JP2006233123A - Manufacturing method of water-dispersible acrylic polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous acrylic adhesive composition excellent in both adhesive power and holding power and especially excellent in the adhesion to a rough surface, and also to provide a manufacturing method of the same. <P>SOLUTION: The manufacturing method of water-dispersible acrylic polymer comprises the emulsion polymerization of a polymerizable monomer component containing a (meth)acrylate in an aqueous medium. The method is characterized by the followings: i.e., the amount of generated radicals, which can be calculated based on the amount of a polymerization initiator to be used, is controlled to 2-150×10<SP>-13</SP>mol/L for the whole amount of the monomer component, and the average molecular weight of the soluble portion in THF (tetrahydrofurane) of the aqueous dispersion prepared is 300,000 or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a water-dispersed acrylic polymer. More specifically, the present invention relates to a production method for obtaining a water-dispersed acrylic polymer having a linear structure and a high molecular weight polymer by emulsion polymerization.

  In recent years, environmental problems have been highlighted, and in various fields, aqueous resins with less addition to the environment are attracting attention. Compared with a solvent-type resin produced using an organic solvent, emulsion polymerization carried out in an aqueous medium does not require an organic solvent, and is used for producing various polymers as a method for producing an environmentally friendly resin. Examples of polymers that can be produced by this emulsion polymerization include water-dispersed acrylic polymers obtained by polymerizing various ethylenically unsaturated monomers.

  In general, the water-dispersed acrylic polymer obtained by emulsion polymerization has a side reaction such as a hydrogen abstraction reaction of a polymer chain, that is, a branching reaction, due to excessive radicals in the reaction system, and the polymer chain has a branched structure. End up. This branching reaction makes it difficult for the particles to fuse with each other, resulting in a decrease in film formability, and the strength of the coating film becomes lower than the apparent molecular weight. One of the problems of water-dispersed acrylic polymers is to improve the film formability and increase the film strength.

  As a method of improving the low film formability, a plasticizer (film-forming aid) that plasticizes the polymer is added to hard polymer particles to improve the fusion between the polymer particles. Is generally used. However, in this method, since the coating is plasticized, it is difficult to develop strength.

Also proposed is a method for improving the fusion property between polymer particles by making the particle shape of the polymer particles “multilayer structure particles” composed of a hard polymer and a soft polymer. (For example, refer to Patent Document 1). However, even in this method, sufficient film formability cannot be obtained and strength is not exhibited.

JP 2003-147150 A

  Accordingly, an object of the present invention is to provide a method for producing a water-dispersed acrylic polymer that suppresses a branching reaction at the time of emulsion polymerization, improves film formability, and has high coating strength.

The inventors obtained the following knowledge as a result of intensive studies to solve the above problems.
(1) By controlling the amount of radical generation calculated from the amount of polymerization initiator used to 2 to 150 × 10 ⁻¹³ mol / l per minute for all monomer components, the branching reaction is suppressed. The obtained polymer chain has a linear structure, and the fusion property between particles is improved, that is, the film forming property is improved.
(2) When the weight-average molecular weight of the water-dispersed acrylic polymer dissolved in THF is 300,000 or more, the coating strength is increased.

The present invention is based on such knowledge.
That is, the present invention is a production method in which a polymerizable monomer component containing (meth) acrylates is emulsion-polymerized in the presence of an aqueous medium, and the radical generation amount calculated from the amount of polymerization initiator used is calculated. The total monomer component is controlled to 2 to 150 × 10 ⁻¹³ mol / l per minute, and the weight average molecular weight of the obtained aqueous dispersion in THF is 300,000 or more. A method for producing a water-dispersed acrylic polymer is provided.

  The present invention is suitable as a method for producing a water-dispersed acrylic polymer having high film strength by improving the film formability by making the polymer chain a linear structure with few branches and further increasing the molecular weight of the polymer. .

First, the production method of the present invention, that is, the amount of radical generation during emulsion polymerization, the amount of radical generation calculated from the amount of polymerization initiator used is 2 to 150 minutes per minute for all monomer components. By controlling to × 10 ⁻¹³ mol / l, the branching reaction is suppressed, and the resulting polymer chain has a linear structure. The radical generation amount is more preferably 5 to 120 × 10 ⁻¹³ mol / l per minute, and further 10 to 100 × 10 ⁻¹³ mol / l further increases the polymerization stability and the branching reaction of the polymer. This is particularly preferable because it is suppressed and the film formability is improved. The “radical generation amount calculated from the amount of polymerization initiator to be used” referred to here is the concentration of radicals generated per minute with respect to all monomers determined by the calculation formula described in the examples below.

If the amount of radicals calculated in calculation exceeds 150 × 10 ⁻¹³ mol / l per minute, side reactions, that is, branching reactions, are likely to occur due to radicals that are excessively present in the reaction system. Therefore, when the polymer chain is branched, the film formability is lowered and the film strength is lowered. On the other hand, if the radical concentration is less than 2 × 10 ⁻¹³ mol / l / min, the concentration of radicals generated is too low and the reaction does not proceed.

  Moreover, a radical polymerization initiator is used as a polymerization initiator used with the manufacturing method of this invention. The type of radical polymerization initiator is not particularly limited, but a persulfate-based or azo-based polymerization initiator is preferable because it is difficult to cause a branching reaction during polymerization.

  The reaction temperature of the emulsion polymerization is not particularly limited, but among these, it is preferably performed in the range of 30 to 90 ° C. When it is lower than 30 ° C., radicals are not easily generated, and the polymerization stability is lowered. On the other hand, when the temperature exceeds 90 ° C., it is difficult to carry out the reaction because the amount of the initiator becomes very small if the radical concentration during the reaction is controlled within the above-mentioned range. Moreover, since it is easy to control the radical density | concentration during superposition | polymerization in the above-mentioned range, it is especially preferable to react below the 10-hour half life temperature of the polymerization initiator used for reaction.

  In addition, controlling the radical concentration during the polymerization within the above-mentioned range suppresses the branching reaction during the polymerization, so that the gel fraction of the film formed from the acrylic polymer obtained is controlled to 20% by weight or less. Can do. In order to improve the film formability, the gel fraction is preferably as low as possible, specifically 10% or less. Furthermore, it is particularly preferable to control to 5% by weight or less. The gel fraction used by this invention means the ratio of the insoluble matter with respect to toluene of the film formed from an acrylic polymer. A gel fraction is based on the numerical value calculated | required by the measuring method and formula described in the postscript Example.

  When the gel fraction of the coating exceeds 20%, the linear structure of the polymer chain is impaired, that is, the degree of branching of the polymer chain is increased, the fusion property between the particles is deteriorated, that is, the film forming property is decreased, and the coating Strength decreases.

  Further, the acrylic polymer has higher film strength as the molecular weight is higher. The production method of the present invention is also a method capable of easily increasing the molecular weight of a polymer. When the weight-average molecular weight of the obtained polymer measured in THF by GPC is 300,000 or more, the coating strength is increased. Furthermore, if it is 350,000 or more, the film strength is further improved, which is preferable. GPC was measured by dissolving the polymer completely in THF so that the concentration was 0.4%, and removing insoluble matter by filtration, and then measuring only the dissolved matter.

  The monomer component used in the method for producing the water-dispersed acrylic polymer of the present invention is not particularly limited, and a monomer containing (meth) acrylate, a monomer containing a carboxyl group, or any other monomer. The mer can be used in any proportion. Among them, it is preferable to use a monomer containing (meth) acrylate and having an alkyl group having 1 to 12 carbon atoms as a main component because polymerization is easy.

  Further, the glass transition temperature (hereinafter referred to as Tg) of the water-dispersed acrylic polymer film obtained by the method for producing the water-dispersed acrylic polymer of the present invention is not particularly limited, and the above monomer may be used depending on the application. Can be combined at any ratio, and Tg can be at any temperature.

  Moreover, you may adjust the molecular weight of a polymer according to a use with the manufacturing method of the water-dispersed acrylic polymer of this invention. In that case, a compound having chain transfer ability can be used as a molecular weight adjusting agent when the monomer component is emulsion-polymerized.

  Next, in the method for producing a water-dispersed acrylic polymer of the present invention, when the monomer component is emulsion-polymerized in an aqueous medium, it can be polymerized using an emulsifier or other dispersion stabilizer. Among them, it is preferable to use an emulsifier having a polymerizable unsaturated group in the molecule, which is generally called “reactive emulsifier”, because the water resistance of the coating is improved in addition to the polymerization stability.

  Moreover, as a manufacturing method of the acryl-type polymer of this invention, the following methods (1)-(3) are mentioned, for example. In general, the production method for obtaining a water-dispersed acrylic polymer by emulsion polymerization is as follows: (1) Polymerization by mixing water, an ethylenically unsaturated monomer, a polymerization initiator, and if necessary, an emulsifier and a dispersion stabilizer. And (2) a so-called pre-emulsion method in which water, an ethylenically unsaturated monomer, and an emulsifier previously mixed are dropped, and (3) a monomer dropping method.

  Among these, the method (2) is preferable because of high polymerization stability. Furthermore, there is a method in which a part of a preliminarily prepared emulsion is dropped and then a reactive emulsifier is dropped together with the remaining emulsion. This method is preferable because not only the polymerization stability is improved, but also the water resistance of the resulting water-dispersed acrylic polymer film is improved. The reactive emulsifier to be added later is not particularly limited, but among these, when the emulsifier represented by the following general formula (1a) or general formula (1b) is used, the reason is unclear, This is particularly preferable because the strength becomes higher.

（式中、Ｒはアルキル基、ｎは整数を示す。）

(In the formula, R represents an alkyl group, and n represents an integer.)

  When the ratio of the emulsion to which the reactive emulsifier represented by the above general formula is added is 10 to 90% by weight of the total emulsion, the strength of the coating is increased. Moreover, it is preferable that it is 20 to 80 weight%. Furthermore, it is particularly preferable that the content is 30 to 70% by weight because the strength of the coating becomes higher.

  Moreover, the average particle diameter of the water-dispersed acrylic polymer obtained by the method for producing the water-dispersed acrylic polymer of the present invention is not particularly limited. 50-1000 nm considered as a general use range is preferable. Here, the average particle diameter of the particles refers to the 50% median diameter of the emulsion particles on the volume basis, and the numerical values are based on values obtained by measurement by the dynamic light scattering method described in Examples below. .

  Further, the solid content concentration of the water-dispersed acrylic polymer obtained by the method for producing the water-dispersed acrylic polymer of the present invention is not particularly limited, but the workability at the time of production and the transportation cost, and It is preferable that the solid content concentration is 40 to 70% by weight from the viewpoint of excellent drying properties when used after drying.

  Further, the water-dispersed acrylic polymer obtained by the method for producing the water-dispersed acrylic polymer of the present invention includes a filler, a pigment, and a pH adjuster as long as the desired effects of the present invention are not inhibited as necessary. , Film forming aids, leveling agents, thickeners, water repellents, tackifiers, antifoaming agents, water-soluble or water-dispersible crosslinking agents, and the like can be used as appropriate.

  The use of the water-dispersed acrylic polymer obtained by the method for producing the water-dispersed acrylic polymer of the present invention is not particularly limited.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples. In the following, unless otherwise specified, “%” represents “% by weight”, and “part” represents “part by weight”.

The evaluation method used in the present invention will be described below.
[Measurement method of strength at break in tensile test at measurement temperature 25 ° C.]
The water-dispersed acrylic polymer obtained in the examples described later was applied on the glass plate so that the thickness after drying was 0.5 mm, dried at 25 ° C. for 24 hours, and then peeled off from the glass plate. Furthermore, what was dried at 100 ° C. for 5 minutes was punched with a No. 2 dumbbell and used as a sample. Using this sample, the tensile strength at the time of carrying out a tensile test at a crosshead speed of 200 mm / min in an atmosphere of 25 ° C. in a Tensilon RTM-100 tensile tester manufactured by Orientec Co., Ltd. was determined. To do.

[Calculation method of radical concentration]
The concentration (C) of radicals generated every minute with respect to the total amount of the polymerizable monomer component was determined by the following formula.
C = c / 2 / t / 60 (mol / l / min)
c: Concentration of polymerization initiator (mol / l)
t: Half-life (h)

The half-life (t) in the above formula was determined by the following formula.
t = ln2 / k
k: Decomposition rate constant

The aforementioned decomposition rate constant (k) was obtained from the following Arrhenius equation.
k = A × exp (−ΔE / RT)
A: Frequency factor ΔE; activation energy (J / mol)
R: Gas constant T: Temperature (K)

[Measurement method of gel fraction]
The water-dispersed acrylic polymer obtained in the examples described later was applied on the glass plate so that the film thickness after drying was 0.3 mm, dried at 25 ° C. for 24 hours, and then peeled off from the glass plate. Furthermore, what was dried at 100 ° C. for 5 minutes was cut into a 50 mm square and used as a sample. Next, the weight (G1) of the sample before being immersed in toluene is measured in advance, and the toluene insoluble portion of the sample after being immersed in a toluene solution at room temperature for 24 hours is separated by filtering through a 300 mesh wire mesh. The weight (G2) of the residue after drying at 110 ° C. for 1 hour was measured, and the gel fraction was determined according to the following formula.

Gel fraction (% by weight) = G2 / G1 × 100

[Method for measuring Tg]
The water-dispersed acrylic polymer obtained in Examples below is applied to a glass plate so that the film thickness after drying is 0.3 mm, dried at 25 ° C. for 24 hours, and then peeled off from the glass plate. A sample dried at 100 ° C. for 5 minutes was weighed in an aluminum cylindrical cell having a diameter of 5 mm and a depth of 2 mm, and a DSC-2920 modulated differential scanning calorie manufactured by TA Instruments was used. Using a meter, an endothermic curve was measured when the temperature was raised from −150 ° C. to 100 ° C. at a temperature rising rate of 20 ° C./min in a nitrogen atmosphere.

[Measurement method of average particle size]
The value of the average particle diameter (50% median diameter based on volume) measured with a Nikkiso Co., Ltd. Microtrac UPA type particle size distribution analyzer was determined.

<Example 1>
In a container, Lattemul E-118B [manufactured by Kao Corporation; active ingredient 25%] and 10 parts of deionized water were uniformly dissolved. Thereto, 300 parts of n-butyl acrylate, 190 parts of methyl methacrylate and 10 parts of acrylic acid were added and emulsified to obtain 610 parts of emulsion A.

A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel was charged with 0.2 part of Latemul E-118B and 375 parts of deionized water, and the temperature was raised to 55 ° C. while blowing nitrogen. did. Under stirring, 5.2 parts of an aqueous ammonium persulfate solution was added, and then 6.1 parts of Emulsion A was charged and polymerized in 1 hour while maintaining 55 ° C. Subsequently, a part (300 parts) of the remaining emulsion A and 10 parts of an aqueous ammonium persulfate solution (active ingredient 5%) were dropped over 3 hours while keeping the reaction vessel at 55 ° C. using a separate dropping funnel. And polymerized. During this time, 5 parts of Aqualon KH-10 [Daiichi Kogyo Seiyaku Co., Ltd .; active ingredient 100%] was added to emulsion A (303.9 parts) that was not added dropwise, and stirred until uniform. B was adjusted.

Immediately after the completion of the dropping of the emulsion A, the emulsion B (308.9 parts) and 10 parts of ammonium persulfate (active ingredient 5%) were used for 3 hours while keeping the reaction vessel at 55 ° C. using separate dropping funnels. The polymerization was conducted dropwise.

  After completion of the dropwise addition, the mixture was stirred at the same temperature for 2 hours, and then the contents were cooled and adjusted with aqueous ammonia (10% active ingredient) so that the pH was 8.0. This was filtered through a 200-mesh wire mesh to obtain the water-dispersed acrylic polymer of the present invention. The water-dispersed acrylic polymer obtained here had a solid content concentration of 50.5%, a viscosity of 200 mPa · s, and an average particle size of 310 nm.

<Example 2>
In a container, Lattemul E-118B [manufactured by Kao Corporation; active ingredient 25%] and 10 parts of deionized water were uniformly dissolved. Thereto, 300 parts of n-butyl acrylate, 190 parts of methyl methacrylate and 10 parts of acrylic acid were added and emulsified to obtain 610 parts of emulsion A.

In a reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel, 0.2 part of Latemul E-118B and 375 parts of deionized water are added, and the temperature is raised to 75 ° C. while blowing nitrogen. did. Under stirring, 5.2 parts of an aqueous ammonium persulfate solution was added, and then 6.1 parts of Emulsion A was charged and polymerized in 1 hour while maintaining 75 ° C. Subsequently, a part (300 parts) of the remaining emulsion A and 20 parts of an aqueous ammonium persulfate solution (active ingredient 1%) were dropped over 6 hours while keeping the reaction vessel at 75 ° C. using a separate dropping funnel. And polymerized.

  After completion of the dropwise addition, the mixture was stirred at the same temperature for 2 hours, and then the contents were cooled and adjusted with aqueous ammonia (10% active ingredient) so that the pH was 8.0. This was filtered through a 200-mesh wire mesh to obtain the water-dispersed acrylic polymer of the present invention. The water-dispersed acrylic polymer obtained here had a solid content concentration of 50.9%, a viscosity of 400 mPa · s, and an average particle size of 280 nm.

<Example 3>
In a container, Lattemul E-118B [manufactured by Kao Corporation; active ingredient 25%] and 10 parts of deionized water were uniformly dissolved. Thereto, 300 parts of n-butyl acrylate, 190 parts of methyl methacrylate, 10 parts of acrylic acid, and 0.25 part of lauryl mercaptan were added and emulsified to obtain an emulsion A610.25 part.

In a reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel, 0.2 part of Latemul E-118B and 375 parts of deionized water are added, and the temperature is raised to 65 ° C. while blowing nitrogen. did. Under stirring, 5.2 parts of a 4,4'-azobis (4-cyanovaleric acid) aqueous solution was added, and then 6.1 parts of Emulsion A was charged and polymerized in 1 hour while maintaining 65 ° C. Subsequently, a part (512.4 parts) of the remaining emulsion A and 17 parts (active ingredient 7.5%) of 4,4′-azobis (4-cyanovaleric acid) aqueous solution were used in separate dropping funnels. Then, the reaction vessel was dropped and polymerized over 5 hours while maintaining the reaction vessel at 65 ° C. During this time, 5 parts of Aqualon KH-0530 [Daiichi Kogyo Seiyaku Co., Ltd .; active ingredient 30%] was added to the emulsion A (91.5 parts) that was not added dropwise, and stirred until uniform. B was adjusted.

Immediately after completion of the dropwise addition of emulsion A, emulsion B (96.5 parts) and 3,4′-azobis (4-cyanovaleric acid) aqueous solution 3 parts (active ingredient 7.5%) were put in separate dropping funnels. The polymerization reaction was carried out dropwise over 1 hour while the reaction vessel was kept at 65 ° C.

  After completion of the dropwise addition, the mixture was stirred at the same temperature for 2 hours, and then the contents were cooled and adjusted with aqueous ammonia (10% active ingredient) so that the pH was 8.0. This was filtered through a 200-mesh wire mesh to obtain the water-dispersed acrylic polymer of the present invention. The water-dispersed acrylic polymer obtained here had a solid content concentration of 49.2%, a viscosity of 190 mPa · s, and an average particle size of 260 nm.

<Example 4>
In a container, Lattemul E-118B [manufactured by Kao Corporation; active ingredient 25%] and 10 parts of deionized water were uniformly dissolved. Thereto, 300 parts of n-butyl acrylate, 190 parts of methyl methacrylate and 10 parts of acrylic acid were added and emulsified to obtain 610 parts of emulsion A.

In a reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel, 0.2 part of Latemul E-118B and 375 parts of deionized water are added, and the temperature is raised to 80 ° C. while blowing nitrogen. did. Under stirring, 5.2 parts of a 4,4'-azobis (4-cyanovaleric acid) aqueous solution was added, and then 6.1 parts of Emulsion A was charged and polymerized in 1 hour while maintaining 80 ° C. Subsequently, a part of the remaining emulsion A (422.7 parts) and 14 parts of 4,4′-azobis (4-cyanovaleric acid) aqueous solution (2% active ingredient) were added using a separate dropping funnel. While maintaining the reaction vessel at 80 ° C., polymerization was carried out dropwise over 4 hours. During this time, 8.3 parts of Aqualon KH-0530 [Daiichi Kogyo Seiyaku Co., Ltd .; active ingredient 30%] was added to Emulsion A (181.2 parts) that was not added dropwise, and stirred until uniform. Emulsion B was prepared.

Immediately after the addition of emulsion A, emulsion B (189.5 parts) and 6,4'-azobis (4-cyanovaleric acid) aqueous solution 6 parts (active ingredient 2%) were used in separate dropping funnels. Then, the polymerization was carried out dropwise over 2 hours while keeping the reaction vessel at 80 ° C.

  After completion of the dropwise addition, the mixture was stirred at the same temperature for 2 hours, and then the contents were cooled and adjusted with aqueous ammonia (10% active ingredient) so that the pH was 8.0. This was filtered through a 200-mesh wire mesh to obtain the water-dispersed acrylic polymer of the present invention. The water-dispersed acrylic polymer obtained here had a solid content concentration of 49.8%, a viscosity of 150 mPa · s, and an average particle size of 340 nm.

<Comparative Example 1>
A water-dispersed acrylic polymer of the present invention was obtained in the same manner as in Example 1 except that the monomer mixture and the polymerization initiator shown in Table 2 were used. The average particle diameter (50% median diameter), solid content concentration, and viscosity of this water-dispersed acrylic polymer were as described in Table 2. The evaluation results of strength, weight average molecular weight, glass transition temperature (actually measured Tg), gel fraction (toluene insoluble fraction) in the tensile test of the film obtained using this water-dispersed acrylic polymer are shown in the second. Shown in the table.

<Comparative example 2>
A water-dispersed acrylic polymer of the present invention was obtained in the same manner as in Example 1 except that the monomer mixture, the polymerization initiator, and the usage ratios of Liquid A and Liquid B shown in Table 2 were used. It was. The average particle diameter (50% median diameter), solid content concentration, and viscosity of this water-dispersed acrylic polymer were as described in Table 2. The evaluation results of strength, weight average molecular weight, glass transition temperature (actually measured Tg), gel fraction (toluene insoluble fraction) in the tensile test of the film obtained using this water-dispersed acrylic polymer are shown in the second. Shown in the table.

<Comparative Example 3>
One part of Aqualon KH-10 and 290 parts of deionized water were placed in a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, and the temperature was raised to 85 ° C. while blowing nitrogen. Under stirring, 0.02 part of ammonium persulfate was added, and then 3 parts of Aqualon KH-10 and deionized water were added to a monomer mixture consisting of 164 parts of n-butyl acrylate, 20 parts of methyl methacrylate and 12 parts of methacrylic acid. A part of the emulsified liquid emulsified by adding 60 parts (5 parts) was added, and polymerization was carried out in 1 hour while maintaining the reaction vessel temperature at 85 ° C. Subsequently, the remaining emulsion (254 parts) and 20 parts of a 1% aqueous solution of ammonium persulfate were dropped into the reaction vessel over 2 hours using a separate dropping funnel while maintaining the temperature in the reaction vessel at 85 ° C. And polymerized. Thereafter, 15 parts of aqueous ammonia (10% active ingredient) was added dropwise over 30 minutes while maintaining the temperature in the reaction vessel at 85 ° C.

  Subsequently, a monomer mixture composed of 60 parts of n-butyl acrylate, 124 parts of methyl methacrylate, and 8 parts of glycidyl methacrylate and 20 parts of a 1% aqueous solution of ammonium persulfate were separately added dropwise while maintaining the temperature in the reaction vessel at 85 ° C. Using a funnel, it was dropped into the reaction vessel over 3 hours for polymerization.

  After completion of the dropwise addition, the mixture was stirred at the same temperature for 2 hours, and then the contents were cooled and adjusted with aqueous ammonia (10% active ingredient) so that the pH was 8.0. This was filtered through a 200-mesh wire mesh to obtain a water-dispersed acrylic polymer. The water-dispersed acrylic polymer obtained here had a solid content concentration of 48.9%, a viscosity of 180 mPa · s, and an average particle size of 240 nm. The average particle diameter (50% median diameter), solid content concentration, and viscosity of this water-dispersed acrylic polymer were as described in Table 1. Table 1 shows the evaluation results of the strength, glass transition temperature (measured Tg), and gel fraction (toluene insoluble fraction) of the coating obtained using this water-dispersed acrylic polymer. . However, the weight average molecular weight could not be measured by GPC because the polymer was not completely dissolved in THF.

The official names of the abbreviations in Tables 1 and 2 are shown below.
BA; n-butyl acrylate MMA; methyl methacrylate MAA; methacrylic acid GMA; glycidyl methacrylate L-SH; lauryl mercaptan APS; ammonium persulfate CVA; 4,4′-azobis (4-cyanovaleric acid)

Claims (4)

A production method of emulsion polymerization of a polymerizable monomer component containing (meth) acrylates in the presence of an aqueous medium, wherein the radical generation amount calculated from the amount of polymerization initiator used is a polymerizable monomer The weight average molecular weight of the component dissolved in THF of the aqueous dispersion obtained by the production method is 2 to 150 × 10 ⁻¹³ mol / l per minute with respect to the total amount of the component. A method for producing a water-dispersed acrylic polymer characterized by the following. The method for producing a water-dispersed acrylic polymer according to claim 1, wherein the temperature in the reaction vessel at the time of emulsion polymerization is 30 to 90 ° C. The method for producing a water-dispersed acrylic polymer according to claim 1 or 2, wherein the polymerization initiator used during emulsion polymerization is a persulfate-based initiator or an azo-based initiator. A production method in which an emulsion containing the polymerizable monomer component and an aqueous surfactant solution is continuously fed into a reaction vessel in which an aqueous medium is present to react, wherein the reaction is performed as a first step reaction. Reaction step (I) in which 10 to 90% by weight of the total drop amount of the emulsion is supplied and reacted, and a surfactant containing in the molecule an unsaturated group that can be polymerized with the remaining emulsion and the polymerizable monomer component The method for producing a water-dispersed acrylic polymer according to claim 1, 2 or 3, further comprising a step (II) in which an agent is continuously fed and reacted simultaneously.