JPH07244399A - Production of electrostatic charge image developing toner - Google Patents

Abstract

PURPOSE:To prevent the deterioration of toner performance such as the deterioration of image quality at the time of taking photograph by making a toner spherical without heat processing. CONSTITUTION:This producing method has a pulverizing process for a toner material containing a resin and a coloring agent, and the pulverized toner is surface ground by an impact grinder to make the toner spherical. That is, the pulverized toner obtained in the pulverizing process is introduced into the impact grinder having grinding zone 4 formed between the outside surface of a rotor 1 rotating around a rotary shaft 2 and the inside surface of a liner 6. The corners or projections of breakage surface of the toner particle, which are generated by the collision of the toner particle with each other or with the wall surface of the a pulverizer, are removed or buried into the toner main body by surface grinding to make the shape spherical. The outside surface of the rotor 1 and the inside surface of the liner 6 has corrugated acute angled grinding blades. As a result, the producing method simple in the process and free from the thermal damage of the toner is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of producing an electrostatic charge image developing toner 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 image includes mixing raw materials such as a resin and a colorant, kneading them, passing through a cooling step, finely pulverizing with a jet mill or the like, and classifying them. For example, the process of making the shape spherical is performed. The purpose of this spheronization step is to improve the decrease in fluidity caused by the shape of the toner particles that have been mechanically destroyed in the pulverization step and have an irregular shape having a large number of protrusions. This spheronization step is generally carried out by passing the toner particles after classification through a high-temperature atmosphere in which the toner surface softens or melts, but the number of steps increases, and the toner particles whose surfaces are softened or melted adhere and aggregate. As a result, various problems occur such as generation of coarse particles and deterioration of toner performance due to heat.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method capable of adjusting the shape of toner particles into a spherical shape without applying heat treatment to the toner. That is, the object of the present invention is to make the toner spherical without heat treatment,
Not only the fluidity is improved, but also the generation of coarse particles due to the adhesion and aggregation of particles, the change in the particle size distribution, and the deterioration of the image quality during actual copying caused by the deterioration of the thermally weak chemical components in the toner components. Another object of the present invention is to provide a method for producing a toner, which achieves the prevention of the performance deterioration of

[0004]

SUMMARY OF THE INVENTION The object of the present invention, however, is to provide a method for producing a toner for developing an electrostatic charge image, which comprises a step of pulverizing a toner material containing a resin and a colorant.
After the pulverization, the pulverized toner is surface pulverized by an impact type pulverizer to make it spherical, which is achieved by adopting a production method.

The present invention will be described in detail below. In the toner manufacturing method of the present invention, an ordinary manufacturing method can be adopted except for the spheroidizing step. As a usual manufacturing method, first, toner raw materials are mixed, kneaded by a melt extruder or the like, extruded in a plate shape, cooled and solidified to obtain a toner material.
As the toner raw material, a resin and a colorant are used as essential components, but if necessary, for example, a charge control agent or another toner property imparting agent can be used.

As the resin, for example, various known resins suitable for toner can be used. For example, styrene resin, vinyl chloride resin, rosin-modified maleic acid 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 can be mentioned. These resins can be used in combination of two or more kinds. In particular, it is preferable to use a styrene resin, a saturated or unsaturated polyester resin and an epoxy resin as the main resin.

The glass transition temperature of the resin preferably has a transition start temperature (inflection point) of 50 ° C. or higher when measured by a thermal analysis method (indicative thermal analyzer, suggestive scanning calorimeter, etc.). . 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 agglomerates or adheres, which causes a problem in use. As the toner colorant, various known colorants can be used, and for example, carbon black, nigrosine, benzidine yellow, quinacridone, rhodamine B, phthalocyanine blue, etc. are preferably used. Colorant is resin 1
It is usually used in an amount of 0.1 to 30 parts by weight, preferably 3 to 15 parts by weight, per 00 parts by weight.

As the charge control agent, various known charge control agents can be used. Examples thereof include positive charge control agents such as quaternary ammonium salts, nigrosine dyes, triphenylmethane dyes, styrene-aminoacrylate copolymers and polyamine resins, and negative charge control agents such as monoazo metal complex salts. The charge control agent is usually used in a proportion of 0.1 to 10 parts by weight per 100 parts by weight of the resin.

Further, as various toner characteristic imparting agents,
For example, in order to prevent offset, a polyalkylene wax such as polyethylene wax or polypropylene wax can be used. Further, in order to improve fluidity and aggregation resistance, inorganic fine particles such as titania, alumina and silica can be used. These toner property imparting agents are usually used in an amount of 0.1 to 1 per 100 parts by weight of the resin.
Used in a proportion of 0 parts by weight.

Further, when the toner is a magnetic toner, ferrite, magnetite, iron, cobalt,
Magnetic particles such as alloys or compounds containing ferromagnetic elements such as nickel can be contained. The magnetic particles are usually used in a proportion of 20 to 70 parts by weight per 100 parts by weight of the binder resin. Next, the toner material is pulverized by a known pulverizer so that the weight average particle diameter is preferably in the range of 20 μm or less. Here, the weight average particle size is a median value particle size of particle size-weight distribution, for example,
It can be measured with a Coulter Electronics Coal Counter. The above crushing step can be performed by a single crusher, but it is also preferable to appropriately combine various crushers and perform crushing in two or more stages.
In the usual toner manufacturing method, a rough milling process using a hammer mill, peel mill, screen mill, free crusher, feather mill, etc., jet mill, impact crusher, fluidized bed type counter jet mill, fine mill, etc. are used. The crushing process is performed in two steps, the intermediate crushing process using an impact crusher, ACM pulsarizer, kryptron, pin mill, etc. is provided between the coarse crushing process and the fine crushing process, and the crushing is performed in three steps. A crushing process such as a process to be performed is exemplified.

In the present invention, the pulverized toner thus obtained is introduced into an impact type pulverizer having a pulverization region formed between the outer surface of the rotor rotating about the rotation axis and the inner surface of the liner, and the toner is Surface crushing that removes the corners and protrusions generated on the fracture surface of the particles generated by volume crushing (crushing that the particles themselves are largely broken) due to collision of particles with each other and collision of the toner particles with the crusher wall surface Is achieved by making the shape spherical. Figure 1
An example of the impact type crusher used in the present invention is shown in FIG.

Conventionally, various shapes of the rotor and liner of the impact type crusher have been proposed. For example, the rotor has a turbine blade shape by embedding a flat plate and the liner has irregular projections, or the rotor. Those having uneven projections on the outer surface and the inner surface of the liner (JP-A-59-105853), and those having a wavy, sharp, acute-angle crushing blade on both the outer surface of the rotor and the inner surface of the liner (JP-A-59-59). No. 127651)
However, as the impact type pulverizer used in the present invention, one having a corrugated acute-angle pulverizing blade on one or both of the outer surface of the rotor and the inner surface of the liner is preferably used. As an example, FIG. 2 shows a case where both have corrugated acute-angle crushing blades.

The gap in the crushing area formed between the rotor and the liner of the impact crusher is preferably 0.1 to 8 m.
m. The gap means the distance between the crest of the rotor crushing blade and the crest of the liner crushing blade. The operating conditions of the impact type crusher are appropriately selected, but the rotational peripheral speed of the rotor is 50 to 180 m / s, and especially 60 to 160 m / s.
Is preferred. Further, in order to prevent the generation of coarse particles and the deterioration of toner performance as described above, the ambient temperature (T) in the crushing area is set to the glass transition temperature (T) of the resin contained in the toner.
It is preferably lower than g), and more preferably a Tg-T value of 8 ° C or higher. Examples of the method of adjusting the temperature in the crushing area include controlling the temperature of the air flowing into the crusher, controlling the feed amount of the crushing toner, and controlling the temperature of the wall surface around the crushing area.

Further, particularly when an impact type crusher is used in the final step of the crushing process, continuous crushing and spheroidizing with one impact type crusher can be mentioned as a mode of the present invention. . However, since the conditions for volume pulverization and the conditions for surface pulverization are different, it is necessary to appropriately adjust the conditions depending on the type of toner. Further, for example, there is a method in which after the volume pulverization is sufficiently performed, the pulverized toner is further retained to pulverize the surface of the pulverized toner. At this time, the residence time of the pulverized toner in the pulverization area is set to be sufficiently longer than that in normal pulverization by using a rotor that is sufficiently long in the rotation axis direction or by reducing the amount of inflowing air that conveys the toner. It should be long.

The crushing area of one impact crusher may be set so as to have a portion where volume crushing is performed and a portion where surface crushing is performed. In such a case, it is sufficient that at least a part of the crushing area is under the condition that the surface crushing is performed, and the condition of the other crushing area is not particularly limited. Specific methods include partially changing the rotational peripheral speed of the rotor, and partially changing the gap in the crushing region using a stepped rotor, a tilted rotor, a stepped liner, a tilted liner, or the like.

The impact type crusher used in the present invention may be a horizontal type as shown in FIG. 1 or a vertical type. In the toner manufacturing method of the present invention, substantially, the toner material is first subjected to volume pulverization and then surface pulverization. Therefore, before supplying the pulverized toner to the impact type pulverizer, a classifying means is provided to coarsely pulverize and finely pulverize. Including a step of separating the objects is also included as one embodiment. Further, as described above, even when crushing and spheroidizing are continuously performed by one impact crusher, a classifying step may be appropriately provided at an intermediate stage thereof.

The toner spheroidized by the above-mentioned pulverizer and discharged from the discharge port is then subjected to a normal classification treatment to recover a toner having a predetermined particle diameter of about 3 to 20 μm, preferably 5 to 15 μm. As the classifier, various classifiers such as an airflow classifier (DS classifier manufactured by Nippon Pneumatic Co., Ltd.), a multi-product simultaneous classifier utilizing the Coanda effect (Elbow Jet manufactured by Nippon Steel Mining Co., Ltd.), a zigzag classifier, etc. Can be adopted. Then, the obtained classified coarse powder and classified fine powder having a particle size other than the predetermined particle size can be recycled by being recycled to the manufacturing process. For example, the classified coarse powder can be recycled to the crushing step for re-crushing, and the classified fine powder can be recycled together with the raw material powder for use in the mixing step and the melt-kneading step.

The toner obtained as described above is further subjected to the step of externally adding various known external additives, and then filled in a predetermined container to be manufactured.

[0019]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. (Example 1)

[0020]

[Table 1] Styrene acrylate copolymer resin 100 parts (softening point 145 ° C, glass transition point 64 ° C) Colorant carbon black MA100 6 parts (manufactured by Mitsubishi Kasei Co., Ltd.) Low molecular weight polypropylene viscol 550P 1 part (Sanyo Kasei Co., Ltd. )) Charge control agent quaternary ammonium salt Bontron P-51 2 parts (manufactured by Orient Chemical Co., Ltd.)

Flakes (average particle size of about 300 μm) obtained by mixing, mixing, kneading and coarsely crushing are mixed with a first-stage impact crusher (turbo mill manufactured by Turbo Industry Co., Ltd.) at a speed of 10 kg / h. (T-250RS type), the temperature of the atmosphere in the crushing region is 50 ° C or less, the number of rotations of the rotor is 13000 rpm (peripheral speed is 171 m / s), the gap between the rotor and the liner is 2 mm, and then the second-stage impact crusher (No. Rotor speed is 11000 rp with the same model as the first crusher)
Sphericalization was performed under the same conditions as in the first step, except that the speed was changed to m (peripheral speed 144 m / s). Then, the obtained toner is classified by an elbow jet classifier (EJ-LABO type),
A product toner particle group having an average particle size of 9.0 μm was obtained. At this time, the practical sphericity defined by the following equation

[0022]

[Equation 1]

A value of 0.88 was obtained by calculating from the micrograph. Further, the fluidity of a toner obtained by mixing 100 parts by weight of this product toner with 0.2 part by weight of silica powder (R972 of Nippon Aerosil Co., Ltd.) was measured by an opening method, and a good value of 15 mmφ was obtained. Obtained. 4 parts by weight of the above toner and 100 parts by weight of a carrier having a ferrite powder as a core material were mixed to form a developer, and an actual copying test was conducted using a copying machine having an organic photoconductor as a photoconductor.
As the replenishment toner in the actual copying test, the same toner as that used for the above developer was used. The result of the live-shooting test was that there was no fog, a high gradation image was obtained, and the live-shooting quality was good. In addition, there was no other inconvenience in use.

Comparative Example 1 A toner product having an average particle size of 9.0 μm was obtained by using the same coarsely pulverized toner as in Example 1 and using a jet pulverizer (I-10 manufactured by Nippon Pneumatic Co., Ltd.). The practical sphericity was 0.82, which was worse than that of the toner obtained in Example 1. Further, the fluidity of the product added with 0.2 parts of silica is 17 mmφ,
It was found that Example 1 was also improved in terms of fluidity. Further, when the addition amount of silica was adjusted to show the same fluidity as in Example 1, 0.50 parts by weight was required, and it was confirmed that in Example 1, sufficient fluidity can be obtained with a small amount of silica added. It was

(Comparative Example 2) A toner was prepared in the same manner as in Example 1 except that the atmosphere temperature in the crushing area of the second-stage impact crusher was 64 ° C.
Coarse particles were generated, and there was a problem that the raw material supply part in the next classification step was clogged. The shape index is 0.
89, 0.2 parts by weight of silica has a fluidity of 15 mmφ
The same spheronization effect as in Example 1 was obtained, but this method is a method of spheroidizing by softening or melting the toner surface, and the spheroidizing method is essentially different from Example 1.
Further, due to the influence of the coarse particles, the gradation in the image quality at the time of actual copying is inferior, and fog is also generated due to the thermal history of the toner, which is inferior to that in Example 1.

[0026]

According to the present invention described above, there is provided a method of spheroidizing a toner for developing an electrostatic charge image, which has a low fog phenomenon and provides a good image quality. The process is simple and the toner is thermally damaged. The production value of the present invention is provided, and the industrial value of the present invention is remarkable.

[Brief description of drawings]

FIG. 1 is a sectional view of an example of a crusher used in the present invention.

FIG. 2 is a sectional view taken along line AA in FIG.

[Explanation of symbols]

 1 rotor 2 rotating shaft 3 crushing blade on outer surface of rotor 4 crushing area 5 crushing blade on inner surface of liner 6 liner 7 supply port 8 discharge port 9 stirring blade 10 stirring blade 11 gap

Claims (7)

[Claims] 1. A method of producing a toner for developing an electrostatic charge image, which comprises a step of pulverizing a toner material containing a resin and a colorant, wherein after pulverizing, the pulverized toner is surface-pulverized by an impact type pulverizer to be spherical. And manufacturing method. 2. The manufacturing method according to claim 1, wherein the atmospheric temperature (T) in the crushing region of the impact crusher is lower than the glass transition temperature (Tg) of the resin contained in the toner. 3. The manufacturing method according to claim 2, wherein Tg-T is 8 ° C. or higher. 4. The manufacturing method according to claim 1, wherein the crushed toner has a weight average particle diameter of 20 μm or less. 5. The method according to claim 1, 2, 3 or 4, wherein one or both of the outer surface of the rotor and the inner surface of the liner of the impact type crusher has a corrugated sharp-angle crushing blade. 6. The rotating peripheral speed of the rotor is 50 to 180 m /
s, Claims 1, 2, 3, 4 or 5
The manufacturing method described in. 7. The gap in the crushing area of the impact crusher is less than 0.
It is 1-8 mm, Claims 1, 2, 3,
The manufacturing method according to 4, 5, or 6.