JP6798435B2 - A method for producing latex, and a method for producing a coating material and fine particles containing the latex. - Google Patents

Description

The present invention relates to a method for producing a latex containing a low molecular weight polymer and / or a macromonomer.

In recent years, there has been an increasing demand for reducing the amount of volatile organic compounds emitted in the painting process of exterior materials and interior materials of automobiles, buildings, home appliances and the like. As one means for achieving this, efforts are underway to replace organic solvent-based paints with water-based paints (coating materials). However, with water-based paints, the water resistance and appearance of the coating film tend to be insufficient. Therefore, in the field of automobile exterior materials and the like, which require a high performance level, the replacement with water-based paints has not progressed at present.

For the water resistance and appearance of the coating film, it is important that the polymer forming the coating film has a low molecular weight. Generally, in emulsion polymerization, it is known that a latex (dispersion liquid) containing a polymer having a low molecular weight can be obtained by using a chain transfer agent such as mercaptan. However, the coating film formed by using this latex has problems of deterioration of weather resistance and odor due to the chain transfer agent.

As a chain transfer agent for radical polymerization of an ethylenically unsaturated monomer, a catalyst using a cobalt complex catalyst is used because it is excellent in effects such as lowering the molecular weight of the polymer and making the particle size of the polymer particles finer. Catalistic Chain Transfer Polymerization (CCTP) has attracted attention, and there are examples of applying the catalytic chain transfer polymerization method to emulsion polymerization (for example, Patent Documents 1 and 2).

On the other hand, in emulsion polymerization for latex production, anionic surfactants, nonionic surfactants or nonionic-anionic mixed surfactants are often used. Anionic surfactants generally have a wide range of application to monomers and stably promote the emulsion polymerization reaction of most monomers (Non-Patent Document 1). Industrially, anionic surfactants are often used in emulsion polymerization for latex production.

Special Table No. 10-508886 JP-A-2002-212210

"Chemistry of Polymer Latex" published by Polymer Publishing Association, p. 36

However, in the emulsion polymerization method using a cobalt complex as a chain transfer agent as in Patent Documents 1 and 2, there is a problem that a large amount of agglomerates are generated during the polymerization. If there are many agglomerates, the yield of latex will decrease. In addition, latex containing a large amount of agglomerates cannot be used as a coating material. In addition, the yield when recovering the polymer fine particles from the latex is also low, and when the latex is used for a next reaction such as copolymerization, there is also a problem that it is difficult to obtain a copolymer having a uniform composition.

An object of the present invention is to provide a method for producing latex and polymer fine particles, which can suppress the generation of agglutinations when the catalytic chain transfer polymerization method is applied to an emulsion polymerization method and can secure a high yield.

The present invention has the following configurations.
[1] A method for producing a latex containing a polymer (A) obtained by emulsion polymerization of an ethylenically unsaturated monomer (a) in the presence of a chain transfer agent, a polymerization initiator and a surfactant. A method for producing a latex, wherein the chain transfer agent contains a cobalt complex (X) represented by the following formula (1), and the surfactant contains 85% by mass or more of a nonionic surfactant.

(However, in the above formula (1), R ^{1 to} R ⁴ are independently alkyl groups, cycloalkyl groups or aryl groups, respectively, and X ^{1 to} X ⁴ are independently fluorine atoms, chlorine atoms and bromine atoms, respectively. , Hydroxy group, alkoxy group, aryloxy group, alkyl group or aryl group.)
[2] The method for producing latex according to [1], wherein the polymerization initiator has a solubility in water at 20 ° C. of 0.1 g / 100 g-H ₂ O or more.
[3] The method for producing latex according to [1] or [2], wherein the polymer (A) contains a macromonomer.
[4] A method for producing a coating material, wherein a latex is obtained by the method for producing latex according to any one of [1] to [3], and a coating material containing the latex is obtained.
[5] A method for producing polymer fine particles, wherein the latex is obtained by the method for producing latex according to any one of [1] to [3], and the solid content of the latex is solidified or spray-dried to obtain polymer fine particles. ..

According to the method for producing latex of the present invention, it is possible to suppress the generation of agglomerates during emulsion polymerization to which the catalytic chain transfer polymerization method is applied, and to secure a high yield.
According to the method for producing a coating material of the present invention, the amount of agglomerates in the latex is reduced, so that a coating material having an excellent appearance can be obtained.
According to the method for producing polymer fine particles of the present invention, the yield of polymer fine particles is high because the amount of aggregates in the latex is reduced.

As used herein, "(meth) acrylate" means "acrylate and / or methacrylate". The same applies to other compounds, where "(meth) acrylic acid" means "acrylic acid and / or methacrylic acid". "(Meta) acryloyl" means "acryloyl and / or methacryloyl". "(Meta) acrylonitrile" means "acrylonitrile and / or methacrylonitrile". "(Meta) acrylamide" means "acrylamide and / or methacrylamide".

[Latex manufacturing method]
The method for producing latex of the present invention comprises a latex containing a polymer (A) obtained by emulsion polymerization of an ethylenically unsaturated monomer (a) in the presence of a chain transfer agent, a polymerization initiator and a surfactant. It is a method for producing, wherein the chain transfer agent contains a cobalt complex (X) described later, and the surfactant contains 85% by mass or more of a nonionic surfactant.

(Ethylene unsaturated monomer (a))
The ethylenically unsaturated monomer (a) used in the production method of the present invention is not particularly limited, and various monomers can be used as needed. For example, the (meth) acrylic acid ester described later and a hydroxyl group are contained. (Meta) acrylic acid ester, carboxyl group-containing vinyl monomer, acid anhydride group-containing vinyl monomer, epoxy group-containing vinyl monomer, amino group-containing (meth) acrylic acid ester, amide group-containing vinyl Examples thereof include a system monomer, a monofunctional vinyl monomer, and a polyfunctional vinyl monomer.

Examples of the (meth) acrylic acid ester having an alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, and t-butyl (meth) acrylate. , 2-Ethylhexyl (meth) acrylate, n-lauryl (meth) acrylate, n-stearyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, 2 Examples thereof include −methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, and phenoxyethyl (meth) acrylate.

Examples of the hydroxyl group-containing (meth) acrylic acid ester include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and glycerol (meth) acrylate.
Examples of the carboxyl group-containing vinyl monomer include (meth) acrylic acid, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, 2- (meth) acryloyloxypropyl hexahydrophthalic acid, and 2- (meth). Acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxypropyl phthalic acid, 2- (meth) acryloyloxyethyl maleic acid, 2- (meth) acryloyloxypropyl maleic acid, 2- (meth) acryloyloxyethyl succinic acid, Examples thereof include 2- (meth) acryloyloxypropyl succinic acid, crotonic acid, phthalic acid, maleic acid, itaconic acid, monomethyl maleate, and monomethyl itaconic acid.

Examples of the acid anhydride group-containing vinyl-based monomer include maleic anhydride, itaconic anhydride and the like.
Examples of the epoxy group-containing vinyl-based monomer include glycidyl (meth) acrylate, glycidyl α-ethylacrylate, and 3,4-epoxybutyl (meth) acrylate.
Examples of the amino group-containing (meth) acrylic acid ester include dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate.
Examples of the amide group-containing vinyl-based monomer include (meth) acrylamide, N-t-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, and N-butoxymethyl ( Meta) acrylamide, diacetone acrylamide, maleic acid amide, maleimide and the like can be mentioned.

Examples of the monofunctional vinyl-based monomer include styrene, α-methylstyrene, vinyltoluene, (meth) acrylonitrile, vinyl chloride, vinyl acetate, vinyl propionate and the like.
Examples of the polyfunctional vinyl monomer include divinylbenzene, ethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and triethylene. Glycoldi (meth) acrylate, tetraethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, trimethylpropantri (meth) acrylate, allyl (meth) acrylate, N, N'-methylenebis (meth) acrylamide And so on.
As the ethylenically unsaturated monomer (a), one type may be used alone, or two or more types may be used in combination.

The ethylenically unsaturated monomer (a) includes methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, and i-butyl because of the susceptibility of chain transfer due to the cobalt complex (X). (Meta) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-lauryl (meth) acrylate, n-stearyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (Meta) acrylate, isobornyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, phenoxyethyl (meth) acrylate are preferable, and methyl (meth) acrylate, ethyl methacrylate, n-butyl Methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, n-lauryl methacrylate, n-stearyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, isobornyl methacrylate, 2-methoxyethyl methacrylate, 2-ethoxy Ethyl methacrylate and phenoxyethyl methacrylate are more preferable, and methyl (meth) acrylate is particularly preferable.

When a reactive surfactant having an ethylenically unsaturated bond is contained in the surfactant component used in the production method of the present invention, the reactive surfactant is used together with the ethylenically unsaturated monomer (a). Polymerize to form the polymer (A). Examples of the reactive surfactant that can be polymerized with the ethylenically unsaturated monomer (a) include various reactive surfactants such as anionic, cationic, nonionic, and zwitterionic.
In the present invention, it is assumed that the reactive surfactant is a surfactant having a surfactant, and the ethylenically unsaturated monomer (a) does not contain the reactive surfactant.

(Chain transfer agent)
The chain transfer agent contains a cobalt complex (X) represented by the following formula (1).

However, in the formula (1), R ^{1 to} R ⁴ are independently alkyl groups, cycloalkyl groups or aryl groups, and X ^{1 to} X ⁴ are independently fluorine atoms, chlorine atoms, bromine atoms and hydroxy atoms, respectively. A group, an alkoxy group, an aryloxy group, an alkyl group or an aryl group.

The alkyl groups of R ^{1 to} R ⁴ may be linear or branched. The alkyl groups of R ^{1 to} R ⁴ preferably have 1 to 12 carbon atoms, and more preferably 1 to 6 carbon atoms.
The cycloalkyl groups of R ^{1 to} R ⁴ preferably have 3 to 11 carbon atoms, and more preferably 3 to 6 carbon atoms.
The aryl group of R ^{1 to} R ⁴ preferably has 6 to 14 carbon atoms, more preferably 6 to 11 carbon atoms.
The R ¹ to R ^4, each independently, a methyl group, an ethyl group, a phenyl group, preferably a methyl phenyl group, a phenyl group is particularly preferred.

R ^{1 to} R ⁴ are appropriately selected in order to adjust the solubility and stability of the cobalt complex (X) in water. In the case of a methyl group or an ethyl group, a cobalt complex (X) having a slight solubility in water is obtained, and in the case of a phenyl group or a methylphenyl group, a cobalt complex (X) having almost no solubility in water is obtained. Be done.

Alkoxy group X ¹ to X ⁴ may be linear, it may be branched. The alkoxy group of X ^{1 to} X ⁴ preferably has 1 to 12 carbon atoms, and more preferably 1 to 6 carbon atoms.
The aryloxy group of X ^{1 to} X ⁴ preferably has 6 to 14 carbon atoms, more preferably 6 to 11 carbon atoms.
The alkyl groups X ^{1 to} X ⁴ may be linear or branched. The alkyl groups of X ^{1 to} X ⁴ preferably have 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms.
The aryl group of X ^{1 to} X ⁴ preferably has 6 to 14 carbon atoms, more preferably 6 to 11 carbon atoms.
As X ^{1 to} X ⁴ , fluorine atoms, chlorine atoms, and bromine atoms are preferable, and fluorine atoms are particularly preferable.

Examples of the cobalt complex (X) include Japanese Patent No. 3587530, Japanese Patent No. 6-23209, Japanese Patent No. 7-35411, US Patent No. 45269945, US Patent No. 4694054, US Patent. Examples thereof include those described in Japanese Patent No. 48337326, US Pat. No. 4,886,861, US Pat. No. 5,324,879, International Publication No. 1995/17435, and Japanese Patent Application Laid-Open No. 9-510499.

Specific examples of the cobalt complex (X) include bis (borondifluorodimethyldioxyiminoshirohexane) cobalt (II), bis (borondifluorodimethylglioxymate) cobalt (II), and bis (borondifluorodiphenylgrioxymate). Cobalt (II), cobalt (II) complex of bicinaluiminohydroxyimino compound, cobalt (II) complex of tetraazatetraalkylcyclotetradecatetraene, N, N'-bis (salicylidene) ethylenediaminocobalt (II) complex , Cobalt (II) complex of dialkyldiazadioxodialkyldodecadien, cobalt (II) porphyrin complex and the like. In general, since it is highly stable in the presence of water and has a high chain transfer effect, bis (borondifluorodiphenylgrioxymate) cobalt (II) (R ^{1 to} R ⁴ : phenyl group, X ^{1 to} X ⁴ : Fluorine atom) is preferable.
As the cobalt complex (X), one type may be used alone, or two or more types may be used in combination.

As the chain transfer agent, it is preferable to use only the cobalt complex (X). As the chain transfer agent, a chain transfer agent (Y) other than the cobalt complex (X) may be used in addition to the cobalt complex (X) as long as the effects of the present invention are not impaired. The other chain transfer agent (Y) is not particularly limited, and examples thereof include mercaptans, hydrogen, α-methylstyrene dimer, and terpenoids. As the other chain transfer agent (Y), one type may be used alone, or two or more types may be used in combination.

The amount of the chain transfer agent used is not particularly limited, but the amount of the cobalt complex (X) used is 0.001 to 0.05 parts by mass with respect to 100 parts by mass of the ethylenically unsaturated monomer (a). Preferably, 0.002 to 0.035 parts by mass is more preferable, and 0.002 to 0.02 parts by mass is further preferable. When the amount of the cobalt complex (X) used is at least the lower limit, the effect of reducing the molecular weight of the polymer (A) can be sufficiently obtained. When the amount of the cobalt complex (X) used is not more than the upper limit, the reaction time can be shortened and the polymer is hard to be colored.
When a reactive surfactant is contained in the surfactant component used in the production method of the present invention, the amount of the cobalt complex (X) used is the ethylenically unsaturated monomer (a) and the reactive surfactant. It is preferable that the range is within the above range with respect to 100 parts by mass of the total amount of the agent.

When a chain transfer agent (Y) other than the cobalt complex (X) is used in addition to the cobalt complex (X), the amount of the other chain transfer agent (Y) used is not particularly limited, but is ethylenically unsaturated. With respect to 100 parts by mass of the monomer (a), 0.0001 to 1.0 parts by mass is preferable, 0.01 to 0.6 parts by mass is more preferable, and 0.05 to 0.3 parts by mass is further preferable. .. When the amount of the other chain transfer agent (Y) used is at least the lower limit, the effect of reducing the molecular weight of the polymer (A) can be sufficiently obtained. When the amount of the other chain transfer agent (Y) used is not more than the upper limit, the reaction time can be shortened and the polymer is less likely to be colored.
When a reactive surfactant is contained in the surfactant component used in the production method of the present invention, the amount of the other chain transfer agent (Y) used reacts with the ethylenically unsaturated monomer (a). It is preferable that the range is within the above range with respect to 100 parts by mass of the total amount of the sex surfactant.

The mass ratio of the cobalt complex (X) to the total mass of the chain transfer agent used is preferably 1% by mass or more, more preferably 3% by mass or more, and 5% by mass from the viewpoint that the effect of the cobalt complex (X) can be easily obtained. % Or more is more preferable, and 100% by mass is particularly preferable.

(Polymer initiator)
The polymerization initiator is not particularly limited as long as it is a polymerization initiator generally used in emulsification polymerization, and for example, persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, cumenehydroperoxide, and lauroyl peroxide. , T-butylhydroperoxide, benzoyl peroxide, di-t-butyl peroxide, t-butylperoxy2-ethylhexanoate, t-hexylperoxy2-ethylhexanoate, t-butylperoxybenzoate, Organic peroxides such as diisopropylperoxycarbonate and diacyl peroxide, azobisisobutyronitrile (AIBN), 2,2'-azobis (2,4-dimethylvaleronitrile) (V-65, Wako Pure Chemical Industries, Ltd.) (Manufactured by Co., Ltd.), 4,4'-azobis (4-cyanovalec acid) (ACVA, manufactured by Otsuka Chemical Co., Ltd.), 2,2'-azobis [2- (2-imidazolin-2-yl) propane ] (VA-061, manufactured by Wako Pure Chemical Industries, Ltd.), 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide] (VA-086, manufactured by Wako Pure Chemical Industries, Ltd.) , 2,2'-Azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride (VA-044, manufactured by Wako Pure Chemical Industries, Ltd.), 2,2'-azobis [2- (2-Imidazolin-2-yl) Propane] Disulfate dihydrate (VA-046B, manufactured by Wako Pure Chemical Industries, Ltd.), 2,2'-azobis (2-methylpropionamidine) dihydrochloride (V) -50, azo compounds such as Wako Pure Chemical Industries, Ltd.) can be mentioned. From the viewpoint of high solubility in water, it is preferable to use persulfates and organic peroxides, and it is more preferable to use persulfates. As the polymerization initiator, one type may be used alone, or two or more types may be used in combination.

As the polymerization initiator, one having high solubility in water is preferable. The solubility in water at 20 ° C. of the polymerization initiator, 0.1g / _{100g-H 2} O or more preferably, 0.5g / _{100g-H 2} O or more preferably, 3.0g / _100g-H 2 O The above is more preferable.
Examples of the polymerization initiator having a solubility in water of 0.1 g / 100 g-H ₂ O or more include persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, cumene hydroperoxide, and t-butyl hydroper. Organic peroxides such as oxides, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] (VA-061, manufactured by Wako Pure Chemical Industries, Ltd.), 2,2'-azobis [2-Methyl-N- (2-hydroxyethyl) propionamide] (VA-086, manufactured by Wako Pure Chemical Industries, Ltd.), 2,2'-azobis [2- (2-imidazolin-2-yl) propane ] Dihydrochloride (VA-044, manufactured by Wako Pure Chemical Industries, Ltd.), 2,2'-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate (VA-046B, Examples thereof include azo compounds such as Wako Pure Chemical Industries, Ltd.) and 2,2'-azobis (2-methylpropion amidine) dihydrochloride (V-50, manufactured by Wako Pure Chemical Industries, Ltd.). Due to its high solubility in water, persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, t-butyl hydroperoxide, 2,2'-azobis [2- (2-imidazolin-2-yl) ) Propane] Dihydrochloride (VA-044, manufactured by Wako Pure Chemical Industries, Ltd.), 2,2'-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate (VA- 046B, manufactured by Wako Pure Chemical Industries, Ltd., 2,2'-azobis (2-methylpropionamidine) dihydrochloride (V-50, manufactured by Wako Pure Chemical Industries, Ltd.) is preferable.

The amount of the polymerization initiator used is not particularly limited, but the ethylenically unsaturated single amount is easy to proceed from the viewpoint of easy progress of polymerization, easy reaction control, easy reduction of the amount of aggregates, and easy reduction of the molecular weight of the polymer (A). With respect to 100 parts by mass of the body (a), 0.0001 to 10 parts by mass is preferable, 0.01 to 5 parts by mass is more preferable, and 0.5 to 2 parts by mass is further preferable. When the amount of the polymerization initiator used is 0.0001 parts by mass or more, the formation of agglomerates during polymerization can be suppressed, and when it is 10 parts by mass or less, the raw material cost can be suppressed. Further, as the amount of the polymerization initiator increases, the amount of aggregates tends to decrease.
When a reactive surfactant is contained in the surfactant component used in the production method of the present invention, the amount of the polymerization initiator used is the ethylenically unsaturated monomer (a) and the reactive surfactant. It is preferable that the total amount is within the above range with respect to 100 parts by mass.

(Surfactant)
Surfactants include nonionic surfactants.
Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxyethylene derivative, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester, and poly. Examples thereof include oxyethylene fatty acid ester, polyoxyethylene hydrogenated castor oil, polyoxyethylene alkylamine, and alkylalkanolamide. In addition, a reactive nonionic surfactant having an ethylenically unsaturated bond in the surfactant component can also be used.

Regarding polyoxyethylene alkyl ethers, for example, Emargen 1135S-70 (trade name, manufactured by Kao Corporation), Emargen 1118S-70 (trade name, manufactured by Kao Corporation), Emargen 1150S-60 (trade name, manufactured by Kao Corporation). (Manufactured by Kao Corporation), Emargen 350 (trade name, manufactured by Kao Corporation), etc.

Examples of the reactive nonionic surfactant having an ethylenically unsaturated bond include ethylene oxide-modified (meth) acrylate and allyloxypolyoxyethylene. Among the ethylene oxide-modified (meth) acrylates, the alkoxylated 2-phenoxyethyl acrylate is available as Sartomer CD9087 (trade name, manufactured by Sartmer). Further, allyloxypolyoxyethylene can be obtained as Adecaria Soap ER-30 (trade name, manufactured by ADEKA Corporation) and the like.
As the nonionic surfactant, one type may be used alone, or two or more types may be used in combination.

The surfactant needs to contain a nonionic surfactant, but as long as the effect of the present invention is not impaired, in addition to the nonionic surfactant, an interface other than the nonionic surfactant is used. Activators may be used. Examples of other surfactants include cationic surfactants, anionic surfactants, and amphoteric surfactants. As the other surfactant, one type may be used alone, or two or more types may be used in combination.

The mass ratio of the nonionic surfactant to the total mass of the surfactant used is preferably 85% by mass or more, more preferably 92% by mass or more, further preferably 97% by mass or more, and particularly preferably 99% by mass or more. The higher the mass ratio of the nonionic surfactant, the more the formation of agglomerates during polymerization can be suppressed.

The amount (solid content) of the surfactant used is not particularly limited, but is preferably 0.001 to 20 parts by mass, preferably 0.002 to 5 parts by mass, based on 100 parts by mass of the ethylenically unsaturated monomer (a). Is more preferable, and 0.01 to 2.5 parts by mass is further preferable. When the amount of the surfactant used is not less than the lower limit, the polymerization stability and the storage stability of the latex are improved. When the amount of the surfactant used is not more than the upper limit, it is easy to maintain the stability when the latex is used as the coating material. Furthermore, it is easy to maintain the stability of the polymer fine particles recovered from the latex.
When the surfactant component used in the production method of the present invention contains a reactive surfactant, the amount of the surfactant used is the ethylenically unsaturated monomer (a) and the reactive surfactant. It is preferable that the total amount of ethylene is in the above range with respect to 100 parts by mass.

(Emulsion polymerization)
The emulsion polymerization of the ethylenically unsaturated monomer (a) in the present invention includes any emulsion polymerization in which the monomer is polymerized in the presence of an emulsifier, such as miniemulsion polymerization and microemulsion polymerization. As the method of emulsion polymerization, various methods such as seed polymerization, batch polymerization, drop polymerization, multi-stage polymerization and the like can be used depending on the purpose.

The emulsion polymerization reaction solution includes a chain transfer agent containing a cobalt complex (X), a polymerization initiator, a surfactant containing a nonionic surfactant, an ethylenically unsaturated monomer (a), water, and others. Known polymerization additives and the like can be used.

The method for preparing the reaction solution is not particularly limited, and examples thereof include the following methods (α) to (γ).
(Α) A method in which an ethylenically unsaturated monomer (a) containing a chain transfer agent is charged in water containing a polymerization initiator, and then a surfactant is added.
(Β) A method in which an ethylenically unsaturated monomer (a) containing a chain transfer agent is added after charging a surfactant in water containing a polymerization initiator.
(Γ) A method in which a surfactant is charged in an ethylenically unsaturated monomer (a) containing a chain transfer agent, and then water containing a polymerization initiator is added.

Examples of the mixing device for preparing the reaction solution include a stirrer equipped with a stirring blade, a homogenizer, various forced emulsification devices such as a homomixer, and a membrane emulsification device.
The reaction solution to be prepared may have any dispersion structure of W / O type (Water in Oil type, water droplet type in oil) and O / W type (Oil in Water type, oil droplet type in water), but particularly in water. It is preferably an O / W type in which oil droplets containing the ethylenically unsaturated monomer (a) are dispersed.

The amount of water used in the reaction solution is preferably 10 to 900 parts by mass, more preferably 100 to 400 parts by mass, based on 100 parts by mass of the ethylenically unsaturated monomer (a). When the amount of water used is not less than the lower limit, it is easy to maintain the stability of emulsion polymerization. When the amount of water used is not more than the upper limit, latex having a high solid content concentration can be easily obtained, and polymer fine particles can be efficiently recovered.
When the surfactant component used in the production method of the present invention contains a reactive surfactant, the amount of water used is the total of the ethylenically unsaturated monomer (a) and the reactive surfactant. It is preferable that the amount is within the above range with respect to 100 parts by mass.

The polymerization temperature can be appropriately set, and is preferably 50 to 130 ° C, more preferably 60 to 85 ° C, and even more preferably 60 to 74 ° C. The higher the polymerization temperature, the shorter the reaction time. The lower the polymerization temperature, the easier it is to reduce the amount of aggregates.

In the method for producing latex of the present invention, latex in which the polymer (A) contains a macromonomer may be produced. The macromonomer is a polymer having a polymerizable functional group, and is also called a macromer. That is, in the method for producing latex of the present invention, latex containing a polymer (A) having a terminal unsaturated structure may be produced. The polymer (A) containing the macromonomer thus obtained can be used in a wide range of applications.

For example, when a latex is produced using an α-methylvinyl monomer (CH ₂ = C (CH ₃ ) Z) as the ethylenically unsaturated monomer (a), the polymer (A) formed is of the formula (2). ) Has a terminal group.

In the method for producing latex of the present invention, by using a surfactant containing a large amount of nonionic surfactant, the amount of micellar reaction field and the amount of ionic groups on the surface of monomeric oil droplets in emulsion polymerization is small, and the micellar reaction field and It is predicted that collision with monomeric oil droplets is likely to occur. Therefore, it is considered that the movement of the cobalt complex (X) from the monomeric oil droplets to the micellar reaction field occurs efficiently, and the catalytic chain transfer polymerization by the cobalt complex (X) occurs efficiently in the micellar reaction field. .. As a result, it is considered that the formation of low molecular weight oligomers by catalytic chain transfer polymerization by the cobalt complex (X) in the monomeric oil droplets is suppressed, and there are few aggregates during emulsion polymerization.

[Dressing material]
The latex obtained by the method for producing latex of the present invention is preferably used as a coating material. Since the latex obtained by the production method of the present invention has a small amount of agglomerates, a coating material having an excellent appearance can be obtained by using it as a raw material for a coating material.

Covering materials include various pigments, defoamers, pigment dispersants, leveling agents, anti-dripping agents, matting agents, UV absorbers, antioxidants, heat resistance improvers, slip agents, preservatives, as required. Etc. may be blended. Further, the coating material may contain other curing agents such as emulsion resins, water-soluble resins, viscosity control agents, and melamines, if necessary.

The solid content of the coating material is formed of latex as a main component, various surfactants, additives and the like, and can be, for example, 20 to 80% by mass.

The covering material obtained by the production method of the present invention is cement mortar, slate board, gypsum board, extruded board, foamable concrete, metal, glass, porcelain tile, asphalt, wood, waterproof rubber material, plastic, calcium silicate base material. It is useful as a surface finish covering material for various materials such as, and is particularly useful as a covering material for skeleton protection of buildings, civil engineering structures, and the like.

As a method of applying the coating material to the surface of various base materials, for example, various coating methods such as a spray coating method, a roller coating method, a bar coating method, an air knife coating method, a brush coating method, a dipping method, and a flow coating method are used. You can choose.

[Polymer fine particles]
By coagulating or spray-drying the solid content of the latex obtained by the method for producing latex of the present invention, polymer fine particles made of the polymer (A) can be obtained. Since the latex obtained by the production method of the present invention has few agglomerates, polymer fine particles can be recovered from the latex solid content in good yield.

As a method for solidifying the solid content, a known method can be used, and the following method is preferable. After the latex is brought into contact with an aqueous solution of a coagulant to coagulate it, it is washed with water having a mass ratio of about 1 to 100 times that of the polymer (A), and dehydrated by filtration or the like to obtain a wet powder. To do. Next, the wet powder is dried with a hot air dryer such as a squeeze dehydrator or a fluidized dryer to obtain polymer fine particles. The drying temperature and drying time can be appropriately determined depending on the type of the polymer (A).

Examples of the spray drying include the following methods. The polymer (A) is recovered as polymer fine particles by spraying (miniaturizing) latex in a drying gas (hot air) using a spray dryer.
As the spray dryer, a known spray dryer can be used, and a dryer having any capacity from a small test scale to an industrial scale can be used. Examples of the spray dryer include a circulation type spray dryer in which a drying gas used for drying is circulated and used. The circulation type spray dryer can reduce the amount of exhaust gas discharged from the dryer as compared with the conventional spray dryer, and it is easy to recover the volatile components contained in the circulation gas, so that the polymer fine particles Suitable for recovery.

The latex spraying method using a spray dryer may be any of a pressure nozzle type, a two-fluid nozzle type, a pressurized two-fluid nozzle type and the like. The temperature of the drying gas is preferably 120 to 250 ° C.
In the present invention, the polymer fine particles of the recovered polymer (A) may be further dried by fluid drying or the like.

The polymer fine particles recovered from the latex are added with a general compounding agent as needed, and are added to various resin molded products by methods such as extrusion molding, injection molding, vacuum molding, blow molding, and compression molding. It is molded.

[Macromonomer copolymer]
When the polymer (A) in the latex obtained by the method for producing latex of the present invention contains a macromonomer, it can be copolymerized with an ethylenically unsaturated monomer (b) to obtain a macromonomer copolymer. it can. Since the latex obtained by the production method of the present invention has few aggregates in the latex, it is easy to make the copolymer composition of the polymer (A) containing a macromonomer and the ethylenically unsaturated monomer (b) uniform. A macromonomer copolymer can be easily produced.

The copolymerization method is not particularly limited, and various methods such as solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization can be used. Water-based polymerization such as suspension polymerization or emulsion polymerization is preferable because the heat generation of polymerization can be easily controlled and the productivity is excellent, and emulsion polymerization is more preferable because latex containing a macromonomer is used.

As the ethylenically unsaturated monomer (b), any monomer may be used as long as it can be copolymerized with the polymer (A) containing a macromonomer, and various monomers can be appropriately used. Examples of the ethylenically unsaturated monomer (b) include the same ones mentioned in the ethylenically unsaturated monomer (a). As the ethylenically unsaturated monomer (b), one type may be used alone, or two or more types may be used in combination.

The macromonomer copolymer may be a block copolymer having a unit derived from the macromonomer and a unit derived from the ethylenically unsaturated monomer (b), and a unit derived from the macromonomer is used in the side chain. It may be a graft copolymer of the ethylenically unsaturated monomer (b) having.

The macromonomer copolymer includes a polymer having only a macromonomer unit, a polymer consisting of only an ethylenically unsaturated monomer (b), an unreacted macromonomer, and an unreacted ethylenically unsaturated monomer ( One or more selected from the group consisting of b) may be included.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the following description. In the following description, "part" means "part by mass".
[Measuring method]
1. 1. Yield The solid content concentration of the normal latex obtained in each example was measured, and the yield (%) was calculated from the following formulas (3) to (5). The normal latex means a net mass, and excludes agglomerates adhering to the polymerization apparatus during polymerization, agglomerates removed by filtration through a 100-mesh stainless mesh, and the like.
Yield (%) = A / B x 100 ... (3)
A = M ₁ / M ₂ x 100 ... (4)
B = M ₃ / M ₄ × 100 ・ ・ ・ (5)
However, in the formula (3), A is the solid content concentration (mass%) of the normal latex, and B is the monomer concentration (mass%) of the charge in the reaction solution. Further, in the formula (4), M ₁ is the mass (g) of the residue after drying the normal latex at 120 ° C. for 2 hours in a nitrogen atmosphere, and M ₂ is the mass (g) of the normal latex before drying. ). In formula (5), M ₃ is the mass (g) of the charged monomer, and M ₄ is the total mass (g) of the charged reaction solution.

2. 2. Agglutination amount The latex after the polymerization reaction was filtered using a 100 mesh stainless mesh, and the agglutination was recovered. The recovered agglomerates were dried at normal pressure at 25 ° C. for 12 hours, and then the mass was measured. However, when a large amount of agglutinates adheres to the reaction apparatus after the polymerization reaction and is larger than the agglutinates recovered by the stainless mesh, and when there are many unreacted monomers in the reaction apparatus after the polymerization reaction, the viscosity is high. When the syrup-like material with a certain amount accumulated at the bottom of the polymerization apparatus and the recovery rate of normal latex was low (yield less than 10%), it was judged as "unmeasurable".

3. 3. Number average molecular weight (Mn) Mass average molecular weight (Mw) and molecular weight distribution (Mw / Mn)
The Mw and Mn of the polymer were measured by gel permeation chromatography (GPC) (manufactured by Tosoh Corporation, trade name: HLC-8220) under the following conditions.
Sample preparation: Normal latex obtained by filtration using a 100-mesh stainless mesh is dried at 120 ° C. for 2 hours in a nitrogen atmosphere, and then tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd., Wako First Grade, Stabilizer). It was dissolved in 2,6-t-butyl-4-methylphenol (dibutylhydroxytoluene) (BHT) containing about 0.03%) so as to be 0.2% by mass.
Column: TSK GUARD COLUMN SUPER H-H (4.6 mmφ x 35 mm, manufactured by Tosoh Corporation) and two TSK-GEL SUPER HM-H (6.0 mmφ x 150 mm, manufactured by Tosoh Corporation) are connected in series. did.
Eluent: tetrahydrofuran Measurement temperature: 40 ° C
Flow rate: 0.6 mL / min Mw and Mn are methyl polymethacrylate (Mp (peak top molecular weight) = 2,100,000, 1,100,000, 600,000, 300,000," manufactured by American Polymer Standards Corporation. It was determined using a calibration curve prepared using 10 types of 122,300, 51,000, 35,000, 11,800, 4,900 and 1,950).

[Manufacturing Example 1]
In a synthesizer equipped with a stirrer, 1.00 g of cobalt (II) acetate tetrahydrate, 1.93 g of diphenylglioxime, and 80 mL of diethyl ether previously deoxidized by nitrogen bubbling were placed in a nitrogen atmosphere at room temperature. Was stirred for 30 minutes. Then, 10 mL of boron trifluoride diethyl ether complex was added, and the mixture was further stirred for 6 hours. The resulting mixture was filtered, the filtrate was washed with diethyl ether and vacuum dried for 15 hours to a reddish brown solid cobalt complex (X-1) (bis (borondifluorodiphenylglycimate) cobalt (II), In the following formula (1), 2.12 g of R ^{1 to} R ⁴ : phenyl group, X ^{1 to} X ⁴ : fluorine atom) was obtained.

[Example 1]
The raw material (a) shown below was placed in a polymerization apparatus equipped with a stirrer, a cooling tube and a thermometer and stirred at 200 rpm to obtain a uniform aqueous solution. Next, while stirring, the raw materials (b) shown below, which had been mixed in advance, were added, and stirring was carried out for 30 minutes to prepare an emulsion. Next, while stirring, the following raw material (c) was added, nitrogen was substituted while stirring at 200 rpm, the temperature was raised to 70 ° C., and the polymerization reaction was continued for about 3 hours. During the course of the reaction, the inside of the polymerization apparatus was kept under a nitrogen atmosphere. Then, the reaction solution was cooled to 40 ° C. to obtain latex (I-1).

Ingredient (a):
Deionized water 385.00 parts Emargen 1135S-70 1.43 parts (1.00 parts as solid content)
Ingredient (b):
Methyl methacrylate 100.00 parts Cobalt complex (X-1) 0.01 parts Raw material (c):
Deionized water 13.00 parts Potassium persulfate 0.80 parts

[Examples 2-9, Comparative Examples 1-5, Reference Example 1]
Latexes (I-2) to (I-15) were obtained in the same manner as in Example 1 except that the type and amount of the polymerization initiator and the surfactant and the polymerization temperature were changed as shown in Table 1.
The evaluation results of each example are shown in Table 1.

The symbols in Table 1 are as follows.
MMA: Methyl Methacrylate (Acryester M, manufactured by Mitsubishi Rayon Co., Ltd.)
KPS: Potassium persulfate (solubility in water at 20 ° C: 5.2 g / 100 g-H ₂ O, manufactured by Wako Pure Chemical Industries, Ltd., Wako First Class)
ACVA: 4,4'-azobis (4-cyanovalec acid) (solubility in water at 20 ° C: insoluble in water (less than 0.1 g / 100 g-H ₂ O), manufactured by Otsuka Chemical Co., Ltd.)
1135S-70: Trade name "Emargen 1135S-70" (nonionic surfactant, solid content 70% by mass, manufactured by Kao Corporation)
1118S-70: Trade name "Emargen 1118S-70" (nonionic surfactant, solid content 70% by mass, manufactured by Kao Corporation)
1150S-60: Trade name "Emargen 1150S-60" (nonionic surfactant, solid content 60% by mass, manufactured by Kao Corporation)
350: Product name "Emargen 350" (nonionic surfactant, manufactured by Kao Corporation)
G-15: Trade name "Neoperex G-15" (anionic surfactant, solid content 16% by mass, manufactured by Kao Corporation)

In Examples 1 to 9 in which latex was produced by the production method of the present invention, the yield was high and the amount of agglomerates in the obtained latex was small.
On the other hand, in Comparative Examples 1 to 5 in which the ratio of the nonionic surfactant to the surfactant was less than 85% by mass, the amount of aggregates was compared with Examples 1 to 9 in which the same amount of cobalt complex was used. The yield was low.
In Reference Example 1 in which an azo initiator having low water solubility was used as the polymerization initiator, emulsion polymerization did not proceed properly, and a viscous syrup-like material accumulated at the bottom of the polymerization apparatus, resulting in a low latex yield. ..

Claims (5)

A method for producing a latex containing a polymer (A) obtained by emulsion polymerization of an ethylenically unsaturated monomer (a) in the presence of a chain transfer agent, a polymerization initiator and a surfactant.
The chain transfer agent contains a cobalt complex (X) represented by the following formula (1).
A method for producing a latex, wherein the surfactant contains 85% by mass or more of a nonionic surfactant.

(However, in the above formula (1), R ^{1 to} R ⁴ are independently alkyl groups, cycloalkyl groups or aryl groups, respectively, and X ^{1 to} X ⁴ are independently fluorine atoms, chlorine atoms and bromine atoms, respectively. , Hydroxy group, alkoxy group, aryloxy group, alkyl group or aryl group.) The method for producing latex according to claim 1, wherein the solubility of the polymerization initiator in water at 20 ° C. is 0.1 g / 100 g-H ₂ O or more. The method for producing latex according to claim 1 or 2, wherein the polymer (A) contains a macromonomer. A method for producing a coating material, which comprises obtaining a latex by the method for producing latex according to any one of claims 1 to 3 to obtain a coating material containing the latex. A method for producing polymer fine particles, wherein the latex is obtained by the method for producing latex according to any one of claims 1 to 3, and the solid content of the latex is coagulated or spray-dried to obtain polymer fine particles.