JP2017053934A - Manufacturing method of capsule toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a capsule toner for improving a manufacturing efficiency, and enabling suppression of a phenomenon where particles for a shell layer are peeled off from core particles and a phenomenon where capsule toner particles aggregate with each other.SOLUTION: There is provided a manufacturing method of capsule toner comprising core particles and a shell layer formed on the surface of each of the core particles, the manufacturing method of capsule toner including: a composite particle forming step of causing water dispersion of particles for a shell layer to be adhered to the surfaces of the core particles to form wet composite particles; and a drying and film forming step of forming the particles for a shell layer into a film on the surface of the core particles of the wet composite particles while drying the wet composite particles by using hot air to generate a capsule toner, where the capsule toner is recovered while containing water.SELECTED DRAWING: Figure 2

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, improves the production efficiency, and the shell layer particle is separated from the core particle to form a capsule. The present invention relates to a capsule toner manufacturing method 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 the low-temperature fixing, the power supplied to the fixing device can be suppressed. However, a toner containing a binder resin having a low softening temperature is easily fused by heat, and the blocking resistance is lowered.

  The surface of toner base particles containing a binder resin having a low softening temperature is coated with resin fine particles having a higher softening temperature and higher heat resistance than the toner base particles to produce a capsule toner. There is a method for improving the blocking resistance without impairing the properties.

  Examples of a method for producing a capsule toner in which resin fine particles are coated on the surface of toner base particles as described above include, for example, a method in which resin fine particles are attached to the surface of toner base particles in an aqueous medium and heated, and a resin on the surface of toner base particles. A method for applying mechanical impact force by adhering fine particles, a method for adhering resin fine particles to the surface of toner base particles and heating in a high temperature air flow of 300 ° C. or more, and a method of spraying resin fine particle emulsion while stirring toner base particles Etc. are known.

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

Japanese Patent No. 2838410 JP-A-2-163754

  Among conventional capsule toner production methods, in the method of spraying the resin fine particle emulsion while stirring the toner base particles, the wet composite particles are formed in the circulating airflow after the wet composite particles are formed by spraying the resin fine particle emulsion. A technique of drying with heating is known.

  However, if the temperature during drying is too low, the drying time becomes longer, and there is a problem that the resin fine particles are peeled off from the toner base particles. The capsule toner thus obtained tends to have difficulty in uniformly adhering 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 a toner aggregate. Things are easier to produce.

  In addition, if the temperature at the time of drying is increased, the drying time is shortened, but there is a problem that the spheroidization of the capsule toner easily occurs.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to suppress the phenomenon that the particles for the shell layer are peeled off from the core particles and the capsule toners are aggregated, and the capsule toner can be made spherical. The object is to provide a method for producing toner.

  The present inventor studied a method of drying wet composite particles using hot air for the purpose of suppressing the phenomenon of shell layer particles peeling from the core particles. As a result, water dispersion of the shell layer particles on the surface of the core particles was performed. It has been found that if moisture is completely removed from the wet composite particles to which the body is adhered, the temperature of the composite particles rises, causing the capsule toners to become spherical and the capsule toners to aggregate. Therefore, moisture remains in the capsule toner in the step of forming the capsule toner by forming the shell layer particles on the surface of the core particle of the wet composite particle while drying the wet composite particle using hot air. By recovering in the state, it was found that the spheroidization of the capsule toner and the aggregation of the capsule toners can be suppressed, and the present invention has been completed.

That is, the method for producing a capsule toner of 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 forming a wet composite particle by attaching an aqueous dispersion of shell layer particles to the surface of the core particle;
A drying / film-forming step of forming capsule toner by forming the shell layer particles on the surface of the core particles of the wet composite particles while drying the wet composite particles using hot air, And a drying / film-forming process in which moisture is collected.

  In a preferred embodiment of the method for producing a capsule toner of the present invention, the capsule toner is collected by utilizing the Coanda effect in the drying / film-forming step.

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

  In another preferred embodiment of the capsule toner manufacturing method of the present invention, the water content in the capsule toner recovered in the drying / filming step is 0.5% by mass or more and 5% by mass or less. The method for producing a capsule toner according to any one of claims 1 to 3.

  According to the present invention, a method for producing a capsule toner capable of improving the production efficiency and suppressing the phenomenon that the particles for the shell layer 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.

  Below, the manufacturing method of the capsule toner of this invention is demonstrated in detail. The capsule toner manufacturing method of the present invention is a capsule toner manufacturing method comprising core particles and a shell layer formed on the surface of the core particles, wherein an aqueous dispersion of shell layer particles is adhered to the surface of the core particles. A composite particle forming step of forming wet composite particles, and using hot air to dry the wet composite particles and forming the shell layer particles on the surface of the core particles of the wet composite particles to produce a capsule toner A drying / film-forming step, wherein the capsule toner is recovered in a state of containing moisture.

  In the method for producing the capsule toner of the present invention, first, wet composite particles are formed by attaching an aqueous dispersion of shell layer particles to the surface of the core particles (composite particle forming step). The wet composite particles obtained by this composite particle formation step include core particles, shell layer particles and water on the surface of the core particles, and the shell layer particles adhere strongly to the core particle surface due to the water wetting effect. Thus, the peeling of the particles for the shell layer from the core particles can be suppressed, and the surface of the core particles can be uniformly coated. In the wet composite particles obtained by the composite particle forming step, the content of water is preferably 3% by mass or more and 50% by mass or less. If the water content is less than 3% by mass, the water wetting effect may not be fully exerted. On the other hand, if the water content exceeds 50% by mass, liquefaction will occur after mixing in the composite particle forming step and handling will be difficult. Sometimes it becomes.

  In the composite particle forming step, as a method for attaching the aqueous dispersion of shell layer particles to the surface of the core particles, means for injecting the aqueous dispersion of shell layer particles onto the core particles or core particles and shell layer particles Various means such as a means for mixing with an aqueous dispersion can be used. For injection of the aqueous dispersion of the shell layer particles onto the core particles, for example, an injection nozzle can be used. Moreover, a known mixer can be used for mixing the aqueous dispersion of the core particles and the shell layer particles. For example, a Henschel mixer (trade name, manufactured by Nihon Coke Industries Co., Ltd.), a super mixer (trade name, Co., Ltd.) Henshell type mixing devices such as Kawata), Mechanomyl (trade name, manufactured by Okada Seiko Co., Ltd.), Ongmill (trade name, manufactured by Hosokawa Micron Corp.), Hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.), High 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 the shell layer particles to the core particles so that the ratio of the shell layer particles to 3 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the core particles. .

  In the method for producing a capsule toner of the present invention, the core particles are not particularly limited, but are preferably particles containing a resin from the viewpoint of use as toner base particles of the capsule toner. Examples of resins that can be used for the core particles include polystyrene resins, styrene-acrylic resins copolymerized with styrene monomers and (meth) acrylic acid monomers and / or (meth) acrylic acid ester monomers, polymethyl methacrylate, and the like. (Meth) acrylic acid ester resins, polyolefin resins such as polyethylene, polyester resins, polyurethane resins, epoxy resins and the like. These resins can 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. or higher and 80 ° C. or lower and a softening temperature of 80 ° C. or higher and 150 ° C. or lower 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 or more and 8 μm or less from the viewpoint of use as toner base particles of capsule toner, and usually have a circularity of 0.96 or less and 0.940 or more and 0.960. The following is preferable.

In the present invention, the circularity of the particles can be measured using, for example, a flow type particle image analyzer “FPIA-3000” (manufactured by Malvern), but is not particularly limited as long as the measurement principle is the same. The measuring principle of this apparatus is to take a still image of particles in a dispersion medium with a CCD camera and perform calculation such as circularity calculation from the image. The sample put in from the chamber is sent to the flat sheath flow cell and sandwiched between sheath liquids 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 of each particle is extracted by image processing of the captured image, and the projected area S, the peripheral length L, and the like of the particle image are measured. From this, the equivalent circle diameter and 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 circumference of the circle calculated from the equivalent circle diameter divided by the circumference of the projected particle image. Is calculated by the following equation.
Circularity = 2 × (π × S) ^1/2 / L
As the sheath liquid, a particle sheath “PSE-900A” (manufactured by Malvern) is used, as a dispersant, a commercially available 5% by weight aqueous dispersion of household detergent, and as a disperser, the autosampler apparatus of the apparatus is used. Then, the sample is dispersed and introduced into the flow type particle image analyzer, and 10,000 particles are measured in a total count in the HPF measurement mode. Then, the binarization threshold at the time of particle analysis is set to 85%, and the average circularity of the particles is obtained as the entire particle size range.

  In the method for producing a capsule toner of the present invention, the shell layer particle aqueous dispersion is obtained by dispersing the shell layer particles in water. The mass ratio (A / B) between (A) and water (B) is preferably 10/90 or more and 50/50 or less.

  The aqueous dispersion of the shell layer particles can be prepared, for example, by performing an emulsion polymerization reaction of the monomer component that is a resin raw material in water, or by emulsifying and dispersing the resin in water with a homogenizer or the like to make fine particles. Can also be prepared.

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

  The resin that can be used for the shell layer particles preferably has a glass transition temperature higher than that of the resin contained in the core particles, and is preferably 50 ° C. or higher and 80 ° C. or lower. 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 shell layer particles preferably have a volume average particle size sufficiently smaller than the average particle size of the core particles, and more preferably 0.1 μm or more and 0.5 μm or less.

  In the method for producing the capsule toner of the present invention, the shell layer particles are then formed on the surface of the core particles of the wet composite particles while drying the wet composite particles obtained by the composite particle forming step using hot air. However, in this drying / film forming process, the capsule toner is collected in a state of containing moisture. By collecting the capsule toner containing water (hydrated capsule toner), it is possible to prevent the capsule toner from being heated excessively and causing spheroidization and aggregation.

  In the drying / film-forming step, by using hot air, drying of the wet composite particles and film formation of the shell layer particles on the surface of the core particles are performed simultaneously. Film formation occurs by deforming the shell layer particles with hot air. In addition, hot air can instantaneously warm the wet composite particles, and the drying time can be shortened, so that the production efficiency of the capsule toner can be improved and the phenomenon that the particles for the shell layer are separated from the core particles is suppressed. You can also.

The drying / film-forming step is performed by using hot air. More specifically, the drying / film-forming step can be performed by blowing hot air on the wet composite particles. Moreover, hot air is comprised from gas, such as air, and as a temperature of the hot air used at the said drying and film-forming process, the temperature of 50 degreeC or more and 500 degrees C or less can be used, but 70 degreeC or more and 200 degrees C or less are preferable. .
If the temperature of the hot air is less than 50 ° C., the drying time becomes longer, and the shell layer particles may be peeled off or incompletely formed. On the other hand, if the temperature of the hot air exceeds 500 ° C., the water-containing capsule toner is recovered. In some cases, the capsule toner may be heated excessively to cause spheroidization or aggregation.

In the drying / filming step, the water-containing capsule toner is preferably recovered by utilizing the Coanda effect. If the Coanda effect is used, the capsule toner can be classified according to the specific gravity and particle size of the capsule toner (that is, the content of water and the fluid resistance contained in the capsule toner). The sufficiently advanced capsule toner can be easily collected. The collection of the water-containing capsule toner using the Coanda effect is not particularly limited, but a powder processing apparatus having a structure shown in FIG.
In the classification using the Coanda effect, the airflow flows along the block side surface, and the path followed by the inertial force is different, so that a plurality of classification points can be set. You may divide into the coarse particle side and the fine particle side, and you may provide an intermediate | middle further. In this step, by returning the coarse particle side having a high water content to the path again, it is possible to recover the proper water content. At this time, it may be returned directly to the route, or may be collected once and then re-entered into the route.

The capsule toner recovered in the drying / filming step is recovered in a state containing moisture, but has been dried using hot air, and the moisture content is determined by the wet composite obtained in the composite particle forming step. Lower than particle. In the capsule toner collected in the drying / filming step, the water content is preferably 0.5% by mass or more and 5% by mass or less. If the water content in the water-containing capsule toner is 5% by mass or less, the adhesion between the capsule particles due to liquid cross-linking does not increase, so that steps such as external addition can be performed, and the electrophotographic image forming apparatus can be used. Although it can be used, when the water content in the water-containing capsule toner is less than 0.5% by mass, the anti-aggregation effect due to the water content is not recognized, and the capsule toner spheroidizes and the capsule toner aggregates. In some cases. The capsule toner having a desired water content level can be collected by appropriately adjusting the flow rate of particles in the drying / filming step, the structure of the apparatus, and the like. 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 dent and the shell of the capsule particle, and liquid crosslinking between the capsule particles does not occur. There is no problem in fluidity and the like, and capsule particles are not aggregated and can be recovered as single particles.
After this, the water content can be further reduced by drying under reduced pressure or airflow drying. In this case, there is no problem even if the content falls below this range.

  In the drying / film-forming step, after blowing hot air onto the wet composite particles, cold air, preferably dry cold air, may be further blown. Thereby, excessive heating of the capsule toner by hot air can be prevented more reliably. The cold air is composed of a gas such as air, and the temperature of the cold air used in the drying / filming step is preferably 5 ° C. or higher and lower than 50 ° C. More specifically, the temperature of the cold air is a temperature not higher than the glass transition temperature of the core particles.

  The capsule toner used in the electrophotographic image forming apparatus preferably has a volume average particle size of 4 μm or more and 8 μm or less, and usually has a circularity of 0.96 or less and 0.940 or more and 0.960 or less. It is preferable. In order to obtain a capsule toner having desired volume average particles, the particle size distribution of the capsule toner collected in the drying / film-forming step can be adjusted as necessary.

  According to the capsule toner manufacturing method of the present invention, a capsule toner including core particles and a shell layer formed on the surface of the core particles is manufactured by performing the composite particle forming step and the drying / film forming step. However, the capsule toner does not expose the surface of the core particles and has excellent blocking resistance, and can be suitably used for an electrophotographic image forming apparatus.

  Next, a powder processing apparatus that can be used in the capsule toner manufacturing method 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 capsule toner manufacturing method of the present invention. The powder processing apparatus of the illustrated example includes an annular flow channel 1 for flowing composite particles, a supply pipe 2 for supplying the composite particles to the annular flow channel 1 in a state of being dispersed in an air stream, and a composite And a recovery tube 3 for recovering the particles from the annular flow path 1, and the drying / film-forming step in the capsule toner manufacturing method of the present invention can be performed.

The flow path 1 is an annular flow path for flowing the composite particles, and the composite particles are circulated in the flow path 1 in the direction of the arrow to form a system in which the composite particles are flowing. In the powder processing apparatus of the illustrated example, the composite particles are circulated by supplying hot air 4 and dry cold air 5 a and 5 b to the flow path 1. In the capsule toner manufacturing method of the present invention, the composite particles circulating in the flow path 1 are wet composite particles. When hot air is blown onto the wet composite particles, the composite particles are exposed to a high temperature and become capsule particles. At this time, if the temperature is kept high, the agglomeration may progress. However, if the wet particle contains water outside the particle, the temperature is lowered during drying and excessive aggregation does not occur.
When the wet composite particles are dried, the water present between the capsule particles decreases, and most of the water is present in the single capsule particles, so that the aggregation between the capsule particles is released and the Coanda effect is utilized. It can be recovered as capsule particles from the recovery tube 3. If there is an excessive water content after the recovery, the capsule particles will be liquid-crosslinked again after the recovery, and aggregates will be formed.

  The supply pipe 2 is a pipe for supplying the composite particles to the annular flow path 1 in a state where the composite particles are dispersed in the air flow, and one end is connected to the flow path 1 and the other end is formed of composite particles. It is connected to a composite particle input unit 6 for supplying wet composite particles obtained by the process. The supply pipe 2 is connected to an air supply port 7 that is a member for supplying hot air from a blower (bag filter) 10 and a heater 12. The wet composite particles input from the composite particle input unit 6 to the supply pipe 2 can be dispersed in the hot air supplied to the supply pipe 2, and the annular flow path 1 in a state where the composite particles are dispersed in the air stream. Can be supplied to. In the capsule toner manufacturing method of the present invention, the wet composite particles can be dried and the shell layer particles can be formed on the surface of the core particles.

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

The recovery tube 3 is a tube for recovering the composite particles from the annular flow path 1, and is configured to recover the composite particles by using the Coanda effect, and functions 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 through the dry particle size distribution measuring device 11 and the composite particle recovery section 8. Connected to a blower (bug filter) 9. In the capsule toner manufacturing method of the present invention, it is possible to collect the water-containing capsule toner in which the water content is lowered to a certain level together with the gas flowing from the annular flow path 1 to the recovery pipe 3. In addition, the illustrated powder processing apparatus includes a cyclone (not shown), which prevents the capsule toner from being discharged together with the gas, and effectively collects the capsule toner from the composite particle recovery unit 8. can do.

  Next, an embodiment of the method for producing a capsule toner of the present invention will be described in detail with reference to the drawings. FIG. 2 is a flowchart showing one embodiment of the capsule toner manufacturing method of the present invention. The capsule toner manufacturing method of the illustrated example includes a toner base particle preparation step S1 for preparing toner base particles, a resin fine particle preparation step S2 for preparing an aqueous dispersion of resin fine particles, and a composite particle forming step for forming wet composite particles. S3, and a drying / film-forming step S4 for producing capsule toner by forming resin fine particles into a film while drying the wet composite particles.

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

(Method for preparing toner mother particles by pulverization method)
In the method for producing toner base particles using a pulverization method, a toner base particle raw material composition containing a binder resin, a colorant and other additives is dry-mixed with a mixer and then melt-kneaded with a kneader. The kneaded material obtained by melt kneading is cooled and solidified, and the solidified material is pulverized by a pulverizer. Thereafter, particle size adjustment such as classification is performed as necessary to obtain toner base particles.

  Known mixers can be used. For example, Henschel mixer (trade name, manufactured by Nippon Coke Industries Co., Ltd.), super mixer (trade name, manufactured by Kawata Co., Ltd.), Mechano Mill (trade name, manufactured by Okada Seiko Co., Ltd.) Henschel type mixing devices such as HONSHELL type, ONGMILL (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 be used also as a kneading machine, for example, common kneading machines, such as a twin-screw extruder, a 3 roll, a laboratory blast mill, can be used. More specifically, for example, 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.), etc. Extruder, Needex (trade name, manufactured by Nihon Coke Kogyo Co., Ltd.) and other open roll type kneaders.

  The kneaded product is cooled and solidified, and then coarsely pulverized into a coarsely pulverized product having a weight average particle size of 100 μm or more and 5 mm or less by a hammer mill or a cutting mill, and the obtained coarsely pulverized product has a weight average particle size of 15 μm, for example. Further pulverized to: For finely pulverizing the coarsely pulverized product, for example, a jet pulverizer using a supersonic jet stream, or a coarsely pulverized product in a space formed between a rotor (rotor) rotating at high speed and a stator (liner) An impact type pulverizer or the like that pulverizes by introduction of the above can be used.

  For the classification, a known classifier capable of removing the excessively pulverized toner base particles by classification by centrifugal force and classification by wind force can be used, for example, a swirl wind classifier (rotary wind classifier) or the like is used. be able to.

(Toner base material)
As described above, the toner base particles include a binder resin and a colorant. The binder resin corresponds to a resin that can be used for the core particles in the capsule toner manufacturing method 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 and (meth) acrylic acid monomer and / or Or a styrene-acrylic resin copolymerized with a (meth) acrylic acid ester monomer, a (meth) acrylic acid ester resin such as polymethyl methacrylate, a polyolefin resin such as polyethylene, a polyester resin, a polyurethane resin, an epoxy resin, etc. Is mentioned. Moreover, you may use resin obtained by mixing a raw material monomer mixture with a mold release agent and performing a polymerization reaction. Binder resin can be used individually by 1 type, or can use 2 or more types together.

  The monomer constituting the styrene resin such as polystyrene resin or styrene-acrylic resin preferably contains a styrene monomer as an essential monomer and, if necessary, a (meth) acryl 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. Moreover, (meth) acryl means acryl and / or methacryl. Examples of the styrene monomer include styrene and alkyl styrene having an alkyl group having 1 to 3 carbon atoms (for example, α-methyl styrene, p-methyl styrene) and the like. Styrene is preferred. 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. C1-C18 alkyl (meth) acrylate; Hydroxyethyl (meth) acrylate etc. Alkyl group C1-C18 hydroxylalkyl (meth) acrylate; Dimethylaminoethyl (meth) acrylate, Diethylaminoethyl (meth) Examples thereof include alkylamino group-containing (meth) acrylates 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 the carboxyl group-containing vinyl monomer include monocarboxylic acids [having 3 to 15 carbon atoms such as (meth) acrylic acid, crotonic acid and cinnamic acid], dicarboxylic acids [having 4 to 15 carbon atoms such as (anhydrous) maleic acid and fumaric acid. , Itaconic acid, citraconic acid], dicarboxylic acid monoester [monoalkyl (carbon number 1 to 18) ester of the above dicarboxylic acid, such as maleic acid monoalkyl ester, fumaric acid monoalkyl ester, itaconic acid monoalkyl ester, citraconic acid monoester Alkyl ester] and the like. 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 kinds thereof Mixtures are preferred.

  A known monomer can be used as the monomer constituting the polyester resin, and examples thereof include a polycondensate of a polybasic acid and a polyhydric alcohol.

  As the polybasic acid, those known as polyester monomers can be used, for example, terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid, naphthalenedicarboxylic acid and other aromatic carboxylic acids, maleic anhydride, Examples thereof include aliphatic carboxylic acids such as fumaric acid, succinic acid, alkenyl succinic anhydride, and adipic acid, and methyl esterified products of these polybasic acids. A polybasic acid can be used individually by 1 type, or can use 2 or more types together.

  As polyhydric alcohols, those known as monomers for polyesters can be used. For example, aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, glycerin, cyclohexanediol, cyclohexanedi Examples include alicyclic polyhydric alcohols such as methanol and hydrogenated bisphenol A, aromatic diols such as an ethylene oxide adduct of bisphenol A, and a propylene oxide adduct of bisphenol A. 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, the polybasic acid and the polyhydric alcohol are contacted in the presence or absence of an organic solvent and in the presence of a polycondensation catalyst. The process is terminated when the acid value, softening temperature, and the like of the resulting polyester reach desired values. Thereby, polyester is obtained. When a methyl esterified product of a polybasic acid is used as part of the polybasic acid, a demethanol polycondensation reaction is performed. In this polycondensation reaction, by appropriately changing the compounding ratio of polybasic acid and polyhydric alcohol, the reaction rate, etc., for example, the carboxyl group content at the end of the polyester can be adjusted, and thus the properties of the resulting polyester Can be denatured. Even when trimellitic anhydride is used as the polybasic acid, a carboxyl group can be easily introduced into the main chain of the polyester, thereby obtaining a modified polyester. A self-dispersible polyester in water in which a hydrophilic group such as a carboxyl group or a sulfonic acid group is bonded to the main chain and / or side chain of the polyester can also be used. Further, polyester and acrylic resin may be grafted.

  The binder resin preferably has a glass transition point of 30 ° C. or higher and 80 ° C. or lower. If the glass transition point of the binder resin is less than 30 ° C., blocking in which the toner thermally aggregates easily occurs in the image forming apparatus, and storage stability may be lowered. When the glass transition point of the binder resin exceeds 80 ° C., the fixability of the toner to the recording medium is lowered, and there is a possibility that fixing failure occurs.

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

  As the colorant, organic dyes, organic pigments, inorganic dyes, inorganic pigments and the like commonly used in the electrophotographic field can be used. Although the usage-amount of a coloring agent is not restrict | limited in particular, Preferably it is 5 mass parts or more and 10 mass parts or less with respect to 100 mass parts of 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, a charge control agent for positive charge control and negative charge control commonly used in this field can be used. The amount of the charge control agent used 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.

  Further, the toner base particles may contain a release agent in addition to the binder resin and the colorant. As the release agent, those commonly used in this field can be used. For example, petroleum wax such as paraffin wax and derivatives thereof, microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin wax (polyethylene wax, polypropylene Wax, etc.) and derivatives thereof, low molecular weight polypropylin wax and derivatives thereof, polyolefin polymer wax (low molecular weight polyethylene wax etc.) and derivatives thereof, hydrocarbon synthetic wax, carnauba wax and the like. The amount of the release agent used is not particularly limited, but 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 preparation step S1 preferably have a volume average particle size of 4 μm or more and 8 μm or less. When the volume average particle diameter 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 preparation step S1 usually have a circularity of 0.96 or less, preferably 0.940 or more and 0.960 or less.

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

  In the resin fine particle preparation step S2, an aqueous dispersion of resin fine particles can be prepared, for example, by performing an emulsion polymerization reaction of a monomer component that is a resin raw material in water, or fine particles by emulsifying and dispersing a resin in water with a homogenizer or the like. Can also be prepared. In addition, it is preferable that mass ratio (A / B) of resin fine particles (A) and water (B) is 10/90 or more and 50/50 or less.

  In the resin fine particle preparation step S2, as the resin used as the resin fine particle raw 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 acid ester monomers, (meth) acrylic acid ester resins such as polymethyl methacrylate, and polyester resins. Among the resin exemplified above, the resin fine particles preferably include a styrene-acrylic resin or a polyester resin. Styrene-acrylic resins have many advantages such as light weight, high strength, high transparency, low cost, and easy to obtain materials with uniform particle diameters.

  In the resin fine particle preparation step S2, the resin used as the resin fine particle raw material may be the same type of resin as the binder resin contained in the toner base particles or a different type of resin. From the viewpoint of performing the surface modification, it is preferable to use a different type of resin. When a resin different from the binder resin contained in the toner mother 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 mother particles, or It is preferably higher than the softening temperature of the component contained in the toner base particles such as a release agent. As a result, the toner manufactured by the manufacturing method of the present embodiment can prevent the toners from fusing together during storage, and can improve storage stability. The softening temperature of the resin used as the resin fine particle raw 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 fixability can be obtained.

  In the resin fine particle preparation step S2, the resin fine particles preferably have a volume average particle size sufficiently smaller than the average particle size 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, it is excellent in plasticity and easily deforms, and a uniform coating layer is formed on the surface of the toner base particles. The particle diameter of the resin fine particles represents a volume average particle diameter measured by a dynamic light scattering method.

  In the resin fine particle preparation step S2, the glass transition temperature of the resin fine 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 higher and 80 ° C. or lower. The softening temperature of the resin fine particles is preferably 80 ° C. or higher and 140 ° C. or lower.

(3) Composite particle forming step S3
In the composite particle forming step S3, a wet composite particle is formed by attaching an aqueous dispersion of resin fine particles to the surface of the toner base particle. In the composite particle forming step S3, as described above, as the method for attaching the aqueous dispersion of resin fine particles to the surface of the toner base particles, as described above, the means for injecting the aqueous dispersion of resin fine particles onto the toner base particles, the toner base particles, Various means such as means for mixing the resin fine particles with the aqueous dispersion can be used. In the wet composite particles obtained by the composite particle forming step S3, the content of water is preferably 3% by mass or more and 50% by mass or less. In the composite particle forming step S3, it is preferable that the aqueous dispersion of resin fine particles is attached to the toner base particles so that the ratio of the resin fine particles to 3 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the toner base particles. .

(4) Drying / film-forming step S4
In the drying / film forming step S4, capsule particles are formed by forming the shell layer particles on the core particle surface of the wet composite particles while drying the wet composite particles obtained in the composite particle forming step S3 using hot air. In this drying / film-forming step S4, the capsule toner is collected in a state containing moisture. In the capsule toner collected 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 / film-forming step S4, the powder processing apparatus shown in FIG. 1 can be preferably used.

  If necessary, the particle size distribution of the capsule toner recovered by the drying / film-forming step S4 may be adjusted (classification step). Examples of the classifier include a rotary classifier TSP separator (trade name, manufactured by Hosokawa Micron Corporation).

  The capsule toner obtained by the production method of the present invention can be used as a developer in an image forming apparatus utilizing an electrophotographic method, but the core particles having a shell layer itself may be used as a one-component developer or a shell. A core particle provided with an external additive may be used as a one-component developer. The mixture of the capsule toner and carrier of the present invention can also be used as a two-component developer.

  The external additive has a 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. Those that have been surface treated (hydrophobized) 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, the two-component developer can be prepared by mixing the capsule toner and a carrier. Here, as the mixing device, for example, a powder mixer such as a V-type mixer (trade name: V-5, manufactured by Tokuju Kogakusho Co., Ltd.) can be used. The mixing ratio of the capsule toner and the carrier is preferably, for example, a mass ratio of 10:90 to 5:95. In addition, it does not specifically limit as a carrier, The carrier normally used for a two-component developer can be used, For example, a ferrite carrier etc. are mentioned.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples. First, a method for measuring each physical property value will be described.

(Physical property measurement)
[Glass transition temperature of binder resin]
Using a differential scanning calorimeter (trade name: Diamond DSC, manufactured by Perkin Elmer), a DSC curve was measured by heating 1 g of a sample at a heating rate of 10 ° C. per minute according to Japanese Industrial Standard (JIS) K7121-1987. . In the obtained DSC curve, the slope is maximized with respect to the straight line obtained by extending the base line on the high temperature side to the low temperature side from the endothermic peak corresponding to the glass transition, and the curve from the rising part of the peak to the vertex. The temperature at the intersection with the drawn tangent was defined as the glass transition temperature (Tg).

[Softening temperature of binder resin]
In a flow characteristic evaluation apparatus (trade name: Flow Tester CFT-100C, manufactured by Shimadzu Corporation), a load of 20 kgf / cm ² (9.8 × 10 ⁵ Pa) was applied to give 1 g of a sample (nozzle diameter 1 mm, length). 1 mm), and heated at a heating rate of 6 ° C. per minute. The temperature at which half of the sample flowed out from the die was determined and used as the softening temperature (Tm).

[Volume average particle diameter of toner base particles and capsule toner]
20 ml of a sample and 1 ml of sodium alkyl ether sulfate are added to 50 ml of an electrolytic solution (trade name: ISOTON-II, manufactured by Beckman Coulter, Inc.), and an ultrasonic dispersion device (trade name: desktop type dual frequency ultrasonic cleaner VS-D100. (Manufactured by As One Co., Ltd.) for 3 minutes at an ultrasonic frequency of 20 kHz to prepare a measurement sample. This sample for measurement was measured using a particle size distribution measuring apparatus (trade name: Multisizer III, manufactured by Beckman Coulter, Inc.) under the conditions of aperture diameter: 100 μm, number of measured particles: 50000 count, and volume particle size distribution of sample particles. From this, the volume average particle size was determined.

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

[Glass transition temperature of resin fine particles]
Using a differential scanning calorimeter (trade name: Diamond DSC, manufactured by Perkin Elmer), a DSC curve was measured by heating 1 g of a sample at a heating rate of 10 ° C. per minute according to Japanese Industrial Standard (JIS) K7121-1987. . In the obtained DSC curve, the slope is maximized with respect to the straight line obtained by extending the base line on the high temperature side to the low temperature side from the endothermic peak corresponding to the glass transition, and the curve from the rising part of the peak to the vertex. The temperature at the intersection with the drawn tangent was defined as the glass transition temperature (Tg).

[Softening temperature of resin fine particles]
Using a flow characteristic evaluation apparatus (trade name: Flow Tester CFT-500D, manufactured by Shimadzu Corporation), 1 g of a sample was heated at a heating rate of 6 ° C. per minute, and a load of 20 kgf / cm ² (9.8 × 10 ⁵ Pa). ) And the temperature at which half of the sample flowed out from the die (nozzle diameter 1 mm, length 1 mm) was determined and used as the softening temperature (Tm).

[Moisture content of wet composite particles]
Using a moisture content measuring device (infrared moisture meter FD-720), 10 g of a sample was weighed on an aluminum container, and the moisture content was determined by weight reduction by evaporating moisture at a temperature setting of 105 ° C. The water content (mass%) was obtained by dividing the weight decrease when the fluctuation range of the weight change was 0.05 mass% / 30 seconds of moisture change by the original weight.

<Example 1>
(1) Toner mother 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 (Eponic Degussa: Nippon 60) are mixed into a biaxial kneader (Ikegai Co., Ltd .: PCM30). Mold) was melt-kneaded so that the maximum temperature was 150 ° C., cooled, and coarsely pulverized to a 1 mm chip with a cutting mill to obtain a carbon black masterbatch.
75 parts by mass of a 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 Kasei Kogyo Co., Ltd .: 550P) Manufactured at a peripheral speed of 35 m / sec of the stirring blade for 10 minutes to obtain a material mixture. The obtained mixture was melt-kneaded so that the maximum temperature might be 175 degreeC with a biaxial kneader (Ikegai company make: PCM30 type | mold), and the melt-kneaded material was obtained by cooling with a drum flaker. This melt-kneaded product is coarsely pulverized with a cutting mill (Orient Co., Ltd .: VM-16), then finely pulverized with a jet mill (Hosokawa Micron Co., Ltd.), and further classified with an air classifier (Hosokawa Micron Co., Ltd.). As a result, toner mother 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 step Styrene, acrylic acid, and butyl acrylate are polymerized to form a styrene-acrylic acid-butyl acrylate copolymer resin having a solid content of 20% by mass and a volume average particle size of 0.10 μm. A fine particle (glass transition temperature 64 ° C., softening temperature 122 ° C.) emulsion was obtained.

(3) Composite particle forming step While mixing 100 parts by mass of the toner base particles with a Henschel mixer (Nihon Coke Kogyo Co., Ltd.), spraying 37.5 parts by mass of the emulsion over 10 minutes using a spray nozzle. As a result, wet composite particles having a shell layer particle ratio of 7.5 parts by mass and a water content of 21.8% by mass with respect to 100 parts by mass of the core particles were obtained. As stirring conditions at this time, the peripheral speed 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) Drying / Filming Process Each part process was adjusted to the following powder processing conditions for the wet composite particles using the powder processing apparatus shown in FIG. First, the supply amount of the dry cold air 5a and 5b from each cold air supply nozzle was adjusted to balance the air amount sent to the recovery side by the blower (bag filter) 10 so that the inside of the apparatus was slightly depressurized from the 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. Thereafter, the drying / film-forming process was started at a supply of wet composite particles of 50 g / min. 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>
Supply amount of hot air 4 1 L / second Temperature of hot air 4 200 ° C.
Supply amount of dry cold air 5a 8L / second Supply amount of dry cold air 5b 1L / second Temperature of dry cold air 5a, 5b 30 ° C

(5) Classification process The classification condition is adjusted using the powder processing apparatus shown in FIG. 1 to adjust the edge of the collection tube 3 as a classifier and adjust the volume average particle diameter on the non-defective product side to about 8 to 9 μm. The coarse powder side is 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 at that time was 8.2 μm. The capsule toner had a circularity of 0.952 and a moisture content of 3.3% by mass.

(6) Moisture adjustment step The obtained capsule particles were transferred to a vacuum dryer (SV mixer) and operated until the water content became 1% by mass or less to obtain non-water-containing capsule particles. After removing coarse aggregates from the encapsulated particles thus obtained using a 500 mesh sieve, the presence or absence of aggregates was examined using a 300 mesh sieve. As a result, 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 of the drying / film forming step.
<Comparative Example 1>
In the powder processing conditions of the drying / filming step, 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 classifier is such that all particles flow to the coarse powder side as classification conditions. Except for adjusting the edge of the recovery tube 3, drying and film formation were performed in the same manner as in Example 1, and after performing the powder treatment until the moisture content became 0.3% by mass, The capsule toner was taken out after being stopped.
<Comparative example 2>
Capsule toners were obtained in the same manner as in Example 1 except that hot air was not used under the powder processing conditions of the drying / filming step (30 ° C. cold air was used instead of hot air).

<Evaluation method>
Hereinafter, the degree of circularity and agglomerates were determined according to the respective criteria. Further, if both determination results are the same, it is set as a comprehensive determination result, and if the determination results are different, the worse determination result is set as the comprehensive determination result. The results are shown in Table 1.
(Judgment of aggregates)
“×” indicates that the aggregate on 300 mesh exceeds 2.0% by mass.
Aggregate on 300 mesh exceeds 0.5% by mass but is 2.0% or less.
Aggregates on 300 mesh with a mass ratio of 0.5% or less
And agglomerates of the capsule toner were determined.
(Judgment of circularity)
A case where the circularity is 0.941 (corresponding to the circularity of the core particle) or more and less than 0.960 is indicated with “◯”.
“△” when the circularity is 0.960 or more and less than 0.965
"X" when the circularity exceeds 0.965
The circularity of the capsule toner was determined.

DESCRIPTION OF SYMBOLS 1 Flow path 2 Supply pipe 3 Recovery pipe 4 Hot air 5 Drying cold wind 6 Composite particle injection part 7 Air supply port 8 Composite particle recovery part 9 Blower (feed)
10 Blower (Bug filter)
11 Dry particle size distribution measuring device 12 Heater

Claims (4)

In 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 forming a wet composite particle by attaching an aqueous dispersion of shell layer particles to the surface of the core particle;
A drying / film-forming step of forming capsule toner by forming the shell layer particles on the surface of the core particles of the wet composite particles while drying the wet composite particles using hot air, A method for producing a capsule toner, comprising: a drying / film-forming step in which moisture is collected.   2. The method for producing a capsule toner according to claim 1, wherein in the drying / filming step, the capsule toner is collected by utilizing a Coanda effect.   The method of producing a capsule toner according to claim 1 or 2, wherein the temperature of the hot air used in the drying / filming step is 50 ° C or more and 500 ° C or less.   The content of water in the capsule toner collected in the drying / filming step is 0.5% by mass or more and 5% by mass or less, according to any one of claims 1 to 3. A method for producing a capsule toner.