JP5470741B2 - Method for producing toner for electrophotography - Google Patents

Description

  The present invention relates to a method for producing an electrophotographic toner, and more particularly, to a method for producing an electrophotographic toner by recycling fine powder.

  A method for producing an electrophotographic toner is known in which raw materials constituting an electrophotographic toner are mixed, melt-kneaded, pulverized and classified, and the fine powder generated in the pulverization and classification process is reused in the production of the toner. (For example, see Patent Documents 1 and 2).

  However, when the fine powder generated in this pulverization and classification process is reused, the bulk density of the raw material mixture decreases due to the added fine powder, and the speed of the raw material supplied to the kneader (particularly the twin screw extrusion type) decreases. A so-called feed-neck phenomenon such as occurrence of bridging or bridging that cannot be supplied to the kneading machine has occurred, resulting in a problem that it cannot be quantitatively and stably supplied to the kneading machine.

  In order to compensate for the decrease in productivity due to such a problem, a method for setting the operation conditions of the kneader in detail (for example, see Patent Document 3) or a method for heating and melting fine powder (for example, Patent Documents 4, 5, and 6). And a method of granulating fine powder (see, for example, Patent Documents 7 and 8), a method of performing a mixing method that requires complicated and advanced techniques (for example, see Patent Documents 9 and 10), water and moisture (For example, see Patent Documents 11, 12, and 13) and the like have been proposed.

  These various methods for recycling fine powders are mainly methods for improving productivity. However, power consumption energy is increased by increasing production facilities, production processes, production time, heating and production time. The total productivity has not been improved.

Also, if the temperature conditions of kneading, the shape of the extrusion screw, etc. are changed or restrictions are born, the dispersion of the originally intended pigment, WAX, and charge control agent may be affected, leading to image defects. There is.
JP-A-6-266158 Japanese Patent Laid-Open No. 5-34976 JP 2004-101845 A JP-A-10-161343 JP-A-8-069126 JP-A-6-186775 JP-A-6-266157 Japanese Patent No. 3355857 JP 2006-259017 A Japanese Patent No. 3451719 JP-A-10-307422 Japanese Patent Laid-Open No. 10-319630 Japanese Patent Laid-Open No. 2006-243592

  The present invention has been made under the circumstances as described above, and maintains good dispersion of pigments, waxes, charge control agents, etc. without requiring an increase in production facilities, production processes, and production time. It is another object of the present invention to provide a method for producing an electrophotographic toner that can be easily and highly productively produced by recycle of fine powder.

To solve the above problems, a first aspect of the present invention, the mixing step of mixing while spraying liquid having a solubility to the binder resin in the toner material containing a binder resin and a colorant Pigments, the mixed Based on a melt-kneading step for melt-kneading the mixture obtained in the step, a pulverizing / classifying step for pulverizing and classifying the melt-kneaded product obtained in the melt-kneading step, and a toner material having a predetermined particle diameter obtained by the pulverizing / classifying step. Collecting the fine powder classified as particles having a particle size smaller than the predetermined particle size so as to be reused as a toner raw material to be mixed in the next mixing step, Provided is a method for producing an electrophotographic toner, wherein the fine powder recovered in the recovery step is returned to the next mixing step to reuse the fine powder .

In this method of manufacturing toner for electrophotography, as before Symbol liquid body, it can be used those having a boiling point lower than the softening point of the binder resin.

  The amount of the liquid added can be 1 to 20% by mass of the raw material excluding fine powder.

Spray before Symbol liquid body can be carried out by mixing machine equipped with two-fluid nozzle.

  According to the present invention, it is possible to manufacture toner by recycling fine powder while maintaining good dispersion of pigments, waxes, charge control agents, etc., without requiring an increase in manufacturing facilities, an increase in manufacturing processes, and an increase in manufacturing time. An electrophotographic toner manufacturing method that can be easily performed with high productivity is provided.

  Hereinafter, embodiments of the present invention will be described.

  The method for producing an electrophotographic toner according to an embodiment of the present invention recycles the fine powder generated in the pulverization and classification process into the raw material mixing process, and has solubility in the binder resin in the mixed raw material and fine powder. It is characterized by spraying a liquid.

  In this way, when the fine powder generated in the pulverization and classification process is recycled to the raw material mixing process, the raw material is uniformly mixed by spraying a liquid having solubility in the binder resin, and the mixing process is performed. It becomes possible to stably supply the raw material mixture at a high speed.

  In addition, when the raw material mixture is kneaded, the resin temperature can be lowered by the heat absorption due to the evaporation of the sprayed liquid, thereby improving the dispersibility.

  In this embodiment, various organic liquids are mentioned as a liquid which is sprayed with respect to the recycled fine powder and raw material and which has solubility with respect to the binder resin.

  When the main resin is a polyester resin, for example, alcohols such as methanol, ethanol, isopropanol and 1-butanol, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate and isobutyl acetate, toluene and xylene Benzene derivatives such as, and furan derivatives such as tetrahydrofuran.

 On the other hand, when the main resin is a styrene acrylic resin, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate and isobutyl acetate, saturated hydrocarbons such as normal hexane and heptane, and benzene such as toluene and xylene Examples thereof include furan derivatives such as derivatives and tetrahydrofuran.

  In addition, since the liquid whose boiling point exceeds the temperature at the time of kneading remains in the toner, it is not possible to use a liquid that may cause a decrease in grindability and an adverse effect on image quality. Accordingly, those having a boiling point lower than the softening point of the binder resin are desirable.

  The addition amount of the liquid is desirably 1 to 20% by mass of the raw material excluding fine powder. If it is less than 1% by mass, the effect of addition is difficult to obtain, and if it exceeds 20% by mass, it may be liquefied or granulated into a lump larger than the kneader screw diameter, which is not desirable.

  Hereinafter, a toner manufacturing method according to an embodiment of the present invention will be described in the order of steps.

  In the raw material mixing step, a mixer having a two-fluid nozzle is used. Examples of the mixing apparatus include a double-con mixer, a drum mixer, a super mixer, a Henschel mixer, and a nauter mixer. For example, as shown in FIG. 1, a Mitsui Mining Co., Ltd. Henschel mixer (FM-20L) with a two-fluid nozzle attached can be used.

  In the mixer shown in FIG. 1, a mixing blade 2 and a discharge port 3 are provided at the inner bottom of the mixer body 1, and an internal mixing type two-fluid nozzle (KAM nozzle, manufactured by Kyoritsu Alloy Co., Ltd.) 4 is arranged at the top. Yes. The mixing blade 2 is driven by a motor 5, and the two-fluid nozzle 4 is connected to a liquid supply hopper 6 and connected to a compressor 7 via a regulator 8 and a pressure gauge 9. The liquid is sprayed from the two-fluid nozzle 4 into the mixer body 1 by supplying liquid from the liquid supply hopper 6 and simultaneously introducing high-pressure air from the compressor 7. An exhaust port 10 provided with a filter is provided at the upper part of the mixer.

  First, as a toner internal additive, raw materials and classified fine powder are weighed and mixed, accommodated in the mixer body 1, and mixed to drive the mixing blade 2 so that the raw materials are uniform. After the raw materials become uniform to some extent, mixing is continued while spraying and spraying the resin-soluble liquid in the liquid supply hopper 6 from the two-fluid nozzle 4. At this time, if the sprayed droplets are too small, they will volatilize instantaneously. Therefore, it is preferable to adjust the liquid supply speed and the pressure air supply amount to adjust the droplet size to 100 μm or more.

  In this way, by spraying a liquid that is soluble in the binder resin, the surfaces of the binder resin particles and the fine powder particles are dissolved, and the fine powder particles adhere to the surface of the binder resin particles. Is uniformly performed, and the supply of the raw material mixture to the kneading step can be stably performed at a high speed.

  Next, the blended and mixed toner raw material mixture is melt-kneaded to melt the resins and disperse the colorant and the like therein. In this melt-kneading step, for example, a continuous kneader can be used. In recent years, single-screw or twin-screw extruders have become mainstream due to the advantage of being capable of continuous production. For example, KTK type twin screw extruder manufactured by Kobe Steel, TEM type manufactured by Toshiba Machine Co., Ltd. Generally used are a twin screw extruder, a twin screw extruder manufactured by Kay Sea Kay Co., Ltd., a PCM type twin screw extruder manufactured by Ikekai Tekko Co., Ltd., and a co-kneader manufactured by Buss Co., Ltd.

  Further, after the color resin composition obtained by melt kneading the toner raw material mixture is melt kneaded, it is rolled with two rolls or the like and cooled by water cooling or the like.

  The cooled product of the colored resin composition thus obtained is then pulverized to a desired particle size in a pulverization step. In the pulverization step, first, coarse pulverization is performed with a crusher, hammer mill, feather mill, etc., and further, a counter jet mill, micron jet, inomizer (manufactured by Hosokawa Micron Co., Ltd.); IDS type mill, PJM jet pulverizer, supersonic jet pulverizer IDS, CPY + UFS (manufactured by Nippon Pneumatic Industry Co., Ltd.); Cross Jet Mill (manufactured by Kurimoto Iron Works Co., Ltd.); Ulmax (manufactured by Nisso Engineering Co., Ltd.); SK Jet O Mill (Seisin Enterprise Co., Ltd.) )); Kryptron (manufactured by Kawasaki Heavy Industries, Ltd.); pulverized with a turbo mill (manufactured by Turbo Industry). In the pulverization step, the toner is pulverized to a predetermined toner particle size step by step.

  Thereafter, toner particles having a desired particle diameter are obtained in the classification step. Examples of classifiers include a class seal, a micron classifier, a sped classifier (manufactured by Seishin Enterprise Co., Ltd.); a turbo classifier (manufactured by Nissin Engineering Co., Ltd.); a micron separator, a turboplex (ATP), and a TSP separator. (Manufactured by Hosokawa Micron Co., Ltd.); Elbow Jet (manufactured by Nippon Steel Mining Co., Ltd.), high-precision airflow classifier DSF, DXF, UFC, Microspin MP (manufactured by Nippon Pneumatic Industry Co., Ltd.); YM Microcut (Yaskawa) Trading Co., Ltd.).

  In the above classification step, the toner particles are separated into toner particles having a desired particle size and non-standard toner particles. The non-standard fine powder is a fine powder having a volume average particle size of 5 μm or less, although it depends on the desired toner particle size. The smaller the desired particle size, the smaller the particle size of the non-standard fine powder. The ratio also changes depending on the desired toner particle size distribution, and is approximately 5 to 30% by mass.

  The obtained toner particles having a desired particle diameter are subjected to an external addition treatment using a desired external additive as necessary. As a method of external addition treatment, a high-speed stirrer that gives a shearing force to powder such as a Henschel mixer and a super mixer is used as an external addition device by mixing a predetermined amount of classified products, silica, and titanium oxide. The toner can be obtained by stirring and mixing.

  Then, if necessary, for example, Ultrasonic (manufactured by Koei Sangyo Co., Ltd.); Resona sieve, Gyroshifter (manufactured by Deoksugaku Kogyo Co., Ltd.); Vibrasonic System (Dalton ( Sonic Clean (manufactured by Shinto Kogyo Co., Ltd.); turbo screener (manufactured by Turbo Kogyo Co., Ltd.); micro shifter (manufactured by Hadano Sangyo Co., Ltd.); using a sieving machine such as a circular vibrating sieve Also good.

  The fine powders that are non-standard toner particles separated in the classification step are recycled to the raw material mixing step described above and mixed with the toner raw material. At that time, a liquid having solubility in the binder resin Spraying is as described above.

Examples Hereinafter, examples of the present invention will be shown, and the present invention will be described more specifically.

  First, raw materials were mixed by using a Henschel mixer (FM-20L) manufactured by Mitsui Mining Co., Ltd. with a two-fluid nozzle as shown in FIG. That is, a predetermined amount of the binder resin shown in Table 1 below and the fine powder from the pulverization / classification process are weighed and mixed, and stored in the mixer body 1, and the mixing blade 2 is driven so that the raw materials become uniform. Mixing was performed. After the raw materials became uniform to some extent, mixing was continued while spraying and spraying the resin-soluble liquid in the liquid supply hopper 6 shown in Table 1 below from the two-fluid nozzle 4.

  Next, the obtained toner raw material mixture was melted and kneaded by a PCM type twin screw extruder (PCM-43) manufactured by Ikekai Tekko Co., Ltd. to melt the resins, and the pigments shown in Table 1 below were contained therein. In addition, an antistatic agent and a release agent were dispersed.

  Next, the obtained kneaded material was rolled with two rolls and cooled by water cooling or the like.

  Thereafter, the cooled product of the obtained colored resin composition was pulverized stepwise to the desired particle size in the pulverization step. That is, first, coarse pulverization and further fine pulverization. In this example, a collision type supersonic jet crusher CPY + UFS manufactured by Nippon Pneumatic Industry Co., Ltd. was used.

  Thereafter, toner particles having a desired particle diameter were obtained in the classification step. As a classifier, a high-precision air classifier UFC manufactured by Nippon Pneumatic Industry Co., Ltd. was used.

  In the above classification step, fine powder having a volume average particle size of 5 μm or less was separated from toner particles having a desired particle size as non-standard toner particles.

  A predetermined amount of an external additive shown in Table 1 below is blended with the obtained toner particles having a desired particle diameter, and externally added by stirring and mixing with a Henschel mixer (FM-20L) manufactured by Mitsui Mining Co., Ltd. The toner was obtained by processing.

  In the toner production process described above, the raw material supply rate, the presence / absence of a bridge / feed neck phenomenon, dams, lumps, and blocking were examined by the following methods.

1. Feeding speed Feeding material with Ikekai Tekko Co., Ltd. PCM type twin screw heavy screw type weight feeder, gradually increasing the feeding speed until the bridge / feed neck phenomenon occurs, and the bridge / feed neck phenomenon Obtain the supply speed just before the occurrence.

2. At the supply speed obtained in the bridge / feed neck phenomenon 1, the raw materials are continuously supplied to the kneader to check whether the raw materials have been stably supplied.

○: Stable supply was possible △: Supply speed was not stable ×: Supply failure due to bridge / feed neck phenomenon 3. Dama, lump, blocking Mixing by Mitsui Mining Co., Ltd. Henschel mixer (FM-20L) The material is checked for lumps, lumps and blocking with a 5 mm sieve.

The above results are shown in Tables 1 and 2 below.

  As is apparent from Tables 1 and 2 above, when the toner raw material and the recycled fine powder are sprayed with a liquid having solubility in the polyester resin and the styrene acrylic resin as the binder resin (Examples 1 to 22). In comparison with Comparative Examples 1 and 2 in which no liquid was sprayed, the supply speed to the kneader was significantly increased. In addition, there was no bridge / feed neck phenomenon, no lumps, lumps, or blocking.

  On the other hand, in Comparative Examples 1 and 2 in which no liquid was sprayed, the supply rate was as low as 15 kg / hr, and supply failure occurred due to the bridge / feed neck phenomenon.

The figure which shows the superconducting fault current limiter which concerns on one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Mixer main body, 2 ... Mixing blade, 3 ... Discharge port, 4 ... Internal mixing type 2 fluid nozzle, 5 ... Motor, 6 ... Liquid supply hopper, 7 ... Compressor, 8 ... Regulator, 9 ... Pressure gauge, 10 ... Exhaust mouth.

Claims (4)

Mixing step of mixing while spraying liquid having a solubility of the binder resin and the binder resin in the toner material containing a coloring Pigments,
A melt-kneading step of melt-kneading the mixture obtained by the mixing step,
A pulverizing and classifying step of pulverizing and classifying the melt-kneaded product obtained by the melt-kneading step,
Toner raw material that produces toner based on the toner material having a predetermined particle diameter obtained by the pulverization and classification process, and fine powder classified as particles having a particle diameter smaller than the predetermined particle diameter is mixed in the next mixing process A recovery process for recovery for reuse ,
Comprising
A method for producing an electrophotographic toner, wherein the fine powder collected in the collecting step is returned to the next mixing step to reuse the fine powder .   2. The method for producing an electrophotographic toner according to claim 1, wherein the liquid has a boiling point lower than a softening point of the binder resin. The method for producing an electrophotographic toner according to claim 1, wherein the amount of the liquid added is 1 to 20% by mass of the raw material excluding fine powder .   The method for producing an electrophotographic toner according to claim 1, wherein the liquid is sprayed by a mixer having a two-fluid nozzle.

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