JPH11109678A - Method for classifying toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for classifying a toner by which a satisfactory toner is obtd. SOLUTION: A group of fine particles which are smaller than a prescribed particle diameter range are removed from powder stock of a toner, a group of coarse particles which are larger than the prescribed particle diameter range are then removed and a group of particles which are in the prescribed particle diameter range are obtd. At the time of removing the fine particles, a gas flow type classifier is used. In the classifier, the fine particles are sucked into a rotating rotor 1 with plural slits 2 by sucking gas from the inside of the rotor 1 and supplying the powdery stock and the gas accompanied by the powdery stock from the outside of the rotor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for classifying a toner for developing an electrostatic image used in electrophotography, electrostatic recording and the like.

[0002]

2. Description of the Related Art Conventionally, a method for producing a toner for developing an electrostatic charge image includes mixing and kneading raw materials such as a resin and a colorant, finely pulverizing with a jet mill or the like after a cooling step, and then subjecting the mixture to a target product particle size range A classification operation for removing particles (coarse particles) and fine particles (fine particles) larger than a predetermined particle size range) is performed, and if necessary, an additive is added.

In this classification process, usually two or more classifiers are combined, and coarse particles are removed first, and then fine particles are removed by the second and subsequent classifiers. This is because when the same raw material weight is treated with a classifier, the number of particles introduced into the classification point, which is the division of fine powder and coarse powder in the classifier, is overwhelmingly large in the process of removing fine particles, and Since the classification accuracy is deteriorated in proportion to the raw material concentration in the apparatus, that is, the processing amount, it is general to first classify coarse particles and reduce the load of the subsequent fine particle classification process.

[0004]

However, between the step of classifying coarse particles and the step of classifying fine particles, coarse particles are usually once removed from a tank or a container in order to balance mass between apparatuses. It is necessary to accumulate the raw material powder thus obtained and supply it again to a process for removing fine particles through a metering device.

[0005] During the accumulation, particles having a product particle diameter and fine particles in the powder raw material are compressed by their own weight and aggregated. Particularly, in the case of a toner having a low softening point, the aggregated fine particles are mixed into the product side during classification in the next step. And lowers product quality. In order to avoid this, the condition of the classifier is changed in the direction of removing more fine powder from the product, but as a result, the product yield decreases.

[0006] Even when the two classifiers are directly connected by means of pneumatic transportation or the like without passing through a tank or a container as described above, coagulation may occur during transportation.
A similar failure occurs. To solve these problems,
If it is attempted to remove coarse particles after removing fine particles first, the amount of raw material supplied to a classifier for classifying fine powder increases compared to the above-described process, and the size of the apparatus must be increased. It was not realistic because the utility costs such as increased.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for classifying a toner for developing an electrostatic image, in which the fine powder as described above is removed first and then the coarse powder is removed. In order to realize the process, the classification of the first stage can be performed even with a small classifier with high efficiency by adopting a classification device with a rotating rotor, in particular, and the classification with little inclusion of fine particles in the product is achieved. Is done.

That is, the gist of the present invention is to classify and remove a group of fine particles finer than a predetermined particle size range from a powder material of a toner, and then classify and remove a group of coarse particles larger than a predetermined particle size range.
A method for classifying toner to obtain a group of particles having a predetermined particle size range, wherein, when classifying and removing the group of fine particles, a gas is sucked from the inside of a rotating rotor having a plurality of slits, and the toner powder is powdered from the outside of the rotor. The present invention provides a method for classifying a toner, which comprises using a gas flow classifier that classifies particles by sucking fine particles into a rotor by supplying a raw material and a gas accompanying the raw material.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As a process for producing toner particles in the present invention, a usual production method can be adopted. As a normal manufacturing method, first mix the toner raw materials,
The mixture is kneaded by a melt extruder, extruded into a plate, cooled and solidified, pulverized and classified, and then an additive is added to obtain a toner material. As the toner raw material, a resin and a colorant are used as essential components. For example, a charge control agent or another toner property imparting agent can be used as necessary.

As the binder resin, for example, various known resins suitable for toner can be used. For example, styrene resins (styrene homopolymer, styrene-acrylate copolymer, styrene-methacrylate copolymer), vinyl chloride resin, rosin-modified maleic resin, phenol resin, epoxy resin, polyester resin, polyethylene resin, polypropylene resin , An ionomer resin, a polyurethane resin, a silicone resin, a ketone resin, an ethylene-ethyl acrylate resin, a xylene resin, a polyvinyl butyral resin, and a polycarbonate resin. Two or more of these resins can be used in combination.

In particular, it is preferable to use a styrene resin, a saturated or unsaturated polyester resin and an epoxy resin as the main resin. In recent years, a binder resin having a softening point and a glass transition point lower than usual is often used for a monocolor toner and a full color toner, but when a binder resin having a softening point and a glass transition point lower than usual is used, In particular, a fine powder having a particle size smaller than the product particle diameter is likely to be coagulated and mixed into the powder having a product particle size. In such a case, the present invention is particularly effective. However, if the softening point and the glass transition point are too low, the image quality may be deteriorated, and the toner may cause blocking during storage.
Softening point is 80-120 ° C, especially 80-110 ° C,
Glass transition point is 40-80 ° C, especially 40-70 ° C
It is preferred that

The softening point of the binder resin which is a thermoplastic resin is measured by using a flow tester method. In a flow tester (CFT500 manufactured by Shimadzu Corporation), the diameter is 1 mm.
Using a nozzle having a length of 10 mm, the heating body is set at 80 ° C., and 1 g of the binder resin is charged. After lightly pressing the plunger and heating for 300 seconds, a pressure of 30 kg / cm ² is applied, and the temperature is raised at a rate of 6 ° C./min. The binder resin is softened by the temperature rise, the binder resin is extruded from the nozzle, and the plunger descends. The softening point is defined as the temperature corresponding to the midpoint of the plunger descent distance from the start to the end of the descent.

The glass transition point of the binder resin, which is a thermoplastic resin, is determined by a differential thermal analyzer (DT-30, manufactured by Shimadzu Corporation).
Approximately 20 mg of a binder resin is put into a sample cell, set in a measuring section, and once heated at a rate of 10 ° C./min.
After heating to 10 ° C. and cooling to room temperature, the temperature was raised again at 10 ° C./min. A tangent was drawn from each of the smooth curves before and after the inflection point of the DTA curve, and the glass transition was determined by the intersection of the tangents. Point.

As the colorant for the toner, various known colorants can be used. For example, carbon black,
Nigrosine, benzidine yellow, quinacridone, rhodamine B, phthalocyanine blue and the like are preferably used. The colorant is usually 0.1 to 100 parts by weight of the resin.
It is used in a proportion of 30 parts by weight, preferably 3 to 15 parts by weight. As the charge control agent, various known charge control agents can also be used. For example, positive charge control agents such as quaternary ammonium salts, nigrosine dyes, triphenylmethane dyes, styrene-aminoacrylate copolymers, polyamine resins, and negative charge control agents such as monoazo metal complex salts and metal alkylsalicylate compounds. Can be The charge controlling agent is usually 0.1 to 10 per 100 parts by weight of the resin.
Used in parts by weight.

Further, as various toner property imparting agents,
For example, polyalkylene wax such as polyethylene wax and polypropylene wax can be used to prevent offset. In order to improve fluidity and coagulation resistance, inorganic fine particles such as titania, alumina, and silica can be used as an internal additive or an external additive. These toner property imparting agents are generally used in a ratio of 0.1 to 10 parts by weight per 100 parts by weight of the resin.

Further, when the toner is a magnetic toner, ferrite, magnetite, iron, cobalt,
Magnetic particles such as an alloy or a compound containing a ferromagnetic element such as nickel can be contained. The magnetic particles are generally used in a proportion of 20 to 70 parts by weight per 100 parts by weight of the binder resin. After mixing and kneading the above-mentioned toner raw materials, the cooled and solidified pellet-shaped toner has a weight average particle size of about 10% by a coarse crusher such as a hammer crusher.
Coarse pulverization is performed so as to be in the range of 0 to 3000 μ, preferably about 300 μ. Here, the weight average particle size is a median value particle size of a particle size-weight distribution, and can be measured by, for example, a Coulter counter manufactured by Coulter Electronics.

As a device for mixing raw materials, a device having rotating parts such as blades and screws in the machine, for example, a Henschel mixer manufactured by Mitsui Mining Co., Ltd., a Ladige mixer manufactured by Matsubo, a Nauta mixer manufactured by Hosokawa Micron, a super mixer manufactured by Kawata Or a general V-type mixer in which the container itself rotates. As the kneading device, a continuous extruder such as a ZSK type extruder manufactured by W & P, BU
It can also be used for general batch-type kneaders such as SS Kneader, Toshiba Kikai TEM extruder, Ikegai PCM extruder, Mitsui Mining Co., Ltd. Kneedex.

As a cooling device, a drum cooler manufactured by Mitsui Mining Co., Mitsubishi Chemical Engineering Co., Ltd., a belt cooler manufactured by NBC, or the like can be used. Examples of crushers include NPK I-type and IDS-type jet mills and Hosokawa Micron A
Jet mills such as FG / TJM, Hosokawa Micron's Hammer Mill, Fitz Mill, Feather Mill, Inomaizer, ACM Pulverizer, Turbo Mill's Turbo Mill, Kawasaki Heavy Industries' KTM, Nisshin Engineering's Super Rotor, NPK's Fine Mill Using an impact-type pulverizer such as the above, pulverization is performed stepwise to a predetermined toner particle size.

On the other hand, as a toner particle forming step other than the above, after mixing the monomer before polymerizing the binder resin and the other toner raw materials described above, the mixture is dispersed in a dispersant such as water and polymerized. The toner particles may be formed by polymerized toner technology. In a normal toner manufacturing method, in the above pulverized product or polymer,
The order of removing finer and coarser than the target product particle size range is as follows: first remove coarse particles, then remove fine particles, so that product particles and fine particles smaller than product particle size aggregate due to increased surface area Then, the amount of raw material supplied to the fine powder removing step, which increases the load on the classifier, has been reduced to ensure the required classification accuracy.

In the present invention, instead of the above-described order, fine particles are first removed, and agglomeration between product particles and fine particles generated between the coarse particle removal process and the fine particle removal process is prevented, so that a high yield and high yield can be achieved. It is possible to obtain a high-quality product with less mixing of fine powder. Also, even if agglomeration occurs between the fine particle removal process and the coarse particle removal process in the present invention, the agglomerates are also removed together with the subsequent coarse particle removal process, so that no agglomerates are mixed into the product. preferable.
If fine particles are removed in the second stage as in the prior art, such agglomerates are not removed.

As a first-stage classifier for removing fine particles smaller than a target product particle diameter range in the above-mentioned pulverized product or polymer, a rotary machine having a plurality of slits 2 as shown in FIG. By using a gas flow classifier that sucks gas from the inside of the rotor 1 and supplies the powdery material of the toner and the gas accompanying the same from the outside of the rotor 1, the fine particles are sucked into the rotor 1 and classified. And, for example, Alpine /
Hosokawa Micron TSP, Nisshin Engineering Turbo Classifier, Condax / Mitsui Mining C
FS-HD, Donaldson made by Donaldson, or the like can be used.

In particular, in the classifier used in the first stage, a spiral guide ring 8 that does not contact the rotor 1 is provided along the circumference of the surface of the rotary rotor 1 so that all the classifying materials are not short-passed. It can surely pass through the classification zone formed on the surface of the rotating rotor 1. The spiral guide 8 is effective because the classification zone on the surface of the rotating rotor 1 can be used evenly by turning the surface of the rotor 1 one or more times. The number of windings depends on the rotor length, but if the number of windings is too large, the pressure loss when suctioning gas increases, and a sufficient air volume cannot be obtained, or a larger suction device is required. , Usually 2
About 5 to about 5 turns are preferable.

In the case of the air-flow classifier used in the present invention, the pressure at the outlet of the small particles (fine powder outlet 6) is larger than that at the outlet of the large particles (coarse powder outlet 7). If a coarse particle group is removed using an air-flow classifier in the classification, the fine powder outlet 6 with a large suction pressure is connected to the second classifier. It is necessary to provide a tank, a fixed-rate feeder, etc. in front of the eye classifier, and cut off the system of pressure reduction. In comparison, if the fine particle group is removed in the first stage of classification, the coarse powder outlet 7 with a small suction pressure is connected to the second stage of the classifier, but in that case, it is not necessary to cut off the system. Since it is possible to directly connect to the second classifier without using a hopper or the like, the apparatus can be simplified. Furthermore, agglomeration that occurs during accumulation in the tank or container can be eliminated.

As a classifier for removing coarse powders in the second and subsequent stages, an air classifier having the above-mentioned rotary rotor is preferable. A DS / DSX classifier manufactured by NPK, a Nippon Mining Co., Ltd. All airflow classifiers generally used in the production of toner such as an elbow jet classifier and a micron separator manufactured by Hosokawa Micron can be used. The above-described devices are combined in two or more stages, and the weight average particle size is 3 to
A toner of 15 μm, preferably 3 to 10 μm is obtained. The toner coarse powder generated in the classification step may be returned to the pulverization step or the first-stage fine particle group classification step and reused. The toner fine powder can be reused by returning to the raw material mixing / kneading step.

When the toner is externally added, a predetermined amount of the classified toner and various known external additives are blended, and the mixture is stirred by a high-speed stirrer such as a Henschel mixer or a super mixer which applies a shearing force to the powder. Good to mix. At this time, since heat is generated inside the external additive machine and aggregates are easily generated, it is preferable to adjust the temperature by means such as cooling the periphery of the external additive container section with water. The internal material temperature is preferably lower than or equal to a control temperature about 10 ° C. lower than the glass transition temperature of the resin.

In order to remove foreign matter and coarse particles, sieving is performed using a vibrating sieve such as a gyro shifter or a Sato type vibrating sieve or a rotary sieve such as a turbo screener, and then filled into a predetermined container to produce a product. Is done.

[0027]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the present invention. Example 1 100 parts by weight of a polyester resin (bisphenol A derivative) I. Pigment Yellow Y-93 3 parts by weight Alkyl salicylic acid metal compound 5 parts by weight is blended, mixed, kneaded, and coarsely pulverized. After that, TSP (325T made by Alpine)
(SP: having a spiral guide), the material after removing the particles of 5 μm or less is temporarily stored in a tank, and the particles of 16 μm or more are removed using the same type of TSP via a quantitative feeder, and the average particle size is 8 0.0 μm product group was obtained.

A toner material obtained by mixing 0.2 parts by weight of silica powder (Nippon Aerosil Co., Ltd. R972) with 100 parts by weight of the toner product was sieved with a 150-mesh vibrating sieve. When the content of particles having a particle size of 5 μm or less in this product toner was measured, it was found to be an extremely sharp particle size distribution of 10% in number frequency and extremely high resolution and high gradation with no fog or toner scattering at the time of actual shooting evaluation. was gotten.

Comparative Example 1 The same equipment as in Example 1 was used, except that the order of the classification step was changed, and particles of 16 μm or more were first removed. When the content of particles having a particle size of 5 μm or less was measured under exactly the same conditions except that the particles were removed, the content frequency was 17% and the content of the fine powder component was higher than that of Example 1;
At the time of actual shooting, defects such as fogging and toner scattering, which are considered to be caused by these particle groups, were observed.

Example 2 100 parts by weight of styrene acrylate copolymer 6 parts by weight of carbon black 1 part by weight of low molecular weight polypropylene 1 part by weight of quaternary ammonium salt 2 parts by weight were blended, and mixed, kneaded, crushed and classified in the same manner as in Example 1. First, after removing particles of 5 μm or less, 20 μm
The above particles were removed to obtain a product group having an average particle size of 9.2 μm. This toner product was mixed with silica powder and sieved in the same manner as in Example 1 except that the amount of silica powder was 0.8 parts by weight and a 200-mesh sieve was used. When the content of particles having a particle size of 5 μm or less in the toner obtained in this example was measured, the distribution was extremely sharp at 11% in terms of the number frequency.
At the time of the actual shooting evaluation, an extremely high-resolution and high-gradation image without fogging and toner scattering was obtained. The product yield at this time was 82%.

Comparative Example 2 The same equipment as in Example 2 was used, but the order of the classification step was changed. First, particles of 20 μm or more were removed, and then particles of 5 μm or less were removed. 5 μm or less under the same classification conditions because particles of 5 μm or less were mixed in the product
The following particle content is higher in number frequency than in Example 2 by 15%
Met. When the classification conditions were changed to the same content as in Example 2, the product yield was 74%, 8% as compared with Example 2.
Dropped.

[0032]

According to the present invention described above, fog and
A method for classifying a toner for developing an electrostatic image, which provides good image quality with little phenomenon such as toner scattering and high product yield, is provided, and the industrial value of the present invention is remarkable.

[Brief description of the drawings]

FIG. 1 is an example (cross-sectional view) of an airflow classifier having a rotating rotor used in the present invention.

[Explanation of symbols]

 Reference Signs List 1 rotating rotor 2 slit 3 powder supply port 4 gas supply port 5 shaft 6 fine powder outlet 7 coarse powder outlet 8 spiral guide

Claims (4)

[Claims] The present invention relates to a toner that obtains a particle group having a predetermined particle size range after classifying and removing fine particle groups finer than a predetermined particle size range from a powdery raw material of a toner, and then classifying and removing coarse particle groups coarser than a predetermined particle size range. A classifying method, in which when removing a class of fine particles, a gas is sucked from the inside of a rotating rotor having a plurality of slits, and a toner powder material and a gas accompanying the gas are supplied from the outside of the rotor. A method of classifying a toner by using an air flow classifier that classifies particles by sucking the particles into a rotor. 2. An airflow classifier has a spiral guide that is not in contact with the rotor on the outer periphery of the rotor, and classifies fine particles while rotating the powdery material of the toner around the rotor along the guide. The method for classifying a toner according to claim 1, wherein: 3. A method of classifying and removing a coarse particle group, wherein a gas is sucked from the inside of a rotary rotor having a plurality of slits, and a powdery toner material and a gas accompanying the gas are supplied from the outside of the rotor. 3. The method for classifying toner according to claim 1, wherein an air-flow type classifier is used to suction and sort particles having a predetermined particle size range into the rotor. 4. A pneumatic classifier used for classifying and removing coarse particle groups has a spiral guide which is not in contact with the rotor on the outer periphery of the rotor, and the powder material of the toner after the fine particle group is classified along the guide. 4. The method for classifying toner according to claim 3, wherein the classifying of the coarse particles is performed while rotating the particles around the rotor.