JP2017057311A - Acrylic resin emulsion for metal surface treatment and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acrylic resin emulsion for metal surface treatment excellent in stability, and a method for producing the same.SOLUTION: There is provided an acrylic resin emulsion for metal surface treatment comprising: (A) a hydrophobic structural unit derived from a (meth)acrylic acid ester monomer; (B) a hydrophilic structural unit derived from a hydrophilic group other than a carboxyl group and a hydrophilic monomer with an ethylenic unsaturated double bond; (C) a structural unit derived from an anionic reactive surfactant comprising an oxyalkylene group and the ethylenic unsaturated double bond, in which the average addition mol number of an oxyalkylene group is 20 or lower; and (D) a structural unit derived from a nonion type reactive surfactant having an oxyalkylene group and an ethylenic unsaturated double bond and in which the average addition mol number of the oxyalkylene group is 25 or higher, where emulsion grains with an acid value of 8.0 mgKOH/g or lower are dispersed into an aqueous medium, and also provided is a method for producing the same.SELECTED DRAWING: None

Description

  The present invention relates to an acrylic resin emulsion for metal surface treatment and a method for producing the same.

  A coating for the purpose of rust prevention or the like is formed on the surface of a metal plate such as an electromagnetic steel plate. As a method of forming such a film, an insulating film treatment liquid (hereinafter referred to as “treatment liquid”) containing chromate, phosphate (for example, aluminum phosphate) and the like, and an acrylic resin emulsion as a binder. The method of using is said to be known.

For example, Patent Document 1 discloses, as a treatment liquid, an aqueous solution of an inorganic film forming substance mainly composed of chromate, a methacrylic ester polymer fine powder, and a carboxylic acid component-containing polymer having a carboxy group. An electrical steel sheet insulating film-forming composition containing an aqueous emulsion is disclosed.
Patent Document 2 discloses a process for forming an electrical steel sheet insulating coating comprising a metal phosphate and an organic resin emulsion having a hydroxyl value of 5 mg to 40 mg KOH / g and a particle diameter of 0.01 μm to 0.5 μm. A liquid is disclosed.

Japanese Patent No. 2769730 Japanese Patent No. 3435080

However, since the carboxy group is ionized in water and has a negative charge, it easily interacts with the positive charge of the metal ion derived from the metal salt. Therefore, in a treatment liquid containing a resin emulsion having a carboxy group, such as a carboxylic acid component-containing polymer aqueous emulsion described in Patent Document 1, the resin is likely to aggregate due to the influence of metal ions, resulting in poor stability. There is. When a metal surface is treated using a treatment liquid that is inferior in stability, a uniform film cannot be formed, so that it is difficult to impart functions such as rust prevention.
On the other hand, there is a resin emulsion that does not have a carboxy group, such as the organic resin emulsion described in Patent Document 2. However, a resin emulsion having only a hydroxyl group as a hydrophilic group may cause a phenomenon that micelles are destroyed by metal ions derived from a metal salt, and its use is preferable from the viewpoint of the stability of the treatment liquid. I can't say that.

  This invention is made | formed in view of the above situations, and makes it a subject to provide the acrylic resin emulsion for metal surface treatments which is excellent in stability, and its manufacturing method.

Specific means for solving the problems include the following aspects.
<1> a hydrophobic structural unit (A) derived from a (meth) acrylic acid ester monomer;
A hydrophilic structural unit (B) derived from a hydrophilic monomer other than a carboxy group and a hydrophilic monomer having an ethylenically unsaturated double bond;
A structural unit (C) derived from an anionic reactive surfactant having an oxyalkylene group and an ethylenically unsaturated double bond and having an average addition mole number of the oxyalkylene group of 20 or less;
A structural unit (D) derived from a nonionic reactive surfactant having an oxyalkylene group and an ethylenically unsaturated double bond, and having an average addition mole number of the oxyalkylene group of 25 or more;
And an acrylic resin emulsion for metal surface treatment in which emulsion particles having an acid value of 8.0 mgKOH / g or less are dispersed in an aqueous medium.

<2> The acrylic resin emulsion for metal surface treatment according to <1>, wherein the oxyalkylene group in the structural unit (C) and the structural unit (D) is an oxyethylene group.
<3> The proportion of the structural unit (C) is 5 parts by mass to 10 parts by mass with respect to 100 parts by mass in total of the structural units derived from all monomers forming the emulsion particles, and <1> or <2 in which the proportion of the structural unit (D) is 10 to 30 parts by mass with respect to 100 parts by mass in total of the structural units derived from all monomers forming the emulsion particles. > Acrylic resin emulsion for metal surface treatment as described in>.
<4> A structural unit derived from a nonionic reactive surfactant in which the emulsion particles have an oxyalkylene group and an ethylenically unsaturated double bond, and the average added mole number of the oxyalkylene group is 20 or less. The acrylic resin emulsion for metal surface treatment according to any one of <1> to <3>, further comprising (E).

<5> The acrylic resin emulsion for metal surface treatment according to <4>, wherein the oxyalkylene group in the structural unit (E) is an oxyethylene group.
<6> The ratio of the structural unit (C) is 5 parts by mass to 10 parts by mass with respect to a total of 100 parts by mass of the structural units derived from all monomers forming the emulsion particles, and the structure The ratio of the unit (D) is 10 to 20 parts by mass with respect to a total of 100 parts by mass of the structural units derived from all monomers forming the emulsion particles, and the structural unit (E The metal according to <4> or <5>, wherein the ratio of) is 1 part by mass to 10 parts by mass with respect to a total of 100 parts by mass of the structural units derived from all monomers forming the emulsion particles. Acrylic resin emulsion for surface treatment.
<7> The acrylic resin emulsion for metal surface treatment according to any one of <1> to <6>, which is used for electrical steel sheet treatment.

<8> An anionic reactive surfactant (c) having an oxyalkylene group and an ethylenically unsaturated double bond and having an average addition mole number of the oxyalkylene group of 20 or less, an oxyalkylene group and ethylene A nonionic reactive surfactant (d) having a polymerizable unsaturated double bond and an average addition mole number of the oxyalkylene group of 25 or more, in the presence of a reactive surfactant,
Polymerize at least a hydrophobic monomer (a) selected from (meth) acrylic acid esters and a hydrophilic monomer (b) having a hydrophilic group other than a carboxy group and an ethylenically unsaturated double bond A method for producing an acrylic resin emulsion for metal surface treatment, comprising an emulsion polymerization step of obtaining emulsion particles having an acid value of 8.0 mgKOH / g or less.

  ADVANTAGE OF THE INVENTION According to this invention, the acrylic resin emulsion for metal surface treatments which is excellent in stability, and its manufacturing method can be provided.

  Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. be able to.

In the present specification, a numerical range indicated using “to” means a range including the numerical values described before and after “to” as a minimum value and a maximum value, respectively.
In this specification, the amount of each component in the acrylic resin emulsion for metal surface treatment is such that when there are a plurality of substances corresponding to each component in the acrylic resin emulsion for metal surface treatment, unless otherwise specified, the metal surface It means the total amount of a plurality of substances present in the acrylic resin emulsion for treatment.

  In the present specification, “(meth) acrylate” is a term including both acrylate and methacrylate, “(meth) acryl” is a term including both acrylic and methacrylic, and “(meth) acryloyl group” "Is a term that encompasses both acryloyl and methacryloyl groups.

  In this specification, the term “process” is not limited to an independent process, and is included in this term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. It is.

[Acrylic resin emulsion for metal surface treatment]
The acrylic resin emulsion for metal surface treatment of the present invention (hereinafter also referred to as “acrylic resin emulsion”) is a hydrophobic structural unit (A) derived from a (meth) acrylic acid ester monomer (hereinafter referred to as “structural unit ( A) ") and a hydrophilic structural unit (B) derived from a hydrophilic monomer other than a carboxy group and a hydrophilic monomer having an ethylenically unsaturated double bond (hereinafter referred to as" structural unit (B) "). And a structural unit derived from an anionic reactive surfactant having an oxyalkylene group and an ethylenically unsaturated double bond, and an average addition mole number of the oxyalkylene group of 20 or less ( C) (hereinafter also referred to as “structural unit (C)”), a nonio having an oxyalkylene group and an ethylenically unsaturated double bond, and having an average addition mole number of the oxyalkylene group of 25 or more. Emulsion particles having a structural unit (D) derived from a type-reactive surfactant (hereinafter also referred to as “structural unit (D)”) and having an acid value of 8.0 mgKOH / g or less. An acrylic resin emulsion dispersed in an aqueous medium.

In general, a carboxy group is ionized in water and has a negative charge, and thus easily interacts with a positive charge of a metal ion derived from a metal salt. Therefore, the processing liquid containing the resin emulsion which has the conventional carboxy group tends to aggregate resin under the influence of a metal ion, and is inferior to stability. Since the processing solution having poor stability cannot form a uniform film on the metal surface, it is difficult to impart functions such as rust prevention. On the other hand, a treatment liquid containing a resin emulsion that does not have a carboxy group and has only a hydroxyl group as a hydrophilic group is also known, but the phenomenon that micelles are destroyed by metal ions derived from metal salts may occur. The stability is not enough.
In contrast, the acrylic resin emulsion of the present invention has a structural unit (A), a structural unit (B), a structural unit (C), and a structural unit (D), and has an acid value of 8.0 mgKOH / Since the emulsion particles having a particle size of g or less are dispersed in an aqueous medium, excellent stability is exhibited.
The reason why the acrylic resin emulsion of the present invention can exhibit such an effect is not clear, but the present inventors presume as follows.

In the aqueous medium, the emulsion particles having the structural unit (A), the structural unit (B), the structural unit (C), and the structural unit (D) are resin particles having the structural unit (A) and the structural unit (B). The structural unit (C) and the structural unit (D) are dispersed on the surface in a form firmly fixed by covalent bonds. In the emulsion particles, the structural unit (C) and the structural unit (D) form a hydrated layer on the surface of the resin particle.
The thickness of the formed hydration layer is determined by the average number of moles of oxyalkylene groups that the structural unit (C) and the structural unit (D) have. The hydrated layer of the emulsion particles in the present invention is thick because it is formed by the structural unit (D) derived from the nonionic reactive surfactant having an oxyalkylene group having an average addition mole number of 25 or more.
When an anion derived from an anionic group (for example, SO ₃ ⁻ ) is exposed on the surface of the emulsion particles, it is affected by metal ions, so that aggregation or the like is likely to occur. The hydrated layer of emulsion particles in the present invention comprises a structural unit (D) derived from a nonionic reactive surfactant having an oxyalkylene group having an average addition mole number of 25 or more, and an oxy group having an average addition mole number of 20 or less. And the structural unit (C) derived from the anionic reactive surfactant having an alkylene group, the anionic group of the structural unit (C) is not exposed on the surface of the emulsion particles, and High density.
Since the emulsion particles in the present invention are formed with a dense and thick hydrated layer that does not expose anionic groups that are easily affected by metal ions on the surface, it is difficult for micelles to break down and aggregate due to metal ions, It is considered excellent in stability.

  Moreover, since emulsion particle | grains have the hydrophilic structural unit (B) derived from the hydrophilic monomer which has hydrophilic groups other than a carboxy group, it is thought that it is excellent in stability.

  Furthermore, since the acrylic resin emulsion of the present invention has an emulsion particle acid value of 8.0 mgKOH / g or less, it is unlikely that micelles are broken or agglomerated by metal ions, and is considered to be excellent in stability.

[Emulsion particles]
The emulsion particles are derived from a hydrophobic structural unit (A) derived from a (meth) acrylic acid ester monomer and a hydrophilic monomer having a hydrophilic group other than a carboxy group and an ethylenically unsaturated double bond. A structure derived from an anionic reactive surfactant having a hydrophilic structural unit (B), an oxyalkylene group and an ethylenically unsaturated double bond, and an average addition mole number of the oxyalkylene group of 20 or less Unit (C) and a structural unit derived from a nonionic reactive surfactant having an oxyalkylene group and an ethylenically unsaturated double bond, and having an average addition mole number of the oxyalkylene group of 25 or more (D And the acid value is 8.0 mgKOH / g or less.
From the viewpoint of further improving the stability of the acrylic resin emulsion, the emulsion particles have an oxyalkylene group and an ethylenic group in addition to the structural unit (A), the structural unit (B), the structural unit (C), and the structural unit (D). A structural unit derived from a nonionic reactive surfactant having an unsaturated double bond and an average addition mole number of an oxyalkylene group of 20 or less (hereinafter also referred to as “structural unit (E)”). Furthermore, it is preferable to have.

Since the carboxy group has a small acid dissociation constant and a strong interaction with metal ions, if the emulsion particles have a carboxy group, aggregation of particles and generation of foreign matters are likely to occur. Therefore, from the viewpoint of the stability of the acrylic resin emulsion, the emulsion particles preferably do not have a carboxy group or have a small amount of carboxy groups even if they have a carboxy group.
The amount of carboxy groups in the emulsion particles can be determined using the acid value of the emulsion particles as an index.
The acid value of the emulsion particles is 8.0 mgKOH / g or less, preferably 7.0 mgKOH / g or less, more preferably 6.0 mgKOH / g or less, from the viewpoint of the stability of the acrylic resin emulsion. Preferably it is 3.0 mgKOH / g or less, More preferably, it is 1.0 mgKOH / g or less, Most preferably, it is 0 mgKOH / g.

In the present specification, the “acid value of emulsion particles” is a value determined according to the following (1) to (6).
(1) About 20 g of acrylic resin emulsion is precisely weighed into a 200 mL beaker.
(2) Dilute the acrylic resin emulsion to 100 mL to 150 mL using deionized water.
(3) An appropriate amount of a cation exchange resin [Amberlite (registered trademark) IR-120B] is added to the diluted acrylic resin emulsion, and the pH of the resulting mixture is adjusted to 3 or less.
(4) Using a 100-mesh filter cloth (aperture: 224 μm), remove the cation exchange resin from the pH-adjusted mixture, wash with deionized water until the washing solution is no longer turbid, and collect the filtrate. . In addition, the presence or absence of turbidity in the washing solution is determined visually.
(5) Conductivity titration of the collected filtrate is performed using a sodium hydroxide solution (0.5 mol / L, volumetric analysis specific solution) to measure the titer.
(6) The acid value is calculated by the following formula. In addition, 0.5 in a formula shows the density | concentration (mol / L) of a sodium hydroxide solution.
Acid value (mgKOH / g) = (0.5 × f × X × 56.1) / (W × NV)
f: titer of 0.5 mol / L sodium hydroxide solution X: titer (mL)
W: Amount of acrylic resin emulsion collected (g)
NV: Nonvolatile content per gram of acrylic resin emulsion (g)

  Hereinafter, each structural unit which the emulsion particles have will be described.

<Structural unit (A)>
The structural unit (A) is a hydrophobic structural unit derived from a (meth) acrylic acid ester monomer. The kind of (meth) acrylic acid ester monomer is not particularly limited as long as it is a hydrophobic monomer.
In the present specification, the “hydrophobic monomer” means a monomer having no hydrophilic group and carboxy group described later.
Examples of the (meth) acrylic acid ester monomer include alkyl (meth) acrylate, alkylene glycol di (meth) acrylate, and fluorine-containing alkyl (meth) acrylate.
Among these, the (meth) acrylic acid ester monomer is preferably at least one selected from the group consisting of alkyl (meth) acrylates and alkylene glycol di (meth) acrylates from the viewpoint of the hardness of the emulsion particles.

  The alkyl part of the alkyl (meth) acrylate may be linear, branched or cyclic. The range of 1-25 is preferable and, as for carbon number of an alkyl site | part, the range of 1-8 is more preferable. When the carbon number of the alkyl moiety is within the above range, the resulting film is excellent in flexibility and robustness.

  Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, s-butyl (meth) acrylate, t -Butyl (meth) acrylate, n-octyl (meth) acrylate, i-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, i-nonyl (meth) acrylate, n-decyl (Meth) acrylate, n-dodecyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate and the like.

The alkylene part of the alkylene glycol constituting the alkylene glycol part of the alkylene glycol di (meth) acrylate may be linear, branched or cyclic. The range of 2-6 is preferable and, as for carbon number of an alkylene part, the range of 2-3 is more preferable. When the number of carbon atoms in the alkylene moiety is within the above range, the resulting coating has excellent fastness.
Specific examples of the alkylene glycol di (meth) acrylate include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, and 1,4-butanediol di (Meth) acrylate, 1,6-hexanediol di (meth) acrylate and the like can be mentioned.

The proportion of the structural unit (A) is, for example, 40% by mass or more based on the total mass of the structural units derived from all the monomers forming the emulsion particles from the viewpoint of flexibility and fastness of the obtained film. Is preferable, 50 mass% or more is more preferable, and 60 mass% or more is still more preferable.
The proportion of the structural unit (A) is, for example, 99% by mass or less based on the total mass of the structural units derived from all the monomers forming the emulsion particles from the viewpoint of the stability of the acrylic resin emulsion. Preferably, 95 mass% or less is more preferable, and 90 mass% or less is still more preferable.

  The emulsion particles may have the structural unit (A) alone or in combination of two or more.

<Structural unit (B)>
The structural unit (B) is a hydrophilic structural unit derived from a hydrophilic monomer other than a carboxy group and a hydrophilic monomer having an ethylenically unsaturated double bond.
The kind of the hydrophilic monomer having a hydrophilic group other than a carboxy group and an ethylenically unsaturated double bond is not particularly limited.

The hydrophilic group other than the carboxy group is not particularly limited, and may be a dissociable group or a nonionic group.
Examples of the dissociable group include a sulfonic acid group and a phosphoric acid group.
Examples of the nonionic group include a hydroxyl group, an amide group in which the nitrogen atom is unsubstituted, a group derived from an alkylene oxide polymer (polyethylene oxide, polypropylene oxide, etc.), a group derived from a sugar alcohol, and the like.
Among these, as the hydrophilic group other than the carboxy group, a hydroxyl group is preferable from the viewpoint of the stability of the acrylic resin emulsion.
The number of hydrophilic groups other than the carboxy group possessed by the hydrophilic monomer may be one or plural.

The ethylenically unsaturated double bond is not particularly limited as long as it is a functional group capable of radical reaction using a polymerization initiator.
Examples of the ethylenically unsaturated double bond include (meth) acryloyl group, vinyl group, allyl group, isopropenyl group, 1-propenyl group, allyloxy group, and styryl group. Among these, as an ethylenically unsaturated double bond, a (meth) acryloyl group is preferable from a reactive viewpoint, for example.
The number of ethylenically unsaturated double bonds that the hydrophilic monomer has may be one or plural, and preferably one.

  Examples of the hydrophilic monomer having a hydrophilic group other than a carboxy group and an ethylenically unsaturated double bond include alkyl (meth) acrylates having a hydrophilic group other than a carboxy group, and poly having a hydrophilic group other than a carboxy group. Examples include alkylene glycol (meth) acrylate.

The alkyl moiety of the alkyl (meth) acrylate having a hydrophilic group other than a carboxy group may be linear, branched or cyclic.
The range of 1-25 is preferable and, as for carbon number of an alkyl site | part, the range of 1-3 is more preferable. When the carbon number of the alkyl moiety is within the above range, the contribution of stability by the hydrophilic group is sufficient, and the stability of the acrylic resin emulsion is excellent.

  Examples of the alkylene glycol constituting the polyalkylene glycol portion of the polyalkylene glycol (meth) acrylate having a hydrophilic group other than a carboxy group include ethylene glycol, propylene glycol, a combination of ethylene glycol and propylene glycol.

Examples of hydrophilic monomers having a hydrophilic group other than a carboxy group and an ethylenically unsaturated double bond include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 3-hydroxypropyl (meth). Acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, 3-methyl-3-hydroxybutyl (meth) acrylate 1,1-dimethyl-3-hydroxybutyl (meth) acrylate, 1,3-dimethyl-3-hydroxybutyl (meth) acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth) acrylate, 2- Ethyl-3-hydroxyhexyl Meth) acrylate, glycerin mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, poly (ethylene glycol - propylene glycol) mono (meth) acrylate.
Among these, as a hydrophilic monomer having a hydrophilic group other than a carboxy group and an ethylenically unsaturated double bond, from the viewpoint of compatibility and copolymerization with other monomers, 2-hydroxyethyl (Meth) acrylate is preferred.

The proportion of the structural unit (B) is preferably 1% by mass or more with respect to the total mass of the structural units derived from all monomers forming the emulsion particles, for example, from the viewpoint of the stability of the acrylic resin emulsion. 5 mass% or more is more preferable, and 10 mass% or more is still more preferable.
Moreover, the ratio of the structural unit (B) is, for example, from the viewpoint of suppressing the hydrophilicity of the film from becoming too high, with respect to the total mass of the structural units derived from all the monomers that form the emulsion particles. 50 mass% or less is preferable, 30 mass% or less is more preferable, and 20 mass% or less is still more preferable.

  The emulsion particles may have the structural unit (B) alone or in combination of two or more.

<Structural units derived from other monomers>
The emulsion particles may have a structural unit derived from a monomer other than the structural unit (A) and the structural unit (B) (hereinafter also referred to as “other structural unit”).
In this case, the total ratio of the structural unit (A) and the structural unit (B) is preferably 50% by mass or more based on the total mass of the structural units derived from all the monomers forming the emulsion particles. 60 mass% or more is more preferable, and 70 mass% or more is still more preferable.

Although the kind of monomer which comprises other structural units is not restrict | limited in particular, From the viewpoint of stability of an acrylic resin emulsion, the monomer which does not have a carboxy group is preferable.
Other monomers constituting the structural unit include aromatic monovinyl [styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, vinyltoluene, etc.], vinyl cyanide [acrylonitrile, Methacrylonitrile, etc.], vinyl esters (vinyl formate, vinyl acetate, vinyl propionate, vinyl versatate, etc.) and various derivatives of these monomers.

  The emulsion particles may have one type of structural unit derived from another monomer, or may have two or more types.

<Structural unit (C)>
The structural unit (C) has an oxyalkylene group and an ethylenically unsaturated double bond, and the average added mole number of the oxyalkylene group is 20 or less (hereinafter referred to as “anionic type”). It is a structural unit derived from a reactive surfactant (also referred to as “c”).
If the anionic reactive surfactant (c) has an oxyalkylene group, an anionic group, and an ethylenically unsaturated double bond, and the average added mole number of the oxyalkylene group is 20 or less, The type is not limited.

Examples of the oxyalkylene group include oxyalkylene groups having an alkylene group having 2 to 4 carbon atoms such as an oxyethylene group, an oxypropylene group, and an oxybutylene group.
Among these, as the oxyalkylene group, an oxyethylene group is preferable. Since the oxyethylene group has higher hydrophilicity than other oxyalkylene groups and can form a high-density hydrated layer on the surface of the resin particles, the stability of the acrylic resin emulsion can be further improved.
The average added mole number of the oxyalkylene group is preferably 5 to 20, more preferably 5 to 10, from the viewpoint of the stability of the acrylic resin emulsion.

Examples of the anionic group include a sulfate ester base and a phosphate ester base.
The anionic group is preferably at least one selected from the group consisting of a sulfate ester base and a phosphate ester base, and more preferably a sulfate ester base.

Examples of the ethylenically unsaturated double bond include (meth) acryloyl group, vinyl group, allyl group, isopropenyl group, 1-propenyl group, allyloxy group, styryl group and the like.
Among these, the ethylenically unsaturated double bond is preferably at least one selected from the group consisting of an isopropenyl group, a 1-propenyl group, an allyloxy group, and a styryl group.

  As the anionic reactive surfactant (c), for example, an anionic reactive surfactant represented by the following structural formula (1) is preferable.

In Structural Formula (1), R ^1a represents an aliphatic alkyl group having 6 to 24 carbon atoms, and X ^1a represents —SO ₃ NH ₄ or —SO ₃ Na.
In Structural Formula (1), n1 represents the average number of repeating oxyethylene units (that is, the average number of added moles of oxyethylene groups). n1 is an integer of 1 to 20, and preferably an integer of 5 to 20.

  Examples of commercially available anionic reactive surfactants represented by the structural formula (1) include Aqualon (registered trademark) KH-10 [active ingredient: polyoxyethylene-1- (allyloxymethyl) alkyl ether ammonium sulfate. [Type of oxyalkylene group: oxyethylene group, average number of added moles: 10], active ingredient: 99% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Aqualon (registered trademark) KH-05 [active ingredient: polyoxy Ethylene-1- (allyloxymethyl) alkyl ether ammonium sulfate [type of oxyalkylene group: oxyethylene group, average number of added moles: 5], active ingredient: 99% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], Adekaria Soap (registered trademark) SR-20 [active ingredient: polyoxyethylene-1- (allyloxymethyl) alkyl ether sulfate ammonium sulfate Um [oxyalkylene group types: oxyethylene group, an average addition molar number: 20], the active ingredient: 100% by weight, and the like (Ltd.) ADEKA Ltd.].

  In addition, as the anionic reactive surfactant (c), for example, an anionic reactive surfactant represented by the following structural formula (2) is preferable.

In Structural Formula (2), R ^2a represents an aliphatic alkyl group having 6 to 24 carbon atoms, R ^3a represents a methyl group, and X ^2a represents —SO ₃ NH ₄ or —SO ₃ Na.
In Structural Formula (2), n2 represents the average number of repeating oxyethylene units (that is, the average number of added oxyethylene groups). n2 is an integer of 1-20, preferably an integer of 5-20.

  Examples of commercially available anionic reactive surfactants represented by structural formula (2) include Aqualon (registered trademark) HS-10 [active ingredient: ammonium polyoxyethylene nonylpropenyl phenyl ether sulfate [type of oxyalkylene group] : Oxyethylene group, average number of added moles: 10], active ingredient: 99% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], Aqualon (registered trademark) BC-10 [active ingredient: polyoxyethylene nonylpropenyl phenyl ether ammonium sulfate [Type of oxyalkylene group: oxyethylene group, average number of added moles: 10], active ingredient: 99% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Aqualon (registered trademark) BC-20 [active ingredient: polyoxy Ethylene nonylpropenyl phenyl ether ammonium sulfate [oxyalkylene group type: oxy Styrene group, an average addition molar number: 20], the active ingredient: 99 wt%, include Dai-ichi Kogyo Seiyaku Co., Ltd.] or the like.

For example, from the viewpoint of the stability of the acrylic resin emulsion, the proportion of the structural unit (C) is 1 part by mass or more with respect to a total of 100 parts by mass of the structural units derived from all monomers forming the emulsion particles. Preferably, 5 parts by mass or more is more preferable.
Moreover, the ratio of the structural unit (C) is, for example, 20 parts by mass with respect to 100 parts by mass in total of the structural units derived from all the monomers forming the emulsion particles from the viewpoint of the fastness of the coating film obtained. The following is preferable, and 10 parts by mass or less is more preferable.

  The emulsion particles may have the structural unit (C) alone or in combination of two or more.

<Structural unit (D)>
The structural unit (D) is a nonionic reactive surfactant having an oxyalkylene group and an ethylenically unsaturated double bond, and the average added mole number of the oxyalkylene group is 25 or more (hereinafter referred to as a nonionic reaction). It is also a structural unit derived from the ionic surfactant (d) ”.
The nonionic reactive surfactant (d) is not limited as long as it has an oxyalkylene group and an ethylenically unsaturated double bond, and the average number of added moles of the oxyalkylene group is 25 or more.

Examples of the oxyalkylene group include oxyalkylene groups having an alkylene group having 2 to 4 carbon atoms such as an oxyethylene group, an oxypropylene group, and an oxybutylene group.
Among these, as the oxyalkylene group, an oxyethylene group is preferable. Since the oxyethylene group has higher hydrophilicity than other oxyalkylene groups and can form a high-density hydrated layer on the surface of the resin particles, the stability of the acrylic resin emulsion can be further improved.
From the viewpoint of the stability of the acrylic resin emulsion, the average number of moles of oxyalkylene group added is preferably 25-50, and more preferably 25-30.

Examples of the ethylenically unsaturated double bond include (meth) acryloyl group, vinyl group, allyl group, isopropenyl group, 1-propenyl group, allyloxy group, styryl group and the like.
Among these, the ethylenically unsaturated double bond is preferably at least one selected from the group consisting of an isopropenyl group, a 1-propenyl group, an allyloxy group, and a styryl group.

  As the nonionic reactive surfactant (d), for example, a nonionic reactive surfactant represented by the following structural formula (3) is preferable.

In Structural Formula (3), R ^1b represents an aliphatic alkyl group having 6 to 24 carbon atoms, and X ^1b represents a hydrogen atom.
In Structural Formula (3), n3 represents the average number of repeating oxyethylene units (that is, the average number of added oxyethylene groups). n3 is an integer of 25-100, Preferably it is an integer of 25-50.

  Examples of commercially available nonionic reactive surfactants represented by the structural formula (3) include Adekaria Soap (registered trademark) ER-30 [active ingredient: polyoxyethylene-1- (allyloxymethyl) alkyl. Ether [type of oxyalkylene group: oxyethylene group (EO), average number of added moles: 30], active ingredient: 65% by mass, manufactured by ADEKA Corporation, Adekaria Soap (registered trademark) ER-40 [active ingredient : Polyoxyethylene-1- (allyloxymethyl) alkyl ether [type of oxyalkylene group: oxyethylene group (EO), average number of added moles: 40], active ingredient: 60% by mass, manufactured by ADEKA Corporation, etc. Is mentioned.

  In addition, as the nonionic reactive surfactant (d), for example, a nonionic reactive surfactant represented by the following structural formula (4) is preferable.

In Structural Formula (4), R ^2b represents an aliphatic alkyl group having 6 to 24 carbon atoms, R ^3b represents a methyl group, and X ^2b represents a hydrogen atom.
In Structural Formula (4), n4 represents the average number of repeating oxyethylene units (that is, the average number of added moles of oxyethylene groups). n4 is an integer of 25-100, Preferably it is an integer of 25-50.

  Examples of commercially available nonionic reactive surfactants represented by Structural Formula (4) include Aqualon (registered trademark) RN-50 [active ingredient: polyoxyethylene nonylpropenyl phenyl ether [type of oxyalkylene group: Oxyethylene group (EO), average added mole number: 50], active ingredient: 65% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], Aqualon (registered trademark) RN-30 [active ingredient: polyoxyethylene nonylpropenyl phenyl Ether [kind of oxyalkylene group: oxyethylene group (EO), average number of added moles: 30], active ingredient: 100% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] and the like.

  In addition, as the nonionic reactive surfactant (d), for example, a nonionic reactive surfactant represented by the following structural formula (5) may be used.

In Structural Formula (5), A ^1b represents a butylene group, and A ^2b represents an ethylene group.
In Structural Formula (5), m1 represents the average number of repeating oxybutylene units (that is, the average number of moles of oxybutylene groups added), and n5 represents the average number of repeating oxyethylene units (that is, oxyethylene groups). The average number of moles added. m1 + n5 is an integer of 25-100, Preferably it is an integer of 25-50.

  Examples of commercially available nonionic reactive surfactants represented by structural formula (5) include Latemul (registered trademark) PD-430S [active ingredient: polyoxyalkylene alkenyl ether [type of oxyalkylene group: oxyethylene] Group (EO) / oxybutylene group (BO), average number of added moles: 30], active ingredient: 25% by mass, manufactured by Kao Corporation, LATEMUL (registered trademark) PD-450 [active ingredient: polyoxyalkylene alkenyl] Ether [kind of oxyalkylene group: oxyethylene group (EO) / oxybutylene group (BO), average added mole number: 50], active ingredient: 100% by mass, manufactured by Kao Corporation] and the like.

For example, from the viewpoint of the stability of the acrylic resin emulsion, the proportion of the structural unit (D) is 1 part by mass or more with respect to a total of 100 parts by mass of the structural units derived from all monomers forming the emulsion particles. Preferably, 10 parts by mass or more is more preferable.
The proportion of the structural unit (D) is, for example, 50 parts by mass with respect to 100 parts by mass in total of the structural units derived from all the monomers that form the emulsion particles from the viewpoint of the fastness of the resulting film. The following is preferable, and 30 parts by mass or less is more preferable.

  In the emulsion particles, from the viewpoint of further improving the stability of the acrylic resin emulsion, the proportion of the structural unit (C) described above is a total of 100 parts by mass of the structural units derived from all monomers forming the emulsion particles. The proportion of the structural unit (D) is 5 parts by mass to 10 parts by mass with respect to a total of 100 parts by mass of the structural units derived from all monomers forming the emulsion particles. It is preferable that it is 30 mass parts.

  The emulsion particles may have the structural unit (D) alone or in combination of two or more.

<Structural unit (E)>
The emulsion particles have a nonionic reactive surfactant (hereinafter referred to as “nonionic reactive interface”) having an oxyalkylene group and an ethylenically unsaturated double bond, and having an average addition mole number of the oxyalkylene group of 20 or less. It is preferable to further have a structural unit (E) derived from “active agent (e)”.
In emulsion particles further having a structural unit (E) having a short oxyalkylene chain, a hydrated layer is formed at a higher density on the surface of the resin particles, so that the micelles are not easily broken by metal ions, and the acrylic resin emulsion is stable. The property is further improved.
The nonionic reactive surfactant (e) is not limited as long as it has an oxyalkylene group and an ethylenically unsaturated double bond, and the average number of moles of the oxyalkylene group added is 20 or less.

Examples of the oxyalkylene group include oxyalkylene groups having an alkylene group having 2 to 4 carbon atoms such as an oxyethylene group, an oxypropylene group, and an oxybutylene group.
Among these, as the oxyalkylene group, an oxyethylene group is preferable. Since the oxyethylene group has higher hydrophilicity than other oxyalkylene groups and can form a hydrated layer having a high density on the surface of the resin particles, the stability of the acrylic resin emulsion is further improved.
The average added mole number of the oxyalkylene group is preferably 5 to 20, more preferably 5 to 10, from the viewpoint of the stability of the acrylic resin emulsion.

Examples of the ethylenically unsaturated double bond include (meth) acryloyl group, vinyl group, allyl group, isopropenyl group, 1-propenyl group, allyloxy group, styryl group and the like.
Among these, the ethylenically unsaturated double bond is preferably at least one selected from the group consisting of an isopropenyl group, a 1-propenyl group, an allyloxy group, and a styryl group.

  As the nonionic reactive surfactant (e), for example, a nonionic reactive surfactant represented by the following structural formula (6) is preferable.

In Structural Formula (6), R ^1c represents an aliphatic alkyl group having 6 to 24 carbon atoms, and X ^1c represents a hydrogen atom.
In Structural Formula (6), n6 represents the average number of repeating oxyethylene units (that is, the average number of added oxyethylene groups). n6 is an integer of 1-20, preferably an integer of 5-20.

  Examples of commercially available nonionic reactive surfactants represented by the structural formula (6) include Adekaria Soap (registered trademark) ER-10 [active ingredient: polyoxyethylene-1- (allyloxymethyl) alkyl. Ether [type of oxyalkylene group: oxyethylene group (EO), average number of added moles: 10], active ingredient: 100% by mass, manufactured by ADEKA Corporation, Adekaria Soap (registered trademark) ER-20 [active ingredient : Polyoxyethylene-1- (allyloxymethyl) alkyl ether [type of oxyalkylene group: oxyethylene group (EO), average number of added moles: 20], active ingredient: 75% by mass, manufactured by ADEKA Corporation, etc. Is mentioned.

  In addition, as the nonionic reactive surfactant (e), for example, a nonionic reactive surfactant represented by the following structural formula (7) is preferable.

In Structural Formula (7), R ^2c represents an aliphatic alkyl group having 6 to 24 carbon atoms, R ^3c represents a methyl group, and X ^2c represents a hydrogen atom.
In Structural Formula (7), n7 represents the average number of repeating oxyethylene units (that is, the average number of moles of oxyethylene groups added). n7 is an integer of 1-20, preferably an integer of 5-20.

  Examples of commercially available nonionic reactive surfactants represented by the structural formula (7) include Aqualon (registered trademark) RN-20 [active ingredient: polyoxyethylene nonylpropenyl phenyl ether [type of oxyalkylene group: Oxyethylene group (EO), average added mole number: 20], active ingredient: 100% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] and the like.

  Further, as the nonionic reactive surfactant (e), for example, a nonionic reactive surfactant represented by the following structural formula (8) may be used.

In Structural Formula (8), A ^1c represents a butylene group, and A ^2c represents an ethylene group.
In Structural Formula (5), m2 represents the average number of repeating oxybutylene units (that is, the average number of moles of oxybutylene groups added), and n8 represents the average number of repeating oxyethylene units (that is, oxyethylene groups). The average number of moles added. m2 + n8 is an integer of 1-20, preferably an integer of 5-20.

  Examples of commercially available nonionic reactive surfactants represented by Structural Formula (8) include Latemul (registered trademark) PD-420 [active ingredient: polyoxyalkylene alkenyl ether [type of oxyalkylene group: oxyethylene] Group (EO) / oxybutylene group (BO), average added mole number: 20], active ingredient: 100% by mass, manufactured by Kao Corporation] and the like.

When the emulsion particles have a structural unit (E), the ratio of the structural unit (E) is, for example, from the viewpoint of the stability of the acrylic resin emulsion, the sum of the structural units derived from all the monomers that form the emulsion particles. 1 mass part or more is preferable with respect to 100 mass parts.
The proportion of the structural unit (E) is, for example, 10 parts by mass with respect to a total of 100 parts by mass of the structural units derived from all monomers forming the emulsion particles, from the viewpoint of the fastness of the resulting coating. The following is preferred.

  Further, when the emulsion particles have a structural unit (E), from the viewpoint of further improving the stability of the acrylic resin emulsion, the proportion of the above structural unit (C) is derived from all monomers that form the emulsion particles. The total of structural units derived from all the monomers that form the emulsion particles in which the proportion of the structural unit (D) is 5 parts by mass to 10 parts by mass with respect to a total of 100 parts by mass of the structural units. With respect to 100 parts by weight, 10 parts by weight to 20 parts by weight, and the proportion of the structural unit (E) is 100 parts by weight in total of the structural units derived from all monomers forming the emulsion particles. And preferably 1 to 10 parts by mass.

  In the emulsion particles, the ratio of the total mass of the structural unit (D) and the structural unit (E) to the mass of the structural unit (C) (the total mass of the structural unit (D) and the structural unit (E) / the structural unit (C)). Mass) is preferably 2 to 10 on a mass basis, more preferably 2 to 5, and still more preferably 3 to 4.

<Aqueous medium>
The aqueous medium is not particularly limited and can be appropriately selected depending on the purpose.
Examples of the aqueous medium include water, a mixed solution of water and an alcohol solvent, and the like. From the viewpoint of the stability of the acrylic resin emulsion, water is preferable as the aqueous medium.
Content of the aqueous medium in an acrylic resin emulsion is not restrict | limited in particular, Preferably it is 20 mass%-80 mass%, More preferably, it is 30 mass%-70 mass%, More preferably, it is 50 mass%-60 mass%. % By mass.

<Other ingredients>
The acrylic resin emulsion of the present invention may contain other components other than those described above, if necessary, within a range not impairing the effects of the present invention.
Examples of other components include various additives such as an antioxidant, an antistatic agent, a pH adjuster, and an antifoaming agent.

[Average particle diameter of emulsion particles]
From the viewpoint of dispersibility, the average particle diameter of the emulsion particles is preferably 50 nm to 300 nm, more preferably 80 nm to 200 nm, and still more preferably 100 nm to 120 nm.
In the present specification, the “average particle diameter of emulsion particles” means “New Experimental Chemistry Lecture 4 Basic Technology 3 Light (II)” pages 725 to 741 edited by the Chemical Society of Japan (July 20, 1977 Maruzen ( It is a value measured by the dynamic light scattering method described in “Issuance”). The specific method is as follows.
The acrylic resin emulsion was diluted with distilled water and sufficiently stirred and mixed. Then, 5 ml was collected in a 10 mm square glass cell using a Pasteur pipette, and this was collected using a dynamic light scattering photometer “Zetasizer 1000HS” [Sysmex ( Set to “Made by Co., Ltd.”. After adjusting the concentration of the acrylic resin emulsion dilution so that the decay rate count rate is 150 Cps to 200 Cps, the results measured under the conditions of a measurement temperature of 25 ° C. ± 1 ° C. and a light scattering angle of 90 ° are processed by a computer. By doing this, the average particle diameter of the emulsion particles in the acrylic resin emulsion is obtained.

[Use]
The acrylic resin emulsion of this invention can be used suitably for an electromagnetic steel plate process, for example.
A film containing chromate, metal phosphate (aluminum phosphate, magnesium phosphate, calcium phosphate, zinc phosphate, etc.) is formed on the surface of the electrical steel sheet for the purpose of rust prevention and the like. In order to satisfactorily impart functions such as rust prevention, it is required that the film formed on the surface of the electromagnetic steel sheet is uniform.
The acrylic resin emulsion of the present invention is excellent in stability, and even when it comes into contact with metal ions, the emulsion particles are difficult to bond with metal ions, and aggregation and foreign matter are less likely to occur. According to the treatment liquid used as a binder such as a metal phosphate, a uniform film can be formed.
That is, the acrylic resin emulsion of the present invention is less likely to cause agglomeration or generation of foreign matter even when a large amount of metal salt such as chromate or metal phosphate is blended, and a uniform film can be formed. It can be suitably used for a treatment liquid for electrical steel sheet treatment containing a high concentration of metal salt.

[Method for producing acrylic resin emulsion for metal surface treatment]
The manufacturing method of the acrylic resin emulsion for metal surface treatment of this invention should just manufacture the above-mentioned acrylic resin emulsion, and is not restrict | limited in particular. As a method for producing the acrylic resin emulsion of the present invention, the method for producing an acrylic resin emulsion of the present embodiment described below is preferable.

  The method for producing an acrylic resin emulsion of the present embodiment (hereinafter also referred to as “production method of the present embodiment”) has an oxyalkylene group and an ethylenically unsaturated double bond, and an average addition of oxyalkylene groups. An anionic reactive surfactant (c) having a mole number of 20 or less (that is, the above-mentioned “anionic reactive surfactant (c)”), an oxyalkylene group and an ethylenically unsaturated double bond. And a nonionic reactive surfactant (d) having an average addition mole number of oxyalkylene groups of 25 or more (that is, the above-mentioned “nonionic reactive surfactant (d)”). In the presence of a surfactant, at least a hydrophobic monomer (a) selected from (meth) acrylic acid esters (hereinafter also referred to as “hydrophobic monomer (a)”) and other than a carboxy group Hydrophilic groups and A hydrophilic monomer (b) having a tyrenic unsaturated double bond (hereinafter also referred to as “hydrophilic monomer (b)”) is polymerized to have an acid value of 8.0 mgKOH / g or less. An emulsion polymerization step for obtaining emulsion particles.

Hereafter, the process in the manufacturing method of this embodiment is demonstrated in detail.
In addition, since it is as having described in the item of the above-mentioned acrylic resin emulsion about the specific example of a component used at each process, and a preferable aspect, description is abbreviate | omitted here.

<Emulsion polymerization process>
In the emulsion polymerization step, at least a hydrophobic monomer (a) and a hydrophilic monomer are present in the presence of a reactive surfactant containing an anionic reactive surfactant (c) and a nonionic reactive surfactant (d). This is a step of polymerizing the polymerizable monomer (b) to obtain emulsion particles having an acid value of 8.0 mgKOH / g or less.
In the emulsion polymerization step, at least the hydrophobic monomer (a) and the hydrophilic monomer (b) are combined with the anionic reactive surfactant (c) and the nonionic reactive surfactant (d). An anionic reactive surfactant (c) and a nonionic reactive surfactant (d) are formed by polymerization of at least a hydrophobic monomer (a) and a hydrophilic monomer (b) by polymerization. Immobilized on the surface of the formed resin particles. The immobilized anionic type reactive surfactant (c) and nonionic type reactive surfactant (d) form a hydrated layer on the surface of the resin particles and become emulsion particles. Here, the thickness of the hydrated layer is determined by the average number of added moles of oxyalkylene groups possessed by the reactive surfactant.
In the emulsion polymerization step, a thick hydrated layer can be formed by using a nonionic reactive surfactant (d) having an oxyalkylene group having an average addition mole number of 25 or more. Further, when the anionic group is exposed on the surface of the emulsion particles, it is affected by metal ions, so that aggregation or the like is likely to occur. However, a nonionic reactive surfactant having an oxyalkylene group having an average addition mole number of 25 or more ( d) and an anionic reactive surfactant (c) having an oxyalkylene group having an average added mole number of 20 or less in combination, whereby an anionic group possessed by the anionic reactive surfactant (c) The hydration layer can be formed densely without exposing anions derived from (eg, SO ₃ ⁻ ) to the surface of the emulsion particles. That is, according to the emulsion polymerization step, emulsion particles in which a dense and thick hydrated layer is formed on the surface of the resin particles can be obtained. Emulsion particles having such a hydrated layer are considered to be excellent in stability because micelles are not easily broken or aggregated by metal ions derived from metal salts.

The polymerization method is not particularly limited. For example, at least a hydrophobic monomer (a) and a hydrophilic monomer (in a reaction vessel equipped with a thermometer, a stirring rod, a reflux condenser, a dropping funnel, etc. b), an anionic reactive surfactant (c), a nonionic reactive surfactant (d), and an aqueous medium such as water, and after raising the temperature in the reaction vessel, a polymerization initiator, A method of proceeding an emulsion polymerization reaction by adding a reducing agent or the like (so-called batch charging method), and at least an anionic reactive surfactant (c) and a nonionic reactive surfactant (d) in a reaction vessel And an aqueous medium such as water, the temperature inside the reaction vessel is raised, and then monomer components [at least the hydrophobic monomer (a) and the hydrophilic monomer (b)] are added dropwise, as appropriate. , A polymerization initiator, a reducing agent and the like to proceed with the emulsion polymerization reaction (so-called monomer) Dropping method), the monomer component was previously emulsified with at least an anionic reactive surfactant (c), a nonionic reactive surfactant (d) and an aqueous medium such as water to obtain a pre-emulsion. Thereafter, a method in which the obtained pre-emulsion is dropped into a reaction vessel and a polymerization initiator, a reducing agent, etc. are added as appropriate to cause the emulsion polymerization reaction to proceed (a so-called emulsion monomer dropping method), and the like can be mentioned.
Among these, as a polymerization method, the emulsion monomer dropping method is preferable from the viewpoint of industrial productivity.

  The polymerization temperature is, for example, 50 ° C to 80 ° C, preferably 60 ° C to 80 ° C. The polymerization time is, for example, 6 hours to 12 hours, preferably 6 hours to 8 hours.

The amount of the hydrophobic monomer (a) used is preferably based on 100 parts by mass of the total amount of monomers as raw materials from the viewpoint of the flexibility and fastness of the resulting film and the stability of the acrylic resin emulsion. Is 40 parts by mass to 99 parts by mass, more preferably 50 parts by mass to 95 parts by mass, and still more preferably 60 parts by mass to 90 parts by mass.
The amount of the hydrophilic monomer (b) used is preferably 1 mass with respect to 100 mass parts of the total amount of monomers as raw materials, from the viewpoint of the hydrophilicity of the resulting film and the stability of the acrylic resin emulsion. Part to 50 parts by weight, more preferably 5 parts by weight to 30 parts by weight, and still more preferably 10 parts by weight to 20 parts by weight.
In the emulsion polymerization step, when using the other monomers described above, the amount of the other monomers used is based on the total amount of monomers as raw materials of 100 parts by mass from the viewpoint of the hydrophilicity of the resulting film. The amount is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably 30 parts by mass or less.

The anionic reactive surfactant (c) is preferably used in an amount of 100 parts by mass based on the total amount of monomers as raw materials, from the viewpoint of the fastness of the resulting coating and the stability of the acrylic resin emulsion. It is 1 mass part-20 mass parts, More preferably, it is 5 mass parts-10 mass parts.
The nonionic reactive surfactant (d) is preferably used in an amount of 100 parts by mass based on the total amount of monomers as raw materials, from the viewpoint of the fastness of the resulting coating and the stability of the acrylic resin emulsion. It is 1 mass part-50 mass parts, More preferably, it is 10 mass parts-30 mass parts.
In the emulsion polymerization step, when the above-described nonionic reactive surfactant (e) is used, the amount of the nonionic reactive surfactant (e) used depends on the fastness of the resulting coating and the stability of the acrylic resin emulsion. From a viewpoint of property, Preferably it is 1 mass part-10 mass parts with respect to 100 mass parts of total amounts of the monomer which is a raw material, More preferably, they are 3 mass parts-8 mass parts.

  In the emulsion polymerization step, when the above-described nonionic reactive surfactant (e) is used, an anionic reactive surfactant (c), a nonionic reactive surfactant (d), and a nonionic reaction The active surfactant (e) is used in an amount of 5 parts by mass to 10 parts by mass, 10 parts by mass to 20 parts by mass, and 1 part by mass to 10 parts by mass with respect to 100 parts by mass of the total amount of monomers as raw materials. It is preferable to do.

  In the emulsion polymerization step, various additives such as a polymerization initiator, a reducing agent, a chain transfer agent, and a pH adjuster may be used.

(Polymerization initiator)
Any polymerization initiator can be used without particular limitation as long as it can be used for ordinary emulsion polymerization. Examples of the polymerization initiator include persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate, organic peroxides such as t-butyl hydroperoxide and cumene hydroperoxide, and hydrogen peroxide.
When using a polymerization initiator in an emulsion polymerization process, a polymerization initiator may be used individually by 1 type, and may be used in combination of 2 or more type.

  The polymerization initiator is used in an amount usually used. The amount of the polymerization initiator used is, for example, 0.1 parts by mass to 2 parts by mass, preferably 0.3 parts by mass to 1.5 parts by mass with respect to 100 parts by mass of the total amount of monomers as raw materials. It is.

(Reducing agent)
In the emulsion polymerization step, a reducing agent can be used together with the above polymerization initiator.
Examples of the reducing agent include sodium metabisulfite, sodium sulfite, sodium hydrogen sulfite, sodium pyrosulfite, sodium pyrophosphate, thioglycolic acid, sodium thiosulfate, ascorbic acid, tartaric acid, citric acid, and glucose.
When using a reducing agent in an emulsion polymerization process, a reducing agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  The reducing agent is used in an amount usually used. The amount of the reducing agent used is, for example, 0.1 parts by mass to 2 parts by mass, preferably 0.3 parts by mass to 1.5 parts by mass with respect to 100 parts by mass of the total amount of monomers as raw materials. is there.

  The manufacturing method of this embodiment may have processes other than an emulsion polymerization process as needed.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the following examples as long as the gist thereof is not exceeded.

[Measurement of average particle size]
The average particle diameter of the emulsion particles in the acrylic resin emulsion produced in this example was “New Experimental Chemistry Course 4 Basic Technology 3 Hikari (II)” edited by The Chemical Society of Japan, pages 725 to 741 (July 1977). The dynamic light scattering method described in 20th Maruzen Co., Ltd.). The specific method is as follows.
The acrylic resin emulsion was diluted with distilled water and sufficiently stirred and mixed. Then, 5 ml was collected in a 10 mm square glass cell using a Pasteur pipette, and this was collected using a dynamic light scattering photometer “Zetasizer 1000HS” [Sysmex ( The product was set up]. After adjusting the concentration of the acrylic resin emulsion dilution so that the decay rate count rate is 150 Cps to 200 Cps, the results measured under the conditions of a measurement temperature of 25 ° C. ± 1 ° C. and a light scattering angle of 90 ° are processed by a computer. Thus, the average particle size of the emulsion particles was obtained.

[Measurement of acid value]
The acid value of the emulsion particles in the acrylic resin emulsion produced in this example was determined according to the following (1) to (6).
(1) About 20 g of acrylic resin emulsion was precisely weighed in a 200 mL beaker.
(2) The acrylic resin emulsion was diluted to 100 mL to 150 mL using deionized water.
(3) A suitable amount of a cation exchange resin [Amberlite (registered trademark) IR-120B] was added to the diluted acrylic resin emulsion, and the pH of the resulting mixture was adjusted to 3 or less.
(4) Using a 100-mesh filter cloth (opening: 224 μm), the cation exchange resin was removed from the pH-adjusted mixture, washed with deionized water until the turbidity of the washing solution disappeared, and the filtrate was collected. . In addition, the presence or absence of turbidity in the washing solution is determined visually.
(5) Conductivity titration of the collected filtrate was performed using a sodium hydroxide solution (0.5 mol / L, volumetric analysis specific solution), and the titration amount was measured.
(6) The acid value was calculated by the following formula. In addition, 0.5 in a formula shows the density | concentration (mol / L) of a sodium hydroxide solution.
Acid value (mgKOH / g) = (0.5 × f × X × 56.1) / (W × NV)
f: titer of 0.5 mol / L sodium hydroxide solution X: titration (unit: mL)
W: Amount of acrylic resin emulsion collected (g)
NV: Nonvolatile content per gram of acrylic resin emulsion (g)

[Manufacture of acrylic resin emulsion]
[Example 1]
In a reaction vessel equipped with a thermometer, a stirring bar, a reflux condenser, and a dropping funnel, 43.3 parts by mass of deionized exchange water was charged, and the temperature in the reaction vessel was raised to 58 ° C. while purging with nitrogen.
On the other hand, in another container, 76.8 parts by mass of deionized water and “AQUALON (registered trademark) KH-10” which is an anionic reactive surfactant (c) [active ingredient: polyoxyethylene-1- (Allyloxymethyl) alkyl ether ammonium sulfate [type of oxyalkylene group: oxyethylene group (EO), average addition mole number: 10], active ingredient: 99 mass%, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] 5.1 mass Parts (active ingredient: 5.0 parts by mass) and “Adekalia Soap (registered trademark) ER-30” which is a nonionic reactive surfactant (d) [active ingredient: polyoxyethylene-1- (allyloxy) Methyl) alkyl ether [type of oxyalkylene group: oxyethylene group (EO), average number of added moles: 30], active ingredient: 65% by mass, manufactured by ADEKA Corp.] 17.5 parts by mass Active ingredient: 11.4 parts by mass) and “Adekalia Soap (registered trademark) ER-10” which is a nonionic reactive surfactant (e) [active ingredient: polyoxyethylene-1- (allyloxymethyl) After adding and stirring 5.7 parts by mass of alkyl ether [type of oxyalkylene group: oxyethylene group (EO), average number of added moles: 10], active ingredient: 100% by mass, manufactured by ADEKA Co., Ltd. Furthermore, 33.7 parts by mass of butyl acrylate [BA: butyl acrylate, hydrophobic monomer (a)] and 23.3 parts by mass of methyl methacrylate [MMA: methyl methacrylate, hydrophobic monomer (a)] And 3.0 parts by mass of ethylene glycol dimethacrylate [EGDM: ethylene glycol dimethacrylate, hydrophobic monomer (a)], 2-hydroxyethyl methacrylate [2HEMA: 2-hydroxyethyl methacryla te, hydrophilic monomer (b)]) 10.0 parts by mass and 30.0 parts by mass of styrene (St, other monomers) were added and stirred to prepare a pre-emulsion.
Next, while maintaining the internal temperature of the reaction vessel at 58 ° C., 3% by mass (6.2 parts by mass) of the pre-emulsion prepared above was added into the reaction vessel, and then a 10% by mass ammonium persulfate aqueous solution. 0.14 parts by mass and 0.14 parts by mass of a 10% by mass aqueous sodium metabisulfite solution were added to initiate the emulsion polymerization reaction.
After the internal temperature of the reaction vessel reached 62 ° C., the remaining total amount of the pre-emulsion prepared above, 0.36 parts by mass of a 2.5% by mass ammonium persulfate aqueous solution (polymerization initiator), and 2.5% by mass An aqueous solution of sodium metabisulfite (reducing agent) 0.36 parts by mass was uniformly added successively over 4 hours to effect emulsion polymerization. After completion of the sequential addition, the obtained emulsion polymer was aged at 62 ° C. for 2 hours and then cooled to room temperature to obtain an acrylic resin emulsion having a pH of 2.3. Solid content of the obtained acrylic resin emulsion was 42 mass%. Moreover, the average particle diameter of the emulsion particles was 99.7 nm, and the acid value was 0 mgKOH / g.

[Example 2]
In Example 1, instead of 5.1 parts by mass (active ingredient: 5.0 parts by mass) of “AQUALON (registered trademark) KH-10” as the anionic reactive surfactant (c), “Adekaria soap” (Registered trademark) SR-20 ”[active ingredient: polyoxyethylene-1- (allyloxymethyl) alkyl ether ammonium sulfate [type of oxyalkylene group: oxyethylene group (EO), average number of added moles: 20], active ingredient : 100% by mass, manufactured by ADEKA Corporation] An acrylic resin emulsion having a pH of 2.3 was obtained in the same manner as in Example 1 except that 5.0 parts by mass was used. Solid content of the obtained acrylic resin emulsion was 42 mass%. Moreover, the average particle diameter of the emulsion particles was 123.4 nm, and the acid value was 0 mgKOH / g.

Example 3
In Example 1, instead of 17.5 parts by mass (active ingredient: 11.4 parts by mass) of “Adekalia Soap (registered trademark) ER-30” as the nonionic reactive surfactant (d), “Aqualon (Registered trademark) RN-50 "[active ingredient: polyoxyethylene nonylpropenyl phenyl ether [type of oxyalkylene group: oxyethylene group (EO), average addition mole number: 50], active ingredient: 65% by mass, first Kogyo Seiyaku Co., Ltd.] An acrylic resin emulsion having a pH of 2.3 was obtained in the same manner as in Example 1 except that 17.5 parts by mass (active ingredient: 11.4 parts by mass) was used. Solid content of the obtained acrylic resin emulsion was 42 mass%. Moreover, the average particle diameter of the emulsion particles was 125.7 nm, and the acid value was 0 mgKOH / g.

Example 4
In Example 1, instead of 17.5 parts by mass (active ingredient: 11.4 parts by mass) of “Adekaria Soap (registered trademark) ER-30” as the nonionic reactive surfactant (d), “Latemul (Registered trademark) PD-430S ”[active ingredient: polyoxyalkylene alkenyl ether [oxyalkylene group type: oxyethylene group (EO) / oxybutylene group (BO), average number of added moles: 30]], active ingredient: 25 % By mass, manufactured by Kao Corporation] An acrylic resin emulsion having a pH of 2.3 was obtained in the same manner as in Example 1 except that 45.6 parts by mass (active ingredient: 11.4 parts by mass) was used. The solid content of the obtained acrylic resin emulsion was 40% by mass. Moreover, the average particle diameter of the emulsion particles was 116.0 nm, and the acid value was 0 mgKOH / g.

Example 5
The use amount of “AQUALON (registered trademark) KH-10” which is an anionic reactive surfactant (c) is changed from 5.1 parts by mass (active ingredient: 5.0 parts by mass) to 2.5 parts by mass (effective (Component: 2.5 parts by mass) An acrylic resin emulsion having a pH of 2.3 was obtained in the same manner as in Example 1 except that the component was changed to 2.5 parts by mass. Solid content of the obtained acrylic resin emulsion was 42 mass%. Moreover, the average particle diameter of the emulsion particles was 140.9 nm, and the acid value was 0 mgKOH / g.

Example 6
The amount of "Adekalia Soap (registered trademark) ER-30" that is a nonionic reactive surfactant (d) is used from 17.5 parts by mass (active ingredient: 11.4 parts by mass) to 8.8 parts by mass. An acrylic resin emulsion having a pH of 2.3 was obtained in the same manner as in Example 1 except that the active ingredient was changed to 5.7 parts by mass. Solid content of the obtained acrylic resin emulsion was 41 mass%. Moreover, the average particle diameter of the emulsion particles was 122.0 nm, and the acid value was 0 mgKOH / g.

Example 7
In Example 1, an acrylic resin emulsion having a pH of 2.3 was obtained in the same manner as in Example 1 except that the nonionic reactive surfactant (e) was not used. Solid content of the obtained acrylic resin emulsion was 41 mass%. Moreover, the average particle diameter of the emulsion particles was 122.7 nm, and the acid value was 0 mgKOH / g.

Example 8
The amount of butyl acrylate (BA) used is changed from 33.7 parts by mass to 13.7 parts by mass, and the amount of styrene (St) used is changed from 30.0 parts by mass to 50.0 parts by mass. Except that, an acrylic resin emulsion having a pH of 2.3 was obtained in the same manner as in Example 7. Solid content of the obtained acrylic resin emulsion was 41 mass%. Moreover, the average particle diameter of the emulsion particles was 110.8 nm, and the acid value was 0 mgKOH / g.

Example 9
The amount of butyl acrylate (BA) used was changed from 33.7 parts by weight to 48.7 parts by weight, and the amount of styrene (St) used was changed from 30.0 parts by weight to 15.0 parts by weight. Except that, an acrylic resin emulsion having a pH of 2.3 was obtained in the same manner as in Example 7. Solid content of the obtained acrylic resin emulsion was 41 mass%. Moreover, the average particle diameter of the emulsion particles was 102.2 nm, and the acid value was 0 mgKOH / g.

Example 10
The amount of methyl methacrylate (MMA) was changed from 23.3 parts by mass to 53.3 parts by mass, and styrene (St) was not used. .3 acrylic resin emulsion was obtained. Solid content of the obtained acrylic resin emulsion was 42 mass%. Moreover, the average particle diameter of the emulsion particles was 115.5 nm, and the acid value was 0 mgKOH / g.

Example 11
The amount of butyl acrylate (BA) used was changed from 33.7 parts by weight to 34.1 parts by weight, and the amount of methyl methacrylate (MMA) used was changed from 23.3 parts by weight to 21.9 parts by weight. In addition, 1.0 part by mass of methacrylic acid (MAA, other monomer) was used, and the amount of “AQUALON (registered trademark) KH-10” that is an anionic reactive surfactant (c) was changed to 5. It is changed from 1 part by weight (active ingredient: 5.0 parts by weight) to 10.1 parts by weight (active ingredient: 10.0 parts by weight), and nonionic surfactant (d) “ADEKA rear soap ( The amount of use of “registered trademark” ER-30 ”was changed from 17.5 parts by mass (active ingredient: 11.4 parts by mass) to 8.8 parts by mass (active ingredient: 5.7 parts by mass). In the same manner as in Example 1, an acrylic resin emulsion having a pH of 2.3 was obtained. Solid content of the obtained acrylic resin emulsion was 42 mass%. Moreover, the average particle diameter of the emulsion particles was 120.0 nm, and the acid value was 6.5 mgKOH / g.

[Comparative Example 1]
In Example 1, instead of 5.1 parts by mass (active ingredient: 5.0 parts by mass) of “AQUALON (registered trademark) KH-10” which is an anionic reactive surfactant (c), anionic type reactivity “Adekalia Soap (registered trademark) SR-3025” which is an anionic reactive surfactant not corresponding to the surfactant (1) [active ingredient: ammonium polyoxyethylene-1- (allyloxymethyl) alkyl ether sulfate [oxy Kind of alkylene group: oxyethylene group (EO), average added mole number: 30], active ingredient: 25% by mass, manufactured by ADEKA Corporation 20 parts by mass (active ingredient: 5.0 parts by mass) Except for the above, an acrylic resin emulsion having a pH of 2.3 was obtained in the same manner as in Example 1. Solid content of the obtained acrylic resin emulsion was 42 mass%. Moreover, the average particle diameter of the emulsion particles was 124.2 nm, and the acid value was 0 mgKOH / g.

[Comparative Example 2]
In Example 1, an acrylic resin emulsion having a pH of 2.3 was obtained in the same manner as in Example 1 except that the anionic reactive surfactant (c) was not used. Solid content of the obtained acrylic resin emulsion was 41 mass%. Moreover, the average particle diameter of the emulsion particles was 68.3 nm, and the acid value was 0 mgKOH / g.

[Comparative Example 3]
The use amount of “AQUALON (registered trademark) KH-10” which is an anionic reactive surfactant (c) is changed from 5.1 parts by mass (active ingredient: 5.0 parts by mass) to 20.2 parts by mass (effective) Component: 20.0 parts by mass) and the same procedure as in Example 1 except that the nonionic reactive surfactant (d) and the nonionic reactive surfactant (e) were not used. An acrylic resin emulsion having a pH of 2.3 was obtained. Solid content of the obtained acrylic resin emulsion was 42 mass%. Moreover, the average particle diameter of the emulsion particles was 85.7 nm, and the acid value was 0 mgKOH / g.

[Comparative Example 4]
In Example 1, Example 1 was used except that the anionic reactive surfactant (c), the nonionic reactive surfactant (d), and the nonionic reactive surfactant (e) were not used. Similarly, an acrylic resin emulsion having a pH of 2.3 was obtained. Solid content of the obtained acrylic resin emulsion was 38 mass%. Moreover, the average particle diameter of the emulsion particles was 412.2 nm, and the acid value was 0 mgKOH / g.

[Comparative Example 5]
In Example 1, instead of 5.1 parts by mass (active ingredient: 5.0 parts by mass) of “AQUALON (registered trademark) KH-10” which is an anionic reactive surfactant (c), an anionic non-reactive "Hytenol (registered trademark) NF-13" which is a functional surfactant [active ingredient: polyoxyethylene distyryl phenyl ether sulfate ammonium salt [type of oxyalkylene group: oxyethylene group (EO), average number of added moles: 13], active ingredient: 98% by mass, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.] 1.1 parts by mass (active ingredient: 1.1 parts by mass), which is a nonionic reactive surfactant (d). Instead of 17.5 parts by mass (active ingredient: 11.4 parts by mass) of Adekaria Soap (registered trademark) ER-30, "Neugen (registered trademark) EM-250, which is a nonionic non-reactive surfactant" [Active ingredient: polyoxyethylene nonylphenyl ether [type of oxyalkylene group: oxyethylene group (EO), average added mole number: 50], active ingredient: 100% by mass, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] 4 parts by mass, and instead of 5.7 parts by mass of “Adekaria Soap (registered trademark) ER-10” which is a nonionic reactive surfactant (e), a nonionic nonreactive surfactant is used. Certain "Neugen (registered trademark) EA-130T" [active ingredient: polyoxyethylene nonylphenyl ether [type of oxyalkylene group: oxyethylene group (EO), average number of added moles: 20], active ingredient: 100% by mass, Daiichi Kogyo Seiyaku Co., Ltd.] An acrylic resin emulsion having a pH of 2.3 was obtained in the same manner as in Example 1 except that 10.3 parts by mass were used. Solid content of the obtained acrylic resin emulsion was 42 mass%. Moreover, the average particle diameter of the emulsion particles was 113.6 nm, and the acid value was 0 mgKOH / g.

[Comparative Example 6]
The amount of butyl acrylate (BA) was changed from 34.1 parts by mass to 35.7 parts by mass, and the amount of methyl methacrylate (MMA) was changed from 21.9 parts by mass to 16.3 parts by mass. And the acrylic resin emulsion of pH 2.3 was obtained like Example 11 except having changed the usage-amount of methacrylic acid (MAA) from 1.0 mass part to 5.0 mass parts. Solid content of the obtained acrylic resin emulsion was 42 mass%. Moreover, the average particle diameter of the emulsion particles was 118.0 nm, and the acid value was 32.6 mgKOH / g.

[Evaluation]
For the acrylic resin emulsions of Examples 1 to 11 and Comparative Examples 1 to 6, the stability was evaluated by the following method.
5 parts by mass of an acrylic resin emulsion, 10 parts by mass of an aluminum phosphate 50% by mass aqueous solution, and 1 part by mass of glycerin were weighed into a reagent bottle, and the reagent bottle was shaken up and down 10 times. The state of the liquid after shaking was visually observed, and the stability of the acrylic resin emulsion was evaluated according to the following evaluation criteria. The results are shown in Tables 1 and 2.
Those practically acceptable are classified into “AA”, “A”, and “B”.

-Evaluation criteria-
AA: No foreign matters or lumps are observed, and no separation occurs.
A: Some foreign matter is observed, but aggregation or separation does not occur.
B: A large amount of foreign matter was observed, and separation occurred over time.
C: A lot of lumps were observed, and the fluidity was lost (gelled) over time.

In Tables 1 and 2, in the column of “kind” of the reactive surfactant, only the symbol and numeric part of the product name are described. For example, “AQUALON (registered trademark) KH-10” is represented as “KH-10”.
In Tables 1 and 2, the “content” column of the reactive surfactant indicates the type of oxyalkylene group and the average number of added moles of the reactive surfactant.
In Tables 1 and 2, “-” means that the corresponding component is not blended.

  As shown in Table 1, a hydrophilic monomer having a hydrophobic structural unit (A) derived from a (meth) acrylic acid ester monomer, a hydrophilic group other than a carboxy group, and an ethylenically unsaturated double bond An anionic reactive surfactant having a hydrophilic structural unit (B) derived from the above, an oxyalkylene group and an ethylenically unsaturated double bond, and an average addition mole number of the oxyalkylene group of 20 or less A structure derived from a nonionic reactive surfactant having a derived structural unit (C), an oxyalkylene group and an ethylenically unsaturated double bond, and an average addition mole number of the oxyalkylene group of 25 or more The acrylic resin emulsions of Examples 1 to 11 in which emulsion particles having a unit (D) and an acid value of 8.0 mgKOH / g or less are dispersed in an aqueous medium, Shift was also excellent in stability.

  A structural unit (E) derived from a nonionic reactive surfactant in which the emulsion particles have an oxyalkylene group and an ethylenically unsaturated double bond, and the average added mole number of the oxyalkylene group is 20 or less. Furthermore, the acrylic resin emulsion (for example, Example 1) which has has the tendency which was more excellent in stability compared with the acrylic resin emulsion (for example, Example 7) which does not further have a structural unit (E).

  An acrylic resin emulsion in which the oxyalkylene group in the structural unit (C) derived from the anionic reactive surfactant and the structural unit (D) derived from the nonionic reactive surfactant is an oxyethylene group (for example, Examples 1) is more stable than an acrylic resin emulsion in which the oxyalkylene group in the structural unit (D) derived from the nonionic reactive surfactant is an oxyethylene group and an oxybutylene group (for example, Example 4). The property was remarkably excellent.

  The proportion of the structural unit (C) derived from the anionic reactive surfactant is 5 to 10 parts by mass with respect to a total of 100 parts by mass of the structural units derived from all monomers forming the emulsion particles. And the proportion of the structural unit (D) derived from the nonionic reactive surfactant is 100 parts by mass in total of the structural units derived from all monomers forming the emulsion particles, The acrylic resin emulsion (for example, Example 1) in the range of 10 to 30 parts by mass is compared with the acrylic resin emulsion (for example, Example 5) in which the proportion of the structural unit (C) is outside the above range. The stability was remarkably excellent. Moreover, the tendency for it to be more excellent in stability was recognized compared with the acrylic resin emulsion (for example, Example 6) from which the ratio of a structural unit (D) remove | deviates from the said range.

On the other hand, instead of the structural unit (C) derived from an anionic reactive surfactant having an oxyalkylene group and an ethylenically unsaturated double bond, and having an average addition mole number of the oxyalkylene group of 20 or less An acrylic resin emulsion having a structural unit derived from an anionic reactive surfactant having an oxyalkylene group and an ethylenically unsaturated double bond, and an average addition mole number of the oxyalkylene group exceeding 20 (for example, Comparative Example 1) was poor in stability.
An acrylic resin emulsion having a structural unit (D) derived from a nonionic reactive surfactant but having no structural unit (C) derived from an anionic reactive surfactant (for example, Comparative Example 2), anionic type An acrylic resin emulsion having a structural unit (C) derived from a reactive surfactant, but not having a structural unit (D) derived from a nonionic reactive surfactant (for example, Comparative Example 3), and an anionic reaction As for the acrylic resin emulsion (for example, comparative example 4) which does not have both the structural unit (C) derived from a surfactant, and the structural unit (D) derived from a nonionic reactive surfactant, all have stability. It was bad.
An acrylic resin emulsion (for example, Comparative Example 5) having a structural unit derived from a non-reactive surfactant instead of a structural unit derived from a reactive surfactant has poor stability.
The acrylic resin emulsion (for example, Comparative Example 6) in which the acid value of the emulsion particles exceeds 8.0 mgKOH / g has poor stability.

Claims (8)

A hydrophobic structural unit (A) derived from a (meth) acrylic acid ester monomer;
A hydrophilic structural unit (B) derived from a hydrophilic monomer other than a carboxy group and a hydrophilic monomer having an ethylenically unsaturated double bond;
A structural unit (C) derived from an anionic reactive surfactant having an oxyalkylene group and an ethylenically unsaturated double bond and having an average addition mole number of the oxyalkylene group of 20 or less;
A structural unit (D) derived from a nonionic reactive surfactant having an oxyalkylene group and an ethylenically unsaturated double bond, and having an average addition mole number of the oxyalkylene group of 25 or more;
And an acrylic resin emulsion for metal surface treatment in which emulsion particles having an acid value of 8.0 mgKOH / g or less are dispersed in an aqueous medium.   The acrylic resin emulsion for metal surface treatment according to claim 1, wherein the oxyalkylene group in the structural unit (C) and the structural unit (D) is an oxyethylene group.   The proportion of the structural unit (C) is 5 to 10 parts by mass with respect to a total of 100 parts by mass of the structural units derived from all monomers forming the emulsion particles, and the structural unit The ratio of (D) is 10 to 30 parts by mass with respect to a total of 100 parts by mass of structural units derived from all monomers forming the emulsion particles. Acrylic resin emulsion for metal surface treatment.   Structural unit (E) derived from a nonionic reactive surfactant in which the emulsion particles have an oxyalkylene group and an ethylenically unsaturated double bond, and the average added mole number of the oxyalkylene group is 20 or less The acrylic resin emulsion for metal surface treatment according to any one of claims 1 to 3, further comprising:   The acrylic resin emulsion for metal surface treatment according to claim 4, wherein the oxyalkylene group in the structural unit (E) is an oxyethylene group.   The proportion of the structural unit (C) is 5 parts by mass to 10 parts by mass with respect to a total of 100 parts by mass of the structural units derived from all monomers forming the emulsion particles, and the structural unit (D ) Is 10 parts by mass to 20 parts by mass with respect to a total of 100 parts by mass of the structural units derived from all monomers forming the emulsion particles, and the ratio of the structural unit (E) The metal surface treatment according to claim 4 or 5, wherein is 1 to 10 parts by mass with respect to a total of 100 parts by mass of structural units derived from all monomers forming the emulsion particles. Acrylic resin emulsion.   The acrylic resin emulsion for metal surface treatment of any one of Claims 1-6 used for an electromagnetic steel plate process. An anionic reactive surfactant (c) having an oxyalkylene group and an ethylenically unsaturated double bond and an average addition mole number of the oxyalkylene group of 20 or less; an oxyalkylene group and an ethylenically unsaturated group In the presence of a reactive surfactant comprising a nonionic reactive surfactant (d) having a double bond and an average addition mole number of oxyalkylene group of 25 or more,
Polymerize at least a hydrophobic monomer (a) selected from (meth) acrylic acid esters and a hydrophilic monomer (b) having a hydrophilic group other than a carboxy group and an ethylenically unsaturated double bond A method for producing an acrylic resin emulsion for metal surface treatment, comprising an emulsion polymerization step of obtaining emulsion particles having an acid value of 8.0 mgKOH / g or less.