JP2007270015A - Emulsion and method for producing the same, and water-based coating composition using the emulsion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an emulsion forming coating films having excellent hardness, to provide a water-based coating composition, and to provide a method for simply producing the emulsion. <P>SOLUTION: This emulsion prepared by emulsifying resin particles in an aqueous medium is characterized in that the resin particles each comprises an outer shell formed from an unsaturated bond-having resin and an alkyd resin encapsulated in the outer shell and has an average particle diameter of 100 nm to 500 nm. Preferably, the resin forming the outer shell contains repeating units originated from an unsaturated fatty acid ester group-containing ethylenic unsaturated monomer. The emulsion 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 capable of forming a coating film having excellent curability and excellent hardness, and an aqueous coating composition using the emulsion. Related to a simple manufacturing method.

  Alkyd resins have been widely used in so-called industrial coatings because they have thermosetting properties and can be produced at low cost. On the other hand, from the viewpoint of environmental protection, there is a social demand to switch from a conventional solvent-based paint to a water-based paint. Since the alkyd resin is hydrophobic, it is difficult to apply the alkyd resin to an aqueous coating as it is.

  Patent Document 1 describes that an aqueous thermosetting resin composition can be obtained by miniemulsion polymerization of an alkyd resin. However, since the unsaturated monomer used in the above-mentioned miniemulsion polymerization uses a monomer having two unsaturated bonds rich in radical polymerization such as allyl methacrylate, the unsaturated bond necessary for the curing reaction after miniemulsion polymerization. There is a problem that it is difficult to remain. As a result, even when the technique described in Patent Document 1 is applied to a paint, a good coating film is often not obtained.

On the other hand, Patent Document 2 discloses an aqueous coating composition by miniemulsion polymerization using a fatty acid-modified polymerizable unsaturated monomer. However, since the amount of the fatty acid-modified polymerizable unsaturated monomer used is limited, there is a problem that sufficient curability cannot be ensured. As a result, the technique described in Patent Document 2 also often fails to obtain a good coating film.
Special table 2003-501499 gazette International Publication No. 2004/074327 Pamphlet

  The present invention has been made in order to solve the above-described conventional problems, and an object of the present invention is to provide an emulsion and an aqueous coating composition that have excellent curability and can form a coating film having excellent hardness. 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 include an outer shell composed of a resin containing a repeating unit derived from an unsaturated fatty acid ester group-containing ethylenically unsaturated monomer, and an alkyd resin encapsulated in the outer shell, the average particle diameter of which is 100 nm to 500 nm.

  In preferable embodiment, the said alkyd resin is contained in the ratio of 10-70 mass% with respect to the total solid content mass of an 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 include an outer shell composed of a resin having an unsaturated bond, and an alkyd resin encapsulated in the outer shell, and the average particle diameter is 100 nm to 500 nm. The outer shell is formed by polymerizing a pre-emulsion in which monomer mixture particles encapsulating the alkyd resin are dispersed in an aqueous medium. The unsaturated bond is derived from an unsaturated fatty acid ester group-containing ethylenically unsaturated monomer.

  In preferable embodiment, content of the said unsaturated fatty acid ester group containing ethylenically unsaturated monomer in the said monomer mixture is 50 mass% or less.

  In a preferred embodiment, the average particle size of the monomer mixture particles is 0.5 to 1.5 times the average particle size of the resin particles.

  According to another aspect of the present invention, a method for producing an emulsion is provided. In this production method, an alkyd resin and a monomer mixture containing an unsaturated fatty acid ester group-containing ethylenically unsaturated monomer are dispersed in an aqueous medium, and the monomer mixture particles containing the alkyd resin are dispersed in the aqueous medium. Preparing a pre-emulsion; and polymerizing the monomer mixture in the pre-emulsion to obtain an emulsion in which resin particles encapsulating the alkyd resin are dispersed in an aqueous medium. The average particle diameter of the resin particles is 100 nm to 500 nm.

  In a preferred embodiment, the average particle size of the monomer mixture particles is 0.5 to 1.5 times the average particle size of the resin particles.

  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 is composed of a resin having a specific unsaturated bond, and the outer shell is encapsulated with the alkyd resin, thereby having excellent curability and excellent It is possible to provide an emulsion and an aqueous coating composition that can form a coating film having high hardness.

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 include an outer shell made of a resin having an unsaturated bond and an alkyd resin encapsulated in the outer shell. 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 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 (total of alkyd resin and outer shell) 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. Alkyd Resin In the present specification, the “alkyd resin” refers to a product obtained by modifying a condensation product of a polybasic acid and a polyhydric alcohol with a fat or an unsaturated fatty acid. The alkyd resin may contain a saturated fatty acid. As the alkyd resin, any appropriate alkyd resin that can function as a coating film forming component may be employed.

  Specific examples of the polyhydric alcohol include glycerin, pentaerythritol, ethylene glycol, trimethylolethane and the like. Specific examples of the polybasic acid include phthalic anhydride, maleic anhydride, trimellitic anhydride and the like. Specific examples of fats and oils include soybean oil.

  The unsaturated fatty acid may be a fatty acid having only one unsaturated bond (double bond) or a fatty acid having two or more unsaturated bonds (so-called polyunsaturated fatty acid). As the unsaturated fatty acid, those having an average carbon number of 13 to 23 are preferably used. Typical examples of such unsaturated fatty acids include myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid, eleostearic acid and the like. Unsaturated fatty acids may be used alone or in combination of two or more. Furthermore, as unsaturated fatty acids, linseed oil fatty acid, safflower oil fatty acid, soybean oil fatty acid, rice bran oil fatty acid, sesame oil fatty acid, castor oil fatty acid, dehydrated castor oil fatty acid, eno oil fatty acid, hemp seed oil fatty acid, cottonseed oil fatty acid, tall oil fatty acid, etc. Dry oils having such non-conjugated double bonds, semi-dry oil fatty acids and the like can be used. These dry or semi-dry oil fatty acids contain the unsaturated fatty acids described above. From the viewpoint of ensuring the resistance of the resulting coating film, dry oil fatty acids and semi-dry oil fatty acids are preferred. The dry oil fatty acid is an unsaturated fatty acid having an iodine value of 130 or more, and the semi-dry oil fatty acid is an unsaturated fatty acid having an iodine value of 100 or more and less than 130.

  The alkyd resin is contained in an amount of preferably 10 to 70% by mass, more preferably 30 to 60% by mass, based on the total solid content mass of the emulsion (that is, resin solid content). When the amount of the alkyd resin is less than 10% by mass, the curability of the emulsion may not be sufficient. On the other hand, when the amount of the alkyd resin exceeds 70% by mass, there is a possibility that an aggregate is formed during the production of the emulsion.

C. Outer shell containing alkyd resin The outer shell contains the alkyd resin. The outer shell is made of a resin having an unsaturated bond. By encapsulating the alkyd resin with a resin having an unsaturated bond, it is possible to obtain an aqueous coating composition that is extremely excellent in curability at the time of coating film formation. One of the great achievements of the present invention is the actual preparation of an emulsion in which resin particles encapsulating an alkyd resin in the outer shell of such a specific material are dispersed in an aqueous medium.

  Preferably, the resin having an unsaturated bond includes a repeating unit derived from an unsaturated fatty acid ester group-containing ethylenically unsaturated monomer. More preferably, the resin is a copolymer containing a repeating unit derived from an unsaturated fatty acid ester group-containing ethylenically unsaturated monomer. Particularly preferably, the content ratio of the repeating unit derived from the unsaturated fatty acid ester group-containing ethylenically unsaturated monomer in the copolymer is 50% by mass or less as a monomer charging ratio. If it exceeds 50% by mass, the polymerization may not proceed sufficiently and the outer shell may not be formed sufficiently. On the other hand, the content ratio of the repeating unit derived from the unsaturated fatty acid ester group-containing ethylenically unsaturated monomer in the copolymer is preferably 20% by mass or more in terms of the monomer charge ratio. If it is less than 20% by mass, the curability and the hardness of the resulting coating film may be insufficient.

  The copolymer can be obtained by copolymerizing an unsaturated fatty acid ester group-containing ethylenically unsaturated monomer and any appropriate other monomer copolymerizable with the ethylenically unsaturated monomer.

  In one embodiment, the unsaturated fatty acid ester group-containing ethylenically unsaturated monomer is obtained by reacting an epoxy group-containing ethylenically unsaturated monomer with an unsaturated fatty acid. As the epoxy group-containing ethylenically unsaturated monomer, typically, an epoxy group-containing (meth) acrylic compound or (meth) allyl glycidyl ether can be used. Specific examples of the epoxy group-containing (meth) acrylic compound include glycidyl acrylate, glycidyl methacrylate, methyl glycidyl acrylate, methyl glycidyl methacrylate, 3,4-epoxycyclohexylmethyl acrylate, 3,4-epoxycyclohexylmethyl methacrylate, and the like. It is done. In the present specification, the “(meth) acrylic compound” includes an acrylic compound and a methacrylic compound. The “(meth) allyl compound” includes allyl compounds and methallyl compounds. The unsaturated fatty acid is as described in the above section B for the alkyd resin. For example, the reaction between glycidyl methacrylate and soybean oil fatty acid is as follows. In the unsaturated fatty acid ester group-containing ethylenically unsaturated monomer obtained by this reaction, a portion derived from glycidyl methacrylate is polymerized by miniemulsion polymerization to form an outer shell, and an unsaturated bond derived from soybean oil fatty acid is excluded. It remains in the repeating unit of the resin constituting the shell. As a result, an emulsion having very excellent curability can be obtained.

  In another embodiment, the unsaturated fatty acid ester group-containing ethylenically unsaturated monomer can also be obtained by esterifying a hydroxyl group-containing polymerizable unsaturated monomer and an unsaturated fatty acid. Specific examples of the hydroxyl group-containing polymerizable unsaturated monomer include a half ester of (meth) acrylic acid and a diol having 2 to 8 carbon atoms (for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate). , 3-hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate] and their ε-capracacton modified products, allyl alcohol, unsaturated carboxylic acid ester having a polyalkylene glycol chain, and the like. The unsaturated fatty acid is as described in the above section B for the alkyd resin.

  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. 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 alkyd resin and the monomer mixture containing the unsaturated fatty acid ester group-containing ethylenically unsaturated monomer are dispersed in an aqueous medium, and the monomer mixture particles containing the alkyd resin are dispersed in an aqueous medium. Preparing a pre-emulsion dispersed therein; and polymerizing a monomer mixture in the pre-emulsion to obtain an emulsion in which resin particles encapsulating the alkyd resin are dispersed in an aqueous medium. By using the mini-emulsion polymerization method, it is possible to encapsulate a hydrophobic substance (for example, alkyd resin) 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 having excellent uniformity can be obtained, and a hydrophobic coating film forming component (for example, alkyd resin) can be applied to the aqueous composition. 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 the unsaturated fatty acid ester group-containing ethylenically unsaturated monomer and the other copolymerizable monomer in a predetermined ratio according to the purpose. As described above, the content of the unsaturated fatty acid ester group-containing ethylenically unsaturated monomer in the monomer mixture is preferably 20 to 50% 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 alkyd resin, the emulsifier, and any appropriate additive as necessary using a high-speed shear emulsifier. According to the production method of the present invention, a pre-emulsion in which the monomer mixture particles are dispersed in the aqueous dispersion medium in a state in which the alkyd resin is encapsulated 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. When the monomer mixture particles have an average particle diameter in such a range and include an alkyd resin, a coating film having extremely excellent curability and excellent hardness can be formed. An emulsion 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 10. 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, tert-butyl peroxide, tert-butyl peroxylaurate, tert-butyl peroxyisopropyl carbonate, tert-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 alkyd resin, the monomer mixture polymerizes while encapsulating the alkyd resin to form an outer shell. . As a result, an emulsion in which resin particles encapsulating alkyd resin (that is, capsule-like resin particles) are obtained is obtained. The polymerization conditions can be appropriately selected according to the type of monomer used in the monomer mixture, the content of the alkyd resin, 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 alkyd resin 457 parts of phthalic anhydride, 209 parts of benzoic acid, 393 parts of trimethylolpropane, 202 parts of pentaerythritol, 440 parts of soybean oil fatty acid, 439 parts of dehydrated castor oil fatty acid, 2 parts of dibutyltin oxide and methyl isobutyl 60 parts of a ketone was charged into a flask equipped with a reflux condenser and heated at 230 ° C. for about 8 hours with stirring in a nitrogen gas atmosphere to react until the resin acid value was 5. The theoretical OH value of this alkyd resin is 100.

(Production Example 2) Production of unsaturated fatty acid ester group-containing ethylenically unsaturated monomer 51.9 parts of soybean oil fatty acid, 27.9 parts of glycidyl methacrylate, 0.16 part of tetra-n-butylphosphonium bromide and hydroquinone monomethyl ether 14 parts were put into a reaction vessel and reacted at a temperature of 170 to 180 ° C. with stirring. The addition reaction of epoxy group and carboxyl group was followed while measuring the amount of residual carboxyl group. It took about 3 hours to complete the reaction.

(Example 1) Aqueous alkyd resin-encapsulated emulsion In 100 parts of a monomer mixture having the composition shown below, 103 parts of the alkyd resin described in Production Example 1 (100 parts of alkyd resin solid content) was dissolved to prepare a solution A. 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 size of the monomer mixture particles in the pre-emulsion C was 343 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 the dropping, the polymerization was completed by maintaining at 80 ° C. for 2 hours to obtain an aqueous alkyd resin-containing emulsion 1. The average particle diameter of the resin particles in the obtained emulsion was 330 nm, and the solid content concentration was 36.2%.
Monomer mixture Unsaturated fatty acid ester group-containing ethylenically unsaturated monomer of Production Example 2 30.0 parts Methyl methacrylate 21.8 parts Ethyl acrylate 11.4 parts n-Butyl acrylate 29.0 parts Styrene 7.0 parts Methacrylic acid 8 copies

(Comparative Example 1)
Emulsion 2 was obtained in the same procedure as in Example 1 except that allyl methacrylate was used in place of the unsaturated fatty acid ester group-containing ethylenically unsaturated monomer described in Production Example 2. The average particle size of the pre-emulsion monomer mixture particles was 284 nm. The average particle diameter of the resin particles of the obtained emulsion was 224 nm, and the solid content concentration was 37.3%.

(Comparative Example 2)
Emulsion 3 was obtained in the same manner as in Example 1 except that no alkyd resin was used and 200 parts of the monomer mixture was used. The average particle size of the pre-emulsion monomer mixture particles was 235 nm. The average particle diameter of the resin particles of the obtained emulsion was 185 nm, and the solid content concentration was 36.1%.

(Example 2) Water-based paint composition 1
The aqueous alkyd resin-encapsulated emulsion 1 (32.5 parts) obtained in Example 1 was diluted with 0.5 part of 10% aqueous sodium hydroxide solution, 50% VXW4940 (metal dryer, manufactured by Solusia Co., Ltd.) 6 parts was added, and the water-based coating composition 1 was obtained by making it shake with a touch mixer. The obtained aqueous coating composition 1 was applied onto a glass plate using a 6 mil doctor blade and dried at 60 ° C. for 1 week to obtain a light yellow transparent cured coating film. When the pencil hardness of the obtained cured coating film was examined, it was 3B. The cured coating film was immersed in acetone at 20 ° C. for 24 hours, and the residual ratio of the coating film was examined. As a result, it was 78%. The results are listed in Table 1 below together with the results of Comparative Examples 3 and 4 described later.

(Comparative Example 3) Water-based paint composition 2
An aqueous coating composition 2 was prepared in the same procedure as in Example 2 except that the emulsion 2 obtained in Comparative Example 1 was used instead of the aqueous alkyd resin-containing emulsion 1 in Example 1, and a cured coating film was formed. Obtained. Furthermore, the obtained coating film was subjected to the same evaluation as in Example 2. The pencil hardness of the coating film was 6B or less, and the coating film residual ratio was 48%. The results are listed in Table 1.

(Comparative Example 4) Water-based paint composition 3
An aqueous coating composition 3 was prepared in the same procedure as in Example 2 except that the emulsion 2 obtained in Comparative Example 2 was used instead of the aqueous alkyd resin-containing emulsion 1 in Example 1, and a cured coating film was formed. Obtained. Furthermore, the obtained coating film was subjected to the same evaluation as in Example 2. The pencil hardness of the coating film was 6B, and the coating film remaining rate was 41%. The results are listed in Table 1.

  As is apparent from Table 1, the coating film obtained from the aqueous coating composition of the example of the present invention has a hardness and a coating film remaining ratio of the coating film obtained from the aqueous coating composition of the comparative example. Both are significantly better. On the other hand, in both Comparative Example 3 in which no unsaturated fatty acid is used and Comparative Example 4 in which no alkyd resin is used, both the hardness and the coating film residual ratio are insufficient. From this, it is surmised that such excellent curing performance is achieved by the synergistic effect of the alkyd resin and the resin having an unsaturated bond derived from the unsaturated fatty acid constituting the outer shell of the resin particles of the emulsion. . This is a finding obtained only by actually preparing an emulsion and an aqueous coating composition by combining such an outer shell resin and an alkyd resin, and is an unexpectedly excellent effect.

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

Claims (8)

An emulsion in which resin particles are dispersed in an aqueous medium,
The resin particles include an outer shell composed of a resin containing a repeating unit derived from an unsaturated fatty acid ester group-containing ethylenically unsaturated monomer, and an alkyd resin encapsulated in the outer shell, and the average particle diameter is 100 nm. An emulsion that is ~ 500 nm.   The emulsion of Claim 1 in which the said alkyd resin is contained in the ratio of 10-70 mass% with respect to the total solid content mass of an emulsion. An emulsion obtained by a miniemulsion polymerization method in which resin particles are dispersed in an aqueous medium,
The resin particles include an outer shell composed of a resin having an unsaturated bond, and an alkyd resin encapsulated in the outer shell, and an average particle diameter thereof is 100 nm to 500 nm,
The outer shell is formed by polymerizing a pre-emulsion in which monomer mixture particles including the alkyd resin are dispersed in an aqueous medium, and the unsaturated bond is derived from an unsaturated fatty acid ester group-containing ethylenically unsaturated monomer. There is an emulsion.   The emulsion according to claim 3, wherein the content of the unsaturated fatty acid ester group-containing ethylenically unsaturated monomer in the monomer mixture is 50% by mass or less.   The emulsion according to claim 3 or 4, wherein an average particle size of the monomer mixture particles is 0.5 to 1.5 times an average particle size of the resin particles. An alkyd resin and a monomer mixture containing an unsaturated fatty acid ester group-containing ethylenically unsaturated monomer are dispersed in an aqueous medium to prepare a pre-emulsion in which the monomer mixture particles containing the alkyd resin are dispersed in the aqueous medium. And a process of
Polymerizing the monomer mixture in the pre-emulsion to obtain an emulsion in which resin particles encapsulating the alkyd resin 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 production method according to claim 6, wherein an average particle diameter of the monomer mixture particles is 0.5 to 1.5 times an average particle diameter of the resin particles. An aqueous coating composition containing the emulsion according to any one of claims 1 to 5.