JP3286033B2 - Aqueous coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous coating composition, and more particularly, to an aqueous coating composition used as a mastic paint, a soundproof paint, a vibration-proof paint, a caulking material, etc. In particular, used to protect the sheet metal processing member from scratches or so-called "chipping" of an outdoor sheet metal processing member such as a floor of an automobile, a tire house, a chassis, a gas tank, a suspension, etc. Based on acrylic (co) polymer emulsion particles with excellent properties such as adhesion to metal processing parts, uniformity and smoothness of coating film, water resistance, gasoline resistance, impact resistance, soundproofing, etc. And a chipping-resistant aqueous coating composition.

[0002]

2. Description of the Related Art Conventionally, as an aqueous chipping-resistant coating material used for outdoor sheet metal processing members of vehicles such as automobiles, an aqueous resin dispersion of an acrylic (co) polymer emulsion is used as a vehicle, and calcium carbonate, Known are those blended with an inorganic filler such as talc, and those based on an acrylic (co) polymer aqueous resin dispersion are disclosed, for example, in JP-A-53-64287 and JP-A-59-64287. No. 75954, JP-A-62-230868, JP-A-63-10678 and JP-A-63-172777.

However, the water-based coating agents for chipping resistance described in these publications have chipping resistance, excellent adhesion to sheet metal processing members, and impact resistance, particularly, for example, impact resistance at cryogenic temperatures of -30 ° C. or lower. (Hereinafter referred to as "low-temperature impact resistance"), etc., as well as anti-swelling properties in the drying process when forming a thick coating film such as 600μ or more, for example. It is not easy, and in order to improve chipping resistance and low-temperature impact resistance, if the amount of the inorganic filler in the coating material is reduced, blisters are easily generated in the baking process, and the filler is used to prevent blistering. When the amount is increased, there is a problem that chipping resistance and low-temperature impact resistance are significantly reduced.

Further, an aqueous coating agent for chipping resistance using a rubber-based latex as a vehicle is disclosed in, for example,
JP-180617, JP-A-59-75954, JP-A-59-1
This is disclosed in, for example, Japanese Patent No. 29213.

However, the aqueous coating composition for chipping resistance using a latex described in these publications has a problem that it is not always sufficient in all of chipping resistance, adhesion and low-temperature impact resistance.

[0006] Further, an aqueous coating agent for chipping resistance comprising a mixture of two or more emulsions having different glass transition temperatures (hereinafter sometimes abbreviated as Tg) is also known. For example, JP-A-53-64287. No. 6,086,045. And the aqueous coating agent for chipping resistance disclosed in this publication,
Tg difference is 10 ° C or more, one Tg is 0 ° C or less, and the other Tg is
g is a mixture of at least two types of resin emulsions having a temperature of 0 ° C. or higher.

However, in the embodiment of the above publication, an acrylic resin emulsion of Tg-35 ° C.
Although an acrylic resin emulsion at + 9 ° C. was used, it was found that it was not always sufficient in terms of chipping resistance and adhesion.

[0008] Further, the coating of the chipping-resistant coating agent on parts other than the body, such as the chassis, gasoline tank, and suspension, of the automobile parts is generally performed on a line different from the body coating line. Attempts have been made to reduce the coating film baking temperature of the coating line to a relatively low temperature of, for example, 100 ° C. or lower, for the purpose of reducing automobile manufacturing costs. In this case, there is an advantage that the problem of blistering can be substantially avoided. However, it has been found that there is a problem that the adhesion of the coating agent to these parts is further reduced.

[0009]

DISCLOSURE OF THE INVENTION The present inventors have developed chipping resistance such as chipping resistance, low-temperature impact resistance, adhesion to a substrate surface, uniformity and smoothness of a coating film, water resistance, and solvent resistance. It has a good balance of various properties as a coating agent for automobiles, and when forming a thick coating film on a sheet metal processing member that is subjected to high-temperature baking, such as an automobile body, it may cause inconvenience such as blisters in the baking process. Intensive research was conducted with the aim of providing a non-chipping resistant aqueous coating composition.

A chipping-resistant aqueous coating composition mainly used for coating sheet metal working members such as parts other than the automobile body, wherein the coating film baking temperature is relatively low, for example, 100 ° C. or less. And when
Provided is a chipping-resistant aqueous coating composition which does not impair the adhesion of a coating film to a substrate surface, which tends to decrease, and which has the above-mentioned other properties as a chipping-resistant coating agent in a well-balanced manner. Further research was carried out for the purpose.

As a result, as a vehicle component of the aqueous coating composition, (A) the following general formula (2) (Meth) acrylic acid ester represented by the formula (wherein, R ³ is
H or a methyl group, R ⁴ is a straight chain having 1 to 20 carbon atoms or
The glass transition temperature that does not contain acrylonitrile to represent branched alkyl groups) containing from 30 to 99.9 wt% (hereinafter Tg sometimes referred) is -10 ° C. or less of acrylic and (co) polymer emulsion, Tg is 30 ° C. It has been found that the above object can be achieved by using the above-mentioned specific polymer emulsion having a relatively high Tg in combination (hereinafter, sometimes referred to as a high Tg emulsion), thereby completing the present invention.

[0012]

Thus, according to the present invention, there is provided an aqueous coating composition comprising polymer fine particles dispersed in an aqueous medium and an inorganic filler, wherein the polymer fine particles are (A) and (B) below,

(A) The following general formula (2) (Meth) acrylic acid ester represented by the formula (wherein, R ³ is
H or a methyl group, R ⁴ is a straight chain having 1 to 20 carbon atoms or
Acrylonitrile-free acrylic (co) polymer emulsion particles having an acrylonitrile content of from 30 to 99.9% by weight (containing a branched alkyl group) of from 50 to 95% by weight, and

(B) The following general formula (1):

[0015]

Embedded image

Wherein R ¹ is H or a methyl group, and Q is-
COOR ² , an aryl group having 6 to 12 carbon atoms, or —C
N and R ² represent a lower alkyl group having 6 or less carbon atoms)

The repeating unit represented by the formula is 30 to 99.9% by weight.
The present invention provides an aqueous coating composition comprising 5 to 50% by weight of emulsion polymer particles having a glass transition temperature of at least 30 ° C.

In the present specification, the expression "emulsion polymer particles" refers to fine particles of a polymer dispersed in an aqueous medium and has an average particle diameter of usually 1 μm or less, preferably 0.05 to 0.5 μm. μ means dispersed particles
It does not necessarily mean only polymer particles obtained by emulsion polymerization.

Hereinafter, the aqueous coating composition of the present invention will be described in more detail.

[0020]Acrylic (co) polymer emulsion particles
(A) Essential components of vehicle in aqueous coating composition of the present invention
Acrylic (co) polymer emulsion particles (A)
Those obtained by emulsion copolymerization of the following monomers (a-1) to (a-4) are preferable.
Good.

(A-1) a (meth) acrylate represented by the following general formula (2),

[0022]

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Wherein R ³ is H or a methyl group, and R ⁴ is a linear or branched alkyl group having 1 to 20 carbon atoms.

(A-2) an ethylenic monomer having a carboxyl group in the molecule, (a-3) having at least one functional group in addition to one radically polymerizable unsaturated group in the molecule A monomer other than the above (a-2), and (a-4) a comonomer other than the above monomers (a-1) to (a-3).

In the monomer (a-1) represented by the general formula (2), R ³ is H or a methyl group, and R ⁴ has 1 carbon atom.
Acrylic acid or methacrylic acid alkyl ester monomers represented by up to 20 linear or branched alkyl groups.

When R ³ is H among these monomers, that is, in the case of an acrylate monomer, R ⁴ is a carbon atom from the viewpoint of easy availability and ease of polymerization reaction. It is preferably a linear or branched alkyl group having the number of 1 to 10. Examples of such an alkyl group include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl, n-hexyl, n- -Heptyl group, n-octyl group, i-octyl group, 2-ethylhexyl group, n-nonyl group, i-nonyl group, n-decyl group and the like, and specifically, methyl acrylate, ethyl acrylate , N-butyl acrylate, i-butyl acrylate, n-octyl acrylate, i-octyl acrylate, 2-ethylhexyl acrylate, i-nonyl acrylate and the like can be suitably used.

When R ³ is a methyl group, that is, in the case of a methacrylic acid ester monomer, R ⁴ has a carbon number of 1 to 1 for the same reason as in the case of the acrylic acid ester monomer.
It is preferably 5 straight-chain or branched alkyl groups.
Examples of such an alkyl group include a methyl group, an ethyl group,
n-propyl group, i-propyl group, n-butyl group, i-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, i-octyl group, 2-ethylhexyl group, Examples thereof include an n-nonyl group, an i-nonyl group, an n-decyl group, an n-dodecyl group, and a t-dodecyl group.
It is particularly preferable to use a methacrylate monomer having a linear or branched alkyl group of from 4 to 4, and specific examples thereof include methyl methacrylate, ethyl methacrylate, and n-methacrylate.
Butyl methacrylate, i-butyl methacrylate and the like can be suitably used.

Examples of the ethylene monomer containing a carboxyl group in the molecule (hereinafter sometimes referred to as a carboxyl group-containing monomer) of the monomer (a-2) include, for example, acrylic acid and methacrylic acid. Α, β-unsaturated mono- or di-carboxylic acid having 3 to 5 carbon atoms such as acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, citraconic acid (hereinafter referred to as ethylene-based carboxylic acid) For example); for example, mono-n-butylmalate, mono-n-butylfumarate, monoethylitaconate, etc., having 4 to 5 carbon atoms.
C1-C12 monoalkyl ester monomers of α, β-unsaturated dicarboxylic acids; for example, ethylene carboxylic acids such as sodium acrylate and ammonium methacrylate or α, β-unsaturated C4-C5 Alkali metal salts or ammonium salts of dicarboxylic acid monoalkyl ester monomers; Of these, the use of ethylene-based carboxylic acids is preferred from the viewpoints of ease of emulsion polymerization and low generation of aggregates, and the use of acrylic acid, methacrylic acid and / or itaconic acid is particularly preferred.

A monomer having at least one functional group in addition to one radically polymerizable unsaturated group in the molecule, and a monomer other than the above (a-2) (a-3 ) As a functional group, for example, acrylamide, methacrylamide,
Ethylene carboxylic acids such as N-methylolacrylamide, N-methylolmethacrylamide, Nn-butoxymethylacrylamide, Ni-butoxymethylacrylamide, N, N-dimethylacrylamide, N-methylacrylamide and the like (preferably, acrylamide, methacrylamide and the like) Amides or derivatives thereof;

Esters of an ethylene carboxylic acid such as glycidyl acrylate, glycidyl methacrylate, glycidyl allyl ether, glycidyl methallyl ether (preferably glycidyl methacrylate) with a saturated alcohol having an epoxy group; 2-hydroxyethyl acrylate, 2-hydroxypropyl Esters of ethylenic carboxylic acid such as acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate and polyhydric saturated alcohol; aminoethyl acrylate, N, N-
Dimethylaminoethyl acrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl methacrylate, etc. (preferably, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl methacrylate) And the like) esters of an ethylene-based carboxylic acid with a saturated alcohol having an amino group or a substituted amino group;

Divinylbenzene, diallyl maleate, diallyl fumarate, diallyl itaconate, diallyl phthalate, triallyl cyanurate, ethylene glycol di (meth) acrylate, 1,4-butanediol di (meth)
Monomers having two or more radically polymerizable unsaturated groups, such as acrylate, 1,6-hexanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, and allyl (meth) acrylate; Can be mentioned.

Further, monomers other than the above-mentioned monomers (a-1) to (a-3) and (a-4) include, for example, aromatic compounds such as styrene, α-methylstyrene, vinyltoluene and ethylvinylbenzene. Group IV vinyl monomers; for example, vinyl vinyl formate, vinyl acetate, propionic acid, C1-C12 saturated fatty acid vinyl monomers such as "vinyl versatate" (trade name); for example, dibutyl malate, dibutyl Α having 4 to 5 carbon atoms such as fumarate, dibutyl itaconate, dioctyl malate, dioctyl fumarate, dioctyl itaconate,
and a monomer group such as a dialkyl ester monomer having 1 to 12 carbon atoms of β-unsaturated dicarboxylic acid.

The monomer components (a-1) to (a-4) described above
Can be varied in a wide range depending on the physical properties and the like required for the acrylic (co) polymer emulsion particles to be formed, but can be generally used within the range shown below. .

[0034] (Note:% by weight is a percentage based on the total amount of monomers.)

Acrylic (co) polymer emulsion particles
(A) is a monomer component (a-1) to (a-4) described above, the presence of a surfactant in the same manner as known per se known acrylic (co) polymer emulsion production method It can be produced by emulsion polymerization in an aqueous medium at a temperature of about 30 to about 100 ° C, preferably about 40 to about 90 ° C, and optionally in the presence of a protective colloid.

As the surfactant, any of nonionic, anionic, cationic and amphoteric surfactants can be used.

As nonionic surfactants, for example, polyoxyalkylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; and polyoxyalkylene alkyl ethers such as polyoxyethylene octyl phenol ether and polyoxyethylene nonyl phenol ether Oxyalkylene alkyl phenol ethers; for example, sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate;

For example, polyoxyalkylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate; for example, polyoxyalkylene fatty acid esters such as polyoxyethylene monolaurate and polyoxyethylene monostearate; for example, oleic acid Glycerin fatty acid esters such as monoglyceride and monoglyceride stearate; polyoxyethylene / polyoxypropylene / block copolymer;

Examples of the anionic surfactant include fatty acid salts such as sodium stearate, sodium oleate and sodium laurate; alkyl alkyl sulfone hydrochlorides such as sodium dodecylbenzenesulfonate; Alkyl sulfates such as sodium monooctyl sulfosuccinate, sodium dioctyl sulfosuccinate and sodium polyoxyethylene lauryl sulfosuccinate and derivatives thereof; for example, polysulfates such as sodium polyoxyethylene lauryl ether sulfate Oxyalkylene alkyl ether sulfates; for example, polyoxyalkylene alkyl such as sodium polyoxyethylene nonyl phenol ether sulfate Reel ether sulfate ester salts: like can be exemplified,

Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate;
For example, lauryl trimethyl ammonium chloride,
Quaternary ammonium salts such as alkylbenzyldimethylammonium chloride; polyoxyethylalkylamine; and the amphoteric surfactants include, for example, alkyl betaines such as lauryl betaine.

Further, these surfactants are obtained by substituting a part of the hydrogen of the alkyl group with fluorine; so-called reactive surfactants having a radical copolymerizable unsaturated bond in the molecular structure of these surfactants. And the like can also be used.

Among these surfactants, nonionic surfactants include polyoxyalkylene alkyl ethers, polyoxyalkylene alkyl phenol ethers, and the like, from the viewpoint of the occurrence of a small amount of aggregates during emulsion polymerization. Examples of the anionic surfactant include alkyl aryl sulfonates, alkyl sulfates, alkyl sulfosuccinates and derivatives thereof, polyoxyalkylene alkyl ether sulfates, polyoxyalkylene alkyl phenol ether sulfates, and the like. Is preferred. These surfactants can be used alone or in appropriate combination.

The amount of these surfactants can be varied depending on the type of surfactant used, etc., but generally, the total of the monomer components (a-1) to (a-4) is 100 parts by weight. About 0.5 to about
Although it can be in the range of 10 parts by weight, the polymerization stability of the aqueous emulsion polymerization, the storage stability of the resulting acrylic (co) polymer emulsion and when used in the chipping-resistant aqueous coating composition, About 1 to 6 parts by weight, especially about 1 to 4 parts by weight, from the viewpoint of excellent adhesion to a substrate such as a sheet metal processing member.
It is preferred to use within the range of parts by weight.

The protective colloid that can be used in the production of the acrylic (co) polymer emulsion includes, for example, polyvinyl alcohols such as partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, and modified polyvinyl alcohol; And cellulose derivatives such as hydroxyethylcellulose, hydroxypropylcellulose and carboxymethylcellulose; and natural polysaccharides such as guar gum.

The use amount of these protective colloids is not strictly limited, and can be changed according to the kind and the like. Usually, the amount of the monomer components (a-1) to (a-4) is total
An amount of about 0 to 3 parts by weight per 100 parts by weight can be exemplified.

The emulsion polymerization of the monomer components (a-1) to (a-4) is performed using a polymerization initiator. Examples of the polymerization initiator that can be used include, for example, persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate;
Organic peroxides such as butyl hydroperoxide, cumene hydroperoxide and p-menthane hydroperoxide; hydrogen peroxide; and the like, and these can be used alone or in combination of two or more.

The amount of the polymerization initiator used is not strictly limited, and can be varied in a wide range depending on the type, reaction conditions, and the like.
(a-1) to (a-4), 100 parts by weight in total, about 0.05 to about 1
The amount used can be exemplified, for example, about 0.1 parts by weight, more preferably about 0.1 to about 0.7 parts by weight, and particularly preferably about 0.1 to about 0.5 parts by weight.

In the emulsion polymerization, a reducing agent can be used in combination, if desired. Examples of the reducing agent that can be used include reducing organic compounds such as ascorbic acid, tartaric acid, citric acid, and glucose; and reducing inorganic compounds such as sodium thiosulfate, sodium sulfite, sodium bisulfite, and sodium metabisulfite. Examples can be given. The amount of these reducing agents used is also not particularly limited, but is generally the total of the monomers (a-1) to (a-4).
The range of about 0.05 to about 1 part by weight per 100 parts by weight can be exemplified.

In the emulsion polymerization, a chain transfer agent may be used if desired. Examples of such a chain transfer agent include cyanoacetic acid; alkyl esters of cyanoacetic acid having 1 to 8 carbon atoms; bromoacetic acid; alkyl esters of bromoacetic acid having 1 to 8 carbon atoms; anthracene, phenanthrene, fluorene, 9 Polycyclic aromatic compounds such as -phenylfluorene; p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid,
Aromatic nitro compounds such as p-nitrophenol and p-nitrotoluene; benzoquinone, 2,3,5,6-tetramethyl-p-
Benzoquinone derivatives such as benzoquinone; borane derivatives such as tributylborane;

Halogenated carbons such as carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene Hydrogens; aldehydes such as chloral and furaldehyde; and alkyl mercaptans having 1 to 18 carbon atoms such as n-dodecyl mercaptan; aromatic mercaptans such as thiophenol and toluene mercaptan; mercaptoacetic acid; 10 alkyl esters; C1-C12 hydroxyalkyl mercaptans such as 2-mercaptoethanol; terpenes such as binene and terpinolene;

When the above-mentioned chain transfer agent is used, the amount thereof is in the range of about 0.005 to about 3 parts by weight based on 100 parts by weight of the total of the monomers (a-1) to (a-4). Is preferred.

The acrylic (co) polymer emulsion formed by the emulsion polymerization described above generally contains 10 to 70% by weight, preferably 30 to 60% by weight, and more preferably 40% by weight.
It can have a solids content in the range of 6060% by weight, and has a viscosity of not more than 10,000 cps, particularly from about 50 to about 5,000 cps when measured at 25 ° C. and 20 rpm using a B-type rotational viscometer.
Is desirably within the range.

The above emulsion is usually 2 to 10, especially 5 to 10
It is desirable to have a pH within the range of 9, and the pH can be adjusted using, for example, aqueous ammonia, an aqueous amine solution, or an aqueous alkali hydroxide solution.

The acrylic (co) polymer emulsion particles (A) used in the aqueous coating composition of the present invention have a Tg
Is 0 ° C. or lower, preferably −10 ° C. or lower, more preferably in the range of −20 to −80 ° C. Tg
A coating film formed from an aqueous coating composition prepared using acrylic (co) polymer emulsion particles having a temperature higher than 0 ° C. generally has low chipping resistance and is not so preferred.

In the present specification, the glass transition temperature (Tg) of the polymer particles is a value measured by the following method.

Glass transition temperature (Tg): About 10 mg of a sample of (co) polymer emulsion was weighed into a cylindrical cell made of aluminum foil having a thickness of about 0.05 mm and having an inner diameter of about 5 mm and a depth of about 5 mm. And dried at 100 ° C. for 2 hours as a measurement sample, using a differential scanning calorimeter [Differental Scanning Calorimeter: “SSC-5000” type manufactured by Seiko Instruments Inc.) at −150 ° C.
Then, the specific heat capacity difference before and after the glass transition temperature of the sample is measured at a heating rate of 10 ° C./min, and Tg is determined from the result.

The average particle size of the acrylic (co) polymer emulsion particles (A) dispersed in the emulsion produced as described above (hereinafter sometimes simply referred to as the particle size) is generally , 0.05 to 1.0 μ, especially 0.1 to 0.5 μ. The particle size of the polymer particles in the emulsion can be controlled, for example, by appropriately selecting the type and amount of the surfactant to be used and the polymerization temperature.

In the present specification, the average particle size of the polymer particles is described in “New Experimental Chemistry Course 4 Basic Technology 3 Hikari (II)” edited by The Chemical Society of Japan, pp. 725-741 (July 20, 1971) This is a value measured by the DLS method described in Maruzen Co., Ltd.), and specifically, a value measured and determined by the method described below.

Average particle diameter: The (co) polymer emulsion is diluted 50,000 to 150,000 times with distilled water, and after sufficiently stirring and mixing,
Approximately 10 using a Pasteur pipette in a 21 mmφ glass cell
ml, and set it at a predetermined position of a dynamic light scattering photometer “DLS-700” (manufactured by Otsuka Electronics Co., Ltd.), measure under the following measurement conditions, and process the measurement result by computer. Determine the average particle size.

[Measurement conditions] Measurement temperature 25 ± 1 ° C. Clock rate 10 μsec Correlation channel (Corelation Channel) 512 Integrated measurement number 200 Light scattering angle 90 °

High Tg emulsion polymer particles (B) In the aqueous coating composition of the present invention, the above-mentioned acrylic (co) polymer emulsion particles (A) are used as a vehicle component.
The high Tg emulsion polymer particles (B) that can be used in combination with the following general formula (1):

[0062]

Embedded image

Wherein R ¹ is H or a methyl group, and Q is-
COOR ² , an aryl group having 6 to 12 carbon atoms, or —C
N and R ² represent a lower alkyl group having 6 or less carbon atoms)

The repeating unit represented by the formula (1) is contained in an amount of 30 to 99.9% by weight, preferably 35 to 98.5% by weight, more preferably 40 to 96% by weight, based on the weight of the polymer. Depending on the type, it is composed of a (co) polymer which can contain one or more other monomer units.

Here, the term “lower” means that the group or compound to which this term is attached has 6 or less carbon atoms, preferably 4 carbon atoms.
Means less than or equal to

Suitable as such another monomer unit is a repeating unit derived from a carboxyl group-containing ethylenic monomer described later, and the (co) polymer preferably contains such a unit in an amount of 0.1%. ~ 10% by weight, more preferably
0.5 to 5% by weight can be contained. Further, the (co) copolymer may contain a repeating unit derived from a hydroxyl group-containing ethylenic monomer described later, preferably in an amount of 1 to 20% by weight, particularly preferably 3 to 15% by weight.

Such a (co) polymer is, for example, (b-1) the following general formula (3)

[0068]

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(Wherein R ¹ and Q are as defined above)

An ethylene monomer represented by the formula: wherein the homopolymer of the monomer is hydrophobic and has a Tg of 40 ° C.
The above monomer and (b-2) a carboxyl group-containing ethylene monomer, preferably (b-3) a hydroxyl group-containing ethylene monomer, and further, if necessary, (b- 4) It can be produced by emulsion polymerization with other copolymerizable monomers.

Examples of the monomer (b-1) include alkyl esters of methacrylic acid having 1 to 4 carbon atoms such as methyl methacrylate, ethyl methacrylate and i-butyl methacrylate; for example, styrene, α-methylstyrene And vinyl aromatic compounds such as vinyl toluene and ethyl vinyl benzene; (meth) acrylonitrile; Among these, methyl methacrylate, styrene and acrylonitrile are preferred as the monomer (b-1) from the viewpoints of availability, ease of emulsion polymerization, and the like.
Each of these monomers can be used alone or 2
More than one species may be used in combination.

The carboxyl group-containing ethylene monomer (b-
As 2), those similar to the carboxyl group-containing ethylene monomer (a-2) described above in the production of the acrylic (co) polymer can be used. Such a monomer (b-
Preferred as 2), as in monomer (a-2),
Acrylic acid, methacrylic acid and itaconic acid.

Further, a hydroxyl group-containing ethylene monomer (b-3)
Include α, β-ethylenically unsaturated monomers containing 1 to 4, preferably 1 hydroxyl group per molecule, such as 2-hydroxyethyl (meth) acrylate, 2-hydroxyethyl Examples thereof include hydroxyalkyl esters of (meth) acrylic acid having 2 to 2 carbon atoms, such as propyl (meth) acrylate.

Other copolymerizable monomers (b-4) that can be used as required include the monomers (a-1) shown in the production of the acrylic (co) polymer, (a-3) and (a-4)
Among them, those other than the above (b-1) and (b-3) can be appropriately selected and used.

As such a monomer (b-4), a monomer
(B-1) other than (meth) acrylate monomers, for example, vinyl formate, vinyl acetate, vinyl propionate,
1-12 carbon atoms such as "vinyl versatate" (trade name)
A saturated fatty acid vinyl monomer; for example, unsaturated α, β-dicarboxylic acid having 4 to 5 carbon atoms such as dibutyl malate, dioctyl malate, dibutyl fumarate, dioctyl fumarate, dibutyl itaconate, dioctyl itaconate, etc. An alkyl diester monomer having 1 to 12 carbon atoms;

The monomers having at least one functional group in addition to one radically polymerizable unsaturated group in the molecule include:
Amides or derivatives thereof of the above-mentioned ethylene-based carboxylic acids, esters of ethylene-based carboxylic acids and saturated alcohols having an epoxy group, esters of ethylene-based carboxylic acids and saturated alcohols having an amino group or a substituted amino group, molecules And a monomer group having two or more radically polymerizable unsaturated groups therein.

Examples of the monomer (b-4) include, in addition to these, monoolefin monomers such as ethylene, propylene, n-butylene and i-butylene; and conjugates such as butadiene, isoprene and chloroprene. Diolefin monomer;
Use of such is also possible.

The monomers (b-4) described above can be used alone or in combination of two or more.
These monomers can be appropriately selected according to the physical properties desired for the polymer to be formed, for example, Tg. Among them, vinyl acetate, “vinyl versatate” (trade name) and butadiene are preferable.

The monomers (b-1) to (b-4) described above are produced by the same emulsion polymerization method as that described above for the method for producing the acrylic latex (co) polymer particles (A). be able to.

In the aqueous coating composition of the present invention, the high Tg emulsion polymer particles (B) which can be used in combination with the above-mentioned acrylic (co) polymer emulsion particles (A) as a vehicle component. Has a Tg of at least 20
What is in ° C is used. The Tg required for the polymer particles (B) is preferably adjusted according to the baking temperature of the coating film formed from the final coating composition, for example, when the baking temperature is about 60 to about 100 ° C. In the case of a coating composition for low-temperature baking, the Tg of the polymer particles (B) used is from 20 ° C to less than 60 ° C,
Conveniently, it is preferably in the range of 30 ° C. to 55 ° C., while in the case of a coating composition for high temperature baking having a baking temperature of about 110 to about 160 ° C., the polymer particles (B The Tg of) is generally at least 60 ° C, preferably at least 70 ° C, more preferably at least 85 ° C.

Thus, the monomers (b-1) to (b-4) for producing the high Tg polymer particles (B) are of the type and use of each monomer so as to satisfy the above Tg. Emulsion polymerization can be performed by selecting the ratio. The following ranges can be exemplified as the general range of the usage ratio of these monomers.

Monomer (b-1): 30 to 99.9% by weight Monomer (b-2): 0.1 to 10% by weight Monomer (b-3): 0 to 30% by weight Monomer (b -4): 0-70% by weight Note: The percentages by weight are based on the total amount of the monomers.

The suitable proportion of each monomer component depends on the use (for low-temperature baking or high-temperature baking) of the aqueous coating composition into which the high Tg polymer particles (B) to be formed are blended. , Can be selected from the following range.

(1) Used for an aqueous coating composition for low-temperature baking
For high Tg polymer particles (B):

(2) Used for aqueous coating composition for high temperature baking
For high Tg polymer particles (B):

The (co) polymer emulsion formed by emulsion polymerization of these monomers (b-1) to (b-4) generally contains high Tg polymer particles (B) as solids in an amount of 10 to 70%. %, Preferably 30 to 65% by weight, more preferably 40 to 60% by weight. The viscosity measured at 25 ° C. and 20 rpm using a B-type rotational viscometer is Usually 10,000c
Conveniently below ps, especially in the range of about 10 to about 5,000 cps.

The above emulsion is usually 2 to 10, especially 5 to
It is desirable to have a pH within the range of 9, and the pH can be adjusted using, for example, aqueous ammonia, an aqueous amine solution, or an aqueous alkali hydroxide solution.

It is desirable that the high Tg emulsion polymer particles (B) generally have a weight average molecular weight of 500,000 or more, especially 800,000 or more. Further, the average particle size of the high Tg polymer particles (B) dispersed in the formed polymer emulsion is generally in the range of 0.05 to 0.5 μm, particularly preferably in the range of 0.1 to 0.3 μm. Control of particle size of polymer particles (B) is acrylic (co) polymer emulsion particles
It can be performed in the same manner as in the control of the particle size in (A).

The aqueous coating composition of the present invention contains, as vehicle components, acrylic (co) polymer emulsion particles (A) and high Tg emulsion polymer particles (B) which are polymerized as described above. Things.

The blending amounts of the polymer emulsions (A) and (B) are determined according to the polymer particles (A) and (B) in these emulsions.
(Ie, solids) based on the total amount of
The (co) polymer emulsion particles (A) are in the range of 50-95%, preferably 55-90% by weight, more preferably 60-85% by weight, and the high Tg emulsion polymer particles (B) are in the range of 5-50%.
%, Preferably 10 to 45% by weight, more preferably 15% by weight.
It can be in the range of 4040% by weight.

The aqueous coating composition of the present invention comprises, together with the polymer fine particles comprising the acrylic (co) polymer emulsion particles (A) and the high Tg emulsion polymer particles (B),
It contains an inorganic filler. The inorganic filler is added to the composition for the purpose of an extender, adjustment of the hardness of the coating film, prevention of blister generation, and the like.In the present invention, such an inorganic filler is used as the inorganic filler. It is preferable to use one or more types containing white carbon (C).

Examples of the above-mentioned white carbon (C) which can be used in the present invention include fine powders such as silicic anhydride by a dry method, hydrous silicic acid by a wet method, and synthetic silicates; (Hereinafter, may be referred to as colloidal silica) obtained by dispersing the fine particles in water to form a colloid.

The silicic anhydride according to the above-mentioned dry method includes the following: thermal decomposition of halogenated silicic acid; air oxidation of SiO reduced by heating and reducing silica sand; thermal decomposition of organosilicon compound;
Hydrated silicic acid by the above-mentioned wet method includes pyrolysis of sodium silicate; pyrolysis of alkaline earth metal silicate; pressure decomposition of organogel; It is produced by a method of producing by-products during fertilizer production. The above synthetic silicate is a method for producing sodium silicate with a soluble salt of aluminum or calcium; a hydrothermal reaction between natural silicic acid or a silicate and a hydroxide of an alkaline earth metal; It is made of

These white carbons are generally ultrafine and bulky white powders having an average particle diameter of 200 μm or less (secondary particles) and a surface area of 10 m 2 / g or more. As dry-processed silicic acid anhydride, for example, “Reolosil GS13”, "Leolo Seal
QS102 "," Leoro Seal QS30 "," Leoro Seal QS3 "
8) (above, manufactured by Tokuyama Soda Co., Ltd.), `` Aerosil 130 '',
Aerosil 200, Aerosil 300, Aerosil 380, Aerosil OX50, Aerosil TT60
0 "," AEROSIL MOX80 "," AEROSIL MOX170 ",
"Aerosil COX84", "Aerosil R972", "Aerosil R974" (all manufactured by Nippon Aerosil Co., Ltd.);

Examples of wet-process hydrated silicic acid include, for example, "Starsil-S" (manufactured by Kamishima Chemical Industry Co., Ltd.), "Carplex # 67", "Carplex # 80", "Carplex".
# 1120 "," Carplex # 100 "," Carplex XR "," Carplex 22S "," Carplex
CS-5, Carplex CS-7, Carplex
CS-701 ”(above, manufactured by Shionogi Pharmaceutical Co., Ltd.),“ Tokushir U ”,“ Carplex UR ”,“ Carplex G ”
u "," Carplex AL-1 "," Carplex U
S '' (above, manufactured by Tokuyama Soda Co., Ltd.),

"Nip seal VN3", "Nip seal A"
Q), "Nip Seal LP", "Nip Seal ER",
"Nip Seal NS", "Nip Seal NS-P", "Nip Seal NS-T", "Nip Seal NS-K", "Nip Seal NA", "Nip Seal L300", "Nip Seal N"
300A, Nip Seal K300, Nip Seal G30
0 "," Nip seal E150K "," Nip seal E150
J, Nip seal E200, Nip seal E22
0 "," Nip Seal E220A "
Co., Ltd.), "Silton R-2", "Silton A"
Mizusawa Chemical Industry Co., Ltd.];

As synthetic silicates, for example, “STARLEX L” (manufactured by Kamishima Chemical Industry Co., Ltd.), “Silmos T”
[Manufactured by Shiroishi Kogyo Co., Ltd.], "Sorex CM", "Flolite R" (manufactured by Tokuyama Soda Co., Ltd.), "Mistron Vapor", "Cyplabond" (manufactured by Nippon Mistron
And the like.

Further, as the colloidal silica, for example,
Product names such as "Snowtex 20", "Snowtex 30" (Nissan Chemical Co., Ltd.), "Adelite AT-30", "Adelite AT-50" (all, Asahi Denka Kogyo) Can be used.

The amount of the white carbon (C) is 0.5 parts based on 100 parts by weight of the total of the acrylic (co) polymer emulsion particles (A) and the high Tg emulsion polymer particles (B).
The amount may be, for example, about 100 parts by weight, preferably about 1 to 80 parts by weight, and more preferably about 2 to 60 parts by weight. If the amount of the white carbon (C) is not less than the lower limit, when the obtained aqueous coating composition is used as an aqueous coating composition for chipping resistance, its blister limit film thickness and chipping resistance are reduced. It is preferable because there is no such thing. On the other hand, when the amount is equal to or less than the upper limit, the coating film is hard and brittle, so that there is no tendency that the chipping resistance is lowered or a normal coating film cannot be obtained.

The aqueous medium used in the aqueous coating composition of the present invention is derived from the above-mentioned emulsion, and is usually water. In some cases, water is mixed with a water-miscible organic solvent. It may be a solvent.

The aqueous coating composition of the present invention may further comprise, for example, calcium carbonate, silica, alumina, kaolin, clay, talc, diatomaceous earth, mica, water in addition to the above-mentioned white carbon (C) as an inorganic filler. Aluminum oxide,
Glass powder, barium sulfate, magnesium carbonate and the like can be contained.

The amount of these inorganic fillers can be varied in a wide range depending on the type and physical properties desired for the coating composition, but the amount of the polymer contained in the composition can be varied. The amount can be generally in the range of 100 to 390 parts by weight, preferably 120 to 380 parts by weight, more preferably 150 to 300 parts by weight, based on 100 parts by weight of the total of the fine particles (A) and (B).

The above-mentioned inorganic filler is generally about 0.5
Desirably, it has an average particle size in the range of from about 50μ, especially from about 1 to about 30μ.

The coating composition of the present invention may optionally contain
As in the ordinary coating composition, it can contain a rust preventive pigment, a coloring pigment, a crosslinking agent and the like.

Examples of the above rust-preventive pigment include lead red; metal chromate salts such as zinc chromate, barium chromate, and strontium chromate; for example, zinc phosphate, calcium phosphate, aluminum phosphate, titanium phosphate, and phosphorus phosphate. Silicon acid or metal phosphates such as ortho or condensed phosphates of these metals; for example, zinc molybdate;
Molybdate metal salts such as calcium molybdate, zinc calcium molybdate, zinc potassium molybdate, zinc potassium phosphomolybdate, potassium potassium phosphomolybdate; for example, calcium borate, zinc borate, barium borate, barium metaborate, calcium metaborate And the like. Among these rust preventive pigments, non-toxic or low-toxic rust preventive pigments such as metal phosphates, metal molybdates and metal borates are preferred.

The amount of the rust preventive pigment is, for example, in the range of 0 to 50 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the polymer fine particles in the coating composition. Can be.

Examples of the color pigment include organic or inorganic color pigments such as titanium oxide, carbon black, red iron oxide, Hansa Yellow, Benzidine Yellow, Phthalocyanine Blue, and quinacridone red. The compounding amount of these color pigments is, for example, in the range of 0 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the polymer fine particles in the coating composition.

The particle size of the rust preventive pigment and the color pigment is preferably in the range of 1 to 50 μm from the viewpoint of the smoothness of the coating film formed from the obtained coating composition.

The aqueous coating composition of the present invention may further contain, if necessary, a crosslinking agent such as a water-soluble polyvalent metal salt; an aziridine compound; a water-soluble epoxy resin; a water-soluble melamine resin; It 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; for example, magnesium acetate and magnesium formate;
Magnesium salts such as magnesium chloride, magnesium sulfate, magnesium nitrate, and magnesium nitrite;
Lead salts such as lead acetate and lead formate; 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; And copper salts such as copper nitrate and copper sulfate; and metal oxides such as zinc oxide which can be dispersed in a certain amount in a basic aqueous solution.

As the aziridine compound, a reaction product of a polyisocyanate compound and ethyleneimine can be used. As the polyisocyanate compound, for example, 1,3-
Or 1,4-phenylene diisocyanate, 2,4- or
Aromatics such as 2,6-tolylene diisocyanate, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, and 1,3-xylylene diisocyanate Polyisocyanate compound; for example, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, 1,8-octamethylene diisocyanate, 1,10-
Aliphatic polyisocyanate compounds such as decamethylene diisocyanate; for example, 1,3,1,4-cyclohexylene diisocyanate, 1-methylcyclohexane-1,3- or 1,4-diisocyanate, 4,4'-dicyclohexylmethane diisocyanate , Isophorone diisocyanate,
An alicyclic polyisocyanate compound such as 1,3-isocyanomethylcyclohexane; a dimer or trimer of these isocyanates; and a divalent or trivalent polyol such as ethylene glycol or trimethylolpropane; Can be exemplified.

Examples of the water-soluble epoxy resin include glycerol diglycidyl ether, and examples of the water-soluble melamine resin include methylol melamine; at least a part of the hydroxyl group of the methylol melamine is methyl alcohol, ethyl alcohol, or n-butyl. Examples thereof include those etherified with an alcohol or the like.

Examples of the water-dispersible blocked isocyanate include those obtained by adding a volatile low-molecular-weight active hydrogen compound to the polyisocyanate compound, such as trimethylolpropane tolylene diisocyanate methyl ethyl ketoxime adduct. Such volatile low molecular active hydrogen compounds, for example,
Aliphatic, alicyclic or aromatic alcohols such as methyl alcohol, ethyl alcohol, n-butyl alcohol, cyclohexyl alcohol, benzyl alcohol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and phenol; for example, dimethylaminoethanol, diethylaminoethanol Hydroxy tertiary amines; ketoximes such as acetoxime and methyl ethyl ketoxime; active methylene compounds such as acetylacetone, acetoacetate and malonate; lactams such as ε-caprolactam;

Among these crosslinking agents, an aziridine compound can be most preferably used from the viewpoints of storage stability of the coating material, normal state to the substrate, and adhesion after immersion in water.

The amount of the crosslinking agent used is, for example, from 0 to 10 parts by weight based on 100 parts by weight of the polymer fine particles (A) and (B) from the viewpoint of suppressing the change with time of the viscosity of the obtained coating composition. Examples thereof include an amount of about 10 parts by weight, preferably about 0.5 to 10, particularly preferably about 1 to 5 parts by weight.

The aqueous coating composition of the present invention may further contain, if necessary, an inorganic dispersant (eg, sodium hexametaphosphate, sodium tripolyphosphate, etc.) and an organic dispersant (eg, “Nobu Cospers 44C” (trade name) Dispersants such as silicone-based defoamers; silicone-based defoamers; polyvinyl alcohol, cellulose derivatives, polycarboxylic acid-based resins, surfactant-based thickeners, and viscosity improvers. Organic solvents such as ethylene glycol, butyl cellosolve, butyl carbitol, and butyl carbitol acetate; antioxidants; preservatives and fungicides; ultraviolet absorbers; antistatic agents;

The aqueous coating composition of the present invention is generally, but not limited to, about 40 to 90% by weight, preferably about 50 to 85% by weight, particularly preferably about 60 to 80% by weight. Containing solids in the range, and 7-11, preferably 8
It can have a pH in the range of 1010 and have a viscosity (in a B-type rotary viscometer, 25 ° C., 20 rpm) in the range of about 3,000-100,000 cps, preferably about 5,000-50,000 cps.

The substrate to which the aqueous coating composition of the present invention can be applied is not particularly limited. For example, a steel plate; for example, a lead-tin alloy plated steel plate (tan sheet steel plate), a tin plated steel plate, an aluminum plated steel plate And various types of plated steel plates such as lead-plated steel plates, chromium-plated steel plates, and nickel-plated steel plates; and coated steel plates such as electrodeposited coated steel plates.

The coating composition of the present invention is obtained by molding such a base material into various shapes by a sheet metal press or the like, or by welding these as various automotive members.
For example, it can be suitably used for coating an electrodeposition-coated surface, a middle-coated surface, or a top-coated surface of a sheet metal processing member outside a vehicle cabin such as a gasoline tank of an automobile, an under floor, a tire house, a front apron, and a rear apron. it can.

The coating composition of the present invention can be applied by a coating method known per se, for example, brush coating, spray coating, roller coating, etc., but airless spray coating is generally preferred.

The coating thickness at this time varies depending on the use of the substrate and the like, but is usually in the range of about 200 to 800 μm, especially about 300 to 600 μm. The coating film can be dried by natural drying, heat drying, or the like.In general, in the case of an aqueous coating composition for low-temperature baking, baking is performed in a heating furnace at a temperature of about 60 to 100 ° C. In the case of an aqueous coating composition for high-temperature baking, it is convenient to pre-dry at a temperature of about 60 to 100 ° C. and then bake in a heating furnace at a temperature of about 110 to 160 ° C. .

[0122]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples.

The preparation of test samples used in the examples and comparative examples and the test method are as follows.

(1) Preparation of Test Piece Each sample was applied to a 0.8 × 100 × 200 mm thick tongue sheet steel plate by an airless spray coating method so that the dried coating film had a predetermined thickness, and was dried by hot air circulation. Heat treatment is performed under a predetermined condition using a vessel.

(2) Limiting thickness of swelling In the spray coating in the preceding paragraph (1), coating was performed by changing the thickness of the dried coating film, and the maximum thickness without blistering during drying was determined. Thickness.

(3) In the section (1) before the adhesion test , a test piece obtained by coating so as to have a dry film thickness of about 500 μ was obtained using a Goban tester [Suga Test Machine Co., Ltd.]
And cut lines having a depth reaching the substrate at an interval of 2 mm each in the vertical and horizontal directions from the coating surface are formed, and 100 goban eyes are formed in 4 cm ² . Attach 24mm wide cellophane tape (manufactured by Nichiban Co., Ltd.)
After 180 ° peeling, the number of eyes remaining on the coating film is counted, and the result is indicated as “number of remaining coating films / 100”.

(4) Before the chipping resistance test In the section (1), a test piece obtained by coating so as to have a dry film thickness of about 500 μ was left under a constant temperature condition of about 25 ° C. for 16 hours. Stepping Stone Testing Machine [Suga Test Machine Co., Ltd.] (JASO M 104
The equivalent) using a vertically No. 6 crushed stone on specimens, after blowing 500 g × 5 times with pneumatic 5 kg / cm ^2,
A salt water spray tester (manufactured by Suga Test Instruments Co., Ltd.) sprays salt water for 72 hours in accordance with JIS Z 2371, visually observes the test pieces, and evaluates them by rusting score.

(5) Before the Water Resistance Adhesion Test In Section (1), a test piece obtained by coating so as to have a dry film thickness of about 500 μm was immersed in deionized water at about 40 ° C. for 7 days, and then taken out. After wiping off the moisture and leaving it at 25 ° C. for 3 hours, it is evaluated in the same manner as in the above (3).

(6) Low temperature impact resistance test In the item (1) before, the test piece was left under a constant temperature condition of −30 ° C. for 3 hours or more, and then subjected to a Dubon type impact resistance test at the same temperature in accordance with JIS K 5400. Do.

The conditions at this time are as follows: a radius of 6.35 ± 0.3
Attach a 3mm shooting die and cradle, sandwich the test piece with the coating surface facing upwards, and weigh a weight of 500 ± 1g to 50cm.
Of the coating film surface, and visually evaluate the degree of damage to the coating film surface according to the following evaluation criteria.

◎ ・ ・ ・ 無 し 変 化 ・ ・ ・ 微 変 化 無 し 無 し ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 無 し ・ ・ ・ 無 し ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・

The weight of the acrylic copolymer emulsion (A)
If Reference Example 1 stirrer, a 2000ml separable flask equipped with a reflux condenser and a thermometer was charged with deionized water 250 parts, were heated to 80 ° C. with a nitrogen flow. Next, 233 parts by weight of deionized water and 10 parts by weight of sodium dodecylbenzenesulfonate (ABS) are placed in another container and stirred to form a uniform aqueous solution, into which 420 parts by weight of butyl acrylate (BA) and methyl methacrylate ( A monomer mixture obtained by uniformly mixing 40 parts by weight of MMA), 25 parts by weight of acrylonitrile (AN) and 15 parts by weight of acrylic acid (AA) is dropped and stirred to form a monomer pre-emulsion. Ammonium persulfate (APS) as emulsion and aqueous solution of polymerization initiator
Then, 30 parts by weight of a 5% by weight aqueous solution of the above was continuously added over 3 hours, then kept at the same temperature for 1 hour, and 4 ml of about 25% by weight aqueous ammonia was added to obtain an acrylic copolymer emulsion.

Table 1 shows the monomer composition, the solid content, the pH, the viscosity, the particle size of the obtained copolymer emulsion, and the Tg of the copolymer particles in this polymerization.

Reference Example 2 and Comparative Reference Example 1 In Reference Example 1, instead of using 420 parts by weight of BA and 40 parts by weight of MMA, 330 parts by weight of BA and 130 parts by weight of styrene (St), or 270 parts by weight of BA and An acrylic copolymer emulsion and an acrylic / styrene copolymer emulsion were obtained in the same manner as in Reference Example 1 except that 190 parts by weight of MMA was used. Table 1 shows the monomer composition, solid content, pH, viscosity, particle size, and Tg of the copolymer particles obtained during the polymerization.

[0135]

[Table 1]

Polymerization of High Tg Polymer Emulsion (B) Reference Example 3 In Reference Example 1, 420 parts by weight of BA, 40 parts by weight of MMA, and AN
A styrene high Tg copolymer emulsion was obtained in the same manner as in Reference Example 1, except that St 485 parts by weight was used instead of 25 parts by weight. Monomer composition during this polymerization,
Table 2 shows the solid content, pH, viscosity, particle size, and Tg of the obtained copolymer emulsion.

Reference Example 4 In Reference Example 3, instead of using 485 parts by weight of St, St
435 parts by weight and 2-hydroxyethyl methacrylate (H
EMA) In the same manner as in Reference Example 3 except for using 50 parts by weight,
A styrene high Tg copolymer emulsion was obtained. Table 2 shows the monomer composition, the solid content, the pH, the viscosity, the particle size, and the Tg of the copolymer particles obtained during the polymerization.

Reference Example 5 In Reference Example 3, instead of using 485 parts by weight of St, MM was used.
An acrylic high Tg copolymer emulsion was obtained in the same manner as in Reference Example 3 except that 485 parts by weight of A was used. In this polymerization, the monomer composition, the solid content of the obtained copolymer emulsion, the pH, the viscosity, the particle size, and the T
g is shown in Table 2.

Reference Example 6 In Reference Example 3, instead of using 485 parts by weight of St, St
300 parts by weight and 2-ethylhexyl acrylate (EHA) 1
A styrene / acrylic high Tg copolymer emulsion was obtained in the same manner as in Reference Example 3 except that 85 parts by weight was used. Table 2 shows the monomer composition, the solid content, the pH, the viscosity, the particle size, and the Tg of the copolymer particles obtained during the polymerization.

Comparative Reference Example 2 In Reference Example 3, instead of using 485 parts by weight of St,
240 parts by weight and 2-ethylhexyl acrylate (EHA) 2
A styrene / acrylic copolymer emulsion was obtained in the same manner as in Reference Example 3 except that 45 parts by weight was used. In this polymerization, the monomer composition, the solid content of the obtained copolymer emulsion, the pH, the viscosity, the particle size, and the T
g is shown in Table 2.

[0141]

[Table 2]

REFERENCE EXPERIMENTAL EXAMPLE 1 140 parts by weight of the acrylic copolymer emulsion of Reference Example 1 (about 70 parts by weight of solid content) and 60 parts by weight of styrene high Tg copolymer emulsion of Reference Example 3 (about 30 parts by weight) and 2.0 parts by weight (solid content of Nobu Cospars 44C, a polycarboxylic acid type manufactured by Sannobuco) as a dispersant
0.88 parts by weight), powdered calcium carbonate as inorganic filler [“SL-700”, average particle size 4.5 μ, Takehara Chemical Industry Co., Ltd.
148 parts by weight, talc (“P-talc”, average particle size 12
μ, manufactured by Tsuchiya Kaolin Industries, Ltd.), 70 parts by weight, 3 parts by weight of carbon black and 12 parts by weight of barium metaborate are uniformly dispersed using a Tispar, and then “Adecanol UH-472” [Asahi Denka (Manufactured by K.K.) 0.5 parts by weight and further agitated, and the proportion of the total pigment (total amount of powdered calcium carbonate, talc, carbon black and barium metaborate) in the coating film (hereinafter abbreviated as PWC) ) At 70% by weight and a solid content of 76.7% by weight.

Various physical property tests were performed using the obtained aqueous coating composition. Table 3 shows the composition of the composition, and Table 4 shows the measurement results of the properties and various physical properties of the composition. The coating film is baked at a high temperature using a hot air circulating dryer (preliminary drying at 80 ° C for 15 minutes, and then baking at 110 ° C for 20 minutes).
Was done.

Comparative Example 1 In Reference Experimental Example 1 , 140 parts by weight of the acrylic copolymer emulsion of Reference Example 1 (about 70 parts by weight in solid content) and 60 parts by weight of the styrene high Tg copolymer emulsion of Reference Example 3 (30 parts by weight solids) Instead of using 200 parts by weight of the acrylic copolymer emulsion of Reference Example 1 (about 100 parts by weight of solids), the styrene high Tg of Reference Example 3 was used.
Reference experiment example 1 except that no copolymer emulsion was used
In the same manner as described above, a chipping-resistant aqueous coating composition having a PWC of 70% by weight was prepared.

Using the obtained aqueous coating composition as a reference material,
Various physical property tests were performed in the same manner as in Test Example 1 . Table 3 shows the composition of the composition, and Table 4 shows the measurement results of the properties and various physical properties of the composition.

Reference Experimental Example 2 and Comparative Example 2 In Reference Experimental Example 1 , except that the acrylic copolymer emulsion of Reference Example 2 or Comparative Reference Example 1 was used instead of using the acrylic copolymer emulsion of Reference Example 1. In substantially the same manner as in Reference Example 1 , a chipping-resistant aqueous coating composition having a PWC of 70% by weight was prepared.

[0147] Using the obtained aqueous coating composition, reference real
Test pieces were prepared in the same manner as in Test Example 1, and various physical property tests were performed. Table 3 shows the composition of the composition, and Table 4 shows the measurement results of the properties and various physical properties of the composition.

Reference Experimental Examples 3 and 4 In Reference Experimental Example 1 , instead of using the styrene high Tg copolymer emulsion of Reference Example 3, the styrene high Tg copolymer emulsion of Reference Example 4 or the acrylic ginseng except for using the system high Tg copolymer emulsion
A chipping resistant aqueous coating composition having a PWC of 70% by weight was prepared in substantially the same manner as in Experimental Example 1 .

[0149] Using the obtained aqueous coating composition, reference real
Test pieces were prepared in the same manner as in Test Example 1, and various physical property tests were performed. Table 3 shows the composition of the composition, and Table 4 shows the measurement results of the properties and various physical properties of the composition.

[0150] In Reference Experiment Example 5 Reference Example 1, except further using aziridine compound "SU-125F" 4 parts by weight [Meisei Chemical Co., Ltd.] (about 1 part by weight solids) as a crosslinking agent by reference In substantially the same manner as in Experimental Example 1 , a chipping-resistant aqueous coating composition containing 70% by weight of PWC was prepared.

[0151] Using the obtained aqueous coating composition, reference real
Test pieces were prepared in the same manner as in Test Example 1, and various physical property tests were performed. Table 3 shows the composition of the composition, and Table 4 shows the measurement results of the properties and various physical properties of the composition.

Examples 1 and 2 In Reference Example 1 , powdered calcium carbonate “SL-700” was used.
Instead of using 148 parts by weight, “SL-700” 145 parts by weight and white carbon (colloidal silica) “Adelite”
AT-30 "(manufactured by Asahi Denka Kogyo Co., Ltd.) 10 parts by weight (solid content: approx. 3
Parts by weight) or “SL-700” 138 parts by weight and white carbon “Nipsil E-200A” [Nippon Silica Industry Co., Ltd.
Production of a chipping-resistant aqueous coating composition having a PWC of 70% by weight in substantially the same manner as in Reference Example 1 except that 10 parts by weight was used.

[0153] Using the obtained aqueous coating composition, reference real
Test pieces were prepared in the same manner as in Test Example 1, and various physical property tests were performed. Table 3 shows the composition of the composition, and Table 4 shows the measurement results of the properties and various physical properties of the composition.

[0154] In Example 3 Example 2, except that further use of the aziridine compound "SU-125F" 4 parts by weight (about 1 part by weight solids) as a crosslinking agent in much the same way as in Example 2, PWC 70 A weight percent of a chipping resistant aqueous coating composition was prepared.

[0155] Using the obtained aqueous coating composition, reference real
Test pieces were prepared in the same manner as in Test Example 1, and various physical property tests were performed. Table 3 shows the composition of the composition, and Table 4 shows the measurement results of the properties and various physical properties of the composition.

[0156] In Reference Example 6 Reference Example 1, instead of using the styrene-based high Tg copolymer emulsion of Reference Example 3, except for using styrene-acrylic high Tg copolymer emulsion of Reference Example 6 Reference Experiment 70% by weight of PWC in almost the same manner as in Example 1.
Was prepared.

Various physical properties tests were performed using the obtained aqueous coating composition. Table 3 shows the composition of the composition, and Table 4 shows the measurement results of the properties and various physical properties of the composition. The coating film was subjected to a low-temperature baking treatment (baking at 80 ° C. for 30 minutes) using a hot-air circulation dryer.

[0158] In Comparative Example 3 Reference Example 6, instead of using a styrene-acrylic high Tg copolymer emulsion of Reference Example 6, except for using styrene-acrylic copolymer emulsion of Comparative Example 2 Reference Experiment In almost the same way as in Example 6 , the PWC
A 70% by weight chipping-resistant aqueous coating composition was prepared.

[0159] Using the obtained aqueous coating composition, reference real
Test pieces were prepared in the same manner as in Test Example 6, and various physical property tests were performed. Table 3 shows the composition of the composition, and Table 4 shows the measurement results of the properties and various physical properties of the composition.

[0160] Reference in Experimental Example 7 Reference Example 6, except for using further 4 parts by weight aziridine compound "SU-125F" as the crosslinking agent (from about 1 part by weight solid content) in substantially the same manner as in Reference Example 6, PWC is 70
A weight percent of a chipping resistant aqueous coating composition was prepared.

[0161] Using the obtained aqueous coating composition, reference real
Test pieces were prepared in the same manner as in Test Example 6, and various physical property tests were performed. Table 3 shows the composition of the composition, and Table 4 shows the measurement results of the properties and various physical properties of the composition.

Reference Experimental Example 8 In Reference Experimental Example 6 , powdered calcium carbonate “SL-700” was used.
Instead of using 148 parts by weight, “SL-700” 145 parts by weight and white carbon (colloidal silica) “Adelite”
AT-30 ”except that 10 parts by weight (about 3 parts by weight of solid content) is used.
In substantially the same manner as in Reference Experimental Example 4 , a chipping-resistant aqueous coating composition having a PWC of 70% by weight was prepared.

[0163] Using the obtained aqueous coating composition, reference real
Test pieces were prepared in the same manner as in Test Example 6, and various physical property tests were performed. Table 3 shows the composition of the composition, and Table 4 shows the measurement results of the properties and various physical properties of the composition.

[0164]

[Table 3]

[0165]

[Table 4]

[0166]

The aqueous coating composition of the present invention contains specific acrylic (co) polymer emulsion particles (A) and high Tg emulsion polymer particles (B) as a vehicle component in a specific amount as essential components. By using the aqueous resin dispersion, excellent physical properties that cannot be achieved by using an ordinary acrylic copolymer emulsion, that is,

As a coating composition for chipping resistance such as chipping resistance, excellent adhesion to metal processing members, flat and uniform coating film formation, water resistance, gasoline resistance, low-temperature impact resistance, and soundproofing properties. It is an excellent aqueous coating composition which has the above properties in a well-balanced manner and does not cause inconveniences such as blisters in the drying step even when an extremely thick coating film of, for example, 600 μm or more is formed.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Serizawa 1-37-41 Hanasaki, Kazo City, Saitama Prefecture (56) References JP-A-56-116759 (JP, A) JP-A-2-32171 (JP, A) JP-A-5-112758 (JP, A) JP-A-60-161465 (JP, A) JP-A-5-179092 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 133/04 C09D 5/00 C09D 125/00

Claims (1)

(57) [Claims] An aqueous coating composition comprising polymer fine particles dispersed in an aqueous medium and an inorganic filler, wherein the polymer fine particles are each independently represented by the following (A) and
(B), (A) The following general formula (2) (Meth) acrylic acid ester represented by the formula (wherein, R ³ is
H or a methyl group, R ⁴ is a straight chain having 1 to 20 carbon atoms or
Acrylonitrile-free acrylic (co) polymer emulsion particles having an acrylonitrile content of 30 to 99.9% by weight ( showing a branched alkyl group) of 50 to 95% by weight, and (B) Formula (1), (Wherein, R ¹ is H or a methyl group, Q is —COOR ² ,
Number 6-12 aryl group carbon or -CN, R ² is at least 60 ° C. glass transition temperature containing 30 to 99.9 weight percent of repeating units represented by the carbon atoms represent more than 6 lower alkyl group), 5 to 50% by weight of emulsion polymer particles , wherein the inorganic filler is at least polymer fine particles.
White based on a total of 100 parts by weight of the children (A) and (B)
Characterized by comprising 0.5 to 100 parts by weight of carbon
Chipping resistance for sheet metal processed parts subjected to high-temperature baking
Water- soluble coating composition.