JP2003300707A - Surface modified metal oxide powder and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface modified metal oxide powder which exhibits excellent fluidity and low depositing property when it is added to various kinds of powder as typified by toner and which is controlled for its charge amount, and to provide a method for manufacturing the powder. <P>SOLUTION: The surface modified metal oxide powder is prepared by depositing a specified amount of a fatty acid metal salt on the surface of metal oxide powder such as silica subjected to hydrophobic treatment so as to obtain ≥60 hydrophobicity degree. The surface modified metal oxide powder is preferably manufactured by treating the powder with a hydrophobic agent such as hexamethyl disilazane and then treated with the fatty acid metal salt. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel surface-modified metal oxide powder and a method for producing the same. More specifically, when added to various powders typified by toners, surface-modified metal oxide powders exhibiting excellent fluidity and low adhesion and having a controlled charge amount, and a method for producing the same. Regarding

[0002]

2. Description of the Related Art Metal oxide powders are widely used for improving the fluidity of powders, and exert their effect by adhering to the surface of powders. For example, it is common practice to use a metal oxide powder such as silica as an additive for toner.

Toner is used as a developer in electrophotographic technology typified by copying machines and laser printers. In the electrophotographic printing process, the latent image formed on the surface of the photoconductor is visualized with precharged toner, the toner on the photoconductor is transferred, and the toner remaining on the photoconductor after cleaning is cleaned. Is done. In the field of this electrophotographic technology, there is a constant pursuit of image fineness and durability.

In terms of image fineness, it is required that the toner has good fluidity and that the toner particles have a small particle size. To improve the fluidity of the toner,
Silica powder treated with a hydrophobizing agent such as dimethyldichlorosilane or hexamethyldisilazane is generally used. These hydrophobic silica powders are excellent in the effect of improving the fluidity, but a large negative charge amount is often a problem. Also, as the toner particles become smaller,
The amount of the metal oxide powder added tends to increase, the influence of the charge amount of the metal oxide powder on the charge amount of the toner increases, and it is necessary to control the charge amount of the metal oxide powder.

Further, in terms of improving durability, the toner remaining on the photoreceptor does not cause filming and deteriorate the photoreceptor, and the cleaning blade and the photoreceptor are not damaged in the cleaning process. It is required that the adhesive force with the toner is small.

In order to reduce the adhesive force between the toner and the photoconductor, JP-A-57-129449 discloses that a toner contains a fatty acid metal salt. The fatty acid metal salt exerts its effect by forming a film on the photoreceptor, but since the size of the fatty acid metal salt is about several μm,
There is a problem that the film formation tends to be non-uniform. Further, in JP-A-5-165250, it is proposed that a fatty acid metal salt is attached to the surface of an inorganic compound and added to the toner, and a fatty acid metal salt is supported on an inorganic compound having a relatively small particle size to form a salt. The fatty acid metal salt film is made uniform.

[0007]

However, the toner using the metal oxide powder in which the fatty acid metal salt is adhered to the surface of the above-mentioned metal oxide powder is a metal oxide powder subjected to a general hydrophobic treatment. The fluidity is inferior to that of the toner added with, and there is still room for improvement.

Therefore, an object of the present invention is to provide a surface-modified metal oxide powder which has a fatty acid metal salt attached to the surface thereof and has an excellent ability to improve fluidity.

Another object of the present invention is to provide a technique capable of controlling the charge amount of metal oxide powder.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems. As a result, it was found that by adhering the fatty acid metal salt to the surface of the metal oxide powder that was subjected to the hydrophobic treatment with a hydrophobicity of 60 or more, excellent fluidity was exhibited when used in various powders. . Furthermore, they have found that the amount of charge of the metal oxide powder can be arbitrarily controlled by selecting a fatty acid metal salt to be attached that has an appropriate amount of charge, and have completed the present invention.

That is, according to the present invention, a surface-modified metal oxide powder characterized in that a fatty acid metal salt is adhered to the surface of a metal oxide powder which has been hydrophobized to have a hydrophobicity of 60 or more, and Hydrophobizing the metal oxide powder to make the hydrophobicity 6
A method for producing a surface-modified metal oxide powder, characterized in that a fatty acid metal salt is adhered after being set to 0 or more.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The metal oxide powder used as a raw material for the surface-modified metal oxide powder of the present invention is not particularly limited. Typical examples include titanium oxide powder, zinc oxide powder, aluminum oxide powder, silica powder and the like.
Preferable is a silica powder that can be obtained with a moderate particle size at low cost. Further, fumed silica produced by burning a silicon compound such as silicon tetrachloride is excellent in the effect of exhibiting fluidity, and is particularly preferable.

In the present invention, the metal oxide powder having any particle size can be used without limitation, but the primary particle size is 5 to 1000 nm for use in addition to toner.
Are preferred.

Here, the particle size of the metal oxide powder is obtained from the BET specific surface area of the metal oxide powder before treatment by the following formula.

R = 6 / ρS R: average particle size (μm) ρ: true specific gravity of metal oxide powder S: BET specific surface area of metal oxide powder (m ² / g) BET specific surface area of metal oxide powder is Confirmed by measuring the BET specific surface area after refluxing the surface-modified metal oxide powder with a solvent such as benzene, washing, filtering, drying, and further heat-treating at a temperature of about 500 ° C. in a nitrogen atmosphere can do.

The surface-modified metal oxide powder of the present invention has been subjected to a hydrophobizing treatment prior to the treatment of adhering the fatty acid metal salt to the metal oxide powder as the raw material. It is important for the surface-modified metal oxide powder to exhibit a fluidity improving effect by setting the hydrophobicity to 60 or more by the hydrophobic treatment. Since the surface of the metal oxide powder is hydrophilic, the compatibility with the fatty acid metal salt is poor. The hydrophobicity-improving effect is dramatically improved by preliminarily imparting hydrophobicity to the degree of hydrophobicity of 60 or more. The reason is that the fatty acid metal salt and the metal oxide surface become more familiar and the fatty acid metal salt becomes more uniform. It is understood that it has become possible to attach the.

In the present invention, the hydrophobicity of the metal oxide powder is measured by the following method.

A metal oxide powder of 0.2 g is added to a volume of 250 ml.
To 50 ml of water in a beaker from above and add methanol from the burette until the total amount of silica is suspended. At this time, so that methanol does not touch the metal oxide fine powder,
Guide the solution into the solution using a tube and constantly stir the solution in the beaker with a magnetic stirrer. The end point is the time point when all the metal oxide powder is suspended. When the volume of added methanol is V _m (ml), the degree of hydrophobicity is calculated by the following equation.

Hydrophobicity = V _m / (50 + V _m ) The hydrophobic group introduced to the surface of the metal oxide powder by the above-mentioned hydrophobic treatment is not particularly limited, but specifically, methylsilyl group, dimethylsilyl group, trimethylsilyl group. Group, ethylsilyl group, diethylsilyl group, triethylsilyl group,
Examples thereof include propylsilyl group, butylsilyl group, pentylsilyl group, hexylsilyl group, octylsilyl group, decylsilyl group and polyalkylsiloxane. Of these, a monomethylsilyl group, a dimethylsilyl group and a trimethylsilyl group are preferred, and a trimethylsilyl group is more preferred for increasing the hydrophobicity. Further, the above hydrophobic group may be mixed.

As the fatty acid metal salt to be attached to the surface of the metal oxide powder which has been subjected to the hydrophobizing treatment, known ones can be used without particular limitation. For example, zinc octylate, tin octylate, zinc stearate, calcium stearate, Aluminum stearate, magnesium stearate, zinc laurate, calcium laurate, aluminum laurate, magnesium laurate and the like can be mentioned. Preferably, zinc octylate, zinc stearate, calcium stearate, and aluminum stearate can be used.

By attaching a fatty acid metal salt having an appropriate amount of charge, it becomes possible to control the amount of charge of the surface-modified metal oxide powder.

The amount of the fatty acid metal salt adhered is about 0.25 to 2.5 mg per 1 m ² of the surface area of the metal oxide powder, so that the fluidity of the fatty acid metal salt is exerted and good fluidity is maintained. It is preferable above.

The method for producing the surface-modified metal oxide powder of the present invention is not particularly limited, but the following method is preferable.

That is, the present invention provides a method for producing a surface-modified metal oxide powder, which comprises subjecting a metal oxide powder to a hydrophobizing treatment to make the hydrophobicity 60 or more and then adhering a fatty acid metal salt thereto. To be done.

As the hydrophobizing agent used in the hydrophobizing treatment of the present invention, known ones can be used without limitation, but methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, trimethylsilanol,
Hexamethyldisilazane, methyltrimethoxysilane,
Examples thereof include methyltriethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, octyltrimethoxysilane, octamethylcyclotetrasiloxane, and dimethylpolysiloxane. Monomethyltrichlorosilane, dimethyldichlorosilane and hexamethyldisilazane are preferably used, and hexamethyldisilazane is more preferably used. Further, the treatment may be performed by combining the above-mentioned hydrophobizing agents.

The treatment with the hydrophobizing agent of the present invention is preferably carried out by bringing the surface of the metal oxide powder into contact with the hydrophobizing agent. For example, it is preferably performed by bringing the surface of the metal oxide powder into contact with the hydrophobizing agent existing in the gas phase or the liquid phase. The treatment may be carried out in a mixer or in a fluidized bed.

When hexamethyldisilazane is used as the hydrophobizing agent, the metal oxide powder is introduced into the container, the container is sealed, and the hexamethyldisilazane is added to the container at a temperature of about 200 to 300 ° C. under an inert gas atmosphere. Partial pressure of methyldisilazane 2
It can be suitably carried out by introducing it so as to be about 5 to 150 kPa and holding it for a certain period of time, preferably for about 1 hour. At this time, the partial pressure of steam in the container is 30 to 10
The presence of about 0 kPa is preferable in order to increase the degree of hydrophobicity of the metal oxide powder.

In the present invention, the treatment with a fatty acid metal salt, which is performed subsequent to the hydrophobic treatment, can be suitably performed by the following method.

For example, while a hydrophobic metal oxide powder is stirred in a mixer, a mixture of a fatty acid metal salt dissolved in a solvent is sprayed, and an inert gas is introduced and maintained at a predetermined temperature for a certain period of time to remove the solvent. It can be suitably performed by removing. The holding temperature is preferably a temperature at which the fatty acid metal salt decomposes or lower and a boiling point or higher of the solvent used. The solvent used has a low surface tension,
A low boiling silicone oil that is well compatible with hydrophobic silica is preferred.

The fatty acid metal salt is solid at room temperature,
When there is a melting point, the fatty acid metal salt and the hydrophobic metal oxide powder are stirred and mixed in the mixer at a temperature below the melting point, the temperature in the mixer is raised to a certain temperature, and at that temperature for a certain period of time, preferably 1 It can be suitably carried out by holding for about 4 hours and then cooling. The temperature to be maintained is not lower than the melting point of the fatty acid metal salt and preferably not higher than the decomposition temperature. Further, in order to suppress the decomposition of the fatty acid metal salt, it is preferable to carry out under an atmosphere of an inert gas.

Further, a fatty acid metal salt is dispersed in a solvent to prepare a slurry-like solution, and the solution is sprayed onto the hydrophobic metal oxide powder stirred and mixed in a mixer to introduce an inert gas. However, it can be preferably carried out by maintaining the temperature for a certain period of time. The holding temperature is a temperature above the melting point of the fatty acid metal salt, and preferably below the decomposition temperature of the fatty acid metal salt. Further, it is preferably higher than the boiling point of the solvent used. The solvent used is preferably a low boiling point silicone oil that has a low surface tension and is well compatible with hydrophobic silica.

[0032]

EXAMPLES The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples. The surface-modified metal oxide powders produced in the following Examples and Comparative Examples were tested for fluidity and charge amount by the following methods.

1. Preparation of mixed powder To the spherical acrylic resin powder having a particle size of 10 μm, 1% by weight of the surface-modified metal oxide powder was added and sufficiently mixed with a mixer. Then, the mixture was allowed to stand for 48 hours at a temperature of 25 ° C. and a humidity of 50% to obtain a mixed powder.

2. The fluidity of the fluid mixed powder was evaluated by measuring the degree of compression with a powder tester (PT-R type manufactured by Hosokawa Micron Co., Ltd.). The smaller the degree of compression, the better the fluidity. ◯: less than 15.5, Δ: 15.5-18, x: more than 18

3. The charge amount of the charge amount mixed powder was determined by the following method. A mixture of iron powder (TEFV-200 / 300, manufactured by Powder Tech Co., Ltd.) and mixed powder was used at a temperature of 25 ° C. and a humidity of 50%.
It was left for 4 hours, then mixed for 3 minutes with a desktop roller mill, and measured by a blow-off charge amount measuring device.

Example 1 400 g of hydrophilic fumed silica having a BET specific surface area of 200 m ² / g was introduced into a mixer having an internal capacity of 20 L and a nitrogen purge was carried out. After that, the temperature in the mixer is 250 ℃
In, the water vapor was introduced into the container until the partial pressure reached 60 kPa, and further 100 kPa of hexamethyldisilazane was introduced, and the mixer was sealed and held for 1 hour. After the hydrophobic treatment, unreacted substances and by-products were purged with nitrogen and dried. Then, the hydrophobic silica powder was extracted from the mixer. The hydrophobicity of the hydrophobic silica powder was 66.

Further, the hydrophobic silica powder was again introduced into the mixer and nitrogen purge was performed. The temperature in the mixer is 23
The temperature was adjusted to 0 ° C. A mixture of zinc octylate dissolved in 1 cSt of silicone oil to 10% was sprayed in the mixer while stirring and mixing. The amount of spray is 100% of zinc octylate hydrophobic silica powder.
It was made to be 20 parts by weight with respect to parts by weight. The treatment amount of zinc octylate per 1 m ^{2 of} silica powder is 1 mg. The silicone oil was removed by keeping the inside of the mixer for 1 hour while purging with nitrogen, and the surface-modified silica powder was extracted from the mixer.

Table 1 shows fluidity and charge amount when the surface-modified silica powder was added to the powder.

Comparative Example 1 BET specific surface area is 200 m ² / g and hydrophobicity is 0.
Fumed silica was introduced into the mixer and a nitrogen purge was performed. The temperature in the mixer was adjusted to 230 ° C. While mixing with stirring, add 1 cS of zinc octylate.
What was melt | dissolved in silicone oil of t so that it might become 10% was sprayed in the mixer. The spray amount was such that the amount of zinc octylate treated was 20 parts by weight with respect to 100 parts by weight of silica powder. The treatment amount of zinc octylate per 1 m ^{2 of} silica powder is 1 mg. The silicone oil was removed by holding the inside of the mixer for 1 hour while purging with nitrogen, and the surface-modified silica powder was extracted from the mixer.

Table 1 shows the fluidity and charge amount when the surface-modified silica powder was added to the powder.

Since no hydrophobizing treatment is performed, the effect of exerting fluidity when added to the powder is low.

Example 2 A hydrophobic silica powder was produced in the same manner as in Example 1.

The hydrophobic silica powder was introduced into the mixer and nitrogen purge was performed. The temperature in the mixer was adjusted to 160 ° C. While stirring and mixing, a slurry solution in which zinc stearate was dispersed in silicone oil of 1 cSt to be 20% was sprayed. The spraying amount was such that the amount of zinc stearate added was 10 parts by weight with respect to 100 parts by weight of the hydrophobic silica powder. The treatment amount of zinc stearate per 1 m ^{2 of} silica powder is 0.5 mg. By holding the inside of the mixer for 4 hours while purging with nitrogen, the silicone oil was removed and the surface-modified silica powder was extracted from the mixer.

Table 1 shows the fluidity and charge amount when the surface-modified silica powder was added to the powder.

Example 3 Treatment was carried out in the same manner as in Example 2 except that the amount of zinc stearate added was 20 parts by weight with respect to 100 parts by weight of the hydrophobic silica powder. Silica powder 1m ²
The amount of zinc stearate to be treated is 1 mg.

Table 1 shows the fluidity and charge amount when the surface-modified silica powder was added to the powder.

Example 4 Treatment was carried out in the same manner as in Example 2 except that the amount of zinc stearate added was 40 parts by weight with respect to 100 parts by weight of the hydrophobic silica powder. Silica powder 1m ²
The amount of zinc stearate to be treated is 2 mg.

Table 1 shows the fluidity and charge amount when the surface-modified silica powder was added to the powder.

Example 5 A treatment was carried out in the same manner as in Example 2 except that the amount of zinc stearate added was 60 parts by weight with respect to 100 parts by weight of the hydrophobic silica powder. Silica powder 1m ²
The amount of zinc stearate to be treated is 3 mg.

Table 1 shows the fluidity and charge amount when the surface-modified silica powder was added to the powder.

Comparative Example 2 BET specific surface area is 200 m ² / g and hydrophobicity is 0.
Fumed silica was introduced into the mixer and a nitrogen purge was performed. The temperature in the mixer was adjusted to 160 ° C. While stirring and mixing, add 1c of zinc stearate.
A slurry solution of 20% dispersed in St silicone oil was sprayed. The amount of zinc stearate added was 20 parts by weight with respect to the silica powder. The treatment amount of zinc stearate per 1 m ^{2 of} silica powder is 1 mg. By holding the inside of the mixer for 4 hours while purging with nitrogen, the silicone oil was removed and the surface-modified silica powder was extracted from the mixer.

Table 1 shows the fluidity and charge amount when the surface-modified silica powder was added to the powder.

Since no hydrophobizing treatment is performed, the effect of exerting fluidity when added to the powder is low.

Comparative Example 3 5 kg of hydrophilic fumed silica having a BET specific surface area of 200 m ² / g was placed in a fluidized bed reactor, dimethyldichlorosilane was 20 g / min, and steam was 180 g / min at 450 ° C.
Nitrogen was bubbled through the heated fluid phase reactor for 40 minutes. After the hydrophobic treatment, unreacted substances and by-products were purged with nitrogen and dried. By the above operation, a hydrophobic silica powder having a hydrophobicity of 52 was obtained.

The hydrophobic silica powder produced by the above method was introduced into a mixer and a nitrogen purge was performed. The temperature in the mixer was adjusted to 160 ° C. While stirring and mixing, a slurry solution in which zinc stearate was dispersed in silicone oil of 1 cSt to be 20% was sprayed. The spraying amount was such that the amount of zinc stearate added was 20 parts by weight with respect to the hydrophobic silica powder. By holding the inside of the mixer for 4 hours while purging with nitrogen, the silicone oil was removed and the surface-modified silica powder was extracted from the mixer.

Table 1 shows the fluidity and charge amount when the surface-modified silica powder was added to the powder. Since the degree of hydrophobicity is insufficient, the effect of exerting fluidity when added to the powder is low.

Comparative Example 4 400 g of hydrophilic fumed silica having a BET specific surface area of 200 m ² / g was introduced into a mixer having an internal volume of 20 L and a nitrogen purge was carried out. After that, the temperature in the mixer is 250 ℃
In the above, 100 kPa of hexamethyldisilazane was introduced, and the mixer was sealed and held for 1 hour. After the hydrophobic treatment, unreacted substances and by-products were purged with nitrogen and dried. Then, the hydrophobic silica powder was extracted from the mixer. The hydrophobicity of the hydrophobic silica powder was 57.

The hydrophobic silica powder produced by the above method was again introduced into the mixer and nitrogen purge was performed. The temperature in the mixer was adjusted to 160 ° C. While stirring and mixing, a slurry solution in which zinc stearate was dispersed in silicone oil of 1 cSt to be 20% was sprayed. The spraying amount was such that the amount of zinc stearate added was 20 parts by weight with respect to the hydrophobic silica powder.
The treatment amount of zinc stearate per 1 m ^{2 of} silica powder is 1
It becomes mg. By holding the inside of the mixer for 4 hours while purging with nitrogen, the silicone oil was removed and the surface-modified silica powder was extracted from the mixer.

Table 1 shows the fluidity and charge amount when the surface-modified silica powder was added to the powder. Since the degree of hydrophobicity is insufficient, the effect of exerting fluidity when added to the powder is low.

Example 6 The hydrophobic silica powder was produced in the same manner as in Example 1.

The hydrophobic silica powder and calcium stearate were mixed in a mixer whose internal temperature was adjusted to 80 ° C. Replace the inside of the container with nitrogen and mix at 200 ℃
Raised the temperature in the mixer until. 200 ℃ in the mixer
The hydrophobic silica powder was treated with molten calcium stearate by holding it at the temperature for 4 hours. The amount of calcium stearate added was set to 20 parts by weight with respect to 100 parts by weight of the hydrophobic silica powder. Silica powder 1m
^The amount of zinc stearate treated per ² is 1 mg.

Table 1 shows fluidity and charge amount when the surface-modified silica powder was added to the powder.

Example 7 The hydrophobic silica powder was produced in the same manner as in Example 1.

The hydrophobic silica powder and aluminum stearate were placed in a mixer whose internal temperature was adjusted to 80 ° C. and mixed. While mixing, the temperature in the mixer was raised to 200 ° C. and maintained for 1 hour, and the hydrophobic silica powder was treated with molten aluminum stearate. The amount of aluminum stearate added is 100 hydrophobic silica powder.
It was made to be 20 parts by weight with respect to parts by weight. The treatment amount of aluminum stearate per 1 m ^{2 of} silica powder is 1
It becomes mg.

Table 1 shows the fluidity and the charge amount when the surface-modified silica powder was added to the powder.

Comparative Example 5 The process for producing the hydrophobic silica powder was carried out in the same manner as in Example 1, but the treatment with the fatty acid metal salt was not carried out.

Table 1 shows fluidity and charge amount when the hydrophobic silica powder was added to the powder.

Comparative Example 6 By the same method as in Example 1, a hydrophobic silica powder was produced. 0.83% by weight of the hydrophobic silica powder and zinc stearate of 0.
17 wt% was added and mixed well with a mixer. Then, it was left for 48 hours under the condition of temperature of 25 ° C. and humidity of 50% to prepare mixed powder.

Table 1 shows the fluidity and chargeability of the mixed powder.

As can be understood from Examples 1, 3, 6, 7 and Comparative Example 5, it is possible to control the charge amount by changing the fatty acid metal salt to be attached.

[0071]

[Table 1]

[0072]

As can be understood from the above description, according to the present invention, a fatty acid metal salt is adhered to the surface of a metal oxide having a hydrophobicity of 60 or more to give a toner. Provided are extremely useful surface-modified metal oxide powders, which have both fluidity and low adhesion, and whose charge amount is controlled, when added to various powders, which are representative. It

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Claims (6)

[Claims] 1. A surface-modified metal oxide powder, characterized in that a fatty acid metal salt is adhered to the surface of a metal oxide powder having a hydrophobicity of 60 or more. 2. The surface-modified metal oxide powder according to claim 1, wherein the amount of the fatty acid metal salt attached is 0.25 mg to 2.5 mg per 1 m ² of surface area of the metal oxide powder. 3. The metal oxide powder according to claim 1, wherein the metal oxide powder is silica powder. 4. A method for producing a surface-modified metal oxide powder, which comprises hydrophobizing a metal oxide powder, adjusting the hydrophobicity to 60 or more, and attaching a fatty acid metal salt thereto. 5. The method for producing a surface-modified metal oxide powder according to claim 4, wherein the hydrophobizing treatment is performed with at least hexamethyldisilazane. 6. The method for producing a surface-modified metal oxide powder according to claim 4, wherein the metal oxide powder is silica powder.