JP6533704B2 - Method of manufacturing capsule toner - Google Patents

Description

  The present invention relates to a method for producing a capsule toner comprising core particles (hereinafter sometimes referred to as toner base particles) and a shell layer formed on the surface of the core particles, and in particular, particles for shell layer are core particles The present invention relates to a method for producing a capsule toner capable of suppressing the phenomenon of peeling from the capsule toner and obtaining a capsule toner excellent in blocking resistance.

  In an image forming apparatus using an electrophotographic method, there is a method of performing low temperature fixing using a toner containing a binder resin having a low softening temperature. By performing low temperature fixing, the power supplied to the fixing device can be suppressed. However, the toner containing the binder resin having a low softening temperature is easily fused by heat, and the blocking resistance is reduced.

  The surface of the toner base particles containing a binder resin having a low softening temperature is covered with resin fine particles having a higher softening temperature and a higher heat resistance than the toner base particles to produce a capsule toner, thereby achieving low temperature fixing of the toner There is a method of improving the blocking resistance without losing the properties.

  As described above, as a method of producing a capsule toner in which resin fine particles are filmed on the surface of toner base particles, for example, a method of adhering resin fine particles on the surface of toner base particles in an aqueous medium and heating; A method of applying mechanical impact force, a method of depositing resin fine particles on the surface of toner base particles and heating in a high temperature air stream of 300.degree. C. or higher, a method of spraying a resin fine particle emulsion while stirring toner base particles, etc. It has been known.

  For example, in Patent Document 1, after a resin particle having a high softening temperature is coated on the surface of a toner base particle having a low softening temperature, a mechanical impact force is applied to form a coating layer composed of resin particles having a high softening temperature There is disclosed a toner in which resin fine particles are fixedly coated to improve low temperature fixing property and blocking resistance. Further, Patent Document 2 discloses a toner in which resin fine particles are fixed to the surface of core particles by mechanical impact force, and the fixing method is improved and the non-offset property is improved with low power consumption.

Patent No. 2838410 JP-A-2-163754

  However, among the conventional methods of manufacturing capsule toner, in the method of attaching resin fine particles to the surface of toner base particles and applying mechanical impact force to this to form a film, usually, the resin fine particles are toner base particles in a dry state. Since it adheres to the surface, there is a problem that aggregation of the resin fine particles occurs, or release (peeling) of the resin fine particles from the toner base particles occurs due to wind pressure or the like generated when applying mechanical impact force. The In the capsule toner thus obtained, it is difficult to uniformly attach the resin fine particles to the surface of the toner base particle, so that a part of the surface of the toner base particle is exposed and blocking easily occurs.

  In addition, it is conceivable to solve the problems that may occur when dried resin fine particles are used by using a method of spraying a resin fine particle emulsion while stirring toner base particles, but, for example, a resin fine particle emulsion is configured New problems arise when drying solvents (water etc). Specifically, in order to dry the water when the resin fine particles are formed into a film, it is predicted that the temperature in the film formation step may be set high or the working time may be lengthened. In this case, It is considered that the capsule toner may be spheroidized or the capsule toner may be aggregated. Furthermore, even if the method of spraying the resin fine particle emulsion while stirring the toner base particles is used, the problem of the release (peeling) of the resin fine particles from the toner base particles when applying the mechanical impact force is still improved. There is room.

  Therefore, an object of the present invention is to provide a method for producing a capsule toner which solves the problems of the prior art, suppresses the phenomenon that shell layer particles peel from core particles, and can obtain a capsule toner excellent in blocking resistance. To provide.

  The present inventor examined the step of attaching the aqueous dispersion of shell layer particles to the surface of the core particle to form the wet composite particle prior to the step of forming the resin fine particles on the surface of the toner base particle. . In the wet composite particles thus obtained, shell layer particles and water are present on the core particle surface, and shell layer particles can be strongly adhered to the core particle surface by the wetting effect of water, and core particles Peeling off particles for shell layer from the above can be suppressed, and the core particle surface can be uniformly coated.

  However, even if the particles for shell layer can be attached to the surface of the core particles by the wetting effect of water, for example, when the wet composite particles are stirred in a stirring apparatus in order to stir the wet composite particles in the air flow. There is a problem that the shell layer particles peel off from the core particle. Then, when the present inventor further examined, it turned out that a part of particles for shell layers will exfoliate from core particles at the time of stirring under the influence of gas, such as air, which exists in a stirring device. For this reason, by stirring the wet composite particles while reducing the pressure in the stirring apparatus to such an extent that the influence of the gas can be ignored, peeling of the shell layer particles from the core particles can be suppressed, and the surface of the core particles is not exposed. It has been found that a capsule toner excellent in blocking resistance can be produced.

  Furthermore, the inventor has also found that when the pressure in the stirring device is excessively reduced, the flowability of the composite particles is reduced, and the water may not be sufficiently dried from the composite particles. When the flowability of the composite particles is significantly reduced, the film formation of the shell layer particles may be affected.

That is, the method for producing a capsule toner according to the present invention is a method for producing a capsule toner comprising core particles and a shell layer formed on the surface of the core particles,
A composite particle is formed by attaching an aqueous dispersion of shell layer particles to the surface of the core particles to form a wet composite particle comprising the core particles, the shell layer particles attached to the surface of the core particles, and water. Process,
The wet composite particles was stirred under 500torr less pressure than 20 torr, while drying the wet composite particles, and characterized in that it comprises a film-forming step for forming a film of the shell layer particles at the surface of the core particles Do.

  In a preferred embodiment of the method for producing a capsule toner according to the present invention, the wet composite particles are stirred at a pressure of 50 torr and 400 torr in the film forming step.

  According to the present invention, it is possible to provide a method for producing a capsule toner capable of suppressing the phenomenon in which the shell layer particles are peeled from the core particles and obtaining a capsule toner having excellent blocking resistance.

It is a schematic sectional drawing of an example of the stirring apparatus which can be used for the manufacturing method of the capsule toner of this invention. It is a flowchart which shows one embodiment of the manufacturing method of the capsule toner of this invention.

  Hereinafter, the method for producing the capsule toner of the present invention will be described in detail. The method for producing a capsule toner according to the present invention is a method for producing a capsule toner comprising a core particle and a shell layer formed on the surface of the core particle, wherein an aqueous dispersion of shell layer particles is attached to the surface of the core particle. A composite particle forming step of forming a wet composite particle, and a film forming step of stirring the wet composite particle under a pressure of 20 to 500 Torr and forming a shell layer particle on the surface of the core particle. I assume.

  In the method for producing a capsule toner of the present invention, first, an aqueous dispersion of shell layer particles is attached to the surface of core particles to form wet composite particles (composite particle forming step). The wet composite particle obtained by this composite particle forming step is provided with the core particle and the shell layer particle and water on the core particle surface, and the shell layer particle is strongly adhered to the core particle surface by the wetting effect of water. As a result, peeling of the shell layer particles from the core particles can be suppressed, and the core particle surface can be uniformly coated. In the wet composite particles, the content of water is preferably 3% by mass or more and 30% by mass or less. If the content of water is less than 3% by mass, the wetting effect of water may not be sufficiently exhibited. On the other hand, if the content of water exceeds 30% by mass, sufficient drying is difficult in the film formation step described later It can be

In the above composite particle forming step, as a method of attaching an aqueous dispersion of shell layer particles to the surface of the core particle, means for spraying the aqueous dispersion of shell layer particles on the core particle, core particle and shell layer particles Various means are available, such as means for mixing with the aqueous dispersion of For injection of the aqueous dispersion of shell layer particles onto the core particles, for example, an injection nozzle can be used. In addition, a known mixer can be used for mixing the aqueous dispersion of the core particles and the particles for shell layer, and, for example, Henschel mixer (trade name, manufactured by Nippon Coke Kogyo Co., Ltd.), super mixer (trade name, Co., Ltd.) (Made by Kawata), Henschel type mixing device such as Mechano Mill (trade name, manufactured by Okada Seiko Co., Ltd.), Ong Mill (trade name, manufactured by Hosokawa Micron Corporation), high speed vacuum dryer or dynamic dryer (trade name, manufactured by Earth Technica Co., Ltd.) Etc.).
The composite particle forming step is not performed under reduced pressure, and is usually performed under normal pressure (750 torr and 780 torr or less), and the temperature in the composite particle forming step is not particularly limited. The temperature is preferably 10 ° C. or more and 30 ° C. or less.

  In the composite particle forming step, it is preferable that the aqueous dispersion of shell layer particles be attached to the core particles so that the ratio of shell layer particles to 100 parts by mass of core particles is 5 parts by mass or more and 10 parts by mass or less. .

  In the method for producing a capsule toner of the present invention, the core particles are not particularly limited, but it is preferable that the core particles are particles containing a resin from the viewpoint of using as a toner base particle of the capsule toner. Examples of resins that can be used for the core particles include polystyrene resins, styrene-acrylic resins obtained by copolymerizing styrene monomers and (meth) acrylic acid monomers and / or (meth) acrylic acid ester monomers, polymethyl methacrylate, etc. (Meth) acrylic ester resins, polyolefin resins such as polyethylene, polyester resins, polyurethane resins, epoxy resins and the like. These resins may be used alone or in combination of two or more.

  The resin that can be used for the core particles preferably has a glass transition temperature of 30 ° C. to 80 ° C., and a softening temperature of 80 ° C. to 150 ° C., from the viewpoint of using the core particles as toner base particles of capsule toner. The acid value is preferably 0 KOHmg / g or more and 30 KOHmg / g or less.

  The core particles preferably have a volume average particle diameter of 4 μm to 8 μm from the viewpoint of use as a toner base particle of capsule toner, and usually, the circularity is 0.96 or less, and 0.940 to 0.960. It is preferable that it is the following.

In the present invention, the circularity of particles can be measured, for example, using a flow type particle image analyzer “FPIA-3000” (manufactured by Malvern Co.), but there is no particular limitation as long as the measurement principle is the same. The measurement principle of this device is to take a still image of particles in the dispersion medium with a CCD camera, and calculate the circularity and the like from the image. The sample introduced from the chamber is sent to the flat sheath flow cell and sandwiched by the sheath liquid to form a flat flow. A still image is taken with a CCD camera while irradiating the sample passing through the cell with strobe light. The contour extraction of each particle is performed by image processing of the captured image, and the projection area S, the peripheral length L, and the like of the particle image are measured. From this, the equivalent circle diameter and the degree of circularity are calculated.
The equivalent circle diameter is the diameter of a circle having the same area as the projected area of the particle image, and the circularity is defined as the perimeter of the circle determined from the equivalent circle diameter divided by the perimeter of the particle projection image , Calculated by the following equation.
Circularity = 2 × (π × S) ^1/2 / L
A particle sheath “PSE-900A” (manufactured by Malvern Co., Ltd.) is used as the sheath liquid, a commercially available household detergent 5% by weight aqueous dispersion is used as the dispersing agent, and the autosampler device of the apparatus is used as the dispersing device. The sample is dispersed, introduced into the above-mentioned flow type particle image analyzer, and 10000 particles are measured by total count in the HPF measurement mode. Then, the binarization threshold value at the time of particle analysis is set to 85%, and the average circularity of particles is determined as the entire particle size range.

  In the method for producing a capsule toner of the present invention, the aqueous dispersion of shell layer particles is one in which the shell layer particles are dispersed in water, but in the aqueous dispersion of shell layer particles, the shell layer particles The mass ratio (A / B) of (A) to water (B) is preferably 30/70 or more and 70/30 or less.

  The aqueous dispersion of particles for the shell layer can be prepared, for example, by conducting an emulsion polymerization reaction of a monomer component which is a resin raw material in water, or by emulsifying and dispersing a resin in water using a homogenizer etc. Can also be prepared.

  The particles for the shell layer are preferably resin fine particles. For example, a resin used for a toner material can be used. For example, polystyrene resin, styrene monomer and (meth) acrylic acid type monomer and / or (meth) Examples thereof include styrene-acrylic resins copolymerized with acrylic ester monomers, (meth) acrylic ester resins such as polymethyl methacrylate, polyester resins, and the like. Among these, styrene-acrylic resins or polyester resins are preferable. The styrene-acrylic resin has many advantages such as light weight, high strength, high transparency, low cost, and easy to obtain material with uniform particle diameter.

  It is preferable that the glass transition temperature of resin which can be used for the particle | grains for said shell layers is higher than the glass transition temperature of resin contained in core particle, and it is preferable that they are 50 degreeC or more and 80 degrees C or less. The softening temperature of the resin that can be used for the shell layer particles is preferably higher than the softening temperature of the resin contained in the core particles, and more preferably 80 ° C. or more and 140 ° C. or less.

  The particles for shell layer preferably have a volume average particle diameter sufficiently smaller than the average particle diameter of the core particles, and more preferably 0.1 μm or more and 0.5 μm or less.

  In the method for producing a capsule toner according to the present invention, next, a step of forming particles for shell layer on the surface of core particles by stirring the wet composite particles obtained in the above composite particle forming step under reduced pressure (film formation Although the film formation step is required, the film formation step is performed by stirring the wet composite particles under a pressure of 20 torr (0.00266 MPa) or more and 500 torr (0.0666 MPa) or less. By stirring the wet composite particles under a pressure of 20 torr or more and 500 torr or less, peeling of shell layer particles from the core particles can be suppressed, whereby the surface of the core particles is not exposed and the blocking resistance is excellent. Capsule toner can be manufactured. When stirring of the wet composite particles is performed under a pressure exceeding 500 torr, the particles of the shell layer are separated from the core particles during stirring due to the influence of the gas present in the stirring device.

  As an apparatus which can be used at the said film-forming process, stirring apparatuses, such as high-speed vacuum dryer (a brand name, Earth Technica Co., Ltd. make), can be used, for example.

  In the film forming step, the wet composite particles are preferably stirred under a pressure of 50 torr (0.00666 MPa) or more and 400 torr (0.0533 MPa) or less. When stirring of the wet composite particles is performed under a pressure of less than 50 torr, there is little flowing air in the stirring device, the flow of the wet composite particles becomes worse, and drying becomes difficult. When the wet composite particles are stirred under a pressure of over 400 torr, the adhesion state of the shell layer particles may be deteriorated.

  In the film forming step, for example, the pressure described above can be easily achieved by evacuating the inside of the stirring apparatus by providing pressure reducing means such as a blower in the stirring apparatus.

  In the stirring of the wet composite particles carried out in the above-mentioned film forming step, the stirring speed is appropriately selected depending on the shape of the stirring means etc. However, if the stirring speed is too fast, for shell layer by stirring for a long time Peeling of particles may occur, while too slow agitating speed may result in insufficient film formation of shell layer particles. The stirring speed of the stirring means is not particularly limited, but is preferably 4 m / s or more and 30 m / s or less.

  In the above-mentioned film formation step, in order to perform film formation of particles for shell layer and drying of composite particles more efficiently, stirring of wet composite particles can also be performed while heating. The temperature at the time of stirring is not particularly limited, but is preferably 50 ° C. or more and 65 ° C. or less. When the temperature at the time of stirring is less than 50 ° C., film formation takes time, and when it exceeds 65 ° C., aggregation tends to occur. In addition, the temperature at the time of stirring refers to the temperature in the stirring apparatus at the time of stirring of a wet composite particle is performed. For example, the temperature at the time of stirring can be easily adjusted by providing heating means such as a temperature control jacket in the stirring device.

  The content of water in the capsule toner obtained in the film forming step is preferably 0% by mass or more and 1.0% by mass or less.

  The capsule toner used in the electrophotographic image forming apparatus preferably has a volume average particle diameter of 4 to 8 μm, and generally has a circularity of 0.96 or less and 0.940 to 0.960. Is preferred. In order to obtain a capsule toner having desired volume average particles, the particle size distribution of the capsule toner obtained by the above-mentioned film forming step can also be adjusted, if necessary.

  According to the method for producing a capsule toner of the present invention, it is possible to produce a capsule toner comprising core particles and a shell layer formed on the surface of the core particles by performing the composite particle forming step and the film forming step. Although the capsule toner can be used, the capsule toner has no exposure to the surface of the core particle and is excellent in blocking resistance, and can be suitably used for an electrophotographic image forming apparatus.

  Next, the stirring device that can be used in the method for producing a capsule toner of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view of an example of a stirring device that can be used in the method for producing a capsule toner of the present invention. The stirring apparatus of the illustrated example includes a container-like member 1, a stirring unit 2, and a pressure reducing unit 3, and can perform the film forming step in the method of manufacturing a capsule toner of the present invention.

  The container-like member 1 has an internal space, where agitation of the wet composite particles takes place. In the upper part of the container 1, an inlet 4 for introducing the wet composite particles is provided, and the wet composite particles can be introduced into the container 1 from the inlet 4. Further, a stirring means 2 described later is provided at the lower part of the container 1. Furthermore, the container-like member 1 is provided with a pipe 5 for connecting with the pressure reducing means 3 at the upper side, and a pipe 6 for collecting capsule toner after completion of the film forming process at the lower side. For example, a solenoid valve (not shown) is provided at the connection portion between the container 1 and the tube 6, and after completion of the film forming process, the solenoid valve can be opened to recover the capsule toner.

  The stirring means 2 is a means for stirring the wet composite particles in the container 1. The stirring means 2 can be used to stir the wet composite particles. In the stirring device of the illustrated example, the stirring means 2 includes a rotating shaft member and a stirring blade. The rotary shaft member has an axis coinciding with the axial direction of the stirring means, and is provided so as to be inserted into a through hole formed to penetrate the lower wall surface of the container 1 in the thickness direction. Is a cylindrical rod-shaped member that rotates about the axis according to. The stirring blade is supported by the rotating shaft member and rotates with the rotation of the rotating shaft member. Here, the stirring speed means the rotation speed of the stirring blade.

  For example, a blower or the like can be used as the decompression unit 3, and the pressure at the time of stirring can be adjusted by discharging the gas inside the container-like member. In the stirring device of the illustrated example, a gas such as air is introduced from the through hole of the container 1 through which the rotary shaft passes, as shown by the arrow, and the container is combined with the pressure reducing means 3 The pressure inside the member can be adjusted more efficiently. Further, by introducing the gas into the container 1, the composite particles can be dried more efficiently. Furthermore, in the stirring device of the illustrated example, a bag filter 7 is provided between the container 1 and the pressure reducing means 3, and the wet composite particles and the composite particles after drying (that is, capsule toner) are discharged together with the gas. Can be prevented.

  In the stirring device of the illustrated example, a temperature control jacket 8 is provided outside the container 1. The temperature control jacket 8 can be used as a heating means, for example, by passing a heating medium through the space inside the jacket, and it becomes possible to heat and stir the wet composite particles. The temperature control jacket 8 can also be used as a cooling means if a cooling medium is passed through the space inside the jacket.

  Next, one embodiment of a method for producing a capsule toner of the present invention will be described in detail with reference to the drawings. FIG. 2 is a flow chart showing one embodiment of the method for producing a capsule toner of the present invention. In the method for producing the capsule toner of the illustrated example, a toner base particle producing step S1 for producing toner base particles, a resin fine particle producing step S2 for producing an aqueous dispersion of resin fine particles, and a composite particle forming step for forming wet composite particles And S3 and a film forming step S4 of manufacturing a capsule toner by forming a film of resin fine particles while drying the wet composite particles, and a collection step S5 of collecting the capsule toner.

(1) Toner mother particle production step S1
In the toner base particle preparation step S1, toner base particles which become the core of the capsule toner and whose surface is to be covered with the fine resin particles are prepared. The toner base particles correspond to core particles in the method for producing a capsule toner of the present invention. The toner base particles are particles containing a binder resin and a colorant, and the preparation method is not particularly limited, and can be obtained by a known method. Examples of the method for producing toner base particles include dry methods such as pulverization methods, suspension polymerization methods, emulsion aggregation methods, dispersion polymerization methods, dissolution suspension methods, and melt emulsification methods. Hereinafter, a method of producing toner base particles by a pulverization method will be described.

(Method of producing toner mother particles by grinding method)
In the method of producing toner base particles using the pulverizing method, a toner base particle material composition containing a binder resin, a colorant and other additives is dry-mixed by a mixer and then melt-kneaded by a kneader. The kneaded material obtained by the melt-kneading is solidified by cooling, and the solidified material is crushed by a grinder. Thereafter, particle size adjustment such as classification is performed as necessary to obtain toner base particles.

  A well-known mixer can be used as the mixer. For example, Henschel mixer (trade name, manufactured by Nippon Coke Industry Co., Ltd.), super mixer (trade name, manufactured by Kawata Co., Ltd.), mechano mill (trade name, manufactured by Okada Seiko Co., Ltd.) And Henschel-type mixers, etc.

  A well-known thing can also be used as a kneader, for example, general kneaders, such as a twin-screw extruder, a 3 roll, a lab blast mill, can be used. More specifically, for example, uniaxial or biaxial, such as TEM-100B (trade name, manufactured by Toshiba Machine Co., Ltd.), PCM-65 / 87, PCM-30 (all of which are trade names, manufactured by Ikegai Co., Ltd.) Kneaders of an open roll type such as an extruder of K. K. K., and KNEDEX (trade name, manufactured by Nippon Coke Industry Co., Ltd.).

  The kneaded product is cooled and solidified, and then roughly crushed into a roughly crushed product having a weight average particle diameter of about 100 μm to about 5 mm by a hammer mill or a cutting mill, and the obtained roughly crushed product has, for example, a weight average particle diameter of 15 μm. It is further finely pulverized to the following. For comminution of the coarsely pulverized material, for example, a jet crusher using supersonic jet air stream, coarsely pulverized material in a space formed between a rotor (rotor) rotating at high speed and a stator (liner) An impact crusher etc. which introduce and crush can be used.

  For classification, a known classifier capable of removing over-crushed toner base particles by centrifugal classification and classification by wind can be used. For example, a rotary type air classifier (rotary type air classifier) or the like can be used. be able to.

(Toner mother particle raw material)
As described above, the toner base particles contain a binder resin and a colorant. The binder resin corresponds to a resin that can be used as core particles in the method for producing a capsule toner of the present invention. The binder resin is not particularly limited, and a known binder resin for black toner or color toner can be used. For example, polystyrene resin, styrene monomer, (meth) acrylic acid type monomer, and / or Or styrene-acrylic resins copolymerized with (meth) acrylic ester monomers, (meth) acrylic ester resins such as polymethyl methacrylate, polyolefin resins such as polyethylene, polyester resins, polyurethane resins, epoxy resins, etc. Can be mentioned. In addition, a mold release agent may be mixed with the raw material monomer mixture, and a resin obtained by performing a polymerization reaction may be used. The binder resin may be used alone or in combination of two or more.

  The monomer constituting the styrene resin such as polystyrene resin and styrene-acrylic resin preferably contains a styrene monomer as an essential monomer and, if necessary, preferably contains a (meth) acrylic monomer and / or a carboxyl group-containing vinyl monomer. Here, the styrene resin means a homopolymer of a styrene monomer or a copolymer of a styrene monomer and another monomer. Also, (meth) acrylic means acrylic and / or methacrylic. Examples of the styrene monomer include styrene and alkylstyrenes having 1 to 3 carbon atoms in the alkyl group (for example, α-methylstyrene, p-methylstyrene) and the like, and two or more types may be used in combination. Preferably it is styrene. Examples of (meth) acrylic monomers include alkyl groups such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate and stearyl (meth) acrylate Alkyl (meth) acrylate having 1 to 18 carbon atoms; hydroxyl alkyl (meth) acrylate having 1 to 18 carbon atoms of alkyl group such as hydroxyl ethyl (meth) acrylate; dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) Examples of the alkylamino group-containing (meth) acrylate having 1 to 18 carbon atoms in the alkyl group such as acrylate; nitrile group-containing vinyl monomers such as acrylonitrile and methacrylonitrile. Examples of carboxyl group-containing vinyl monomers include monocarboxylic acids [C3-15, such as (meth) acrylic acid, crotonic acid, cinnamic acid], dicarboxylic acids [C4-15, such as (anhydrides), maleic acid, fumaric acid , Itaconic acid, citraconic acid], dicarboxylic acid monoester [monoalkyl (1 to 18 carbon atoms) ester of the above dicarboxylic acid, for example, monoalkyl ester of maleic acid, monoalkyl ester of fumaric acid, monoalkyl ester of itaconic acid, mono citraconic acid Alkyl ester] etc. can be mentioned. Among these (meth) acrylic monomers and carboxyl group-containing vinyl monomers, alkyl (meth) acrylates having 1 to 18 carbon atoms, acrylonitrile, methacrylonitrile, (meth) acrylic acid, dicarboxylic acid monoesters, and two or more of them. Mixtures are preferred.

  A well-known thing can be used as a monomer which comprises a polyester resin, For example, the polycondensate of a polybasic acid and a polyhydric alcohol etc. are mentioned.

  As the polybasic acid, those known as monomers for polyester can be used, and examples thereof include aromatic carboxylic acids such as terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid, naphthalene dicarboxylic acid, and maleic anhydride, Aliphatic carboxylic acids such as fumaric acid, oxalic acid, alkenyl succinic anhydride, adipic acid and the like, methyl esters of these polybasic acids and the like can be mentioned. The polybasic acids can be used alone or in combination of two or more.

  As the polyhydric alcohol, those known as monomers for polyester can be used, and examples thereof include aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, and glycerin, cyclohexanediol, cyclohexanediyl Aliphatic polyhydric alcohols such as methanol and hydrogenated bisphenol A, ethylene oxide adducts of bisphenol A, aromatic diols such as propylene oxide adduct of bisphenol A, and the like. A polyhydric alcohol can be used individually by 1 type, or can use 2 or more types together.

  The polycondensation reaction between the polybasic acid and the polyhydric alcohol can be carried out according to a conventional method, for example, contacting the polybasic acid with the polyhydric alcohol in the presence or absence of an organic solvent and in the presence of a polycondensation catalyst. When the acid value of the polyester to be produced, the softening temperature, etc. reach the desired values, the process is completed. This gives a polyester. When a polybasic acid methyl ester is used as part of the polybasic acid, a demethanol polycondensation reaction is carried out. In this polycondensation reaction, the terminal carboxyl group content of the polyester can be adjusted, for example, by suitably changing the compounding ratio of polybasic acid and polyhydric alcohol, the reaction rate, etc. Can be denatured. In addition, even when trimellitic anhydride is used as a polybasic acid, a carboxyl group can be easily introduced into the main chain of the polyester, whereby a modified polyester can be obtained. Self-dispersible polyesters in water can also be used by attaching hydrophilic groups such as carboxyl groups and sulfonic acid groups to the main chain and / or side chains of polyester. In addition, polyester and acrylic resin may be grafted and used.

  The binder resin preferably has a glass transition temperature of 30 ° C. or more and 80 ° C. or less. When the glass transition point of the binder resin is less than 30 ° C., blocking that the toner thermally aggregates within the image forming apparatus is likely to occur, and storage stability may be reduced. When the glass transition point of the binder resin exceeds 80 ° C., the fixability of the toner on the recording medium is lowered, and there is a possibility that a fixing failure may occur.

  Further, the binder resin preferably has a softening temperature of 80 ° C. or more and 150 ° C. or less. Furthermore, the binder resin preferably has an acid value of 0 KOHmg / g to 30 KOHmg / g.

  As the colorant, organic dyes, organic pigments, inorganic dyes, inorganic pigments and the like that are commonly used in the field of electrophotography can be used. The amount of the colorant used is not particularly limited, but is preferably 5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The toner base particles may contain a charge control agent in addition to the binder resin and the colorant. As the charge control agent, charge control agents for positive charge control and negative charge control commonly used in this field can be used. The use amount of the charge control agent is not particularly limited, but is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the binder resin.

  In addition to the binder resin and the colorant, the toner base particles may contain a release agent. As the releasing agent, those commonly used in this field can be used. For example, paraffin wax and its derivative, petroleum wax such as microcrystalline wax and its derivative, Fischer Tropsch wax and its derivative, polyolefin wax (polyethylene wax, polypropylene Wax etc.) and derivatives thereof, low molecular weight polypropylene waxes and derivatives thereof, hydrocarbon based synthetic waxes such as polyolefin polymer waxes (low molecular weight polyethylene waxes etc) and derivatives thereof, carnauba wax and the like. The use amount of the release agent is not particularly limited, but it is preferably 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The toner base particles obtained in the toner base particle producing step S1 preferably have a volume average particle diameter of 4 μm to 8 μm. When the volume average particle size of the toner base particles is 4 μm or more and 8 μm or less, a high-definition image can be stably formed over a long period of time.

  The toner base particles obtained in the toner base particle producing step S1 usually have a circularity of 0.96 or less and preferably 0.940 or more and 0.960 or less.

(2) Resin fine particle preparation step S2
In the fine resin particle preparation step S2, an aqueous dispersion of fine resin particles used for forming a layer (shell layer) covering the toner base particles is prepared. Here, the aqueous dispersion of resin fine particles corresponds to the aqueous dispersion of shell layer particles in the method for producing a capsule toner of the present invention. The resin fine particles are used as a material to form a film on the surface of the toner base particle in the subsequent film forming step S3. By using resin fine particles as a film-forming material on the surface of toner base particles, for example, it is possible to prevent the occurrence of aggregation due to melting of low melting point components such as a release agent contained in toner base particles during storage.

  In the fine resin particle preparation step S2, an aqueous dispersion of fine resin particles can be prepared, for example, by carrying out an emulsion polymerization reaction of a monomer component which is a resin raw material in water, or the resin is emulsified and dispersed in water by a homogenizer etc. It can also be prepared by The mass ratio (A / B) of the resin fine particles (A) to the water (B) is preferably 30/70 to 70/30.

  In the resin particle preparation step S2, as a resin used as a resin particle material, for example, a resin used for a toner material can be used. For example, polystyrene resin, styrene monomer and (meth) acrylic acid monomer and / or ( Examples thereof include styrene-acrylic resins copolymerized with (meth) acrylic ester monomers, (meth) acrylic ester resins such as polymethyl methacrylate, polyester resins, and the like. Among the resins exemplified above, the resin fine particles preferably include a styrene-acrylic resin or a polyester resin. The styrene-acrylic resin has many advantages such as light weight, high strength, high transparency, low cost, and easy to obtain material with uniform particle diameter.

  The resin used as the resin fine particle material in the resin fine particle preparation step S2 may be the same type of resin as the binder resin contained in the toner base particles, or may be a different type of resin. It is preferable to use different types of resins from the viewpoint of surface modification of When a resin of a type different from the binder resin contained in the toner base particles is used as the resin used as the resin fine particle raw material, the softening temperature of the resin used as the resin fine particle raw material is the binder resin contained in the toner base particles The softening temperature is preferably higher than the softening temperature of the components contained in the toner base particles such as the release agent. By this, the toner manufactured by the manufacturing method of the present embodiment can prevent the toners from being fused during storage, and can improve storage stability. The softening temperature of the resin used as the resin fine particle material is preferably 80 ° C. or more and 140 ° C. or less, although it depends on the image forming apparatus in which the toner is used. By using a resin having a softening temperature in such a range, a toner having both storage stability and fixing ability can be obtained.

  In the resin particle preparation step S2, the resin particles preferably have a volume average particle diameter sufficiently smaller than the average particle diameter of the toner base particles, and more preferably 0.1 μm or more and 0.5 μm or less. When the volume average particle diameter of the resin fine particles is 0.1 μm or more and 0.5 μm or less, the resin particles are excellent in plasticity and easily deformed, and a homogeneous coating layer is formed on the surface of the toner base particles. The particle size of the resin fine particles represents the volume average particle size measured by the dynamic light scattering method.

  In the resin particle preparation step S2, the glass transition temperature of the resin particles is preferably higher than the glass transition temperature of the binder resin contained in the toner base particles, and is preferably 50 ° C. or more and 80 ° C. or less. The softening temperature of the resin fine particles is preferably higher than the softening temperature of the binder resin contained in the toner base particles, and is preferably 80 ° C. or more and 140 ° C. or less.

(3) Composite particle formation step S3
In the composite particle formation step S3, an aqueous dispersion of resin fine particles is attached to the surface of the toner base particles to form wet composite particles. In the composite particle forming step S3, as a method of adhering the water dispersion of resin fine particles to the surface of the toner mother particles, as described above, means for jetting the water dispersion of resin fine particles onto the toner mother particles, Various means such as means for mixing the resin fine particles with the aqueous dispersion can be used. The content of water in the wet composite particles obtained by the above composite particle forming step S3 is preferably 3% by mass or more and 30% by mass or less. In the composite particle forming step S3, it is preferable to attach the aqueous dispersion of resin fine particles to the toner base particles so that the ratio of the resin fine particles to 100 parts by mass of the toner base particles is 5 parts by mass or more and 10 parts by mass or less. .

(4) Film formation process S4
The film formation step S4 is a step of forming fine particles of resin fine particles on the surface of the toner base particles by stirring the wet composite particles obtained in the above-mentioned composite particle formation step S3, but the wet composite particles are produced under a pressure of 20 to 500 Torr. It is done by stirring the particles. As an apparatus for stirring the wet composite particles, for example, a stirring apparatus such as a high speed vacuum dryer (trade name, manufactured by Earth Technica Co., Ltd.) can be used. Preferably, the stirring apparatus shown in FIG. 1 is used. Can.

(5) Recovery step S5
The recovery step S5 is a step of recovering the capsule toner obtained through the film formation step S4. For example, the stirring device shown in FIG. 1 can be used, and after completion of the film forming step, the solenoid valve (not shown) provided at the connection portion between the container 1 and the tube 6 is opened to recover the capsule toner. can do.

  The capsule toner obtained by the manufacturing method of the present invention can be used as a developer in an image forming apparatus using an electrophotographic system, but a core particle having a shell layer and an external additive externally added is used as a one-component developer You may use it. The mixture of the capsule toner of the present invention and the carrier can also be used as a two-component developer.

  The external additive has the function of imparting fluidity to the toner and controlling the charge amount of the toner, and examples thereof include silica, titanium oxide, silicon carbide, aluminum oxide, barium titanate and the like, and silicone resin Those which have been surface-treated (hydrophobicized) with a silane coupling agent or the like are preferred.

  When the capsule toner of the present invention is used as a two-component developer, a two-component developer can be prepared by mixing the capsule toner and a carrier. Here, as a mixing device, for example, a powder mixer such as a V-type mixer (trade name: V-5, manufactured by Tokusyu Co., Ltd.) can be used. The blending ratio of the capsule toner to the carrier is preferably, for example, 10:90 to 5:95. The carrier is not particularly limited, and carriers generally used in two-component developers can be used, and examples thereof include ferrite carriers.

  EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples. First, methods of measuring each physical property value will be described.

(Measurement of physical properties)
[Glass transition temperature of binder resin]
A differential scanning calorimeter (trade name: Diamond DSC, manufactured by Perkin Elmer) was used to measure a DSC curve by heating 1 g of the sample at a temperature rising rate of 10 ° C./min according to Japanese Industrial Standard (JIS) K7121-1987. . In the obtained DSC curve, a straight line extending the baseline on the high temperature side from the endothermic peak corresponding to the glass transition to the low temperature side, and a point where the slope is largest with respect to the curve from the rising portion to the peak of the peak The temperature at the point of intersection with the drawn tangent was taken as the glass transition temperature (Tg).

[Softening temperature of binder resin]
In a flow property evaluation device (trade name: flow tester CFT-100C, manufactured by Shimadzu Corporation), a load of 20 kgf / cm ² (9.8 × 10 ⁵ Pa) is applied to make a sample 1 g die (nozzle diameter 1 mm, length) The temperature was set so as to extrude from 1 mm, and heating was performed at a temperature rising rate of 6 ° C./min, and the temperature when half the amount of the sample flowed out from the die was determined as the softening temperature (Tm).

[Volume Average Particle Size of Toner Base Particles and Capsule Toner]
20 mg of a sample and 1 ml of sodium alkylether sulfate are added to 50 ml of an electrolytic solution (trade name: ISOTON-II, manufactured by Beckman Coulter, Inc.), and an ultrasonic disperser (trade name: tabletop two-frequency ultrasonic cleaner VS-D100) A sample for measurement was prepared by dispersing for 3 minutes at an ultrasonic frequency of 20 kHz by As One Corporation. The sample for measurement is measured using a particle size distribution measuring apparatus (trade name: Multisizer III, manufactured by Beckman Coulter, Inc.) under the conditions of an aperture diameter of 100 μm and the number of measurement particles: 50000 counts, and volume particle size distribution of sample particles. The volume average particle size was determined from

[Volume average particle diameter of resin fine particles]
A dynamic light scattering particle size distribution measuring apparatus (trade name: Nanotrac, manufactured by Nikkiso Co., Ltd.) was used to measure the volume average particle size of the resin fine particles. In order to prevent aggregation of the measurement sample (resin fine particles), the dispersion containing the measurement sample dispersed in an aqueous solution containing Family Fresh (manufactured by Kao Corporation) is charged and stirred, and then injected into the above-mentioned apparatus, and measurement is performed twice. It went and calculated the average value. As measurement conditions, the measurement time is 30 seconds, the sample particle refractive index is 1.49, the dispersion medium is water, and the dispersion medium refractive index is 1.33. The volume particle size distribution of the measurement sample was measured, and the particle size at which the cumulative volume from the small particle size side in the cumulative volume distribution was 50% was calculated as the volume average particle size (μm) of the resin fine particles from the measurement results.

[Glass transition temperature of resin particles]
A differential scanning calorimeter (trade name: Diamond DSC, manufactured by Perkin Elmer) was used to measure a DSC curve by heating 1 g of the sample at a temperature rising rate of 10 ° C./min according to Japanese Industrial Standard (JIS) K7121-1987. . In the obtained DSC curve, a straight line extending the baseline on the high temperature side from the endothermic peak corresponding to the glass transition to the low temperature side, and a point where the slope is largest with respect to the curve from the rising portion to the peak of the peak The temperature at the point of intersection with the drawn tangent was taken as the glass transition temperature (Tg).

[Softening temperature of resin particles]
A 1 g sample is heated at a temperature rising rate of 6 ° C./min using a flow property evaluation apparatus (trade name: flow tester CFT-500 D, manufactured by Shimadzu Corporation), and a load of 20 kgf / cm ² (9.8 × 10 ⁵ Pa The temperature at which half of the sample flowed out of the die (nozzle diameter 1 mm, length 1 mm) was determined, and was used as the softening temperature (Tm).

Example 1
(1) Toner mother particle preparation process 100 parts by mass of styrene-acrylic resin (manufactured by Mitsubishi Rayon Co., Ltd.), 5 parts by mass of carbon black, and 4 parts by mass of polypropylene wax (manufactured by Sanyo Chemical Industries, Ltd .: 550P) The mixture was mixed for 10 minutes at a circumferential speed of 35 m / sec of a stirring blade by Nippon Koge Industrial Co., Ltd. to obtain a material mixture. The obtained mixture was melt-kneaded with a twin-screw kneader (made by Ikegai: PCM 30 type) so that the maximum temperature would be 175 ° C. and cooled with a drum flaker to obtain a melt-kneaded product. The melt-kneaded product is roughly pulverized by a cutting mill (Orient Ltd .: VM-16), finely pulverized by a jet mill (manufactured by Hosokawa Micron Corporation), and further classified by an air classifier (manufactured by Hosokawa Micron Corporation). Thus, toner base particles having a volume average particle diameter of 6.5 μm and a glass transition temperature of 50 ° C. were produced. The circularity of the toner base particles was 0.945.

(2) Resin fine particle preparation process Styrene-acrylic acid-butyl acrylate copolymer resin having a solid content of 40% by mass and a volume average particle diameter of 0.10 μm by polymerizing styrene, acrylic acid and butyl acrylate A fine particle (glass transition temperature 64 ° C., softening temperature 120 ° C.) emulsion was obtained.

(3) Composite Particle Forming Step While mixing 100 parts by mass of the toner base particles with a Henschel mixer (manufactured by Nippon Coke Kogyo Co., Ltd.), 15 parts by mass of the above emulsion is sprayed over 10 minutes using a spray nozzle. The wet composite particles were obtained in which the ratio of particles for shell layer to 100 parts by mass of core particles is 6 parts by mass and the content of water is 8% by mass. As the stirring conditions at this time, the circumferential velocity of the stirring blade was set to 15 m / sec, the rotating shaft cooling air volume was set to 10 L / min, the cooling air temperature was set to 20 ° C., and the Henschel mixer wall surface temperature was set to 20 ° C.

(4) Film Formation Step The above wet composite particles were stirred by a high-speed vacuum dryer (manufactured by Earth Technica Co., Ltd.) to form a film for shell layer particles on the surface of the core particles. As the stirring conditions at this time, the circumferential velocity of the stirring blade was set to 10 m / sec, the wall temperature of the stirring device was set to 60 ° C., and the pressure was adjusted to 50 torr (0.00666 MPa) by setting the vacuum pump.

(5) Recovery Step After completion of the film formation step, the pressure in the stirring device was returned to atmospheric pressure, and the capsule toner was recovered. The capsule toner had a water content of 0.5% by mass and a circularity of 0.957.

(6) External Addition Step 100 parts by mass of capsule toner particles and 2 parts by mass of hydrophobic silica fine particles having an average particle diameter of 12 nm of primary particles as an external additive are Henschel mixer (trade name: FM20C, manufactured by Mitsui Mining Co., Ltd.) The mixture was stirred and mixed for 3 minutes at a circumferential velocity of 30 m / sec of the rotating member to obtain an externally added capsule toner.

(7) Two-component developer preparation process 8 parts by mass of the above-mentioned external additive capsule toner and 92 parts by mass of a ferrite carrier having a volume average particle diameter of 50 μm are mixed in a V-type mixer (trade name: V-5, manufactured by Dekushou Seisakusho Co., Ltd.) The mixture was charged and mixed for 30 minutes to obtain a two-component developer having a toner concentration of 8%.

<Examples 2 to 13 and Comparative Examples 1 to 6>
In the film forming step, the same procedure as in Example 1 was followed, except that the stirring device, the peripheral velocity of the stirring blade, the wall temperature of the stirring device and the pressure in the stirring device were changed to the values shown in Table 1, The externally added capsule toner and the two-component developer of Example 13 and Comparative Examples 1 to 6 were produced. The Henschel mixer used in the film forming step is a Henschel mixer manufactured by Nippon Coke Industry Co., Ltd.

<Evaluation method>
[Peeling evaluation of resin fine particles]
A dispersion liquid is prepared by dispersing 0.02 g of the above-mentioned external added capsule toner in a commercially available household detergent 5% by weight aqueous dispersion, and using a flow type particle image analyzer "FPIA-3000" (manufactured by Malvern Co., Ltd.) The equivalent circle diameter was measured. As a disperser, the sample was dispersed using an autosampler of the apparatus, and a total count of 10000 particles was measured in the HPF mode. After measurement, the analysis particle diameter was limited to a circle equivalent diameter of 2 μm or less, the number frequency of microparticles was determined, and the ratio to the whole range was determined. This numerical value was taken as the ratio of the resin fine particle which peeled. In addition, automatic focus adjustment is performed using standard latex particles before the start of measurement. The criteria for peeling evaluation are as follows.
○: Good. The ratio of 2 μm or less is less than 10%.
:: Yes. The ratio of 2 μm or less is 10% or more and less than 20%.
X: Defective. The ratio of 2 μm or less is 20% or more.

[Evaluation of blocking resistance]
The developing unit of a commercial copying machine (trade name: MX-5111FN, manufactured by Sharp Corporation) is filled with the above two-component developer so that it is not developed on the photoreceptor, and only the developing unit is After being driven for a continuous time, the presence or absence of toner aggregates and the state of the two-component developer conveyed by the developing roller were visually confirmed. Evaluation criteria for blocking resistance are as follows.
○: Good. No toner aggregates are observed, and the two-component developer is uniformly transported by the developing roller.
:: There is no problem in practical use. Although toner aggregates are confirmed, the two-component developer is uniformly transported on the developing roller.
X: Defective. Toner aggregates are observed, and the two-component developer is not uniformly transported on the developing roller.

Reference Signs List 1 container-like member 2 stirring means 3 pressure reducing means 4 inlet 5 pipe 6 pipe 7 bag filter 8 temperature control jacket

Claims (2)

In a method of producing a capsule toner comprising a core particle and a shell layer formed on the surface of the core particle,
And attached so the aqueous dispersion of the shell layer particles to the surface of the core particles, said core particles and the composite particles to form a wet composite particles comprising said shell layer particles and water adhering to the surface of the core particles Forming process,
The wet composite particles was stirred under a pressure of less than 500torr than 20 torr, while drying the wet composite particles, a film-forming step for forming a film of the shell layer particles at the surface of the core particles
A method of producing a capsule toner, comprising: Wherein the film-forming step, agitation of the wet composite particles, method for producing the encapsulated toner according to claim 1, characterized in that it is performed under 400torr less pressure than 50 torr.

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