JP5566865B2 - Method for producing polymer emulsion - Google Patents

Description

  The present invention relates to a method for producing a polymer emulsion.

  Polymer emulsions obtained by emulsion polymerization of vinyl monomers such as vinyl acetate and acrylic esters can be used as they are in the fields of paints, adhesives, adhesives, paper processing, fiber processing, etc. Widely used industrially. In the emulsion polymerization, as an emulsifier, an anionic surfactant such as a linear alkyl sulfate, a linear alkyl benzene sulfonate, a polyoxyethylene alkyl ether sulfate, a polyoxyethylene alkyl phenyl ether sulfate, and a polyoxy Nonionic surfactants such as ethylene linear alkyl ether and polyoxyethylene alkylphenyl ether are used alone or in a mixed system of anionic and nonionic surfactants.

  Emulsifiers in emulsion polymerization not only affect the initiation and growth reactions of polymerization, but also the stability of the polymer emulsion during polymerization (polymerization stability), and the mechanical and chemical stability of the resulting polymer emulsion. It has a great influence on freezing stability and storage stability. However, the polymerization stability, mechanical stability, and water resistance of the coating film are still not fully satisfactory.

  The performance required for these surfactants for emulsion polymerization is that the polymerization stability, the mechanical stability and chemical stability of the resulting polymer emulsion are good, the emulsion particle size is small, the viscosity is low, and There are no environmental problems. In order to satisfy these performances, many reactive surfactants having reactive groups copolymerizable with various monomers have been proposed (Patent Documents 1 to 3).

JP 2002-80506 A JP-A-63-319035 JP 2005-232330 A

  However, in the current emulsion polymerization, further improvement in water resistance of the coating film is required. Therefore, the present invention provides a method for producing a polymer emulsion having excellent water resistance of a coating film in addition to good polymerization stability and emulsion particle size.

  That is, the present invention uses a reactive anionic surfactant (a) and a non-reactive anionic surfactant (b) having a critical micelle concentration (CMC) of 0.30% by weight or less. A method for producing a polymer emulsion comprising emulsion-polymerizing a monomer (A) containing a monomer, comprising the step I: the reactive anionic surfactant (a) and the non-reactive anionic surfactant (b) The monomer (A) is polymerized under the condition that the existing weight ratio [b / (a + b)] satisfies 0.40 to 1.00, and Step II: The reaction solution obtained in Step I is further added to the reaction solution. Adding the reactive anionic surfactant (a) and the monomer (A) to polymerize the monomer (A), the reactive anionic surfactant used in Steps I and II above ( Total amount of a) The method for producing a nonreactive anionic surfactant weight ratio of the total amount of (b) [b / (a + b)] is a polymer emulsion is 0.01 to 0.30.

  According to the present invention, it is possible to produce a polymer emulsion having good polymerization stability and emulsion particle size, and excellent in water resistance of the coating film.

  In the emulsion polymerization reaction, the present invention uses, in combination, a reactive anionic surfactant (a) and a non-reactive anionic surfactant (b) having a CMC of 0.30% by weight or less, and the emulsification. In the initial stage of the polymerization reaction (for example, during the seed polymerization reaction), by performing a reaction using a predetermined amount of component (b), in addition to good polymerization stability and emulsion particle size, the water resistance of the coating film is improved. Excellent polymer emulsions are obtained, especially based on the finding that the water resistance of the coating is improved.

  That is, in one aspect, the present invention uses a reactive anionic surfactant (a) and a non-reactive anionic surfactant (b) having a critical micelle concentration (CMC) of 0.30% by weight or less. A method for producing a polymer emulsion comprising emulsion polymerization of a monomer (A) containing a vinyl monomer, wherein the reactive anionic surfactant (a) and the non-reactive anionic surfactant Polymerization of the monomer (A) under the condition that the existing weight ratio [b / (a + b)] of the agent (b) satisfies 0.40 to 1.00, and Step II: Reaction obtained in Step I And further adding the reactive anionic surfactant (a) and the monomer (A) to the liquid to polymerize the monomer (A), and the reactive anionic property used in the above steps I and II. Surface activity A method for producing a polymer emulsion in which the weight ratio [b / (a + b)] of the total amount of the surfactant (a) and the total amount of the non-reactive anionic surfactant (b) is 0.01 to 0.30 (hereinafter referred to as Also referred to as “production method of the present invention”.

In the production method of the present invention, in addition to good polymerization stability and emulsion particle size, a polymer emulsion excellent in water resistance of the coating film can be obtained. In the present invention, by using a certain amount or more of the non-reactive anion activator (b) component in the polymerization in Step I, the emulsion particle size is reduced and the component (b) is confined inside the emulsion. It is considered that the existence probability of the component (b) in the vicinity of the particle surface is reduced, and the water resistance is improved. However, the present invention need not be limited to this mechanism.

  In the present specification, good polymerization stability means that there are few aggregates in the produced emulsion. Specifically, the polymerization stability can be evaluated by the method described in Examples.

  In this specification, that the emulsion particle size is good means that the average particle size of the produced emulsion does not become large, that is, it is small. Specifically, the average particle size is 100 to 150 nm, preferably It means 110-130 nm. In this specification, the average particle diameter of the emulsion refers to the average particle diameter based on the scattering intensity distribution measured at a detection angle of 90 degrees in the dynamic light scattering method, and specifically measured by the method described in the examples. it can.

  In the present specification, the excellent water resistance of the coating film means that the water resistance of the coating film of the produced emulsion is excellent, and specifically, the hot water whitening resistance of the coating film is excellent. The hot water whitening resistance can be evaluated by the method described in Examples.

[Component (a)]
In the present specification, the component (a) refers to a reactive anionic surfactant (a). Examples of the component (a) include reactive anionic surfactants having a reactive double bond in the molecule, and particularly known reactive anionic surfactants conventionally used in emulsion polymerization reactions. Can be mentioned.

  The component (a) is preferably a compound having a hydrocarbon group having a reactive double bond and an anionic group.

  The hydrocarbon group having a reactive double bond is preferably a straight chain or branched chain alkenyl group having 3 to 18 carbon atoms, more preferably 3 to 12 carbon atoms. From the viewpoint of improving the properties, an alkenyl group having a reactive double bond at the terminal is more preferable, and specific examples include an allyl group and a 3-methyl-3-butenyl group.

  As the anionic group, a carboxy group, a sulfonic acid group, a sulfuric acid group, and a phosphoric acid group can be used. From the viewpoint of improving the surface activity and improving the water resistance of the coating film, a sulfuric acid group is preferable. Examples of the base used for neutralization include lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, trimethylamine, triethanolamine, and tributylamine.

  The component (a) preferably further has one or more hydrophobic groups from the viewpoint of enhancing the surface activity and improving the water resistance of the coating film. Examples of the hydrophobic group include a linear or branched alkyl group having 8 to 22 carbon atoms, or an oxyalkylene group having 3 to 18 carbon atoms in an alkylene group. Examples of the alkyl group include octyl group, 2-ethylhexyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, and behenyl group. The oxyalkylene group preferably has 4 to 18 carbon atoms, and more preferably an oxybutylene group. The average added mole number of the oxyalkylene group is preferably 1 to 20, more preferably 1 to 15, and still more preferably 1 to 10.

  Component (a) may further have an oxyethylene group from the viewpoint of enhancing the surface activity and improving the water resistance of the coating film, and a bonding group between the hydrophobic group and the anionic group. It is preferable to use as. The average added mole number of the oxyethylene group is preferably 1 to 100, more preferably 4 to 80, and more preferably 4 to 50.

  As the preferred component (a), polyoxyalkylene alkenyl ether sulfate ester salt is preferable from the viewpoint of obtaining an emulsion having good polymerization stability and emulsion particle size and excellent water resistance of the coating film, and polyoxybutylene polyoxyethylene alkenyl. Ether sulfate ester salts are more preferred. The alkylene group preferably has 2 to 4 carbon atoms, and the alkenyl group is preferably a 3-methyl-3-butenyl group or an allyl group. The average addition mole number of the polyoxybutylene group and the average addition mole number of the polyoxyethylene group are preferably as described above. Examples of the base for forming the salt include those described above, and sodium salts and ammonium salts are preferable.

  Specific examples of the polyoxyalkylene alkenyl ether sulfate salt include reactive surfactants disclosed in JP 2002-80506 and JP 2003-261605 (polyoxybutylene polyoxyethylene alkenyl ether sulfate ester trade name: Latemul PD-104 (manufactured by Kao Corporation)).

  The molecular weight of component (a) is preferably 250 to 6000, more preferably 500 to 3000, from the viewpoint of obtaining an emulsion excellent in water resistance of the coating film.

[Component (b)]
In the present specification, the component (b) refers to a non-reactive anionic surfactant (b) having a CMC of 0.30% by weight or less. Here, CMC refers to the critical micelle concentration, and specifically can be measured by the method described in the Examples. As the component (b), an anionic surfactant having a sulfonic acid group or a sulfuric acid group is preferable from the viewpoint of obtaining an emulsion having good polymerization stability and emulsion particle size and excellent water resistance of the coating film. Those having a hydrocarbon group of 11 to 22, more preferably 11 to 18 carbon atoms are preferred. Specifically, LAS (linear alkyl benzene sulfonate), alkane sulfonate (SAS), and polyoxyethylene alkyl ether sulfate salt are preferable, and LAS is more preferable. Examples of the base for forming the salt include those described above, and the salt is preferably a sodium salt or an ammonium salt.

  The CMC of component (b) is 0.30% by weight or less, but is preferably 0.20% by weight or less from the viewpoint of reducing the particle size of the emulsion and improving the water resistance of the coating film. Further, CMC is preferably 0.01% by weight or more from the viewpoint of suppressing excessive reduction in particle size and polymerization stability. Therefore, from these viewpoints, the CMC of the component (b) is preferably 0.01 to 0.30% by weight, and more preferably 0.01 to 0.20% by weight. In addition, the non-reactive anionic surfactant in which the CMC value falls within the above range is available as, for example, a commercial product.

  Among these, from the viewpoint of improving the water resistance of the coating film, it is preferable that the component (a) contains a polyoxyalkylene alkenyl ether sulfate ester salt and the component (b) contains a linear alkylbenzene sulfonate salt.

[Monomer (A)]
In the present specification, the monomer (A) refers to a monomer to be subjected to emulsion polymerization in the production method of the present invention. Monomer (A) may consist of a single type of monomer, or may be a composition or mixture containing two or more types of monomers. The monomer (A) contains a vinyl monomer from the viewpoint of obtaining an emulsion having good polymerization stability and emulsion particle size and excellent water resistance of the coating film. From the viewpoint of obtaining an emulsion excellent in water resistance of the coating film in the monomer (A), the vinyl monomer is preferably 50% by weight or more, more preferably 80% by weight or more, and still more preferably 90% by weight or more.

  Specific examples of vinyl monomers that can be used as the monomer (A) include styrene monomers such as styrene, α-methylstyrene, and chlorostyrene; preferably 1 to 1 carbon atoms such as methyl acrylate, ethyl acrylate, and butyl acrylate. 22, more preferably 1-12, more preferably 1-6 acrylates having an alkyl group; methyl methacrylate, ethyl methacrylate, etc., preferably 1-22 carbon atoms, more preferably 1-12, further Preferably a methacrylic acid ester having 1 to 6 alkyl groups; (meth) acrylic acid such as acrylic acid and methacrylic acid (referring to acrylic acid, methacrylic acid or a mixture thereof); vinyl chloride, vinyl bromide, vinylidene chloride, etc. Of vinyl halides and vinylidene halides; vinyl acetate, propion Vinyl esters such as vinyl and the like.

  Other monomers include nitriles such as acrylonitrile and methacrylonitrile; conjugated dienes such as butadiene and isoprene. As described above, these monomers may be polymerized alone or in combination of two or more.

  Among these, the monomer (A) is preferably composed of a styrene monomer, an acrylate ester, and a methacrylate ester from the viewpoint of obtaining an emulsion having good polymerization stability and emulsion particle size and excellent water resistance of the coating film. More preferably, it comprises a hydrophobic monomer containing at least one selected from the group and (meth) acrylic acid.

  From the above viewpoint, the weight ratio of the hydrophobic monomer to (meth) acrylic acid (hydrophobic monomer / (meth) acrylic acid) is preferably 90/10 to 99.5 / 0.5, and 95/5. ˜99.5 / 0.5 is more preferred, and 95/5 to 99/1 is even more preferred.

The production method of the present invention includes the following two steps.
Step I: Conditions where the existing weight ratio [b / (a + b)] of the reactive anionic surfactant (a) and the non-reactive anionic surfactant (b) satisfies 0.40 to 1.00 And a step of polymerizing the monomer (A).
Step II: A step of adding the reactive anionic surfactant (a) and the monomer (A) to the reaction solution obtained in Step I to polymerize the monomer (A) to obtain a polymer emulsion.

  In Step I, the existing weight ratio [b / (a + b)] is preferably 0.60 or more, more preferably 0, from the viewpoint of obtaining an emulsion having good polymerization stability and emulsion particle size and excellent water resistance of the coating film. .70 or more, more preferably 0.80 or more, and from the viewpoint of productivity for producing a pre-emulsion described later with the component (a), it is 1 or less, and preferably less than 1. From these viewpoints, the existing weight ratio [b / (a + b)] is preferably 0.60 to 1, more preferably 0.70 to 1, still more preferably 0.70 to less than 1, More preferably, it is 0.80 or more and less than 1.

  In Step II, it is preferable to further add component (b) in addition to component (a) and monomer (A). In that case, the method of adding component (a) and monomer (A), preferably further component (b) in advance and then adding them to the system (pre-emulsion method) is preferred from the viewpoint of simplicity in production.

  The weight ratio [b / (a + b)] of the total amount of the component (a) and the total amount of the component (b) used in the steps I and II is a viewpoint of obtaining an emulsion having a good emulsion particle size and excellent water resistance of the coating film. From the viewpoint of obtaining an emulsion having 0.01 or more, preferably 0.05 or more, more preferably 0.13 or more, and good polymerization stability and excellent water resistance of the coating film, it was 0.30 or less. 0.25 or less is preferable, 0.23 or less is more preferable. From these viewpoints, 0.01 to 0.30, 0.05 to 0.25 is preferable, and 0.13 to 0.23. Is preferred.

  The total weight ratio [(a) / (b)] of the total amount of the component (a) and the total amount of the component (b) used through the steps I and II is excellent in the polymerization stability and emulsion particle size, and the water resistance of the coating film. From the viewpoint of obtaining an emulsion having excellent properties, it is preferably 99/1 to 70/30, more preferably 90/10 to 75/25.

  The weight ratio [(a + b) / monomer (A)] of the total amount of the component (a) and the total amount of the component (b) to the total amount of the monomer (A) used through the steps I and II is the polymerization stability. From the viewpoint of obtaining an emulsion having good properties and emulsion particle size and excellent water resistance of the coating film, it is preferably 0.001 to 0.2, more preferably 0.005 to 0.05.

  The weight ratio [(a) / monomer (A)] of the total amount of component (a) to the total amount of monomer (A) used through the steps I and II is good in polymerization stability and emulsion particle size. From the viewpoint of obtaining an emulsion having excellent water resistance, it is preferably 0.001 to 0.1, more preferably 0.005 to 0.05, and the weight ratio of the total amount of component (b) to the total amount of monomers (A) [ (B) / monomer (A)] is preferably 0.0005 to 0.05, more preferably 0.001 from the viewpoint of obtaining an emulsion having good polymerization stability and emulsion particle size and excellent water resistance of the coating film. ~ 0.01.

  Regarding the component (a), the weight ratio used in each of the steps I and II (step I / step II) is that the component (a) is mainly used in the step II, the emulsion particle size is good, and the water resistance of the coating film is improved. From the viewpoint of obtaining an excellent emulsion, 0 to 0.40 is preferable, more than 0 and 0.40 or less is more preferable, 0.01 to 0.30 is more preferable, and 0.03 to 0.13 is even more preferable.

  Regarding the component (b), the weight ratio (step II / step I) used in each of the steps I and II is mainly the component (b) in the step I, and has good polymerization stability and emulsion particle size. From the viewpoint of obtaining an emulsion having excellent water resistance, 0 to 0.50 is preferable, 0 to 0.30 is more preferable, and 0 to 0.20 is more preferable.

Regarding the monomer (A), the weight ratio used in each of the steps I and II (step I / step II) is to produce an emulsion having a small particle diameter by the polymerization of the step I and to be excellent in water resistance of the coating film in the step II. From the viewpoint of obtaining an emulsion, 1/99 to 15/85 is preferable, and 3/97 to 10/90 is more preferable.

  As the monomer addition method in the production method of the present invention, a monomer dropping method, a monomer batch charging method, a pre-emulsion method, or the like can be used. The pre-emulsion method is preferred from the viewpoint of polymerization stability.

In one embodiment, the production method of the present invention can be a production method including the following steps (i) to (iv).
Step (i): An aqueous phase containing component (a) is prepared.
Step (ii): An emulsion of monomer (A) is prepared using the aqueous phase of step (i).
Step (iii): A part of the emulsion of step (ii), a polymerization initiator, component (b), and further component (a) as necessary are mixed and polymerized to produce a seed polymer.
Step (iv): The remaining part of the emulsion of step (ii) is added dropwise to the seed polymer polymerized in step (iii) to complete the emulsion polymerization to produce a polymer emulsion.

  Steps (i) to (iii) in this embodiment correspond to step I of the production method of the present invention, and step (iv) corresponds to step II.

  As the polymerization initiator used in the production method of the present invention, any polymerization initiator can be used as long as it is used in ordinary emulsion polymerization. Specifically, persulfates such as potassium persulfate and ammonium persulfate, organic peroxides such as hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide, azobisdiisobutyronitrile, 2 Azo initiators such as 2-azobis (2-amidinopropane) dihydrochloride. Among these, persulfate is preferable. Furthermore, redox initiators in which a reducing agent such as sodium sulfite, Rongalite, ascorbic acid or the like is combined with peroxide can also be used.

In step (i), component (a) and water are mixed to prepare an aqueous phase containing component (a). Furthermore, you may add a polymerization initiator as needed. In the aqueous phase, the content of the component (a) is preferably 0.5 to 20% by weight, more preferably 1 to 10% by weight.
In step (ii), the aqueous phase of step (i) and monomer (A) are mixed to prepare an emulsion. The mixing temperature is preferably 5 to 40 ° C. In the emulsion, the content of the monomer (A) is preferably 30 to 80% by weight, and more preferably 40 to 70% by weight.
In step (iii), a part of the emulsion of step (ii), a polymerization initiator, component (b), and further component (a) as necessary are mixed and charged, and polymerization is started to produce a seed polymer.
The content of the monomer (A) during mixing preparation is preferably 1 to 30% by weight, and more preferably 2 to 20% by weight.

  The polymerization temperature in Step I is adjusted by the decomposition temperature of the initiator, but is preferably 50 to 90 ° C, and in the case of persulfate, 70 to 85 ° C is preferable. The polymerization time is preferably about 10 minutes to 2 hours, more preferably about 30 minutes to 1 hour.

  The end point of the polymerization reaction in Step I is preferably such that the polymerization reaction rate of the monomer (A) added in Step I is 95% by weight or more. The polymerization reaction rate can be determined by measuring the amount of unreacted monomer by gas chromatography or the like.

  In the step (iv), the remainder of the emulsion of the step (ii) is dropped on the seed polymer polymerized in the step (iii) to complete the emulsion polymerization to produce a polymer emulsion.

  In the above embodiment, the dropping time of the monomer (A) emulsion in the step (iv) is preferably 1 to 8 hours, and the aging time is preferably 1 to 5 hours. The polymerization temperature is the same as in step I.

  The polymer coating film made of the polymer emulsion produced by the production method of the present invention is excellent in water resistance, and can be preferably used in the field of paints, particularly the water-based paint field and the adhesive product field. Accordingly, the present invention provides, as another aspect, a method for producing a polymer coating film, which comprises producing a polymer emulsion by the production method of the present invention and forming a coating film of the polymer emulsion. The present invention relates to a film manufacturing method.

  The manufacturing method of the polymer coating film of this invention can be made into embodiment according to a use. For example, in an adhesive application, a polymer emulsion having a low polymer Tg (glass transition temperature) such as 2-ethylhexyl acrylate and n-butyl acrylate is produced by the production method of the present invention. If this polymer emulsion is blended with a thickener, tackifier, etc., if necessary, it is applied to a substrate such as paper or film, and dried with hot air to form a polymer coating having a thickness of about 20 μm. A pressure-sensitive adhesive product having excellent properties and adhesive performance can be obtained.

  Alternatively, in coating applications, a polymer emulsion such as n-butyl acrylate / methyl methacrylate copolymer is produced by the production method of the present invention. By coating this polymer emulsion with a film-forming aid, pigment, etc., as necessary, on a building wall material, etc., so that the dry film thickness is about 100 μm, and then drying it naturally or hot air A coating film excellent in water resistance and weather resistance can be obtained.

  Polymer emulsion composition by the following emulsion polymerization method using the reactive anionic surfactant (a), non-reactive anionic surfactants (b) and (c), and monomer mixture (A) shown below. (Examples 1 to 10, Comparative Examples 1 to 8) were produced, and the polymerization stability, emulsion particle size, and hot water whitening resistance of the polymer emulsion coating film were evaluated by the methods described below. In the following description, “%” means “wt%” unless otherwise specified.

The following (a-1) and (a-2) were used as the reactive anionic surfactant (a) (hereinafter also simply referred to as “component (a)”).
(A-1): Polyoxybutylene polyoxyethylene alkenyl ether sulfate ammonium salt (trade name: Latemul PD-104, manufactured by Kao Corporation)
(A-2): Polyoxyethylene 2-allyloxy-1-alkoxymethyl ethyl ether sulfate ammonium salt (trade name: Rear Soap SR-1025, manufactured by Adeka)

The following (b-1), (b-2) and (b-3) were used as the non-reactive anionic surfactant (b) (hereinafter also simply referred to as “component (b)”). The critical micelle concentration (CMC) was measured as follows.
(B-1): Linear alkylbenzene sulfonate sodium salt (trade name: Neoperex G-25, manufactured by Kao Corporation, CMC = 0.06 wt%)
(B-2): Alkanesulfonate sodium salt (trade name: Latemul PS, manufactured by Kao Corporation, CMC = 0.07 wt%)
(B-3): Polyoxyethylene lauryl ether sulfate sodium salt (trade name: EMAL 20C, manufactured by Kao Corporation, CMC = 0.10 wt%)

The following (c-1) and (c-2) are used as the non-reactive anionic surfactant (c) (hereinafter also simply referred to as “component (c)”) which is a comparative component of component (b). used. The critical micelle concentration (CMC) was measured as follows.
(C-1): alkyl diphenyl ether disulfonate sodium salt (trade name: Perex SS-L, manufactured by Kao Corporation, CMC = 0.70 wt%)
(C-2): Polyoxyethylene alkyl ether sulfate sodium salt (trade name: Latemul E-118B, manufactured by Kao Corporation, CMC = 0.55 wt%)

CMC measurement method The CMC of the surfactant was measured as follows. 100 mL of distilled water was placed in a beaker and the electric conductivity was measured while stirring (electric conductivity meter was CM-20S type, cell CG-511B, manufactured by Toa Radio Industry Co., Ltd.). 0.2 mL of a surfactant solution adjusted to a predetermined concentration in advance was dropped into the beaker, and the electric conductivity was read each time the solution was dropped. When the surfactant concentration of the titrant is xmol L ⁻¹ and the amount of titrated titrant is ymL, the surfactant concentration C in the solution in the beaker is C = x · y / (100 + y). The inflection point when the electric conductivity is plotted against C is CMC (temperature 25 ° C.).

<Emulsion polymerization method: production of emulsion of Example 1>
The emulsion of Example 1 was produced according to the following steps (i) to (iv).
Step (i): In a 1 L flask equipped with a stirrer and a raw material inlet, 112.5 g of ion-exchanged water, 0.36 g of potassium persulfate as a polymerization initiator, and 3.6 g of component (a-1) are mixed to obtain surface activity. An aqueous agent solution was prepared.
Step (ii): While stirring the aqueous solution at 500 r / min, a monomer mixture of butyl acrylate 110.8 g, methyl methacrylate 110.8 g, and acrylic acid 3.4 g was added dropwise over about 5 minutes and stirred for 30 minutes. As a result, a monomer emulsion dropping liquid (341.5 g) was obtained.
Step (iii): Next, in a 1 L separable flask equipped with a stirrer, a reflux condenser, and a raw material charging port, 162.5 g of ion-exchanged water, 0.09 g of potassium persulfate as a polymerization initiator, component (b-1) 0.90 g and 17.1 g (5 wt% amount, 0.18 g of component (a)) of the monomer emulsion dropping solution were charged, heated to 80 ° C., and seed polymerization was performed for 30 minutes. In step (iii), the proportion of component (b) in the total anionic surfactant (component (a) + (b)) was 83.3%.
Step (iv): The remaining emulsion dropping solution (324.4 g) was added dropwise over 3 hours, and after completion of the addition, the mixture was further aged for 1 hour to obtain a polymer emulsion of Example 1. The proportion of component (b) in the total anionic surfactant (component (a) + (b)) used in steps (i) to (iv) was 20.0%.

<Production of emulsions of Examples 3 to 6, 8 to 10, Reference Examples 2 and 7, and Comparative Examples 1 to 8>
What was shown in following Table 1 was used as a component (a), and the component (b) or component (c) shown in following Table 1 was used as a component (b). Further, component (b-1) 0 charged in step (iii) of Example 1 was added in place of 3.6 g of component (a-1) of step (i) of Example 1 and the components shown in Table 2 below were added. In addition to 90 g, the components shown in Table 2 below were added to prepare emulsions of Examples 3 to 6, 8 to 10, Reference Examples 2 and 7, and Comparative Examples 1 to 8. Table 3 below shows the ingredients and amounts used in Steps I and II to make each emulsion. In addition, the process I in following Table 3 points out the process to the seed polymerization of the process (i)-(iii) of the said emulsion polymerization method, and the process II points out the said process (iv).

<Performance evaluation method>
With respect to the emulsions of Examples 1 to 10 and Comparative Examples 1 to 8 produced, the polymerization stability, the emulsion particle size, and the water resistance of the coating film were evaluated under the following conditions. The results are shown in Table 3 below.

(1) Polymerization stability After aging for 1 hour in the above emulsion polymerization step (iv), the obtained polymer emulsion is cooled to 30 ° C. or lower, filtered through a 200 mesh stainless steel wire mesh, and aggregates in the emulsion are recovered. did. Aggregates adhered to the flask and the stirring blade were also collected. The collected aggregate was washed with water, dried and weighed at 26.6 kPa and 105 ° C. for 2 hours, and the amount of aggregate was determined. Polymerization stability was expressed in terms of the weight percent of aggregates relative to the total amount of monomers used.

(2) Emulsion particle size The obtained polymer emulsion is neutralized with 25% aqueous ammonia to adjust the pH to 8-9, and a dynamic light scattering particle size measurement device (trade name: N4 Plus, manufactured by Beckman Coulter, Inc.) is used. Then, the average particle diameter of the polymer emulsion particles after neutralization was measured and used as the emulsion particle diameter.

(3) Water resistance of coating film (warm water whitening resistance of polymer emulsion coating film)
The neutralized polymer emulsion was coated on a transparent acrylic plate using an applicator so that the dry film thickness was 50 μm, and dried with a hot air dryer at 100 ° C. for 10 minutes. After this acrylic plate was immersed in warm water of 60 ° C. for 48 hours, the haze value of the coating film was measured using a haze meter. The hot water whitening resistance is better as the haze value is smaller.

  As is clear from the results of Table 3 above, Examples 1 to 10 are superior to Comparative Examples 1 to 8 in that the coating film has excellent water resistance while maintaining good polymerization stability and good emulsion particle size. (Warm water whitening resistance).

  The method for producing a polymer emulsion of the present invention is useful in the fields of paints, adhesives, paper processing, fiber processing, plastics, rubber and the like.

Claims (6)

A monomer containing a vinyl monomer using a reactive anionic surfactant (a) and a non-reactive anionic surfactant (b) having a critical micelle concentration (CMC) of 0.30% by weight or less (A) A method for producing a polymer emulsion comprising emulsion polymerization of
Step I: Conditions where the existing weight ratio [b / (a + b)] of the reactive anionic surfactant (a) and the non-reactive anionic surfactant (b) satisfies 0.60 or more and 0.87 or less. Polymerizing the monomer (A) below, and
Step II: further comprising adding the reactive anionic surfactant (a) and the monomer (A) to the reaction liquid obtained in Step I to polymerize the monomer (A),
The weight ratio [b / (a + b)] of the total amount of the reactive anionic surfactant (a) and the total amount of the non-reactive anionic surfactant (b) used in the steps I and II is 0.01. A process for producing a polymer emulsion, which is ˜0.30.   The manufacturing method of the polymer emulsion of Claim 1 whose weight ratio (process I / process II) of the reactive anionic surfactant (a) used by the said process I and II is 0-0.40.   The polymer emulsion according to claim 1 or 2, wherein a weight ratio (step II / step I) of the non-reactive anionic surfactant (b) used in the steps I and II is 0 to 0.50. Production method.   The monomer (A) includes one or more hydrophobic monomers selected from the group consisting of styrene monomers, acrylic acid esters, and methacrylic acid esters, and (meth) acrylic acid. A method for producing a polymer emulsion as described in 1. above.   The method for producing a polymer emulsion according to any one of claims 1 to 4, wherein the reactive anionic surfactant (a) comprises a polyoxyalkylene alkenyl ether sulfate ester salt.   The non-reactive anionic surfactant (b) includes at least one selected from the group consisting of linear alkylbenzene sulfonates, alkane sulfonates, and polyoxyethylene alkyl ether sulfates. To 5. The method for producing a polymer emulsion according to any one of 5 to 5.