JP2018172504A - Aqueous coating material composition and coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous rustproof coating material composition which achieves excellent oil level suitability and initial water resistance, and shows an extremely small amount of formaldehyde emission to the air.SOLUTION: An aqueous coating material composition contains a water-dispersible resin, a rustproof pigment and water, where the water-dispersible resin is a resin having a weight average molecular weight of 5,000-300,000, and containing a first monomer having a polymerizable unsaturated group and a non-aromatic hydrocarbon group that is a group other the polymerizable unsaturated group and has 4 or more carbon atoms, and at least one second monomer having a polymerizable unsaturated group as repeating units, and a content of the first monomer-derived repeating unit in a non-volatile content of the aqueous coating material composition is 3-37 mass%.SELECTED DRAWING: None

Description

  The present invention relates to a water-based coating composition and a coating method using the water-based coating composition, and in particular, an aqueous solution that achieves both excellent oil surface suitability and initial water resistance, and extremely low formaldehyde emission to the atmosphere. The present invention relates to a rust preventive coating composition.

  Conventionally, organic solvent-based anti-rust paints have been used for coating steel surfaces.However, in recent years, from the viewpoint of environmental protection and work environment improvement, organic solvent-based paints are shifting to water-based paints. Various studies have been conducted on the anticorrosion paint to be applied. For example, International Publication No. 2013/140953 (Patent Document 1) proposes an aqueous epoxy resin coating composition having excellent corrosion resistance.

  However, since water and oil are incompatible, there are problems such as poor appearance and reduced adhesion due to repelling when the steel surface with oils on the surface is coated with water-based paint. Water-based paints that are excellent in adhesion to the surface of a base material to which oil has adhered have been studied.

  Japanese Patent Application Laid-Open No. 7-41702 (Patent Document 2) discloses an aqueous copolymer resin emulsion, a rust preventive pigment, a hydrophilic organic solvent, a thickener, a dispersant, a wetting agent, and an antifoaming agent in a specific ratio. Recycled oil surface rust preventive water-based resin paint composition is described, which enables direct coating on the surface of metal bases with complicated shapes to which oils are attached. It is said that it is possible to provide a water-based coating composition that is promptly spilled, free from cracks and repellency, has a good edge cover, is excellent in rust prevention, and has good water resistance.

JP-A-2001-181557 (Patent Document 3) discloses (a) CH ₂ = CRCOO (C _n H _2n COO) _m —H [wherein, R represents a hydrogen atom or a methyl group, and n represents 2 The integer of -10 is shown, m shows the integer of 1-5. ] (B) (i) a monomer having two or more α, β-ethylenically unsaturated groups in the molecule, and (ii) a reactivity with a carboxyl group One or more monomers selected from the group consisting of an ethylenically unsaturated monomer containing a functional group, and (iii) an ethylenically unsaturated monomer containing an alkoxysilyl group, and (c) the above Unlike the monomers (a) and (b), it contains an emulsion resin obtained by emulsion polymerization of an ethylenically unsaturated monomer copolymerizable therewith at a specific ratio as a binder. A water-based paint composition is described, which makes it possible to add oil level adhesion, blocking resistance, water resistance with little addition of VOC, which is a source of environmental pollution and odor generation, and even if it is used. Water-based paint assembly that forms a coating with excellent properties It is set to be able to provide goods.

  Japanese Patent Application Laid-Open No. 2013-209447 (Patent Document 4) is selected from the group consisting of alkyd resins, drying oils, semi-drying oils and fats and oils composed of these fatty acids, and processed fats and oils using the fats and oils as main raw materials. An aqueous resin comprising an aqueous resin obtained by reacting a polymerizable vinyl monomer at a specific ratio with one or more reaction components, and having an oil length of 20 to 70 A resin composition is described, whereby a normally dry aqueous rust preventive paint composition capable of forming a rust preventive paint film that is not only dry dry water but also excellent in oil surface adhesion and paint film properties. You can offer things.

International Publication No. 2013/140953 JP 7-41702 A JP 2001-181557 A JP 2013-209447 A

  The coating composition described in Patent Document 2, for example, when the oil adhering to the steel surface is a relatively hydrophilic oil, is familiar with the oil, but for example to the surface of the fragile black skin remaining steel Adhesion was insufficient and it was difficult to perform sufficient coating. Further, the coating composition described in Patent Document 3 also has adhesion to, for example, a metal substrate surface that is insufficiently degreased, but sufficient coating is applied to the fragile black skin remaining steel material surface. It was difficult to do. As described above, the coating compositions described in Patent Documents 2 to 3 are not applicable to base materials that require high oil surface suitability such as fragile black skin residual steel.

  On the other hand, the coating composition prepared from the resin composition described in Patent Document 4 realizes excellent oil surface suitability that can be applied to fragile black skin remaining steel materials and the like. However, since the water-based resin used in Patent Document 4 has an alkyd site derived from a reactive portion such as an alkyd resin in the resin skeleton, it takes time to completely cure the coating film, and the water resistance during that time is poor. There was a problem that the amount of formaldehyde released into the atmosphere was large.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art and provide an aqueous rust-preventive coating composition that achieves both excellent oil surface suitability and initial water resistance and extremely low formaldehyde emission into the atmosphere. There is to do. Another object of the present invention is to provide a coating method capable of forming a coating film that has both excellent oil surface suitability and initial water resistance and has an extremely small amount of formaldehyde emission to the atmosphere.

  As a result of intensive studies to achieve the above object, the present inventor determined a specific weight average molecular weight obtained from a polymerizable unsaturated monomer having a non-aromatic hydrocarbon group having 4 or more carbon atoms and another monomer. It has been found that a water-based coating composition having excellent oil surface suitability can be provided by blending a copolymer having such a content that the content of repeating units derived from the polymerizable unsaturated monomer in the nonvolatile content is a specific ratio. The present invention has been completed. In addition, a copolymer of a polymerizable unsaturated monomer having a non-aromatic hydrocarbon group having 4 or more carbon atoms and another monomer does not need to have a resin skeleton such as an alkyd resin. It has excellent water resistance and can suppress the amount of formaldehyde emitted into the atmosphere.

That is, the aqueous coating composition of the present invention is an aqueous coating composition containing a water-dispersible resin, a rust preventive pigment and water,
The water dispersible resin is a resin having a weight average molecular weight of 5,000 to 300,000, and is a group other than the polymerizable unsaturated group and the polymerizable unsaturated group, and has 4 or more carbon atoms. A resin comprising as a repeating unit a first monomer having a non-aromatic hydrocarbon group and at least one second monomer having a polymerizable unsaturated group;
Content of the repeating unit derived from the 1st monomer in the non volatile matter of the said water-based coating composition is 3-37 mass%, It is characterized by the above-mentioned.

  In the suitable example of the water-based coating composition of this invention, the pigment volume concentration in the said non-volatile content is 30-65 volume%.

In another preferred embodiment of the aqueous coating composition of the present invention, the viscosity at a shear rate of 0.1 s ⁻¹ is 50 to 200 Pa · s, and the viscosity at a shear rate of 1,000 s ⁻¹ is 0.2 to ¹ Pa · s. s.

  In another preferred embodiment of the aqueous coating composition of the present invention, the water-dispersible resin has a 50 volume% particle diameter (D50) in the range of 50 to 300 nm.

  In another preferred embodiment of the aqueous coating composition of the present invention, the water-dispersible resin has a weight average molecular weight in the range of 5,000 to 200,000.

  In another preferred embodiment of the aqueous coating composition of the present invention, the water-dispersible resin has a glass transition temperature in the range of −50 to 40 ° C.

In another preferred embodiment of the aqueous coating composition of the present invention, the first monomer includes a monomer (a) in which the non-aromatic hydrocarbon group has 6 or more carbon atoms,
The content of the repeating unit derived from the monomer (a) in the nonvolatile content is 1 to 30% by mass.

  Moreover, the coating method of this invention is characterized by including the process of coating the base material which oil adhered to the surface with said aqueous coating composition, and forming a coating film.

  According to the aqueous coating composition of the present invention, it is possible to provide an aqueous rust preventive coating composition that achieves both excellent oil surface suitability and initial water resistance, and has an extremely small amount of formaldehyde emitted to the atmosphere.

  In addition, according to the coating method of the present invention, it is possible to provide a coating method capable of forming a coating film having both excellent oil surface suitability and initial water resistance and an extremely small amount of formaldehyde emission to the atmosphere. .

  Hereinafter, the aqueous coating composition of the present invention (hereinafter, also simply referred to as the coating composition of the present invention) will be described in detail. The coating composition of the present invention is an aqueous coating composition containing a water-dispersible resin, a rust preventive pigment, and water, and the water-dispersible resin is a resin having a weight average molecular weight of 5,000 to 300,000. A first monomer having a polymerizable unsaturated group and a group other than the polymerizable unsaturated group and a non-aromatic hydrocarbon group having 4 or more carbon atoms, and a polymerizable unsaturated group It is a resin containing at least one second monomer as a repeating unit, and the content of the repeating unit derived from the first monomer in the nonvolatile content of the aqueous coating composition is 3 to 37% by mass. And

  In the coating composition of the present invention, the water-dispersible resin is a resin that can be distributed in water to form a heterogeneous system (for example, an emulsion or a suspension), and the polymerizable unsaturated group and the polymerizable resin. A first monomer having a group other than an unsaturated group and having a non-aromatic hydrocarbon group having 4 or more carbon atoms and at least one second monomer having a polymerizable unsaturated group are repeated. It is a resin included as a unit. In the coating composition of the present invention, excellent oil surface suitability is obtained by blending a water-dispersible resin so that the content of the repeating unit derived from the first monomer is included in the nonvolatile content at a specific ratio. Can be demonstrated. In addition, the water-dispersible resin can exhibit excellent oil surface suitability without having a resin skeleton like an alkyd resin, so that both excellent oil surface suitability and initial water resistance can be achieved, It is also possible to reduce formaldehyde emission into the atmosphere.

  The water-dispersible resin includes a first monomer having a polymerizable unsaturated group and a non-aromatic hydrocarbon group having 4 or more carbon atoms other than the polymerizable unsaturated group as a repeating unit. This improves oil surface suitability.

  Here, the “polymerizable unsaturated group” is an unsaturated group that causes a polymerization reaction, and examples thereof include a carbon-carbon double bond constituting an acryloyl group, a methacryloyl group, a vinyl group, or an allyl group. The “monomer having a polymerizable unsaturated group” is a monomer that causes a polymerization reaction via the polymerizable unsaturated group.

  The “non-aromatic hydrocarbon group” is a hydrocarbon group having no aromatic ring, and examples thereof include a linear or branched hydrocarbon group and a cyclic hydrocarbon group. In addition, a carbon group composed of a combination of a straight chain, a branched chain and a ring structure, such as a hydrocarbon group whose ring structure is bonded to a straight chain or a branched chain, or a hydrocarbon group whose linear or branched chain is bonded to a ring structure. A hydrogen group is also included. In the present invention, the “non-aromatic hydrocarbon group” is a group other than the polymerizable unsaturated group.

  In the coating composition of the present invention, when the number of carbon atoms of the “non-aromatic hydrocarbon group” of the first monomer constituting the water-dispersible resin is 4 or more, an effect of improving oil surface suitability can be obtained. From the viewpoint of improving the oil surface suitability, the “non-aromatic hydrocarbon group” preferably has 6 or more carbon atoms, more preferably 9 or more. On the other hand, the upper limit of the carbon number of the “non-aromatic hydrocarbon group” is not particularly limited, but from the viewpoint of coating film hardness (blocking resistance), the carbon number of the “non-aromatic hydrocarbon group” is preferably 18 or less. 16 or less is more preferable.

  In the present invention, specific examples of the “non-aromatic hydrocarbon group” include n-butyl, isobutyl, t-butyl, cyclohexyl, methylcyclohexyl, ethylcyclohexyl, cycloheptyl, n-heptyl, n-octyl, 2-ethylhexyl. , Nonyl, decyl, lauryl, cetyl, stearyl and the like. The first monomer may have one or more of these “non-aromatic hydrocarbon groups”.

  Specific examples of the first monomer include n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, ethylcyclohexyl (meth) ) Acrylate, cycloheptyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) Examples include acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, and the like. In addition, the said 1st monomer may be used individually by 1 type, and may be used in combination of 2 or more type.

In the coating composition of this invention, content of the repeating unit derived from the 1st monomer in a non volatile matter is 3-37 mass%. When the content of the repeating unit derived from the first monomer in the nonvolatile content is 3% by mass or more, excellent oil surface suitability can be exhibited. On the other hand, if the content of the repeating unit derived from the first monomer in the nonvolatile content is 37% by mass or less, sufficient water dispersibility of the resin can be ensured. In the water-based coating composition of the present invention, the content of the repeating unit derived from the first monomer in the nonvolatile content is preferably 8 to 37% by mass. The content of the repeating unit derived from the first monomer in the volatile component is adjusted by adjusting the proportion of the water-dispersible resin in the nonvolatile component and the proportion of the first monomer constituting the water-dispersible resin. It can be adjusted easily.
Further, as described above, the number of carbon atoms of the non-aromatic hydrocarbon group of the first monomer is preferably 6 or more. For this reason, in the coating composition of the present invention, the first monomer contains the monomer (a) in which the carbon number of the non-aromatic hydrocarbon group is 6 or more, and the monomer ( The content of the repeating unit derived from a) is preferably 1 to 30% by mass, and more preferably 1 to 28% by mass.

  In the coating composition of the present invention, the ratio of the repeating unit derived from the first monomer in the repeating units constituting the water-dispersible resin is preferably in the range of 21 to 72% by mass.

  The water-dispersible resin is a resin containing at least one second monomer having a polymerizable unsaturated group as a repeating unit in addition to the first monomer. If the water-dispersible resin is composed only of the first monomer, sufficient water-dispersibility of the resin cannot be ensured. Here, the “second monomer” is a monomer different from the first monomer in the “monomer having a polymerizable unsaturated group”, and can be copolymerized with the first monomer.

  Specific examples of the second monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, toluyl (meth) acrylate, glycidyl (meth) acrylate, and the like. (Meth) acrylic acid ester monomers; aromatic polymerizable unsaturated monomers such as styrene, α-methylstyrene, chlorostyrene, vinyl toluene, vinyl naphthalene, phenyl (meth) acrylate, benzyl (meth) acrylate, vinyl benzoate Vinyl monomers such as vinyl acetate and vinyl propionate; N-alkoxy-substituted amide monomers such as N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, and N-butoxymethyl (meth) acrylamide; Fluoroethylene, perfluoro Fluorine-containing vinyl monomers such as propylene and vinylidene fluoride; silicon-containing vinyl monomers such as vinyltrimethoxysilane and vinyltriethoxysilane; dialkyl esters of maleic acid and fumaric acid; alkenes such as ethylene and propylene; butadiene and isoprene Conjugated dienes; monomers such as vinyl chloride, vinylidene chloride, allyl chloride; (meth) acrylic acid, fumaric acid, maleic acid, itaconic acid, vinyl benzoic acid, maleic acid monomethyl ester, maleic acid monobutyl ester, itaconic acid mono Butyl ester, sulfonic acid group-containing (meth) acrylate, phosphoric acid group-containing (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxy Lactone adducts to butyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, ring-opening adducts of ethylene oxide to 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate, and the opening of propylene oxide. Cycloadduct, 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate dimer or trimer, N, N-dimethylaminoethyl (meth) acrylate, N, N-methylethylaminoethyl (Meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dipropylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-methylpropylaminopropyl ( (Meth) acrylate, N, N-diethylaminopropyl (meth) Acrylate, N, N-dipropylamino-propyl (meth) acrylate, N, N-dimethylaminopropyl acrylamide, N, N-diethylaminopropyl acrylamide, 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate. In addition, the said 2nd monomer may be used individually by 1 type, and may be used in combination of 2 or more type.

  The water-dispersible resin is selected from the group consisting of styrene, α-methylstyrene, chlorostyrene, vinyl toluene, vinyl naphthalene, phenyl (meth) acrylate, benzyl (meth) acrylate, and vinyl benzoate among the second monomers. It is preferable that at least one aromatic polymerizable unsaturated monomer is included as a repeating unit. By using such an aromatic polymerizable unsaturated monomer, it is possible to improve coating film performance such as water resistance when it is used as a coating film. In the aqueous coating composition of the present invention, the ratio of the repeating unit derived from the aromatic polymerizable unsaturated monomer in the repeating unit constituting the water-dispersible resin is, for example, in the range of more than 0% by mass and 79% by mass or less. is there.

  Among the second monomers, the water-dispersible resin is 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, Lactone adducts to 2-hydroxyethyl (meth) acrylate, ring-opening adducts of ethylene oxide or propylene oxide to 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate, and 2 -Containing at least one hydroxy group-containing polymerizable unsaturated monomer selected from the group consisting of a dimer or a trimer of hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate as a repeating unit. preferable. By using such a hydroxy group-containing polymerizable unsaturated monomer, the water dispersibility of the resin can be improved. In the aqueous coating composition of the present invention, the proportion of the repeating unit derived from the hydroxy group-containing polymerizable unsaturated monomer in the repeating unit constituting the water-dispersible resin is preferably more than 0% by mass and 5% by mass or less. .

  The water dispersible resin includes (meth) acrylic acid, fumaric acid, maleic acid, itaconic acid, vinyl benzoic acid, maleic acid monomethyl ester, maleic acid monobutyl ester, itaconic acid monobutyl ester, among the second monomers. It is preferable that at least one acid group-containing polymerizable unsaturated monomer selected from the group consisting of a sulfonic acid group-containing (meth) acrylate and a phosphoric acid group-containing (meth) acrylate is included as a repeating unit. By using such an acid group-containing polymerizable unsaturated monomer, the water dispersibility of the resin can be improved. In the aqueous coating composition of the present invention, the ratio of the repeating unit derived from the acid group-containing polymerizable unsaturated monomer in the repeating units constituting the water-dispersible resin is preferably in the range of 3 to 7% by mass.

  In the coating composition of the present invention, the water-dispersible resin is preferably used in the form of a dispersion. Here, a dispersion containing a water-dispersible resin (hereinafter also referred to as a resin dispersion) means a heterogeneous system in which the resin is distributed in water or a solvent containing water as a main solvent. And additives such as surfactants.

  In the coating composition of the present invention, the resin dispersion may be prepared by, for example, applying a water-dispersible resin in water using a surfactant as necessary while applying a forced shearing force by using a high-speed stirrer or the like. It can be prepared by emulsifying. Alternatively, the resin dispersion can be prepared as follows. A resin dispersion can be prepared by adding a surfactant to the water-dispersible resin that is polymerized in an organic solvent medium and performing phase conversion into water, if necessary. For example, the organic solvent contained in the resin dispersion may be removed. The resin dispersion can also be prepared by performing polymerization in water using water as a medium.

  The water-dispersible resin can be synthesized by copolymerization of the first monomer and the second monomer. When polymerization is performed, for example, 2,2′-azobisisobutyronitrile, 2,2′- Azo polymerization initiators such as azobis-2-methylbutyronitrile and 2,2′-azobis-2,4-dimethylvaleronitrile; benzoyl peroxide, di (3-methylbenzoyl) peroxide, benzoyl (3-methylbenzoyl) ) Peroxide, t-butylperoxyisobutyrate, t-butylperoxy-2-ethylhexanoate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxyisopropyl monocarbonate Heavy organic peroxide polymerization initiators such as 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane It is preferred to use an initiator. A polymerization initiator may be used individually by 1 type, and may be used in combination of 2 or more type.

  Further, when performing the above polymerization, a chain transfer agent such as 2-mercaptoethanol, n-octyl mercaptan, dodecyl mercaptan, 2,4-diphenyl-4-methyl-1-pentene may be used as necessary. it can. A chain transfer agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  When the polymerization is carried out in an organic solvent, the organic solvent is preferably a polar organic solvent that can be mixed with water, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, Isobutyl alcohol, sec-butyl alcohol, t-butyl alcohol, isoamyl alcohol, sec-amyl alcohol, t-amyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-propyl ether, ethylene glycol monoisopropyl ether , Ethylene glycol mono n-butyl ether, ethylene glycol monoisobutyl ether, diethylene glycol mono n-propyl ether, diethylene glycol Isopropyl ether, diethylene glycol mono n-butyl ether, diethylene glycol monoisobutyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol mono n-butyl ether, dipropylene glycol mono Examples include n-propyl ether, dipropylene glycol monoisopropyl ether, dipropylene glycol mono n-butyl ether, dipropylene glycol monoisobutyl ether, 3-methyl-3-methoxybutanol, acetone, methyl ethyl ketone, diethyl ketone and the like. If necessary, aromatic organic solvents such as xylene and toluene, aliphatic organic solvents such as hexane and cyclohexane, ester organic solvents such as ethyl acetate and butyl acetate, and the like can be used in combination.

  In the preparation of the water-dispersible resin, neutralization may be performed using a basic substance after polymerization. Examples of basic substances include trimethylamine, triethylamine, tripropylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, methylamine, ethylamine, propylamine, butylamine, amylamine, morpholine, monoethanolamine, diethanolamine, dimethylethanol Examples include amine, diethylethanolamine, triethanolamine, 2-amino-2-methyl-1-propanol, ammonia, sodium hydroxide, sodium carbonate, sodium bicarbonate, and the like. A basic substance may be used individually by 1 type, and may be used in combination of 2 or more type.

  In the coating composition of the present invention, the water-dispersible resin has a weight average molecular weight in the range of 5,000 to 300,000, preferably in the range of 5,000 to 200,000. More preferably in the range of 10,000 to 100,000, and still more preferably in the range of 10,000 to 100,000. When the molecular weight is within the specified range, the oil surface suitability is excellent, and the durability of the coating film, particularly the initial water resistance, can be improved. In the present invention, the weight average molecular weight is a value measured by gel permeation chromatography, and polystyrene is used as the standard substance.

  In the coating composition of the present invention, the water-dispersible resin preferably has a glass transition temperature of −50 to 40 ° C., more preferably −30 to 20 ° C., and −10 to 20 It is more preferable that it is ° C. If the glass transition temperature is within the specified range, the familiarity with the oil present on the surface of the coating film is improved, the oil surface suitability is further improved, and the coating film performance such as coating film hardness can be improved.

In the present invention, the glass transition temperature (Tg) means a value calculated using the following FOX equation.
1 / Tg = W1 / Tg1 + W2 / Tg2 + ... + Wi / Tgi + ... + Wn / Tgn
In the FOX formula, Tg is a glass transition temperature (K) of a polymer composed of n types of monomers, and Tg (1, 2, i, n) is a glass transition temperature (K) of a homopolymer of each monomer. Yes, W (1, 2, i, n) is the mass fraction of each monomer, and W1 + W2 +... + Wi +.

  In the coating composition of the present invention, the water dispersible resin preferably has an acid value of 25-60. If the acid value is within the above specified range, water dispersibility can be improved. In the present invention, the acid value of the resin means the number of mg of potassium hydroxide necessary to neutralize 1 g of the resin.

  In the coating composition of the present invention, the nonvolatile content is preferably 55 to 73% by mass, and more preferably 55 to 65% by mass. Moreover, in the water-based coating composition of this invention, it is preferable that content of the water-dispersible resin in a non volatile matter is 15-45 mass%, and it is more preferable that it is 27-43 mass%. The non-volatile content refers to components excluding volatile components such as water and organic solvents, and is a component that finally forms a coating film. In the present invention, the coating composition is 130 ° C. The components remaining after drying for 60 minutes are treated as non-volatile components.

In the coating composition of the present invention, the water-dispersible resin preferably has a 50 volume% particle diameter (D50) in the range of 50 to 300 nm, and more preferably in the range of 50 to 200 nm. If it is 50 volume% particle diameter in the specified range, the oil level suitability can be improved more reliably. In the present invention, 50% by volume particle size (D50) refers to 50% particle size (D ₅₀ ) of volume-based particle size distribution, and is a laser diffraction / scattering type particle size distribution measuring device (for example, SALD-7000: Shimadzu Corporation). Can be determined from the particle size distribution measured using And the particle diameter in this invention is represented by the spherical equivalent diameter by a laser diffraction and a scattering method.

  As the rust preventive pigment used in the coating composition of the present invention, known materials can be used, for example, zinc powder, zinc oxide, barium metaborate, calcium silicate, aluminum phosphate, aluminum tripolyphosphate, zinc phosphate, phosphorous acid. Zinc, potassium phosphite, calcium phosphite, aluminum phosphite, zinc calcium phosphate, zinc aluminum phosphate, zinc phosphomolybdate, aluminum phosphomolybdate, magnesium phosphate, vanadic acid / phosphoric acid mixed pigment, etc. . Moreover, in the water-based coating composition of this invention, it is preferable that content of the antirust pigment in a non volatile matter is 3-10 mass%.

  In the coating composition of the present invention, the pigment volume concentration in the nonvolatile content is preferably 30 to 65% by volume, more preferably 30 to 50% by volume, and still more preferably 30 to 47% by volume. . If the pigment volume concentration is within the above specified range, the paint can be integrated with the oil adhering to the base material to form a coating film, and the coating film after drying has excellent rust prevention and water resistance. Have. In addition, the pigment here refers to all the pigments contained in a coating composition, and when pigments other than a rust preventive pigment are used, the pigment is also contained. The pigment volume concentration (PVC: Pigment Volume Concentration) in the non-volatile component can be obtained by calculation from the composition and specific gravity of each component constituting the non-volatile component.

  The coating composition of the present invention is a water-based paint, and the water-based paint is a paint containing water as a main solvent. In the coating composition of the present invention, the water content is preferably 27 to 45 mass%, more preferably 35 to 45 mass%. The coating composition of the present invention can be completely water-based, and the ratio of water in the solvent used is preferably 50% by mass or more, and most preferably 100% by mass.

  In the coating composition of the present invention, as other components, various resins, pigments, organic solvents, surface conditioners, wetting agents, dispersants, emulsifiers, thickeners, anti-settling agents, anti-skinning agents, anti-sagging agents , Antifoaming agent, color separation preventing agent, leveling agent, drying agent, plasticizer, film forming aid, antifungal agent, antibacterial agent, insecticide, light stabilizer, ultraviolet absorber, antistatic agent and conductivity imparting An agent or the like can be appropriately blended depending on the purpose. These components can use a commercial item suitably. In addition, the organic solvent may be used for these components. In the water-based coating composition of the present invention, the content of the organic solvent is preferably 15% by mass or less, and most preferably 0% by mass.

  Here, examples of the resin as the other component include resins usually used in the paint industry. Specifically, acrylic resins, silicone resins, acrylic silicone resins, styrene acrylic copolymer resins, polyesters Resin, fluorine resin, rosin resin, petroleum resin, coumarone resin, phenol resin, urethane resin, melamine resin, urea resin, epoxy resin, cellulose resin, xylene resin, alkyd resin, aliphatic hydrocarbon resin, butyral resin, maleic acid resin , Fumaric acid resin, vinyl resin, amine resin, ketimine resin and the like. These resins may be used alone or in combination of two or more. In particular, in the coating composition of the present invention, the resin as the other component is selected from acrylic resin, silicone resin, acrylic silicone resin, styrene acrylic copolymer resin, polyester resin, fluorine resin, urethane resin, and epoxy resin. On the contrary, since the alkyd resin is excellent in oil surface suitability but inferior in initial water resistance, the oil length in the coating composition of the present invention may be 20 or less even when used. More preferred.

  Examples of the other component pigments include pigments commonly used in the paint industry. Specifically, pigments such as titanium dioxide, iron oxide, carbon black, silica, talc, mica. And extender pigments such as calcium carbonate and barium sulfate, and bright pigments such as aluminum, nickel, chromium, tin, copper, silver, platinum, gold, stainless steel, and glass flakes. These pigments may be used alone or in combination of two or more.

  When the coating composition of the present invention contains a solvent other than water, the solvent is preferably a polar organic solvent that can be mixed with water, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol. , N-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, t-butyl alcohol, isoamyl alcohol, sec-amyl alcohol, t-amyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-propyl ether , Ethylene glycol monoisopropyl ether, ethylene glycol mono n-butyl ether, ethylene glycol monoisobutyl ether, diethylene glycol mono n-propyl ether, diethyl Glycol monoisopropyl ether, diethylene glycol mono n-butyl ether, diethylene glycol monoisobutyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol mono n-butyl ether, di Examples include propylene glycol mono n-propyl ether, dipropylene glycol monoisopropyl ether, dipropylene glycol mono n-butyl ether, dipropylene glycol monoisobutyl ether, 3-methyl-3-methoxybutanol, acetone, methyl ethyl ketone, and diethyl ketone.

  The coating composition of the present invention can be prepared by mixing various components appropriately selected as necessary.

The coating composition of the present invention preferably has a viscosity at a shear rate of 0.1 s ⁻¹ of 50 to 200 Pa · s and a viscosity at a shear rate of 1,000 s ⁻¹ of 0.2 to ¹ Pa · s. If the viscosity is within the above specified range, the coating workability is excellent, and the paint can partially penetrate the fragile surface of the base material and the oil surface adhesion surface and dry to form an integrated coating film. A coating composition having excellent oil surface suitability can be obtained. In the present invention, the viscosity is measured after adjusting the liquid temperature to 23 ° C. using a rheometer ARES manufactured by TA Instruments.

  In the coating composition of the present invention, the coating means is not particularly limited, and known coating means such as brush coating, roller coating, trowel coating, spatula coating, spray coating and the like can be used.

In addition, the base material that can be coated with the coating composition of the present invention is not particularly limited. For example, steel, galvanized steel (for example, tin plate), tin-plated steel (for example, tin plate), stainless steel, A metal base material containing at least a part of a metal or alloy such as magnesium alloy, aluminum, and aluminum alloy is preferable. These base materials are often attached with oils such as rust preventive oil and rolling oil, and coating using the coating composition of the present invention is effective. In particular, according to the coating composition of the present invention, it is possible to suitably perform coating even on a substrate having a black skin as adhered to the surface of the steel material. Usually, the base material to which the black skin adheres has a large amount of oil in the gaps of the black skin, etc., and excellent oil surface suitability is required.
The base material includes a base material that has been subjected to various surface treatments, for example, oxidation treatment or primer treatment, and the old coating film (before the coating composition of the present invention is applied) is applied to at least a part of the base material surface. May already be present).

  Examples of the base material that can be coated with the coating composition of the present invention include base materials of various materials as described above, and specific examples thereof include various building materials, buildings and structures, and members thereof. It is done. In the present invention, a building means a structure built for the purpose of living or staying by a person, such as a house, building, factory, etc., and a structure is a purpose for living or staying by a person. Means a structure constructed for other purposes, such as bridges, tanks, plant piping, and chimneys. Examples of members of buildings and structures include roofs and walls.

  Next, the coating method of the present invention will be described in detail. The coating method of the present invention includes a step of coating a base material on which oil has adhered to the surface with an aqueous coating composition to form a coating film, wherein the aqueous coating composition comprises the above-described book. It is an aqueous coating composition of the invention. For this reason, according to the coating method of this invention, it can coat suitably also to the base material with which oil adhered to the surface.

  In the coating method of the present invention, examples of the oil adhering to the substrate surface include metal processing oils such as rust preventive oil, rolling oil, cutting oil, and press oil, and various commercial products are assumed.

  Further, in the coating method of the present invention, the base material is as described in the description of the coating composition of the present invention described above, and in particular, according to the coating method of the present invention, it is found on the steel material surface. Coating can also be suitably performed on a base material having a black skin adhered to the surface.

  In the coating method of the present invention, the coating means is not particularly limited, and known coating means such as brush coating, roller coating, trowel coating, spatula coating, spray coating and the like can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

<Synthesis Example 1>
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and the like, 120 parts by mass of methyl ethyl ketone is added and heated and stirred. After reaching 90 ° C., 380 parts by mass of styrene, 360 parts by mass of n-butyl acrylate, 2- A mixture obtained by previously mixing 20 parts by mass of hydroxyethyl methacrylate and 40 parts by mass of a polymerization initiator (manufactured by Kayaku Akzo Co., Ltd .: Kayaester O) was added dropwise over 5 hours. After completion of the dropwise addition, a mixture of 10 parts by mass of a polymerization initiator (manufactured by Kayaku Akzo Co., Ltd .: Kayaester O) and 20 parts by mass of methyl ethyl ketone was added dropwise over 1 hour while maintaining 90 ° C. The resulting mixture was continuously reacted at 90 ° C. for 6 hours and then cooled. The obtained mixture was diluted with 50 parts by mass of methyl ethyl ketone to obtain a resin solution 1 having a nonvolatile content of 80% by mass and a resin weight average molecular weight of 17,000.

<Synthesis Examples 2 to 26>
Resin solutions 2 to 26 were prepared in the same manner as in Synthesis Example 1 except that the reactions were performed according to the formulation shown in Tables 1 and 2. Tables 1 and 2 show the nonvolatile content and the weight average molecular weight of the resin for each resin solution.

<Synthesis Example 27>
In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, etc., 330 parts by mass of resin solution 1, 3 parts by mass of 2-methacryloyloxyethyl isocyanate (produced by Showa Denko KK: Karenz MOI), and 10 parts by mass of methyl ethyl ketone The mixture was heated and stirred, and after reaching 90 ° C., stirring was continued for 2 hours. Subsequently, 45 parts by mass of styrene, 15 parts by mass of n-butyl acrylate, 20 parts by mass of acrylic acid, and 10 parts by mass of a polymerization initiator (manufactured by Kayaku Akzo Co., Ltd .: Kayaester O) were obtained in advance. The mixture was added dropwise over 1 hour. After completion of dropping, a mixture of 10 parts by mass of a polymerization initiator (manufactured by Kayaku Akzo Co., Ltd .: Kayaester O) and 10 parts by mass of methyl ethyl ketone was added dropwise over 2 hours while maintaining 90 ° C. The mixture was further stirred at 90 ° C. for 6 hours and then cooled. 22 parts by mass of dimethylethanolamine was added to the obtained mixture and stirred, and 530 parts by mass of ion-exchanged water was further added. From this, 80 parts by mass of methyl ethyl ketone was distilled off at 50 ° C. under reduced pressure (about 50 mmHg) using an evaporator, and then 50 parts by mass of ion-exchanged water and 50 parts by mass of ethylene glycol mono-n-butyl ether were added. 35% by mass, glass transition temperature (Tg) of water-dispersible resin 17 ° C., acid value of water-dispersible resin 42 mgKOH / g, 50% by volume of water-dispersible resin (D50) 70 nm, weight of water-dispersible resin A resin dispersion 1 having an average molecular weight of 32,000 was obtained. In addition, it is thought that 50 volume% particle diameter (D50) of water dispersible resin here is substantially the same as the particle diameter after preparation of a coating composition.

<Synthesis Examples 28, 30 to 48, 52 to 54, and 56 to 63>
Resin dispersions 2, 4-22, 26-28, and 30-37 were prepared in the same manner as in Synthesis Example 27, except that the reaction was performed according to the formulation shown in Tables 3-5. For each resin dispersion, the nonvolatile content, the glass transition temperature (Tg) of the water-dispersible resin, the acid value of the water-dispersible resin, the 50 vol% particle diameter (D50) of the water-dispersible resin, and the weight of the water-dispersible resin The average molecular weight is shown in Tables 3-5. The resin dispersions 34, 35, and 37 prepared according to Synthesis Examples 60, 61, and 63 could not be evaluated later because of poor resin dispersion.

<Synthesis Example 29>
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, etc., 330 parts by mass of the resin solution 3 and 10 parts by mass of methyl ethyl ketone were added and stirred with heating. After reaching 90 ° C., 45 parts by mass of styrene and n-butyl A mixture obtained by previously mixing 15 parts by mass of acrylate, 20 parts by mass of acrylic acid, and 3 parts by mass of a polymerization initiator (manufactured by Kayaku Akzo Co., Ltd .: Kayaester O) was added dropwise over 1 hour. After completion of dropping, a mixture of 10 parts by mass of a polymerization initiator (manufactured by Kayaku Akzo Co., Ltd .: Kayaester O) and 10 parts by mass of methyl ethyl ketone was added dropwise over 2 hours while maintaining 90 ° C. The mixture was further stirred at 90 ° C. for 6 hours and then cooled. 22 parts by mass of dimethylethanolamine was added to the obtained mixture and stirred, and 530 parts by mass of ion-exchanged water was further added. From this, 80 parts by mass of methyl ethyl ketone was distilled off at about 50 ° C. under reduced pressure (about 50 mmHg) using an evaporator, and 50 parts by mass of ion-exchanged water and 50 parts by mass of ethylene glycol mono-n-butyl ether were added. 35% by mass, glass transition temperature (Tg) of water-dispersible resin 19 ° C., acid value of water-dispersible resin 44 mgKOH / g, 50% by volume of water-dispersible resin (D50) 114 nm, weight of water-dispersible resin A resin dispersion 3 having an average molecular weight of 38,000 was obtained.

<Synthesis Examples 49-51 and 55>
Resin dispersions 23 to 25 and 29 were prepared in the same manner as in Synthesis Example 29 except that the reactions were carried out according to the formulation shown in Tables 3 to 5. For each resin dispersion, the nonvolatile content, the glass transition temperature (Tg) of the water-dispersible resin, the acid value of the water-dispersible resin, the 50 vol% particle diameter (D50) of the water-dispersible resin, and the weight of the water-dispersible resin The average molecular weight is shown in Tables 3-5.

<Additional resin dispersion>
A resin dispersion was prepared according to Example 1 of JP-A No. 2001-181557. The weight average molecular weight of the resin in the resin dispersion exceeded the detection limit and was a resin having a weight average molecular weight exceeding 300,000.
Also, a resin dispersion was prepared according to Synthesis Example 10 of JP2013-209447A.

  Next, the manufacture example of a water-based antirust coating composition is shown below.

<Production Example 1>
47.0 parts by mass of the resin dispersion 1 obtained in Synthesis Example 27, 0.5 parts by mass of a pigment dispersant (manufactured by Big Chemie Japan Co., Ltd .: Disperbyk-190), an antifoaming agent (manufactured by Big Chemie Japan Co., Ltd.): byk-093) 0.5 parts by mass, coloring pigment (manufactured by Toda Pigment Co., Ltd .: 130ED) 5.0 parts by mass, rust preventive pigment (manufactured by Teika Co., Ltd .: K-White # 140W) 5.0 parts by mass, and constitution 37 parts by mass of pigment (manufactured by Takehara Chemical Industry Co., Ltd .: Sunlite SL-1000) was mixed in advance, and then dispersed in a ball mill for 30 minutes. While stirring with a disper (paint stirrer), 5 parts by mass of ion-exchanged water was added to the mixture after the dispersion treatment to obtain an aqueous rust preventive coating composition (Example 1).

<Production Examples 2 to 48>
In accordance with the formulation shown in Tables 6 to 10, aqueous rust preventive coating compositions of Examples 2 to 44 and Comparative Examples 1 to 3 and 5 were prepared by the same method as in Production Example 1.

<Additional aqueous rust preventive coating composition>
A water-based anticorrosive coating composition of Comparative Example 4 was prepared according to Production Example 3-1 (Preparation Example of Undercoat Paint 3-1) of International Publication No. 2013/140953.

  About the water-based anticorrosive coating composition of said Examples 1-44 and Comparative Examples 1-3 and 5, using TA Instruments rheometer ARES, shear rate 0.1 (1 / s) and 1000 (1 / Each viscosity in s) (both viscosities at a temperature of 23 ° C.) was measured, and the results are shown in Tables 6-10. In the table, the viscosity at a shear rate of 0.1 (1 / s) is shown as viscosity 1, and the viscosity at a shear rate of 1000 (1 / s) is shown as viscosity 2.

  About the water-based anticorrosive coating composition of said Examples 1-44 and Comparative Examples 1-5, a test board is produced according to the following preparation methods 1 and 2, and oil-surface adhesion evaluation A and B with the following method and reference | standard The coating film hardness evaluation, the rust prevention evaluation, the formaldehyde emission amount evaluation, and the initial water resistance evaluation were performed. The results are shown in Tables 6-10.

<Method 1 for preparing test plate>
After degreasing black skin steel plate (SPHC (hot rolled mild steel plate and steel strip JIS G3131): 1.6 × 70 × 150 mm) with xylene, antirust oil [JIS K 2246 (1994) NP-3-2] The coating was uniformly applied at a coating amount of 1.0 g / m ² and left for 1 week in an atmosphere of 23 ° C. and 50% RH to obtain a target test plate.

<Method 2 for preparing test plate>
After degreasing black skin steel plate (SPHC (hot rolled mild steel plate and steel strip JIS G3131): 1.6 × 70 × 150 mm) with xylene, antirust oil [JIS K 2246 (1994) NP-3-2] The coating was uniformly applied to a coating amount of 3.0 g / m ² and left for 1 week in an atmosphere of 23 ° C. and 50% RH to obtain a target test plate.

<Oil surface adhesion evaluation A>
The water-based anticorrosive coating compositions of Examples 1 to 44 and Comparative Examples 1 to 5 were applied to a test plate produced according to the above production method 1 with a 4 mil applicator and left for 1 week in an atmosphere of 23 ° C. and 50% RH. And dried to prepare a coating film, and then the adhesion stability with cellophane adhesive tape was tested according to JIS K 5675 7.11 adhesion stability, and peeled off at a specified area (cellophane adhesive tape 50 mm length). The area (attachment area ratio) of the coating film that was not applied was calculated and evaluated according to the following criteria.
A: The adhesion area ratio was 98% or more.
A: The adhesion area ratio was 70% or more and less than 98%.
X: The adhesion area ratio was less than 70%.

<Oil surface adhesion evaluation B>
The test plate prepared according to the above preparation method 2 was coated with the water-based anticorrosive coating compositions of Examples 1 to 44 and Comparative Examples 1 to 5 with a 4 mil applicator and left for 1 week in an atmosphere of 23 ° C. and 50% RH. And dried to prepare a coating film, and then the adhesion stability with cellophane adhesive tape was tested according to JIS K 5675 7.11 adhesion stability, and peeled off at a specified area (cellophane adhesive tape 50 mm length). The area (attachment area ratio) of the coating film that was not applied was calculated and evaluated according to the following criteria.
A: The adhesion area ratio was 98% or more.
A: The adhesion area ratio was 70% or more and less than 98%.
X: The adhesion area ratio was less than 70%.

  In the present specification, the water-based anticorrosive coating composition having excellent oil surface suitability refers to those having an evaluation result of ◎ and ○ in the oil surface adhesion evaluation A, and the oil surface adhesion described above. In the evaluation B, the evaluation results of “、” and “○” mean that the water-based anticorrosive coating composition has further excellent oil surface suitability.

<Evaluation of coating film hardness>
A specific measurement method based on JIS K 5400-1959 will be described (see JP 2009-255549 A). First, a pseudo rocker is placed on a horizontal surface and adjusted with a weight for vertical stabilization so that the vertical axis is perpendicular to the horizontal plane. Set and fix the standard glass plate on the test plate fixing device, place the level on the standard glass plate surface, and adjust the height with the adjustment feet of the test plate fixing device so that it is horizontal in the vertical and horizontal directions. Adjust. Place a pseudo rocker with the vertical axis adjusted on the test plate (standard glass plate), apply a rolling motion to the rock rocker, cover the wind shield, and observe the state of the level from outside the wind shield. The time when the hour of the level B of the Sword Locker is hidden behind the oyster of the level B is not visible for the first time is counted as 0 (start). Thereafter, the count is incremented by 1 for each reciprocation of the rolling motion, and is counted until the millet of the level C is hidden behind the oyster of the level C for the first time, and this value is used as the pseudo rocker value.
Since the standard glass plate has a pseudo rocker value of 50, the inclination of each of the spirit levels B and C is adjusted so that the pseudo rocker value becomes 50 ± 1 after five measurements. Also, the vertical position of the period adjusting weight is adjusted so that the time required for 50 ± 1 reciprocation is 60 ± 5 seconds. Next, the test plate is changed to a standard methacryl methyl plate (polymethyl methacrylate), and the inclination of each of the level levels B and C is adjusted so that the five rocker lock values are 20 ± 1. This is repeated, and when the measured values of both standard plates satisfy the above-mentioned standard, the spirit levels B and C are fixed. The ambient temperature is 20 to 23 ° C., and the humidity is 20 to 40% RH. The test plate is changed to a sample whose pseudo rocker value is to be measured, and the pseudo rocker value is measured in the same manner as described above. Five identical samples are prepared (n = 5), the pseudo rocker value is measured for each, and the average of the three of the five pseudo rocker values is determined as the final value. This final value is the pseudo rocker value of the target sample, and the value obtained by doubling this is the coating film hardness.
In addition, about the sample for a measurement, the water-based antirust coating composition of Examples 1-44 and Comparative Examples 1-5 was produced by apply | coating with a 6 mil applicator on the glass plate 150 mm long and 70 mm wide.
A: Coating film hardness 12 or more ○ +: Coating film hardness 7 or more and 11 or less ○: Coating film hardness 3 or more and 6 or less ×: Coating film hardness 3 or less

<Rust prevention evaluation>
With respect to the water-based anticorrosive coating composition, the anticorrosive property was evaluated in accordance with the test method for cycle corrosion (cycle D) defined in 7.12.
○: Passed the criteria described in d) Evaluation and Judgment in 36 cycles.
X: It failed in the criteria as described in d) evaluation and determination in 36 cycles.

<Evaluation of formaldehyde emission>
The measured value of formaldehyde emission was determined in accordance with the measurement method defined in JIS K5600-4-1: 2012 for the water-based anticorrosive coating composition.
○: Formaldehyde emission amount is 0.12 mg / L or less ×: Formaldehyde emission amount exceeds 0.12 mg / L

<Initial water resistance evaluation>
After the test plate produced by the same method as the above rust prevention evaluation was left to stand in an atmosphere of 23 ° C. and 50% RH for 8 hours and dried, the lower half of the test plate was placed in 23 ° C. tap water for 24 hours. The appearance of the test plate soaked and taken out was immediately observed, and the initial water resistance was evaluated according to the following criteria.
(Double-circle): The coating film of the immersion part did not swell, and there was no difference in hue visually compared with the non-immersion part.
○: The coating film of the soaked part was not swollen, but the hue difference from the non-soaked part was clear.
X: Swelling was recognized in the coating film of the immersion part.

Claims (8)

An aqueous paint composition comprising a water-dispersible resin, a rust preventive pigment and water,
The water dispersible resin is a resin having a weight average molecular weight of 5,000 to 300,000, and is a group other than the polymerizable unsaturated group and the polymerizable unsaturated group, and has 4 or more carbon atoms. A resin comprising as a repeating unit a first monomer having a non-aromatic hydrocarbon group and at least one second monomer having a polymerizable unsaturated group;
Content of the repeating unit derived from the 1st monomer in the non volatile matter of the said water-based coating composition is 3-37 mass%, The water-based coating composition characterized by the above-mentioned.   The aqueous coating composition according to claim 1, wherein the pigment volume concentration in the non-volatile content is 30 to 65% by volume. The viscosity at a shear rate of 0.1 s ^-1 is 50 to 200 Pa · s, and the viscosity at a shear rate of 1,000 s ^-1 is 0.2 to ¹ Pa · s. Water-based paint composition.   The water-based paint composition according to any one of claims 1 to 3, wherein the water-dispersible resin has a 50% by volume particle diameter (D50) in the range of 50 to 300 nm.   The water-dispersible resin composition according to any one of claims 1 to 4, wherein the water-dispersible resin has a weight average molecular weight in the range of 5,000 to 200,000.   The water-dispersible resin composition according to any one of claims 1 to 5, wherein the water-dispersible resin has a glass transition temperature in a range of -50 to 40 ° C. The first monomer includes a monomer (a) in which the non-aromatic hydrocarbon group has 6 or more carbon atoms,
Content of the repeating unit derived from the monomer (a) in the said non volatile matter is 1-30 mass%, The water-based coating composition as described in any one of Claims 1-6 characterized by the above-mentioned.   The coating method characterized by including the process of apply | coating the base material which oil adhered to the surface with the water-based coating composition as described in any one of Claims 1-7, and forming a coating film.