JP2008250171A - Method for manufacturing toner for electrostatic charge image development - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing toner for electrostatic charge image development, which has excellent dispersibility of a polylactic acid-based resin, easy pulverizing property and excellent preservability of the environment. <P>SOLUTION: The method for manufacturing the toner for electrostatic charge image development comprises: melting and kneading a toner source material containing a binder resin containing a polylactic acid-based resin by 10 to 50 pts.mass with respect to 100 pts.mass of the binder resin, and a colorant and a release agent, in a sealed kneading machine; cooling the obtained melt mixture; and pulverizing the cooled and solidified melt mixture. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a toner for developing an electrostatic image containing a polylactic acid resin used in electrophotography, electrostatic recording method and the like.

  In general, an image forming apparatus such as an electrophotographic copying machine or printer forms a latent image on a photoconductive photoconductor, and the latent image forms a carrier or a charging member constituting a part of a developing device. Insulating electrostatic charge image developing toner that has obtained triboelectric charge by friction is electrostatically attached and developed, and then the formed toner image is transferred to a transfer medium such as plain paper or film, and then heated. The basic principle is to form a copy image or a print image by fixing on a transfer medium by pressurization, solvent vapor or the like.

The toner for developing an electrostatic charge image is produced by a polymerization method, a pulverization method, or the like, and a production method by a pulverization method has been used for a long time. According to the production method by the pulverization method, the toner raw material in which the binder resin is blended with the colorant, the release agent, etc. is melt-kneaded using a kneader, then cooled to solidify the mixture, and then pulverized with the pulverizer. By doing so, a toner for developing an electrostatic image can be obtained.
Of the toner production methods by the pulverization method, a method using an extruder is widely used for melt-kneading (see Patent Documents 1 and 2).
In the method using an extruder, after kneading, extrusion is performed, and the process proceeds to the next pulverization step. At that time, the extruder can continuously extrude the kneaded mixture. Thereafter, the extruded kneaded mixture is cooled in air and then pulverized. Therefore, according to this manufacturing method, since it can produce continuously, it is excellent in productivity.

On the other hand, petroleum resins such as polyester resins have been mainly used as binder resins for toner raw materials. However, due to the recent demand for environmental issues, especially the demand for carbon dioxide reduction, it is considered to use non-petroleum resin, especially polylactic acid resin, which has a small cost difference from petroleum resin, as the toner raw material. It has been.
However, since the kneaded mixture containing the polylactic acid resin becomes too tough, kneading and pulverization are difficult, and the polylactic acid resin has crystallinity, so that the transparency is low and the toner alone is not suitable. It is difficult to use as a binder resin.
Then, utilization of polylactic acid-type resin as a binder resin by mixing with another component is examined (refer patent document 3).
JP-A-8-69126 JP 2000-284536 A JP 2004-93829 A

However, even when the polylactic acid resin is mixed with other components, the method using an extruder includes a polylactic acid resin in order to reduce the load on the extruder during extrusion. The fluidity of the kneaded mixture must be ensured, and kneading must be performed at a high temperature. Further, due to internal heat generation due to shearing and dispersion during kneading, heat generation of the kneaded mixture and the screw of the extruder was extremely high, and the temperature became higher than necessary, and an appropriate temperature setting could not be performed. Therefore, the fluidity is too high to perform kneading sufficiently, the polylactic acid resin and other components are not sufficiently kneaded, and a toner having excellent dispersibility of the polylactic acid resin cannot be obtained.
An object of the present invention is to provide a method for producing a toner for developing an electrostatic charge image that is excellent in dispersibility of a polylactic acid resin, is easily pulverized, and is excellent in environmental conservation.

The method for producing an electrostatic charge image developing toner of the present invention comprises a toner raw material containing a binder resin, a colorant, and a release agent containing 10-50 parts by mass of a polylactic acid resin with respect to 100 parts by mass of the binder resin. Is melt-kneaded in a closed kneader, the resulting molten mixture is cooled, and the cooled and solidified molten mixture is pulverized.
In the method for producing a toner for developing an electrostatic charge image of the present invention, the closed kneader is preferably a pressure type closed kneader.
In the method for producing a toner for developing an electrostatic charge image of the present invention, the colorant is contained in an amount of 2 to 10 parts by mass with respect to 100 parts by mass of the binder resin, and the colorant is a pigment that has not been masterbatched. Also good.
In the method for producing an electrostatic charge image developing toner of the present invention, the release agent is preferably contained in an amount of 2 to 15 parts by mass with respect to 100 parts by mass of the binder resin.
In the method for producing a toner for developing an electrostatic charge image of the present invention, the binder resin is preferably a polyester resin.

  In the production method of the present invention, by using a closed kneader, it is possible to obtain a toner for developing an electrostatic charge image that is excellent in dispersibility of a polylactic acid resin, is easily pulverized, and is excellent in environmental conservation. it can.

Next, although one embodiment of the manufacturing method of the present invention will be described, the present invention is not limited to this embodiment.
The toner raw material needs to use 10 to 50 parts by mass of a polylactic acid resin in at least 100 parts by mass of the binder resin, and a binder resin containing 20 to 30 parts by mass of a polylactic acid resin is more preferable. .
When the content of the polylactic acid resin is more than 50 parts by mass with respect to 100 parts by mass of the binder resin, the kneaded mixture becomes too hard, so that it is difficult to knead and pulverize. Due to the crystallinity, only toners with excellent transparency can be obtained. When the content of the polylactic acid-based resin is less than 10 parts by mass, the effect of environmental conservation is diminished.
The polylactic acid-based resin is mainly composed of a lactic acid component, and may contain a lactic acid copolymer and a blend polymer thereof in addition to a lactic acid homopolymer. The weight average molecular weight of the polylactic acid resin is generally 50,000 to 500,000.
The lactic acid copolymer is obtained by copolymerizing a lactic acid monomer or a cyclic lactic acid dimer and other components copolymerizable therewith. Examples of such other components include dicarboxylic acids having two or more ester bond-forming functional groups, polyhydric alcohols, hydroxycarboxylic acids, lactones, etc., and various polyesters and various polyethers composed of these various components. And various polycarbonates.

  In addition, as a binder resin other than polylactic acid resin, polyester resin, styrene- (meth) acrylic acid copolymer resin, thermoplastic elastomer, styrene resin, (meth) acrylic acid resin, olefin resin (Eg, α-olefin resins such as polyethylene and polypropylene), vinyl resins (eg, polyvinyl chloride, polyvinylidene chloride, etc.), polyamide resins, polyether resins, urethane resins, epoxy resins, polyphenylene oxides Resin, terpene phenol resin, hydrogenated rosin, cyclized rubber, cycloolefin copolymer resin and the like. These can be used alone or in combination of two or more. Among these, polyester resins and styrene- (meth) acrylic acid copolymer resins are preferable from the viewpoint that the image quality characteristics, durability, and productivity of the toner can be satisfied in a balanced manner.

The toner raw material includes a colorant and a release agent. Examples of the colorant include the following.
Examples of the black pigment include carbon black, activated carbon, and a low magnetic force magnetic material.
Examples of the magenta pigment include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 163, 202, 206, 207, 209; I. Pigment violet 19; C.I. I. Butlet 1, 2, 10, 13, 15, 23, 29, 35 etc. are mentioned.
Examples of cyan pigments include C.I. I. Pigment blue 2, 3, 15, 16, 17; I. Bat Blue 6; C.I. I. Acid Blue 45 etc. are mentioned.
Examples of yellow pigments include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 65, 73, 74, 83, 94, 97, 155, 180 Can be mentioned.
The amount of the colorant is usually 2 to 10 parts by mass with respect to 100 parts by mass of the binder resin, and 3 to 8 parts by mass is preferable in order to obtain a toner excellent in dispersibility of the colorant.
Further, in the present invention, dispersibility can be improved by using a closed kneader. Therefore, in addition to a commonly used masterbatch pigment that is easily dispersed and easy to handle as a colorant. A pigment that is not masterbatch (so-called raw pigment) can be used.

Release agents include polyolefin waxes such as polyethylene wax, polypropylene wax and modified polyethylene wax; synthetic waxes such as Fischer-Tropsch wax; petroleum waxes such as paraffin wax and microcrystalline wax; animal waxes such as beeswax and whale wax Plant waxes such as carnauba wax, candelilla wax and rice wax; hardened oils such as hardened castor oil; and mineral waxes such as montan wax, ozokerite and ceresin. These release agents can be used alone or in combination of two or more.
By containing a release agent, the offset resistance can be improved. The offset is a fixing process by a contact heating method performed using a heating member such as a heat roller. The toner particles are fixed on the heating member, and the fixed toner is re-transferred onto the transfer medium and the subsequent toner is fixed. A phenomenon that stains images. By containing a release agent, such fixing of toner particles can be prevented.

  The content of the release agent is usually about 2 to 15 parts by mass, preferably 2 to 8 parts by mass with respect to 100 parts by mass of the binder resin. When the content of the release agent exceeds 15 parts by mass, re-aggregation of the release agent is likely to occur in the production process, and the dispersibility tends to deteriorate. On the other hand, when the content of the release agent is less than 2 parts by mass, the offset resistance may be deteriorated.

The toner raw material preferably contains a charge control agent as required. This makes it easier to control the charging of the toner.
Examples of positively chargeable charge control agents include modified products of nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate Diorganotin oxides such as dibutyltin oxide, dioctyltin oxide and dicyclohexyltin oxide; diorganotin borates such as dibutyltin borate, dioctyltin borate and dicyclohexyltin borate; pyrididium salts, azines, triphenylmethane compounds, cationic functional groups And low molecular weight polymers having These positively chargeable charge control agents may be used alone or in combination of two or more. Among these positively chargeable charge control agents, nigrosine compounds and quaternary ammonium salts are preferably used.

Examples of negatively chargeable charge control agents include acetylacetone metal complexes, monoazo metal complexes, naphthoic acid or salicylic acid metal complexes or salts, organometallic compounds, chelate compounds, low molecular weight polymers having an anionic functional group, and the like. Can be mentioned. These negatively chargeable charge control agents can be used alone or in combination of two or more. Among these negatively chargeable charge control agents, salicylic acid metal complexes and monoazo metal complexes are preferably used.
The content of the charge control agent is usually in the range of 0.1 to 5.0 parts by mass, preferably 0.5 to 3.0 parts by mass with respect to 100 parts by mass of the binder resin.

It is preferable that the toner raw material further contains magnetic powder as necessary. Examples of magnetic powder include metals such as cobalt, iron, and nickel; alloys of aluminum, copper, iron, nickel, magnesium, tin, zinc, gold, silver, selenium, titanium, tungsten, zirconium, and other metals; aluminum oxide And metal oxides such as iron oxide and nickel oxide; ferrite, magnetite and the like.
In the case of a magnetic toner, the content of the magnetic powder is usually 10 to 60 parts by mass, preferably 20 to 40 parts by mass with respect to 100 parts by mass of the binder resin.

  The toner raw material further contains various additives as required, for example, stabilizers (for example, UV absorbers, antioxidants, thermal stabilizers, etc.), flame retardants, antifogging agents, dispersants, nucleating agents, plastics. Agents (phthalate esters, fatty acid plasticizers, phosphoric acid plasticizers, etc.), polymer antistatic agents, low molecular antistatic agents, compatibilizers, conductive agents, fillers, fluidity improvers, etc. May be.

  In the present invention, the toner raw materials are melt-kneaded in a closed kneader, the molten mixture obtained by the melt-kneading is cooled and solidified, and the cooled and solidified mixture is pulverized.

Next, the melt-kneading process of the method for producing an electrostatic charge image developing toner of the present invention will be described.
In the present invention, kneading is performed in a closed kneader. In the case of a closed kneader, unlike a case where an extruder is used, even a relatively hard kneaded mixture containing a polylactic acid resin can be kneaded while adjusting the fluidity.
In addition, if it is a closed kneader, heat generation of the kneaded mixture and the rotor of the kneader caused by internal heat generation due to shearing and dispersion during kneading can be suppressed by reducing the number of rotations of the rotor. Temperature setting can be performed.
In the present invention, the kneading of the polylactic acid resin mixture is preferably performed at 60 to 200 ° C, more preferably 80 to 180 ° C. Thereby, it can fully knead | mix and can improve the dispersibility of a polylactic acid-type resin, and the kneaded mixture in which the coloring agent and release agent which are additives were disperse | distributed appropriately can be obtained. If the kneading is performed at 60 ° C. or lower, the polylactic acid resin may not be sufficiently melted and may not be sufficiently kneaded. In addition, since the polylactic acid-based resin does not melt sufficiently, the function of fusing as a binder resin cannot be sufficiently exhibited, and additives such as colorants are easily released. Further, when kneading is performed at 200 ° C. or higher, the dispersibility of the polylactic acid resin obtained due to excessively high fluidity tends to be deteriorated, and the dispersibility of the colorant and the release agent as additives is deteriorated. Cheap.
In addition, the kneading | mixing temperature in this application is not the preset temperature of a kneading machine but the resin temperature at the time of kneading | mixing.

The closed kneader used in the present invention may be any closed kneader as long as it can perform the above steps, but is preferably a pressure type closed kneader. By kneading while applying pressure, kneading can easily proceed, and the kneaded mixture can be easily densified.
Specific examples of the closed kneader include a pressure type closed kneader wonder kneader manufactured by Moriyama (see Japanese Patent No. 3574618), a pressure type closed kneader (trade name: “Pressure type kneader” DS3-20 type ").
Since the kneading machine is excellent in cooling capacity, it is possible to adjust the temperature appropriately during kneading, and it is easy to improve the dispersibility of the polylactic acid resin of the toner and the dispersibility of the colorant and the release agent.

Thereafter, the kneaded mixture is cooled and solidified, and pulverized by a pulverizer. Since the dispersibility of the polylactic acid-based resin is sufficient, pulverization can be easily performed, and an electrostatic charge image developing toner can be obtained. There is no restriction | limiting in particular in the grinder to be used, For example, a jet type fine grinder, a mechanical fine grinder, etc. are mentioned.
Then, it is preferable to classify with a classifier. Thereby, a toner for developing an electrostatic charge image having a uniform particle diameter can be obtained. Moreover, there is no restriction | limiting in particular also in the classifier to be used, For example, a wind classifier etc. are mentioned.

  In the production method of the present invention, an electrostatic charge image developing toner excellent in dispersibility of the polylactic acid resin and excellent in environmental conservation can be obtained by using a closed kneader.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

First, a polylactic acid resin was synthesized as follows.
0.10% by mass of tin octylate as a catalyst and 0.15% by mass of dodecyl alcohol as a reaction initiator were added to a raw material lactide (LL-lactide 95 mol%, meso-lactide 5 mol%) prepared in advance by a known method. Thereafter, polymerization was performed while gradually raising the temperature from 100 ° C to 200 ° C. Next, the produced polymer was allowed to stand for 48 hours at 100 ° C. under a reduced pressure of 5 Torr, and the remaining lactide was devolatilized to obtain a polylactic acid-forming decomposable resin X.

<Example 1>
And as a binder resin,
Polylactic acid resin (glass transition temperature (Tg): 53.2 ° C., flow initiation temperature (Ti) / flow softening temperature (Tm): 153 ° C./170° C., number average molecular weight (Mn): 57000, weight average molecular weight ( Mw): 125000, residual lactide concentration 480 ppm, L / D molar ratio: L (mol%) / D (mol%) = 91.8 (mol%) / 8.2 (mol%)) 27.03 parts by mass Polyester resin A (glass transition temperature (Tg): 69 ° C., flow softening temperature: 160 ° C., number average molecular weight (Mn): 5300, weight average molecular weight (Mw): 151700) 15.75 parts by mass polyester resin B (glass transition Temperature (Tg): 64 ° C., flow softening temperature: 99 ° C., number average molecular weight (Mn): 2200, weight average molecular weight (Mw): 5800) 47.32 parts by mass as a colorant
As a magenta pigment (trade name: “Red No. 8” manufactured by Dainichi Seika Kogyo Co., Ltd.)
Wax (Nippon Yushi Co., Ltd., trade name: “WEP-8”) 4.5 parts by mass charge control agent,
Boron complex particles (trade name: “LR-147” manufactured by Nippon Carlit Co., Ltd.) A pressure-type closed kneader (trade name: “pressurized kneader DS3-20” manufactured by Moriyama Co., Ltd.) with 0.9 parts by mass or more of raw materials The kneading machine was set at 150 ° C. and melt kneaded at a rotor rotation speed of 30 rpm for 30 minutes to obtain a kneaded mixture.
Therefore, the mass part of the polylactic acid resin X contained in 100 parts by mass of the binder resin is:
27.03 × 100 / (27.03 + 15.75 + 47.32) = 30
Met.

A portion of the resulting kneaded mixture was sampled and immediately measured for the resin temperature during kneading and found to be 153 ° C.
<Dispersibility>
A part of the kneaded mixture was observed with a cross section using an optical microscope, and the dispersibility of the polylactic acid resin, the colorant and the release agent was evaluated.
Specifically, the dispersibility of the polylactic acid-based resin was evaluated as “◯” when the domain diameter of the largest mass of the polylactic acid-based resin was less than 5 μm, and “x” when it was 5 μm or more.
The dispersibility of the colorant was evaluated as ○ when the domain diameter of the largest block of the pigment was less than 3 μm, Δ when 3 μm or more and less than 6 μm, and × when 6 μm or more.
Further, the dispersibility of the release agent was evaluated by measuring the domain diameter of the largest block of the release agent. If less than 5 μm, it was evaluated as ◯ if it was less than 5 μm and less than 10 μm.
Next, the preset temperature of the kneader was set to 20 ° C., and after kneading for 5 minutes, it was stopped and left for 10 minutes.

Subsequently, the obtained kneaded mixture was coarsely pulverized with a hammer mill (manufactured by Hosokawa Micron), and further jet mill (PJM-1, manufactured by Nippon New Matchk Industry Co., Ltd.) under conditions of a pulverization pressure of 5 kg / cm ² and a feed amount of 2 kg / hour. A pulverized product was obtained. The pulverizability was evaluated by the pulverized product. Then, it was classified with an airflow classifier, which is an air classifier, to obtain toner base particles having a volume average particle size of 8 μm.
The grindability was evaluated as follows.
<Crushability>
The volume average particle size and number distribution of the pulverized product were measured using a particle size distribution measuring device (Multisizer II, manufactured by Beckman Coulter, Inc.), and the pulverization property was evaluated according to the following criteria.
○: Volume average particle diameter of less than 10 μm and particles of 5 μm or less are less than 50 number% Δ: Volume average particle diameter of less than 10 μm and particles of 5 μm or less are 50 number% or more X: Volume average particle diameter 10μm or more

Next, to the obtained toner base particles,
Hydrophobic silica (trade name: “RY-50”, volume average particle size 40 nm, manufactured by Nippon Aerosil Co., Ltd.) 0.3 parts by mass,
1 part by mass of hydrophobic silica (trade name: “H2000 / 4M”, volume average particle size 10 nm) manufactured by Wacker Chemical Co., Ltd.
Was added and mixed with a Henschel mixer at a peripheral speed of 40 m / sec for 10 minutes to obtain a toner of Example 1.

<Comparative Example 1>
Comparative Example 1 was carried out in the same manner as in Example 1 except that polylactic acid resin X: 54.06 parts by mass polyester resin A: 9.0 parts by mass polyester resin B: 27.04 parts by mass was used as the binder resin. No toner was obtained.
Therefore, the mass part of the polylactic acid resin X contained in 100 parts by mass of the binder resin is:
54.06 × 100 / (54.06 + 9.0 + 27.04) = 60
Met.
The resin temperature during kneading was 149 ° C.

<Comparative example 2>
A double-screw extruder (trade name: “PCM30” manufactured by Ikegai Co., Ltd.) was used in place of the pressure-type closed kneader (trade name: “Pressurized Kneader DS3-20 Model” manufactured by Moriyama Co., Ltd.). The temperature was 100 ° C. Otherwise, the toner of Comparative Example 2 was obtained in the same manner as in Example 1.
Note that the pressurized closed kneader of Comparative Example 1 cannot circulate cooling water in the blade.
The resin temperature during kneading was 140 ° C.
Table 1 shows the main conditions and measurement results of Examples and Comparative Examples.

<Evaluation results>
As shown in Table 1, in Example 1, the toner for developing an electrostatic charge image has excellent dispersibility of the polylactic acid resin, is easily pulverized, and is excellent in environmental conservation by using a polylactic acid diameter resin. Could be manufactured. The toner was also excellent in dispersibility of the colorant and the release agent.
When the toner of Example 1 was actually printed using a non-magnetic one-component printer, the color of the pigment was good, a glossy and high-quality image was obtained, and excellent in anti-fusing and storage properties. There was no practical problem.
On the other hand, in Comparative Example 1, only a toner that was difficult to grind was obtained because the dispersibility of the polylactic acid resin, the colorant, and the release agent was insufficient.
When the toner of Comparative Example 1 was actually printed using a non-magnetic one-component printer, fusing occurred on the developing roller and the charging blade, resulting in image defects and practical problems.
Further, in Comparative Example 2, only a toner that was difficult to pulverize because the dispersibility of the polylactic acid resin and the release agent was insufficient, and the dispersibility during coloring was slightly insufficient.
When the toner of Comparative Example 2 was actually printed using a non-magnetic one-component printer, fusing occurred on the developing roller and the charging blade, resulting in image defects and practical problems.

Claims (5)

  Obtained by melt-kneading a toner raw material containing a binder resin containing 10 to 50 parts by mass of a polylactic acid resin, a colorant, and a release agent with respect to 100 parts by mass of the binder resin in a closed kneader. A method for producing a toner for developing an electrostatic charge image, comprising cooling a molten mixture and pulverizing the cooled and solidified molten mixture.   The method for producing a toner for developing an electrostatic charge image according to claim 1, wherein the closed kneader is a pressure type closed kneader.   The colorant is contained in an amount of 2 to 10 parts by mass with respect to 100 parts by mass of the binder resin, and the colorant is a pigment that has not been masterbatched. A method for producing a toner for developing electrostatic images.   The method for producing a toner for developing an electrostatic charge image according to any one of claims 1 to 3, wherein the releasing agent is contained in an amount of 2 to 15 parts by mass with respect to 100 parts by mass of the binder resin. 5. The method for producing a toner for developing an electrostatic charge image according to claim 1, wherein the binder resin is a polyester resin.