JP2939609B2 - Method for producing electrophotographic toner and toner for electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner and a method for producing the same. In particular, the present invention relates to a method for improving the dispersion of an internal additive such as a colorant and a release agent in a toner.

[0002]

2. Description of the Related Art Toner for electrophotography (hereinafter abbreviated as toner) is prepared by mixing, melting and kneading a binder resin, a colorant, a release agent and, if necessary, a charge controlling agent, and cooling, solidifying, pulverizing and classifying. Can be further obtained, further fluidity imparting agent, charge control agent,
A mixing step of attaching and fixing a cleaning aid or the like to the surface of the toner particles is provided.

In a toner, it is essential that components such as a colorant, a releasing agent, and a charge controlling agent are uniformly and finely dispersed in a binder resin. It is presumed to be determined. If each component is unevenly dispersed in the binder resin, or a state in which the dispersion unit is large even if it is uniformly dispersed, the process after melt-kneading, that is, the pulverizing process, the coloring agent, the mold release, Agent,
Since the toner is pulverized at a portion where the charge control agent is unevenly distributed or a portion where the dispersion unit is large, the toner is pulverized in a state where the toner is exposed or released. Thereby,
A toner having a non-uniform component composition is produced, resulting in a remarkable decrease in the powder fluidity of the toner and a broad charge amount distribution. When the dispersion is remarkably poor, only a single component or particles having uneven composition are mixed in the toner. For example, when the particle component is a release agent, not only the chargeability is significantly different, but also because it is not transferred inside the copying machine, it is rubbed by a cleaning blade and filmed on the photoreceptor, or the developing roll and the charging blade Rubbing between the developer rolls, forming a fibrous shape on the developing roll, which may cause generation of "streaks". When the particle component is a colorant, the color tone of a color toner is impaired. Further, when the colorant is a magnetic powder, so-called free magnetic powder is generated from the aggregates of the magnetic powder and the unevenly distributed portion of the magnetic powder, thereby damaging the surface of the photoreceptor in the copying machine or holding it on the developer carrier. It may accumulate as it is and may cause defects such as uneven density. In addition, pulverization in a portion having a large dispersion unit means that there are particles that are not pulverized until a desired particle size is reached, and the particle size distribution of the pulverized product becomes a broad toner. In particular, when using a low molecular weight polyethylene as a mold release agent, it has been found that a small amount of addition is effective in preventing smudge and further increases the pulverizability, but on the other hand, when the dispersion unit is large, It has the disadvantage that the particle size distribution is very broad.

[0004] In recent years, high image quality, high reliability, and high speed have been demanded for all copying machines, printers, and the like. One of the requirements for toner is a reduction in particle size. When the toner is reduced in particle size, it is required that the dispersion units, uniformity, and particle size distribution of the respective constituent components are more excellent than those of the conventional toner.

As a general kneading apparatus, one having one or more rotary shafts (screw, rotor, roll, etc.) is used, but a screw extruder is used in view of continuous productivity, abrasion resistance and the like. Mainly used. Usually, a screw extruder used for the production of toner is an apparatus as shown in FIG. Two screw shafts, each of which is composed of a combination of a feed screw for mainly transporting raw materials and a kneading disk for kneading, pass through, and a barrel surrounds the periphery thereof. The barrel can be heated and cooled with a heater, water, oil, or the like, and the screw can be cooled with water or the like.

[0006] Toner raw material is supplied from a feed port and sent to a kneading section by a feed screw. At this time, the barrel of the feed screw portion is heated, and the raw material is changed to a molten state while passing through. The melted raw material is filled and kneaded by receiving a shearing force in the kneading section, and then discharged.

The colorant and the charge control agent have a sufficiently high kneading temperature and can be sufficiently wetted and dispersed in a state where the binder resin is completely melted. Is difficult to disperse from the viewpoints that the compatibility with the binder resin is not so good from the beginning, and that the viscosity is very low during kneading, so that the kneading device is hardly sheared. Therefore, the release agent
Even if the dispersion unit remains large or even once finely dispersed, it is discharged in a re-agglomerated state due to the low viscosity state.

Contrary to this case, if the kneading temperature is lowered,
The release agent is sufficiently finely dispersed by being sufficiently sheared by the kneading device, but because the viscosity of the binder resin is too high, the colorant and the charge control agent are hardly wetted. Or, it is discharged from the kneading apparatus in a state where it is unevenly distributed in the binder resin.

As methods for preventing the dispersion unit of the release agent from increasing, Japanese Patent Application Laid-Open Nos.
The method described in -118713 is proposed,
In each case, after the kneading action has been completed, there is no effect if the dispersion unit during kneading is large and non-uniform. Further, the method described in JP-A-4-194869 aims to uniformly disperse the polyolefin in the resin by defining the ratio of the viscosity of the resin to the viscosity of the polyolefin at the kneading temperature. Since attention is paid to those having a size of 10 μm or more, there is a problem as to whether or not a toner having a small particle size can be handled. As described above, in the melt-kneading step, it is still difficult to achieve both the uniform fine dispersion of the release agent capable of coping with the toner having a small particle size and the uniform fine dispersion of the colorant and the charge control agent as other components. In the situation.

[Problems to be solved by the invention]

The present invention has been made to solve the above-mentioned drawbacks. That is, an object of the present invention is to provide a method for producing a toner in which both a release agent and a colorant are uniformly and finely dispersed in a binder resin. Another object of the present invention is to provide a toner in which both a release agent and a colorant are uniformly and finely dispersed in a binder resin, an image having a stable concentration is obtained, and there is no obstacle to a photoreceptor. It is in. Another object of the present invention is to provide a toner having a volume average particle diameter of 4 to 9 μm in which both a release agent and a colorant are uniformly and finely dispersed in a binder resin. It is a further object of the present invention to provide a toner having a sharp volume average particle size of 4 to 9 μm in particle size distribution.

[Means for Solving the Problems]

The method for producing an electrophotographic toner according to the present invention comprises:
A step of melt-kneading an electrophotographic toner material comprising a binder resin, a colorant and a release agent, wherein the step of melt-kneading comprises a feed screw portion and at least one kneading portion. Melt kneading using an extruder, and the screw portion of the extruder has (1) a barrel temperature in a first barrel portion having a feed screw portion and at least a kneading portion;
The discharge port is set so as to be in a range of + 40 ° C. to + 70 ° C. with respect to the melting temperature of the binder resin, and (2) in a second barrel portion including a feed screw portion or a feed screw portion having a kneading portion. The temperature of the kneaded material immediately after is set so as to be in the range of +20 to -30 ° C with respect to the softening point of the release agent. The electrophotographic toner of the present invention is obtained by melt-kneading an electrophotographic toner material comprising a binder resin, a colorant and a release agent using a screw extruder having a feed screw portion and at least one kneading portion. At this time, (1) in the first barrel portion having the feed screw portion and at least the kneading portion, the barrel temperature is set to be in a range of + 40 ° C. to + 70 ° C. with respect to the melting temperature of the binder resin; Also,
(2) In a second barrel portion including a feed screw portion or a feed screw portion having a kneading portion,
The temperature of the kneaded material immediately after the discharge port is +2 with respect to the softening point of the release agent.
Melt kneading by setting to be in the range of 0 to -30 ° C,
Then, it is manufactured by pulverization, and has a volume average particle size of 4 to 9 μm.

The screw extruder used in the present invention has a feed screw section and at least one kneading section, and comprises a first barrel section and a second barrel section. 1 and 2 are schematic views of a screw extruder used in the present invention, in which part A is a first barrel part and part B is a second barrel part. Further, t1 ° C. means the temperature of the first barrel portion, and t2 ° C. means the temperature of the second barrel portion.

In the present invention, as shown in FIG. 1, the screw extruder has a kneading section in the first half. A portion from the kneading portion to the discharge port is basically provided with a feed screw portion. In FIG. 2, a kneading portion is also provided in the second barrel portion.

The toner raw material is supplied from a feed port, and is sent to a kneading section by a feed screw. At this time, the first barrel portion of the feed screw portion is heated to change the toner raw material into a molten state, and is sent to the kneading portion (kneading A in the figure). At this time, the barrel temperature is set at + 40 ° C. to the melting temperature of the binder resin.
It is necessary to set in the range of + 70 ° C. As a result, the binder resin is brought into a molten state, and the colorant and the charge control agent optionally added are subjected to shearing at the kneading portion, and are uniformly and finely dispersed. When the melting temperature of the binder resin is lower than + 40 ° C., the viscosity of the resin is too high, so that the colorant and the charge control agent are hardly wetted, and the dispersion is insufficient. On the other hand, the melting temperature of the binder resin +
If the temperature is higher than 70 ° C., the viscosity of the resin becomes too low, so that the kneading shear force is hardly applied, the dispersion of the colorant and the charge controlling agent does not proceed, the resin itself may be decomposed, and It is not preferable because it is uneconomical in the operation of lowering the temperature of the kneaded material to a desired temperature when adjusting the temperature of the kneaded material in the next stage.

The length of the kneading portion in the first barrel portion is preferably at least 0.07 L or more from the viewpoint of shearing and dispersing when the total screw length is L. However, if the length is extremely long, a portion to be used in the next stage is shortened. Therefore, it is desirable to set the length to a range of 0.15 L or less. The kneading disk of the kneading section includes a disk having a feeding ability, a disk having a return ability, a neutral disk, and the like, and a combination of several kinds thereof can be used. Further, it is also possible to provide a vent port in front of the kneading portion and to bleed air from the toner raw material to increase the filling rate. This makes it easier for the kneading portion to be subjected to shearing more effectively. By these actions, the toner raw material kneaded material that has passed through the kneading portion is in a state where the colorant and the charge control agent are uniformly and finely dispersed.

Next, in the second barrel portion, the temperature at the outlet of the kneaded material is + 20 ° C. to the softening point of the release agent.
Adjust so as to be in the range of −30 ° C. By adjusting / setting the temperature in this range, the shearing force applied by the extruder is effectively applied, and the dispersion unit of the release agent in the kneaded material can be reduced and maintained. If the temperature at the outlet of the kneaded material is set to a temperature higher than + 20 ° C. than the softening point of the release agent, it is difficult to apply shearing, so that the dispersion unit is difficult to be fine, and even if it is fine, Difficult to maintain state. On the other hand, 30 ° C below the softening point
When it becomes lower than, the dispersion unit can be finer,
It is not preferable because the viscosity of the resin becomes too high, the load on the extruder increases, and the dischargeability deteriorates.

As a method of adjusting the temperature at the discharge port of the kneaded material to be in a range of + 20 ° C. to −30 ° C. with respect to the softening point of the release agent, the temperature of the barrel of the extruder is set by cooling or heating. Change, cooling of the screw, and injection of a liquid such as water, ethanol, or methanol into the kneaded material through a nozzle attached to the barrel, and cooling using the latent heat of evaporation. Alternatively, they can be used in combination. Above all, cooling by injection of liquid is particularly effective because heat can be directly removed from the kneaded material. Since there are a plurality of barrels, the injection position and injection position can be arbitrarily selected.

The screw configuration of this part is such that the shear rate: γ (sec ⁻¹ ) represented by the following equation is 2800
If it is within the range of <γ <10000, it is possible to sufficiently disperse the release agent only by stirring in the feed screw. Here, π = pi, D = screw diameter (m
m), N = screw rotation speed (rpm), h = clearance between screw and barrel (mm) Shear rate γ = (π × D × N) ÷ (h × 60)

When it is desired to disperse the release agent more finely,
When it is desired to effectively disperse the release agent by shortening the total screw length, the kneading portion (0.05 L to 0.25 L) in the second barrel portion with respect to the total screw length L is used. In the figure, kneading B) can be provided. If the length is longer than 0.25 L, it is not preferable in terms of cooling for suppressing the temperature of the kneaded material generating heat due to shearing, which is uneconomical. Similar to the kneading portion of the first barrel portion, the kneading disc includes a disc having a feeding ability, a disc having a return ability, a neutral disc, and the like, and these can be used in combination of several kinds.

As described above, by adjusting the temperature of the kneaded material, the release agent in the kneaded material is finely dispersed, and is discharged from the outlet of the kneader without increasing the dispersion unit. Other components, such as the colorant and the charge control agent, which have already been uniformly and finely dispersed, can pass through the second barrel portion without impairing the dispersion state. This makes it possible to obtain a kneaded material in which the dispersion of the release agent and the dispersion of the colorant and the charge control agent are compatible.

The present invention is applicable to both one-component toners and two-component toners. As the binder resin for the toner, any resin that has been conventionally used for toner can be used. For example, synthetic resins such as styrene resin, acrylic resin, olefin resin, diene resin, polyester resin, polyamide resin, epoxy resin, silicone resin, phenol resin, petroleum resin, urethane resin, and natural resin The binder resin having a melting temperature in the range of 110 ° C to 140 ° C can be used. Particularly, a styrene-acrylic resin or a polyester resin is preferable. The melting temperature was determined to be 1 × 10 ⁴ Pa · s on the temperature-apparent viscosity curve.
The temperature at the time. The melt viscosity is a value determined as follows. (Measurement of Melt Viscosity) A temperature-apparent viscosity curve was obtained using a flow tester CFT-500F type (manufactured by Shimadzu Corporation). Heating rate 3.0 ° C / min Starting temperature 80.0 ° C Ultimate temperature 150.0 ° C Measurement interval 3.0 seconds Preheating time 300.0 seconds Cylinder pressure 10.0 kgf / cm ² Die hole diameter 1.0 mm Die length 1.0mm

The releasing agent is preferably a paraffin having 8 or more carbon atoms, polyolefin, or the like. Examples thereof include paraffin wax, paraffin latex, microcrystalline wax, low-molecular-weight polypropylene, low-molecular-weight polyethylene, and the like. These may be used alone or in combination. Can be used. The preferred range of the softening point is 110 ° C to 150 ° C.
It is. In the present invention, when using two or more release agents,
It is preferable to adjust / set the temperature of the release agent having the lowest softening point. (Measurement of softening point) It is a value measured by JIS K-2207 softening point test method (ring and ball method).

Examples of colorants for toner particles include carbon black, nigrosine dye, aniline blue, calcoil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, and lamp. Black, Rose Bengal,
C. I. Pigment Red 48: 1, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 122,
C. I. Pigment Yellow 12, C.I. I. Pigment Yellow 97, C.I. I. Pigment Blue 15: 1,
C. I. Pigment Blue 15: 3 and the like can be exemplified as typical ones.

When used as a magnetic toner, a part or all of the colorant may be replaced with a magnetic substance. As the magnetic material, any known magnetic material that has been generally used can be used.
For example, it is formed of metals such as iron, cobalt and nickel and alloys thereof, metal oxides such as Fe ₃ O ₄ , γ-Fe ₂ O ₃ and cobalt-added iron oxide, and various ferrites such as MnZn ferrite and NiZn ferrite. Things are used. The average particle size of these magnetic materials is generally 0.0
A range of 5 to 0.5 μm is appropriate. In addition, a material which has been subjected to a surface treatment with a silane coupling agent or the like for imparting chargeability and dispersibility can be used. However, in the present invention, the effect is great when the magnetic powder is not treated.

The charge controlling agent that can be added as needed includes fluorine-containing surfactants, metal-containing dyes such as salicylic acid metal complexes and azo metal compounds, and copolymers containing maleic acid as a monomer component. Polymeric acids such as coalescing, quaternary ammonium salts, azine dyes such as nigrosine and the like can be added.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. Example 1 Binder resin: 46% by weight of styrene-n-butyl acrylate copolymer (copolymerization ratio: 82/18, Mw = 150,000, Tg = 58 ° C., melting temperature = 118 ° C.) Magnetic powder: magnetite (uncoated surface) Treatment) 50% by weight (volume average diameter 0.15 μm) Release agent A: Polypropylene wax (softening point: 146 ° C.) 2% by weight Release agent B: Polyethylene wax (softening point: 134 ° C.) 1% by weight Charge control agent: Spy Ron Black TRH (manufactured by Hodogaya Chemical Co., Ltd.) 1% by weight

The above composition was mixed and stirred to obtain a kneaded material. Next, this mixture was kneaded with a screw extruder having a screw configuration shown in FIG. 1 under the conditions shown in Table 1. The temperature of the kneaded material at the outlet at this time was 135 ° C. The obtained kneaded material was rolled and cooled by a water-cooling type cooling conveyor, and then pulverized and classified to obtain a toner having a volume average particle size of about 7 μm. 0.5% silica having an average particle diameter of 16 nm and 0.7% of an average particle diameter of 0.3 μm titania are added to the toner particles as an external additive based on the weight of the toner, and a 5 liter Henschel mixer (Mitsui Miike Koki Co., Ltd.) ) Was mixed for 10 minutes to obtain toner 1. (Measurement of particle size distribution) Measured by Coulter Multisizer II of Coulter Electronics.

Examples 2 to 3 and Comparative Examples 1 to 4 The same toner components as in Example 1 were kneaded by the screw extruder shown in FIG. 2 or 3 under the kneading conditions shown in Table 1. Processing was carried out under the same conditions as in Example 1 to produce Toners 2 to 6 . In Comparative Example 4 , toner could not be produced because continuous kneading was not possible.

[0029]

[Table 1]

With respect to the toners 1 to 6 prepared above, the number of magnetic powder aggregates and the dispersion diameter of the release agent were measured. 10 more
A printing test of about 20,000 sheets was performed in an environment of 15 ° C. and 15% RH. The image quality characteristics after printing 20,000 sheets were evaluated. Table 2 shows the results. (Measurement of the number of magnetic powder aggregates)
Then, a 900-magnification photograph was taken with a transmission electron microscope, and the number of (magnetic powder) aggregates having a diameter or major axis of 5 μm or more in a visual field of 200 μm × 200 μm was counted. (Measurement of Release Agent Dispersion Diameter) Using a cutter such as a microtome, a toner
m, taken with a transmission electron microscope at a magnification of 4500 times, and the particles having the largest diameter, about 100
Each release agent was randomly selected, and the dispersion unit (particle size) was determined by an image analyzer. (Evaluation of image quality characteristics) Regarding the density, the minimum optical density during measurement of 100 sheets is as follows.
1.4 or more: 、, 1.2 to 1.4: ○, 0.8 to 1.2
△, × means 0.8 or less. The adhesion of the photoreceptor and the scratches on the photoreceptor were evaluated by observing the surface of the photoreceptor after printing 20,000 sheets. ◎ means very good, ○ means good, and × means bad.

[0031]

[Table 2]

[0032]

According to the present invention, the temperature is controlled as described above using a screw extruder having a portion for dispersing the colorant and a portion for dispersing the release agent. A toner in which each of the release agent and the colorant is uniformly and finely dispersed can be obtained. Therefore, the obtained toner has an excellent particle size distribution, does not hinder the photoreceptor, and continuously provides an image having a stable density.

[Brief description of the drawings]

FIG. 1 is an example of a screw extruder used in the present invention.

FIG. 2 is another example of the screw extruder used in the present invention.

FIG. 3 is an example of a screw extruder used in a conventional production method.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-6-266159 (JP, A) JP-A-6-188713 (JP, A) JP-A-6-161153 (JP, A) JP-A-5-161153 JP-A-5-72806 (JP, A) JP-A-1-161255 (JP, A) JP-A-4-81772 (JP, A) JP-A-1-137267 (JP, A) JP-A-3-86224 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/08

Claims (5)

(57) [Claims] 1. A method for producing an electrophotographic toner, comprising a step of melt-kneading an electrophotographic toner material comprising a binder resin, a colorant and a release agent, wherein the step of melt-kneading comprises at least a feed screw portion and Melt kneading using a screw extruder having one kneading part, and the screw part of the extruder comprises (1) a first screw having a feed screw part and at least a kneading part.
In the barrel portion, the barrel temperature is set to be in a range of + 40 ° C. to + 70 ° C. with respect to the melting temperature of the binder resin, and (2) a feed screw portion or a feed screw portion having a kneading portion A second barrel portion, wherein the temperature of the kneaded material immediately after the discharge port is set so as to be in a range of +20 to -30 ° C with respect to the softening point of the release agent; Method. 2. The length of the kneading portion in the first barrel portion is from 0.07 to 0.07 times the total screw length.
The method for producing an electrophotographic toner according to claim 1, wherein the ratio is 15 times. 3. A liquid is added from the outside in the second barrel portion of the screw extruder so that the temperature of the kneaded material immediately after the discharge port is in the range of +20 to -30 ° C. with respect to the softening point of the release agent. The method for producing an electrophotographic toner according to claim 1, wherein: 4. An electrophotographic toner material comprising a binder resin, a colorant and a release agent is melt-kneaded using a screw extruder having a feed screw part and at least one kneading part. (1) In the first barrel portion having the feed screw portion and at least the kneading portion, the barrel temperature is +4 with respect to the melting temperature of the binder resin.
Set to be in the range of 0 ° C to + 70 ° C, and
(2) In a second barrel portion including a feed screw portion or a feed screw portion having a kneading portion,
The temperature of the kneaded material immediately after the discharge port is +2 with respect to the softening point of the release agent.
Melt kneading by setting to be in the range of 0 to -30 ° C,
Next, an electrophotographic toner having a volume average particle size of 4 to 9 μm, which is manufactured by pulverizing. 5. The electrophotographic toner according to claim 4, wherein two or more release agents are used.