JP3295484B2 - 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 having water resistance, adhesion, weather resistance, and excellent rust and corrosion resistance and used as a paint or an adhesive.

[0002]

2. Description of the Related Art An aqueous coating composition of this type includes, for example, a silyl group-containing vinyl monomer substituted with an alkoxyl group in the presence of a water-soluble copolymer containing a tertiary amino group-containing vinyl monomer. A polymer obtained by emulsion polymerization of another vinyl monomer is disclosed (JP-A-60-127376).
issue). In the above aqueous coating composition, the silyl group substituted by the alkoxyl group contained in the copolymer hydrolyzes to form a crosslinked chain by a siloxane bond, and a coating film having excellent water resistance and chemical resistance is obtained. .

[0003]

However, in the above-mentioned conventional aqueous coating composition, the crosslinking reaction is not sufficient and curing at a low temperature for a short time does not provide satisfactory coating performance. For example, rust prevention and corrosion prevention for metals, weather resistance and freeze-thaw resistance for exterior materials, and physical properties such as flexibility and adhesion for plastic films are particularly important. Currently, aqueous coating compositions that satisfy these various properties are Not provided.

[0004]

According to the present invention, there is provided, as a means for solving the above-mentioned conventional problems, an emulsion of a polymer A containing a phosphoric acid group in a molecule and at least one hydrolyzable polymer in a molecule. It comprises a compound B having a silyl group and an epoxy group, and the compound B is converted into a hydrolyzate or a partial hydrolyzate to form an emulsion of the polymer A.
The present invention provides an aqueous coating composition which is water-dilutable in water.

[Polymer A Containing Phosphate Group in Molecule] The polymer A containing a phosphate group in a molecule used in the present invention is a polymerizable monomer having a phosphoric acid group in a molecule. Is a copolymer of a monomer (phosphate group-containing monomer) and another polymerizable monomer copolymerizable with the monomer, wherein the phosphate group-containing monomer is the copolymer 1 to 30% by weight, preferably 1
-10% by weight. As the phosphate group-containing monomer, for example,

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Embedded image Alternatively, a reaction product of phosphoric acid and a compound having an epoxy group such as glycidyl methacrylate, allyl glycidyl ether, and phosphoric acid

Embedded image And a reactant. Two or more of the above phosphate group-containing monomers may be used in combination.

Other monomers copolymerizable with the above-mentioned phosphoric acid group-containing monomer include, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, tetrahydro acrylate Furfuryl acrylate, methyl methacrylate, ethyl methacrylate, n-
Butyl methacrylate, iso-butyl methacrylate, 2-
Ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, n-butyl vinyl ether, iso-butyl vinyl ether, styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl chloride, chloride Vinylidene, vinyl fluoride, vinylidene fluoride, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, allyl alcohol, glycidyl acrylate, glycidyl methacrylate, glycidyl allyl ether, acrylic acid, Methacrylic acid, itaconic acid, crotonic acid, maleic acid, maleic anhydride,
Citraconic acid, acrylamide, methacrylamide, N
-Vinyl monomers such as methylolacrylamide and N-methylolmethacrylamide. Two or more of the above monomers may be used in combination.

The phosphate group-containing polymer A of the present invention can be obtained by solution polymerization or emulsion polymerization of a mixture of the above-mentioned phosphate group-containing monomer and the above other monomer. A normal water-soluble solvent can be used, and as the water-soluble solvent, for example, methanol,
Ethanol, alcohols such as isopropanol, acetone, ketones such as methyl ethyl ketone, ethylene glycol monoethyl ether, glycol ethers such as ethylene glycol monobutyl ether, tetrahydrofuran, one or more kinds of dioxane, or one or more of the above water-soluble organic solvents. There is a mixed solvent of one or more kinds and a small amount of water, and the polymerization initiator includes benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, azobisisobutyronitrile, azobisdimethylvaleronitrile, etc. Oil-soluble initiators.

In the emulsion polymerization, any of ordinary anionic, nonionic and cationic surfactants is used. Examples of the anionic surfactant include higher alcohol sulfate (Na salt or amine salt), alkyl allyl sulfone Acid salts (Na salts), alkyl naphthalene sulfonates, alkyl naphthalene sulfonate condensates, alkyl phosphates, dialkyl sulfosuccinates, rosin soaps, and the like. Nonionic surfactants include polyoxyethylene alkyl ether, Polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, polyoxyethylene alkylamine, polyoxyethylene alkyl amide,
There are sorbitan alkyl ester, polyoxyethylene sorbitan alkyl ester and the like, and as the cationic surfactant, there are trimethylaminoethylalkylamide halogenide, alkylpyridinium sulfate, alkyltrimethylammonium halogenide and the like. In addition to the above surfactants, for example, surfactants having the following general formula (manufactured by Kao Soap Co., Ltd., trade name: Ramtell S-120, 120)
A, 180, 180A)

Embedded image Where R is a C ₁₂ or C ₁₃ alkyl group, M is Na, N
H ₄ . Alternatively, a surfactant having the following general formula (manufactured by Sanyo Chemical Co., Ltd .: trade name Eleminor JS-2)

Embedded image Alternatively, a surfactant having the following general formula (manufactured by Daiichi Kogyo Seiyaku Co., Ltd .: trade name Aqualon HS-10)

Embedded image Reactive surfactants having a vinyl group such as are desirable for the present invention. Since the reactive surfactant copolymerizes with the monomer mixture, it hardly affects the water resistance of the obtained copolymer composition. Then, two or more surfactants may be mixed.

Examples of the polymerization initiator used in the emulsion polymerization of the present invention include water-soluble inorganic initiators such as ammonium persulfate, potassium persulfate, sodium persulfate and sodium perborate, and 2,2′-azobis (2-methyl Propionamidine) dihydrochloride, 2,2'-azobis (2-
Redox initiation using a water-soluble organic initiator such as methyl-N-phenylpropionamidine) dihydrochloride, or a combination of the above inorganic or organic initiator and a reducing agent such as sodium sulfite, sodium bisulfite, sodium hyposulfite, and ascorbic acid. An agent system is exemplified. The above examples do not limit the present invention.

The above-mentioned monomer mixture obtained by mixing a phosphoric acid group-containing monomer with another monomer is subjected to emulsion polymerization in an aqueous solution in which the above-mentioned surfactant is dissolved, using the above-mentioned polymerization initiator. The concentration of the monomer mixture in the emulsion polymerization is usually about 20 to 60% by weight, and the polymerization initiator is usually 0.01 to 5% by weight based on the monomer mixture.
% By weight, and the polymerization temperature is usually from normal temperature to about 90 ° C. The polymerization is performed in an inert gas atmosphere such as nitrogen gas, if desired.

[Compound B having a hydrolyzable silyl group and an epoxy group] As the compound B having at least one hydrolyzable silyl group and an epoxy group in one molecule, for example,

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Embedded image These can be made into a hydrolyzate or a partial hydrolyzate with a specific catalyst, so that they can be diluted with water. Also, other than the above silane compound, for example, Here _{R: CH 3, C 2 H} 5 CH 2 = CHSiCl 3 CH 2 = CHSi (OC 2 H 4 OCH 3) 3 CH 2 = CHSi (OC 2 H 5) 3 CH 2 = CHSi (OCH 3) 3 CH ₂ = C (CH ₃ ) COOC ₃ H ₆ Si (OCH ₃ ) ₃ H ₂ NC ₂ H ₄ NHC ₃ H ₆ Si (OCH ₃ ) ₃ HSC ₃ H ₆ Si (OCH ₃ ) ₃ Compound B having a hydrolyzable silyl group and an epoxy group in the molecule can also be synthesized by condensing in the presence of the above-mentioned hydrolyzable silyl group and a silane compound having an epoxy group.
As the catalyst for the synthesis reaction, known catalysts such as acids such as hydrochloric acid and acetic acid, organic tins such as dioctyltin malate and dibutyltin dilaurate, and aluminum chelating agents such as aluminum acetylacetone and ethyl aluminum acetoacetate can be used.

[Formulation] The compound B is 1 to 100% by weight based on the polymer A,
Desirably, about 5 to 50% by weight is mixed. The mixing ratio of the compound B is preferably within this range in terms of the balance of various physical properties, but the present invention is not limited thereto.

[Coating] The coating composition of the present invention thus obtained is coated on a substrate by a usual coating method such as spraying, roll coater, flow coater, spin coating, dipping, etc., and the coating thickness is 1 μm. Painted to about 100 μm as desired. The coating film obtained by the above coating is crosslinked even at room temperature drying, but it is also possible to shorten the curing time by forcibly drying by heating.

[0014]

The coating composition of the present invention is water-dilutable, can minimize the use of organic solvents, and eliminates problems such as toxicity and flammability of organic solvents. When the coating composition of the present invention is coated on a substrate, a ring-opening reaction between a phosphoric acid group of polymer A and an epoxy group of compound B in the coating film, or phosphoric acid acts as a catalyst to form a polymer in compound B An ether reaction occurs, which imparts flexibility to the coating. It is known that phosphoric acid imparts adhesion to metal-based substrates.However, phosphoric acid simultaneously acts as a curing catalyst for siloxane bonds of hydrolyzable silyl groups, and is thus obtained. The resulting coating film is strongly crosslinked at room temperature, and becomes a coating film having excellent adhesion, flexibility, weather resistance and the like.

[0015]

【Example】

Example 1 (Production of Copolymer A Having Phosphate Group) 200 parts by weight of isopropyl alcohol (hereinafter simply referred to as "parts") was charged into a reactor equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet tube. To 80 ° C. To a dropping funnel prepared separately, 40 parts of methyl methacrylate, 2-
Hydroxyethyl methacrylate 25 parts, Phosmer M
(Product name: acid phosphoxyethyl methacrylate manufactured by Unichemical Co., Ltd.) 20 parts, butyl acrylate 15
Of azobisisobutyronitrile and 0.5 part of azobisisobutyronitrile is added dropwise to the reactor over 2 hours. After 1 hour, 0.1 part of azobisisobutyronitrile was added to methyl ethyl ketone 3
A solution dissolved in 0 parts was added and reacted at 80 ° C. for 5 hours. The solution polymer thus obtained has a solid content of 3
It was a 0.3% by weight (hereinafter simply referred to as%) colorless and transparent resin liquid. Next, 16.2 parts of dimethylethanolamine,
233 parts of ion-exchanged water was added, and the organic solvent was removed by azeotropic distillation over 2 hours to obtain a milky white copolymer solution having a solid content of 30%. This solution is referred to as copolymer I.

Example 2 (Production of Copolymer A Having Phosphate Group) Using the same equipment as in Example 1, 100
The portion was charged and heated to 80 ° C. while replacing with nitrogen. Separately, 80 parts of methyl methacrylate, 50 parts of butyl acrylate
Part, Phosmer M10 parts, ion-exchanged water 170 parts, Aqualon HS-10 (Daiichi Kogyo Seiyaku Co., Ltd .: anionic reactive surfactant) 2 parts, and potassium persulfate 0.5 part with a homogenizer to emulsify a monomer emulsion. After dropwise addition over 2 hours, the mixture was kept at 85 ° C. for 3 hours to obtain a milky white copolymer emulsion having a solid content of 40%. This emulsion is designated as copolymer II.

Example 3 (Production of Compound B Having Hydrolyzable Silyl Group and Epoxy Group) A 500 ml flask was charged with 100 parts of γ-glycidoxypropyltrimethoxysilane and 100 parts of ion-exchanged water, and acetic acid was added. 0.001 g was added, and the mixture was reacted for 5 hours while controlling the internal temperature at 10 ° C. to obtain a partial hydrolyzate of the γ-glycidoxypropyltrimethoxysilane. This partial hydrolyzate is referred to as compound III.

Example 4 (Preparation of Compound B Having Hydrolyzable Silyl Group and Epoxy Group) 50 g of δ-glycidoxybutyltrimethoxysilane is placed in a 500 ml flask. Was synthesized according to the same operation as in Example 3 except that the weight of the compound was changed to 50 g. The compound thus obtained is converted into a compound
IV.

Comparative Example 1 (Production of Comparative Copolymer V) A colorless and transparent polymer having a solid content of 30% was polymerized according to the same formulation and operation as in Example 1, except that phosmer M was changed to 10 parts of methacrylic acid. Comparative copolymer V, which was a copolymer solution, was obtained.

Comparative Example 2 (Production of Comparative Copolymer VI) A milky white copolymer having a solid content of 40% was polymerized according to the same blending and operation as in Example 2 except that phosmer M was changed to 10 parts of methacrylic acid. Comparative copolymer VI, which was a combined emulsion, was obtained.

[Comparative Example 3] (Production of Comparative Compound VII) Is used as Comparative Compound VII, except that 50 g of CH ₂ ＝ CHSi (OCH ₃ ) ₃ and 50 g of CH ₂ ＣＨCHSi (OCH ₃ ) ₃ are used.

Samples were prepared from the copolymers or compounds obtained in Examples 1 to 4 and Comparative Examples 1 to 3 according to the formulations shown in Table 1, and the samples were sprayed onto a polished mild steel plate to a thickness of 30 μm. The test results of various physical properties after coating as described above, forcibly drying at 110 ° C. for 30 minutes, and then allowing to stand at room temperature for one week are shown.

[Table 1] Gel fraction: The coating film formed on the Teflon plate was peeled off, and was subjected to an ultrasonic machine in acetone for 30 minutes to calculate the proportion (% by weight) of an insoluble portion. Adhesion: Cross-cut cellophane tape peel test Water resistance: 40 ° C.-72 hours Salt spray resistance: Test result after 120 hours according to JIS-K5400 Numerical values are maximum peeling width on one side after test Impact resistance: 500 g load by DuPont method Result of impact test at a height of 50 cm at a temperature Cold repetition test: (−20 ° C .: 2 hours / 50 ° C .: 2 hours) as one cycle Weather resistance: Sunshine weather meter

According to Table 1, Samples 1 and 2 prepared with the aqueous coating composition of the present invention had good gel fraction, adhesion, water resistance, salt spray resistance, impact resistance, cold repetition, and weather resistance. In Comparative Samples 2, 3 and 4 using Comparative Copolymers V and VI in which the phosphate group was replaced with methacrylic acid, even when a compound having an epoxy group and a hydrolyzable silyl group was used. Comparative compound VII having only a hydrolyzable silyl group having no epoxy group even when a copolymer having a phosphate group was used, as can be seen from Comparative sample 1.
Is also poor in physical properties.

[0024]

Accordingly, in the present invention, the use of an aqueous coating composition having no danger of toxicity, flammability, etc., allows the use of an aqueous coating composition,
A coating film having good water resistance, salt spray resistance, flexibility and weather resistance can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C09D 185/02

Claims (1)

(57) [Claims] 1. An emulsion of a polymer A containing a phosphoric acid group in a molecule, and a compound B having at least one hydrolyzable silyl group and an epoxy group in a molecule,
An aqueous coating composition characterized in that the compound B is made into a hydrolyzate or a partial hydrolyzate so that it can be diluted with water in an emulsion of the polymer A.