JPS6161627A - Method for sphering toner - Google Patents

Abstract

PURPOSE:To improve the fluidity and blocking resistance by pulverizing the roughly crushed material of a toner composition in a moment in the spiral flow of air at ultrahigh speed whose temp. is regulated to an appropriate temp., softening the surface of a toner binding resin and sphering the material. CONSTITUTION:50pts.wt. styrene. acryl resin, 50pts.wt. magnetite, 2pts.wt. low mol.wt. polypropylene, and 0.5pts.wt. calcium stearate are premixed by a Henschel mixer. The mixture is melted and kneaded by a biaxial extruder at 150 deg.C, and allowed to cool in the air to obtain a kneaded material. The material is crushed in a cutting mill to prepare a roughly crushed material 2 having <= about 3mm mean grain diameter. Said roughly crushed material 2 is charged at 30 deg.C and 70% humidity into a pulverizing zone 13 at a rate of 45kg/hr along with influent air 3 at 15 deg.C, and pulverized. The obtained pulverized toner is classified into particles having 12mum mean particle diameter and uniform particle size distribution.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for spheronizing a toner, in particular, a coarsely pulverized toner composition is pulverized simultaneously, and at the same time, the surface of the toner is spheroidized, thereby improving the fluidity of the toner. This invention relates to a method for spheroidizing toner that can significantly improve blocking resistance.

(Prior Art) Toner for electrophotography is manufactured in one, for example, three-dimensional manner. First, the binder resin 1 colorant or magnetic material and other moving agents are melted and dispersed using a kneading device such as a heated roll, a mixer, or a niegu, and then the kneaded composition is allowed to cool. Next.

This is coarsely pulverized using a hammer mill, cutting mill, thalassoher, etc., then finely pulverized using a jet mill, etc., and classified if necessary. The above-mentioned pulverization using a jet mill is a mechanical pulverization method in which the coarsely pulverized material is introduced into a high-pressure jet stream, and is collided with the air stream against a collision plate to be pulverized.

Therefore, the fractured surface of the toner inevitably becomes irregular in shape and has many protrusions. This is particularly noticeable in the case of magnetic toner containing a hard magnetic material such as magnetite in a proportion as high as about 50% by weight.

Therefore, the fluidity of the toner becomes extremely poor.

For example, when these toners are used alone or mixed with a carrier to form a magnetic brush on a developing sleeve, lumps may form on the sleeve surface. Toner particles adhere unevenly to the sleeve surface. This causes blur or white smudges in the copied image. In order to improve the fluidity of such toner, silica powder is added as a lubricant to the toner. However, the silica powder attached around the toner migrates to the photoreceptor, resulting in fogging or the like on the copied image. Furthermore, these toners may damage the surface of the photoreceptor due to their protrusions. Therefore, after pulverization, the toner is usually spheroidized using hot air. However, the spheroidization process using hot air is performed at a temperature at which the resin surface of the toner melts. Therefore,
The resin surface is melted, making the toner particle size and magnetic force non-uniform.

Furthermore, spheroidization using hot air requires large equipment and requires a large amount of thermal energy.

Toner production costs increase.

(Object of the Invention) The object of the present invention is to provide a method for spheroidizing toner that has excellent fluidity and anti-blocking property by simultaneously pulverizing and spheroidizing the surface without using hot air treatment or impact abrasion methods. There is a particular thing. Another object of the invention is that it requires less energy consumption.

The object of the present invention is to provide a method for spheronizing toner at low cost. Still another object of the present invention is to provide a method for easily and continuously forming toner into spheres.

(Structure of the Invention) In preparing a toner with excellent fluidity and anti-blocking property, the present invention instantaneously pulverizes the toner in an ultra-high-speed air flow, and at the same time maintains the temperature at the time of pulverization at an appropriate level. It was completed based on the novel concept of softening the surface of the binder resin of the toner and making it spherical by controlling the toner. Therefore, (1) the toner spheroidizing method of the present invention consists of: (1) a coarsely pulverized toner composition containing a binder resin and a colorant as main components; (2) A step of pulverizing the coarsely pulverized material by means of air flow and pressure vibration of the air in the pulverizing region.

(3) While the coarsely pulverized material is being pulverized, the atmospheric temperature in the pulverizing region is adjusted to around the glass transition temperature of the binder resin of the coarsely pulverized material, thereby at least the surface of the resulting pulverized material. and (4) spherical cough? A step of discharging the pulverized product as toner together with air from the pulverization region to the outside of the system is included, thereby achieving the above object.

(Example) The present invention will be described below with reference to examples.

The toner used in the toner spheronization method of the present invention is as follows.

Main ingredients are binder resin and colorant. As the binder resin, all resins commonly used in this field can be used.

For example, styrene/acrylic resin.

Polyester resin, etc. As a coloring agent.

In addition to black pigments such as carbon blank, colored pigments may also be used. Additionally, magnetic materials can be used as pigments, such as magnetite and gamma hematite.

Nickel ferrite or the like is used. In addition to the above-mentioned essential components, various auxiliary agents may be added to the toner as necessary. For example, charge control agents such as nigrosine base, silicone oil, low molecular weight polypropylene or
It is a mold release agent for various waxes, etc.

The above components are mixed in a predetermined ratio, and the mixture is melt-kneaded using, for example, a Miki thermal roll mill or a twin-screw extruder.

The obtained kneaded product is cooled at room temperature. These are then coarsely ground into particles having an average particle size of about 3 mm or less using a cutting mill or a hammer mill. This coarsely pulverized toner composition is pulverized and simultaneously spheronized in accordance with the method of the present invention using, for example, a spheronizing device 1 shown in FIG. 1 to obtain a desired toner.

The spheronization device 1 includes a cylindrical casing 11 and a rotor 12 disposed within the casing 11 coaxially with the casing axis. A plurality of grooves are provided in the liner 110 on the inner peripheral surface of the casing 11 in the direction of the rotor shaft 120. The rotor 12 is provided with a plurality of blades 121 made of a wear-resistant metal material or the like. Between the liner 110 and the rotor blade 121, there is a space of a suitable size (for example, a gap of several dragons), and the pulverization region 13
is formed. The high-speed rotation of the rotor blades 121 generates an ultra-high-speed air flow in the pulverization region 13 and high-frequency pressure vibrations generated thereby. The generation of air turbulence and pressure oscillations is effectively enhanced by the grooves of the liner 110.

On the upstream side of the casing 11, an inlet 111 for the coarsely pulverized toner composition 2 and inflow air 3 is provided.

The input port 111 is connected to an external device such as a powder feeder, a cooling blower, or a heater. A swirl chamber 112 is provided below the input port 111. The rotor blade 1 near this swirl chamber 112
21 contains the input coarsely ground material 2 and/or the incoming air 3.
A distributor 122 is appropriately provided for evenly distributing the powder into the pulverizing region 13.

A discharge port 113 is provided on the downstream side of the casing 11,
It is connected to an external device such as a cyclone collector or a bag filter. As such an apparatus 1, 2, for example, a Turbo Mill manufactured by Turbo Kogyo Co., Ltd. may be employed.

The coarsely pulverized toner composition 2 introduced into the spheronizing device 1 is continuously pulverized as follows.

At the same time, it becomes spherical. Coarsely pulverized material 2 having an average particle size of about 3 yen or less is continuously introduced together with inflowing air 3 from an input port 111 at an appropriate speed. What is the temperature of incoming air 3?

The ambient temperature in the finely pulverized region 13 is set in advance to be around the glass transition temperature of the binder resin of the coarsely pulverized toner composition 2 . The temperature T of this inflowing air 3 is expressed by the linear formula (
1): T=(Tg-ΔT)±5
...(1) Here, T is the inflow air temperature (℃), Tg
is the glass transition temperature (℃) of the toner binder resin, and ΔT
ranges from about 45°C to 55°C in elevated temperatures (°C).

The coarsely ground material 2 and the incoming air 3 are fed into the swirl chamber 112.
, and the distributor-1
22, and the particles are evenly distributed in the pulverization area 13. The coarsely pulverized material 2 in this pulverization region 13 is instantaneously pulverized by ultrahigh-speed air flow and pressure vibration. Since temperature-controlled inflow air 3 is constantly supplied into the pulverization region 13 from the inlet 111, a rapid temperature rise is suppressed despite the generation of frictional heat during pulverization, and the toner binding resin is maintained near the glass transition temperature of .

When the glass transition temperature of the binder resin is high, the inflowing air 3 is heated by a heater (not shown) or the like as necessary and then introduced into the pulverization region 13. In this way, the binder resin is maintained near the glass transition temperature, so that the protrusions that appear on the fractured surface of the finely pulverized toner are softened and removed, resulting in a finely pulverized toner 20 that is appropriately spherical. It will be done. The rotational speed of the rotor 12 is set in advance to, for example, 5,000 to 11,000 rpm so that the average particle size of the spherical finely pulverized toner 20 is 5 μm to 15 μm. The spherical finely pulverized toner 20 is discharged from the discharge port 113 together with the air 30.
is discharged from the system. At this time, the temperature near the discharge port 113 is about 40°C to about 50°C or less. Next, the spherical pulverized toner 20 is appropriately separated from air 30 and collected by an outside system, for example, a cyclone dust collector.

When a magnetic substance is used as the colorant, the magnetic substance can be uniformly dispersed on the surface of the obtained spherical finely pulverized magnetic toner 20 without being unevenly distributed in the binder resin.

A specific example of this embodiment will be described below.

First, styrene/acrylic resin (glass transition temperature Tg;
66°C) 50 parts by weight, magnetite (particle size 0.3μIl)
l~0.9μ deviation; bulk specific gravity 0.46g/tal)
50 parts by weight.

Two parts by weight of low molecular weight polypropylene and 0.5 parts of calcium stearate were premixed in a Henschel mixer. This was further melt-kneaded at 150° C. using a twin-screw extruder, and then allowed to cool. This kneaded product was coarsely pulverized using a cutting mill so that the average particle size was approximately 3.5 mm or less.

This coarsely pulverized product 2 was pulverized under five types of pulverization conditions shown below.

Based on the comparison, the coarsely pulverized material 2 was charged into the pulverizing region 13 of the apparatus 1 together with room temperature air at a rate of 45 kg per hour under an environment of a room temperature of 30° C. and a humidity of 70%. The rotation speed of the rotor 12 was set to 7000 rpa+. Fine grinding area 13
As the atmospheric temperature within the pulverization zone 13 rose to 80.degree. C., the toner adhered to such an extent that it became impossible to continue operating the apparatus 1.

It was found from Comparative Example 1 that the atmospheric temperature within the pulverization region 13 of the apparatus 1 increased by about 50°C.

Fine pulverization was carried out under the same pulverization conditions as in Comparative Example 1, except that the temperature of the air 3 flowing in above the extracted blood was cooled to 15°C. The atmospheric temperature within the pulverization area 13 was 65°C. The obtained finely pulverized toner was classified so that the average particle size was 12 μm and the particle size distribution was constant. The spheroidization of the classified finely pulverized toner was measured using a powder tester (manufactured by Line Micron Co., Ltd.). The specific gravity (bulk specific gravity) of the loose appearance is 0.60. The apparent hardening had a specific gravity (tap specific gravity) of 0.81 and a degree of sphericity of 25.9%. The spherical shape of the finely ground toner particles was confirmed by microscopic observation. Next, 30 g of the obtained finely pulverized toner was put into a drop tester 4 shown in FIG.
was rotated for 5 minutes, and the amount of toner falling at that time was examined.

The amount of toner falling was 6.9 g in 15 minutes, and it was confirmed that the toner had extremely good fluidity. Blocking resistance was also good. The results are shown in the table below. The degree of sphericity in the table is determined by the following equation (2). The smaller the displayed value, the higher the degree of sphericity.

Degree of Spheroidization (%) Fine pulverization was performed under the same conditions as in Example 1 except that the room temperature was 5° C. and the temperature of the inflowing air 3 was heated to 15° C. with a heater. The atmospheric temperature in the pulverization area 13 is as in Example 1.
The temperature was <65°C. below.

The same results as in Example 1 were also obtained regarding the degree of sphericity, fluidity, and blocking resistance of the toner.

The results are shown in the table below.

Fine pulverization was carried out under the same conditions as in Example 1, except that the main room temperature was 5° C. and the inflow air 3 was room temperature air. The atmospheric temperature within the pulverization region 13 rose to 50°C. The obtained finely pulverized toner was classified in the same manner as in Example 1, and the degree of 2-spheroidization was examined. The specific gravity of the loose appearance is 0.56, and the specific gravity of the hardened appearance is 0.79.

The degree of sphericity was 29.1%. Both values were inferior to those of Example 1 and Example 2. Microscopic observation revealed that these toner particles contained toner particles that did not have a spherical shape. Furthermore, in the same manner as in Example 1,
The amount of toner falling was investigated.

The value was 6.6 g/5 minutes, and compared to Examples 1 and 2, the fluidity was inferior. A slight amount of toner blocking was also observed. The results are shown in the table below.

几1u11 The coarsely ground material 2 used in Example 1 was milled using a conventional jet mill (1
The toner was pulverized using a type jet mill (manufactured by Nippon Pneumatic Kogyo Co., Ltd.) and classified in the same manner as in Example 1 to obtain a pulverized toner. The spherical shape of this slightly shaped toner was determined by the fact that the apparent looseness had a specific gravity of 0.48 and the apparent hardened specific gravity had a specific gravity of 0.70. Example 2 and Comparative Example 2
was found to be inferior to finely ground toner. When the finely pulverized toner particles were observed under a microscope, it was found that there were toner particles that were not unispherical. moreover.

The falling amount of this finely pulverized toner was examined in the same manner as in Example 1, and the value was 5.9 g/5 minutes.

Example 1. It was found that the fluidity was inferior to the finely pulverized toners of Example 2 and Comparative Example 2. Furthermore, toner blocking was observed. The results are shown in the table below.

(Margin below) (Effect of the invention) According to the toner spheroidization method of the present invention, as described above.

By pulverizing the coarsely pulverized toner composition in a turbulent flow of air at an appropriately controlled temperature, the surface of the toner becomes spherical, and an electrophotographic toner with excellent fluidity can be continuously prepared. . Moreover, even when a magnetic substance is contained as a colorant, the d-type substance can be uniformly dispersed on the surface of this finely pulverized toner. As a result, the copied images obtained using this toner are extremely clear without image unevenness. The bronking resistance of the toner is also improved. Furthermore, according to the present invention, toner can be supplied at low cost because the toner can be processed easily and continuously using a device with such a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a front cross-sectional view of essential parts showing an embodiment of the apparatus used in the spheronization method of the present invention, and FIG.
FIG. 2 is a perspective view of an apparatus used in an experiment to examine the fluidity of toner obtained by the spheronization method. DESCRIPTION OF SYMBOLS 1... Spheronization device, 2... Coarsely pulverized toner composition, 3... Inflowing air, 4... Fall amount tester, 11.
...Casing, 12... Rotor, 13... Finely pulverized region, 20... Spheroidized finely pulverized toner, 30.
... Air, 41 ... Roller +, 110 ... Liner, 111 ... Inlet, 112 ... Vortex chamber, 11
3...Discharge port, 120...Rotor shaft, 121...
・Blade, 122...Distributor - 0 or more

Claims (1)

[Claims] 1. (1) A step of continuously introducing a coarsely pulverized toner composition containing a binder resin and a colorant as main components into a pulverizing region together with temperature-controlled incoming air. , (2) finely pulverizing the coarsely pulverized material by air overflow and air pressure vibration in the pulverizing region; (3) reducing the atmosphere within the pulverizing region while pulverizing the coarsely pulverized material; a step of softening at least the surface of the resulting finely pulverized material to make it spherical by adjusting the temperature to around the glass transition temperature of the binder resin of the coarsely pulverized material; and (4) sphericalized pulverized material. A method for spheronizing toner, comprising: discharging the toner from the pulverization region to the outside of the system together with air. 2. The first aspect of the present invention is that the atmospheric temperature in the pulverization area is adjusted by the temperature of the incoming air and the amount of coarsely pulverized material.
The toner spheronization method described in Section 1. 3. The toner spheroidization method according to claim 1, wherein the temperature of the inflowing air is controlled according to the following formula: T=(Tg-ΔT)±5, where T is the inflowing air temperature (°C ), Tg is the glass transition temperature (°C) of the toner binder resin, and ΔT is the rising temperature (°C
) in the range of about 45°C to 55°C.