JP3094695B2 - Manufacturing method of electrophotographic toner - Google Patents

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 used for electrophotographic copying.

[0002]

2. Description of the Related Art Toners used in electrophotography are generally produced by melt-mixing a binder resin, a colorant and necessary additives, and pulverizing and classifying the melt-kneaded product. It is a common practice to add waxes that are incompatible with the binder resin as necessary additives in order to prevent the occurrence of high-temperature offset during heat roll fixing.

However, since the added wax is not compatible with the binder resin, it is difficult to uniformly disperse the wax in the binder resin with a small particle size. But easy to separate.

If the size of the wax separated from the toner particles is a fine powder much smaller than the particle size of the toner,
Even if it is removed in the classification process, or even if it is not removed, the fine powder will fate together with the toner in a state where it is stuck to the toner particles and will not adversely affect the photoreceptor and the copied image, etc. When the distance is close, the fine powder is not cut even in the classification step, and is scattered in the toner product. Since the free wax that has entered into the product does not contain a colorant or a charge control agent, the chargeability of the free wax is significantly different from that of the product toner.

[0005] During the copying process, the wax adhered to the electrostatic latent image on the photoreceptor together with the toner particles is not transferred even in the transfer process onto copy paper, and free wax remains on the photoreceptor. The wax remaining on the photoreceptor is not cleaned by the cleaner blade in the cleaning step, and is left as it is on the photoreceptor. This fusion wax is further thinly stretched and filmed on the photoreceptor.

Further, toner adheres to the filmed wax, and black spots (black spots) are formed on the photoreceptor in a streak shape. Since the filming and the black spot fused material do not leak electric charge, fogging occurs in a copied image, or when toner is further developed on them,
The toner is transferred to the paper and causes image noise.

[0007] Recently, the particle size of the toner has been reduced in order to enhance the definition of the image. In the case of such a toner, it is particularly necessary to uniformly disperse the wax with a small particle size.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and in which wax has a small particle diameter and is uniformly dispersed. It is an object of the present invention to provide a method for producing a toner that does not cause black spots, fogging, etc.

[0009]

Means for Solving the Problems That is, the present invention provides (1)
Relative to 100 parts by weight of the thermoplastic resin having an average particle diameter of 500~5000μm
Mixer that can apply 1 to 7 parts by weight of wax
By the average particle size of the thermoplastic resin is 300 ~ 800μm
Mixing until small, depending on the (2) extrusion kneader the mixture obtained in step (1)
And set temperature (T _s ): T _m −20 ° C. ≦ T _s ≦ T _m + 20 ° C. (where T _m is the softening of the thermoplastic resin)
In the range of the point), made by the process cooling the T _m + 35 ° C. step of melt-kneading as discharge at a temperature, and (3) above (2) kneaded product obtained in the step of, pulverized and classified The present invention relates to a method for producing an electrophotographic toner.

In the method for producing a toner of the present invention, at least a thermoplastic resin and a wax are first added (hereinafter, referred to as a “mixing step”). The thermoplastic resin to be used may be a resin known as a toner binder resin, for example, a styrene-acrylic copolymer resin or a polyester resin.
0 ° C., preferably 90-150 ° C., more preferably 10 ° C.
Use a temperature between 0 and 140 ° C. Softening point is 160 ℃
If a higher one is used, the fixing temperature must be increased, and fixing defects are likely to occur. Softening point is 80 ℃
When the lower one is used, the glass transition point becomes lower, the heat-resistant storage stability is deteriorated, and the toner tends to be solidified and aggregated.

As the wax, paraffin waxes such as low molecular weight polypropylene, low molecular weight polyethylene, ethylene bisamide, microcrystalline wax, carnauba wax and beeswax are preferably used.
It is preferable that the wax has a melting point of 90 to 180 ° C., and more preferably 100 to 180 ° C., which is incompatible with the thermoplastic resin used as the binder resin of the toner and has a releasing property.
A temperature of 170 ° C, more preferably 110 to 160 ° C, is used. If a material having a melting point higher than 180 ° C. is used, the wax does not melt at the time of fixing and does not bleed at the interface between the fixing roller and the toner. When a toner having a melting point lower than 90 ° C. is used, the heat resistance of the toner is reduced and the toner is easily solidified and aggregated. Here, "the resin and the wax are not compatible" refers to a state in which the wax is dispersed in the resin in an island shape when melt-kneaded, and is not taken into the molecular chains of the resin.

The wax is added in an amount of 1 to 7 parts by weight, preferably 2 to 6 parts by weight, based on 100 parts by weight of the thermoplastic resin. If the amount is less than 1 part by weight, the effect on high temperature offset is small, and if it is more than 7 parts by weight, free wax increases and filming black spots on the photoreceptor increase.

As additives other than the wax, those usually used such as a colorant and a charge control agent, and other desired additives may be used as needed.

In the present invention, the above additives are mixed with a thermoplastic resin. The mixing may be performed by pulverizing a thermoplastic resin in advance, or may be performed by simultaneously performing the pulverization and mixing using a bulk resin.

When a resin that has been pulverized in advance is used, its average particle size is 500 to 5000 μm, preferably 500 to 2 μm.
It is preferable to use a sieve or the like to make the particle size uniform so that the particle size becomes 000 μm. This is a requirement required from the viewpoint of uniformly mixing and dispersing the colorant, the charge control agent, the wax, and the like.

When mixing using a mixer capable of imparting a shearing force to the raw materials, the particle size needs to be adjusted to the same range as above, but the heat generation ratio of the mixed raw materials during mixing is 3%.
C./min. To 20.degree. C./min., And desirably under such conditions that the difference in average particle size before and after mixing is 300 to 800 .mu.m. If the rate of heat generation is too high, the raw materials aggregate due to heat storage, and if the rate of heat generation is low, mixing and dispersion are insufficient. Further, when the mixing is performed under the condition that the difference between the particle diameters before and after mixing becomes too large, the calorific value of the mixer increases. If the difference is too small, it is difficult to disperse efficiently and the bite is poor. (The bite is a problem that the raw material does not enter the screw of the kneading machine sufficiently.)
And adversely affect production efficiency.

Next, the mixture obtained in the mixing step is melt-kneaded (hereinafter referred to as "melt-kneading step").

The kneading machine is, for example, a twin-screw continuous extrusion kneading machine.
In this case, the set temperature (T _s ) of the melt-kneading is set as follows: T _m −20 ° C. ≦ T _s ≦ T _m + 20 ° C. (where T _m is the softening of the thermoplastic resin)
Point ), and the conditions are such that the resin is discharged at a temperature of Tm + 35 ° C or lower.

When the set temperature is lower than T _m -20 ° C., the resin and the wax are not sufficiently melted, and the load on the kneading machine is too high, so that kneading cannot be performed. Further, since the resin does not melt sufficiently, the function of fusing the resin is not sufficiently exhibited, and additives such as pigments are liberated, which causes filming. When the set temperature is T _m + 20 ° C. or higher, the components are melt-kneaded in a state where a sufficient shearing force is not applied, so that the wax, the charge control agent, the pigment, and the like are not sufficiently dispersed.
It causes filming, black spots and fog.

The reason for adjusting the discharge temperature of the resin to be equal to or lower than T _m + 35 ° C. is that when the discharge temperature is higher than T _m + 35 ° C., the melt kneading set temperature (T _S ) is set to Tm + 20 ° C. or higher. The same problems as those in the above case, that is, low shearing force at the time of melt-kneading, and accompanying problems such as filming, black spots and fog occur.

Finally, the kneaded material obtained in the above-mentioned melt-kneading step is cooled and pulverized and classified (hereinafter referred to as “pulverized classification step”).

The cooling may be performed by natural cooling by receiving the discharged material obtained in the melt-kneading step on a pad or the like, or by forced cooling, for example, by guiding the discharged material to a press roller or the like and applying pressure. Is also good. In the case of forced cooling, particularly when pressure is applied, the discharged molten kneaded material has a T _m -20.
It is preferable that the temperature is not rapidly cooled or stretched (pressed) to a temperature of ° C., and the temperature is gradually cooled. When quenched or stretched (pressed), problems such as insufficient dispersion of wax, wax particles having a large particle size, dispersion of rice grains or dispersion of leaves are caused, and accordingly, black spots on the photoreceptor are caused. Phenomenon such as filming occurs.

In the particles obtained as described above, wax is uniformly dispersed in the form of a sphere having a molecular diameter of 0.2 to 3.0 μm and / or a spindle having a major axis of 1.0 to 4.0 μm. I have.

Finally, the melt-kneaded material is pulverized and classified according to a conventional method to obtain a toner having an average diameter of 5 to 15 μm.

Hereinafter, the present invention will be further described with reference to examples.

EXAMPLES Example 1 100 parts by weight of styrene-acrylic copolymer resin Number average molecular weight (Mn): 4200, Mw / Mn: 52 (Mw; weight average molecular weight) Glass transition point (Tg): 61 ° C., softening point (Tm): 125 ° C ・ Carbon black (MA # 8; manufactured by Mitsubishi Kasei Kogyo) 8 parts by weight ・ Nigrosine dye (Bontron N-01; manufactured by Orient Chemical Industries) 4 parts by weight ・ Low molecular weight polypropylene (Biscol 550P; 4 parts by weight (manufactured by Sanyo Chemical Industries)

The average particle size of the mixture of the above materials was measured using a multistage vibrating sieve and found to be 840 μm. This mixture was put into a Henschel mixer and mixed and stirred at 2000 rpm for 3 minutes. The temperature of the mixture is 25
C. to 46.degree. Average particle size after mixing is 320μ
m.

The twin-screw extruder (PCM30) was set to 120
The mixture obtained above was set at a temperature of ° C. and extruded and kneaded. The temperature of the resin discharged at this time was 151 ° C.
The discharged resin mass was gradually cooled until the temperature reached 93 ° C., and then rapidly cooled with cold air to coarsely pulverize the cooled product.

Next, the obtained coarsely pulverized product is pulverized to an average diameter of 8.2 μm by a jet pulverizer, and then coarse and fine powders are cut by a DS classifier to obtain toner particles having an average diameter of 8.7 μm. Obtained.

Finally, the obtained toner was subjected to a surface treatment by adding 0.2% by weight of hydrophobic silica (H2000; manufactured by Hoechst). The toner thus obtained is referred to as toner A.

Example 2 100 parts by weight of polyester resin Number average molecular weight (Mn): 7100, Mw / Mn: 40 (Mw; weight average molecular weight) Glass transition point (Tg): 66 ° C, softening point : 132 ° C Carbon Black (Regal 330; manufactured by Cabot) 8 parts by weight ・ Cr-containing oil-soluble dye (Bontron S-34; manufactured by Orient Chemical Industries) 2 parts by weight ・ Low molecular weight polypropylene (Viscol TS-200; manufactured by Sanyo Chemical Industries) 4 parts by weight

The average particle size of the mixture of the above materials was measured using a multistage vibrating sieve and found to be 1040 μm. This mixture was put into a Henschel mixer and mixed and stirred at 2000 rpm for 3 minutes. Due to this mixing and stirring, the temperature of the mixture becomes 2
The temperature rose from 4 ° C to 48 ° C. The average particle size after mixing is 550
μm.

The twin-screw extruder (PCM30) was set to 130
The mixture obtained above was set at a temperature of ° C. and extruded and kneaded. The temperature of the resin discharged at this time was 162 ° C.
The discharged resin mass was gradually cooled until the temperature reached 98 ° C., and then rapidly cooled with cold air to coarsely pulverize the cooled product.

Next, the obtained coarsely pulverized product is pulverized to an average diameter of 8.2 μm by a jet pulverizer, and then coarse and fine powders are cut by a DS classifier to obtain toner particles having an average diameter of 8.5 μm. Obtained.

Finally, the obtained toner was added at a ratio of 0.2% by weight of hydrophobic silica (H2000; manufactured by Hoechst) to perform a surface treatment. The toner thus obtained is referred to as toner B.

[0035] Using the Comparative Example Table 1 material, under the conditions shown in Table 1,
Toners C to G were obtained in the same manner as in Example 1 .

[Table 1]

The toners A to G prepared in Examples were dissolved in chloroform and centrifuged. Ten minutes later, the wax floating on the surface was collected, and a SEM photograph was taken to measure the particle size of the wax. The results are shown in Table 2 below.

[0037]

[Table 2]

In the table, D _W is the average diameter of the spherical wax.
(D _W ). a and b represent the average (a) of the major axis of the spindle-shaped wax and the average (b) of the major axis, respectively.

The toners A to G thus obtained were sufficiently mixed with a separately prepared binder type carrier (average diameter: 62 μm) and charged. For the negatively charged toner, the copier EP8600 (Minolta Camera Co., Ltd.) was used. For the positively charged toner, the copier EP8600 was modified, and the printing durability test was performed by changing the photoconductor to an organic photoconductor. . The results are shown in Table 3 below.

[0040]

[Table 3]

The ranking in the above table was performed as follows. Filming of photoreceptor; ◎: no filming at all ○: slight filming but no problem in practical use ×: filming occurs and fogging occurs Black spot fusion (black spot (BS)); No black spot fusion △: Black spot fusion is observed on the photoreceptor, but does not occur in the copy image ×: Black spot appears in the copy image

[0042]

According to the toner of the present invention, the wax is uniformly dispersed with a small particle diameter, and the toner is fused to the photoreceptor due to the separation of the wax, filming, and a black spot, fogging and the like are caused. Absent.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroyuki Fukuda Osaka International Building Minolta Camera Co., Ltd. 2-3-1-13 Azuchicho, Chuo-ku, Osaka City, Osaka (56) References JP-A-4-194869 (JP, A) JP-A-4-195068 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (2)

(57) [Claims] (1) 1 to 7 parts by weight of wax is added to 100 parts by weight of a thermoplastic resin having an average particle diameter of 500 to 5000 μm, and a shearing force is applied.
The average particle size of the thermoplastic resin by a mixer capable of imparting
Step size are mixed until 300~800μm decreases, due to (2) extrusion kneader the mixture obtained in step (1)
And set temperature (T _s ): T _m −20 ° C. ≦ T _s ≦ T _m + 20 ° C. (where T _m is the softening of the thermoplastic resin)
In the range of the point), made by the process cooling the T _m + 35 ° C. step of melt-kneading as discharge at a temperature, and (3) above (2) kneaded product obtained in the step of, pulverized and classified A method for producing an electrophotographic toner. 2. The thermoplastic resin has a softening point of 80 to 160 ° C.
The method for producing an electrophotographic toner according to claim 1, wherein the melting point of the wax is 90 to 180C.