JP2009180810A - Method of reducing residual monomer derived from binder resin in toner and method of manufacturing toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing toner easily reducing residual monomer without impairing necessary functions as toner with a simple structure without requiring special facilities/apparatus, and to thereby provide the toner having high safety and mitigating the problem of odor. <P>SOLUTION: A pulverized material is used as the binder resin for toner, which is obtained by performing once or more times the at least two steps including a melt kneading step of melting and kneading a raw material resin by a biaxial kneading machine or the like and a pulverizing step of cooling the molten kneaded mixture obtained by the melt kneading step and pulverizing it by a jet mill pulverizer or the like so that the particle size of the pulverized material is ≤10 μm. Thus, the residual monomer derived from the binder resin in the toner is reduced, and the toner having high safety and mitigating the problem of odor is obtained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrostatic charge image developing toner used in an electrophotographic system and the like, and more particularly, to a method for reducing a residual monomer derived from a binder resin in a toner, a method for producing the toner, and a toner obtained by these methods.

  In electrophotographic image formation, an electrostatic image is generally developed and visualized with toner, and the toner image obtained by development is transferred to a sheet and then fixed by heat and pressure.

  One method for producing toner used for image formation is a pulverization method. As a general production method of the pulverization method, raw materials such as a binder resin, a colorant, a release agent, and a charge control agent are mixed in a dry method, then melt-kneaded with a twin screw extruder or the like, cooled and solidified, and then roughened. Crushing to obtain a kneaded coarsely crushed product. After that, fine pulverization is performed with a jet mill or the like, and the particle size is adjusted with a classifier so as to obtain an appropriate particle size distribution. Further, the toner is obtained by performing surface treatment by mixing with silica or the like in a mixer.

  As the toner resin, a styrene copolymer, a polyester resin, an epoxy resin, or the like is used. In recent years, due to safety and odor problems, reduction of residual monomers in a resin has been demanded. In particular, it is known that styrene copolymers have a large amount of volatile components such as styrene derived from raw materials.

  As a method for reducing the residual monomer in the toner resin, a method of mixing a reaction mixture and water at 100 to 300 ° C. in a resin production process is known (for example, see Patent Document 1). Also known is a method of heating the resin to bring the volatile content to 3% by mass or less, then injecting water or water vapor into the resin, maintaining the pressurized state, and then reducing the pressure to maintain the reduced pressure. (For example, see Patent Document 2). However, any of these methods has a lack of productivity because the process is batch-type and it takes time to deaerate.

On the other hand, in view of the problem that recycle toner that recycles toner is remarkably inferior in terms of odor at the time of fixing as compared with replenishment toner (virgin toner), in order to reduce the amount of residual monomer to 300 ppm or less, This suggests that the residual monomer is forcibly removed by increasing the kneading temperature at the time of hot-melt kneading the binder resin and the colorant or the like (for example, see Patent Document 3). However, the method of increasing the kneading temperature in this way causes deterioration based on the structural change of the resin itself, and has a problem that it is inferior in chargeability and durability as a toner.
JP-A-2005-350511 JP 2000-143721 A JP 2000-298374 A

  The present invention has been made under such circumstances, and is a toner that can easily reduce the residual monomer without impairing the functions required as a toner, while having a simple configuration without requiring special equipment and devices. It is an object of the present invention to provide a toner having high safety and less odor problems, which is obtained by these methods.

  In order to solve the above problems, the first aspect of the present invention includes at least two steps of a melt-kneading step for melt-kneading a raw material resin and a pulverizing step for cooling and pulverizing the melt-kneaded product obtained in the melt-kneading step. There is provided a method for reducing a residual monomer derived from a binder resin in a toner, wherein a pulverized product obtained by performing at least once is used as a binder resin for a toner.

  In such a method for reducing the residual monomer derived from the binder resin in the toner, the melt kneading step includes a twin screw extrusion kneader, a single screw extrusion kneader, and a heatable twin screw or single screw feeder. It can be performed by means selected from

  The pulverization step can be performed with a jet mill pulverizer so that the particle size of the pulverized product is 10 μm or less. The raw resin is a styrene copolymer.

  The second aspect of the present invention is obtained by performing at least two steps of a melt kneading step of melting and kneading a raw material resin and a pulverizing step of cooling and crushing the melt kneaded product obtained in the melt kneading step at least once. There is provided a method for producing a toner, wherein the pulverized product is used as a binder resin for toner, and a raw material mixture containing the binder resin for toner, a colorant and a wax is melt-kneaded, then cooled and pulverized.

  In such a toner production method, the melt-kneading step is performed by means selected from the group consisting of a twin screw extrusion kneader, a single screw extrusion kneader, and a heatable twin screw or single screw feeder. I can do it.

  The pulverization step can be performed with a jet mill pulverizer so that the particle size of the pulverized product is 10 μm or less. The raw resin is a styrene copolymer.

  The third aspect of the present invention provides a toner manufactured by the toner manufacturing method according to the second aspect of the present invention as described above.

  According to the method for reducing the residual monomer derived from the binder resin in the toner and the method for producing the toner according to the present invention, the residual monomer in the binder resin is subjected to the conventional general kneading process without requiring any special equipment or device. A certain reduction. Further, by pulverizing the resin and making the particles smaller, the release of volatile components is further promoted, and by repeating these, it is possible to reduce the residual monomer derived from the binder resin in the toner than before. . Accordingly, it is possible to easily reduce the residual monomer without impairing the functions necessary for the toner, and thus it is possible to provide a toner that is highly safe and has few odor problems.

  The inventors of the present application, while advancing the development and production of pulverized toner, reduce the amount of styrene generated by kneading the raw material resin multiple times to make the styrene copolymer a binder resin, It has been found that the release of volatile components can be promoted by reducing the particle size after kneading.

  The kneader and pulverizer used in the present invention can use the equipment itself used in conventional pulverized toner, and can easily reduce volatile components.

  The best mode for carrying out the invention will be described below with reference to the drawings.

  According to one embodiment of the present invention, there are provided a method for reducing a residual monomer derived from a binder resin in a toner and a method for producing a toner, a melt-kneading step of melt-kneading a raw material resin, and a melt-kneaded product obtained in the melt-kneading step. A pulverized product obtained by performing at least two pulverization steps of cooling and pulverization at least once is used as a binder resin for toner.

  FIG. 1 is a block diagram showing a residual monomer reduction method and a toner production method according to an embodiment of the present invention. As shown in FIG. 1, the raw material resin to be used as a binder resin is first supplied to a kneader, where it is melt-kneaded.

  As the kneading machine, it is preferable to use an extrusion kneading machine such as a twin screw extrusion kneading machine and a single screw extrusion kneading machine, a heatable biaxial or single screw screw feeder, etc., but it has a superheating function and a mixing function. Anything is acceptable.

  The melt-kneaded product from the kneader is usually cooled and coarsely crushed according to the method used for producing the toner. The cooling means and the coarse crushing means are not particularly limited, and those usually used for toner production can be employed.

  For example, a cooling means by rolling or blowing airflow can be used for cooling, and for example, a Rotoplex (2 mm screen manufactured by Hosokawa Micron Corporation) pulverizer can be used for coarse crushing. Here, the crushed pulverized product is preferably further pulverized to a predetermined particle size by a jet mill pulverizer (impact plate pulverizer).

  In the present invention, the pulverized product obtained by such a pulverization step is used as a binder resin in conventional toner production. In other words, as shown in the figure, it is supplied together with other raw materials as a binder resin to the first mixing step of the conventional toner manufacturing step. In the present invention, the residual monomer derived from the binder resin can be further reduced by returning the pulverized product to the melt-kneading step again.

  Next, the pulverized product in which the binder resin-derived residual monomer is reduced in advance in this way is mixed with a colorant, a charge control agent, wax, and the like by a mixer. As a mixing machine, arbitrary things, such as a Henschel mixer, a super mixer, a V-type blender, and a Nauta mixer, can be used.

  This raw material mixture is then fed to a kneader where it is melt kneaded. As the kneading machine, any type of extrusion kneading machine such as a twin-screw extrusion kneading machine and a single-screw extrusion kneading machine, an open roll type kneading machine such as a continuous two-roll mill, a continuous three-roll mill, and a batch roll mill can be used. Things can be used.

  The melt-kneaded product from the kneader is usually cooled, roughly pulverized and finely pulverized according to the method used for toner production, classified to a predetermined particle size, and further mixed with an external additive such as silica to obtain an electrostatic charge image. A developing toner is obtained. As the cooling means and the pulverizing means, those usually used for the production of toner as described above can be adopted. For classification, various air classifiers can be used.

  FIG. 2 is a side view showing a twin-screw extrusion kneader as an example of a kneader used in the raw material resin melt kneading step according to an embodiment of the present invention. This twin-screw extrusion kneader includes a hopper 1 to which a raw material mixture is supplied, a barrel 2, a screw 3, a deaeration port 4, and a die nozzle 5 from which a melt-kneaded product is discharged. The drawing also shows a drawing roller 6, a transport conveyor 7, and a container 8 connected to the die nozzle 5.

  The barrel 2 is heated to a predetermined temperature by a heater (not shown), and two cylindrical screws 3 arranged in the barrel 2 so that the axes thereof are parallel or have a predetermined angle. Is arranged. The screw 3 rotates in the same direction or in the opposite direction.

  The raw material mixture supplied from the hopper 1 is introduced into the barrel 2 and melted by the heat from the heated barrel 2 in the gap between the screws and is kneaded by the compression force and shearing force due to the rotation of the screw. Then, it moves to the die nozzle 5 side along the spiral blade of the screw 3 and is discharged from the stretching roller 6 connected to the die nozzle 5.

  A deaeration port 4 is disposed in the vicinity of the die nozzle 5 side of the barrel 2, and volatile components in the raw material mixture are discharged from the deaeration port 4 while being melt-kneaded.

  A transport conveyor 7 is disposed in the vicinity of the stretching roller 6, and the molten mixture discharged from the stretching roller 6 is transported by the transport conveyor 7 while being cooled, accommodated in a container 8, and then subjected to a pulverization process. The

  Hereinafter, examples and comparative examples in which the method for reducing a binder resin-derived residual monomer according to an embodiment of the present invention described above was performed under various production conditions will be described.

<Preparation of resin>
First, resins having different conditions were prepared as follows.

Resin 1 (one kneading-coarse crushing)
Styrene acrylic resin for toner (manufactured by Mitsubishi Rayon Co., Ltd .: softening point 148 ° C., hereinafter referred to as “resin A”) is melt-kneaded with a twin-screw extruder shown in FIG. The resin 1 was obtained by rough crushing with a plex (manufactured by Hosokawa Micron Corporation, 2 mm screen).

Resin 2 (kneading once-fine grinding)
Resin 1 was pulverized by an impact pulverizer such that the average particle size became 9.0 μm, and resin 2 was obtained.

Resin 3 (kneading 2 times-coarse crushing)
Resin 2 was melt-kneaded again with a twin-screw extruder, stretched, cooled, and roughly crushed to obtain resin 3.

Resin 4 (kneading 2 times-fine grinding)
Resin 3 was pulverized with an impact pulverizer so that the average particle size became 9.0 μm, and resin 4 was obtained.

Resin 5 (kneading 3 times-roughing)
Resin 4 was melt-kneaded again with a twin-screw extruder, stretched, cooled, and roughly crushed to obtain resin 5.

Resin 6 (3 times kneading-fine grinding)
Resin 5 was pulverized with an impact pulverizer such that the average particle size became 9.0 μm, and resin 6 was obtained.

<Kneading conditions, softening point measurement, particle size measurement>
As the above kneading conditions, a twin screw extruder (screw diameter 43 mm, L / D = 34) as shown in FIG. 2 was used, the kneaded material temperature at the kneading outlet was measured, and the kneaded material temperature was 180 ± 20 ° C. The kneading temperature was set so that The screw rotation speed was 300 rpm and the supply rate was 25 kg / h. During the kneading, deaeration was performed from the exhaust port 4 using a vacuum pump (not shown).

  The softening point of the resin was determined using a flow tester (manufactured by Shimadzu Corporation, CFT-500D) under the conditions of sample: 1 g, heating rate: 6 ° C./min, load: 20 kg, nozzle: diameter 1 mm, length 1 mm. It was calculated by the 1/2 method (the temperature at which half of the sample flowed out was taken as the softening point).

  The particle size is a small sample, purified water, and surfactant in a beaker and dispersed with an ultrasonic cleaner. Multisizer II (manufactured by Coulter) under the conditions of 100 μm aperture and 50,000 counts. Was used to determine the volume average particle size.

Example 1
90% by mass of resin 1 as a binder resin and C.I. 4 parts by weight of I pigment red 57: 1, 1 part by weight of “LR-147” (manufactured by Nippon Carlit Co., Ltd .: organoboron compound) as a charge control agent, and “Carnauba wax No. 1 powder” (Yo Kato) as a release agent 5 parts by mass of imported product) was mixed using a Henschel mixer (Mitsui Mining Co., Ltd.).

  The mixture is melt-kneaded with the twin-screw extruder shown in FIG. 2 (similar kneading conditions as in the production of resins 1 to 6), stretched, cooled, and coarsely crushed with a Rotoplex (2 mm screen manufactured by Hosokawa Micron). Then, the mixture was pulverized and classified by a collision type pulverizer to obtain colored fine particles having an average particle diameter of 6.0 μm. As an external additive, 2 parts by mass of “R972” (manufactured by Nippon Aerosil Co., Ltd .: hydrophobic silica) was added to 100 parts by mass of the obtained colored fine particles and mixed with a Henschel mixer to obtain a toner.

Examples 2-6
A toner was obtained in the same manner as in Example 1 except that resin 2 to resin 6 were used instead of resin 1, respectively.

Comparative Example A toner was obtained in the same manner as in Example 1 except that resin A was used as it was instead of resin 1.

  The toner samples of Examples 1 to 6 and Comparative Example prepared as described above were evaluated by the following residual monomer simple measurement method, and the results shown in Tables 1 and 2 were obtained.

<Styrene detection concentration>
An instrument as shown in FIG. 3 was prepared. 2.0 g of each sample was weighed into a 50 cc beaker 9, and the upper opening was covered with an aluminum foil lid 11 and heated in an oven (not shown) set at 180 ° C. for 5 minutes. After heating, the beaker 9 was taken out, and the generated gas was sucked with a gas detector 12 (XP-3160, a target gas by Shin Cosmos Electric Co., Ltd.), and the maximum value of styrene concentration was read.

<Odor evaluation>
Sensory evaluation of odor was performed simultaneously with the measurement of styrene concentration.
In the sensory test, the odor level was determined by five examiners according to the following evaluation criteria.
4: Does not smell at all 3: Slightly smells (a level that does not matter)
2: Smell (level of concern)
1: Very smelly (unpleasant level)

As apparent from Tables 1 and 2 below, in the toners of Examples 1 to 6 prepared by melt-kneading a styrene resin as a binder resin in advance before the conventional toner manufacturing process, the conventional toner manufacturing method was used. It can be seen that the amount of styrene generated is lower than that of the produced comparative toner.
That is, in Example 1, the amount of styrene generated is reduced by using a resin once melt-kneaded and crushed by a twin screw extruder as a binder resin for the toner.
Further, in Example 2, the amount of styrene generated is further reduced by using a resin once melt-kneaded and finely pulverized by a twin screw extruder as a binder resin for the toner.

  It can also be seen that the amount of styrene generated gradually decreases by repeating the kneading and pulverization in Example 3 and thereafter.

The amount of styrene generated is, of course, the amount of residual styrene monomer derived from the styrene resin, and it is considered that the styrene gas was degassed by repeated kneading and pulverization based on the present invention.

  From the above, it has been found that the present invention can easily reduce the residual monomer derived from the binder resin in the toner. Therefore, according to the method of the present invention, it is possible to provide a toner having high safety and less odor problem.

It is a block diagram showing a residual monomer reducing method and a toner manufacturing method according to an embodiment of the present invention. It is a side view of the twin-screw extrusion kneader used for one Embodiment of this invention. It is a simplified diagram explaining the simple measuring method of the residual monomer which concerns on one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Hopper, 2 ... Barrel, 3 ... Screw, 4 ... Deaeration port, 5 ... Die nozzle, 6 ... Stretching roller, 7 ... Conveyor, 8 ... Container, 9 ... Beaker, 10 ... Resin, 11 ... Cover, 12 ... Gas detector.

Claims (9)

  A pulverized product obtained by performing at least two steps of a melt-kneading step of melt-kneading a raw material resin and a pulverizing step of cooling and pulverizing the melt-kneaded product obtained in the melt-kneading step is used for binding a toner. A method for reducing a residual monomer derived from a binder resin in a toner, characterized by being used as a resin.   2. The melt kneading step is performed by means selected from the group consisting of a twin screw extrusion kneader, a single screw extrusion kneader, and a heatable biaxial or single screw feeder. Of reducing residual monomer derived from binder resin in toner.   The method for reducing residual monomer derived from a binder resin in toner according to claim 1, wherein the pulverizing step is performed by a jet mill pulverizer such that the particle size of the pulverized product is 10 μm or less.   4. The method for reducing a residual monomer derived from a binder resin in a toner according to claim 1, wherein the raw material resin is a styrene copolymer. A pulverized product obtained by performing at least two steps of a melt-kneading step of melt-kneading a raw material resin and a pulverizing step of cooling and pulverizing the melt-kneaded product obtained in the melt-kneading step is used for binding a toner. With resin,
A method for producing a toner, comprising melting and kneading a raw material mixture containing a binder resin for a toner, a colorant and a wax, and then cooling and pulverizing the mixture.   6. The melt kneading step is performed by means selected from the group consisting of a twin screw extruder kneader, a single screw extruder kneader, and a heatable twin screw or single screw feeder. Toner production method.   7. The toner manufacturing method according to claim 5, wherein the pulverizing step is performed by a jet mill pulverizer such that the particle size of the pulverized product is 10 μm or less.   The method for producing a toner according to claim 5, wherein the raw resin is a styrene copolymer.   A toner produced by the production method according to claim 5, 6, 7 or 8.

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