JP3456025B2 - Method for producing toner for developing electrostatic images - 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 an electrostatic charge image toner used in electrophotography, electrostatic recording and the like. More specifically, the present invention relates to a method for producing a toner for developing an electrostatic charge image, in which fine toner powder is recycled and reused.

[0002]

2. Description of the Related Art A developer used in an electronic copying machine or the like is once attached to an image carrier such as a photoconductor on which an electrostatic charge image is formed in the developing process, and then is transferred to the photoconductor in the transferring process. After being transferred from the sheet to the transfer sheet, it is fixed on the copy sheet surface in the fixing step. At that time, as a developer for developing the electrostatic charge image formed on the latent image holding surface, a two-component developer consisting of a carrier and a toner and a one-component developer not requiring a carrier (magnetic toner, non-magnetic toner). )It has been known.

Toners contained in the developer include positively chargeable toners and negatively chargeable toners. Conventionally, as those imparting chargeability to positively chargeable toners, nigrosine dyes and quaternary ammonium salts have been used. Further, as a material for imparting chargeability to a negatively chargeable toner, a charge control agent such as a metal-containing dye or a coating agent for imparting a predetermined chargeability to a carrier has been known. An example of a toner manufacturing flow that is normally performed is shown in FIG. First, a resin and additives such as a colorant are blended and mixed in a predetermined amount, melt-kneaded with a kneader, cooled, pulverized, and classified. Further, after the classified toner and the external additive are stirred and mixed, a coarse product is sieved and filled in a container.

Conventionally, the toner fine powder generated has been recycled by recycling a predetermined amount to the raw material blending / mixing process in view of the environment and the production cost, as described in JP-A-5-34976. . However, in the conventional toner fine powder recycling method, when the toner fine powder is melted and kneaded again in the kneader, molecular cutting of the resin in the toner fine powder occurs again, and the fixing performance such as toner hot offset is deteriorated due to the decrease of the molecular weight of the resin, mechanical This is not preferable because it causes deterioration of durability performance due to a decrease in strength. In particular, the decrease in the molecular weight of the resin in the toner tends to occur remarkably when a resin containing a crosslinking component, or a resin having at least two peaks of molecular weight containing a low molecular weight material and a high molecular weight material is used. It is in. Further, when the toner fine powder is mixed with the raw material, it is difficult to uniformly mix the raw material (a) and the toner composition becomes non-uniform, and (b) the bulk density of the raw material becomes smaller than that of the raw material containing no fine powder. When the raw materials are supplied to the kneading machine, the bite is deteriorated, the toner productivity is lowered, the load during the kneading is hard to be applied, and the dispersibility of the additives becomes poor. When the toner is continuously supplied from the storage / supply container to the kneading machine, the toner composition becomes non-uniform during the production process due to the difference in particle size and specific gravity between the raw material and the fine powder inside the storage / supply container. It was not preferable because it was likely to deteriorate.

In particular, in recent years, (a) the flow softening temperature of the binder resin used for the toner is designed to be lower than the fixing surface due to the increase in speed of the copying machine and the shortening of the first copy time. If the toner has a small particle size due to the decrease in strength, susceptibility to excessive pulverization, a large amount of fine powder, and (b) image quality improvement of the copy, the classification efficiency will decrease and the fine powder will increase more than before. As a result, the amount of recycled toner fine powder has increased, and it has become difficult to ensure productivity without deterioration of toner performance.

[0006]

Therefore, the first aspect of the present invention
It is an object of the invention to provide a method for producing a toner having a small change in the molecular weight of a resin and excellent in fixing performance and durability. A second object is to provide a method for producing a toner having a uniform composition with good dispersibility of additives in the toner. A third object is to provide a toner that has little environmental dependence and is excellent in storage stability. The fourth purpose is that image characteristics, image quality, charging characteristics, etc. are stable even when continuous copying is performed.
It is to provide a toner having excellent durability performance. A fifth object of the present invention is to provide a toner manufacturing method having good productivity even if toner fine powder is reused.

[0007]

As a result of various studies by the present inventors, it was found that the toner performance can be improved by kneading and reusing the toner fine powder in a kneading step different from that of the raw material to improve the toner performance. Reached That is, the gist of the present invention is a method for producing a toner for developing an electrostatic image <br/> recycled toner fines toner production process having a kneading step a, the toner fines consists only of the feed unit screw screw
After a kneading step b of kneading with a continuous extruder having
Mostly, the kneading step a as a kneaded product obtained through the kneading step b
The present invention resides in a method for producing a toner for developing an electrostatic charge image, which is recycled in the subsequent steps .

The present invention will be described in detail below. As the resin used in the present invention, known resins suitable for toner can be used. For example, polystyrene, polychlorostyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer. Polymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer and styrene- Phenyl acrylate copolymer, etc.), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-
Ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-chloromethyl acrylate copolymer, styrene-acrylonitrile-acrylic ester copolymer, etc. Styrene resin (styrene or styrene-substituted homopolymer or copolymer), vinyl chloride resin, rosin-modified maleic acid resin, phenol resin, epoxy resin, polyester resin, polyethylene resin, polypropylene resin, ionomer resin, polyurethane Resins, silicone resins, ketone resins, ethylene-ethyl acrylate copolymer resins, xylene resins, polyvinyl butyral resins, polycarbonate resins and the like are available, but as particularly preferred resins for use in the present invention, styrene resins, saturated resins Others can be mentioned unsaturated polyester resins and epoxy resins. Further, the above resins are not limited to be used alone, but may be used in combination of two or more kinds.

The flow softening temperature (Tm) of the resin is 8
The temperature is preferably 0 to 150 ° C, more preferably 90 to 140 ° C. If the temperature is lower than 80 ° C, the fixing temperature to the paper is low and good, but hot offset is likely to occur, the toner is easily crushed inside the developing tank, and the spent phenomenon in which the toner is fixed to the carrier surface or the doctor blade may occur. However, there is a problem in that the charging characteristics are deteriorated, the charging characteristics are deteriorated, and the durability performance of the developer is deteriorated. On the other hand, if it is higher than 150 ° C., there are problems such as a high fixing temperature on paper and poor toner pulverizability.

The glass transition temperature of the resin is preferably 45 ° C. or higher, and when the temperature is lower than 45 ° C., the toner is hard to agglomerate or stick when left at a high temperature of 40 ° C. for a long time, resulting in poor storage stability. There are problems in use, such as easy formation of toner aggregates in the addition step, and easy formation of aggregates on screens, side walls, etc. of the sieving device. The resin may be produced by known solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization or the like, and the polymerization method of the low molecular weight polymer and the high molecular weight polymer may be different as necessary. Further, from the viewpoint of the odor of the toner, the total amount of light-boiling components such as residual monomer and residual solvent amount in the resin is 1,000 ppm or less, and particularly 500 ppm.
The following are preferred. Each test method of the resin used in the present specification will be described below.

[Flow Softening Temperature (Tm)] In a flow tester (CFT-500 manufactured by Shimadzu Corporation),
Sample 1g, nozzle 1mm × 10mm die, load 30K
g, a preheating time of 50 ° C. for 5 minutes, and a temperature rise rate of 3 ° C./min. The measurement is performed. [Glass transition temperature (Tg)] In a differential thermal analyzer (DTA-40 manufactured by Shimadzu Corporation), a temperature rising rate of 10 ° C /
A tangent line is drawn at the transition (inflection) start portion of the curve measured under the condition of minutes, and the intersection temperature is taken as the glass transition temperature.

As the colorant used in the present invention, known pigments and dyes may be used. For example, carbon black,
Titanium oxide, zinc white, alumina white, calcium carbonate, ultramarine blue, navy blue, phthalocyanine blue, phthalocyanine green, Hansa yellow G, rhodamine dye, chrome yellow, quinacridone, benzidine yellow, rose bengal, triallyl methane dye, anthraquinone dye, Colorants such as monoazo and diazo dyes and pigments may be used alone or in combination of two or more. The content of the colorant may be an amount sufficient to color the toner so that a visible image can be formed by development, and for example, resin 100
1 to 20 parts by weight, especially 3 to 15 parts by weight is suitable for the parts by weight.

Further, known positively-charged or negatively-charged charge control agents may be used alone or in combination in the toner, and the amount thereof may be selected according to the desired charge amount ratio, for example, resin 100. About 0.05 to 10 parts by weight is preferable with respect to parts by weight. Examples of positively chargeable charge control agents include nigrosine dyes, quaternary ammonium salt compounds,
Triphenylmethane compounds, imidazole compounds,
Examples include polyamine resins. As the negative charge control agent, a metal-containing azo dye such as Cr, Co, Al or Fe,
Examples thereof include metal salicylate compounds, metal alkylsalicylate compounds, and carlix arene compounds. Furthermore, if necessary, other internal additives may be used alone or in combination as an auxiliary agent, and examples thereof include a low molecular weight olefin polymer of a known release agent and a filler.

The toner manufacturing flow of the present invention is shown in FIGS.
An example will be described in accordance with No. 4, but the invention is not limited to the following description as long as the gist thereof is not exceeded. First, a manufacturing process of a toner using a virgin material will be described. As the toner internal additive, at least a resin and a colorant are weighed and blended in predetermined amounts, and examples of the mixing device include a double cone mixer, a V type mixer, a drum type mixer, a super mixer, a Henschel mixer, and Now. There is a tar mixer.

Next, in the kneading step, a batch type (for example,
A pressure kneader, a Banbury mixer, etc.) or a continuous kneader is used, but in recent years, single-screw or twin-screw extruders have become mainstream because of their superiority in continuous production. For example, KTK manufactured by Kobe Steel Ltd. Type twin screw extruder, TEM type twin screw extruder manufactured by Toshiba Machine Co., Ltd., twin screw extruder manufactured by KCK, PCM type twin screw extruder manufactured by Ikegai Tekko KK, twin screw extruder manufactured by Kuriyama Seisakusho, Bus Co-kneader made by the company is good. After the kneading, the toner is rolled by two rolls or the like, and is subjected to a cooling step of cooling by air cooling, water cooling, or the like.

Next, in the pulverizing step, coarse pulverization is performed by a crusher, hammer mill, feather mill, etc., and fine pulverization is performed by a jet mill, a high-speed rotor rotary mill, etc., and the toner particles are pulverized stepwise. After crushing, inertia classification type elbow jet, centrifugal force classification type microplex, D
The toner is classified with an S separator or the like, and the average particle size is 3 to 1
5 μm toner is obtained. The toner coarse powder generated in the classification step may be returned to the pulverization step and reused.

Further, when the toner is externally added, a classified toner and various known external additives are mixed in a predetermined amount, and a high-speed stirrer such as a Henschel mixer or a super mixer which gives a shearing force to the powder is used. It is better to stir and mix. At this time, since heat is generated inside the external additive machine and aggregates are easily generated, it is preferable to adjust the temperature by means such as cooling the periphery of the container part of the external additive machine with water. The internal material temperature is preferably set to a control temperature which is lower than the glass transition temperature of the resin by 10 ° C. or more.

As the external additive, various known inorganic or organic external additives can be used. In particular, titania, silica, alumina, zinc oxide, magnesium oxide and the like are used in order to improve the fluidity of the toner and suppress cohesion. Inorganic fine powder is preferred.
The mixing amount of the external additive depends on the external additive to be used and the average particle size and particle size distribution of the toner particles, but an amount that provides a desired toner fluidity is good, for example, 0 based on 100 parts by weight of the toner particles. It is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 8 parts by weight. If the mixing amount is less than 0.01 parts by weight, there is no fluidity improving effect and the storage stability performance at high temperature is poor, and if the mixing amount is more than 10 parts by weight, a part of the external additive liberated causes photoconductor filming. Or, it is not preferable because it accumulates inside the developing tank and causes troubles such as deterioration of the charging function of the developer.

From the viewpoint of stability in a high-humidity environment, the external additive is preferably an inorganic fine powder which has been subjected to a hydrophobic treatment with a treatment agent such as a known silane coupling agent, and is further charged. When considering the property, dimethyldichlorosilane, monooctyltrichlorosilane, hexamethyldisilazane, silicone oil, etc. are used as the treatment agent that imparts negative chargeability, and aminosilane, etc. is used as the treatment agent that imparts positive chargeability. do it.

In addition, as a toner external additive, magnetite, ferrite, conductive titanium, antimony oxide, tin oxide, cerium oxide, hydrotalcites, etc., which are known for the purpose of adjusting resistance, polishing agents, etc., are used for improving fluidity. An appropriate amount of fine powder such as a compound, acrylic beads, silicone beads, and polyethylene beads may be mixed, and the mixing amount is preferably 0.005 to 10 parts by weight with respect to 100 parts by weight of the toner. The obtained toner is a one-component developer that does not use a carrier (a magnetic one-component toner containing a magnetic substance such as magnetite or a non-magnetic one-component toner containing no magnetic substance), or iron powder, ferrite, or magnetite. , A two-component developer mixed with a magnetic carrier such as a magnetic resin carrier.

In the method of reusing the toner fine powder in the present invention, in the example of FIG. 2, the toner fine powder is supplied to the kneading step b, and then the toner is supplied to the cooling step a. In the example of FIG. 3, the toner fine powder is supplied from the kneading step b to the fine pulverizing step a through the cooling step b and the coarse pulverizing step b. In the example of FIG. 4, the toner fine powder is supplied to the external addition step a through a kneading step b, a cooling step b, a pulverizing step b and a classifying step b. Kneading process b
As the extruder used in step 1, the same batch type or continuous type as in the kneading step a can be used, but a continuous type extruder is preferable in terms of productivity.

An example of an extruder used in the kneading step a is shown in FIG.
As shown in FIGS. 11 to 11, the barrel is divided into a plurality of parts, and has a heating means such as an electric heater and a cooling means such as a cooling pipe inside the barrel, and is adjusted to a desired temperature by a temperature control panel. . Inside the barrel, there is provided a screw in which biaxial screws mesh with each other and rotate in the same direction at a high speed of about 100 to 500 rpm. The structure of the screw can be selected at any time, but it may be composed of, for example, a feed screw and a kneading screw as shown in FIG. The toner raw material mixture is fed from the hopper to the feeding screw by the screw feeder and gradually preheated. A strong share is applied to the first kneading screw, so that the raw material is self-heated to disperse the raw material. Or, it changes from a semi-molten state to a molten state. Further, by providing a second kneading portion screw at the rear portion or changing the screw shape and configuration to bring the kneaded material to a high temperature state in which it is sufficiently melted, the wettability of the resin and the colorant can be improved. . Further, it is preferable to provide a plurality of vent ports at the rear of the portion where the kneaded product becomes in a molten state for degassing, and further, by vacuum suctioning a part or all of the vent ports with a pump, etc. Is preferable, the dispersibility is improved, and the removal efficiency of volatile components is improved, which is preferable.

The number of axes of the continuous extruder is preferably one or two. The number of screw threads may be appropriately selected from 2 or 3 threads in consideration of dispersibility, productivity, kneading temperature and the like. The size of the extruder is preferably such that the kneaded material screw feed part, kneading part and multiple vent ports can be arranged sufficiently, the barrel inner diameter is D (mm), and the length from the raw material supply port to the outlet is set. When L (mm) is set, L / D is 20 or more, preferably 25 or more.

An example of an extruder used in the kneading step b is shown in FIG.
Although shown in FIG. 2, the basic structure may be the same as that of the extruder used in the kneading step a. However, in order to supply the toner fine powder to make the inside of the extruder in a molten state and to suppress the molecular cutting of the toner fine powder, preferably the screw is mainly provided with the feed section screw, and particularly the feed section screw is formed. Preferably, a vent port may be provided if necessary. Further, the L / D of the extruder is only required to secure a length such that the kneaded product is sufficiently melted, and in order to reduce the molecular cutting of the toner fine powder, the L / D
Is 35 or less, preferably 30 or less. Further, the number of screw shafts may be one or two, and the number of threads may be two or three, but considering productivity and economic efficiency, one and two threads are preferable.

Further, the toner fine powder is mainly returned to the kneading step b for reuse, but a part of the toner fine powder may be returned to the raw material mixing and mixing step a. Further, if necessary, a step of blending and mixing a part of the resin, other additives, and the fine toner powder may be provided before the kneading step b. Note that the toner fine powder refers to a toner having fine particles generated in a classification step or a fine toner collected by a collecting device, and is not limited to this, and the average particle diameter of a desired classification toner is smaller than the average particle diameter. The toner having the above is collectively referred to as toner fine powder. The average particle size of the toner may be measured with a commercially available particle size distribution measuring device, for example, Coulter Counter T manufactured by Coulter Co.
It may be measured by A-II.

[0026]

EFFECT OF THE INVENTION By using the method for producing a toner for developing an electrostatic image of the present invention, even a large amount of fine toner powder can be recycled in the production process with good productivity and efficiency, and can be reused. The toner in which fine powder is reused has little performance deterioration, has good fixing performance, has stable image and image quality characteristics even during continuous use, and has excellent durability performance. Is provided.

[0027]

[Raw material mixing and mixing step a]

[0028]

[Table 1] Styrene / n-butyl acrylate copolymer resin 100 parts (Tm = 130 ° C, Tg = 60 ° C) Colorant carbon black MA-100S (Mitsubishi Kasei Co., Ltd.) 6 parts Charge control agent Bontron P-51 (Orient Chemical Industry Co., Ltd.) 2 parts-Low molecular weight polypropylene 2 parts (number average molecular weight of vapor pressure osmometry = 7,500) were mixed and mixed with a Nauta mixer. [Kneading step a] Continuous extruder (PCM-4 manufactured by Ikegai Co., Ltd.)
It was kneaded in 6). The schematic diagram of the extruder was the same as that shown in FIGS.

[0029]

[Table 2] L (length) / D (inner diameter) of kneading machine = 35 ・ Number of screw shafts: 2 (rotating in the same direction) ・ Kneaded material supply: 50 kg / Hr

[Cooling Step a] Cooling was performed with a belt cooler. [Coarse crushing step a] Coarse crushing to 2 mm or less with a hammer mill. [Kneading Step b] Toner fine powder (average particle diameter 4.5 μm) generated from the toner already manufactured was used as a raw material and kneaded with a continuous extruder (FS-40 manufactured by Ikegai Co., Ltd.). The schematic diagram of the extruder was the same as that shown in FIG.

[0031]

[Table 3] L (length) / D (inner diameter) of the kneading machine = 25 ・ Number of screw shafts: 1 shaft ・ Kneaded material supply: 17 kg / Hr

[Cooling Step b] It was cooled by a belt cooler. [Coarse crushing step b] It was roughly crushed to 2 mm or less with a hammer mill. [Fine pulverizing step a] The coarsely pulverized material obtained through the coarse pulverizing step a and the coarse pulverizing step b was supplied and finely pulverized by a jet mill. [Classification step a] Classification was carried out by an air classifier to obtain a black toner having an average particle size of 9μ.

[External Addition Step a] Silica powder (R972 from Nippon Aerosil Co., Ltd.) based on 100 parts by weight of the black toner.
0.35 parts and magnetite fine powder (Toda Kogyo EP
(T1000) 0.2 part was externally added with a Henschel mixer to obtain an externally added toner. [Sieving Step a] The externally added toner was sieved by a Sato type vibrating screen equipped with a 100 mesh screen. [Filling step a] This step was omitted.

[Evaluation of Toner] 4 parts of the externally added toner and Cu—Zn— surface-coated with a resin containing methyl silicone
96 parts of a ferrite carrier (average particle size = 100 μm) was stirred and mixed with a V-type mixer to prepare a developer. Using this developer as a starting developer and externally added toner as a replenishment toner, a 30,000-sheet actual copying test was carried out with a copier equipped with a negatively chargeable organic photoconductor photoreceptor at a copying speed of 60 sheets / min. . Further, the molecular weight distribution of the obtained toner was measured, and a fixing test was carried out at a sheet passing speed of 60 sheets / minute copying speed to confirm the operating temperature range. As a result, this toner does not cause hot offset up to 230 ° C.
The amount of toner scattering after the actual copying of 10,000 sheets was small, and the fixing characteristics and the actual copying characteristics were good.

Comparative Example 1 A toner was manufactured according to the manufacturing flow of FIG. [Raw material mixing and mixing step a]

[0036]

[Table 4]   ・ Styrene / n-butyl acrylate copolymer resin 100 parts     (Tm = 130 ° C, Tg = 60 ° C)   ・ Colorant Carbon black MA-100S (Mitsubishi Kasei Co., Ltd.) 6 parts   ・ Charge control agent Bontron P-51 (Orient Chemical Industry Co., Ltd.) 2 parts   ・ Low molecular weight polypropylene 2 parts     (Number average molecular weight of vapor pressure osmometry = 7,500)   ・ Toner fine powder [fine powder ratio is 25%] 37 parts Was mixed and mixed with a Nauta mixer.

[Other Steps] From the kneading step a to the sieving step a, the same operations as in Example 1 were performed. [Evaluation of Toner] As a result of evaluating the toner in the same manner as in Example 1, the toner produced in Comparative Example 1 had a hot offset generation temperature of 210 ° C., which is a fixing characteristic, and had a toner scattering amount in a 30,000-sheet actual copying test. About 3 times more than in Example 1,
There was a problem.

[Brief description of drawings]

FIG. 1 is an example of a normal toner manufacturing flow.

FIG. 2 is a first example of a toner manufacturing flow of the present invention.

FIG. 3 is a second example of the toner manufacturing flow of the invention.

FIG. 4 is a third example of the toner manufacturing flow of the invention.

FIG. 5 is a schematic view of a twin-screw type continuous extruder.

6 is a cross-sectional view taken along the line A-A 'in FIG.

FIG. 7 shows an example of a kneading section screw (31) and a feeding section screw (30)

FIG. 8 is a schematic view showing an example of a paddle of a feeding section screw.

FIG. 9 is a schematic view showing an example of a paddle of a kneading portion screw.

FIG. 10 is a schematic view showing an example of a paddle of a kneading section screw.

FIG. 11 is a schematic view showing an example of a paddle of a kneading section screw.

FIG. 12 is a schematic view of a single-screw type continuous extruder.

[Explanation of symbols]

1 Raw material supply port 2 Vent port 1 3 Vent port 2 4 vent 3 5 barrels 6 barrel C1 7 barrel C2 8 barrel C3 9 barrel C4 10 barrel C5 11 barrel C6 12 barrel C7 13 barrel C8 14 barrel C9 15 dies 16 exit 20 Raw material hopper 21 screw feeder 24 vacuum pump 30 Feeding unit screw 31 Kneading part screw 40 Drive

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Claims (6)

(57) [Claims] 1. A toner manufacturing process including a kneading process a .
In the method of manufacturing the toner for developing an electrostatic image in which the fine powder of toner is recycled, the fine powder of toner is composed of only the screw at the feeding section.
Kneading step b of kneading with a continuous extruder having a screw
And a kneaded product which has been subjected to the kneading step b.
A method for producing a toner for developing an electrostatic charge image, which is recycled in a step after the kneading step a . 2. The electrostatic charge image developing according to claim 1, wherein the barrel inner diameter D of the continuous extruder and the length L from the raw material supply port to the outlet have a relationship of L / D ≦ 35. Toner manufacturing method. 3. The method for producing an electrostatic image developing toner according to claim 1, wherein the number of screw shafts of the continuous extruder is one. 4. The method for producing an electrostatic image developing toner according to claim 1, wherein the continuous extruder has two screw threads. 5. The toner fine powder is formed only by the screw of the feeding section.
That kneaded in a continuous extruder, cooling, manufacturing method of the electrostatic image developing toner according to any one of claims 1 to 4, characterized in that the recycling after grinding. 6. The toner fine powder is composed of only the screw of the feeding section.
That kneaded in a continuous extruder, cooling, pulverizing, classifying the re Sa <br/> claims 1 to either the <br/> toner according to 5, characterized in that cycle after Manufacturing method.