JP2016108546A - Method for producing paint emulsion resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of producing a paint emulsion resin having a high solid content even when a monomer mixture having a high styrene-monomer content is emulsion-polymerized.SOLUTION: There is provided a method for producing a paint emulsion resin, which comprises: a pre-emulsion solution preparation step of preparing a pre-emulsion solution which contains a monomer mixture comprising 20-50 mass% of a styrene monomer (a) and 50-80 mass% of an α,β-ethylenically unsaturated monomer (b) which is copolymerizable with (a); and an emulsion resin formation step of forming an emulsion resin by emulsion-polymerizing the monomer mixture, wherein the paint emulsion resin obtained by this production method has a number-average particle diameter of 500 nm or less and a solid concentration of 50 mass% or more, the α,β-ethylenically unsaturated monomer (b) contains a (meth)acrylic monomer (b1) having a monomer reactivity ratio r1 of 0.7 or less with respect to styrene, the content of the (meth)acrylic-monomer (b1) in the monomer mixture is 10-60 mass% and in the emulsion resin formation step, after the polymerization rate of the monomer mixture is in the range of 45-90%, a surfactant is added in a plurality of times.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing an emulsion resin for paint.

  In general, liquid coating compositions can be roughly classified into two types: solvent-based coating compositions containing organic solvents and aqueous coating compositions. In general, water-based paint compositions are widely used because they contain a small amount of organic solvent and have a low environmental impact. Many of such aqueous coating compositions contain an emulsion resin. By including an emulsion resin in the aqueous coating composition, it is possible to prepare a coating composition having a high solid content compared to an aqueous coating composition containing only a water-soluble resin, and the design range of the coating composition. There are advantages such as spreading. On the other hand, water-based paint compositions are required to be dried and cured more quickly while ensuring paint stability. Therefore, a method for producing an emulsion resin having a higher solid content is required.

  In JP-A-7-233208 (Patent Document 1), a monomer or a monomer mixture mainly composed of (meth) acrylic acid ester is emulsion-polymerized while continuously or intermittently adding a surfactant. A method for producing an acrylic emulsion characterized by the above is described (claim 1). It is described that this production method can produce an acrylic emulsion having a high solid content, high particle stability, low viscosity, and excellent mechanical stability (paragraph [0010] etc. ). However, the acrylic emulsion obtained by the method of Patent Document 1 has no explanation for blending a high concentration of styrene. In addition, the configuration is different from the present invention in that the styrene content is low in Examples and the like.

  In JP-A-7-238201 (Patent Document 2), a basic compound is added to a monomer mixture mainly composed of (meth) acrylic acid ester and an acidic monomer to neutralize or partially neutralize and then emulsify. A method for producing an acrylic emulsion characterized by polymerization is described (claim 1). It is described that an acrylic emulsion having a low viscosity and a high solid content can be produced very easily by this production method (paragraph [0010]). However, the acrylic emulsion obtained by the method of Patent Document 2 also has no explanation for high-concentration styrene blending. In addition, the configuration is different from the present invention in that the styrene content is low in Examples and the like. An emulsion resin having a low styrene content has a drawback of poor alkali resistance. When the blending amount of styrene is small, it is difficult to obtain the effect of improving the mechanical strength of the coating film due to the rigid structure derived from the aromatic ring. For this reason, it is difficult to obtain durability improvement effects such as excellent wear resistance, washing resistance and adhesion.

  Japanese Patent Application Laid-Open No. 2001-342201 (Cited Document 3) is characterized in that a vinyl monomer is emulsion-polymerized in an aqueous medium in which an electrolyte substance is dissolved while the concentration of the electrolyte substance is reduced. And a method for producing a resin emulsion (claim 1 and the like). It is described that an emulsion having a high concentration, a low viscosity, and extremely reduced generation of aggregates can be produced by this method ([0006] paragraph, etc.). However, when the concentration of the electrolyte substance in the resin emulsion increases, the electrolyte concentration in the coating film increases, and the water resistance of the coating film may be inferior. The acrylic emulsion obtained by the method of Patent Document 3 is also different from the present invention in that the styrene content is low.

Japanese Patent Laid-Open No. 7-233208 Japanese Patent Laid-Open No. 7-238201 JP 2001-342201 A

  The present invention solves the above-mentioned conventional problems, and its object is to provide a coating emulsion resin having a high solid content even in the case of emulsion polymerization of a monomer mixture having a high styrene monomer content. It is to provide a method that can be manufactured.

In order to solve the above problems, the present invention provides the following aspects.
[1]
A method for producing an emulsion resin for paint,
The above method
Preparing a pre-emulsion solution comprising a monomer mixture consisting of 20-50% by weight of styrene monomer (a) and α, β-ethylenically unsaturated monomer (b) copolymerizable with (a), 50-80% by weight, A pre-emulsion solution preparation step, and an emulsion resin forming step of emulsion-polymerizing the monomer mixture to form an emulsion resin;
Including
The emulsion resin for paints obtained by the above production method has a number average particle size of 500 nm or less and a solid content concentration of 50% by mass or more.
The α, β-ethylenically unsaturated monomer (b) includes a (meth) acrylic monomer (b1) having a monomer reactivity ratio r1 with styrene of 0.7 or less,
The content of the (meth) acrylic monomer (b1) in the monomer mixture is 10 to 60% by mass,
In the emulsion resin forming step, after the polymerization rate of the monomer mixture is in the range of 45% to 90%, the surfactant is added in multiple portions.
Manufacturing method of emulsion resin for paint.
[2]
The addition of the surfactant multiple times in the emulsion resin formation step is preferably performed in an amount that is increased by 20% by mass or more with respect to the amount of the surfactant added in the subsequent surfactant addition.
[3]
The monomer (b) includes an α, β-ethylenically unsaturated monomer having an acid group,
The neutralization rate of the monomer mixture (b) in the pre-emulsion solution is preferably 1.5 to 30%.
[4]
The emulsion resin for paints obtained by the above production method preferably has a residual monomer concentration of less than 1000 ppm.
[5]
After the emulsion resin formation step,
After adding the oil-soluble polymerization initiator, further adding a reducing agent to polymerize the residual monomer, a residual monomer polymerization step,
The aspect which further contains is mentioned.
[6]
The oil-soluble polymerization initiator preferably has a water solubility at 20 ° C. of 1 g / L or less.
[7]
It is preferable that the total amount of the surfactant added in the emulsion resin forming step is 10 to 40% by mass with respect to the total amount of the surfactant used in the method for producing the emulsion resin for paint.

  According to the production method of the present invention, even when a monomer mixture having a high content of styrene monomer is subjected to emulsion polymerization, an emulsion resin for coating having a high solid content can be produced. By preparing a coating composition using the emulsion resin for coating obtained by the production method of the present invention, it becomes possible to blend many rigid styrene skeletons derived from aromatic rings. Thereby, the mechanical strength of the coating film obtained can be improved. By the production method of the present invention, it is possible to prepare a coating composition that provides a highly durable coating film having excellent wear resistance, alkali resistance, washing resistance, adhesion, and the like.

Background of the Invention The background to the present invention will be described. The present inventors have shown that in the preparation of an aqueous coating composition, by increasing the styrene content contained in the emulsion resin for coating, the performance such as alkali resistance of the resulting coating composition can be improved. I found it. On the other hand, in the production of an emulsion resin, if the styrene monomer content in the monomer mixture used for the preparation is high, the production of the emulsion resin becomes difficult, especially the production of an emulsion resin for paints having a high solid content. It has been found through experiments that it becomes very difficult. In the copolymerization by emulsion polymerization, generally, a monomer mixture is first dispersed / dissolved in water, and then the monomer is copolymerized through a process of being absorbed in micelles or particles as a polymerization reaction field. Since styrene monomer generally has low solubility in water, when the content of styrene monomer is high, in the copolymerization under the condition of low water content, it is difficult for the monomer mixture to be dispersed / dissolved in water, and the polymerization reaction The amount of monomer mixture absorbed into the field micelles or particles is significantly reduced. Therefore, it has been found that the copolymerization reaction does not proceed and it is difficult to obtain a stable emulsion resin. More specifically, it has been found that when a coating emulsion resin having a high solid content is produced, when a monomer mixture having a high styrene monomer content is used, a problem of gelation may occur.

  The inventors of the present invention have repeatedly studied for the purpose of solving the above-mentioned problems. As a result, the kind of α, β-ethylenically unsaturated monomer copolymerizable with the styrene monomer and the mass ratio thereof are adjusted, and In emulsion polymerization, by adjusting the timing of adding a surfactant, etc., even when a monomer mixture having a high styrene monomer content is subjected to emulsion polymerization, a coating emulsion resin having a high solid content is produced. I found that I could do it. Hereafter, the manufacturing method of this invention is explained in full detail. In the present specification, “emulsion resin for paint” may be simply referred to as “emulsion resin”.

Method for producing emulsion resin for paint The method for producing the emulsion resin for paint of the present invention is as follows.
Preparing a pre-emulsion solution comprising a monomer mixture consisting of 20-50% by weight of styrene monomer (a) and α, β-ethylenically unsaturated monomer (b) copolymerizable with (a), 50-80% by weight, A pre-emulsion solution preparation step, and an emulsion resin formation step of forming an emulsion resin by emulsion polymerization of the monomer mixture,
Is included. In this method, the α, β-ethylenically unsaturated monomer (b) includes a (meth) acrylic monomer (b1) having a monomer reactivity ratio r1 with styrene of 0.7 or less, and the monomer Content of the said (meth) acryl monomer (b1) in a mixture is 10-60 mass%. Furthermore, in the emulsion resin forming step, the surfactant is added in a plurality of times after the polymerization rate of the monomer mixture is in the range of 45% to 90%.

Pre-emulsion solution preparation step In the pre-emulsion solution preparation step, a pre-emulsion solution containing a monomer mixture is prepared. In the present specification, the “pre-emulsion solution” means a solution containing the monomer mixture used for preparing the emulsion resin. This pre-emulsion solution can be prepared by mixing the monomer mixture, a solvent, and additives such as a neutralizing agent and a surfactant as necessary.

  The monomer mixture is composed of 20 to 50% by mass of a styrene monomer (a) and 50 to 80% by mass of an α, β-ethylenically unsaturated monomer (b) copolymerizable with the styrene monomer (a). The mass ratio is more preferably 25 to 50% by mass of the styrene monomer (a) and 50 to 75% by mass of the α, β-ethylenically unsaturated monomer (b), and the styrene monomer (a) 30 to 50%. More preferably, it is 50 mass% and 50-70 mass% of (alpha), (beta) -ethylenically unsaturated monomer (b). When the content of the styrene monomer (a) exceeds 50% by mass, the reactivity of the monomer mixture is lowered, the stability of the resulting emulsion resin is lowered, and the residual monomer amount may be increased. When the content of the styrene monomer (a) is less than 20% by mass, the effect of improving the mechanical strength derived from the rigid skeleton derived from styrene cannot be expressed sufficiently, and the coating composition containing the emulsion resin is used. The effect of improving durability such as alkali resistance, washing resistance, and adhesion in the formed coating film cannot be sufficiently obtained.

  Specific examples of the styrene monomer (a) include styrene and styrene derivatives. Examples of the styrene derivative include α-alkylstyrene (eg, α-methylstyrene), p-alkylstyrene (eg, p-methylstyrene, t-butylstyrene), p-alkyloxystyrene (eg, p-methoxystyrene). , P-chlorostyrene, 4-hydroxystyrene, and the like. The styrene content in the styrene monomer (a) is preferably 50 to 100% by mass, and more preferably 80 to 100% by mass. More preferably, only styrene is used as the styrene monomer.

As an α, β-ethylenically unsaturated monomer (b) copolymerizable with a styrene monomer, for example,
Acrylic monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate , 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, phenyl (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, (meth ) (Meth) acrylic such as dicyclopentadienyl acrylate, dihydrodicyclopentadienyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate Acid esters, acrylic acid, methacrylic acid Etc.;
An adduct of the above acrylic monomer and ε-caprolactone;
Α, β-ethylenically unsaturated monomers having acid groups, such as 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl succinic acid, ω-carboxy-polycaprolactone mono (meth) acrylate, isocrotonic acid, α-hydro -Ω-((1-oxo-2-propenyl) oxy) poly (oxy (1-oxo-1,6-hexanediyl)), maleic acid, fumaric acid, itaconic acid, 3-vinylsalicylic acid, 3-vinylacetyl Salicylic acid, 2-acrylamido-2-methylpropanesulfonic acid, etc .;
Α, β-ethylenically unsaturated monomers having a hydroxyl group, such as allyl alcohol, methallyl alcohol;
Polymerizable amide compounds such as (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N , N-dioctyl (meth) acrylamide, N-monobutyl (meth) acrylamide, N-monooctyl (meth) acrylamide 2,4-dihydroxy-4′-vinylbenzophenone, N- (2-hydroxyethyl) acrylamide, N- ( 2-hydroxyethyl) methacrylamide and the like;
Polymerizable aromatic compounds such as vinyltoluene, divinylbenzene, vinylnaphthalene, 2-vinylpyridine and 4-vinylpyridine;
Polymerizable nitriles such as acrylonitrile, methacrylonitrile and the like;
Polymerizable alkylene oxide compounds such as (meth) acrylic acid (poly) oxyethylene, (meth) acrylic acid (poly) propylene glycol;
Polyfunctional vinyl compounds such as allyl (meth) acrylate, (poly) oxyethylene di (meth) acrylate, trimethylolpropane tri (meth) acrylate and the like;
Polymerizable amine compounds such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate;
α-olefins such as ethylene, propylene and the like;
Vinyl esters such as vinyl acetate, vinyl propionate, vinyl versatate, etc .;
Dienes such as butadiene, isoprene and the like;
Vinyl halides such as vinyl chloride and vinylidene chloride;
Polymerizable carbonyl compounds such as acrolein, diacetone (meth) acrylamide, formylstyrene, vinyl methyl ketone, vinyl ethyl ketone, vinyl isobutyl ketone, acryloxyalkylpropanals, methacryloxyalkylpropanals, diacetone acrylate, diacetone Acetone methacrylate, acetonyl acrylate, 2-hydroxypropyl acrylate acetyl acetate, butanediol acrylate acetyl acetate, etc .;
Polymerizable acetoacetoxy compounds, such as acetoacetoxyethyl (meth) acrylate, acetoacetoxyethyl (meth) acrylate, and the like;
Polymerizable alkoxysilyl compounds such as γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropyldimethylmethoxysilane, γ- (meth) acrylic Roxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropyldimethylethoxysilane, vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxy Silane, trimethoxysilylstyrene, dimethoxymethylsilylstyrene, triethoxysilylstyrene, diethoxymethylsilylstyrene, etc .;
Can be mentioned. The α, β-ethylenically unsaturated monomer can be variously selected according to the purpose. In this specification, (meth) acrylic acid ester means both acrylic acid ester and methacrylic acid ester.

  In the present invention, the α, β-ethylenically unsaturated monomer (b) includes a (meth) acrylic monomer (b1) having a monomer reactivity ratio r1 with styrene of 0.7 or less. The content of the (meth) acrylic monomer (b1) in the monomer mixture is 10 to 60% by mass (10 to 60 parts by mass with respect to 100 parts by mass of the monomer mixture). As for content of the said (meth) acryl monomer (b1), it is more preferable that it is 15-55 mass%.

  Here, the monomer reactivity ratio r1 with styrene is the reaction in the case where M1 and M2 are copolymerized when monomer M1 is styrene and monomer M2 is another monomer such as a (meth) acrylic monomer. It is an index showing the ease of doing it. When r1 is 1 or more, it indicates that the monomers M1 are easily polymerized. Moreover, when r1 is less than 1, it shows that M1 and M2 are easily copolymerized. This reactivity ratio r1 can be obtained as a literature value. For example, in POLYMER HANDBOOK, fourth edition, volume 1, WILLY-INTERSCIENCE, A John Wiley & Sons, Inc., Publication Copolymer Reactivity Ratios II / 249-II / 260, M1 is styrene and M2 is another monomer. The reactivity ratio r1 is described.

Specific examples of the (meth) acrylic monomer (b1) having a monomer reactivity ratio r1 with styrene of 0.7 or less include, for example, methacrylic acid (r1: 0.21), acrylic acid (r1: 0.25), Methyl methacrylate (r1: 0.5), n-butyl methacrylate (r1: 0.56), i-butyl methacrylate (r1: 0.55), ethyl methacrylate (r1: 0.55), glycidyl methacrylate (r1: 0) .54), cyclohexyl methacrylate (r1: 0.58), benzyl methacrylate (r1: 0.45), phenyl methacrylate (r1: 0.25), and the like.
Among these (meth) acrylic monomers (b1), methacrylic acid, acrylic acid, methyl methacrylate, n-butyl methacrylate and the like have high copolymerizability with styrene, and Tg design of the resulting coating film is easy. In view of ease of material acquisition, product price, and the like. As the (meth) acrylic monomer (b1), only one type may be used, or two or more types may be used in combination.

  The reactivity ratio r1 in the (meth) acrylic monomer (b1) is more preferably 0.6 or less, and further preferably 0.5 or less. In the α, β-ethylenically unsaturated monomer (b), the (meth) acrylic monomer (b1) having a monomer reactivity ratio r1 with styrene of 0.7 or less is contained in the above mass range, whereby styrene The reactivity between the monomer (a) and the α, β-ethylenically unsaturated monomer (b) is in an optimum range for the preparation of the emulsion resin, and the polymerization reaction proceeds favorably, resulting in stability over time, etc. There is an advantage that an excellent emulsion resin can be obtained.

  In the production method of the present invention, a monomer mixture containing 20 to 50% by mass of a styrene monomer (a) and 50 to 80% by mass of an α, β-ethylenically unsaturated monomer (b) is used, where α, The β-ethylenically unsaturated monomer (b) contains a (meth) acrylic monomer (b1) having a monomer reactivity ratio r1 with styrene of 0.7 or less, and further, the (meth) in the monomer mixture. The content of the acrylic monomer (b1) is 10 to 60% by mass, so that the emulsion resin for paint having a high content of the styrene monomer (a) and a solid content concentration of 50% by mass or more is preferable. Can be manufactured. For example, when producing a coating emulsion resin having a high solid content, in the case of using a monomer mixture in which the content of the styrene monomer (a) exceeds 50% by mass, the polymerization of styrene proceeds preferentially. As a result, there is a high risk of thickening and gelation.

  In addition to the monomer mixture, the pre-emulsion solution contains a solvent and, if necessary, a neutralizing agent and a surfactant. Water is preferably used as the solvent contained in the pre-emulsion solution. If necessary, an organic solvent that does not react with the monomer mixture can also be used as a solvent.

  The pre-emulsion solution preferably contains a neutralizing agent. The neutralizing agent here means a basic substance that can be contained in the monomer mixture and neutralizes the acid group of the α, β-ethylenically unsaturated monomer having an acid group. As the α, β-ethylenically unsaturated monomer having an acid group, α, β-ethylenic acid having an acid group exemplified in acrylic acid, methacrylic acid, and the above α, β-ethylenically unsaturated monomer (b) Examples include unsaturated monomers. Specific examples of the neutralizing agent include ammonium hydroxide, aqueous ammonia, potassium hydroxide, calcium hydroxide, aluminum hydroxide, sodium hydrogen carbonate and the like.

The neutralization rate of the monomer mixture (b) in the pre-emulsion solution is preferably 1.5 to 30%, more preferably 2 to 30%, and further preferably 3 to 30%. . If the neutralization rate is less than 1.5%, the neutralization stabilization effect of the emulsion may not be obtained. On the other hand, if it exceeds 30%, the viscosity of the emulsion increases, which may make the production difficult.
In the present specification, the neutralization rate of the monomer mixture (b) refers to the amount of the α, β-ethylenically unsaturated monomer having an acid group and the neutralizing agent (basic substance) contained in the monomer mixture. It can be determined by calculating from the amount (molar ratio).

  By including a neutralizing agent in the pre-emulsion solution, the viscosity of the pre-emulsion solution can be designed to be low, and there are advantages such as improvement in manufacturing workability.

  The pre-emulsion solution may contain a surfactant as necessary. By including the surfactant in the pre-emulsion solution, there are advantages that the monomer dispersion performance is improved and the polymerization reaction proceeds well in the polymerization of the monomer mixture. Examples of the surfactant include an anionic surfactant, a nonionic surfactant, and a polymerizable surfactant.

  As the anionic surfactant, a commonly used anionic surfactant can be used. Specific examples of anionic surfactants include, for example, alkyl fatty acid salts, alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl phenyl ether sulfates, polyoxyethylene polycyclic phenyl ether sulfates, polyoxyethylene aryls. Examples thereof include ether sulfates, alkylbenzene sulfonates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, sulfosuccinic acid alkyl disalts, polyoxyethylene sulfosuccinic acid alkyl disalts, and acylmethyl taurine. Examples of the salt include ammonium salt, alkali metal salt, alkaline earth metal salt, alkanolamine salt and the like. Among these surfactants, polyoxyethylene alkylphenyl ether ammonium sulfate and polyoxyethylene polycyclic phenyl ether ammonium sulfate are more preferable.

  As the nonionic surfactant, a commonly used nonionic surfactant can be used. Specific examples of nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene hydrogenated castor oil, polyoxyethylene alkylphenyl ether, polyoxyethylene sorbitan fatty acid ester, sorbitan fatty acid ester, alkyl fatty acid diethanolamide, alkyldimethylamine. And oxides.

  Examples of the polymerizable surfactant include a polymerizable surfactant having a double bond having radical polymerization ability in the molecule. Specific examples of such polymerizable surfactants include, for example, alkylallylsulfosuccinate, methacryloyl polyoxyalkylene sulfate, polyoxyethylene nonylpropenyl phenyl ether sulfate, and the like. When these polymerizable surfactants are used, the content of the polymerizable surfactant is incorporated as part of the α, β-ethylenically unsaturated monomer (b) copolymerizable with (a). .

  These surfactants may be used alone or in combination of two or more. Moreover, you may use a commercial item as surfactant.

  The amount of the surfactant contained in the pre-emulsion solution is preferably 0.05 to 8 parts by mass and more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the pre-emulsion solution. .

Emulsion resin forming step In the emulsion resin forming step, the monomer mixture is subjected to emulsion polymerization to form an emulsion resin. Examples of the method for emulsion polymerization of the monomer mixture include a method of sequentially dropping a pre-emulsion solution containing the monomer mixture into a polymerization reaction vessel.

The polymerization reaction vessel into which the pre-emulsion solution is dropped preferably contains an aqueous medium in advance. Examples of the aqueous medium that can be contained in the polymerization reaction vessel include an aqueous medium containing water and a polymerization initiator as necessary. As a polymerization initiator, for example,
Persulfate polymerization initiators such as potassium persulfate, sodium persulfate, ammonium persulfate,
2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate 2,2′-azobis (2-methylpropionamidine) dihydrochloride, 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate, 2,2′-azobis [ 2- (2-imidazolin-2-yl) propane], 2,2′-azobis (1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2′-azobis [2-methyl-N— Water-soluble azo polymerization initiators such as (2-hydroxyethyl) propionamide],
Organic peroxidation such as t-butyl peroxyacetate, t-butylperoxyisononanoate, di-t-butyl peroxide, di-t-amyl peroxide, t-butyl hydroperoxide, t-amyl hydroperoxide And hydrogen peroxide,
Etc.
These polymerization initiators may be used alone or in combination of two or more.

  The pre-emulsion solution is dropped into the polymerization reaction vessel sequentially and the polymerization reaction is performed, for example, at room temperature to 95 ° C., more preferably 70 to 90 ° C., for 1 to 24 hours, more preferably 2 to 12 hours, and further preferably Examples include a mode in which the pre-emulsion solution is dropped over 2 to 6 hours. In addition, conditions, such as these temperature and dripping time, can be suitably changed according to the reactor used, reaction scale, etc.

  In the method of the present invention, in the emulsion resin forming step, after the polymerization rate of the monomer mixture exceeds 45%, the surfactant is added in a plurality of times. “The surfactant is added after the polymerization rate of the monomer mixture exceeds 45%” means that the surfactant is not added in the emulsion resin formation step in a state where the polymerization rate of the monomer mixture is less than 45%. Means that. In addition, the surfactant contained in the pre-emulsion solution as needed does not correspond to the “addition of surfactant in the emulsion resin forming step” referred to herein. Moreover, the upper limit of the polymerization rate when starting the addition of the surfactant is 90%.

  In the above step, it is more preferable to add the surfactant after the polymerization rate of the monomer mixture exceeds 50%. The upper limit of the polymerization rate when starting the addition of the surfactant is more preferably 85%.

  In this emulsion resin forming step, “adding the surfactant in a plurality of times” is in contrast to the state of “adding the surfactant continuously”, and the surfactant is added in 2 or It means a state where it is added in divided portions. The addition of the surfactant may include, for example, an aspect of adding 2 to 20 times, preferably adding 2 to 10 times, and adding 2 to 7 times. Is more preferable. The term “one time” as used herein means a state in which a predetermined amount of surfactant is added in one shot, and does not mean a state of continuous dripping.

  A polymerization rate means the ratio (mass%) which the monomer mixture superposed | polymerized and became a polymer. This polymerization rate can be determined by sampling the reaction mixture and measuring the mass of the polymer produced.

  As the surfactant to be added in the emulsion resin forming step, the above-described surfactant can be used. As the surfactant, polyoxyethylene alkylphenyl ether ammonium sulfate, polyoxyethylene polycyclic phenyl ether ammonium sulfate, or the like is more preferably used.

  The addition of the surfactant multiple times in the emulsion resin forming step is preferably performed in the subsequent surfactant addition in an amount increased by 20% by mass or more with respect to the previous surfactant addition amount. More specifically, for example, when the addition amount of the first surfactant is z parts by mass, the addition amount of the second surfactant is z × 1.2 parts by mass or more. . The upper limit of the amount of addition of the surfactant in the subsequent addition is not particularly limited, but may be, for example, 5 times or less, more preferably 3 times or less, and 2 times or less. Is more preferable. As described above, in the emulsion resin forming step of the present invention, it is more preferable that the amount of the surfactant added in a plurality of times is increased as the amount is added later. By increasing the amount of surfactant added later, the particle size of the emulsion resin changes according to the reaction time, thereby forming an emulsion resin having a high solid content concentration and better storage stability. There is an advantage that becomes possible.

  The total amount of surfactant (active ingredient amount) added in the emulsion resin forming step is preferably 0.05 to 10 parts by mass, and 0.1 to 5 parts by mass with respect to 100 parts by mass of the monomer mixture. It is more preferable that it is 0.2 to 3 parts by mass. For example, the total amount of the surfactant added in the emulsion resin forming step is 0.55 to 1.5 parts by mass with respect to 100 parts by mass of the monomer mixture, and this surfactant is added in four portions. In this case, the first addition amount is 0.1 parts by mass, the second addition amount is 0.12-0.2 parts by mass, the third addition amount is 0.15-0.4 parts by mass, 4 The aspect from which the addition amount of the 1st time will be 0.18-0.8 mass part is mentioned.

  The total amount of the surfactant added in the emulsion resin forming step is preferably 10 to 40% by mass with respect to the total amount of the surfactant used in the method for producing the emulsion resin for paints, and 15 to 30% by mass. % Is more preferred. Here, “total amount of surfactant used in the method for producing emulsion resin for paint” refers to the amount of surfactant contained in the pre-emulsion solution and the total amount of surfactant added in the emulsion resin forming step. Means the total amount.

  The emulsion resin obtained by the production method of the present invention has a number average particle size of 500 nm or less. The number average particle diameter of the emulsion resin in the present specification can be determined by a dynamic and / or electrophoretic light scattering method using a particle size measuring device (for example, ELS-Z manufactured by Otsuka Electronics Co., Ltd.). The number average particle size of the emulsion resin is more preferably 450 nm or less, and still more preferably 400 nm or less.

  The solid content concentration of the emulsion resin is preferably 50% by mass or more, more preferably 55% by mass or more, further preferably 60% by mass or more, and further preferably 65% by mass or more.

  The emulsion resin obtained by the production method of the present invention is characterized by containing a large amount of a styrene component. In addition, for example, even when the solid content concentration is as high as 50% by mass or more, the production stability and the dispersion stability are excellent. Such a feature is more preferable in that the number average molecular weight is 500 nm or less as described above, and the particle size distribution is, for example, a bimodal distribution. The particle size distribution can be determined by measuring the particle size distribution using the particle size measuring apparatus as described above. In the high solid content emulsion resin, when the particle size distribution is a bimodal distribution, it is considered that the particle filling state is high and the dispersion stability is improved. In the present specification, the solid content is measured by determining the difference in mass before and after drying when dried at 150 ° C. for 1 hour.

In the production method of the present invention, after the emulsion resin formation step,
After adding the oil-soluble polymerization initiator, further adding a reducing agent to polymerize the residual monomer, a residual monomer polymerization step,
The embodiment including is more preferable. By including this step, the amount of residual monomer derived from the monomer mixture can be reduced, and problems such as odor can be solved. The concentration of the residual monomer contained in the obtained emulsion resin is preferably less than 1000 ppm, and more preferably less than 900 ppm. In the present specification, the concentration of the residual monomer can be measured using a liquid chromatograph / mass spectrometer.

The oil-soluble polymerization initiator preferably has a water solubility at 20 ° C. of 1 g / L or less. As such an oil-soluble polymerization initiator, for example,
t-butylperoxy-2-ethylhexanoate, benzoyl peroxide, t-butylperoxybenzoate, t-butyl hydroperoxide, t-butylperoxy-3,5,5-trimethylhexanoate, di- organic peroxides such as t-butyl peroxide, and
2,2′-azobis [N- (2-propenyl) -2-methylpropionamide], 2,2′-azobisisobutyronitrile, 2,2′-azobis (4-methoxy-2,4-dimethyl) Valeronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (N-butyl-2-methylpropion) Amide) and other oily azo polymerization initiators,
Etc.
These oil-soluble polymerization initiators may be used alone or in combination of two or more.

  As the oil-soluble polymerization initiator, for example, it is more preferable to use one or more selected from the group consisting of t-butylperoxy-2-ethylhexanoate.

  The amount of the oil-soluble polymerization initiator added in the residual monomer polymerization step is preferably 0.05 to 5 parts by mass, more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the monomer mixture. Preferably, it is 0.2-2 mass parts.

As the reducing agent, for example,
Reducing organic compounds such as L-ascorbic acid, L-ascorbate (such as sodium ascorbate), tartaric acid, citric acid, glucose, formaldehyde sulfoxylate metal salts, and sodium thiosulfate, sodium sulfite, sodium acid sulfite, Reducing inorganic compounds such as sodium metabisulfite and ferrous chloride,
Etc.
These reducing agents may be used alone or in combination of two or more.

  As the reducing agent, for example, one kind selected from the group consisting of L-ascorbic acid, tartaric acid, citric acid, glucose, formaldehyde sulfoxylate metal salt, sodium thiosulfate, sodium sulfite, sodium acid sulfite, sodium metabisulfite, or It is more preferable to use more than that.

  The amount of the reducing agent added in the residual monomer polymerization step is preferably 0.05 to 5 parts by mass, more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the monomer mixture. More preferably, it is 2-2 mass parts.

  In the residual monomer polymerization step, it is preferable that the oil-soluble polymerization initiator is added first, and the reducing agent is added after a certain period of time. As a more preferable embodiment, for example, an embodiment in which the reducing agent is added after 10 minutes or more have elapsed since the oil-soluble polymerization initiator is added is preferable. This elapsed time is more preferably 15 minutes or more, and further preferably 20 minutes or more. By adding the oil-soluble polymerization initiator and the reducing agent under such conditions, there is an advantage that the amount of residual monomer can be extremely effectively reduced. In addition, as mentioned above, you may repeat repeatedly the addition which adds an oil-soluble polymerization initiator first, and adds the said reducing agent after that as needed.

In the production method of the present invention, such as an additive, in addition to the above components, an additive as necessary may be used in any step. Examples of the additive include a polymerization regulator such as a chain transfer agent and a buffer. The polymerization regulator may be added in advance to the pre-emulsion solution in the pre-emulsion solution preparation step, or may be added by an arbitrary procedure in the emulsion resin formation step.
Examples of the chain transfer agent include alcohols such as methanol, ethanol, propanol and butanol; carboxylic acids having 2 to 8 carbon atoms such as acetone, methyl ethyl ketone, cyclohexane, acetophenone, acetaldehyde, propionaldehyde, n-butyraldehyde, furfural, benzaldehyde and the like. And mercaptans such as dodecyl mercaptan, lauryl mercaptan, normal mercaptan, thioglycolic acid, octyl thioglycolate, and thioglycerol. Two or more of these may be used in combination.
Examples of the buffer include sodium acetate, ammonium acetate, dibasic sodium phosphate, and the like. Two or more of these may be used in combination.

  According to the production method of the present invention, even when a monomer mixture having a high styrene monomer content is subjected to emulsion polymerization, it is possible to produce a coating emulsion resin having a high solid content. The mechanical strength of the coating film obtained is improved by preparing a coating composition using a coating emulsion resin obtained by the production method of the present invention and having a high content of rigid styrene component derived from an aromatic ring. To do. Thereby, the coating composition which provides the coating film which has the outstanding abrasion resistance, alkali resistance, washing | cleaning resistance, adhesiveness, etc. which has the outstanding durability can be prepared. Furthermore, the emulsion resin obtained by the production method of the present invention has a solid content of 50% or more. The solid content may be an emulsion resin having a very high solid content, for example, a solid content of 60% or more, and further a solid content of 65% or more. When the emulsion resin has a high solid content, there is an advantage that the degree of design freedom in the preparation of the coating composition is significantly improved. Moreover, since the solid content of the emulsion resin used for the preparation of the coating composition is high, there is also an advantage that the energy required in the production and transportation of the coating composition can be reduced.

Coating Composition The present invention also relates to a coating composition containing an emulsion resin obtained by the above production method. Examples of the coating composition include the emulsion resin and, if necessary, a pigment, a design material (such as sand, cinnabar, color sand, beads, color chips, mineral chips, glass chips, wood chips, and color beads), pigments Examples thereof include a coating composition containing a dispersant, other resin components, a thickener, a pH adjuster, a solvent and additives.

  The pigment is not particularly limited, for example, an azo chelate pigment, an insoluble azo pigment, a condensed azo pigment, a monoazo pigment, a disazo pigment, a diketopyrrolopyrrole pigment, a benzimidazolone pigment, a phthalocyanine pigment, Indigo pigment, thioindigo pigment, perinone pigment, perylene pigment, dioxane pigment, quinacridone pigment, isoindolinone pigment, naphthol pigment, pyrazolone pigment, anthraquinone pigment, anthorapyrimidine pigment, metal complex Organic color pigments such as pigments: yellow lead, yellow iron oxide, chromium oxide, molybdate orange, bengara, titanium yellow, zinc white, carbon black, titanium dioxide, cobalt green, phthalocyanine green, ultramarine, cobalt blue, phthalocyanine blue, Cobalt bio Inorganic colored pigments such as iron; mica pigments (titanium dioxide-coated mica, colored mica, metal-plated mica); graphite pigments, alumina flake pigments, metal titanium flakes, stainless steel flakes, plate-like iron oxide, phthalocyanine flakes, metal-plated glass Examples include flakes, other colored and colored flat pigments; titanium oxide, calcium carbonate, barium sulfate, barium carbonate, magnesium silicate, clay, talc, silica, calcined kaolin extender pigments, and the like.

When a pigment is contained in the coating composition, it is preferable to improve the pigment dispersion performance using a pigment dispersant. Polymer pigment dispersions such as DISPERBYK ^(trademark) -102, 180, 184, 185, 187, 190, 191, 192, 193, 194N, 198, 199, 2010, 2012, 2015, 2096 as pigment dispersants Agents and the like.

  When a coating composition contains a pigment, it is preferable that the pigment mass concentration (PWC) with respect to solid content of a coating composition exists in the range of 5-70 mass%. When the PWC is less than 5% by mass, the base concealing property is inferior, and when the PWC exceeds 70% by mass, the weather resistance may be lowered. The pigment mass concentration (PWC) is more preferably 20 to 45% by mass.

  Other resin components include, for example, epoxy resins; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polycarbonate resins; polyurethane resins; cellulose derivatives such as nitrocellulose, cellulose acetate, and cellulose acetate butyrate; polyvinyl chloride; Vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylonitrile-butadiene Copolymers, copolymers such as acrylonitrile-butadiene-styrene copolymer; polybutadiene; chlorinated rubber; petroleum resin; polyvinyl butyral; polyvinyl alcohol; Polyolefins such as pyrene; polyvinylidene fluoride; chlorinated polyethylene, halogenated polyolefins such as chlorinated polypropylene amino resin, Po isocyanate, curing agent such as blocked polyisocyanate; and like these reactants or modified product; and the like.

  Examples of thickeners include inorganic thickeners such as colloidal silica, bentonite, montmorillonite and colloidal alumina; acrylic thickeners such as polyacrylic acid and acrylic copolymers; urethane-associated thickeners; alkali swelling thickeners Agents; Copolymer thickeners such as modified polyoxyethylene / urethane block copolymers; Cellulose thickeners such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and hydrophobic group-modified hydroxycellulose; polyethylene glycol ethers, nonionic surfactants Surfactants such as alginate; polysaccharides such as alginate, guar gum and mannan; water-soluble resins such as polyacrylic acid, polyvinyl alcohol and polyvinylpyrrolidone;

  Examples of the pH adjuster include ammonia, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, monobutylamine, dibutylamine, tributylamine and other alkylamines, diethanolamine, Alkanolamines such as diisopropanolamine, triethanolamine, dimethylethanolamine, diethylethanolamine, ethylenediamine, propylenediamine, diethylenetriamine, alkylenepolyamines such as triethylenetetramine, ammonia, ethyleneimine, pyrrolidine, piperidine, piperazine, morpholine, and Alkaline such as sodium hydroxide and potassium hydroxide Shokushio and the like.

  Examples of the solvent include water and various organic solvents. Examples of organic solvents include coating compositions such as alcohol, ethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoethyl hexyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, propylene glycol monophenyl ether, and the like. Organic solvents generally used in the field are mentioned.

  As additives, for example, in the field of coating compositions, such as film-forming aids, surface conditioners, preservatives, fungicides, antifoaming agents, light stabilizers, ultraviolet absorbers, antioxidants, pH adjusters, etc. Commonly used additives are listed.

  It does not specifically limit as a preparation method of a coating composition, It can prepare by stirring each component mentioned above with a stirrer etc. When pigments or design materials are included in the coating composition, those having good dispersibility can be mixed with a stirrer, and as another method, a sand grind mill is added to a vehicle containing water, a surfactant or a dispersant. It is also possible to add a material that has been dispersed in advance using the above.

  The coating composition of the present invention can be applied to various substrates. Examples of the base material include various cements, ceramic building materials, lightweight foamed concrete, mortar, slate plates, roofs, tiles, ALC and other inorganic building materials; various glasses; metal base materials such as steel plates, aluminum and stainless steel; It is done.

  As a coating method of the coating composition, any appropriate method can be used depending on the type and shape of the object (base material) to be coated. As a method of coating the aqueous coating composition, for example, commonly used coating methods such as dipping, brushing, flow coating, roller, roll coater, air spray, airless spray, curtain flow coater, roller curtain coater, die coater, etc. Etc. can be used.

As one aspect of the coating composition of the present invention, it can be used as an undercoating composition that forms an undercoating film by coating the substrate and leaving it to stand. When using the coating composition of this invention as an undercoat coating composition, you may pre-process a base material as needed. Examples of the base pretreatment include a method of coating a base conditioner such as a sealer. Furthermore, the coating composition of the present invention can also be used as an undercoat coating composition for coating on an old coating film. When the coating composition of the present invention is used as an undercoat coating composition, it can be applied by a general coating method such as brushing, spraying or roller so that the coating amount is 50 to 500 g / m ² , for example. . This painting may be performed in a plurality of times.

As another embodiment of the coating composition of the present invention, it can be used as a top coating composition in which a top coating film is formed by coating and leaving on a base coating film formed as needed. When the coating composition is used as the top coating composition, it can be applied by a general coating method such as brushing, spraying or roller so that the coating amount is 50 to 500 g / m ² . This painting may be performed in a plurality of times.

  The coating composition of the present invention includes an emulsion resin obtained by emulsion polymerization of a monomer mixture having a high styrene monomer content. Therefore, a coating film having excellent alkali resistance, water resistance, chemical resistance, weather resistance, etc. can be formed by drying after coating the coating composition of the present invention. Since the coating composition of the present invention has excellent alkali resistance, weather resistance, etc., it is suitable for, for example, coating of inorganic building materials such as concrete, wall surfaces such as inner walls or outer walls of buildings, roofs, etc. Can be used.

  The following examples further illustrate the present invention, but the present invention is not limited thereto. In the examples, “parts” and “%” are based on mass unless otherwise specified.

＊プレエマルション溶液中のモノマー濃度：８０％ Production Example 1
A glass Kolben was charged with 15.0 parts by weight of water (hereinafter sometimes referred to simply as “parts”) and heated to 80 ° C.
After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., the monomer emulsion (pre-emulsion solution) described in the following table was added at a constant rate over 5 hours. It was dripped at.

* Monomer concentration in pre-emulsion solution: 80%

Furthermore, during the polymerization, when a total amount of 0.87 parts of the same surfactant as described above, 30% aqueous solution of polyoxyethylene alkylphenyl ether ammonium sulfate, was added to glass Kolben from another outlet, the polymerization rate reached 50%. From this, it was divided into a total of 4 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 50%): 0.10 parts 2 hours: 0.17 parts 3 hours: 0.27 parts 4 hours: 0.33 parts

After completion of dropping of the pre-emulsion and the surfactant, the mixture was further maintained for 60 minutes and then cooled to 60 ° C.
When the temperature reached 60 ° C., 0.3 part of t-butylperoxy-2-ethylhexanoate was added and held for 30 minutes.
Subsequently, a solution in which 0.4 part of ascorbic acid was dissolved in 1 part of water was added, and then kept at 60 ° C. for 90 minutes.
Thereafter, the operation of addition was repeated twice, followed by cooling.
The obtained emulsion was a stable emulsion having a solid content of 69.3%, a viscosity of 3794 mPas, a pH of 1.8, and an average particle size of 248 nm.

The polymerization rate was calculated as follows. That is, 1.0 g of the reaction mixture was weighed, allowed to stand at 150 ° C. for 1 hour to volatilize volatile components, and then weighed again to determine the mass loss. Using this mass reduction amount as the residual monomer, the polymerization rate was determined by the following formula.
Polymerization rate (%) = [1- (mass reduction amount / reaction mixture substance amount before volatile treatment)] × 100

＊プレエマルション溶液中のモノマー濃度：８０％ Production Example 2
A glass Kolben was charged with 15.0 parts by weight of water and heated to 80 ° C.
After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours. Added.

* Monomer concentration in pre-emulsion solution: 80%

Further, during the polymerization, when a total amount of 0.77 parts of the same surfactant as described above, 30% aqueous solution of polyoxyethylene alkylphenyl ether ammonium sulfate, was added to glass Kolben from another outlet, the polymerization rate reached 82%. From this, it was divided into a total of 3 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 82%): 0.17 parts 2 hours: 0.27 parts 3 hours: 0.33 parts

  After completion of the dropping, polymerization was carried out in the same manner as in Production Example 1. The obtained emulsion was a stable emulsion having a solid content of 69.3%, a viscosity of 400 mPas, pH 5.2, and an average particle size of 374 nm.

＊プレエマルション溶液中のモノマー濃度：８１％ Production Example 3
A glass Kolben was charged with 15.0 parts by weight of water and heated to 80 ° C.
After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours. Added.

* Monomer concentration in pre-emulsion solution: 81%

Furthermore, during the polymerization, when a total amount of 0.77 parts of the same surfactant as the above, 30% aqueous solution of polyoxyethylene alkylphenyl ether ammonium sulfate, was added to glass Kolben from a different port, the polymerization rate reached 71%. From this, it was divided into a total of 3 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 71%): 0.17 parts 2 hours: 0.27 parts 3 hours: 0.33 parts

After completion of the dropping, polymerization was carried out in the same manner as in Production Example 1. The obtained emulsion was a stable emulsion having a solid content concentration of 69.5%, a viscosity of 597 mPas, pH 5.0 and an average particle size of 314 nm.

＊プレエマルション溶液中のモノマー濃度：８０％ Production Example 4
A glass Kolben was charged with 15.0 parts by weight of water and heated to 80 ° C.
After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours. Added.

* Monomer concentration in pre-emulsion solution: 80%

Furthermore, during the polymerization, when a total amount of 0.77 parts of the same surfactant as described above, 30% aqueous solution of polyoxyethylene alkylphenyl ether ammonium sulfate, was added to glass Kolben from another outlet, when the polymerization rate reached 80%. From this, it was divided into a total of 3 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 80%): 0.17 parts 2 hours: 0.27 parts 3 hours: 0.33 parts

After completion of the dropping, polymerization was carried out in the same manner as in Production Example 1. The obtained emulsion was a stable emulsion having a solid content of 69.3%, a viscosity of 228 mPas, pH 5.1 and an average particle size of 339 nm.

＊プレエマルション溶液中のモノマー濃度：８０％ Production Example 5
A glass Kolben was charged with 15.0 parts by weight of water and heated to 80 ° C. After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours. Added.

* Monomer concentration in pre-emulsion solution: 80%

Further, during the polymerization, when a total amount of 0.77 parts of the same surfactant as described above, 30% aqueous solution of polyoxyethylene alkylphenyl ether ammonium sulfate, was added to glass Kolben from another outlet, the polymerization rate reached 82%. From this, it was divided into a total of 3 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 82%): 0.17 parts 2 hours: 0.27 parts 3 hours: 0.33 parts

After completion of the dropping, polymerization was carried out in the same manner as in Production Example 1.
The obtained emulsion was a stable emulsion having a solid content concentration of 69.0%, a viscosity of 1011 mPas, a pH of 5.0 and an average particle size of 265 nm.

＊プレエマルション溶液中のモノマー濃度：８１％ Production Example 6
A glass Kolben was charged with 15.0 parts by weight of water and heated to 80 ° C.
After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours. Added.

* Monomer concentration in pre-emulsion solution: 81%

Furthermore, during polymerization, when a total amount of 0.77 part of polyoxyethylene alkylphenyl ether ammonium sulfate 30% aqueous solution, which is the same surfactant as described above, was added to glass Kolben from another outlet, the polymerization rate reached 85%. From this, it was divided into a total of 3 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 85%): 0.17 parts 2 hours: 0.27 parts 3 hours: 0.33 parts

After completion of the dropping, polymerization was carried out in the same manner as in Production Example 1.
The obtained emulsion was a stable emulsion having a solid content concentration of 69.8%, a viscosity of 821 mPas, pH 5.2 and an average particle size of 430 nm.

＊プレエマルション溶液中のモノマー濃度：８１％ Production Example 7
A glass Kolben was charged with 15.0 parts by weight of water and heated to 80 ° C.
After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours. Added.

* Monomer concentration in pre-emulsion solution: 81%

Furthermore, during the polymerization, when a total amount of 0.77 parts of the same surfactant as described above, 30% aqueous solution of polyoxyethylene alkylphenyl ether ammonium sulfate, was added to glass Kolben from another outlet, when the polymerization rate reached 80%. From this, it was divided into a total of 3 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 80%): 0.17 parts 2 hours: 0.27 parts 3 hours: 0.33 parts

After completion of the dropping, polymerization was carried out in the same manner as in Production Example 1.
The obtained emulsion was a stable emulsion having a solid content concentration of 69.7%, a viscosity of 231 mPas, a pH of 5.1 and an average particle size of 360 nm.

＊プレエマルション溶液中のモノマー濃度：８１％ Production Example 8
A glass Kolben was charged with 15.0 parts by weight of water and heated to 80 ° C.
After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours. Added.

* Monomer concentration in pre-emulsion solution: 81%

Furthermore, during the polymerization, when a polymerization rate of 79% aqueous solution of polyoxyethylene alkylphenyl ether ammonium sulfate, which is the same surfactant as described above, was added to glass Kolben from another outlet in a total amount of 0.77 parts. From this, it was divided into a total of 3 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 79%): 0.17 parts 2 hours: 0.27 parts 3 hours: 0.33 parts

After completion of the dropping, polymerization was carried out in the same manner as in Production Example 1.
The obtained emulsion was a stable emulsion having a solid content concentration of 69.0%, a viscosity of 940 mPas, pH 5.0 and an average particle size of 287 nm.

＊プレエマルション溶液中のモノマー濃度：８０％ Production Example 9
A glass Kolben was charged with 15.0 parts by weight of water and heated to 80 ° C.
After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours. Added.

* Monomer concentration in pre-emulsion solution: 80%

Further, during the polymerization, when a total amount of 0.77 parts of the same surfactant as described above, 30% aqueous solution of polyoxyethylene alkylphenyl ether ammonium sulfate, was added to glass Kolben from another outlet, the polymerization rate reached 82%. From this, it was divided into a total of 3 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 82%): 0.17 parts 2 hours: 0.27 parts 3 hours: 0.33 parts

  After completion of the dropping, polymerization was carried out in the same manner as in Production Example 1. The obtained emulsion was a stable emulsion having a solid content of 69.3%, a viscosity of 480 mPas, a pH of 5.2, and an average particle diameter of 310 nm.

＊プレエマルション溶液中のモノマー濃度：７８％ Production Example 10
A glass Kolben was charged with 15.0 parts by weight of water and heated to 80 ° C.
After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours. Added.

* Monomer concentration in pre-emulsion solution: 78%

Further, during the polymerization, when a total amount of 0.77 parts of the same surfactant as described above, 30% aqueous solution of polyoxyethylene alkylphenyl ether ammonium sulfate, was added to glass Kolben from another outlet, the polymerization rate reached 82%. From this, it was divided into a total of 3 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 82%): 0.17 parts 2 hours: 0.27 parts 3 hours: 0.33 parts

  After completion of the dropping, polymerization was carried out in the same manner as in Production Example 1. The obtained emulsion was a stable emulsion having a solid content concentration of 69.2%, a viscosity of 1830 mPas, a pH of 5.2, and an average particle diameter of 322 nm.

＊プレエマルション溶液中のモノマー濃度：８０％ Production Comparative Example 1
A glass Kolben was charged with 15.0 parts by weight of water and heated to 80 ° C.
After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours. Added.

* Monomer concentration in pre-emulsion solution: 80%

Furthermore, during the polymerization, when a total amount of 0.87 parts of the same surfactant as described above, 30% aqueous solution of polyoxyethylene alkylphenyl ether ammonium sulfate, was added to glass Kolben from another outlet, the polymerization rate reached 39%. From this, it was divided into a total of 4 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 39%): 0.10 parts 2 hours: 0.17 parts 3 hours: 0.27 parts 4 hours: 0.33 parts

After completion of the dropping, polymerization was carried out in the same manner as in Production Example 1.
The obtained emulsion was an emulsion having a solid content concentration of 58.8% and an average particle size of 310 nm. The obtained emulsion was in a very high viscosity state, and the viscosity could not be measured.

＊プレエマルション溶液中のモノマー濃度：８０％ Production Comparative Example 2
A glass Kolben was charged with 15.0 parts by weight of water and heated to 80 ° C.
After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours. Added.

* Monomer concentration in pre-emulsion solution: 80%

Further, during the polymerization, when a total amount of 0.77 parts of the same surfactant as the above, 30% aqueous solution of polyoxyethylene alkylphenyl ether ammonium sulfate, was added to glass Kolben from another outlet, the polymerization rate reached 51%. From this, it was divided into a total of 3 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 51%): 0.17 parts 2 hours: 0.27 parts 3 hours: 0.33 parts

After completion of the dropping, polymerization was carried out in the same manner as in Production Example 1.
The obtained emulsion was an emulsion having a solid content concentration of 55.8% and an average particle diameter of 267 nm. The obtained emulsion was in a very high viscosity state, and the viscosity could not be measured.

＊プレエマルション溶液中のモノマー濃度：８０％ Production Comparative Example 3
A glass Kolben was charged with 15.0 parts by weight of water and heated to 80 ° C.
After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours. Added.

* Monomer concentration in pre-emulsion solution: 80%

Furthermore, during polymerization, when a total amount of 0.77 parts of polyoxyethylene alkylphenyl ether ammonium sulfate 30% aqueous solution, which is the same surfactant as described above, was added to glass Kolben from another outlet, the polymerization rate reached 84%. From this, it was divided into a total of 3 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 84%): 0.17 parts 2 hours: 0.27 parts 3 hours: 0.33 parts

After completion of the dropping, polymerization was carried out in the same manner as in Production Example 1.
The obtained emulsion was an emulsion having a solid content concentration of 65.1% and an average particle diameter of 323 nm. The obtained emulsion was in a very high viscosity state, and the viscosity could not be measured.

＊プレエマルション溶液中のモノマー濃度：８０％ Production Comparative Example 4
A glass Kolben was charged with 15.0 parts by weight of water and heated to 80 ° C.
After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours. Added.

* Monomer concentration in pre-emulsion solution: 80%

Further, during the polymerization, when a polymerization rate of 50% was obtained from another outlet, a glass colben was added to a total amount of 0.77 part of a 30% aqueous solution of polyoxyethylene alkylphenyl ether ammonium sulfate, which is the same surfactant as described above. From this, it was divided into a total of 3 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 50%): 0.17 parts 2 hours: 0.27 parts 3 hours: 0.33 parts

After completion of the dropping, polymerization was carried out in the same manner as in Production Example 1.
The obtained emulsion was an emulsion having a solid content concentration of 54.3% and an average particle size of 243 nm. The obtained emulsion was in a very high viscosity state, and the viscosity could not be measured.

Production Comparative Example 5
Polymerization was carried out in the same manner as in Production Example 1 except that the surfactant to be added from Production Example 1 was added in advance.
The obtained emulsion was an emulsion having a solid content concentration of 58.6% and an average particle size of 194 nm. The obtained emulsion was in a very high viscosity state, and the viscosity could not be measured.

Production Comparative Example 6
A total amount of 0.87 parts of the same surfactant as the above 30% polyoxyethylene alkylphenyl ether ammonium sulfate aqueous solution was divided into a total of 4 times every hour from the point when the polymerization rate of Production Example 4 reached 41%. The polymerization was carried out in the same manner as in Production Example 4 except that each time was added all at once in the following amounts.

1 hour (41% polymerization rate): 0.10 parts 2 hours: 0.17 parts 3 hours: 0.27 parts 4 hours: 0.33 parts

The obtained emulsion was an emulsion having a solid content concentration of 61.0% and an average particle size of 210 nm. The obtained emulsion was in a very high viscosity state, and the viscosity could not be measured.

Production Comparative Example 7
A total amount of 0.6 parts of 30% aqueous solution of polyoxyethylene alkylphenyl ether ammonium sulfate, which is the same surfactant as described above, was divided into a total of 2 times every hour from the time when the polymerization rate of Production Example 4 reached 93%. The polymerization was carried out in the same manner as in Production Example 4 except that each time was added all at once in the following amounts.

1 hour (polymerization rate 93%): 0.27 parts 2 hours: 0.33 parts

The obtained emulsion was an emulsion having a solid content concentration of 63.3% and an average particle size of 424 nm. The obtained emulsion was in a very high viscosity state, and the viscosity could not be measured.

＊プレエマルション溶液中のモノマー濃度：８０％ Production Comparative Example 8
A glass Kolben was charged with 15.0 parts by weight of water and heated to 80 ° C.
After adding a solution prepared by dissolving 0.5 part of ammonium persulfate in 2 parts of water while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours. Added.

* Monomer concentration in pre-emulsion solution: 80%

Furthermore, during the polymerization, when a total amount of 0.87 parts of a 30% aqueous solution of polyoxyethylene alkylphenyl ether ammonium sulfate, which is the same surfactant as described above, was added to glass Kolben, the polymerization rate reached 65%. From this, it was divided into a total of 4 times every hour, and each time was added all at once in the following amounts.

1 hour (polymerization rate 65%): 0.10 parts 2 hours: 0.17 parts 3 hours: 0.27 parts 4 hours: 0.33 parts

After completion of the dropping, polymerization was carried out in the same manner as in Production Example 1.
The obtained emulsion was an emulsion having a solid content concentration of 69.4%, 250 mPas, pH 5.1 and an average particle diameter of 301 nm.

＊プレエマルション溶液中のモノマー濃度：８５％ Production Comparative Example 9
A glass Kolben was charged with 23.5 parts by mass of water and heated to 80 ° C.
After adding 0.5 part of ammonium persulfate while controlling the temperature at 80 ° C., a monomer emulsion (pre-emulsion solution) having the following composition was added at a constant rate over 5 hours.
However, the viscosity of the pre-emulsion solution was very high and could not be dropped.

* Monomer concentration in pre-emulsion solution: 85%

  The following tests were conducted on the emulsion resins prepared according to the above production examples and production comparative examples. The test results are shown in the following table.

Measurement of solid content 2 g of a sample was collected, dried in a mini jet oven (manufactured by Toyama Sangyo Co., Ltd.) at 150 ° C. for 1 hour, and then calculated from the following equation using the mass before and after drying. .
Solid content (%) = (mass after drying) / (mass before drying) × 100

Measurement of emulsion viscosity The viscosity was measured at 25 ° C. and 6 rpm using a TVB10 viscometer (manufactured by Toki Sangyo Co., Ltd.).

Measurement of number average particle diameter of emulsion resin The number average particle diameter of the emulsion resin was measured using ELS-Z (manufactured by Otsuka Electronics Co., Ltd.). In addition, about the calculation of a number average particle diameter, it calculated by the cumulant analysis method from the obtained diffusion coefficient.

Measurement of pH The pH was measured at 25 ° C. using a pH meter (manufactured by Toa-DKK).

The symbols in the above table mean the following.
MAA: methacrylic acid AA: acrylic acid MMA: methyl methacrylate nBMA: n-butyl methacrylate nBA: n-butyl acrylate 2-EHA: 2-ethylhexyl acrylate DAAm: diacetone acrylamide The numerical value is the r1 value of each monomer (monomer reactivity ratio with styrene, quoted from POLYMER HANDBOOK 4th Edition).

  Although all the emulsion resins obtained by the production examples had a high solid content, the viscosity was low and the viscosity could be measured. That is, it was stable as an emulsion.

  In Production Comparative Examples 1 and 2, the amount of (meth) acrylic monomer having a monomer reactivity ratio r1 with styrene of 0.7 or less in the monomer mixture is less than 10% by mass. Therefore, the emulsions obtained by these production comparative examples were in a very high viscosity state, and the viscosity could not be measured. The emulsion resin obtained in these production comparative examples also has a solid content concentration that is significantly lower than the solid content concentration of the emulsion resin obtained in the production example. This indicates that a large amount of unreacted monomer remains. Since such an emulsion resin has a very high viscosity, it cannot be made into a paint. This is because the viscosity of the emulsion resin is extremely high, so that the dispersibility with other components constituting the coating composition is greatly reduced, and the dispersion stability of the resulting coating composition is poor. . Therefore, it is not suitable as an emulsion resin for paint. There is also a problem that the odor derived from the unreacted monomer is strong.

  In Production Comparative Example 3, the amount of the (meth) acrylic monomer (b1) having a monomer reactivity ratio r1 with styrene of 0.7 or less exceeds 60% by mass. Therefore, the emulsion obtained by Production Comparative Example 3 was in a very high viscosity state, and the viscosity could not be measured. The emulsion resin obtained in Production Comparative Example 3 also has a solid content concentration that is significantly lower than the solid content concentration of the emulsion resin obtained in Production Example. That is, many unreacted monomers remain. Further, since the obtained emulsion resin has a very high viscosity, it cannot be made into a paint. Therefore, it is not suitable as an emulsion resin for paint.

  In Production Comparative Example 4, the amount of styrene monomer (a) exceeds 50% by mass. Therefore, the emulsion obtained by Production Comparative Example 4 was in a very high viscosity state, and the viscosity could not be measured. In this production comparative example, since the content of the styrene monomer (a) is large, the hydrophobicity in the polymerization system becomes too high, and the dispersion and dissolution of the pre-emulsion solution in water does not proceed well, Since the amount of the monomer mixture absorbed into the micelles or particles, which is the place for the polymerization reaction, was significantly reduced, the polymerization reaction did not proceed smoothly. As a result, it was considered that the viscosity was extremely high and the viscosity could not be measured. In the emulsion resin obtained in Production Comparative Example 4, the solid content concentration is also significantly lower than the solid content concentration of the emulsion resin obtained in Production Example. That is, many unreacted monomers remain. Furthermore, since such an emulsion resin has a high viscosity, it cannot be made into a paint. Therefore, it is not suitable as an emulsion resin for paint.

  In Production Comparative Example 5, no surfactant was added in the emulsion resin formation step. Therefore, it is considered that many emulsions having the same particle size exist without particles having different particle sizes coexisting in the system. And the interaction between these emulsion particles increases, and as a result, it becomes a very high viscosity state, and it is considered that the viscosity could not be measured. The emulsion resin obtained in Production Comparative Example 5 also has a solid content concentration that is significantly lower than the solid content concentration of the emulsion resin obtained in Production Example. That is, many unreacted monomers remain. Furthermore, since such an emulsion resin has a high viscosity, it cannot be formed into a paint. Therefore, it is not suitable as an emulsion resin for paint.

  In Production Comparative Example 6, in the emulsion resin formation step, the surfactant is added before the polymerization rate of the monomer mixture exceeds 45%. In this case, the surfactant is added before the size of the emulsion resin particles reaches the optimum range. For this reason, it is considered that the particle size distribution optimum for the high solid content could not be achieved in the polymerization system, and the viscosity could not be measured due to the extremely high viscosity state. The emulsion resin obtained in Production Comparative Example 6 also has a solid content concentration that is significantly lower than the solid content concentration of the emulsion resin obtained in Production Example. That is, many unreacted monomers remain. Furthermore, since such an emulsion resin has a high viscosity, it cannot be made into a paint. Therefore, it is not suitable as an emulsion resin for paint.

  In Production Comparative Example 7, the surfactant is added after the polymerization rate of the monomer mixture exceeds 90% in the emulsion resin formation step. Therefore, it is considered that the surfactant was insufficient, the particles became unstable, and the interaction between the particles became strong, which resulted in a very high viscosity state and the viscosity could not be measured. The emulsion resin obtained in Production Comparative Example 7 also has a solid content concentration that is significantly lower than the solid content concentration of the emulsion resin obtained in Production Example. That is, many unreacted monomers remain. Furthermore, since such an emulsion resin has a high viscosity, it cannot be formed into a paint. Therefore, it is not suitable as an emulsion resin for paint.

  Production Comparative Example 8 is an example in which the content of styrene monomer is 10% by mass and the amount of styrene monomer is less than the range in the present invention. It was found that the emulsion resin obtained by this production example has poor alkali resistance. The results of this experiment are detailed below.

  Production Comparative Example 9 is a production comparative example corresponding to Example 1 described in JP-A-7-233208. In this production comparative example, the viscosity of the pre-emulsion solution containing the monomer mixture was very high, and the pre-emulsion solution could not be dropped using a commonly used dropping device. On the other hand, it was possible to forcibly drop the pre-emulsion solution using equipment such as a pump. However, since the viscosity of the pre-emulsion solution is very high, the polymerization workability is very poor and the production efficiency is extremely poor. The emulsion resin obtained in Production Comparative Example 9 also has a solid content concentration that is significantly lower than the solid content concentration of the emulsion resin obtained in Production Example. That is, since the viscosity of the pre-emulsion solution is very high and an optimum particle size cannot be formed during the emulsion polymerization, a large amount of unreacted monomer remains. Furthermore, since it does not contain a rigid styrene unit, it is inferior in alkali resistance and washing resistance (an index of wear resistance), and film distortion is likely to occur, resulting in a significant decrease in adhesion. Therefore, it is not suitable as an emulsion resin for paint.

Example 1 Preparation of top coating composition
Preparation of pigment paste 6 parts by mass of ion-exchanged water, thickener (trade name “SP-600N”, manufactured by Daicel Chemical Industries, hydroxyethyl cellulose-based thickener) 0.1 part by mass, pigment dispersant (trade name “Disperbyk” -190 ", manufactured by Big Chemie) 1.5 parts by mass, titanium dioxide (trade name" TI-PURE R-706 ", manufactured by DuPont) 22.2 parts by mass, industrial preservative (trade name" Best Side 201 " , Manufactured by Nippon Soda Co., Ltd.), 0.1 part by mass, and antifoaming agent (trade name “BYK-018”, manufactured by Big Chemie), 0.1 part by mass in a stainless steel container, mixed, and glass beads are added. The mixture was stirred and dispersed with a disper for 30 minutes to obtain a pigment paste.

Preparation of top coating composition 100 parts by weight of emulsion resin obtained in Production Example 1, 30 parts by weight of pigment paste, 6 parts by weight of film-forming aid, 1 part by weight of ethylene glycol, 0.1 part by weight of pH adjuster, Aqueous top coating composition 1 by sufficiently mixing 0.6 parts by mass of foaming agent, 0.2 parts by mass of thickener 1, 0.4 parts by mass of thickener 2, and 11.2 parts by mass of ion-exchanged water. Got.

Examples 2-4
An aqueous top coating composition was prepared in the same manner as in Example 1, except that the emulsion resin obtained in Production Example 2, 4 or 7 was used instead of the emulsion resin obtained in Production Example 1. 2-4 were obtained.

Comparative Example 1
Example 1 is the same as Example 1 except that the emulsion resin used in the preparation of the aqueous top coating composition obtained in Example 1 was changed from that in Production Example 1 to the emulsion resin obtained in Production Comparative Example 8. In the same manner, an aqueous top coating composition 5 was obtained.

The components used in the preparation of the top coating composition are as follows.
(Film forming aid)
Film-forming aid: Trade name “CS-12”, manufactured by Chisso Corporation, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (pH adjuster)
pH adjuster: 25% aqueous ammonia, manufactured by Wako Pure Chemical Industries, Ltd. (antifoaming agent)
Antifoaming agent: trade name “BYK-024”, manufactured by Big Chemie (Thickener 1)
Thickener 1: Trade name “Adecanol UH-420”, manufactured by Asahi Denka Co., Ltd., urethane associative thickener (Thickener 2)
Thickener 2: Trade name “Primal TT-615”, manufactured by Rohm and Haas, alkali swelling thickener

  About the water-based top coat composition obtained by the said Example and comparative example, the coating-film performance (A coating-film external appearance, water resistance, alkali resistance, washing | cleaning resistance, accelerated weather resistance) was investigated. The washing resistance was examined as an index of wear resistance. The test method is as follows. The test results are shown in the following table.

Nippe Ultra Sealer III (manufactured by Nippon Paint Co., Ltd., styrene-acrylic resin-based sealer having a carboxyl group) is applied to a flexible coating plate (compliant with JIS A 5430) using a brush at a coating amount of 100 g / m ^2. After standing for 16 hours (temperature: 23 ° C., humidity: 50%), the evaluation paint was applied at a coating amount of 100 g / m ² , using a brush with a paint interval of 3 hours, and applied twice. Then, after leaving it to stand for 24 hours, it was evaluated (visually).
○: No abnormalities are observed in the coating film ×: Abnormalities such as cracks, itchiness and pinholes are observed

Nippe Ultra Sealer III (manufactured by Nippon Paint Co., Ltd., styrene-acrylic resin-based sealer having a carboxyl group) is applied to a water-resistant flexible board (JIS A 5430 compliant) using a brush at a coating amount of 100 g / m ^2. After standing for a period of time (temperature 23 ° C., humidity 50%), the evaluation paint was applied at a coating amount of 100 g / m ² , using a brush, with a paint interval of 3 hours, and applied twice. Then, it dried and cured for 7 days, the water-resistant test board was created, and it was immersed in 20 degreeC water for 7 days. After the immersion, after taking out and washing with water, the state of the coating film surface was observed and evaluated within 30 minutes.
○: There is no swelling, cracking, peeling, etc. in the coating film △: There are swelling, cracking, peeling, etc. locally in the coating film ×: There are swelling, cracking, peeling, etc. in the entire coating film

Nippe Ultra Sealer III (manufactured by Nippon Paint Co., Ltd., styrene-acrylic resin-based sealer having a carboxyl group) is applied to an alkali-resistant flexible plate (JIS A 5430 compliant) with a brush at a coating amount of 100 g / m ^2. After standing for a period of time (temperature 23 ° C., humidity 50%), the evaluation paint was applied at a coating amount of 100 g / m ² , using a brush, with a paint interval of 3 hours, and applied twice. Then, it dried for 7 days and produced the alkali-proof test board. The obtained test plate was immersed in a 3% aqueous solution of sodium hydroxide at 20 ° C. for 7 days. After taking out and washing, the state of the coating film surface was observed within 30 minutes.
○: There is no swelling, cracking, peeling, etc. on the coating film △: There is swelling, cracking, peeling, etc. locally on the coating film ×: There are swelling, cracking, peeling, etc. on the coating film as a whole

Washing resistance (JIS K 5663 synthetic resin emulsion paint, 1 type)
Apparatus: It has the function of 6.3 wet abrasion test apparatus of JIS K 5600-5-11. It has a test tank, a soap bath, a brush, etc., and the brush reciprocates on the coating film of the test piece. thing.

Preparation of test piece:
An evaluation paint was applied to a hard vinyl chloride sheet (specified in JIS K 6734) using a 6 mil applicator, and dried for 7 days to prepare a wash resistance test plate. The test was conducted in accordance with JIS K 5663 7.12.
operation:
The test piece was fixed horizontally on the test stand of the test tank of the cleaning test apparatus with the coating surface facing upward. Place a brush fully soaked with 0.5% soap solution on the coated surface of the test piece, drop 0.5% soap solution on the rubbing surface, and keep the wet surface with a brush. Rubbed 500 times and rubbed. Thereafter, the test piece was taken out, washed with water, dried, and then visually evaluated.
○: Even after the brush reciprocation process (500 times), the paint film was not torn and the substrate was not exposed due to wear. ×: The brush reciprocation process (500 times) was performed. Later, the paint film is torn in the rubbed area, and the substrate is exposed due to wear.

Nippe Ultra Sealer III (manufactured by Nippon Paint Co., Ltd., styrene-acrylic resin-based sealer having a carboxyl group) is applied to the accelerated weather-resistant flexible board (JIS A 5430 compliant) with a brush at a coating amount of 100 g / m ² , After standing for 16 hours (temperature: 23 ° C., humidity: 50%), the evaluation paint was applied at a coating amount of 100 g / m ² using a brush with a paint interval of 3 hours and applied twice. After that, dry-cured for 7 days to create an accelerated weathering test plate, and after 240 hours of irradiation, the test specimen was taken out and allowed to stand in the room for 1 hour according to JIS K 5600-7-7 (xenon lamp method). Carried out.
○: No swelling, peeling, cracking, etc. when the chalking grade is 1 or less, and there is no significant change in color compared to the sample board. ×: The chalking grade is 2 or more, or peeling, cracking occurs, or color. Chalkification with large change: conforms to JIS K 5600-8-6.

All of the water-based top coating compositions of the examples prepared using the emulsion resins obtained by the manufacturing examples have a coating film appearance, water resistance, alkali resistance, washing resistance (abrasion resistance), and weather resistance acceleration. It was confirmed to be excellent.
On the other hand, it was confirmed that the water-based top coating composition prepared using the emulsion resin obtained in Production Comparative Example 8 was greatly inferior in alkali resistance and washing resistance (abrasion resistance) and inferior in water resistance. It was done.

Preparation of aqueous undercoat paint composition
Example 5
100 parts by weight of the emulsion resin obtained in Production Example 3, 8 parts by weight of a film-forming aid, 14 parts by weight of titanium dioxide, 97 parts by weight of calcium carbonate, 1.6 parts by weight of a thickener, and 7.4 parts by weight of an additive Were mixed well to obtain an aqueous undercoat paint composition 1.

Example 6
An aqueous undercoat paint composition 2 was obtained in the same manner as in Example 5 except that the emulsion resin of the aqueous undercoat paint composition of Example 5 was changed from that of Production Example 3 to that of Production Example 5.

Example 7
An aqueous undercoat paint composition 3 was obtained in the same manner as in Example 5 except that the emulsion resin of the aqueous undercoat paint composition of Example 5 was changed from that of Production Example 3 to that of Production Example 6.

Example 8
An aqueous undercoat paint composition 4 was obtained in the same manner as in Example 5 except that the emulsion resin of the aqueous undercoat paint composition of Example 5 was changed from that of Production Example 3 to that of Production Example 8.

Comparative Example 2
An aqueous undercoating composition 5 was obtained in the same manner as in Example 5 except that the emulsion resin of the aqueous undercoating composition of Example 5 was changed from that of Production Example 3 to that of Production Comparative Example 8.

  About the water-based top coat composition obtained by the said Example and comparative example, the coating-film performance (alkali resistance, water resistance, adhesiveness) was investigated. The test method is as follows. The test results are shown in the following table.

Evaluation test The above-mentioned aqueous undercoat paint compositions 1 to 5 were each applied at a coating amount of 300 mg / m ² on a 70 × 150 mm slate plate prepared by applying a two-component urethane paint at a coating amount of 150 mg / m ² to prepare a base. Thus, an evaluation test plate was obtained. The following various tests were performed on the obtained evaluation test plate and evaluated.

Alkali resistance The obtained evaluation test plate was immersed in a 3% aqueous solution of sodium hydroxide at 20 ° C. for 7 days. After taking out and washing, the state of the coating film surface was observed within 30 minutes.
○: There is no swelling, cracking, peeling, etc. on the coating film. △: There are swelling, cracking, peeling, etc. locally on the coating film.

Water resistance The obtained evaluation test plate was immersed in water at 20 ° C. for 7 days. After taking out and washing with water, the state of the coating film surface was observed and evaluated within 30 minutes.
○: There is no swelling, cracking, peeling, etc. on the coating film △: There is swelling, cracking, peeling, etc. locally on the coating film ×: There are swelling, cracking, peeling, etc. on the coating film as a whole

Adhesion After the obtained evaluation test plate was allowed to stand at room temperature for 16 hours, a crosscut having a depth reaching the slate plate with a cutter knife was inserted. Then, after sticking a gum tape on a cut part, it peeled off rapidly and evaluated the peeling state.
○: No peeling occurs on the coating film Δ: The coating film peeling area is less than 75% of the sticking area of the gum tape ×: The coating film peeling area is 75% or more of the sticking area of the gum tape

It was confirmed that all of the water-based undercoat paint compositions of Examples prepared using the emulsion resin obtained by the Production Examples were excellent in alkali resistance, water resistance and adhesion.
On the other hand, it was confirmed that the water-based undercoating composition prepared using the emulsion resin obtained in Production Comparative Example 8 was greatly inferior in alkali resistance and adhesion, and inferior in water resistance.

  According to the production method of the present invention, even when a monomer mixture having a high content of styrene monomer is subjected to emulsion polymerization, an emulsion resin for coating having a high solid content can be produced. By preparing a coating composition using the emulsion resin for coating obtained by the production method of the present invention, it becomes possible to blend many rigid styrene skeletons derived from aromatic rings. Thereby, the mechanical strength of the coating film obtained can be improved. According to the production method of the present invention, there is an advantage that it is possible to prepare a coating composition that provides a coating film having excellent wear resistance, alkali resistance, washing resistance, adhesion, and the like and excellent in durability.

Claims (7)

A method for producing an emulsion resin for paint,
The method
Preparing a pre-emulsion solution comprising a monomer mixture consisting of 20-50% by weight of styrene monomer (a) and α, β-ethylenically unsaturated monomer (b) copolymerizable with (a), 50-80% by weight, A pre-emulsion solution preparation step, and an emulsion resin formation step of forming an emulsion resin by emulsion polymerization of the monomer mixture,
Including
The emulsion resin for paints obtained by the production method has a number average particle size of 500 nm or less and a solid content concentration of 50% by mass or more,
The α, β-ethylenically unsaturated monomer (b) includes a (meth) acrylic monomer (b1) having a monomer reactivity ratio r1 with styrene of 0.7 or less,
The content of the (meth) acrylic monomer (b1) in the monomer mixture is 10 to 60% by mass,
In the emulsion resin formation step, after the polymerization rate of the monomer mixture is in the range of 45% to 90%, the surfactant is added in several portions.
Manufacturing method of emulsion resin for paint.   The addition of a plurality of surfactants in the emulsion resin forming step is added in an amount that is increased by 20% by mass or more with respect to the amount of the surfactant added in the subsequent surfactant addition. The manufacturing method as described. The monomer (b) includes an α, β-ethylenically unsaturated monomer having an acid group,
The neutralization rate of the monomer mixture (b) in the pre-emulsion solution is 1.5 to 30%.
The manufacturing method of Claim 1 or 2.   The emulsion resin for coatings obtained by the said manufacturing method is a manufacturing method in any one of Claims 1-3 whose residual monomer density | concentration is less than 1000 ppm. After the emulsion resin formation step,
After adding the oil-soluble polymerization initiator, further adding a reducing agent to polymerize the residual monomer, a residual monomer polymerization step,
The manufacturing method in any one of Claims 1-4 which further includes these.   The said oil-soluble polymerization initiator is a manufacturing method of Claim 5 whose solubility in water in 20 degreeC is 1 g / L or less.   The total amount of the surfactant added in the emulsion resin forming step is 10 to 40% by mass with respect to the total amount of the surfactant used in the method for producing the emulsion resin for paints. The manufacturing method of crab.