JP2010266630A - Resin for electrophotographic toner and electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin for an electrophotographic toner and an electrophotographic toner having good pulverizing property and fixing property even when a biodegradable resin is used as a binder resin. <P>SOLUTION: The resin for the electrophotographic toner is obtained when the biodegradable resin is hydrolyzed by using superheated steam to reduce its molecular weight to 5,000-50,000. The electrophotographic toner contains the resin for an electrophotographic toner, and a colorant. Preferably, a polylactic acid-based resin is used as the biodegradable resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrophotographic toner resin and an electrophotographic toner, and more particularly to an electrophotographic toner resin containing a biodegradable resin and an electrophotographic toner using the same 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 the toner used for such image formation, a toner prepared by kneading a mixture of a binder resin and a colorant or a charge control agent, and adjusting the particle size distribution by pulverization is used.

  Conventionally, petroleum-derived resins such as styrene / acrylic resins and polyester resins have been used as binder resins for 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.

  As one of them, there is a proposal to use a microbial aliphatic polyester having biodegradability as a binder resin (see, for example, Patent Document 1). Such a microbial aliphatic polyester is used as a toner resin. If used as it is, the grindability is poor and it is difficult to obtain the desired particle size distribution. In addition, since the softening temperature of the toner is high, there is a problem that the fixing temperature must be set high.

  In order to improve these problems, proposals have been made to lower the softening temperature by adding a large amount of plant-based wax to the biodegradable resin (see, for example, Patent Document 2). However, it is possible to lower the softening temperature of the toner by adding a large amount of wax. However, the toner easily aggregates due to the wax component. Deteriorating causes problems such as inferior toner transportability in the developing device.

  In addition, in order to obtain low-temperature fixability and fixing stability, there is a proposal using a binder resin containing two kinds of resins having different softening points and a biodegradable resin (for example, see Patent Document 3). According to this proposal, the low softening point resin serves as a bridge between the high softening point resin and the biodegradable resin, and the biodegradable resin is uniformly dispersed in the binder resin. However, in this proposal, the blending ratio of the biodegradable resin in the binder resin is about 13% by mass, and remains at most 33% by mass. The reason is not clear, but as one of the causes, increasing the blending ratio of the biodegradable resin further causes poor dispersion of the biodegradable resin, and the developability decreases due to variations in charging performance, etc. This is thought to be because durability deteriorates.

  Conventionally, a biodegradable resin is mixed with a colorant and other additives, melt kneaded, and the material is dispersed. Among biodegradable resins, for example, polylactic acid has a melting point of about 170 ° C., and when used alone for toner, has a high softening temperature and poor grindability. In order to improve this problem, it is necessary to mix a large amount of a low softening point substance, and in this case, the viscosity difference between the polylactic acid and the low softening point substance in melt-kneading is large, and uniform dispersion is difficult. Therefore, even if a binder resin is added as proposed in Patent Document 3, there is a limit to the amount of biodegradable resin blended.

  As described above, there are many problems in making a biodegradable resin the main resin component of a toner binder resin, and even when a part of the binder resin is replaced with a biodegradable resin, the amount of the compound is limited. Therefore, it is desired that more biodegradable resins can be blended as toner resins while maintaining the properties as binder resins.

JP-A-4-179967 Japanese Patent No. 2597452 JP 2006-91278 A

  The present invention has been made under the circumstances as described above. An electrophotographic toner resin and an electrophotographic toner that include a biodegradable resin as a binder resin and that can obtain good pulverizability and fixability are provided. The purpose is to provide.

  As a result of intensive studies to solve the above problems, the present inventors have hydrolyzed a biodegradable resin using superheated steam to reduce its molecular weight, and have good grindability and fixability. It has been found that an electrophotographic toner resin and an electrophotographic toner having the above can be obtained.

That is, according to the first aspect of the present invention, the biodegradable resin having a number average molecular weight exceeding 50,000 is hydrolyzed with superheated steam so that the number average molecular weight of the biodegradable resin is 5,000 to 50. An electrophotographic toner resin characterized by being obtained by reducing to 1,000,000 is provided.

  Preferably, the pressure is applied during the hydrolysis.

  According to a second aspect of the present invention, there is provided an electrophotographic toner obtained by melting, kneading, pulverizing and classifying a raw material containing at least the resin for electrophotographic toner and a colorant.

  In the above electrophotographic toner resin and electrophotographic toner, a polylactic acid resin can be used as the biodegradable resin.

  According to the present invention, there are provided an electrophotographic toner resin and an electrophotographic toner capable of obtaining good pulverization property and fixing property even though a biodegradable resin is contained as a binder resin.

  In addition, a method of polymerizing a low molecular weight resin from the beginning is conceivable with respect to the method of the present invention, but at present, there is no technique for producing a low molecular weight product at a low cost as a mass-produced product, and a biodegradable resin is used for a short time. The present invention, in which the molecular weight is adjusted by hydrolysis, contributes to cost reduction.

It is a figure which shows a superheated steam generator. It is a figure which shows the hydrolysis processing apparatus using superheated steam.

Hereinafter, various embodiments of the present invention will be described.
The electrophotographic toner resin according to the first embodiment of the present invention is obtained by hydrolyzing a biodegradable resin using superheated steam to reduce the molecular weight of the biodegradable resin.

  And preferably, it is obtained by applying pressure during the hydrolysis.

  Usable biodegradable resins include, for example, polyhydroxybutyrate, poly (hydroxybutyrate / hydroxyhexanoate) as a microorganism production system, esterified starch, cellulose acetate, chitosan, chemical synthesis as a natural product system Examples of the system include polylactic acid, polycouplertone, polybutylene succinate, polyvinyl alcohol, and polyglycolic acid.

  Specifically, Nature Works sells polylactic acid resin commercially, and recently, Teles, a joint venture of Metabolic and ADM, has been producing polyhydroxyalkanoic acid-based biodegradable resins every year. It has begun to be used for applications that make use of biodegradability, such as announcing a production plan of 10,000 tons.

ポリ乳酸は、乳酸がエステル結合により結合したポリマーであり、近年注目を集めている。即ち、自然界には、エステル結合を切断する酵素（エステラーゼ）が広く分布していることから、ポリ乳酸は環境中でこのような酵素により徐々に分解されて、単量体である乳酸に変換され、最終的には二酸化炭素と水になる。 A polylactic acid resin which is a typical biodegradable resin is a resin having the following structural formula.

Polylactic acid is a polymer in which lactic acid is bonded by an ester bond, and has recently attracted attention. In other words, in nature, enzymes that cleave ester bonds (esterases) are widely distributed, so polylactic acid is gradually decomposed by such enzymes in the environment and converted into lactic acid, which is a monomer. And eventually carbon dioxide and water.

  The manufacturing method of biodegradable resin is not specifically limited, A conventionally well-known method can be used. Among known production methods, for example, in polylactic acid, fermenting starch such as corn as a raw material to obtain lactic acid, followed by dehydration condensation directly from lactic acid monomer, or cyclic dimer lactide from lactic acid There is a method of synthesis by ring-opening polymerization in the presence of a catalyst. There are optical isomers in lactic acid, and there are L-lactic acid and D-lactic acid, and either lactic acid alone or in a mixture may be used.

  In addition, commercially available polylactic acid is synthesized by a ring-opening polymerization method for obtaining a higher molecular weight in order to improve heat resistance, and the number-average molecular weight is mainly 100,000 or more. . Such a high molecular weight polylactic acid has a too high softening point and poor fixability, and also has poor grindability. Therefore, it is necessary to hydrolyze the resin and reduce the molecular weight.

  In addition, polylactic acid has a tendency to increase the odor of the resin due to the occurrence of monomer components that are reduced in molecular weight while maintaining a relatively molecular weight distribution during hydrolysis. Odor is a big problem and a problem.

  In order to hydrolyze the biodegradable resin, the biodegradable resin may be placed under specific conditions of high temperature and high humidity. However, as a result of repeated research by the present inventors in order to set high temperature and high humidity conditions, It has been found that by hydrolyzing a degradable resin with superheated steam, hydrolysis is carried out in a short time, and it is effective in improving storage stability and reducing odor.

  Therefore, the method for hydrolyzing the resin for electrophotographic toner according to the first embodiment of the present invention is performed using superheated steam.

  Here, superheated steam refers to a thermally radioactive gas obtained by further heating saturated steam with an apparatus as shown in FIG. Normally, saturated steam of 100 ° C generated by boiling water becomes superheated steam, which is higher than 100 ° C when heated further, and when it reaches a temperature of about 200 ° C, it becomes a completely colorless and transparent gas. I can see it.

  By the way, when heating the saturated steam, the case where the steam is higher than 100 ° C. in the sealed container is distinguished from the high pressure steam, and the case where the steam is higher than 100 ° C. at normal pressure is distinguished from the normal pressure superheated steam. Although it may say, in this invention, all shall be handled as superheated steam.

  Conventionally, when it comes to steam at a temperature higher than 100 ° C., it refers to high-pressure steam in a sealed container, but the apparatus has been enlarged and continuous operation has been difficult, whereas atmospheric superheated steam is Atmospheric pressure, that is, atmospheric pressure, an apparatus is simple, and there is an advantage that continuous operation can be carried out on the conveyor, which has been attracting attention in recent years.

  As a feature of superheated steam, it has been used in the food industry because it has higher efficiency in transferring heat than dry air and has the ability to dry substances, and it has a deoiling effect. In addition, since the atmosphere is very low in oxygen, it is used in various applications as a heat treatment that suppresses the oxidation reaction.

  FIG. 1 is a schematic diagram showing a superheated steam generator used for the hydrolysis of the present invention. As shown in the figure, the superheated steam generator 1 includes a water softener 2, a boiler 3, a steam heater 4, a water conduit 5 for introducing tap water into the water softener 2, and water softening from the water softener 2 to the boiler 3. A water feed pipe 6 and a water feed pump 7, a steam feed pipe 8 that feeds steam from the boiler 3 to the steam heater 4, a superheated steam feed pipe 9 that sends out superheated steam generated by the steam heater 4, and each of the above pipes It is provided with adjusting valves 10, 11, 12 and the like disposed therein. The steam heater 4 of this example includes a so-called IH heater using induction heating in the heating section, and can be set to ± 1 ° C. or less with respect to the set temperature.

  Moreover, FIG. 2 is a figure which shows the hydrolysis processing apparatus explaining the hydrolysis method of this invention. As shown in the figure, the hydrolysis treatment device 13 includes a superheated steam conduit 14 for introducing superheated steam, which is produced by the superheated steam generator 1 described above and sent from the superheated steam feed tube 9, into the mixing stirrer 16, and an exhaust pipe. 15, a motor 18 for rotating the stirring blade 17, adjustment valves 19 and 20, and the like. In this example, the pressure in the mixing agitator 16 can be adjusted (pressurized) by appropriately operating the adjusting valve 20.

  According to the first embodiment of the present invention, hydrolysis using the apparatus as shown in FIGS. 1 and 2 and subsequent rinsing / drying are performed to reduce the molecular weight with less odor. A degradable resin can be obtained.

  Here, the specific number average molecular weight of the biodegradable resin having a reduced molecular weight is 100,000 or less, more preferably 50,000 or less, and further preferably 5,000 to 50,000. If the molecular weight is too high, it will be difficult to sufficiently lower the softening point and improve the grindability. On the other hand, if the molecular weight is too small, there is a possibility of deteriorating the storage stability of the toner after becoming a product.

  As described above, the biodegradable resin having a reduced molecular weight has a softening point that is reduced, pulverization is improved, and optimal properties as a resin for toner. If the number average molecular weight of the biodegradable resin is less than 5,000, the resin is fused in the machine at the time of pulverization, and further pulverization becomes difficult, and toner cannot be formed.

  The electrophotographic toner according to the second embodiment of the present invention can be produced by a conventionally known method using the above-described resin for electrophotographic toner having a reduced molecular weight as the binder resin. For example, after mixing a biodegradable resin, a colorant, and other additives as necessary, the raw material mixture is kneaded with a kneader such as a biaxial kneader, a pressure kneader, or an open roll, and then the kneaded product is mixed. After cooling, the toner can be obtained by pulverizing with a pulverizer such as a jet mill and classifying with an air classifier.

  Since the obtained electrophotographic toner has a reduced molecular weight of the biodegradable resin as described above, the softening point is lowered, and the grindability and fixability are improved.

  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 and the like. Of these, hydrophobized silica is preferable, and the primary particle size commercially available from Nippon Aerosil Co., CABOT Co., etc. As for the thing of 7-40 nm, you may mix 2 or more types for a function improvement.

  A conventionally known colorant can be used as the colorant used in the toner according to the second embodiment of the present invention. 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 in the form of a masterbatch in which a resin and a colorant are dispersed in high concentration in advance.

  In addition, a conventionally known release agent can be added to the toner according to the second embodiment of the present invention 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, the release agent has a relatively low melting point of about 60 to 100 ° C., and specifically, carnauba wax and synthetic ester wax are preferred. In consideration of environmental impact, natural product carnauba wax is more preferable. The addition amount of the release agent is preferably 1 to 10% by mass with respect to the whole toner.

  In addition, a conventionally known charge control agent can be added to the toner according to the second embodiment of the present invention as necessary. For example, a quaternary ammonium salt, a resin containing an amino group, etc. as a positive charge control agent, a metal complex salt of salicylic acid, a metal complex salt of benzyl acid, a calixarene type phenolic condensate, a carboxyl as a negative charge control agent There are resins containing groups. The blending amount of the charge control agent is preferably 0.1 to 5% by mass with respect to the whole toner.

  Further, a conventionally known toner resin can be added to the toner according to the second embodiment of the present invention, if necessary. Conventionally known toner resins include styrene / acrylic resins, polyester resins, and the like. From the viewpoint of pigment dispersibility and low-temperature fixability, polyester resins developed for toners are preferred. The toner resin may be used alone or in combination of two or more. Considering the influence on the environment, which is one of the objects of the present invention, the toner resin is preferably 0 to 50% by mass with respect to the whole toner.

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

  In addition, a conventionally known hydrolysis inhibitor can be added to the toner according to the second embodiment of the present invention as necessary. Examples of the hydrolysis inhibitor include carbodiimide compounds, isocyanate compounds, and oxazoline compounds. By such a hydrolysis inhibitor, the residual monomer and the hydroxyl group and carboxyl terminal produced by decomposition can be blocked, and the hydrolysis chain reaction can be suppressed. In the embodiment of the present invention, by adding a hydrolysis inhibitor, the original hydrolysis resistance is improved, and an effect is also obtained for adjusting the molecular weight of the biodegradable resin.

  As a specific hydrolysis inhibitor, “Carbodilite LA-1” manufactured by Nisshinbo Co., Ltd., which is a polycarbodiimide compound, is commercially available. It is preferable that the addition amount of a hydrolysis inhibitor is 0.01-10 mass% with respect to biodegradable resin, and 0.05-5 mass% is more preferable. When the amount is too large, the transparency is deteriorated and the color of the toner tends to be deteriorated.

  Furthermore, a conventionally known crystal nucleating agent can be added to the toner of the present invention according to the second embodiment of the present invention, if necessary. Inorganic nucleating agents such as talc, organic carboxylic acid metal salts such as sodium benzoate, phosphoric acid ester metal salts, organic nucleating agents such as benzylidene sorbitol, carboxylic acid amide, and the like.

Examples Examples and comparative examples of the present invention will be described below, and the present invention will be described more specifically.
1. The measuring method of each physical-property value of the component used in the Example and the comparative example.
(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.

(Measurement of molecular weight)
Equipment: GPC (manufactured by Shimadzu Corporation), detector RI
The molecular weight Mn is a number average molecular weight measured by GPC (gel permeation chromatography) using a calibration curve prepared with a polystyrene sample having a known molecular weight as a standard.

2. Production of biodegradable resin used in Examples and Comparative Examples (Production treatment 1 of low molecular weight polylactic acid 1 (condition 1))
3 kg of polylactic acid (manufactured by Kaisho Biochemical Co., Ltd .: REVODE 101B, molecular weight (Mn = 120,000) is charged into a 15 L mixing stirrer (hydrolysis apparatus described above / see FIG. 2) and stirred at 120 ° C. The superheated water vapor was blown at a rate of 20 kg / h to hydrolyze, the pressure was released, then rinsed with pure water and dried in a hot air dryer (60 ° C. setting) for 1 hour.

  The hydrolysis treatment time was varied as shown in Table 1 below to prepare polylactic acids having different molecular weights.

(Production process 2 of low molecular weight polylactic acid (condition 2))
3 kg of polylactic acid (manufactured by Kaisho Biochemical Co., Ltd .: REVODE101B, molecular weight (Mn = 120,000)) is charged into a 15 L mixing stirrer, and hydrolyzed by blowing superheated steam at 120 ° C. at 20 kg / h while stirring. At that time, the pressure was adjusted to 0.14 to 0.17 MPa, then rinsed with pure water and dried for 1 hour in a hot air dryer (60 ° C. setting).

  The hydrolysis treatment time was varied as shown in Table 1 below to prepare polylactic acids having different molecular weights.

(Production process 3 of low molecular weight polylactic acid (condition 3))
Polylactic acid (manufactured by Kaisho Biochemical Co., Ltd .: REVODE101B, molecular weight (Mn = 120,000) was hydrolyzed in a constant temperature and humidity chamber set at a temperature of 80 ° C. and a humidity of 80% RH. And dried for 1 hour with a hot air dryer (60 ° C. setting).

  The hydrolysis treatment time was varied as shown in Table 1 below to prepare polylactic acids having different molecular weights.

(Production process 4 of low molecular weight polylactic acid (condition 4))
Polylactic acid (manufactured by Kaisho Biochemical Co., Ltd .: REVODE101B, molecular weight (Mn = 120,000)) was put into a hot water tank set at a temperature of 95 ° C. and hydrolyzed. At 1 ° C.) for 1 hour.

  The hydrolysis treatment time was varied as shown in Table 1 below to prepare polylactic acids having different molecular weights.

Example 1
Next, each component of the following blending amount was put into a Henschel mixer (standard feather mounted, Mitsui Mining Co., Ltd.) and mixed.

Binder resin: Hydrolyzed resin 1-1 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 (manufactured by Nippon Wax Co., Ltd.) 6 parts by mass The obtained mixed powder was melt-kneaded with a twin-screw extruder (screw diameter 43 mm, L / D = 34), then stretched, cooled, and rotated with a Rotoplex (2 mm screen manufactured by Hosokawa Micron Corporation). Crushed. After that, the particles are pulverized and classified with a collision type pulverizer (Nippon Pneumatic Industry IDS-2) and a wind classifier (Nippon Pneumatic Industry DSX-2) so that the average particle diameter of the toner becomes 9.0 μm. Got.

  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.

(Examples 2-8, Comparative Examples 1-4)
A toner was obtained in the same manner as in Example 1 except that various hydrolyzed resins shown in Table 2 below were used as the binder resin.
The fog, density stability, storage stability, fixability, and grindability of the toners of Examples 1 to 8 and Comparative Examples 1 to 4 obtained as described above were tested and evaluated by the following test methods.

(Test 1-Cover)
The toner is mounted on a non-magnetic one-component developing device “Casio Page Prest N-5” (manufactured by Casio Computer Co., Ltd .: color printer 29 sheets per minute (A4 horizontal), process speed 129 mm / sec) in a normal environment (25 After printing 10,000 sheets of 5% print images continuously using plain paper (XEROX-P paper A4 size) at 50 ° C and 50% RH), blank paper is printed, and the front door is opened during printing. Thus, the printing was forcibly terminated, and the fog toner on the OPC drum at that time was copied onto a mending tape and affixed to a white paper, and compared with a tape from which the fog toner was not collected. The measurement was carried out by obtaining the maximum value of the difference before and after the fog from the XYZ value obtained using a spectroscopic color difference meter “SE-2000” manufactured by Nippon Denshoku Co., Ltd., and evaluated according to the following criteria.

A: The fogging value is less than 2 and good.
○: The fogging value is 2 or more and less than 5, which is good.
Δ: Fog value is 5 or more and less than 10. There is no problem in practical use.
X: A fogging value of 10 or more is bad.

(Test 2-concentration stability)
Using the same apparatus as in Test 1, 14,000 sheets of 5% printed images were continuously printed in a normal environment (25 ° C., 50% RH). In the middle, an A4 solid image is printed every 2,000 sheets, and the image density is measured at the four corners and the center five points to obtain the average density. (At that time, the image defect portion due to white streaks or the like is not measured.) Among the average densities obtained at each sampling point, the density stability is obtained from the maximum value and the minimum value according to the following formula and evaluated according to the following criteria.

Concentration stability (%) = Minimum average density / Maximum average density × 100
A: Concentration stability is 95% or better.
Good: Concentration stability is good at 85% or more.
Δ: Concentration stability is 75% or more and there is no practical problem.
X: The density stability is poor at less than 75%.

(Test 3—Preservability)
10 g of the toner was put in a glass beaker and left in a constant temperature and humidity chamber at 50 ° C. and 90% RH for 8 hours, and then the aggregation state of the toner was visually confirmed and evaluated according to the following criteria.
A: No toner aggregation is observed.
○: Almost no aggregation of toner is observed.
Δ: Slight aggregation of toner is observed.
X: Aggregation of toner is clearly recognized.

(Test 4-Fixability)
The fixing unit is modified so that the temperature of the fixing unit of the same apparatus as in Test 1 can be varied, and a fixing tester is obtained. After obtaining an unfixed image with this apparatus, the fixing temperature of the upper roll was varied in a range of 100 to 200 ° C. every 10 ° C., and the unfixed image was passed through a fixing device. At that time, the lower roll was set at a temperature 10 ° C. lower than the set temperature of the upper roll. 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.

A: The non-offset region is 30 ° C. or higher.
○: The non-offset region is 20 ° C. or higher.
(Triangle | delta): A non-offset area | region is 20 degrees C or less.
X: A non-offset area | region is 10 degrees C or less.

(Test 5-Grindability)
When pulverizing and classifying the kneaded coarsely pulverized product in the pulverization / classification step, the determination is made based on the yield (mass%) of the particles serving as the toner base. In reality, there is no problem if the yield is 70% or more. At this time, the pulverization conditions are adjusted so that the volume average particle diameter of the toner is 9 μm, the number ratio of 3 μm or less as fine powder is 5% or less, and the volume ratio of 16 μm or more as coarse powder is 3% or less.

○: Yield 65% or more.
X: Yield less than 65%.
The results of the above tests 1 to 5 are shown in Table 2 below.

From Table 2 above, the following is clear.
As the binder resin, the toner according to Examples 1 to 8 using a resin that is hydrolyzed with superheated steam and has a molecular weight adjusted to a range of 5,000 to 50,000, is fogging and density stability. In addition, excellent results were exhibited in all the characteristics of storage stability, fixability and grindability, and in particular, a toner having good storage stability and odor could be obtained.

  On the other hand, in Comparative Examples 1 and 2 in which the molecular weight was adjusted to less than 5,000, the molecular weight of the biodegradable resin was too low, so that fusion occurred in the pulverizer during toner pulverization, and pulverization could be continued. could not. For reference, when a biodegradable resin whose molecular weight is adjusted to a value exceeding 50,000 is used as a binder resin, although it is not shown in the table, it has poor fixability and grindability and cannot be used. Met.

  In Comparative Example 3, the hydrolysis treatment time is long and the productivity is poor, and the storage stability and odor are inferior. In Comparative Example 4, the hydrolysis treatment time is long and the productivity is poor, and the storage stability is poor. It became.

  The present invention can be used for a resin for an electrophotographic toner containing a biodegradable resin and an electrophotographic toner using the resin for a binder resin.

  DESCRIPTION OF SYMBOLS 1 ... Superheated steam generator, 2 ... Water softener, 3 ... Boiler, 4 ... Steam heater, 5 ... Water conduit, 6 ... Water feed pipe, 7 ... Water feed pump, 8 ... Steam feed pipe, 9 ... Superheated steam feed pipe, DESCRIPTION OF SYMBOLS 10,11,12,19,20 ... Adjustment valve, 13 ... Hydrolysis processing apparatus, 14 ... Superheated steam conduit, 15 ... Exhaust pipe, 16 ... Mixing stirrer, 17 ... Stirring blade, 18 ... Motor.

Claims (5)

  A resin for electrophotographic toner obtained by hydrolyzing a biodegradable resin with superheated steam to reduce the molecular weight of the biodegradable resin to a predetermined value.   2. The resin for electrophotographic toner according to claim 1, wherein pressure is applied during the hydrolysis.   3. The resin for electrophotographic toner according to claim 1, wherein the biodegradable resin is a polylactic acid resin.   The resin for electrophotographic toner according to claim 1, wherein the reduced biodegradable resin has a molecular weight of 5,000 to 50,000.   An electrophotographic toner obtained by melting, kneading, pulverizing, and classifying a raw material containing at least the resin for an electrophotographic toner according to claim 1 and a colorant.

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