JP2015179117A - Method for manufacturing electrophotographic toner using polylactic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrophotographic toner, capable of using polymer polylactic acid as a binder resin of a toner without hydrolysis.SOLUTION: A resin master batch is obtained by a method including the step of melting and mixing a first mixture including a polylactic acid having a weight average molecular weight of 20,000-110,000 and a grinding aid without including a release agent and slowly cooling and solidifying the obtained mixture to prepare a resin master batch comprising the steps of: forming the first mixture into a compound such that the grindability index of the resin master batch is 20 or more; and pulverizing the resin master batch. The electrophotographic toner is manufactured by a method including the step of pulverizing and mixing a second mixture including the resin master batch after the pulverization and a release agent to pulverize and classify the obtained mixture.

Description

  The present invention relates to a method for producing an electrophotographic toner using polylactic acid.

  Electrophotographic image formation is performed by developing and visualizing an electrostatic charge image with toner, transferring the toner image obtained by development onto paper, and then fixing it with heat and pressure. The toner is manufactured by melt-kneading a mixture obtained by blending a binder resin with a colorant, a charge control agent, and the like, pulverizing and classifying the mixture, and adjusting the particle size distribution to a predetermined level. Conventionally, petroleum-derived resins such as styrene / acrylic resins and polyester resins have been used as binder resins for such toners.

  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.

  Patent Documents 1 and 2 propose toners mainly using polylactic acid, which is one of bioplastics. When polylactic acid is used as the binder resin for the pulverized toner, the use of high molecular weight polylactic acid makes pulverization difficult in the manufacturing process or worsens low-temperature fixing during fixing. Yes. Low molecular weight polylactic acid has a problem in the long-term storage stability of the toner due to the influence of an increase in terminal carboxyl groups and the influence of residual monomers. In addition, since the commercially available polylactic acid is mainly a polymer polylactic acid and has a problem in grindability, when it is used as a binder resin, it is necessary to hydrolyze polylactic acid (Patent Literature). 3). Hydrolysis of polylactic acid has a long processing time and a heavy burden in terms of workability and cost.

JP 2008-262179 A JP 2007-197602 A JP2012-032628A

  In view of the above circumstances, an object of the present invention is to provide a method for producing an electrophotographic toner that can be used as a binder resin for a toner without hydrolyzing high-molecular polylactic acid.

  In one embodiment of the present invention, a first mixture containing polylactic acid having a weight average molecular weight of 20,000 to 110,000 and a grinding aid and not a release agent is melt-kneaded, and the obtained kneaded product is cooled. And solidifying the resin masterbatch, wherein the first mixture has a composition such that the grindability index of the resin masterbatch is 20 or more, and the resin masterbatch is pulverized. An electrophotographic toner comprising: a step of melting and kneading and classifying the kneaded product obtained by melt-kneading the second mixture containing the pulverized resin masterbatch and the release agent. A manufacturing method is provided.

  Another aspect of the present invention is to melt knead a first mixture containing polylactic acid having a weight average molecular weight of 20,000 to 110,000 and a grinding aid and not containing a release agent, and the resulting kneaded product is A step of cooling and solidifying to prepare a resin masterbatch, wherein the first mixture has a composition such that the grindability index of the resin masterbatch is 20 or more; and the resin masterbatch And a pulverizing step. A method for producing a resin master batch is provided.

  According to the present invention, there is provided a method for producing an electrophotographic toner that can be used as a binder resin for a toner without hydrolyzing high-molecular polylactic acid.

Hereinafter, embodiments of the present invention will be described.
In order to solve the problem of grindability, the present inventors added a grinding aid to a toner raw material containing polymer polylactic acid, and melt-kneaded this to form a plate with a rolling roll. As a result of bending, a problem was encountered in which fibrous foreign matter (hereinafter referred to as whiskers) was generated at the bent portion. The whisker generated here is not pulverized in the subsequent pulverization step, and remains as a fibrous foreign substance on the toner particles, which adversely affects toner performance (for example, image and fluidity). Further, when the whiskers are generated, it is difficult to remove them in the toner manufacturing process.

  The inventors of the present invention have made the polymer polylactic acid into a master batch with a formulation containing a grinding aid but not containing a release agent, and melt-kneading this resin master batch with a toner raw material containing the release agent. As a result, it was found that generation of whiskers occurring during melt kneading can be prevented, and the present invention has been completed.

That is, the method for producing an electrophotographic toner according to an embodiment of the present invention includes:
Resin master by melting and kneading a first mixture containing polylactic acid having a weight average molecular weight of 20,000 to 110,000 and a grinding aid and not containing a release agent, and cooling and solidifying the obtained kneaded product. A step of preparing a batch, wherein the first mixture has a composition such that the grindability index of the resin master batch is 20 or more;
Crushing the resin masterbatch;
Melting and kneading the second mixture containing the pulverized resin masterbatch and the release agent, and pulverizing and classifying the obtained kneaded product.

  In this embodiment, polylactic acid is masterbatched with a formulation containing a grinding aid but no mold release agent, and the resulting resin masterbatch has a grindability index of 20 or more. A toner is manufactured by melt-kneading with a toner material containing a release agent. Thereby, generation | occurrence | production of the beard which occurs at the time of melt-kneading can be prevented.

  In this embodiment, first, a first mixture containing polylactic acid having a weight average molecular weight of 20,000 to 110,000 and a grinding aid and not containing a release agent is melt-kneaded, and the obtained kneaded product is cooled. And solidify to prepare a resin masterbatch.

  The polylactic acid has a weight average molecular weight of 20,000 to 110,000, preferably 30,000 to 80,000. In this embodiment, in order to reduce the labor and cost for preparing polylactic acid, it is desirable to use commercially available polylactic acid having the above-mentioned weight average molecular weight. When the weight average molecular weight of the polylactic acid is less than 20,000, the storage stability as a toner tends to be inferior, and the fixability tends to deteriorate. When the weight average molecular weight is more than 110,000, the grindability is lowered. The polylactic acid may be crystalline polylactic acid or amorphous polylactic acid. Polylactic acid has a softening point of, for example, 80 to 195 ° C. The polylactic acid is preferably blended in an amount of 25% or more of the toner mass considering the influence on the environment.

  The 1st mixture which is a raw material of a resin masterbatch contains a grinding aid in order to improve the grindability of polylactic acid. The grinding aid is a resin that has a property of being easily broken when force is applied as compared with polylactic acid. It is a resin that breaks when processed at a rotation / second. As a grinding aid, a resin generally used as a grinding aid in the technical field can be used. One type of grinding aid may be used, or a plurality of types may be used in combination. Specifically, tackifier resins (resins used as tackifiers), polyester resins, styrene acrylic resins, and the like can be used.

  Examples of resins that can be used as grinding aids are shown in the table below.

  The first mixture which is a raw material of the resin master batch may contain additives such as a colorant and a charge control agent, but does not contain a release agent. If the first mixture contains a release agent, it will cause whiskers during melt-kneading, so the first mixture does not contain a release agent.

  In the present embodiment, the first mixture has a composition such that the grindability index of the resin master batch is 20 or more. The grindability index can be 20-80, preferably 20-50.

  In this specification, the “grindability index” is an index representing the ease of crushing of the resin masterbatch. Specifically, the first mixture was melt-kneaded and cooled to be solidified. The value calculated | required according to the following method using the resin masterbatch is pointed out.

That is, the resin master batch is coarsely pulverized with a mini blender (model number: MB-2 Osaka Chemical) for 10 seconds. From the coarsely pulverized resin master batch, a resin powder that passes through a sieve of 16 mesh (aperture: 1 mm) but does not pass through a sieve of 22 mesh (aperture: 710 μm) is obtained. 10 g of the obtained resin powder is weighed. The weighed resin powder is sieved with a vibrating sieve with a mesh of 710 μm for 10 minutes. The weight of the resin powder that has passed through the vibrating screen is measured. The measured weight (A) g of the resin powder is introduced into the following formula, and the grindability index is calculated.
Formula: Millability index = (A) g / collected weight before vibrating sieve (10 g) × 100.

  In the present embodiment, by adjusting the blending amount of the grinding aid, the first mixture can be made to have a composition such that the grindability index of the resin master batch is 20 or more. More specifically, by blending the grinding aid in an amount of, for example, 10 to 80% by mass with respect to the mass of the first mixture, the pulverizability index of the resin masterbatch is 20 It can be set as the composition which becomes the above. Preferably, the grinding aid can be blended in an amount of 10 to 40% by mass with respect to the mass of the first mixture. When the blending amount of the grinding aid is increased, the grindability index increases. However, when the grinding aid is blended in an amount exceeding 80% by weight with respect to the weight of the first mixture, the ratio of the bioplastic in the toner is increased. Since it falls, it is not preferable.

  The composition of the first mixture is desirably determined in advance so that the grindability index of the resin master batch is 20 or more.

  In the present embodiment, the melt kneading of the first mixture can be preferably performed by a twin screw extruder. After melt-kneading, this is cooled and solidified to prepare a resin master batch, which is pulverized by a pulverizer. Thereafter, the second mixture containing the pulverized resin master batch and the release agent is melt-kneaded.

  The second mixture contains a release agent, and may contain components of toner raw materials such as a colorant and a charge control agent as necessary. Further, the second mixture may contain a grinding aid. The melt-kneading of the second mixture can also be preferably performed by a twin screw extruder.

  In the method according to the present embodiment, by causing the second mixture to contain a release agent and not causing the first mixture to contain a release agent, it is possible to prevent the occurrence of whiskers that occur during melt-kneading.

  A conventionally known release agent can be used as the release agent. Examples of such release agents include olefinic waxes such as polypropylene wax, polyethylene wax, and Fischer-Tropsch wax, natural waxes such as carnauba wax, rice wax, and scale insect wax, and synthetic ester waxes. In order to improve low-temperature fixability and high-speed printing performance, a release agent having a relatively low melting point of about 60 to 100 ° C. is preferable, and specifically, carnauba wax and synthetic ester wax are preferable. In consideration of environmental impact, natural product carnauba wax is more preferable. The compounding amount of the release agent is preferably 1 to 15% by mass with respect to the toner mass. In this specification, “toner mass” is defined as the total mass of toner raw materials including polylactic acid, a grinding aid, and a release agent, and does not include external additives such as silica.

  Examples of waxes that can be used as release agents are shown in the table below.

  The second mixture is melt-kneaded, and the obtained kneaded product is cooled and solidified, and then pulverized with a pulverizer and then classified with an air classifier or the like, whereby a toner can be obtained. Here, the particle size of the toner is not particularly limited, but is usually adjusted to be 5 to 10 μm. An external additive can be added to the toner thus obtained in order to improve fluidity, adjust chargeability, and improve durability.

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

  In the present embodiment, the colorant may be contained in either the first mixture or the second mixture, and conventionally known ones can be used. 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, a single colorant having high safety is preferable.

  The content of these colorants is preferably 1 to 10% by mass with respect to the toner mass. Moreover, you may use the masterbatch which disperse | distributed resin and a coloring agent in high concentration previously as a coloring agent.

  In this embodiment, a charge control agent can be included as a toner raw material as necessary, and the charge control agent may be contained in either the first mixture or the second mixture. As the charge control agent, conventionally known ones can be used. For example, a quaternary ammonium salt as a positive charge control agent, a resin containing an amino group, a metal complex salt of salicylic acid as a negative charge control agent, Examples thereof include metal complex salts of benzylic acid, phenolic condensates of calixarene type, and resins containing carboxyl groups. The addition amount of the charge control agent is preferably 0.1 to 5% by mass with respect to the toner mass.

  In this embodiment, as a toner material, in addition to polylactic acid, a conventionally known toner resin can be added as necessary, and the toner resin can be either the first mixture or the second mixture. It may be contained in. Examples of such resins include styrene resins, acrylic resins, and polyester resins. From the viewpoints of pigment dispersibility and low-temperature fixability, polyester resins developed for toners are preferable. These resins may be used alone or in combination of two or more. The blending amount of these resins is preferably 0 to 50% by mass with respect to the toner mass in consideration of the influence on the environment.

  In the present embodiment, a conventionally known hydrolysis inhibitor can be added as a toner raw material as necessary, and the hydrolysis inhibitor is contained in either the first mixture or the second mixture. May be. Examples of the hydrolysis inhibitor include carbodiimide compounds, isocyanate compounds, and oxazoline compounds. Such a hydrolysis inhibitor can seal a residual monomer or a hydroxyl group produced by decomposition or a terminal of a carboxyl machine and suppress a hydrolysis chain reaction. As a hydrolysis inhibitor, carbodilite LA-1 (manufactured by Nisshinbo Industries, Inc.), which is a polycarbodiimide compound, is commercially available. The addition amount of the hydrolysis inhibitor is preferably 0.01 to 15% by mass and more preferably 1 to 10% by mass with respect to polylactic acid.

  In the exemplary embodiment, a conventionally known crystal nucleating agent can be added as a toner raw material as necessary, and the crystal nucleating agent is contained in either the first mixture or the second mixture. Good. Examples of the crystal nucleating agent include inorganic nucleating agents such as talc, organic carboxylic acid metal salts such as sodium benzoate, organic metal nucleating agents such as phosphate ester metal salts, benzylidene sorbitol, and carboxylic acid amide.

Examples of the present invention and comparative examples are shown below, and the present invention will be described more specifically.
[Example 1]
<Production of resin master batch>
The following components were added to a Henschel mixer (standard feather mounted, manufactured by Mitsui Mining Co., Ltd.) at the following blending amount and mixed (first mixture).
Polylactic acid resin: Polylactic acid resin (manufactured by Kaisei Biological Co., Ltd., weight average molecular weight 80,000, softening point 112 ° C.) 90 parts by mass Grinding aid: Pencel D135 (manufactured by Arakawa Chemical, softening point 135 ° C.) 10 parts by mass.

  The obtained mixed powder was melt-kneaded with a twin-screw extruder (manufactured by Ikegai Co., Ltd., screw diameter 43 mm, L / D = 34), and this melt-kneaded product was set at 10 ° C. for circulating water of the rolling roll. And then cooled. The kneaded product after cooling was coarsely crushed with a Rotoplex (manufactured by Hosokawa Micron Corporation, 2 mm screen). As a result, a “pulverized resin master batch” was obtained.

<Production of toner>
A release agent, a colorant, and a charge control agent were mixed into the pulverized resin master batch (second mixture). That is, the following components were added to a Henschel mixer (with standard feathers, manufactured by Mitsui Mining Co., Ltd.) at the following blending amount and mixed. As a colorant, a pigment master batch comprising 50 parts by mass of a phthalocyanine pigment (manufactured by Dainichi Seika Kogyo Co., Ltd.) and 50 parts by mass of a polyester resin (manufactured by Kao Corporation, Mw 13,000 softening point 100 ° C.) was used.
Crushed resin master batch 100 parts by weight Release agent: Carnauba wax No. 1 powder (manufactured by Nippon Wax Co., Ltd.) 3 parts by weight Colorant: Phthalocyanine pigment master batch 8 parts by weight Charge control agent: "LR-147" ( Nippon Carlit Co., Ltd.) 1 part by mass.

  The obtained mixed powder was melt-kneaded with a twin-screw extruder (manufactured by Ikegai Co., Ltd., screw diameter 43 mm, L / D = 34), and this melt-kneaded product was set at 10 ° C. for circulating water of the rolling roll. The cooled kneaded product was coarsely crushed with a Rotoplex (manufactured by Hosokawa Micron Corporation, 2 mm screen). Thereafter, 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 8.0 μm. Got.

  0.4 parts by mass of “RY200” (manufactured by Nippon Aerosil Co., Ltd .: hydrophobic silica, primary particle size 12 nm) as an external additive, and “RX50” (Nippon Aerosil Co., Ltd.) as an external additive to 100 parts by mass of the obtained fine particles Manufactured: Hydrophobic silica, primary particle diameter 50 nm) 3 parts by mass was added, and the mixture was stirred and mixed for 3 minutes with a Henschel mixer (with stirring strengthening blades, manufactured by Mitsui Mining Co., Ltd.) to obtain a toner.

[Examples 2 to 18]
Toners of Examples 2 to 18 were produced according to the same procedure as in Example 1. For the toners of Examples 2-18, the composition of the first mixture was changed as described in Table 3. For Examples 15-18, the first mixture already contained colorants and / or charge control agents, so they were not added when preparing the second mixture.

[Comparative Example 1]
The following components were added to a Henschel mixer (with standard feathers, manufactured by Mitsui Mining Co., Ltd.) in the following blending amount and mixed.
Polylactic acid resin: Polylactic acid resin (manufactured by Kao Corporation, Mw 80,000, softening point 112 ° C.) 100 parts by mass Grinding aid: Pencel D135 (manufactured by Arakawa Chemical, softening point 135 ° C.) 20 parts by weight Release agent: carnauba wax No. 1 powder (manufactured by Nippon Wax Co., Ltd.) 3 parts by mass Colorant: phthalocyanine pigment master batch 8 parts by mass Charge control agent: “LR-147” (manufactured by Nippon Carlit Co., Ltd.) 1 part by mass.

  The obtained mixed powder was melt-kneaded with a twin-screw extruder (manufactured by Ikegai Co., Ltd., screw diameter 43 mm, L / D = 34), and this melt-kneaded product was set at 10 ° C. for circulating water of the rolling roll. And then cooled. The kneaded product after cooling was roughly crushed with a Rotoplex (manufactured by Hosokawa Micron Corporation, 2 mm screen).

[Comparative Examples 2 to 9]
Toners of Comparative Examples 2 to 9 were produced in the same manner as in Comparative Example 1. For the toners of Comparative Examples 2 to 9, as shown in Table 4, the composition of the toner raw material was changed.

[Evaluation method]
<With or without beard>
The mixture discharged from the twin-screw extruder (in the case of the example, the second mixture is used) is formed into a plate shape with a rolling roll. Whether the whisker is generated when the mixture in the form of a plate is bent is determined visually.
○ No beard x Beard.

<Crushability index>
The resin sample is coarsely pulverized for 10 seconds with a mini blender (model number: MB-2 Osaka Chemical). As the resin sample, in the case of the example, a resin master batch is used, and in the case of the comparative example, a melt-kneaded product of the toner raw material is stretched and cooled. From the coarsely pulverized resin sample, a resin powder that passed through a sieve of 16 mesh (aperture: 1 mm) but did not pass through a sieve of 22 mesh (aperture: 710 μm) was obtained. 10 g of the obtained resin powder is weighed. The weighed resin powder is sieved with a vibrating sieve with a mesh of 710 μm for 10 minutes. The weight of the resin powder that has passed through the vibrating screen is measured. The measured weight (A) g of the resin powder is introduced into the following formula, and the grindability index is calculated.
Formula: Millability index = (A) g / collected weight before vibrating sieve (10 g) × 100.

[Evaluation results]
The results of “whisker presence / absence” and “grindability index” are shown in Tables 3 and 4.

  In Examples 1 to 18, polylactic acid was masterbatched with a formulation containing a grinding aid but no release agent, and the resulting resin masterbatch had a grindability index of 20 or more, and then a resin masterbatch This was melt kneaded with a toner material containing a release agent to produce a toner. As a result, in Examples 1-18, while the problem of the pulverization property of polylactic acid was solved, generation | occurrence | production of the beard which occurs after melt-kneading could be prevented. As a result, the toners of Examples 1 to 18 were able to prevent a decrease in toner performance due to the generation of whiskers.

  On the other hand, in Comparative Examples 1 to 9, polylactic acid was melt-kneaded with a toner raw material containing a grinding aid and a release agent without making a master batch to produce a toner. In Comparative Examples 1, 2, 4, 5, 8, and 9, when polylactic acid was melt-kneaded together with a grinding aid, a release agent, a colorant, and a charge control agent, a toner was produced. Was seen. In Comparative Example 3, polylactic acid was melt-kneaded together with a grinding aid and a release agent to produce a toner. As a result, generation of beard was observed after melt-kneading. In Comparative Examples 6 and 7, since no grinding aid was added, the grindability index was low and grinding was difficult.

  These results indicate that the pulverizability index of the resin masterbatch can be set to 20 or more, so that the problem of polylactic acid pulverizability can be solved, and the subsequent toner production without adding a release agent to the raw material mixture of the resin masterbatch It shows that the problem of beard that occurs after melt-kneading can be solved by adding a release agent in the process.

  In this example, a polyester resin was used for masterbatching the pigment. However, a colorant obtained by masterbatching the pigment with a polylactic acid resin (Mw 60,000 softening point 112 ° C.) has no effect on the effect. It was confirmed.

The invention described in the scope of claims at the beginning of the application will be appended.
[1] A first mixture containing polylactic acid having a weight average molecular weight of 20,000 to 110,000 and a grinding aid and not containing a release agent is melt-kneaded, and the obtained kneaded product is cooled and solidified. Preparing a resin masterbatch, wherein the first mixture has a composition such that the grindability index of the resin masterbatch is 20 or more,
Crushing the resin masterbatch;
A method for producing an electrophotographic toner, comprising: melt-kneading the second mixture containing the pulverized resin masterbatch and a release agent, and pulverizing and classifying the obtained kneaded product.
[2] The resin masterbatch preparation step adjusts the blending amount of the grinding aid so that the first mixture has a composition such that the grindability index of the resin masterbatch is 20 or more. The method for producing an electrophotographic toner according to [1], wherein the method is a process.
[3] The method for producing an electrophotographic toner according to [1] or [2], wherein the first mixture contains a colorant.
[4] The method for producing an electrophotographic toner according to [1] or [2], wherein the second mixture contains a colorant.
[5] The method for producing an electrophotographic toner according to [3] or [4], wherein the first mixture contains a charge control agent.
[6] The method for producing a toner for electrophotography according to [3] or [4], wherein the second mixture contains a charge control agent.
[7] A first mixture containing polylactic acid having a weight average molecular weight of 20,000 to 110,000 and a grinding aid and not containing a release agent is melt-kneaded, and the obtained kneaded product is cooled and solidified. Preparing a resin masterbatch, wherein the first mixture has a composition such that the grindability index of the resin masterbatch is 20 or more,
And a step of pulverizing the resin master batch.

Claims (7)

Resin master by melting and kneading a first mixture containing polylactic acid having a weight average molecular weight of 20,000 to 110,000 and a grinding aid and not containing a release agent, and cooling and solidifying the obtained kneaded product. A step of preparing a batch, wherein the first mixture has a composition such that the grindability index of the resin master batch is 20 or more;
Crushing the resin masterbatch;
A method for producing an electrophotographic toner, comprising: melt-kneading the second mixture containing the pulverized resin masterbatch and a release agent, and pulverizing and classifying the obtained kneaded product.   The step of preparing the resin masterbatch is a step of adjusting the blending amount of the pulverization aid so that the first mixture has a composition such that the pulverizability index of the resin masterbatch is 20 or more. The method for producing an electrophotographic toner according to claim 1.   The method for producing a toner for electrophotography according to claim 1, wherein the first mixture contains a colorant.   The method for producing an electrophotographic toner according to claim 1, wherein the second mixture contains a colorant.   The method for producing a toner for electrophotography according to claim 3 or 4, wherein the first mixture contains a charge control agent.   5. The method for producing an electrophotographic toner according to claim 3, wherein the second mixture contains a charge control agent. Resin master by melting and kneading a first mixture containing polylactic acid having a weight average molecular weight of 20,000 to 110,000 and a grinding aid and not containing a release agent, and cooling and solidifying the obtained kneaded product. A step of preparing a batch, wherein the first mixture has a composition such that the grindability index of the resin master batch is 20 or more;
And a step of pulverizing the resin master batch.