JP6533722B2 - Method of manufacturing capsule toner - Google Patents

Description

  The present invention relates to a method for producing a capsule toner comprising a core particle and a shell layer formed on the surface of the core particle, and in particular, to improve the production efficiency, the shell layer particles are exfoliated from the core particle The present invention relates to a method of manufacturing a capsule toner capable of suppressing the phenomenon of toner aggregation.

  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 for producing a capsule toner in which resin fine particles are coated 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 fine particles and 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 ° C. or higher, and a method of spraying resin fine particle emulsion while stirring toner base particles. Etc. are 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

  Among the conventional methods for producing capsule toner, in the method of spraying the resin fine particle emulsion while stirring the toner base particles, after forming the wet composite particles by spraying the resin fine particle emulsion, the wet composite particles are circulated in the circulating air flow. There is known a method of drying by heating.

  However, when the temperature at the time of drying is too low, the drying time becomes long, and there is a problem that peeling of the resin fine particles from the toner base particles occurs. In the capsule toner thus obtained, it is difficult to uniformly attach the resin fine particles to the surface of the toner base particles, so that a part of the surface of the toner base particles is exposed, and the capsule toners aggregate to form toner aggregation. It becomes easy to produce things.

  In addition, if the drying temperature is increased, although the drying time is shortened, there is a problem that the capsule toner is likely to be spherical.

  Therefore, an object of the present invention is a capsule that solves the problems of the above-mentioned prior art and is capable of suppressing the phenomenon that particles for shell layer separate from core particles to cause aggregation of capsule toners and spheroidization of capsule toner. To provide a method of producing toner.

  The present inventor examined a method of drying the wet composite particles using hot air for the purpose of suppressing the phenomenon that the particles for shell layer peel off from the core particles, and the water dispersion of the particles for shell layer on the surface of the core particles It has been found that when the moisture is completely removed from the wet composite particles formed by adhering the body, the temperature of the composite particles is increased, which causes spheroidization of the capsule toner and aggregation of the capsule toners. For this reason, while the wet composite particles are dried using hot air, particles for shell layer are formed into a film on the surface of the core particles of the wet composite particles to form a capsule toner, and the capsule toner contains water. It has been found that by collecting in the state, it is possible to suppress the occurrence of spheroidizing of the capsule toner and the aggregation of the capsule toner, and the present invention has been completed.

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 forming step of depositing an aqueous dispersion of shell layer particles on the surface of the core particles to form a wet composite particle;
By using hot air to dry the wet composite particles, the shell layer particles are formed into a film on the surface of the core particles of the wet composite particles to produce a capsule toner having a circularity of 0.950 or more and less than 0.960. Drying and filming steps, wherein the capsule toner includes a drying and filming step in which the capsule toner is recovered in a state of containing water at a content of 1.5% by mass or more and 2.9% by mass or less. I assume.

  In a preferred embodiment of the method for producing a capsule toner according to the present invention, the capsule toner is recovered by utilizing the Coanda effect in the drying / filming step.

  In another preferred embodiment of the method for producing a capsule toner according to the present invention, the temperature of the hot air used in the drying / filming step is 50 ° C. or more and 500 ° C. or less.

In another preferable embodiment of the method for producing a capsule toner according to the present invention, in the composite particle forming step, the aqueous dispersion of the shell layer particles is sprayed while mixing the core particles, and the surface of the core particles is obtained. The particles for shell layer are attached to the above to form the wet composite particles containing water at a content of 21.8% by mass to 50% by mass.

  According to the present invention, a method for producing a capsule toner capable of improving the production efficiency and suppressing the phenomenon that the shell layer particles are separated from the core particles and the capsule toners are aggregated, and the capsule toner is made spherical. Can be provided.

It is a schematic sectional drawing of an example of the powder processing 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. And forming a particle for shell layer on the surface of the core particle of the wet composite particle while drying the wet composite particle by using a composite particle forming step of forming the wet composite particle and hot air. It is characterized in that it is a drying and filming step, and the capsule toner includes a drying and filming step in which the capsule toner is recovered in a state of containing water.

  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. The content of water in the wet composite particles obtained by the above composite particle forming step is preferably 3% by mass or more and 50% 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 50% by mass, liquefaction is difficult after mixing in the composite particle forming step. 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.) (Mixed by Kawata), Henschel type mixing device such as Mechanomill (trade name, manufactured by Okada Seiko Co., Ltd.), Ongmill (trade name, manufactured by Hosokawa Micron Corporation), hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.), Hi Examples thereof include a speed vacuum dryer and a dynamic dryer (trade name, manufactured by Kawasaki Heavy Industries, Ltd.).

  In the composite particle forming step, it is preferable to attach the aqueous dispersion of shell layer particles to the core particles so that the ratio of shell layer particles to 100 parts by mass of core particles is 3 parts by mass or more and 20 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 10/90 or more and 50/50 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. Moreover, it is preferable that the softening temperature of resin which can be used for the said particle | grains for shell layers is 80 degreeC or more and 140 degrees 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.

  Next, in the method for producing a capsule toner of the present invention, while the wet composite particles obtained in the above composite particle forming step are dried using hot air, the shell layer particles are coated on the surface of the core particles of the wet composite particles. In the drying / filming process, the capsule toner is recovered in a state of containing water, although it is necessary to carry out a process (drying / filming process) to form a capsule toner. By collecting the capsule toner (water-containing capsule toner) in a water-containing state, it is possible to prevent the capsule toner from being excessively heated to cause spheroidization or aggregation.

  In the above-mentioned drying / filming process, drying of the wet composite particles and filmization of the shell layer particles on the surface of the core particles are simultaneously performed by using hot air. Film formation occurs when the shell layer particles are deformed by hot air. Further, since hot air can warm the wet composite particles instantaneously and can shorten the drying time, it is possible to improve the production efficiency of the capsule toner and to suppress the phenomenon that the shell layer particles peel off from the core particles. It can also be done.

Although the said drying and film formation process are performed by using a hot air, more specifically, it can carry out by blowing a hot air on wet composite particle | grains. Further, the hot air is composed of a gas such as air, and the temperature of the hot air used in the above-mentioned drying / filming process can be a temperature of 50 ° C. to 500 ° C., preferably 70 ° C. to 200 ° C. .
If the temperature of the hot air is less than 50 ° C., the drying time will be long and peeling of the shell layer particles or incomplete film formation may occur. On the other hand, if the temperature of the hot air exceeds 500 ° C., recovery of the water-containing capsule toner And the capsule toner may be excessively heated to cause spheronization or aggregation.

In the above-mentioned drying / filming process, the water-containing capsule toner is suitably recovered by utilizing the Coanda effect. By using the Coanda effect, the capsule toner can be classified according to the specific gravity and particle size of the capsule toner (that is, the water content and fluid resistance contained in the capsule toner), so that drying and film formation can be achieved. The sufficiently advanced capsule toner can be easily recovered. Recovery of the water-containing capsule toner utilizing the Coanda effect is not particularly limited, but a powder processing apparatus having a structure shown in FIG. 1 described later can be suitably used.
In classification using the Coanda effect, a plurality of classification points can be set because the air flow flows along the side of the block and the path traced by the inertia force is different. The coarse particle side and the fine particle side may be divided or an intermediate may be provided. In this step, by returning the coarse particles having a high water content back into the path, it is possible to recover an appropriate water content. At this time, it may be returned directly to the path, or may be collected once and then reintroduced into the path.

The capsule toner recovered in the drying / filming process is recovered in a state containing water, but is subjected to drying using hot air, and the moisture content thereof is the wet composite obtained in the composite particle forming process. Lower than particles. In the capsule toner recovered in the drying / film forming process, the moisture content is preferably 0.5% by mass or more and 5% by mass or less. If the content of water in the water-containing capsule toner is 5% by mass or less, adhesion between capsule particles due to liquid crosslinking does not increase, and processes such as external addition can be performed, and an image forming apparatus of an electrophotographic system Although it is possible to use it, when the water content in the water-containing capsule toner is less than 0.5% by mass, the aggregation preventing effect by the water content is not recognized, and the capsule toner becomes spherical and aggregation of the capsule toner occurs. In some cases. Incidentally, by appropriately adjusting the flow rate of particles in the drying and film forming process, the structure of the apparatus, and the like, it is possible to recover a capsule toner having a desired water content level. In particular, in the case of a capsule toner having a water content of 0.5% by mass to 5% by mass, water is stored only in the vicinity of the depression and shell of the capsule particle, and liquid crosslinking of the capsule particles does not occur. There is no problem in fluidity, etc., and the capsule particles do not aggregate and can be recovered as single particles.
After this, it is also possible to reduce the water content by drying under reduced pressure, air flow type drying, etc., and in that case, there is no problem even if it falls below this range.

  In the above-described drying / filming step, after blowing hot air onto the wet composite particles, cold air, preferably dry cold air may be further blown. By this, it is possible to more reliably prevent the excessive heating of the capsule toner by the hot air. The cold air is composed of a gas such as air, and the temperature of the cold air used in the drying / filming process is preferably 5 ° C. or more and less than 50 ° C. More specifically, the temperature of the cold air is a temperature below the glass transition temperature of the core particles.

  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 recovered in the above-mentioned drying / filming process can also be adjusted, if necessary.

  According to the method for producing a capsule toner of the present invention, a capsule toner comprising core particles and a shell layer formed on the surface of the core particles is produced by performing the composite particle forming step and the drying / filming step. However, 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, a powder processing apparatus which 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 powder processing apparatus that can be used in the method for producing a capsule toner of the present invention. The powder processing apparatus of the illustrated example includes an annular flow passage 1 for flowing composite particles, a supply pipe 2 for supplying the annular particles with the composite particles dispersed in an air flow, and It is provided with a recovery pipe 3 for recovering particles from the annular flow path 1, and it is possible to carry out the drying and film forming step in the method for producing a capsule toner of the present invention.

The flow channel 1 is an annular flow channel for flowing composite particles, and by circulating the composite particles in the flow channel 1 in the direction of the arrow, a system in which the composite particles are flowing is formed. In the powder processing apparatus of the illustrated example, the composite particles are circulated by supplying the hot air 4 and the dry cold air 5 a and 5 b to the flow path 1. In the method for producing a capsule toner of the present invention, the composite particles circulating in the flow path 1 are wet composite particles, and when the wet composite particles are sprayed with hot air, they are exposed to high temperature to become capsule particles. At this time, if the temperature is high, aggregation may proceed, but if it is a wet particle containing water on the outside of the particle, the temperature is lowered during drying and excessive aggregation does not occur.
As the drying of the wet composite particles proceeds, the water present between the capsule particles is reduced, and most of the particles are present in the single particle capsule particles, whereby the cohesion between the capsule particles is solved and the Coanda effect is utilized. Capsule particles can be recovered from the recovery pipe 3. If there is excessive water content after this collection, the capsule particles will be liquid-crosslinked again after collection and form aggregates.

  The supply pipe 2 is a pipe for supplying composite particles to the annular flow path 1 in a state of being dispersed in the air flow, one end of which is connected to the flow path 1 and the other end is for forming composite particles It is connected to the composite particle input part 6 which inputs the wet composite particles obtained by the process. Further, an air supply port 7 which is a member for supplying the hot air from the blower (bug filter) 10 and the heater 12 is connected to the supply pipe 2. The wet composite particles introduced into the supply pipe 2 from the composite particle input part 6 can be dispersed in the hot air supplied into the supply pipe 2 and the annular flow path 1 in the state where the composite particles are dispersed in the air flow Can be supplied. In the method for producing a capsule toner of the present invention, this makes it possible to dry the wet composite particles and to form a film for shell layer particles on the surface of the core particles.

  In the powder processing apparatus of the illustrated example, dry cold air 5a, 5b is supplied to the flow path 1 using a jet nozzle or the like. In the method for producing a capsule toner of the present invention, this can more reliably prevent excessive heating of the capsule toner due to hot air.

The recovery pipe 3 is a pipe for recovering composite particles from the annular flow path 1 and is configured to be able to recover composite particles by utilizing the Coanda effect, and acts as a classifier. One end of the recovery pipe 3 is connected to the flow path 1, and the other end is for discharging the gas in the annular flow path 1 via the dry particle size distribution measuring device 11 and the composite particle recovery unit 8. Blower (Bug Filter) 9 is connected. In the method for producing a capsule toner according to the present invention, this makes it possible to recover the water-containing capsule toner in which the water content has decreased to a certain level, together with the gas flowing from the annular flow path 1 to the recovery pipe 3. In the illustrated powder processing apparatus, a cyclone (not shown) is provided to prevent the capsule toner from being discharged together with the gas, and the capsule toner is effectively recovered from the composite particle recovery unit 8. can do.

  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 drying / filming step S4 of manufacturing a capsule toner by filming resin fine particles while drying the wet composite particles.

(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.) Hengschel-type mixers such as Angmill (trade name, manufactured by Hosokawa Micron Corporation), hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.), Cosmo system (trade name, manufactured by Kawasaki Heavy Industries, Ltd.), 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 be film-formed on the surface of the toner base particles in the subsequent drying / 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 10/90 or more and 50/50 or less.

  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. Moreover, it is preferable that the softening temperature of resin fine particles is 80 degreeC or more and 140 degrees 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 50% 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 3 parts by mass to 20 parts by mass. .

(4) Drying and membrane formation step S4
In the drying / filming step S4, while the wet composite particles obtained in the above composite particle forming step S3 are dried using hot air, the shell layer particles are filmed on the surface of the core particles of the wet composite particles to obtain a capsule toner In the drying / filming step S4, the capsule toner is recovered in a state of containing water. In the capsule toner recovered in the drying / film forming step S4, the water content is preferably 0.5% by mass or more and 5% by mass or less. In the drying / filming step S4, the powder processing apparatus shown in FIG. 1 can be suitably used.

  If necessary, the particle size distribution of the capsule toner recovered in the drying / film formation step S4 may be adjusted (classification step). As a classifier, for example, a rotary classifier TSP separator (trade name, manufactured by Hosokawa Micron Corporation) and the like can be mentioned.

  The capsule toner obtained by the production method of the present invention can be used as a developer in an image forming apparatus using an electrophotographic method, but core particles having a shell layer may be used as a one-component developer, or a shell An external additive may be added to a core particle having a layer and used as a one-component developer. 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).

[Water content of wet composite particles]
A 10 g sample was weighed on an aluminum container using a water content measuring device (infrared moisture meter FD-720), and the amount of water was determined by weight loss obtained by evaporating the water at a temperature setting of 105 ° C. The amount of weight loss at the time when the fluctuation range of the weight change became a moisture change amount of 0.05% by mass / 30 seconds was divided by the original weight to obtain the moisture content (% by mass).

Example 1
(1) Toner Base Particle Preparation Step 100 parts by mass of styrene-acrylic resin (manufactured by Mitsubishi Rayon Co., Ltd.) and 30 parts by mass of carbon black (manufactured by Evonik Degussa: Nipex 60) are used as a biaxial kneader (manufactured by Ikegai: PCM 30) The mixture was melt-kneaded with a mold to a maximum temperature of 150 ° C., cooled, and then roughly crushed with a cutting mill to a chip of 1 mm to obtain a master batch of carbon black.
75 parts by mass of styrene-acrylic resin (manufactured by Mitsubishi Rayon Co., Ltd.), 25 parts by mass of a master batch of carbon black, and 4 parts by mass of polypropylene wax (manufactured by Sanyo Chemical Industries, Ltd .: 550P) Made for 10 minutes at a circumferential speed of 35 m / sec of a stirring blade 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 0.941.

(2) Resin fine particle preparation process A styrene-acrylic acid-butyl acrylate copolymer resin having a solid content of 20% by mass and having 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 122 ° C.) emulsion was obtained.

(3) Composite particle formation process While mixing 100 parts by mass of the toner base particles with a Henschel mixer (manufactured by Nippon Coke Kogyo Co., Ltd.), 37.5 parts by mass of the above emulsion is sprayed for 10 minutes using a spray nozzle. As a result, a wet composite particle having a content of water of 21.8% by mass and a ratio of 7.5 parts by mass of particles for shell layer to 100 parts by mass of core particles was obtained. 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 10 L / min, the cooling air temperature was 20 ° C., and the Henschel mixer wall surface temperature 20 ° C.

(4) Drying and Film Forming Process With respect to the above wet composite particles, the process of each part was adjusted so as to satisfy the following powder processing conditions using the powder processing apparatus shown in FIG. At first, the amount of dry cold air 5a, 5b supplied from the respective cold air supply nozzles was adjusted, and the air volume sent to the recovery side by the blower (bag filter) 10 was balanced to reduce the pressure inside the machine slightly from atmospheric pressure.

  Next, the air supply port 7 of the hot air 4 was opened to adjust the hot air supply amount, and the output of the blower (bag filter) 10 was further adjusted to maintain the reduced pressure state. After that, the drying / filming process was started at a supply of 50 g / min of the wet composite particles. The supply temperature of the hot air 4 at that time was 200 ° C., and the in-machine temperature was 44 ° C.

<Powder processing conditions>
Hot air 4 supply rate 1 L / sec Hot air 4 temperature 200 ° C
Supply of dry cold air 5a 8L / s supply of dry cold air 5b 1L / s of dry cold air 5a, temperature of 5b 30 ° C

(5) Classification process The classification condition adjusts the volume average particle diameter on the non-defective side so as to be approximately 8 to 9 μm by adjusting the edge of the collection pipe 3 which is a classifier using the powder processing apparatus shown in FIG. The coarse powder side was set to have a particle size distribution higher than that. The volume average particle diameter of the capsule toner collected from the non-defective product side at that time was 8.2 μm. The circularity of the capsule toner was 0.952, and the water content was 3.3% by mass.

(6) Water Adjustment Step The obtained capsule particles were transferred to a decompression dryer (SV mixer), and the operation was performed until the water content became 1% by mass or less, to obtain non-water-containing capsule particles. The encapsulated particles thus obtained were subjected to removal of coarse aggregates using a 500-mesh sieve, and the presence of aggregates was examined using a 300-mesh sieve to find that the aggregates were 0.5% by mass or less.

Example 2 to Example 5
A capsule toner was obtained in the same manner as in Example 1 except that the temperature of the hot air 4 and the temperature of the dry cold air 5a, 5b were changed to the values shown in Table 1 under the powder processing conditions in the drying and film forming step.
Comparative Example 1
Under the powder processing conditions in the drying and film forming process, the temperature of the hot air 4 and the temperature of the dry cold air 5a, 5b are changed to the values shown in Table 1, and the classification conditions are such that all particles flow to the coarse powder side Drying and film formation are carried out in the same manner as in Example 1 except that the edge of the recovery pipe 3 is adjusted, and powder processing is performed until the water content reaches 0.3 mass%, and then the powder processing apparatus is It was stopped and the capsule toner was taken out.
Comparative Example 2
A capsule toner was obtained in the same manner as in Example 1 except that hot air was not used (powder using cold air at 30 ° C. instead of hot air) under powder processing conditions in the drying and film forming process.

<Evaluation method>
Hereinafter, the determination of the degree of circularity and the aggregate was performed according to each of the determination criteria. Further, if both determination results are the same, it is regarded as a comprehensive determination result, and if it is a different determination result, the worse determination result is regarded as a comprehensive determination result. The results are shown in Table 1.
(Judgment of aggregates)
Aggregates on 300 mesh "X" that exceeds 2.0% by mass ratio
Aggregates of 300 mesh size above 0.5% by mass ratio but 2.0% or less
Aggregates of 300 mesh on a mass ratio of 0.5% or less "○"
Then, the aggregation of the capsule toner was determined.
(Judging circularity)
If the circularity is 0.941 (corresponding to the circularity of core particles) or more and less than 0.960, "○"
"△" when the degree of circularity is 0.960 or more and less than 0.965
"X" when the degree of circularity exceeds 0.965
Then, the roundness of the capsule toner was determined.

DESCRIPTION OF SYMBOLS 1 flow path 2 supply pipe 3 collection pipe 4 hot air 5 dry cold air 6 composite particle input part 7 air supply port 8 composite particle collection part 9 blower (feed)
10 blowers (bug filter)
11 dry particle size distribution measuring device 12 heater

Claims (4)

In a method of producing a capsule toner comprising a core particle and a shell layer formed on the surface of the core particle,
A composite particle forming step of depositing an aqueous dispersion of shell layer particles on the surface of the core particles to form a wet composite particle;
By using hot air to dry the wet composite particles, the shell layer particles are formed into a film on the surface of the core particles of the wet composite particles to produce a capsule toner having a circularity of 0.950 or more and less than 0.960. Drying and filming steps, wherein the capsule toner includes a drying and filming step in which the capsule toner is recovered in a state of containing water at a content of 1.5% by mass or more and 2.9% by mass or less. Method of producing capsule toner.   2. The method for producing a capsule toner according to claim 1, wherein the capsule toner is recovered by utilizing the Coanda effect in the drying / filming process.   The method for producing a capsule toner according to claim 1 or 2, wherein the temperature of the hot air used in the drying and film forming step is 50 ° C or more and 500 ° C or less. In the composite particle forming step, the aqueous dispersion of particles for shell layer is sprayed while mixing the core particles, and the particles for shell layer are adhered to the surface of the core particles to obtain a water content of 21.8. The method for producing a capsule toner according to any one of claims 1 to 3, wherein the wet composite particles are formed to have a content of from 50% by mass to 50% by mass .