JPH09269612A - Production of electrostatic latent image developing toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic latent image developing toner having excellent storage property against heat and having wide offset resistance range, and to provide a production method for an electrostatic latent image developing toner for low temp. fixing having excellent storage property against heat. SOLUTION: This production method consists of a process to mix binder resin particles (A) and binder particles (B) in a dry state, a process to melt and knead the mixture, a process to pulverize the kneaded material after cooling, and a process to classify the pulverized material. The binder particles (A) consist of a binder resin having 130 to 150 deg.C softening point and 60 to 70 deg.C glass transition temp., and have 500 to 15000μm volume average particle size. The binder resin particles (B) consist of a binder resin having 90 to 150 deg.C softening point and 53 to 64 deg.C glass transition temp., and have the volume average particle size 1.5 to 2.5 times as that of the binder particles (A).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a toner for developing an electrostatic latent image which can be fixed at a low temperature.

[0002]

2. Description of the Related Art As a fixing method for an image forming apparatus such as an electrophotographic apparatus, a pressure fixing method, a non-contact heat fixing method such as flash fixing or an oven fixing, and a contact heating fixing method such as a heat roll fixing are adopted. In particular, the contact heating fixing method can achieve higher speed than the pressure fixing method, has higher thermal efficiency than the non-contact heating fixing method, and can use a relatively high-temperature heat source, which makes the device compact and saves energy. This is the most popular fixing method because it can be achieved. In recent years, further speeding up and energy saving have been demanded for such a contact heat fixing type electrophotographic apparatus, and therefore low temperature fixing characteristics have been required for the toner. If low-temperature fixing is realized, not only energy saving of the electrophotographic apparatus can be achieved, but also warm-up time can be shortened and more comfortable operability can be obtained.

By the way, the above-mentioned contact heating fixing system has a problem that an offset phenomenon occurs. For example, in the heat roll fixing method, a part of the toner forming the image is transferred to the surface of the heat roll at the time of fixing, and this is retransferred to the transfer paper that is sent next, and the image is contaminated. Conventionally, as a technique for preventing the offset phenomenon of the toner for heat roll fixing, a technique of adding a synthetic wax such as polypropylene as an offset preventing agent (release agent) into the toner has been known. It is necessary to select a wax that sufficiently melts in the low fixing temperature range and functions as an offset preventing agent. For example, JP-A-60-252366 and JP-A-03-5.
Japanese Patent No. 764 describes the use of natural wax such as carnauba wax as an anti-offset agent.

On the other hand, the binder resin constituting the toner is required to have excellent properties such as heat-resistant storage property and fixing property, but in order to improve heat-resistant storage property, it is necessary to increase the glass transition point. Is effective, and lowering the softening point is effective for improving fixability. However, in the resin characteristics, the glass transition point and the softening point are closely related to each other, and it is difficult to satisfy the above characteristics with one kind of binder resin from the viewpoint of resin design. It is known that a mixture of a binder resin having a low softening point (relatively having a low glass transition point) is used.

However, in order to obtain a toner showing good characteristics by using such two kinds of resins, it is necessary to uniformly disperse and contain two kinds of binder resins in the toner particles. However, since such binder resins have different particle sizes pulverized in the step of mixing the raw materials during the production of the toner, it has been possible to obtain a uniform mixture of these binder resin particles. Therefore, in the final product toner, one binder resin is unevenly distributed,
This causes a problem that heat resistance is reduced.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a toner for developing an electrostatic latent image, which has excellent heat resistant storage stability and has a wide non-offset area. Another object of the present invention is to provide a method for producing a toner for developing an electrostatic latent image for low temperature fixing, which is excellent in heat resistant storage property.

[0007]

The present invention has a softening point of 13
It is composed of a binder resin having a glass transition point of 60 to 70 ° C. at 0 to 150 ° C. and a volume average particle size of 500 to 15.0.
Binder resin particles A of 00 μm and a softening point of 90
A step of dry mixing with a binder resin particle B having a glass transition point of 53 to 64 ° C. at −105 ° C. and having a volume average particle diameter of 1.5 to 2.5 times that of the binder resin particle A, The present invention relates to a method for producing a toner for developing an electrostatic latent image, which comprises a step of melt-kneading this mixture, a step of pulverizing a cooled kneaded material, and a step of classifying the pulverized material.

The present invention comprises a binder resin particle, a colorant,
From the step of dry-mixing the offset preventive agent and, if necessary, the charge control agent, magnetic powder, toner classification fine powder, and the like, the step of melt-kneading this mixture, the step of pulverizing the cooled kneaded material, and the step of classifying the pulverized material. And a method for producing the toner.

In the present invention, the softening point is 130-15.
Binder resin A having a glass transition point of 60 to 70 ° C. at 0 ° C.
And a softening point of 90 to 105 ° C. and a glass transition point of 53 to 6
Binder resin B at 4 ° C. is used. By using the binder resin A having the above thermal characteristics, the heat resistant storage stability of the toner can be improved and the non-offset area can be expanded. Further, by using the binder resin B having the above-mentioned thermal characteristics, it is possible to improve the fixability of the toner, particularly the low-temperature fixability.

By the way, even if the toner is manufactured by simply using the above-mentioned two kinds of binder resins A and B in the above-mentioned manufacturing method, the effect of using two kinds of binder resins, that is, improvement in heat-resistant storage property and non-offset region. It was found that expansion and improvement in fixability could not be obtained. According to the findings of the present inventors, this is considered to be caused by the following phenomenon. That is, in the mixing step, when a mixing device such as a Henschel mixer is used, shearing force is applied to the material to be mixed, and the material to be mixed is mixed while being ground by the shearing force, but since the pulverizability of the two kinds of binder resins is different, The particle sizes of the binder resin A and the binder resin B in the obtained mixture are greatly different, and the difference in particle size causes uneven distribution of the binder resin particles A and the binder resin particles B in the mixture. It When the mixture is non-uniform and uneven distribution of each binder resin particle occurs,
Since the ratio of each binder resin particle of the mixture sent to the kneader is not constant, uneven distribution also occurs in the content of each binder resin in the kneaded product obtained by sequentially melt kneading, and finally the kneaded product That is, the content of each binder resin in each toner particle obtained by pulverizing the toner is not uniform. In such a case, the obtained toner becomes a mixture of toner particles containing almost no binder resin A and toner particles containing a large amount of binder resin A, so that a toner having desired characteristics can be obtained. Will not be possible.

From this point of view, in the present invention, the volume average particle diameter of the binder resin particles A used in the mixing step is 500.
˜15,000 μm, and the volume average particle diameter of the binder resin particles B is 1.5 to 2.5 of the binder resin particles A.
The mixture is adjusted to 5 times, so that even if each binder resin particle is crushed by shearing force of a Henschel mixer or the like during mixing, the particle size after crushing is almost the same and the mixture has excellent uniform mixing property. Will be obtained.

In producing the toner in the present invention, first, the binder resin particles, the colorant and, if necessary, the components such as the charge control agent, the anti-offset agent, the classified fine powder and the magnetic powder can be mixed under high shear by a Henschel mixer or the like. Mix with a simple mixer. Further, in order to further improve the uniform mixing property, first, only two kinds of binder resin particles or a mixture thereof with a charge control agent or an anti-offset agent is mixed (first mixing step), and the obtained mixture, colorant and If necessary, charge control agent, offset prevention agent, finely divided powder,
Separate two-stage mixing may be performed in which components such as magnetic powder are mixed (second mixing step). Next, the obtained homogeneous mixture is melt-kneaded to obtain a kneaded product in which components such as a colorant and wax are uniformly dispersed in a binder resin, and the cooled kneaded product is crushed, and then coarse powder and fine powder are classified. And the volume average particle size is 5
12 μm toner is produced. Incidentally, the coarse powder generated by the classification can be supplied again to the crushing step for use,
Further, the fine powder can be supplied to the above-mentioned mixing step and used as a toner raw material.

[0013] The mixing conditions in the above mixing step cannot be generally stated because they differ depending on the mixing apparatus and materials used, but basically, it suffices to set the materials so that they are uniformly mixed. For example, a Henschel mixer. When mixing using, the peripheral speed may be set to 10 to 70 m / sec, and the mixing time may be set to about 30 seconds to 10 minutes. It is preferable to externally add a fluidizing agent such as silica, alumina, or titania or a cleaning aid such as resin particles to the obtained toner particles as a post-treatment agent.

As the binder resins A and B, the thermoplastic resins having the above-mentioned thermal characteristics can be used. For example, polyester resin, polystyrene resin,
Acrylic resins, methacrylic resins, styrene-acrylic copolymer resins, styrene-methacrylic copolymer resins, epoxy resins, polyolefin resins and the like can be mentioned, and these can be used alone or in combination. . The mixing ratio of the binder resin A and the binder resin B varies depending on the setting conditions such as the fixing temperature of the image forming apparatus using the finally obtained toner, but the binder resin A is too much or the binder resin B is too little. If the binder resin A is too small or the binder resin B is too much, the heat resistant storage property is impaired. Therefore, the binder resin A / binder resin B is 3/7 by weight. -9/1, preferably 5 / 5-8 / 2 are suitable.

As the offset preventing agent, it is preferable to use one having a softening point of 60 to 110 ° C. from the viewpoint of producing a low temperature fixing toner. A natural wax is suitable as such a wax. Preferred natural waxes include carnauba wax, rice wax, sazol wax, beeswax and the like. In addition to the above-mentioned offset preventing agent, the following offset preventing agent may be added to the toner according to the present invention in order to expand the non-offset region on the high temperature side. Such a wax has a softening point of 1
A wax at 10 to 150 ° C., preferably 120 to 150 ° C. can be used, and examples thereof include polyethylene wax, oxidized polyethylene wax, polypropylene wax, oxidized polypropylene wax and the like.
The toner obtained by the present invention can be applied as a two-component toner used with a carrier, a magnetic-component toner to which magnetic powder is added, or a non-magnetic-component toner.

[0016]

The present invention will be described more specifically with reference to the following examples. Manufacture of synthetic resin Synthesis of polyester resin (A) [Blending raw material] Bisphenol A- (2,2) -Propylene oxyside adduct 23 parts by weight Isophthalic acid 12 〃 Succinic acid 2 〃 Diethylene glycol 2 〃 Glycerin 1 〃

A 5 L four-necked flask equipped with a reflux condenser, a water separator, a nitrogen gas inlet tube, a stirrer, and a thermometer was placed in the above-described amount of polyvalent carboxylic acid and polyhydric alcohol and dehydration catalyst. As a total amount of these compounds, 0.05 wt% of dibutyltin oxide was charged, and then dehydration polycondensation was performed at an internal temperature of 240 ° C. while introducing nitrogen gas into the flask to obtain a polyester resin (A-1). .

Next, 1,000 parts by weight of the polyester resin obtained above and 1 part of xylene were placed in a 5 L 4-necked flask equipped with a reflux condenser, a water separator, a nitrogen gas inlet tube, a stirrer and a thermometer. 2,000 parts by weight were charged and, after dissolution, this was kept at a temperature of 120 ° C. under a nitrogen stream, to which 50 parts by weight of diphenylmethane-4,4'-diisocyanate (MD
I) was divided into 4 portions, added every 4 hours in 4 portions, and reacted at this temperature for another 1 hour. Then, the flask was equipped with a solvent separator, the internal temperature was gradually raised, and xylene was distilled off under normal pressure.
Volatile components were completely distilled off at 0 mmHg and the softening point was 145.
A urethane-modified polyester resin (A) having a glass transition temperature of 68 ° C. was obtained.

Synthesis of polyester resin (B) [Raw materials] Bisphenol A- (2,2) -propylene oxide adduct 16.2 parts by weight Isophthalic acid 4.7 〃 Succinic acid 1.7 〃 Diethylene glycol 1.0 〃 Using the above raw materials, a polymer was synthesized in the same manner as the polyester resin (A-1) to obtain a polyester resin (B) having a softening point of 95 ° C and a glass transition point of 56 ° C.

Synthesis of styrene-acrylic resin (C) [Raw materials] Styrene 90 parts by weight n-Butyl methacrylate 10 〃 3,3,5-Trimethylcyclohexanone 0.1 〃 Di-t-butylperoxyketal 8 〃 Toluene 100 〃

The above raw materials were placed in a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, sufficiently dissolved, and then oxygen was expelled through a nitrogen stream. Next, gradually raise the temperature to 80 ° C., and
Hold at 0 ° C. for 3 hours. The temperature was further raised to 110 ° C., kept for 10 hours, cooled to room temperature, and kept at that temperature. Next, put it in a heating vacuum vessel, 80 ° C, 10 mmHg-0.1
The solvent was removed at mmHg to synthesize a styrene-acrylic resin (C) having a softening point of 135 ° C. and a glass transition point of 65 ° C.

Synthesis of Styrene-Acrylic Resin (D) [Raw Material] Styrene 80 parts by weight n-Butyl acrylate 20 〃 Benzoyl peroxide 15 〃 Toluene 500 〃

The above raw materials were placed in a reaction vessel equipped with a stirrer, a cooling tube and a thermometer, sufficiently dissolved, and then oxygen was driven out through a nitrogen stream. Next, gradually raise the temperature to 80 ° C., and
Hold at 0 ° C. for 3 hours. The temperature was further raised to 110 ° C., kept for 3 hours, cooled to room temperature, and kept at that temperature. Next, put it in a heating vacuum oven, and then at 80 ° C, 10 mmHg-0.1 m.
Desolvated with mHg, softening point is 95 ° C, glass transition point is 5
Styrene-acrylic resin (D) at 5 ° C was synthesized.

Reference Example [Raw material] Polyester resin (A) 80 parts by weight (volume average particle diameter 1,000 μm, softening point 145 ° C., glass transition point 68 ° C.) Polyester resin (B) 20 〃 (volume average particle diameter 1, 600 μm, softening point 95 ° C., glass transition point 56 ° C.) Charge control agent 2 〃 (Bontron S-34; manufactured by Orient Chemical Co.) Carnauba wax 2.5 〃 (shape: flake, thickness 1.2 mm, particle size distribution: 50 mm mesh or more 1% by weight, 20 mm mesh or less 95% by weight 5 mm mesh or more 64% by weight, penetration: 1-2, softening point: 85 ° C., acid value: 5, manufactured by Kato Yoko Co., Ltd.)

After mixing the above toner compositions with a Henschel mixer (first mixing), 5 parts by weight of carbon black (Mogal L: manufactured by Cabot) was further charged into the Henschel mixer and mixed (second mixing). The obtained mixture is melt-kneaded by a twin-screw extrusion kneader, the obtained kneaded product is cooled, coarsely pulverized by a feather mill and finely pulverized by a jet mill, and then classified by an air stream classifier to remove fine powder. Toner particles having a volume average particle diameter of 8.5 μm were obtained.

[0026] except that charged with carbon black in a Henschel mixer at a classified fine powder 10 weight parts generated in the classification step of Example 1 Reference Example 1 second mixing step to obtain toner particles in the same manner as in Reference Example 1. 0.5% by weight of hydrophobic silica (H-2000: manufactured by Hoechst) was mixed with the toner particles by a Henschel mixer, and surface treatment was performed to obtain a toner A.

Example 2 The toner composition used in Example 1 (polyester resin,
A toner B having a volume average particle size of 8.4 μm was obtained by the same material and manufacturing method as in Example 1 except that the charge control agent, carnauba wax, carbon black, and classified fine powder) were simultaneously mixed with a Henschel mixer.

Example 3 The volume average particle diameter of the polyester resin (B) was 2,300 μm.
A toner C having a volume average particle diameter of 8.2 μm was obtained by using the same material and manufacturing method as in Example 1 except that the toner C was changed to m.

Example 4 The volume average particle diameter of the polyester resin (A) is 700 μm.
In addition, the volume average particle size of the polyester resin (B) is 1,
Toner D having a volume average particle diameter of 8.1 μm was obtained by using the same material and manufacturing method as in Example 1 except that the toner D was changed to 400 μm.

Example 5 The volume average particle diameter of the polyester resin (A) was 1,400 μ.
m and the volume average particle diameter of the polyester resin (B) was changed to 2,200 μm to obtain a toner E having a volume average particle diameter of 8.1 μm by the same material and manufacturing method as in Example 1.

Example 6 Carnauba wax was added in an amount of 1.5 parts by weight, and low molecular weight polypropylene (TS-200, softening point: 145
Toner F having a volume average particle size of 8.2 μm was obtained by the same material and manufacturing method as in Example 1 except that 1.0 part by weight of the toner was used.

Reference Example 2 [Raw material] 80 parts by weight of styrene-acrylic resin (C) (volume average particle diameter 1000 μm, softening point 135 ° C., glass transition point 65 ° C.) 20 parts by weight of styrene-acrylic resin (D) (volume average Particle size 1600 μm, softening point 95 ° C., glass transition point 55 ° C.) Charge control agent 3 〃 (Nigrosine base EX: manufactured by Orient Chemical Industry Co., Ltd.) Carnauba wax 3.5 〃 (shape: flake, thickness: 1.2 mm, particles Diameter distribution: 1% by weight for 50 mm mesh or more, 95% by weight for 20 mm mesh or less, 64% by weight for 5 mm mesh or more, Penetration: 1-2, Softening point: 85 ° C, Acid value: 5, manufactured by Kato Yoko )

After mixing the above toner compositions with a Henschel mixer (first mixing), carbon black (M
7 parts by weight of A # 8 (manufactured by Mitsubishi Chemical Co., Ltd.) were put into a Henschel mixer and mixed (second mixing). The obtained mixture is melt-kneaded by a twin-screw extrusion kneader, the obtained kneaded product is cooled, coarsely pulverized by a feather mill, finely pulverized by a jet mill, and then classified by an air stream classifier to remove fine powder. Toner particles having a volume average particle diameter of 8.3 μm were obtained.

Example 7 Toner particles were obtained in the same manner as in Reference Example 2 except that 10 parts by weight of the finely divided powder obtained in the classification step of Reference Example 2 was charged into a Henschel mixer together with carbon black in the second mixing step. 0.5% by weight of hydrophobic silica (H-2000: manufactured by Hoechst) is mixed with the toner particles by a Henschel mixer to perform surface treatment, and the volume average particle diameter is 8.3 μm.
m Toner G was obtained.

Example 8 The same material as in Example 7 except that the toner composition (styrene-acrylic resin, charge control agent, carnauba wax, carbon black, classified fine powder) used in Example 7 was mixed at the same time with a Henschel mixer. Then, a toner H having a volume average particle diameter of 8.2 μm was obtained by the manufacturing method.

Example 9 Carnauba wax was added in an amount of 2.0 parts by weight, and low molecular weight polypropylene (Viscole 550P, softening point:
Toner I having a volume average particle diameter of 8.3 μm was obtained by the same material and manufacturing method as in Example 7 except that 1.5 parts by weight of 150 ° C., manufactured by Sanyo Kasei Co., Ltd.) was used.

Comparative Example 1 The volume average particle size of the polyester resin (B) was 1,300 μm.
A toner J having a volume average particle diameter of 8.4 μm was obtained by the same material and manufacturing method as in Example 1 except that the toner M was changed to m.

Comparative Example 2 The polyester resin (B) had a volume average particle diameter of 2,700 μm.
Toner K having a volume average particle diameter of 8.1 μm was obtained by the same material and manufacturing method as in Example 1 except that the toner was changed to m.

Comparative Example 3 The volume average particle size of the styrene-acrylic resin (D) was 1.2
A toner L having a volume average particle diameter of 8.3 μm was obtained by using the same material and manufacturing method as in Example 7 except that the toner L was changed to 00 μm.

In the present invention, heat resistance and offset property were evaluated by the following methods and criteria. When 5 g of the heat-resistant toner was placed in a glass bottle and placed in an environment of 60 ° C. for 5 hours, toner aggregation was found to be X, toner aggregation was hardly seen, and nothing was observed. . Offset property Regarding the toners A to F, J and K prepared as described above, an electrophotographic printer (SP1000, manufactured by Minolta) in which the setting temperature of the fixing roller is variably modified is used, and the setting temperature of the roller is set at 5 ° C. intervals. The toner image was fixed by changing the temperature to 100 to 220 ° C. and the temperature range in which no offset occurred was determined. For toners G to I and L, an electrophotographic copying machine was used in which a carrier for the following copying machine was mixed with a developer mixed so that the toner mixing ratio was 5% by weight, and the setting temperature of the fixing roller was variably modified. (EP410
0, manufactured by Minolta Co., Ltd., and set the roller temperature to 5 ° C.
The toner image was fixed by changing the temperature every 100 to 220 ° C., and the temperature range in which no offset occurred was determined.
Table 1 shows the evaluation results of the toners obtained in Examples and Comparative Examples.

[0041]

[Table 1]

[0042]

According to the toner manufacturing method of the present invention, a clear image can be stably obtained without offset in a wide fixing temperature range, and toner agglomeration hardly occurs even when stored at high temperature. Therefore, it is possible to provide a toner excellent in heat resistant storage stability.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hidenobu Tajima, 2-13-3 Azuchi-cho, Chuo-ku, Osaka City, Osaka Prefecture Minolta Co., Ltd. (72) Katsuji Nagasawa, Azuchi-cho, Chuo-ku, Osaka-shi, Osaka Prefecture 2-chome 3-13 Osaka International Building Minolta Co., Ltd.

Claims (1)

[Claims] 1. A binder resin particle A having a softening point of 130 to 150 ° C. and a glass transition point of 60 to 70 ° C. and a volume average particle diameter of 500 to 15,000 μm, and a softening point of 90. A step of dry mixing with a binder resin particle B having a glass transition point of 53 to 64 ° C. at −105 ° C. and having a volume average particle diameter of 1.5 to 2.5 times that of the binder resin particle A, A method for producing a toner for developing an electrostatic latent image, comprising the steps of melt-kneading this mixture, crushing a cooled kneaded material, and classifying the crushed material.