JPH04145449A - Production of toner for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To efficiently produce a toner in large quantities by adding a flowability rendering agent to toner particles obtd. by pulverization, mixing them, classifying this mixture and removing the fine powder. CONSTITUTION:A toner is composed essentially of a binding resin such as polystyrene or a styrene-propylene copolymer and a colorant such as carbon black or aniline black. In order to form a visible image having sufficiently high density, the colorant is used in the toner particles by about 1-20wt.%. A flowability rendering agent is then added to the toner particles by 0.3-7.0wt.%, preferably 1.0-5.0wt.% of the amt. of the toner particles and they are mixed. This mixture is classified, the fine powder is removed and a toner having a prescribed particle size range is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a toner for developing electrostatic images used in electrophotography.

[Conventional technology]

The method for producing toner for developing electrostatic images includes mixing a colorant and a binder resin, melting and kneading the resulting mixture, and then
The mixed wire/pulverization method, which involves fine pulverization, is commonly used.
Then, a classification step is performed to obtain toner particles in a specific particle size range according to the requirements for toner characteristics (resolution, fog, etc.), and after that, a fluidity imparting agent, a charge control agent, etc. A mixing step is provided to attach and fix cleaning aids and the like to the surface of the toner particles. FIG. 2 is a flowchart of a conventional method for producing toner for developing electrostatic images, in which a mixing step of adding and mixing a fluidity imparting agent is provided after the classification step.

Further, Japanese Patent Application Laid-Open No. 53-58244 describes that, in the production of magnetic toner, hydrophobic silica fine powder is mixed before classification.

[Problem to be solved by the invention]

However, when we aim to improve image quality and speed by reducing the toner particles, lowering the melting point of the binder resin to lower the fixing temperature, and increasing the amount of wax used as a release agent, the following problems occur. A phenomenon has started to appear.

(1) After pulverization, toner particles are triboelectrically charged, and the electrostatic attraction causes them to stick to the device wall or agglomerate among themselves. However, as the surface area of the toner increases due to the reduction in particle size, it causes further adhesion and Aggregation becomes more likely to occur.

(2) Due to the low melting point of the binder resin, toner particles tend to aggregate with each other after pulverization.

(3) When the amount of the release agent is increased, the pulverization property is improved, but since a large amount of the release agent is exposed on the surface of the pulverized particles, aggregation of toner particles occurs.

(4) When the toner is a chromatic color, the stickiness of the colorant increases, so it is more difficult to use than a black toner using carbon black.
Powder fluidity deteriorates.

Due to the deterioration of powder properties as described above, the following problems have occurred in the classification process.

(1) Due to toner aggregation and adhesion, the supply stability of the classification feeder is lost.

(2) If the supply section of the classifier is clogged with toner aggregates, supply instability will occur due to toner aggregation and adhesion, resulting in supply constraints and, as a result, the throughput must be reduced. be.

(3) Even if the aggregates are fed into the classifier, they are discharged without being sufficiently broken up, so the desired particle size distribution cannot be obtained and the classification efficiency decreases.

On the other hand, in the case described in JP-A No. 53-58244, a gravity drop type mixer such as a V-type mixer, a tubular mixer, etc. is used to mix hydrophobic silica fine powder. As stated in the above, it takes a long time to complete the mixing, and if the fine hydrophobic silica powder is strongly aggregated, it is difficult to break it up and mix it. Therefore, in this publication, in order to efficiently mix the intermediate toner, 0, 2 to 4 spherical substances made of glass, ceramic, iron, etc. are added to the mixing system to break up the aggregates of fine silica powder. It is proposed to speed up the mixing process and shorten the mixing completion time. However, this method requires an operation to remove the spherical substances after the mixing operation of the intermediate toner and fine silica powder, and if there is a change in toner type, these spherical substances must be removed. It also has the disadvantage of requiring additional cleaning operations.

In addition, although the mixing method described in the publication improves the supply performance and classification efficiency, the adhesion between the fine silica powder and the intermediate toner is weak, so the fine silica powder is removed by the classification operation after mixing, and the product after classification is Powder fluidity may deteriorate. Therefore, after the classification operation, it is necessary to add and mix the fluidity imparting agent again, and when looking at the entire toner manufacturing process, there is a problem that the productivity cannot be said to be good.

The present invention solves the above problems, has high efficiency,
Another object of the present invention is to provide a method for producing a toner for developing an electrostatic image, which is accompanied by a fine powder classification method that can increase throughput.

[Means to solve the problem]

The present invention relates to a method for producing a toner for developing an electrostatic image, which comprises mixing a colorant and a binder resin, melting and kneading the resulting mixture, and then finely pulverizing the toner particles obtained by the pulverization. A fluidizing agent is added to the powder, and the powder is mixed in a fluidized state using a mixer that moves at high speed using air current or mechanical force, so as not to substantially cause pulverization, and then the fine powder side is removed to obtain a specific particle size. The present invention is characterized in that it includes a classification step for classifying products into a range of products.

FIG. 1 is a flowchart of the manufacturing method of the present invention,
After the pulverization step, a mixing step is provided in which a fluidity imparting agent is added and mixed, and then a classification step is provided in which the material is classified.

In the present invention, the toner for developing an electrostatic image is composed of at least a binder resin and a colorant, and a charge control agent and a release agent are added as necessary.

As the binder resin, polystyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-acrylic ester copolymer, styrene-methacrylic ester copolymer,
Examples include acrylic resin, polyester resin, vinyl chloride resin, and epoxy resin.

Colorants include carbon black, aniline black, nigrosine dye, aniline blue, chrome yellow,
Examples include ultramarine blue, oil red, phthalocyanine blue, lamp black, rose bengal, and mixtures thereof. These colorants need to be contained in a proportion such that a visible image of sufficient density is formed, and are usually used in toner particles in a proportion of about 1 to 20% by weight.

As the charge control agent, nigrosine dye, chromium-containing complex,
Quaternary ammonium salts and the like are used, and these need to be selected depending on the polarity of the toner particles.

As the mold release agent, polyolefins (eg, polyethylene, polypropylene), alkylamides (eg, ethylene bisstearylamide), polytetrafluoroethylene, etc. are used.

These materials are mixed, and the resulting mixture is melted and kneaded by a conventional method, and then pulverized to obtain toner particles. The pulverization is usually performed so that the average particle size is 5 to 15 μm.

Next, a fluidity imparting agent is added to the obtained toner particles and mixed.

In the present invention, fluidity imparting agents include fine particles of metal oxides such as silica, alumina, magnesia, zirconia, ferrite, and magnetite, and those fine particles are combined with silane coupling agents, titanate coupling agents, zircoaluminates, and quaternized Those surface-treated or coated with treatment agents such as ammonium salts, fatty acids, fatty acid metal salts, fluorine-based activators, solvents, and polymers, fine particles of fatty acids or metal salts thereof such as stearic acid and zinc stearate, and those fine particles. Fine particles of polymers such as polystyrene, polymethyl methacrylate, and polyvinylidene fluoride that have been surface-treated with a treatment agent, and those fine particles that have been surface-treated or coated with the treatment agent are used. The average particle size of these fluidity imparting agents used is in the range of 0.01 to 3 μm.

The amount of these fluidity imparting agents added is 0 to the toner particles.
．． A range of 3 to 7.0% by weight, particularly 1.0 to 5.0% by weight is preferred.

The toner particles and the fluidity imparting agent are mixed by moving the powder in a fluidized state at high speed by air current or mechanical force so as not to substantially cause pulverization.

As the mixer, a high-speed fluid mixer such as a Henschel mixer, a UM mixer, a Kawata super mixer, etc. is used. Additionally, hybridization systems known as surface modification machines, such as Ongmil, Mechanomill, and Kryptron, can also be used.

The mixture is then classified in a classification step and the fine powder side is removed to obtain toner having a predetermined particle size range.

The present invention is most effective when the particle size of the toner is in a volume average particle size range of 5 to 15 μm, especially toner with a volume average particle size of 8.5 μm or less.

In the present invention, as the classifier, an inertial classifier, a forced vortex type centrifugal classifier, a free vortex type centrifugal classifier, etc. can be used. Specifically, Elbow Jet (manufactured by Nippon Steel Mining)
, AccuCut (=DONASELEC) (manufactured by Donaldson Japan), Turbo Classifier (manufactured by Nisshin Engineering), Diversion Separator (manufactured by Nippon Pneumatic Industries (Kiku), Cyclone, etc.).
It is not limited to these.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Toner A Polyester/styrene-n-butyl 70 parts by weight Chil methacrylate/polypropylene=35155/10 copolymer styrene/n-
Butyl acrylate - 20 parts by weight Citronitrile - 70.5/24.515 Crosslinked polymer Colorant (C, 1, pigment - 10 parts by weight Red 48:1) After melt-kneading the above components, pulverize with a jet mill. Toner particles having a volume average particle size of .=11.0 μm were obtained.

Next, 30 parts by weight of titanium oxide was added to 1000 parts by weight of the obtained toner particles, and 350 (6 parts by 1 + pm) was added using a 51 Henschel mixer (manufactured by Mitsui Miike Kokoki ■).
Mixed for a minute. Next, the resulting mixture was mixed with Accucut A.
-12 (manufactured by Japan Donaldson ■), D, o = 1
．． IJ, czms Amount of fine powder less than 5 pm: 18% by number
Classification was carried out with the following objectives in mind.

The classification results and particle size distribution measurement results are shown in Table 1.

The particle size distribution was measured using a Coulter Counter TA-n model (
(manufactured by Coulter Electronics).

In addition, in the table, the ND value was determined from the Rosin-Rammler diagram. The larger the ND value, the sharper the particle size distribution.

Comparative Example 1 For toner particles similar to those in Example 1, 51
The same glue as in Example 1, except that the mixing treatment with the Henschel mixer was not performed. Classification was carried out with the aim of determining the value and amount of fine powder. The classification results and particle size distribution measurement results are
Shown in the table.

Next, 30 parts by weight of titanium oxide was added to 1000 parts by weight of the obtained classified product, and a 51 Henschel mixer treatment was performed.

Example 2 The components of toner A in Example 1 were melted and kneaded, and D5.
= 8.2 μm, and the obtained toner particles were subjected to a mixing treatment in the same manner as in Example 1, and then transferred to Accucut using Co., Ltd. D. =8.5μm, 5μ
Classification was performed with the aim of achieving a fine powder amount of 22% by number or less.

The classification results and particle size distribution measurement results are shown in Table 1.

Comparative Example 2 The same toner particles as in Example 2 were classified with the aim of achieving the same D50 value and fine powder amount as in Example 2, except that the mixing treatment with a 51 Henschel mixer was not performed. The classification results and particle size distribution measurement results are shown in Table 1.

Next, 30 parts by weight of titanium oxide was added to 1000 parts by weight of the obtained classified product, and subjected to 51 Henkel mixer treatment. The results obtained are shown in Table 1.

Example 3 Toner B Melt viscosity 140°C 10' poise,
115℃IQ'poise (7o-Tester 1
: Measured at) Polyester resin (Tg=63°C) 95
Parts by weight Colorant (C, 1, Pigment, 5 parts by weight Red 122) After melt-kneading the above components, they were pulverized with a jet mill to obtain a volume average particle size. =7 μm toner particles were obtained.

Next, 15 parts by weight of titanium oxide was added to 1000 parts by weight of the obtained toner particles, and mixed for 6 minutes at 3500 rpm using a 51 Henschel mixer (manufactured by Mitsui Miike Koki ■). Next, the resulting mixture is Accucut ^-
12 (manufactured by Nippon Donaldson ■), D5o=7.
Classification was performed with the aim of reducing the amount of fine particles of 7 μm and 4 pm to 2020 particles.

The classification results and particle size distribution measurement results are shown in Table 1.

Comparative Example 3 The same paste as in Example 1, except that the same toner particles as in Example 3 were not mixed in a 51 Henschel mixer. Classification was carried out with the aim of determining the value and amount of fine powder. The classification results and particle size distribution measurement results are shown in Table 1.

Next, 15 parts by weight of titanium oxide was added to 1000 parts by weight of the obtained classified product, and a 51 Henschel mixer treatment was performed.

The classification operation in the above Examples and Comparative Examples was performed on toners (
That is, the rotation speed and air volume of the classifier were determined from a preliminary test using the toner of the comparative example, and then the main test was conducted by gradually increasing the supply amount based on the preliminary test conditions.

As is clear from Table 1 below, in the present invention, all toners could be classified by increasing the supply amount. On the other hand, in the case of the comparative example, the maximum supply amount was the value shown in Table 1. This is because toner clogging and adhesion at the classifier supply port caused by agglomeration made stable supply impossible. Regarding the supply amount, in the examples of the present invention, 2 to 2 of the comparative examples
It was possible to increase it five times.

Regarding the yield, the examples of the present invention exceeded the comparative examples,
The smaller the target particle size, the greater the effect, and no decrease in yield was observed even when the supply amount was increased.

Regarding the particle size distribution, the following results were obtained. That is, when the supply amount is the same, the amount of fine powder of 5 μm or less or 4 μm or less and the amount of coarse powder of 20.0 μm or more are smaller in the example of the present invention than in the comparative example, resulting in a product with a sharp particle size distribution. is obtained. Especially, D5o is 8.2μm
The effect was significant in the case of toner.

In the above examples and comparative examples, the classification feeder is as follows:
An experiment was conducted to determine the feeding accuracy of the toner used in Example 1 and Comparative Example 1, although Akicolate Model 102 (Kuma Engineering) was used. The second result is
Shown in the table.

As is clear from Table 2 in the margin table below, in the case of the mixed toner of the example, the feeding accuracy is excellent at any supply amount, but the toner of the comparative example without the mixing process is excellent. In some cases, the feeding accuracy was poor.

As a result, we had no choice but to stop supplying Aquicolate 102 type. Therefore, this test is 5ynj
ron Magnetic Feede+ F-TOI
Human (FMC Corp) was used.

Further, for the toners obtained in Examples 1 to 3 and Comparative Examples 1 to 3, the remaining amount of the fluidity imparting agent, the degree of aggregation of the toner, the compression ratio, and the amount of coarse particles (106 μm or more, 45 μm or more) were measured. The results are shown in Table 3.

In addition, the remaining amount of fluidity imparting agent is determined by measuring the strength of titanium oxide with fluorescent X.
It was determined by the line.

The degree of aggregation was determined by leaving it in an environment of 45°C and 50% humidity for 17 hours, passing it through 1000μm and 106μn1 wire sieves, and dividing the amount of toner on each sieve by the amount of toner passed through, and expressed as a percentage. It is something.

The compression ratio is determined using a powder tester (manufactured by Hosokawa Micron ■)
Measured by.

The amount of coarse particles is determined by sieving 100 g of toner with each wire sieve and showing the amount of toner on the sieve as a percentage.

As is clear from Table 3 below, in the examples of the present invention, the fluidity imparting agent is reduced compared to the toner of the comparative example, but the values of the degree of cohesion and compression ratio are at the same level. It can be seen that the powder fluidity is not lost.

Further, regarding the amount of coarse particles, the toner of the example of the present invention had a much smaller amount than that of the comparative example. This is because even if aggregated particles were generated during the mixing process, they were crushed or re-agglomerated by classification.

Furthermore, 7 parts by weight of the toner of the example of the present invention and the toner of the comparative example were each taken, mixed with 93 parts by weight of carrier, and then each was made into 50,000 copies using FX5075 (manufactured by Fuji Xerox ■). I went running.

As a result, compared to the developer using the toner of the comparative example, in the developer using the toner of the example of the present invention, the fluidity imparting agent invasion into the carrier was 1/3 or less, and the charging Sexual deterioration has been significantly reduced. As a side effect, the life of the developer in the example was extended by more than three times.

In the same copy running as above, when the toner of the comparative example was used, white spots were observed in the image area of the copy, and it was observed that aggregates of the fluidity imparting agent were developed. On the other hand, in the case of the toner of the example, images of clear image quality without occurrence of white spots were obtained, and the same problem did not occur even when copying 20,000 copies. As a side effect, the occurrence of defects such as white spots in image quality was also eliminated.

〔Effect of the invention〕

As is clear from the comparison of the above examples and comparative examples, in the present invention, a fluidity imparting agent is added to toner particles obtained by pulverization, and after mixing, classification is performed in a classification step, which improves processing efficiency. It is possible to perform classification with high efficiency and increased throughput. This effect is particularly noticeable in the case of small particle diameter toners and low melting point toners.

[Brief explanation of the drawing]

FIG. 1 shows a flowchart of the manufacturing method of the present invention, and FIG. 2 shows a flowchart of a conventional manufacturing method.

Claims (3)

[Claims] (1) In a method for producing a toner for developing an electrostatic image, which comprises mixing a colorant and a binder resin, melting and kneading the resulting mixture, and then finely pulverizing the toner, the toner particles obtained by the finely pulverizing A fluidizing agent is added and the powder is moved in a fluid state at high speed using air current or mechanical force, using a mixer.
A method for producing a toner for developing an electrostatic image, comprising a classifying step of removing fine powder and classifying the toner into particles within a specific particle size range after mixing so as not to substantially cause pulverization. (2) The method for producing a toner for developing an electrostatic image according to claim 1, wherein the toner for developing an electrostatic image is a chromatic toner. (3) The volume average particle diameter of the toner for developing electrostatic images is 8.5μ
3. The method for producing a toner for developing an electrostatic image according to claim 1 or 2, wherein the toner is less than or equal to m.