JP2013060491A - Method for producing polylactic acid resin for electrophotographic toner, polylactic aid resin for electrophotographic toner, method for manufacturing electrophotographic toner, and electrophotographic toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polylactic acid resin for an electrophotographic toner with reduced odor.SOLUTION: The method for producing a polylactic acid resin for an electrophotographic toner includes a step for hydrolyzing a polylactic acid resin having a number average molecular weight of 10,000 or more under heated and pressurized conditions to prepare a modified polylactic acid resin having a number average molecular weight of 3,000-10,000. The polylactic acid resin during hydrolyzing and/or the hydrolyzed polylactic acid resin are treated in an alkaline aqueous solution of pH8-12.

Description

  The present invention relates to a method for producing a polylactic acid resin for an electrophotographic toner, a polylactic acid resin for an electrophotographic toner obtained by the method, a method for producing an electrophotographic toner using the same, and an electrophotographic toner obtained by the method.

  Conventionally, petroleum-derived resins such as styrene / acrylic resins and polyester resins have been used as toner binder resins. In recent years, in consideration of the environment, a method has been proposed in which a biodegradable resin that has a low environmental impact at the time of disposal, and further, a biomass plastic made from renewable resources is used as a resin for toner. Bioplastics refer to biomass plastics and biodegradable plastics that contribute to finite resource considerations and reduce environmental impact.

  The inventors have adjusted the molecular weight of the bioplastic and made it possible to use the bioplastic as a main resin for toner. Specifically, a commercially available polylactic acid is not used as it is, but by reducing the molecular weight by hydrolysis or the like, a softening temperature can be lowered and a resin with improved grindability can be obtained. Can be used as a main resin for toner. Polylactic acid that has been reduced in molecular weight to a molecular weight suitable for toner is called a modified polylactic acid resin.

  When used as a binder resin for toner, polylactic acid is generally reduced in molecular weight to a molecular weight size of 3,000 to 10,000 from the viewpoint of grindability (see, for example, Patent Document 1). The modified polylactic acid resin thus prepared has a unique sweet odor. Although the causative substance of such odor is not specified, it is considered that the monomer component lactic acid or lactide component is the causative substance. When such a modified polylactic acid resin is made into a toner, the produced toner also has an odor peculiar to polylactic acid. In particular, the odor becomes noticeable when the toner is heated. For this reason, a sweet odor is generated during fixing.

  In the modified polylactic acid resin, the higher the acid value of polylactic acid, the better the pulverization efficiency, but the amount of carboxylic acid in the resin increases and the odor increases. So far, in order to reduce the odor of the toner using the modified polylactic acid resin as the binder resin, an acid value adjusting agent for adjusting the acid value of the toner to 10 or less has been added to the toner raw material mixture. (Patent Document 2).

JP 2010-66491 A JP 2011-2592 A

  Japanese Patent Application Laid-Open No. 2004-228688 addresses the reduction of the odor of polylactic acid during the production of the toner, and does not address the reduction of the odor of polylactic acid at the raw material stage.

  Therefore, an object of the present invention is to provide a method for producing a polylactic acid resin for an electrophotographic toner that reduces the odor of polylactic acid at the raw material stage, that is, the odor is reduced. Another object of the present invention is to provide a polylactic acid resin for electrophotographic toner with reduced odor by this production method. Furthermore, the present invention provides a method for producing an electrophotographic toner with reduced odor by using this polylactic acid resin for electrophotographic toner, and provides an electrophotographic toner with reduced odor by this production method. With the goal.

  One embodiment of the present invention is a modification in which a polylactic acid resin having a number average molecular weight exceeding 10,000 is hydrolyzed under heat and pressure conditions to have a number average molecular weight of 3,000 to 10,000. A process for preparing a polylactic acid resin, wherein the polylactic acid resin during hydrolysis and / or the polylactic acid resin after hydrolysis is treated with an alkaline aqueous solution having a pH of 8 to 12; A method for producing a lactic acid resin is provided.

  Another aspect of the present invention provides a polylactic acid resin for an electrophotographic toner obtained by the above-described production method.

  Still another embodiment of the present invention is characterized by comprising a step of melt-kneading a raw material mixture containing the above-described polylactic acid resin for electrophotographic toner and a colorant, and a step of pulverizing and classifying the obtained kneaded product. An electrophotographic toner manufacturing method is provided.

  Yet another embodiment of the present invention provides an electrophotographic toner obtained by the above-described production method.

  According to the present invention, a method for producing a polylactic acid resin for electrophotographic toner with reduced odor and a polylactic acid resin for electrophotographic toner with reduced odor are provided. The present invention also provides a method for producing an electrophotographic toner with reduced odor and an electrophotographic toner with reduced odor.

The figure which shows an example of the pressure vessel used for the method of this invention. The figure which shows an example of the pressure vessel used for the method of this invention.

  Embodiments of the present invention will be described below.

  As a result of researches to solve the above-mentioned problems, the present inventors have found that the polylactic acid resin has a pH of 8 to 12 during and / or after hydrolysis of the raw polylactic acid to a molecular weight size suitable for the toner. It has been found that by treating with an alkaline aqueous solution, the odor of the polylactic acid resin can be reduced, and the present invention has been completed.

That is, in one embodiment, the method for producing a polylactic acid resin for an electrophotographic toner of the present invention comprises:
A step of preparing a modified polylactic acid resin having a number average molecular weight of 3,000 to 10,000 by hydrolyzing a polylactic acid resin having a number average molecular weight exceeding 10,000 under heating and pressing conditions Including
The hydrolyzed polylactic acid resin and / or the hydrolyzed polylactic acid resin is treated with an alkaline aqueous solution having a pH of 8 to 12.

  In this embodiment, the treatment with an alkaline aqueous solution having a pH of 8 to 12 may be performed by hydrolyzing the polylactic acid resin in an alkaline aqueous solution having a pH of 8 to 12.

  Alternatively, in the present embodiment, the treatment with an alkaline aqueous solution having a pH of 8 to 12 may be performed by washing the hydrolyzed polylactic acid resin with an alkaline aqueous solution having a pH of 8 to 12.

  Hereinafter, “when the hydrolysis of the polylactic acid resin is performed in an alkaline aqueous solution having a pH of 8 to 12” will be described as a first embodiment, and “when the hydrolyzed polylactic acid resin is washed with an alkaline aqueous solution having a pH of 8 to 12”. However, the method of this embodiment is not limited to these. That is, in this embodiment, the polylactic acid resin may be exposed to an alkaline aqueous solution having a pH of 8 to 12 at least once during the hydrolysis reaction and / or after the hydrolysis reaction.

  That is, in the first aspect, the polylactic acid resin may be placed in an alkaline aqueous solution having a pH of 8 to 12 throughout the hydrolysis reaction, or an alkaline solution having a pH of 8 to 12 over at least a part of the hydrolysis reaction. It may be placed in an aqueous solution. In the second embodiment, after the hydrolysis reaction, the polylactic acid resin may be washed with an alkaline aqueous solution having a pH of 8 to 12 or placed in an alkaline aqueous solution having a pH of 8 to 12 for a predetermined period. Later, it may be washed.

  In addition, the first aspect and the second aspect may be combined. After the hydrolysis of the polylactic acid resin is performed in an alkaline aqueous solution having a pH of 8 to 12, the polylactic acid resin after hydrolysis is subjected to an alkaline process having a pH of 8 to 12. You may wash | clean with aqueous solution.

  In the present embodiment, a polylactic acid resin having a number average molecular weight exceeding 10,000 (hereinafter also referred to as a raw material polylactic acid resin) may be produced by a conventionally known method or is commercially available. Polylactic acid may be used. In the present embodiment, the raw polylactic acid resin has a number average molecular weight exceeding 10,000, and generally has a number average molecular weight of 70,000 to 150,000.

  As a conventionally known method, fermenting starch such as corn as a raw material to obtain lactic acid, followed by dehydration condensation directly from a lactic acid monomer, or ring-opening polymerization in the presence of a catalyst via a cyclic dimer from lactic acid There is a way to synthesize. There are optical isomers in lactic acid, and there are L-lactic acid and D-lactic acid, and any of these lactic acids may be used alone or in a mixture. The number average molecular weight of polylactic acid can be arbitrarily adjusted by varying the reaction conditions during polymerization.

  Commercially sold polylactic acid is synthesized by a ring-opening polymerization method for obtaining higher molecular polylactic acid for improving heat resistance, and the number average molecular weight is 100,000 or more. Is the mainstream. As commercially available polylactic acid, for example, REVODE110 or REVODE101B manufactured by Marine Life Materials Co., Ltd., or Nature Works manufactured by Nature Works, Inc. can be used.

  In the present embodiment, the hydrolysis of the raw material polylactic acid resin is performed under heat and pressure conditions. In the first embodiment, the hydrolysis is performed in an alkaline aqueous solution having a pH of 8-12. On the other hand, in the second embodiment, the hydrolysis is performed in water.

In the first embodiment, the alkaline aqueous solution having a pH of 8 to 12 has a concentration necessary for obtaining a pH of 8 to 12, for example, 1.0 × 10 ^{−2 to} 1.0 × 10 ⁻⁶ (mol in the case of an alkaline substance having a monovalent OH group. / L) or 1.0 × 10 ^-2 (mol / L) or more of alkaline components. Examples of the alkaline component include sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium bicarbonate, sodium carbonate and the like. When an alkaline aqueous solution is used, the odor generated by hydrolysis of the polylactic acid resin can be suppressed. In the second embodiment, the water can be any water such as tap water or water purified with an ion exchange resin.

  Water or an alkaline aqueous solution having a pH of 8 to 12 can be used, for example, in an amount of 50 to 100% by mass relative to the raw material polylactic acid resin.

  The heating and pressing conditions can be, for example, 120 to 127 ° C. and 0.11 to 0.16 MPa. If it is lower than 120 ° C., it takes a long time to hydrolyze, and the merit of pressurizing becomes small. On the other hand, when the temperature is higher than 127 ° C., the polylactic acid resin can be dissolved, which is not preferable. The pressurizing condition is determined according to the saturated vapor pressure at the heating temperature. Hydrolysis may be performed while mixing and stirring, or may be performed without mixing and stirring. By mixing and stirring, the polylactic acid resin in the reaction vessel is circulated throughout the reaction vessel, so that reaction conditions can be given more uniformly.

  The raw polylactic acid resin can be hydrolyzed using a pressure vessel. The pressure vessel may or may not be equipped with a stirrer.

  FIG. 1 is a schematic view showing an example of a pressure vessel equipped with a stirrer. A pressure vessel 10 shown in FIG. 1 is arranged so as to surround a container body 11, a lid 12 that forms a sealed space with the container body 11, and a side surface of the container body 11, and is a high-temperature and high-pressure steam for heating the inside of the container. Is provided with a stirrer 14 having a stirring portion for stirring a raw material containing a polylactic acid resin. The container body 11 contains a raw polylactic acid resin and water or an alkaline aqueous solution. In order to heat the inside of the container, high-temperature and high-pressure steam generated by a boiler (not shown) is fed into the jacket portion 13 in accordance with the illustrated arrow. The inside of the container is heated by the high-temperature and high-pressure steam in the jacket portion 13, and when heated to a temperature higher than 100 ° C., the internal pressure rises according to the saturated vapor pressure curve, and the heating and pressurizing condition is created. Under such heat and pressure conditions, the raw polylactic acid resin is hydrolyzed. The raw polylactic acid resin undergoes hydrolysis while being mixed and stirred by the stirrer 4. In order to release the pressure in the container after completion of the hydrolysis reaction, the container body 11 includes an exhaust port 15.

  FIG. 2 is a schematic view showing an example of a pressure vessel not equipped with a stirrer. The pressure vessel 20 shown in FIG. 2 has a configuration of an autoclave, and water is contained inside the vessel, so that a high temperature and high pressure state is created by heating. That is, the pressure vessel 20 shown in FIG. 2 is heated by the vessel main body 21, a lid 22 that forms a sealed space with the vessel main body 21, a heating device 23 for creating heating and pressurizing conditions, and a high pressure that is heated by the heating device 23. Water 24 for becoming steam, a mesh container 25 for holding a sample, and a support base 26 for supporting the mesh container 25 are provided.

  In the present embodiment, a modified polylactic acid resin having a number average molecular weight of 3,000 to 10,000 is prepared by performing the hydrolysis for an appropriate time. In any case where the number average molecular weight is less than 3,000 or more than 10,000, the grindability is inferior and it becomes difficult to make a toner.

  The molecular weight of polylactic acid has a correlation with the acid value, and the acid value increases as the molecular weight of polylactic acid decreases. Therefore, the modified polylactic acid resin having a number average molecular weight of 3,000 to 10,000 is hydrolyzed until the acid value of the polylactic acid resin becomes 18 to 30, using the acid value of the polylactic acid resin as an index. Can be obtained. If the acid value is smaller than 18, fine pulverization is difficult when the toner is formed, and if the acid value is larger than 30, it is excessively pulverized and particle size control is difficult.

  Specifically, the hydrolysis reaction time can be determined using the acid value of the polylactic acid resin as an index as described below.

  For the raw polylactic acid resin (for each lot in the case of commercially available polylactic acid), a calibration curve showing the relationship between the hydrolysis reaction time and the acid value is prepared in advance. That is, the raw polylactic acid resin is hydrolyzed in a small autoclave (for example, Alef TR-24S) under predetermined heating and pressing conditions for various reaction times, and the acid value of each of the obtained samples is determined. And a calibration curve showing the relationship between reaction time and acid value is prepared. Based on the prepared calibration curve, the reaction time for obtaining a desired acid value is determined. The modified polylactic acid resin having a desired acid value can be prepared by hydrolyzing polylactic acid using the determined reaction time and predetermined heating and pressing conditions. For example, as described in Examples below, a raw material polylactic acid resin having a molecular weight (Mn) of 100,000 is heated in an aqueous solution of sodium hydroxide at 127 ° C. and 0.16 MPa for 120 minutes. By performing the hydrolysis, a modified polylactic acid resin having an acid value of 24.3, that is, a molecular weight Mn 6,300 can be prepared.

  For the method of measuring the acid value of polylactic acid and the method of measuring the molecular weight of polylactic acid, reference can be made to the examples described later.

  In this embodiment, the raw polylactic acid resin is in a pellet state in water or an alkaline aqueous solution having a pH of 8 to 12, and its shape is maintained without being solubilized during hydrolysis, and the modified polylactic acid resin remains in the pellet state. A lactic acid resin is obtained.

  In the first aspect, the modified polylactic acid resin adjusted to a desired molecular weight size is separated from the alkaline aqueous solution. Thereafter, the obtained modified polylactic acid resin may or may not be washed with water. If necessary, the modified polylactic acid resin is dried to obtain the polylactic acid resin of the present invention.

In the second aspect, the modified polylactic acid resin adjusted to a desired molecular weight size is washed with the above-mentioned alkaline aqueous solution having a pH of 8 to 12 after being separated from water. In the washing, for example, the modified polylactic acid resin is mixed with an alkaline aqueous solution having a pH of 8 to 12 at least 1.0 × 10 ^{−2 to} 1.0 × 10 ⁻⁶ (mol / L), and the mixture is stirred for a time of 10 to 60 minutes. Can be done. The alkaline aqueous solution for washing can be used, for example, in an amount of 80 to 100% by mass with respect to the modified polylactic acid resin. After washing, the modified polylactic acid resin is separated from the alkaline aqueous solution. Thereafter, the obtained modified polylactic acid resin may or may not be washed with water. If necessary, the modified polylactic acid resin is dried to obtain the polylactic acid resin of the present invention.

  The polylactic acid resin of this invention can reduce the sweet odor peculiar to polylactic acid by processing with the alkaline aqueous solution of pH 8-12 in the manufacture process. In particular, in the first aspect, since it is treated with an alkaline aqueous solution having a pH of 8 to 12 during the hydrolysis reaction, in addition to the above effects, there is also an effect that odor generated during the production can be reduced.

  Using the polylactic acid resin of the present invention, an electrophotographic toner can be produced according to a known method. For example, after mixing a binder resin containing the polylactic acid resin of the present invention having a number average molecular weight of 3,000 to 10,000, a colorant, and other raw materials containing other necessary additives, a twin-screw kneader And kneading with a kneader such as a pressure kneader or an open roll to obtain a kneaded product. After cooling the kneaded product, the toner can be obtained by pulverizing with a pulverizer such as a jet mill and classifying with an air classifier.

  The raw material mixture may contain a known toner resin other than polylactic acid resin, and may contain a known release agent, charge control agent, hydrolysis inhibitor, etc. as other necessary additives. .

  The particle size of the toner is not particularly limited, but is usually adjusted to 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., Ltd., etc. . 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.

  The toner using the polylactic acid resin of the present invention can reduce the sweet odor peculiar to polylactic acid generated during heating, and particularly can reduce the odor generated during fixing.

  Examples of the present invention and comparative examples are shown below, and the present invention will be described more specifically.

[1] Example of the first embodiment (example in which hydrolysis of polylactic acid resin is performed in an alkaline aqueous solution having a pH of 8 to 12)
[1-1] Production of modified polylactic acid resin Examples 1 to 3
Polylactic acid resin “REVODE110” (Marine Biomaterials Co., Ltd.) (molecular weight Mn 100,000, pellet state) and alkaline aqueous solution (0.01 mol / l sodium hydroxide aqueous solution) adjusted to pH 12 in the amounts shown in Table 1 below. Then, it was put into a pressurized reaction vessel 60L with a stirrer (manufactured by Shinagawa Kogyo Co., Ltd., 60NQVP modified). The temperature was raised to 127 ° C. while stirring slowly under a condition of 15 rpm or less in a sealed state. It was kept at 127 ° C. and 0.16 MPa for 120 minutes. Thereafter, the pressure was released to atmospheric pressure to obtain a modified polylactic acid resin (pellet state).

Examples 4-5
Instead of “REVODE110”, “REVODE101B” (Marine Biomaterials) (molecular weight Mn 120,000, pellet state) was used as the polylactic acid resin. “REVODE101B” and an alkaline aqueous solution adjusted to pH 12 (0.01 mol / L sodium hydroxide aqueous solution) in an amount shown in Table 1 below, a pressurized reaction vessel 60L with a stirrer (manufactured by Shinagawa Kogyo Co., Ltd.) To 60NQVP). It heated up to 120 degreeC, stirring slowly on the conditions of 15 rpm or less in the airtight state. It was kept at 120 ° C. and 0.11 MPa for 120 minutes. Thereafter, the pressure was released to atmospheric pressure to obtain a modified polylactic acid resin (pellet state).

  The obtained modified polylactic acid resin prepared the polylactic acid resin of the present invention by separating the resin pellet and the alkaline aqueous solution and evaporating water from the resin pellet.

  In addition, since the alkaline component of alkaline aqueous solution has adhered to the polylactic acid resin of this invention, after isolate | separating a resin pellet and alkaline aqueous solution, you may wash | clean with water in order to rinse an alkaline component.

Comparative Examples 1-4
The polylactic acid resins of Comparative Examples 1 and 2 were prepared in the same manner as in Examples 1 and 2 except that the alkaline aqueous solution was replaced with water (tap water). The polylactic acid resins of Comparative Examples 3 to 4 were prepared in the same manner as in Examples 4 to 5 except that the alkaline aqueous solution was replaced with water (tap water).

[1-2] Preparation of Toner Using the polylactic acid resin of the present invention prepared in [1-1] and the polylactic acid resin of the comparative example, a toner was prepared as follows.

  The polylactic acid resin prepared in [1-1] was coarsely crushed with a Rotoplex crusher (2 to 3 mmφ mesh). The following formulation was mixed with a Henschel mixer.

Binder resin: Polylactic acid resin of the present invention or polylactic acid resin of comparative example 100 parts by mass Colorant: Carbon black (MOGUL L manufactured by CABOT Co., Ltd.) 4 parts by mass Release agent: Carnauba wax No. 1 powder (Nippon Wax) 3 parts by mass charge control agent: “LR-147” (manufactured by Nippon Carlit Co., Ltd.) 1 part by mass.

  After the obtained mixed powder was melt-kneaded with a twin-screw extruder (screw diameter 43 mm, L / D = 34), the melt-kneaded product was stretched and cooled by setting the circulating water of the rolling roll to 10 ° C., The kneaded product after cooling was 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 a wind classifier (Nippon Pneumatic Industry DSX-2) so that the average particle diameter of the toner becomes 9.0 μm. Got.

[1-3] Measurement of acid value The acid value of the polylactic acid resin of the present invention prepared in [1-1] and the polylactic acid resin of the comparative example were measured as follows.

Measurement method of acid value (according to JIS: K-0070) A sample was weighed into a beaker, and chloroform was added thereto, followed by shaking until the sample was completely dissolved. This solution was subjected to potentiometric titration with a potassium hydroxide ethanol standard solution (0.1 mol / L) using a potentiometric titrator (AT-500N: Kyoto Electronics Industry Co., Ltd.), and the acid value was determined by the following formula (1). Asked.

Acid value = 5.611 × A × f / B (1)
A: 0.1 mol / L potassium hydroxide ethanol standard solution used for titration (ml)
f: Factor of 0.1 mol / L potassium hydroxide ethanol standard solution B: Sample collection amount (g).

  Table 1 shows the acid value of the polylactic acid resin prepared in [1-1]. It was confirmed that the acid values of all the polylactic acid resins of Examples 1 to 5 and Comparative Examples 1 to 4 were between 18 and 30 which are appropriate values as a toner raw material. The acid value of the polylactic acid resin varied depending on the lot of the raw polylactic acid resin.

[1-4] Measurement of molecular weight About the polylactic acid resin of the present invention prepared in [1-1] and the polylactic acid resin of Comparative Example, molecular weight measurement was performed using GPC (manufactured by Shimadzu Corporation) and detector RI. Went. 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.

  Table 1 shows the molecular weight of the polylactic acid resin prepared in [1-1]. It was confirmed that the molecular weights of all the polylactic acid resins in Examples 1 to 5 and Comparative Examples 1 to 4 were between 3,000 and 10,000 which are appropriate values as a toner raw material.

[1-5] Odor Determination Odor determination was performed on the polylactic acid resin prepared in [1-1] and the toner prepared in [1-2].

  The odor determination of the polylactic acid resin was evaluated by smelling the odor of the polylactic acid resin immediately after preparation. To determine the odor of the toner, 2.0 g of toner was put in a 180 ° C. oven in a sealed state, taken out after 30 minutes, and evaluated by smelling the odor.

  The case where no odor is felt is determined as “◯”, the case where a specific sweet odor is felt is determined as “x”, and the results are shown in Table 1.

[1-6] Results Examples 1 to 5 show examples in which polylactic acid was hydrolyzed in an alkaline aqueous solution according to the method of the present invention. Such polylactic acid resin of the present invention was able to reduce the odor to such an extent that it was not felt by the sense of smell. Also, the toner using the polylactic acid resin of the present invention was able to reduce the odor generated during heating to the extent that it is not felt by the sense of smell.

  On the other hand, the polylactic acid resin of Comparative Examples 1-4 shows the example which hydrolyzed polylactic acid in water. Both the polylactic acid resins of Comparative Examples 1 to 4 and the toner using the same produced a unique sweet odor.

[2] Example of the second embodiment (an example in which the polylactic acid resin after hydrolysis is washed with an alkaline aqueous solution having a pH of 8 to 12)
[2-1] Production of modified polylactic acid resin Examples 6 to 7
The polylactic acid resins of Examples 6 to 7 were prepared in the same manner as the polylactic acid resins of Comparative Examples 1 and 2 prepared in [1-1] above.

That is, a polylactic acid resin “REVODE110” (Marine Biomaterials Co., Ltd.) (molecular weight Mn 100,000, in a pellet state) and water (tap water) in the amounts shown in Table 2 below and a pressurized reaction vessel equipped with a stirrer It was put into 60L (Shinagawa Kogyo Co., Ltd., 60NQVP modified). The temperature was raised to 127 ° C. while stirring slowly under a condition of 15 rpm or less in a sealed state. It was kept at 127 ° C. and 0.16 MPa for 120 minutes. Thereafter, the pressure was released to atmospheric pressure to obtain a modified polylactic acid resin.
When the lid of the pressurized reaction vessel was opened, there was a unique sweet smell that the polylactic acid resin was hydrolyzed.

The prepared modified polylactic acid resin was washed with an alkaline aqueous solution. The alkaline aqueous solution used in each example is as follows.
Example 6: 25% (wt / wt) aqueous sodium hydroxide solution (pH 12)
Example 7: 4% (wt / wt) aqueous sodium hydroxide solution (pH 11-12).

  Specifically, the entire amount of the prepared modified polylactic acid resin is put into a container 60L with a stirrer (manufactured by Shinagawa Kogyo Co., Ltd., 60NQVP), and 25 L of an alkaline aqueous solution is put therein. The modified polylactic acid resin was washed while stirring the mixed solution for 30 minutes.

In order to separate the modified polylactic acid resin and the alkaline aqueous solution, water was drained using a mesh with a hole smaller than 2 to 3 mm. This obtained the polylactic acid resin of Examples 6-7.
In addition, since the alkaline component of alkaline aqueous solution has adhered to the modified polylactic acid resin after washing | cleaning, in order to rinse an alkaline component, you may wash | clean with water further.

Examples 8-9
The polylactic acid resins of Examples 8 to 9 were prepared in the same manner as the polylactic acid resins of Comparative Examples 3 to 4 prepared in [1-1] above.

That is, a polylactic acid resin “REVODE101B” (Marine Biomaterials Co., Ltd.) (molecular weight Mn 120,000, pellet state) and water (tap water) in the amounts shown in Table 2 below and a pressurized reaction vessel equipped with a stirrer It was introduced into 60L (manufactured by Shinagawa Kogyo Co., Ltd., 60NQVP modified). It heated up to 120 degreeC, stirring slowly on the conditions of 15 rpm or less in the airtight state. It was kept at 120 ° C. and 0.11 MPa for 120 minutes. Thereafter, the pressure was released to atmospheric pressure to obtain a modified polylactic acid resin.
When the lid of the pressurized reaction vessel was opened, there was a unique sweet smell that the polylactic acid resin was hydrolyzed.

The prepared modified polylactic acid resin was washed with an alkaline aqueous solution. The alkaline aqueous solution used in each example is as follows.
Example 8: 10% (wt / wt) aqueous sodium carbonate solution (pH 9-11)
Example 9: 5% (wt / wt) aqueous sodium bicarbonate solution (pH 8-11).

  Specifically, the entire amount of the prepared modified polylactic acid resin is put into a container 60L with a stirrer (manufactured by Shinagawa Kogyo Co., Ltd., 60NQVP), and 25 L of an alkaline aqueous solution is put therein. The modified polylactic acid resin was washed while stirring the mixed solution for 60 minutes.

In order to separate the modified polylactic acid resin and the alkaline aqueous solution, water was drained using a mesh with a hole smaller than 2 to 3 mm. This obtained the polylactic acid resin of Examples 8-9.
In addition, since the alkaline component of alkaline aqueous solution has adhered to the modified polylactic acid resin after washing | cleaning, in order to rinse an alkaline component, you may wash | clean with water further.

Comparative Examples 5-8
The polylactic acid resins of Comparative Examples 5 to 8 were prepared in the same manner as in Examples 6 to 9, respectively. However, the prepared modified polylactic acid resin was washed with water instead of washing with an alkaline aqueous solution.

  That is, the total amount of the modified polylactic acid resin thus prepared is put into a container 60L with a stirrer (manufactured by Shinagawa Kogyo Co., Ltd., 60NQVP), and the amount of water (tap water) does not overflow there. The modified polylactic acid resin was washed while stirring the mixed solution for 10 minutes.

  In order to separate the modified polylactic acid resin and water, the water was cut using a mesh with a hole smaller than 2 to 3 mm. This obtained the polylactic acid resin of Comparative Examples 5-8.

[2-2] Preparation of Toner Using the polylactic acid resins of Examples 6 to 9 and the polylactic acid resins of Comparative Examples 5 to 8, toners were prepared as described in the column [1-2].

[2-3] Measurement of acid value The acid value of the polylactic acid resin prepared in [2-1] was measured according to the above method, and the results are shown in Table 2. It was confirmed that the acid values of all the polylactic acid resins of Examples 6 to 9 and Comparative Examples 5 to 8 were between 18 and 30 which are appropriate values as a toner raw material.

[2-4] Measurement of molecular weight The molecular weight of the polylactic acid resin prepared in [2-1] was measured according to the above method, and the results are shown in Table 2. It was confirmed that the molecular weights of all the polylactic acid resins of Examples 6 to 9 and Comparative Examples 5 to 8 were between 3,000 and 10,000 which are appropriate values as a toner raw material.

[2-5] Odor Determination About the polylactic acid resin prepared in [2-1] and the toner prepared in [2-2], the odor determination was performed as described in the column [1-5].

[2-6] Results Examples 6 to 9 show examples in which the hydrolyzed polylactic acid resin was washed with an alkaline aqueous solution according to the method of the present invention. Such polylactic acid resin of the present invention was able to reduce the odor to such an extent that it was not felt by the sense of smell. Also, the toner using the polylactic acid resin of the present invention was able to reduce the odor generated during heating to the extent that it is not felt by the sense of smell.

  On the other hand, Comparative Examples 5-8 show the example which wash | cleaned the polylactic acid resin after hydrolysis with water. Each of the polylactic acid resins of Comparative Examples 5 to 8 and the toner using the same produced a unique sweet odor.

Hereinafter, the invention described in the scope of claims of the present application will be appended.
[1] A polylactic acid resin having a number average molecular weight exceeding 10,000 is hydrolyzed under heat and pressure conditions to obtain a modified polylactic acid resin having a number average molecular weight of 3,000 to 10,000. Including the step of preparing,
A method for producing a polylactic acid resin for an electrophotographic toner, comprising treating the polylactic acid resin during hydrolysis and / or the polylactic acid resin after hydrolysis with an alkaline aqueous solution having a pH of 8 to 12.
[2] The method for producing a polylactic acid resin for an electrophotographic toner according to [1], wherein the treatment is performed by hydrolyzing the polylactic acid resin in an alkaline aqueous solution having a pH of 8 to 12.
[3] The production of the polylactic acid resin for an electrophotographic toner according to [1], wherein the treatment is performed by washing the hydrolyzed polylactic acid resin with an alkaline aqueous solution having a pH of 8 to 12. Method.
[4] A polylactic acid resin for an electrophotographic toner obtained by the production method according to any one of [1] to [3].
[5] A step of melt-kneading a raw material mixture containing the polylactic acid resin for an electrophotographic toner according to [4] and a colorant;
A method for producing an electrophotographic toner, comprising a step of pulverizing and classifying the obtained kneaded product.
[6] An electrophotographic toner obtained by the method according to [5].

10, 20 ... Pressure vessel 11, 21 ... Container body 12, 22 ... Cover 13 ... Jacket part 14 ... Stirrer 15 ... Exhaust port 23 ... Heating device 24 ... -Water 25 ... Mesh container 26 ... Support stand

Claims (6)

A step of preparing a modified polylactic acid resin having a number average molecular weight of 3,000 to 10,000 by hydrolyzing a polylactic acid resin having a number average molecular weight exceeding 10,000 under heating and pressing conditions Including
A method for producing a polylactic acid resin for an electrophotographic toner, comprising treating the polylactic acid resin during hydrolysis and / or the polylactic acid resin after hydrolysis with an alkaline aqueous solution.   The method for producing a polylactic acid resin for an electrophotographic toner according to claim 1, wherein the treatment is performed by hydrolyzing the polylactic acid resin in an alkaline aqueous solution having a pH of 8 to 12.   The method for producing a polylactic acid resin for an electrophotographic toner according to claim 1, wherein the treatment is performed by washing the hydrolyzed polylactic acid resin with an alkaline aqueous solution having a pH of 8 to 12.   A polylactic acid resin for an electrophotographic toner, obtained by the production method according to claim 1. Melt-kneading a raw material mixture comprising the polylactic acid resin for electrophotographic toner according to claim 4 and a colorant;
A method for producing an electrophotographic toner, comprising a step of pulverizing and classifying the obtained kneaded product.   An electrophotographic toner obtained by the method according to claim 5.

Images