JPH0547112B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a microcapsule type toner used in electrophotography, electrostatic printing, magnetic recording, and the like. Conventionally, toners for electrostatic photography, electrostatic printing, or magnetic recording have mainly been prepared by dispersing and kneading dyes and pigments in resin, and if necessary, magnetic materials.
It is used after being ground into fine particles of about 30μ. The performance required for toner is developability, fixability,
They have a wide range of properties such as durability, stability, and environmental resistance, and it is difficult for a single material to satisfy all of these properties. For this reason, a so-called microcapsule toner has been proposed, in which a material with good fixability is used as a core substance, and the core material is surrounded by a material with excellent developability. In particular, in recent years, instead of a heat fixing method, toner is fixed by pressing it against a fixing base material (often on a transfer paper) using pressure. Many machines using the pressure fixing method have been announced.
This fixes the toner with pressure, so no heat source is required, there is no risk of fire, the equipment can be simplified, there is no waiting time for the fixing device to heat up, and it is adaptable to high speeds. However, all of the products announced so far have a linear fixing pressure of 35Kg/cm.
Due to the need to increase the strength of the fixing device,
There are problems such as the fixing material becoming heavy, and the fixing surface of the obtained fixing material becoming glossy or wrinkled. For this reason, efforts are being made to make the toner softer and lower the fixing pressure. However, when the toner becomes softer, the toner aggregates or fuses in the developing device with a small amount of force, resulting in poor durability. It becomes significantly lower and the storage stability becomes worse. For this reason, many microcapsule toners have been published in which a soft material is used as a core material and the periphery is covered with a hard resin, as seen in Japanese Patent Publication No. 8104/1983. However, until now, many products with sufficient practicality have not been announced. this is,
For one thing, materials that are suitable as toner materials are
It is difficult to uniformly impart development suitability as a toner, particularly charge controllability, to the material of the microcapsule, especially the material constituting the wall. In addition, there are problems such as wall materials peeling off due to the impact force received during the development process, and there are still many issues that need to be resolved in order to put microcapsule toner into practical use, such as the completeness of the coating and the durability of the coating. This is the current situation. Conventionally, many manufacturing methods have been proposed to solve these problems. (Tasushi Kondo “Microcapsules”) For example, spray dryer method, electrostatic coalescence method,
In-liquid drying methods, interfacial polymerization methods, phase separation methods, in-situ polymerization methods, and combination methods thereof are disclosed. In the encapsulation process, the core particles are dispersed in a solution in which the shell material is dissolved or dispersed, and the dispersion liquid is discharged using a two-fluid nozzle or disc atomizer to coat the surface of the core particles with the shell material. When this method is adopted, a capsule toner having a coarse particle size in which the particles are coalesced may be obtained, and particles called free shells consisting only of shell material may also be produced as a by-product. When an interfacial polymerization method is used in the encapsulation process, the reaction generally takes a long time, resulting in a decrease in productivity. Furthermore, since the range of materials that can be used in the interfacial polymerization method is very narrow, it is extremely difficult to appropriately control the characteristics of the capsule toner obtained using the interfacial polymerization method, such as triboelectric charging characteristics. . Furthermore, even when a phase separation method is used in the encapsulation process, there are various problems. The phase separation method described here shows sufficient solubility in the shell material. By adding a non-solvent that is substantially insoluble to the shell material into the so-called good solvent, the shell material is added to the surface of the core particle which has been dispersed or solubilized in the good solvent. This is a method of coating the In this method, it is essential that the binder constituting the core particles does not dissolve in the good solvent during the process of dispersing the core particles in the good solvent. If a portion of the core material were to be solubilized, the core material would be mixed into the resulting shell film, resulting in destabilization of triboelectric charging characteristics and contamination of the sleeve. Furthermore, once the core material has been solubilized, it precipitates due to the action of the non-solvent, resulting in a by-product of capsule toner that does not contain a colorant and has extremely high tribo, which is likely to cause background fog and sleeve unevenness. Furthermore, in the phase separation method, selection of a good solvent and non-solvent for the shell material is extremely important. That is, if the selection is incorrect, the shell material will precipitate too quickly, resulting in poor product stability and reproducibility.On the other hand, if the precipitation point is too late, the equipment will become bulky, leading to a decrease in productivity. An object of the present invention is to provide a method for producing microcapsule toner that solves the above-mentioned drawbacks. Another object of the present invention is to provide a method for producing a microcapsule toner that is free from adhesion and aggregation, has high coating integrity, and has excellent functional separation. Another object of the present invention is to provide a manufacturing method for producing microcapsule toner at low cost and with good reproducibility. Specifically, the object of the present invention is to use N-methylpyrrolidone, dimethyl sulfoxide, and The mixing enthalpy of a good solvent selected from the group consisting of dimethylformamide and a non-solvent selected from the group consisting of water and alcohol is 5 KCal/mol or less, and the temperature at which the shell material precipitates is -5 to -35 An object of the present invention is to provide a method for producing a capsule toner, which is characterized in that a shell material is precipitated on the surface of core particles containing at least paraffin wax and polyethylene under conditions of .degree. The core materials used in the present invention include polyethylene wax, oxidized polyethylene, paraffin, fatty acids,
fatty acid ester, fatty acid amide, fatty acid metal salt,
Waxes such as higher alcohols; ethylene-vinyl acetate resin, cyclized rubber, etc. can be used alone, in mixtures, or in the form of reactants. Preferably, (a) a resin having a hardening effect with a Vickers hardness of 2 to 8 Kg/mm ² when the applied load is 10 g and the load is maintained for 15 seconds, and (b) a critical surface tension at 20°C of 15 to 40 dyne. /
A mixture containing at least two resins, (c) a resin with a release property imparting effect of 0.1 to 50 kg/mm ² and (c) a resin with a fixation imparting effect with a compressive modulus of 0.1 to 50 Kg/mm 2, is prepared in advance by adding a radical generator. A binder resin containing a heat-treated material that has been heat-treated in the presence of a heat-treated resin is effective. The resin having the hardening effect (a) used here is a substance exhibiting a Vickers hardness of 2 to 8 Kg/mm ² when the applied load is 10 g and the load is maintained for 15 seconds. In other words, the hardening effect means that when the obtained core particles are encapsulated, the shape of the core particles will not change or be crushed by such external force, and the obtained capsule toner will have a hardness. There is resistance to external forces generated during the filling process or during storage, and there is resistance force between the sleeve and toner, between the sleeve and the blade, between the toner and the toner due to the rotation of the sleeve under the desired magnetic field. In the step of cleaning the toner remaining on the drum after transfer, it is necessary to provide appropriate strength against the friction between the cleaning member and the drum. The Bitkers hard material used in the present invention is
It can be measured using a microhardness meter (MVK-F) manufactured by Akashi Seisakusho. The measurement method was based on JIS Z2244, and the loading speed was set so that the applied load was 10 g and the required time was 15 seconds, and the test temperature was 23±5°C. A specific example of a substance having the effect (a) is carnauba wax (Vickers hardness Hv=
3.6), natural waxes such as Candeli wax (Hv=4.8), and synthetic waxes such as polyethylene wax. If a substance having the effect (a) with a Vickers hardness of less than 2 kg/mm ² is used, the toner will be destroyed by the external force that moves the sleeve and toner relative to each other, causing toner adhesion on the sleeve. do. As a result, the original function between the toner and the sleeve, such as the generation of sufficient frictional electrification and the function of preventing toner particles from coagulating with each other, is reduced, causing uneven coating. On the other hand, if a substance having this effect exceeding 8 kg/mm ² is used, the pressure fixing properties will be insufficient. As a substance having particularly preferable hardening effect (a), it is advantageous to use carnauba wax having an acid value in the range of 0 to 2 (more preferably 0 to 1). If carnauba wax with an acid value exceeding 2 is used, the carnauba wax will self-emulsify when atomized in an aqueous dispersion medium in the presence of a dispersant, resulting in core particles with an extremely wide particle size distribution. You can only get what you have. Furthermore, carnauba wax has extremely high hardness and relatively low melt viscosity, so the stirring power required for atomization is small, and it is difficult to use with commonly used stirring equipment.
This is advantageous in solving the problem of not being able to achieve the desired atomization. More preferably, it has a large function of encapsulating the magnetic material used during the formation of the core particle. The material having the release property imparting effect (b) used in the present invention has a critical surface tension of 15 to 15 at 20°C.
Preferred is a material exhibiting 40 dyne/cm. A specific example is polyfluorinated vinyl (critical surface tension;
γc = 28), Teflon (γc = 18.5), polyethylene (γc = 31), polyisobutene (γc = 27), ethylene-acrylic acid copolymer 92:8 mol% (γc = 44),
Ethylene-propylene copolymer (γc = 28), ethylene-tetrafluoroethylene copolymer (γc = 26)
~27), ethylene-vinyl acetate copolymer (γc = 37), isobutene-isoprene copolymer (γc = 27), polypropylene (γc = 29-34), polymethyl methacrylate (γc = 39), polyvinyl chloride (γc=39). Especially polyfluorinated vinyl,
Teflon, polyethylene, etc. are preferred. If a substance having action (b) with a critical surface tension of less than 15 dyne/cm is used, there should be sufficient space between the substance having action (a), action (c) and the shell material to be included as a core material. No interaction occurs,
No effect can be expected on the uniform dispersion of the core material or on the delamination properties caused by external forces. On the other hand, the critical surface tension
If a substance having this effect exceeding 50 dyne/cm is used, it will cause a decrease in image density and drum filming under high humidity conditions due to its high water absorption. Furthermore, when forming core particles using a wet method,
It has the disadvantage that it causes self-emulsification and only particles with a significantly wide particle size distribution can be obtained. As the substance having the fixability imparting function (c) used in the present invention, a substance exhibiting a compressive elastic modulus of 0.1 to 50 kg/mm ² is used. The compressive elastic modulus of the present invention can be measured in accordance with JIS-K7208. The measurement conditions are Shimadzu Autograph DCS-2000 manufactured by Shimadzu Corporation.
A sample piece molded to a size of 12 mm and 30 mm in height was placed on the pressure surface, and the test speed was 9 mm per minute.The compressive modulus of elasticity was calculated from the slope of the straight line at the beginning of the resulting compressive stress-strain curve. Calculate and find. Specific examples of substances having the effect (c) used in the present invention include paraffin wax, polyamide resin, microcrystalline wax, ethylene-
Examples include vinyl acetate copolymers. Particularly preferably, Paraffin 155 (manufactured by Nippon Seiro Co., Ltd.; compressive modulus E = 10 Kg/mm ² ), SPO145 (manufactured by Nippon Seiro Co., Ltd.; E = 15
Kg/mm ² ), Polymide S-40E (manufactured by Sanyo Chemical Co., Ltd.; E
= 12Kg/mm ² ), and microcrystalline wax (manufactured by Nippon Chemical Co., Ltd.; E = 26Kg/mm ² ). The fixability-imparting component needs to be sufficiently sensitive to stress from the fixing device when an unfixed image is fixed on an object to be fixed by the fixing device. However, if the object is excessively deformed in response to external force, the deformation will extend to the inside of the object, increasing the strength of the interface between the toner and the object. On the contrary, it has the disadvantage of becoming weaker. If a material having the effect (c) with a compressive modulus of elasticity of 0.1 Kg/mm ² or less was used, the image would "crush" or "bleed". On the other hand, if a substance having the effect (c) of 50 kg/mm ² or more is used, the fixing performance will be extremely poor, such as the fixing material may "peel off" from the fixing object. The amount of the resin having the functions (a), (b), and (c) used in the present invention is 5 to 60 parts by weight, based on 100 parts by weight of the total binder resin in the core material. , preferably 10 to 50 parts by weight, (b) 5 to 60 parts by weight, preferably 10 to 50 parts by weight, and (c) 20 to 90 parts by weight, preferably 20 to 80 parts by weight. is preferred. In the present invention, the above (a) hardening effect, (b)
It is necessary to heat-treat a mixture containing at least two types of resins out of the three components of releasing property imparting function and (c) fixing property imparting function in the presence of a radical generator. Reactions caused by this heat treatment include radical reactions such as hydrogen abstraction reactions by radical generators or radicals generated by heating, and intramolecular or intermolecular crosslinking reactions. When a radical generator is applied, it is preferable to carry out the heat treatment in the absence of a solvent such as an organic solvent that dissolves the resin. A method using a polymerization initiator is preferred because radical generation is easy and reliable at a relatively low temperature. Examples of the polymerization initiator include peroxide compounds (specific examples thereof are shown in Table 1), hydroperoxides such as cumene hydroperoxide, di-tert-
So-called radical polymerization initiators such as alkyl peroxides such as butyl peroxide, potassium peroxosulfate, ammonium peroxosulfate, hydrogen peroxide, and 2,2-azobisisobutyronitrile are preferably used. Preferred is hydrogen peroxide, n-butyl-4,4-bis-, which has good safety, easy availability, and reactivity.
tert-butyl peroxyvalerate (NOF Corporation)
Particularly preferred is Perhexa V).

【table】

[Table] By performing heat treatment in the presence of a radical generator, which is one of the features of the present invention, features that were completely unanticipated in the past, namely, the hardness imparting component contained in the core material and the imparting of mold release properties. It is possible to prevent phase separation of active ingredients, fixability-imparting active ingredients, etc. and migration of components due to changes over time, and as a result, core particles with uniform mechanical and electrophotographic properties can be produced. In the present invention, other core substances include, when making core particles, for example, when using a method of granulating core particles using a water-repelling dispersant in an aqueous solvent.
It is preferable to combine a cationic property-imparting compound or an anionic property-imparting compound that induces a charge opposite to the charge induced by dissociation of the dispersant in the aqueous medium. When obtaining core particles in the presence of a water-repellent dispersant in an aqueous medium, it is common to use a dispersant having a sufficiently small particle size relative to the particles to be obtained. In other words, the fact that the particle size of the dispersant is very small means that it is highly energetically activated and has the advantage of selectively adhering to the particle surface. In addition, when a polar solvent such as water is used as a medium according to the present invention, it is advantageous for the dispersant to also have a highly polar functional group, and these dispersants can occupy the surface of the core particle. Further desired atomization is possible due to ionic interaction. It is also expected that by making effective use of this functional group, it can be removed, for example, when it is not needed. In other words, if it is desired to obtain a desired particle size, it can be achieved by arbitrarily selecting the amount of the slightly water-soluble dispersant added. However, simply using a dispersant selected in this manner does not necessarily ensure that the dispersant is selectively and uniformly deposited only on the surface of the core particle, and is insufficient to obtain uniform particles. For this purpose, the dispersant is uniformly attached to the surface of the core particles, and the dispersant is further imparted with cationic properties to induce a charge opposite to the charge induced by dissociation in the aqueous medium in the core material to be atomized. It is necessary to combine compounds or anionic properties imparting compounds. For example, typical examples of dispersants that can be dissociated as anions in water include silica and bentonite, and hydrophobic amines are generally used as compounds imparting utionic properties to these dispersants. Particularly preferred examples of cationic properties imparting compounds that are sufficiently compatible with other components contained in the core material include long-chain aliphatic amines or grafting compounds produced from polyethylene and monomers containing amine groups. Specifically, after heating and dissolving Duomin T (Lion Armor) and polyethylene wax, an aprotic polar solvent containing an amino group-containing vinyl monomer and a radical initiator was added, and the mixture was heated again. There are amino-modified waxes etc. On the other hand, aluminum oxide is a dispersant that can be dissociated as a cation in water. Compounds imparting anionic properties include hydrophobic long-chain aliphatic carboxylic acids such as stearic acid and oleic acid. Also, long chain aliphatic dicarboxylic acids, carboxylic anhydrides, e.g.
Examples include C ₈ α-olefin and maleic anhydride reactants or half esters thereof. As the coloring agent contained in the core material of the capsule toner of the present invention, known dyes and pigments and magnetic substances can be used. Examples include various types of carbon black, aniline black, naphthol yellow, molybdenum orange, rhodamine lake, alizarin lake, methyl violet lake, phthalocyanine blue, nigrosine methylene blue, rose bengal, and quinoline yellow. When the capsule toner of the present invention is a magnetic toner, the magnetic substance contained in the core substance is as follows:
These include ferromagnetic elements such as iron, cobalt, nickel, and manganese, and alloys and compounds containing these such as magnetite and ferrite. This magnetic substance may also be used as a coloring agent. Furthermore, the magnetic material particles may be treated with various hydrophobizing agents such as silane coupling agents, titanium coupling agents, surfactants, and the like. The content of this magnetic substance is from 15 to 100 parts by weight of all the resin in the core material.
100 parts by weight is good. Furthermore, the apparent viscosity of the molten mixture of toner consisting of the core material binder resin, colorant, and magnetic substance measured at 120°C at a shear rate of 10 sec ^-1 is 1% of the apparent viscosity measured at a shear rate of 0.5 sec ^-1. /5 or less is desirable from the viewpoint of fixability and manufacturing method. The fact that the faster the shearing speed is, the lower the apparent viscosity is, is generally called thixotropy.
This highly thixotropic material promotes deformation of the toner due to shear between pressure rollers during pressure fixing, thereby improving fixing performance. In addition, as described later, in the method of granulating the core material by melt-kneading it, pouring it into an aqueous medium, and applying strong shearing force using a homomixer or the like in the presence of an emulsifier, etc. During said shearing, the apparent viscosity of the core substance decreases, thereby improving granulation properties, while after shearing, the apparent viscosity increases, leading to coalescence of particles and coloring inside the particles. Reduces agglomeration and distortion of pigments such as agents and magnetic materials. Although various viscosity meters are used to measure viscosity, a rotating double cylinder (rotor) type viscometer was used in the present invention. In the case of a rotor type viscometer, the shear rate is determined by the following formula. D=2ω/1-(Rb/Rc) ² =2・2πN/60/1-(
Rb/Rc) ² = 0.2094N/1-(Rb/Rc) ² (sec ^-1 ) Rc: Cup radius (cm) Rb: Rotor radius (cm) h: Rotor height (cm) ω: Rotor rotational angular speed N : Rotational speed (rpm) Also, the shear stress is S=M/2πRb ² h, M: viscous torque, η=S/D, η: viscosity, so the torque can be measured from the shape of the rotor of the viscometer. Then you can know the shear rate viscosity. In addition, binder resins that generally have pressure fixing properties have a relatively low melt viscosity, so shear (shearing force) does not work between the binder resin and pigments such as colorants and magnetic materials during melt-kneading. As a result, the dispersion of the pigment into the binder resin becomes insufficient, resulting in the formation of many particles in which no coloring material is present inside the toner particles, or particles in which the coloring material is unevenly distributed within the toner particles, which impairs the performance of the toner. This tends to lower the image quality, which in turn has an adverse effect on image quality, durability, stability, etc. Therefore, the particle size of the pigment particles in the toner particles is
It is desirable to disperse to a particle size of 5μ or less, preferably 2μ or less, and for this purpose, it is necessary to use a media instead of the two-roll, twin-screw extruder kneader, etc. that have been conventionally used to melt and disperse toner components. It is desirable to melt-knead and disperse for a sufficiently long time using attritors, ball mills, or sand mills. The degree of dispersion of pigment substances can be determined by dispersing the toner in an embedding resin such as epoxy resin, curing it, cutting it into ultrathin sections with a microtome, and observing it with a transmission electron microscope. The dispersibility can also be determined by using a particle size gauge (grind gauge, model manufactured by Yoshimitsu Seishin Co., Ltd.). The shell material used in the present invention is a cross-linked material with a number average molecular weight of about 3,000 to 30,000 because it needs to have sufficient solubility in the solvent used in the phase separation method and good film-forming properties when the solvent is removed. Polymer compounds that do not have are generally used. Specific examples include resins made of the following monomers. Styrene and its substituted products such as styrene, p-chlorostyrene, p-dimethylamino-styrene; methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, N,N methacrylate -dimethylaminoethyl ester, acrylic acid N,N
-dimethylaminoethyl ester, methacrylic acid N,N'-diethylaminoethyl ester, acrylic acid N,N-diethylaminoethyl ester,
Methacrylic acid 2-piperidinoethyl ester, acrylic acid 2-piperidinoethyl ester, methacrylic acid 2-methylamino-2-methyl-nopropanol ester, acrylic acid 2-methylamino-2-methyl-nopropanol ester
Esters or ester derivatives of acrylic acid or methacrylic acid such as 2-methyl-1-propanol ester; maleic anhydride, half ester, half amide, or diesterimide of maleic anhydride, vinylpyridine, vinylcarbazole, 5-ethyl -2-vinylpyridine, 2-
Methyl-5-vinylpyridine, N,N-divinylaniline, trans-1,2-bis(2-pyridyl)ethylene, 2-vinylquinoline, 2-(N,
N-dimethylamino)-4-vinylpyrimidine,
4-vinylpyrimidine, 3-cinnamoylpyridine, 4-methacryloxybenzylideneaniline, diallylmelamine, 2,4-dimethyl-6-
Nitrogen vinyl such as vinyl-triazine, 4,6-diamino-2-vinyltriazine, N-vinylimidazole; vinyl acetals such as vinyl formal, vinyl butyral; vinyl monomers such as vinyl chloride, acrylonitrile, vinyl acetate; vinylidene chloride, Vinylidene monomers such as vinylidene fluoride; olefin monomers such as ethylene and propylene. Also, polyester, polycarbonate, polysulfonate, polyamide, polyurethane, polyurea, epoxy resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, melamine resin, polyphenylene Homopolymers, copolymers, or mixtures of polyether resins such as nylene oxide, thioether resins, etc. can be used. Preferably, it exhibits sufficient solubility in the solvent used in the phase separation method, has good film-forming properties, and has low humidity and
A styrenic copolymer consisting of a styrene/acrylic acid ester derivative or a styrene/methacrylic acid ester derivative that exhibits stable characteristics against temperature changes is preferred. As mentioned above, solid core particles that are solid at room temperature and are used for pressure fixing are generally preferably granulated in an aqueous system, but the production of the core particles of the present invention is not limited to an aqueous system. It is also possible to produce the toner by melting, kneading, and pulverizing (in the atmosphere), which are used in the production of ordinary heat-fixable toners, and if necessary, by performing a classification process. Core materials for heat-fixable toners include materials that exhibit rubber elasticity such as styrene-butadiene resin,
Alternatively, a three-dimensional network such as a polyester resin having trifunctional or higher functional groups, a resin containing a carboxylic acid group crosslinked with metal, or a mixture of crosslinking monomers to provide crosslinks between the main chains. When a heat roll fixing device with a structure is used, it is resistant to thermal offset, and by mixing an appropriate amount of low molecular weight components with these to broaden the molecular weight distribution, the fixing temperature can be kept relatively low. , thermal offset properties can also be improved. As the encapsulation method used in the present invention, a phase separation method is adopted. The phase separation method consists of the following steps. That is, a dispersion liquid is prepared in which core particles that are insoluble in the solvent are uniformly dispersed in a solution in which a high molecular weight polymer forming the shell film of the capsule toner is dissolved in a solvent, and then the high molecular weight polymer and the By adding a non-solvent that has no solubility to the core particles and is freely miscible with the solvent to the dispersion and uniformly mixing them, a fine particle rich in the high molecular weight polymer can be created in a good solvent. Oil droplets are deposited. The mixing enthalpy of both solvents required for precipitation at this time is 5 KCal/mol or less, and it is necessary to control the temperature during precipitation to -5 to -35°C. The generated oil droplets gradually gather on the surface of the core particle, resulting in the formation of a liquid phase coating.
Further, it is manufactured by solidifying this coating and then separating the obtained capsule toner. The mixing enthalpy of the good solvent and non-solvent in which the shell material was dissolved when the shell material was precipitated was calculated as follows. The chemical potential of the system when the shell material is precipitated by adding a non-solvent to a solution containing the shell material is expressed as equation (1). μ=μ ₀ + RTlnX ₁ ...( ₁ ) R: _Gas constant T: Temperature at the time of precipitation X ₁ = n ₁ / n ₁ + n ₂ + n ₃ ...(2) n ₁ : Number of moles of non-solvent during precipitation n ₂ : Number of moles of good solvent during precipitation n ₃ : Mol of shell material during precipitation By partially differentiating equation (1) with respect to temperature and rearranging the equation, we get (3)
The formula is obtained. γlnX ₁ /γT=ΔH/RT ² (3) By integrating the equation (3), plotting the function of lnX ₁ and 1/T, and finding its slope, the enthalpy of mixing can be obtained. Specifically, the shell material was added to a good solvent of 100c.c.
A homogeneous solution containing 2.5g of solubilized water is controlled in advance at a constant temperature. The point at which the cloudiness does not disappear by gradually adding a non-solvent to this is called the precipitation point.
When we plotted the mole fraction of the non-solvent and the temperature at each precipitation point, good linearity was obtained, and from the slope it was determined that the mixture of a good solvent that dissolved the shell material and the non-solvent when the shell material was precipitated was obtained. The enthalpy was calculated. The results are shown in Table 1. When the mixing enthalpy at the time of precipitation exceeds 5 KCal/mol, the shell material dissolved in a good solvent will not precipitate even if a large amount of non-solvent is added, which is extremely disadvantageous in production. Preferably, when the shell material is precipitated, the mixing enthalpy of the good solvent in which the shell material is dissolved and the non-solvent is 0.01~
A system of 4KCal/mol is effective. If the mixing enthalpy of precipitation is less than 0.01 KCal/mol, the shell material dissolved in a good solvent will precipitate with a small amount of nonsolvent added, making it difficult to control the speed of nonsolvent addition and affecting the reproducibility and stability of encapsulation. There is a disadvantageous tendency.

[Table] In the method of obtaining a capsule toner by the phase separation method which is a feature of the present invention, it is essential that the temperature at which the shell material is precipitated is controlled at -5 to -35°C.
If encapsulation is performed at a temperature higher than -5°C, the core material will be solubilized when the core particles are dispersed in a good solvent in advance, and when a non-solvent is added in the next step, a core containing no coloring material will be formed. Because encapsulated toner with particles as the core is produced as a by-product, and the solubilized core material destabilizes minute oil droplets that are generated in the initial stage of precipitation of the shell material, so-called free shells that do not contain core particles are produced. It is easy to produce particles called by-products. On the other hand, −35
At temperatures lower than 0.degree. C., manufacturing problems in controlling the system at cryogenic temperatures and the efficiency of producing toner within a unit time become significantly worse when encapsulation is carried out. Furthermore, in the present invention, the addition rate of the nonsolvent to the good solvent core particle dispersion is C/A×B=0.005 to 20, more preferably C/A×B=0.01 to 10, and even more preferably C It is preferable to control the addition rate within the range of /A×B=0.05 to 5. Here, A: shell material concentration in good solvent (g/);
B: Good solvent amount ( ); C: Non-solvent addition rate (ml/min). If C/A×B is less than 0.01, encapsulation takes time and production efficiency drops significantly. If C/A×B is 20 or more, heat generation during addition becomes intense, making it difficult to control the temperature of the dispersion liquid, and also causes coalescence of capsule toners and free shells, which is undesirable. In the encapsulation process using the phase separation method of the present invention, it is also possible to use a dispersant and a dispersion aid in combination in a good solvent in which the shell material is dissolved. Specific examples include styrene-maleic anhydride copolymers, aliphatic α-olefin-maleic anhydride copolymers, organic acids, and organic amines. It is also possible to add or mix various dyes and pigments, hydrophobic colloidal silica, etc. to the capsule toner produced by the production method of the present invention for the purpose of charge control, imparting fluidity, coloring, etc. The volume average particle diameter of the capsule toner is preferably 3 to 20 μm. More preferably 8~
15 μm is effective. The toner contains 1 to 30% by weight, more preferably 5 to 15% by weight of colored dyes and pigments.
0.01~ with hard material around the soft solid core containing
It is coated to a thickness of 2 μm, preferably 0.1 to 0.6 μm. The present invention will be explained in more detail by showing specific examples below. Example 1 Commercially available carnauba wax (manufactured by Noda Wax Co., Ltd.) 1
Kg is taken into a 2- to 4-necked flask, and the pressure inside the container is reduced to 1 to 2 mmHg in a nitrogen atmosphere. While maintaining reduced pressure, heat the inside of the container to 250℃,
Allow to react for 8 hours. The acid value of the carnauba wax obtained at this time was 0.5. To 400g of this carnauba wax (Hv=3.6) and polywax 655 (manufactured by Petrolite; γc=
200g of polyethylene consisting of 31dyne/cm), and
Transfer 400 g of paraffin wax consisting of SPO145 (E = 15 Kg/mm ² ) to a 2-4 neck flask, add 1 g of Perhexa V (manufactured by NOF Corporation; temperature 105°C to obtain a half-life of 10 hours), and place it inside the container. was heated to 150°C and heat treated for 2 hours. Furthermore, the following mixture
The mixture was kneaded at 120° C. using an attritor at 200 rpm for 3 hours. The kneaded product had an apparent viscosity of 600 cps at a shear rate of 10 sec ^-1 at 120°C, and an apparent viscosity of 6500 cps at a shear rate of 0.5 sec ^-1 . Further, the particle size of the magnetite particles in the kneaded material was 1.5 μ at the maximum. Above reactant 70 parts by weight Styrene/dimethylaminoethyl methacrylate copolymer (hereinafter referred to as St.DM copolymer)
30 parts by weight Magnetite 80 parts by weight On the other hand, 20 g of water and 20 g of hydrophilic silica (Aerosil #200; manufactured by Nippon Aerosil Co., Ltd.) which is negatively charged in water were collected in advance into a 20 Ajihomo mixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). Warmed to ℃. Put 1 kg of the above kneaded material into this dispersion medium, and
Pelletization was carried out for 1 hour under the conditions of sec, number of passes 6.9 times/min. After completion of granulation, cooling was performed using a heat exchanger. 50g of sodium hydroxide in this dispersion
was added and stirring continued for 5 hours. As a result of analyzing the obtained spherical core particles by fluorescent X-ray analysis, no residual silica was found. Furthermore, using a centrifuge, filtration and water washing are performed to determine the number average particle size.
Core particles with a volume average particle size of 9.1 μm, a volume average particle size of 10.5 μm, and a volume average particle size variation coefficient of 18.7% were obtained with a yield of 95%. After drying the obtained core particles, the mixture consisting of the above composition was thoroughly mixed at -25°C using the 20Ajihomo mixer again. Core particles: 1 kg St.DM copolymer: 80 g After dispersion, ethanol was gradually added dropwise at 20 ml/min while maintaining the temperature. The mixing enthalpy during precipitation at this time was 3.0 KCal/mol.
The obtained capsule toner had no coalescence of particles, and when observed with a scanning electron microscope (SEM), it had a smooth surface shape although it had some irregularities. This toner is externally added with 0.5% silica for positive use, and PC-30
(manufactured by Canon Inc.) for image printing. Maintains good image density for the number of durable sheets.
We promoted up to 3000 copies. Regarding fixing properties, linear pressure 13
Sufficient fixing performance was shown even at kg/cm. Example 2 Parafine wax (1550F) 200 parts by weight Polyethylene (Hiwax 200P manufactured by Mitsui Petrochemicals) 100 parts by weight magnetite (BL-250; manufactured by Titan Industries)
180 parts by weight were melted and mixed at 150°C, sprayed, cooled, and solidified using a two-fluid nozzle with an air temperature set at 120°C, and then classified to obtain magnetic core fine particles with a particle size of 5 to 20 μm. Ta. Coulter counter model TA for viscosity distribution
(manufactured by Coulter Electronics), the following measured values were obtained. Number average diameter 9.71μm 6.35μm or less 15.7% Volume average diameter 13.50μm 20.2μm or more 6.2% 1 kg of the obtained core particles was pre-packaged with a jacket 20
After dispersing 80 g of S+-DM copolymer in a solution of dimethyl sulfoxide (DMSO) 4 in an Ajihomo mixer at a solution temperature of -25°C, the temperature was maintained in the dispersion. Ethanol (E+OH) was gradually added dropwise at a rate of 20 ml/min.
The mixing enthalpy of precipitation at this time is 3.5KCal/
It was hot in mol. Example 3 1 kg of core particles produced by the method described in Example 1 was placed in a solution of 80 g of S+-DM copolymer solubilized in 4 dimethylformamide (DMF) at a temperature of 1 kg. After dispersing at -25℃, water was added to the dispersion at 15℃ while maintaining the temperature.
It was gradually added dropwise at a rate of ml/min. The mixing enthalpy at this time was 0.4 KCal/mol. The particle size distribution of the obtained capsule toner had a volume average particle diameter of 11.5 μm. Example 4 1 kg of core particles produced by the method described in Example 1 was dispersed in a solution containing the following shell material at a solution temperature of -25°C (S+-DM (number average molecular weight 20000) S+-DM (number average molecular weight 5000) DMF 57.1g 22.9g 4 After cooling, add water to the dispersion while maintaining the temperature.
It was gradually added dropwise at a rate of 20 ml/min. The mixing enthalpy at this time was 0.6 KCal/mol. The particle size distribution of the obtained capsule toner was 11.1 μm in volume average particle size.
It was hot. The obtained capsule toner was prepared in Example 1.
It also had good properties. Example 5 In the encapsulation process according to the method described in Example 4, water was added while maintaining the temperature at -5°C during precipitation.
A capsule toner was obtained by gradually dropping the mixture at a rate of 20 ml/min. The particle size distribution of the obtained capsule toner was 12.5 μm in volume average particle size. Example 6 In the encapsulation process according to the method described in Example 4, water was added while maintaining the temperature at -10°C during precipitation.
A capsule toner was obtained by gradually dropping the mixture at a rate of 20 ml/min. The particle size distribution of the obtained capsule toner was 12.1 μm in volume average particle size. Example 7 In the encapsulation process according to the method described in Example 4, acetone was used as a good solvent, and water was gradually added dropwise at a rate of 20 ml/min while maintaining the precipitation temperature at -25°C to obtain a capsule toner. Ta. The mixing enthalpy at this time was 1.2 KCal/mol. The particle size distribution of the obtained capsule toner was 12.6 μm in volume average particle size. Comparative Example 1 In the encapsulation process according to the method described in Example 4, the good solvent was DMF, and the temperature during precipitation was
Water was gradually added dropwise while maintaining the temperature at 10°C to obtain a capsule toner. The mixing enthalpy at this time was 0.6 KCal/mol. The particle size distribution of the obtained capsule toner was 16.5 μm in volume average particle diameter, and as a result of image formation using PC-30, it showed more reverse fog and poorer image density than the capsule toner of Example 4. It was hot. Comparative Example 2 In the encapsulation method described in Example 4, the good solvent was DMF and the temperature during precipitation was -
While maintaining the temperature at 25°C, methyl ethyl ketone (MEK) was gradually added dropwise as a non-solvent to obtain a capsule toner. The mixing enthalpy at this time was 5.1 KCal/mol or more. The particle size distribution of the obtained capsule toner had a volume average particle diameter of 15.8 μm, and a large amount of free shells formed only from shell material were produced as by-products. PC
-30 was used to display the image, Example 4
Compared to the above, there was unevenness on the sleeve, more ground fog, and much poorer image density.

Claims (1)

[Claims] 1. In a method for producing a capsule toner by a phase separation method, a good quality material selected from the group consisting of N-methylpyrrolidone, dimethyl sulfoxide, and dimethylformamide in which the shell material containing a styrene copolymer is precipitated is dissolved. The mixing enthalpy of the solvent and a non-solvent selected from the group consisting of water and alcohol is 5 KCal/mol or less, and the temperature at which the shell material precipitates is -5 to -
A method for producing a capsule toner, which comprises depositing a shell material on the surface of core particles containing at least paraffin wax and polyethylene under a condition of 35°C.