JP2004167491A - Method for manufacturing electrostatic charge image developing toner and apparatus for pulverizing and classifying toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a toner which has little inclusion of coarse particles and makes it possible to obtain good image quality. <P>SOLUTION: The method for manufacturing the electrostatic charge image developing toner comprises pulverizing a coarsely pulverized toner containing at least a resin and coloring matter, then classifying the same. The pulverization is performed by introducing the coarsely pulverized toner into a mechanical pulverizer having a rotor rotating around a revolving shaft and having rugged parts on its outer surface, a liner fitted to the outer side of the rotor and having rugged parts on its inner surface, and a pulverizing space formed between the outer surface of the rotor and the inner surface of the liner. The classification is performed by a simultaneous classifying machine for multiple products utilizing a Coanda effect. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a method for producing a toner for developing an electrostatic charge image used in an electrophotographic method, an electrostatic recording method and the like, and a pulverizing and classifying apparatus for the toner.

  Conventionally, a method for producing a toner for developing an electrostatic image has been conducted by mixing and kneading raw materials such as a resin and a colorant, and after passing through a cooling step, for example, coarsely pulverizing with a hammer-type pulverizer or the like. A method of pulverizing the product, followed by preliminary pulverization, if necessary, or direct pulverization to obtain a pulverized product having an average particle size of several μm to about several tens μm has been adopted. This pulverized product is separated into only particles having a predetermined particle size distribution in a classification step, and is used as a toner for developing an electrostatic image.

Conventionally, as a pulverizer for pulverizing the coarse pulverized material, a jet-type pulverizer utilizing supersonic jet airflow is used in a space formed between a rotor (rotor) rotating at a high speed and a stator (liner). An impact-type crusher or the like that crushes by introducing a crushed product is mainly used. As the classifier, an air classifier (DS classifier manufactured by Nippon Pneumatic Co., Ltd.), a multi-product simultaneous classifier (Elbow Jet manufactured by Nittetsu Mining Co., Ltd.), a zigzag classifier, and the like are used.

  As an industrial-scale facility, a production line is usually composed of a combination of one or two pulverizers and two to four classifiers.

  By the way, in such a method for producing a toner, it is difficult to efficiently produce the toner by finely pulverizing the coarsely pulverized toner using a jet pulverizer because the power consumption is large and the energy efficiency is low. On the other hand, the impact-type pulverizer has high energy efficiency, but has a problem that instantaneous heat generation at the time of pulverization is large and coarse particles of, for example, 40 μm or more are mixed in the toner pulverized product. In the subsequent classification process, the coarse particles are removed by a vibrating sieve or the like as much as possible.However, since the particles collide with the inner wall of the classifier and bounce off or jump into the product side with probability, the coarse particles passing through the sieve are removed. It gets mixed in. Then, there is a problem that bad phenomena such as filming and comet occur in the image quality due to the presence of the mixed coarse particles.

  The present inventors have conducted intensive studies in order to solve the above-mentioned problems.As a result, in the step of pulverizing the coarsely pulverized toner, the outlet of the impact type pulverizer was devised to be mixed into the product remarkably. The present inventors have found that the amount of coarse particles is reduced, and have reached the present invention. That is, an object of the present invention is to provide a method for producing a toner having a sharp particle size distribution with less generation of coarse particles in a toner product. Another object of the present invention is to provide a method for producing a toner capable of giving good image quality without causing bad phenomena such as filming and comet. Another object of the present invention is to provide a method for producing a toner which is energy-efficient and consumes very little power in addition to a simple apparatus configuration.

Accordingly, an object of the present invention is to provide a method for producing a toner for developing an electrostatic image by crushing a coarsely crushed toner containing at least a resin and a colorant, and then classifying the crushed material. A rotor having an uneven portion on the outer surface, and a liner fitted on the outer side and having an uneven portion on the inner surface, and a crushing space formed between the outer surface of the rotor and the inner surface of the liner. Wherein the coarsely pulverized toner is introduced into a mechanical pulverizer having the above-mentioned method, and the classification is performed by a multi-product simultaneous classifier utilizing the Coanda effect. Achieved by

  Further, an object of the present invention is an apparatus that pulverizes and classifies a coarsely pulverized toner containing at least a resin and a colorant, and that rotates around a rotation axis and has a concavo-convex portion on an outer surface; An impact-type pulverizer which has a liner which is fitted on the outside with a space therebetween and has an uneven portion on the inner surface, and a gap between the rotor and the liner is a pulverization space; This is achieved by using a pulverizing and classifying apparatus for toner, which comprises a multi-product simultaneous classifier used.

  According to the present invention, it is possible to provide a method for producing a toner having a sharp particle size distribution with few coarse particles on an industrial production scale with a simple apparatus configuration.

  Hereinafter, the present invention will be described in detail. In the toner production method of the present invention, an ordinary production method can be adopted except for the pulverization and classification steps. As a usual production method, first, toner raw materials are mixed, kneaded by a melt extruder or the like, extruded into a plate shape, and cooled and solidified pellets are obtained. As a toner raw material, a binder 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 resin, vinyl chloride resin, rosin-modified maleic resin, phenol resin, epoxy resin, polyester resin, polyethylene resin, polypropylene resin, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl acrylate resin, xylene Resin, polyvinyl butyral resin, polycarbonate resin and the like. 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.

As for the glass transition temperature of the binder resin, the transition start temperature (inflection point) when measured by a thermal analysis method (indicative thermal analyzer, indicative scanning calorimeter, or the like) is preferably 50 ° C. or more. When the glass transition temperature is lower than 50 ° C., when the toner is left at a high temperature of 40 ° C. or higher for a long time, the toner may be aggregated or fixed, which causes a problem in use.
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 used in an amount of usually 0.1 to 30 parts by weight, preferably 3 to 15 parts by weight, per 100 parts by weight of the resin.

  As the charge control agent, various known charge control agents can also be used. For example, a positive charge control agent such as a quaternary ammonium salt, a nigrosine dye, a triphenylmethane dye, a styrene-aminoacrylate copolymer, and a polyamine resin, and a negative charge control agent such as a monoazo metal complex salt are exemplified. The charge control agent is used usually in a ratio of 0.1 to 10 parts by weight per 100 parts by weight of the resin.

  As various toner property imparting agents, for example, polyalkylene wax such as polyethylene wax and polypropylene wax can be used to prevent offset. In addition, inorganic particles such as titania, alumina, and silica can be used to improve fluidity and coagulation resistance. 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, it can contain magnetic particles such as ferrite, magnetite, and alloys or compounds containing ferromagnetic elements such as iron, cobalt, and nickel. 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. Next, the pelletized toner solidified by cooling is coarsely pulverized by a coarse pulverizer such as a hammer type pulverizer so that the weight average particle diameter is approximately in a range of about 100 μm to 3000 μm, and preferably about 300 μm. Here, the weight average particle size is a median value particle size of a particle size-weight distribution, which can be measured by, for example, a Coulter Electronics Co., Ltd. call counter.

  In the present invention, in the step of further pulverizing the thus obtained coarsely pulverized toner, the coarsely pulverized toner is introduced into an impact-type pulverizer having a specific improved outlet, and the weight average particle diameter is from several μm to several tens μm. And preferably pulverized to 3 to 20 μm. It is also possible to use two or more impact-type pulverizers or to combine them with a jet-type pulverizer in order to increase the pulverization efficiency.

  As shown in Fig. 1, the principle of the impact type pulverizer is that a cylindrical rotor (1) rotating at a rapid speed by a rotating shaft (3) and a fixed or rotating liner (2) outside the rotor are minute. The material to be pulverized is placed through a charging port (4) and transported through a pulverizing space, which is a minute gap (8) separated by a rotor (1) and a liner (2). In the process of being discharged and discharged from the discharge port (5).

Irregular portions (crushing blades) are provided on the outer surface of the rotor and the inner surface of the liner of the impact-type crusher, and various shapes have been proposed, but the impact-type crusher used in the present invention. Particularly, as shown in FIG. 2, those having a corrugated acute-angle pulverizing blade on at least one of the outer surface of the rotor and the inner surface of the liner, preferably both, are preferably used.
By the way, in the conventional pulverizer, as shown in an enlarged view of the outlet portion of the pulverizing space in FIG. 3, the liner length is usually longer than the rotor length by about 10 to 20 mm at the outlet portion. there were. However, as a result of investigations by the present inventors, it has been found that the generation of coarse particles is mainly caused by uneven grooves at the outlet of the liner. By smoothing at least a part of the surface of the liner on the outlet side, that is, by providing a smooth portion having no irregularities (grooves) provided on the surface of the liner, coarse particles mixed into the product are markedly reduced. It has been found that the number decreases. Probably, in the conventional structure, at the outlet portion of the crushing space where the temperature of the object to be crushed is the highest and the speed at which the inside of the machine moves rapidly drops, the outlet portion of the liner, particularly the groove (uneven portion) at the extension portion, It is considered that the toner powder melted and softened due to the heat generated during the pulverization was adhered, and grew to generate coarse particles.

  Various methods are conceivable as a method for providing a smooth portion on at least a part of the surface of the liner at the outlet of the pulverizing space according to the present invention. As one of them, as shown in FIG. 4, a smooth portion is formed on the surface in the range of 0.1 mm to 200 mm, preferably 10 mm to 100 mm, and more preferably 40 mm to 70 mm (a + b in FIG. 4) from the final end of the liner. The provided shape is mentioned. As shown in FIG. 4, it is preferable that the smooth portion has a planar shape in which the uneven portion is removed. Further, it is preferable that not only the surface of only the extending portion of the liner be made smooth, but also the surface of the liner facing the surface of the rotor be made smooth. It is particularly preferable that the smooth portion is formed in the range of 0.1 mm to 100 mm, preferably 10 mm to 70 mm, and 30 to 50 mm (a) from the final end of the opposing rotor in the direction of the inlet. Note that the preferable range of the smoothing portion varies depending on the size of the apparatus.

The gap (8) provided between the rotor and the liner is usually several mm or less, but is 0.1 mm to 5 mm, preferably 0.3 to 3.0 m for use in the toner manufacturing method of the present invention.
m, more preferably in the range of 0.5 to 2.5 mm, 1.0 to 2.0 mm. This gap means the distance between the peak of the rotor crushing blade and the peak of the liner crushing blade.
Other operating conditions of the impact-type pulverizer are appropriately selected, but the ambient temperature is preferably 30 to 50 ° C., and the rotation speed of the rotor is preferably 50 to 180 m / s, and more preferably 60 to 140 m / s. The toner that has been processed by the above-described pulverizer and discharged from the discharge port is then subjected to a normal classification process to collect toner having a predetermined particle size of about 3 to 20 μm, preferably 5 to 15 μm.

As a classifier, it is preferable to employ a multi-product simultaneous classifier (Elbow Jet manufactured by Nippon Steel Mining Co., Ltd.) utilizing the Coanda effect, in particular, because coarse, medium, and fine powders can be simultaneously and accurately separated. Then, the obtained coarse powder and fine powder having a particle size other than the predetermined particle size can be circulated and reused in the production process. For example, the coarse powder can be circulated to the pulverizing step and re-pulverized, and the fine powder can be circulated and used together with the raw material powder in the mixing step and the melt kneading step.

  The toner obtained as described above further undergoes a step of externally adding various known external additives, and then is filled into a predetermined container to be commercialized.

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 unless it exceeds the gist of the present invention.
(Example 1)

(Table 1)
100 parts of styrene acrylate copolymer resin (softening point 145 ° C, glass transition point 64 ° C)
Colorant carbon black MA100 6 parts (Mitsubishi Kasei Co., Ltd.)
1 part of low molecular weight polypropylene biscol 550P (manufactured by Sanyo Chemical Co., Ltd.)
Charge control agent Quaternary ammonium salt Bontron P-51 2 parts (Orient Chemical Co., Ltd.)
Flakes obtained by mixing, kneading and coarsely pulverizing (average particle size of about 300 μm) impact at a speed of 200 kg / h and having an outlet portion in which the outlet portion of the pulverizing space is improved as shown in FIG. A pulverizer (Turbo Kogyo Co., Ltd., Turbo Mill T-800RS) is used to perform pulverization at an ambient temperature of 50 ° C. or less and a rotor (rotary body) rotation speed of 3200 rpm, and thereafter, the pulverized product is subjected to an elbow jet classifier (EJ-45). -3S type) to obtain a group of product toner particles having an average particle diameter of 10 μm.

  At this time, the generation rate of coarse particles having a particle size of 40 μm or more contained in the pulverized product before classification was 0.07%, and the generation rate of coarse powder generated by the conventional pulverizer shown in Comparative Example 1 without improvement was 0.28%. Was 1/4. 4 parts of the toner obtained by this method and 100 parts of a carrier having ferrite powder as a core material were mixed and stirred, and a real copying test was performed on the obtained developer using a copying machine using an organic photoconductor as a photosensitive member. . The toner for replenishment used in the actual test was the same toner as the toner used for the developer.

As a result, the actual image quality such as copy density and fogging was good, and there was no occurrence of filming, comet, etc., and the toner and developer were excellent in quality.
(Comparative Example 1) In the same manner as in Example 1 except that the same coarsely pulverized toner as in Example 1 was used, and an impact-type pulverizer in which the outlet of the pulverizing space was not improved as shown in FIG. A toner product was obtained.

At this time, the generation rate of coarse particles of 40 μm or more contained in the pulverized product before classification was 0.28%. A real-image test was performed using this toner in the same manner as in Example 1. As a result, fog and black spots were frequently generated, and the image quality was unsatisfactory.
(Example 2)

(Table 2)
100 parts of styrene acrylate copolymer resin (softening point 145 ° C, glass transition point 64 ° C)
5.5 parts of colorant carbon black # 30 (Mitsubishi Chemical Corporation)
2 parts of low molecular weight polypropylene biscol 550P (manufactured by Sanyo Chemical Co., Ltd.)
Charge control agent Quaternary ammonium salt Bontron P-51 2 parts (Orient Chemical Co., Ltd.)
The flakes (average particle size of about 300 μm) obtained by mixing, kneading and coarsely pulverizing are mixed at a speed of 200 kg / h to improve the outlet portion of the pulverizing space as shown in FIG. Pulverization is performed in an atmosphere temperature of 50 ° C. or less and a rotor (rotating body) rotation speed of 3300 rpm using a turbo mill T-800RS (trade name, manufactured by Turbo Industries, Ltd.), and then the pulverized product is subjected to an elbow jet classifier (EJ-45-3S). To obtain a product toner particle group having an average particle diameter of 10 μm.

  At this time, the rate of generation of coarse particles of 40 μm or more contained in the pulverized product before classification was 0.07%, and the rate of generation of coarse powder generated by the conventional unimproved pulverizer shown in Comparative Example 2 was 0.24%. Was 1/3. 4 parts of the toner obtained by this method and 100 parts of a carrier having ferrite powder as a core material were mixed and stirred, and a real copying test was performed on the obtained developer using a copying machine using an organic photoconductor as a photosensitive member. . The toner for replenishment used in the actual test was the same toner as the toner used for the developer.

As a result, the actual image quality such as copy density and fogging was good, and there was no occurrence of filming, comet, etc., and the toner and developer were excellent in quality.
(Comparative Example 2) The same procedure as in Example 2 was carried out except that the same coarsely pulverized toner as in Example 2 was used, and an impact-type pulverizer in which the outlet of the pulverizing space was not improved as shown in FIG. A toner product was obtained.

  At this time, the generation rate of coarse particles of 40 μm or more contained in the pulverized product before classification was 0.24%. A real-image test was performed using this toner in the same manner as in Example 1. As a result, fog and black spots were frequently generated, and the image quality was unsatisfactory.

FIG. 1 is a schematic cross-sectional view of a general impact-type pulverizer. FIG. 2 is an enlarged view of a vertical section of a rotor and a liner of an AA line of the impact crusher of FIG. 1. Cross-sectional enlarged view of the crushing space outlet of a conventional impact crusher An example of an enlarged cross-sectional view of a pulverizing space outlet of an impact type pulverizer of the present invention

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Rotor 2 Liner 3 Rotating shaft 4 Inlet 5 Outlet 6 Liner uneven part 7 Rotor uneven part 8 Crushing space

Claims (10)

  After pulverizing a coarsely pulverized toner containing at least a resin and a colorant, the method for producing a toner for developing an electrostatic image by classifying the pulverized product, wherein the pulverization rotates around a rotation axis and has an uneven portion on an outer surface. Coarse toner pulverization by an impact type pulverizer having a rotor, a liner fitted on the outside thereof and having an uneven portion on the inner surface, and a pulverization space formed between the outer surface of the rotor and the inner surface of the liner. Wherein the classification is performed by a multi-product simultaneous classifier utilizing the Coanda effect.   2. The method according to claim 1, wherein a smooth portion is provided on at least a part of a surface of the liner at a toner outlet of the pulverizing space.   3. The method according to claim 2, wherein a smooth portion of the liner projects from the rotor.   The method for producing a toner for developing an electrostatic image according to any one of claims 1 to 3, wherein at least one of an outer surface of the rotor and an inner surface of the liner has a sharp crushing blade having a wavy shape.   The method according to any one of claims 1 to 4, wherein a gap provided between the rotor and the liner is 0.1 to 5 mm.   An apparatus for crushing and classifying a coarsely pulverized toner containing at least a resin and a colorant, the rotor being rotated about a rotation axis and having an uneven portion on an outer surface, and fitted with a space outside the rotor. And an impact-type pulverizer having a liner having an uneven portion on the inner surface, wherein a gap between the rotor and the liner is a pulverizing space, and a multi-product simultaneous classifier utilizing the Coanda effect. And a pulverizing and classifying apparatus for toner.   The pulverizing and classifying apparatus for toner according to claim 6, wherein a smooth portion is provided on at least a part of a surface of the liner at a toner outlet of the pulverizing space.   8. The pulverizing and classifying apparatus for toner according to claim 7, wherein a smooth portion of the liner protrudes from the rotor.   The toner classifier according to any one of claims 6 to 8, wherein at least one of the outer surface of the rotor and the inner surface of the liner has a corrugated acute-angle pulverizing blade. The apparatus according to any one of claims 6 to 9, wherein a gap provided between the rotor and the liner is 0.1 to 5 mm.

Images