JP2008303109A - Hydrophobic orthotitanic acid microparticules and toner for electrophotography - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide hydrophobic orthotitanic acid microparticles excellent in hydrophobicity, dispersibility, and safeness and usable for various applications such as an outer additive of a toner for electrophotographies. <P>SOLUTION: A substrate consisting of orthotitanic acid is treated with an alkoxysilane in an amount of 50-200 mass%, then neutralized with an acid, filtered, cleaned, and dried at 100-170°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is excellent in hydrophobicity and dispersibility, and is composed of ultraviolet absorbers such as paints, plastics and fibers, charge control agents for electrophotographic toners, orthotitanate fine particles used for fluidizing agents, and electrons using the same. The present invention relates to a photographic toner.

  In addition to being used for cosmetics, paints, inks, plastics, photocatalysts and the like, ultrafine particles of titanium oxide are widely used for charge control agents and fluidizing agents for electrophotographic toners. In these applications, titanium oxide or metatitanic acid whose surface has been subjected to a hydrophobic treatment is used in order to improve dispersibility and prevent hygroscopicity.

  Conventionally, the base fine particles include titanium oxide synthesized by vapor phase oxidation of titanium tetrachloride and titanium alkoxide, titanium oxide dehydrated and fired by sulfuric acid method, or metatitanic acid synthesized by sulfuric acid method hydrolysis reaction. The silane coupling agent is treated in the gas phase (Patent Document 1), in an aqueous solution, or in an organic solvent (Patent Documents 2 to 5).

First, titanium oxide synthesized by vapor phase oxidation of titanium tetrachloride and titanium oxide dehydrated and fired by the sulfuric acid method can be manufactured relatively inexpensively, but the specific surface area is small, Dispersibility was also poor. Further, titanium oxide synthesized by vapor phase oxidation of titanium alkoxide is treated with a silane coupling agent, has a high degree of hydrophobicity, a large specific surface area, good dispersibility, but is expensive. In addition, in the “List of risk information on carcinogenicity” by IARC (International Cancer Research Institute), the titanium oxide as the substrate is group 3B (cannot be classified as carcinogenic to humans (unknown)) to group 2B ( Since the rank has been changed to (possibly carcinogenic to humans), development of hydrophobic fine particles that can replace hydrophobic titanium oxide fine particles is strongly desired.
Japanese Patent Laid-Open No. 1-153529 JP-A-5-019528 JP-A-5-221640 JP-A-8-269359 Japanese Patent Application Laid-Open No. 8-048910

  Accordingly, an object of the present invention is to provide fine particles that have a high degree of hydrophobicity and a high specific surface area, and that can produce fine particles with good dispersibility relatively easily and inexpensively, and that can substitute for titanium dioxide.

  The present inventors pay attention to orthotitanic acid, which is materially different from titanium oxide, and its transparency, and to develop fine particles having a high degree of hydrophobicity, a specific surface area, and excellent in cost and safety. As a result of intensive studies, hydrophobic orthotitanate fine particles having a specific surface area coated with a specific amount of alkoxysilane can be used as a charge control agent or a fluidizing agent for electrophotographic toner without impairing the original transparency. The present invention was completed by finding out that it was excellent in various uses including the beginning.

That is, the hydrophobic orthotitanate fine particles of the present invention are coated with 50 to 200% by mass of alkoxysilane with respect to orthotitanic acid as a substrate, no X-ray diffraction peak is observed, and the specific surface area is 100 to 100%. The increase ΔL in the colorimetric value L of the black toner externally added at 300 m ² / g and 2% by mass is 0.8 or less with respect to the black toner before external addition.

  In the hydrophobic orthotitanate fine particles, the alkoxysilane used is represented by the general formula RnSiR′m (R: hydrocarbon group, R ′: alkoxy group, n = 1-3 integer, m = 1-3 integer. N + m = 4), and the hydrocarbon group R of the alkoxysilane preferably has 3 to 10 carbon atoms.

  Further, the hydrophobic orthotitanate fine particles preferably have a degree of hydrophobicity of 30 to 75% and a triboelectric charge amount with respect to iron powder of −100 to −30 μC / g.

  Further, the hydrophobic orthotitanate fine particles of the present invention are suitably used for an electrophotographic toner.

  According to the present invention, it is possible to produce fine particles having a higher specific surface area than conventional titanium oxide obtained by using a titanium tetrachloride vapor phase method or a sulfuric acid method without using expensive titanium alkoxide, Since it has high hydrophobicity and specific surface area and does not have carcinogenicity or toxicity problems, it can be used in various fields including electrophotographic toners.

(Ortho titanic acid)
In the present invention, orthotitanic acid has a chemical formula of Ti (OH) _{4 as} a main component, and has a diffraction peak in X-ray as shown in FIG. 1 later compared with titanium oxide or metatitanic acid. This is not allowed. Moreover, when it bakes at a temperature higher than 700 degreeC, it has the characteristic which produces | generates a rutile type titanium oxide. In addition, various safety-related laws and regulations are not subject to IARC, including the Japanese Chemical Substances Control Law (1-730 (titanic acid)), US TSCA (20338-08-3 (Titanium hydroxide)), In addition, it is registered in EINECS (243-744-3 (Tetrahydrytitanium)) in Europe.

(Hydrophobic orthotitanate fine particles)
What is important in the present invention is that the hydrophobic orthotitanic acid is coated with 50 to 200% by mass, preferably 80 to 180% by mass, more preferably 100 to 150% by mass of alkoxysilane with respect to orthotitanic acid as a substrate. The calorimetric value L of a black toner having a specific surface area of 100 to 300 m ² / g, preferably 120 to 250 m ² / g, more preferably 150 to ²⁰⁰ m ² / g, and 2% by mass added externally. The increase in value ΔL is 0.8 or less with respect to the black toner before external addition.

(Alkoxysilane coating amount and specific surface area)
When the coating amount of alkoxysilane is less than 50% by mass, the degree of hydrophobicity is lowered, which is not preferable. Moreover, when it exceeds 200 mass%, aggregation will occur and the specific surface area will be less than 100 m ² / g, which is not preferable.

(transparency)
When the hydrophobic orthotitanate fine particles of the present invention are externally added with 2% by mass to a black toner at a predetermined ratio described later, the increase ΔL in the colorimetric value L is 0. 0% with respect to the black toner before external addition. 8 or less. By being in this range, the fine particle powder is highly transparent, and there is an effect that the original color of the non-added toner is not contaminated.

(Hydrophobicity and triboelectric charge)
The hydrophobicity of the hydrophobic orthotitanate fine particles of the present invention is preferably 30 to 75%, and the triboelectric charge amount with respect to the iron powder is preferably −100 to −30 μC / g. Within this range, it can be used as an external additive suitable for a negatively chargeable toner. If the degree of hydrophobicity is less than 30%, moisture is likely to be adsorbed, and more than 75% is not preferable because the amount of alkoxysilane treated increases and aggregation becomes strong.

(Method for producing hydrophobic orthotitanate fine particles)
The hydrophobic orthotitanate fine particles of the present invention are typically treated with 50 to 200% by weight of alkoxysilane with respect to orthotitanic acid as a substrate, neutralized with acid, filtered and washed, and then 100 to 170. Obtained by drying at 0C.

(Method for producing orthotitanic acid fine particles)
The orthotitanic acid used as the base of the hydrophobic orthotitanic acid fine particles of the present invention is hydrolyzed by adding ice-cooled water to titanium tetrachloride, or a cold aqueous solution of titanium tetrachloride or titanium sulfate is neutralized with an alkali. Obtained by the method. As the alkali at this time, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate, ammonia and the like can be used, but the liquid temperature during neutralization needs to be kept at 30 ° C. or lower. . A temperature higher than 30 ° C. is not preferable because metatitanic acid is generated. The particle shape is indefinite, and the primary particle size according to the electron micrograph may be 0.01 to 0.1 μm.

(Method of hydrophobizing orthotitanate fine particles)
In order to hydrophobize the orthotitanic acid fine particles, the present inventors attempted monodispersion by pulverizing and dispersing the powder obtained by drying the orthotitanic acid fine particles serving as a base, and treating the alkoxysilane with an aqueous system. In this method, strong agglomeration was caused when the orthotitanic acid was dried. Therefore, although it could be made hydrophobic, the specific surface area was small, the dispersibility was inferior, it was not much different from conventional ultrafine titanium oxide, and the crystal structure belonged to titanium dioxide. Therefore, as a result of continuing investigations to solve this problem, by adding alkoxysilane in a slurry state and performing a coating treatment, orthotitanic acid is a solid-liquid solution even though it is orthotitanic acid which is a hydrate. The separated and dried powder had a high degree of hydrophobicity and a specific surface area, and was fine particles with good dispersibility that remained non-aggregated after drying. Moreover, it was found that even when 2% by mass of black toner was externally added, the blackness was not impaired.

  The alkoxysilane to be coated is preferably one having 3 to 10 carbon atoms in the hydrocarbon group R. Those having 1 or 2 carbon atoms are not preferred because the molecular chain length is short, so the degree of hydrophobicity is low, and the particles are not sufficiently separated during drying, causing aggregation and reducing dispersibility. On the other hand, those having 11 or more carbon atoms are not preferable because the molecular chain length is too long and the molecular chains are entangled and cause aggregation, and the specific surface area decreases. In order to increase the degree of hydrophobicity, an emulsion of a silicone oil such as polydimethylsiloxane and a titanate coupling agent are also effective. However, since the molecular chain is long, it is not preferable for the same reason. In addition, the alkoxysilane can be used in combination of two or more, and the alkoxysilane to be added is a coating treatment by using a pre-hydrolyzed solution in pure water or a solution obtained by adding alcohol to pure water. Can be done quickly.

  When alkoxysilane is added, it is preferably pH 1.5 or lower or pH 7 or higher, more preferably pH 0.8 to 1 or pH 8 to 9. By controlling the pH within the above range, aggregation of orthotitanic acid can be suppressed and the coating treatment with alkoxysilane can be promoted uniformly. In addition, after stirring and holding, neutralization is performed using an acid or an alkali so that the pH is preferably 4 to 8, and more preferably 5 to 7. The temperature of the slurry during the reaction is preferably 20 to 50 ° C, more preferably 30 to 40 ° C.

  Alkoxysilane has a general formula RnSiR′m (where R is an alkyl group, phenyl group, vinyl group, gridoxy group, mercapto group, methacryl group-containing hydrocarbon group, n is an integer of 1 to 3, R ′ is an alkoxy group, m Is an integer of 1 to 3, n + m = 4). For example, propyltrimethoxysilane, i-butyltrimethoxysilane, n-butyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyl Examples include trimethoxysilane, n-dodecyltriethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, 3-gridoxypropyltrimethoxysilane, etc., and hydrocarbon group R having 3 to 10 carbon atoms Is preferred.

The coating amount of alkoxysilane is 50 to 200% by mass, preferably 80 to 180% by mass, and more preferably 100 to 150% by mass with respect to the orthotitanic acid of the substrate. As described above, when it is less than 50% by mass, the degree of hydrophobicity is lowered, which is not preferable. Moreover, when it exceeds 200 mass%, aggregation will occur and the specific surface area will be less than 100 m ² / g, which is not preferable.

  Examples of the acid used for neutralization include hydrochloric acid, sulfuric acid, nitric acid, and acetic acid. Examples of the alkali include sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonia. For coating with good dispersion, hydrochloric acid, nitric acid, acetic acid, sodium hydroxide, and ammonia are preferred.

  The drying temperature after washing with water is 100 ° C to 170 ° C, preferably 110 ° C to 150 ° C. If it is lower than 100 ° C., the drying efficiency is poor and the degree of hydrophobicity is low. When the temperature is higher than 170 ° C., thermal decomposition of the hydrocarbon group occurs, causing discoloration and a decrease in the degree of hydrophobicity.

  Hereinafter, the present invention will be described in more detail with reference to examples. The following examples are given for illustrative purposes only, and the scope of the invention is not limited thereby.

[Manufacture of orthotitanate fine particles]
While stirring 5 L of 160 g / L sodium carbonate, neutralization reaction was performed by gradually adding a cold aqueous solution of 200 g / L titanium sulfate while maintaining the liquid temperature at 30 ° C. or lower so as to maintain the pH at 8.0. And orthotitanic acid was obtained. The usage amount of the cold aqueous solution of titanium sulfate was 1 L. The obtained orthotitanic acid was filtered and washed with water, and then water was added to the washed cake to form a slurry again.

[Example 1]
A slurry for 100 g of orthotitanic acid was collected, 5 mol / L sodium hydroxide was added, and the slurry pH 8.0 was kept at 35 ° C. while being heated and stirred, while stirring, 200 g of i-butyltrimethoxysilane hydrolysis solution. (100% by mass as i-butyltrimethoxysilane) was added, and the mixture was stirred and held for 4 hours. Then, 6 mol / L hydrochloric acid was added to neutralize to pH 6.5, followed by filtration and washing with water.

  The filtered and washed cake was dried at 170 ° C. and then finely pulverized by a jet type fine pulverizer to obtain the desired hydrophobic orthotitanic acid fine particles.

[Example 2]
In Example 1, except that 200 g of i-butyltrimethoxysilane hydrolyzed solution was changed to 300 g of i-butyltrimethoxysilane hydrolyzed solution (150% by mass as i-butyltrimethoxysilane), the same as in the case of the same example. By processing, the desired hydrophobic orthotitanate fine particles were obtained.

[Example 3]
The same treatment as in Example 2 was performed except that the neutralization pH was set to 5.5 in Example 2, and target hydrophobic orthotitanate fine particles were obtained.

[Example 4]
In Example 3, except that the drying temperature was set to 170 ° C., the same treatment as in the case was performed to obtain the desired hydrophobic orthotitanate fine particles.

[Example 5]
In Example 1, except that the slurry pH when adding the i-butyltrimethoxysilane hydrolysis solution was 9.0, the neutralization pH was 5.5, and the drying temperature was 130 ° C. The same treatment was performed to obtain the desired hydrophobic orthotitanate fine particles.

[Example 6]
In Example 5, except that the slurry pH at the time of adding 100 g (100% by mass) of i-butyltrimethoxysilane was 1.0, the same treatment as in the case of the same example was carried out to obtain the desired hydrophobic ortho Titanate fine particles were obtained.

[Example 7]
In Example 6, except that 100 g of i-butyltrimethoxysilane was changed to 70 g (70% by mass) of i-butyltrimethoxysilane, treatment was performed in the same manner as in the same example to obtain the desired hydrophobic orthotitanate fine particles. Got.

[Example 8]
In Example 6, except that 100 g of i-butyltrimethoxysilane was changed to 50 g (50% by mass) of i-butyltrimethoxysilane and the drying temperature was 100 ° C. Hydrophobic orthotitanate fine particles were obtained.

[Example 9]
In Example 6, except that 100 g of i-butyltrimethoxysilane was changed to 150 g (150% by mass) of n-propyltrimethoxysilane, the treatment was performed in the same manner as in the same example to obtain the desired hydrophobic orthotitanic acid. Fine particles were obtained.

[Example 10]
In Example 6, except that 100 g (100% by mass) of i-butyltrimethoxysilane was changed to 150 g (150% by mass) of n-hexyltrimethoxysilane, treatment was performed in the same manner as in the same example to obtain the target hydrophobicity. Orthotitanic acid fine particles were obtained.

[Example 11]
In Example 6, except that 100 g (100% by mass) of i-butyltrimethoxysilane was changed to 262.5 g of n-octyltriethoxysilane hydrolysis solution (150% by mass as n-octyltriethoxysilane), The same treatment as in the case was performed to obtain the desired hydrophobic orthotitanate fine particles.

[Example 12]
In Example 6, 100 g (100% by mass) of i-butyltrimethoxysilane was changed to 350 g of n-decyltrimethoxysilane hydrolysis solution (200% by mass as n-decyltrimethoxysilane). The same treatment was performed to obtain the desired hydrophobic orthotitanate fine particles.

[Example 13]
In Example 6, except that 100 g (100 mass%) of i-butyltrimethoxysilane was combined with 100 g (100 mass%) of i-butyltrimethoxysilane and 10 g (10 mass%) of fluorosilane, the same example In the same manner as above, the desired hydrophobic orthotitanate fine particles were obtained.

[Comparative Example 1]
In Example 3, in place of 150 g (150% by mass) of i-butyltrimethoxysilane, polydimethylsiloxane emulsion (SM-7060 manufactured by Toray Dow Corning Silicone Co., Ltd.) was changed to 50% by mass as silicone oil and dried. Hydrophobic orthotitanate fine particles were obtained by the same treatment as in the same example except that the temperature was 150 ° C.

[Comparative Example 2]
In Example 6, except that 100 g (100% by mass) of i-butyltrimethoxysilane was changed to ethyltrimethoxysilane (R has 2 carbon atoms), the same treatment as in the same example was performed to obtain orthotitanate fine particles. Obtained.

[Comparative Example 3]
The orthotitanic acid slurry of Example 1 was adjusted to pH 6.5 by adding a 5 mol / L sodium hydroxide aqueous solution, then filtered and washed with water. The hydrophilic titanium dioxide powder obtained by drying at 110 ° C. and calcining at 600 ° C. was returned to water, and finely pulverized into a slurry using a wet ball mill. Subsequently, 100 g of slurry as TiO ₂ was collected from this, and 6 mol / L hydrochloric acid was added with stirring to adjust the pH to 1.2. Next, 5 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 2.0, and the mixture was kept warm at 35 ° C., 20 g of i-butyltrimethoxysilane was added with stirring, and the mixture was stirred and maintained for 30 minutes. Was added, neutralized to pH 6.0, filtered and washed with water.

  The filtered and washed cake was dried at 170 ° C. and then finely pulverized by a jet type fine pulverizer to obtain hydrophobic titanium dioxide fine particles.

[Comparative Example 4]
A 5 mol / L aqueous sodium hydroxide solution was added to the metatitanic acid slurry while stirring, and the mixture was stirred and maintained at pH 9.0 for 1 hour. Then, the mixture was neutralized to pH 5.5 with 6 mol / L hydrochloric acid, filtered and washed with water. Water was added to the washed cake to form a slurry again, and 6 mol / L hydrochloric acid was added to pH 1.2 while stirring to maintain a pH of 1.2 for 2 hours, followed by peptization. From this peptized slurry, 100 g of metatitanic acid was fractionated, and 5 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 2.5. While maintaining the temperature at 35 ° C. while stirring, 50 g of i-butyltrimethoxysilane (50 mass) %) Was added and neutralized to pH 6.0 by adding a 5 mol / L aqueous sodium hydroxide solution, followed by filtration and washing with water.

  The cake after filtration and washing with water was dried at 170 ° C. and then finely pulverized by a jet type fine pulverizer to obtain hydrophobic metatitanic acid fine particles.

  The measurement results of the samples obtained in Examples 1 to 13 and Comparative Examples 1 to 4 are shown in Table 1. These measured values are values measured in the following manner.

(Specific surface area)
It measured by BET method using Gemini 2360 made from MICROMETORICS INSTRUMENT CO.

(Hydrophobicity)
An aqueous solution containing 2.5% by mass of methanol was prepared in a test tube, a small amount of fine powder was added, and the presence or absence of sedimentation was confirmed. As the degree of hydrophobicity, precipitation mass% to sedimentation mass% were displayed as the degree of hydrophobicity (%). Hydrophobic means that the degree of hydrophobicity is at least 10% or more.

(Frictional charge)
Fine powder and reduced iron powder (TSV-100, manufactured by Powder Tech Co., Ltd.) were mixed and measured with a blow-off powder charge measuring device (TB-200, manufactured by Toshiba Chemical Corporation).

(transparency)
50 g of black toner and 1 g of fine particles were collected and mixed for 3 minutes using a sample mill SK-M manufactured by Kyoritsu Riko Co., Ltd. 5 g of the external toner was placed in an aluminum ring placed on a molding die, and the molding die was set in a small hydraulic automatic press machine and press molded. The molded sample was measured using an SM color computer MODEL SM-7 manufactured by Suga Test Instruments Co., Ltd. It was determined that the smaller the increase ΔL in the colorimetric value L of the black toner before external addition, the more the original color of the toner is not contaminated, that is, the transparency of the fine particle powder is high.

(Identification by X-ray diffraction)
Identification was carried out under the measurement conditions of a target Cu, 50 kV × 200 mA with a rotor flex RAD-RC manufactured by Rigaku Denki Kogyo.

＊１） ６００℃で加熱（焼成）し、オルトチタン酸を二酸化チタンとしたもの。
＊２）２質量％を外添した黒色トナーのＬ値−未外添黒色トナーのＬ値(１２．６)

* 1) Heated (baked) at 600 ° C. to make orthotitanic acid titanium dioxide.
* 2) L value of black toner with 2% by mass added externally-L value of non-externally added black toner (12.6)

From the results of Table 1, the hydrophobic orthotitanate fine particles obtained in Examples 1 to 13 have a specific surface area of 100 to 300 m ² / g, a degree of hydrophobicity of 30 to 75%, and friction against iron powder. It can be seen that the charge amount is −100 to −30 μC / g, and ΔL is 0.8 or less with respect to the black toner before external addition.

  From the above, it was confirmed that hydrophobic orthotitanate fine particles useful as an electrophotographic toner or the like were obtained.

2 is an X-ray diffraction chart of pigment grade anatase-type titanium dioxide, metatitanic acid, orthotitanic acid heated to 600 ° C. to form titanium dioxide, and orthotitanic acid.

Claims (5)

The substrate is orthotitanic acid coated with 50 to 200% by mass of alkoxysilane, no X-ray diffraction peak is observed, the specific surface area is 100 to 300 m ² / g, and 2% by mass is externally added. Hydrophobic orthotitanate fine particles, wherein the increase ΔL in the colorimetric value L value of the black toner is 0.8 or less compared to the black toner before external addition.   The alkoxysilane is represented by the general formula RnSiR′m (R: hydrocarbon group, R ′: alkoxy group, n: an integer of 1 to 3, m: an integer of 1 to 3, n + m = 4). The hydrophobic orthotitanate fine particles according to claim 1.   The hydrophobic orthotitanate fine particles according to claim 2, wherein the hydrocarbon group R of the alkoxysilane has 3 to 10 carbon atoms.   The hydrophobic orthotitanate fine particles according to claim 1, wherein the degree of hydrophobicity is 30 to 75%, and the triboelectric charge amount with respect to iron powder is -100 to -30 µC / g.   An electrophotographic toner comprising the hydrophobic orthotitanate fine particles according to any one of claims 1 to 4.

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