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WO2025182280A1 - Composition de revêtement aqueuse - Google Patents

Composition de revêtement aqueuse

Info

Publication number
WO2025182280A1
WO2025182280A1 PCT/JP2024/045998 JP2024045998W WO2025182280A1 WO 2025182280 A1 WO2025182280 A1 WO 2025182280A1 JP 2024045998 W JP2024045998 W JP 2024045998W WO 2025182280 A1 WO2025182280 A1 WO 2025182280A1
Authority
WO
WIPO (PCT)
Prior art keywords
acrylic
resin particles
epoxy resin
meth
acrylate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2024/045998
Other languages
English (en)
Japanese (ja)
Inventor
直子 上里
大作 伊藤
亜美 滋野
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kansai Paint Co Ltd
Original Assignee
Kansai Paint Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kansai Paint Co Ltd filed Critical Kansai Paint Co Ltd
Publication of WO2025182280A1 publication Critical patent/WO2025182280A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
    • C09D163/10—Epoxy resins modified by unsaturated compounds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/08—Anti-corrosive paints
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/65—Additives macromolecular

Definitions

  • the present invention relates to an aqueous coating composition.
  • the typical process involves applying molding oil, degreasing the formed steel, preheating it to the desired temperature (around 80-110°C), and then airlessly painting it with anti-rust paint.
  • the above process is carried out in a short time (about 5 minutes from forming the steel to bundling the painted steel), so the anti-rust paint must be quick-drying and highly hard. Furthermore, since the painted steel is bound, stacked and transported by crane within minutes, the paint must also have excellent blocking resistance (preventing the paint films from sticking together).
  • Patent Document 1 discloses an aqueous coating composition containing 10 to 80 parts by weight of a water-based acrylic-modified alkyd resin (A) and 20 to 90 parts by weight of a water-based acrylic-modified epoxy resin (B) as a binder, which is a coating composition that has excellent adhesion to oily surfaces, high-temperature finish, roll-touch coating film peelability, blocking resistance, and rust prevention properties.
  • Patent Document 2 discloses an aqueous rust-preventive composition characterized by blending 100 parts by weight of an aqueous resin composition consisting of 20 to 100 parts by weight of a styrene-butadiene copolymer with a glass transition point of 30 to 80°C and 0 to 80 parts by weight of an ethylene-acrylic acid copolymer with 1 to 30 parts by weight of a water-soluble solvent and 0.01 to 2.0 parts by weight of an aqueous chromium compound in terms of chromate ions, and adjusting the pH to 7 or higher.
  • an aqueous resin composition consisting of 20 to 100 parts by weight of a styrene-butadiene copolymer with a glass transition point of 30 to 80°C and 0 to 80 parts by weight of an ethylene-acrylic acid copolymer with 1 to 30 parts by weight of a water-soluble solvent and 0.01 to 2.0 parts by weight of an aqueous chromium compound in terms of chromate ions
  • Patent Document 3 discloses an aqueous coating composition characterized by containing, as resin components, urethane resin particles having a specific weight-average molecular weight range and glass transition temperature range, and acrylic resin particles having a specific glass transition temperature range.
  • the aqueous coating composition described in Patent Document 1 is excellent in rust prevention and film-forming properties (quick drying), it is insufficient in blocking resistance. Furthermore, the aqueous anticorrosive composition described in Patent Document 2 has excellent anticorrosive properties, but contains harmful chromium compounds, and is therefore undesirable from the standpoint of environmental protection.
  • the aqueous coating composition described in Patent Document 3 is excellent in quick drying, blocking resistance and rust prevention, but the coating film performance such as water resistance (water-resistant adhesion) is sometimes insufficient.
  • the object of the present invention is to provide an aqueous coating composition that can be used for both ambient-dry and baked coating, has excellent film-forming properties, water resistance (water-resistant adhesion), blocking resistance, and rust prevention, and is free of environmentally hazardous substances (such as lead and chromium), and can form a highly hard coating film.
  • An aqueous coating composition comprising acrylic-modified epoxy resin particles (A) having a glass transition temperature of 30°C or higher, acrylic resin particles (B) having a glass transition temperature of 30°C or lower, and an organic solvent (C), wherein the acrylic-modified epoxy resin particles (A) account for 20 to 60 mass% and the acrylic resin particles (B) account for 40 to 80 mass% in terms of solid content relative to the total solid content of the acrylic-modified epoxy resin particles (A) and the acrylic resin particles (B), and the weighted average boiling point of the organic solvent (C) is 200°C or lower.
  • aqueous coating composition according to item 1, further comprising at least one of a rust inhibitor (D) and a pigment (E).
  • a coating method comprising the steps of preheating an object to be coated, applying the aqueous coating composition described in any one of items 1 to 3 above, and then drying the applied surface using residual heat.
  • the aqueous paint composition of the present invention uses a combination of acrylic-modified epoxy resin particles with a high glass transition temperature and acrylic resin particles with a low glass transition temperature as resin components, and is characterized by the weighted average boiling point of the contained organic solvent being below a specific temperature. This makes it possible to achieve both film-forming properties (quick drying) and blocking resistance, and to obtain a paint film that also has excellent rust prevention and water resistance.
  • the aqueous coating composition of the present invention can be used for both ambient-drying and baking coating.
  • the aqueous coating composition of the present invention can be used not only for outdoor painting (ambient-drying painting) at construction sites and the like, but also for efficient painting (usually baking painting) on production lines for coated steel materials, etc., thereby achieving the effect of producing coated articles such as coated steel materials with excellent rust prevention properties.
  • the aqueous coating composition of the present invention contains acrylic-modified epoxy resin particles (A) having a glass transition temperature of 30°C or higher, acrylic resin particles (B) having a glass transition temperature of 30°C or lower, and an organic solvent (C), and the aqueous coating composition contains 20 to 60 mass% of acrylic-modified epoxy resin particles (A) and 40 to 80 mass% of acrylic resin particles (B) in terms of solid content relative to the total solid content of the acrylic-modified epoxy resin particles (A) and the acrylic resin particles (B), and the weighted average boiling point of the organic solvent (C) is 200°C or lower.
  • the aqueous paint composition of the present invention (hereinafter sometimes referred to as "the paint") will be described in detail below.
  • the acrylic-modified epoxy resin particles (A) are particles of an epoxy resin modified with an acrylic, and the acrylic-modified epoxy resin can be produced, for example, by the following methods (1) to (3).
  • component (A) A method of graft polymerizing a polymerizable unsaturated monomer, such as an acrylic monomer, onto an epoxy resin by a hydrogen abstraction reaction.
  • the acrylic-modified epoxy resin produced by method (3) is preferred from the viewpoint of obtaining a coating film with good film-forming properties and excellent rust prevention properties.
  • Epoxy resin (a1) is a resin obtained by reacting a polyphenol compound with an epihalohydrin, such as epichlorohydrin.
  • examples of the polyphenol compound include bis(4-hydroxyphenyl)-2,2-propane (also known as “bisphenol A”), 4,4-dihydroxybenzophenone, bis(4-hydroxyphenyl)methane (also known as “bisphenol F”), and 4,4-dihydroxydiphenyl sulfone (also known as "bisphenol S”). From the standpoint of rust prevention, bisphenol A-type epoxy resin is preferred for epoxy resin (a1).
  • Bisphenol A epoxy resins can be obtained, for example, by polymerizing bisphenol A and epichlorohydrin.
  • Bisphenol A epoxy resins can also be obtained by a two-stage polymerization method in which bisphenol A is added to a bisphenol A epoxy resin with a relatively low epoxy equivalent.
  • the above-mentioned bisphenol A epoxy resins with a relatively low epoxy equivalent weight generally have an epoxy equivalent weight of 160 to 2,000.
  • Commercially available products include, for example, jER828EL, jER1001, jER1004, and jER1007 manufactured by Mitsubishi Chemical Corporation; Araldite AER250, Araldite AER260, Araldite AER6071, Araldite AER6004, and Araldite AER6007 manufactured by Asahi Kasei Epoxy Corporation; Epomic R140, Epomic R301, Epomic R304, and Epomic R307 manufactured by Mitsui Chemicals, Inc.; and Adeka Resin EP-4100 and Adeka Resin EP-5100 manufactured by Asahi Denka Corporation.
  • the bisphenol A epoxy resin may also be a modified epoxy resin obtained by modifying a bisphenol A epoxy resin with a dibasic acid.
  • the bisphenol A epoxy resin to be reacted with the dibasic acid preferably has a number average molecular weight of 2,000 to 8,000 and an epoxy equivalent weight in the range of 1,000 to 4,000.
  • the dibasic acid may be a compound represented by the following general formula: HOOC-(CH 2 ) n -COOH (In the formula, n is an integer from 1 to 12.)
  • dibasic acids include succinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, dodecanedioic acid, and hexahydrophthalic acid, with adipic acid being preferred.
  • the bisphenol A-type modified epoxy resin can be obtained by reacting a mixture of the bisphenol A-type epoxy resin and a dibasic acid in the presence of an esterification catalyst such as tri-n-butylamine, an organic solvent, etc., at a reaction temperature of 120 to 180°C for 1 to 4 hours.
  • an esterification catalyst such as tri-n-butylamine, an organic solvent, etc.
  • the above-mentioned bisphenol A-type modified epoxy resins are preferred because the dibasic acid molecular chains introduced into the epoxy resin molecules act as plasticizing components, improving the coating's adhesion to substrates and rust prevention properties.
  • the epoxy resin (a1) used in producing the acrylic-modified epoxy resin preferably has a number average molecular weight in the range of 2,000 to 30,000, particularly 5,000 to 30,000, and an epoxy equivalent in the range of 1,000 to 10,000, particularly 1,500 to 10,000, from the viewpoints of the dispersion stability and viscosity of the resulting acrylic-modified epoxy resin in an aqueous medium, the rust resistance of the resulting coating film, and the finish.
  • the carboxyl group-containing acrylic resin (a2) (hereinafter sometimes abbreviated as "acrylic resin (a2)") used to produce the acrylic-modified epoxy resin by reacting it with the above-mentioned epoxy resin (a1) is an acrylic copolymer containing a carboxyl group-containing polymerizable unsaturated monomer such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, or fumaric acid as the monomer skeleton.
  • the weight-average molecular weight of the acrylic copolymer be in the range of 5,000 to 100,000, particularly 10,000 to 100,000, and that the resin acid value be in the range of 150 to 700 mgKOH/g, particularly 200 to 500 mgKOH/g.
  • acrylic resin (a2) other than the carboxyl group-containing polymerizable unsaturated monomer
  • alkyl esters of acrylic acid or methacrylic acid having 1 to 22 carbon atoms such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, benzyl (meth)acrylate, and stearyl (meth)acrylate; cyclohexyl (meth)acrylate, isobornyl (meth)acrylate; aromatic vinyl monomers, such as styrene, ⁇ -methylstyrene, and vinyltoluene; 2-hydroxyethyl (meth)acrylate, hydroxypropyl (eth)acrylate, 2-hydroxyeth
  • Suitable hydroxyl group-containing acrylic monomers include caprolactone-modified alkyl (meth)acrylates, which are obtained by ring-opening addition reaction of 1 mole of hydroxyalkyl (meth)acrylates such as hydroxyhexyl (meth)acrylate and hydroxyethyl (meth)acrylate with 1 to 5 moles of ⁇ -caprolactone; acrylamide monomers such as acrylamide, methacrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, N-n-propoxymethyl (meth)acrylamide, N-isopropoxymethyl (meth)acrylamide, N-n-butoxymethyl (meth)acrylamide, N-sec-butoxymethyl (meth)acrylamide, and N-tert-butoxymethyl (meth)acrylamide; acrylonitrile, methacrylonitrile, vinyl acetate, ethylene, and butadiene.
  • hydroxyalkyl (meth)acrylates such as
  • (meth)acrylate means “acrylate or methacrylate.”
  • (meth)acrylic acid means “acrylic acid or methacrylic acid.”
  • (meth)acryloyl means “acryloyl or methacryloyl.”
  • (meth)acrylamide means "acrylamide or methacrylamide.”
  • Acrylic resin (a2) can be obtained by copolymerizing a monomer mixture of the above-mentioned carboxyl group-containing polymerizable unsaturated monomer and the above-mentioned other monomers, for example, in an organic solvent in the presence of a radical polymerization initiator and/or a chain transfer agent at 80 to 150°C for 1 to 10 hours.
  • Examples of the polymerization initiator include organic peroxide initiators and azo initiators.
  • Examples of the organic peroxide initiators include benzoyl peroxide, t-butylperoxy 2-ethylhexanoate, di-t-butyl peroxide, t-butylperoxybenzoate, and t-amylperoxy 2-ethylhexanoate.
  • Examples of the azo initiators include azobisisobutyronitrile and azobisdimethylvaleronitrile.
  • Examples of the chain transfer agents include ⁇ -methylstyrene dimer and mercaptans.
  • Acrylic-modified epoxy resins can be obtained, for example, by esterifying epoxy resin (a1) and acrylic resin (a2) in an organic solvent in the presence of an esterification catalyst, for example, a tertiary amine such as triethylamine or dimethylethanolamine, or a trialkylphosphine such as triphenylphosphine, at 80 to 120°C for 0.5 to 8 hours.
  • an esterification catalyst for example, a tertiary amine such as triethylamine or dimethylethanolamine, or a trialkylphosphine such as triphenylphosphine, at 80 to 120°C for 0.5 to 8 hours.
  • the mass ratio of epoxy resin (a1) to acrylic resin (a2) can be selected appropriately depending on factors such as coating workability and coating film performance, but it is preferable that the solids mass ratio of resin (a1)/resin (a2) be in the range of 10/90 to 95/5, and particularly 20/80 to 90/10.
  • solid content refers to the proportion of non-volatile components in a sample, excluding volatile components such as water and organic solvents. This can be determined by drying approximately 2 g of a sample at 105°C for 3 hours and then measuring the mass before and after drying.
  • solid content mass refers to the mass of non-volatile components in a sample.
  • the acrylic-modified epoxy resin preferably has an acid value in the range of 20 to 120 mg KOH/g, particularly 30 to 100 mg KOH/g, and a weight-average molecular weight in the range of 1,000 to 40,000, particularly 2,000 to 20,000.
  • the weight-average molecular weight and number-average molecular weight are values calculated by converting the retention time (retention volume) measured by gel permeation chromatography using tetrahydrofuran as the solvent, based on the average molecular weight of polystyrene.
  • the gel permeation chromatograph may be, for example, an "HLC8120GPC” (manufactured by Tosoh Corporation), and four columns, “TSKgel G-4000HXL,” “TSKgel G-3000HXL,” “TSKgel G-2500HXL,” and “TSKgel G-2000HXL” (all product names manufactured by Tosoh Corporation), are used under the following conditions: mobile phase: tetrahydrofuran, measurement temperature: 40°C, flow rate: 1 mL/min, detector: RI.
  • Acrylic-modified epoxy resin particles (A) can be obtained by neutralizing the above-mentioned acrylic-modified epoxy resin and dispersing it in an aqueous medium to form an aqueous dispersion.
  • the neutralizing agent used for neutralization is not particularly limited as long as it is used as a neutralizing agent in the art, but amines, ammonia, etc. are preferred.
  • Representative examples of the above amines include triethylamine, triethanolamine, dimethylethanolamine, diethylethanolamine, morpholine, etc.
  • dimethylethanolamine and triethylamine are preferred from the standpoint of particle stability.
  • the degree of neutralization of the acrylic-modified epoxy resin is not particularly limited, but it is preferable to neutralize it in the range of 0.3 to 2.0 equivalents, and particularly 0.5 to 1.0 equivalents, relative to the carboxyl groups in the acrylic-modified epoxy resin.
  • aqueous media for producing an aqueous dispersion of acrylic-modified epoxy resin particles (A) include water and mixtures of water and organic solvents.
  • organic solvent Any organic solvent known in the art can be used as long as it does not affect the stability of the acrylic-modified epoxy resin particles (A) and is uniformly miscible with water.
  • organic solvents include ethylene glycol monobutyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, and diethylene glycol monoethyl ether.
  • organic solvents that do not mix uniformly with water can also be used as long as they are inactive and do not have any reactivity with the acrylic-modified epoxy resin particles (A) and do not affect the stability of the acrylic-modified epoxy resin particles (A).
  • organic solvents examples include aromatic hydrocarbon solvents such as toluene and xylene, ester solvents such as ethyl acetate and butyl acetate, and ketone solvents such as methyl ethyl ketone.
  • the above organic solvent has a boiling point of 200°C or less, particularly 170°C or less.
  • Aqueous dispersions of acrylic-modified epoxy resin particles (A) can be prepared according to methods commonly used in the art, such as a method in which the acrylic-modified epoxy resin is gradually added to an aqueous medium containing a neutralizing agent while stirring the aqueous medium; a method in which the acrylic-modified epoxy resin is neutralized with a neutralizing agent and then an aqueous medium is added to the stirred acrylic-modified epoxy resin; or a method in which the acrylic-modified epoxy resin is added to a stirred aqueous medium.
  • An emulsifier such as a surfactant can also be used to improve the dispersibility of the acrylic-modified epoxy resin particles (A).
  • the emulsifier may be any of the well-known anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, polymeric surfactants, reactive surfactants, and other surfactants commonly used in epoxy emulsions. Of these, anionic surfactants and nonionic surfactants are preferred.
  • anionic surfactants include alkyl sulfates such as sodium dodecyl sulfate, potassium dodecyl sulfate, and ammonium dodecyl sulfate; sodium dodecyl polyglycol ether sulfate; sodium sulforicinoleate; alkyl sulfonates such as alkali metal salts of sulfonated paraffin and ammonium salts of sulfonated paraffin; fatty acid salts such as sodium laurate, triethanolamine oleate, and triethanolamine abietate; alkylaryl sulfonates such as sodium benzenesulfonate and alkali metal sulfates of alkali phenol hydroxyethylene; high alkyl naphthalene sulfonates; naphthalene sulfonate-formalin condensates; dialkyl sulfosuccinates; polyoxyethylene alkyl
  • nonionic surfactants include ethylene oxide and/or propylene oxide adducts of alcohols having 1 to 18 carbon atoms, ethylene oxide and/or propylene oxide adducts of alkylphenols, and ethylene oxide and/or propylene oxide adducts of alkylene glycols and/or alkylenediamines.
  • the alcohols having 1 to 18 carbon atoms that constitute the nonionic surfactants include methanol, ethanol, propanol, 2-propanol, butanol, 2-butanol, tertiary butanol, amyl alcohol, isoamyl alcohol, tertiary amyl alcohol, hexanol, octanol, decane alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, and stearyl alcohol.
  • the alkylphenols include phenol, methylphenol, 2,4-di-tert-butylphenol, 2,5-di-tert-butylphenol, 3,5-di-tert-butylphenol, 4-(1,3-tetramethylbutyl)phenol, 4-isooctylphenol, 4-nonylphenol, 4-tert-octylphenol, and 4-decane.
  • alkylene glycols examples include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, and 1,6-hexanediol.
  • alkylene diamines examples include those in which the alcoholic hydroxyl groups of these alkylene glycols have been substituted with amino groups.
  • the ethylene oxide and propylene oxide adducts may be random or block adducts.
  • the amount used there are no particular restrictions on the amount used, and any amount can be used. However, if the mass ratio to the acrylic-modified epoxy resin particles is less than 0.01, sufficient dispersibility may not be achieved, and if it exceeds 0.3, the water resistance of the resulting coating may decrease, so a ratio of 0.01 to 0.3 is preferred, and 0.05 to 0.2 is even more preferred.
  • the weight-average molecular weight of the acrylic-modified epoxy resin particles (A) is preferably within the range of 1,000 to 40,000, particularly 1,500 to 30,000, and even more particularly 2,000 to 20,000.
  • the glass transition temperature (Tg) of the acrylic-modified epoxy resin particles (A) is 30°C or higher, preferably 40 to 100°C, and particularly preferably 50 to 90°C. Having a glass transition temperature (Tg) of 30°C or higher for the acrylic-modified epoxy resin particles (A) increases hardness, improving the blocking resistance and rust prevention properties of the aqueous coating composition.
  • the glass transition temperature (Tg) of the acrylic-modified epoxy resin particles (A) is determined by differential scanning calorimetry (DSC). Specifically, using a differential scanning calorimeter "DSC-220U” (Seiko Instruments Inc.), a sample is placed in a measuring cup and vacuum-suctioned to completely remove the solvent. The change in heat quantity is then measured in the range of -20°C to +200°C at a heating rate of 3°C/min, and the first change in the baseline on the low-temperature side is measured as the glass transition temperature.
  • DSC-220U differential scanning calorimeter
  • the average particle diameter of the acrylic-modified epoxy resin particles (A) is preferably within the range of 50 to 500 nm, more preferably 100 to 350 nm, and even more preferably 150 to 280 nm.
  • the average particle size can be measured by a common measuring means such as laser light scattering.
  • the average particle size of resin particles is a value measured at 20° C. using a submicron particle size distribution analyzer after diluting with deionized water in a conventional manner.
  • a submicron particle size distribution analyzer for example, a "COULTER N4 type" (trade name, manufactured by Beckman Coulter, Inc.) can be used.
  • the acrylic resin particles (B) may be those synthesized by either emulsion polymerization or solution polymerization, and both may be used in combination. However, from the viewpoint of blocking resistance, those synthesized by emulsion polymerization are preferably used.
  • the acrylic resin of the acrylic resin particles (B) also includes copolymer resins such as acrylic styrene resin, acrylic urethane resin, acrylic silicone resin, acrylic alkyd resin, and acrylic SBR resin (excluding acrylic-modified epoxy resin).
  • Emulsion polymerization can be carried out by conventional methods such as seed polymerization and mini-emulsion polymerization. For example, it can be carried out by emulsion polymerizing a polymerizable unsaturated monomer using a polymerization initiator in the presence of an emulsifier.
  • this can be done by dissolving an emulsifier in water or an aqueous medium containing an organic solvent such as alcohol as needed, and then adding the polymerizable unsaturated monomer and polymerization initiator dropwise while heating and stirring. It is also possible to add dropwise a polymerizable unsaturated monomer that has been previously emulsified using an emulsifier and water.
  • Anionic surfactants and nonionic surfactants are suitable as the emulsifiers.
  • anionic surfactants include sodium salts and ammonium salts of alkyl sulfonic acids, alkyl benzene sulfonic acids, alkyl phosphates, etc.
  • nonionic surfactants include polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene phenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, sorbitan monolaurate, sorbitan monostearate, sorbitan monostearate, sorbitan trioleate, polyoxyethylene sorbitan monolaurate, etc.
  • reactive anionic surfactants include ELEMINOL JS-1, ELEMINOL JS-2 (manufactured by Sanyo Chemical Industry Co., Ltd.), S-120, S-180A, S-180, LATEMUL PD-104, LATEMUL PD-420, LATEMUL PD-430S, LATEMUL PD-450 (manufactured by Kao Corporation), AQUALON HS-10, AQUALON KH-10 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), ADEKA REASOAP SE-10N, ADEKA REASOAP SE-20N, ADEKA REASOAP SR-1025, ADEKA REASOAP ER-10, ADEKA REASOAP ER-20, ADEKA REASOAP ER-30, ADEKA REASOAP ER-40 (manufactured by ADEKA Corporation), and ANTOX MS-60 (manufactured by Nippon Nyukazai Co., Ltd.
  • One or more of the above-mentioned emulsifiers and other dispersion stabilizers can be used in the emulsion polymerization reaction.
  • the amount of the emulsifier used is preferably 0.1 to 15% by mass, particularly 0.5 to 10% by mass, and even more particularly 1 to 5% by mass, based on the total amount of all monomers used.
  • polymerization initiator examples include organic peroxides such as benzoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, cumene hydroperoxide, tert-butyl peroxide, tert-butyl peroxylaurate, tert-butylperoxyisopropyl carbonate, tert-butyl peroxyacetate, and diisopropylbenzene hydroperoxide; azobisisobutyronitrile, azobis(2,4-dimethylamino)methylpropional;
  • suitable polymerization initiators include azo compounds such as azobis(2-methylpropiononitrile), azobis(2-methylbutyronitrile), 4,4'-azobis(4-cyanobutanoic acid), dimethylazobis(2-methylpropionate), azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], and azobis ⁇ 2-methyl-N
  • polymerization initiators can be used alone or in combination of two or more. If necessary, the above polymerization initiators can also be used in combination with a reducing agent such as sugar, sodium formaldehyde sulfoxylate, or an iron complex to form a redox initiator.
  • a reducing agent such as sugar, sodium formaldehyde sulfoxylate, or an iron complex to form a redox initiator.
  • the amount of the polymerization initiator used is generally 0.1 to 5% by mass, and preferably 0.2 to 3% by mass, based on the total amount of all monomers used.
  • the method of adding the polymerization initiator is not particularly limited and can be selected appropriately depending on the type and amount.
  • the initiator may be added in advance to the monomer mixture or aqueous medium, or may be added all at once or dropwise during polymerization.
  • a chain transfer agent can also be used to adjust the molecular weight of the resulting acrylic resin particles (B).
  • chain transfer agents include compounds containing a mercapto group, such as lauryl mercaptan, t-dodecyl mercaptan, octyl mercaptan, 2-ethylhexyl thioglycolate, 2-methyl-5-tert-butylthiophenol, mercaptoethanol, thioglycerol, mercaptoacetic acid (thioglycolic acid), mercaptopropionate, and n-octyl-3-mercaptopropionate.
  • its amount is generally preferably in the range of 0.05 to 10% by mass, and particularly 0.1 to 5% by mass, based on the total amount of all monomers used.
  • the concentration of all polymerizable unsaturated monomers during the emulsion polymerization reaction is typically within the range of 0.1 to 60% by mass, preferably 0.5 to 50% by mass, and more preferably 1.0 to 50% by mass.
  • the reaction temperature is primarily determined by the initiator; for example, it is preferably 60 to 90°C for azo compounds and 30 to 70°C for redox initiators. Generally, the reaction time can be 1 to 8 hours.
  • the polymerizable unsaturated monomer conventionally known ones can be used, for example, reactive group-containing polymerizable unsaturated monomers and other polymerizable unsaturated monomers can be used.
  • the reactive group of the reactive group-containing polymerizable unsaturated monomer include reactive functional groups such as a hydroxyl group, an acid group, a carbonyl group, an N-methylol alkyl ether group, an isocyanate group, an epoxy group, an amino group, an alkoxysilyl group, a carbodiimide group, and a hydrazide group.
  • hydroxyl group-containing polymerizable unsaturated monomers examples include 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, ⁇ -caprolactone-modified tetrahydrofurfuryl (meth)acrylate, ⁇ -caprolactone-modified hydroxyethyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-hydroxy-3-butoxypropyl (meth)acrylate, and monohydroxyethyl phthalate (meth)acrylate.
  • 2-hydroxyethyl (meth)acrylate hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and ⁇ -caprolactone-modified hydroxyethyl (meth)acrylate can be preferably used.
  • acid group-containing polymerizable unsaturated monomers examples include carboxyl group- or acid anhydride group-containing polymerizable unsaturated monomers.
  • polymerizable unsaturated monomers containing a carboxyl group or an acid anhydride group examples include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, and ⁇ -carboxyethyl acrylate, as well as their acid anhydrides. Of these, acrylic acid and methacrylic acid are preferred.
  • polymerizable unsaturated monomers containing an acid group other than a carboxyl group or an acid anhydride group examples include 2-acrylamido-2-methylpropanesulfonic acid, allylsulfonic acid, styrenesulfonic acid sodium salt, sulfoethyl methacrylate, and its sodium or ammonium salts.
  • carbonyl group-containing polymerizable unsaturated monomers examples include acrolein, diacetone acrylamide, diacetone methacrylamide, formylstyrene, and vinyl alkyl ketones having 4 to 7 carbon atoms, such as vinyl methyl ketone, vinyl ethyl ketone, and vinyl butyl ketone. Of these, diacetone acrylamide and diacetone methacrylamide are particularly preferred.
  • N-methylol alkyl ether group-containing polymerizable unsaturated monomer is N-methylol acrylamide butyl ether.
  • An isocyanate group-containing polymerizable unsaturated monomer is a compound that has at least one unblocked isocyanate group and at least one radically polymerizable double bond per molecule.
  • Examples include methacryloyl isocyanate, 2-isocyanatoethyl methacrylate, m- or p-isopropenyl- ⁇ , ⁇ '-dimethylbenzyl isocyanate, or a 1:1 (molar ratio) adduct of a hydroxyl group-containing polymerizable unsaturated monomer and a diisocyanate compound (for example, an equimolar adduct of 2-hydroxyethyl acrylate and isophorone diisocyanate).
  • epoxy group-containing polymerizable unsaturated monomers examples include glycidyl acrylate and glycidyl methacrylate.
  • Commercially available products can also be used, such as "CYCLOMER A-200” (alicyclic epoxy group-containing monomer) and "CYCLOMER M-100” (alicyclic epoxy group-containing monomer) manufactured by Daicel Corporation.
  • amino group-containing polymerizable unsaturated monomers examples include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminopropyl acrylamide, and dimethylaminopropyl methacrylamide.
  • alkoxysilyl group-containing polymerizable unsaturated monomers include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltributoxysilane, (meth)acryloyloxymethyltrimethoxysilane, (meth)acryloyloxyethyltrimethoxysilane, ⁇ -(meth)acryloyloxypropyltrimethoxysilane, ⁇ -(meth)acryloyloxypropyltriethoxysilane, (meth)acryloyloxyethyltriethoxysilane, (meth)acryloyloxypropyltributoxysilane, vinyltris- ⁇ -methoxyethoxysilane, divinylmethoxysilane, and divinyldi- ⁇ -methoxyethoxysilane.
  • polymerizable unsaturated monomers include, for example, alkyl or cycloalkyl esters of (meth)acrylic acid having 1 to 24 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and cyclohexyl (meth)acrylate; alkoxyalkyl esters of (meth)acrylic acid having 1 to 16 carbon atoms, such as methoxybutyl acrylate, methoxybutyl methacrylate, methoxyethyl acrylate, methoxyethyl methacrylate, ethoxybutyl acrylate, ethoxybutyl methacrylate, and phenoxyethyl (meth)acrylate; styrene, vinyl Examples include aromatic unsaturated monomers such as toluene, ⁇ -methyl
  • crosslinked resin particles can be produced by using a polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule as a monomer component.
  • polymerizable unsaturated monomers having two or more polymerizable unsaturated groups in one molecule include allyl (meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and 1,6-hexane
  • Examples include diol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, glycerol di(meth)acrylate, 1,1,1-trishydroxymethylethane di(meth)acrylate, 1,1,1-trishydroxymethylethane tri(meth)acrylate, 1,1,
  • allyl (meth)acrylate, ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate can be suitably used.
  • the glass transition temperature of the acrylic resin particles (B) is 30°C or lower, preferably within the range of -20 to 30°C, and more preferably -10 to 30°C.
  • the glass transition temperatures of the homopolymers of each monomer are values taken from POLYMER HANDBOOK, Fourth Edition, edited by J. Brandrup, E. h. Immergut, and E. A. Grulke (1999).
  • the glass transition temperature is the value obtained by synthesizing a homopolymer of that monomer so that the weight-average molecular weight is approximately 50,000 and measuring the glass transition temperature by differential scanning calorimetry.
  • acrylic resin particles (B) that meet the above glass transition temperature requirements can also be used.
  • examples of commercially available products include Pliotec HDT 12 (acrylic SBR resin) manufactured by OMNOVA, LX407S10 manufactured by Zeon Corporation, JONCRYL PDX-7616A, JONCRYL PDX-7787, JONCRYL PDX-7741, and JONCRYL PDX-7356 manufactured by BASF, and U-DOUBLE EF-015, U-DOUBLE EF-016, and U-DOUBLE EF-017 manufactured by Nippon Shokubai Co., Ltd.
  • the acrylic resin particles (B) may have an average particle size preferably within the range of 10 to 1,000 nm, more preferably 20 to 500 nm, and even more preferably 40 to 300 nm.
  • Acrylic-modified epoxy resin particles (A) and acrylic resin particles (B), particularly if they contain acid groups, are preferably neutralized with a basic compound from the standpoint of dispersion stability.
  • the basic compound may suitably be ammonia or a water-soluble amino compound, such as monoethanolamine, ethylamine, dimethylamine, diethylamine, triethylamine, propylamine, dipropylamine, isopropylamine, diisopropylamine, triethanolamine, butylamine, dibutylamine, 2-ethylhexylamine, ethylenediamine, propylenediamine, methylethanolamine, dimethylethanolamine, diethylethanolamine, 2-amino-2-methylpropanol, diethanolamine, or morpholine.
  • a water-soluble amino compound such as monoethanolamine, ethylamine, dimethylamine, diethylamine, triethylamine, propylamine, dipropylamine, isopropylamine, diisopropylamine, triethanolamine, butylamine, dibutylamine, 2-ethylhexylamine, ethylenediamine, propylened
  • the hydroxyl value is preferably 1 to 150 mgKOH/g, more preferably 2 to 100 mgKOH/g, and even more preferably 5 to 90 mgKOH/g.
  • the acrylic-modified epoxy resin particles (A) and acrylic resin particles (B) may also have a core/shell structure.
  • shell portion refers to the polymer layer present in the outermost layer of a resin particle
  • core portion refers to the polymer layer present in the inner layer of a resin particle excluding the shell portion
  • core/shell structure refers to a structure having the core portion and shell portion.
  • the core/shell structure is typically a layer structure in which the core portion is completely coated with the shell portion. However, depending on the mass ratio of the core portion to the shell portion, the amount of monomer in the shell portion may be insufficient to form a layer structure.
  • the complete layer structure described above is not necessary; the core portion may be partially coated with the shell portion, or a polymerizable unsaturated monomer, a component of the shell portion, may be graft-polymerized onto a portion of the core portion.
  • the concept of a multilayer structure in the core/shell structure also applies to acrylic-modified epoxy resin particles (A) and acrylic resin particles (B) in which a multilayer structure is formed in the core portion.
  • a core/shell structure can be obtained, for example, by reacting monomer compositions with different compositions in multiple stages.
  • the acrylic-modified epoxy resin particles (A) form a core/shell structure in which the epoxy resin portion forms the core and the acrylic resin portion forms the shell.
  • the aqueous coating composition of the present invention contains, as resin components, 20 to 60 mass % of acrylic-modified epoxy resin particles (A) and 40 to 80 mass % of acrylic resin particles (B) in solid content relative to the total solid content of both.
  • the amount of component (A) is 25 to 55% by mass and the amount of component (B) is 45 to 75% by mass, and more preferably, the amount of component (A) is 30 to 50% by mass and the amount of component (B) is 50 to 70% by mass.
  • the content of component (A) is 20% by weight or more, the blocking resistance and water-resistant adhesion of the resulting coating film are improved, and when the content of component (B) is 40% by weight or more, the film-forming properties are improved.
  • the aqueous coating composition of the present invention may contain resins other than components (A) and (B) as necessary.
  • epoxy resins other than component (A) acrylic resins other than component (B), urethane resins, polyester resins, etc.
  • resins commonly used as curing agents such as amino resins, phenolic resins, polyisocyanate compounds, and carbodiimide compounds.
  • water-based paint is used in contrast to organic solvent-based paint, and generally refers to a paint in which a film-forming resin, pigment, etc. are dispersed and/or dissolved in water or a medium primarily composed of water (aqueous medium).
  • aqueous medium primarily composed of water
  • the paint composition of the present invention is an aqueous paint
  • the water content in the paint composition is preferably within the range of 10 to 90% by mass, preferably 20 to 80% by mass, and more preferably 30 to 70% by mass.
  • the organic solvent-based paint is a paint that contains substantially no water as a solvent or in which all or most of the solvent is an organic solvent.
  • Examples of the organic solvent (C) contained in the aqueous coating composition of the present invention include ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester-based solvents such as ethyl acetate, butyl acetate, methyl benzoate, ethyl ethoxypropionate, ethyl propionate, and methyl propionate; alcohol-based solvents such as 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, and 2-ethyl-1-hexanol; ether-based solvents such as tetrahydrofuran, dioxane, and dimethoxyethane; glycol ether-based solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether acetate,
  • the organic solvent (C) may be any solvent that does not affect the stability of the aqueous coating composition of the present invention. However, it is preferable that the organic solvent does not contain toluene, xylene, or the like, in view of its impact on the human body and the environment.
  • the organic solvent (C) functions as a plasticizer during the film-forming process and disappears from the coating film after film formation.
  • the organic solvent component be an organic solvent having a 1-octanol/water partition coefficient (LogP OW ) of 1 or less.
  • organic solvent examples include propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, isopropyl alcohol, ethylene glycol monobutyl ether, and isopropyl alcohol.
  • organic solvent (C) refers to all organic solvents contained in the aqueous coating composition of the present invention, including those contained in the aqueous medium of the aqueous dispersion of the acrylic-modified epoxy resin particles (A) and the acrylic resin (B), as well as organic solvents contained in the medium of the optional components described below, and organic solvents optionally added to the coating to ensure coating film performance, coating workability, etc.
  • the weighted average boiling point of the organic solvent (C) contained is 200°C or less from the viewpoint of blocking resistance and film-forming ability.
  • the weighted average boiling point of organic solvent (C) is 200°C or less, sufficient blocking resistance is obtained.
  • the weighted average boiling point of organic solvent (C) is too low, the film-forming ability of the aqueous paint composition may decrease, so the weighted average boiling point is preferably 110°C or higher.
  • the weighted average boiling point of organic solvent (C) is preferably 110 to 200°C, more preferably 110 to 180°C, even more preferably 120 to 180°C, and particularly preferably 120 to 170°C.
  • organic solvents can be used alone or in combination of two or more depending on the purpose, particularly blocking resistance, film-forming properties, viscosity adjustment, etc.
  • the content of organic solvent (C) in the aqueous coating composition of the present invention is preferably within the range of 1 to 100% by mass, particularly 1 to 70% by mass, even more particularly 2 to 50% by mass, and even more particularly 2 to 40% by mass, based on the total solids content of the acrylic-modified epoxy resin particles (A) and the acrylic resin particles (B).
  • the solids concentration of the aqueous coating composition of the present invention is preferably adjusted to a solids content of 10% by mass or more, particularly 25 to 50% by mass, and even more particularly 30 to 45% by mass, from the standpoint of ease of coating work and reducing the amount of organic solvents emitted.
  • solids refer to the residue after volatile components have been removed, and the residue may be in either a solid or liquid state at room temperature.
  • the solid mass can be calculated by multiplying the sample mass before drying by the solids percentage, which is the ratio of the amount of material remaining after drying to the mass before drying.
  • the aqueous coating composition of the present invention preferably contains at least one of a rust inhibitor (D) and a pigment (E).
  • the aqueous coating composition of the present invention preferably contains a rust inhibitor to improve rust prevention properties.
  • the rust inhibitors that can be used include those typically used in paints, such as zirconium compounds, vanadium compounds, silicon oxide, sulfur-containing organic compounds, and rust-preventive pigments.
  • anti-rust pigments examples include zinc oxide, phosphite compounds, phosphate compounds, nitrite compounds, molybdate compounds, bismuth compounds, and metal ion-exchanged silica.
  • the aqueous coating composition of the present invention preferably contains a pigment to improve rust prevention, impart a desired color, etc.
  • the pigment include coloring pigments and extender pigments.
  • coloring pigments include titanium oxide, zinc molybdate, calcium molybdate, carbon black, graphite, iron black, Prussian blue, ultramarine, cobalt blue, copper phthalocyanine blue, indanthrone blue, yellow lead, synthetic yellow iron oxide, red iron oxide, transparent red iron oxide, bismuth vanadate, titanium yellow, zinc yellow, ochre, monoazo yellow, disazo, isoindolinone yellow, metal complex azo yellow, quinophthalone yellow, benzimidazolone yellow, monoazo red, unsubstituted quinacridone red, azo lake (Mn salt), quinacridone magenta, anthanthrone orange, dianthraquinonyl red, perylene maroon, perylene red, diketopyrrolopyrrole chrome vermilion, chlorinated phthalocyanine green, brominated phthalocyanine green, and others such as pyrazolone orange, benzimidazolone orange, dioxazine violet,
  • extender pigments examples include clay, silica, barium sulfate, talc, calcium carbonate, white carbon, diatomaceous earth, magnesium aluminum carbonate flakes, and mica flakes.
  • barium sulfate and talc are preferred for use from the perspective of rust prevention.
  • the aqueous coating composition of the present invention contains a rust inhibitor (D) and/or a pigment (E), from the standpoint of rust prevention and film-forming properties, it is preferable that the total solid content of the rust inhibitor (D) and pigment (E) be 10 to 400% by mass, particularly 20 to 350% by mass, and even more particularly 50 to 300% by mass, relative to the total solid content of the acrylic-modified epoxy resin particles (A) and acrylic resin particles (B).
  • the aqueous coating composition of the present invention may further contain additives such as catalysts, pigment dispersants, film-forming aids, anti-settling agents, rheology control agents, anti-foaming agents, coating surface conditioners, UV absorbers, UV stabilizers, and pH adjusters, as needed.
  • additives such as catalysts, pigment dispersants, film-forming aids, anti-settling agents, rheology control agents, anti-foaming agents, coating surface conditioners, UV absorbers, UV stabilizers, and pH adjusters, as needed.
  • the aqueous coating composition of the present invention is capable of forming a coating film that is quick-drying, has excellent blocking resistance, and is easy to apply, as well as having excellent rust prevention and water resistance. Therefore, it is particularly suitable for use as an anti-rust coating for steel materials used in construction applications, particularly lightweight steel structures.
  • the aqueous coating composition of the present invention can be applied to the above-mentioned steel material by a known method such as roll coating, spray coating, brush coating, electrostatic coating, dipping, electrodeposition coating, curtain coating, or roller coating, and then dried to form a coating film.
  • the thickness of the coating film formed using the aqueous coating composition of the present invention is not particularly limited, but it can usually be applied in the range of 10 to 100 ⁇ m, preferably 10 to 80 ⁇ m.
  • the coating method of the present invention includes the steps of preheating the substrate, applying the aqueous coating composition of the present invention, and then drying using residual heat.
  • Coating using the aqueous coating composition of the present invention can be either room-dry coating or baked coating.
  • the heating and drying conditions for baked coating can be set appropriately, but for example, on a steel production line, coating is typically carried out by preheating the substrate to a temperature of 70 to 200°C, preferably 80 to 120°C, and then drying for 3 to 5 minutes using residual heat (the substrate temperature immediately after coating, approximately 60 to 100°C).
  • the present invention will be explained in more detail below with reference to production examples, working examples, and comparative examples. However, the present invention is not limited to these. In each example, “parts” and “%” are by mass unless otherwise specified. Furthermore, the coating film thickness is based on the cured coating film.
  • the resulting resin (a2-1) had a glass transition temperature of 126°C, a resin acid value of 293 mgKOH/g, and a weight-average molecular weight of 22,000.
  • the glass transition temperature, acid value, weight average molecular weight, and solids content of the obtained carboxyl group-containing acrylic resin are shown in Table 1.
  • the acrylic-modified epoxy resin particles (A-1) had a glass transition temperature (Tg) of 85.4°C and a resin acid value of 37 mgKOH/g.
  • the composition of the mixture of (1) and (2) is as follows: (1) jER1010 (Note 3) 84 parts (2) Carboxyl group-containing acrylic resin (a2-1) solution 40 parts (16 parts as solids)
  • jER1001 Epoxy resin manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin with an epoxy equivalent of approximately 475.
  • jER1007 Epoxy resin manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin with an epoxy equivalent of approximately 1975.
  • jER1010 Epoxy resin manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin with an epoxy equivalent of approximately 4500.
  • the obtained acrylic resin particles (B-1) had a glass transition temperature of -6.0°C, an average particle size of 165 nm, a hydroxyl value of 4.4 mgKOH/g, and an acid value of 22.8 mgKOH/g.
  • the average particle size was measured using a submicron particle size distribution measuring device "COULTER N4" (manufactured by Beckman Coulter, Inc.) by diluting with deionized water at 20°C.
  • Examples 1 to 9 and Comparative Examples 1 to 9 ⁇ Production of aqueous coating composition>
  • the raw materials were thoroughly mixed in a stirrer according to the formulations shown in Tables 4 and 5 below, and the pigment was dispersed until the grain size (particle size of the coarse pigment particles) was 30 ⁇ m or less.
  • Deionized water was then added to adjust the solids content, producing aqueous coating compositions No. 1 to 18 with a solids content of 50 mass%.
  • Aqueous coating compositions No. 10 to 18 are for comparative examples.
  • compositions in Tables 4 and 5 are solid mass ratios, and the weighted average boiling point (°C) of the organic solvent (C) is also shown.
  • the mass of the organic solvent (C) indicates the content in the aqueous coating composition relative to the total solid mass (100) of the acrylic-modified epoxy resin particles (A) and acrylic resin particles (B).
  • the Pliotec HDT12 (acrylic SBR resin, glass transition temperature (Tg) 27.6°C, average particle size 140 nm, solids mass concentration 50%, pH 8.0) used in the examples is manufactured by OMNOVA, and JONCRYL PDX-7616A (glass transition temperature (Tg) 9.0°C, average particle size 100 nm, solids mass concentration 44%, solids acid value 30 mg KOH/g, pH 7.8) is an acrylic resin particle manufactured by BASF.
  • test plate for aqueous coating composition No. 1 The surface of a polished cold-rolled steel plate measuring 70 ⁇ 150 ⁇ 0.8 mm was polished with water-resistant abrasive paper of 280 grit, and then degreased with toluene to prepare a test material.
  • Test plates I-1 to IV-1 were prepared using the test materials according to the following (I) to (IV).
  • Example 1 The aqueous coating composition No. 1 obtained in Example 1 was applied to the above substrate using a film applicator so that the cured film thickness was 35 ⁇ m, and then dried for 8 hours in an environment of 23°C and 50% humidity to obtain test panel I-1.
  • the aqueous coating composition No. 1 obtained in Example 1 was spray-painted onto them so that the cured film thickness was 35 ⁇ m, and then aged in an environment of 23°C and 50% humidity to obtain two test panels II-1.
  • the curing time varies depending on the blocking resistance test temperature, and is approximately 1 to 10 minutes, since the blocking resistance test is started once the test plate temperature has cooled to the following blocking resistance test temperatures (55°C, 45°C, 35°C). (Specifically, it is several minutes at 55°C and approximately 10 minutes at 35°C.)
  • Example 1 The aqueous coating composition No. 1 obtained in Example 1 was spray-painted onto the above substrate to a cured film thickness of 35 ⁇ m, and then cured for 7 days in an environment of 23°C and 50% humidity to obtain test panel III-1.
  • Test panels I-2 to I-18, II-2 to II-18, III-2 to III-18, and IV-2 to IV-18 were obtained using aqueous coating compositions Nos. 2 to 18 in the same manner as in the preparation of the test panels for aqueous coating composition No. 1.
  • test plates I-1 to I-18, II-1 to II-18, III-1 to III-18, and IV-1 to IV-18 obtained by the above test plate production were subjected to performance evaluation according to the following test methods.
  • the test results are shown in Tables 4 and 5 below.
  • Each test panel I-1 to I-18 was visually and microscopically (30x magnification) observed for cracks in the coating to evaluate film-forming ability.
  • the evaluation criteria are as follows. In the following evaluation criteria, A is the pass level. A: No cracks in the coating film were observed even when observed under a microscope (30x magnification). B: No cracks are observed with the naked eye, but cracks in the coating are observed when observed under a microscope (30x magnification). C: Cracks in the coating film are visually observed.
  • each test plate III-1 to III-18 was coated with the same aqueous coating composition No. 1 to 18 as the front surface, and dried. After making notches on the front and back surfaces according to the method specified in JIS K 5600-7-9, 7.5 (method of making notches) a), a cyclic corrosion test was carried out for 36 cycles under the conditions specified in JIS K 5600-7-9, Appendix 1 (Cycle D). After 36 cycles, the test plate was thoroughly washed with ion-exchanged water, the moisture on the surface of the test plate was wiped off, and the rust prevention properties were evaluated according to the following evaluation criteria.
  • a and B are acceptable levels.
  • Blocking resistance Two test plates from each of II-1 to II-18 were placed one on top of the other with the coated surfaces facing each other, and weights were placed on them so that the pressure was 40 kgf/ cm2 . These were then maintained at each test plate temperature (55°C, 45°C, 35°C) for one hour. The weights were then removed, the plates were cooled to room temperature, and the blocking resistance was evaluated based on the state of pressure bonding and the degree of peeling.
  • the evaluation criteria are as follows. In the following evaluation criteria, the higher the temperature, the more severe the test conditions, with A, B, and C being pass levels. A: When tested at 55°C, no pressure bonding between the two plates was observed. B: When tested at 45°C, no pressure bonding between the two plates was observed.
  • each test plate IV-1 to IV-18 were protected with a paint or anticorrosive vinyl tape that was sufficiently resistant to water, and then immersed in deionized water at 23 ° C for 24 hours according to JIS K 5600-6-1, Clause 7 [Method 1 (immersion method)].
  • the test plate was then removed and the surface water was wiped off with filter paper as specified in JIS P3801. After drying for 30 minutes in an environment of 23 ° C and 50%, 100 2 mm x 2 mm grids were made on the coated surface according to JIS K 5600-5-6 (1990). Adhesive tape was applied to the surface, and the remaining state of the grid coating film after rapid peeling was examined.
  • the adhesion was evaluated according to the following evaluation criteria.
  • a and B are acceptable levels.
  • A: Remaining number/total number 100/100, no chipping of the edges of the cross-hatched pattern is observed.
  • B: Number of remaining pieces/total number 100 pieces/100 pieces, and chipped edges of the cross-hatched pattern are observed.
  • C: Remaining number/total number 80-99/100
  • D: Remaining number/total number 0-79/100
  • Pencil hardness The pencil hardness of the coated surface of each test panel IV-1 to IV-18 was measured in accordance with JIS K 5600-5-4 (1999) "Scratch hardness (pencil method)." The order of pencil hardness is 2B ⁇ B ⁇ HB ⁇ F ⁇ H ⁇ 2H. A hardness of B or higher is good and meets the passing standard.
  • the aqueous coating composition of the present invention can be used for both ambient-dry and baked coating, and can be used efficiently not only outdoors at construction sites and other locations, but also on production lines for coated steel materials, etc.
  • Coated articles such as coated steel materials that do not contain environmentally hazardous substances (such as lead and chromium) and have excellent film-forming properties, rust prevention, water resistance, and blocking resistance can be produced with high productivity.

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Abstract

Cette composition de revêtement aqueuse contient des particules de résine époxy modifiée acrylique (A) ayant une température de transition vitreuse de 30 °C ou plus, des particules de résine acrylique (B) ayant une température de transition vitreuse de 30 °C ou moins, et un solvant organique (C). La composition comprend, en tant que teneur en solides, 20 à 60 % en masse des particules de résine époxy modifiée acrylique (A) et 40 à 80 % en masse des particules de résine acrylique (B) par rapport à la teneur totale en solides des particules de résine époxy modifiée acrylique (A) et des particules de résine acrylique (B). Le point d'ébullition moyen pondéré du solvant organique (C) est inférieur ou égal à 200 °C.
PCT/JP2024/045998 2024-02-27 2024-12-25 Composition de revêtement aqueuse Pending WO2025182280A1 (fr)

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WO2025226485A3 (fr) * 2024-04-22 2025-12-18 Swimc Llc Compositions de revêtement à base de résine époxy et utilisations associées

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JP2012021136A (ja) * 2010-06-18 2012-02-02 Nippon Shokubai Co Ltd 防錆塗料用水性樹脂組成物
JP2020002327A (ja) * 2018-07-02 2020-01-09 関西ペイント株式会社 水性塗料組成物
JP2022154462A (ja) * 2021-03-30 2022-10-13 大日本塗料株式会社 塗料組成物および塗膜

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