JPH09265207A - Production of electrostatic latent image developing toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic latent image developing toner for low temp. fixing which causes no development defects such as fog and filming. SOLUTION: At least binder resin particles, a coloring agent and wax particles having the following property are mixed. The mixture is molten, kneaded, cooled, pulverized and classified. The wax particles have <=3 needle penetration degree and has such a distribution of particle size that proportion of particles having >=50mm mesh is <=2wt.%, the proportion of particles having <=20mm mesh is >=90wt.%, and the proportion of particles having >=5mm mesh is >=50wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing 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 to the toner as an offset preventing agent (release agent) 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.

As such a low-temperature fixing toner, for example, JP-A-60-252366 and JP-A-03-57 are available.
Japanese Unexamined Patent Publication No. 64 describes that natural wax such as carnauba wax is used as an anti-offset agent. However, each of the above publications does not describe the technical means for containing the natural wax in a state of being uniformly dispersed in the toner particles. In order to obtain a low-temperature fixing toner having good properties by using the above-mentioned natural wax as an offset preventive agent, it is necessary to uniformly disperse a predetermined amount of the natural wax in the toner particles. However, since natural wax is excessively pulverized in the step of mixing the raw materials during the production of the toner, it is difficult to obtain a uniform mixture with the binder resin particles and the like. As a result, a wax uneven product is produced in the final product toner, which easily causes fog in the non-image area and filming on the photoconductor, and a low-temperature fixing toner having good characteristics cannot be obtained.

[0005]

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 for low temperature fixing, which does not cause a defective phenomenon such as fog or filming.

[0006]

According to the present invention, at least a binder resin particle, a colorant and a penetration degree of 3 or less and a particle size distribution of 50 mm mesh or more and 2% by weight or less, 20
a step of mixing wax particles having a mesh of 90 mm% or less and a weight of 5 mm or more and 50% by weight, a step of melting and kneading the mixture, a step of crushing the cooled kneaded material, and a step of classifying the crushed material And a method for producing a toner for developing an electrostatic latent image, comprising:

The wax having a penetration of 3 or less, preferably 2 or less used in the present invention is added to the binder resin to function as an anti-offset agent, and the softening point thereof is preferably 60 to 110 ° C. . A natural wax is suitable as such a wax. Preferred natural waxes include carnauba wax, rice wax, sazol wax, beeswax and the like. In the above, the degree of penetration of the wax refers to a value obtained according to the test method defined in JIS-K-2235-1980.

In order to obtain a good low temperature fixing toner using such a wax, it is necessary to disperse the finally obtained toner particles in the binder resin uniformly.
In addition, the wax content of each toner particle needs to be substantially the same. In order to achieve uniform dispersion of the wax in the binder resin, it is necessary to obtain a mixture in which the binder resin particles and the wax particles are uniformly mixed in the raw material mixing step during production. If the mixture is non-uniform and the wax particles are unevenly distributed, the wax particle content of the mixture sent to the kneader will not be constant, so the wax content of each toner particle in the kneaded product obtained by sequentially melt-kneading will be included. This is because the amount becomes uneven. In such a case, the obtained toner becomes a mixture of toner particles containing almost no wax, toner particles containing a large amount of wax, toner particles consisting of only wax, etc., and thus low temperature fixing having desired properties is achieved. Unable to obtain toner for
Fog in the non-image area and filming on the photoconductor occur.

However, the above-mentioned wax is more fragile than the binder resin, and in the mixing step at the time of production, only the wax is finely pulverized at an early stage due to the action of the shearing force of the mixing device, and the difference in particle diameter from the binder resin particles is caused. However, it was difficult to obtain a uniform mixture. The present invention has a particle size distribution in which 50 mm mesh or more is 2% by weight or less, 20 mm mesh or less is 90% by weight or more, and 5 mm mesh or more is 50% by weight or more in dry mixing of binder resin particles and wax particles. By using wax particles, a uniform mixture can be obtained. That is, when the wax is broken during mixing, the particle size becomes the same as that of the binder resin particles, and uniform mixing of both is achieved. Furthermore, the above-mentioned wax particles have a thickness of 1.
A flake shape of 5 mm or less (flake shape like corn flakes) is preferable from the viewpoint of achieving uniform mixing, and the binder resin particles are 500 μm to 30 mm.
Those having a volume average particle diameter of the order of magnitude are preferable.

In producing the toner in the present invention, first, binder resin particles, the wax particles, a colorant and, if necessary, a charge control agent, a high temperature offset preventing wax, classification fine powder, magnetic powder and other components are added to a Henschel mixer. Mix with a mixer capable of high shear mixing such as.
Further, in order to further improve the uniform mixing property, first, the binder resin particles and the wax particles are mixed (first mixing step), and the obtained mixture and the colorant and, if necessary, the charge control agent and the high temperature offset preventing agent are mixed. Separate two-stage mixing may be performed in which components such as wax, classified fine powder, and magnetic powder are mixed (second mixing step).

In the present invention, 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 coarsely kneaded. The powder and fine powder are classified to produce a toner having a volume average particle diameter of 5 to 12 μm. The coarse powder generated by the classification can be supplied again to the pulverizing step for use, and the fine powder can be supplied to the mixing step for use as a toner raw material. The mixing conditions in the above mixing step cannot be generally stated because they vary depending on the mixing apparatus and materials used, but basically, it may be set so that each material is uniformly mixed, for example, using a Henschel mixer. When mixing, the peripheral speed is 10 to 70 m
/ Sec, and the mixing time may be 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.

In addition to the above wax, a wax for preventing high temperature offset may be added to the toner according to the present invention. Such a wax has a softening point of 110 to 1
Wax at 50 ° C., preferably 120 to 150 ° C. can be used, and examples thereof include polyethylene wax, oxidized polyethylene wax, polypropylene wax, and oxidized polypropylene wax. When these waxes are added, they are added in an amount of 0.5 to 5 parts by weight, preferably 1 to 3 parts by weight, based on 100 parts by weight of the binder resin.

The binder resin has a softening point of 9
A resin having a glass transition point of 0 to 135 ° C., preferably 95 to 130 ° C. and a glass transition point of 55 to 75 ° C., preferably 57 to 68 ° C. can be used. For example, polyester resin, polystyrene resin, acrylic resin, meta Acrylic resin,
Examples thereof include a styrene-acrylic copolymer resin, a styrene-methacrylic copolymer resin, an epoxy resin, and a polyolefin resin, and these can be used alone or in combination. 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.

[0014]

The present invention will be described more specifically with reference to the following examples. Reference Example 1 [Blending composition] 100 parts by weight of bisphenol A type polyester resin (volume average particle size 1000 μm, softening point 113 ° C., glass transition point 63 ° C.) charge control agent 2 〃 (Bontron S-34: manufactured by Orient Chemical Industry Co., Ltd.) Carnauba wax 2.5 〃 (shape: flake, thickness: 1.2 mm, particle size distribution: 1% by weight of 50 mm mesh or less, 95% by weight of 20 mm mesh or less, 64% by weight of 5 mm mesh or more, penetration: 1-2, softening point: 85 ° C., acid value: 5, manufactured by Kato Yoko Co., Ltd. The above toner composition was mixed with a Henschel mixer (first).
After 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, finely pulverized by a jet mill, and then classified by an air stream classifier to remove fine powder. Volume average particle size 8.5 μm
Was obtained.

[0015] 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 Carnauba wax was added in an amount of 1.5 parts by weight, and oxidized low molecular weight polypropylene (TS-200, softening point: 14
5 ° C, acid value: 3.5, manufactured by Sanyo Kasei Co., Ltd.) 1.0 part by weight
Average volume particle size was made by the same material and manufacturing method as in Example 1 except that the mixture was added to a Henschel mixer in the mixing step.
2 μm of Toner C was obtained.

Example 4 Carnauba wax was converted to Sazol wax (A1, shape: flake, thickness: 1.3 mm, particle size distribution: 1% by weight of 50 mm mesh or less, 93% by weight of 20 mm mesh or less, 5 mm mesh or more 55% by weight, penetration: 1
2. Softening point: 90 ° C., acid value: 28, manufactured by Kato Yoko Co., Ltd.) Toner D having a volume average particle diameter of 8.2 μm was obtained by the same material and manufacturing method as in Example 1.

Example 5 Carnauba wax was used as Fischer-Tropsch wax (C-60, shape: flake, thickness: 1.1 mm, particle size distribution: 1% by weight of 50 mm mesh or more, 90% by weight of 20 mm mesh or less, 5 mm mesh The above is 60% by weight, penetration hardness: 1-2, softening point: 100 ° C., acid value: 2
No. 8, manufactured by Kato Yoko Co., Ltd.), and toner E having an average particle size of 8.5 μm is manufactured by the same material and manufacturing method as in Example 1 except that
I got

Reference Example 2 [Blend composition] 100 parts by weight of styrene-acrylic copolymer resin (volume average particle diameter 1000 μm, softening point 112 ° C., glass transition point 61 ° C.) Charge control agent 3 〃 (Nigrosine base EX: Orient Chemistry) Carnauba wax 3.5 〃 (shape: flakes, thickness: 1.2 mm, particle size distribution: 1% by weight of 50 mm mesh or less, 95% by weight of 20 mm mesh or less, 64% by weight of 5 mm mesh or more, Penetration: 1-2, softening point: 85 ° C., acid value: 5, manufactured by Kato Yoko Co., Ltd. The above toner composition was mixed with a Henschel mixer (first).
After mixing, 7 parts by weight of carbon black (MA # 8: manufactured by Mitsubishi Chemical Co., Ltd.) 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, 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 6 Toner particles were obtained in the same manner as in Reference Example 2 except that 10 parts by weight of the classified fine powder generated 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.
Toner F of m was obtained.

Example 7 Example 6 was repeated except that the toner composition used in Example 6 (styrene-acrylic copolymer resin, charge control agent, carnauba wax, carbon black, classified fine powder) was simultaneously mixed in a Henschel mixer. Toner G having a volume average particle diameter of 8.4 μm was obtained using the same material and manufacturing method.

Example 8 Carnauba wax was added in an amount of 2.0 parts by weight, and low molecular weight polypropylene (Viscole 550P, softening point: 15)
Toner H having an average volume particle size of 8.2 μm was obtained by the same material and manufacturing method as in Example 6 except that 1.5 parts by weight of the same was added to the Henschel mixer in the first mixing step. .

Comparative Example 1 Carnauba wax was used in the same manner as in Example 1 except that the carnauba wax was changed to powdery (particle size distribution: 5 mm mesh or less, 60% by weight, penetration 1-2). Toner I having a volume average particle diameter of 8.4 μm was obtained.

Comparative Example 2 The same material and manufacturing method as in Example 3 except that the carnauba wax was changed to powder-like (particle size distribution: 5 mm mesh or less, 60% by weight, penetration: 1-2) carnauba wax. Thus, a toner J having an average particle size of 8.1 μm was obtained.

Comparative Example 3 Carnauba wax was changed to block-like carnauba wax (thickness: 3.0 mm, particle size distribution: 20 mm mesh or more 35% by weight, 50 mm mesh or more 5% by weight, penetration: 1-2). A toner K having a volume average particle size of 8.2 μm was obtained by using the same material and manufacturing method as in Example 3 except that the above was used.

Comparative Example 4 The same material as in Example 4 except that Sazol Wax A1 in powder form (particle size distribution: 5 mm mesh or less, 60% by weight, penetration: 1-2) was used. Then, a toner L having a volume average particle size of 8.4 μm was obtained by the manufacturing method.

Comparative Example 5 Fischer-Tropsch wax was powdered (particle size distribution: 5 mm mesh or less 60% by weight, penetration: 1 to
A toner M having an average particle diameter of 8.4 μm was obtained by the same material and manufacturing method as in Example 5, except that the Fischer-Tropsch wax C-60 in 2) was used.

Comparative Example 6 The same material and manufacturing method as in Example 6 except that the carnauba wax was changed to powder-like (particle size distribution: 60% by weight of 5 mm mesh or less, needle penetration hardness: 1-2). To obtain a toner N having an average particle size of 8.4 μm.

Comparative Example 7 Carnauba wax was changed to carnauba wax having a block shape (thickness 3.0 mm, particle size distribution: 20 mm mesh or more 35% by weight, 50 mm mesh or more 5% by weight, penetration: 1-2). A toner O having a volume average particle size of 8.2 μm was obtained by using the same material and manufacturing method as in Example 6 except for the above.

[0031] Toner A~E and I~M prepared as printing test described above, an electrophotographic printer (SP-1000, manufactured by Minolta Co., Ltd.) was remodeled set temperature of the fixing roller 130 ° C. using a continuous A printing durability test of 6,000 sheets was carried out, and the fog and filming conditions at the end of printing durability of 3,000 sheets and 6,000 sheets were evaluated, and the results are shown in Table 1.

[0032]

[Table 1]

[Judgment Criteria] Fog : No fog at all Δ: Fog is partially generated on the image, causing a problem in practical use ×: Fog is generated on the image Photoreceptor filming ◎: None at all ○: On the photoconductor There is little filming on the image, but there is no problem in practice because the fog that causes this is not occurring. △: Filming occurs on the photoconductor, and the fog that causes this is partly on the image. Occurs and there is a problem in practical use. X: Filming occurs on the photoconductor, and fog caused by this occurs on the image, which is a practical problem.

The toners F to H, N and O were mixed with the carrier for the following copying machine so that the toner mixing ratio was 5% by weight, and the fixing roller was set at a temperature of 130 ° C. (EP-4100, manufactured by Minolta)
The continuous printing test of 60,000 sheets was performed using
The BS (black spot fusion) and filming states at the end of 000 sheets and 60,000 sheets were evaluated, and the results are shown in Table 2.

[0035]

[Table 2]

[Judgment Criteria] BS (black spot fusion) ○: None at all △: BS is observed on the photoconductor, but it does not occur on the image and practically does not occur ×: Also on the image BS has occurred and there is a problem in practical use

[0037]

According to the method for producing a toner of the present invention, it is possible to provide a toner capable of stably obtaining a clear image by fixing at a low temperature and free from fogging, filming, BS and the like even after the end of printing durability. You can

 ─────────────────────────────────────────────────── ─── 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. At least a binder resin particle, a colorant, and a penetration degree of 3 or less and a particle size distribution of 50 mm mesh or more to 2 wt% or less, 20 mm mesh or less to 90 wt% or more, and 5 mm mesh or more to 50 wt%. % Of wax particles are mixed, the mixture is melt-kneaded, the cooled kneaded product is ground, and the ground product is classified. Method.