JP3409100B2 - Manufacturing method of toner - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a dry toner for developing an electrostatic image in electrophotography, electrostatic recording, electrostatic printing and the like.

[0002]

2. Description of the Related Art A method of developing an electrostatic charge image is as follows. (1) A developing solution in which fine toner containing various colorants and a binder resin as main components is dispersed in an insulating organic liquid. And a dry developing method using (2) a fine powder developer called a toner in which a polar control agent and a colorant are dispersed and contained in a natural or synthetic resin. In the dry developing method, the electrostatic charge image is developed using toner, and if necessary, transferred onto a transfer sheet, and then fused onto the transfer sheet. At that time, the fusion of the toner image is performed by contact with the solution vapor, pressurization or heating. According to the dry developing method (2), a copy can be obtained in a dry state, and the copying speed is high, so that it is widely used.

However, when developing an electrostatic image with a dry developer, the toner often adheres to the non-image area to cause so-called scumming, and the toner does not adhere sufficiently to the image area. The image density may be reduced. Further, when a large number of copies are made by a copying machine, the image density is reduced earlier than the life of the developer, and the phenomenon of background smearing, which is so-called filming, causes deterioration in durability. These are all caused by poor dispersion of the colorant, the polarity control agent and the release agent in the toner. If the colorant, the polarity control agent, and the release agent are poorly dispersed, the toner has a low charging ability or a large variation in the charging ability, and the image density is lowered. In addition, the toner adheres to the non-image area due to a decrease in the charging ability, and scumming occurs, and if the release agent is poorly dispersed, the release agent is released on the toner surface and filming on the carrier surface occurs. Durability decreases.

In order to eliminate such inconvenience, in order to produce a toner having a high concentration and a high durability without causing scumming, the dispersibility of the colorant, the polarity control agent and the release agent in the toner is improved. Manufacturing methods have been taken to increase the As one of means for improving the dispersibility by kneading, there is a method of reducing the kneading amount per unit time. This is to reduce the kneading amount, thereby relatively increasing the residence time in the kneader and increasing the dispersion time.
Further, there is a so-called masterbatch method in which a part of the binder resin and a colorant and a part or all of the polarity control agent are first kneaded, and then cooled and ground, and this is kneaded again with the rest of the materials ( JP-A-3-164750). In this way
The material dispersed by kneading is cooled, pulverized and classified to obtain a product.

By the way, the "cooling" here is carried out for the purpose of solidifying in order to obtain a powdery toner. In this cooling, the colorant dispersed in the kneading, the polarity control agent, and the releasing agent are separated by cooling as quickly as possible. It was found that the effect of preventing re-aggregation in the kneaded product of the molding agent can be obtained. For example, in the case of a toner prepared by crushing and classifying a toner solidified by air cooling after being left without cooling, scumming, a decrease in developing density, and a decrease in carrier life are caused as compared with a toner prepared by cooling. Many are seen. In addition, there is a method of rolling the kneaded product into a plate shape of about 2 to 5 [mm] with a rolling roller or the like in order to facilitate pulverization when cooling.
Further, this rolling has an advantage that the surface area of the material is increased and cooling is promoted, so that the cooling device can be downsized. As a rolling method, there is also a cooling type rolling method in which a cooling solvent is filled or circulated in the roller to accelerate the cooling rate and prevent reaggregation of the colorant, the polarity control agent and the release agent.

At present, the most efficient means for cooling the kneaded material is the above-mentioned cooling type rolling method, which is generally used. However, in this method, the thickness of the material is at most about 1 [mm], so that the cooling rate inside the material is slow and a difference occurs in the cooling rate between the surface and the central portion. In such a case, even if a uniform dispersion state is obtained by the kneading machine, the speed of aggregation is different due to the difference in the cooling rate, resulting in a non-uniform dispersion state. Therefore, even in the toner after pulverization and classification, the dispersion of the colorant, the polarity control agent, and the release agent in the binder resin becomes non-uniform, which may cause scumming, decrease in concentration, and further decrease in carrier life. There is.

In order to solve these problems, Japanese Unexamined Patent Application Publication No.
No. 97969 proposes a method of rapidly cooling a kneaded product. According to this method, the cooling speed when cooling the kneaded material is within 5 [seconds] after discharging from the discharge port of the kneading machine, or at 14 [° C./s] or higher, so that the toner in the crushed toner is cooled. Since there is less free polyethylene, there is no offset, sleeve contamination, reverse fog development, etc.
It is said that a toner having excellent physical and chemical properties can be obtained. However, even with the method that satisfies this condition, it is the current situation that sufficient quality cannot be obtained depending on the cooling condition.

[0008]

An object of the present invention is to keep a colorant, a polarity control agent, a release agent and the like in a dispersed state without re-aggregation or release in a kneading step, and to keep a constant cooling rate. It is an object of the present invention to provide a method of obtaining a toner having a narrow charge amount distribution as a quality of a toner, causing no background stain and a decrease in image density when an image is formed, and having excellent offset resistance.

[0009]

SUMMARY OF THE INVENTION The present inventors define cooling conditions after mixing and melting and kneading predetermined raw materials in a normal toner manufacturing process, or adopt a new cooling system. It has been found that high quality toner can be obtained. The present invention has been made on the basis thereof.

According to the present invention, (1) at least a binder resin, a colorant and a charge control agent as main materials are kneaded in a kneader, cooled and solidified, crushed and classified to give a predetermined toner. In the method for producing a toner to be obtained, an external force is applied to the kneaded product discharged to the outside of the kneader immediately while it is transferred to a cooling device, and the cooling rate in the cooling device is 20 [° C. / s] or more, and (2) The method for producing a toner according to (1), wherein the temperature after cooling the kneaded material is equal to or lower than the glass transition point of the binder resin. Method, (3) The toner according to the above (1), characterized in that the main raw material to which a release agent is further added is used, and the temperature of the kneaded product after cooling is set to the glass transition point of the release agent or lower. Manufacturing method, (4) In the above (1), thickness of kneaded product The method of manufacturing a toner, wherein 0.5 [mm] in the following thin film faster the cooling rate, also it has less variation in the kneaded product of cooling rate,
(5) In the above (1), the kneaded product has a diameter of 1 [mm].
Provided is a method for producing a toner, characterized in that the cooling rate is increased and the variation in cooling rate in the kneaded material is reduced in the following rod shape.

According to the present invention, (6) said (4)
In the above, as a means for forming the kneaded material into a thin film, a rolling roller heated to a predetermined temperature is provided between the kneading machine and the cooling device, and the kneaded material is passed through this, and the temperature of the kneaded material is at least that of the binder resin. By forming a thin film in a state of being kept at a temperature equal to or higher than the outflow starting temperature, and then cooling with the cooling device,
(7) A method for producing a toner, characterized in that a thin film is easily formed. (7) In (5), as a means for forming a kneaded product into a rod shape, a hollow heated to a predetermined temperature between a kneading machine and a cooling device. A pipe is provided through which the kneaded material is passed, and the kneaded material is formed into a rod shape while maintaining the temperature at least at the outflow starting temperature of the binder resin, or the kneaded material is stretched into a rod shape by a stretching machine, and then, Provided is a method for producing a toner, which is characterized by facilitating rod formation by cooling with a cooler. "Predetermined temperature" here
After all, means a temperature equal to or higher than the outflow start temperature of the binder resin.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. The cooling conditions and the cooling method in the present invention are the usual pulverized toner manufacturing steps, that is, the cooling step after the mixing of the raw materials and the melt-kneading, and any method regardless of the method and the conditions of the mixing and the melt-kneading. Can also be applied to. In the conventional cooling method, as described above, even if a high dispersion in the melt-kneading step, a uniform dispersion state is created, the colorant, the polarity control agent, and the release agent are reaggregated in the cooling step, or
It has been difficult to obtain excellent quality as a toner due to liberation. In particular, as a recent tendency, when the toner has a smaller particle size in order to obtain a high image quality, this tendency has become more remarkable. The inventors of the present invention, the highly kneaded material which is highly dispersed by the kneading machine, after being discharged from the kneading machine, the kneaded material is conveyed to the cooling step while applying an external force, and as the cooling condition of the cooling step, the molten kneaded material is used. It was found that conventional problems can be solved by rapidly cooling at a certain rate or more. Therefore, specifically, the kneaded product is moved to the cooling device while applying, for example, a compressive force to the kneaded product, and the cooling is more preferably 20 [° C./s] from the start of cooling, more preferably 5
It is achieved by quenching at a rate faster than 0 [° C / s].

The reason why the quality of the toner changes depending on the cooling rate is that although it is generally in a highly dispersed and uniformly dispersed state by melt kneading, the quality when discharged from a kneader (kneaded product) The temperature is higher than the softening point of the binder resin, and the molecular motion is easily activated. Furthermore, in a highly dispersed state by kneading, the total interfacial area between the polymer substance (binder resin) and particles such as colorants, charge control agents and release agents is very large, so the total interfacial free energy is also large. . If this is left as it is at the temperature, the binder resin itself, which is a polymer substance, and the colorant, charge control agent, release agent, etc. in the binder resin,
This is because it is attempted to reduce the total interfacial energy, that is, the most stable existing state is attempted, and those with high dispersion and uniform dispersion will reaggregate and recombine. The degree of this re-aggregation / re-bonding is related to temperature and time, and the higher the temperature and the slower the time, the more the quality tends to deteriorate.

When this phenomenon was examined in more detail,
The following was newly found. That is, the kneaded material that has been highly dispersed by melt-kneading does not undergo the above-mentioned re-aggregation and re-bonding for a certain period of time even if it is held at the product temperature when it is discharged from the kneading machine. This fixed time will vary somewhat depending on the type and combination of binder resin, colorant, charge control agent, release agent, etc., but after a certain period of time, changes such as reaggregation and recombination will suddenly occur. Get off. However, when an external force is applied to the kneaded material by some means, the movement of particles in the polymer is suppressed during that time. Furthermore, after maintaining such a state, a rapid cooling condition of 20 [° C./s] or more is applied to obtain a colorant, a charge control agent,
It was found that re-aggregation and re-bonding of the release agent can be suppressed. In the method proposed in JP-A-2-97969, the cooling rate from the start of cooling is 20 [° C /
If [s] is not reached, the target quality toner may not be obtained.

Further, by setting the quality of the kneaded product after cooling to be equal to or lower than the lowest glass transition point in the raw material, the effect becomes remarkable. The reason is that, as is clear from the above, re-aggregation and recombination can be suppressed by increasing the viscosity of the kneaded material, and the control temperature is such that the glass transition point at which the composition of the polymer substance begins to change. (Tg) is the most effective.
Specifically, in a kneaded product containing no mold release agent, a kneaded product containing a mold release agent such as low molecular weight polyethylene or carnauba wax at a temperature not higher than the glass transition point of the binder resin and added to prevent offset. Then, it is desirable that the temperature is not higher than the glass transition point of this release agent.

On the other hand, as a cooling method for achieving this cooling condition, it is conceivable to use an ordinary cooling device having a large heat exchange amount, but generally, in a rolling type cooling machine, the thickness after cooling and solidification is It becomes about 1 [mm]. However, when the toner has a thickness of about 1 mm, looking at each of the toner particles, one that was present on the surface and one that was present at the center when cooled And, the particles have different charging characteristics and offset properties. This tendency tends to be more remarkable as the toner particles are smaller. In order to solve this, it is necessary to make the cooling rate uniform. Specifically, the thickness before cooling is a thin film having a thickness of 0.5 [mm] or less, more preferably 0.1 [mm]. mm] or less. The kneaded product can be formed into a thin film by passing the kneaded product through a rolling roller heated to a predetermined temperature (a temperature above the outflow starting temperature of the binder resin). For the same purpose, the kneaded product before cooling has a rod shape of 1 [mmφ] or less,
More preferably, there is a method of forming a rod shape of 0.5 [mmφ] or less. The kneaded product can be formed into a rod shape, for example, by passing the kneaded product through a hollow pipe heated to a predetermined temperature (a temperature above the outflow start temperature of the binder resin) or by stretching.

The toner kneaded product discharged to the outside of the kneading machine is formed into a thin film or rod having a thickness or a certain thickness or less before being cooled and solidified, so that the surface area is greatly increased as compared with the conventional method. And the cooling efficiency is significantly improved. The cooling device can be either water-cooled or air-cooled. Furthermore, since the kneaded product is formed into a thin film or a rod, the particle size can be reduced to 1 [mm] or less during transportation between processes without the need for coarse crushing with a normal hammer mill, etc. Has the merit of being able to reduce the amount of capital investment.

[0018]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples. Parts herein are by weight.

Examples 1 to 10 and Comparative Examples 1 to 5 (a) In Examples 1 to 5 and Comparative Example 1, 100 parts of styrene-butyl methacrylate copolymer (Tg = 71 [° C.]) carbon black 10 parts Nigrosine (2 parts) is mixed and melt-kneaded with a kneader. (B) In Examples 6 to 10, styrene-butyl methacrylate copolymer (Tg = 71 [° C.]) 100 parts Carbon black 5 parts Low molecular weight polyethylene (Tg = 59 [° C.]) Nigrosine 2 parts were mixed, Melt and knead with a kneader. (C) The kneaded product obtained by the above method is passed while being sandwiched by a steel belt type rolling mill while reaching the cooling rollers, and further, the cooling rollers (surface temperature 15
[° C.]), rolling and cooling, cooling to room temperature on a cooling conveyor, and coarse pulverization with a hammer mill. Further, crush with a jet crusher and classify with a wind-powered classifier for 5 to 20
A fine powder of [μm] is obtained. To 100 parts of this fine powder, 0.4 part of colloidal silica was added to obtain a toner. As the evaluation items, the electrical resistance, charge amount, charge amount distribution, offset resistance, background stain density, image density, and carrier durability were tested by the methods shown in Table 1.

(D) Comparative Examples 2 and 3 are Examples 1 to 1.
In the same formulation and under the same conditions as in Example 5, the mixture was melted and kneaded, and was introduced into a cooling roller (surface temperature 15 [° C.]) without passing through a rolling mill while reaching a cooling conveyor. After that, Example 1
Toner was formed in the same manner as in No. 5, and the test was conducted by the method shown in Table 1.

(E) In Comparative Example 4, the rolling mill was not passed through while mixing, melting and kneading under the same formulation and under the same conditions as in Examples 6 to 10 and reaching the cooling conveyor.
5 [° C.]). Thereafter, the toner was formed in the same manner as in Examples 6 to 10, and the test was conducted by the method shown in Table 1.

(F) In Comparative Example 5, the kneaded product obtained by melt-kneading under the same formulation and under the same conditions as in Examples 6 to 10 and Comparative Example 3 was allowed to stand without passing through a rolling mill or a cooling roller,
The toner was gradually cooled to room temperature by air cooling, and subsequently, through the above-mentioned pulverization and classification steps, colloidal silica having the same formulation was further added to obtain a toner, and the toner was tested by the method shown in Table 1.

(G) Further, in Examples 1 to 10 and Comparative Examples 1 to 4, when the kneaded product obtained by the above method is rolled and cooled by a cooling roller, it is cooled immediately after the discharge port of the kneader. Non-contact infrared irradiation temperature measuring devices are provided at three positions immediately before the roller and immediately after the cooling roller, and the temperature at each point is set to t1, t2, and t3 from the kneading machine side, and the temperature change of the kneaded product Δt1 = t1. -T2, Δt2 = t2-t3
Was measured. Further, t1−t3 = ΔT. Further, the passing times s1 and s2 of the kneaded material between the respective temperature measuring devices were measured to obtain the cooling rates V1 and V2. Further, s1 + s2 = S, and the cooling rate V = ΔT / S from the kneader discharge port to after passing through the cooling roller was obtained. In addition,
Cooling speed V of the kneaded material between the kneader and the cooling roller
1 can be adjusted by moving the position of the cooling roller. The cooling speed V2 of the cooling roller can be adjusted by adjusting the gap of the cooling roller and adjusting the rotation speed of the cooling roller. Examples 1 to 1 in which different cooling rates were obtained by adjusting these
The cooling conditions of 0 and Comparative Examples 1 to 5 are summarized in Table 2.

[0024]

[Table 1]

[0025]

[Table 2]

According to the evaluation method based on Table 1, Examples 1 to 1
Table 3 summarizes the results of evaluation of 0 and Comparative Examples 1 to 5.

[Table 3]

Examples 11 and 12 and Comparative Examples 6 and 7 Here, Examples and Comparative Examples have the same formulation as Examples 6 to 10,
When cooling the kneaded product obtained by kneading under the same conditions, a rolling roller for rolling the kneaded product is provided at the rear of the kneading machine discharge port, a tension roller is provided at the rear of the kneading device, and the rolled product is stretched into a thin film to naturally It was cooled by cooling. For the rolling roller, a rubber heat roller, which is generally used for a fixing unit in a copying machine or the like, was used by heating to about 140 ° C. to facilitate rolling. The thickness of the kneaded product after solidification was measured with a dial gauge. The room temperature at this time was 21 ° C. and the humidity was 40%. The kneaded material prepared by the above method was pulverized, classified, and colloidal silica was added and mixed in the same manner as in Examples 1 to 10 to obtain a toner. Table 4 summarizes the evaluation results of Examples 11 and 12 and Comparative Examples 6 and 7 by the evaluation method based on Table 1.

[0028]

[Table 4]

Examples 13 and 14 and Comparative Examples 8 and 9 In these Examples and Comparative Examples, when the kneaded products obtained by kneading under the same formulation and under the same conditions as in Examples 6 to 10 were cooled,
A stretching machine for stretching the kneaded product into a rod shape was provided behind the discharge port of the kneading machine to form a rod shape, and cooled by spontaneous cooling. Further, the diameter of the kneaded product after solidification was measured with a dial gauge.
The room temperature at this time was 21 ° C. and the humidity was 40%.
The kneaded material prepared by the above method was pulverized, classified, and colloidal silica was added and mixed in the same manner as in Examples 1 to 10 to obtain a toner. Table 5 shows the evaluation results of Examples 13 and 14 and Comparative Examples 8 and 9 summarized by the evaluation method based on Table 1.

[0030]

[Table 5]

[0031]

According to the invention of claim 1, a colorant dispersed in a binder resin and a polarity control agent are not re-aggregated by kneading, and a toner with low background stain, high density and high durability is obtained. You can According to the invention of claim 2, the colorant and the polarity control agent dispersed in the binder resin by kneading do not re-aggregate, and a toner with low background stain, high concentration and high durability can be obtained. According to the invention of claim 3, re-aggregation of the colorant, the polarity control agent and the release agent dispersed in the binder resin by kneading does not occur, and the release agent is released from the toner surface in the pulverizing step. Without doing so, it is possible to obtain a toner with low background stain, high density and high durability. According to the invention of claim 4, re-aggregation of the colorant, the polarity control agent and the release agent dispersed in the binder resin by kneading does not occur, and the release agent is released from the toner surface in the pulverizing step. No, low soiling, high density,
In addition to being able to obtain a highly durable toner, the energy required for pulverization can be reduced due to the thin material thickness. According to the invention of claim 5, the reaggregation of the colorant, the polarity control agent and the release agent dispersed in the binder resin by kneading does not occur, and the release agent is released from the toner surface in the pulverizing step. In addition to being able to obtain low-contamination, high-concentration, high-durability toner without doing so, the energy required for pulverization can be reduced due to the small material diameter.
According to the invention of claim 6 or 7, when the kneaded product is made into a thin film or formed into a rod, the change in the viscosity of the material in the rolling section is suppressed to a small level, and the material becomes a problem when the film is continuously formed into a thin film or formed into a rod. It is possible to eliminate the occurrence of breakage, and it is possible to stably obtain toner with low background stain, high density, and high durability.

Continuation of the front page (56) Reference JP-A-2-97969 (JP, A) JP-A-7-152205 (JP, A) JP-A-6-138704 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) G03G 9/08

Claims (7)

(57) [Claims] 1. A method for producing a toner, comprising at least a binder resin, a colorant and a charge control agent as main raw materials, kneading the mixture with a kneader, cooling and solidifying, crushing and classifying to obtain a predetermined toner, While the kneaded product discharged to the outside of the kneading machine is immediately transferred to the cooling device, an external force is applied to the kneading product, and the cooling rate in the cooling device is 20 [° C / s] from the start of cooling.
A method for producing a toner characterized by the above. 2. The method for producing a toner according to claim 1, wherein the temperature of the kneaded material after cooling is set to be equal to or lower than the glass transition point of the binder resin. 3. The production of a toner according to claim 1, wherein the main raw material to which a release agent is further added is used, and the temperature of the kneaded product after cooling is set to be equal to or lower than the glass transition point of the release agent. Method. 4. The kneaded product according to claim 1, having a thickness of 0.
A method for producing a toner, characterized in that a thin film having a thickness of 5 [mm] or less is used to accelerate the cooling rate and to reduce variations in the cooling rate within the kneaded product. 5. The kneaded material according to claim 1, having a diameter of 1
A method for producing a toner, characterized in that the cooling rate is increased by forming a rod having a size of [mm] or less, and the variation in the cooling rate within the kneaded material is reduced. 6. The kneaded product according to claim 4, wherein a rolling roller heated to a predetermined temperature is provided between the kneader and the cooling device as a means for forming the kneaded product into a thin film, and the kneaded product is passed through the rolling roller. A method for producing a toner, wherein the temperature is maintained at least at a temperature at the time of being discharged from the kneader to form a thin film, and then the film is cooled by the cooling device to facilitate thinning. 7. The method according to claim 5, wherein the kneaded product is rod-shaped and a predetermined heated hollow pipe is provided between the kneading machine and the cooling device, and the kneaded product is passed through the hollow pipe to keep the temperature of the kneaded product at least. Characterized by facilitating the bar-shape by making the bar-shape while keeping the temperature at the time of being discharged from the kneader, or stretching the kneaded product by a stretching machine to make a bar-shape, and then cooling it by the cooler. Toner manufacturing method.