JPH0954457A - Production of toner for developing electrostatic charge image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently use a dispersion stabilizer without causing environmental pollution by recovering slightly water-soluble calcium phosphate used as the dispersion stabilizer, regenerating and reuti-lizing it as well as to obtain a toner having <=10μm average particle diameter and a sharp particle size distribution. SOLUTION: A polymerizable monomer compsn. contg. a colorant and an electrostatic charge controlling agent is dispersed in an aq. medium with a dispersion stabilizer and suspension polymn. is carried out to produce the objective toner. At this time, fine particles of slightly water-soluble calcium phosphate deposited by adding an aq. soln. of <=pH4 contg. at least phosphate ions and calcium ions to an aq. alkali soln. so that the pH of the alkali soln. is not reduced to <5 after the addition are used as the dispersion stabilizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a toner for developing an electrostatic charge image in an electrophotographic method, an electrostatic recording method and an electrostatic printing method, and more particularly to a small particle diameter and a sharp particle diameter. The present invention relates to a method for producing an electrostatic charge image developing toner which efficiently utilizes a dispersion stabilizer to be used while obtaining an electrostatic charge image developing toner having a distribution.

[0002]

2. Description of the Related Art Conventionally, in order to obtain a dry toner containing a colorant and a resin as main components, a thermoplastic resin is melted, and a coloring agent such as a dye or a pigment is added thereto, and if necessary, a magnetic material and a frictional charge control agent. A method of adding an offset preventive agent, a lubricant, etc., thoroughly mixing, cooling and solidifying, finely pulverizing, and then performing classification for obtaining a desired particle size has been carried out. However, such a method has a large number of steps, is costly, it is difficult to uniformly disperse the colorant, the yield for obtaining the desired particle size range is low, and the obtained toner is The irregular shape causes deterioration of the fluidity of the powder. On the other hand, various methods for producing a toner by a suspension polymerization method, which have improved the above-mentioned drawbacks, have been proposed.

The suspension polymerization method is generally a method in which a polymerizable monomer composition containing a charge control agent, a colorant and the like is suspended in an aqueous medium and polymerized, and usually polyvinyl alcohol, gelatin and the like. The water-soluble high molecular weight substance, or poorly water-soluble inorganic salt powder such as calcium phosphate, calcium carbonate, etc. is present in the medium as a dispersion stabilizer, and the monomer droplets are made fine by mechanical shearing force, and then polymerization is performed. .

However, even in this suspension polymerization method, it is not possible to obtain a toner having a particle size distribution which is actually required, by a synthetic method or a dispersion method which is usually performed.

The coefficient of variation y is defined by the following equation (1) as a measure showing the spread of the particle size distribution of the toner, and will be described below.

Y = s / x × 100 (%) (1) Here, x is a volume average particle size (μm) obtained by a particle size measuring device such as a Coulter counter, and s is a particle similarly obtained. The standard deviation (μm) of the volume distribution of diameter is shown.
The coefficient of variation y is a measure showing that the larger the value, the wider the particle size distribution, and the smaller the value, the narrower the particle size distribution.

More specifically, a toner obtained by classification by a conventional pulverization method generally has a coefficient of variation of 27 to 35% when the average particle size is about 11 μm. If the particle size distribution is further narrowed by classification, the recovery rate of the toner will be significantly reduced, but the improvement in image quality and other performance aspects can hardly be expected.

On the other hand, in the suspension polymerization method, the average particle size is 11
In the case of synthesizing particles of around μm, the coefficient of variation usually has a value of 40 to 70% or more. In particular, recently, in order to achieve high resolution, a toner having a particle size of 10 μm or less is required, and it is more difficult to obtain such a sharp particle size distribution having an average particle size of 10 μm or less.

Therefore, in order to make the particle size distribution of the suspension polymerization method sharp as described above, Japanese Patent Laid-Open No. 7-49586 discloses that a slightly water-soluble inorganic salt used as a dispersant is dissolved in an aqueous solution. A method for obtaining fine particles of a poorly water-soluble inorganic salt by adding an alkali to make it strongly alkaline and precipitating the poorly water-soluble inorganic salt is described, but in this method, the poorly water-soluble inorganic salt is a poorly water-soluble calcium phosphate. When it is, a large amount of dibasic calcium phosphate different from hydroxyapatite, which is good as a dispersant, is generated in the initial stage of adding alkali, which adversely affects the effect as a dispersant, and obtains a sharp particle size distribution at 10 μm or less. Is very difficult.

On the other hand, the sparingly water-soluble calcium phosphate used as a dispersant is removed by solubilizing it in the aqueous phase by subjecting the suspension to acid treatment after polymerization. The acid-treated liquid is very inefficient after being separated from the toner particles and then disposed of, resulting in environmental pollution because it contains phosphorus.

[0011]

DISCLOSURE OF THE INVENTION The present invention provides a toner having an average particle size of 10 μm or less and a sharp particle size distribution in a suspension polymerization method, and recovers and regenerates a poorly water-soluble calcium phosphate used as a dispersion stabilizer. The purpose of the present invention is to efficiently use the dispersion stabilizer by reusing it without causing environmental pollution.

[0012]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, in the suspension polymerization method, an electrostatic charge image having a sharp particle size distribution with an average particle size of 10 μm or less was obtained. By obtaining and recovering the developing toner and recovering and reusing the poorly water-soluble calcium phosphate used as the dispersion stabilizer, the dispersion stabilizer can be efficiently used without environmental pollution, and the toner for electrostatic charge image development can be obtained. They have found that they can be obtained and have completed the present invention.

That is, according to the present invention, a polymerizable monomer composition containing a colorant and a charge control agent is dispersed in an aqueous medium using a dispersion stabilizer and then suspension polymerized to develop an electrostatic image. In a method for producing a toner, a dispersion stabilizer having a pH of at least phosphate and calcium ions of 4
The following aqueous solution is added to an alkaline aqueous solution, and the final pH after the addition is adjusted so as not to become less than 5, and the precipitated fine particles of poorly water-soluble calcium phosphate are used, and the toner for developing an electrostatic image is characterized by the following: Manufacturing method.

In the present invention, a polymerizable monomer composition containing a colorant and a charge control agent is dispersed in an aqueous medium using a dispersion stabilizer and then suspension polymerized to develop an electrostatic image. In a method for producing a toner, a dispersion stabilizer having a pH of at least phosphate and calcium ions of 4
The following aqueous solution and alkaline aqueous solution are continuously supplied and mixed, and the final pH after the mixing is adjusted so that the final pH does not become less than 5, and the precipitated hardly water-soluble calcium phosphate fine particles are used. The present invention relates to a method for producing a toner for developing an electrostatic image.

In the present invention, when suspension polymerization is carried out using a sparingly water-soluble calcium phosphate as a dispersion stabilizer of a polymerizable monomer in an aqueous medium, an aqueous solution having a pH of 4 or less in which at least phosphate ions and calcium ions are present. Is added to an alkaline aqueous solution, and the final pH after the addition is adjusted so as not to be less than 5, fine particles of poorly water-soluble calcium phosphate are precipitated, and the fine particles are used as a dispersant.
Alternatively, an aqueous solution having a pH of 4 or less in which at least phosphate ions and calcium ions are present and an alkaline aqueous solution are continuously supplied and mixed, and adjusted so that the final pH after the completion of the mixing does not become less than 5. Fine particles are deposited and used as a dispersant.

After the suspension polymerization, the suspension is adjusted to pH 4 or less, the sparingly water-soluble calcium phosphate is dissolved, solid-liquid separation is performed to separate the polymer, and the recovered acid aqueous solution is finally prepared by the above-mentioned method. A method for producing a toner for developing an electrostatic charge image, which comprises adjusting the pH so as not to become less than 5 and precipitating fine particles of poorly water-soluble calcium phosphate, and using the fine particles of poorly water-soluble calcium phosphate again as a dispersion stabilizer. Is provided.

The toner manufacturing method of the present invention will be specifically described below. The preparation of an aqueous solution containing at least phosphate ions and calcium ions and having a pH of 4 or less is not particularly limited, and can be performed by the methods 1) to 4), for example.
1) A method of mixing phosphoric acid and a calcium salt such as calcium chloride, 2) A method of adjusting the pH of a solution obtained by mixing a phosphate aqueous solution such as a sodium phosphate aqueous solution and a calcium salt such as calcium chloride to 4 or less with an acid, 3) Difficult Method of adding an acid to an aqueous suspension containing water-soluble calcium phosphate, 4)
A method of adding a sparingly water-soluble calcium phosphate powder or an aqueous suspension containing a sparingly water-soluble calcium phosphate to an aqueous acid solution.
Add these aqueous solutions to the final pH in an aqueous alkaline solution with stirring.
Of less than 5, preferably pH of less than 10 is added to precipitate fine particles of poorly water-soluble calcium phosphate.

When the pH is less than 5, the precipitated poorly water-soluble calcium phosphate particles tend to aggregate, and the toner dispersion stability cannot be kept good. Also, the lower the pH is below 5,
The amount of sparingly water-soluble calcium phosphate is reduced.

The term "fine particles of poorly water-soluble calcium phosphate" as used herein refers to particles having a volume average particle size of 10 μm or less, and it is very difficult to prepare toner particles having an average particle size of 10 μm or less among particles having a volume average particle size of 10 μm or less. is there.

Further, the smaller the particle size of the fine particles, the easier the preparation of toner particles of 10 μm or less. When the pH at the time of precipitation is 5 or more, preferably 10 or more, the precipitated particles become fine.

The phosphate ion and calcium ion concentration is preferably such that the concentration of the sparingly water-soluble calcium phosphate in the liquid in which the sparingly water-soluble calcium phosphate is deposited is 0.1 to 20% by weight. If it is less than 0.1% by weight, the concentration is very low and the productivity is low. On the other hand, if it exceeds 20% by weight, the apparent viscosity of the liquid increases, sufficient mixing is not carried out, and a hardly water-soluble calcium phosphate having a stable particle diameter cannot be obtained.

In order to keep the dispersion stability of the monomer composition before polymerization and the polymer composition during polymerization in suspension polymerization, the sparingly water-soluble calcium phosphate obtained here is hydroxyapatite. Considering that, the Ca / P molar ratio is close to 1.67, specifically 1.5 to 1.8.
Is preferred.

As a method of precipitation, an aqueous solution containing at least phosphate ions and calcium ions is added to an alkaline aqueous solution or they are continuously mixed.

When an aqueous solution containing at least phosphate ions and calcium ions is added to the alkaline aqueous solution, if the addition time is long, the particles precipitated in the initial stage grow and the particle size becomes large. It is desirable to add within 30 minutes with stirring, more preferably within 10 minutes.

Further, in the case of continuous mixing, an aqueous solution containing at least phosphate ions and calcium ions and an alkaline aqueous solution are continuously supplied into the mixing chamber from different supply ports, continuously mixed, and precipitated. Let

The mixing chamber is not particularly specified, but for improving mixing, a mixing chamber, a stirring blade, a stationary blade, or a mixing chamber having a different shape may be used. In order to prevent particle growth, it is desirable that the residence time in the mixing chamber be within 15 minutes or that the operation be performed in a mixed state close to a plug flow.

In the present invention, the temperature at the time of mixing the aqueous solution containing at least phosphate ions and calcium ions and the alkaline aqueous solution and the temperature at the subsequent aging are 30 ° C. or higher, preferably 40 ° C. or higher, and the aging period is 0.5. Do more than an hour.

Aging in the present invention means mixing an aqueous solution containing at least phosphate ions and calcium ions with an alkaline aqueous solution and then leaving the mixture at 30 ° C. or higher for 0.5 hours or more with stirring. The higher the temperature, the longer the time. The longer is the more effective. It is considered that aging promotes crystallization and causes disintegration of aggregated particles. The sparingly water-soluble calcium phosphate particles change to a smaller particle size, making it easy to prepare toner particles of 10 μm or less and stabilizing the quality. Things are obtained.

The suspension in which the sparingly water-soluble calcium phosphate is deposited may be used as it is as a dispersion stabilizer. Also,
When recovering and reusing, the acid added during pH adjustment, impurity ions depending on the basic substance, the eluate from the surfactant or polymer used as a dispersion aid, and impurities removed by washing with water during solid-liquid separation. Rinse off to obtain sparingly water-soluble calcium phosphate. By removing these, the dispersion stability of the droplets of the polymerizable monomer composition and the toner performance are improved.

When the solid-liquid separation operation as described above is performed,
Aggregation occurs in that step, and a large amount of poorly water-soluble calcium phosphate having a particle size of 10 μm or more is used. If used as it is, it becomes difficult to obtain a toner having a particle size of 10 μm or less, and the particle size distribution becomes broad. Therefore, a sparingly water-soluble calcium phosphate having a volume average particle size distribution of 10 μm or less is obtained by dispersing in water before use. Examples of the dispersion method include a general high-speed rotation type, a stationary blade or an in-vessel shape, a high-pressure blow-out type, a swirl nozzle type, or a wet medium agitation type pulverizer.

As a method for regenerating the poorly water-soluble calcium phosphate in the present invention, after suspension polymerization, an acid is added to the suspension to adjust the pH to 4 or less to dissolve the poorly water-soluble calcium phosphate. Then, in the solid-liquid separation step, the polymer and the aqueous solution are separated, and the resulting aqueous solution is used as an aqueous solution containing at least phosphate ions and calcium ions to obtain a poorly water-soluble calcium phosphate by the above-mentioned method,
Used as a dispersion stabilizer. The solid-liquid separation can be performed by natural sedimentation separation, centrifugation, pressure filtration, vacuum filtration, centrifugal filtration, or the like.

In the present invention, a colorant, a charge control agent, a wax, and if necessary, a toner property improving agent are added to the polymerizable monomer composition, and these are mixed and dispersed. An oil droplet of the monomer composition is formed by using a disperser in an aqueous medium containing a poorly aqueous solution calcium phosphate as a dispersion stabilizer for the monomer composition obtained by dissolving a polymerization initiator in this dispersion. . At this time, a surfactant may be added as a dispersion aid.

The poorly water-soluble calcium phosphate in the present invention refers to tricalcium phosphate (Ca ₃ (PO ₄ ) ₂ ) and hydroxyapatite (mCa ₃ (PO ₄ ) ₂ .nCa (OH) ₂ ).

These poorly water-soluble inorganic compound powders are added in a total amount of 0.2 to 400 to 100 parts by weight of the polymerizable monomer composition.
Add parts by weight in portions. The amount of addition in divided addition is 0.1 to 300 parts by weight at the start of dispersion, during or after dispersion.
0.1 to 300 parts by weight, preferably 0.5 to 150 at the beginning of dispersion
Part by weight, 0.5 to 150 parts by weight during or after dispersion is used. If the amount of the poorly water-soluble inorganic compound powder added is less than 0.2 parts by weight, the dispersing effect is insufficient and aggregated particles are formed, which is not preferable. If it exceeds 400 parts by weight, the viscosity will increase and the stirring will be non-uniform, and aggregated particles will be generated, which is not preferable.

As the dispersion aid, anionic, cationic, amphoteric or nonionic surfactants may be used.

Examples of the anionic surfactant include higher fatty acid salts such as sodium oleate and sodium stearate, higher alcohol sulfate ester salts such as sodium lauryl sulfate and ammonium lauryl sulfate, and alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate. Sodium alkyl naphthalene sulfonate, β-
Naphthalene sulfonic acid derivative such as sodium salt of naphthalene sulfonic acid formaldehyde condensate, dialkyl sulfosuccinic acid sodium salt, sulfosuccinic acid derivative such as phenoxyethyl allyl sulfosuccinic acid ammonium salt, dialkyl phosphate, polyoxyethylene alkyl ether sulfate, Examples thereof include polyoxyethylene alkylphenol ether sulfate and alkylsulfuric acid triethanolamine. Of these, sodium dodecylbenzenesulfonate and sulfosuccinic acid derivatives are particularly preferable.

Examples of the cationic surfactant include alkylamine salts such as stearylamine hydrochloride and dioleylamine sulfate, quaternary alkylammonium salts such as stearyltrimethylammonium chloride, and amine oxides such as lauryldimethylamine oxide. Examples of the surfactant include alkyl betaines such as lauryl betaine, and examples of the nonionic surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene alkyl aryl ethers such as polyoxyethylene nonylphenyl ether. ,
Examples thereof include sorbitan fatty acid esters such as sorbitan monolaurate.

These surfactants are used in an amount of 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the poorly water-soluble inorganic compound powder. Also, two or more of these may be mixed and used. These surfactants may be added partially at the start of dispersion, the rest may be added during or after the dispersion, or all at the start of dispersion.

In the present invention, a combination in which calcium phosphate is used as the poorly water-soluble inorganic compound powder and an anionic surfactant is used as the surfactant is particularly preferable.

The charge control agent used in the present invention includes:
It may be either a positively chargeable one or a negatively chargeable one. For example, when a negatively chargeable charge control agent such as an azo complex dye is used, the negatively chargeable toner may be a positively chargeable toner such as nigrosine. In the case of using the above toner, a positively chargeable toner can be obtained, and the toner can be used properly according to need. The amount of charge control agent added is 100 parts by weight of the polymerizable monomer.
The amount is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight.

As the polymerizable monomer used in the present invention, a polymerizable monomer having 3 to 25 carbon atoms can be used. Examples thereof include styrene, p-chlorostyrene, p-methylstyrene, vinyl acetate and propion. Vinyl acetate, vinyl benzoate, methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-
Butyl methacrylate, diethylaminoethyl methacrylate, t-butylaminomethyl methacrylate, acrylonitrile, 2-vinylpyridine, 4-vinylpyridine and the like are used alone or in combination.

Further, in the present invention, a polyfunctional monomer such as divinylbenzene, ethylene glycol dimethacrylate, trimethylolpropane triacrylate, glycidyl methacrylate or glycidyl acrylate is added as a crosslinking agent to the above-mentioned monomers to further improve durability. An excellent toner can be manufactured. The amount of the polyfunctional monomer added is 0.05 to 20 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the polymerizable monomer.

As the colorant used in the present invention, in the case of a black toner, various carbon blacks produced by a thermal black method, an acetylene black method, a channel black method, a furnace black method, a lamp black method and the like, and a color toner In case of copper phthalocyanine, monoazo pigment (CIPigment Red 5, CIPigment Orang
e 36, CIPigment Red 22), disazo pigment (CIPi
gment Yellow 83), anthraquinone pigment (CIPigmen
t Blue 60), disazo dyes (Solvent Red 19), rhodamine dyes (Solvent Red 49) and the like.

The polymerization initiator used in the present invention includes
Commonly used oil-soluble peroxide or azo initiators can be used. For example, benzoyl peroxide, lauroyl peroxide, 2,2'-azobisisobutyronitrile, 2,2'-
Azobis- (2,4-dimethylvaleronitrile), orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide and the like can be mentioned. These are used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the polymerizable monomer.

As the so-called releasing agent used in the present invention, a known low molecular weight olefin polymer may be contained for the purpose of preventing offset, improving fluidity, improving fixing property and the like. This low molecular weight olefin polymer is preferably present during the polymerization of the monomer together with the colorant used in the present invention. Examples of the low molecular weight olefin polymer used in the toner obtained in the present invention include polyethylene, polypropylene, ethylene vinyl acetate copolymer, chlorinated polyethylene wax and the like. The above-mentioned low molecular weight olefin polymer is used in an amount of 1 to 20 parts by weight, preferably 3 to 15 parts by weight, per 100 parts by weight of the resin component of the toner.
If the amount is less than 1 part by weight, the offset prevention effect may not be sufficient, and if it exceeds 20 parts by weight, gelation may occur during polymerization, which is not preferable.

The toner obtained in the present invention can contain a magnetic material and can be used as a one-component toner. When a magnetic substance is contained, it is preferably dispersed in a polymerizable monomer and used in the same manner as the colorant.
The content of the magnetic substance is 20 to 2 with respect to 100 parts by weight of the polymerizable monomer.
The amount is preferably 00 parts by weight, more preferably 50 to 150 parts by weight.

The present invention can be applied to a capsule toner produced by an interfacial polymerization method or an in situ polymerization method.

Using the toner obtained in the present invention,
For example, in order to form an image by an electrophotographic method, a selenium photoreceptor or an inorganic photoconductive material such as zinc oxide, cadmium sulfide, cadmium selenide, cadmium sulfate selenide, lead oxide, or mercury sulfide is used in a binder resin. A photoconductor provided with a photoconductive layer dispersed and contained on a conductive support, or anthracene,
A photoreceptor is used in which a photosensitive layer containing an organic photoconductive material such as polyvinylcarbazole, if necessary, in a binder resin is provided on a conductive support. The entire surface of the photosensitive layer of such a photoreceptor is charged by corona discharge using, for example, a corotron or scorotron charger, and then imagewise exposed to light or the like to form an electrostatic charge image.
Next, this electrostatic image is developed by a developer comprising a mixture of the toner obtained in the present invention and glass beads or an iron powder carrier, for example, by a cascade method or a magnetic brush method to form a toner image. The toner image is transferred onto the transfer paper by being pressed against the transfer paper under corona discharge, for example. The toner image transferred on the transfer paper is heated and fixed by a hot roll fixing device covered with a fluororesin or silicone rubber having a releasing property.

In the present invention, as the substance used for adjusting the pH, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, etc. are used as the acid. Examples of the basic substance include ammonium hydroxide, potassium hydroxide, sodium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, ammonium hydrogencarbonate, sodium hydrogencarbonate, sodium phosphate and the like, and hydrates thereof. Alternatively, its aqueous solution is used.

[0050]

BEST MODE FOR CARRYING OUT THE INVENTION A specific example of the process for producing the toner for developing an electrostatic image according to the present invention will be described below. PH4 containing at least phosphate and calcium ions
The following aqueous solution is added to the alkaline aqueous solution, or both solutions are continuously supplied and mixed to obtain a suspension of sparingly water-soluble calcium phosphate fine particles of 10 μm or less. This solution may be used as it is as an aqueous medium, but substances such as generated ions may be removed by adjusting the pH. The final pH of the aqueous solution is adjusted so as not to be less than 5, and the polymerizable monomer, the colorant, the charge control agent, the release agent and, if necessary, the magnetic material are mixed and stirred, and then the polymerization initiator is dissolved. Next, this mixed solution is added to an aqueous dispersion medium in which a sparingly water-soluble calcium phosphate and a surfactant are dispersed and dissolved in water,
The polymerizable monomer composition is dispersed, oil droplets are formed, and a suspension is obtained.

After dispersion, a sparingly water-soluble calcium phosphate and, if necessary, a surfactant may be added in order to make the oil droplets stably exist.

Further, for dispersing the polymerizable monomer composition of the present invention in an aqueous medium, the following dispersing machine can be used.

As the high-speed rotary disperser, TK homomixer (made by Tokushu Kika Kogyo Co., Ltd.), CLEARMIX (made by M Technique Co., Ltd.), slasher (made by Mitsui Miike Seisakusho Co., Ltd.), Milder ( (Manufactured by EBARA CORPORATION), T.
K. High Line Mill (manufactured by Tokushu Kika Kogyo Co., Ltd.), TK Homomic Line Flow (made by Tokushu Kika Kogyo Co., Ltd.), TK Pipeline Homo Mixer (made by Tokushu Kika Kogyo Co., Ltd.), T.
K. Homomic Line Mill (made by Tokushu Kika Kogyo Co., Ltd.), T.
K. Hibis Line Mixer (made by Tokushu Kika Kogyo Co., Ltd.),
DISHO (manufactured by Korma Co., Ltd.) and the like. As a disperser using stationary blades or in-tank shape, ALM homogenizer (manufactured by Gorlin Co.), static mixer PSM (manufactured by Betzhold Co., Ltd.), Sulzer mixer (Sruzer Brothers Co., Ltd.)
), Hi Mixer (Toray Co., Ltd.), Noritake Static Mixer (Noritake Co., Ltd.), TK Fiscarin (Special Kika Kogyo Co., Ltd.), TK-ROSS LPD Mixer (Special Kika Kogyo Co., Ltd.) )), TK-ROSS ISG Mixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), and Kose Magella (manufactured by China Explosives Co., Ltd.). Manufactured) etc.

After the dispersion is completed, the suspension is heated to carry out suspension polymerization to obtain a polymer. Then, an acid is added to the suspension to adjust the pH to 4 or less, and the sparingly water-soluble calcium phosphate is dissolved. After that, solid-liquid separation is performed to separate the polymer and the acid aqueous solution. The separated polymer is further washed with water and solid-liquid separation repeatedly, and after the polymer is washed, it is dried and subjected to a surface treatment such as attaching fine powder of silica or the like to the toner. To get Further, the separated aqueous acid solution is added to an alkaline aqueous solution or both solutions are continuously supplied and mixed to adjust the final pH so as not to become less than 5, to precipitate a sparingly water-soluble phosphate. Further, after the sparingly water-soluble calcium phosphate is deposited, the solution is aged under stirring at 30 ° C. or higher for 0.5 hour or longer. By aging, a stable product with a small particle size is obtained.

The suspension in which the sparingly water-soluble phosphate is deposited is
It contains impurities ions depending on the acid and base added during pH adjustment, or the eluate from the surfactant or polymer used as a dispersion aid, so after washing away the impurities with water, solid-liquid separation is performed. To obtain sparingly water-soluble calcium phosphate. At this time, if necessary, washing with water and solid-liquid separation may be repeated. The hardly water-soluble calcium phosphate obtained by solid-liquid separation is used again as a dispersant after adding an appropriate amount of water.

[0056]

EFFECTS OF THE INVENTION Toner for developing an electrostatic image having a small particle size and a narrow particle size distribution is obtained by polymerizing using a minute water-insoluble calcium phosphate which is obtained by controlling the conditions for forming the slightly water-soluble calcium phosphate. Will be possible. Also,
By collecting and reusing the sparingly water-soluble calcium phosphate used as the dispersion stabilizer, the dispersion stabilizer can be used efficiently without causing environmental pollution.

[0057]

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 Styrene 85 g, 2-ethylhexyl acrylate 15 g,
A mixture of 6 g of carbon black (manufactured by Mitsubishi Kasei Co., Ltd., # 44) and 1.5 g of a charge control agent (manufactured by Hodogaya Chemical Co., Ltd., Aizenspiron Black TRH) was mixed with TK Homo Mixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) And mixed for 10 minutes. 2, in this mixture
5 g of 2'-azobisisovaleronitrile was dissolved to prepare a polymerizable monomer composition. Meanwhile, 100% 48% NaOH aqueous solution
Ion-exchanged water was added to g to prepare 2000 g of an aqueous NaOH solution in a 5-liter separable flask. Next, 2000 g of 0.21 mol / liter H ₃ PO ₄ aqueous solution was placed in a 5 liter beaker, 78 g of CaCl ₂ was added with stirring, and the pH was adjusted to
An aqueous solution of 2 was obtained. This aqueous solution was gradually added to the previously prepared aqueous NaOH solution with vigorous stirring for 30 minutes and mixed and stirred at a temperature of 20 ° C. to precipitate hydroxyapatite fine particles. The pH at this time was 12. About 5 minutes after mixing, this suspension was filtered under reduced pressure to obtain a hydroxyapatite hydrous cake.
476 g were obtained. Add 5000 g of deionized water to this cake,
After stirring, vacuum filtration was performed again and washing with water was performed. This operation was repeated three times, and ion-exchanged water was added to the obtained hydroxyapatite hydrous cake to obtain a suspension containing 2% of hydroxyapatite. Sodium dodecylbenzenesulfonate (0.025 g) was added to this suspension (300 g), and the mixture was dispersed at TK Homomixer at 10,000 rpm for 5 minutes to prepare an aqueous medium. The above polymerizable monomer composition was added to the aqueous medium, and the mixture was further stirred and dispersed at TK Homomixer at 10,000 rpm for 5 minutes to suspend and disperse. This suspension in a separable flask at a stirring speed of 100 rpm with a normal stirrer, under a nitrogen atmosphere, 75
The polymerization reaction was carried out at 8 ° C for 8 hours. Further, 12 g of 35% hydrochloric acid was added to adjust the pH to 2, and the filtrate was recovered after filtration. The water-containing toner cake is washed with water and then dried under reduced pressure at 40 ° C.
It was dried for 10 hours. The particle size distribution of the obtained toner was measured with a Coulter counter (TA-II type, aperture diameter 50 μm). The obtained toner had an average particle diameter of 9.5 μm and a coefficient of variation of 38%.

Example 2 Example 1 was repeated except that the addition time to the aqueous NaOH solution was 2 minutes. The average particle size of the obtained toner is
The coefficient of variation was 9.2 μm and the coefficient of variation was 33%.

Example 3 Except that the temperature at the time of precipitation of hydroxyapatite was 70 ° C. and then the mixture was aged for 4 hours at 70 ° C. with stirring.
The same method as in Example 2 was used. The obtained toner had an average particle size of 8.4 μm and a coefficient of variation of 28%.

Example 4 280 g of the filtrate recovered in Example 3 was added to 8% NaOH under vigorous stirring.
It was added to the aqueous solution over 1 minute, and hydroxyapatite was precipitated at a temperature of 70 ° C. The pH at that time was 12. Then, while stirring as it was, aging was carried out at 70 ° C. for 4 hours and filtration was carried out to obtain 25 g of a hydroxyapatite hydrous cake. This cake was washed with water and dispersed as in Example 1 to obtain 250 g of a hydroxyapatite 2% suspension. For the shortage, 50 g of the suspension obtained in Example 3 was added, and 0.025 g of sodium dodecylbenzenesulfonate was added to this suspension, and T.
K. Homomixer was dispersed at 10,000 rpm for 5 minutes, then the polymerizable monomer composition was added, and TK homomixer was added at 10,000 rpm.
The mixture was stirred for 5 minutes to suspend and disperse. The suspension was subjected to a polymerization reaction in a separable flask at 75 ° C. for 8 hours under a nitrogen atmosphere at a stirring speed of 100 rpm with a normal stirrer.
Further, 12 g of 35% hydrochloric acid was added to adjust the pH to 2, and the filtrate was recovered after filtration. The water-containing toner cake was washed with water and then dried under reduced pressure at 40 ° C. for 10 hours. The particle size distribution of the obtained toner was measured with a Coulter counter (TA-II type, aperture diameter 50 μm). The obtained toner had an average particle size of 8.4 μm and a coefficient of variation of 28%.

Example 5 To 80 g of 48% NaOH aqueous solution was added ion-exchanged water to obtain 2000 g of Na.
Adjust the OH solution into a 5 liter separable flask,
The same procedure as in Example 1 was carried out except that the pH of the hydroxyapatite fine particles deposited was 7. The obtained toner had an average particle diameter of 9.9 μm and a coefficient of variation of 40%.

Example 6 An aqueous solution of NaOH and an aqueous solution containing phosphate ions and calcium ions were supplied from separate supply ports into a vessel having an internal volume of 400 cc with a residence time of 1 minute to deposit hydroxyapatite. The procedure was as in Example 5. The obtained toner had an average particle size of 9.4 μm and a coefficient of variation of 35%.

Comparative Example 1 50 g of tricalcium phosphate was dissolved in 2600 g of a 1.6% hydrochloric acid aqueous solution, and the aqueous solution was homomixer (made by Tokushu Kika Co., Ltd.).
A 48% NaOH aqueous solution was gradually added to the mixture while stirring at 10,000 rpm in the solution, and was added until pH 12 was reached to precipitate hydroxyapatite. Then, 35% hydrochloric acid was further added to adjust the pH to 8 to obtain a hydroxyapatite 1.75% suspension. Sodium dodecylbenzenesulfonate 0.025
After adding g and dispersing at TK homomixer 10000 rpm for 5 minutes, the polymerizable monomer composition was added, and further stirred at TK homomixer 10000 rpm for 5 minutes to suspend and disperse. The suspension was subjected to a polymerization reaction in a separable flask at 75 ° C. for 8 hours under a nitrogen atmosphere at a stirring speed of 100 rpm with a normal stirrer. Further, 12 g of 35% hydrochloric acid was added, and the filtrate was recovered after filtration. The water-containing toner cake was washed with water and then dried under reduced pressure at 40 ° C. for 10 hours. The particle size distribution of the obtained toner is measured by Coulter counter (TA-II type, aperture size
50 μm). The average particle size of the obtained toner is 10.5.
μm, the coefficient of variation was 42%.

Comparative Example 2 Deionized water was added to 75 g of a 48% NaOH aqueous solution to give 2000 g of Na.
Adjust the OH solution into a 5 liter separable flask,
The same procedure as in Example 1 was carried out except that the pH of the hydroxyapatite fine particles deposited was 4.5. Polymerization stability was extremely poor, causing agglomeration of lumps.

The average particle size and coefficient of variation of Examples 1 to 6 and Comparative Examples 1 and 2 are summarized in Table 1 below.

[0067]

[Table 1]

Claims (4)

[Claims] 1. A toner for developing an electrostatic charge image is produced by dispersing a polymerizable monomer composition containing a colorant and a charge control agent in an aqueous medium using a dispersion stabilizer and then subjecting it to suspension polymerization. In the method, as a dispersion stabilizer, an aqueous solution containing at least phosphate ions and calcium ions and having a pH of 4 or less was added to an alkaline aqueous solution, and the final pH after the addition was adjusted so that the final pH was not less than 5 to cause precipitation. A process for producing a toner for developing an electrostatic charge image, which comprises using fine particles of poorly water-soluble calcium phosphate. 2. A toner for developing an electrostatic image is produced by dispersing a polymerizable monomer composition containing a colorant and a charge control agent in an aqueous medium using a dispersion stabilizer and then subjecting it to suspension polymerization. In the method, as a dispersion stabilizer, an aqueous solution containing at least phosphate ions and calcium ions and having a pH of 4 or less and an alkaline aqueous solution are continuously supplied and mixed,
A method for producing a toner for developing an electrostatic charge image, which comprises using fine particles of sparingly water-soluble calcium phosphate which have been precipitated and adjusted so that the final pH after mixing is not lower than 5. 3. The electrostatic charge according to claim 1 or 2, wherein after the fine particles of sparingly water-soluble calcium phosphate are precipitated, the suspension is aged at 30 ° C. or higher for 0.5 hour or more with stirring. Method for producing toner for image development. 4. After suspension polymerization using fine particles of sparingly water-soluble calcium phosphate as a dispersion stabilizer, the suspension is adjusted to pH 4 or lower to dissolve the sparingly water-soluble calcium phosphate, and in the solid-liquid separation step. After separation from the polymer composition,
4. The method for producing a toner for developing an electrostatic charge image according to claim 1, wherein the sparingly water-soluble calcium phosphate is regenerated from the recovered aqueous solution and is reused as a dispersion stabilizer.