JP2003251269A - High-durability double-layered coating film and method of forming the same and building material for facing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide double layered coating films which are excellent in basic characteristics, such as weatherability, water resistance and discoloration resistance and are improved in the adhesion property of the coating films as well. <P>SOLUTION: The double layered coating films have (a) a first coating film layer which is formed of a water-base coating material composition essentially consisting of an aqueous dispersion of an acrylic polymer having a glass transition temperature of -20 to 70°C and (b) a second coating film layer which consists of a water-base coating material composition essentially consisting of an aqueous dispersion of an acrylic polymer containing silicone and containing an organic silicone unit of 5 to 60 parts by mass per 100 parts by mass solid content (in terms of solid component) in the dispersion in this solid content and is formed on the first coating film layer, in which the difference between the solubility parameters of the respective acrylic resin components of the acrylic polymer being the essential component of the water-base coating material composition forming (a) the first coating film layer and the polymer forming (b) the second coating film layer is ≤0.5. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly durable multi-layer coating film applied to an outer wall, an inner wall or a roof of a building such as a house or a building, an inorganic building material such as a ceramic building material, and a method for forming the same.

[0002]

2. Description of the Related Art Various exterior coatings are applied to the walls of buildings such as houses and buildings in order to maintain their quality and appearance while being exposed to wind and rain and being directly exposed to sunlight. Such paints have weather resistance against water and rain, water resistance, discoloration resistance,
Although basic performance such as adhesion to the substrate is required,
In recent years, water-based materials have been developed due to environmental pollution, safety and hygiene in painting work.

Various studies have been conducted on such exterior coatings, but in recent years, the demand for improved performance has become more and more remarkable, and the appearance can be maintained for a long period of time even in a severe outdoor environment. Obtaining a coating film having excellent weather resistance and durability could not be sufficiently realized by conventional techniques.

In order to solve such a problem, a clear paint containing an inorganic component is applied on the enamel paint,
It is also being made to improve durability and weather resistance as well as appearance. However, when the clear coating material contains a large amount of inorganic components, the adhesion between the first coating layer and the second coating layer deteriorates, causing a problem that cracks or peeling easily occur.

Japanese Patent Laid-Open No. 2000-160095 describes an exterior building material having at least two coating layers of a water-based coating material containing a polymer having a cyclohexyl group on the surface of a ceramic exterior building material. However, even with such a coating layer, it has not been possible to achieve both improved coating adhesion and high durability.

JP-A-9-98586 and JP-A-9-98586
208642, JP-A-10-182774, JP-A-11-255846, JP-A-2000-
Japanese Patent No. 264971 discloses an aqueous coating composition having an organic silicone unit. However, the above problems cannot be solved by simply using a coating material such as these as the second coating layer.

[0007]

In view of the above situation, the present invention provides a multilayer coating film having excellent basic properties such as weather resistance, water resistance, discoloration resistance, and improved adhesion of the coating film. That is the purpose.

[0008]

The present invention provides a first coating formed from (a) an aqueous coating composition containing an acrylic polymer aqueous dispersion having a glass transition temperature of −20 to 70 ° C. as a main component. A membrane layer and (b) a silicone-containing acrylic polymer aqueous dispersion as a main component, and 5 to 60 parts by mass of an organic silicone unit per 100 parts by mass (solid content conversion) of the solid content in the solid content of the dispersion. Consisting of an aqueous coating composition containing, having a second coating layer formed on the first coating layer, (a) the main of the aqueous coating composition forming the first coating layer In the multilayer coating film, the difference in solubility parameter between the acrylic polymer as the component and the acrylic resin component as the polymer forming the second coating layer (b) is 0.5 or less. is there.

The present invention (a) has a glass transition temperature of -70 to.
The acrylic polymer having a temperature of 35 ° C. is used as a core portion, the acrylic polymer having a glass transition temperature of 25 to 80 ° C. is used as a shell portion, and the glass transition temperature of the polymer of the core portion is the glass of the polymer of the shell portion. 20 ° C lower than the transition temperature,
The mass ratio between the core portion and the shell portion is 2/8 to 8 /
A first coating layer formed from an aqueous coating composition containing a polymer aqueous dispersion, in which the multi-layered structure particle 2 is dispersed, as a main component, and (b) a silicone-containing acrylic polymer aqueous dispersion. The first coating film comprises a main component and an aqueous coating composition containing 5 to 60 parts by mass of an organic silicone unit per 100 parts by mass of the solid content (as calculated as solid content) in the solid content of the dispersion. Having a second coating layer formed on the layer, (a) an acrylic polymer which is the main component of the aqueous coating composition forming the first coating layer, and (b) a second coating layer. It is also a multi-layer coating film characterized in that the difference in solubility parameter between the respective acrylic resin components of the polymer forming the polymer is 0.5 or less.

The first coating layer is an acrylic obtained from 5 to 70 parts by mass of a substituted or unsubstituted cycloalkyl group-containing polymerizable monomer and 30 to 95 parts by mass of another polymerizable monomer. It is preferably formed from an aqueous coating composition containing an aqueous polymer dispersion as a main component.

The first coating layer comprises 0.1 to 10 parts by mass of an alkoxysilyl group-containing polymerizable monomer having 1 to 14 carbon atoms in 100 parts by mass of all monomers in the dispersion. It is preferably formed from the composition. The first coating layer is preferably formed from an aqueous coating composition having a pigment.

The present invention (a) has a glass transition temperature of -20 to
A first coating layer forming step of coating a first coating layer formed from an aqueous coating composition containing an acrylic polymer aqueous dispersion at 70 ° C. as a main component on an object to be coated, and (b)
Subsequent to the first coating layer formation step, 5 to 60 parts by mass per 100 parts by mass (solid content conversion) of the solid content of the dispersion containing the silicone-containing acrylic polymer aqueous dispersion as a main component. A multilayer coating film forming method comprising a second coating film layer forming step of applying an aqueous coating composition containing an organic silicone unit of to a coating object,
(a) Acrylic polymer that is the main component of the aqueous coating composition that forms the first coating layer, and (b) Acrylic polymer that is the main component of the aqueous coating composition that forms the second coating layer. The difference in the solubility parameter of each acrylic resin component of the coalescence,
The method for forming a multilayer coating film is 0.5 or less.

The present invention is also an exterior building material having the above-mentioned multilayer coating film. The present invention will be described in detail below.

The coating composition used for forming the first coating layer for forming the multilayer coating film of the present invention contains an acrylic polymer aqueous dispersion as a main component. The above-mentioned acrylic polymer aqueous dispersion has a lower glass transition temperature (Tg)-
It has an acrylic polymer having a temperature of 20 ° C. and an upper limit of 70 ° C.

If the Tg is less than -20 ° C, the blocking resistance of the resulting coating film is lowered. If it exceeds 70 ° C, the film-forming property of the obtained coating film is deteriorated and the hot water resistance is deteriorated. The lower limit of Tg is more preferably −15 ° C., further preferably −10 ° C. The upper limit is more preferably 50 ° C., further preferably 40 ° C.

In the present invention, the Tg of the polymer is
Derivation of the mass fraction of each monomer that constitutes the body from each monomer
The value of Tg (K: represented by Kelvin) of the homopolymer
The reciprocal of the sum of each quotient obtained by dividing and
Can be calculated. The acrylic polymer is
If the polymer has an a / shell structure, the core
Minutes, Tg of each shell component is calculated by the above method
The core component Tg _A, Core component in polymer particles
Mass fraction of W_A, Tg of shell component_B, Polymer
The mass fraction of the shell component in the particles is W_BAs below general
formula 1 / Tg = W_A/ Tg_A+ W_B/ Tg_B The Tg represented by is the polymer Tg.

The acrylic polymer is obtained from a polymerizable monomer. The above-mentioned polymerizable monomer means one having at least one unsaturated bond such as a vinyl group in the molecule, and includes a derivative of acrylic acid or methacrylic acid. The polymerizable monomer is not particularly limited, and examples thereof include ethylenically unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, maleic acid and itaconic acid; methyl (meth) acrylate, (meth) acrylic Ethylenic unsaturated carboxylic acid alkyl ester monomers such as ethyl acidate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate; ethyl maleate, butyl maleate, ethyl itaconate, butyl itaconate, etc. Monoester monomer of ethylenically unsaturated dicarboxylic acid; (meth) acrylic acid 2-
Hydroxyethyl, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate,
A hydroxyl group-containing ethylenically unsaturated carboxylic acid alkyl ester monomer such as a reaction product of 2-hydroxyethyl (meth) acrylate and ε-caprolactone; aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, Ethylenic unsaturated carboxylic acid aminoalkyl ester monomers such as butylaminoethyl (meth) acrylate; Ethylenic unsaturated monomers such as aminoethyl (meth) acrylamide, dimethylaminomethyl (meth) acrylamide, methylaminopropyl (meth) acrylamide Saturated carboxylic acid aminoalkyl amide monomer; other amide group-containing ethylenically unsaturated carboxylic acid monomer such as acrylamide, methacrylamide, N-methylol acrylamide, methoxybutyl acrylamide, diacetone acrylamide; Unsaturated fatty acid glycidyl ester monomers such as glycidyl acetate and glycidyl methacrylate; vinyl cyanide monomers such as (meth) acrylonitrile and α-chloroacrylonitrile; saturated aliphatic carboxylic acids such as vinyl acetate and vinyl propionate Vinyl ester monomers; styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene and the like can be mentioned. These can be used alone or in combination of two or more. In the present specification, (meth) acrylic acid refers to acrylic acid or methacrylic acid.

Of these, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate and styrene are more preferred.

The acrylic polymer preferably has a substituted or unsubstituted cycloalkyl group-containing polymerizable monomer. The cycloalkyl group has 4 to 4 carbon atoms.
Those having 20 are preferable. When the cycloalkyl group is substituted, the substituent is not particularly limited as long as it is a linear or branched hydrocarbon group having 1 to 4 carbon atoms, and further substituted with a hydroxyl group or the like. It may have been done.

When the acrylic polymer has the cycloalkyl group-containing polymerizable monomer, the resulting coating film has excellent weather resistance, discoloration resistance, hydrolysis resistance, crack resistance,
In addition to imparting water resistance, gloss and gloss retention, it can also impart excellent film forming properties, blocking resistance and temperature change resistance in cooperation with other components.

The cycloalkyl group-containing polymerizable monomer is not particularly limited, and examples thereof include cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate,
Methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, hydroxymethylcyclohexyl (meth) acrylate, cyclooctyl (meth) acrylate, cyclodecyl (meth) acrylate,
Cyclododecyl (meth) acrylate etc. can be mentioned. These can be used alone or in combination of two or more. Among these, especially cyclohexyl (meth) acrylic acid and methylcyclohexyl (meth)
Acrylic acid is preferred.

The cycloalkyl group-containing polymerizable monomer is preferably contained in the multilayer structure particles in a ratio of 5 parts by mass as the lower limit and 70 parts by mass as the upper limit. When the amount of the cycloalkyl group-containing polymerizable monomer in the multi-layered structure particles is less than 5 parts by mass, the weather resistance of the resulting coating film decreases, and when it exceeds 70 parts by mass, the film-forming property of the resulting coating film. May decrease, and hot water resistance may deteriorate. The lower limit is preferably 10 parts by mass, more preferably 20 parts by mass, and the upper limit is preferably 65 parts by mass, more preferably 55 parts by mass.

The above-mentioned polymerizable monomer contains an alkoxysilyl group-containing polymerizable monomer having 1 to 14 carbon atoms in a ratio of a lower limit of 0.1 parts by mass and an upper limit of 10 parts by mass in 100 parts by mass of all monomers. Preferably. One to three alkoxyl groups having 1 to 14 carbon atoms can be bonded to the silicon atom constituting the alkoxysilyl group having 1 to 14 carbon atoms. The alkoxyl group is likely to be hydrolyzed to form a silanol group particularly in an acidic environment. Since the silanol group forms a siloxane bond by dehydration bonding to crosslink or increase the molecular weight, the film-forming property of the resulting coating film, blocking resistance and temperature change resistance are significantly improved, and particularly excellent. Excellent weather resistance and hot water resistance can be obtained.

In the above-mentioned alkoxysilyl group-containing polymerizable monomer, a hydrocarbon group containing a polymerizable unsaturated bond such as a vinyl group is contained in the silicon atom constituting the alkoxysilyl group at least separately from the alkoxyl group. Combining one. Since it has the unsaturated bond, the alkoxysilyl group-containing polymerizable monomer can also be subjected to addition polymerization, and in addition to the effect of the siloxane bond, the film-forming property, blocking resistance and resistance Remarkably improves temperature variability.

The above-mentioned alkoxysilyl group-containing polymerizable monomer is not particularly limited as long as it is a polymerizable monomer containing an alkoxysilyl group having 1 to 14 carbon atoms, and examples thereof include (meth)
Trimethoxysilylpropyl acrylate, triethoxysilylpropyl (meth) acrylate, tributoxysilylpropyl (meth) acrylate, dimethoxymethylsilylpropyl (meth) acrylate, methoxydimethylsilylpropyl (meth) acrylate, vinyltrimethoxy Examples thereof include silane, vinyltriethoxysilane, vinyldimethoxymethylsilane, vinylmethoxydimethylsilane, vinyltris (β-methoxyethoxy) silane and the like. These can be used alone or in combination of two or more. Among these, trimethoxysilylpropyl (meth) acrylate, triethoxysilylpropyl (meth) acrylate, vinyltrimethoxysilane, and vinyltriethoxysilane are particularly preferable.

The above-mentioned alkoxysilyl group-containing polymerizable monomer is preferably contained in a ratio of the lower limit of 0.1 parts by mass and the upper limit of 10 parts by mass in 100 parts by mass of all the monomers. If the amount of the alkoxysilyl group-containing polymerizable monomer in the dispersion particles is less than 0.1 parts by mass, crosslinking due to a siloxane bond or high molecular weight will be insufficient, and the weather resistance of the resulting coating film will decrease. In some cases, if it exceeds 10 parts by mass, stable production during polymerization may be difficult. The lower limit is preferably 0.5 parts by mass, more preferably 1 part by mass, and the upper limit is preferably 8 parts by mass, more preferably 7 parts by mass.

Polymerizable monomers other than the above cycloalkyl group-containing polymerizable monomer and alkoxysilyl group-containing polymer monomer are the lower limit of 10 parts by mass and the upper limit of 9 in the acrylic polymer.
It is preferably contained in a ratio of 4.8 parts by mass. When the amount of the other polymerizable monomer in the multilayer structured particles is less than 10 parts by mass, it becomes difficult to adjust the glass transition temperature of the acrylic polymer forming the core part or the shell part to the above range. However, if it exceeds 94.8 parts by mass, the content of the cycloalkyl group-containing polymerizable monomer decreases, and the object of the present invention may not be sufficiently achieved. The above lower limit is preferably 19 parts by mass,
It is more preferably 31 parts by mass, and the upper limit is preferably 89 parts by mass, more preferably 78 parts by mass.

The acrylic polymer further has 1 to 1 carbon atoms.
It may contain 14 alkoxysilane compounds. When the above-mentioned alkoxysilane compound is contained, the resulting coating film can be provided with excellent basic properties as a coating such as excellent weather resistance, water resistance, gloss retention, and adhesion to an inorganic base material. Membrane property, temperature change resistance,
Furthermore, blocking resistance, which is the subject of the present invention, can also be imparted. These characteristics are excellent even when the alkoxysilane compound is not contained, but even when the alkoxysilane compound is contained,
The same effect can be obtained.

The alkoxysilane compound has 1 carbon atom.
It is not particularly limited as long as it is an alkoxysilane compound having an alkoxysilyl group of 1 to 14, and the alkoxysilyl group having 1 to 14 carbon atoms may be linear or branched. Also, 1 to 4 of the above-mentioned alkoxysilyl groups may be bonded to the silicon atoms constituting the above-mentioned alkoxysilane compound. In the present invention, the alkoxysilane compound is
Unlike the above alkoxysilyl group-containing polymerizable monomer,
The compound does not have a polymerizable unsaturated bond such as a vinyl group.

The alkoxysilane compound is not particularly limited, and examples thereof include tetramethoxysilane, trimethoxymethylsilane, dimethoxydimethylsilane, methoxytrimethylsilane, tetraethoxysilane, triethoxyethylsilane, diethoxydiethylsilane, ethoxytriethylsilane. , Γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, and the like. These can be used alone or in combination of two or more. Of these, tetramethoxysilane, trimethoxymethylsilane, dimethoxydimethylsilane, methoxytrimethylsilane, γ
-Glycidoxypropyltrimethoxysilane is particularly preferred.

The above-mentioned alkoxysilane compound can be contained in the above acrylic polymer at a ratio of a lower limit of 0.1 parts by weight and an upper limit of 10 parts by weight. If the amount of the alkoxysilane compound in the multilayer structure particles is less than 0.1 parts by mass, crosslinking or high molecular weight based on a siloxane bond will be insufficient, and the weather resistance of the resulting coating film will be likely to decrease. If it exceeds the amount, stable production during polymerization becomes difficult. The lower limit is preferably 0.5 parts by mass, more preferably 1 part by mass, and the upper limit is preferably 8 parts by mass, more preferably 7 parts by mass. In the present invention, the acrylic polymer may contain components other than the respective monomers described above.

The acrylic polymer particles in the aqueous coating composition forming the first coating layer have a glass transition temperature of −
The acrylic polymer having a temperature of 70 to 35 ° C. is used as a core portion, the acrylic polymer having a glass transition temperature of 25 to 80 ° C. is used as a shell portion, and the glass transition temperature of the polymer of the core portion is the polymer of the shell portion. 20 ° C. or more lower than the glass transition temperature of, and the mass ratio of the core part to the shell part is 2/8.
It is preferably a multi-layer structure particle having a particle size of 8/2. It is preferable to use the above-mentioned acrylic polymer particles as the above-mentioned multi-layer structure particles because the blocking resistance of the coating film is improved.

The above-mentioned multilayer structure particles have a Tg of lower limit of -70.
It is preferable to use an acrylic polymer having a temperature of 35 ° C. and an upper limit of 35 ° C. as the core portion. If the Tg of the acrylic polymer constituting the core part is less than -70 ° C, the long-term stability of the acrylic polymer aqueous dispersion may decrease, and if it exceeds 35 ° C, the coating film obtained is The film property may be deteriorated, the hot water resistance may be deteriorated, and the blocking resistance may be decreased. The lower limit of Tg is preferably −40 ° C., more preferably −25 ° C. The upper limit of Tg is preferably 2
It is 0 ° C., and more preferably 10 ° C.

The above-mentioned multi-layered structure particles have a Tg of lower limit of 2
An acrylic polymer having a temperature of 5 ° C. and an upper limit of 80 ° C. is preferably used as the shell portion. If the Tg of the acrylic polymer constituting the shell portion is less than 25 ° C, the blocking resistance of the resulting coating film will decrease, and if it exceeds 80 ° C, the film-forming property of the resulting coating film will decrease and the hot water resistance will increase. Sex deteriorates. The lower limit of Tg is preferably 35 ° C, more preferably 45 ° C.
The upper limit of Tg is preferably 75 ° C, more preferably 70 ° C.

The Tg of the polymer of the core portion is preferably 20 ° C. or more lower than the Tg of the polymer of the shell portion. When the difference between the Tg of the polymer of the core portion and the Tg of the polymer of the shell portion is less than 20 ° C, the film-forming property is lowered and the blocking resistance is lowered. It is more preferably 40 ° C. or more, and even more preferably 60 ° C. or more. The Tg of each of the polymer of the core part and the polymer of the shell part is calculated in the same manner as the above-mentioned polymer.

The mass ratio of the core portion to the shell portion is
It is preferably 2/8 to 8/2. When the mass ratio of the core part and the shell part is less than 2/8, the film forming property of the obtained coating film is deteriorated and the hot water resistance is deteriorated, and when it exceeds 8/2, the obtained coating film is obtained. Blocking resistance of is reduced.
The above mass ratio is preferably 3/7 or more, more preferably 5
/ 5 or more, preferably 7/3 or less.

The average particle size of the acrylic polymer particles is
The lower limit is preferably 70 nm and the upper limit is 300 nm.
If the average particle size of the acrylic polymer particles is less than 70 nm, it becomes difficult to produce the particles, and if it exceeds 300 nm, the dispersibility of the multilayer structure particles in the acrylic polymer aqueous dispersion is deteriorated. The lower limit is more preferably 80 nm, further preferably 100 nm, and the upper limit is more preferably 250 nm, further preferably 100-.
It is 200 nm. Such an average particle size can be obtained by selecting the type and amount of the emulsifier within the range described below.

For the acrylic polymer aqueous dispersion used in the aqueous coating composition for forming the first coating layer of the present invention, a usual emulsion polymerization method such as batch polymerization, monomer dropping polymerization and emulsion monomer dropping polymerization is appropriately selected. Can be manufactured. In particular, the emulsion monomer dropping polymerization is suitable for ensuring stability during production.

The emulsion polymerization carried out when preparing the acrylic polymer aqueous dispersion can be carried out using an emulsifier. The emulsifier is not particularly limited, and a common emulsifier, for example, a non-reactive emulsifier having no polymerizable unsaturated bond such as vinyl group in the molecule, and / or a polymerizable group such as vinyl group in the molecule. Reactive emulsifiers with unsaturated bonds can be used. The non-reactive emulsifier is not particularly limited, and examples thereof include sodium dodecylbenzene sulfonate, sodium lauryl sulfate, ammonium lauryl sulfate, sodium diphenyl ether sulfonate, and polyoxyethylene alkyl ester. The reactive emulsifier is not particularly limited and includes, for example, Aqualon HS series such as Aqualon HS-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Aqualon RN series (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Eleminol JS-2 (Sanyo Kasei). (Manufactured by Kogyo Co., Ltd.) and the like. These are one type or two
A mixture of more than one type can be used.

The above-mentioned reactive emulsifier is a water-soluble monomer having a polymerizable unsaturated bond such as vinyl group in the molecule and a hydrophilic group, and a normal emulsifier only adsorbs on the surface of the produced particles. On the other hand, since it is incorporated into the produced particles as one component of the polymer in the polymerization process, it has a characteristic that the emulsifier is not released from the polymer by water after the film formation. Therefore, the stability of the aqueous coating composition using such a reactive emulsifier is improved. In the present invention, the above-mentioned reactive emulsifiers are particularly preferable in view of the stability of the obtained aqueous coating composition and the hot water resistance of the obtained coating film, and examples thereof include Aqualon HS-10 and the like.
Series (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) or Eleminor JS
2 (manufactured by Sanyo Kasei Co., Ltd.) can be preferably used, but ammonium lauryl sulfate, which is a non-reactive emulsifier, can also be preferably used.

The amount of the reactive emulsifier to be used is a lower limit of 0.5 part by mass and an upper limit of 100 parts by mass of the total amount of the polymerizable monomers used in the emulsion polymerization carried out when preparing the acrylic polymer aqueous dispersion. The proportion is preferably 5 parts by mass. If the amount of the reactive emulsifier used in the total amount of the polymerizable monomers is less than 0.5 parts by mass, the stability of the resulting acrylic polymer aqueous dispersion tends to deteriorate, and if it exceeds 5 parts by mass, The hot water resistance of the resulting coating film tends to decrease. The lower limit is more preferably 1 part by mass, more preferably 1.5 parts by mass, and the upper limit is more preferably 4.5 parts by mass, further preferably 4 parts by mass.

The emulsion polymerization carried out when preparing the acrylic polymer aqueous dispersion can be carried out using a polymerization initiator. The above-mentioned polymerization initiator is one that generates a radical by heat or a reducing substance to add-polymerize a monomer, and a water-soluble polymerization initiator or an oil-soluble polymerization initiator can be used.

The water-soluble polymerization initiator is not particularly limited, and examples thereof include persulfate-based initiators such as ammonium persulfate, sodium persulfate and potassium persulfate, and inorganic initiators such as hydrogen peroxide. Can be mentioned. These can be used alone or in combination of two or more.

The oil-soluble polymerization initiator is not particularly limited, and examples thereof include benzoyl peroxide, t-butyl peroxybenzoate, t-butyl hydroperoxide, t-butyl peroxy (2-ethylhexanoate), Organic peroxides such as t-butylperoxy-3,5,5-trimethylhexanoate and di-t-butylperoxide, 2,2′-azobisisobutyronitrile, 2,2′-azobis- Examples include azobis compounds such as 2,4-dimethylvaleronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), and 1,1′-azobis-cyclohexane-1-carbonitrile. it can. These can be used alone or in combination of two or more.

In the present invention, since the emulsion polymerization is mainly carried out in an aqueous medium, it is preferable to use the water-soluble polymerization initiator, for example, ammonium persulfate can be preferably used. The water-soluble polymerization initiator or the oil-soluble polymerization initiator, sodium sulfite, ferrous chloride, ascorbate, it is also possible to use in combination with a reducing agent such as Rongalit, thereby, to accelerate the emulsion polymerization rate or Also, it becomes easy to carry out emulsion polymerization at low temperature.

The emulsion polymerization carried out when preparing the above acrylic polymer aqueous dispersion can be carried out using an aqueous medium. The aqueous medium is not particularly limited, and for example, water or a mixed system of alcohol such as methanol, ethanol, 1-propanol, 2-propanol or 1-butanol and water can be used.

The emulsion polymerization carried out when preparing the above acrylic polymer aqueous dispersion is preferably carried out in an aqueous medium having a pH lower limit of 2 and an upper limit of 6. When the pH of the aqueous medium is less than 2, the acidity is too strong, which promotes corrosion inside the reaction vessel and is inconvenient in handling. When it exceeds 6, the hydrolysis reactivity of the alkoxysilyl group or the alkoxysilane group is poor. Since the crosslinking becomes insufficient, it is difficult to maintain the storage stability of the obtained acrylic polymer aqueous dispersion for a long period of time, and the hot water resistance of the obtained coating film deteriorates. The lower limit of the pH is more preferably 2.5, and the upper limit of the pH is more preferably 5.5, further preferably 5.

After the emulsion polymerization which is carried out when preparing the above acrylic polymer aqueous dispersion, it is preferable to adjust the resulting reaction solution within the range of the lower limit of pH 7 and the upper limit of pH 10.
As a result, the carboxyl groups contained in the resulting acrylic polymer aqueous dispersion are neutralized, the cross-linking structure becomes sufficient, and the dispersed particles do not aggregate even after long-term storage and have excellent stability. Since the body is obtained, an aqueous coating composition having excellent film forming properties can be obtained. The lower limit of the pH is more preferably adjusted to 8, more preferably 8.5, and the upper limit of the pH is more preferably adjusted to 10, more preferably 9.5. Such pH adjustment can be performed by adding a basic substance.

The basic substance is not particularly limited,
Examples thereof include ammonia, tributylamine, triethylamine, monoethanolamine, dimethylethanolamine, methylethanolamine, morpholine, N-methylmorpholine, amine compounds such as aminomethylpropanol, and alkali metal compounds such as sodium and potassium. . These can be used alone or in combination of two or more. Of these, amine compounds are preferred in the present invention from the viewpoint of hot water resistance.

When the polymer particles are multi-layer structure particles, the emulsion polymerization method used for preparing the acrylic polymer aqueous dispersion is not particularly limited.
In the presence of an aqueous medium, etc., a highly hydrophilic monomer containing methyl methacrylate as a main component is emulsion-polymerized to obtain Tg.
Of the acrylic polymer having a temperature of 25 to 80 ° C. is formed (first step), and then a monomer capable of forming a polymer having higher hydrophobicity than the polymer for the shell is dropped. Then, it is supplied into the shell part formed in the first step and emulsion-polymerized to form the core part made of an acrylic polymer having Tg of −70 to 35 ° C. (second step). Through the steps, the acrylic polymer aqueous dispersion can be obtained. Thus, by using a monomer having a higher hydrophobicity than the shell portion when forming the core portion, it becomes easier for the monomer to enter the inside of the previously formed shell portion. It is possible to obtain an ideal multi-layer structure particle that meets the purpose of the invention.

The emulsifier can be added to either the core or the shell, or both the core and the shell. Since the dispersibility of the obtained acrylic polymer aqueous dispersion is further improved, the emulsifier is preferably added to the shell portion.

The aqueous coating composition used for forming the first coating layer of the present invention preferably contains a pigment. The pigment is not particularly limited, for example, azo chelate pigments, insoluble azo pigments, condensed azo pigments,
Monoazo pigment, disazo pigment, diketopyrrolopyrrole pigment, benzimidazolone pigment, phthalocyanine pigment, indigo pigment, thioindigo pigment, perinone pigment, perylene pigment, dioxane pigment, quinacridone pigment, iso Organic coloring pigments such as indolinone pigments, naphthol pigments, pyrazolone pigments, anthraquinone pigments, anthorapyrimidine pigments, metal complex pigments; yellow lead, yellow iron oxide, chromium oxide, molybdate orange, red iron oxide, titanium Inorganic color pigments such as yellow, zinc white, carbon black, titanium dioxide, cobalt green, phthalocyanine green, ultramarine blue, cobalt blue, phthalocyanine blue and cobalt violet; mica pigments (titanium dioxide coated mica, colored mica, metal plated mica); Lafite pigments, alumina flake pigments, metallic titanium flakes, stainless flakes, plate-shaped iron oxide, phthalocyanine flakes, metal plated glass flakes, other colored flat pigments; titanium oxide, calcium carbonate, barium sulfate, barium carbonate, magnesium silicate, Examples include extender pigments such as clay, talc, silica and calcined kaolin. In the multilayer coating film of the present invention, it is preferable that the first coating film layer is formed as a base coating film containing the pigment and the second coating film layer is formed as a clear coating film.

The pigment contained in the aqueous coating composition for forming the first coating layer has a lower limit of 5 in pigment mass concentration (PWC) with respect to the solid content of the aqueous coating composition for forming the first coating layer. It is preferably within the range of mass% and the upper limit of 60 mass%. When the PWC is less than 5% by mass, the undercoating hiding property is poor, and when the PWC is more than 60% by mass, the weather resistance may deteriorate. The lower limit is more preferably 20% by mass and the upper limit is more preferably 45% by mass.

The aqueous coating composition used for forming the first coating layer of the present invention contains a polymerization degree adjusting agent, a particle size adjusting agent, a viscosity adjusting agent, a filler, a dispersant, an ultraviolet absorbing agent, if necessary. Agent,
Light stabilizer, antioxidant, antifreeze, algae control agent, antifoaming agent,
A film-forming aid, a thickener, a preservative, an antifungal agent, an antifoaming agent and the like can be included.

The aqueous coating composition used for forming the first coating layer of the present invention has a lower boiling point of 1 as the film-forming aid.
An organic solvent having a lower limit of 0.1 and an upper limit of 20 at 50 ° C. and an upper limit of 300 ° C. and a butyl acetate of 100 is used as a lower limit of 1 part by mass and an upper limit of 20 mass as 100 parts by mass of the polymer particles. It is preferable to contain a part. Thereby, the film-forming property at low temperature or in a short time can be improved. The lower limit of the boiling point of the organic solvent is more preferably 170 ° C., further preferably 200 ° C., and the upper limit of the boiling point is 270 ° C., further preferably 250 ° C.
The lower limit of the evaporation rate with butyl acetate as 100 is preferably 0.5, more preferably 1, and the upper limit of the evaporation rate with butyl acetate as 100 is preferably 17, and more preferably 15.

The organic solvent is not particularly limited as long as it has the above-mentioned properties, and for example, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monobutyl ether. Examples thereof include acetate, ethylene glycol dibutyl ether, and 2,2,4-trimethylpentane-1,3-diol monoisobutyrate. These can be used alone or in combination of two or more. Of these, ethylene glycol monoethyl ether is particularly preferable.

The aqueous coating composition used for forming the first coating layer of the present invention may contain a hindered amine light stabilizer as a light stabilizer from the viewpoint of weather resistance. The hindered amine light stabilizer is not particularly limited, and examples thereof include Sanol LS144 and Sanol LS29.
2, Sanor LS440, Sanor LS770 (above,
Sankyosha), tinuvin 123, tinuvin 144 (above,
Ciba Specialty Chemicals), ADEKA STAB L
A-57, ADEKA STAB LA-62, ADEKA STAB LA
-63P, ADEKA STAB LA-67, ADEKA STAB LA
-77, ADEKA STAB LA-501, ADEKA STAB LA
-503, ADEKA STAB LA-601 (all manufactured by Asahi Denka Co., Ltd.), Sanduvor 3051 Disp. (Made by Clariant Co., Ltd.) and the like. These can be used alone or in combination of two or more.

The above-mentioned hindered amine light stabilizer has a lower limit of 0.1 parts by mass with respect to 100 parts by mass of the above-mentioned multilayer structure particles,
It is preferable that the upper limit is 5 parts by mass. The lower limit is more preferably 0.5 parts by mass, further preferably 1 part by mass, and the upper limit is more preferably 4.5 parts by mass,
More preferably, it is 4 parts by mass. These can be appropriately selected according to the purpose of use.

The aqueous coating composition for the first coating layer of the present invention may contain an ultraviolet absorber from the viewpoint of weather resistance. The ultraviolet absorber is not particularly limited, and includes, for example, Sea Soap 103 (manufactured by Shiraishi Calcium Co., Ltd.), Tinuvin 900, Tinuvin 1130, Tinuvin 384, Tinuvin 327 (above, manufactured by Ciba Specialty Chemicals), ADK STAB LA-31, ADK STAB LA. -3
2, ADEKA STAB LA-36, ADEKA STAB 1413
(Above, manufactured by Asahi Denka Co., Ltd.), Sanduvor 3041
Disp. , Sanduvor PT21 Disp.
(These are Clariant products).
These can be used alone or in combination of two or more.

The ultraviolet absorber is preferably contained in a ratio of a lower limit of 0.1 parts by mass and an upper limit of 5 parts by mass with respect to 100 parts by mass of the acrylic polymer. The lower limit is more preferably 0.5 part by mass, further preferably 1 part by mass,
The upper limit is more preferably 4.5 parts by mass, further preferably 4 parts by mass. These can be appropriately selected according to the purpose of use.

The method for preparing the aqueous coating composition used for forming the first coating layer is not particularly limited, and it can be carried out by stirring each of the above-mentioned compounds with a stirrer or the like. Those having good dispersibility can be mixed with a stirrer or added to a vehicle composed of water, a surfactant, a dispersant or the like, which has been previously dispersed by a sand grind mill or the like.

The second coating layer used in the present invention is formed on the first coating layer, and the coating composition for forming the second coating layer is an emulsion type acrylic polymerizable resin. The main component is a dispersion.

The emulsion-type acrylic polymerizable dispersion used for the second coating layer is exemplified by the cyclohexyl ester which can be used for the emulsion-type acrylic polymerization dispersion used for the first coating layer. Alkyl group-containing polymerizable monomer, ethylenically unsaturated carboxylic acid monomer, ethylenically unsaturated carboxylic acid alkyl ester monomer, ethylenically unsaturated dicarboxylic acid monoester monomer, hydroxyl group-containing ethylenically unsaturated monomer Saturated carboxylic acid alkyl ester monomer, ethylenically unsaturated carboxylic acid aminoalkylamide monomer, amide group-containing ethylenically unsaturated carboxylic acid monomer, unsaturated fatty acid glycidyl ester monomer, vinyl cyanide monomer Body, saturated aliphatic carboxylic acid vinyl ester monomer, styrene-based monomer, alkoxysilyl group-containing polymerizable monomer, etc. It is possible to use. These can be used alone or in combination of two or more.

Of these, methyl methacrylate, 2-ethylhexyl acrylate, cyclohexyl methacrylate, acrylic acid, n-butyl acrylate and n-butyl methacrylate are preferred.

The method of polymerizing the acrylic polymerizable aqueous dispersion, which is the main component of the coating composition for forming the second coating layer of the present invention, from the above-mentioned monomer is a method of forming the above-mentioned first coating layer. The same method as that for the acrylic polymerizable aqueous dispersion can be used, and it can be used as an emulsifying agent, a polymerization initiator, and various additives in emulsion polymerization in the acrylic polymer forming the first coating layer. Anything can be used.

In the acrylic polymerizable aqueous dispersion which is the main component of the coating composition for forming the second coating layer of the present invention, 100 parts by mass of the solid content of the solid content of the dispersion (solid content conversion). ), It is necessary to contain the lower limit of 5 parts by mass and the upper limit of 60 parts by mass of the organic silicone unit. In the present invention, the organic silicone unit means a constituent portion of a polymer derived from an organic silicone raw material. When the content of the organic silicone unit is 5 parts by mass or less, the durability of the coating film is insufficient,
If the amount is 60 parts by mass or more, cracks and peeling easily occur over time. The lower limit of the content is more preferably 12 parts by mass, further preferably 13 parts by mass, and the upper limit of the content is more preferably 50 parts by mass, further preferably 40 parts by mass.

As a method of introducing the above-mentioned organosilicone unit, a method of carrying out emulsion polymerization of a mixture of an organosilicone compound and an acrylic polymerizable monomer to carry out hydrolysis, condensation reaction and radical polymerization, and a method of using a monomer having a silicone functional group Examples thereof include a method of polymerizing and a method of reacting an organic silicone compound with an acrylic polymer to bond the organic silicone compound to the surface of the acrylic polymer particles. A combination of two or more methods described above may be used.

The organosilicon compound used in the above method is not particularly limited, and examples thereof include organosilane and
Examples thereof include a hydrolyzate of organosilane and a condensate of organosilane.

The above-mentioned organosilane generally has the following general formula (1) (R ¹ ) _n Si (OR ² ) _4-n (1) (In the formula, when two R ¹ are present, they are the same or different,
A monovalent organic group having 1 to 8 carbon atoms is shown. R ² is the same or different and represents an alkyl group having 1 to 5 carbon atoms or an acyl group having 1 to 6 carbon atoms. Is an integer of 0 to 2. ).

The organosilane hydrolyzate is a compound in which the OR ² group of the organosilane represented by the general formula (1) is hydrolyzed. It is not necessary that all ² to 4 OR ² groups contained in the above-mentioned organosilane are hydrolyzed, and for example, only one is hydrolyzed, two or more are hydrolyzed, or these It may be a mixture of.

The above-mentioned organosilane condensate is condensed with the silanol groups of the hydrolyzate of organosilane to form Si--O.
-Si bond is formed. The above-mentioned organic silicone compound may be a compound in which all silanol groups are condensed, a compound in which a small amount of silanol groups is condensed, a mixture of compounds having different degrees of condensation, and the like.

In the general formula (1), R ¹ has 1 to ¹⁰ carbon atoms.
Examples of the monovalent organic group of 8 include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group,
i-butyl group, sec-butyl group, t-butyl group, n-
Alkyl groups such as hexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group; acyl groups such as acetyl group, propionyl group, butyryl group, valeryl group, benzoyl group, trioyl group, caproyl group; vinyl group, Allyl group, cyclohexyl group, phenyl group, epoxy group, glycidyl group, (meth) acryloxy group, ureido group,
In addition to an amide group, a fluoroacetamide group, an isocyanate group, and the like, a substituted derivative of these groups can be given.

The substituent in the substituted derivative of R ¹ is, for example, a halogen atom, a substituted or unsubstituted amino group, a hydroxyl group, a mercapto group, an isocyanate group, a glycidoxy group, a 3,4-epoxycyclohexyl group, (meth). Examples thereof include acryloxy group, ureido group, ammonium base and the like. However, the carbon number of R ¹ including these substituted derivatives is 8 or less including the carbon atoms in the substituent. When two R ¹ 's are present in the general formula (1), they may be the same or different.

Examples of the alkyl group having 1 to 5 carbon atoms for R ² include, for example, methyl group, ethyl group, n-propyl group,
i-propyl group, n-butyl group, sec-butyl group, t
-Butyl group, n-pentyl group and the like can be mentioned, and examples of the acyl group having 1 to 6 carbon atoms include an acetyl group,
Examples thereof include a propionyl group, a butyryl group, a valeryl group and a caproyl group. A plurality of R ^{2 s} in the general formula (1) may be the same or different from each other.

The above-mentioned organosilane is not particularly limited, and examples thereof include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane and tetra-i-.
Tetraalkoxysilanes such as propoxysilane and tetra-n-butoxysilane; methyltrimethoxysilane,
Methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, i-propyltrimethoxysilane, i-propyltriethoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, n-pentyltrimethoxysilane,
n-hexyltrimethoxysilane, n-heptyltrimethoxysilane, n-octyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane , 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane,
3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-hydroxyethyltrimethoxysilane, 2-hydroxyethyltriethoxysilane, 2-hydroxypropyltrimethoxysilane, 2-hydroxypropyltriethoxysilane, 3-
Hydroxypropyltrimethoxysilane, 3-hydroxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3- Glycidoxypropyltrimethoxysilane,
3-glycidoxypropyltriethoxysilane, 2-
(3,4-Epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltri Trialkoxysilanes such as ethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane; dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, di-n
-Propyldimethoxysilane, di-n-propyldiethoxysilane, di-i-propyldimethoxysilane, di-
i-propyldiethoxysilane, di-n-butyldimethoxysilane, di-n-butyldiethoxysilane, di-n
-Pentyldimethoxysilane, di-n-pentyldiethoxysilane, di-n-hexyldimethoxysilane, di-
n-hexyldiethoxysilane, di-n-heptyldimethoxysilane, di-n-heptyldiethoxysilane, di-n-octyldimethoxysilane, di-n-octyldiethoxysilane, di-n-cyclohexyldimethoxysilane, di In addition to dialkoxysilanes such as -n-cyclohexyldiethoxysilane, diphenyldimethoxysilane and diphenyldiethoxysilane, methyltriacetyloxysilane, dimethyldiacetyloxysilane and the like can be mentioned.

Of these, preferably used is
Trialkoxysilanes and dialkoxysilanes. Further, as the trialkoxysilanes, methyltrimethoxysilane and methyltriethoxysilane are preferable, and as the dialkoxysilanes, dimethyldimethoxysilane and dimethyldiethoxysilane. Is preferred.

The organosilicon compound is preferably at least one selected from the above organosilanes, hydrolysates of the above organosilanes, and condensates of the above organosilanes. That is, even if only one of these three organosilicon compounds is used,
It may be a mixture of two or more species. It is more preferable to use the organosilane and a condensate of the organosilane (hereinafter also referred to as “polyorganosiloxane”) in combination. The aqueous coating composition forming the second coating layer, by co-condensing the organosilane and the polyorganosiloxane, hardness, chemical resistance, weather resistance, film formability,
It is preferable from the viewpoint of forming a coating film having excellent properties such as transparency and crack resistance. Further, there is an advantage that the polymerization stability when the vinyl compound is polymerized after the emulsification is remarkably improved and the polymerization can be carried out with a high solid content, so that the industrialization is easy.

When the organosilane and the polyorganosiloxane are used in combination, dialkoxysilanes are preferably used as the organosilane. When a dialkoxysilane is used, a linear component is added as a molecular chain to increase the flexibility of the obtained particles.
Further, when a coating film is formed using the obtained aqueous dispersion, it is possible to obtain a coating film having excellent transparency. As the dialkoxysilanes, dimethyldimethoxysilane, dimethyldiethoxysilane and the like are particularly preferable.

When the organosilane and the polyorganosiloxane are used in combination, the polyorganosiloxane may be trialkoxysilane alone, or 40 to 95 mol% trialkoxysilane and 60 to 5 mol% dialkoxysilane. It is preferable that the condensate is a combination of By using the dialkoxysilane in combination with the trialkoxysilane, it is possible to soften the obtained coating film and improve the alkali resistance.

The above polyorganosiloxane is used as a condensate of organosilane by previously hydrolyzing and condensing the above organosilane. At this time, when the polyorganosiloxane is prepared, it is preferable that the organosilane is hydrolyzed and condensed by adding an appropriate amount of water to the organosilane and, if necessary, an organic solvent. Here, the amount of water used is 1 mol of organosilane,
The lower limit is preferably 1.2 mol and the upper limit is preferably 3.0 mol. The lower limit is more preferably 1.3 mol and the upper limit is more preferably 2.0 mol.

The polystyrene reduced weight average molecular weight of polyorganosiloxane (hereinafter referred to as "Mw") has a lower limit of 80.
It is preferably 0 and the upper limit is 100,000.
The lower limit is more preferably 1000 and the upper limit is more preferably 50,000.

As the polyorganosiloxane, a commercially available product can be used. The above-mentioned commercial products are not particularly limited, and include, for example, MKC silicate manufactured by Mitsubishi Chemical Corporation, ethyl silicate manufactured by Colcoat, silicone resin manufactured by Toray Dow Corning, Toshiba Silicone Co., Ltd.
Silicon resin manufactured by Shin-Etsu Chemical Co., Ltd., hydroxyl group-containing polydimethylsiloxane manufactured by Dow Corning Asia Co., Ltd., silicon oligomer manufactured by Nippon Unica Co., Ltd., and the like. These may be used as they are, or may be used after being condensed.

When an organosilane and a polyorganosiloxane are used in combination as the above-mentioned organosilicon compound, the mixing ratio of both is such that the above organosilane (calculated as a complete hydrolysis condensate) has an upper limit of 95% by mass and a lower limit of 5% by mass. It is preferably within the range. The upper limit is more preferably 90% by mass, and the lower limit is more preferably 10% by mass. The polyorganosiloxane (completely hydrolyzed condensate conversion) is preferably within a range of a lower limit of 5% by mass and an upper limit of 95% by mass. The lower limit is more preferably 10% by mass, and the upper limit is more preferably 90% by mass. In the above range, organosilane + polyorganosilane = 100 mass%.

When the content of the above polyorganosiloxane is less than 5% by mass, the surface of the obtained coating film may be sticky or the curability of the coating film may be deteriorated, which is not preferable. On the other hand, when it exceeds 95% by mass, the proportion of the organosilane component becomes too small, making it difficult to emulsify the mixture containing the above-mentioned organic silicone compound, and further lowering the polymerization stability of the polymerizable monomer after emulsification, and further emulsifying. The stability of the subsequent emulsion is lowered, or the film-forming property of the obtained organic-inorganic composite is lowered, which is not preferable. Here, the completely hydrolyzed condensate means that the R ² O-group of the organosilane is 10
It means that it is hydrolyzed to 0% to become a SiOH group and further completely condensed to have a siloxane structure.

It is preferable that the organic silicone compound is mixed with a polymerizable monomer during the polymerization of the acrylic polymer to obtain an acrylic polymer aqueous dispersion containing an organic silicone unit.

When the organosilicone unit is added to the polymer particles in the aqueous coating composition for forming the second coating layer by the above method, the total amount of the polymerizable monomer and the organosilicone compound used as raw materials is The ratio of the contained organic silicone compound is the content of the organic silicone unit. When a monomer having a silicone group is used in the polymerizable monomer, the content of the monomer having a silicone group is calculated as an organic silicone compound.

The second coating layer is preferably a clear coating layer. That is, it is preferable to make the surface of the coating film smooth by the above-mentioned second coating layer to give gloss and to obtain a multilayer coating film having a good appearance and durability.

The water-based coating composition for forming the second coating film layer contains, in addition to the above-mentioned polymer, a polymerization degree adjusting agent, if necessary.
Particle size adjusting agent, viscosity adjusting agent, filler, dispersant, ultraviolet absorber, light stabilizer, antioxidant, antifreezing agent, antialgae agent, defoaming agent, film forming aid, thickening agent, preservative , Antifungal agent, antifoam agent,
It may contain pigments, matting agents (gloss modifiers), colored aggregates, colored mica and the like.

The aqueous coating composition used for forming the second coating layer has a lower boiling point of 150 as the film-forming aid, which is similar to the coating composition for forming the first coating layer. ℃,
An organic solvent having an upper limit of 300 ° C. and an evaporation rate with butyl acetate of 100 as a lower limit of 0.1 and an upper limit of 20 has a lower limit of 1 part by mass and an upper limit of 20 with respect to 100 parts by mass of the polymer particles.
It is preferable to contain the compound by mass. The more preferable example of the above film-forming aid is the same as the case of the aqueous coating composition used for forming the above-mentioned first coating layer.

The aqueous coating composition used for forming the second coating layer is a hindered amine light stabilizer and ultraviolet light which can be used for the aqueous coating composition used for forming the first coating layer. Absorbents can be added individually. When the hindered amine light stabilizer and the ultraviolet absorber are blended, the hindered amine light stabilizer and the ultraviolet absorber that can be used, and the amount used are the aqueous solutions used for forming the first coating layer. It is similar to the coating composition.

The method for preparing the aqueous coating composition used for forming the second coating layer is not particularly limited, and it can be carried out by stirring each of the above-mentioned compounds with a stirrer or the like. Those having good dispersibility can be mixed with a stirrer or added to a vehicle composed of water, a surfactant, a dispersant or the like, which has been previously dispersed by a sand grind mill or the like.

In the present invention, the difference in solubility parameter between the respective acrylic resin components of the acrylic polymer forming the first coating layer and the acrylic polymer forming the second coating layer is 0.5 or less, Preferably, it is 0.3 or less.

The above-mentioned solubility parameter (SP value) is a measure of solubility and is measured as follows. (References SUH, CLARKE [JPSA]
-1,5,1671-1681 (1967)]) As a sample, 0.5 g of a resin is weighed in a 100 ml beaker, 10 ml of acetone is added using a whole pipette, and dissolved by a magnetic stirrer. For this sample, at a measurement temperature of 20 ° C., 50
The poor solvent is added dropwise using a ml buret, and the point at which turbidity occurs is the drop amount. As the poor solvent, ion-exchanged water is used as the high SP poor solvent, and n-hexane is used as the low SP poor solvent, and turbidity point measurement is performed. The SP value δ of the resin is given by the following calculation formula.

Δ = (V _ml ^1/2 δ _ml + V _mh ^1/2 δ _mh ) /
^{_{(V ml 1/2 + V mh 1/2}} ) V m = V 1 V 2 / (φ 1 V 2 + φ 2 V 1) δ m = φ 1 δ 1 + φ 2 δ 2 V i: solvent molecular volume (ml /
mol) φ _i : Volume fraction of each solvent at the cloud point δ _i : SP value of solvent ml: Low SP poor solvent mixed system mh: High SP poor solvent mixed system

Since the resins having similar solubility parameter values have high affinity and have a property of mutually dissolving, the multi-layer coating film of the present invention has high adhesion and peeling, cracking, A coating film having excellent durability can be obtained without causing problems such as the above. When a dispersion in which particles having a multi-layer structure are dispersed is used as the coating composition for forming the first coating layer of the present invention, the solubility parameter of such particles forms the resin forming the core layer and the shell layer. The solubility parameter of each resin to be measured is measured, and the arithmetic average of these is used as the solubility parameter of the acrylic resin. When the second coating layer of the present invention is acrylic polymer particles containing an organic silicone unit, the solubility parameter of the acrylic polymer excluding the organosilicon compound polymer is the solubility parameter of the acrylic resin.

The substrate on which the multilayer coating film of the present invention is formed is not particularly limited, and examples thereof include a metal substrate, a plastic substrate and an inorganic material substrate. The metal substrate is not particularly limited, for example, an aluminum plate,
Iron plate, galvanized steel plate, aluminum zinc plated steel plate,
A stainless steel plate, a tin plate, etc. can be mentioned. Examples of the plastic substrate include an acrylic plate, a polyvinyl chloride plate, a polycarbonate plate, an ABS plate, a polyethylene terephthalate plate, and a polyolefin plate. As the above-mentioned inorganic material base material, JIS A 542
2, ceramic base materials, glass base materials and the like described in JIS A5430 and the like can be mentioned. Among these, in the present invention, inorganic material base materials, particularly wall surfaces or roofs such as inner walls or outer walls of buildings such as houses and buildings, building materials for ceramics, concrete, ALC, and other inorganic building materials are preferable, and ceramics for ceramics Building materials are more preferred.

The above-mentioned base material may be subjected to a surface treatment in order to improve adhesion and impart rust prevention. The base material may be coated with an undercoat paint (sealer), or an undercoat paint and an intermediate paint, and the back surface of the base material may be coated with a back surface paint. These can be appropriately selected according to the purpose of use.

In order to form the multilayer coating film of the present invention, the first coating film layer is formed on the substrate, and then the second coating film is formed on the first coating film layer. Allow the layers to form. The method for applying the coating composition to form the multilayer coating film of the present invention is not particularly limited, and examples thereof include dipping, brushes, rollers, and
Roll coater, air spray, airless spray,
Curtain flow coater, roller curtain coater,
A commonly used coating method such as a die coater can be used. These can be appropriately selected depending on the use of the base material.

The multilayer coating film of the present invention usually has a dry film thickness of preferably 5 μm or less and 3 or less with respect to the above-mentioned substrate.
It can be coated to have a thickness of 50 μm. It is preferably 20 to 300 μm.

For the first coating layer and the second coating layer of the present invention, after coating each coating composition, a lower limit of 50 ° C.,
It can be formed by drying at a maximum drying temperature of 150 ° C. for about 1 to 30 minutes.

The multilayer coating film of the present invention is excellent in hydrolysis resistance and light discoloration resistance because the acrylic polymer used in the second coating layer has an organic silicone unit, and the first coating layer is Of the solubility parameter of the respective acrylic resin components of the acrylic polymer which is the main component of the water-based coating composition forming the film and the acrylic polymer which is the main component of the aqueous coating composition used for forming the second coating layer Is 0.5 or less, the adhesion between the first coating layer and the second coating layer is good, and the durability is excellent without causing problems such as cracks and peeling.

The exterior building material having the above-mentioned multi-layer coating film has excellent durability and weather resistance, and therefore has an excellent property of long life.

[0103]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(Production Method of Acrylic Polymer Aqueous Dispersion) Production Example 1 Production of Aqueous Dispersion A 50 parts by mass of deionized water and Aqualon HS10 (Daiichi Kogyo Seiyaku Co., Ltd.) 0.5 as a reactive emulsifier in a reaction vessel. The mass temperature was set to 85 ° C. Among them, 20 parts by mass of methyl methacrylate, 5 parts by mass of styrene, 5 parts by mass of n-butyl acrylate, 0.5 part by mass of acrylic acid, 20 parts by mass of deionized water and Aqualon HS10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 0 A pre-emulsion solution consisting of 0.5 parts by mass, an aqueous solution of a polymerization initiator consisting of 0.1 parts by mass of ammonium persulfate as a water-soluble polymerization initiator and 10 parts by mass of deionized water are added dropwise over 2 hours to produce a shell part. did. During the emulsion polymerization, the pH of the polymerization reaction liquid was kept at 3.0. Thereafter, 20 parts by mass of cyclohexyl methacrylate, 20 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of methyl methacrylate, 1.0 part by mass of acrylic acid, 3 parts by mass of trimethoxysilylpropyl methacrylate, 40 parts by mass of deionized water, and A pre-emulsion solution consisting of 1.0 part by mass of Aqualon HS10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and a polymerization initiator aqueous solution consisting of 0.2 part by mass of ammonium persulfate and 10 parts by mass of deionized water were added dropwise over 2 hours, and further. Stirring was continued for 3 hours to produce a core part. The reaction temperature was cooled to 30 ° C., 5.5 parts by mass of 10% aqueous ammonia was added to adjust the pH to 8.5, and an aqueous dispersion A having a nonvolatile content concentration of 45% was obtained. The solubility parameter of the acrylic resin in the water-soluble dispersion A (hereinafter referred to as Sp value) was 9.56.

Production Examples 2 and 3 Production of Aqueous Dispersions B to C Aqueous dispersions B and C were obtained in the same manner as in Production Example 1 using the raw material monomers shown in Table 1. The Sp value of the acrylic resin of the obtained water-soluble dispersion is shown in Table 1.

Production Example 4 Production of Aqueous Dispersion D 50 parts by mass of deionized water and 0.5 parts by mass of Aqualon HS10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a reactive emulsifier were put in a reaction vessel, and the content temperature was 85 ° C. And Among them, 30 parts by mass of cyclohexyl methacrylate, 10 parts by mass of n-butyl acrylate, 25 parts by mass of 2-ethylhexyl acrylate, 35 parts by mass of methyl methacrylate, 1.5 parts of acrylic acid.
Parts by weight, 1 part by weight of trimethoxypropyl methacrylate,
A pre-emulsion liquid consisting of 60 parts by mass of deionized water and 1.5 parts by mass of Aqualon HS10 (Daiichi Kogyo Seiyaku Co., Ltd.), and 0.3 parts by mass of ammonium persulfate as a water-soluble polymerization initiator,
Then, a polymerization initiator aqueous solution containing 20 parts by mass of deionized water was added dropwise over 4 hours. The stirring was continued for another 3 hours. During the emulsion polymerization, the pH of the polymerization reaction liquid was kept at 2.8. The reaction temperature was cooled to 30 ° C., 8.5 parts by mass of 10% aqueous ammonia was added to adjust the pH to 8.5, and an aqueous dispersion D having a nonvolatile content concentration of 45% was obtained. The Sp value of the acrylic resin of the water-soluble dispersion C was 9.53.

[0107]

[Table 1]

(Manufacture of Polymer Dispersion Containing Organosilicone Unit) Manufacture Example 5 Manufacture of Aqueous Dispersion a A homogeneous solution prepared by mixing the raw materials shown in Table 2 was ice-cooled and then sodium dodecylbenzenesulfonate was mixed as an emulsifier. In addition to the product hopper, while stirring with an agitator, driving air of 4 kgf / cm ² was applied to emulsify with a high pressure homogenizer [Microfluidizer M-110Y; manufactured by Mizuho Industry Co., Ltd.]. This emulsion was placed in a separable flask, and a predetermined amount of an initiator: potassium persulfate aqueous solution shown in Table 2 was added with stirring. After nitrogen replacement 6
It heated at 5 degreeC and superposed | polymerized for 4 hours. The polymerization results are shown in Table 2 together. The Sp value of the acrylic resin in the above aqueous dispersion was 9.51.

Production Examples 6 and 7 Production of Aqueous Dispersions b and c Aqueous dispersions b and c were obtained in the same manner as in Production Example 5 using the acrylic monomer in Table 2 and the organic silicone compound. . The Sp values of Dispersions b and c are shown in Table 2.

[0110]

[Table 2]

Example 1 (Production of First Aqueous Coating Composition for Coating Layer) 3 parts by mass of BKY190 (manufactured by Big Chem Co., Ltd.) as a pigment dispersant, and titanium oxide (trade name: titanium CR- as a pigment for a white coating). 9
5, manufactured by Ishihara Sangyo Co., Ltd.), and 200 parts by mass (in terms of solid content) of the acrylic polymer aqueous dispersion A obtained in Production Example 1 in a titanium white dispersion paste consisting of 90 parts by mass and 20 parts by mass of deionized water. 2 parts by mass of Sanol LS292 (manufactured by Sankyo Co., Ltd.) as a hindered amine-based light stabilizer, and Texanol (manufactured by Eastman Co.) as a film-forming aid.
6 parts by mass and 200 parts by mass of deionized water were added to obtain an aqueous coating composition.

(Production of Aqueous Coating Composition for Second Coating Layer)
To 250 parts by mass (solid content) of the organic silicone unit-containing polymer dispersion a obtained in Production Example 5, 10 parts by mass of Texanol (manufactured by Eastman) as a film forming aid and Tinuvin 384 as an ultraviolet absorber. 2 parts (manufactured by Ciba Specialty Chemicals), 2 parts by mass of SANOL LS292 (manufactured by Sankyo Co.) as a hindered amine light stabilizer.
100 parts by mass of deionized water was added to obtain a second aqueous coating composition for a coating layer.

(Method for forming coating film) ASE-60 (manufactured by Rohm & Haas Co.) as a thickening agent was added to the first aqueous coating composition for coating film layer obtained as described above so as to be 30 seconds in NK2 cup. Was added, and a flat plate (manufactured by Ube Board) coated with a sealer was spray-coated so as to have a dry film thickness of 40 μm, and dried at 100 ° C. for 5 minutes to form a first coating layer. Then, to the second aqueous coating composition for coating layer obtained above, ASE-60 was added as a thickener so as to be 25 seconds in NK2 cup, and a dry film thickness of 30 μm was added.
To obtain a coating film, and dried at 100 ° C. for 5 minutes to form a coating film.

Examples 2-8 and Comparative Examples 1, 2 The first coating composition and the second coating composition were prepared in the same manner as in Example 1, using each dispersion as described in Table 3. Was produced to form a multilayer coating film.

(Evaluation Method) Examples 1 to 8 and Comparative Examples 1 and 2
The following evaluations were performed for each of the coating films obtained in. The results are shown in Table 3. 1. Primary adhesiveness 4 mm After messing 25 mask loss, Cellotape (registered trademark) was attached and a peeling test was performed to visually evaluate the peeling degree. ○ No abnormality (25/25) △ 18/25 to 24/25 × 17/25 or less

2. The hot water-resistant coated plate was immersed in 40 ° C. hot water, and the appearance of the coating film after 20 days was visually evaluated. 〇 No abnormality. △ Gloss decreased. × Whitening and blistering occurred.

3. The boiling water resistant coated plate was immersed in boiling water at 90 ° C., and the appearance of the coating film after 2 hours was visually evaluated. 〇 No abnormality. △ Gloss decreased. × Whitening and blistering occurred.

4. Freeze-thaw resistant coated plate was frozen in air (-20 ° C) for 2 hours and thawed in water (10
(° C) 1 hour was set as one cycle, and a cycle test was carried out to evaluate the appearance of the coating film after 400 cycles. 〇 No abnormality. △ 15 times magnified with a magnifying glass. × There is a crack by visual observation.

5. The accelerated weathering coated plate was subjected to an accelerated test (4 hours irradiation, 4 hours wet) with a Dainippon Plastic die plastic metal weather, and the appearance of the coating film after the test time of 1600 hours was evaluated. ○ Gloss retention rate 80% or more and color difference less than 3 △ Gloss retention rate 50% or more and less than 80% Color difference 3 or more 6
Less than x Gloss retention less than 50% Color difference 6 or more

[0120]

[Table 3]

The coating film of the comparative sample is inferior in adhesion due to peeling, and insufficient results are obtained in the test results of hot water resistance, boiling water resistance, freeze-thaw resistance, and accelerated weathering resistance. On the other hand, the multilayer coating film of the present invention was excellent in all of these characteristics.

[0122]

Since the multilayer coating film of the present invention has the above-mentioned constitution, it is excellent in weather resistance and durability, and peeling or cracking between the first coating layer and the second coating layer occurs. Since it can withstand outdoor use and use throughout the summer and winter, there is no particular need for wall surfaces such as inner walls or outer walls of buildings such as houses and buildings, roofs, ceramic building materials, concrete, and other inorganic building materials. Excellent as a coating film used for top coating.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09D 183/04 C09D 183/04 (72) Inventor Masahiko Akahori 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Int Co., Ltd. (72) Inventor Harunori Goji 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Paint Co., Ltd. F-term (reference) 4D075 AE03 CA13 CA32 CA38 CB06 DA06 DB11 DC02 DC03 EA06 EA10 EA43 EB32 EB42 EB53 EB54 EB54 EB56 EC11 4J038 CC021 CC081 CF021 CG001 CG011 CG031 CG061 CG141 CG161 CG171 CH041 CH071 CH121 CH171 CH201 CJ131 CL001 DL032 GA15 KA06 KA08 MA03 MA08 MA10 MA13 NA01 NA03 NA04 PB05

Claims (7)

[Claims] 1. A first coating layer formed from an aqueous coating composition comprising (a) an acrylic polymer aqueous dispersion having a glass transition temperature of -20 to 70 ° C. as a main component, and (b) From an aqueous coating composition containing a silicone-containing acrylic polymer aqueous dispersion as a main component and containing 5 to 60 parts by mass of an organic silicone unit per 100 parts by mass of the solid content (in terms of solid content) in the solid content of the dispersion. And having a second coating layer formed on the first coating layer, and (a) an acrylic polymer which is the main component of the aqueous coating composition forming the first coating layer.
(b) A multi-layer coating film, wherein the difference in the solubility parameter of each acrylic resin component of the polymer forming the second coating film layer is 0.5 or less. 2. (a) An acrylic polymer having a glass transition temperature of -70 to 35 ° C. as a core portion and a glass transition temperature of 2
An acrylic polymer having a temperature of 5 to 80 ° C. is used as a shell part, and the glass transition temperature of the polymer of the core part is lower than the glass transition temperature of the polymer of the shell part by 20 ° C. or more, and the core part and the shell part are A first coating layer formed from an aqueous coating composition containing as a main component a polymer aqueous dispersion in which multi-layered particles having a mass ratio of 2/8 to 8/2 are dispersed.
And (b) a silicone-containing acrylic polymer aqueous dispersion as a main component, wherein the solid content in the solid content of the dispersion is 10
A second coating layer formed on the first coating layer, which is composed of an aqueous coating composition containing 5 to 60 parts by weight of an organic silicone unit per 0 parts by weight (in terms of solid content). ,
(a) Difference in solubility parameter between respective acrylic resin components of the acrylic polymer which is the main component of the aqueous coating composition which forms the first coating layer and (b) the polymer which forms the second coating layer Is 0.5 or less, a multilayer coating film. 3. The first coating layer comprises 5 to 70 parts by mass of a substituted or unsubstituted cycloalkyl group-containing polymerizable monomer,
The multilayer coating film according to claim 1 or 2, which is formed from an aqueous coating composition containing an acrylic polymer aqueous dispersion obtained from 30 to 95 parts by mass of another polymerizable monomer as a main component. 4. The first coating layer is an aqueous solution containing an alkoxysilyl group-containing polymerizable monomer having 1 to 14 carbon atoms in an amount of 0.1 to 10 parts by mass based on 100 parts by mass of all the monomers in the dispersion. The multilayer coating film according to claim 1, which is formed from a coating composition. 5. The multilayer coating film according to claim 1, 2, 3 or 4, wherein the first coating film layer is formed from an aqueous coating composition having a pigment. 6. (a) A first coating layer formed from an aqueous coating composition containing an acrylic polymer aqueous dispersion having a glass transition temperature of −20 to 70 ° C. as a main component, to be coated. First coating layer forming step of coating to, and (b) subsequent to the first coating layer forming step, the silicone-containing acrylic polymer aqueous dispersion as the main component, in the solid content of the dispersion 5 to 60 per 100 parts by mass of the solid content (solid content conversion)
A method for forming a multilayer coating film comprising a second coating film layer forming step of coating a water-based coating composition containing an organic silicone unit of parts by mass on an object to be coated, comprising: The acrylic polymer as the main component of the aqueous coating composition forming the coating layer of (b), and (b) the respective acrylic polymers of the acrylic polymer as the main component of the aqueous coating composition forming the second coating layer A method for forming a multilayer coating film, wherein the difference in solubility parameter between resin components is 0.5 or less. 7. An exterior building material having the multilayer coating film according to claim 1, 2, 3, 4 or 5.