Emulsifier-free polymer emulsion whose dispersion is stabilized with highly concentrated styrenesulfonic acid, and method for manufacturing the same

Abstract

To provide: an emulsifier-free polymer emulsion whose dispersion is stabilized with highly concentrated styrenesulfonic acid or its salt; and a simple method for manufacturing the emulsion.SOLUTION: An emulsifier-free polymer emulsion whose dispersion is stabilized with highly concentrated styrenesulfonic acid or its salt can be simply manufactured by subjecting styrenesulfonate and oil-soluble vinyl monomer to solution polymerization in an aqueous solvent including a specific water-soluble organic solvent, followed by distillation of the water-soluble organic solvent.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an emulsifier-free polymer emulsion stabilized by dispersion with a high concentration of styrenesulfonic acid or a salt thereof, and a method for producing the same.

Background Art

[0002] Polymer emulsions are used as main raw materials for aqueous paints, aqueous adhesives, aqueous primers, aqueous film coatings, aqueous inks, and aqueous binders, etc. In addition, they are used as latex agglutination diagnostic agents, colloidal crystals, toner particles, and members of solid oxide fuel cells and lithium secondary batteries (for example, Patent Documents 1 to 11).

[0003] As an industrial production method of polymer emulsions, the emulsion polymerization method is the mainstream. In the traditional emulsion polymerization method, an oil-soluble vinyl monomer is solubilized and emulsified and dispersed in water using an emulsifier, and then a water-soluble radical polymerization initiator is added to perform radical polymerization of the oil-soluble vinyl monomer in a heterogeneous system.

[0004] Although the emulsifier plays an important role in solubilizing the monomer and stabilizing the polymer emulsion (also referred to as colloidal stability), it may cause foaming of the emulsion and may have an adverse effect on the adhesion and water resistance of the coating film when adhesives and paints are applied to various substrates. Therefore, a so-called emulsifier-free emulsion polymerization method (also referred to as a soap-free emulsion polymerization method or a surfactant-free emulsion polymerization method) that does not use a general emulsifier or reduces the amount of emulsifier used as much as possible has been actively studied and partially put into practical use (for example, Patent Documents 1 and 2).

[0005] A typical example of the emulsion polymerization method without an emulsifier is a method using a small amount of sodium styrene sulfonate instead of a general emulsifier. When sodium styrene sulfonate is immobilized on the surface of polymer particles by copolymerization, the colloidal stability is dramatically improved (for example, Non-Patent Document 1). An emulsion stabilized with sodium styrene sulfonate, which is a strong acid salt, has a feature that its stability against electrolytes and pH is much higher compared to an emulsion stabilized with a weak acid salt such as acrylate.

[0006] However, since sodium styrene sulfonate has high radical polymerization reactivity and is soluble only in water, for example, even if the addition amount is increased for the purpose of further improving colloidal stability, the introduction amount of sodium styrene sulfonate on the surface of polymer particles cannot be increased. The addition amount of sodium styrene sulfonate to all vinyl monomers in the emulsion polymerization of an oil-soluble vinyl monomer without an emulsifier is considered to be the highest at 3.6% by weight (among which, the introduction rate to the particle surface is about 85%) (for example, Non-Patent Document 1). That is, sodium styrene sulfonate in the aqueous phase is preferentially polymerized by the initiating radicals generated in the aqueous phase, and a water-soluble polymer containing a large amount of sodium styrene sulfonate is generated in the aqueous phase. Since the water-soluble polymer causes aggregation, enlargement of polymer particles, and deterioration of coating film physical properties, it is necessary to avoid it as much as possible (for example, Non-Patent Documents 2 to 4).

[0007] In addition, since the polymer emulsion is a heterogeneous dispersion system, its physical properties are determined by not only the primary structure of the polymer chain itself and the emulsion system of the emulsion, but also the polymer particle size and particle size distribution. That is, the particle size and particle size distribution strongly affect the colloidal stability, viscosity, film-forming property of the polymer emulsion, and adhesion of the coating film to the substrate. Therefore, a method for producing fine seeds necessary for controlling the particle size of the polymer emulsion and a seed emulsion polymerization method using the seeds have been actively studied and partially put into practical use (for example, Patent Documents 3 and 4).

[0008] If it were possible to increase the amount of sodium styrene sulfonate introduced without generating a water-soluble polymer and to produce a polymer emulsion with a smaller particle size and a narrower particle size distribution, it would be extremely useful as a seed for seed emulsion polymerization and would also be useful as a raw material for moisture-permeable paints (for example, Patent Documents 9 and 10). Therefore, there has been a strong demand for its production method.

[0009] By the way, core-shell type polymer particles with an average particle size of 50 to 1000 nm into which sodium styrene sulfonate has been introduced at a high concentration of 10% by weight or more and a method for producing the same have been reported (for example, Patent Document 8). Certainly, sodium styrene sulfonate is introduced into the shell layer at a high concentration, but in order to immobilize sodium styrene sulfonate, which is only soluble in water, in the shell layer, it is essential to crosslink and insolubilize the polymer with a divinyl monomer such as N,N'-methylenebisacrylamide.

[0010] Also, polymer particles having a particle size of 50 nm to 5 μm and containing 0.01% to 20% by weight of an acidic functional group and a method for producing the same have been reported (for example, Patent Document 6). However, the amount of sodium styrene sulfonate having an acidic functional group introduced is substantially 1.0% by weight or less, and like Patent Document 8, it is crosslinked with a crosslinkable monomer such as divinylbenzene. Since all of the above have the shell layer or the entire particle crosslinked, the film-forming property and the adhesion to various substrates are impaired, and there are also problems such as difficulty in significantly growing the seed even when emulsion polymerization is carried out using this as a seed.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

[0012] [Non-Patent Document 1] Sevilay Bilgin; European Polymer Journal, 93 (2017), pp. 480 - 494 [Non-Patent Document 2] Osamu Kubo; Journal of the Adhesion Society of Japan, Vol. 18, No. 12 (1982), pp. 530 - 535 [Non-Patent Document 3] Sevilay Bilgin; Progress in Organic Coatings, 162 (2022), 106591 [Non-Patent Document 4] Lorena Farias-Cepeda; Colloid Polymer Science, 294 (2016), pp. 1571 - 1576 [Non-Patent Document 5] Tsukigase; Polymer Transactions, Vol. 64, No. 3 (2007), pp. 147 - 154 [Summary of the Invention] [Problems to be Solved by the Invention]

[0013] The present invention has been made in view of the above background and problems, and an object thereof is to provide an emulsifier-free polymer emulsion dispersed and stabilized with a high concentration of styrenesulfonic acid, and a method for producing the same. [Means for Solving the Problems]

[0014] As a result of intensive studies by the present inventors, in an aqueous solvent containing a specific water-soluble organic solvent, after solution polymerization of a water-soluble styrenesulfonate and an oil-soluble vinyl monomer, by distilling off the water-soluble organic solvent, It has been found that an emulsifier-free polymer emulsion dispersed and stabilized with a high concentration of styrenesulfonic acid or a salt thereof can be obtained, and the present invention has been completed.

[0015] That is, the present invention relates to the following. [1] An emulsifier-free polymer emulsion in which the contained water-soluble organic solvent is distilled off from a solution of a copolymer obtained by radical copolymerization of (A) a styrenesulfonate and (B) a vinyl monomer other than the styrenesulfonate in an aqueous solvent containing a water-soluble organic solvent, wherein the amount of (A) the styrenesulfonate is 30% by weight to 55% by weight based on the total of (A) the styrenesulfonate and (B) the vinyl monomer other than the styrenesulfonate, and the average particle diameter of the polymer particles is 50 nm to 500 nm. Emulsifier-free polymer emulsion. [2] The emulsifier-free polymer emulsion according to item [1], wherein the water-soluble organic solvent is a water-soluble organic solvent having a lower boiling point than water. [3] The emulsifier-free polymer emulsion according to item [1], wherein the water-soluble organic solvent is at least one water-soluble organic solvent selected from the group consisting of dimethoxymethane, acetone, 1,1-dimethoxyethane, 1,2-dimethoxyethane, methanol, ethanol, 2-propanol, 1-propanol, tert-butanol, acetonitrile, methyl ethyl ketone, and tetrahydrofuran. [4] The surfactant-free polymer emulsion according to item [1], wherein the weight average molecular weight determined by gel permeation chromatography of the copolymer is 5,000 Daltons (Da) to 200,000 Daltons (Da). [5] The surfactant-free polymer emulsion according to item [1], wherein the styrene sulfonate is one or more selected from the group consisting of sodium 4-styrenesulfonate, lithium 4-styrenesulfonate, potassium 4-styrenesulfonate, ammonium 4-styrenesulfonate, N,N-dimethylcyclohexylamine 4-styrenesulfonate, sodium 4-styrenesulfonyl(trifluoromethylsulfonylimide), lithium 4-styrenesulfonyl(trifluoromethylsulfonylimide), and potassium 4-styrenesulfonyl(trifluoromethylsulfonylimide). [6] The surfactant-free polymer emulsion according to item [1], wherein 70% by weight or more of the vinyl monomers other than the (B) styrene sulfonate are one or more oil-soluble vinyl monomers selected from the group consisting of (C) styrenes, acrylic esters, and methacrylic esters, and less than 30% by weight of the vinyl monomers other than the (B) styrene sulfonate are vinyl monomers copolymerizable with radicals with one or more oil-soluble vinyl monomers selected from the group consisting of (D) styrenes, acrylic esters, and methacrylic esters. [7] A method for producing a surfactant-free polymer emulsion according to item [1], wherein (A) styrene sulfonate and (B) vinyl monomers other than styrene sulfonate are solution polymerized using a radical polymerization initiator in an aqueous solvent containing the water-soluble organic solvent, and then the water-soluble organic solvent is distilled off. [8] The method for producing a surfactant-free polymer emulsion according to item [7], wherein the addition amount of (A) styrene sulfonate is 30% by weight to 55% by weight based on the total of the monomers (A) and (B), and the ratio of the water-soluble organic solvent in the aqueous solvent is 30% by weight to 60% by weight. [9] An aqueous paint, an aqueous adhesive, an aqueous coating agent, an aqueous binder, an aqueous ink, or a conductive polymer, characterized by containing the surfactant-free polymer emulsion according to items [1] to [6].

Advantages of the Invention

[0016] The polymer emulsion without emulsifier of the present invention is characterized in that it is dispersion-stabilized with a high concentration of styrenesulfonic acid or its salt, and has both a fine particle size and colloidal stability due to the sulfonic groups immobilized on the particle surface. Therefore, it can be used as a seed for seed emulsion polymerization without emulsifier, and can also be used as a raw material for functional fine particles and moisture-permeable paints.

Brief Description of Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0018] Hereinafter, the modes for carrying out the present invention will be described in detail.

[0019] Sodium styrenesulfonate (hereinafter abbreviated as NaSS) is an extremely convenient monomer for emulsion polymerization of oil-soluble vinyl monomers in water without an emulsifier. However, as described above, there were significant limitations on the addition amount and introduction amount of NaSS. That is, as long as polymerization is carried out in a heterogeneous system (emulsion polymerization system) such as Patent Document 6 (Japanese Patent Application Laid-Open No. 2009-57479) and Patent Document 8 (Japanese Patent Application Laid-Open No. 2013-7011), there is a limit to the introduction amount of NaSS that is only soluble in water. Therefore, it was necessary to insolubilize the hydrophilic or water-soluble polymer produced by copolymerization of NaSS with a crosslinkable monomer such as a divinyl monomer.

[0020] The inventors of the present invention polymerized (A) a styrenesulfonate represented by NaSS and (B) a vinyl monomer other than the styrenesulfonate in a homogeneous solution system using a radical polymerization initiator in an aqueous solvent containing a specific water-soluble organic solvent, and then distilled off the water-soluble organic solvent to obtain an emulsifier-free polymer emulsion stabilized with a high concentration of styrenesulfonic acid or a salt thereof, leading to the present invention.

[0021] Examples of the (A) styrenesulfonate used in the present invention include sodium 4-styrenesulfonate, lithium 4-styrenesulfonate, potassium 4-styrenesulfonate, ammonium 4-styrenesulfonate, N,N-dimethylcyclohexylamine 4-styrenesulfonate, sodium 4-styrenesulfonyl(trifluoromethylsulfonylimide), lithium 4-styrenesulfonyl(trifluoromethylsulfonylimide), potassium 4-styrenesulfonyl(trifluoromethylsulfonylimide), etc., and they can be used according to the application.

[0022] As the vinyl monomer other than (B) styrene sulfonate used in the present invention, there is no particular limitation as long as it can be radically polymerized with styrene sulfonate. For example, styrene, chlorostyrene, dichlorostyrene, bromostyrene, dibromostyrene, fluorostyrene, trifluorostyrene, nitrostyrene, cyanostyrene, α-methylstyrene, p-chloromethylstyrene, p-cyanostyrene, p-acetoxystyrene, p-styrenesulfonyl chloride, ethyl p-styrenesulfonyl, methyl p-styrenesulfonyl, propyl p-styrenesulfonyl, p-butoxystyrene, 2-vinylpyridine, 4-vinylpyridine, 4-vinylbenzoic acid, 3-isopropenyl-α,α'-dimethylbenzyl isocyanate, divinylbenzene, divinylbenzenesulfonic acid, divinylbenzenesulfonate and other styrenes, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, decyl acrylate, lauryl acrylate, octyl acrylate, dodecyl acrylate, stearyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, bornyl acrylate, 2-ethoxyethyl acrylate, 2-butoxyethyl acrylate, 2-hydroxyethyl acrylate, tetrahydrofurfuryl acrylate, methoxyethylene glycol acrylate, ethyl carbitol acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 3-(trimethoxysilyl)propyl acrylate, polyethylene glycol acrylate, glycidyl acrylate, 2-(acryloyloxy)ethyl phosphate, 2,2,3,3-tetrafluoropropyl acrylate, 2,2,2-trifluoroethyl acrylate, 2,2,3,3,3-pentafluoropropyl acrylate, 2,2,3,4,4,Acrylic esters such as 4-hexafluorobutyl, ethylene glycol diacrylate, triethylene glycol diacrylate, trimethylolpropane triacrylate, polyethylene glycol diacrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, sec-butyl methacrylate, i-butyl methacrylate, i-propyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, lauryl methacrylate, octyl methacrylate, dodecyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, bornyl methacrylate, benzyl methacrylate, phenyl methacrylate, glycidyl methacrylate, polyethylene glycol methacrylate, 2-hydroxyethyl methacrylate, tetrahydrofurfuryl methacrylate, methoxyethylene glycol methacrylate, ethyl carbitol methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 2-(methacryloyloxy)ethyl phosphate, 2-(dimethylamino)ethyl methacrylate, 2-(diethylamino)ethyl methacrylate, 3-(dimethylaminopropyl) methacrylate, 2-(isocyanato)ethyl methacrylate, 2,4,6-tribromophenyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,2-trifluoroethyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,4,4,Methacrylic acid esters such as 4-hexafluorobutyl, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, polyethylene glycol dimethacrylate, etc., N-cyclohexylmaleimide, N-methylmaleimide, N-ethylmaleimide, N-phenylmaleimide, N-(chlorophenyl)maleimide, N-(methylphenyl)maleimide, N-(isopropylphenyl)maleimide, N-(sulfophenyl)maleimide, N-methylphenylmaleimide, N-bromophenylmaleimide, N-naphthylmaleimide, N-hydroxyphenylmaleimide, N-methoxyphenylmaleimide, N-carboxyphenylmaleimide, N-(nitrophenyl)maleimide, N-benzylmaleimide, N-(4-acetoxy-1-naphthyl)maleimide, N-(4-oxy-1-naphthyl)maleimide, N-(3-fluoranthenyl)maleimide, N-(5-fluoresceinyl)maleimide, N-(1-pyrenyl)maleimide, N-(2,3-xylyl)maleimide, N-(2,4-xylyl)maleimide, N-(2,6-xylyl)maleimide, N-(aminophenyl)maleimide, N-(tribromophenyl)maleimide, N-[4-(2-benzimidazolyl)phenyl]maleimide, N-(3,5-dinitrophenyl)maleimide, N-(9-acridinyl)maleimide, 4,4'-diphenylmethane bismaleimide, phenylenebismaleimide and other maleimides, 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, 2-cyano-1,3-butadiene, 1-chloro-1,3-butadiene, 2-(N-piperidylmethyl)-1,3-butadiene, 2-triethoxymethyl-1,3-butadiene, 2-(N,N-dimethylamino)-1,3-butadiene, N-(2-methylene-3-butenoyl)morpholine, 2-methylene-3-butenylphosphonic acid diethyl and other 1,3-butadienes, acrylamide, N-methylacrylamide, N-ethylacrylamide, 2-hydroxyethylacrylamide, N,N-diethylacrylamide, acryloylmorpholine, N,Acrylamide compounds such as N-dimethylaminopropylacrylamide, isopropylacrylamide, N-methylolacrylamide, sulfophenylacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamido-1-methylsulfonic acid, diacetoneacrylamide, acrylamide alkyltrialkylammonium chloride, N,N'-methylenebisacrylamide, polyethylene glycol diacrylamide, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, 2-hydroxyethylmethacrylamide, N,N-diethylmethacrylamide, N,N-dimethylmethacrylamide, N-methylolmethacrylamide, methacryloylmorpholine, N,N-dimethylaminopropylmethacrylamide, isopropylmethacrylamide, 2-methacrylamido-2-methylpropanesulfonic acid, methacrylamide alkyltrialkylammonium chloride, N,Methacrylamides such as N'-methylenedimethacrylamide and polyethylene glycol dimethacrylamide; diesters of fumaric acid such as dibutyl fumarate, dipropyl fumarate, diethyl fumarate, dicyclohexyl fumarate, bis(2-ethylhexyl) fumarate, and dodecyl fumarate; monoesters of fumaric acid such as butyl fumarate, propyl fumarate, and ethyl fumarate; diesters of maleic acid such as dibutyl maleate, dipropyl maleate, and diethyl maleate; monoesters of maleic acid such as butyl maleate, propyl maleate, ethyl maleate, and dicyclohexyl maleate; acid anhydrides such as maleic anhydride and citraconic anhydride; and others such as vinyl pyrrolidone, sulfophenyl itaconimide, acrylonitrile, methacrylonitrile, fumaronitrile, α-cyanoethyl acrylate, citraconic acid, citraconic anhydride, vinyl acetic acid, vinyl propionate, vinyl pivalate, vinyl versamate, crotonic acid, itaconic acid, fumaric acid, maleic acid, mono-2-(methacryloyloxy)ethyl phthalate, mono-2-(methacryloyloxy)ethyl succinate, mono-2-(acryloyloxy)ethyl succinate, methacryloxypropyltrimethoxysilane, methacryloxypropyl dimethoxysilane, acrolein, vinyl methyl ketone, N-vinyl acetamide, N-vinyl formamide, vinyl ethyl ketone, vinyl sulfonic acid, allyl sulfonic acid, dehydroalanine, sulfur dioxide, isobutene, N-vinyl carbazole, vinylidene dicyanide, paraquinodimethane, chlorotrifluoroethylene, tetrafluoroethylene, norbornene, N-vinyl carbazole, vinyl chloride, vinylidene chloride, acrylic acid, methacrylic acid, etc.

[0023] 70% by weight or more of the vinyl monomers other than the above (B) styrene sulfonate are one or more oil-soluble vinyl monomers selected from the group consisting of (C) styrenes, acrylic esters, and methacrylic esters, which are highly versatile oil-soluble vinyl monomers such as styrenes, acrylic esters, and methacrylic esters. The other vinyl monomer (D) copolymerizable with these radicals is less than 30% by weight. The vinyl monomer (D) imparts properties such as polarity, water resistance, solvent resistance, and reactivity to polymers composed of highly versatile oil-soluble vinyl monomers such as styrenes, acrylic esters, and methacrylic esters, and the type and amount used can be determined according to the application.

[0024] The amount of the styrene sulfonate (A) used relative to the total amount of the vinyl monomers used is 30% to 55% by weight. If the styrene sulfonate is less than 30% by weight, agglomerates may easily precipitate during polymerization or during solvent evaporation after polymerization. If it exceeds 55% by weight, it may be difficult to form an emulsion. Therefore, it is preferably 30% to 50% by weight.

[0025] The total monomer concentration during polymerization is appropriately adjusted according to the solubility of the monomers used and the molecular weight of the target polymer, but is usually 5% to 30% by weight, preferably 5% to 20% by weight. If the total monomer concentration is less than 5% by weight, productivity may deteriorate. If it exceeds 30% by weight, the particle size of the polymer emulsion may become coarse.

[0026] The aqueous solvent referred to in the present invention is a mixed solvent composed of water and a water-soluble organic solvent. As the water-soluble organic solvent, an organic solvent having a boiling point lower than that of water is preferred, and examples thereof include dimethoxymethane, acetone, 1,1-dimethoxyethane, 1,2-dimethoxyethane, methanol, ethanol, 2-propanol, 1-propanol, tert-butanol, acetonitrile, methyl ethyl ketone, and tetrahydrofuran. In the present invention, first, in order to carry out radical copolymerization of (A) styrene sulfonate and (B) a vinyl monomer other than styrene sulfonate in a homogeneous solution system, at least these monomers need to be dissolved in a polymerization solvent. Therefore, the composition of the above aqueous solvent is appropriately adjusted according to the composition of the monomers to be used. Usually, the proportion of the aqueous organic solvent in the polymerization solvent is 30% by weight to 70% by weight, preferably 30% by weight to 60% by weight. When the aqueous organic solvent exceeds 70% by weight, the solubility may be insufficient depending on the type of styrene sulfonate, and when the aqueous organic solvent is less than 30% by weight, the solubility of the oil-soluble vinyl monomer may be insufficient.

[0027] As the radical polymerization initiator used in the above solution polymerization, there is no particular limitation as long as it can dissolve in the polymerization solution. For example, di-t-butyl peroxide, dicumyl peroxide, t-butyl cumyl peroxide, benzoyl peroxide, dilauryl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)-cyclohexane, cyclohexanone peroxide, t-butyl peroxybenzoate, t-butyl peroxyisobutyrate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxyisopropyl carbonate, cumyl peroxy octoate, peroxides such as potassium persulfate, ammonium persulfate, hydrogen peroxide, 2,2’-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2’-azobis(2,4-dimethylvaleronitrile), 2,2’-azobis(2-methylpropionitrile), 2,2’-azobis(2-methylbutyronitrile), 1,1’-azobis(cyclohexane-1-carbonitrile), 1-[(1-cyano-1-methylethyl)azo]formamide, dimethyl 2,2’-azobis(2-methylpropionate), 4,4’-azobis(4-cyanovaleric acid), 2,2’-azobis(2,4,4-trimethylpentane), 2,2’-azobis{2-methyl-N-[1,1’-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2’-azobis{2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2’-azobis{2-(2-imidazolin-2-yl)propane]disulfate dihydrate, 2,2’-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl)propane]}dihydrochloride, 2,2’-azobis(1-imino-1-pyrrolidino-2-methylpropane)dihydrochloride, 2,2’-azobis(2-methylpropionamidine)dihydrochloride, 2,2’-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]tetrahydrate, 1,Examples of the azo compounds include 1'-azobis(1-acetoxy-1-phenylmethane), 4,4'-diazenediylbis(4-cyanopentanoic acid)·α-hydro-ω-hydroxy poly(oxyethylene) polycondensate, and the like.

[0028] Further, if necessary, these polymerization initiators may be used in combination with reducing agents such as ascorbic acid, erythorbic acid, aniline, tertiary amine, Rongalit, hydrosulfite, sodium sulfite, sodium bisulfite, sodium thiosulfate, and sodium hypophosphite. Among these, from the viewpoint of versatility, persulfate, t-butyl hydroperoxide, and azo compounds are preferred. However, when controlling the molecular weight by living radical polymerization, azo compounds are preferred.

[0029] The usage amount of these radical polymerization initiators is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of all monomers.

[0030] The weight average molecular weight of the emulsifier-free polymer emulsion of the present invention can be adjusted according to the use, but is preferably 5,000 Daltons (Da) to 600,000 Daltons, and more preferably 5,000 Daltons to 200,000 Daltons. If it is less than 5,000 Daltons, the emulsion may not be formed even after distilling off the water-soluble solvent. If it exceeds 600,000 Daltons, agglomerates may be formed.

[0031] Hereinafter, a method for producing an emulsifier-free polymer emulsion dispersed and stabilized with a high concentration of styrenesulfonic acid or a salt thereof according to the present invention will be described.

[0032] For example, an aqueous solvent, a styrenesulfonate, and a vinyl monomer other than the styrenesulfonate are charged into a reactor, and after removing oxygen in the polymerization system by introducing nitrogen while stirring, a radical polymerization initiator is added and heated at an arbitrary temperature. When a specific polymerization conversion rate is reached, the heating is terminated, and the polymerization is terminated by adding a polymerization inhibitor or the like.

[0033] Subsequently, as the solubility of the polymer decreases with the distillation of the water-soluble organic solvent, emulsification occurs. At this time, since a high concentration of styrene sulfonate units is incorporated into the polymer, the polymer is emulsified without precipitating as agglomerates. The particle size of the polymer emulsion varies greatly depending on the polymer concentration, polymer composition and molecular weight, and the aqueous solvent composition. Since a high concentration of styrene sulfonate is copolymerized in the polymer emulsion, the colloidal stability is extremely high. Residual vinyl monomers other than styrene sulfonate can be distilled off together with the solvent or removed by methods such as steam stripping after the water-soluble organic solvent is distilled off. Also, if styrene sulfonate remains, it can be removed by methods such as ultrafiltration, ion exchange column, or centrifugation.

[0034] In addition, the monomers can be added all at once in a batch. Moreover, not limited to this, for example, considering the reactivity difference with monomer (B), styrene sulfonate (A) or its aqueous solution with high polymerization reactivity can be added dropwise sequentially at any time, or a predetermined amount can be added in two or more portions. The molecular weight of the polymer constituting the emulsion can be adjusted not only by the addition conditions of the monomers, the concentration of the monomers, and the addition amount of the radical polymerization initiator, but also by a molecular weight regulator (chain transfer agent).

[0035] The above-mentioned molecular weight regulators are not particularly limited as long as they can be dissolved in the polymerization solution. Examples include disulfides such as diisopropylxanthogen disulfide, diethylxanthogen disulfide, diethylthiuram disulfide, 2,2'-dithiobipropionic acid, 3,3'-dithiobipropionic acid, 4,4'-dithiobibutanoic acid, 2,2'-dithiobisbenzoic acid; mercaptans such as n-dodecyl mercaptan, octyl mercaptan, t-butyl mercaptan, thioglycolic acid, thiomalic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, thiosalicylic acid, 3-mercaptobenzoic acid, 4-mercaptobenzoic acid, thiomalonic acid, dithiosuccinic acid, thiomaleic acid, thiomaleic anhydride, dithiomaleic acid, thioglutaric acid, cysteine, homocysteine, 5-mercaptotetrazoleacetic acid, 3-mercapto-1-propanesulfonic acid, 3-mercaptopropane-1,2-diol, mercaptoethanol, 1,2-dimethylmercaptoethane, 2-mercaptoethylamine hydrochloride, 6-mercapto-1-hexanol, 2-mercapto-1-imidazole, 3-mercapto-1,2,4-triazole, cysteine, N-acylcysteine, glutathione, N-butylaminoethanethiol, N,N-diethylaminoethanethiol; iodinated hydrocarbons such as iodoform; benzyl dithiobenzoate, 2-cyanoprop-2-yl dithiobenzoate, diphenylethylene, p-chlorodiphenylethylene, p-cyanodiphenylethylene, α-methylstyrene dimer, isopropanol, organic tellurium compounds, sulfur, sodium sulfite, potassium sulfite, sodium bisulfite, potassium bisulfite, sodium pyrosulfite, potassium pyrosulfite, sodium hypophosphite, etc. The amount of the molecular weight regulator used is preferably 10 parts by weight or less per 100 parts by weight of the total vinyl monomers.

[0036] In the present invention, the polymerization temperature is 10°C to 100°C, similar to ordinary radical polymerization, more preferably 40°C to 90°C, and even more preferably 60°C to 90°C from the viewpoint of polymerization conversion rate. The polymerization time is preferably 3 hours to 50 hours, and more preferably 3 hours to 30 hours. When polymerizing by the sequential addition method, the time for continuously adding the monomer mixture containing the molecular weight regulator and the polymerization initiator is usually 1 hour to 4 hours.

[0037] In the case of the living radical polymerization method described above, since the polymerization proceeds while reversibly generating radicals from dormant species and a runaway reaction is unlikely to occur, bulk polymerization by all-at-once addition may be more preferable than sequential addition polymerization in terms of polymerization conversion rate and molecular weight controllability.

[0038] The production method of the emulsion-free polymer emulsion of the present invention is a solution polymerization method, not an emulsion polymerization method. Therefore, general emulsifiers are usually unnecessary. However, for the purpose of suppressing the precipitation of agglomerates during polymerization or solvent distillation and promoting emulsification, an emulsifier may be added in the range of 0.50% by weight or less based on the total amount of the polymerization solution. Examples of emulsifiers include anionic emulsifiers such as higher fatty acid salts, alkenyl succinates, rosin acid salts, sodium alkyl sulfates, sodium higher alcohol sulfates, alkylbenzene sulfonates, alkyl diphenyl ether disulfonates, sulfonates of higher fatty acid amides, sulfate salts of higher fatty acid alkanolamides, alkyl sulfobetaines; nonionic emulsifiers such as polyoxyethylene alkyl ethers, polyoxyethylene styrenated phenyl ethers, polyoxyethylene sorbitan fatty acid esters, higher fatty acid alkanolamides, polyvinyl alcohol; cationic emulsifiers such as alkylamine salts, quaternary ammonium salts, alkyl ether type quaternary ammonium salts; amphoteric emulsifiers such as alkyl betaines, alkyl sulfobetaines, alkylamine oxides; and reactive emulsifiers such as Latemul (registered trademark, manufactured by Kao), Ereminol (registered trademark, manufactured by Sanyo Chemical Industries), Aqualon (registered trademark, manufactured by Daiichi Kogyo Seiyaku). Among the above, nonionic emulsifiers with high solubility in the polymerization solution are more preferred. However, since the emulsion may become unstable depending on the temperature during polymerization and solvent distillation, an emulsifier having an appropriate hydrophilic-lipophilic balance (also referred to as HLB) is selected according to solubility and temperature. Also, in order to suppress polymer formation by the emulsion polymerization mechanism, the addition of the emulsifier is more preferred during solvent distillation.

[0039] The emulsifier-free polymer emulsion of the present invention is characterized by being dispersed and stabilized with a high concentration of styrene sulfonic acid or its salt, and has both fine particle size and colloidal stability due to the sulfonic groups immobilized on the particle surface. Therefore, it can be used as a seed for emulsion-free seed emulsion polymerization, and can also be used as components of aqueous paints, aqueous adhesives, aqueous primers, aqueous film coatings, aqueous inks and aqueous binders, latex agglutination diagnostic agents, colloidal crystals, toner particles, and fuel cells and lithium secondary batteries.

[0040] Regarding seed emulsion polymerization, there are many reported examples such as Patent Documents 3 and 4 and Non-Patent Document 1 described above. For example, the surfactant-free polymer emulsion of the present invention is charged into a reactor as a seed, and further the above-described vinyl monomer (B) is added. After deoxygenation by the above-described method, the above-described radical polymerization initiator is added to carry out seed emulsion polymerization. At this time, since the total surface area of the polymer particles increases as the seed particles grow, styrene sulfonate or the above-described emulsifier may be additionally added according to the particle growth. The polymerization temperature is usually 10°C to 80°C, and the polymerization time is usually 2 hours to 10 hours. The amount of the seed used with respect to the vinyl monomer (B) is usually 3% by weight to 15% by weight in terms of polymer conversion, and more preferably 5% by weight to 10% by weight.

[0041] In addition, since the surfactant-free polymer emulsion of the present invention has extremely high colloidal stability, metal cations can be removed by performing cation exchange treatment using a strong acid type cation exchange resin. Alternatively, 2 equivalents to 10 equivalents of a strong acid such as sulfuric acid are added to the cations in the system, and the metal cations can be removed as sulfates by methods such as ultrafiltration. The strong acid type polymer emulsion from which metal cations have been removed can be expected to be used as a solid acid catalyst or a dopant for a conductive polymer.

Examples

[0042] The present invention will be described more specifically by the following examples, but the present invention is not limited by these examples in any way.

[0043] <Reagents Used> The study was carried out using industrially available reagents. St: Styrene (Wako Special Grade, purity 99%, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) MBA: n-Butyl methacrylate (Wako Grade 1, purity 95%, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) MMA: Methyl methacrylate (Wako Special Grade, purity 98%, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) MAM: Methacrylamide (Wako Grade 1, purity 97%, manufactured by Fujifilm Wako Pure Chemical Corporation) CHMI: N-Cyclohexylmaleimide (purity 97%, manufactured by Fujifilm Wako Pure Chemical Corporation) AN: Acrylonitrile (Wako Grade 1, purity 97%, manufactured by Fujifilm Wako Pure Chemical Corporation) NaSS: Sodium styrenesulfonate (purity 87.8%, moisture 7.53%, manufactured by Tosoh Finechem Corporation) LiSS: Lithium styrenesulfonate (purity 86.6%, moisture 9.30%, manufactured by Tosoh Finechem Corporation) AmSS: Ammonium styrenesulfonate (purity 97.6%, moisture 0.72%, manufactured by Tosoh Finechem Corporation) V-50: 2,2’-Azobis(2-methylpropionamidine) dihydrochloride (Wako Grade 1, purity 97%, manufactured by Fujifilm Wako Pure Chemical Corporation) V-501; 4,4’-Azobis(4-cyanovaleric acid) (Wako Grade 1, purity 98%, manufactured by Fujifilm Wako Pure Chemical Corporation) VA-086; 2,2’-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (Wako Grade 1, purity 98%, manufactured by Fujifilm Wako Pure Chemical Corporation)

[0044] <Measurement of Polymerization Conversion Rate and Molecular Weight by Gel Permeation Chromatography (GPC) (Aqueous System)> Quantification (area%) of raw material monomers and polymers was performed using HLC-8320 manufactured by Tosoh Corporation. The polymerization solution and the following eluent were precisely weighed into a sample bottle to prepare an approximately 0.05 wt% solution, and GPC measurement was performed under the following conditions. The conversion rate was calculated from the peak area derived from each monomer before polymerization and the peak area derived from the monomer after polymerization. The concentration was appropriately adjusted according to the sensitivity of each monomer. Column: TSKgel (registered trademark) Guard Column AW-H / TSKgel (registered trademark) AW6000 / TSKgel (registered trademark) AW3000 / TSKgel (registered trademark) AW2500 Eluent: 0.05 M Sodium Sulfate Aqueous Solution / Acetonitrile = 65 / 35 (Vol ratio) Solution Flow Rate · Injection Volume · Column Temperature: 0.6 ml / min, Injection Volume: 10 μl, Column Temperature: 40 °C Detector: UV detector (wavelength 230 nm / styrenesulfonate and N - cyclohexylmaleimide, 254 nm / styrene, 210 nm / n - butyl methacrylate, methacrylamide and acrylamide) Calibration curve: Prepared from the peak top molecular weight and elution time using standard sodium polystyrenesulfonate (manufactured by Sowa Kagaku).

[0045] <Measurement of molecular weight by gel permeation chromatography (GPC) (DMF system)> When the polymer did not dissolve in the above eluent, measurement was performed in the DMF system. The model used was the same as above. Column: TSKgel (registered trademark) guard column Super AW - H / TSKgel (registered trademark) Super AW - 5000 / TSKgel (registered trademark) Super AW - 3000 Eluent: N,N’ - dimethylformamide (containing 10 mM lithium bromide) Sample concentration: Dissolved in the above eluent and adjusted to 0.05 wt% - 0.1 wt% Flow rate · Injection volume · Column temperature: 0.5 ml / min, injection volume 10 μl, column temperature 40 °C Detector: Differential refractive index (RI) Calibration curve: Prepared from the peak top molecular weight and elution time using standard polyethylene oxide (manufactured by Tosoh Corporation).

[0046] <Measurement of aggregation rate after polymerization> The water - soluble organic solvent was distilled off, and after cooling, the polymer emulsion was filtered using a stainless steel wire mesh with 150 mesh (aperture 0.10 mm). The aggregates on the wire mesh were vacuum - dried (100 °C × 3 h) together with the wire mesh, and the aggregation rate was calculated from the following formula. Aggregation rate (wt%) = 100 × [(dry weight of (wire mesh + aggregates) - dry weight of wire mesh)] / (total weight of monomer composition)

[0047] <Calculation of polymer content (solid content) of polymer emulsion> Precisely weigh approximately 5.0 g of the polymer emulsion from which aggregates have been removed into a 50-ml standard flask, and subject the entire flask to vacuum drying (100 °C × 3 hours), and calculate using the following formula. Polymer content (wt%) = 100 × [(weight of the dried (flask + polymer emulsion) - weight of the flask)] / [(weight of the (flask + polymer emulsion) before drying - weight of the flask)] Note that the "polymer content of the polymer emulsion" refers to the weight after drying the polymer emulsion, that is, the amount of solid content, and is sometimes referred to as "pure solid content".

[0048] <Measurement of Residual Water-Soluble Solvent in Polymer Emulsion> Precisely weigh approximately 50 g of isopropanol into a 50-ml standard flask, precisely weigh approximately 0.5 g of the polymer emulsion into it, shake well, and then analyze the supernatant using gas chromatography (GC-2025, manufactured by Shimadzu Corporation) (column = NB-5 GL Sciences Inc., detector: FID hydrogen flame ionization detector) to confirm that the residual solvent in the polymer emulsion is 0.5 wt% or less. The residual solvent content was quantified by the absolute calibration curve method using various water-soluble solvents. When isopropanol was used as the polymerization solvent, approximately 50 g of acetone was precisely weighed into a 50-ml standard flask, and the residual solvent was analyzed in the same procedure as above.

[0049] <Measurement of Particle Size of Polymer Emulsion by Dynamic Light Scattering Method> Using NANOTRAC UPA-UT151 manufactured by Nikkiso Co., Ltd., the D50% particle size (median diameter) was measured as the average particle size. Note that this measurement method calculates the particle size assuming the sample as spherical particles, and the median diameter is the diameter at which the sample is divided into two equal parts in terms of quantity when divided at a certain particle size. Also, SD is the standard deviation and is an indication of the particle size distribution width.

[0050] <Quantification of Sulfonate Groups on the Surface of Polymer Particles> Quantification was performed with reference to the said Patent Document 8. The polymer emulsion was diluted with pure water so that the solid content became about 2.5% by weight, and dialysis was carried out using a dialysis tube (Spectra / Por4, fractionation molecular weight 12,000 Da to 14,000 Da) manufactured by Spectrum Laboratories while replacing the pure water until the electric conductivity became constant. The emulsion purified by dialysis was passed through a strongly acidic cation exchange column (Amberlite (registered trademark) R-120B manufactured by Organo Corporation, regenerated with hydrochloric acid) to convert the sulfonate group (salt type) to a sulfonic acid group (acid type). Subsequently, conductivity titration (LAQAact D-74 manufactured by Horiba Advanced Technology Co., Ltd.) of the acid-type emulsion was carried out using a 5 mM aqueous NaOH solution, and the density of the sulfonate groups on the polymer particle surface was calculated from the following formula.

[0051]

Equation

[0052] Production of LiSS / St copolymer emulsion in Example 1 (1) 575.10 g of pure water, 575.00 g of methanol, and 137.98 g of LiSS were charged into a 3 L four-necked glass flask equipped with a reflux condenser, a nitrogen inlet tube, and a paddle-type stirrer, and dissolved while stirring at room temperature. 120.48 g of styrene was added thereto and dissolved while stirring at room temperature. 5.00 g of polymerization initiator V-50 was added thereto and dissolved while stirring at room temperature. Subsequently, after the system was depressurized with an aspirator, the operation of introducing nitrogen was repeated for degassing. Thereafter, the reactor was immersed in an oil bath at 60 °C and polymerized for 10 hours while stirring. Thereafter, 2.00 g of polymerization initiator V-50 was additionally added, and polymerization was continued at 60 °C for another 10 hours. Thereafter, 0.42 g of polymerization initiator V-50 was additionally added, and polymerization was continued at 60 °C for another 10 hours. The methanol concentration in the aqueous solvent taking into account the moisture in LiSS was 49.2% by weight, and the LiSS concentration in all vinyl monomers was 50.05% by weight.

[0053] The reaction solution was withdrawn using a syringe, and the polymerization conversion rate was tracked by GPC. As a result, it was confirmed that LiSS and styrene were consumed at almost the same rate with the polymerization time (Figure 1). Although the molecular weight distribution of the polymer became broad (Figure 2), since the reaction solution remained transparent throughout, it was judged that the target lithium styrene sulfonate / styrene copolymer was formed. Subsequently, when methanol was distilled off from the above polymerization solution using a rotary evaporator, the solution became cloudy and emulsified as the methanol was distilled off. The solid content of the emulsion was 35.1 wt%, no aggregates were observed, and the median diameter of the polymer particles was 422 nm (Figure 3).

[0054] Example 2 Production of LiSS / St copolymer emulsion (2) Into a 2 L four-necked glass flask equipped with a reflux condenser, a nitrogen inlet tube, and a paddle-type stirrer, 315.00 g of pure water, 460.00 g of 2-propanol, and 83.00 g of LiSS were charged and dissolved while stirring at room temperature. 74.60 g of styrene was added thereto and dissolved while stirring at room temperature. 4.00 g of polymerization initiator V-501, 13.48 g of 8.7 wt% NaOH aqueous solution, and 2.00 g of polymerization initiator VA-086 were added thereto and dissolved while stirring at room temperature. Subsequently, after evacuating the system with an aspirator, the operation of introducing nitrogen was repeated for degassing. Thereafter, the reactor was immersed in an oil bath at 80 °C and polymerized for 30 hours while stirring. The concentration of 2-propanol in the aqueous solvent taking into account the moisture in LiSS was 58.48 wt%, and the concentration of LiSS in all vinyl monomers was 49.32 wt%.

[0055] The reaction solution was withdrawn using a syringe, and the polymerization conversion was tracked by GPC. As a result, it was confirmed that LiSS and styrene were consumed at almost the same rate with the polymerization time (Figure 4). The molecular weight distribution of the polymer showed unimodality (Figure 5), and since the reaction solution remained transparent throughout, it was judged that the target lithium styrene sulfonate / styrene copolymer was formed. Subsequently, 2-propanol was distilled off from the above polymerization solution using a rotary evaporator. As 2-propanol was distilled off, the solution became turbid and emulsified. The solid content of the emulsion was 38.5 wt%, no aggregates were observed, and the median diameter of the polymer particles was 94 nm (Figure 6). Despite the same copolymerization amount of LiSS as in Example 1, the polymer particle size decreased because the molecular weight decreased.

[0056] Example 3 Preparation of LiSS / BMA / MAM Copolymer Emulsion Into a 1 L four-necked glass flask equipped with a reflux condenser, a nitrogen inlet tube, and a paddle-type stirrer, 214.56 g of pure water, 292.65 g of 2-propanol, and 45.00 g of LiSS were charged and dissolved while stirring at room temperature. 80.00 g of n-butyl methacrylate and 10.00 g of methacrylamide were added thereto and dissolved while stirring at room temperature. After adding a polymerization initiator solution (a solution prepared by dissolving 4.00 g of V-50 in an aqueous solvent composed of 19.74 g of pure water and 24.49 g of 2-propanol), the system was depressurized with an aspirator, and then the operation of introducing nitrogen was repeated for degassing. Thereafter, the reactor was immersed in an oil bath at 65 °C and polymerized for 10 hours while stirring. Thereafter, 2.04 g of the polymerization initiator V-50 was additionally added, and the polymerization was continued at 60 °C for another 20 hours. The concentration of 2-propanol in the aqueous solvent taking into account the water content in LiSS was 56.79% by weight, the concentration of LiSS in all vinyl monomers was 31.26% by weight, and the concentration of monomer (C) in vinyl monomer (B) was 88.68% by weight.

[0057] As a result of tracking the polymerization conversion rate by GPC, it was confirmed that LiSS and styrene were consumed at almost the same rate with the polymerization time. Since the molecular weight distribution of the polymer showed unimodality and the reaction solution remained transparent throughout, it was judged that the target lithium styrene sulfonate / n-butyl methacrylate / methacrylamide copolymer was formed. Subsequently, 2-propanol was distilled off from the above polymerization solution using a rotary evaporator. As 2-propanol was distilled off, the solution became turbid and emulsified. The solid content of the emulsion was 39.1 wt%, no aggregates were observed, and the median diameter of the polymer particles was 120 nm. Despite the lower copolymerization amount of LiSS compared to Example 1, the polymer particle size became smaller because a monomer with higher hydrophilicity than styrene was used as monomer (B).

[0058] Production of NaSS / St copolymer emulsion in Example 4 (1) 315.00 g of pure water, 460.00 g of 2-propanol, and 87.00 g of NaSS were charged into a 2 L four-necked glass flask equipped with a reflux condenser, a nitrogen inlet tube, and a paddle-type stirrer, and dissolved while stirring at room temperature. 74.70 g of styrene was added thereto and dissolved while stirring at room temperature. 3.04 g of polymerization initiator V-501, 9.88 g of 8.7 wt% NaOH aqueous solution, and 3.00 g of polymerization initiator VA-086 were added thereto and dissolved while stirring at room temperature. Subsequently, after evacuating the system with an aspirator, the operation of introducing nitrogen was repeated for degassing. Thereafter, the reactor was immersed in an oil bath at 80 °C and polymerized for 30 hours while stirring. The concentration of 2-propanol in the aqueous solvent taking into account the moisture in NaSS was 57.89 wt%, and the concentration of NaSS in all vinyl monomers was 50.81 wt%.

[0059] The reaction solution was withdrawn using a syringe, and the polymerization conversion was traced by GPC. As a result, it was confirmed that NaSS and styrene were consumed at almost the same rate with the polymerization time. Since the molecular weight distribution of the polymer showed unimodality and the reaction solution was transparent throughout, it was judged that the target sodium styrene sulfonate / styrene copolymer was produced. Subsequently, 2-propanol was distilled off from the above polymerization solution using a rotary evaporator. As 2-propanol was distilled off, the solution became turbid and emulsified. The solid content of the emulsion was 35.2 wt%, no aggregates were observed, and the median diameter of the polymer particles was 410 nm.

[0060]

Table 1

[0061] Example 5 Production of NaSS / St copolymer emulsion (2) Into a 1 L four-necked glass flask equipped with a reflux condenser, a nitrogen inlet tube, and a paddle stirrer, 214.56 g of pure water, 292.65 g of 2-propanol, and 44.90 g of NaSS were charged and dissolved while stirring at room temperature. 80.39 g of styrene was added thereto and dissolved while stirring at room temperature. After adding a polymerization initiator solution (a solution prepared by dissolving 6.04 g of V-50 in an aqueous solvent consisting of 19.74 g of pure water and 24.49 g of 2-propanol), the system was depressurized with an aspirator, and then the operation of introducing nitrogen was repeated for degassing. Thereafter, the reactor was immersed in an oil bath at 65°C and polymerized for 30 hours while stirring. The concentration of 2-propanol in the aqueous solvent taking into account the water content in NaSS was 56.87% by weight, and the concentration of NaSS in all vinyl monomers was 33.13% by weight.

[0062] The reaction solution was withdrawn using a syringe, and the polymerization conversion rate was tracked by GPC. As a result, it was confirmed that NaSS and styrene were consumed at almost the same rate with the polymerization time. Since the molecular weight distribution of the polymer showed unimodality and the reaction solution remained transparent throughout, it was judged that the target sodium styrene sulfonate / styrene copolymer was produced. Subsequently, 2-propanol was distilled off from the above polymerization solution using a rotary evaporator. As 2-propanol was distilled off, the solution became turbid and emulsified. The solid content of the emulsion was 35.3 wt%, no aggregates were observed, and the median diameter of the polymer particles was 440 nm.

[0063] Example 6 Preparation of AmSS / St / BMA Copolymer Emulsion 315.00 g of pure water, 460.00 g of 2-propanol, and 45.00 g of AmSS were charged into a 2 L four-necked glass flask equipped with a reflux condenser, a nitrogen inlet tube, and a paddle-type stirrer, and dissolved while stirring at room temperature. 35.00 g of styrene and 35.00 g of butyl methacrylate were added thereto and dissolved while stirring at room temperature. 4.00 g of polymerization initiator V-501, 13.50 g of 8.7 wt% aqueous NaOH solution, and 2.00 g of polymerization initiator VA-086 were added thereto and dissolved while stirring at room temperature. Subsequently, after evacuating the system with an aspirator, the operation of introducing nitrogen was repeated for degassing. Thereafter, the reactor was immersed in an oil bath at 80 °C and polymerized for 30 hours while stirring. The concentration of 2-propanol in the aqueous solvent taking into account the moisture in AmSS was 59.03 wt%, and the concentration of AmSS in all vinyl monomers was 39.28 wt%.

[0064] The reaction solution was withdrawn using a syringe, and the polymerization conversion was traced by GPC. As a result, it was confirmed that NaSS and styrene were consumed at almost the same rate with the polymerization time. Since the molecular weight distribution of the polymer showed unimodality and the reaction solution remained transparent throughout, it was judged that the target ammonium styrenesulfonate / styrene / n-butyl methacrylate copolymer was formed. Subsequently, 2-propanol was distilled off from the above polymerization solution using a rotary evaporator. As 2-propanol was distilled off, the solution became turbid and emulsified. The solid content of the emulsion was 35.5 wt%, no aggregates were observed, and the median diameter of the polymer particles was 140 nm.

[0065] Comparative Example 1 Production of NaSS / St copolymer Into a 3 L four-necked glass flask equipped with a reflux condenser, a nitrogen inlet tube, and a paddle stirrer, 1215.10 g of pure water, 646.00 g of 2-propanol, and 184.70 g of NaSS were charged and dissolved while stirring at room temperature. 44.30 g of styrene was added thereto and dissolved while stirring at room temperature. After adding 50.00 g of a polymerization initiator solution (prepared by dissolving 4.60 g of V-50 in 54.40 g of pure water), the system was depressurized with an aspirator, and then the operation of introducing nitrogen was repeated for degassing. Thereafter, the reactor was immersed in an oil bath at 75 °C and polymerized for 8 hours while stirring. Thereafter, 9.00 g of the remaining polymerization initiator solution was additionally added, and polymerization was continued at 75 °C for another 16 hours. The concentration of 2-propanol in the aqueous solvent taking into account the water content in NaSS was 33.31% by weight, and the concentration of NaSS in all vinyl monomers was 78.71% by weight.

[0066] The reaction solution was withdrawn using a syringe, and the polymerization conversion rate was tracked by GPC. As a result, it was confirmed that NaSS and styrene were consumed at almost the same rate with the polymerization time. Since the molecular weight distribution of the polymer showed unimodality and the reaction solution remained transparent throughout, it was determined that the target sodium styrene sulfonate / styrene copolymer was produced. Subsequently, 2-propanol was distilled off from the above polymerization solution using a rotary evaporator, but it remained as a homogeneous aqueous solution without emulsification. This is because the content of sodium styrene sulfonate in the polymer was too high.

[0067] Comparative Example 2 Production of NaSS / St Copolymer Into a 2 L four-necked glass flask equipped with a reflux condenser, a nitrogen inlet tube, and a paddle-type stirrer, 330.00 g of pure water, 308.00 g of 2-propanol, and 44.50 g of NaSS were charged and dissolved while stirring at room temperature. 19.80 g of styrene was added thereto and dissolved while stirring at room temperature. After adding 25.00 g of a polymerization initiator solution (prepared by dissolving 1.80 g of V-50 in 26.00 g of pure water), the system was depressurized with an aspirator, and then the operation of introducing nitrogen was repeated for degassing. Thereafter, the reactor was immersed in an oil bath at 75 °C and polymerized for 8 hours while stirring. Thereafter, 2.80 g of the remaining polymerization initiator solution was additionally added, and the polymerization was continued at 75 °C for another 16 hours. The 2-propanol concentration in the aqueous solvent taking into account the moisture in NaSS was 45.92% by weight, and the NaSS concentration in all vinyl monomers was 66.59% by weight.

[0068] The reaction solution was withdrawn using a syringe, and the polymerization conversion rate was tracked by GPC. As a result, it was confirmed that NaSS and styrene were consumed at almost the same rate with the polymerization time. Since the molecular weight distribution of the polymer showed unimodality and the reaction solution remained transparent throughout, it was judged that the target sodium styrene sulfonate / styrene copolymer was formed. Subsequently, 2-propanol was distilled off from the above polymerization solution using a rotary evaporator, but it remained as a homogeneous aqueous solution without emulsification. The reason for not emulsifying despite the sodium styrene sulfonate content in the polymer being less than that in Comparative Example 1 is that the molecular weight was too small. That is, it is clear that the copolymerization amount and molecular weight of styrene sulfonic acid or its salt are extremely important for emulsification.

[0069] Production of Comparative Example 3 AmSS / St Copolymer Into a 2 L four-necked glass flask equipped with a reflux condenser, a nitrogen inlet tube, and a paddle stirrer, 172.80 g of pure water, 274.90 g of 2-propanol, and 17.72 g of AmSS were charged and dissolved while stirring at room temperature. 79.83 g of styrene was added thereto and dissolved while stirring at room temperature. After adding a polymerization initiator solution (prepared by dissolving 5.00 g of polymerization initiator V-501 in 26.00 g of pure water and 15.95 g of 8.7 wt% NaOH aqueous solution), the system was depressurized with an aspirator, and then the operation of introducing nitrogen was repeated for degassing. Thereafter, the reactor was immersed in an oil bath at 70 °C and polymerized for 24 hours while stirring. The concentration of 2-propanol in the aqueous solvent taking into account the moisture in NaSS was 57.58 wt%, and the concentration of NaSS in all vinyl monomers was 16.45 wt%.

[0070] The reaction solution was withdrawn using a syringe, and the polymerization conversion rate was tracked by GPC. As a result, it was confirmed that AmSS and styrene were consumed at almost the same rate with the polymerization time. Since the molecular weight distribution of the polymer showed unimodality and the reaction solution remained transparent throughout, it was judged that the target ammonium styrenesulfonate / styrene copolymer was formed. Subsequently, when 2-propanol was distilled off from the above polymerization solution using a rotary evaporator, a large amount of aggregates were formed and it could not be emulsified. This is because the ammonium styrenesulfonate content in the polymer was too low compared to Example 6.

[0071]

Table 2

[0072] Example 7 Preparation of AmSS / St Copolymer Emulsion Into a reflux condenser tube, a nitrogen inlet tube, and a 300 ml four-necked glass flask equipped therewith, 50.28 g of pure water, 12.00 g of AmSS, and 0.85 g of polymerization initiator V-50 were charged and dissolved at room temperature while stirring with a magnetic stirrer. 10.00 g of styrene and 50.42 g of acetone were added thereto and dissolved while stirring at room temperature. Subsequently, while cooling the flask with ice, the pressure was reduced with an aspirator, and then the operation of introducing nitrogen was repeated for degassing. Thereafter, the reactor was immersed in an oil bath at 60 °C and polymerized for 30 hours while stirring. The acetone concentration in the aqueous solvent taking into account the moisture in AmSS was 49.78% by weight, and the AmSS concentration in all vinyl monomers was 54.19% by weight.

[0073] The reaction solution was withdrawn using a syringe, and as a result of tracking the polymerization conversion rate by GPC, it was confirmed that AmSS and styrene were consumed at almost the same rate with the polymerization time. Since the molecular weight distribution of the polymer showed unimodality and the reaction solution remained transparent throughout, it was determined that the target AmSS / St copolymer was formed. Subsequently, when acetone was distilled off from the above polymerization solution using a rotary evaporator, the solution became turbid and emulsified as the acetone was distilled off. The solid content of the emulsion was 30.5 wt%, no aggregates were observed, and the median diameter of the polymer particles was 480 nm.

[0074] Example 8 Preparation of AmSS / St / CHMI Copolymer Emulsion Into a reflux condenser tube, a nitrogen inlet tube, and a 300 ml four-necked glass flask equipped therewith, 50.00 g of pure water, 12.00 g of AmSS, and 0.85 g of polymerization initiator V-50 were charged and dissolved at room temperature while stirring with a magnetic stirrer. A solution prepared by dissolving 7.00 g of styrene and 3.00 g of N-cyclohexylmaleimide (CHMI) in 50.50 g of acetone was added thereto. Subsequently, while cooling the flask with ice, the pressure was reduced with an aspirator, and then the operation of introducing nitrogen was repeated for degassing. Thereafter, the reactor was immersed in an oil bath at 60°C and polymerized for 30 hours while stirring. The acetone concentration in the aqueous solvent taking into account the water content in AmSS was 49.95% by weight, and the AmSS concentration in all vinyl monomers was 54.34% by weight. The concentration of monomer (C) in vinyl monomer (B) was 70.43% by weight.

[0075] As a result of tracking the polymerization conversion rate by GPC, it was confirmed that AmSS, styrene, and N-cyclohexylmaleimide were consumed at almost the same rate with the polymerization time. Since the molecular weight distribution of the polymer showed unimodality and the reaction solution remained transparent throughout, it was judged that the target AmSS / St / CHMI copolymer was formed. Subsequently, acetone was distilled off from the above polymerization solution using a rotary evaporator. As acetone was distilled off, the solution became cloudy and emulsified. The solid content of the emulsion was 30.3 wt%, no aggregates were observed, and the median diameter of the polymer particles was 320 nm.

[0076] Example 9 Preparation of AmSS / St / AN Copolymer Emulsion 50.00 g of pure water, 12.00 g of AmSS, and 0.95 g of polymerization initiator V-50 were charged into a reflux cooling tube, a nitrogen introduction tube, and an attached 300 ml four-necked glass flask, and dissolved at room temperature while stirring with a magnetic stirrer. A solution prepared by dissolving 8.00 g of styrene and 3.00 g of acrylonitrile (AN) in 50.50 g of acetone was added thereto. Subsequently, while cooling the flask with ice, the pressure was reduced with an aspirator, and then the operation of introducing nitrogen was repeated for degassing. Thereafter, the reactor was immersed in an oil bath at 60 °C and polymerized for 30 hours while stirring. The acetone concentration in the aqueous solvent taking into account the moisture in AmSS was 49.95% by weight, and the AmSS concentration in all vinyl monomers was 51.96% by weight. The concentration of monomer (C) in vinyl monomer (B) was 73.13% by weight.

[0077] As a result of tracking the polymerization conversion rate by GPC, it was confirmed that AmSS, styrene, and acrylonitrile were consumed at almost the same rate with the polymerization time. Since the molecular weight distribution of the polymer showed unimodality and the reaction solution remained transparent throughout, it was determined that the target AmSS / St / AN copolymer was formed. Subsequently, acetone was distilled off from the above polymerization solution using a rotary evaporator. As acetone was distilled off, the solution became cloudy and emulsified. The solid content of the emulsion was 30.6 wt%, no aggregates were observed, and the median diameter of the polymer particles was 280 nm.

[0078]

Table 3

Industrial Applicability

[0079] The emulsifier-free polymer emulsion of the present invention is dispersed and stabilized with a high concentration of styrenesulfonic acid or its salt, and can be used as a seed for emulsifier-free seed emulsion polymerization or functional fine particles, so it is extremely useful industrially.

Claims

1. An emulsifier-free polymer emulsion obtained by distilling off the contained water-soluble organic solvent from a solution of a copolymer in which (A) a styrene sulfonate and (B) a vinyl monomer other than the styrene sulfonate are radically copolymerized in an aqueous solvent containing a water-soluble organic solvent, wherein the amount of (A) styrene sulfonate is 30% to 55% by weight based on the total of (A) styrene sulfonate and (B) vinyl monomer other than the styrene sulfonate, the average particle diameter of the polymer particles is 50 nm to 500 nm, an emulsifier-free polymer emulsion.

2. The emulsifier-free polymer emulsion according to claim 1, wherein the water-soluble organic solvent is a water-soluble organic solvent having a lower boiling point than water.

3. The emulsifier-free polymer emulsion according to claim 1, wherein the water-soluble organic solvent is at least one water-soluble organic solvent selected from the group consisting of dimethoxymethane, acetone, 1,1-dimethoxyethane, 1,2-dimethoxyethane, methanol, ethanol, 2-propanol, 1-propanol, tert-butanol, acetonitrile, methyl ethyl ketone, and tetrahydrofuran.

4. The emulsifier-free polymer emulsion according to claim 1, wherein the weight average molecular weight of the copolymer determined by gel permeation chromatography is 5,000 Daltons (Da) to 200,000 Daltons (Da).

5. The emulsifier-free polymer emulsion according to claim 1, wherein the styrene sulfonate is at least one selected from the group consisting of sodium 4-styrenesulfonate, lithium 4-styrenesulfonate, potassium 4-styrenesulfonate, ammonium 4-styrenesulfonate, N,N-dimethylcyclohexylamine 4-styrenesulfonate, sodium 4-styrenesulfonyl(trifluoromethylsulfonylimide), lithium 4-styrenesulfonyl(trifluoromethylsulfonylimide), and potassium 4-styrenesulfonyl(trifluoromethylsulfonylimide).

6. At least 70% by weight of the vinyl monomer (B) other than the styrene sulfonate is at least one oil-soluble vinyl monomer selected from the group consisting of (C) styrenes, acrylic esters, and methacrylic esters. Less than 30% by weight of the vinyl monomer other than styrene sulfonate is a vinyl monomer copolymerizable with one or more oil-soluble vinyl monomers selected from the group consisting of (D) styrenes, acrylic esters, and methacrylic esters. The emulsifier-free polymer emulsion according to claim 1.

7. A method for producing the emulsifier-free polymer emulsion according to claim 1, wherein in an aqueous solvent containing the water-soluble organic solvent, (A) styrene sulfonate and (B) a vinyl monomer other than styrene sulfonate are solution-polymerized using a radical polymerization initiator, and then the water-soluble organic solvent is distilled off.

8. The addition amount of (A) styrene sulfonate is 30% to 55% by weight based on the total of (A) styrene sulfonate and (B) a vinyl monomer other than styrene sulfonate. The proportion of the water-soluble organic solvent in the aqueous solvent is 30% to 60% by weight. The method for producing the emulsifier-free polymer emulsion according to claim 7.

9. An aqueous paint, an aqueous adhesive, an aqueous coating agent, an aqueous binder, an aqueous ink, or a conductive polymer, characterized by containing the emulsifier-free polymer emulsion according to any one of claims 1 to 6.

Images