One-component epoxy resin coating composition

Abstract

To provide a one-pack epoxy resin coating composition which is a high solid type using an organic solvent containing no aromatic compound corresponding to a specialization rule, and is excellent in compatibility as coating performance, water spot property as coating film performance, rust-prevention property and blocking resistance.SOLUTION: A coating composition contains at least one kind of a modified epoxy resin (A) selected from an amine-modified epoxy resin (A1), an isocyanate-modified epoxy resin (A2) and an acrylic-modified epoxy resin (A3), a pigment (B), and a solvent (C) containing no aromatic compound, wherein the solvent (C) contains a glycol ether-based solvent and an alcoholic solvent, and a content of the solvent (C) is 40 mass% or less with respect to the coating composition.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a one-component epoxy resin coating composition.

Background Art

[0002] Conventionally, paints containing epoxy resins have been used as paints for steel fixtures because they have excellent chemical resistance, corrosion resistance, and adhesion. However, recently, there has been a demand for paints with high functions that can meet social requirements such as preventing pollution of the natural environment, conserving resources, and protecting human health, in addition to protecting steel fixtures and enhancing their aesthetics.

[0003] One of them is a so-called high-solid type paint in which the solid content in the paint during painting is as high as 70% by mass or more, which improves the painting appearance and workability. Among them, a high-solid type one-component epoxy resin paint with a low content of organic solvents is required because it is easy to ensure the film thickness in a short time and reduces the load on the global environment. However, when water droplets adhere due to rainfall or the like in a state where the paint is not completely dried after application, the traces of the water droplets remain even after drying, resulting in a problem (water spot property) of deteriorating the appearance quality.

[0004] In addition, even for high-solid type paints, since they contain organic solvents, workers who apply the paint to steel fixtures and users who use steel fixtures may be at risk of health problems due to the chemical substances of the organic solvents. To prevent this, for example, the "Law Concerning the Examination and Regulation of Chemical Substances and Manufacturing etc." (Chemical Substances Control Law) and the Specific Chemical Substances Hazard Prevention Regulations (Specified Chemical Substances Regulations) have been established, and various regulations have been provided. In particular, the Specified Chemical Substances Regulations define specific chemical substances that may cause occupational cancer, dermatitis, neuropathy, etc. in workers, and it is required to regulate these specific chemical substances.

[0005] Therefore, in order to solve these conventional problems, for example, Patent Document 1 discloses a binder for paints using an amine-modified epoxy resin that has chemical resistance, rust prevention properties, and excellent adhesion to non-ferrous metals. Among them, a paint composition having a composition with a resin solid content of around 30% by mass using xylene or cyclohexanone is described. In addition, Patent Document 2 discloses a paint composition containing a modified epoxy resin obtained by reacting a bisphenol-type epoxy resin with amines and drying oil fatty acids and an aliphatic hydrocarbon solvent, which has excellent rust prevention properties, impact resistance, and adhesion. In addition, Patent Document 3 discloses a paint composition containing a modified epoxy resin, an epoxy ester resin, a pigment, and a solvent, with the solvent content being 40% or less.

[0006] However, in Patent Document 1, there is a problem that it uses an organic solvent of an aromatic compound having a benzene ring such as xylene or cyclohexanone, and the resin solid content is around 30% by mass, which does not correspond to high-solid type paints. In addition, the examples are only bisphenol A type epoxy resins, and there is also a problem that it does not correspond to water spots. In Patent Document 2, although the resin is around 50% by mass, there are not many pigments, and there is a problem that it does not correspond to high-solid type paints with a solid content of 70% by mass or more in the paint. In addition, there is a problem that the weak solvent system used does not correspond to the specialization rules. In addition, in Patent Document 3, although it is a high-solid type paint, there is a problem that sufficient consideration has not been given to using a solvent that does not contain specific chemical substances such as aromatic compounds.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] By corresponding to the specialization rules, solvents that do not contain aromatic compounds have not been sufficiently studied in the past, and there is a problem that they are very inferior in compatibility to conventional one-component epoxy resins. Also, even if the ratio of the solvent is increased to achieve compatibility, there is a problem that the water spot resistance, rust prevention property, and blocking resistance are reduced as compared with conventional high-solid type one-component epoxy resin coating compositions.

[0009] Therefore, an object of the present invention is to provide a one-component epoxy resin coating composition that is excellent in compatibility as a coating performance even in a high-solid type depending on the type and combination of the resin of the coating composition with respect to a solvent that does not contain an aromatic compound corresponding to the specialization rules. Furthermore, an object of the present invention is to provide a one-component epoxy resin coating composition that is of a high-solid type, has a low viscosity and excellent coating properties, and furthermore, is excellent in water spot resistance, rust prevention property, and blocking resistance as the coating film performance formed.

MEANS FOR SOLVING THE PROBLEMS

[0010] The features of the present invention are listed below. (1) A coating composition comprising at least one kind of modified epoxy resin (A) selected from an amine-modified epoxy resin (A1), an isocyanate-modified epoxy resin (A2), and an acrylic-modified epoxy resin (A3), a pigment (B), a solvent (C) that does not contain an aromatic compound, and wherein the solvent (C) includes a glycol ether-based solvent and an alcohol-based solvent, and the content of the solvent (C) is 40% by mass or less with respect to the coating composition. A one-component epoxy resin coating composition. (2) The one-component epoxy resin coating composition according to (1), wherein the mass ratio of the pigment (B) in the solid content of the coating composition is 60% by mass or more and 90% by mass or less. (3) The one-component epoxy resin coating composition according to (1), wherein the mass ratio of the pigment (B) in the solid content of the coating composition is 75% by mass to 85% by mass. (4) The one-component epoxy resin coating composition according to (1), wherein the pigment (B) contains an extender pigment (B1) having an oil absorption of 10 ml / 100 g or more and 40 ml / 100 g or less. (5) The one-component epoxy resin coating composition according to (1), wherein the solvent (C) contains a solvent having an ester structure. (6) The one-component epoxy resin coating composition according to (1), wherein the mass ratio of the glycol ether solvent to the solvent (C) is 1 / 7 or more and 1 / 2 or less. (7) The one-component epoxy resin coating composition according to (1), wherein the coating composition further contains an epoxy ester resin (E). (8) The one-component epoxy resin coating composition according to (7), wherein the mass ratio of the modified epoxy resin (A) to the epoxy ester resin (E) (modified epoxy resin (A) / epoxy ester resin (E)) is in the range of 40 / 60 or more and 90 / 10 or less. (9) The one-component epoxy resin coating composition according to (7), wherein the mass ratio of the modified epoxy resin (A) to the epoxy ester resin (E) (modified epoxy resin (A) / epoxy ester resin (E)) is in the range of 40 / 60 or more and 70 / 30 or less. (10) The one-component epoxy resin coating composition according to (7), wherein the mass ratio of the total value of the modified epoxy resin (A) and the epoxy ester resin (E) in the solid content of the coating composition is 5% by mass or more and 25% by mass or less. (11) The one-component epoxy resin coating composition according to (7), wherein the mass ratio of the total value of the modified epoxy resin (A) and the epoxy ester resin (E) in the solid content of the coating composition is 15% by mass or more and 20% by mass or less.

Advantages of the Invention

[0011] According to the present invention, for a solvent containing no aromatic compound, depending on the type and combination of the resin of the paint composition, even in the high-solid type, it has excellent compatibility as paint performance, low viscosity and excellent paintability, and further, as the performance of the formed paint film, it is possible to provide a one-component epoxy resin paint composition excellent in water spot resistance, rust prevention and blocking resistance.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the one-component epoxy resin paint composition of the present invention will be described in detail.

[0013] <One-component epoxy resin paint composition> The one-component epoxy resin paint composition of the present invention is a paint composition containing at least one modified epoxy resin (A) selected from an amine-modified epoxy resin (A1), an isocyanate-modified epoxy resin (A2), and an acrylic-modified epoxy resin (A3), a pigment (B), and a solvent (C) containing no aromatic compound. The solvent (C) containing no aromatic compound contains at least a glycol ether solvent and an alcohol solvent, and has a content of 40% by mass or less with respect to the paint composition.

[0014] <Modified epoxy resin (A)> In the high-solid type one-component epoxy resin paint composition of the present invention, an epoxy resin is used, and in particular, a modified epoxy resin (A) is used. The epoxy resin that can be used in the present invention may be a one-component type or a two-component type, but since it has good initial drying properties and can be dried at room temperature, and also has excellent workability such as painting, it is used in a one-component paint composition. The modified epoxy resin (A) of the present invention is selected from at least one selected from an amine-modified epoxy resin (A1), an isocyanate-modified epoxy resin (A2), and an acrylic-modified epoxy resin (A3).

[0015] <<Amine-modified epoxy resin (A1)>> The amine-modified epoxy resin (A1) is produced by reacting an epoxy resin with amines. Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, aliphatic type epoxy resin, etc. Any epoxy resin may be used, but here, a bisphenol F type epoxy resin (hereinafter simply referred to as "bisphenol type epoxy resin") that is used as an adhesive or a paint and has excellent adhesion and rust prevention properties is preferred. The epoxy groups of this unmodified bisphenol type epoxy resin are ring-opened by amines, and amino groups are introduced into the resin. By introducing such amino groups, the adhesion is further improved, and the adhesion of the paint film of the paint can be improved.

[0016] Examples of the unmodified bisphenol type epoxy resin of the amine-modified epoxy resin (A1) include those obtained by the reaction of bisphenols with haloepoxides such as epichlorohydrin or β-methylepichlorohydrin. Examples of bisphenols include the reaction products of phenol or 2,6-dihalophenol with aldehydes or ketones such as formaldehyde, acetaldehyde, acetone, acetophenone, cyclohexanone, benzophenone, etc., as well as those obtained by the oxidation of dihydroxyphenyl sulfide with a peracid, the etherification reaction of hydroquinones, etc. Considering the molecular weight of the resulting amine-modified epoxy resin (A1) and the manufacturability of the production process, etc., the epoxy equivalent of the bisphenol type epoxy resin is preferably 3000 or less. When the epoxy equivalent of the bisphenol type epoxy resin greatly exceeds 3000, the molecular weight of the resulting amine-modified epoxy resin (A1) increases and the compatibility decreases.

[0017] In addition, examples of the amines that are components of the amine-modified epoxy resin (A1) include various amines such as alkanolamines, aliphatic amines, aromatic amines, alicyclic amines, and aromatic nucleus-substituted aliphatic amines, and one or more of these can be appropriately selected and used. Specific examples of such amines include alkanolamines such as diethanolamine, diisopropanolamine, di-2-hydroxybutylamine, N-methylethanolamine, N-ethylethanolamine, and N-benzyethanolamine; aliphatic amines such as primary amines like ethylamine, propylamine, butylamine, hexylamine, laurylamine, stearylamine, palmitylamine, oleylamine, and elsylamine, and secondary amines like diethylamine, dipropylamine, and dibutylamine; aromatic amines such as toluidines, xylylidines, cumidines (isopropyl anilines), hexylanilines, nonylanilines, and dodecylanilines; alicyclic amines such as cyclopentylamines, cyclohexylamines, and norbornylamines; and aromatic nucleus-substituted aliphatic amines such as benzylamine and phenethylamine. Among these amines, those having 2 to 20 carbon atoms are preferred.

[0018] <<Isocyanate-modified epoxy resin (A2)>> In addition, the isocyanate-modified epoxy resin (A2) used in the present invention is similarly produced by reacting isocyanates with the constituent components of bisphenol-type epoxy resins. Examples of isocyanates include aliphatic isocyanates, alicyclic isocyanates, aromatic isocyanates, and modified products thereof. Examples of aliphatic isocyanates include hexamethylene diisocyanate, lysine diisocyanate, lysine triisocyanate, etc. Examples of alicyclic isocyanates include isophorone diisocyanate. Examples of aromatic isocyanates include tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate, triphenylmethane triisocyanate, tris(isocyanatophenyl) thiophosphate, etc. Examples of isocyanate modified products include urethane prepolymers, hexamethylene diisocyanate biuret, hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, etc.

[0019] The epoxy equivalent of the bisphenol-type epoxy resin is preferably 3000 or less in consideration of the molecular weight of the resulting isocyanate-modified epoxy resin (A2), production workability, etc. When the epoxy equivalent of the bisphenol-type epoxy resin greatly exceeds 3000, the molecular weight of the resulting isocyanate-modified epoxy resin (A2) increases and the compatibility decreases.

[0020] <<Acrylic-modified epoxy resin (A3)>> In addition, the acrylic-modified epoxy resin (A3) used in the present invention is similarly produced by polymerizing an acrylate monomer with the constituent components of a bisphenol-type epoxy resin. Examples of the acrylate monomer include monomers having one or more acryloyloxy groups or methacryloyloxy groups. Specifically, C1-C18 alkyl esters or cycloalkyl esters of acrylic acid or methacrylic acid such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-, i- or t-butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, lauryl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-, i- or t-butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate; C2-C8 hydroxyalkyl esters of acrylic acid or methacrylic acid such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, hydroxybutyl methacrylate, etc. These monomers can be used alone or in combination of two or more. Here, for the copolymerization reaction of the bisphenol-type epoxy resin and the acrylate monomer, various known organic peroxides and azo compounds such as benzoyl peroxide, tert-butyl peroctoate, 2,2-azobisisobutyronitrile, 2,2-azobis(2,4-dimethylvaleronitrile) can be used.

[0021] The epoxy equivalent of the bisphenol-type epoxy resin is preferably 3000 or less in consideration of the molecular weight of the resulting acrylic-modified epoxy resin (A3) and the production workability. When the epoxy equivalent of the bisphenol-type epoxy resin greatly exceeds 3000, the molecular weight of the resulting acrylic-modified epoxy resin (A3) increases and the compatibility decreases.

[0022] The modified epoxy resin of the present invention can be obtained as a commercially available product. For example, EPICLON series (H-304-40, H-403-45, H-408-40, H-601-55, 9052-40MT, H-360, EXA-192, EXA-123, H-353, 7070-40K, 7070-50M, P-439, H-301-35PX, H-303-45M, H-304-40, EXA-8403, EXA-8415, EXA-8528, EXA-8486) (the above are modified epoxy resins manufactured by DIC Corporation), arachid series (9201N, 9203N, 9205, 9208, 9212), Modepix 408, KA-1492, KA-1494D, KA-1439A, KA-1435R, KA-1474B, KA-1433J (the above are modified epoxy resins manufactured by Arakawa Chemical Industries, Ltd.), Epoxy series (810ST, 811, 813, 814, 818, 861, 863, 864, 871T, 872, 877, 891, 878, 879) (the above are modified epoxy resins manufactured by Mitsui Chemicals, Inc.), etc. can be mentioned.

[0023] The modified epoxy resin (A) is contained in an amount of 4% by mass or more and 20% by mass or less, preferably 6% by mass or more and 15% by mass or less, based on the solid content of the coating composition (the component that functions as a coating film after coating, drying, and curing, and is measured under the measurement conditions: dried at 130 °C for 40 minutes). If the modified epoxy resin (A) is less than 4% by mass of the solid content in the coating composition, the water spot resistance, rust prevention property, and blocking resistance will decrease. If it exceeds 20% by mass, the compatibility will decrease. In addition, for the modified epoxy resin (A) with respect to compatibility, water spot resistance, rust prevention property, and blocking resistance, the weight average molecular weight is preferably 10,000 or more and 100,000 or less, and more preferably 20,000 or more and 50,000 or less. If the number average molecular weight is less than 10,000, the water spot resistance, rust prevention property, and blocking resistance will decrease. Also, if the number average molecular weight exceeds 100,000, the compatibility will decrease. In the present invention, the weight average molecular weight is the value measured by size exclusion chromatography (SEC), and polystyrene is used as the standard substance.

[0024] In addition, the glass transition point (Tg) and softening point (Ts) of the modified epoxy resin (A) in the coating composition are not particularly limited. However, if the glass transition point (Tg) is too high, the rust prevention property and water spot resistance will decrease, and if the glass transition point (Tg) is too low, the blocking resistance will decrease. Therefore, the glass transition point (Tg) is preferably in the range of 20°C or higher and 110°C or lower, and more preferably in the range of 60°C or higher and 85°C or lower. With a modified epoxy resin (A) having a high polymer with a glass transition point (Tg) of 60°C or higher and 85°C or lower, a high-hardness coating film excellent in blocking resistance can be formed. Also, if the softening point (Ts) is too high, the rust prevention property and water spot resistance will decrease, and if the glass transition point (Tg) is too low, the blocking resistance will decrease. Therefore, the softening point (Ts) is preferably in the range of 80°C or higher and 150°C or lower. The glass transition point (Tg) is measured by a differential scanning calorimeter (DSC) in accordance with JIS K 7121. The softening point (Ts) is measured by the ring and ball method based on JIS K 2351.

[0025] <Pigment (B)> The coating composition of the present invention contains a pigment (B). As the pigment (B), it is necessary to contain at least an extender pigment (B1) in order to form a coating film having excellent water spot resistance, rust prevention property, and blocking resistance. Further, if necessary, a coloring pigment (B2), a rust prevention pigment (B3), and a metallic pigment (B4) can be included.

[0026] <<Extender Pigment (B1)>> The extender pigment (B1) is a white or colorless pigment. Since it has a low refractive index and has little effect on hiding power even when mixed with a vehicle, it is used as a bulking agent for adjusting coloring power, gloss, strength, feel of use, etc. As the extender pigment (B1), known materials can be used, and examples thereof include precipitated barium sulfate, silica, cristobalite, calcium carbonate, alumina, alum, clay, magnesium hydroxide, and magnesium oxide. Further, the extender pigment (B1) may be a pigment having a thin and flat shape such as a foil (scaly pigment), and specific examples thereof include glass flakes, talc, mica, and kaolin clay.

[0027] Due to its shape, the scaly extender pigment (B1) exhibits an effect of inhibiting the intrusion of corrosion factors such as water, oxygen, and chlorides, and an effect of reducing the internal stress of the coating film. By reducing the internal stress of the coating film, the adhesion of the coating film to the substrate can be further improved. In addition, the one-component epoxy resin coating composition of the present invention aims to form a coating film with a dry film thickness of 35 to 45 μm by a single coating at room temperature, and the use of a scaly pigment capable of reducing the internal stress of the coating film is very effective. Note that the scaly pigment may be part or all of the pigments used in the one-component epoxy resin coating composition of the present invention.

[0028] <<Coloring Pigment (B2)>> The coating composition of the present invention may contain a coloring pigment (B2), a rust preventive pigment (B3), and a bright pigment (B4) in addition to the extender pigment (B1). The coloring pigment (B2) is roughly classified into inorganic pigments and organic pigments according to its composition. Examples of inorganic pigments include titanium oxide, red iron oxide, yellow iron oxide, carbon black, etc., and examples of organic pigments include phthalocyanine blue, phthalocyanine green, naphthol red, quinacridone red, benzimidazolone yellow, Hansa yellow, benzimidazolone orange, and dioxazine violet.

[0029] <<Rust Preventive Pigment (B3)>> As the rust preventive pigment, known materials can be used, and examples thereof include zinc powder, zinc oxide, barium metaborate, calcium silicate, aluminum phosphate, condensed aluminum phosphate, aluminum tripolyphosphate, zinc phosphate, zinc phosphite, potassium phosphite, calcium phosphite, aluminum phosphite, calcium zinc phosphate, aluminum zinc phosphate, zinc phosphomolybdate, aluminum phosphomolybdate, magnesium phosphate, vanadic acid / phosphoric acid mixed pigment, and the like.

[0030] <<Bright pigment (B4)>> As the bright pigment, known materials can be used, and specific examples thereof include scaly metal pigments in which metals such as zinc, nickel, chromium, tin, copper, silver, platinum, gold, and aluminum are in a thin and flat shape like foil, and pearl pigments in which talc or mica is surface-treated with a metal oxide such as titanium oxide. Note that the scaly metal pigments include pigments of alloys such as stainless steel. These bright pigments may be used alone or in combination of two or more.

[0031] In addition, the pigment (B) contained in the coating composition of the present invention contains an extender pigment (B1) having an oil absorption of 10 ml / 100 g or more and 40 ml / 100 g or less. Here, the oil absorption is measured by the refined linseed oil method using linseed oil according to the JIS standard (JIS K 5101-13-1). When the oil absorption of the pigment (B) exceeds 40 ml / 100 g and is large, the surface area of the pigment is large and the surface shape becomes complicated, so that the compatibility as the coating performance, the water spot resistance, the rust prevention property, and the blocking resistance as the coating film performance are improved. When the oil absorption is less than 10 ml / 100 g and is small, particularly, the rust prevention property and the blocking resistance are greatly reduced. Further, a range of 15 ml / 100 g or more and 30 ml / 100 g or less is preferable.

[0032] In the paint composition of the present invention, the content of the pigment in the solid content of the film-forming component is preferably 60% by mass or more and 90% by mass or less, and more preferably 75% by mass or more and 85% by mass or less. Further, as each component of the pigment, the extender pigment (B1) is 55% by mass or more and 90% by mass or less, preferably 65% by mass or more and 85% by mass or less of the pigment (B), the coloring pigment (B2) is 3% by mass or more and 30% by mass or less, preferably 5% by mass or more and 20% by mass or less, and the rust preventive pigment (B3) is 1% by mass or more and 15% by mass or less, preferably 5% by mass or more and 10% by mass or less. By setting it within this range, a high-concentration paint composition can be obtained, and the water spot resistance, rust prevention property, and blocking resistance as film properties can be improved, and a strong film can be obtained.

[0033] <Solvent (C) containing no aromatic compounds> Normally, a solvent (D) containing an aromatic with high solubility of organic compounds is used in the paint composition. However, the paint composition of the present invention is a solvent (C) containing no aromatic compounds, and uses a solvent containing a glycol ether solvent and an alcohol solvent, and provides a one-component epoxy resin paint composition excellent in compatibility as paint performance and water spot resistance, rust prevention property, and blocking resistance as film performance. Aromatic solvents are difficult to dissolve in water due to the presence of a benzene ring, but have high solubility of organic compounds and high volatility due to low boiling points, so the painting work efficiency can be increased. However, since it is harmful to the human body and carcinogenic, there is a risk of causing occupational cancer, dermatitis, neuropathy, etc. to workers. Therefore, the solvent (C) containing no aromatic compounds of the present invention does not contain a solvent containing an aromatic compound, and contains an alcohol solvent and a glycol ether solvent, so that the solubility with the modified epoxy resin (A) is increased and the compatibility of the paint performance is achieved, and the water spot resistance, rust prevention property, and blocking resistance as film performance can be improved.

[0034] Alcohol solvents are solvents having a hydroxyl group in the molecule. Specifically, monohydric alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, normal propyl alcohol, isobutyl alcohol, normal butyl alcohol, 2-ethylbutyl alcohol, 2-ethylhexyl alcohol, cyclohexanol, and methyl amyl alcohol, and dihydric alcohols such as ethylene glycol and propylene glycol can be mentioned.

[0035] In addition, glycol ether solvents are solvents having both a hydroxyl group and an ether group in the molecule. Specifically, propylene glycol monomethyl ether (1-methoxy-2-propanol), ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether (butyl cellosolve), 3-methoxy-3-methyl-1-butanol, ethylene glycol monopropyl ether, etc. can be mentioned.

[0036] Note that aromatic solvents are solvents containing aromatic compounds and are compounds having a benzene ring in a resonance state in the molecule. Examples include benzene, toluene, xylene, ethylbenzene, naphthalene, styrene monomer, C9 aromatic hydrocarbon mixture to C11 aromatic hydrocarbon mixture, etc.

[0037] Furthermore, the solvent (C) containing no aromatic compound of the present invention can contain a solvent having an ester structure. The solvent having an ester structure has R-C(=O)-OR' (R, R' are alkyl groups, etc.) in the molecule. The alcohol solvents and glycol ether solvents are miscible in any ratio. Specifically, ethyl acetate, butyl acetate, isobutyl acetate, etc. can be mentioned. Therefore, the compatibility with the modified epoxy resin (A) can be enhanced.

[0038] The content of the solvent (C) containing no aromatic compound in the present invention is 40% by mass or less based on the coating composition. When the content of the solvent (C) containing no aromatic compound in the present invention exceeds 40% by mass, the compatibility is improved, but the water spot resistance, rust prevention property, and blocking resistance decrease. In addition, the working time until drying in the coating operation becomes longer, and the working efficiency decreases. Furthermore, the possibility that the coating operator absorbs the solvent increases, and the possibility of health damage increases. The lower limit of the content of the solvent (C) containing no aromatic compound in the present invention is the content at which the viscosity becomes such that coating operation is impossible with respect to the coating composition. Thus, by including the solvent (C) containing no aromatic compound in the present invention in at least one kind of modified epoxy resin (A) selected from an amine-modified epoxy resin (A1), an isocyanate-modified epoxy resin (A2), and an acrylic-modified epoxy resin (A3) and the pigment (B), a coating composition excellent in coating performance and coating film performance can be obtained.

[0039] Also, the mass ratio of the glycol ether solvent to the solvent (C) containing no aromatic compound is 1 / 7 or more and 1 / 2 or less. The glycol ether solvent has more hydrogen bonds via hydroxy groups and stronger intermolecular forces than the alcohol solvent, so it has a relatively high melting point and viscosity for its molecular weight and easily dissolves the epoxy resin as a solvent. Therefore, when the glycol ether solvent is less than 1 / 7 with respect to the solvent (C) containing no aromatic compound, the amount of the alcohol solvent increases, the solubility of the resin deteriorates, and the rust prevention property and blocking resistance decrease. When the glycol ether solvent exceeds 1 / 2 with respect to the solvent (C) containing no aromatic compound, the water spot resistance decreases.

[0040] <Epoxy ester resin (E)> Further, the coating composition of the present invention preferably contains an epoxy ester resin (E). The epoxy ester resin (E) of the present invention is preferably one obtained by reacting a fatty acid with an epoxy group of an epoxy resin for modification. Examples of the epoxy ester resin (E) include an adduct of an epoxy resin and an acid such as an aliphatic acid, a reaction product of this adduct with an isocyanate compound or a hydroxycarboxylic acid, and a vinyl-modified product thereof. The epoxy ester resin (E) in the present invention preferably has a weight average molecular weight of 10,000 or more and 100,000 or less, and more preferably 20,000 or more and 50,000 or less. If the weight average molecular weight is less than 10,000, the water spot resistance, rust prevention property, and blocking resistance will decrease. On the other hand, if it exceeds 100,000, the compatibility will decrease.

[0041] The glass transition point (Tg) and softening point (Ts) of the epoxy ester resin (E) of the present invention are not particularly limited, but the glass transition point is -20°C or more and 100°C or less, more preferably -10°C or more and 60°C or less, and even more preferably 0°C or more and 40°C or less. The softening point is -20°C or more and 100°C or less, more preferably -20°C or more and 70°C or less, and even more preferably -10°C or more and 40°C or less.

[0042] Examples of the epoxy ester resin (E) used in the present invention include those having an acid value of 5 or more and 100 or less, among which those having an acid value of 15 or more and 40 or less are preferable, and those having an acid value of 20 or more and 35 or less are more preferable.

[0043] The mass ratio of the modified epoxy resin (A) to the epoxy ester resin (E) (modified epoxy resin (A) / epoxy ester resin (E)) is in the range of 40 / 60 or more and 90 / 10 or less, preferably in the range of 40 / 60 or more and 70 / 30 or less. By setting it within this range, the generation of water spots can be suppressed while increasing the coating solid content to enable high solidification. In the present invention, the mass ratio of the total value of the modified epoxy resin (A) and the epoxy ester resin (E) in the solid content of the coating composition is 5% by mass or more and 25% by mass or less, preferably 15% by mass or more and 20% by mass or less.

[0044] <Epoxy resin (F)> In the coating composition of the present invention, a low-molecular-weight epoxy resin (F) may be contained to improve adhesion. Examples of this low-molecular-weight epoxy resin (F) include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, aliphatic type epoxy resin, glycidylamine type epoxy resin, and the like. This epoxy resin (F) is contained in an amount of 2 to 7% by mass of the solid content of the coating composition of the present invention.

[0045] The low-molecular-weight epoxy resin (F) is contained in a range of 5 or more and 20 or less with respect to 100 of the total mass of the modified epoxy resin (A) and the epoxy ester resin (E). Since it is unmodified and has a small molecular weight, when this ratio exceeds 20, the water spot resistance, rust prevention property, and blocking resistance decrease. When this ratio is less than 5, the compatibility decreases. Further, the low-molecular-weight epoxy resin (F) has a weight average molecular weight in the range of 300 or more and 1000 or less, preferably in the range of 500 or more and 900 or less. Thereby, the compatibility as a coating performance and the water spot resistance, rust prevention property, and blocking resistance as a coating film performance can be improved. However, when the weight average molecular weight is less than 300, the rust prevention property and blocking resistance decrease, and when the weight average molecular weight exceeds 1000, the water spot resistance decreases.

[0046] <Other additives (G)> The paint composition of the present invention can be appropriately blended with other resins, matting agents, flexibility imparting agents, surface modifiers, wetting agents, dispersants, emulsifiers, viscosity modifiers, anti-settling agents, anti-skinning agents, anti-dripping agents, defoaming agents, anti-color separation agents, leveling agents, drying agents, plasticizers, film-forming aids, fungicides, antibacterial agents, insecticides, light stabilizers, ultraviolet absorbers, antistatic lubricants, antistatic agents, conductivity imparting agents, etc. as other additives according to the purpose. Commercially available products can be preferably used for these components.

[0047] <<Anti-settling agent (G1)>> The anti-settling agent of the present invention is used to prevent the sedimentation of light diffusing particles dispersed in the paint main component composition when the paint main component composition contains an organic solvent. As the anti-settling agent, known ones can be used. Also, the above-mentioned antistatic agent and anti-blocking agent (fatty acid amide, etc.) can be used as the anti-settling agent. The anti-settling agent may be used alone or in combination of two or more.

[0048] <<Defoaming agent (G2)>> Examples of the defoaming agent (G2) of the present invention include silicone-based defoaming agents and non-silicone-based defoaming agents. The silicone-based defoaming agent is a defoaming agent containing a surfactant polysiloxane or its modified product, and the non-silicone-based defoaming agent is a defoaming agent not containing polysiloxane or its modified product. Examples of the silicone-based defoaming agent include polysiloxane, fluorine-modified siloxane, amino-modified siloxane, alkyl-modified siloxane, etc. Examples of the non-silicone-based defoaming agent include higher alcohol-based, higher alcohol derivative-based, fatty acid-based, etc. Particularly from the viewpoint of the finished appearance when painted with a roller, the defoaming agent (G2) is preferably a fluorine-modified silicone-based defoaming agent. The content of the defoaming agent (G2) is preferably in the range of 0.05 to 5.0 parts by mass, more preferably in the range of 0.1 to 3.5 parts by mass, based on 100 parts by mass of the resin component contained in the main agent.

[0049] <<Surface modifier (G3)>> The surface preparation agent of the present invention is not particularly limited, and examples thereof include fluorine-based additives, cellulose-based additives, and the like. The above-mentioned fluorine-based additives have the effect of preventing repelling when applied to FRP materials by reducing the surface tension and enhancing the wettability. Specific examples of the above-mentioned fluorine-based additives include, for example, Mega Fac F-558 (manufactured by Dainippon Ink and Chemicals, Inc.).

[0050] These additives (G) can further improve the compatibility, water spot resistance, rust prevention property, and blocking resistance of the paint composition of the present invention. In the one-component epoxy resin paint composition of the present invention, these additives (G) may be used alone or in combination of two or more. The content of the additive (G) is preferably 0.1 to 10% by mass in the paint composition of the present invention.

[0051] <Manufacturing method of one-component epoxy resin paint composition> The one-component epoxy resin paint composition of the present invention is prepared, for example, by blending a binder resin, a pigment, a solvent, and various additives appropriately selected as needed, and stirring and kneading them. In that case, it is preferable to use an SG mill or the like to disperse them as uniformly as possible.

[0052] <Coating method> The method for applying the one-component epoxy resin paint composition of the present invention is not particularly limited, and known coating methods such as dipping method, spin coating method, flow coating method, roll coating method, spray coating method, blade coating method, and air knife coating method can be mentioned.

[0053] <Uses of one-component epoxy resin paint composition> The one-component epoxy resin coating composition of the present invention can be used for spray coating or dipping coating. For example, it can be used to form a coating film on the surface of metal substrates of structures such as buildings and structures, vehicles (automobiles, etc.), furniture, fittings, electronic devices (home appliances, etc.) and their parts. The metal substrate is not particularly limited, and its shape is, for example, plate-like, sheet-like, foil-like, etc. Also, examples of the metal constituting the substrate include steel, galvanized steel, stainless steel, magnesium alloy, aluminum, aluminum alloy, etc. Among them, steel is preferred. Furthermore, various surface treatments, such as oxidation treatment, may be applied to the metal substrate. As an example, substrates obtained by subjecting steel or aluminum to oxidation treatment by methods such as anodizing, phosphate treatment, chromate treatment, and non-chromate treatment can be used. In addition, the metal substrate also includes various plastic substrates provided with a metal thin film on the surface (the shape thereof includes, for example, a housing having a three-dimensional structure and a film, etc.). For forming the metal film, vapor deposition, sputtering, plating methods, etc. can be used. Examples of the metal thin film include thin films of metals such as aluminum, tin, zinc, gold, silver, platinum, and nickel. The coating amount of the one-component epoxy resin coating composition of the present invention can be changed according to the type and use of the substrate to be coated.

Examples

[0054] <Preparation of Examples 1 to 25 and Comparative Examples 1 to 7> According to the formulation shown in Table 1 (the values are in parts by mass), at least one kind of modified epoxy resin (A) selected from an amine-modified epoxy resin (A1), an isocyanate-modified epoxy resin (A2), and an acrylic-modified epoxy resin (A3), a pigment (B), a solvent (C) that does not contain an aromatic compound, and other raw materials were premixed and then subjected to dispersion treatment with a bead mill. After adding the modified epoxy resin (A) and an acrylic resin to this dispersion-treated mixture while stirring, the other raw materials were also added while stirring in the same manner to obtain a one-component epoxy resin coating composition (Examples 1 to 25, Comparative Examples 1 to 7). NV refers to the non-volatile content (%) in the resin. The non-volatile content means the components remaining when the coating composition is dried under the measurement conditions: 130 °C for 40 minutes.

[0055] The details of the raw materials used and the formulation examples are shown in Table 1. (A-1) Modified epoxy resin solution (trade name: KA-1494D, manufactured by Arakawa Chemical Industries, Ltd., NV: 50%, solvent components: 30% propylene glycol monomethyl ether, 30% propylene glycol monomethyl ether acetate, 20% cyclohexanone, 20% propyl acetate) (A-2) Modified epoxy resin solution (trade name: Modepix 408, manufactured by Arakawa Chemical Industries, Ltd., NV: 40%, solvent components: 30% propylene glycol monomethyl ether, 30% propylene glycol monomethyl ether acetate, 20% cyclohexanone, 20% propyl acetate) (A-3) Modified epoxy resin solution (trade name: Arakyd 9212, manufactured by Arakawa Chemical Industries, Ltd., NV: 40%, solvent components: 50% xylene, 20% propylene glycol monomethyl ether acetate, 20% cyclohexanone, 10% n-butanol) (E-1) Epoxy ester resin solution (NV: 60%, from Synthesis Example 1) (F-1) Epoxy resin solution (a solution obtained by diluting Mitsubishi Chemical Corporation's epoxy resin jER834 (weight average molecular weight 500) with xylene. Xylene content 10% by mass.) (F-2) Epoxy resin solution (a solution obtained by diluting Mitsubishi Chemical Corporation's epoxy resin jER834 (weight average molecular weight: 500) with butyl acetate. Butyl acetate content: 20%) (F-3) Epoxy resin solution (a solution obtained by diluting Mitsubishi Chemical Corporation's epoxy resin jER1001 (weight average molecular weight: 900) with butyl acetate. Butyl acetate content: 40%) (F-4) Liquid epoxy resin solution (Mitsubishi Chemical Corporation's epoxy resin jER828 (weight average molecular weight: 370), NV: 100%)

[0056] (B1-1) Extender pigment (trade name: TF heavy calcium, manufactured by Maruo Calcium Co., Ltd., calcium carbonate, oil absorption: 23 ml / 100 g) (B1-2) Extender pigment (product name: precipitated barium sulfate, manufactured by Sakai Chemical Industry Co., Ltd., oil absorption: 20 ml / 100 g) (B1-3) Extender pigment (product name: Talc S, manufactured by Nippon Talc Refining Co., Ltd., talc, oil absorption: 25 ml / 100 g) (B2-1) Color pigment (product name: TITONE R-5N, manufactured by Sakai Chemical Industry Co., Ltd., titanium oxide, oil absorption: 20 ml / 100 g) (B3-1) Anti-rust pigment (product name: Zinc Phosphate PZ20, manufactured by SNCZ, zinc phosphate)

[0057] (C-1) Solvents that do not contain aromatic compounds (butyl acetate) (C-2) Solvents that do not contain aromatic compounds (n-butyl alcohol) (C-3) Solvents that do not contain aromatic compounds (propylene glycol monomethyl ether) (D-1) Solvents containing aromatic compounds (xylene) (D-2) Solvents containing aromatic compounds (C9-C11 aromatic mixtures)

[0058] (G1-1) Suspension inhibitor (product name: Disparlon PF920, manufactured by Kusumoto Chemical Industries, oxidized polyolefin suspension inhibitor, NV: 20%) (G2-1) Defoamer (product name: FLOWLEN AC300HF, manufactured by Kyoeisha Chemical Co., Ltd., acrylic defoamer, NV: 77%) (G3-1) Surface conditioner (a silicone oil-based surface conditioner manufactured by Shin-Etsu Silicone Co., Ltd., product name: KF-69 (NV: 100%) diluted with butyl acetate. Butyl acetate content: 99%)

[0059] Here, Synthesis Example 1 of an epoxy ester resin solution (NV: 60%) will be described. <Synthesis Example 1> A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dehydration device, and a nitrogen gas inlet tube was charged with 36 parts by mass of an epoxy resin (jER1004, manufactured by Mitsubishi Chemical Corporation), 24 parts by mass of soybean oil, 15 parts by mass of butyl acetate, and 12 parts by mass of propylene glycol monomethyl ether. The mixture was heated and stirred under a nitrogen atmosphere, and the reaction was carried out at 250 °C until the acid value reached 3 mgKOH / g or less, and then cooled. Next, 13 parts by mass of butyl acetate was charged to obtain the target epoxy ester resin solution (E-1) (non-volatile content: 60%).

[0060] Table 1-1 shows Examples 1 to 9 prepared according to the formulation, Table 1-2 shows Examples 10 to 17 prepared according to the formulation, and Table 1-3 shows Examples 18 to 25 prepared according to the formulation. Table 2 shows Comparative Examples 1 to 7 prepared according to the formulation.

[0061]

Table 1-1

[0062]

Table 1-2

[0063]

Table 1-3

[0064]

Table 2

[0065] <Evaluation of Paint Performance and Coating Film Performance> The compatibility of Examples 1 to 25 and Comparative Examples 1 to 7 was evaluated as the paint performance. In addition, the water spot resistance, rust prevention property, and blocking resistance of the coating films on the test panels (coated bodies) of Examples 1 to 25 and Comparative Examples 1 to 7 were evaluated. The test panels were prepared by uniformly coating the prepared one-component epoxy resin paint composition on a zinc-plated steel sheet subjected to non-chromate treatment using an air spray, and drying at a constant temperature for a certain period of time to form a test coating film. The evaluation method will be described below. Table 3 also shows the evaluation results of Examples 1 to 25. Furthermore, Table 4 shows the evaluation results of Comparative Examples 1 to 7.

[0066] <<Compatibility>> A solution of modified epoxy resin (A) and epoxy ester resin (E) solution, and epoxy resin (F) in the same amount as the paint formulation were placed in a mixed solution of solvent (C) containing no aromatic compounds and solvent (D) containing aromatic compounds, stirred, and then allowed to stand at 25°C for 24 hours. Thereafter, visual confirmation of separation was performed. The evaluation criteria are as follows. ○: Dissolved in the solvent and does not separate even after 24 hours. ×: Dissolves in the solvent but separates after 24 hours. Or does not dissolve.

[0067] <<Water spot resistance>> Coating was performed using an air spray so that the film thickness after drying was 30 μm or more and 40 μm or less. After coating, it was allowed to stand in an environment of 23°C and 50% RH for 1 hour. Thereafter, 2 ml of ion-exchanged water was dropped onto the coating film surface using a dropper, and a polycup with a capacity of about 50 ml was covered to prevent evaporation. After 18 hours from dropping, the water droplets were removed and it was confirmed whether discoloration marks such as whitening were visible on the coating film surface, and evaluation was performed according to the following criteria. ○: No water spot marks remain at all. △: Slight water spot marks remain. ×: Obvious water spot marks remain. -: Evaluation cannot be performed because the compatibility between the resin and the solvent in the paint is poor.

[0068] <<Rust prevention property>> The rust prevention property was evaluated by a salt spray resistance test. In the salt spray test, a cross cut was made with a cutter knife on the coating film surface formed on the test plate. The test coated plate was subjected to a salt spray test at 35°C for 240 hours, the occurrence of rust was observed, and the abnormal width from the cut part was evaluated according to the following criteria. ○: No rust or swelling is observed outside the cross cut part, and the rust is less than 1 mm from the cut part. △: No rust or swelling is observed outside the cross-cut area, and the rust is within 1 - 3 mm from the cut area. ×: Rust and swelling are observed throughout the coating film. -: Evaluation cannot be performed because the compatibility between the resin and the solvent in the paint is poor.

[0069] <<Blocking Resistance>> The paint composition adjusted to the specified dilution amount using a dedicated thinner was applied to two 100×100×0.3 mm tin plates by air spraying so that the dry film thickness was 30 - 40 μm. After standing for 2 hours in an environment of 23°C and 50% RH, the two painted surfaces were overlapped, and a load of 20 kg (0.2 kg / cm 2 ) was applied over 1 hour. Then, the coated plates were separated, and the peeling and adhesion of the surface coating film were evaluated according to the following criteria. ○: No peeling or adhesion, and no trace remains on the coating film surface. △: Slight peeling of the coating film is observed at the plate ends, etc. ×: Peeling of the coating film is observed throughout the coating film. -: Evaluation cannot be performed because the compatibility between the resin and the solvent in the paint is poor.

[0070]

Table 3

[0071]

Table 4

[0072] From the results shown in Table 3, the one-component epoxy resin paint compositions of Examples 1 - 25 all had evaluations of "〇" or "△" in terms of compatibility, water spot resistance, and rust prevention, and there were no practical problems.

[0073] From the results shown in Table 4, since the one-component epoxy resin coating composition of Comparative Example 1 does not contain the modified epoxy resin (A), the mass ratio of the modified epoxy resin (A) to the epoxy ester resin (E) (modified epoxy resin (A) / epoxy ester resin (E)) is 0 / 100, and it does not separate even after 24 hours, and the compatibility is "〇", but the other coating film properties such as water spot resistance, rust prevention property, and blocking resistance are "×".

[0074] The one-component epoxy resin coating composition of Comparative Example 2 has a large total amount of the modified epoxy resin (A) and the epoxy ester resin (E) in the solid content and does not contain the pigment (B). Also, the content of the solvent (C) that does not contain aromatic compounds exceeds 40%. As a result, the compatibility and rust prevention property were "〇", but the other coating film properties such as water spot resistance and blocking resistance were "×".

[0075] The one-component epoxy resin coating composition of Comparative Example 3 contains the modified epoxy resin (A-3) using a solvent containing an aromatic compound, so the compatibility is "×", and the other coating film properties such as water spot resistance, rust prevention property, and blocking resistance are also "×".

[0076] The one-component epoxy resin coating composition of Comparative Example 4 does not contain the solvent (C) that does not contain aromatic compounds and contains the solvent (D) that contains aromatic compounds, so the mass ratio of the glycol ether-based solvent to the solvent (C) that contains aromatic compounds is outside the scope of the invention. As a result, the compatibility is "×", and the other coating film properties such as water spot resistance and rust prevention property are also "×".

[0077] The one-component epoxy resin coating composition of Comparative Example 5 does not contain the glycol ether-based solvent with the solvent (C) that does not contain aromatic compounds, so the mass ratio of the glycol ether-based solvent to the solvent (C) that contains aromatic compounds is outside the scope of the invention. As a result, the compatibility is "×", and the other coating film properties such as water spot resistance and rust prevention property are also "×".

[0078] The one-component epoxy resin coating composition of Comparative Example 6 does not contain an alcohol-based solvent in a solvent (C) that does not contain an aromatic compound. As a result, the compatibility was "×", and the water spot resistance of other coating film properties was also "×".

[0079] The one-component epoxy resin coating composition of Comparative Example 7 contains a solvent (C) that does not contain an aromatic compound, but the content exceeds 40% by mass. As a result, the blocking resistance was "×".

[0080] From the results of these Examples 1 to 25 and Comparative Examples 1 to 7, it was found that the one-component epoxy resin coating composition of the present invention has no practical problems with respect to compatibility, water spot resistance, rust prevention, and blocking resistance.

Claims

1. At least one kind of modified epoxy resin (A) selected from an amine-modified epoxy resin (A1), an isocyanate-modified epoxy resin (A2), and an acrylic-modified epoxy resin (A3), a pigment (B), a solvent (C) that does not contain an aromatic compound, and a paint composition comprising: the solvent (C) includes a glycol ether solvent, an alcohol solvent, and a solvent having an ester structure, the content of the solvent (C) is 40% by mass or less with respect to the paint composition, the glycol ether solvent has a mass ratio to the solvent (C) of 0.14 or more and 0.56 or less, a one-component epoxy resin paint composition that does not contain a solvent (D) containing an aromatic compound.

2. The one-component epoxy resin paint composition according to Claim 1, wherein the mass ratio of the pigment (B) in the solid content of the paint composition is 60% by mass or more and 90% by mass or less.

3. The one-component epoxy resin paint composition according to Claim 1, wherein the mass ratio of the pigment (B) in the solid content of the paint composition is 75% by mass to 85% by mass.

4. The one-component epoxy resin paint composition according to Claim 1, wherein the pigment (B) includes an extender pigment (B1) having an oil absorption of 10 ml / 100 g or more and 40 ml / 100 g or less.

5. The one-component epoxy resin paint composition according to Claim 1, wherein the paint composition further includes an epoxy ester resin (E).

6. The one-component epoxy resin paint composition according to Claim 5, wherein the mass ratio of the modified epoxy resin (A) to the epoxy ester resin (E) (modified epoxy resin (A) / epoxy ester resin (E)) is in the range of 40 / 60 or more and 90 / 10 or less.

7. The one-component epoxy resin paint composition according to Claim 5, wherein the mass ratio of the modified epoxy resin (A) to the epoxy ester resin (E) (modified epoxy resin (A) / epoxy ester resin (E)) is in the range of 40 / 60 or more and 70 / 30 or less.

8. The one-component epoxy resin paint composition according to Claim 5, wherein the mass ratio of the total value of the modified epoxy resin (A) and the epoxy ester resin (E) in the solid content of the paint composition is 5% by mass or more and 25% by mass or less.

9. The one-component epoxy resin coating composition according to claim 5, wherein the mass ratio of the total value of the modified epoxy resin (A) and the epoxy ester resin (E) in the solid content of the coating composition is 15% by mass or more and 20% by mass or less.

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