EP2867270A1

EP2867270A1 - Water-based epoxy resin emulsion

Info

Publication number: EP2867270A1
Application number: EP20130810347
Authority: EP
Inventors: Kenji Itoh; Yoshio Yoshida; Akiko Ono; Andreas Taden; Melanie Hagenbucher; Katharina Landfester
Original assignee: Henkel AG and Co KGaA; Max Planck Gesellschaft zur Foerderung der Wissenschaften eV
Current assignee: Henkel AG and Co KGaA; Max Planck Gesellschaft zur Foerderung der Wissenschaften eV
Priority date: 2012-06-28
Filing date: 2013-06-27
Publication date: 2015-05-06
Also published as: WO2014003208A1; EP2867270A4; JP2014009270A; WO2014003208A8

Abstract

An object of the present invention is to provide a water-based epoxy resin emulsion being environmentally-friendly, and having an excellent storage stability and an excellent rust-proof property; and to provide a water-based paint comprising the water-based resin emulsion. The present invention relates to a water-based epoxy resin emulsion in which an epoxy resin (B) is emulsified and dispersed in an aqueous medium (C) in the presence of a reactive emulsifier (A), wherein an average particle diameter of the water- based epoxy resin emulsion is 500 nm or less.

Description

DESCRIPTION

Title of Invention

WATER-BASED EPOXY RESIN EMULSION

Technical Field

[0001] The present invention relates to a water-based epoxy resin emulsion and a water-based paint comprising the same.

Background Art

[0002] Solvent-based two-component paint primarily composed of an epoxy resin are used for large steel structures, and the like, but recently production of more water-based paints have been proceeded by the requirement of reduced

environmental impact.

[0003] For making water-based epoxy resins, Patent Literature 1 discloses a method of making a water-based epoxy resin by introducing a hydrophilic group into an epoxy resin to convert the resin to a self-emulsifying epoxy resin. A dispersion of the water-based epoxy resin described in Patent Literature 1 does not comprise an emulsifier to disperse the resin, thereby being free of a dissolved emulsifier; however, due to the introduced hydrophilic group, the inherent cohesiveness and rust-proof properties of the epoxy resin are affected.

[0004] Patent Literature 2 discloses a method of making a highly hydrophobic epoxy resin into a water-based epoxy resin by using an epoxy resin into which a hydrophilic group is introduced as an emulsifier. Patent Literature 2 discloses that the obtained water-based epoxy resin dispersion cures at room temperature with a curing agent such as polyamine; however, a large amount of the emulsifier used for making the water-based epoxy resin is present unevenly in the cured coating film or bleeds out on the coating film surface, thereby reducing the mechanical strength of the cured coating film. In addition, environmental pollution caused by the emulsifier eluted from the cured coating film is also inevitable.

[0005] Patent Literature 3 discloses that an epoxy resin emulsion having a particle diameter of about 600 to 800 nm is obtained by subjecting an epoxy-amine adduct, as an emulsifier, to the phase-inversion emulsification. Since the emulsifier has an epoxy group and reactive, the emulsifier is fixed in the cured coating film when the epoxy resin is cured, leading to reduce the bleeding out or the elution of emulsifier as described above. However, the epoxy resin emulsion of Patent Literature 3 is likely to cause coagulation or sediment of particles, hence having poor storage stability.

Citation List

Patent Literature

[0006]

Patent Literature l: Japanese Patent Laid-Open No. H09(l997)"241482

Patent Literature 2- Japanese Patent Laid pen No. H08(l996)-253552

Patent Literature 3: Japanese Patent LaidOpen No. 2000-504372

Summary of Invention

Technical Problem

[0007] An object of the present invention is to provide a water-based epoxy resin emulsion which solves the above problems, is environmentally-friendly, and has excellent storage stability and excellent rust-proof properties, and to provide a water-based paint comprising the water-based epoxy resin emulsion.

Solution to Problem

[0008] The present inventors conducted extensive studies to solve the above problems and found that the storage stability, rust-proof properties, and the like, are notably improved in a water-based epoxy resin emulsion obtained by emulsifying and dispersing an epoxy resin in an aqueous medium in the presence of a reactive emulsifier, by adjusting an average particle diameter to be within the predetermined range.

[0009] More specifically, the present invention and the preferred embodiments of the present invention are as follows.

[0010] 1. A water-based epoxy resin emulsion in which an epoxy resin (B) is emulsified and dispersed in an aqueous medium (C) in the presence of a reactive emulsifier (A),

wherein an average particle diameter of the water-based epoxy resin emulsion is 500 nm or less. [0011] 2. The water-based epoxy resin emulsion according to the above 1, wherein a degree of particle diameter distribution of the water-based epoxy resin emulsion is 1.0 to 1.4.

[0012] 3. The water-based epoxy resin emulsion according to the above 1 or 2, wherein the reactive emulsifier (A) has an epoxy group.

[0013] 4. The water-based epoxy resin emulsion according to any one of the above 1 to 3, wherein the epoxy resin (B) comprises an epoxy resin having at least two epoxy groups in a molecular.

[0014] 5. A water-based paint comprising a water-based epoxy resin emulsion according to any one of the above 1 to 4.

[0015] 6. The water-based paint according to the above 5, further comprising an amine curing agent.

Advantageous Effects of Invention

[0016] The water-based epoxy resin emulsion of the present invention has excellent storage stability and the emulsifier does not bleed out from a cured coating film, thereby being free from concern about environmental pollution and also having excellent rust-proof properties, and the like.

Description of Embodiments

[0017] A water-based epoxy resin emulsion of the present invention is a water- based epoxy resin emulsion in which an epoxy resin (B) is emulsified and dispersed in an aqueous medium (C) in the presence of a reactive emulsifier (A), wherein an average particle diameter of the water-based epoxy resin emulsion is 500 nm or less.

[0018] In the present specification, the "epoxy group" is a bonding group having the epoxy structure (a 3-membered cyclic structure composed of carbon-oxygen- carbon), the carbon-carbon moiety may be a part of the linear or branched hydrocarbon structure or a part of the hydrocarbon structure forming a 5- or 6" membered cyclic structure, or the like. These hydrocarbon structures may optionally have halogen such as fluorine, chlorine, or bromine, or a functional group such as a hydroxy group or a nitrile group, bonded thereto. The carbon atom forming the epoxy structure may further have an alkyl group such as a methyl group, an aryl group such as a phenyl group, or halogen, bonded thereto. Examples of these epoxy groups include a glycidyl group, and the bonding group represented by the following formula (2). The glycidyl group, industrially manufactured from allyl alcohol and epichlorohydrin, is easy to obtain and hence desirable.

[0019]

wherein Ri and R2 respectively represent a hydrocarbon group having 1 to 12 carbon atoms, and m represents an integer of 0 to 3.

[OO2O] Each component comprised in the water-based epoxy resin emulsion of the present invention will be described.

[0021] <Reactive emulsifier (A)>

The reactive emulsifier (A) is an emulsifier having a reactive functional group in a molecule, which is suitable for soap free method. The term, soap free, herein means a technique for reducing free emulsifiers in a cured coating film.

[ΟΟ22] More specifically, the reactive emulsifier (A) has a hydrophilic moiety (a hydrophilic group, a hydrophilic block, or the like) and a hydrophobic moiety (a hydrophobic group, a hydrophobic block, or the like) and further has a functional group, as a reactive functional group, capable of co-curing with an epoxy resin (B)

[0023] The term "reactive" in the "reactive emulsifier" refers to having the reactivity at the time of curing reaction of the epoxy resin (B), and, more specifically, having a functional group reactive to a curing agent of the epoxy resin. Preferable examples of the reactive functional group include an ethylenic

unsaturated group, an acetylenic unsaturated group, a carbonyl group, an isocyanate group, an isothiocyanate group, an epoxy group and an oxetane group, and an epoxy group is more preferable in the light of easy synthesis, stability and reactivity. In this case, the reactive emulsifier (A) can react with a curing agent of an epoxy resin. For this reason, during the curing reaction, the reactive emulsifier (A) can copolymerize with the epoxy resin (B) described later and fixed in the epoxy resin (B), whereby problems such as the emulsifier being unevenly present in a cured coating film or bleeding out on the cured coating film surface do not arise and there is no concern about environmental pollution.

[0024] In the present invention, the reactive emulsifier (A) preferably has an HLB value ranging from 10 to 17. The HLB value is calculated by the following formula.

[0025] HLB = (molecular weight of the hydrophilic moiety in a molecule) /

(molecular weight of the hydrophilic moiety in a molecule + molecular weight of the hydrophobic moiety in a molecule) X 100 / 5

[0026] The reactive emulsifier (A) may be any type of anionic, nonionic or cationic, but is preferably nonionic in view of the storage stability, curability, rust^¬ proof properties of a cured coating film, and the like. The reactive emulsifier (A) may be used singly or two or more may be used in combination.

[0027] Examples of the nonionic reactive emulsifier (A) include those having a representative structure comprising a polyalkylene oxide block comprising a repeating structure as the hydrophilic moiety such as ethylene oxide or propylene oxide, and an aromatic ring and/or alkyl chain as the hydrophobic moiety. The HLB value, in consideration of the size of the hydrophobic moiety, may be adjusted by varying the length of polyalkylene oxide block, in other words, the number of repeating alkylene oxide.

[0028] The emulsifier is not particularly limited but specific examples include an adduct of epoxy/active hydrogen compound having at least one epoxy obtained by reacting, for example, a compound having active hydrogen (having a

hydrophilic or hydrophobic moiety) such as an amine compound or a thiol compound with an epoxy resin (having a hydrophobic or hydrophilic moiety) having at least 2 epoxy groups in a molecule.

[0029] In the case of epoxy/amine adduct, the epoxy /amine adduct may be synthesized from, for example, (l) a hydrophobic epoxy resin and a hydrophilic amine, or (2) a hydrophilic epoxy resin and a hydrophobic amine; and these combinations may be optionally selected so that an HLB value preferably ranges from 10 to 17.

[0030] (l) When synthesizing the reactive emulsifier from a hydrophobic epoxy resin and a hydrophilic amine, the usable hydrophobic epoxy resins include an aromatic epoxy resin, an alicyclic epoxy resin, and an aliphatic epoxy resin which have at least two epoxy groups and a hydrocarbon group respectively selected from an aromatic ring, an aliphatic ring, a chain aliphatic group, and the like, in its molecule. The epoxy resins commonly used are typically classified under the hydrophobic epoxy resin. Examples of the aromatic epoxy resin include bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin; novolac type epoxy resins such as phenol novolac type epoxy resin and cresol novolac type epoxy resin; biphenyl type epoxy resin such as YX4000, trade name, manufactured by Japan Epoxy Resins Co., Ltd.; epoxy resins having the basic skeleton of a polycyclic aromatic group such as naphthalene, anthracene, or terphenyl; others such as tetraglycidyl diaminodiphenylmethane (TGDDM), triglycidyl para-aminophenol, and triglycidyl meta- aminophenol.

[0031] Epoxy resins having epoxy group with ring distortion such as a

cyclohexene oxide structure and a cyclopentene oxide structure in its molecule (for example, compounds represented by the following formulae (l) to (5), described later in the explanation of epoxy resin (B)), alicyclic epoxy resins such as hydrogenated bisphenol type epoxy resin; and linear or branched aliphatic epoxy resins such as alkylene diglycidyl ether may be used.

[0032] The hydrophobic epoxy resin may be selected according to the purpose of use, but, for the general use, the bisphenol type epoxy resin, particularly bisphenol A type epoxy resin (i.e., bisphenol A diglycidyl ether) may be used.

When synthesizing the reactive emulsifier (A), the hydrophobic epoxy resin may be used singly, or two or more may be used in combination. [0033] The hydrophilic amine has a hydrophilic group, and it is preferably monoamine or diamine having an amino group at the molecular terminal and more preferably monoamine. The preferable hydrophilic group is typically a polyoxyalkylene chain. Specific examples of the hydrophilic amine include polyalkylene glycol (polyoxyalkylene amine) having an amino group at the terminal thereof. The polyoxyalkylene chain preferably comprises an ethylene oxide unit and/or a propylene oxide unit, and particularly preferably comprises 60% by mass or more of the ethylene oxide unit in the polyoxyalkylene chain. The length of polyoxyalkylene chain (i.e., the number of repeating oxyalkylene) is selected so that the reactive emulsifier has a predetermined HLB value.

Examples of the commercial product include JEFFAMINE M-1000 (manufactured by Huntsman Corporation). When synthesizing the reactive emulsifier (A), the hydrophilic amine compound may be used singly, or two or more may be used in combination.

[0034] (2) When synthesizing the reactive emulsifier from the hydrophilic epoxy resin and the hydrophobic amine, the hydrophilic epoxy resin has at least two epoxy groups and a hydrophilic group in a molecule. The preferable hydrophilic group is typically a polyoxyalkylene chain. Specific examples of the hydrophilic epoxy resin preferably include polyalkylene glycol having a glycidyl group at both terminals of a molecule. The polyoxyalkylene chain preferably comprises an ethylene oxide unit and/or a propylene oxide unit, and particularly preferably comprises 60% by mass or more of the ethylene oxide unit in the polyoxyalkylene chain. The length of polyoxyalkylene chain (i.e., the number of repeating oxyalkylene) is selected so that the reactive emulsifier has a predetermined HLB value. A specific example is polyethylene glycol diglycidyl ether. When synthesizing the reactive emulsifier (A), the hydrophilic epoxy resin may be used singly, or two or more may be used in combination.

[0035] The hydrophobic amine preferably has a hydrophobic group, and it is preferably monoamine or diamine having an amino group at the molecular terminal and more preferably monoamine. The hydrophobic group is preferably a hydrocarbon group such as an aromatic group, a chain aliphatic group, or an alicyclic group. Examples of the hydrophobic amine include amine having at least one alkyl group, wherein the alkyl group has preferably 4 to 22, and more preferably 6 to 22, carbon atoms. When synthesizing the reactive emulsifier (A), the hydrophobic amine compound may be used singly, or two or more may be used in combination. [0036] Examples of the combination for synthesizing the reactive emulsifier (A) include the combination of bisphenol A diglycidyl ether and JEFFAMINE M-1000, and the combination of polyethylene glycol diglycidyl ether and hexadecylamine.

[0037] The method for synthesizing the reactive emulsifier (A) is not

particularly limited, but when at least one epoxy group is present in its molecule, it may be carried out by reacting a mixture having, a molar ratio of , for example, an epoxy resin : an amine compound = 2 : 1 to 1 ^'· 1, with heating at a temperature of 80 to 150°C.

[0038] <Epoxy resin (B)>

The epoxy resin (B) is emulsified and dispersed in an aqueous medium in the presence of the above reactive emulsifier (A). In the present invention, the epoxy resin (B) is suitably selected according to the purpose of use, but preferably comprises a resin having at least 2 epoxy groups in a molecule, and, in view of the curability and rust-proof properties of a cured coating film, comprises those having an epoxy equivalent of preferably 100 to 1000, and more preferably 150 to 700.

[0039] Examples of epoxy resins (B) include epoxy resins having an aromatic ring, alicyclic epoxy resins, and other various epoxy resins. The epoxy resin may be used singly or two or more may be used. Additionally, the epoxy resin preferably has at least one aromatic ring in the light of excellent mechanical strength and heat resistance of a cured product.

[0040] Examples of the epoxy resin having aromatic ring include bisphenol type epoxy resins such as a bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy resin! novolac type epoxy resins such as phenol novolac type epoxy resin and cresol novolac type epoxy resin! biphenyl type epoxy resin such as YX4000, trade name, manufactured by Japan Epoxy Resins Co., Ltd.! epoxy resins having the basic skeleton of polycyclic aromatic groups such as naphthalene, anthracene, or terphenyl; others such as tetraglycidyl

diaminodiphenylmethane (TGDDM), triglycidyl para-aminophenol, and triglycidyl meta-aminophenol. The epoxy resin having aromatic ring usually has one or more epoxy groups, preferably two or more epoxy groups in its molecule, and the epoxy equivalent of the resin may be selected as appropriate. [0041] The epoxy resin having no aromatic ring includes alicyclic epoxy resins having epoxy group with ring distortion such as a cyclohexene oxide structure and a cyclopentene oxide structure in its molecule (for example, compounds

represented by the following formulae (l) to (5)):

[0042]

; hydrogenated bisphenoHype epoxy resins (those in which the benzene-ring in bisphenoHype epoxy resins such as bisphenol-A-type epoxy resins, bisphenol-F- type epoxy resins and bisphenol-S-type epoxy resins is hydrogenated);

dicyclopentadiene-type epoxy resins such as glycidyl ether of dicyclopentadiene phenol novorac! aliphatic alkyl mono- or di-glycidyl ethers such as

cyclohexanedimethanol diglycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether and allyl glycidyl ether; alkyl glycidyl esters such as glycidyl methacrylate and tertiary carboxylic acid glycidyl esters; styrene oxide; aromatic alkyl mono- glycidyl ethers such as phenyl glycidyl ether, cresyl glycidyl ether, p-s-butylphenyl glycidyl ether and nonylphenyl glycidyl ether; and tetrahydrofurfuryl alcohol glycidyl ether.

[0043] The epoxy resins which do not have these aromatic rings may be used singly, or are preferably used in combination with other epoxy resins, particularly with an epoxy resin having an aromatic ring. In these instances, it is preferable to select the epoxy resin wherein two or more epoxy groups are comprised in its molecule. [0044] In addition, examples include brominated epoxy resins of each of the above epoxy resins, and modified products of each of the above epoxy resins with a polyester resin, a phenol resin, a melamine resin, or the like,

[0045] It is preferable that the epoxy resin (B) is suitably selected from one or two or more epoxy resins according to the purpose of use, but typically preferably comprises at least one selected from bisphenol type epoxy resins such as bisphenol A type epoxy resin and bisphenol F type epoxy resin, and novolac type epoxy resins.

[0046] A commercial product may be used as the epoxy resin (B), and examples include jER828 (manufactured by Mitsubishi Chemical Corporation), Epotote YD- 011 (manufactured by Nippon Steel Chemical Co., Ltd.), YD-902LD

(manufactured by Nippon Steel Chemical Co., Ltd.), and EPPN201 (Nippon Kayaku Co., Ltd.). These may be used singly, or two or more may be used in combination.

[0047] The epoxy resin may further comprise other known diluents, and vinyl ethers, oxetane compounds, polyols, or the like, may be suitably used.

[0048] <Aqueous medium (C)>

The "aqueous medium (C)" refers to common water such as distilled water, ion exchange water and pure water, or a mixed solvent of the "water" and a "water-soluble solvent." The aqueous medium may further comprise impurities such as an oligomer resin as long as the object of the present invention is not affected. The "water-soluble solvent" is not particularly limited as long as it is a solvent dissolved in water, and specific examples include alcohols such as methanol, ethanol, and isopropanol, and lower aldehydes such as formaldehyde and acetaldehyde.

[0049] The water-based epoxy resin emulsion of the present invention has an average particle diameter of 500 nm or less, and preferably 50 nm or more, more preferably 100 nm or more, more preferably 150 nm or more, and further preferably 200 nm or more. In the present invention, the "average particle diameter" means the particle diameter measured using a dynamic light scattering instrument and determined by the cumulant analysis. [0050] When the water-based epoxy resin emulsion has an average particle size of 500 nm or less, the water-based epoxy resin emulsion is free of coagulation or sedimentation of particles even when stored for an extended period of time and hence has excellent stability. Further, the adhesiveness to a substrate, water resistance and rust-proof performance are enhanced. Accordingly, a water-based epoxy resin emulsion, for example, suitable to be a raw material for a coating agent for metals or an undercoat agent thereof can be obtained.

[0051] Additionally, the water-based epoxy resin emulsion of the present invention preferably has a degree of particle diameter distribution of 1.0 to 1.4. In the present specification, the "degree of particle diameter distribution" is a value obtained using the formula Dw/Dn, wherein Dw is a weight average particle size and Dn is a number average particle size, each of which is calculated based on measurement results using a dynamic light scattering instrument. When the degree of particle diameter distribution of the water-based epoxy resin emulsion is within the range, coarsening of the particle is hindered and the storage stability of the water-based epoxy resin emulsion is likely to be maintained.

[0052] The water-based epoxy resin emulsion of the present invention is obtained by emulsifying and dispersing the epoxy resin (B) in the aqueous medium (C) in the presence of the reactive emulsifier (A).

[0053] The water-based epoxy resin emulsion of the present invention is not particularly limited, but is produced by using preferably 1 to 50% by mass, more preferably 10 to 30% by mass, of the reactive emulsifier (A) and 1 to 70% by mass, more preferably 20 to 50% by mass, of the epoxy resin (B), relative to the total mass of the reactive emulsifier (A), the epoxy resin (B) and the aqueous medium (C).

[0054] Examples of the method for emulsifying and dispersing the epoxy resin (B) in the aqueous medium (C) include a method in which the reactive emulsifier (A) and the epoxy resin (B) are added to the aqueous medium (C), mixed with stirring to carry out the preliminary emulsification, followed by main

emulsification such as microfluidization, by a high shearing force using a disperser. According to the viscosity of the epoxy resin, an organic solvent such as acetone or ethyl acetate, or a reactive diluent for epoxy resins, may be used to reduce the viscosity for carrying out the emulsification and dispersion. [0055] Examples of the disperser to carry out the emulsification, particularly the main emulsification, include batch type emulsification equipments such as a batch mixer (manufactured by Silverson Machines, Inc.), a homogenizer (manufactured by IKA), polytron (manufactured by KINEMATICA AG), and TK autohomomixer (manufactured by Tokushu Kika Kogyo, Co., Ltd.); continuous type emulsification equipments such as Ebara Milder (manufactured by EBARA CORPORATION), TK fill mix and TK pipeline homo mixer (manufactured by Tokushu Kika Kogyo, Co., Ltd.), a colloid mill (manufactured by Shinko Pantec Co., Ltd.), a slasher, a trigonal wet pulverizer (manufactured by Mitsui Miike Machinery Co., Ltd.), CAVITRON (manufactured by Eurotec Ltd.), Fine Flow Mill (manufactured by Pacific Machinery & Engineering Co., Ltd.), and a static mixer (manufactured by Noritake Co., Limited); high-pressure emulsification equipments such as

Microfluidizer (manufactured by Microfluidics Corporation), Nanomizer

(manufactured by NANOMIZER Inc.), and APV Gaulin (manufactured by Gaulin Corporation); film emulsification equipments such as a film emulsification equipments (manufactured by REICA Co., Ltd.); vibration emulsification equipments such as VIBRO MIXER (manufactured by REICA Co., Ltd.); and ultrasonic emulsification equipments such as an ultrasonic homogenizer

(manufactured by Branson). Among these, apparatuses which are preferable in the light of uniform particle size include Microfluidizer, APV Gaulin, the batch mixer, Ebara Milder and the ultrasonic homogenizer.

[0056] The method for the main emulsification, for example, may use

Microfluidizer (manufactured by Microfluidics Corporation) and carried out, for example, by using G10Z (minimum channel width of 87 μπι) or H210Z (minimum channel width of 210 μιη) as an interaction chamber and H30Z (minimum channel width of 200 μπι) or H230Z (minimum channel width of 400 μιη) as an auxiliary module, at a process pressure of 2000 to 30000 psi, preferably 5000 to 20000 psi. The water-based epoxy resin emulsion of the present invention, to which a shearing force is applied when passed through a channel of several hundreds μηι under a pressure of 2000 to 30000 psi, is easily emulsified and dispersed to the predetermined particle diameter having the predetermined degree of particle diameter distribution, thereby also enhancing the storage stability.

[0057] <Waterbased paint, other purposes of use>

The water-based epoxy resin emulsion according to the present invention can be used as the raw material for water-based paints, glass fiber binders, cosmetics, agricultural chemicals, or the like; however, the emulsion is preferably used for water-based paints and glass fiber binders, and more preferably for water-based paints.

[0058] In these purposes of use, to obtain cured products such as coating films or binders using the water-based epoxy resin emulsion of the present invention, the water-based epoxy resin emulsion of the present invention is mixed with a curing agent and applied to an object material, then, the aqueous medium is removed, for example, at room temperature or under heating if necessary, and further the coated object material is kept at room temperature or under heating if necessary, to obtain a cured product. When cured, since the reactive emulsifier (A) simultaneously reacts and cures, there is no problem such as bleeding out of the emulsifier.

[0059] Hereinafter, the water-based paint will be described. The water-based paint of the present invention comprises at least the water-based epoxy resin emulsion of the present invention described above and a curing agent. The water-based paint of the present invention is preferably a 2-component paint which separately provides the paint main agent comprising the water-based epoxy resin emulsion and a curing agent, and the components are mixed immediately before use and applied.

[0060] For the curing agent, a compound having a group having an active hydrogen reactive to epoxy, for example, an amino group or a mercapto group, is used, and the compound having an amino group, that is, an amine compound (hereinafter referred to as an amine curing agent) is preferable. Additionally, the curing agent is preferably water-soluble or water-dispersible.

[0061] Examples of the amine curing agent include aliphatic polyamine, alicyclic polyamine, aromatic polyamine, polyamide, polyamideamine, and heterocyclic amines, or modified products thereof, and water-soluble or water-dispersible agents are particularly used. Examples of the water-soluble or water-dispersible amine curing agent include amine compounds having a polyoxyalkylene chain comprising an ethylene oxide unit and/or a propylene oxide unit as the hydrophilic group in a molecule. Examples include a polyamine compound which is polyoxyalkylene -modified using a polyoxyalkylene-modified epoxy compound having a polyoxyalkylene chain in a molecule. [0062] These amine curing agents are already known and described in, for example, Japanese Patent Laid pen No. H09(l997)-241482 (Patent Literature 1), Japanese Patent Laid pen No. H09(1997)-87361, and Japanese Patent Laid^¬ Open No. 2001-240727.

[0063] The mixing ratio of the curing agent to the water-based epoxy resin emulsion is not particularly limited, and, for example, when a water-based amine compound is used as the curing agent, it is preferable to mix so that an active hydrogen group in the amine compound is preferably 0.5 to 1.5 equivalent, more preferably 0.8 to 1.2 equivalent, relative to an equivalent of the epoxy group comprised in the water-based epoxy resin emulsion. During the curing reaction, heating is carried out as necessary.

[0064] The water-based paint according to the present invention may comprise a known pigment, a filler, a rust-proof agent, a thickener, a dispersant, a defoaming agent, a preservative, a film forming auxiliary, or the like, as necessary, as long as it comprises the water-based epoxy resin emulsion of the present invention.

These additives, in the case of 2-component paints, may be contained in either the paint main agent comprising the water-based epoxy resin emulsion or the curing agent, but are typically contained in the paint main agent.

[0065] The pigments are not particularly limited and typically classified into organic pigments and inorganic pigments.

[0066] Examples of the organic pigment include insoluble azo pigments such as fast yellow, diazo yellow, diazo orange, and naphthol red; phthalocyanine

pigments such as copper phthalocyanine; lake pigments such as fanal lake, tannin lake, and catanol; isoindoline pigments such as isoindoline yellow greenish, and isoindoline yellow reddish,; quinacridone pigments; perylene pigments such as perylene scarlet and perylene maroon.

[0067] Examples of the inorganic pigment include carbon black, white lead, red lead, chrome yellow, silver vermilion, ultramarine blue, cobalt oxide, titanium dioxide, titanium yellow, strontium chromate, molybdenum red, molybdenum white, iron black, lithopone, emerald green, Guignet's green, and cobalt blue.

[0068] The filler refers to a substance added for the purpose of improving the performance, reducing the cost, or the like, and is not particularly limited. Specific examples include calcium carbonate, magnesium carbonate, silica, talc, clay, and alumina.

[0069] The rust-proof agent refers to a substance added to inhibit the corrosion of a material, and is not particularly limited. Examples include red lead, white lead, lead suboxide, basic white lead sulfate, basic lead chromate, calcium

plumbate, zinc dichromate, cyanamide plumbate, zinc powder, dichloromate, barium chromate, sodium nitrite, dicyclohexyl ammonium nitrile,

cyclohexylamine carbonate, and anti-rust oils.

[0070] The thickener is not particularly limited. Examples of an alkali thickener include modified acrylic polymer, examples of an associative thickener include urethane-modified polyethers and polyethers. Examples of the alkali thickener include hydroxyethyl cellulose (SP600 (trade name) manufactured by Daicel Chemical Industries, Ltd.), SN Thickener 615 (trade name) manufactured by SAN NOPCO LIMITED, ASE60 (trade name) manufactured by R & H

Company, and KA10K (trade name) manufactured by Henkel Japan Ltd.

Further, examples of the associative thickener include SN812 (trade name) manufactured by SAN NOPCO LIMITED., RM8W (trade name) manufactured by R & H Company, and UH752 (trade name) manufactured by ADEKA

CORPORATION.

[0071] The dispersant is not particularly limited. Examples include Primal 850 (trade name) manufactured by Rohm and Haas Company, DEMOL EP (trade name) manufactured by Kao Corporation, Discoat N-14 (trade name)

manufactured by DaHchi Kogyo Seiyaku Co., Ltd., Orotan 165A (trade name) (manufactured by R & H), SN Dispersant 5020 (trade name) manufactured of SAN NOPCO LIMITED.

[0072] The defoaming agent is not particularly limited. Examples include hydrophobic silica, metallic soaps, amide, modified silicones, silicone compounds, polyethers, emulsions, and powders. Examples of the hydrophobic silica include NOPCO SN Defoamer 777 (trade name) manufactured by SAN NOPCO LIMITED, SN Defoamer VL (trade name) manufactured by SAN NOPCO LIMITED;

examples of the metallic soap include NOPCO NXZ (trade name) manufactured by SAN NOPCO LIMITED; examples of the amide defoaming agent include NOPCO 267-A (trade name) manufactured by SAN NOPCO LIMITED; examples of the modified silicone defoaming agent include Silicone KM80 (trade name) manufactured by Shin-Etsu Chemical Co., Ltd.; examples of the silicone compound defoaming agent include SN Defoamer 12 IN (trade name)

manufactured by SAN NOPCO LIMITED; examples of the polyether defoaming agent include SN Defoamer PC (trade name) manufactured by SAN NOPCO LIMITED; examples of the emulsion defoaming agent include NOPCO KF-99 (trade name) manufactured by SAN NOPCO LIMITED; examples of the powder foaming agent include SN Defoamer 14-HP (trade name) manufactured by SAN NOPCO LIMITED.

[0073] The preservative agent is not particularly limited. Examples include ACTICIDE LG (trade name) manufactured by Thor Japan Limited, and

ACTICIDE MBS (trade name) manufactured by Thor Japan Limited.

[0074] The film forming auxiliary agent is not particularly limited. Examples include 2,2,4-trimethylpentanediol-l,3-monoisobutarate (CS-12 (trade name) manufactured by Chisso Corporation), 2,2,4-trimethylpentanediol-l,3- diisobutarate (CS-16 (trade name) manufactured by Chisso Corporation), benzyl alcohol, butyl glycol, 2-ethylhexylglycol, phenylpropylene glycol, dibutyl diglycol; organic esters of polyvalent alcohol monoalkyl ethers such as dipropylene glycol mono n-butyl ether, tripropylene mono glycol n-butyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, and diethylene glycol mono n-butyl ether; 3-ethoxypropionate esters, acetic acid 3-methoxy-3-methyl-butyl, and benzoate, adipic polyester.

[0075] The water-based paint according to the present invention can be applied to various substrates, for example, the common substrates such as metals and inorganic building materials, but it is particularly suitable for undercoating to metals. As described earlier, the water-based epoxy resin emulsion of the present invention has an average particle diameter as small as 500 nm or less, thereby improving the adhesiveness of resin to a substrate and enhancing the rust-proof performance. Further, due to the use of a reactive emulsifier having an epoxy group in a molecule as the reactive emulsifier, the emulsifier is fixed in a cured coating film and hence does not bleed out on the coating film surface, whereby the impairment of the mechanical properties and water resistance of the cured coating film is inhibited, and further, there is no concern about

environmental pollution caused by the eluted emulsifier. [0076] In addition, the water-based paint according to the present invention is also preferable to be a sealer for inorganic building materials, or the like. As described earlier, the epoxy resin emulsion of the present invention has an average particle diameter as small as 500 nm or less, and hence it infiltrates well into inorganic building materials and is capable of enhancing the water resistance, mechanical strength, and the like, of inorganic building materials.

[0077] Typically, to impart good appearance, and further to enhance weather resistance, chemical resistance, contamination resistance, water resistance, rustproof properties, and the like, the water-based paint according to the present invention is used as an undercoat and a topcoat is applied on the coated film formed by the undercoat. The topcoat is not particularly limited as long as it is known as a topcoat.

[0078] Examples of the topcoat paints include polyester resin-based paints, silicon polyester resin-based paints, polyurethane resin-based paints, acrylic resin-based paints, and fluororesin-based paints.

[0079] The water-based paint according to the present invention can be applied to a wide variety of purposes and examples include various undercoating for plastic molded products, household electric appliances, steel products, large structures, vehicles (e.g., for solid color, metallic base or clear top for repairing automobiles), construction, tiles, and woodworks.

[0080] Examples of the method for applying the water-based paint include immersion coating (dip coating), air spraying, airless spraying, electrostatic coating, roll coater coating, flow coating, roller coating, and brushing.

Examples

[0081] Hereinafter, the present invention will further be described in details with reference to Examples and Comparative Examples, but is not limited only to Examples. In Examples below, "part" and "%" refer to "part by mass" and "% by mass", respectively.

[0082] <Synthesis of epoxy reactive emulsifier (I)>

Into a glass three-neck flask equipped with a thermometer, a stirrer and a condenser tube, jER828 (148 g) as a hydrophobic epoxy resin and polyether monoamine JEFFAMINE M-1000 (200 g) as a hydrophilic monoamine were added, and the mixture was stirred at 150°C for 6 hours, thereby obtaining 340 g of an epoxy reactive emulsifier (I) (HLB value was 11.8). The obtained epoxy reactive emulsifier (I) was analyzed using a high speed GPC system, HLC-8220GPC, equipped with Super Multipore HZ-M manufactured by Tosoh Corporation, and found to have a weight average molecular weight of 7200, using a calibration curve using polystyrene as a standard substance to convert molecular weight.

[0083] Production Example 1>

The obtained epoxy reactive emulsifier (I) (32 g) in the above was dissolved in 103 g of water, the epoxy resin jER828 (160 g) was added thereto and the mixture was stirred at 400 rpm for 30 minutes to carry out the preliminary emulsification. The obtained preliminary emulsified product was microfluidized at 10000 psi using a microfluidizer equipped with GlOZ as an interaction chamber and H210Z as an auxiliary module, thereby obtaining an intended water-based epoxy resin emulsion (Example l). In comparative example, an emulsion was produced as the above procedure except that it was not microfluidized

(Comparative Example 1).

[0084] Production Example 2>

An aqueous solution in which the epoxy reactive emulsifier (I) (40 g) was dissolved in 240 g of water was added to a solution in which the epoxy resin Epotote YD-011 (200 g) was dissolved in acetone (100 g) and stirred at 400 rpm for 30 minutes to carry out the preliminary emulsification. The obtained

preliminary emulsified product was microfluidized at 10000 psi using a

microfluidizer equipped with GlOZ as an interaction chamber and H210Z as an auxiliary module, and the solvent was collected using a rotary evaporator, thereby obtaining an intended water-based epoxy resin emulsion (Example 2). In comparative example, an emulsion was produced as the above procedure except that it was not microfluidized (Comparative Example 2).

[0085] Production Example 3>

An aqueous solution in which the epoxy reactive emulsifier (I) (40 g) was dissolved in 240 g of water was added to a solution in which the epoxy resin Epotote YD-902LD (200 g) was dissolved in acetone (200 g) and stirred at 400 rpm for 30 minutes to carry out the preliminary emulsification. The obtained preliminary emulsified product was microfluidized at 10000 psi using a

microfluidizer equipped with GlOZ as an interaction chamber and H210Z as an auxiliary module, and the solvent was collected using a rotary evaporator, thereby obtaining an intended water-based epoxy resin emulsion (Example 3). In comparative example, an emulsion was s produced as the above procedure except that it was not microfluidized (Comparative Example 3).

[0086] <Production Example 4>

An aqueous solution in which the epoxy reactive emulsifier (I) (30 g) was dissolved in 180 g of water was added to a solution in which the epoxy resin jER828 (50 g) and Epotote YD-011 (100 g) was dissolved in ethyl acetate (75 g) and stirred at 400 rpm for 30 minutes to carry out the preliminary emulsification. The obtained preliminary emulsified product was microfluidized at 10000 psi using a microfluidizer equipped with G10Z as an interaction chamber and H210Z as an auxiliary module, and the solvent was collected using a rotary evaporator, thereby obtaining an intended water-based epoxy resin emulsion (Example 4). In comparative example, an emulsion was produced as the above procedure except that it was not microfluidized (Comparative Example 4).

[0087] (Comparative Example 5)

A non-reactive emulsifier NOIGEN EA-167D (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) (32 g) was dissolved in 103 g of water, the epoxy resin jER828 (160 g) was added thereto and the mixture was stirred at 400 rpm for 30 minutes to carry out the preliminary emulsification. The obtained preliminary emulsified product was microfluidized at 10000 psi using a microfluidizer equipped with G10Z as an interaction chamber and H210Z as an auxiliary module, thereby obtaining an intended water-based epoxy resin emulsion (Comparative Example 5).

[0088] <Measurement of average particle diameter and degree of particle diameter distribution

The water-based epoxy resin emulsions obtained in the above Examples and Comparative Examples were measured for the average particle diameter and the degree of particle diameter distribution using LASER PARTICLE ANALYZER PAR-III manufactured by Otsuka Electronics Co., Ltd. The results are shown in Table 1.

[0089] <Storage stability test>

The water-based epoxy resin emulsions obtained in the above Examples 1 to 4 and Comparative Examples 1 to 5 each were kept at 50°C for 30 days. Using LASER PARTICLE ANALYZER PAR-III manufactured by Otsuka Electronics Co., Ltd., the average particle diameters immediately after the preparation and after 30-day standing were measured to calculate the particle diameter ratio. The calculation formula to determine the particle diameter ratio is as follows.

Particle diameter ratio= average particle diameter (after standing) / average particle diameter (immediately after preparation)

[0090] Evaluations of the storage stability of the water-based epoxy resin emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 5 are shown in Table 1. The evaluation criteria are as follows.

oo: No particle coagulation or sedimentation was found. Particle diameter ratio was 1 or more but less than 1.1.

o: No particle coagulation or sedimentation was found. Particle diameter ratio ranged from 1.1 to 1.4.

NO particle coagulation or sedimentation was found. Particle diameter ratio was more thanl.4.

x: Particle coagulation or sedimentation was found.

[0091]

[Table 1]

Ex. = Example

Com-Ex. = Comparative Example N=impossible to measure

[0092] <Rust-proof properties test by salt water spray>

Each of the water-based epoxy resin emulsions obtained in the above Examples 1 to 4 was mixed with the equivalent of a water-based amine curing agent EB30 (manufactured by Henkel Japan Ltd.), applied to an iron plate using a 6-mill coater and dried at room temperature for 3 hours, and then, aged for 24-hour at 50°C, thereby obtaining an epoxy resin cured coating film. The obtained cured coating film was cut crosswise using a cutter, allowed to stand in a salt water sprayer to spray salt water at 35°C and the time required for the rust width on the cross-cut area to grow 2 mm was measured.

[0093] For Comparative Examples, the water-based epoxy resin emulsion produced in the above Comparative Example 5 and the water-based epoxy resin emulsions prepared using an epoxy resin and a non-reactive emulsifier by the conventional emulsification method (Comparative

Examples 6 to 9) were used. The epoxy resin emulsified and dispersed in the water-based epoxy resin emulsions was jER828 in Comparative

Example 6, YD-011 in Comparative Example 7, YD-902LD in Comparative Example 8 and EPPN201 in Comparative Example 9.

[0094] Using the water-based epoxy resin emulsions of Comparative Example 5 and Comparative Examples 6 to 9, the salt water spray test was carried out in the same manner as the above Examples and the rust-proof properties was evaluated. The evaluation criteria are as follows. The results are shown in Table 2.

[0095]

o: Time required for the rust width on the cross-cut area to grow 2 mm was 96 hours or more but less than 120 hours.

Δ: Time required for the rust width on the cross-cut area to grow 2 mm was 72 hours or more but less than 96 hours.

X· Time required for the rust width on the cross-cut area to grow 2 mm was less than 72 hours.

[0096]

[Table 2] Com- Conr Com- Com- Conr

Ex.1 Ex.2 Ex.3 Ex.4

Ex.5 Ex.6 Ex.7 Ex.8 Ex.9

Rust-proof

properties

test

hours^* 96 96 96 96 72 72 72 72 <24 evaluation o o o o Δ Δ Δ Δ

hours^* : Time required for the rust width on the cross-cut area to grow to 2 mm after spraying salt water

[0097] As described above, the water-based epoxy resin emulsions of Examples 1 to 4 were obtained using the reactive emulsifier and by microfluidization, and have an average particle diameter of 500 nm or less. The degree of particle diameter distribution is also narrow because of the microfluidization treatment. On the other hand, in Comparative

Examples 1 rto 4 in which the -same reactive emulsifier was used as those in- Examples 1 to 4>' however, the epoxy resin emulsions were obtained without the microfluidization and the average particle diameters exceed 5000 nm. The epoxy resin emulsions of Comparative Examples 5 to 9 are those produced using the non-reactive emulsifier.

[0098] As shown in Table 1, the water-based epoxy resin emulsions obtained in Examples 1 to 4 each had no particle sedimentation or coagulation even left to stand at 50°C for 30 days, thereby exhibiting good storage stability. The water-based epoxy resin emulsions of Examples 2, 3 and 4 had the particle diameters ratio of 1.1 or less on 30 days later, resulting in particularly excellent storage stability. Further, as shown in Table 2, the water-based epoxy resin emulsions of Examples 1 to 4 also had excellent rust-proof properties.

[0099] On the other hand, in all of the water-based epoxy resin emulsions of Comparative Examples 1 to 4 which had the average particle diameters exceeding 5000 nm, the coagulation at 50°C on day 3 were observed.

Further, the water-based epoxy resin emulsion of Comparative Example 5, in which the reactive emulsifier was not used, did not have the particle coagulation or sedimentation but had low rust-proof properties. The water-based epoxy resin emulsions of Comparative Examples 6 to 9 in which the reactive emulsifier was not used also had low rust-proof properties.

[0100] Accordingly, it is suggested that the water-based epoxy resin emulsion can achieve high storage stability by microfluidizing to give an average particle diameter of 500 nm or less and further preferably to give a narrow degree of particle diameter distribution. It is further revealed that rust-proof properties can be attained when the reactive emulsifier is used.

[0101] Thus, the water-based epoxy resin emulsions of Examples 1 to 4 can be stored for a longer period and have better rust-proof properties than the water-based epoxy resin emulsions of Comparative Examples 1 to 9, which are proven to be very useful as water-based paints (e.g. coating agents for metals).

Claims

1. A water-based epoxy resin emulsion in which an epoxy resin (B) is emulsified and dispersed in an aqueous medium (C) in the presence of a reactive emulsifier (A),

wherein an average particle diameter of the water-based epoxy resin emulsion is 500 nm or less.

2. The water-based epoxy resin emulsion according to Claim 1, wherein a degree of particle diameter distribution of the water-based epoxy resin emulsion is 1.0 to 1.4.

3. The water-based epoxy resin emulsion according to Claim 1 or 2, wherein the reactive emulsifier (A) has an epoxy group.

4. The water-based epoxy resin emulsion according to any one of Claims 1 to 3, wherein the epoxy resin (B) comprises an epoxy resin having at least two epoxy groups in a molecular.

5. A water-based paint comprising the water-based epoxy resin emulsion according to any one of Claims 1 to 4.