JPH06116529A - Acrylic resin aqueous coating composition - Google Patents

Abstract

(57) [Summary] [Purpose] It can also be used for outdoor metal working parts of vehicles such as under floors of automobiles, tire houses, gasoline tanks, chassis, suspensions, etc., for example, forming a thick coating film of 600μ or more. Also provided is an acrylic resin aqueous coating composition having excellent chipping resistance that does not cause blisters or cracks in the coating during the drying step. A coating aqueous resin composition comprising an acrylic copolymer aqueous dispersion having a specific particle structure, an inorganic filler, and thermally expandable polymer beads and / or hollow polymer beads.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an acrylic resin aqueous coating composition such as a mastic paint, a soundproof paint, an antivibration paint, a caulking material and the like. Aqueous coating composition for acrylic resin, which is used as a coating material for protecting the metal working member from scratches caused by flying stones on outdoor metal working members such as gasoline tanks, chassis and suspensions, so-called "chipping",

Even when a thick coating film having a thickness of, for example, 600 μ or more is formed, no blisters or cracks are generated in the film during the drying process, and the formed film has a thickness of, for example, about 300 μ. Excellent chipping resistance even when the film is relatively thin, that is, chipping resistance at room temperature (hereinafter sometimes referred to as normal chipping resistance) and chipping resistance when the coating film is wet (hereinafter, Wet chipping resistance); impact resistance at room temperature and extremely low temperature such as -30 ° C (hereinafter sometimes referred to as low temperature impact resistance); excellent adhesion to metal working members; coating film Uniformity and smoothness; water resistance; gasoline resistance; soundproofing; and other properties as a chipping-resistant coating material in a well-balanced manner.
Regarding an acrylic resin aqueous coating composition having excellent properties,

More specifically, an acrylic resin containing an aqueous acrylic copolymer dispersion having a specific particle structure, an inorganic filler, heat-expandable polymer beads and / or hollow polymer beads. It relates to an aqueous coating composition.

[0004]

2. Description of the Related Art Conventionally, a rubber-based latex or acrylic emulsion is used as a vehicle and a powdered inorganic substance such as calcium carbonate or talc is used as a water-based chipping-resistant coating agent used for outdoor metal working members of vehicles such as automobiles. A mixture of agents is known. These coating agents are required to maintain the elasticity of the coating from the viewpoint of chipping resistance, so there is a natural limit to the amount of powder filler to be blended,
Further, it is required to have a much thicker film thickness than that of a general coating agent, and for example, it is applied by airless spray coating or the like so that a dry film has a thickness of about 200 to 800 μm.

Generally, in the case of an aqueous coating material, when an attempt is made to form a thick coating having a small content of an inorganic filler, water evaporates at one time during heating and drying, so that the coating is apt to blister, and thus these aqueous coatings are used. In a coating agent for chipping resistance, the balance between the chipping resistance and the anti-blister property of the coating film has been studied as a serious problem to be solved, for example, JP-A-59-75954 and JP-A-62- 230868
Several proposals described in Japanese Patent Laid-Open No. 63-10678 and Japanese Patent Laid-Open No. 63-172777 are known.

However, these proposals do not always sufficiently overcome the above-mentioned problems of the balance between chipping resistance and anti-blistering property of the coating,
Further, it has also been found that there are cases in which the adhesion of the coating film immediately after being wet with water to the metal-working member (hereinafter sometimes referred to as water-resistant adhesion) is reduced.

The inventors of the present invention, as described above, for example, 600
Even when forming a thick film such as μ or more, blistering does not occur in the drying process, and excellent chipping resistance is achieved even when the formed film is, for example, about 300 μ, which is relatively thin for this type of film. Property, in particular, it can exhibit excellent chipping resistance even at an extremely low temperature such as −30 ° C., and further, adhesion to the metal-working member of the base material,
Rust prevention, flat and uniform film formation, water resistant adhesion,
As a result of conducting research to obtain an aqueous coating composition having excellent properties such as gasoline resistance, cold bending resistance, impact resistance, and soundproofing,

For example, in the presence of an acrylic copolymer emulsion having a Tg of about 0 ° C. copolymerized with a carboxyl group, an acrylic monomer having a composition capable of forming a copolymer having a Tg of about -40 ° C. These Tg's can be obtained by emulsion copolymerization.
It is possible to prepare an aqueous dispersion of composite particles composed of two kinds of acrylic copolymers different in the above, and by using this aqueous dispersion as a vehicle, an excellent aqueous coating capable of solving the above-mentioned problems. It has been found that a composition is obtained.

[0009]

However, the aqueous coating composition described above has a problem that cracks may be generated in the coating due to shrinkage due to the compounding amount and shape of the inorganic filler or due to rapid drying. As a result of further studies, it was found that the aqueous coating composition further contained, for example, heat-expandable polymer beads or hollow polymer beads that expanded by heating at about 110 ° C. The inventors have found that it is possible to obtain an excellent aqueous coating composition capable of preventing the occurrence of cracks in the coating while maintaining the excellent properties of the coating composition, and completed the present invention.

[0010]

The present invention comprises an acrylic copolymer aqueous dispersion (A), an inorganic filler (B), heat-expandable polymer beads and / or hollow polymer beads (C). An acrylic resin aqueous coating composition comprising:
The dispersed particles of the acrylic copolymer aqueous dispersion (A) are at least two types of acrylic (co) polymers having different glass transition points.
It is a composite particle formed by polymerization, and the total monomer composition constituting the dispersed particle is the following (a) to (d) [however, the total of (a) to (d) is 100% by weight] ,

(A) The following general formula (1),

[0012]

[Chemical 5]

(In the formula, R ¹ represents a linear or branched alkyl group having 4 to 12 carbon atoms)

40% to 90% by weight of an acrylic acid ester represented by the following formula, wherein the homopolymer has a glass transition point of -30 ° C or lower,

(B) 0.5 to 10% by weight of α, β-unsaturated mono- or di-carboxylic acid having 3 to 5 carbon atoms, (c) the following general formula
(2),

[0016]

[Chemical 6]

(Wherein R ² is H or a methyl group,
X is an aryl group having 6 to 8 carbon atoms, a cyano group, the following general formula
(3) or (4),

[0018]

[Chemical 7]

[0019]

[Chemical 8] Wherein R ³ represents a straight chain or branched alkyl group having 1 to 20 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group or an aralkyl group, and R ⁴ represents H or a direct alkyl group having 1 to 12 carbon atoms. Indicates a chain or branched alkyl group)

A monomer represented by:
0 to 60% by weight of a monomer other than (a), and

(D) A monomer having at least one functional group in addition to one radically polymerizable unsaturated group in the molecule, which is a monomer other than the above-mentioned monomer (b). The purpose of the present invention is to provide an acrylic resin aqueous coating composition comprising 5% by weight.

The present invention will be described in detail below.

The dispersed particles of the acrylic copolymer aqueous dispersion (A) used in the present invention have at least 2 different Tg.
It is a composite particle composed of one kind of acrylic (co) polymerization, and the dispersed particle is composed mainly of an acrylic acid ester monomer (a) represented by the following general formula (1).

[0024]

[Chemical 9]

In the monomer (a) represented by the above general formula (1), R ¹ has 4 to 12 carbon atoms, preferably 4 to 10 carbon atoms,
Particularly preferably, it is represented by a linear or branched alkyl group having 6 to 9 carbon atoms, and the homopolymer has a glass transition point of -30.
An acrylic acid ester-based monomer having a temperature of not higher than 0 ° C. can be mentioned.

Examples of such a group R ¹ include n-butyl group, n-hexyl group, n-octyl group, i-octyl group, 2-ethylhexyl group, n-nonyl group, i-nonyl group, n Examples include -decyl group and n-dodecyl group.

Specific examples of such acrylic acid ester include n-butyl acrylate, n-hexyl acrylate, n-octyl acrylate, i-octyl acrylate, 2-ethylhexyl acrylate, n-nonyl acrylate and i-nonyl acrylate. Can be illustrated.

The amount of the above-mentioned monomer (a) acrylic acid ester-based monomer used is 40 to 90% by weight, preferably 45 to 90% by weight based on 100% by weight of the total of the monomers (a) to (d). It is 85% by weight, particularly preferably 50-80% by weight. If the amount of the monomer (a) used is less than the lower limit and is too small, the resulting copolymer becomes too hard and loses rubber elasticity to reduce the chipping resistance of the coating composition. Is not preferable, while
If the amount exceeds the upper limit and the amount is too large, the resulting copolymer becomes too soft and loses the toughness, and the chipping resistance of the coating composition is lowered, which is not preferable.

The dispersed particles of the aqueous dispersion (A) used in the present invention include the above-mentioned monomer (a) and the monomer (b) as an α, β-unsaturated mono- or di-carbon having 3 to 5 carbon atoms. -Contains carboxylic acid as a constituent monomer component.

Examples of such a monomer (b) include:
Examples thereof include acrylic acid, methacrylic acid, crotonic acid, citraconic acid, itaconic acid, maleic acid and fumaric acid. Of these, use of acrylic acid, methacrylic acid and / or itaconic acid is preferred from the viewpoints of ease of emulsion polymerization, generation of aggregates, and the like.

The amount of the monomer (b) used is generally 0.5 to 10% by weight, preferably 1 to 5% by weight, based on 100% by weight of the total amount of the monomers (a) to (d). . If the amount of the monomer (b) used exceeds the upper limit and is too large, the water resistance of the obtained coating composition may decrease, which is not preferable. On the other hand, if the amount used is too small, such as below the lower limit, the occurrence of aggregates during the aqueous emulsion polymerization, the destruction of the emulsified state, or the decrease in the storage stability of the resulting acrylic copolymer aqueous dispersion may occur. It is not preferable because the resulting water-based chipping-resistant coating composition may have insufficient adhesion to a substrate such as a sheet metal working member.

Further, the dispersed particles of the aqueous dispersion used in the present invention include the above-mentioned monomers (a) and (b), and if necessary, the following general formula (2),

[0033]

[Chemical 10]

The monomer (c) represented by can be contained as a constituent monomer component.

In the above-mentioned monomer (c), R ² is H or a methyl group, X is an aryl group having 6 to 8 carbon atoms, a cyano group, the following general formula (3) or (4): ,

[0036]

[Chemical 11]

[0037]

[Chemical 12]

A group represented by the following formula (provided that R ³ has 1 to 20 carbon atoms)
A linear or branched alkyl group, alkenyl group, cycloalkyl group, aryl group or aralkyl group of R
⁴ is H or a linear or branched alkyl group having 1 to 12 carbon atoms).

Examples of the monomer (c) include aromatic vinyl compounds in which X in the general formula (2) is an aryl group having 6 to 8 carbon atoms, such as styrene, α-methylstyrene and vinyltoluene. , Ethylvinylbenzene and the like; vinyl cyanide-based monomers in which X is a cyano group, such as acrylonitrile and methacrylonitrile.

As the monomer (c), X in the general formula (2) is the general formula (3), R ² is H and R ³ is a straight chain or a branched chain having 1 to 20 carbon atoms. A branched alkyl group,
Acrylate ester monomers other than the monomer (a) can be preferably used.

Specific examples of such acrylic acid ester monomers include, for example, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, i-butyl acrylate, t-butyl acrylate, tridecyl acrylate, Examples thereof include stearyl acrylate, oleyl acrylate, cyclohexyl acrylate, benzyl acrylate and the like.

Further, as the monomer (c), the above-mentioned general formula (2)
X in the general formula (3), R ² is a methyl group, and R ³ is a linear or branched alkyl group having 1 to 20 carbon atoms,
A methacrylic acid ester monomer which is an alkenyl group, a cycloalkyl group, an aryl group or an aralkyl group can be preferably used.

Specific examples of such a methacrylic acid ester monomer include, for example, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, n-octyl methacrylate. , 2-ethylhexyl methacrylate, i-decyl methacrylate, lauryl methacrylate, tridecyl methacrylate, cetyl methacrylate, stearyl methacrylate, oleyl methacrylate, cyclohexyl methacrylate,
Examples thereof include benzyl methacrylate, and the use of methyl methacrylate is preferable.

Further, as the monomer (c), a saturated group in which X in the general formula (2) is the general formula (4), R ² is H and R ⁴ has 1 to 12 carbon atoms. Examples thereof include fatty acid vinyl monomers such as vinyl formate, vinyl acetate, vinyl propionate and vinyl versatate.

The amount of the monomer (c) used is 0 to 60% by weight, preferably 15 to 55% by weight, based on 100% by weight of the total of the monomers (a) to (d). And particularly preferably 20 to 50% by weight. If the amount of the monomer (c) used is at least the lower limit value, the copolymer obtained will have appropriate toughness along with flexibility, and if at most the upper limit value, it will be obtained. Since the copolymer does not become too hard and has a suitable rubber elasticity, in any case, the coating composition is excellent in chipping resistance, which is preferable.

Further, the aqueous dispersion (A) used in the present invention
The dispersed particles of are at least 1 in addition to the monomer (a) to (c) and, if necessary, the monomer (d), that is, one radically polymerizable unsaturated group in the molecule. A monomer having one functional group and other than the monomer (b) can be contained as a constituent monomer component.

Examples of such a monomer include amides of (meth) acrylic acid such as acrylamide, methacrylamide, diacetone acrylamide, N-methylol acrylamide, N-methylol methacrylamide or derivatives thereof; for example, glycidyl. Esters of (meth) acrylic acid such as acrylate and glycidyl methacrylate with a saturated alcohol having an epoxy group;

For example, esters of (meth) acrylic acid such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate and the like and polyvalent saturated alcohols; for example, dimethylaminoethyl (Meth) such as methacrylate and diethylaminoethyl methacrylate
Esters of acrylic acid and a saturated alcohol having an amino group;

For example, two or more of divinylbenzene, diallyl phthalate, triallyl cyanurate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol dimethacrylate, allyl methacrylate and the like. A monomer having a radically polymerizable unsaturated group;
And the like.

The amount of these monomers (d) used is from the monomers (a) to
The total amount of (d) is preferably 0 to 5% by weight based on 100% by weight. If the amount used is 5% by weight or less, problems such as the generation of aggregates during the aqueous emulsion polymerization and the destruction of the emulsion state, or the deterioration of the storage stability of the resulting acrylic copolymer aqueous dispersion may occur. It is preferable because it does not occur, and the resulting coating composition has excellent chipping resistance.

The dispersed particles of the acrylic copolymer aqueous dispersion (A) used in the present invention have at least 2 different Tg.
It is a composite particle consisting of one type of acrylic (co) polymerization.

The term "composite particles" as used in the present invention means particles in which the same dispersed particles are composed of at least two kinds of (co) polymers. In this case, these (co) polymers may be mixed with each other, or may be in a state of being block-bonded or grafted or cross-linked to such an extent that rubber elasticity is not lost.

The morphology of the dispersed composite particles is not necessarily limited, and may be spherical particles in which at least two (co) polymers are mixed, and, for example, a core and a shell may be used. It may be a "replacement ball-shaped" multi-layered particle having "gourd-shaped" particles in which spheres composed of two different (co) polymers are joined, or one (co) polymer Consisting of spheres or two or more
It may be a "replacement-shaped" multi-layered particle composed of a (co) polymer and a plurality of hump-shaped particles composed of at least another (co) polymer attached to the multi-layered particle. Among these various particle forms, “replacement ball-shaped” multi-layer particles are preferable from the viewpoint of various physical properties of the obtained coating composition.

Generally, when the photorefractive indexes of two or more (co) polymers, which are the constituents of the composite particles, are greatly different from each other, they have the same composition as each of the two or more (co) polymers. The film obtained by blending the emulsion (co) polymer emulsion becomes opaque, but the film of the aqueous dispersion containing the dispersion complex particles of the acrylic copolymer used in the present invention has a characteristic that it is almost transparent. is doing.

Such an acrylic copolymer aqueous dispersion
The method for producing (A) is not particularly limited, but for example, first, in the presence of a surfactant and / or a protective colloid, the monomers (a) and (b), and if necessary, Emulsion polymerization of the monomers (c) and (d) in an aqueous medium to prepare an acrylic copolymer emulsion (first stage polymerization), and then the monomer (a) is added in the presence of the emulsion. A method of adding a monomer as an essential component and further (co) polymerizing (second-stage polymerization) can be suitably adopted.

The composition of the monomer component (hereinafter sometimes abbreviated as M ₁ component) used in the first-stage polymerization for preparing the acrylic copolymer emulsion is the above-mentioned monomer.
(a) to (d) are appropriately combined and selected so that the resulting copolymer has a Tg (hereinafter sometimes abbreviated as Tg ₁ ) of -30 to + 10 ° C, preferably -20 to 5 ° C. Preferably.
If the Tg ₁ is less than or equal to the upper limit, the copolymer obtained will not be too hard, and will retain suitable rubber elasticity. If the Tg ₁ is at least the lower limit, the copolymer will be adequate. Since it has flexibility and retains toughness, it is preferable in any case since it exhibits excellent chipping resistance when used as a coating composition.

The amount of the M ₁ component is generally 50 to 95% by weight with respect to 100% by weight of all the monomers constituting the dispersion composite particles of the acrylic copolymer aqueous dispersion (A). %, Preferably 60 to 90% by weight. When the amount of M ₁ is at least the lower limit value, problems such as generation of aggregates and destruction of the emulsified state during the second stage polymerization, or deterioration of storage stability of the resulting aqueous dispersion are less likely to occur, and Since the coating film of the obtained coating composition retains appropriate flexibility and toughness, it is preferable because the chipping resistance at room temperature does not deteriorate. On the other hand, if it is at most the upper limit value, the coating film of the obtained coating composition will not become too hard, and the chipping resistance at extremely low temperature such as -30 ° C will be excellent, which is preferable.

The M ₁ component is the monomer component as described above.
(b) is preferably included, and the amount thereof is 30% by weight or more, preferably 50% by weight or more based on the total amount of the monomer component (b) contained in the dispersion composite particles. Is good. M ₁
If the amount of the monomer component (b) in the component is at least the lower limit value, generation of aggregates or destruction of the emulsified state during the second stage polymerization, or storage of the resulting aqueous dispersion (A) This is preferable because problems such as a decrease in stability hardly occur.

As the surfactant used in the first-stage polymerization in the present invention, nonionic surfactants such as polyoxyalkylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; , Polyoxyethylene octylphenol ether, polyoxyethylene nonylphenol ether and other polyoxyalkylene alkylphenol ethers;

For example, sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate and other sorbitan fatty acid esters; for example, polyoxyethylene sorbitan monolaurate and other polyoxyalkylene sorbitan fatty acid esters; for example, polyoxyethylene monolaurate. Polyoxyalkylene fatty acid esters such as laurate and polyoxyethylene monostearate;

Examples thereof include glycerin fatty acid esters such as oleic acid monoglyceride and stearic acid monoglyceride; polyoxyethylene / polypropylene / block copolymers;

Examples of the anionic surfactants include fatty acid salts such as sodium stearate, sodium oleate and sodium laurate; alkylaryl sulfonates such as sodium dodecylbenzenesulfonate; sodium lauryl sulfate and the like. Alkyl sulfate ester salts of

For example, alkyl sulfosuccinate ester salts such as sodium monooctyl sulfosuccinate, sodium dioctyl sulfosuccinate, sodium polyoxyethylene lauryl sulfosuccinate and derivatives thereof; for example, polyoxyalkylene alkyl such as sodium polyoxyethylene lauryl ether sulfate. Ether sulfate salts;

For example, polyoxyalkylene alkylaryl ether sulfate ester salts such as sodium polyoxyethylene nonylphenol ether sulfate;

Examples of the cationic surfactants include alkylamine salts such as laurylamine acetate; quaternary ammonium salts such as lauryltrimethylammonium chloride and alkylbenzyldimethylammonium chloride; and polyoxyethylalkylamine. Etc.

Examples of the amphoteric surfactants include alkyl betaines such as lauryl betaine.

It is also possible to use those obtained by substituting part of the hydrogen atoms of the alkyl group of these surfactants with fluorine.

Further, a so-called reactive surfactant having a radical copolymerizable unsaturated bond in the molecular structure of these surfactants can also be used.

Among these surfactants, the nonionic surfactants include polyoxyalkylene alkyl ethers and polyoxyalkylene alkyl phenol ethers, from the viewpoint of generation of aggregates during emulsion polymerization and the like.

Examples of the anionic surfactants include alkylaryl sulfonates; alkyl sulfates; alkyl sulfosuccinic acid ester salts and derivatives thereof; polyoxyalkylene alkyl ether sulfuric acid ester salts; polyoxyalkylene alkylphenol ether sulfuric acid ester salts; And the like are preferred.

These surfactants can be used alone or in appropriate combination.

The amount of these surfactants used is usually about 0.3 to 10 parts by weight based on 100% by weight of all the monomer components constituting the dispersed particles of the acrylic copolymer dispersion (A). Used as a water-based coating composition for chipping resistance of the present invention, good polymerization stability of aqueous emulsion polymerization, easy formation of dispersion composite particles, good storage stability of copolymer aqueous dispersion At this time, from the viewpoint of excellent adhesion to a substrate such as a sheet metal working member, about 0.5 to 5 parts by weight, particularly about 1 to
It is preferable to use 3 parts by weight.

Examples of protective colloids usable in the acrylic (co) polymer emulsion used in the present invention include, for example, polyvinyl alcohols such as partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol and modified polyvinyl alcohol;

Examples thereof include cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose and carboxymethyl cellulose salt; and natural polysaccharides such as guar gum.

The amount of these protective colloids used is, for example, about 0 to 3 parts by weight based on 100% by weight of all the monomer components constituting the dispersed particles of the acrylic copolymer dispersion (A). Can be illustrated.

In the first-stage polymerization and the second-stage polymerization described below (hereinafter sometimes simply referred to as emulsion polymerization) in the present invention, examples of the polymerization initiator include ammonium persulfate, potassium persulfate, and persulfate. Persulfates such as sodium; t-butyl hydroperoxide,
Organic peroxides such as cumene hydroperoxide and p-menthane hydroperoxide; hydrogen peroxide; and the like can be used alone or in combination of two or more.

The amount of the polymerization initiator used can be appropriately selected, but is, for example, about 0.05 to 1 part by weight, more preferably about 0.1 to 0.7 part by weight, particularly preferably about 0.1 to 0.7 part by weight, based on 100 parts by weight of the M ₁ component used in total. The amount used is preferably about 0.1 to 0.5 part by weight.

In addition, a reducing agent may be used in combination during emulsion polymerization, if desired. Examples of the reducing agent include reducing organic compounds such as ascorbic acid, tartaric acid, citric acid, glucose; and reducing inorganic compounds such as sodium thiosulfate, sodium sulfite, sodium bisulfite, and sodium metabisulfite. .

The amount of the reducing agent to be used can be appropriately selected. For example, it is about 100 parts by weight of the M ₁ component used in total.
The amount used may be exemplified as 0.05 to 1 part by weight.

Furthermore, a chain transfer agent can be optionally used in the emulsion polymerization. Examples of such a chain transfer agent include cyanoacetic acid; cyanoacetic acid having 1 to 8 carbon atoms; bromoacetic acid; bromoacetic acid having 1 to 8 carbon atoms; for example, anthracene, phenanthrene, fluorene, 9 -Aromatic compounds such as phenylfluorene;

Aromatic nitro compounds such as p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, p-nitrotoluene; for example, benzoquinone, 2,3,5,6-tetra Methyl-p-
Benzoquinone derivatives such as benzoquinone; Borane derivatives such as tributylborane;

For example, carbon tetrabromide, carbon tetrachloride, 1,1,2,
Halogenated hydrocarbons such as 2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, 3-chloro-1-propene;

For example, aldehydes such as chloral and furaldehyde; alkyl mercaptans having 1 to 18 carbon atoms;
For example, aromatic mercaptans such as thiophenol and toluene mercaptan; mercaptoacetic acid; C1-10 alkyl esters of mercaptoacetic acid; C1-12 hydroxyalkyl mercaptans; for example, terpenes such as binene and terpinolene. And the like.

When the above chain transfer agent is used, the amount thereof is about 0.005 to 100 parts by weight based on 100 parts by weight of the M ₁ component.
It is preferably 3.0 parts by weight.

As a preferred embodiment of the first stage polymerization,
In an aqueous medium containing or not containing a surfactant and / or protective colloid, the M ₁ component,
Surfactant and / or protective colloid, polymerization initiator,
Moreover, the aspect which adds the reducing agent used sequentially as needed can be illustrated.

The polymerization temperature in the first stage polymerization is generally in the range of about 30 to 100 ° C, preferably about 40 to 90 ° C.

The acrylic copolymer aqueous dispersion (A) used in the present invention contains the above monomer (a) in the presence of the acrylic copolymer emulsion obtained by the first-stage polymerization. It can be suitably produced by adding a monomer as an essential component (hereinafter sometimes abbreviated as M ₂ component) and carrying out the second stage polymerization.

The composition of the above-mentioned M ₂ component is such that the Tg of the (co) polymer obtained by (co) polymerizing only the M ₂ component (hereinafter referred to as "copolymer") by appropriately combining the monomers (a) to (d) , Tg ₂ ) may be 0 ° C. or lower, preferably −10 ° C. or lower, particularly preferably −20 to −100 ° C. When the Tg ₂ is not more than the upper limit value, the obtained copolymer does not become too hard and retains a suitable rubber elasticity,
Further, when the content is at least the lower limit value, the obtained copolymer has appropriate flexibility and also retains toughness, so that in any case, when a coating composition is obtained, excellent chipping resistance is exhibited. preferable.

In order to sufficiently bring out the desired effect, Tg ₁ is preferably higher than Tg ₂ , Tg ₁ is more preferably higher than Tg ₂ by 10 ° C. or higher, and higher than ₁₅ to 100 ° C. Is particularly preferable.

Among the compositions of the M ₂ component, preferred is a linear or branched alkyl ester of acrylic acid having 6 to 9 carbon atoms such as 2-ethylhexyl acrylate among the monomers (a). As a component, if necessary, linear or branched alkyl, alkenyl, cycloalkyl having 4 to 20 carbon atoms of (meth) acrylic acid such as styrene, vinyl versatate or butyl methacrylate among the monomers (c), A hydrophobic monomer such as an aryl or aralkyl ester monomer, and an α, β-unsaturated mono- or di-carboxylic acid having 3 to 5 carbon atoms such as acrylic acid which is the monomer (b). Combinations can be mentioned.

The amount of the monomer component (b) that can be contained in the M ₂ component is 70% by weight or less based on the total amount of the monomer component (b) contained in the dispersion composite particles. It is preferably 50% by weight or less.

The amount of the M ₂ component is generally 5 to 50% by weight based on 100% by weight of all the monomers constituting the dispersion composite particles of the acrylic copolymer aqueous dispersion (A). %, Preferably 10-40% by weight. When the amount of M ₂ is at least the lower limit value, the coating film of the obtained coating composition does not become too hard, and the chipping resistance at an extremely low temperature such as −30 ° C. is excellent, which is preferable. On the other hand, if it is at most the upper limit, problems such as generation of aggregates and destruction of the emulsified state during the second-stage polymerization, or deterioration of storage stability of the resulting aqueous dispersion are less likely to occur, and
Since the coating film of the obtained coating composition retains appropriate flexibility and toughness, it is preferable because the chipping resistance at room temperature does not decrease.

As a preferred embodiment of the second stage polymerization,
An example is a mode in which the M ₂ component, the polymerization initiator and, if necessary, a reducing agent are sequentially added to the acrylic copolymer emulsion obtained by the first-stage polymerization.

The polymerization temperature in the second stage polymerization is generally in the range of about 30 to 100 ° C, preferably about 40 to 90 ° C.

The thus obtained acrylic copolymer aqueous dispersion (A) used in the present invention is not particularly limited, but generally the solid content is about 10 to 70% by weight and the pH is 2-1.
0, viscosity 10000cps or less (B type rotational viscometer, 25 ℃, 20rp
m), the average particle size of the dispersed particles is 0.05 to 0.5μ, and the solid content is about 30 to 65% by weight (particularly about 40 to 60% by weight), the pH is 2 to 8, and the viscosity because of the ease of production and good productivity. About 50-5000cp
s, preferably 0.1 to 0.4 μ.

Ammonia water, water-soluble amines, an aqueous solution of alkali hydroxide, or the like can be used as the pH regulator.

In the present invention, the Tg of the acrylic (co) polymer is the differential scanning calorimeter.
lorimeter). The average particle size of the dispersed particles of the acrylic copolymer aqueous dispersion (A) and the turbidity of the copolymer film are measured according to the following methods.

Average particle size: The aqueous copolymer dispersion was diluted to 50,000 to 15 times with distilled water, thoroughly mixed with stirring, and
About 10 ml using a Pasteur pipette in a mmφ glass cell
It is sampled, set in a predetermined position of a dynamic light scattering photometer "DLS-700" (manufactured by Otsuka Electronics Co., Ltd.), and measured under the following conditions.

Measurement temperature 25 ±
1 ℃ Clock Late (Clock Late) 10μ
sec Correlation channel (Corel. Channel) 512 Total number of measurements 200 times Light scattering angle 90 ° Calculate the average particle size by computer processing the above measurement results.

Copolymer film turbidity test: Aqueous acrylic copolymer dispersion was applied to a washed glass plate using a 20 mil doctor blade and kept in a constant temperature and humidity chamber at 20 ° C. and 65% RH. After leaving it for 16 hours to dry, it is further dried at 120 ° C. for 20 minutes to form an acrylic copolymer film. This film is manufactured by Tokyo Denshoku Co., Ltd.
Turbidity is measured by TC-HIIIDP ".

The acrylic resin aqueous coating composition of the present invention comprises an acrylic copolymer aqueous dispersion (A) consisting of dispersed composite particles of a specific composition as described above, an inorganic filler (B) and a thermal expansion property. Polymer beads and / or hollow polymer beads
And (C).

Inorganic filler preferably usable in the present invention
(B) is, for example, calcium carbonate, silica, alumina,
Examples include kaolin, clay, talc, diatomaceous earth, mica, aluminum hydroxide, glass powder, barium sulfate, magnesium carbonate and the like.

The amount of the inorganic filler (B) used is
With respect to 100 parts by weight of the composite particles, for example, 100 to 390 parts by weight, preferably 120 to 380 parts by weight, particularly preferably 150.
An amount of about 300 parts by weight can be exemplified. When the amount used is at least the lower limit value, blisters are less likely to occur during coating film formation by heating and drying the aqueous coating composition, and the resulting coating film has excellent chipping resistance, which is preferable. This is preferable because the finished appearance of the coating film, the adhesion to a substrate such as a sheet metal working member, and the chipping resistance are excellent.

The average particle size of the inorganic filler (B) is preferably about 1 to 50 μm, particularly preferably about 5 to 30 μm. If the average particle size is equal to or more than the lower limit value, the workability at the time of preparation of the aqueous coating composition is excellent, and thus it is preferable. If the average particle size is equal to or less than the upper limit value, the smoothness of the coating film of the aqueous coating composition,
It is preferable because it is excellent in chipping resistance and water resistance.

The heat-expandable polymer beads that can be used in the acrylic resin aqueous coating composition of the present invention are polymer beads having a thermoplastic resin as a shell wall in a heat-vaporizable foaming agent or a heat-decomposable type. It contains a foaming agent.

The above-mentioned thermoplastic resin is not particularly limited as long as it softens at the heating temperature for forming a film using the obtained coating composition, but is, for example, 60 to 130 ° C. In particular, it is preferable to use a resin that softens at about 70 to 120 ° C., for example, polyolefin, polyacrylonitrile, polyacrylate, polystyrene,
Examples thereof include vinyl resins such as polyvinyl chloride, polyvinylidene chloride and copolymers thereof; polyester resins; silicone resins; thermoplastic urethane resins; and other thermoplastic resins.

Examples of the heating vaporizing type foaming agent include boiling point-
It is possible to use organic solvents such as hydrocarbons, halogenated hydrocarbons, esters, ethers, and ketones, which have a low boiling point of about 50 to + 50 ° C.

Examples of the heat decomposition type foaming agent include, for example,
Nitroso compounds such as N, N'-dinitrosopentamethylenetetramine and N, N'-dimethyl-N, N'-dinitrosoterephthalamide; for example, azo compounds such as azodicarbonamide;
For example, sulfonyl hydrazide compounds such as benzenesulfonyl hydrazide, p, p'-oxybis (benzenesulfonylamide), benzene-1,3-disulfonyl hydrazide, toluenesulfonyl hydrazide and their derivatives; p-toluenesulfonyl semicarbazide; trihydrazinotriazine , Etc. can be mentioned.

These heat-expandable polymer beads have a heat-expansion temperature of, for example, 60 to 180 ° C., particularly 7 to 180 ° C.
It is about 0 to 160 ° C., and various stability before and after thermal expansion, excellent in safety, and easily available are good, and a vinyl resin such as acrylonitrile-vinylidene chloride copolymer is used as a shell wall. It is particularly preferable that a hydrocarbon-based organic solvent such as isobutane is included as a heating vaporization type foaming agent.

Further, the heat-expandable polymer beads have an average particle diameter before thermal expansion of 1 to 50 µ, particularly about 3 to 40 µ, and an average particle diameter after thermal expansion of 5 to 300 µm.
It is preferably μ, and particularly preferably about 20 to 200 μ.

Examples of such heat-expandable polymer beads that can be preferably used in the present invention include Matsumoto Microspheres F-30 and F-50 [above, Matsumoto Yushi-Seiyaku Co., Ltd.], EXPAN. Cell WU ^# 642, WU ^# 551, WU ^# 46
1, DU ^# 551, DU ^# 461, DU ^# 051 (above, Japan Philite
Manufactured by K.K., etc. can be mentioned.

Some of these heat-expandable polymer beads are commercially available in the form of so-called "wet cake" containing water for the reason of easy handling, and the above-mentioned "Matsumoto Microsphere F". -30, F-50 "and" Expansell WU ^# 642, WU ^# 551, WU ^# 461 "are this type.

The hollow polymer beads which can be used in the present invention include, for example, polyolefin, polyacrylonitrile, polyacrylate, polystyrene, polyvinyl chloride, polyvinylidene chloride and the same as those in the heat-expandable polymer beads. Examples thereof include those having a shell wall made of a thermoplastic resin such as a copolymer, a polyester resin, a silicone resin, a thermoplastic urethane resin, and the like. For example, the thermally expandable polymer beads are preliminarily thermally expanded under appropriate heating conditions. What can be used suitably. In addition to these, those using a thermosetting resin such as an amino resin, a phenol resin, an unsaturated polyester resin as the shell wall can also be used.

The average particle diameter of such hollow polymer beads is generally about 1 to 500 μ, preferably about 5 to 300 μ.

Hollow polymer beads that can be preferably used in the present invention include, for example, Expancel DE ^#
551, WE ^# 551 [above, manufactured by Nippon Philite Co., Ltd.] and the like are commercially available. Some of these hollow polymer beads are commercially available as so-called "wet cake" containing water for reasons such as ease of handling, as in the case of the above-mentioned heat-expandable polymer beads, "Expansell WE ^# 551" is this type.

The amount of the thermally expandable polymer beads and / or hollow polymer beads (C) used in the present invention is generally 0.1 to 40 parts by weight, preferably 0.5 to 100 parts by weight of the composite particles (A). To 30 parts by weight, particularly preferably 1 to 20
Parts by weight. When the amount used is at least the lower limit value, cracking of the obtained coating film can be prevented, and when it is at most the upper limit value, the obtained coating film is smooth and the chipping resistance of the coating film is high. It is preferable because it does not decrease.

The acrylic resin aqueous coating composition of the present invention comprises an acrylic copolymer aqueous dispersion (A) consisting of dispersion composite particles having a specific composition as described above, an inorganic filler (B), and a heat Along with the expandable polymer beads and / or hollow polymer beads (C), a rust preventive pigment may be contained, if necessary.

Examples of the above-mentioned rust preventive pigments include, for example, lead tin; metal chromates such as zinc chromate, barium chromate and strontium chromate; zinc phosphate, calcium phosphate, aluminum phosphate, titanium phosphate. , Silicon phosphate, or metal phosphates such as ortho or condensed phosphates of these metals;

For example, metal molybdates such as zinc molybdate, calcium molybdate, zinc calcium molybdate, zinc potassium molybdate, zinc potassium phosphomolybdate, calcium potassium phosphomolybdate; for example, calcium borate, zinc borate, boric acid. Examples thereof include metal salts of boric acid such as barium, barium metaborate, calcium metaborate, and the like.

Among these antirust pigments, metal phosphates,
The use of non-toxic or low-toxic rust-preventive pigments such as metal molybdate and metal borate is preferred.

The amount of the rust preventive pigment used is the above-mentioned dispersion composite particles.
For example, an amount of about 0 to 50 parts by weight, preferably about 5 to 30 parts by weight can be exemplified with respect to 100 parts by weight.

The acrylic resin aqueous coating composition of the present invention may contain organic or inorganic color pigments such as titanium oxide, carbon black, red iron oxide, oxide yellow, copper phthalocyanine blue and the like.

The amount of these color pigments used may be, for example, 0 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the composite particles.

The particle diameter of these rust preventive pigments and color pigments is preferably about 1 to 50 μ from the viewpoint of the smoothness of the coating film of the obtained coating composition.

The acrylic resin aqueous coating composition of the present invention may further contain a water-soluble polyvalent metal salt; an aziridine compound; a water-soluble epoxy resin; a water-soluble melamine resin;
A cross-linking agent such as a water-dispersible blocked isocyanate can be contained.

Examples of the above water-soluble polyvalent metal salts include zinc salts such as zinc acetate, zinc formate, zinc sulfate and zinc chloride; aluminum salts such as aluminum acetate, aluminum nitrate and aluminum sulfate; , Calcium salts such as calcium formate, calcium chloride, calcium nitrate and calcium nitrite;

For example, barium salts such as barium acetate, barium chloride and barium nitrite; magnesium salts such as magnesium acetate, magnesium formate, magnesium chloride, magnesium sulfate, magnesium nitrate and magnesium nitrite; for example lead acetate and formic acid. Lead salt such as lead;

For example, nickel salts such as nickel acetate, nickel chloride, nickel nitrate, and nickel sulfate; manganese salts such as manganese acetate, manganese chloride, manganese sulfate, and manganese nitrate; for example, copper chloride, copper nitrate, copper sulfate, and the like. Copper salt;

As the aziridine compound, a reaction product of a polyisocyanate compound and ethyleneimine can be used,

Examples of the polyisocyanate compound include m- or p-phenylene diisocyanate, 2,4- or 2,6-tolylene diisocyanate, m- or p-xylylene diisocyanate and 4,4'-diphenylmethane diisocyanate. Aromatic diisocyanate compound;

Aliphatic or alicyclic diisocyanate compounds such as hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated products of the above aromatic diisocyanate compounds, and dimer acid diisocyanates;

Examples thereof include dimers or trimers of these isocyanates; adducts of these isocyanates with divalent or trivalent polyols such as ethylene glycol and trimethylolpropane.

Examples of the water-soluble epoxy resin include glycerol diglycidyl ether and the like.

As the water-soluble melamine resin, for example, methylol melamine; at least a part of the hydroxyl group of the methylol melamine is methyl alcohol, ethyl alcohol,
Examples thereof include those etherified with n-butyl alcohol and the like.

Examples of the water-dispersible blocked isocyanate include trimethylolpropane tritolylene diisocyanate methyl ethyl ketoxime adduct and the like in which the above-mentioned polyisocyanate compound is impregnated with a volatile low-molecular active hydrogen compound.

Examples of such a volatile low molecular weight active hydrogen compound include methyl alcohol, ethyl alcohol, n-butyl alcohol, cyclohexyl alcohol,
Aliphatic, alicyclic or aromatic alcohols such as benzyl alcohol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether and phenol;

For example, hydroxy tertiary amines such as dimethylaminoethanol and diacylaminoethanol; ketoximes such as acetoxime and methylethylketoxime; active methylene compounds such as acetylacetone, acetoacetic acid ester and malonic acid ester;
lactams such as ε-caprolactam; and the like.

The amount of these cross-linking agents used is, for example, 0 to 10 parts by weight, preferably 0.5 to 10 parts by weight, relative to 100 parts by weight of the above composite particles, from the viewpoint of suppressing the change with time of viscosity of the obtained coating composition. An amount of 10, particularly preferably about 1 to 5 parts by weight can be exemplified.

The acrylic resin aqueous coating composition of the present invention may further contain an inorganic dispersant (eg, sodium hexametaphosphate, sodium tripolyphosphate, etc.), an organic dispersant [eg, Nopcos Perth 44C (trade name, Polycarboxylic acid type; San Nopco Ltd.] dispersant; for example, silicone type antifoaming agent;

For example, thickeners and viscosity improvers such as polyvinyl alcohol, cellulose derivatives, polycarboxylic acid resins, surfactants; organic such as ethylene glycol, butyl cellosolve, butyl carbitol, butyl carbitol acetate, etc. A solvent; an antiaging agent; an antiseptic / antifungal agent; an ultraviolet absorber; an antistatic agent, etc. can be added and mixed.

The acrylic resin aqueous coating composition of the present invention is not particularly limited, but generally has a solid content of about
10-85% by weight, preferably about 30-80% by weight, particularly preferably about 50-70% by weight; pH 7-11, preferably 8-10;
Viscosity 100000 cps or less (B type rotational viscometer, 25 ° C, 20 rpm),
It is preferably about 5000 to 50000 cps.

Examples of the base material of the sheet metal working member to which the acrylic resin aqueous coating composition of the present invention can be suitably used include, for example, steel sheets; for example, lead-tin alloy plated steel sheets (tan sheet steel sheets), tin plated steel sheets. , Various plated steel plates such as aluminum-plated steel plates, lead-plated steel plates, chrome-plated steel plates and nickel-plated steel plates; coated steel plates such as electrodeposition coated steel plates;

That is, the coating composition is obtained by forming such a base material into various shapes by a sheet metal press or the like and welding these as various automobile members, for example, an automobile gasoline tank, an underfloor, a tire. It can be suitably used for coating an electrodeposition coated surface, a medium coated surface or an upper coated surface of a sheet metal working member outside the vehicle such as a house, a front apron and a rear apron.

For coating, a conventionally known method can be adopted, and an airless spray coating method is often used.

The dry film thickness of a suitable chipping-resistant coating film that can be formed by using the acrylic resin aqueous coating composition of the present invention is about 200 to 800 μ, particularly about 300 to 600 μ. Is preferred. When the film thickness is less than the upper limit, blistering does not occur in the heating and drying step, and when it is more than the lower limit, chipping resistance is excellent, which is preferable.

The coating surface may be dried at room temperature or by heating, but preferably, it is pre-dried at a temperature of about 80 ° C. and then heated in a heating furnace at a temperature of about 120 to 160 ° C. It is better to heat dry.

[0147]

[Examples] Examples, comparative examples and reference examples are given below.
The present invention will be described in more detail. The preparation and test methods of the test samples used in the above Examples and Comparative Examples are as follows.

(1) Preparation of test piece After washing the surface of 0.8 × 100 × 200 mm tan sheet steel sheet manufactured by Nippon Steel Co., Ltd. with a thinner, each sample was coated with a dry film by an airless spray coating method. To a thickness of 80 ° C, pre-dry at 80 ° C for 15 minutes using a hot-air circulation dryer, and then heat-treat at 120 ° C for 20 minutes.

(2) Blister limit film thickness In spray coating in the above (1), the dry coating film thickness is changed to obtain the maximum film thickness without blistering during drying. And

(3) Crack Limit Film Thickness In spray coating in the above (1), the dry film thickness is changed to obtain the maximum film thickness without cracks during drying. And

(4) Normal state chipping resistance test In the previous item (1), the test piece obtained by coating so as to have a dry film thickness of about 300 μ was left for 16 hours under a constant temperature condition of about 25 ° C. Using an office cutter, make a cut line with a mark of x each having a depth of about 5 cm from the coating surface to the substrate.

The test piece was fixed by leaning against the horizontal plane at an angle of 60 °, and the coated surface was vertically moved from a height of 2 m to a vertical direction of 2 m.
Using a 5 mmφ PVC pipe, drop the nut (M-6) continuously toward the cross part of the cut line, and evaluate the total weight of the dropped nut when the base material is exposed.

(5) Wet chipping resistance test In the previous section (1), a test piece obtained by coating so as to have a dry film thickness of about 300 μ was immersed in deionized water at about 40 ° C. for 7 days and then taken out. Wipe off the water and then make a cut line with a cross like the previous (3) item, leave it at 25 ° C for 3 hours,
A chipping resistance test is carried out in the same manner as in the previous item (3) and evaluated in the same manner.

(6) Low temperature impact resistance test In the previous paragraph (1), the test piece was left for 3 hours or more under the constant temperature condition of -30 ° C, and then at the same temperature according to JIS K-5400, the DuPont type impact resistance test. I do.

At this time, the condition is that the radius of the tester is 6.35 ± 0.03.
Attach a mm shotgun and pedestal, sandwich the test piece with the coating surface facing upward, drop a weight of 500 ± 1 g from the height of 50 cm onto the shot die, and visually check the degree of damage to the coating surface. Is evaluated according to the following evaluation criteria.

◎ ・ ・ No change at all ○ ・ ・ ・ ・ ・ ・ Slightly small cracks occurred △ ・ ・ ・ ・ Small cracks occurred frequently × ・ ・ ・ ・ Large cracks occurred

Reference Example 1 A 2 liter separable flask equipped with a stirrer, a reflux condenser and a thermometer was charged with 474 g of deionized water, 5 g of sodium dodecylbenzenesulfonate and 5 g of polyoxyethylene nonylphenol ether (HLB about 16), The temperature was raised to 70 ° C while flowing nitrogen. Butyl acrylate (BA) 20
Monomer mixture that evenly mixes 4.75 g, methyl methacrylate (MMA) 134.75 g and acrylic acid (AA) 10.5 g
(M ₁ ) and 30 g of a 5 wt% aqueous solution of ammonium persulfate (APS) as a polymerization initiator aqueous solution were continuously added over 3 hours, and then the mixture was kept at the same temperature for 1 hour to obtain an acrylic copolymer emulsion. It was

Then, to this acrylic copolymer emulsion, 120 g of 2-ethylhexyl acrylate (2EHA), 25.5 g of styrene (St) and 4.5 g of AA were uniformly mixed, and a monomer mixture (M ₂ ) and 5 parts by weight of APS were added. % Aqueous solution (10 g) was continuously added over 1 hour, and then the mixture was maintained at the same temperature for 2 hours to obtain an aqueous acrylic copolymer dispersion.

Compositions of M ₁ and M _{2 in} this polymerization, Tg ₁ and Tg ₂ , solid content, pH and viscosity of the resulting acrylic copolymer aqueous dispersion, and from the aqueous dispersion were obtained. Table 1 shows the turbidity values of the obtained films.

Reference Examples 2 to 4 Acrylic copolymer aqueous dispersions were obtained in the same manner as in Example 1 except that the monomer composition was changed. The respective compositions of M ₁ and M _{2 in} the polymerization, Tg ₁ and Tg ₂ , the solid content, pH, viscosity of the resulting acrylic copolymer aqueous dispersion, and the film obtained from the aqueous dispersion Table 1 shows the values of turbidity.

[0161]

[Table 1]

Example 1 200 parts by weight of the aqueous acrylic copolymer dispersion of Reference Example 1 (about 100 parts by weight in solid content), and "Matsumoto Microsphere F-50" as a thermally expandable polymer bead [trade name;
Matsumoto Yushi-Seiyaku Co., Ltd .; water content about 30% by weight; particle size before thermal expansion 10 to 20 μ; particle size after thermal expansion 30 to 80 μ; softening temperature of shell wall 100 to 105 ° C.) 3 parts by weight (water content Body weight excluding about 2.1
Parts by weight, including the weight of the organic solvent as the heat-vaporization type foaming agent), and ground calcium carbonate SL-700 [trade name; manufactured by Takehara Chemical Industry Co., Ltd .; average particle size]
4.5μ] 115 parts by weight and light calcium carbonate [manufactured by Maruo Calcium Co., Ltd .; major axis about 2.0μ, minor axis about 0.4μ] 100 parts by weight,

3 parts by weight of carbon black as a coloring pigment, 12 parts by weight of barium metaborate as an anticorrosion pigment, Nopco Perth 44C as a dispersant [trade name; manufactured by San Nopco Ltd .;
Polycarboxylic acid type] 2 parts by weight (solid content: about 0.88 parts by weight),
Adekanol UH-472 [trade name; manufactured by Asahi Denka Kogyo Co., Ltd .; surfactant system] 1.5 parts by weight (solid content: about 0.45 parts by weight) as a thickener and Nopco 8034 [trade name; San Nopco (stock) as a defoaming agent. )) 0.6 parts by weight are evenly dispersed using a disper,

The ratio of the total pigment [heat-expandable polymer, powdered inorganic filler (heavy calcium carbonate and light calcium carbonate), carbon black and barium metaborate] in the dry film of the composition (hereinafter, An acrylic resin aqueous coating composition having a PWC of 70% by weight and a solid content of 76.3% by weight was prepared.

Various physical property tests were conducted using the obtained acrylic resin aqueous coating composition. The composition of the composition is shown in Table 2, and the measurement results of various physical properties are shown in Table 3.

Examples 2 to 4 and Comparative Example 1 Example 1 is the same as Example 1 except that the amount of heat-expandable polymer beads used is changed or not used, and the amount of heavy calcium carbonate used is adjusted accordingly. An acrylic resin aqueous coating composition was prepared in the same manner as.

Various physical property tests were carried out using the obtained acrylic resin aqueous coating composition. The composition of the composition is shown in Table 2, and the measurement results of various physical properties are shown in Table 3.

Example 5 Instead of using “Matsumoto Microsphere F-50” as the heat-expandable polymer beads in Example 1,
"Expansell WU ^# 551" [Product name: Nippon Philite
Co., Ltd .; water content about 30% by weight; particle size before thermal expansion about 10μ;
Particle diameter after thermal expansion of about 40μ; softening temperature of shell wall 100-140 ℃
An acrylic resin aqueous coating composition was prepared in the same manner as in Example 1 except that 3 parts by weight (main body weight excluding water, about 2.1 parts by weight, including the weight of the organic solvent as the heat-vaporizable foaming agent) was used. did.

Various physical property tests were carried out using the obtained acrylic resin aqueous coating composition. The composition of the composition is shown in Table 2, and the measurement results of various physical properties are shown in Table 3.

Example 6 Instead of using 3 parts by weight of the thermally expandable polymer beads "Matsumoto Microsphere F-50" in Example 1, hollow polymer beads "Expancel WE ^# 551" are used.
[Brand name: manufactured by Nippon Philite Co., Ltd .; moisture content of about 85% by weight;
Particle size: about 40μ] 12 parts by weight (body weight excluding water is about 1.8
(Parts by weight) was used to prepare an acrylic resin aqueous coating composition in the same manner as in Example 1 except that the amount of heavy calcium carbonate used was adjusted.

Various physical property tests were carried out using the obtained acrylic resin aqueous coating composition. The composition of the composition is shown in Table 2, and the measurement results of various physical properties are shown in Table 3.

Examples 7 to 10 In the same manner as in Example 1, except that the acrylic copolymer aqueous dispersion of Reference Example 1 is used, the acrylic copolymer aqueous dispersions of Reference Examples 2 to 5 are used. An aqueous acrylic resin coating composition was prepared in the same manner as in 1.

Various physical property tests were carried out using the obtained acrylic resin aqueous coating composition. The composition of the composition is shown in Table 2, and the measurement results of various physical properties are shown in Table 3.

[0174]

[Table 2]

[0175]

[Table 3]

[0176]

The acrylic resin aqueous coating composition of the present invention is, for example, a mastic paint, a soundproof paint, a vibration-proof paint,
Aqueous resin composition for coating such as caulking material, among others, an acrylic resin excellent in chipping resistance used as a coating agent for protecting outdoor metal working members such as vehicles, particularly automobile chassis, gasoline tanks and suspensions. A resin aqueous coating composition,

Even when a thick coating film having a thickness of, for example, 600 μ or more is formed, blistering or cracking does not occur in the coating film in the drying process, and the formed film has a thickness of, for example, about 300 μ. It is an acrylic resin aqueous coating composition having excellent chipping resistance even when the coating is relatively thin.

The acrylic resin aqueous coating composition of the present invention contains an acrylic copolymer aqueous dispersion having a specific particle structure, an inorganic filler, heat-expandable polymer beads and / or hollow polymer beads. It is characterized by

As a result, excellent physical properties that cannot be achieved by using a conventional aqueous copolymer emulsion, that is, chipping resistance at room temperature, and particularly when the film is wet; for example, -30 Impact resistance at extremely low temperatures such as ℃; excellent adhesion to metalworking members; flat and uniform film formation; water resistance; gasoline resistance; soundproofing and other properties as a chipping resistant coating Can be combined well.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryotaka Takahata 3-24-26 Yokodai, Isogo-ku, Yokohama-shi, Kanagawa Nippon Carbide Industry Co., Ltd. Yokohama Dormitory

Claims (1)

[Claims] 1. An acrylic resin aqueous coating comprising an acrylic copolymer aqueous dispersion (A), an inorganic filler (B), and thermally expandable polymer beads and / or hollow polymer beads (C). Composition, wherein the dispersed particles of the acrylic copolymer aqueous dispersion (A) are composite particles composed of at least two types of acrylic (co) polymerization having different glass transition points, and The total monomer composition of the dispersed particles is
(a) to (d) [however, the total of (a) to (d) is 100% by weight], (a) the following general formula (1), (Wherein R ¹ represents a straight-chain or branched alkyl group having 4 to 12 carbon atoms), and its homopolymer has a glass transition point of −30 ° C. or lower. %, (B) C3 to C5 α, β-unsaturated mono- or di-
Carboxylic acid 0.5 to 10% by weight, (c) the following general formula (2), (However, in the formula, R ² is H or a methyl group, and X is a carbon number 6
~ 8 aryl group, cyano group, the following general formula (3) or
(4), [Chemical formula 3] [Chemical 4] Wherein R ³ represents a straight chain or branched alkyl group having 1 to 20 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group or an aralkyl group, and R ⁴ represents H or a direct alkyl group having 1 to 12 carbon atoms. A chain or branched alkyl group), which is a monomer other than the above-mentioned monomer (a).
To 60% by weight, and (d) a monomer having at least one functional group in addition to one radically polymerizable unsaturated group in the molecule, which is a monomer other than the monomer (b). 0 to 5% by weight,
An acrylic resin aqueous coating composition comprising: