JP4706780B2 - Method for producing electrophotographic toner - Google Patents

Description

The present invention relates to an electrophotographic toner and a method of manufacturing the same, a biodegradable resin a process for producing an electrophotographic toner chromatography using as a binder resin.

  Image formation by electrophotography is performed by developing and visualizing an electrostatic image with toner, transferring the obtained toner image onto a sheet, and then fixing it with heat and pressure. As a toner used for such image formation, a so-called pulverized toner obtained by kneading a mixture of a binder resin and a colorant or a charge control agent, and pulverizing and classifying and adjusting to a predetermined particle size distribution has been widely known. It has been.

  In such a pulverized toner manufacturing process, as a pulverizer used in the pulverization step, there are dry pulverizers such as an airflow pulverizer and a mechanical pulverizer, but the former has the ability to pulverize to a smaller particle diameter. An airflow type pulverizer is generally used for the production of a small particle diameter toner which is excellent and has a low-temperature fixability which is recently required.

  The airflow pulverizer uses a high-pressure gas such as a jet stream, conveys the object to be pulverized by the jet stream, collides the object to be crushed with a collision member, and pulverizes by the impact force.

  However, as the toner particle size is reduced, the energy required for pulverization has increased, and the technical difficulty of the airflow pulverizer and the soot has increased. One of the causes that makes it difficult to pulverize into a small particle size toner is known to increase electrostatic cohesion between particles, and the energy that should be used to pulverize the particles in the pulverizer is used to release the aggregation. Used, not enough energy is used to pulverize the particles, reducing the efficiency of pulverization.

  In contrast to the dry pulverizer, a wet pulverizer is also known. For example, in order to obtain fine particles and emulsions of raw materials in the fields of cosmetics, foods, medicines, paints, etc., high-pressure wet atomization devices that use high-pressure jets of fluid in which material particles are dispersed have been used. . As one example of this high-pressure wet atomization apparatus, for example, particles in a fluid are used by utilizing an impact when jets formed by injecting a raw material liquid into a chamber collide with a collision wall in the chamber or when jets collide with each other. There is a jet abutting device that performs fine particle formation, dispersion emulsification, and the like (see, for example, Patent Document 1).

  Conventionally, petroleum-derived resins such as styrene / acrylic resins and polyester resins have been used as binder resins for use in toners. However, in recent years, in consideration of the environment, a method has been proposed in which a biodegradable resin that has a low environmental impact during disposal is used as a binder resin for toner.

  One of the most promising resins as a biodegradable resin is polylactic acid. However, general-purpose polylactic acid is a crystalline polyester having a melting point of about 170 ° C., a glass transition point of about 60 ° C., and a molecular weight of about 1 to 150,000. When general-purpose polylactic acid is used as it is as a resin for toner, it is hard. There are problems that the grindability is poor and that the softening temperature is high and it is not suitable for low-temperature fixing.

  In order to solve such a problem, a method for improving the pulverization property by using a polyester resin together with polylactic acid has been proposed (for example, see Patent Document 2). However, in this proposal, polyester of petroleum-derived raw materials is still used, and the environmental conservation effect is reduced.

  In addition, a technique is known in which a biodegradable resin is heat treated to increase crystallinity and then pulverized (see, for example, Patent Document 3), which increases hardness by increasing crystallinity. It is intended to enhance the polishing ability and the cleaning ability. The main use of the obtained powder is an abrasive, and the biodegradable resin used has a high molecular weight. Although Patent Document 2 also describes use as a resin for toner, it is extremely difficult to pulverize to a particle size of 10 μm or less required by the toner in view of its molecular weight and the like.

  There is also a proposal of blending a terpene phenol copolymer and a specific wax into a polylactic acid-based biodegradable resin (see, for example, Patent Document 4). In this proposal, blending a terpene phenol copolymer that has low toughness of polylactic acid and low resin strength but is effective for low-temperature fixability provides good low-temperature fixability and grindability without sacrificing durability. It can be made compatible.

  However, the blending amount of the polylactic acid-based biodegradable resin is limited to about 30% by weight. If the blending amount is further increased, the grindability is deteriorated and it becomes difficult to prepare a toner. Also, the melt viscosity becomes high, and the low-temperature fixability deteriorates.

  In addition, a method for producing a toner containing polylactic acid by dissolving polylactic acid in a solvent or dispersing in a liquid containing a solvent has been proposed (for example, see Patent Document 5). However, if the solvent remains in the toner, the solvent may volatilize at the time of fixing the toner, which may harm the health of the user of the image forming apparatus. Therefore, it is necessary to remove the solvent sufficiently. Therefore, it is not a preferable method.

Japanese Patent No. 3151706 JP 2008-250171 A JP 2007-197602 A Japanese Patent No. 3779221 JP 2009-058628 A

  As described above, there are many problems in using a biodegradable resin as a main component of the binder resin of the toner, and even when a part of the biodegradable resin is replaced, the blending amount is limited, while maintaining good characteristics. Therefore, it is desired that more biodegradable resin can be blended as a binder resin for toner.

  The present invention has been made under the circumstances as described above, and provides an electrophotographic toner that includes a polylactic acid-based resin as a binder resin and that provides good pulverization and fixing properties, and a method for producing the same. For the purpose.

In order to solve the above problems, a first aspect of the present invention includes a step of kneading a raw material mixture containing a binder resin containing polylactic acid, a step of pulverizing the kneaded material obtained in the kneading step after cooling , A hydrolysis treatment step for obtaining a pulverized product dispersion water by hydrolyzing by immersing the pulverized product obtained in the pulverization step in water and stirring while heating , with a wet pulverizer for the pulverized product dispersion water wet grinding process step of performing wet grinding to obtain a fine particle dispersion water, filtered and dried drying and filtering particulates from the particle-dispersed water, comprising the step of externally added and mixed with additives to particles obtained by the filtering and drying process An electrophotographic toner manufacturing method is provided.

In order to solve the above problems, the second aspect of the present invention includes a step of kneading a raw material mixture containing a binder resin containing polylactic acid, and a step of pulverizing the kneaded product obtained in the kneading step after cooling. , hydrolysis by stirring the pulverized product obtained in the pulverization step wet pulverization treatment step was immersed in water by performing the wet powder crushing in a wet pulverizer to obtain a fine particle dispersion water, while heated the fine particles dispersing water A hydrolysis treatment step for performing decomposition, a filtration drying step for filtering and drying fine particles from the fine particle dispersion obtained in the hydrolysis treatment step, and a step for externally adding an additive to the fine particles obtained in the filtration drying step. An electrophotographic toner manufacturing method is provided.

  According to the present invention, there is provided an electrophotographic toner and a method for producing the same that can provide good grindability and fixability despite containing a biodegradable resin as a binder resin.

It is a typical schematic diagram showing an example of a wet atomization apparatus used for wet pulverization processing and explaining a state of pulverization in a chamber.

Hereinafter, various embodiments of the present invention will be described.
The electrophotographic toner according to an embodiment of the present invention is obtained by kneading a raw material mixture containing a binder resin containing polylactic acid, and then subjecting the cooled and pulverized pulverized product to hydrolysis and wet pulverization in water. It is characterized by comprising fine particles obtained by filtration and drying.

  In the electrophotographic toner according to the exemplary embodiment, the hydrolysis treatment and the wet pulverization treatment may be performed in the order or in the reverse order. That is, after the pulverized product obtained in the pulverization step is immersed in water and stirred while heating, the hydrolysis treatment is performed, and then the wet pulverization treatment is performed, or the pulverized product obtained in the above pulverization step is added to water. After the immersion and wet pulverization treatment, the hydrolysis treatment is performed by stirring while heating.

In addition, the wet pulverization process can use a commercially available wet atomization apparatus suitably.
FIG. 1 is a schematic diagram illustrating an example of a wet atomization apparatus used in the wet pulverization process of the present invention and illustrating a state of pulverization in a chamber.

  As shown in the figure, a chamber is formed inside a housing body (not shown), and first channels each having flow paths 3a and 4a into which coarsely pulverized and kneaded material dispersion water 2 into which coarsely pulverized and kneaded material 1 is dispersed are introduced. The nozzle 3 and the second nozzle 4 cause the coarsely pulverized kneaded material dispersion water 2 to be injected at high pressure from the mutual injection ports 3b, 4b toward the jet abutting portion X set at a substantially central position of the chamber. The housing body is attached at a predetermined angle.

  The coarsely pulverized kneaded material dispersion water 2 is, for example, supplied and mixed with a coarsely pulverized kneaded material 1 and water in a raw material tank (not shown), and sent from the raw material tank to a pressure intensifier by a water pump mechanism (not shown) for pressurization. After that, as shown by arrows a and b in FIG. 1, high pressure is supplied to the flow paths 3a and 4a divided into two hands, and injection is performed from the injection ports 3b and 4b (white arrows c and d).

  As a result of the collision, the coarsely pulverized kneaded product dispersion water 2 that has been jetted and collided becomes the treatment liquid 6 containing the finely pulverized kneaded product 5 in which the coarsely pulverized kneaded product 1 is made into fine particles. And is collected in the collection tank. The treatment liquid 6 collected in the collection tank is returned to the raw material tank again by opening a valve (not shown), and the collision process is sequentially repeated.

  According to the first embodiment of the present invention, the pulverized product is hydrolyzed in water and wet pulverized using the apparatus shown in FIG. At the same time, it is possible to obtain a toner having good storage stability.

  It does not specifically limit as a manufacturing method of polylactic acid used by this embodiment, A conventionally well-known method can be used. There is a method of fermenting starch such as corn as a raw material to obtain lactic acid, and then dehydrating and condensing directly from lactic acid monomer, or a method of synthesizing from lactic acid via cyclic dimer lactide by ring-opening polymerization in the presence of a catalyst. .

  A conventionally known colorant can be used as the colorant used in the toner according to the exemplary embodiment. For example, as a black colorant, carbon black and as a blue colorant, C.I. I. Pigment 15: 3, and red colorants include C.I. I. Pigment 57: 1, 122, 269, and yellow colorants include C.I. I. Pigment 74, 180, 185 and the like. In consideration of the influence on the environment which is one of the objects of the present invention, a single colorant having high safety is preferable.

  The content of these colorants is preferably 1 to 10% by mass with respect to the whole toner. The colorant may be used in the form of a masterbatch in which a resin and a colorant are dispersed in high concentration in advance.

  A conventionally known release agent can be added to the toner according to the exemplary embodiment as necessary. Examples of such release agents include olefinic waxes such as polypropylene wax, polyethylene wax, and Fischer-Tropsch wax, natural waxes such as carnauba wax, rice wax, and scale insect wax, and synthetic ester waxes.

  In order to improve low-temperature fixability and high-speed printing performance, a release agent having a relatively low melting point of about 60 to 100 ° C. is preferable, and specifically, carnauba wax and synthetic ester wax are preferable. In consideration of environmental impact, natural product carnauba wax is more preferable.

The compounding amount of the release agent is preferably 1 to 10% by mass with respect to the whole toner.
A conventionally known charge control agent of positive charge or negative charge can be added to the toner according to the exemplary embodiment as necessary. Examples of the positive charge control agent include quaternary ammonium salts, resins containing amino groups, and the like. Examples of the negative charge control agent include metal complexes of salicylic acid, metal complexes of benzylic acid, and calixarene type phenolic compounds. Examples include condensates and resins containing carboxyl groups.

The blending amount of the charge control agent is preferably 0.1 to 5% by mass with respect to the whole toner.
In addition to polylactic acid, conventionally known toner resins can be added to the toner according to the exemplary embodiment, if necessary. Examples of such resins include styrene / acrylic resins and polyester resins. From the viewpoint of pigment dispersibility and low-temperature fixability, polyester resins developed for toners are preferred. Resin may be individual or may mix 2 or more types.

  The amount of the resin for toner is preferably 0 to 50% by mass with respect to the whole toner in consideration of the influence on the environment which is one of the objects of the present invention.

  As other resin materials, a low molecular weight resin can be added to improve grindability, fixability and the like. Here, the low molecular weight resin is a resin in an oligomer region having a molecular weight of several hundred to several thousand, and examples thereof include rosin and rosin derivatives, polyterpene resins, terpene phenol resins, and petroleum resins that are commercially available as tackifiers.

  Here, the particle size of the toner is not particularly limited, but is usually adjusted to be 5 to 10 μm. An external additive can be added to the toner thus obtained in order to improve fluidity, adjust chargeability, and improve durability.

  As the external additive, inorganic fine particles are generally used, and examples thereof include silica, titania, alumina, etc. Among them, silica subjected to hydrophobic treatment (commercially available from Nippon Aerosil Co., Ltd., CABOT Co., Ltd.) is preferable. The particle diameter of the inorganic fine particles is preferably 7 to 40 nm as the primary particle diameter, and two or more kinds may be mixed for improving the function.

  Examples of the present invention and comparative examples are shown below, and the present invention will be described more specifically. In addition, the measuring method of each physical-property value of the component used by the Example and the comparative example is as follows.

(Measurement of glass transition point (Tg))
Apparatus: Differential scanning calorimeter (manufactured by Shimadzu Corporation: DSC-60)
Sample: 8mg
Temperature raising conditions: The temperature is raised to 160 ° C. at 10 ° C./min, cooled to 35 ° C. at a temperature lowering rate of 10 ° C./min, and then raised again to 160 ° C. at 10 ° C./min. At the second temperature increase, the intersection of two tangents of the curve portion obtained by the transition was taken as the glass transition point.

(Measurement of softening point)
Apparatus: Flow tester (manufactured by Shimadzu Corporation, CFT-500D)
Sample: 1g
Temperature increase rate: 6 ° C / min Load: 20kg
Nozzle: 1mm diameter, 1mm length
1/2 method: The temperature at which half of the sample flowed out was taken as the softening point.

(Measurement of toner particle size)
Equipment: Multisizer II (manufactured by Coulter, Inc.)
Sample: A small amount of sample, purified water, and a surfactant were placed in a beaker and dispersed with an ultrasonic cleaner.
Measurement: The aperture was 100 μm, the count was 50,000, and the volume average particle size was obtained.

Example 1
Each component of the following blending amount was put into a Henschel mixer (standard feather mounted, manufactured by Mitsui Mining Co., Ltd.) and mixed.
Polylactic acid (glass transition point 57 ° C., softening point 160 ° C.) 90 parts by weight Colorant: Carbon black (MOGUL L manufactured by CABOT Co., Ltd.) 4 parts by weight Release agent: Carnauba wax No. 1 powder (Nippon Wax Co., Ltd.) 5 parts by mass Charge control agent: E-84 (manufactured by Orient Chemical Co., Ltd.) 1 part by mass

  The obtained mixed powder was melt-kneaded with a twin-screw extruder (screw diameter 43 mm, L / D = 34), and then stretched and cooled to obtain a kneaded product. The obtained kneaded material was coarsely pulverized with a rotoplex (manufactured by Hosokawa Micron Corporation, 2 mm screen).

  100 parts by mass of this coarsely pulverized product was placed in a stirring vessel equipped with a heater, 500 parts by mass of ion-exchanged water was added, and the mixture was stirred at 200 rpm / 95 ° C. for 8 hours (hydrolysis treatment).

  Thereafter, the concentration of the pulverized product dispersion water is adjusted to crushed product / ion exchange water = 1/2, and the pulverized product is added to a wet atomizer (Starburst pulverizer manufactured by Sugino Machine Co., Ltd.) at 30 ° C. and pulverized (wet pulverization treatment). To obtain a suspension of fine particles. The water pressure during pulverization was 8 times at 48 MPa. This suspension was filtered and dried to obtain fine particles.

  As an external additive, 2 parts by mass of “RY200” (manufactured by Nippon Aerosil Co., Ltd .: hydrophobic silica, primary particle size of 12 nm) is added to 100 parts by mass of the obtained fine particles, and a Henschel mixer (with stirring reinforcing wings, Mitsui) is added. (Mine Co., Ltd.) for 3 minutes with stirring to obtain a toner having an average particle size of 9.8 μm (softening point: 140 ° C.).

Examples 2 and 3
A toner was obtained in the same manner as in Example 1 except that the conditions at the time of pulverization (the water pressure during pulverization and the number of times the pulverizer was passed) were set to the values shown in Table 2 below (average particle diameter). Are 9.2 μm and 8.8 μm, respectively, and the softening point is 140 ° C. as in Example 1.

Example 4
Without performing the above hydrolysis treatment on the coarsely pulverized product obtained in the same manner as in Example 1, the concentration of the coarsely pulverized product dispersion water was adjusted to coarsely pulverized product / ion-exchanged water = 1/2, and 30 ° C. Were put into a wet atomizer (Starburst pulverizer manufactured by Sugino Machine Co., Ltd.) and pulverized (wet pulverization treatment) to obtain a fine particle suspension. Next, this suspension was stirred (hydrolysis treatment) at 200 rpm for 5 hours at 50 ° C., then filtered and dried to obtain fine particles. Thereafter, a toner having an average particle diameter of 9.7 μm was obtained in the same manner as in Example 1 (softening point 141 ° C.).

Examples 5 and 6
A toner was obtained (average particle diameter) in the same manner as in Example 4 except that the conditions at the time of pulverization by the wet atomization apparatus (water pressure during pulverization and the number of times the pulverizer was passed) were set to the values shown in Table 2 below. Are 9.3 μm and 8.7 μm, respectively, and the softening point is 141 ° C. as in Example 4.

Comparative Example 1
The suspension obtained in the same manner as in Example 4 was filtered and dried without hydrolyzing to obtain fine particles. Thereafter, a toner having an average particle diameter of 9.7 μm was obtained in the same manner as in Example 1 (softening point: 160 ° C.).

Comparative Example 2
The coarsely pulverized product obtained in the same manner as in Example 1 was pulverized with an airflow pulverizer. However, the pulverization property was remarkably poor, and it was not possible to finely pulverize the toner particle size (less than 10 μm). It was.

Comparative Example 3
The polylactic acid before being charged into the Henschel mixer is stirred in ion-exchanged water at 200 rpm for 8 hours at 95 ° C. and subjected to hydrolysis pretreatment, the dispersion is filtered and dried, and hydrolyzed polylactic acid. Got. Using this polylactic acid that had been subjected to hydrolysis pretreatment, a kneaded product was obtained in the same manner as in Example 1, and the obtained kneaded product was coarsely pulverized. The coarsely pulverized product was pulverized with an airflow pulverizer to obtain fine particles. From the obtained fine particles, a toner having an average particle diameter of 9.9 μm was obtained in the same manner as in Example 1 (softening point 140 ° C.).

  The fixability and grindability of the toners of Examples 1 to 6 and Comparative Examples 1 to 3 obtained as described above were tested and evaluated by the following test methods.

Test 1-Fixability Fixing temperature of non-magnetic one-component developing device “Casio Page Presto N-5” (manufactured by Casio Computer Co., Ltd .: color printer 29 sheets per minute (A4 horizontal) machine, process speed 129 mm / sec) Is modified so that it can be changed to a fixing tester. After obtaining an unfixed image with this apparatus, the fixing temperature was varied in the range of 100 to 200 ° C. every 10 ° C., and the unfixed image was passed through a fixing device. The cold offset, hot offset, and peeled nail trace of the image sample were visually evaluated, and a non-offset area was obtained and evaluated. The process speed was 129.3 mm / sec, and the paper was XEROX P paper A4 size (weight 64 g / m ² ). The oil supply roll of the fixing device was removed.

(Double-circle): A non-offset area | region is 30 degreeC or more.
○: The non-offset region is 20 ° C. or higher.
X: Non-offset area | region is less than 20 degreeC.
X: A non-offset area | region is less than 10 degreeC.

Test 2-Crushability Judged from the pulverization water pressure and the number of passes when pulverizing the kneaded coarsely pulverized product.

A: Water pressure × number of passes is less than 800 ○: Water pressure × number of passes is 800 or more X: Cannot be crushed The above test results are shown in Table 1.

From Table 1 above, the following is clear.
That is, polylactic acid was hydrolyzed in advance for Comparative Example 2 in which untreated polylactic acid was used as a binder resin and pulverization was attempted with a conventional airflow pulverizer (pulverization was extremely difficult and toner could not be formed). In the case of the comparative example 3 processed, it turns out that the grindability is improving.

On the other hand, it can be seen from the results of Examples 1 to 6 and Comparative Example 1 that the pulverization is facilitated by employing the wet pulverization treatment.
In Comparative Example 3, although pulverization was possible, the power consumption of the airflow pulverizer was larger than that of the wet pulverizer and the productivity was also inferior to that of the wet pulverizer.

  In particular, Examples 1 to 6 in which the pulverized product was hydrolyzed and wet pulverized in water were able to efficiently perform fine pulverization and to obtain a toner having good fixability.

  On the other hand, Comparative Example 1 in which wet pulverization is performed in the same manner is inferior in fixability because it is converted into toner without being hydrolyzed.

  Moreover, since Examples 1-3 are pulverized after making it easy to grind polylactic acid by hydrolysis, pulverization efficiency is good in Examples 4-6. Since the contact area between water and water is larger than that of the coarsely pulverized product, hydrolysis can be achieved to a required level at a low temperature in a short time, and the hydrolysis efficiency is good.

  As for the pulverization conditions during wet pulverization, the water pressure and the number of passes are greatly related to energy during production and labor, and affect productivity. In other words, it is desirable that the water pressure be as low as possible and the number of times of passage is small. Since Examples 1-3 are small compared with Examples 4-6 in the product of a water pressure and the frequency | count of threading, it can be said that the efficiency at the time of a grinding | pulverization is excellent.

  When Examples 1 to 3 and 4 to 6 are compared, the grinding efficiency is 1 to 3, and the hydrolysis efficiency is 4 to 6. Therefore, the order of hydrolysis and wet grinding is not particularly limited.

  From these, it is found that the combined use of the hydrolysis treatment and wet pulverization treatment of the present invention is most preferable.

  The present invention can be used for an electrophotographic toner containing a polylactic acid resin as a biodegradable resin as a binder resin.

  DESCRIPTION OF SYMBOLS 1 ... Coarse pulverized kneaded material, 2 ... Coarse pulverized kneaded material dispersion water, 3a, 4a ... Flow path, 3b, 4b ... Injection port, 5 ... Finely pulverized kneaded material, 6 ... Treatment liquid, X ... Jet collision part.

Claims (2)

A step of kneading a raw material mixture containing a binder resin containing polylactic acid, a step of crushing the kneaded product obtained in the kneading step after cooling , and immersing the crushed product obtained in the crushing step in water and heating Hydrolysis treatment step for obtaining pulverized product dispersion water by stirring while stirring, wet pulverization treatment step for obtaining fine particle dispersion water by performing wet pulverization on the pulverized product dispersion water in a wet pulverizer , filtration and drying steps, the production method of an electrophotographic toner characterized by comprising the step of mixing externally added additives into fine particles obtained by the filtration drying step of fine particles were filtered and dried from the microparticle dispersion water. A step of kneading a raw material mixture containing a binder resin containing polylactic acid, a step of pulverizing the kneaded product obtained in the kneading step after cooling, a wet pulverizer wherein the pulverized product obtained in the pulverizing step is immersed in water wet grinding process of performing wet powder crushed to obtain a fine particle dispersion water in hydrolysis treatment step of performing hydrolysis by stirring while heating the fine particle dispersion water, fine particles obtained in hydrolysis step A method for producing an electrophotographic toner comprising: a filtration drying step of filtering and drying fine particles from dispersed water; and a step of externally adding an additive to the fine particles obtained in the filtration drying step.

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