JP2007270016A - Emulsion, method for producing the same, and an aqueous coating composition using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an emulsion having good curability and being capable of forming a coating film having good hardness and also reducing VOC, and a method for producing such emulsion with ease and simplicity. <P>SOLUTION: The emulsion of the present invention is prepared by dispersing resin particles in an aqueous medium. The resin particle contains the outer shell that is composed of a resin having at least one functional group selected from among a carboxyl group, a sulfonic acid group, a phosphate group, and a hydroxy group and a hydrophobic hardener that is included in the outer shell. The resin particle has an average particle diameter between 100 nm and 500 nm. Preferably, the hydrophobic hardener is a carbodiimide compound or an oxazoline compound. The emulsion of the present invention is obtained by a mini-emulsion polymerization method. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an emulsion, a method for producing the same, and an aqueous coating composition using the emulsion. More specifically, the present invention relates to an emulsion having excellent curability, capable of forming a coating film having excellent hardness, and capable of reducing VOC, and an aqueous coating composition using the emulsion, The present invention relates to a simple method for producing such an emulsion.

  In recent years, from the viewpoint of environmental protection, there is a social demand for switching from solvent-based paints to water-based paints. Furthermore, it is desired to reduce VOC (volatile organic compounds) as well as simply convert to water-based paint.

  A paint containing a curing agent is generally used mainly in industrial fields including automobiles because it has superior physical properties of the coating film compared to a paint not containing it. Here, since the curing agent contained in the solvent-type paint is often hydrophobic, it is difficult to apply it to the aqueous paint as it is.

  Patent Document 1 discloses an aqueous dispersion containing a hydrophobic crosslinking agent. Blocked polyisocyanates and melamine resins are described as hydrophobic crosslinking agents. According to Patent Document 1, it is described that a hydrophobic crosslinking agent can be stably present in water by emulsification. However, both the blocked polyisocyanate and the melamine resin described in Patent Document 1 cannot reduce VOC because desorption components are generated during curing.

  On the other hand, carbodiimide and oxazoline are known as a curing agent that reacts with a carboxyl group introduced into the resin in order to hydrophilize the hydrophobic resin. If the carboxyl group remains in the coating film, it causes problems such as a decrease in water resistance. Therefore, it is expected that the above two kinds of curing agents can further exert their superiority when applied to water-based paints. . Furthermore, since the two types of curing agents undergo an addition reaction, no desorbed material is generated, and it is expected to reduce VOC. However, since these curing agents are hydrophobic, they are difficult to apply to aqueous systems.

Patent Document 2 proposes that a polycarbodiimide that is hydrophobic is applied to an aqueous system by miniemulsion polymerization of a monomer composition containing polycarbodiimide. However, the curability of the emulsion obtained by the technique described in Patent Document 2 is quite insufficient, and the resulting coating film is far from practical use.
Special table 2003-53240 gazette JP 2004-26309 A

  The present invention has been made in order to solve the above-described conventional problems. The object of the present invention is to form a coating film having excellent curability and excellent hardness and reducing VOC. It is to provide an emulsion and an aqueous coating composition that can be used, and a simple method for producing such an emulsion.

  The emulsion of the present invention is an emulsion in which resin particles are dispersed in an aqueous medium. The resin particles react with the outer shell composed of a resin having at least one functional group selected from a carboxyl group, a sulfonic acid group, a phosphoric acid group and a hydroxyl group, and the functional group encapsulated in the outer shell. And a hydrophobic curing agent having a curable functional group to be obtained, and an average particle size thereof is 100 nm to 500 nm.

  In a preferred embodiment, the content of the curable functional group is larger than the content of the functional group of the outer shell.

  In a preferred embodiment, the hydrophobic curing agent is a carbodiimide compound. In a more preferred embodiment, the carbodiimide compound is contained in a proportion of 20 to 80% by mass with respect to the total solid mass of the emulsion.

  In a preferred embodiment, the hydrophobic curing agent is an oxazoline compound. In a more preferred embodiment, the oxazoline compound is contained in a proportion of 20 to 80% by mass with respect to the total solid mass of the emulsion.

  An emulsion according to another embodiment of the present invention is an emulsion obtained by a miniemulsion polymerization method, in which resin particles are dispersed in an aqueous medium. The resin particles react with the outer shell composed of a resin having at least one functional group selected from a carboxyl group, a sulfonic acid group, a phosphoric acid group and a hydroxyl group, and the functional group encapsulated in the outer shell. And a hydrophobic curing agent having a curable functional group to be obtained, and an average particle size thereof is 100 nm to 500 nm. It is not necessary for the outer shell to completely cover the coating additive to be included, and it is sufficient that the outer shell can be stably present in the aqueous medium as resin particles. The outer shell is formed by polymerizing a pre-emulsion in which monomer mixture particles containing the hydrophobic curing agent are dispersed in an aqueous medium. The monomer mixture includes a carboxyl group-containing ethylenically unsaturated monomer, a sulfonic acid group-containing ethylenically unsaturated monomer, a phosphoric acid group-containing ethylenically unsaturated monomer, and / or a hydroxyl group-containing ethylenically unsaturated monomer.

  In a preferred embodiment, the hydrophobic curing agent includes the carboxyl group-containing ethylenically unsaturated monomer, the sulfonic acid group-containing ethylenically unsaturated monomer, the phosphate group-containing ethylenically unsaturated monomer, and / or the hydroxyl group-containing ethylenically unsaturated monomer. It is used at a ratio of 200 to 800 parts by mass with respect to 100 parts by mass of the saturated monomer.

  According to another aspect of the present invention, a method for producing an emulsion is provided. This production method includes a hydrophobic curing agent having a curable functional group capable of reacting with at least one functional group selected from a carboxyl group, a sulfonic acid group, a phosphoric acid group and a hydroxyl group, and a carboxyl group-containing ethylenically unsaturated monomer. A sulfonic acid group-containing ethylenically unsaturated monomer, a phosphoric acid group-containing ethylenically unsaturated monomer and / or a monomer mixture containing a hydroxyl group-containing ethylenically unsaturated monomer in an aqueous medium, and the hydrophobic curing agent Preparing a pre-emulsion in which the encapsulated monomer mixture particles are dispersed in an aqueous medium; polymerizing the monomer mixture in the pre-emulsion and dispersing the resin particles encapsulating the hydrophobic curing agent in the aqueous medium; Obtaining a prepared emulsion. The average particle diameter of the resin particles is 100 nm to 500 nm.

  In a preferred embodiment, the hydrophobic curing agent includes the carboxyl group-containing ethylenically unsaturated monomer, the sulfonic acid group-containing ethylenically unsaturated monomer, the phosphate group-containing ethylenically unsaturated monomer, and / or the hydroxyl group-containing ethylenically unsaturated monomer. It is used at a ratio of 200 to 800 parts by mass with respect to 100 parts by mass of the saturated monomer.

  According to still another aspect of the present invention, an aqueous coating composition is provided. This water-based coating composition contains the above emulsion.

  According to the present invention, the outer shell of the resin particles dispersed in the emulsion has a carboxyl group, a sulfonic acid group, a phosphoric acid group and / or a hydroxyl group (hereinafter, these may be collectively referred to as an outer shell functional group). By coating the outer shell with a hydrophobic curing agent composed of a resin and having a curable functional group that can react with the outer shell functional group, a coating film having excellent curability and excellent hardness can be obtained. Emulsions and aqueous coating compositions that can be formed can be provided. Furthermore, according to the present invention, the hydrophobic curing agent can be contained in the emulsion at a high concentration (more specifically, the amount of the curable functional group is larger than the amount of the outer shell functional group). Become. As a result, it is possible to satisfactorily prevent carboxyl groups and / or hydroxyl groups from remaining in the resulting coating film, and thus it is possible to obtain a coating film having excellent water resistance.

A. Overall Configuration of Emulsion The emulsion of the present invention is an emulsion in which resin particles are dispersed in an aqueous medium. The resin particles can react with an outer shell composed of a resin having a carboxyl group, a sulfonic acid group, a phosphoric acid group and / or a hydroxyl group (outer shell functional group), and an outer shell functional group encapsulated in the outer shell. And a hydrophobic curing agent having a curable functional group. The outer shell does not need to completely cover the encapsulating hydrophobic curing agent, and it is sufficient that the outer shell can be stably present in the aqueous medium as resin particles. The average particle diameter of the resin particles is 100 nm to 500 nm, preferably 200 nm to 400 nm. When the average particle diameter of the resin particles in the emulsion is in such a range, a coating film excellent in transparency and durability can be formed. The resin solid content in the emulsion is preferably 20 to 50% by mass. The average particle size of the resin particles is a value obtained by diluting the sample with deionized water and measuring the sample at 25 ° C. using a laser scattering particle size distribution analyzer (trade name ELS-800, manufactured by Otsuka Electronics Co., Ltd.). is there.

B. Hydrophobic Curing Agent As the hydrophobic curing agent, any appropriate hydrophobic curing agent having a curable functional group capable of reacting with the outer shell functional group can be adopted. Representative examples of such hydrophobic curing agents include carbodiimide compounds and oxazoline compounds. A hydrophobic hardening | curing agent may be used individually or in combination of 2 or more types.

  Preferably, the hydrophobic curing agent is contained in the emulsion in such a ratio that the amount of the curable functional group is equal to or greater than the amount of the outer shell functional group. More preferably, the content ratio of the curable functional group and the outer shell functional group is 1: 1 to 1.5: 1. When the content ratio of the curable functional group is less than 1: 1, the carboxyl group, sulfonic acid group, phosphoric acid group and / or hydroxyl group of the outer shell remains in the coating film. It may be insufficient. When the content ratio of the curable functional group is larger than 1.5: 1, the storage stability of the emulsion may be lowered, or the obtained coating film may be yellowed. According to the present invention, the inner core of the hydrophobic substance is formed very clearly in the aqueous medium by encapsulating the hydrophobic curing agent in the resin particles of the emulsion (and the monomer mixture particles of the pre-emulsion) at a very high concentration. Is done. As a result, it is considered that the balance between the aqueous medium and the hydrophobic substance is improved, and the stability of the emulsion is improved. In addition, since the molecular weight of the hydrophobic curing agent is smaller than the molecular weight of the outer shell resin, it has excellent fluidity when forming a coating film, and the contact between the curing agent and the outer shell resin (coating film forming component) is very good. Realized. Therefore, the reaction opportunity of a hardening | curing agent and outer shell resin (coating film formation component) increases, and the coating film excellent in mechanical strength can be obtained. Moreover, since the number of the crosslinking points of the coating film obtained increases by containing a hardening | curing agent in high concentration, the coating film excellent in sclerosis | hardenability and mechanical strength can be obtained.

  The hydrophobic curing agent is preferably contained in a proportion of 20 to 80% by mass, more preferably 30 to 70% by mass, and particularly preferably 30 to 60% by mass with respect to the total solid mass of the emulsion. When the content of the hydrophobic curing agent is less than 20% by mass, the carboxyl group, sulfonic acid group, phosphoric acid group and / or hydroxyl group of the outer shell remains in the coating film, and as a result, the water resistance of the coating film May become insufficient. If the content of the hydrophobic curing agent exceeds 80% by mass, the pre-emulsion cannot be prepared or even if it can be prepared, the hydrophobic curing agent may be separated during the polymerization reaction or during storage of the resulting emulsion. . As a result, unevenness, gelation, sedimentation or the like occurs, and the stability of the emulsion may be insufficient. Furthermore, the curability of the emulsion becomes insufficient, and the resulting coating film may have insufficient hardness, chemical resistance, weather resistance, water resistance, rust resistance, and the like.

B-1. Carbodiimide compound In this specification, the “carbodiimide compound” refers to a compound having at least one carbodiimide group (—N═C═N—) in the molecule. The carbodiimide compound may be an oligomer or a polymer. Such a carbodiimide compound can be typically obtained by a condensation reaction involving decarbonization of a diisocyanate compound. The carbodiimide compound thus obtained typically has a carbodiimide group in the molecular chain and has an isocyanate group at both ends. In the present invention, the carbodiimide compounds may be used alone or in combination of two or more.

  The diisocyanate compound is typically an organic diisocyanate compound. Examples of organic diisocyanates include aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and mixtures thereof. Specific examples include 1,5-naphthylene diisocyanate, 4,4-diphenylmethane diisocyanate, 4,4-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate. 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, hexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane 4,4'-diisocyanate, methylcyclohexane diisocyanate, tetramethylxylylene diisocyanate, 1,6-hexamethylene diisocyanate, etc. It is.

  A carbodiimidization catalyst is usually used for the condensation reaction. Specific examples of the carbodiimidization catalyst include 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, 3-methyl-1 -Phenyl-2-phospholene-1-oxide, 3-methyl-1-phenyl-3-phospholene-1-oxide, phospholene oxides such as these 3-phospholene isomers, and the like. From the viewpoint of catalytic ability, 3-methyl-1-phenyl-2-phospholene-1-oxide and 3-methyl-1-phenyl-3-phospholene-1-oxide are preferable.

  When the carbodiimide compound has an isocyanate group at the molecular end, the terminal isocyanate group is preferably modified. By modifying the terminal isocyanate group, the reactivity with water can be appropriately suppressed. Examples of the modifying agent for modifying the terminal isocyanate group include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, n-hexanol, cyclohexanol, benzyl alcohol, cyclohexane methanol, and 2-ethylhexanol. C1-C12 primary or secondary alcohols such as 1-dodecanol; 1 carbon atoms such as methylamine, ethylamine, n-propylamine, n-butylamine, n-hexylamine, benzylamine, n-dodecylamine Secondary amines having 2 to 8 carbon atoms such as primary amines of -12, diethylamine, dipropylamine, dibutylamine, dibenzylamine, dioctylamine, N-ethyl-n-propylamine, N-ethyl-n-butylamine Is mentioned . Preferably, it is a primary or secondary alcohol or a primary or secondary amine having 8 or less carbon atoms.

  The carbodiimide compound is contained in an amount of preferably 20 to 80% by mass, more preferably 30 to 70% by mass, and particularly preferably 30 to 60% by mass with respect to the total solid content mass of the emulsion. When the content of the carbodiimide compound is less than 20% by mass, the outer shell functional group remains in the coating film, and as a result, the water resistance of the coating film may be insufficient. When the content of the carbodiimide compound exceeds 80% by mass, there is a possibility that an aggregate is formed during the production of the emulsion.

B-2. Oxazoline Compound As used herein, “oxazoline compound” refers to a compound having at least one oxazoline group in the molecule. Preferably, the oxazoline compound is a compound having two or more 2-oxazoline groups in the molecule. Representative examples of such compounds include (a) reaction products of polycarboxylic acids (eg, dicarboxylic acids), nitrile compounds (eg, dinitriles, trinitriles) and ethanolamines, and (b) containing oxazoline groups Examples thereof include polymers. In the present invention, the oxazoline compounds may be used alone or in combination of two or more.

上記式中、Ｒ^１、Ｒ^２、Ｒ^３およびＲ^４は、各々独立に、水素原子、ハロゲン、アルキル、アラルキル、フェニルまたは置換フェニル基である。すなわち、２−オキサゾリン基は、水素の１または２以上が置換されていてもよい。 The 2-oxazoline group is represented by formula (1):

In the above formula, R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, halogen, alkyl, aralkyl, phenyl or substituted phenyl group. That is, in the 2-oxazoline group, one or more of hydrogen may be substituted.

  Examples of the reaction product (a) include 2,2′-bis- (2-oxazoline), 2,2′-methylene-bis- (2-oxazoline), 2,2′-ethylene-bis- ( 2-oxazoline), 2,2′-trimethylene-bis- (2-oxazoline), 2,2′-tetramethylene-bis- (2-oxazoline), 2,2′-hexamethylene-bis- (2-oxazoline) ), 2,2′-octamethylene-bis- (2-oxazoline), 2,2′-ethylene-bis- (4,4′-dimethyl-2-oxazoline), 2,2′-p-phenylene-bis -(2-oxazoline), 2,2'-m-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene-bis- (4,4'-dimethyl-2-oxazoline), bis- (2-Oxazolinyl cycl Hexane) sulfide, bis - (2-oxazolinyl sulfonyl norbornane), and sulfides.

上記式中、Ｒ^１、Ｒ^２、Ｒ^３およびＲ^４は、各々独立に、水素原子、ハロゲン、アルキル、アラルキル、フェニルまたは置換フェニル基であり、Ｒ５は、付加重合性不飽和結合を有する非環状有機基である。 Examples of the oxazoline group-containing polymer (b) include homopolymers or copolymers obtained by polymerizing an addition-polymerizable oxazoline and at least one other polymerizable monomer as required. Examples of the addition polymerizable oxazoline include a compound represented by the formula (2):

In the above formula, R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, halogen, alkyl, aralkyl, phenyl or substituted phenyl group, and R 5 is a non-reactive group having an addition polymerizable unsaturated bond. It is a cyclic organic group.

  Specific examples of the addition polymerizable oxazoline include, for example, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl- 2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline and the like. 2-Isopropenyl-2-oxazoline is preferred. This is because an oxazoline group-containing polymer suitable for use in the emulsion of the present invention can be obtained and is easily available industrially. When the oxazoline group-containing polymer is a copolymer, the amount of the addition polymerizable oxazoline used can be appropriately set according to the purpose. Specifically, the amount of addition polymerizable oxazoline used in the copolymer is preferably 10% by mass or more in terms of the monomer charge ratio. When the amount used is less than 1% by mass, the ability as a curing agent may not be sufficiently exhibited, and as a result, the durability and water resistance of the coating film may be impaired.

  As the other polymerizable monomer, any suitable monomer that can be copolymerized with the addition-polymerizable oxazoline and does not react with the oxazoline group may be employed. Specific examples include (meth) acrylic acid esters such as methyl (meth) acrylate, butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate; unsaturated nitriles such as (meth) acrylonitrile; ) Unsaturated amides such as acrylamide and N-methylol (meth) acrylamide; Vinyl esters such as vinyl acetate and vinyl propionate; Vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; Halogenated α, β-unsaturated monomers such as vinyl, vinylidene chloride and vinyl fluoride; α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene, and the like. These may be used alone or in combination of two or more.

  The oxazoline group-containing polymer (b) can be obtained by any appropriate polymerization method (for example, solution polymerization) using the addition polymerizable oxazoline and, if necessary, the other polymerizable monomer. The supply form of the oxazoline group-containing polymer is preferably an organic solvent solution or no solvent. Any appropriate solvent can be adopted as the solvent as long as the oxazoline group-containing polymer can be dissolved. Specific examples include hydrophobic solvents such as toluene, xylene, ethyl acetate, butyl acetate, methyl isobutyl ketone, propylene glycol methyl ether acetate, diethylene glycol dibutyl ether, texanol, or a mixed solvent thereof.

  The molecular weight of the oxazoline group-containing polymer is preferably 3,000 to 30,000, more preferably 5,000 to 15,000.

  The oxazoline compound is preferably contained in a proportion of 20 to 80% by mass, more preferably 30 to 70% by mass, and particularly preferably 30 to 60% by mass with respect to the total solid mass of the emulsion. When the content of the oxazoline compound is less than 20% by mass, the outer shell functional group remains in the coating film, and as a result, the water resistance of the coating film may be insufficient. When the content of the oxazoline compound exceeds 80% by mass, there is a possibility that an aggregate is formed during the production of the emulsion.

C. Outer shell enclosing the hydrophobic curing agent The outer shell encloses the hydrophobic curing agent. The outer shell is composed of a resin having a carboxyl group, a sulfonic acid group, a phosphoric acid group, and / or a hydroxyl group (outer shell functional group). By encapsulating a hydrophobic curing agent (especially a carbodiimide compound and / or an oxazoline compound) with such a resin having an outer shell functional group, an aqueous coating composition having extremely excellent curability during coating film formation is obtained. Can do.

  The resin constituting the outer shell is typically a carboxyl group-containing ethylenically unsaturated monomer, a sulfonic acid group-containing ethylenically unsaturated monomer, a phosphoric acid group-containing ethylenically unsaturated monomer, or a hydroxyl group-containing ethylenically unsaturated monomer. (Hereinafter, these may be collectively referred to as an outer shell functional group-containing ethylenically unsaturated monomer) may be a homopolymer obtained by homopolymerization. Alternatively, a copolymer obtained by copolymerizing at least one shell functional group-containing ethylenically unsaturated monomer and any other suitable monomer copolymerizable with the shell functional group-containing ethylenically unsaturated monomer It may be. When the resin is a copolymer, the content ratio of the repeating unit derived from the outer shell functional group-containing ethylenically unsaturated monomer is 3 to 40% by mass in terms of the monomer charge ratio. If it is less than 3% by mass, there are too few outer shell functional groups, and the curability at the time of coating film formation may be insufficient. If it exceeds 40% by mass, polymerization may not proceed sufficiently, and the outer shell may not be formed sufficiently.

  Specific examples of the carboxyl group-containing ethylenically unsaturated monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and adducts thereof with ε-caprolactone (for example, “Aronix M-5300” manufactured by Toagosei Co., Ltd.). ); An adduct of a hydroxyl group-containing ethylenically unsaturated monomer and an acid anhydride group-containing compound; and an adduct of an acid anhydride group-containing ethylenically unsaturated monomer and a monoalcohol. These can be used alone or in combination of two or more.

  Specific examples of the sulfonic acid group-containing ethylenically unsaturated monomer include vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-sulfoethyl methacrylate, 2-sulfobutyl methacrylate, styrene sulfonic acid, sulfophenyl allyl ether, Examples thereof include sulfophenylmethallyl ether, 2-acrylamido-2-methylpropanesulfonic acid, and their ammonia salts, organic amine salts, alkali metal salts, and the like.

  Specific examples of the phosphoric acid group-containing ethylenically unsaturated monomer include phosphoxyethyl methacrylate, phosphoxypropyl methacrylate, phosphoxypolyoxyethylene glycol monomethacrylate, phosphoxypolyoxypropylene glycol monomethacrylate, methacryloyloxyethyl phosphate monoethanol. Examples include amine half salts, vinylphosphonic acid, allylphosphonic acid, α-phosphonostyrene, 2-acrylamido-2-methylpropanephosphonic acid, and salts thereof (for example, ammonia salt, organic amine salt, alkali metal salt). .

  Specific examples of the hydroxyl group-containing ethylenically unsaturated monomer include half esters of (meth) acrylic acid and C2-C8 diol [for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3 -Hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate] and their ε-capracton modified products. These can be used alone or in combination of two or more.

  Specific examples of the other monomers include methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, n-butyl methacrylate, n-butyl acrylate, isobutyl methacrylate, isobutyl acrylate, t-methacrylic acid t- Butyl, t-butyl acrylate, 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, lauryl methacrylate, phenyl acrylate, isobornyl methacrylate, isobornyl acrylate, cyclohexyl methacrylate, t-butylcyclohexyl methacrylate, t -Butylcyclohexyl, dicyclopentadienyl methacrylate, dicyclopentadienyl acrylate, dihydrodicyclopentadienyl methacrylate, dihydrodicyclopentadienyl acrylate ( T) Acrylic acid ester; Styrene monomers such as styrene, α-methylstyrene, t-butylstyrene, parachlorostyrene, vinylnaphthalene; methacrylamide, acrylamide, N-methylolmethacrylamide, N-methylolacrylamide, N-butoxymethyl Methacrylamide, N-butoxymethylacrylamide, N, N-dimethylmethacrylamide, N, N-dimethylacrylamide, N, N-dibutylmethacrylamide, N, N-dibutylacrylamide, N, N-dioctylmethacrylamide, N, N -Dioctylacrylamide, N-monobutylmethacrylamide, N-monobutylacrylamide, N-monooctylmethacrylamide, N-monooctylacrylamide, N- (2-hydroxyethyl) acryl Amide monomers such as luamide and N- (2-hydroxyethyl) methacrylamide; vinyl ketone and the like. Furthermore, a monomer that causes internal crosslinking in the resin particles (typically, a monomer containing two or more unsaturated double bonds) can also be used. Specific examples of such a monomer include divinylbenzene, polyethylene glycol dimethacrylate, diallyl phthalate and the like. The other monomer may be used alone or in combination of two or more. The number, type, combination, and amount of other monomers used are appropriately set according to the purpose as long as they can be emulsified and the monomer mixture particles and resin particles having the desired average particle diameter can be obtained. Can be done.

D. Method for Producing Emulsion The emulsion of the present invention can be prepared by a miniemulsion polymerization method. In the miniemulsion polymerization method, the hydrophobic curing agent and a monomer mixture containing at least one outer shell functional group-containing ethylenically unsaturated monomer are dispersed in an aqueous medium, and the hydrophobic curing agent is encapsulated. Preparing a pre-emulsion in which the monomer mixture particles are dispersed in an aqueous medium; and polymerizing the monomer mixture in the pre-emulsion to produce an emulsion in which the resin particles encapsulating the hydrophobic curing agent are dispersed in the aqueous medium. Obtaining. By using the mini-emulsion polymerization method, it is possible to encapsulate the hydrophobic curing agent in the resin particles without causing the monomer to diffuse and move from the pre-emulsion oil droplets into the water to undergo emulsion polymerization. As a result, a coating film excellent in uniformity can be obtained, and a hydrophobic curing agent can be applied to the aqueous composition. For example, the outer shell is composed of a carboxyl group, sulfonic acid group, phosphoric acid group and / or hydroxyl group-containing resin and reacts with outer shell functional groups such as carbodiimide compounds and oxazoline compounds as a curing agent to be encapsulated in the outer shell. By using a curing agent having a functional group to be obtained, the outer shell resin reacts with the curing agent and cures to form a coating film. In the present invention, the curing agent can be encapsulated at a high concentration (in the state where the number of functional groups of the curing agent is larger than the number of functional groups of the outer shell). Is virtually absent. As a result, a coating film having excellent water resistance can be formed. Hereinafter, a specific procedure in an example of the miniemulsion polymerization method used in the present invention will be described.

  First, a monomer mixture is prepared. The monomer mixture is prepared by mixing at least one of the outer shell functional group-containing ethylenically unsaturated monomer and the other copolymerizable monomer in a predetermined ratio depending on the purpose. Each of the outer shell functional group-containing ethylenically unsaturated monomers may be used alone. Therefore, in the present specification, the “monomer mixture” means a carboxyl group-containing ethylenically unsaturated monomer, a sulfonic acid group-containing ethylenically unsaturated monomer, a phosphoric acid group-containing ethylenically unsaturated monomer, or a hydroxyl group-containing ethylenically unsaturated monomer alone. Includes cases. As described above, the content of the outer shell functional group-containing ethylenically unsaturated monomer in the monomer mixture is preferably 3 to 40% by mass. The monomer mixture may be pre-emulsified using any suitable disperser (eg, homomixer, dispermixer).

  Next, a pre-emulsion is obtained by emulsifying the obtained monomer mixture, the above-described hydrophobic curing agent, emulsifier, and any appropriate additive as necessary using a high-speed shear emulsifier. Preferably, the shell functional group-containing ethylenically unsaturated monomer and the hydrophobic curing agent in the monomer mixture are such that the content of the curable functional group is greater than the content of the shell functional group in the resulting emulsion. Used in ratio. More specifically, a hydrophobic hardening | curing agent may be used in the ratio of 200-800 mass parts with respect to 100 mass parts of outer shell functional group containing ethylenically unsaturated monomers.

  According to the production method of the present invention, a pre-emulsion in which monomer mixture particles are dispersed in an aqueous dispersion medium in a state of including a hydrophobic curing agent can be realized. The average particle size of the monomer mixture particles in the pre-emulsion is preferably set to 0.5 to 1.5 times, more preferably 0.8 to 1.2 times the average particle size of the resin particles in the resulting emulsion. obtain. More specifically, the average particle size of the monomer mixture particles is preferably 200 nm to 500 nm, and more preferably 300 nm to 400 nm. The monomer mixture particles have an average particle diameter in such a range and include a hydrophobic curing agent to form a coating film having extremely excellent curability and excellent hardness. Can be obtained. The average particle size of the monomer mixture particles can be controlled by adjusting the amount of emulsifier and shearing conditions (eg, rotational speed, shear stress, shear time, pressure at shear).

  Any appropriate apparatus can be adopted as the high-speed shearing emulsifier as long as a desired pre-emulsion can be obtained. Specific examples include a high-speed rotary shear type stirrer, a colloid mill, a high-pressure colloid mill, a high-pressure jet type emulsifier / disperser, an ultrasonic emulsifier / disperser, and a high-pressure homogenizer. For example, a high-speed rotary shear type stirrer atomizes a liquid by utilizing a strong shearing effect and / or impact force that occurs in a minute gap between a rotary blade and a stationary ring. T. as a stirrer. The rotation speed when using K-Robomix (registered trademark; manufactured by Primix Co., Ltd.) is, for example, 10,000 to 20,000 rpm, and the stirring time is, for example, 5 to 60 minutes. Therefore, it is preferable to control the stirrer so that the peripheral speed is 10 to 30 m / sec.

  As the emulsifier, an anionic emulsifier or a nonionic emulsifier is typically used. Specific examples of anionic emulsifiers include dodecyl benzene sulfonate, lauryl sulfate, alkyl diphenyl ether disulfonate, dialkyl sulfosuccinate, polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene polycyclic phenyl ether sulfate, poly Examples thereof include oxyethylene alkyl ether sulfates. Specific examples of the nonionic emulsifier include polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene polycyclic phenyl ether, polyoxyethylene sorbitan fatty acid ester and the like. The addition amount of the emulsifier is preferably 1 to 15 parts by mass with respect to 100 parts by mass of the monomer mixture. When the amount of the emulsifier is less than 1 part by mass, there is a possibility that an aggregate is formed during the production of the emulsion. If the amount of the emulsifier exceeds 15 parts by mass, the water resistance of the resulting coating film may be reduced.

  The emulsifier may be a reactive emulsifier. A reactive emulsifier is a surfactant having an ethylenically unsaturated bond. Reactive emulsifiers are classified into three types: anionic, cationic and nonionic. The reactive emulsifier may be used in combination with the above normal emulsifier, or may be used alone. A reactive emulsifier may be included in the monomer mixture. When the reactive emulsifier is used, the amount used (the total of the reactive emulsifier and the normal emulsifier when used in combination with the above ordinary emulsifier) is 1 to 15 parts by mass with respect to 100 parts by mass of the monomer mixture. In addition, when a reactive emulsifier is included in the monomer mixture and the reactive emulsifier has an ionic group (that is, an anionic type or a cationic type), the amount used is preferably 5 It is below mass parts.

  Specific examples of commercially available anionic reactive emulsifiers include Eleminol JS series (manufactured by Sanyo Kasei Kogyo Co., Ltd.), Laterum S series, Latemu PD series, SASK series (manufactured by Kao Corporation), Aqualon HS series (manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ), Adekaria soap SE, SR series (Asahi Denka Co., Ltd.), Antox MS-60 (Nippon Emulsifier Co., Ltd.) and the like. Specific examples of commercially available cationic reactive emulsifiers include Latemul K series (manufactured by Kao Corporation). Specific examples of commercially available nonionic reactive emulsifiers include Aqualon RN series (Daiichi Kogyo Seiyaku Co., Ltd.), Adekaria soap NE, ER series (Asahi Denka Co., Ltd.) and the like.

  Specific examples of the additive include a polymerization initiator and a chain transfer agent.

  The polymerization initiator may be either oil-soluble or water-soluble. Examples of the oil-soluble polymerization initiator include organic peroxides such as benzoyl peroxide, parachlorobenzoyl peroxide, lauroyl peroxide, t-butyl perbenzoate, octanoyl peroxide, stearoyl peroxide; azobisiso Examples thereof include azo compounds such as butyronitrile, 2,2′-azobis (2-methylbutyronitrile), and 2,2′-azobis (2,4-dimethylvaleronitrile). Examples of water-soluble polymerization initiators include cumene hydroperoxide, t-butyl peroxide, t-butyl peroxylaurate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, and diisopropylbenzene hydroperoxide. Organic peroxides: azobis (2-methylpropiononitrile), 4,4′-azobis (4-cyanobutanoic acid), dimethylazobis (2-methylpropionate), azobis [2-methyl-N- (2- Azo compounds such as hydroxyethyl) -propionamide] and azobis {2-methyl-N- [2- (1-hydroxybutyl)]-propionamide}; persulfates such as potassium persulfate, ammonium persulfate and sodium persulfate Is mentioned. These may be used alone or in combination of two or more. If necessary, a reducing agent such as sugar, sodium formaldehyde sulfoxylate, or iron complex may be used in combination with the polymerization initiator to form a redox polymerization system. The polymerization initiator can be preferably used at a ratio of 0.1 to 3 parts by mass with respect to 100 parts by mass of the monomer mixture.

  Any appropriate chain transfer agent capable of adjusting the molecular weight of the resin constituting the outer shell to a desired range can be adopted as the chain transfer agent. Specific examples include lauryl mercaptan, t-dodecyl mercaptan, octyl mercaptan, 2-ethylhexyl thioglycolate, 2-methyl-5-t-butylthiophenol, α-methylstyrene dimer, and the like. The chain transfer agent can be preferably used at a ratio of 0.5 to 5 parts by mass with respect to 100 parts by mass of the monomer mixture.

  Next, the pre-emulsion is subjected to miniemulsion polymerization to obtain an emulsion. By carrying out miniemulsion polymerization of the pre-emulsion dispersed in the aqueous dispersion medium with the monomer mixture particles encapsulating the hydrophobic curing agent, the monomer mixture is polymerized while enclosing the hydrophobic curing agent, and the outer Form a shell. As a result, an emulsion in which resin particles encapsulating the hydrophobic curing agent (that is, capsule-like resin particles) are dispersed is obtained. The polymerization conditions can be appropriately selected according to the type of monomer used in the monomer mixture, the content of the hydrophobic curing agent, and the like. In one embodiment, the polymerization temperature in the miniemulsion polymerization is 40 to 100 ° C., and the polymerization time is 4 to 8 hours. As described above, the emulsion of the present invention is obtained.

E. Aqueous coating composition The aqueous coating composition of the present invention contains the above emulsion. The solid content of the emulsion in the aqueous coating composition is preferably 30% by mass or more, more preferably 50% by mass or more, based on the total solid content of the aqueous coating composition. When the solid content ratio of the emulsion is less than 30% by mass, the water resistance of the resulting coating film tends to decrease.

  The water-based paint composition of the present invention may further contain any appropriate paint additive in addition to the emulsion. Specific examples of paint additives include curing catalysts (eg, metal dryers), pH adjusters (eg, ammonia water, sodium hydroxide), antifoaming agents, leveling agents, ultraviolet absorbers, antioxidants, flame retardants. , Antistatic agents, compatibilizers, crosslinking agents, thickeners, electrostatic assistants, plasticizers, heat stabilizers, light stabilizers, and the like. The number, type and amount of paint additives to be added can be appropriately selected according to the purpose. Needless to say, the coating composition of the present invention may further contain a coloring material (for example, pigment) and other resin components depending on the purpose.

  The water-based paint composition of the present invention is a clear paint, enamel paint, architectural use, automotive exterior coating, automotive parts and other coating applications, printing ink and other coating materials, nonwoven fabric bonding agents, adhesives, fillers, It can be suitably used for forming materials, resists, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples. Unless otherwise specified, parts and% in the examples are based on mass.

(Production Example 1) Production of n-dibutylamine-modified HMDI carbodiimide solution In 500 ml of Kolben, 250 parts of 4,4'-dicyclohexylmethane diisocyanate (hereinafter referred to as HMDI) was added to 3-methyl-1-phenyl-3-phospholene- 2.5 parts of 1-oxide was added and stirred at 170 ° C. in a nitrogen stream. When the carbodiimide value calculated from the isocyanate equivalent obtained by titrating the remaining amine was reacted completely with excess n-dibutylamine and titrated for the remaining amine using bromophenol blue as an indicator, the reactor The mixture was cooled and 220 parts of a 3: 7 mixture of styrene (referred to as St) and n-butyl methacrylate (referred to as nBMA) was added at 90 ° C. to obtain 420 parts of a 50% solid solution. The solution was cooled to about 5 ° C., and a solution consisting of 63.96 parts of n-dibutylamine and 63.96 parts of St / nBMA mixed solution was added dropwise over about 2 hours with stirring. It was confirmed by the IR spectrum after the reaction that the absorption of the isocyanate group disappeared. The obtained reaction liquid was returned to room temperature in about 2 hours. Thus, 520 parts of a solution of n-dibutylamine modified HMDI carbodiimide was obtained.

(Production Example 2) Production of n-dibutylamine-modified TDI carbodiimide solution 2,6-tolylene diisocyanate (hereinafter referred to as TDI) was used in place of 4,4'-dicyclohexylmethane diisocyanate, and the synthesis temperature was 120 ° C. It was manufactured in the same manner as in Production Example 1 except that.

(Production Example 3) Production of n-dibutylamine-modified HDI carbodiimide solution 1,6-hexamethylene diisocyanate (hereinafter referred to as HDI) was used in place of 4,4′-dicyclohexylmethane diisocyanate, and the synthesis temperature was 150 ° C. It was manufactured in the same manner as in Production Example 1 except that.

(Production Example 4) Production of Oxazoline Group-Containing Polymer 100 parts of xylene were charged into a flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer and a dropping funnel, and the temperature was raised to 90 ° C. Perbutyl O (t-butylperoxy-2-ethylhexanoate) was added to a monomer mixture comprising 40 parts of methyl methacrylate, 40 parts of n-butyl acrylate, and 20 parts of 2-isopropenyl-2-oxazoline while blowing nitrogen gas there. (Manufactured by Nippon Oil & Fats Co., Ltd.) A solution of 5 parts was added dropwise over 3 hours, held at the same temperature for 3 hours, and then cooled to room temperature to give an oxazoline group-containing polymer solution having a nonvolatile content of 49.8%. Obtained. The molecular weight of this oxazoline-containing polymer was 9,000.

Example 1 Preparation of Hydrophobic Curing Agent (Carbodiimide Compound) Encapsulated Emulsion 1 In a mixture (mixed monomer) of 16.7 parts of hydroxyethyl methacrylate and 83.3 parts of n-butyl acrylate, n- A solution A was prepared by dissolving 100 parts of a dibutylamine-modified HMDI carbodiimide solution. On the other hand, Latem PD104 (Kao Co., Ltd. anionic emulsifier, 20% solid content) was dissolved in 80 parts of ion-exchanged water to prepare Solution B. Next, the solution A and the solution B were mixed. K. Pre-emulsion C was prepared by applying mechanical shearing with Robomix (registered trademark) (manufactured by Primix Co., Ltd.) at a rotational speed of 15,000 rpm for 40 minutes and then diluting with 50 parts of ion-exchanged water. The average particle diameter of the monomer mixture particles in the pre-emulsion C was 311 nm. Subsequently, in 177 parts of ion-exchanged water maintained at 80 ° C., the pre-emulsion C and an aqueous initiator solution D in which 0.3 part of ammonium persulfate was dissolved in 40.0 parts of ion-exchanged water were taken over 3 hours. Continuous dripping. After completion of dropping, the mixture was held at 80 ° C. for 2 hours to complete the polymerization, and a hydrophobic curing agent-containing emulsion 1 was obtained. The average particle diameter of the resin particles in the obtained emulsion was 290 nm, the solid content concentration of the emulsion was 36%, and the pH was 4.93. 25% aqueous ammonia was added to adjust the pH to 9.55.

  The hydrophobic curing agent-containing emulsion 1 was applied onto an aluminum plate using a # 50 bar coater and dried at 140 ° C. for 20 minutes to obtain a coating film. The state of the obtained coating film was evaluated by finger touch. Further, the obtained coating film was extracted for 6 hours under reflux with acetone, and the remaining rate of the coating film was examined. The results are shown in Table 1 below together with the results of Examples 2 to 8 and Comparative Examples 1 and 2 described later.

(Example 2) Preparation of emulsion 2 containing hydrophobic curing agent (carbodiimide compound) Example 1 except that the n-dibutylamine-modified TDI carbodiimide solution of Production Example 2 was used instead of the n-dibutylamine-modified HMDI carbodiimide solution. In the same manner as above, a hydrophobic curing agent-containing emulsion 2 was obtained. The average particle diameter of the resin particles in the obtained emulsion was 340 nm, the solid content concentration of the emulsion was 35.5%, and the pH was 5.91. 25% aqueous ammonia was added to adjust the pH to 9.65. This hydrophobic hardener-containing emulsion 2 was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

(Example 3) Preparation of emulsion 3 containing hydrophobic curing agent (carbodiimide compound) Example 1 except that the n-dibutylamine-modified HDI carbodiimide solution of Production Example 3 was used instead of the n-dibutylamine-modified HMDI carbodiimide solution. In the same manner as above, a hydrophobic curing agent-containing emulsion 3 was obtained. The average particle diameter of the resin particles in the obtained emulsion was 300 nm, the solid content concentration of the emulsion was 36%, and the pH was 6.23. 25% aqueous ammonia was added to adjust the pH to 9.45. This hydrophobic hardener-encapsulating emulsion 3 was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

Example 4 Preparation of Hydrophobic Curing Agent (Carbodiimide Compound) Encapsulated Emulsion 4 Except that 16.7 parts of methacrylic acid and 11.4 parts of dimethylaminoethanol were used instead of 16.7 parts of hydroxyethyl methacrylate. In the same manner as in Example 1, a hydrophobic curing agent-containing emulsion 4 was obtained. The average particle diameter of the resin particles in the obtained emulsion was 280 nm, the solid content concentration of the emulsion was 36%, and the pH was 5.5. 25% aqueous ammonia was added to adjust the pH to 9.5. This hydrophobic hardener-containing emulsion 4 was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

(Example 5) Preparation of emulsion 5 including hydrophobic curing agent (carbodiimide compound) 1 part of Rongalite (NaHSO ₂ · CH ₂ O · 2H ₂ O) was added to Solution B, and 0.3 part of ammonium persulfate was added. Instead, a hydrophobic curing agent-containing emulsion 5 was obtained in the same manner as in Example 2 except that 1 part of Kayabutyl H-70 (70% aqueous solution of t-butyl hydroperoxide, manufactured by Kayaku Akzo) was used. The average particle diameter of the resin particles in the obtained emulsion was 300 nm, the solid content concentration of the emulsion was 35.5%, and the pH was 6.9. This hydrophobic hardener-containing emulsion 5 was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

Example 6 Preparation of Encapsulating Emulsion 6 with Hydrophobic Curing Agent (Oxazoline Compound) Manufactured into a mixture of 45 parts of styrene, 47.3 parts of n-butyl acrylate, 7.7 parts of methacrylic acid and 8.1 parts of dimethylaminoethanol. Solution E was prepared by mixing 100 parts of the oxazoline-containing polymer solution of Example 4. On the other hand, Latem PD104 (an anionic emulsifier manufactured by Kao Corporation, solid content 20%) 30 parts was dissolved in 80 parts of ion-exchanged water to prepare Solution F. Next, the solution E and the solution F were mixed. K. Pre-emulsion G was prepared by applying mechanical shearing with Robomix (registered trademark) (manufactured by Primics Co., Ltd.) at a rotational speed of 15,000 rpm for 40 minutes and then diluting with 50 parts of ion-exchanged water. The average particle size of the monomer mixture particles in the pre-emulsion G was 253 nm. Subsequently, an appropriate amount of 25% aqueous ammonia was added to 177 parts of ion-exchanged water to adjust the pH to 9.0 and maintained at 70 ° C. The pre-emulsion G and an initiator aqueous solution H in which 0.3 part of ammonium persulfate was dissolved in 40.0 parts of ion-exchanged water were continuously added dropwise over 3 hours. After completion of dropping, the mixture was held at 70 ° C. for 2 hours, then heated to 80 ° C. and stirred for 1 hour to complete the polymerization, whereby a hydrophobic curing agent-containing emulsion 6 was obtained. The average particle diameter of the resin particles in the obtained emulsion was 260 nm, the solid content concentration of the emulsion was 36%, and the pH was 9.0. This hydrophobic hardener-encapsulating emulsion 6 was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

(Example 7) Preparation of emulsion 7 encapsulating hydrophobic curing agent (carbodiimide compound) A salt of 26.9 parts of phosphoxyethyl methacrylate and 11.4 parts of dimethylaminoethanol was used in place of 16.7 parts of hydroxyethyl methacrylate. Except for the above, a hydrophobic curing agent-containing emulsion 7 was obtained in the same manner as in Example 1. The average particle diameter of the resin particles in the obtained emulsion was 230 nm, the solid content concentration of the emulsion was 35%, and the pH was 5.7. 25% aqueous ammonia was added to adjust the pH to 9.1. This hydrophobic curing agent-containing emulsion 7 was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

Example 8 Preparation of Emulsion 8 Encapsulating Hydrophobic Curing Agent (Carbodiimide Compound) 26.6 parts of 2-acrylamido-2-methyl-1-propanesulfonic acid and dimethylaminoethanol 11 instead of 16.7 parts of hydroxyethyl methacrylate A hydrophobic curing agent-containing emulsion 8 was obtained in the same manner as in Example 1 except that 4 parts of salt was used. The average particle diameter of the resin particles in the obtained emulsion was 210 nm, the solid content concentration of the emulsion was 35%, and the pH was 5.7. 25% aqueous ammonia was added to adjust the pH to 9.7. This hydrophobic hardener-containing emulsion 8 was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
In a mixture of 16.7 parts of hydroxyethyl methacrylate, 129.75 parts of n-butyl acrylate, and 46.45 parts of styrene, 7.1 parts of the n-dibutylamine-modified HMDI carbodiimide solution described in Preparation Example 1 was dissolved. Was prepared. Emulsion 7 was obtained in the same manner as in Example 1 except that Solution I was used instead of Solution A. The average particle size of the monomer mixture particles in the pre-emulsion was 311 nm, the average particle size of the resin particles in the emulsion 7 was 250 nm, the solid content concentration of the emulsion was 36%, and the pH was 5.01. 25% aqueous ammonia was added to adjust the pH to 9.3. This emulsion 7 was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
Emulsion 8 was obtained in the same manner as in Comparative Example 1, except that 16.7 parts of methacrylic acid and 11.4 parts of dimethylaminoethanol were used instead of 16.7 parts of hydroxyethyl methacrylate. The average particle diameter of the resin particles in the emulsion 8 was 230 nm, the solid content concentration of the emulsion was 36%, and the pH was 6.3. 25% aqueous ammonia was added to adjust the pH to 9.5. This emulsion 8 was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

  As is clear from Table 1, the coating film obtained from the curing agent-incorporating emulsion of the example of the present invention has much higher curability than the coating film obtained from the emulsion of the comparative example. Recognize. Such an excellent effect increases the ratio of the curable functional group of the hydrophobic curing agent to the functional group (specifically, carboxyl group, sulfonic acid group, phosphoric acid group and / or hydroxyl group) of the outer shell resin. It is surmised that this will be achieved. This is a knowledge obtained only after actually preparing an emulsion containing a hydrophobic curing agent at a high concentration that realizes such a ratio. More specifically, the hydrophobic core is encapsulated in the emulsion resin particles (and pre-emulsion monomer mixture particles) at a very high concentration, so that the inner core of the hydrophobic substance is formed very clearly in the aqueous medium. As a result, it is considered that the balance between the aqueous medium and the hydrophobic substance is improved, and the stability of the emulsion is improved. Moreover, since the number of the crosslinking points of the coating film obtained increases by containing a hardening | curing agent in high concentration, it is thought that the coating film excellent in sclerosis | hardenability and excellent in mechanical strength is obtained.

The emulsion and aqueous coating composition of the present invention can be suitably used as a coating considering environmental issues.

Claims (11)

An emulsion in which resin particles are dispersed in an aqueous medium,
The resin particle reacts with the outer shell made of a resin having at least one functional group selected from a carboxyl group, a sulfonic acid group, a phosphoric acid group and a hydroxyl group, and the functional group encapsulated in the outer shell. A hydrophobic curing agent having a curable functional group capable of
An emulsion in which the average particle size of the resin particles is 100 nm to 500 nm.   The emulsion according to claim 1, wherein the content of the curable functional group is larger than the content of the functional group of the outer shell.   The emulsion according to claim 1 or 2, wherein the hydrophobic curing agent is a carbodiimide compound.   The emulsion of Claim 3 in which the said carbodiimide compound is contained in the ratio of 20-80 mass% with respect to the total solid content mass of an emulsion.   The emulsion according to claim 1 or 2, wherein the hydrophobic curing agent is an oxazoline compound.   The emulsion according to claim 5, wherein the oxazoline compound is contained in a proportion of 20 to 80% by mass with respect to the total solid mass of the emulsion. An emulsion obtained by a miniemulsion polymerization method in which resin particles are dispersed in an aqueous medium,
The resin particle reacts with the outer shell made of a resin having at least one functional group selected from a carboxyl group, a sulfonic acid group, a phosphoric acid group and a hydroxyl group, and the functional group encapsulated in the outer shell. A hydrophobic curing agent having a curable functional group capable of
The average particle diameter of the resin particles is 100 nm to 500 nm,
The outer shell is formed by polymerizing a pre-emulsion in which monomer mixture particles encapsulating the hydrophobic curing agent are dispersed in an aqueous medium, and the monomer mixture is a carboxyl group-containing ethylenically unsaturated monomer, sulfonic acid group An emulsion comprising an ethylenically unsaturated monomer, a phosphoric acid group-containing ethylenically unsaturated monomer and / or a hydroxyl group-containing ethylenically unsaturated monomer.   The hydrophobic curing agent is added to 100 parts by mass of the carboxyl group-containing ethylenically unsaturated monomer, the sulfonic acid group-containing ethylenically unsaturated monomer, the phosphoric acid group-containing ethylenically unsaturated monomer and / or the hydroxyl group-containing ethylenically unsaturated monomer. On the other hand, the emulsion of Claim 7 used in the ratio of 200-800 mass parts. Hydrophobic curing agent having a curable functional group capable of reacting with at least one functional group selected from a carboxyl group, a sulfonic acid group, a phosphoric acid group and a hydroxyl group, a carboxyl group-containing ethylenically unsaturated monomer, and a sulfonic acid group Monomer mixture particles in which an ethylenically unsaturated monomer, a monomer mixture containing a phosphoric acid group-containing ethylenically unsaturated monomer and / or a hydroxyl group-containing ethylenically unsaturated monomer is dispersed in an aqueous medium, and the hydrophobic curing agent is encapsulated therein Preparing a pre-emulsion dispersed in an aqueous medium;
Polymerizing the monomer mixture in the pre-emulsion to obtain an emulsion in which resin particles encapsulating the hydrophobic curing agent are dispersed in an aqueous medium,
The method for producing an emulsion, wherein the resin particles have an average particle diameter of 100 nm to 500 nm.   The hydrophobic curing agent is added to 100 parts by mass of the carboxyl group-containing ethylenically unsaturated monomer, the sulfonic acid group-containing ethylenically unsaturated monomer, the phosphoric acid group-containing ethylenically unsaturated monomer and / or the hydroxyl group-containing ethylenically unsaturated monomer. On the other hand, the manufacturing method of Claim 9 used in the ratio of 200-800 mass parts. An aqueous coating composition containing the emulsion according to any one of claims 1 to 8.