JP2010133994A - Resin for electrophotographic toner and electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin for 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 electrophotographic toner is obtained by hydrolyzing a biodegradable resin with warm water to reduce the molecular weight to 5,000 to 50,000. The electrophotographic toner contains the above resin for an electrophotographic toner, and a colorant. Preferably, a polylactic acid-based resin is used as the biodegradable resin. <P>COPYRIGHT: (C)2010,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 machine.

  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.

  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.

  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.

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 with hot water to reduce its molecular weight, and thus have good grindability and fixability. It has been found that an electrophotographic toner resin and an electrophotographic toner are obtained.

  According to a first aspect of the present invention, there is provided an electrophotographic toner obtained by hydrolyzing a biodegradable resin with warm water to reduce the molecular weight of the biodegradable resin to a predetermined value. Provide resin.

  The hydrolysis can be caused by immersing the biodegradable resin in warm water of 95 ° C. or higher.

  According to a second aspect of the present invention, there is provided an electrophotographic toner comprising the above 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.

  Moreover, the molecular weight of the reduced biodegradable resin can be set to 5,000-50,000. In addition, the resin for electrophotographic toner and the electrophotographic toner described above can further contain a hydrolysis inhibitor.

  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.

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 warm water to reduce the molecular weight of the biodegradable resin.

  And the said hydrolysis can be produced by immersing the said biodegradable resin in 95 degreeC or more warm water.

  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 the electrophotographic toner resin according to the first embodiment of the present invention, the biodegradable resin is hydrolyzed by placing the biodegradable resin under specific conditions of high temperature and high humidity. Although a suitable toner resin can be obtained by reducing the molecular weight of the resin, an appropriate condition is prepared using a hot water tank in order to set a high temperature and high humidity condition.

  As a specific condition of the hot water tank, it is preferable to hydrolyze the biodegradable resin by immersing it in warm water of 95 ° C. or higher. In this case, it is possible to reduce the molecular weight of the biodegradable resin to 10,000 in about 10 hours. Moreover, by soaking in warm water, the hydrolyzability to the resin becomes uniform and unevenness is eliminated. After the treatment in the hot water tank, the hot water is drained and rinsed with new pure water, so that the resin residue is eliminated and no odor is generated after the subsequent drying. In this manner, hydrolysis and odor reduction can be achieved by performing hydrolysis using a hot water tank, followed by rinsing and drying.

  By performing hydrolysis under the above conditions, a biodegradable resin having a reduced molecular weight 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 is commercially available from Nippon Aerosil Co., Ltd., CABOT Co., etc. The primary particle diameter is preferably 7 to 40 nm, and two or more kinds may be mixed for improving the function.

  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.

  Furthermore, 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.

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 softening point)
Apparatus: Flow tester (manufactured by Shimadzu Corporation, CFT-500D)
Sample: 1g
Temperature increase rate: 6 ° C / min Load: 20kg Nozzle: 1mm in diameter, 1mm in 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.

(Measurement of glass transition point (Tg))
Apparatus: Differential scanning calorimeter (manufactured by Shimadzu Corporation: DSC-60)
Sample: 8mg
Temperature raising condition: 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 time of 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 release agent melting point)
The same measurement as the glass transition point was performed, and the peak temperature of the endothermic curve due to the release agent at the second temperature increase was taken as the melting point. When the endothermic curve is two or more peaks, the average value of each peak was taken as the peak.

(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 process 1 of low molecular weight polylactic acid)
Polylactic acid (manufactured by Kaisho Biochemical Co., Ltd .: REVODE101B, molecular weight (Mn = 120,000)) was placed in a hot water tank set at a temperature of 95 ° C. and hydrolyzed. Dried.

(Process for producing low molecular weight polylactic acid 2)
Polylactic acid (manufactured by Kaisho Biochemical Co., Ltd .: REVODE 101B, molecular weight (Mn = 120,000)) was hydrolyzed by placing it in a constant temperature and humidity chamber set at a temperature of 80 ° C. and a humidity of 80% RH.

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

  FIG. 1 is a graph showing the processing time and the molecular weight reduction change due to the manufacturing processes 1 and 2 described above.

Example 1
Polylactic acid 1-2 with reduced molecular weight prepared by the above-described method 1 for producing low molecular weight polylactic acid and each component of the following blending amount were put into a Henschel mixer (standard feather mounted, manufactured by Mitsui Mining Co., Ltd.) Mixed.
Polylactic acid 1-2 with reduced molecular weight (molecular weight: 50,000) 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 ( 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). After that, the melt was taken out, stretched, cooled, and coarsely crushed with a Rotoplex (manufactured by Hosokawa Micron Corporation, 2 mm screen). After that, the particles are pulverized and classified with a collision type pulverizer (Nippon Pneumatic Industry IDS-2) and an air 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.

Example 2
Instead of the above-mentioned polylactic acid 1-2 (molecular weight: 50,000), polylactic acid 1-3 (molecular weight: 35,000) produced by the above-mentioned low molecular weight polylactic acid production method 1 and reduced to a different molecular weight is used. An electrophotographic toner was produced in the same manner as in Example 1 except for the above.

Example 3
Instead of the above polylactic acid 1-2 (molecular weight: 50,000), polylactic acid 1-4 (molecular weight: 14,000) produced by the above-mentioned low molecular weight polylactic acid production method 1 and reduced to a different molecular weight is used. An electrophotographic toner was produced in the same manner as in Example 1 except for the above.

Example 4
Instead of the above polylactic acid 1-2 (molecular weight: 50,000), polylactic acid 1-5 (molecular weight: 10,000) prepared by the method 1 of low molecular weight polylactic acid reduced to a different molecular weight is used. An electrophotographic toner was produced in the same manner as in Example 1 except for the above.

Example 5
Instead of the above polylactic acid 1-2 (molecular weight: 50,000), polylactic acid 1-6 (molecular weight: 7,000) prepared by the above-mentioned low molecular weight polylactic acid production method 1 and reduced to a different molecular weight is used. An electrophotographic toner was produced in the same manner as in Example 1 except for the above.

Example 6
Instead of the above polylactic acid 1-2 (molecular weight: 50,000), polylactic acid 1-7 (molecular weight: 5,000) prepared by the above-mentioned low molecular weight polylactic acid production method 1 and reduced to a different molecular weight is used. An electrophotographic toner was produced in the same manner as in Example 1 except for the above.

Comparative Example 1
Except for using high-molecular-weight commercially available polylactic acid (REVODE101B, molecular weight: 120,000) not subjected to molecular weight reduction treatment instead of the above polylactic acid 1-2 (molecular weight: 50,000), Examples In the same manner as in Example 1, an electrophotographic toner was produced.

Comparative Example 2
Instead of the polylactic acid 1-2 (molecular weight: 50,000), the polylactic acid 1-1 (molecular weight: 70,000) having a reduced molecular weight prepared by the method 1 of the low molecular weight polylactic acid preparation process was used. An electrophotographic toner was prepared in the same manner as in Comparative Example 1 except for the above.

Comparative Example 3
Instead of the above polylactic acid 1-2 (molecular weight: 50,000), polylactic acid 1-8 (molecular weight: 3,000) produced by the above-mentioned low molecular weight polylactic acid production method 1 and reduced to a different molecular weight is used. An electrophotographic toner was produced in the same manner as in Comparative Example 1 except that.

Comparative Example 4
Instead of the above-mentioned polylactic acid 1-2 (molecular weight: 50,000), polylactic acid 2-1 (molecular weight: 70,000) produced by the above-mentioned low molecular weight polylactic acid production method 2 and reduced to a different molecular weight is used. An electrophotographic toner was produced in the same manner as in Comparative Example 1 except that.

Comparative Example 5
Instead of the above-mentioned polylactic acid 2-1 (molecular weight: 70,000), polylactic acid 2-2 (molecular weight: 50,000) produced by the above-mentioned low molecular weight polylactic acid production process 2 and reduced to a different molecular weight is used. An electrophotographic toner was produced in the same manner as in Comparative Example 1 except that.

Comparative Example 6
Instead of the above-mentioned polylactic acid 2-1 (molecular weight: 70,000), polylactic acid 2-3 (molecular weight: 35,000) produced by the above-mentioned low molecular weight polylactic acid production process 2 and reduced to a different molecular weight is used. An electrophotographic toner was produced in the same manner as in Comparative Example 1 except that.

Comparative Example 7
Instead of the above-mentioned polylactic acid 2-1 (molecular weight: 70,000), polylactic acid 2-4 (molecular weight: 14,000) produced by the above-mentioned low molecular weight polylactic acid production method 2 and reduced to a different molecular weight is used. An electrophotographic toner was produced in the same manner as in Comparative Example 1 except that.

Comparative Example 8
Instead of the above polylactic acid 2-1 (molecular weight: 70,000), polylactic acid 2-5 (molecular weight: 10,000) prepared by the above-mentioned low molecular weight polylactic acid production process 2 and reduced to a different molecular weight is used. An electrophotographic toner was produced in the same manner as in Comparative Example 1 except that.

Comparative Example 9
Instead of the above polylactic acid 2-1 (molecular weight: 70,000), polylactic acid 2-6 (molecular weight: 7,000) produced by the above-mentioned low molecular weight polylactic acid production process 2 and reduced to a different molecular weight is used. An electrophotographic toner was produced in the same manner as in Comparative Example 1 except that.

Comparative Example 10
Instead of the above-mentioned polylactic acid 2-1 (molecular weight: 70,000), polylactic acid 2-7 (molecular weight: 5,000) produced by the above-mentioned low molecular weight polylactic acid production method 2 and reduced to a different molecular weight is used. An electrophotographic toner was produced in the same manner as in Comparative Example 1 except that.

Comparative Example 11
Instead of the above-mentioned polylactic acid 2-1 (molecular weight: 70,000), polylactic acid 2-8 (molecular weight: 3,000) produced by the above-mentioned low molecular weight polylactic acid production method 2 and reduced to a different molecular weight is used. An electrophotographic toner was produced in the same manner as in Comparative Example 1 except that.

  With respect to Examples 1 to 6 and Comparative Examples 1 to 11 obtained as described above, the fogging, concentration stability, fixability, grindability, and odor of the toner were tested and evaluated by the following test methods.

Test 1-fogging Non-magnetic one-component developing device “Casio Page Presto N-5” (manufactured by Casio Computer Co., Ltd .: 29 color printers per minute, process speed 129 mm / sec) mounted with toner 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 (50 ° C, 50% RH), perform blank paper printing and open the front door while printing. Thus, printing was forcibly terminated, and the fog toner on the OPC drum at that time was copied onto a mending tape and pasted on a blank sheet, and compared with a tape from which fog toner was not collected. In the measurement, the maximum value of the difference before and after fogging was determined as the fog value 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 fog value is less than 2 and good. B: The fog value is 2 or more and less than 5. Δ: The fog value is 5 or more and less than 10. No problem in practical use ×: fog value is 10 or worse

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
◎: Concentration stability is 95% or more, good ○: Concentration stability is 85% or more, good △: Concentration stability is 75% or more, practically no problem ×: Concentration stability is less than 75%, bad

Test 3-Fixability A modification tester is modified so that the temperature of the fixing part of the same apparatus as in Test 1 can be varied. 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 4-Crushability When pulverizing and classifying the kneaded and crushed product in the pulverization / classification step, the determination is made based on the yield (% by mass) of particles serving as a 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 ×: Yield less than 65%

Test 5-Odor After the production of low molecular weight polylactic acid, it was evaluated whether or not it smelled by smelling the resin.
(Evaluation criteria)
○: No smell ×: Smell The results of the above tests 1 to 5 are shown in Table 2 below.

  From Table 2 above, the following is clear. That is, in the case of using a biodegradable resin having a molecular weight reduced to 50,000 to 5,000 (Examples 1 to 6) by the hydrolysis method (production process 1) using hot water of the present embodiment. In all of tests 1 to 5, good results are shown.

  On the other hand, in Comparative Examples 5 to 10 using a biodegradable resin having a molecular weight reduced to 5,000 to 50,000 by performing hydrolysis by a different method (Production Process 2), the image quality and pulverization properties are good. Although a toner could be obtained, it was not preferable because a smell as a resin remained.

  In contrast, when a commercially available biodegradable resin (polylactic acid REVODE101B) having a high molecular weight (120,000) that has not been subjected to a molecular weight reduction treatment is used as it is (Comparative Example 1), the molecular weight is reduced by about 70,000. In each of the cases (Comparative Examples 2 and 4), it was attempted to produce a toner, but the toner could not be pulverized and could not be made into a toner.

  Further, in Comparative Examples 3 and 11, the molecular weight of the biodegradable resin was too low, and fusion occurred in the pulverizer when the toner was pulverized, and the pulverization could not be continued.

It is a graph which shows the relationship between the hydrolysis process conditions of biodegradable resin (polylactic acid) as electrophotographic toner resin which concerns on one Embodiment of this invention, and molecular weight reduction.

Claims (6)

  A resin for electrophotographic toner obtained by hydrolyzing a biodegradable resin with warm water to reduce the molecular weight of the biodegradable resin to a predetermined value.   The electrophotographic toner resin according to claim 1, wherein the hydrolysis is caused by immersing the biodegradable resin in warm water of 95 ° C. or more.   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.   The electrophotographic toner resin according to claim 1, further comprising a hydrolysis inhibitor.   An electrophotographic toner comprising the electrophotographic toner resin according to claim 1 and a colorant.

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