JP3456010B2 - Manufacturing method of 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 in an image forming apparatus using an electrophotographic method such as an electrophotographic copying machine or a laser beam printer.

[0002]

2. Description of the Related Art Usually, a toner is prepared by mixing a toner material including a binder resin, a colorant, a charge control agent, a release agent (wax) and other additives such as magnetic powder, melt-kneading, and then pulverizing. , Classified and manufactured.

[0003]

In this case, the step of blending and mixing the toner materials is extremely important. That is,
If the mixing of each material is not sufficient in the mixing step, only inconvenient toner having performance fluctuations can be obtained as a toner. However, since each toner material has its own unique physical characteristics (particle size, apparent specific gravity, triboelectrification property, etc.), coagulation between the materials is likely to occur even if they are charged at once and mixed.
Therefore, satisfactory results have not always been obtained, such that the obtained toner has defects such as variations in charge amount and uneven coloring, and has a problem in durability for long-term or continuous use. . In addition, in order to solve the above problems, attempts have been made to increase the stirring and mixing intensity (increase the mixing speed and mixing time) in order to improve the uniformity of dispersion in mixing, but this unnecessarily reduces productivity. Not only that, the toner is charged up due to excessive dispersion of the specific components such as the charge control agent and the colorant, which causes a new problem of image quality deterioration. In particular, in the production of toner having a small particle size (average particle size of 10 μm or less), the above-mentioned problems have been obstacles. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and has been made to solve the problem. The object is to prevent variations in charge amount and uneven coloring even when a toner having a small particle size is used, and to improve charge-up. Another object of the present invention is to provide a method for producing a toner that does not deteriorate in image quality due to the above and has high durability during long-term or continuous use.

[0004]

DISCLOSURE OF THE INVENTION As a result of intensive investigations by the present inventors in order to achieve such an object, a method of stepwise mixing toner materials in a mixing step, preferably a colorant and / or
Further, they have found that the above object is satisfied by a method for producing a toner in which a charge control agent is mixed at an intermediate stage or a final stage of the mixing process, and thus reached the present invention. That is, the gist of the present invention is to provide a method for producing a toner, which comprises a step of mixing a toner material comprising at least a binder resin and a colorant and / or a charge control agent.
Of at least one toner material selected from the group consisting of
At least part of the mixing, either in the middle of the mixing process or at the end
It exists in the manufacturing method of the toner characterized by performing in steps .

In the toner manufacturing method of the present invention, each toner material is added and mixed stepwise in the mixing step. That is, in the mixing step, the mixing is carried out through two or more steps. In particular, since the charge control agent and / or the colorant, which has a great influence on the toner performance, is added in the middle stage or the final stage of the mixing process, the difference between the respective materials is increased as compared with the case where the mixing is performed all at once from the beginning. The required agglomeration and overdispersion of certain components can be eliminated at the same time. Therefore,
According to the manufacturing method of the present invention, it is possible to efficiently manufacture a toner that solves the above-mentioned problems, without requiring labor. Hereinafter, the method for producing the toner of the present invention will be described in detail.

First, a binder resin, a colorant, a charge control agent, and other additives, which are constituent materials of the toner, are mixed and mixed at a predetermined ratio. As a device in this case, a gravity dropping type mixer such as a V blender or a ball mill, a high speed fluid type mixer such as a Henschel mixer (manufactured by Mitsui Miike Machinery Co., Ltd.) or a super mixer (manufactured by Kawata Co., Ltd.) is used. The present invention is characterized in that this mixing is carried out stepwise, and preferably at least a part of the charge control agent and / or the colorant in the toner material is mixed in the middle step or the final step of the mixing step. Of the charge control agent and the colorant, the material added in the mixing step may be the colorant alone or the charge control agent alone, or both the colorant and the charge control agent components may be added. When both components are added, the colorant and the charge control agent may be added simultaneously at a certain stage of mixing, or the colorant may be added first and mixed, and then the charge control agent may be added at a subsequent stage. The order of addition may be reversed.
Further, the remaining amount may be mixed after mixing a part of the charged amount of the toner material. Further, a mixture of some toner materials and a mixture of other toner materials may be mixed. In addition, as the mixing condition, the number of rotations of stirring of the apparatus may be the same from the beginning, or may be changed according to the addition during or at the end.

The mixing time is appropriately set according to the constituent materials to be mixed and the characteristics of the mixing apparatus. If necessary,
The mixing device itself may be changed according to the addition in the middle stage or the final stage. In the present invention, a particularly preferable embodiment of the mixing step is to use a high speed fluid mixer such as a Henschel mixer or a super mixer as a mixing device, and to mix a colorant and / or a charge control agent added during or at the end. The conditions are to lower the stirring and mixing strength as compared with the conditions of the preceding stage (for example, lowering the stirring rotation speed, shortening the mixing time, or performing them in combination).

[0008] Here, the high-speed fluid type mixer means that the blade attached to the bottom of the mixing container is rotated at a high speed to disperse the powdery particles like a fluid by the strong shearing and impact action of the blade for mixing. This is the type of mixer used. This type of mixer has stronger stirring strength than the gravity drop type mixer,
This is advantageous in terms of productivity because efficient mixing can be performed in a short time. However, on the contrary, the fine particles such as the colorant and the charge control agent are likely to be excessively dispersed. Therefore, it has been found that more preferable results can be obtained by adding these components at an intermediate stage or a final stage and weakening the stirring and mixing strength at that time.

Further, in these high-speed flow type mixers, the temperature rise in the mixing tank due to the strong stirring action as described above is observed. In some cases, these heat generations adversely affect each toner material, and in particular, when a phenomenon in which the binder resin coagulates and solidifies occurs, the dispersibility and mixing property of the material deteriorates. Therefore, in the present invention, it is preferable to control the temperature in the mixing tank of the mixing device used in the mixing step to be equal to or lower than the glass transition temperature of the binder resin. Above all, it is particularly preferable to carry out under the following conditions.

[0010]

## EQU1 ## Temperature in mixing tank ≦ Tg−5 (° C.) (where Tg is the glass transition temperature of the binder resin used) Particularly desirably, the following conditions are preferable.

[0011]

[Equation 2] Temperature in mixing tank ≤ Tg-10 (° C)

By performing the mixing under the above conditions, the resin is not aggregated and solidified, and the deterioration of the dispersibility and mixing of other materials can be avoided. In order to keep the temperature inside the mixing tank within the above conditions, it is desirable to take measures such as installing a cooling device such as water cooling outside the mixing tank. It is preferable to control the temperature in all stages of the mixing process, but the temperature may be controlled only in a part of the mixing process. After mixing, the mixture is melt-kneaded. The apparatus used in the melt-kneading step is a two- or three-roll machine, a Banbury mixer,
Examples include a single-screw or twin-screw extruder. In this step, a component compatible with the binder resin is melted with the resin, and a component such as a charge control agent not compatible with the binder resin is dispersed in the melted resin.

Next, after the molten and kneaded product is cooled and solidified,
The toner is manufactured through the steps of coarse pulverization, fine pulverization and classification. A hammer mill, a cutter mill, or the like is used for coarse pulverization, a high-speed rotary fine pulverizer, a jet pulverizer, or the like is used for fine pulverization, and a forced spiral centrifugal classifier, an inertial classifier, or the like is used for classification. The method for producing a toner of the present invention is not limited to a non-magnetic black toner for normal monochromatic image formation, as long as the requirement that the toner materials are mixed stepwise in the mixing step is satisfied, and a magnetic toner or a full color image formation The present invention can be applied to the production of various conventionally known toners for electrophotography, such as the above color toner.

As the toner material used in the present invention, all the conventionally known toner materials can be used, for example, as follows. Binder resin: Styrene / acrylic copolymer resin, polyester resin, epoxy resin, etc. Colorant: Carbon black, monoazo pigment, disazo pigment, quinacridone pigment, copper phthalocyanine pigment,
Charge control agents such as anthraquinone dyes and rhodamine dyes: Nigrosine compounds (including modified products), quaternary ammonium compounds, styrene amino resins, etc. for positive charging, metal-containing complex dyes for negative charging,
Other additives such as complex compounds of alkylsalicylic acid with chromium, zinc, etc .: As a releasing agent (wax), low-molecular-weight polyethylene or polypropylene, etc., as magnetic powder when producing magnetic toner, magnetite fine particles, ferrite fine particles, etc.

[0015]

EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples. In the examples and comparative examples, “part” is “part by weight”. Example 1 The toner formulation was as follows.

[0016]

[Table 1]   Binder resin component Styrene / n-butyl acrylate resin 100 parts                       (Softening point about 140 ° C, Tg about 60 ° C)   ・ Wax component Low molecular weight polypropylene 3 parts                       (Sanyo Kasei Co., Viscole 660P)   ・ Colorant component carbon black 8 parts                       (Mitsubishi Carbon, Mitsubishi Carbon Black # 40)   ・ Charge control agent component Nigrosine dye 3 parts                       (Bontron N09 manufactured by Orient Chemical Co., Ltd.)

In the production, first, the binder resin component and the wax component are mixed by a Henschel mixer for about 30 minutes, then the apparatus is stopped, the colorant component and the charge control agent component are added therein, and further, Mixing was performed for about 3 minutes, and the mixing was completed. It should be noted that the temperature in the mixing tank is kept at about 50 by water cooling throughout the entire mixing process.
The temperature was set to ℃ or below. Then, the mixture was melted and kneaded by heating with a twin-screw extruder. The obtained kneaded product was cooled and solidified, then roughly pulverized with a feather mill and finely pulverized with a jet mill. Further, toner fine powder having a particle size of 5 μm or less was cut by a rotor rotary classifier to make the particle size uniform (about 8 μm in average particle size).
m). Hydrophobic silica was added to this classified product using a Henschel mixer to prepare a toner. 6 parts of this toner and 94 parts of a ferrite carrier having an average particle size of about 50 μm were mixed with a V blender to prepare a developer.

As an evaluation test for these toners and developers, image quality confirmation and durability confirmation (50,000 sheets continuous actual copying test) were carried out by actual copying using a commercially available copying machine using an organic photoconductor drum as a photoconductor. It was The results are shown in Table 1.
The image density was measured using a Macbeth reflection densitometer for the solid area of the image, and the fog was measured using a Hunter whiteness meter to measure the difference in whiteness of the background portion of the paper before and after passing the paper. The charge amount of the developer was also measured by the blow-off method, and the result was expressed as Q / M.

[0019]

[Table 2]

According to Table 1, the image quality has a sufficient image density and a low fog level, and moreover, the initial image quality was maintained over 50,000 sheets. Further, it was found that the charge amount of the developer during that time also changed extremely stably.

Comparative Example 1 Using the same formulation as in Example 1, all the ingredients were charged at the same time when mixing with a Henschel mixer,
A toner and a developer were prepared in the same manner as in Example 1 except that mixing was carried out for 1 minute, and an evaluation test was also conducted in the same manner. The results are shown in Table 2.

[0022]

[Table 3]

According to Table 2, the image density is significantly reduced particularly in continuous shooting, and the image quality is significantly deteriorated.
Further, during that time, the developer charge amount also showed a significant charge-up tendency, and it was confirmed that the developer lacked stability. It is considered that this is due to excessive dispersion in the mixing step of the colorant and charge control agent components. Example 2 The toner formulation was as follows.

[0024]

[Table 4]   -Binder resin component Bisphenol A propylene oxide 100 parts                       Synthesis of adduct and terephthalic acid as main components                       Polyester resin                       (Softening point approx. 140 ° C, Tg approx. 65 ° C)   ・ Wax component Low molecular weight polypropylene 3 parts                       (Sanyo Kasei Co., Viscole 550P)   ・ Colorant component carbon black 10 parts                       (MITSUBISHI KASEI, MITSUBISHI CARBON BLACK MA600)   ・ Charge control agent component Chromium metal dye 3 parts                       (Bontron S34, manufactured by Orient Chemical Co., Ltd.)

In the production, first, the binder resin component and the wax component are mixed with a super mixer for about 40 minutes, then the apparatus is temporarily stopped, the colorant component and the charge control agent component are added therein, and further, Mixing was performed for about 5 minutes, and the mixing was completed. It should be noted that the temperature in the mixing tank is about 50 ° C. by water cooling throughout the entire mixing process.
Below. Then, the mixture was melted and kneaded by heating with a twin-screw extruder. The obtained kneaded product was cooled and solidified, then roughly pulverized with a feather mill and finely pulverized with a jet mill. further,
The toner fine powder having a particle size of 5 μm or less was cut by a rotor rotary classifier to have a uniform particle size (average particle size of about 7 μm). Hydrophobic titania was added to this classified product using a Henschel mixer to prepare a toner. 7 parts of this toner and 93 parts of magnetite carrier having an average particle size of about 50 μm
A developer was prepared by mixing with a blender. As an evaluation test for these toners and developers, image quality confirmation and durability confirmation (5,000 sheets continuous copying test) were carried out by actual copying using a commercially available laser beam printer using an organic photoconductor drum as a photoconductor. The results are shown in Table 3. The evaluation method was the same as in Example 1.

[0026]

[Table 5]

According to Table 3, the image quality has a sufficient image density and a low fog level, and the almost initial image quality was maintained over 5,000 sheets. Further, it was found that the charge amount of the developer during that time also changed extremely stably.

Example 3 Using the same formulation as in Example 2, when mixing with a supermixer, the resin component, wax component and colorant component were first charged and mixed for about 40 minutes, and then once. The apparatus was stopped, the charge control agent component was added thereto, and the mixture was further mixed for about 5 minutes to complete the mixing. In addition, the temperature in the mixing tank was set to about 50 ° C. or lower by performing water cooling throughout the mixing process. Hereinafter, a toner and a developer were prepared in the same manner as in Example 2, and the evaluation test was also performed in the same manner. The results are shown in Table 4.

[0029]

[Table 6]

According to Table 4, the image quality has a sufficient image density and a low fog level, and the almost initial image quality was maintained over 5,000 sheets. Further, it was found that the charge amount of the developer during that time also changed extremely stably.

Example 4 Using the same formulation as in Example 2, when mixing with a supermixer, the resin component, the wax component and the charge control agent component were first charged and mixed for about 40 minutes.
The apparatus was once stopped, the colorant component was added thereto, and the mixture was further mixed for about 5 minutes, and the mixing was completed. In addition, the temperature in the mixing tank was set to about 50 ° C. or lower by performing water cooling throughout the mixing process. Hereinafter, a toner and a developer were prepared in the same manner as in Example 2, and the evaluation test was also performed in the same manner. The results are shown in Table 5.

[0032]

[Table 7]

According to Table 5, the image quality has a sufficient image density and a low fog level, and the almost initial image quality was maintained over 5,000 sheets. Further, it was found that the charge amount of the developer during that time also changed extremely stably.

Comparative Example 2 Except that the same formulation as in Example 2 was used and all the ingredients were charged at the same time when mixing with a super mixer, and the mixture was mixed for about 40 minutes. A toner and a developer were prepared by the operation, and the evaluation test was conducted in the same manner. The results are shown in Table 6.

[0035]

[Table 8]

According to Table 6, the image density was significantly reduced especially in continuous shooting, and the image quality was significantly deteriorated.
Further, during that time, the developer charge amount also showed a significant charge-up tendency, and it was confirmed that the developer lacked stability. It is considered that this is due to excessive dispersion in the mixing step of the colorant and charge control agent components.

[0037]

As described above, according to the toner manufacturing method of the present invention, even when a small particle size toner is manufactured, variations in charge amount and coloring unevenness do not occur, and deterioration of image quality due to charge-up does not occur. Furthermore, it becomes possible to efficiently manufacture a toner having excellent durability even during long-term or continuous use.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiji Nagashima 1 Fukuda-cho, Joetsu City, Niigata Prefecture Inside the Naoetsu Plant of Mitsubishi Kasei Co., Ltd. (56) References JP-A-5-34976 (JP, A) JP-A-5 -61250 (JP, A) JP-A-3-164750 (JP, A) JP-A-6-95431 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 9/08

Claims (4)

(57) [Claims] 1. A method for producing a toner, comprising a step of mixing a toner material comprising at least a binder resin and a colorant and / or a charge control agent, the colorant and the charge control agent
At least one toner material selected from the group consisting of
Of at least a part of the
A method for producing a toner, which is carried out at the final stage . 2. A small amount selected from colorants and charge control agents.
Mixing at least a portion of at least one toner material,
The method according to claim 1, which is performed in the final stage of the mixing process.
A method for producing the toner described above. 3. A colorant and a charge control agent are selected from the group consisting of:
At least one toner material selected is a charge control agent
The toner according to claim 1 or 2, characterized in that
Build method. 4. The method for producing a toner according to claim 1, wherein the temperature in the mixing tank of the mixing device used in the mixing step is equal to or lower than the glass transition temperature of the binder resin.