particularly limited, but is preferably 120 nm or less in terms of both film forming properties and adhesion resistance. The average particle diameter of the component (A) can be measured by a dynamic light scattering method.

  In the present invention, with respect to the component (A), the solubility in water is 10 g / 100 g or more, the hydrophilic solvent (B) having a boiling point of 200 ° C. or more (hereinafter referred to as “component (B)”), and the solubility in water. A hydrophobic solvent (C) (hereinafter referred to as “component (C)”) having a boiling point of less than 10 g / 100 g and a boiling point of 200 ° C. or higher is mixed. In the present invention, an excellent effect in film-forming stability can be obtained by using these two components having different solubility characteristics in water.

In a multilayer structure type emulsion composed of a high Tg shell part and a low Tg core part, the core part tends to be relatively hydrophobic. If only a hydrophobic solvent is added as a film-forming aid to such a multilayer structure type emulsion, the hydrophobic solvent is unevenly distributed in the core part, and the plasticizing effect at the shell part becomes insufficient, resulting in poor film formation. May cause. In particular, in a high humidity environment, the uneven distribution of the hydrophobic solvent in the core portion becomes remarkable, and the problem of poor film formation is likely to occur.
On the other hand, in the present invention, by using the (B) component and the (C) component together as a film forming aid, a certain level is maintained in the plasticized state in the emulsion particles, and the environment during film formation changes. Even in such a case, a predetermined film forming performance can be exhibited.

  (B) As a component, what satisfy | fills the above-mentioned conditions can be used. Specific compounds that can be used as the component (B) include, for example, ethylene glycol monophenyl ether, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether acetate, triethylene glycol, triethylene glycol monomethyl ether, Triethylene glycol monoethyl ether, tetraethylene glycol, dipropylene glycol, dipropylene glycol monopropyl ether, tripropylene glycol monomethyl ether, 1,3-butanediol, 1,4-butanediol, 1,5-pentadiol, N -Methylpyrrolidone and the like. The solubility of the component (B) in water is 10 g / 100 g or more, preferably 20 g / 100 g or more, more preferably ∞.

  Examples of the component (C) include ethylene glycol monohexyl ether, ethylene glycol dibutyl ether, diethylene glycol monohexyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol dibutyl ether, propylene glycol phenyl ether, dipropylene glycol monobutyl ether, and dipropylene glycol tertiary. Butyl ether, tripropylene glycol monobutyl ether, octylene glycol, 2-ethylhexylene glycol, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, 2,2,4-trimethyl-1,3- Examples include pentanediol diisobutyrate and benzyl alcohol. The solubility of the component (C) in water is less than 10 g / 100 g, preferably less than 5 g / 100 g, more preferably less than 2 g / 100 g.

  The weight ratio of the component (B) to the component (C) is usually 95: 5 to 5:95, preferably 90:10 to 10:90, more preferably 80:20 to 20:80, still more preferably. 70:30 to 30:70. In this invention, the outstanding film-forming stabilization effect can be acquired by using both components together in this ratio.

  The total amount of the component (B) and the component (C) is usually adjusted to 1 to 50 parts by weight, preferably 2 to 30 parts by weight with respect to 100 parts by weight of the solid content of the component (A). If the mixing ratio of these components is too small, a sufficient plasticizing effect cannot be obtained, and cracks and the like are likely to occur during film formation. When the mixing ratio is too large, there is a possibility that problems such as taking more time than necessary for drying the coating film and causing stickiness on the surface of the coating film may occur.

  In addition to the above-described components, the water-based paint of the present invention can be mixed with components that can be used in ordinary paints. Examples of such components include pigments, aggregates, fibers, thickeners, film-forming aids, leveling agents, wetting agents, plasticizers, antifreezing agents, antiseptics, antifungal agents, anti-algae agents, and antibacterial agents. Agents, dispersants, adsorbents, ultraviolet absorbers, antioxidants, light stabilizers, catalysts, crosslinking agents and the like. The aqueous paint of the present invention can be produced by uniformly mixing these components by a conventional method.

  Among these, color pigments, extender pigments and the like that can be generally blended into paints can be used as the pigment. Examples of color pigments include titanium oxide, zinc oxide, carbon black, lamp black, bone black, graphite, black iron oxide, copper chrome black, cobalt black, copper manganese iron black, red potato, molybdate orange, permanent red, and permanent. Carmine, anthraquinone red, perylene red, quinacridone red, yellow iron oxide, titanium yellow, first yellow, benzimidazolone yellow, chrome green, cobalt green, phthalocyanine green, ultramarine, bitumen, cobalt blue, phthalocyanine blue, quinacridone violet, dioxazine Violet etc. are mentioned. Examples of extender pigments include heavy calcium carbonate, precipitated calcium carbonate, kaolin, talc, clay, porcelain clay, china clay, barium sulfate, barium carbonate, silica, diatomaceous earth, and resin beads. In the present invention, when such a pigment is mixed, a stable film-forming property can be exhibited even if the pigment volume concentration is 10% or even 15% or more.

The water-based paint of the present invention can be applied by a known method. As a coating method, for example, spray coating, roller coating, brush coating, or the like can be employed. The coating amount at the time of painting can be appropriately set according to the form of the paint, the desired finish appearance, etc., but is usually about 0.1 to 3 kg / m ² . At the time of painting, the viscosity of the paint can be appropriately adjusted by diluting with water or the like. The dilution ratio is usually about 0 to 20% by weight.
The coating and drying of the paint of the present invention may be usually performed at room temperature (about 5 to 40 ° C.), but may be performed at a high temperature as necessary. The coating composition of the present invention can exhibit stable film-forming properties even when coating is performed in an environment with a relative humidity of 80% or more (more preferably 90% or more).

  Examples are given below to clarify the features of the present invention. In the production of the water-based paints of the examples, the following raw materials were used.

Multilayer structure type synthetic resin emulsion 1 (core monomer component: methyl methacrylate / 2-ethylhexyl acrylate / methacrylic acid = 61/38/1, shell monomer component: methyl methacrylate / 2-ethylhexyl acrylate / methacrylic acid = 79/20 / 1, core part Tg: 0 ° C., shell part Tg: 42 ° C., core-shell weight ratio: 50/50, solid content 50% by weight, average particle diameter 130 nm)

Multilayer structure type synthetic resin emulsion 2 (core monomer component: methyl methacrylate / 2-ethylhexyl acrylate / methacrylic acid = 49/50/1, shell monomer component: methyl methacrylate / 2-ethylhexyl acrylate / methacrylic acid = 79/20 / 1, core part Tg: −22 ° C., shell part Tg: 42 ° C., core-shell weight ratio: 30/70, solid content 50% by weight, average particle diameter 110 nm)

Solvent 1: Triethylene glycol monoethyl ether (water solubility ∞, boiling point 256 ° C.)
Solvent 2: tripropylene glycol monomethyl ether (water solubility ∞, boiling point 242 ° C.)
Solvent 3: diethylene glycol dibutyl ether (water solubility 0.3 g / 100 g, boiling point 255 ° C.)
Solvent 4: 2,2,4-trimethyl 1,3-pentanediol monoisobutyrate (solubility in water 0.9 g / 100 g, boiling point 244 ° C.)
・ Pigment (titanium oxide, average particle size 0.2 μm, specific gravity 4.2)
・ Dispersant: Polycarboxylic acid-based dispersant (solid content 30% by weight)
・ Thickener: Polyurethane thickener (solid content 30% by weight)
-Antifoaming agent: Silicon-based antifoaming agent (solid content 50% by weight)

Example 1
200 parts by weight of multilayer structure type synthetic resin emulsion 1, 6 parts by weight of solvent 1, 6 parts by weight of solvent 3, 85 parts by weight of pigment, 3 parts by weight of dispersant, 1 part by weight of thickener, defoaming agent A water-based paint 1 (pigment volume concentration 17%) was produced by uniformly mixing 1 part by weight of
Next, in an environment of a temperature of 23 ° C. and a relative humidity of 50%, the aqueous paint 1 was spray-coated on a slate plate at a coating amount of 0.3 kg / m ² and dried and cured for 48 hours. The film-forming state of the coating film formed by the above method was confirmed visually (Test 1). The evaluation criteria are “◎” for no abnormalities, “○” for almost no abnormalities, “△” for some abnormalities, and “A” for obvious abnormalities. × ”. Further, even in an environment of a temperature of 30 ° C. and a relative humidity of 90%, coating was performed in the same manner, and the film forming state was confirmed (Test 2). The results are shown in Table 1.

(Example 2)
200 parts by weight of multilayer structure type synthetic resin emulsion 2, 6 parts by weight of solvent 1, 6 parts by weight of solvent 3, 85 parts by weight of pigment, 3 parts by weight of dispersant, 1 part by weight of thickener, defoaming agent A water-based paint 2 (pigment volume concentration 17%) was produced by uniformly mixing 1 part by weight of
This water-based paint 2 was tested in the same manner as in Example 1. The results are shown in Table 1.

(Example 3)
200 parts by weight of multilayer structure type synthetic resin emulsion 2, 6 parts by weight of solvent 2, 6 parts by weight of solvent 4, 85 parts by weight of pigment, 3 parts by weight of dispersant, 1 part by weight of thickener, defoaming agent A water-based paint 3 (pigment volume concentration 17%) was produced by uniformly mixing 1 part by weight of
This water-based paint 3 was tested in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
200 parts by weight of multilayer structure type synthetic resin emulsion 1, 12 parts by weight of solvent 1, 85 parts by weight of pigment, 3 parts by weight of dispersant, 1 part by weight of thickener, and 1 part by weight of antifoaming agent are uniformly mixed As a result, water-based paint 4 (pigment volume concentration 17%) was produced.
This water-based paint 4 was tested in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
200 parts by weight of multilayer resin emulsion 1, 1 part by weight of solvent 3, 85 parts by weight of pigment, 3 parts by weight of dispersant, 1 part by weight of thickener, and 1 part by weight of antifoaming agent are uniformly mixed As a result, an aqueous paint 5 (pigment volume concentration 17%) was produced.
This water-based paint 5 was tested in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
By uniformly mixing 200 parts by weight of the multilayer structure type synthetic resin emulsion 1, 85 parts by weight of the pigment, 3 parts by weight of the dispersant, 1 part by weight of the thickener, and 1 part by weight of the antifoaming agent, the aqueous paint 6 (Pigment volume concentration 17%) was produced.
This water-based paint 6 was tested in the same manner as in Example 1. The results are shown in Table 1.

Claims (4)

Each of the core part and the shell part comprises a polymer of a monomer group containing at least one or more (meth) acrylic acid alkyl esters,
The (meth) acrylic acid alkyl ester having an alkyl group having 4 or more carbon atoms and having a homopolymer having a glass transition temperature (hereinafter referred to as “Tg”) of −30 ° C. or less has a core portion rather than a shell portion. Is set to be high,
A multilayer structure type synthetic resin emulsion (A) having a Tg of -80 to 20 ° C. in the core part, a Tg of 0 to 100 ° C. in the shell part, and a Tg of the shell part higher than the Tg of the core part,
An essential component is a hydrophilic solvent (B) having a solubility in water of 10 g / 100 g or more and a boiling point of 200 ° C. or more, and a hydrophobic solvent (C) having a solubility in water of less than 10 g / 100 g and a boiling point of 200 ° C. or more,
The hydrophilic solvent (B) and the hydrophobic solvent (C) are contained in a total of 1 to 50 parts by weight per 100 parts by weight of the solid content of the multilayer structure type synthetic resin emulsion (A), and the hydrophilic solvent ( B) and the weight ratio of the hydrophobic solvent (C) is 95: 5 to 5: 95 der is, water-based paint which is characterized in that the coating and drying at 5 to 40 ° C..   2. The multilayer structure type synthetic resin emulsion (A) contains 50% by weight or more of a shell part in the resin solid content, and Tg of the core part is 40 ° C. or more lower than Tg of the shell part. Water-based paint.   The water-based paint according to claim 1 or 2, wherein the multilayer structure type synthetic resin emulsion (A) has an average particle size of 120 nm or less.   The water-based paint according to any one of claims 1 to 3, wherein coating and drying are performed at a relative humidity of 80% or more.