JP3972709B2 - Method for producing polymerized toner - Google Patents

Description

【０１３０】
【発明の効果】
本発明によれば、水系分散媒体中に分散させた重合性単量体組成物の液滴の安定性を損なうことなく、工業的規模での安定した重合操作が可能であり、しかも重合缶内でのスケールや凝集物の発生を顕著に抑制することができる重合トナーの製造方法が提供され。本発明の製造方法によれば、不安定な微小液滴を含有する水分散液の安定性を向上させることができる。
【０１３１】
また、本発明の製造方法によれば、不安定な液滴を含有する水系分散液であっても、重合缶内への投入時に、予め溜めてある水系分散媒体により落下による衝撃が緩和されて、液滴の合一や破壊などの不都合を生じることが抑制される。
【０１３２】
本発明の製造方法によれば、小粒径で、球形度が高く、粒径分布がシャープな重合トナーを安定的かつ効率的に得ることができる。また、本発明の製造方法によれば、重合缶内壁などへのスケールの付着を抑制することができるので、重合缶壁の熱伝達係数を高く維持することができる。
【図面の簡単な説明】
【図１】図１は、本発明の製造方法に使用される重合缶の一例を示す断面図である。
【符号の説明】
１：重合缶
２：ジャケット
３：撹拌装置のモータ
４：撹拌翼
５：水系分散媒体の配管
６：シャワーノズル
７：噴霧液
８：重合缶の下部に溜まった水系分散媒体
９：投入口
１０：排出用の配管[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polymerized toner for use in a printing machine or copying machine that forms an image by electrophotography, and more specifically, a droplet of a polymerizable monomer composition dispersed in an aqueous dispersion medium. The present invention relates to a method for producing a polymerized toner that can perform a stable polymerization operation on an industrial scale without impairing the stability of the toner, and can remarkably suppress the generation of scales and aggregates in a polymerization can.
[0002]
[Prior art]
In an image forming apparatus such as an electrophotographic apparatus or an electrostatic printing apparatus, an electrostatic charge image developing toner (hereinafter abbreviated as “toner”) is used as a developer for developing an electrostatic latent image. As the toner, generally, colored particles in which additive components such as a colorant, a charge control agent, and a release agent are dispersed in a binder resin are used.
[0003]
Conventionally, as the toner, a pulverized toner obtained by pulverizing and classifying a resin composition in which a colorant and other additives are melt-mixed in a thermoplastic resin has been mainly used. Therefore, it is possible to omit complicated steps such as pulverization and classification, and polymerized toners having good image quality are widely used.
[0004]
Generally, a polymerized toner is prepared by introducing a polymerizable monomer composition containing at least a polymerizable monomer and a colorant into an aqueous dispersion medium containing a dispersion stabilizer, and providing a stirring device having a high shearing force. It is manufactured by a method of forming a droplet of the polymerizable monomer composition by dispersing it and then polymerizing using a polymerization initiator.
[0005]
When producing a polymerized toner on an industrial scale, an aqueous dispersion in which droplets of a polymerizable monomer composition are dispersed in an aqueous dispersion medium containing a dispersion stabilizer is generally used in another container or mixing device. After the preparation, the aqueous dispersion is put into a polymerization can (that is, a polymerization reactor) to carry out a polymerization reaction. The reason is that if an aqueous dispersion containing droplets of a polymerizable monomer composition is prepared in a polymerization can and polymerization is carried out in the same polymerization can, a large amount of scale and coarse particles are likely to be generated. It is.
[0006]
In recent years, in electrophotographic image forming apparatuses, there are increasing demands for higher image quality, higher printing speed, colorization, energy saving, cost reduction, miniaturization, and so on. Various improvements have been demanded for polymerized toners. More specifically, (1) In order to increase the image definition, the particle size of the polymerized toner should be 10 μm or less, more preferably 9 μm or less, and (2) improve developability and transferability. Therefore, to increase the sphericity of the polymerized toner and sharpen its particle size distribution, (3) To lower the fixing temperature of the polymerized toner in order to increase the printing speed, colorize, and save energy (4) Increasing the size of the polymerization toner production apparatus has become the mainstream improvement means.
[0007]
However, when such improved means for polymerized toner is employed, the polymerization reaction system of the polymerized toner tends to become unstable. For example, in order to produce a polymerized toner having a small particle size, when forming a droplet of a polymerizable monomer composition in an aqueous dispersion medium, the droplet must be reduced in size. As the particle size of the liquid becomes smaller, the viscosity of the aqueous dispersion containing the liquid droplets increases and becomes unstable.
[0008]
Further, if a release agent is added more than usual in the polymerizable monomer composition in order to lower the fixing temperature of the polymerized toner, the droplets of the polymerizable monomer composition tend to become unstable. Furthermore, various pigments used as a colorant for coloring a polymerized toner have high hydrophilicity and are less dispersible in a polymerizable monomer than carbon black. In order to improve the dispersibility of the pigment, a dispersion aid may be added. Addition of such a highly hydrophilic pigment or dispersion aid tends to make the droplets of the polymerizable monomer composition unstable.
[0009]
As described above, the aqueous dispersion containing minute droplets of the polymerizable monomer composition is very unstable by itself. In an aqueous dispersion containing unstable droplets, coalescence of the droplets and destruction of the droplets are likely to occur. Further, when the aqueous dispersion is charged into the polymerization can, droplets are likely to adhere to the inner wall of the polymerization can.
[0010]
In addition, if the polymerization can is enlarged for mass production of polymerized toner, the drop is large when an aqueous dispersion in which droplets of polymerizable monomer are dispersed is introduced into the polymerization can from the top of the polymerization can. The aqueous dispersion crashes into the bottom of the polymerization can and the liquid droplets are likely to become more unstable. In the polymerization can, various impacts such as coalescence of droplets composed of the polymerizable monomer composition, breakage of the droplets, adhesion of the droplets to the can wall, etc. are caused by the impact caused by the drop when the aqueous dispersion is charged. Inconvenient phenomena are likely to occur.
[0011]
As a result, it becomes difficult to obtain a polymerized toner having a small particle size, a high sphericity, and a sharp particle size distribution. If the particle size distribution of the polymerized toner becomes broad or the shape thereof is not spherical but irregular (unshaped), developability and transferability deteriorate. Furthermore, the scale adheres to the inner wall of the polymerization can and the stirring device, and aggregates are likely to be generated on the bottom of the can. The increase in scale and aggregates not only lowers the yield of the polymerized toner, but also causes problems such as mixing of foreign matters into the polymerized toner. The adhesion of the scale to the can wall lowers the heat transfer coefficient of the polymerization can, making it difficult to control the polymerization temperature or reducing the heat transfer efficiency from the jacket during polymerization.
[0012]
Up to now, several methods have been proposed for preventing the adhesion of scales in the production process of polymerized toners, but they are unsatisfactory as means for solving the above problems. For example, Japanese Patent Laid-Open No. 10-153878 discloses a method of spraying an aqueous dispersion medium in which water or a dispersion stabilizer is mixed on the inner wall of a gas phase portion in a polymerization can during suspension polymerization in the polymerization can. Has been. According to this method, it is possible to suppress the adhesion of scale to the inner wall of the polymerization can in the vapor phase portion of the polymerization can and the inner wall of the auxiliary equipment, but there is no scale prevention effect in the liquid phase portion.
[0013]
In JP-A-10-260553, a hydrophilic organic solvent is brought into contact with the inner wall of the polymerization can, penetrated into the scale attached to the inner wall, and then contacted by a method such as spraying water on the inner wall. And a method for removing the scale is disclosed. After removing the scale by washing, a dispersion of a composition containing a monomer and a colorant is charged into the polymerization can to conduct polymerization. According to this method, the scale adhering to the inner wall of the polymerization can can be easily scraped off, but there is no effect of preventing the reaction system from becoming unstable or generating scale in the liquid phase part.
[0014]
Japanese Patent Application Laid-Open No. 2001-188382 proposes a method of cooling the surface of a portion of a polymerization toner polymerization apparatus protruding from a gas phase portion in a polymerization can with a cooling medium. According to this method, the scale is reduced by reducing the polymerization rate of the unreacted monomer condensed in the portion protruding into the gas phase portion or preventing the polymer particles adhering to the protruding portion from drying. It can suppress adhering. However, this method has no effect of preventing scaling at the liquid phase part.
[0015]
That is, in these known methods, the instability of the aqueous dispersion containing fine droplets of the polymerizable monomer composition is eliminated, or when the aqueous dispersion is put into the polymerization can, It cannot be mitigated that the instability of the droplet increases by crashing into the bottom of the liquid. Also, these methods cannot prevent or suppress the formation of scale in the liquid phase part during polymerization.
[0016]
[Problems to be solved by the invention]
An object of the present invention is to allow a stable polymerization operation on an industrial scale without impairing the stability of minute droplets of a polymerizable monomer composition dispersed in an aqueous dispersion medium. It is an object of the present invention to provide a method for producing a polymerized toner capable of remarkably suppressing the generation of scale and aggregates therein.
[0017]
As a result of intensive studies to achieve the above object, the present inventors have determined that a polymerizable monomer composition containing at least a polymerizable monomer and a colorant is a first aqueous dispersion containing a dispersion stabilizer. After being dispersed as droplets in the medium, a fine liquid can be obtained by mixing a second aqueous dispersion medium containing 0.1 to 5% by weight of a dispersion stabilizer with the aqueous dispersion containing the droplets. It has been found that even a droplet can significantly improve the stability of an aqueous dispersion containing the droplet.
[0018]
In addition, when at least a part of the second aqueous dispersion is stored in advance in the lower part of the polymerization can and an aqueous dispersion containing droplets is introduced from above, the impact due to dropping is reduced, and the droplets Inconveniences such as coalescence and destruction are suppressed. Furthermore, when at least a part of the second aqueous dispersion is sprayed into the polymerization can while being sprayed on the inner wall of the polymerization can, an accessory device in the polymerization can, or both, the production of scales and aggregates can be made more effective. Can be prevented.
[0019]
According to such a method, a polymerized toner having a small particle size, a high sphericity, and a sharp particle size distribution can be obtained stably and efficiently. Moreover, the production | generation of a scale and an aggregate can be suppressed notably, and also the heat transfer coefficient of a superposition | polymerization can wall can be maintained high. The present invention has been completed based on these findings.
[0020]
[Means for Solving the Problems]
  According to the present invention, after dispersing a polymerizable monomer composition containing at least a polymerizable monomer and a colorant as droplets in an aqueous dispersion medium containing a dispersion stabilizer, a polymerization initiator In a method for producing a polymerized toner comprising a step of producing colored polymer particles by polymerization according to
(1) Forming droplets of a polymerizable monomer composition containing at least a polymerizable monomer and a colorant in a first aqueous dispersion medium (A) containing a dispersion stabilizer, Step 1 of preparing a first aqueous dispersion (B) in which is dispersed;
(2)Second aqueous dispersion medium containing 0.1 to 5% by weight of dispersion stabilizer (C) In the polymerization can, the first aqueous dispersion ( B ) In the polymerization can,First aqueous dispersion (B)And the secondMixed with the biaqueous dispersion medium (C),TheFor 100 parts by weight of the polymerizable monomer in the first aqueous dispersion (B),TheA second aqueous dispersion (D) containing 10 to 150 parts by weight of the second aqueous dispersion medium (C).In the polymerization canStep 2 to prepare;as well as
(3)SaidIn the polymerization can,SaidStep 3 of polymerizing the polymerizable monomer composition dispersed as droplets in the second aqueous dispersion (D) with a polymerization initiator to produce colored polymer particles;
A process for producing a polymerized toner comprising a series of steps consisting of:
[0021]
DETAILED DESCRIPTION OF THE INVENTION
1.First aqueous dispersion containing droplets of polymerizable monomer composition
The polymerized toner can be obtained by polymerizing a polymerizable monomer composition containing at least a polymerizable monomer and a colorant in an aqueous dispersion medium containing a dispersion stabilizer. Prior to the polymerization, the polymerizable monomer composition is put into an aqueous dispersion medium containing a dispersion stabilizer and dispersed using a stirrer having a high shearing force. Are prepared, and an aqueous dispersion containing the droplets is prepared.
[0022]
A polymer toner having a core-shell structure is obtained by suspension polymerization of a polymerizable monomer composition containing at least a polymerizable monomer and a colorant in an aqueous dispersion medium containing a dispersion stabilizer. The obtained colored polymer particles are used as a core, and the polymerizable monomer for shell is polymerized in the presence of the core. The polymer layer formed by polymerizing the shell monomer is the shell.
[0023]
In the production method of the present invention, a first aqueous dispersion containing fine droplets of a polymerizable monomer composition is prepared by the above-described method, and the first aqueous dispersion is prepared before polymerization in a polymerization can. And a second aqueous dispersion medium are mixed to prepare a second aqueous dispersion.
[0024]
In addition to the polymerizable monomer and the colorant, the polymerizable monomer composition includes a crosslinkable monomer, a macromonomer, a molecular weight regulator, a charge control agent, a release agent, a lubricant, a dispersion as necessary. Various additives such as auxiliaries can be included.
[0025]
(1) Polymerizable monomer
Examples of the polymerizable monomer for forming the binder resin include a monovinyl monomer, a crosslinkable monomer, and a macromonomer. This polymerizable monomer is polymerized to become a binder resin component in the polymer particles.
[0026]
Specific examples of the monovinyl monomer include aromatic vinyl monomers such as styrene, vinyltoluene, and α-methylstyrene; (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, Propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, (meth) acrylamide And (meth) acrylic acid derivatives; monoolefin monomers such as ethylene, propylene and butylene; and the like.
[0027]
Monovinyl monomers may be used alone or in combination of a plurality of monomers. Of these monovinyl monomers, aromatic vinyl monomers alone, combinations of aromatic vinyl monomers and (meth) acrylic acid derivatives, and the like are preferably used.
[0028]
When a crosslinkable monomer and a crosslinkable polymer are used together with a monovinyl monomer, hot offset is effectively improved. A crosslinkable monomer is a monomer having two or more vinyl groups. Specifically, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; diethylenically unsaturated carboxylic acid esters such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and 1,4-butanediol diacrylate; N , N-divinylaniline, a compound having two vinyl groups such as divinyl ether, a compound having three or more vinyl groups such as pentaerythritol triallyl ether and trimethylolpropane triacrylate, and the like.
[0029]
The crosslinkable polymer is a polymer having two or more vinyl groups in the polymer, and specifically, a polymer such as polyethylene, polypropylene, polyester, or polyethylene glycol having two or more hydroxyl groups in the molecule. And esters obtained by condensation reaction of unsaturated carboxylic acid monomers such as acrylic acid and methacrylic acid.
[0030]
These crosslinkable monomers and crosslinkable polymers can be used alone or in combination of two or more. The amount used is usually 10 parts by weight or less, preferably 0.01-7 parts by weight, more preferably 0.05-5 parts by weight, particularly preferably 0.1-3 parts per 100 parts by weight of the monovinyl monomer. Parts by weight.
[0031]
It is preferable to use a macromonomer together with a monovinyl monomer because the balance between storage stability at high temperature and fixability at low temperature is improved. The macromonomer has a polymerizable carbon-carbon unsaturated double bond at the end of the molecular chain, and is an oligomer or polymer having a number average molecular weight of usually 1,000 to 30,000. When the number average molecular weight is within the above range, it is preferable because fixability and storage stability can be maintained without impairing the meltability of the macromonomer.
[0032]
Examples of the polymerizable carbon-carbon unsaturated double bond at the end of the macromonomer molecular chain include an acryloyl group and a methacryloyl group, and a methacryloyl group is preferred from the viewpoint of ease of copolymerization. The macromonomer is preferably one that gives a polymer having a glass transition temperature higher than that of a polymer obtained by polymerizing the monovinyl monomer.
[0033]
Specific examples of the macromonomer include styrene, a styrene derivative, a methacrylic acid ester, an acrylic acid ester, acrylonitrile, a methacrylonitrile, a polymer obtained by polymerizing two or more kinds alone, and a macromonomer having a polysiloxane skeleton. Among these, hydrophilic ones are preferable, and a polymer obtained by polymerizing methacrylic acid ester or acrylic acid ester alone or in combination thereof is particularly preferable.
[0034]
When the macromonomer is used, the amount used is usually 0.01 to 10 parts by weight, preferably 0.03 to 5 parts by weight, more preferably 0.05 to 1 with respect to 100 parts by weight of the monovinyl monomer. Parts by weight. When the amount of the macromonomer is within the above range, the toner fixability is maintained and the storage stability is improved.
[0035]
(2) Colorant
As the colorant, various pigments and dyes used in the field of toner such as carbon black and titanium white can be used. Examples of the black colorant include carbon black and nigrosine-based dyes and pigments; magnetic particles such as cobalt, nickel, iron tetroxide, manganese iron oxide, zinc iron oxide, and nickel iron oxide. When carbon black is used, it is preferable to use carbon black having a primary particle size of 20 to 40 nm because good image quality can be obtained and the safety of the toner to the environment is enhanced. As a color toner colorant, a yellow colorant, a magenta colorant, a cyan colorant, or the like can be used.
[0036]
As the yellow colorant, condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, allylamide compounds, and the like are used. Specifically, for example, C.I. I. Pigment Yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 74, 83, 90, 93, 95, 95, 97, 109, 110, 111, 120, 128, 129, 138, 147, 155, 168, 180, 181 and the like. In addition, Nephthol Yellow S, Hansa Yellow G, C.I. I. Examples thereof include bat yellow.
[0037]
Examples of the magenta colorant include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. Specifically, for example, C.I. I. Pigment Red 2, 3, 5, 6, 7, 23, 48, 48: 2, 48: 3, 48: 4, 57, 57: 1, 58, 60, 63, 64, 68, 81, 81: 1, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 149, 163, 166, 169, 170, 177, 184, 185, 187, 202, 206, 207, 209, 220, 251 and 254. In addition, C.I. I. Pigment violet 19 and the like.
[0038]
Examples of cyan colorants include copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, basic dye lake compounds, and the like. Specifically, for example, C.I. I. Pigment Blue 1, 2, 3, 6, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, 17, 60, 62, 66, and the like. In addition, phthalocyanine blue, C.I. I. Bat Blue, C.I. I. Acid blue and so on.
[0039]
These colorants can be used alone or in combination of two or more. The colorant is generally used in a proportion of 0.1 to 50 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the polymerizable monomer.
[0040]
(3) Lubricant / dispersion aid
Lubricants such as fatty acid metal salts composed of fatty acids such as oleic acid and stearic acid, fatty acids and metals such as Na, K, Ca, Mg, and Zn for the purpose of uniform dispersion of the colorant in the toner particles; Alternatively, a dispersion aid such as a titanium coupling agent may be used. Such lubricants and dispersants are usually used at a ratio of about 1/1000 to 1/1 based on the weight of the colorant.
[0041]
(4) Charge control agent
In order to improve the chargeability of the polymerized toner, it is preferable to include various positively chargeable or negatively chargeable charge control agents in the polymerizable monomer composition. Examples of the charge control agent include metal complexes of organic compounds having a carboxyl group or a nitrogen-containing group, metal-containing dyes, nigrosine, charge control resins, and the like.
[0042]
Specifically, Bontron N-01 (manufactured by Orient Chemical Co., Ltd.), Nigrosine Base EX (manufactured by Orient Chemical Co., Ltd.), Spiron Black TRH (manufactured by Hodogaya Chemical Co., Ltd.), T-77 (manufactured by Hodogaya Chemical Co., Ltd.) Bontron S-34 (made by Orient Chemical Industries), Bontron E-81 (made by Orient Chemical Industries), Bontron E-84 (made by Orient Chemical Industries), Bontron E-89 (made by Orient Chemical Industries), Bontron F-21 (made by Orient Chemical Industries), COPY CHARGE NX VP434 (made by Clariant), COPY CHARGENEG VP2036 (made by Clariant), TNS-4-1 (made by Hodogaya Chemical Co., Ltd.), TNS-4-2 (Hodogaya) Chemical Industry), LR-147 (Nippon Carlit), copyable -Charge control agents such as PR (manufactured by Clariant); charge control resins such as quaternary ammonium (salt) group-containing copolymers and sulfonic acid (salt) group-containing copolymers; Among these, the charge control resin is preferable.
[0043]
The charge control agent is usually used in a proportion of 0.01 to 10 parts by weight, preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the polymerizable monomer.
[0044]
(5) Release agent
A release agent can be included in the polymerizable monomer composition for the purpose of preventing offset or improving the releasability at the time of hot roll fixing. Examples of mold release agents include polyolefin waxes such as low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight polybutylene; plant-based natural waxes such as candelilla, carnauba, rice, wood wax, jojoba; paraffin, microcrystalline, petrolactam, etc. And other modified waxes; synthetic waxes such as Fischer-Tropsch wax; polyfunctional ester compounds such as pentaerythritol tetramyristate, pentaerythritol tetrapalmitate, dipentaerythritol hexamyristate; and the like. These can be used alone or in combination of two or more.
[0045]
Of these, synthetic waxes, terminal-modified polyolefin waxes, petroleum waxes, polyfunctional ester compounds and the like are preferable. Among polyfunctional ester compounds, in the DSC curve measured by a differential scanning calorimeter, the endothermic peak temperature at the time of temperature rise is in the range of 30 to 200 ° C, preferably 40 to 160 ° C, more preferably 50 to 120 ° C. Use of a polyfunctional ester compound such as pentaerythritol ester or dipentaerythritol ester having the same endothermic peak temperature in the range of 50 to 80 ° C. is particularly preferable in terms of the balance between the fixing property and the releasability of the toner.
[0046]
Among polyfunctional ester compounds such as pentaerythritol ester having an endothermic peak temperature in the range of 30 to 200 ° C. and dipentaerythritol ester having the endothermic peak temperature in the range of 50 to 80 ° C., the molecular weight is 1, More than 000 and more than 5 parts by weight at 25 ° C. with respect to 100 parts by weight of styrene, and those having an acid value of 10 mg / KOH or less are more preferable because they have a remarkable effect on the fixing temperature of the toner. The endothermic peak temperature is a value measured by ASTM D3418-82.
[0047]
The ratio of the release agent used is usually 0.1 to 50 parts by weight, preferably 0.5 to 20 parts by weight, more preferably 1 to 10 parts per 100 parts by weight of the binder resin (polymerizable monomer). Parts by weight.
[0048]
(6) Polymerization initiator
Examples of the polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate; 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis [2-methyl-N- (2- Hydroxyethyl) propionamide], 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile Azo compounds such as: di-t-butyl peroxide, dicumyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexano Ate, t-butyl peroxypivalate, di-isopropyl peroxydicarbonate, di-t-butyl peroxyisophthalate, 1 1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, etc. peroxides such as t- butyl peroxy isobutyrate and the like. Moreover, the redox initiator which combined these polymerization initiators and reducing agents can be used.
[0049]
Among these, it is preferable to select an oil-soluble polymerization initiator that is soluble in the polymerizable monomer to be used, and a water-soluble polymerization initiator can be used in combination with this, if necessary. The polymerization initiator is usually used in a proportion of 0.1 to 20 parts by weight, preferably 0.3 to 15 parts by weight, more preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the polymerizable monomer. .
[0050]
The polymerization initiator can be added in advance to the polymerizable monomer composition, but in the case of suspension polymerization, the suspension after the completion of the droplet formation process or in the middle of the polymerization reaction, in the case of emulsion polymerization It can also be added directly to the emulsion after the emulsification step or during the polymerization reaction.
[0051]
(7) Molecular weight regulator
In the polymerization, it is preferable to add a molecular weight modifier. Examples of the molecular weight modifier include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, 2,2,4,6,6-pentamethylheptane-4-thiol; carbon tetrachloride, four And halogenated hydrocarbons such as carbon bromide; The molecular weight modifier can be added before the polymerization starts or during the polymerization. The molecular weight modifier is usually used in a proportion of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, with respect to 100 parts by weight of the polymerizable monomer.
[0052]
(8) Dispersion stabilizer
The dispersion stabilizer used in the present invention is preferably one containing a colloid of a hardly water-soluble metal compound. Examples of the hardly water-soluble metal compounds include sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate and magnesium carbonate; phosphates such as calcium phosphate; metal oxidation such as aluminum oxide and titanium oxide A metal hydroxide of aluminum hydroxide, magnesium hydroxide, ferric hydroxide, and the like. Among these, a dispersant containing a colloid of a hardly water-soluble metal hydroxide is preferable because it can narrow the particle size distribution of the polymer particles and improve the sharpness of the image.
[0053]
The dispersant containing the colloid of the hardly water-soluble metal compound is not limited by its production method, but the hardly water-soluble metal hydroxide obtained by adjusting the pH of the aqueous solution of the water-soluble polyvalent metal compound to 7 or more It is preferable to use a colloid of a water-soluble metal hydroxide produced by a reaction in a water phase of a water-soluble polyvalent metal compound and an alkali metal hydroxide. The colloid of a slightly water-soluble metal compound has a number particle size distribution D50 (50% cumulative value of the number particle size distribution) of 0.5 μm or less and a D90 (90% cumulative value of the number particle size distribution) of 1 μm or less. Is preferred.
[0054]
The dispersion stabilizer is generally used at a concentration of 0.1 to 5% by weight, preferably 0.2 to 3% by weight, based on the aqueous dispersion medium. If the concentration of the dispersion stabilizer is too low, droplets of the polymerizable monomer composition tend to become unstable, and scales and polymerization aggregates are likely to be generated. If the concentration of the dispersion stabilizer is too high, the droplets become too fine, or the viscosity of the aqueous dispersion becomes too high, resulting in a decrease in polymerization stability.
[0055]
In the present invention, a dispersant containing a water-soluble polymer can be used as necessary. Examples of the water-soluble polymer include polyvinyl alcohol, methyl cellulose, gelatin and the like. In the present invention, it is not necessary to use a surfactant, but it can be used to stably carry out suspension polymerization within a range in which the environmental dependence of charging characteristics does not increase.
[0056]
(9) Preparation of first aqueous dispersion medium (A)
As the aqueous dispersion medium, water such as ion-exchanged water is generally used, but if desired, alcohol or the like may be used in combination with water. A first aqueous dispersion medium (A) containing the dispersion stabilizer is prepared by adding a predetermined amount of the dispersion stabilizer to the aqueous dispersion medium and stirring. Alternatively, a solution in which a water-soluble polyvalent metal compound is dissolved in an aqueous dispersion medium and a solution in which an alkali metal hydroxide salt is dissolved in an aqueous dispersion medium are mixed, and a hardly water-soluble metal is reacted by a reaction in an aqueous phase. A first aqueous dispersion medium (A) containing the colloid as a dispersion stabilizer may be prepared by forming a hydroxide colloid.
[0057]
The ratio of the first aqueous dispersion medium (A) to be used is usually 150 to 1,000 parts by weight, preferably 250 to 500 parts by weight with respect to 100 parts by weight of the polymerizable monomer. If the ratio is too small, the polymerization stability is lowered, and scales and aggregates are likely to be generated. If the ratio is too large, the productivity is decreased and the yield is decreased.
[0058]
(10) Preparation of first aqueous dispersion (B) containing droplets
A polymerizable monomer, a colorant, other additives and the like are mixed using a mixer, and if necessary, wet-grinded using a media-type wet pulverizer (for example, a bead mill) or the like. A meter composition is obtained. The polymerizable monomer composition is dispersed in the first aqueous dispersion medium (A) containing a dispersion stabilizer, stirred, and uniform droplets of the monomer composition (volume average particle diameter is 50 to 1000 μm). Primary droplets of the same degree). The polymerization initiator may be added after the droplets become uniform in the aqueous dispersion medium in order to avoid premature polymerization.
[0059]
A polymerization initiator is added to and mixed with the suspension in which the droplets of the polymerizable monomer composition are dispersed in the first aqueous dispersion medium (A), and the droplets are then dispersed using a high-speed rotary shearing stirrer. Stir until the particle size is close to the desired toner particle. In this way, the first aqueous dispersion (B) containing fine droplets (secondary droplets having a volume average particle size of about 1 to 12 μm) is prepared.
[0060]
The volume average particle size and particle size distribution of the fine droplets of the polymerizable monomer composition affect the volume average particle size and particle size distribution of the polymerized toner. When the particle diameter of the droplet is too large, the generated polymer toner particles are increased, and the resolution of the image is lowered. If the particle size distribution of the droplets is wide, the fixing temperature varies, causing problems such as fogging and toner filming. Therefore, it is desirable that the droplets are granulated so as to be reduced to the expected size of the toner particles.
[0061]
The volume average particle diameter of the droplets of the polymerizable monomer composition is usually 1 to 12 μm, preferably 2 to 10 μm, more preferably 3 to 8 μm. In order to obtain a high-definition image, particularly when a polymer toner having a small particle diameter is used, the volume average particle diameter of the droplet is preferably 2 to 9 μm, more preferably 3 to 8 μm, and further about 3 to 7 μm. It is desirable to do. The particle size distribution (volume average particle size / number average particle size) of the droplets of the polymerizable monomer composition is usually 1 to 3, preferably 1 to 2.5, and more preferably 1 to 2. In particular, when granulating fine droplets, an aqueous dispersion medium containing a monomer composition in a gap between a rotor rotating at high speed and a stator surrounding the rotor and having small holes or comb teeth. A method of distributing the is preferable.
[0062]
One or more of the above-mentioned monovinyl monomers are selected as the polymerizable monomer. To lower the fixing temperature of the toner, the glass transition temperature (Tg) is usually 80 ° C. or lower, preferably 40 to 80 ° C. More preferably, it is preferable to select a monomer or a combination of monomers that can form a polymer at about 50 to 70 ° C. In the present invention, the Tg of the copolymer constituting the binder resin is a calculated value (calculated Tg) calculated according to the type and use ratio of the monomer used.
[0063]
2.Method for producing polymerized toner
According to the conventional method, the first aqueous dispersion (B) in which minute droplets of the polymerizable monomer composition are dispersed is introduced into a polymerization can (polymerization reactor) and polymerized. On the other hand, in the present invention, the first aqueous dispersion (B) is mixed with the second aqueous dispersion medium (C) to prepare the second aqueous dispersion (D), and then polymerization is performed. By devising a method for preparing the second aqueous dispersion (D), the polymerization reaction can be carried out more stably.
[0064]
(1) Second aqueous dispersion medium (C) containing a dispersion stabilizer
The second aqueous dispersion medium (C) can be prepared in the same manner as the first aqueous dispersion medium (A). That is, the same dispersion stabilizer as that used for dispersing the polymerizable monomer composition can be used. Among them, colloids of poorly water-soluble metal hydroxides (for example, magnesium hydroxide colloids) produced by a reaction in the aqueous phase of a water-soluble polyvalent metal compound and an alkali metal hydroxide are preferable. In order to prepare such a colloidal solution, a solution in which a water-soluble polyvalent metal compound is dissolved in an aqueous dispersion medium and a solution in which an alkali metal hydroxide salt is dissolved in an aqueous dispersion medium are mixed to form an aqueous phase. It is preferable to employ a method in which a hardly water-soluble metal hydroxide colloid is produced by a reaction in the medium.
[0065]
The concentration of the dispersion stabilizer in the second aqueous dispersion medium (C) is 0.1 to 5% by weight, preferably 0.2 to 3% by weight. If the concentration of the dispersion stabilizer in the second aqueous dispersion medium (C) is too low, the action of improving the stability of the first aqueous dispersion (B) becomes insufficient, and the formation of scales and aggregates is suppressed. The effect is reduced. On the other hand, when the concentration of the dispersion stabilizer is too high, there is a possibility that the particle size distribution of the polymerized toner becomes broad or the viscosity of the second aqueous dispersion (D) becomes too large and becomes unstable.
[0066]
(2) Step 1
Step 1 in the production method of the present invention is a step of preparing the first aqueous dispersion (B). That is, Step 1 forms droplets of a polymerizable monomer composition containing at least a polymerizable monomer and a colorant in the first aqueous dispersion medium (A) containing a dispersion stabilizer, This is a step of preparing a first aqueous dispersion (B) in which the droplets are dispersed.
[0067]
(3) Step 2
In step 2 of the production method of the present invention, the first aqueous dispersion (B) is mixed with the second aqueous dispersion medium (C) containing 0.1 to 5% by weight of a dispersion stabilizer, and the first aqueous dispersion is mixed. In the step of preparing a second aqueous dispersion (D) containing 10 to 150 parts by weight of the second aqueous dispersion medium (C) with respect to 100 parts by weight of the polymerizable monomer in the liquid (B). is there.
[0068]
In the first aqueous dispersion (B), the dispersion stabilizer contained in the first aqueous dispersion medium (A) is consumed by adhering to the periphery of minute droplets, and dispersed therein. In the presence of the second aqueous dispersion medium (C) containing the stabilizer, the stability of the droplets is increased by the new dispersion stabilizer. On the other hand, when the concentration of the dispersion stabilizer in the first aqueous dispersion medium (A) to be used first is increased, the droplets of the polymerizable monomer composition become too fine or the viscosity is low. The increase is greater.
[0069]
There are various modes for preparing the second aqueous dispersion (D). As a method for preparing the second aqueous dispersion (D), the first aqueous dispersion (B) and the second aqueous dispersion medium (C) are mixed in a mixing container or a mixing device, etc. There is a method in which, after preparing (D), the second aqueous dispersion (D) is charged into a polymerization can.
[0070]
As another method, there is a method of preparing the second aqueous dispersion (D) in the polymerization can by introducing the first aqueous dispersion (B) and the second aqueous dispersion medium (C) into the polymerization can. is there. The first aqueous dispersion (B) and the second aqueous dispersion medium (C) can be charged into the polymerization can at the same time or separately.
[0071]
  The polymerization can be charged not only from the top but also from the bottom through a pipe.In the present invention,Second aqueous dispersionMediumAfter charging (C) into the polymerization can, the first aqueous dispersion (B) is charged into the polymerization can to prepare the second aqueous dispersion (D) in the polymerization can.Preferably adopt the method.
[0072]
Further, using a mixing container or a mixing device, the first aqueous dispersion (B) and a part of the second aqueous dispersion medium (C) are mixed to prepare an aqueous dispersion (D1), and After the remainder of the second aqueous dispersion medium (C) is charged into the polymerization can, the aqueous dispersion (D1) is charged into the polymerization can to prepare the second aqueous dispersion (D) in the polymerization can. The method to do can be adopted.
[0073]
In these methods, at least a part of the second aqueous dispersion medium (C) to be charged into the polymerization can is put into the polymerization can while being sprayed on the inner wall of the polymerization can, an accessory device in the polymerization can, or both. It is preferable to prevent the generation and adhesion of scale.
[0074]
Further, at least a part of the second aqueous dispersion medium (C) charged in the polymerization can is stored in the lower part of the polymerization can, and then the first aqueous dispersion (B) or the aqueous dispersion (D1) is polymerized. It is preferable to put into the can in order to reduce the impact when the first aqueous dispersion (B) or the aqueous dispersion (D1) is introduced from the upper part of the polymerization can.
[0075]
At least a part of the second aqueous dispersion medium (C) containing the dispersion stabilizer is preferably charged in advance in the polymerization can and stored in the lower part, but the charging method is not particularly limited, You may throw in from the upper part of a superposition | polymerization can, and you may throw in using piping from the lower part. As a preferable charging method, a method in which the second aqueous dispersion medium (C) is sprayed (sprayed) into the polymerization can is mentioned.
[0076]
The spraying method will be specifically described with reference to the drawings. FIG. 1 is a cross-sectional view of a polymerization can. A polymerization can 1 (polymerization reactor) 1 includes a jacket 2 for temperature adjustment, a motor 3 for rotating a stirring blade, a stirring blade 4, an aqueous dispersion containing droplets of a polymerizable monomer composition ( An inlet 9 for B), a pipe 10 for discharging a reaction liquid (slurry), and the like are arranged. The temperature inside the polymerization can is adjusted by passing a heat medium or a refrigerant through the jacket. As the heat medium, warm water is preferable. A shower nozzle 6 is arranged in the polymerization can 1 so that the second aqueous dispersion medium (C) from the pipe 5 can be sprayed into the polymerization can 1.
[0077]
The second aqueous dispersion medium (C) is charged into the polymerization can while being sprayed from the shower nozzle 6 onto the inner wall of the polymerization can, the stirring blade, or both. In FIG. 1, the spray liquid 7 is sprayed toward the upper part (gas phase part) in the polymerization can 1 and wets the inner wall of the upper part. However, the spraying direction may be changed to the direction of the side wall or the stirring blade. . According to the spraying direction shown in FIG. 1, the aqueous dispersion medium (C) sprayed on the upper inner wall of the polymerization can eventually reaches the lower part along the side wall. In this way, by attaching the inner wall of the polymerization can, the stirring blade, and the like with the second aqueous dispersion medium (C), the adhesion of scale can be effectively suppressed.
[0078]
In the production method of the present invention, the second aqueous dispersion medium (C) charged into the polymerization can 1 is preferably stored in the lower portion of the polymerization can 1. The second aqueous dispersion medium (C) 8 stored in the lower part of the polymerization can 1 is used to remove the first aqueous dispersion (B) containing droplets of the polymerizable monomer composition from, for example, the inlet 9. When throwing into the inside, the impact caused by dropping is reduced. If the second aqueous dispersion medium (C) is not stored in the lower part of the polymerization can 1, the first aqueous dispersion (B) will directly collide with the bottom of the polymerization can, etc. Undesirable phenomenon is likely to occur.
[0079]
In order to store the second aqueous dispersion medium (C) in the lower part of the polymerization can, it is necessary to adjust the input amount. By spraying a small amount of the second aqueous dispersion medium (C), it is difficult to store an amount sufficient to alleviate the impact at the time of charging the first aqueous dispersion liquid (B) in the lower part of the polymerization can. .
[0080]
In the present invention, the second aqueous dispersion medium (C) containing a dispersion stabilizer is used at a ratio of 10 to 150 parts by weight with respect to 100 parts by weight of the polymerizable monomer. This ratio is preferably 15 to 130 parts by weight, more preferably 20 to 100 parts by weight. By adjusting the use ratio of the second aqueous dispersion medium (C) within the above range, a sufficient amount of the second aqueous dispersion medium (C) can be stored in the lower part of the polymerization can.
[0081]
If the input amount of the second aqueous dispersion medium (C) is too small, the amount of liquid accumulated in the lower part of the polymerization can will be too small, and the first aqueous dispersion liquid (B) is introduced from the upper part of the polymerization can. In this case, the impact at the time of dropping cannot be sufficiently mitigated, and it becomes difficult to suppress adhesion of scales and formation of aggregates. Also, if the input amount of the first aqueous dispersion medium (C) is too small, the inner wall of the polymerization canister and the stirring blade cannot be sufficiently wetted, and the first aqueous dispersion liquid (B) adheres, resulting in a scale. It becomes easy to generate. If the amount of the second aqueous dispersion medium (C) charged into the polymerization can is too large, the yield may decrease or the efficiency of the polymerization reaction may decrease.
[0082]
When the first aqueous dispersion (B) and the second aqueous dispersion medium (C) are mixed in advance and then introduced into the polymerization can, the second aqueous dispersion (D ) Is formed, so even if it is introduced from the top of the polymerization can, coalescence and destruction of the droplets are alleviated. From the viewpoint of the stability of the polymerization reaction system, it is preferable to introduce the second aqueous dispersion (D) from the bottom of the polymerization can through a pipe.
[0083]
Among the various methods described above, the first aqueous dispersion (B) is polymerized from the viewpoint of alleviating the impact caused by charging the first aqueous dispersion (B) from the top of the polymerization can and suppressing the formation of scales and aggregates. Before being charged into the can, the second aqueous dispersion medium (C) is charged into the polymerization can at a ratio of 10 to 150 parts by weight with respect to 100 parts by weight of the polymerizable monomer, and the second aqueous system. A method of storing the dispersion medium (C) in the lower part of the polymerization can is preferred. Furthermore, at that time, it is preferable to adopt a method in which the second aqueous dispersion medium (C) is introduced into the polymerization can while being sprayed on the inner wall of the polymerization can, the auxiliary equipment in the polymerization can, or both.
[0084]
(4) Step 3
After the step 2, the polymerizable monomer composition dispersed as droplets in the second aqueous dispersion (D) is polymerized with a polymerization initiator in the polymerization can to produce colored polymer particles. The polymerization temperature is usually 5 to 120 ° C, preferably 35 to 95 ° C. If the polymerization temperature is too low, a polymerization initiator having a high catalytic activity must be used, which makes it difficult to manage the polymerization reaction. When the polymerization temperature is too high, when an additive that melts at a low temperature such as a release agent is included, this may bleed on the surface of the polymerized toner, resulting in poor storage stability.
[0085]
In this polymerization step, if desired, the water-based dispersion medium (C) or water is sprayed continuously or intermittently from the shower nozzle 6 to wet the upper inner wall and other attached devices in the gas phase part of the polymerization can. Can be held.
[0086]
After step 3, colored polymer particles can be recovered from the reaction mixture (slurry) to obtain a polymerized toner. In order to obtain polymer particles (capsule toner) having a core-shell structure, the following step 4 is added.
[0087]
(5) Step 4
In the present invention, the colored polymer particles produced in the above step are used as core particles, and a polymer monomer for shell is polymerized in the presence of the core particles to form a polymer layer covering the core particles. Core-shell type polymer particles (that is, capsule toner) can be produced. If a water-soluble polymerization initiator is added when the shell polymerizable monomer is added to the polymerization reaction system, polymer particles having a core-shell structure are easily formed.
[0088]
As the polymerizable monomer for the shell, when a monomer that forms a polymer having a Tg higher than the glass transition temperature (Tg) of the polymer component constituting the core particle is used, the storage stability of the toner can be improved. . On the other hand, by setting the Tg of the polymer component constituting the core particle low, the fixing temperature of the polymerized toner can be lowered or the melting characteristics can be improved, thereby enabling printing (copying, printing, etc.) High speed, full color, OHP (overhead projector) transparency, etc. can be dealt with suitably.
[0089]
As the polymerizable monomer for forming the core particle and the shell, a preferable monomer can be appropriately selected from the aforementioned monovinyl monomers. As the core polymerizable monomer used in the capsule toner, those capable of forming a polymer having a Tg of usually 60 ° C. or lower, preferably 40 to 60 ° C. are suitable. If the glass transition temperature of the polymer component forming the core particles is too high, the fixing temperature becomes high, and if it is too low, the storage stability is lowered. The polymerizable monomer for the core is often used in combination of two or more monomers in order to adjust the glass transition temperature. The Tg of the polymer is a calculated value (calculated Tg) calculated according to the type and use ratio of the polymerizable monomer to be used.
[0090]
The weight ratio of the polymerizable monomer for the core and the polymerizable monomer for the shell is usually 40/60 to 99.9 / 0.1, preferably 60/40 to 99.7 / 0.3, more preferably Is 80 / 20-99.5 / 0.5. If the ratio of the polymerizable monomer for the shell is too small, the effect of improving the storage stability is small, and if it is excessive, the effect of reducing the fixing temperature is small.
[0091]
The Tg of the polymer formed by the polymerizable monomer for shell is usually more than 50 ° C and 120 ° C or less, preferably more than 60 ° C and 110 ° C or less, more preferably more than 80 ° C and 105 ° C or less. The difference in Tg between the polymer formed from the core polymerizable monomer and the polymer formed from the shell polymerizable monomer is preferably 10 ° C. or higher, more preferably 20 ° C. or higher, particularly Preferably it is 30 degreeC or more. As the polymerizable monomer for the shell, it is preferable to use monomers that form a polymer having a Tg exceeding 80 ° C., such as styrene and methyl methacrylate, alone or in combination of two or more.
[0092]
The polymerizable monomer for shell is preferably added to the polymerization reaction system as droplets smaller than the average particle diameter of the core particles. When the particle size of the shell polymerizable monomer droplets is too large, it is difficult to form a polymer layer uniformly around the core particles. In order to make the polymerizable monomer for the shell into small droplets, the mixture of the polymerizable monomer for the shell and the aqueous dispersion medium is finely dispersed using, for example, an ultrasonic emulsifier. What is necessary is just to add the obtained dispersion liquid to a reaction system. When the polymerizable monomer for shell is a relatively water-soluble monomer (for example, methyl methacrylate) having a solubility in water at 20 ° C. of 0.1% by weight or more, It is not necessary to perform the fine dispersion process because it is easy to move quickly, but it is preferable to perform the fine dispersion process in order to form a uniform shell. When the polymerizable monomer for shell is a monomer having a solubility in water at 20 ° C. of less than 0.1% by weight (for example, styrene), it is subjected to fine dispersion treatment or solubility in water at 20 ° C. Is preferably added to the reaction system by adding 5% by weight or more of an organic solvent (for example, alcohols) to the reaction system.
[0093]
A charge control agent can be added to the polymerizable monomer for shell. The charge control agent is preferably the same as that used in the core particle production described above. When used, the charge control agent is usually 0.01 to 10 weights with respect to 100 weight parts of the shell polymerizable monomer. Parts, preferably 0.1 to 5 parts by weight.
[0094]
In order to produce a core-shell type polymerized toner, a shell polymerizable monomer or an aqueous dispersion thereof is added all at once, continuously or intermittently to a suspension containing core particles. . In order to form the shell, it is preferable to add a water-soluble radical initiator when the polymerizable monomer for shell is added. If a water-soluble polymerization initiator is added during the addition of the shell polymerizable monomer, the water-soluble polymerization initiator enters the vicinity of the outer surface of the core particle to which the shell polymerizable monomer has migrated, and the core particle surface. It is thought that it becomes easy to form a polymer (shell).
[0095]
Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate; 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis- Examples thereof include azo initiators such as [2-methyl-N- [1,1-bis (hydroxymethyl) ethyl] propionamide]. The amount of the water-soluble polymerization initiator is usually 0.1 to 50% by weight, preferably 1 to 20% by weight, based on 100 parts by weight of the polymerizable monomer for shell.
[0096]
The average thickness of the shell is usually 0.001 to 1.0 μm, preferably 0.003 to 0.5 μm, and more preferably 0.005 to 0.2 μm. If the shell thickness is too large, the fixing property is lowered, and if it is too small, the storage property is lowered. When the core particle diameter and shell thickness of the polymerization toner can be observed with an electron microscope, it can be obtained by directly measuring the particle size and shell thickness randomly selected from the observation photograph. When it is difficult to observe the core and the shell with a microscope, it can be calculated from the particle size of the core particle and the amount of the polymerizable monomer that forms the shell.
[0097]
3.Polymerized toner
The volume average particle diameter (dv) of the polymerized toner (including capsule toner having a core / shell type structure) obtained by the production method of the present invention is usually 1 to 12 μm, preferably 2 to 11 μm, more preferably 3 to 10 μm. It is. In the case of obtaining a high-definition image by increasing the resolution, it is particularly desirable to reduce the volume average particle diameter of the toner to preferably 2 to 9 μm, more preferably 3 to 8 μm, and particularly preferably 3 to 7 μm.
[0098]
The particle size distribution represented by volume average particle size (dv) / number average particle size (dp) of the polymerized toner of the present invention is usually 1.7 or less, preferably 1.5 or less, more preferably 1.3 or less. It is. If the volume average particle diameter (dv) of the polymerized toner is too large, the resolution tends to be lowered. When the particle size distribution (dv / dp) of the polymerized toner is large, the ratio of the polymerized toner having a large particle size increases, and the resolution tends to decrease.
[0099]
The polymerized toner of the present invention has a sphericity (Sc / Sr) represented by a value (Sc / Sr) obtained by dividing the area (Sc) of a circle having the diameter of the absolute maximum length of the particle by the actual projected area (Sr) of the particle. However, it is preferably 1 to 1.3, more preferably 1 to 1.2. When a substantially spherical polymerized toner is used, the transfer efficiency of the toner image on the photoreceptor to the transfer material is improved.
[0100]
4).Developer
The polymerized toner of the present invention can be used as a toner component of various developers, but is preferably used as a nonmagnetic one-component developer. When the polymerized toner of the present invention is a non-magnetic one-component developer, an external additive can be mixed as necessary. Examples of the external additive include inorganic particles and organic resin particles that act as a fluidizing agent and an abrasive.
[0101]
Examples of the inorganic particles include silicon dioxide (silica), aluminum oxide (alumina), titanium oxide, zinc oxide, tin oxide, barium titanate, and strontium titanate. As organic resin particles, methacrylic acid ester polymer particles, acrylic acid ester polymer particles, styrene-methacrylic acid ester copolymer particles, styrene-acrylic acid ester copolymer particles, a core is a styrene polymer, and a shell is methacrylic acid. Examples thereof include core / shell type particles formed of an ester copolymer.
[0102]
Among these, inorganic oxide particles are preferable, and silicon dioxide is particularly preferable. The surface of the inorganic fine particles can be hydrophobized, and silicon dioxide particles that have been hydrophobized are particularly suitable. Two or more types of external additives may be used in combination. In the case of using a combination of external additives, a method of combining inorganic particles having different average particle sizes or a combination of inorganic particles and organic resin particles is preferable. . The amount of the external additive is not particularly limited, but is usually 0.1 to 6 parts by weight with respect to 100 parts by weight of the polymerized toner. In order to attach the external additive to the polymerized toner, the polymerized toner and the external additive are usually placed in a mixer such as a Henschel mixer and stirred.
[0103]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited only to these examples. Parts and% are based on weight unless otherwise specified. Measuring methods such as physical properties and characteristics are as follows.
[0104]
(1) Droplet particle size of polymerizable monomer composition
The volume average particle diameter (dv) of the droplets of the polymerizable monomer composition in the aqueous dispersion medium and the ratio (dv / dp) between the volume average particle diameter (dv) and the number average particle diameter (dp) The expressed particle size distribution was measured by a particle size distribution measuring device (SALD2000A type, manufactured by Shimadzu Corporation). The particle size distribution was measured under the conditions of a refractive index of 1.55 to 0.20i and an ultrasonic irradiation time of 5 minutes.
[0105]
(2) Particle size and particle size distribution of polymer particles
The particle size distribution represented by the volume average particle size (dv) of the polymer particles and the ratio (dv / dp) of the volume average particle size (dv) to the number average particle size (dp) is determined by Multisizer (manufactured by Coulter Co., Ltd.). ). The measurement with this multisizer was performed under the conditions of an aperture diameter of 100 μm, a medium isotone, a concentration of 10%, and a measurement particle number of 100,000.
[0106]
(3) sphericity
The sphericity of the polymer particles (Sc / Sr) is determined by taking an electron micrograph of the polymer particles, and using the image processing analyzer Luzex IID (manufactured by Nireco Corporation) to measure the area ratio of the particles to the frame area. = Maximum 2%, Total number of processed particles = 100. The value obtained by dividing the area (Sc) of the maximum outer circumference circle by the substantial cross-sectional area (Sr) and averaging the measured values.
[0107]
(4) Aggregate amount
After completion of the suspension polymerization reaction, the slurry was transferred from the polymerization can to the slurry tank using a pump. Aggregates remaining at the bottom of the polymerization can after collection were collected, dried, and then weighed. The weight of the aggregate is a. The total solid weight calculated from the polymerization recipe (assuming 100% complete reaction) is b. The aggregate amount (% by weight) was calculated by the formula “Aggregate amount = (a / b) × 100”. When several batches of suspension polymerization were continuously carried out in the same polymerization vessel, the average value (unit = wt% / batch) was determined.
[0108]
(5) Scale amount
After the aggregates were carried out from the reaction can, the scale adhered to the tube wall or the like was dropped with a water jet, the dropped scale was collected and dried, and the weight was weighed. Let A be the weight of the scale. Let B be the total solids weight calculated from the polymerization recipe (assuming the reaction is 100% complete). The scale amount (% by weight) was calculated by the formula “Aggregate amount = (A / B) × 100”. When several batches of suspension polymerization were carried out in the same polymerization vessel, the average value (unit =% by weight / batch) was calculated.
[0109]
(6) Heat transfer coefficient of polymerization tube wall
Measure the water temperature on the inner side and the outer side of the jacket placed on the outer periphery of the polymerization can, calculate the area of the can wall in contact with the jacket and the flow rate of water flowing to the jacket, and based on those values The heat transfer coefficient was calculated.
[0110]
[Example 1]
1.Preparation of polymerizable monomer composition for core
80.5 parts of styrene, 19.5 parts of n-butyl acrylate, 0.5 part of divinylbenzene, and a polymethacrylic acid ester macromonomer (manufactured by Toa Gosei Chemical Co., Ltd., trade name “AA6”, Tg = 94 ° C.) 5 parts of polymerizable monomer for core (calculated Tg = about 55 ° C.), 7 parts of carbon black (trade name “# 25”, manufactured by Mitsubishi Chemical Corporation), charge control resin (trade name, manufactured by Fujikura Kasei Kogyo Co., Ltd.) “FCF626N”: 1 part of a styrene resin containing 7% of a sulfonic acid group-containing acrylamide monomer) and 1.0 part of t-dodecyl mercaptan were stirred and mixed with a normal stirrer. To further uniformly disperse. Furthermore, 10 parts of dipentaerythritol hexamyristate (solubility in styrene at 25 ° C. = 10 g / 100 g or more, endothermic peak temperature = 65 ° C., molecular weight = 1514) is added, mixed, dissolved, and the core polymerizable monomer A body composition was obtained. All the preparations of the polymerizable monomer composition were performed at room temperature.
[0111]
2.Preparation of the first aqueous dispersion medium
To an aqueous solution in which 9.5 parts of magnesium chloride is dissolved in 250 parts of ion-exchanged water, an aqueous solution in which 5.8 parts of sodium hydroxide is dissolved in 50 parts of ion-exchanged water is gradually added with stirring. An aqueous dispersion medium containing a slightly water-soluble metal hydroxide colloid) was prepared. All of the aqueous dispersion media were prepared at room temperature. When the particle size distribution of the colloid was measured with a SALD particle size distribution analyzer (Shimadzu Corporation), the particle size was D50 (50% cumulative value of the number particle size distribution) of 0.36 μm and D90 (number particle size distribution). 90% cumulative value) was 0.80 μm.
[0112]
3.Droplet formation process
The polymerizable monomer composition was charged into the aqueous dispersion medium containing the magnesium hydroxide colloid obtained as described above at room temperature and stirred until the droplets were stabilized. Thereafter, 5 parts of t-butylperoxy-2-ethylhexanoate (manufactured by Nippon Oil & Fats Co., Ltd., trade name “Perbutyl O”) was added as a polymerization initiator, and then 15% using an Ebara Milder (manufactured by Ebara Seisakusho). High shear stirring was performed at a rotation speed of 1,000 rpm for 30 minutes to form droplets of the polymerizable monomer composition. The first aqueous dispersion medium containing droplets of the polymerizable monomer composition is referred to as “first aqueous dispersion”.
[0113]
4).Preparation of aqueous dispersion of polymerizable monomer for shell
At room temperature, 1 part of methyl methacrylate (calculated Tg = 105 ° C.) and 100 parts of water were finely dispersed in an ultrasonic emulsifier to obtain an aqueous dispersion of a shell polymerizable monomer. The droplet diameter of the polymerizable monomer for shell was measured by adding the obtained droplet to a 1% sodium hexametaphosphate aqueous solution at a concentration of 3% and measuring with a Microtrac particle size distribution analyzer. .6 μm.
[0114]
5.Preparation of second aqueous dispersion medium
An aqueous solution in which 1.51 parts of magnesium chloride is dissolved in 39.64 parts of ion-exchanged water and an aqueous solution in which 0.92 parts of sodium hydroxide (alkali hydroxide) is dissolved in 7.93 parts of ion-exchanged water are gradually added with stirring. In addition, 50 parts of a second aqueous dispersion medium (concentration of magnesium hydroxide colloid = 3.9% by weight) containing magnesium hydroxide colloid (slightly water-soluble metal hydroxide colloid) was prepared. Hereinafter, this second aqueous dispersion medium is simply referred to as a “colloid solution”. 50 parts of this colloidal solution (colloid concentration = 1.4% by weight) is the number of parts relative to 100 parts of the core polymerizable monomer.
[0115]
A shower nozzle having a discharge port of 1.0 mmφ was arranged on the upper part of a stainless steel reaction can equipped with a stirrer at the lower part. From this shower nozzle, 50 parts of the colloidal solution was sprayed from the upper part in the reaction can, so that the inner wall of the can and the stirring blade were wetted, and collected in the lower part of the polymerization can.
[0116]
6).Suspension polymerization
A first aqueous dispersion containing droplets of the polymerizable monomer composition was charged from the upper part of the reaction can in which the colloidal solution was stored in the lower part. At this time, the colloidal solution accumulated in the lower part of the reaction vessel alleviated the impact caused by the dropping of the first aqueous dispersion. Further, the second aqueous dispersion composed of a mixture of the second aqueous dispersion medium (colloid solution) and the first aqueous dispersion was a dispersion excellent in stability in which droplets were stably dispersed.
[0117]
The polymerization reaction was started by raising the temperature in the polymerization can to 90 ° C., and when the polymerization conversion reached approximately 100%, sampling was performed and the particle diameter of the produced colored polymer particles was measured. As a result, the volume average particle diameter (dv) of the colored polymer particles was 6.4 μm, and the volume average particle diameter (dv) / number average particle diameter (dp) was 1.18.
[0118]
Next, an aqueous dispersion of the polymerizable monomer for shell and 0.3 part of a water-soluble initiator (trade name: VA086, manufactured by Wako Pure Chemical Industries, Ltd.) were dissolved in 65 parts of distilled water, and this was dissolved in a reactor. The polymerization was continued for 3 hours, the reaction was stopped, and a pH 9.5 reaction solution (slurry) containing polymer particles was obtained.
[0119]
The reaction liquid containing the polymer particles obtained as described above was discharged, and the agglomerates that had settled at the bottom of the polymerization can were taken out, dried and weighed. Moreover, the scale adhering to the can wall of the polymerization can and the stirrer was washed away with a water jet, the scale was collected, dried, and weighed.
[0120]
The thermal conductivity (first time) calculated from the water temperature on the inner and outer sides of the jacket disposed on the outer periphery of the polymerization can, the area in contact with the jacket wall of the jacket and the amount of water flowing in the jacket is 0.37 kW / ° C · m.²Met.
[0121]
The same polymerization reaction was repeated 5 times using the same polymerization can. The average value of the amount of aggregates over 5 polymerizations was 0.1% / batch. The average value of the scale amount was 0.6% / batch, and the polymerized toner could be produced stably. On the other hand, the fifth heat transfer coefficient is 0.34 kW / ° C. · m²It did not drop so much, and the influence of the scale was small.
[0122]
7.Recovery process
While stirring the slurry containing the produced polymer particles at room temperature, the pH of the system is adjusted to 4 or less with sulfuric acid, water is separated by filtration, and 500 parts of ion-exchanged water is newly added and reslurried. And washed with water. Thereafter, dehydration and water washing are repeated again several times at room temperature, and after solids are separated by filtration, the polymer particles having a core / shell structure are obtained by drying overnight at 45 ° C. in a dryer. It was.
[0123]
8).Polymerized toner
The resulting polymer particles had a volume average particle size (dv) of 6.5 μm and a volume average particle size (dv) / number average particle size (dp) of 1.16. The shell thickness calculated from the amount of the polymerizable monomer for shell and the core particle diameter was 0.03 μm. The sphericity (Sc / Sr) of the polymer particles was 1.2. The glass transition temperature of the polymer particles as determined by differential scanning calorimetry (DSC) was 63 ° C.
[0124]
9.Non-magnetic one-component developer
To 100 parts of the core-shell type polymer particles obtained as described above, 0.6 part of hydrophobized colloidal silica (trade name: RX300 [manufactured by Nippon Aerosil Co., Ltd.]) is added at room temperature, using a Henschel mixer. A non-magnetic one-component developer was prepared by stirring. When image evaluation was performed using the thus obtained non-magnetic one-component developer, an image having an extremely high resolution with an image density as high as 1.42 and free from fog and unevenness was obtained. .
[0125]
[Example 2]
The same as Example 1 except that the colloid concentration of the second aqueous dispersion medium (colloid solution) was changed from 1.4% by weight to 4.0% by weight and the input amount was changed from 50 parts to 20 parts. Operated. The results are shown in Table 1.
[0126]
[Example 3]
Same as Example 1 except that the colloid concentration of the second aqueous dispersion medium (colloid solution) was changed from 1.4 wt% to 0.5 wt% and the input amount was changed from 50 parts to 100 parts. Operated. The results are shown in Table 1.
[0127]
[Comparative Example 1]
The same operation as in Example 1 was conducted except that the amount of the second aqueous dispersion medium (colloid solution) charged was changed from 50 parts to 5 parts. The results are shown in Table 1.
[0128]
[Comparative Example 2]
The same operation as in Example 1 was conducted except that 50 parts of the second aqueous dispersion medium (colloid solution) charged into the polymerization can was changed to 50 parts of ion-exchanged water. The results are shown in Table 1.
[0129]
[Table 1]

[0130]
【The invention's effect】
According to the present invention, it is possible to perform a stable polymerization operation on an industrial scale without impairing the stability of the droplets of the polymerizable monomer composition dispersed in the aqueous dispersion medium, and in the polymerization can. A method for producing a polymerized toner capable of remarkably suppressing the generation of scales and aggregates in the toner is provided. According to the production method of the present invention, it is possible to improve the stability of an aqueous dispersion containing unstable microdroplets.
[0131]
Further, according to the production method of the present invention, even when an aqueous dispersion containing unstable droplets, the impact due to dropping is mitigated by the aqueous dispersion medium stored in advance when it is put into the polymerization can. Inconveniences such as coalescence and destruction of droplets are suppressed.
[0132]
According to the production method of the present invention, a polymerized toner having a small particle size, a high sphericity, and a sharp particle size distribution can be obtained stably and efficiently. Further, according to the production method of the present invention, it is possible to suppress the adhesion of the scale to the inner wall of the polymerization can, so that the heat transfer coefficient of the polymerization can wall can be kept high.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a polymerization can used in the production method of the present invention.
[Explanation of symbols]
1: Polymerization can
2: Jacket
3: Motor of stirring device
4: Stirring blade
5: Piping of aqueous dispersion medium
6: Shower nozzle
7: Spray solution
8: Aqueous dispersion medium collected at the bottom of the polymerization can
9: Input port
10: Pipe for discharge

Claims (4)

A polymerizable monomer composition containing at least a polymerizable monomer and a colorant is dispersed as droplets in an aqueous dispersion medium containing a dispersion stabilizer, and then polymerized with a polymerization initiator to give a colored weight. In a method for producing a polymerized toner including a step of generating coalesced particles,
(1) Forming droplets of a polymerizable monomer composition containing at least a polymerizable monomer and a colorant in a first aqueous dispersion medium (A) containing a dispersion stabilizer, Step 1 for preparing a first aqueous dispersion (B) in which is dispersed ;
(2) A second aqueous dispersion medium (C) containing 0.1 to 5% by weight of a dispersion stabilizer is charged into the polymerization can, and then the first aqueous dispersion ( B ) is charged into the polymerization can. by, mixing said first aqueous dispersion and (B) and said second aqueous dispersion medium (C), relative to 100 parts by weight of the polymerizable monomer of the first aqueous dispersion (B) , the second aqueous dispersion (D) step 2 is prepared in the polymerization vessel the containing said second aqueous dispersion medium (C) in a proportion of 10 to 150 parts by weight; in and (3) the polymerization in the can, step 3 to produce the second aqueous dispersion (D) a polymerizable monomer composition dispersed as droplets in the colored polymer particles by polymerizing a polymerization initiator;
A process for producing a polymerized toner comprising a series of steps comprising: Said second aqueous dispersion medium to be introduced into the polymerization in the can at least a part of (C), the inner wall of the polymerization vessel, the service appliance in the polymerization reactor or in claim 1 to be introduced into the spraying while polymerization in the can in both, The manufacturing method as described. Claim to introduce the second aqueous dispersion medium was charged in the polymerization in the can at least a part of (C) from Keep in reservoir at the bottom of the polymerization vessel, the first aqueous dispersion (B) in the polymerization vessel 3. The production method according to 1 or 2 . Wherein after the step 3, the polymerization was charged shell forming polymerizable monomer in the can, by further continuing the polymerization, the colored polymer particles coated core-shell structure by polymer layer The production method according to claim 1, further comprising a step 4 of producing polymer particles having the following.

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