JP4078182B2 - Method for producing colored particles used for toner for electrostatic charge development and toner - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to colored particles used in toner for developing an electrostatic latent image formed on an image carrier by an electrophotographic process or an ion flow method, and a method and apparatus for manufacturing the same.
[0002]
[Prior art]
Toners used in electrophotography are in the direction of smaller particle sizes and higher pigment concentrations to meet the recent demands for high-definition images and low consumption, and generally have an average particle size of 5 to 15 μm and a pigment concentration of 5 to 5. Obtained as fine particles of about 10% by weight.
[0003]
As a method for producing such fine particles, a so-called melt-kneading pulverization method in which a resin, a pigment, or the like is melt-kneaded and then mechanically pulverized is generally used. In the melt-kneading pulverization method, high dispersion can be imparted to the pigment at the time of melt-kneading, so that the dispersibility of the pigment can be improved. However, because of mechanical pulverization, the equipment process until obtaining a desired toner as the particle size becomes smaller Not only is expensive and expensive, but the shape of the resulting particles is indefinite and inferior in fluidity and storability, and the charging stability and storability are inferior because pigments and wax appear on the surface. , And so on.
[0004]
On the other hand, in recent years, a toner production method called a polymerization method such as suspension polymerization or emulsion polymerization aggregation method has been proposed. The polymerization method is advantageous in terms of storage stability because it can be manufactured from small particle size and true sphere to irregular shape, and it can be encapsulated in hydrophobic pigment and wax because it is produced in water. is there. However, since polymerization is accompanied during granulation, the resin is limited to an acrylic resin, and since hydrophilic emulsifiers and dispersion stabilizers are used, there are problems such as environmental dependency of toner and wastewater treatment during production. .
[0005]
Moreover, there is a submerged drying method as a method not involving polymerization at the time of granulation. Toner prepared by in-liquid drying method can be prepared by polyester resin that cannot be prepared by polymerization method, but the same wastewater treatment problem as polymerization method and adverse effects on environment by using solvent to dissolve resin And problems such as complicated operation.
[0006]
An object of the present invention is to provide a method for producing colored particles for use in an electrostatic charge developing toner that solves the above-described problems.
[0007]
On the other hand, Patent Document 1 proposes a method for producing fine particles using a supercritical fluid. This method is merely a method for producing fine particles to be externally added to the toner, and does not describe any method for producing a toner in which a pigment is combined.
[0008]
The inventors of the present invention have found that a resin in which a resin is precipitated by encapsulating a resin and a pigment in a supercritical fluid and then reducing the pressure can be produced. Yes.
[0009]
Since the supercritical fluid is a gas at normal pressure, neither a drying process nor wastewater treatment is necessary. In addition, if carbon dioxide gas is used for the supercritical fluid, a harmful organic solvent is not used, so that it is an environmentally friendly manufacturing method. Furthermore, since it does not accompany polymerization at the time of granulation, it can be produced even with a polyester resin or the like. Further, since the shape of the obtained particles is from a spherical shape to a substantially spherical shape, it is a production method that can solve the problems of conventional toners, such as being advantageous in terms of storage stability.
[0010]
[Problems to be solved by the invention]
However, in this method using a supercritical fluid, since the pigment and the resin are precipitated at the same time, there is a limit to granulation while maintaining dispersibility. In particular, there is a problem that the dispersibility of the pigment cannot be maintained when trying to combine a higher amount of pigment than in the past.
Since the concentration and dispersibility of the pigment adversely affect the toner consumption and optical characteristics, an early solution has been desired.
[0011]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-133417 [Patent Document 2]
Japanese Patent Laid-Open No. 2001-312098
[Means for Solving the Problems]
As a result of diligent research, the present inventors have found that the above problem can be solved by adopting a specific process in a colored particle manufacturing method and manufacturing apparatus used for toners using supercritical fluid or subcritical fluid. The present invention has been reached.
[0013]
Method for producing colored particles of the present invention, in order to solve the above problems, melt-kneading at least a binder resin and a colorant, then heating the melt-kneaded product with a supercritical fluid or subcritical fluid It is characterized in that the toner is taken out from the supercritical fluid or subcritical fluid by stirring to disperse the melt-kneaded material and then reducing the pressure.
[0014]
Dispersibility of the pigment can be increased by melt-kneading the resin and the pigment in advance. By dispersing this melt-kneaded material in a supercritical fluid, a toner having a small particle size and a narrow distribution can be obtained. Since the supercritical fluid changes to a gas when the pressure is reduced, a cleaning / drying process is not required, and thus a toner can be produced by a simple method.
[0015]
Further , in the method for producing colored particles of the present invention, at least the binder resin and the colorant are previously melt-kneaded, and then the melt-kneaded product is heated and stirred in a supercritical fluid or subcritical fluid to obtain a melt-kneaded product. When the toner is taken out from the supercritical fluid or subcritical fluid by reducing the pressure after dispersion, a fluororesin as a dispersion stabilizer is melted and kneaded as a resin that dissolves in the supercritical fluid or subcritical fluid. in addition to, your Ku further compounded in the supercritical fluid or subcritical fluid. When the molten kneaded material is stirred and dispersed in a supercritical fluid or subcritical fluid , the fluororesin as a dispersion stabilizer is dissolved in the supercritical fluid or subcritical fluid, and then decompressed. The melted fluorine-based resin is insolubilized and deposited on the surface of the particles in which the melt-kneaded material is dispersed, whereby a toner having a capsule structure in which pigments and waxes are combined can be produced.
[0016]
Moreover, it is preferable that the manufacturing method of the colored particle of this invention adds a wax at the time of melt-kneading. By blending the wax at the time of melt-kneading, the wax can be atomized to a predetermined particle size, and the adverse effect on storage stability can be suppressed by being located inside the particle.
[0017]
In the method for producing colored particles of the present invention, it is preferable to include a charge control agent in the supercritical fluid or subcritical fluid. By adding the charge control agent to the supercritical fluid or subcritical fluid, it becomes possible to localize the toner near the surface of the toner, and a toner having high chargeability can be obtained in a small amount.
[0018]
Furthermore, in the method for producing colored particles of the present invention, the supercritical fluid or subcritical fluid is preferably carbon dioxide. Carbon dioxide has a relatively low critical point of about 31 ° C., and the resin can be softened by having a slight affinity with the resin. Therefore, it can be produced at a relatively low temperature, and colored particles can be provided by an environmentally friendly method with low production energy costs.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0020]
The method for producing colored particles used in the toner of the present invention is to melt and knead at least a binder resin and a colorant in advance, and then add the melt-kneaded material into a supercritical fluid or subcritical fluid, and then heat and stir to melt and knead. In this method, the colored particles used in the toner are taken out of the supercritical fluid or subcritical fluid by dispersing the substance and then reducing the pressure.
[0021]
The kneader used in the present invention is not particularly limited. For example, a general kneader such as a twin screw extruder, three rolls, or a lab blast mill can be used. TEM-100B (manufactured by Toshiba Machine), PCM- Examples thereof include uniaxial or biaxial extruders such as 65/87 (manufactured by Ikegai) or open roll systems such as knee dicks (manufactured by Mitsui Mining Co., Ltd.). Among them, particularly in the melt kneading operation, in order to disperse the additive efficiently, high shear kneading at a low temperature is desirable so that the resin viscosity at the time of melting is not excessively lowered, and an open roll type is particularly desirable.
[0022]
Next, the melt-kneaded product is put into a supercritical fluid or a subcritical fluid. Here, a supercritical fluid or subcritical fluid is a fluid in which the density in the gas phase and the liquid phase is equal when the temperature and pressure of the substance are set to a certain condition (critical point) or higher. A fluid under a temperature or pressure near or above is called a supercritical fluid.Also, even if it is less than the supercritical point or near the critical point, it becomes a state close to the supercritical fluid. Called a critical fluid.
[0023]
In supercritical fluids or subcritical fluids (in the following description of supercritical fluids, subcritical fluids are included unless otherwise specified), both gas properties and liquid properties appear. For example, density is close to liquid (several hundred times that of gas), viscosity is close to gas (1/10 to 1/100 of liquid), diffusion coefficient is 1/10 to 1/100 of liquid, heat conduction The degree can be close to liquid (about 100 times that of gas).
[0024]
As described above, the supercritical fluid has the same thermal conductivity as that of a normal liquid, but has a low viscosity. Therefore, the supercritical fluid is excellent in that a high-melting and high-viscosity melt-kneaded material is dispersed. In addition, since it is easily changed to a gas by decompression, it is remarkably excellent in terms of dryness.
[0025]
Here, examples of substances that can be used as the supercritical fluid include CO ₂ , N ₂ , CH ₄ , C ₂ H ₆ , CF ₃ H, NH ₃ , CF ₃ Cl, CH ₃ OH, C ₂ H ₅ OH, H ₂ O, and the like. Among these, as described above, the critical point is relatively low, and CO ₂ can be most suitably used from the viewpoint of safety.
[0026]
For the purpose of improving the solubility of the resin or lowering the viscosity of the resin, a cosolvent can be used in the supercritical fluid. Examples of cosolvents that can be used at this time include alcohols (methanol, ethanol, isopropanol, butanol, etc.), ketones (methyl ethyl ketone, acetone, cyclohexanone, etc.), ethers (diethyl ether, tetrahydrofuran, etc.), hydrocarbons, and the like. (Toluene, benzene, cyclohexane, etc.), esters (ethyl acetate, butyl acetate, methyl acetate, alkyl carboxylic acid ester, etc.), halogenated hydrocarbons (chlorobenzene, dichloromethane, etc.), and the like. Among these, alcohols are preferable from the viewpoint of suppressing modification of toner particles by a solvent and reducing environmental load, and ethanol is most preferably used among them.
[0027]
The resin component contained in the melt-kneaded material is not particularly limited as long as it is thermoplastic and does not dissolve in the supercritical fluid. For example, styrene resins such as polystyrene, styrene / butadiene copolymer, styrene / acrylic copolymer, ethylene resins such as polyethylene, polyethylene / vinyl acetate copolymer, polyethylene / vinyl alcohol copolymer, polymethyl methacrylate In addition, acrylic resins such as phenol resins, epoxy resins, allyl phthalate resins, polyamide resins, polyester resins, polyether resins, and maleic resins can be used.
[0028]
In general, the colorant component only needs to contain a pigment of any one of black, cyan, magenta, and yellow.
[0029]
Examples of the black pigment include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, nonmagnetic ferrite, magnetic ferrite, and magnetite.
[0030]
Examples of blue pigments include bitumen, cobalt blue, alkali blue lake, and Victoria blue lake.
[0031]
Examples of magenta pigments include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risol red, pyrazolone red, watching red, calcium salt, lake red C, lake red D, brilliant carmine 6B, eosin lake, There are Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B, and the like.
[0032]
Yellow pigments include yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, and quinoline. There are yellow rake, permanent yellow NCG, tartrage rake and so on.
[0033]
A dispersion stabilizer may be used to stably disperse the resin particles in the supercritical fluid. Although it does not specifically limit as a dispersion stabilizer, A fluororesin, a silicone resin, an epoxy resin, and a urethane resin are mentioned. Although there is no limitation in particular as a compounding quantity, Preferably it is 10 weight% or less, More preferably, 5 weight% or less is desirable. When it exceeds 10% by weight, there is a problem in storage stability as powder performance.
[0034]
In the present invention, it is preferable to add wax during melt-kneading. The wax is not particularly limited. For example, petroleum wax such as paraffin wax, oxidized paraffin wax and microcrystalline wax, mineral wax such as montan wax, animal and plant wax such as beeswax and carnauba wax, and polyolefin wax. (Polyethylene, polypropylene, etc.), synthetic polyolefin wax such as oxidized polyolefin wax, Fischer-Tropsch wax, and the like. These release agents may be used alone or in combination of two or more.
[0035]
As the charge control agent that is preferably blended in the supercritical fluid, various substances from low molecular weight compounds to high molecular weight compounds can be used. Examples thereof include quaternary ammonium salt compounds, nigrosine compounds, organometallic complexes, chelate compounds, and polymer compounds obtained by homopolymerizing or copolymerizing monomers having amino groups. These charge control agents may be used alone or in combination of two or more.
[0036]
Next, a manufacturing apparatus for producing the colored particles of the present invention will be described. As a production apparatus for producing a toner, for example, Una O to diagrammatic configuration are exemplified in FIG. First, gas is supplied to the reaction vessel 7 from the gas cylinder 1 filled with a substance to be a supercritical fluid. This gas is raised to a desired pressure by the pressurizing pump 2. Similarly, the auxiliary agent 3 is also raised to a desired pressure by the pressure pump 4. These high-pressure gas and auxiliary agent 3 are sent to the reaction vessel 7 through valves 5 and 6. At this time, although not shown, the temperature of the high-pressure gas may be adjusted to a desired temperature with a preheating coil or the like. Moreover, before introducing into the reaction vessel 7, the supercritical gas and the auxiliary agent 3 are not shown, but may be mixed in another vessel in advance.
[0037]
In the reaction vessel 7, a melt-kneading component 14 and a charge control agent 15 (in some cases, a capsule resin 16 and a dispersion stabilizer 17) are enclosed, and this reaction vessel 7 is, for example, a heater 8 or not shown. It is comprised so that it may become desired temperature in a constant temperature water tank etc. Further, the inside of the reaction vessel 7 is adjusted to a desired pressure by the valves 5 and 6. These temperature and pressure are monitored by a thermometer 12 and a pressure gauge 13. Thus, the supercritical fluid 18, the auxiliary agent 3, the melt kneading component 14, and the charge control agent 15 (optionally the capsule resin 16 and the dispersion stabilizer 17) are mixed in the reaction vessel 7. It becomes a state. At this time, stirring is performed in the reaction vessel 7 with the stirring device 19 until a predetermined particle diameter is obtained.
[0038]
Thereafter, the colored particles 11 are collected in the particle collection box 10 and the reaction vessel 7 by opening the decompression valve 9 shown in FIG.
[0039]
【Example】
Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples.
[0040]
"Evaluation of toner characteristics"
The particle size and distribution of the toner particles are a volume average particle size and a coefficient of variation measured with a laser diffraction particle size measuring device (LA-920; manufactured by Horiba, Ltd.). If the coefficient of variation was 28% or less, it was judged that the distribution was narrow.
[0041]
The shape was measured by reflection electron microscope observation (SEM), and the average value of the ratio of the short diameter to the long diameter of 25 toners was measured as a shape factor. Shape factor = represented by minor axis / major axis, and 0.95 or more was judged to be close to a true sphere.
[0042]
Regarding the pigment dispersibility, the maximum value of the pigment dispersion diameter in 10 toner particles was visually confirmed by embedding the toner with a resin and observing the thin film section with a transmission electron microscope (TEM). If the maximum diameter was 0.7 μm or less, it was judged that the dispersibility was good.
[0043]
[Creation of melt-kneaded product << P-1 >>]
Raw materials in a ratio of 178 parts by weight of styrene-acrylic resin (MW = 22500, softening point = 129 ° C.) and 22 parts by weight of carbon black (manufactured by Cabot; MOGAL-L) were put into a Henschel mixer and mixed for 10 minutes. The raw material mixture was melt-kneaded and dispersed at 130 ° C. or lower with a Niedix MOS140-800 manufactured by Mitsui Mining Co., Ltd. to obtain a black-colored melt-kneaded product “P-1”.
[0044]
[Creation of melt-kneaded material << P-2 >> and << P-3 >>]
Polyether resin: TPO-349 (manufactured by Mitsui Chemicals, Inc .; softening point = 121 ° C.) 170 parts by weight, phthalocyanine pigment (Fastogen Blue 5415; manufactured by Dainippon Ink & Chemicals) 20 parts by weight, polypropylene wax 10 parts by weight Part of the raw material mixture was charged into a Henschel mixer, and the raw material mixture mixed for 10 minutes was melt-kneaded and dispersed at 130 ° C. or lower with a Niedix MOS140-800 manufactured by Mitsui Mining Co., Ltd. Got.
[0045]
The resin and the pigment are each made of polyester resin; EP208 (manufactured by Sanyo Chemical Industries, Ltd .; softening point = 117 ° C.) and yellow pigment (Fast Yellow 7410; manufactured by Sanyo Color Co., Ltd.). It was dispersed to obtain a yellow melt-kneaded product << P-3 >>.
[0046]
[Preparation of Toner Particles << T-1 >>]
150 parts by weight of melt-kneaded product << P-1 >> and polyurethane resin (BYK-182; manufactured by BYK-Chemie) in a 1000 ml ³ high-pressure reactor equipped with a stirrer, heater, temperature and pressure monitor with comb-shaped wings 3 parts by weight were charged. After setting and sealing the heater temperature at 120 ° C., carbon dioxide gas was supplied by a pressure pump until the pressure became 15 MPa while stirring at 100 RPM. Thereafter, 350 ml of ethanol was supplied, and then the set temperature was changed to 95 ° C. and stirred until the internal temperature reached 90 ° C. The pressure in the reaction vessel at that time was 24 MP. Thereafter, the stirring speed was increased to 1800 RPM and dispersion was performed for about 1 h. Thereafter, the decompression valve was opened, and the mixture in the reaction vessel was discharged into a particle collection box to collect toner particles << T-1 >>. The obtained particles had an average particle size of 7.5 μm, a variation coefficient of 22 and a narrow distribution, a shape factor of 0.98, a substantially spherical shape, a maximum pigment particle size of 0.52 μm and high dispersibility.
[0047]
[Production of Toner Particles << T-2 >> and << T-3 >>
Into a 1000 ml ³ high-pressure reactor equipped with a stirrer, heater, temperature and pressure monitor having comb-shaped wings, 150 parts by weight of the melt-kneaded product << P-2 >> and 3 parts by weight of a fluorine-based resin were charged. After setting and sealing the heater temperature at 130 ° C., carbon dioxide gas was supplied by a pressure pump until the pressure became 25 MPa while stirring at 100 RPM. The set temperature was changed to 85 ° C., and stirring was continued until the internal temperature reached 80 ° C. Thereafter, the stirring speed was increased to 2000 RPM and dispersion was performed for about 1 h. Thereafter, the pressure reducing valve was opened, and the mixture in the reaction vessel was discharged into a particle collection box to collect toner particles << T-2 >>. The obtained particles had an average particle size of 6.8 μm, a variation coefficient of 24, a narrow distribution, a shape factor of 0.99, an almost spherical shape, a maximum pigment particle size of 0.49 μm, and high dispersibility.
[0048]
10 parts by weight of styrene-acrylic resin (ST / NBMA / GMA = 30/20/50; MW = 33500, softening point = 130 ° C.), 2 parts by weight of ammonium salicylate (charging preparation agent) and 350 ml of ethanol in a high pressure reaction vessel Capsule-type toner particles << T-3 >> were obtained in the same manner as in the toner preparation example of << T-1 >> except that it was added to the toner. The obtained particles had an average particle size of 6.5 μm, a variation coefficient of 26, a narrow distribution, a shape factor of 0.96, an almost spherical shape, a maximum pigment particle size of 0.62 μm, and high dispersibility.
[0049]
[Production of Toner Particles << T-4 >> and << T-5 >>
Into a 1000 ml ³ high-pressure reactor equipped with a stirrer, heater, temperature and pressure monitor having comb-shaped wings, 150 parts by weight of the melt-kneaded product << P-3 >> and 4 parts by weight of a fluorine-based resin were charged. After setting and sealing the heater temperature at 130 ° C., carbon dioxide gas was supplied by a pressure pump until the pressure became 25 MPa while stirring at 100 RPM. The mixture was stirred until the internal temperature reached 120 ° C. The set temperature was changed to 85 ° C., and stirring was continued until the internal temperature reached 80 ° C. Thereafter, the stirring speed was increased to 2000 RPM to disperse for about 1 h, and then the decompression valve was opened, and the mixture in the reaction vessel was discharged into a particle collection box to collect toner particles << T-4 >>. The obtained particles had an average particle size of 6.9 μm, a variation coefficient of 25, a narrow distribution, a shape factor of 0.98, a substantially spherical shape, a maximum pigment particle size of 0.56 μm, and high dispersibility.
[0050]
Obtained toner particles << T-4 >> 100 parts by weight, polyester resin; FZ-100 (MW = 33500, softening point = 130 ° C.) 8 parts by weight, ammonium salicylate (charge preparation agent) 2 parts by weight and ethanol 300 ml It mix | blended and sealed in the high pressure reaction container. Thereafter, carbon dioxide was supplied by a pressure pump while stirring at 200 RPM until the pressure reached 25 MPa. The temperature in the high-pressure vessel at that time was maintained at 50 ° C. After stirring for about 1 hour, the pressure reducing valve was opened, and the mixture in the reaction vessel was discharged into a particle collection box to obtain capsule-type toner particles << T-5 >>. The average particle diameter of the obtained particles was 6.9 μm, and it was almost spherical with a single peak distribution. The obtained particles had an average particle size of 7.9 μm, a variation coefficient of 23, a narrow distribution, a shape factor of 0.99, an almost spherical shape, a maximum pigment particle size of 0.68 μm, and high dispersibility.
[0051]
【The invention's effect】
In the method for producing colored particles used in the toner of the present invention, since the binder resin and the colorant are melt-kneaded in advance, the dispersibility can be maintained even if the pigment concentration is increased. In addition, since the molten kneaded material is put into a supercritical fluid or subcritical fluid and then heated and stirred to disperse the molten kneaded material, it is spherical and the pigment is compounded in the resin, so it is environmentally friendly and storable. Therefore, it is possible to provide a toner for developing an electrostatic charge by a production method that is high in environmental impact and does not require harmful organic solvents or wastewater treatment.
[Brief description of the drawings]
FIG. 1 is a schematic view of a toner production apparatus used for producing toner of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1; Gas cylinder, 2; Pressurization pump, 3; High-pressure gas and entrainer (addition aid), 4; Pressurization pump, 5,6; Valve, 7; Reaction vessel, 8: Heater, 9; ; Particle repair box, 11; toner particles, 12; thermometer, 13; pressure gauge, 14; melt-kneaded component, 15; charge control material, 16; resin for capsule, 17; dispersion stabilizer, 18; Supercritical fluid, 19; stirring device.

Claims (5)

At least a melt-kneaded product previously produced by melt-kneading a binder resin and a colorant is heated and stirred in a supercritical fluid or a subcritical fluid to disperse the melt-kneaded product, and then depressurized, thereby supercritical. In a method for producing colored particles used in a toner for electrostatic charge development that extracts colored particles from a fluid or subcritical fluid ,
As a resin that dissolves in the supercritical fluid or subcritical fluid, a fluororesin as a dispersion stabilizer is added to the melt-kneaded product, and is further blended in the supercritical fluid or subcritical fluid. A method for producing colored particles used in an electrostatic charge developing toner. The method for producing colored particles used in the electrostatic charge developing toner according to claim 1, wherein a wax is added during the melt kneading. Method for producing a supercritical fluid or characterized also contain a charge control agent in the subcritical fluid according to claim 1 or 2 colored particles used in the electrostatic image developing toner according to. The supercritical fluid or subcritical fluid, the production method of the colored particles used in the toner for developing an electrostatic image according to any one of claims 1 to 3, characterized in that carbon dioxide. An electrostatic charge developing toner produced by the method according to claim 1 .

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