JP2007271820A - Method for manufacturing electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing electrophotographic toner which is good in fogging property, image quality and durability by improving the dispersibility of toner internal additives without requiring a pigment masterbatch. <P>SOLUTION: The method for manufacturing the electrophotographic toner comprises: a step of mixing materials including a binder resin, a colorant, a release agent and a charge control agent; a step of melt-kneading the material mixture with an open kneading machine; a step of pulverizing a kneaded product after solidification by cooling; and a step of classifying pulverized powder, wherein at the mixing step, water in an amount of 10-50 mass% is added to the materials. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an electrophotographic toner, and more particularly, to a method for producing an electrophotographic toner having good fog characteristics, image quality, and durability.

  In general, image formation by electrophotography is performed by developing and visualizing an electrostatic image with charged toner, and transferring and fixing the toner image obtained by development onto a sheet. As a method for producing such a toner used for image formation, there are a pulverization method, a polymerization method, and the like. In general, the pulverization method dominates.

  A general production method of the pulverization method is to mix raw materials such as a binder resin, a colorant, a release agent, and a charge control agent in a dry manner, then melt and knead with a twin-screw extruder or the like, and after cooling and solidifying, Crushing is performed to obtain a kneaded crushed material. Thereafter, fine pulverization is performed with a jet mill or the like, and the particle size is adjusted with a classifier so as to obtain an appropriate particle size distribution. Further, the toner is obtained by performing surface treatment by mixing with silica etc. in a mixer.

  The required performance of electrophotographic toners in recent years has become increasingly sophisticated. The main requirements for toners are to reduce the particle size, reduce oil, fix at low temperature, increase transfer efficiency, and improve image quality. As a common toner elemental technology, it is necessary to finely and uniformly disperse an internal toner additive such as pigment, CCA and WAX in the binder resin.

  An example of a technique for improving the dispersibility of the toner internal additive includes optimization of kneading conditions and surface treatment of each additive material. Further, as a method for improving the dispersibility of the pigment, improving the dispersion level by pre-kneading the pigment with a resin (master batch) is regularly used in the color toner manufacturing method.

  As such a masterbatch method, a water addition kneading method using water as a dispersion aid has been proposed (see, for example, Patent Documents 1 to 3), and it can be expected to further improve the dispersibility of the pigment.

However, this technique promotes the dispersion of the toner pigment, but cannot improve the dispersibility of other additives such as CCA and WAX.
JP 2004-191787 A JP-A-9-101632 JP-A-4-230770

  The present invention has been made under the circumstances as described above, and improves the dispersibility of the toner internal additive without the need for a pigment masterbatch, and thereby has excellent fog characteristics, image quality, and durability. It is an object to provide a method for producing a toner.

  In order to solve the above problems, a first aspect of the present invention is a step of mixing raw materials including a binder resin, a colorant, a release agent, and a charge control agent, and melt kneading the raw material mixture with an open type kneader. In the method for producing an electrophotographic toner comprising a step, a step of cooling and solidifying the kneaded product, and a step of pulverizing, and a step of classifying the pulverized product. A method for producing an electrophotographic toner is provided.

  In such a method for producing an electrophotographic toner, carnauba wax can be used as a release agent.

  The electrophotographic toner produced by the above method desirably has a particle size of 5 to 7 μm.

  The second aspect of the present invention provides an electrophotographic toner produced by the above method.

  According to the present invention, it is possible to improve the dispersibility of the internal additive by adding water at the time of mixing the raw materials, whereby an electrophotographic toner having good fog characteristics, image quality, and durability can be obtained. Obtainable.

  The best mode for carrying out the invention will be described below.

  The method for producing an electrophotographic toner according to an embodiment of the present invention is characterized in that water is added to a raw material and mixed, and the mixture is kneaded with an open kneader.

  As described above, it is considered that the following action is caused by adding water to the raw material and mixing, and kneading the mixture with an open type kneader.

  That is, the electrostatic aggregation of the pigment, the release agent, and the charge control agent, and the ion aggregation due to a small amount of impurities are alleviated by the addition of water, whereby the mixing is performed uniformly. In addition, the viscosity increases due to the heat of vaporization due to the addition of water and the evaporation of water, and the dispersibility is improved because a strong shearing force is applied during kneading. Furthermore, by kneading with an open type kneader, the heat generated during kneading is dissipated into the atmosphere, and the melt viscosity does not decrease, so that high dispersibility is obtained.

  With the above operation, an electrophotographic toner having good fog characteristics, image quality, and durability can be obtained by adding water to the raw material and kneading with an open kneader.

  In the method for producing an electrophotographic toner according to an embodiment of the present invention, the amount of water added to the raw material must be 10 to 50% by mass of the raw material. If the amount of water is less than 10% by mass, the effect due to the addition of water cannot be obtained.

  The toner manufacturing method according to an embodiment of the present invention is performed as follows.

First, materials such as a binder resin, a colorant, a release agent, and a charge control agent are measured, and the materials are measured and mixed by a mixer. As a mixing machine, arbitrary things, such as a Henschel mixer, a super mixer, a V-type blender, and a Nauta mixer, can be used.
At the time of mixing, 10 to 50% by mass of the raw material is added. The addition of water can be performed using, for example, a Henschel mixer 1 as shown in FIG. That is, a separating funnel 2 is attached to the material addition port of the upper lid of the Henschel mixer 1 via the rubber plug 3, and a predetermined amount of distilled water is accommodated in the separating funnel 2. When mixing the raw materials in the Henschel mixer 1, the cock of the separatory funnel 2 is opened and water is added. After mixing, the raw material mixture is discharged from the discharge port 4.

  The raw material mixture is then fed to an open roll kneader where it is melt kneaded. As an open roll type kneader, an arbitrary type such as a continuous two-roll mill, a continuous three-roll mill, and a batch-type roll mill can be used.

  FIG. 2 is a front view showing an open type continuous two-roll mill. The open-type continuous two-roll mill includes a hopper 11 to which a raw material mixture is supplied, two open-type rolls 12 and 13 arranged in parallel, and a discharge unit 14 from which a kneaded product is discharged. ing. Helical grooves for transporting the kneaded material are formed on the surfaces of the rolls 12 and 13.

  The raw material mixture supplied between the rolls 12 and 13 from the hopper 11 is repeatedly compressed and kneaded by the rotation of the rolls 12 and 13 while being wound around the surfaces of the rolls 12 and 13. It moves to the discharge part 14 side by the groove, and the kneaded material is discharged from there.

  The melt-kneaded material discharged from the open roll type kneader is usually cooled, pulverized, and classified to a predetermined particle size according to the method used for toner production to obtain a toner particle matrix. The cooling means, the pulverizing means, and the classification means are not particularly limited, and those usually used for toner production can be employed. For example, a cooling means by rolling or blowing an air flow can be used for cooling, and an airflow pulverizer such as a collision plate pulverizer can be used for pulverization, and various airflow classifiers can be used for classification. Can be used.

  An electrophotographic toner can be obtained by adding an external additive such as silica to the toner particle matrix thus obtained, followed by mixing and stirring.

  The electrophotographic toner thus produced preferably has a particle size of 5 to 7 μm.

  As described above, the electrophotographic toner obtained according to the first embodiment of the present invention is manufactured by melt-kneading the raw material mixture to which water has been added with an open roll kneader. With excellent dispersion, it has excellent fog characteristics, image quality, and durability.

  EXAMPLES Hereinafter, the Example and comparative example of this invention are shown and this invention is demonstrated more concretely.

  First, raw material mixing conditions, water addition conditions, external additive mixing conditions, kneading conditions, softening points, glass transition points, and particle diameter measuring methods in the following Examples and Comparative Examples will be described.

1. Raw material mixing conditions The raw materials are mixed using a Henschel mixer 1 as shown in FIG. 1, and the input amount is adjusted to be in the range of 70 to 80% with respect to the volume of the Henschel mixer 1. As a stirring blade, a standard blade is attached and rotated at a peripheral speed of 20 m / sec.

2. Water Addition Conditions Distilled water is weighed in advance into a separating funnel 2 attached via a rubber stopper 3 to the material addition port of the upper lid of the Henschel mixer 1 shown in FIG. 10 seconds after the start of stirring of the raw material stored in the Henschel mixer 1, the cock of the separatory funnel 2 is opened to start the addition of water, and the addition of the necessary amount is completed within 30 seconds.

3. External additive mixing conditions The external additive is mixed using a Henschel mixer. The input amount is adjusted to be in the range of 70 to 80% with respect to the volume of the Henschel mixer. The stirring blade is equipped with a strong stirring blade and is rotated at a peripheral speed of 40 m / sec.

4). Kneading conditions (1) Kneading roll gap by open type continuous two-roll mill (NDX 160, manufactured by Mitsui Mining Co., Ltd.): 0.1 mm
F roll Supply temperature: 120 ° C, discharge temperature: 120 ° C, rotation speed: 75rpm
B roll Supply temperature: 30 ° C, discharge temperature: 30 ° C, rotation speed: 50rpm
(2) Kneading with a twin-screw extrusion kneader (PCM-43, manufactured by Ikegai Co., Ltd.) Screw rotation speed: 250 rpm
Barrel cylinder temperature C1: 50 ° C
C2 to C8: 120 ° C.
Adapter: 120 ° C
Die nozzle: 120 ° C.

5). Measurement of softening point Apparatus: Flow tester (CFT-500D: manufactured by Shimadzu Corporation)
Sample: 1g
Temperature increase rate: 6 ° C / min Load: 20kg
Nozzle: 1mm diameter, 1mm length
1/2 method: The temperature at which half of the sample flows out is taken as the softening point.

6). Measurement of glass transition point (Tg) Device: differential scanning calorimeter (DSC-60: manufactured by Shimadzu Corporation)
Sample: 8mg
Temperature raising conditions: The temperature is raised to 160 ° C. at 10 ° C./min, cooled to 35 ° C. at a temperature lowering rate of 10 ° C./min, and then raised again to 160 ° C. at 10 ° C./min.

  At the time of the second temperature increase, the intersection of two tangents of the curve portion obtained by the transition is defined as the glass transition point.

7). Particle size measurement device: Multisizer II (Coulter)
Sample: Place a small amount of sample, purified water, and surfactant in a beaker and disperse with an ultrasonic cleaner.

  Measurement: The aperture is 100 μm, the count is 50,000, and the volume average particle diameter is obtained.

Example 1
As a binder resin, 90 parts by mass of a polyester resin (softening point 120 ° C., Tg 67 ° C.) and as a colorant (raw pigment), C.I. I. 5 parts by weight of Pigment Red 122, 4 parts by weight of Carnauba Wax No. 1 powder (Yoyuki Kato) as a release agent, 1 part by weight of E-84 (Orient Chemical Co., Ltd.) and 10 parts by weight of water as a charge control agent Was put into a Henschel mixer (standard feather mounted: manufactured by Mitsui Mining Co., Ltd.) and mixed with stirring for 3 minutes.

  The obtained mixed powder is melt-kneaded with an open roll type twin screw extruder (NDX160), stretched, cooled, and coarsely crushed with a Rotoplex (2 mm screen: manufactured by Hosokawa Micron), followed by a collision type pulverizer / air classification. The fine particles were obtained by pulverization and classification so that the average particle diameter of the toner was 6.0 μm.

  As an external additive, 2 parts by mass of “RY200” (hydrophobic silica: manufactured by Nippon Aerosil Co., Ltd.) is added to 100 parts by mass of the obtained fine particles, and the mixture is stirred for 3 minutes with a Henschel mixer (with stirring reinforcement blades: manufactured by Mitsui Mining Co., Ltd.). The toner was obtained by mixing.

Example 2
A toner was obtained in the same manner as in Example 1 except that the amount of water added to the raw material was 30 parts by mass.

Example 3
A toner was obtained in the same manner as in Example 1 except that the amount of water added to the raw material was 50 parts by mass.

Comparative Example 1
A toner was obtained in the same manner as in Example 1 except that water was not added to the raw material.

Comparative Example 2
A toner was obtained in the same manner as in Example 1 except that the amount of water added to the raw material was 60 parts by mass.

Comparative Example 3
A toner was obtained in the same manner as in Example 1 except that PCM43 (manufactured by Ikegai Co., Ltd.) was used as the kneader.

Comparative Example 4
A toner was obtained in the same manner as in Example 2 except that PCM43 (manufactured by Ikegai Co., Ltd.) was used as the kneader.

Comparative Example 5
A toner was obtained in the same manner as in Example 3 except that PCM43 (manufactured by Ikegai Co., Ltd.) was used as the kneader.

  The toner samples obtained in the above Examples and Comparative Examples were subjected to the following tests to evaluate the characteristics.

Test 1-fogging Non-magnetic one-component developing device “Casio Page Presto N-5” (manufactured by Casio Computer Co., Ltd .: color printer 29 sheets per minute (A4 horizontal) machine, process speed 129 mm / sec) mounted with normal toner (25 ° C, 50% RH) Using normal paper (XEROX-P paper A4 size), 5% print images were continuously printed on 10,000 sheets, then blank paper was printed. Then, printing was forcibly terminated, and the fog toner on the OPC drum at that time was copied onto a mending tape and compared visually.

  In comparison with Comparative Example 1, the case of Equivalent was evaluated as ◯, the case of less fog than Comparative Example 1 as ◎, and the case where the amount of fog was larger than Comparative Example 1 as x.

Test 2-High image quality Using the equipment used in Test 1, in a normal environment (25 ° C, 50% RH), continuous printing of 5% print images using plain paper (XEROX-P paper A4 size) After that, a halftone image and a solid image were printed, and the uniformity of the image was evaluated. In comparison with Comparative Example 1, it was evaluated as ◯ when equal, ◎ when better than Comparative Example 1, and × when it was not more uniform than Comparative Example 1.

Test 3-Durability Using the same apparatus as in Test 1, 14,000 sheets of 5% print images were continuously printed in a normal environment (25 ° C, 50% RH). In the middle, solid images and halftone images were printed every 2,000 sheets, and the number of white stripes generated by blade fusion was evaluated.

◎: Not generated up to 14,000 sheets ○: Generated after 12,000 sheets ×: Generated with less than 12,000 sheets Test 4-kneading supply performance In the kneading process, the raw material supply amount was changed from 25 kg / h to 45 kg / h. The feed rate was gradually increased to 5 kg / h until the feed neck phenomenon was observed.

A: Supply amount of 40 kg / h or more (good)
○: Supply amount of 30 kg / h or more (acceptable)
X: Supply amount of 25 kg / h or less (productivity is insufficient)
Test 5-Residual Moisture Ratio 2 g of toner was dried in a constant temperature bath at 130 ° C. for 1 hour, and the weight change (loss on drying) before and after was evaluated as the residual moisture ratio.

○: Change rate 0.5% or less (no problem in quality)
×: Change rate of 0.5% or more (there is a quality problem)
Test 6-OHP Transparency Using the apparatus used in Test 1, in a normal environment (25 ° C., 50% RH), a solid image was printed using OHP paper (manufactured by 3M: CG3710) and evaluated according to the following criteria. did.

A: The maximum transmittance is 80% or more and practically very good. ○: The maximum transmittance is 60 to 80%. There is no practical problem. X: The maximum transmittance is less than 60% and there is a practical problem. It is shown in Table 3 below.

  From Table 3 above, the following is clear. That is, in the mixing step, the toners of Examples 1 to 3 obtained by adding 10 to 50% by mass of water to the raw material and performing kneading with an open type kneader are fogging, image quality, durability, kneading supply performance, It shows excellent performance in both the residual moisture content and OHP transparency.

  On the other hand, the toner of Comparative Example 1 in which water was not added to the raw material was inferior in fog, image quality, durability, and OHP transparency. It is inferior in all the characteristics of image quality, durability, kneading supply performance, residual moisture content, and OHP transparency. On the other hand, when the amount of water is too much, the kneading and feeding performance is extremely lowered, which makes it difficult to manufacture the toner.

  Further, the toners of Comparative Examples 3 to 5 obtained by kneading with a non-open type kneader showed inferior characteristics despite the addition of water to the raw material.

The figure which shows the Henschel mixer provided with the separating funnel which adds water used for one Embodiment of this invention. The front view which shows the open type continuous type 2 roll mill used for one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Henschel mixer, 2 ... Separation funnel, 3 ... Rubber stopper, 4 ... Discharge port, 11 ... Hopper, 12, 13 ... Roll, 14 ... Discharge part.

Claims (4)

Mixing raw materials including a binder resin, a colorant, a release agent, and a charge control agent;
Melting and kneading the raw material mixture with an open kneader,
In the method for producing an electrophotographic toner comprising the steps of cooling and solidifying the kneaded product and then pulverizing, and classifying the pulverized product,
In the mixing step, 10 to 50% by mass of water is added to the raw material.   The method for producing a toner for electrophotography according to claim 1, wherein the release agent is carnauba wax.   The toner production method according to claim 1, wherein the toner has a particle size of 5 to 7 μm.   An electrophotographic toner produced by the toner production method according to claim 1.

Images