JP2013249215A - Surface treatment method of hydrophilic sol-gel silica particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hydrophobic sol-gel silica powder having high hydrophobicity and low loss on drying and containing a modest amount of carbon.SOLUTION: In a dry surface treatment, an inert gas and a hydrophobizing agent are fed into a reaction vessel in a state where hydrophilic sol-gel silica particles are housed, and the silica particles are surface-treated while being fluidized. The linear velocity of the inert gas fed into the reaction vessel per cross-sectional area of the reaction vessel is set to be in the range of 1-12 m/s, the bulk density of the hydrophilic sol-gel silica particles during the surface treatment is set to be in the range of 0.6-0.9 time the bulk density of the silica particles when left at rest in the reaction vessel, and the bulk density of the silica particles at the heat treatment in the reaction vessel is set to be in the range of 150-300 g/L.

Description

  The present invention relates to a surface treatment method for obtaining hydrophobic sol-gel silica powder by hydrophobizing hydrophilic sol-gel silica silica particles by a dry method. In the present specification, the “surface treatment of particles by a dry method” refers to a surface treatment performed without immersing or suspending treated particles in a liquid, for example, a method of contacting particles with a vapor of a treatment compound, Examples thereof include a method in which particles are made into a fluid state and a liquid or solution of a treatment compound is sprayed or dropped.

  Fine silica powder is widely used by adding to electrostatic charge developing toners for copiers, printers, facsimiles, plate making systems, etc. by modifying and treating the surface to improve chargeability and hydrophobicity. Yes. The fine silica powder as an external toner additive is intended to improve toner flowability, control charging properties, long-term storage stability, control cleaning properties, control developer deterioration behavior, and the like.

  Conventionally, the silica powder used for such a use is generally used as a fluidity improver for imparting fluidity to a toner, and silica particles obtained by hydrophobizing fine silica particles produced by a dry method are generally used. When silica particles produced by this dry method are subjected to a surface treatment with a predetermined organic substance, the surface treatment is generally carried out by a dry method in order to maintain high dispersibility of the silica particles (for example, patents). Reference 1). However, the silica powder produced by the method of Patent Document 1 can only obtain a fine powder having an average primary particle size of 7 to 30 nm. On the other hand, silica powder produced by hydrophobizing silica particles produced by a wet method is also used as a toner external additive. Among them, a hydrophobic sol-gel silica powder produced by hydrophobizing so-called sol-gel silica particles produced by a sol-gel method is particularly used. Unlike the silica powder disclosed in Patent Document 1 above, it is possible to produce a large particle size product having a primary particle size of about 100 nm, and the particle size is uniform, and further in a form closer to monodispersion. The aggregated particle state is maintained. Because of these advantages, the sol-gel silica powder is used as a toner external additive, and a spacer for preventing the toner external additive having a small particle diameter from being embedded in the toner by taking advantage of the characteristics of the large particle diameter. It is widely used as a material for producing an effect.

Generally, toner is agitated inside a copying machine or the like, and is charged by friction with a carrier or the like. The developing function is manifested by the highly controlled chargeability. However, when the toner is continuously stirred in the apparatus for a long time, the strong frictional force resulting from the stirring becomes a stress and the deterioration of the toner proceeds. For example, the toner external additive is buried in the toner surface, thereby losing the intended function as a contact point between the toner surface and the external environment.
However, as described above, the mechanical load on the toner has increased in recent years, and the hardness of the toner base has decreased due to the softening of the binder resin of the toner. As a result, the importance of measures for preventing the toner external additives from being buried in the toner is increasing.

  Such embedding of the toner additive is particularly noticeable when the primary particle diameter of the toner additive powder particles is less than 20 nm. For the purpose of preventing this, particles of toner external additive powder having primary particles of 100 nm or more may be used as a supplementary spacer. In particular, hydrophilic sol-gel silica particles produced by a sol-gel method using silicon alkoxide as a raw material are preferably used because they have a uniform particle size and are spherical and have a high fluidity-imparting effect.

  In recent years, toner particles have become smaller in size due to higher image quality of electrophotography, and in addition to this, the mechanical load on the toner has been increasing due to higher printing speed and colorization of electrophotography. Therefore, control of the deterioration behavior of the toner is particularly important in order to ensure the durability of the toner performance over time. However, on the other hand, for the purpose of shortening the printing standby time and saving energy, the binder resin used for the toner, that is, the toner base resin, is required to have a low temperature fixability, so the hardness of the toner base resin tends to be softened. is there.

As a method for hydrophobizing sol-gel silica particles produced by this sol-gel method, hydrophilic spherical sol-gel silica particles obtained by hydrolyzing and condensing hydrocarbylsilane or its partial hydrolysis-condensation product or a combination thereof are made hydrophobic. The average primary particle size including the step of heat-treating the spherical spherical sol-gel silica fine particles obtained by heat treatment to obtain heat-treated spherical sol-gel silica fine particles and the step of hydrophobizing the heat-treated spherical sol-gel silica fine particles is 0. A method for producing 01 to 5 μm highly hydrophobic spherical sol-gel silica fine particles has been disclosed (see, for example, Patent Document 2).
The hydrophobizing treatment of the hydrophilic spherical sol-gel fine particles shown in Patent Document 2 is performed by a wet method. In this method, for example, an aqueous dispersion containing hydrophilic sol-gel silica particles, a hydrocarbon solvent, an aromatic solvent, an organic solvent dispersion such as a ketone solvent dispersion, or a mixed solvent dispersion of a water-hydrophilic organic solvent. In the liquid, the following general formula:
R ³ ₃ SiNHSiR ³ ₃
Wherein R ³ is the same or different and is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, or the following general formula:
R ³ ₃ SiX
(Wherein R ³ is the same as above, and X is an OH group or a hydrolyzable group), or a combination thereof, and the hydrophilic sol-gel silica particle surface The reactive groups remaining in the substrate are hydrophobized by triorganosilylation.

JP-A-11-92687 (Claim 1, paragraph [0006], paragraph [0051]) JP 2007-99582 (Claim 1, paragraph [0040])

  When the silica powder obtained by hydrophobizing silica particles produced by the sol-gel method disclosed in Patent Document 2 is applied to the toner external additive, the sol-gel silica particles contain water or an organic solvent due to the production method. The silica particles are very easily aggregated and have a high bulk density. Therefore, when a surface treatment is attempted on the sol-gel silica particles by a dry method, the sol-gel silica silica particles cannot be sufficiently dispersed, and thousands of particles are formed together with the primary particles. In many cases, agglomerates of silica particles are formed and it is difficult to perform uniform surface treatment.

  In addition, when applying silica powder obtained by hydrophobizing sol-gel silica particles produced by the wet sol-gel method disclosed in Patent Document 2 to the toner external additive, the hydrophobizing agent is dispersed in the solvent together with the sol-gel silica particles. In order to surface-treat the silica particles, generally, a long process is required because processes such as filtration and drying are required. In addition, since some hydrophobizing agents are generally decomposed by moisture, there is a problem that it is difficult to obtain sufficient hydrophobicity. This defect not only prevents the aggregate of silica particles from sufficiently serving as an external toner additive, but also causes other adverse effects due to the large aggregate. Further, when the surface is modified, since the hydrophobizing agent cannot sufficiently react to the inside of the aggregate of silica particles, there is a problem that unreacted processing spots are generated and it is difficult to hydrophobize.

  For the above reasons, an effective surface treatment method for hydrophobizing hydrophilic sol-gel silica particles produced by a wet method by a dry method has not been found so far.

  As a result of intensive studies to solve the above problems, the present inventors have performed a surface treatment for hydrophobizing hydrophilic sol-gel silica particles by a dry method according to a specific range of bulk density, a specific range of gas flow rate, and stirring conditions. When carried out, the inventors have found a production method for obtaining a hydrophobic sol-gel silica powder having high hydrophobicity, low loss on drying and containing an appropriate carbon content.

  In order to solve the problems of the surface treatment method of sol-gel silica particles conventionally produced by a wet method, the present invention is a hydrophobic sol-gel silica having high hydrophobicity and low loss on drying and containing an appropriate carbon content. An object of the present invention is to provide a surface treatment method for hydrophilic sol-gel silica particles to obtain a powder.

A first aspect of the present invention is to provide hydrophilic sol-gel silica particles obtained by hydrolyzing and condensing a silicon alkoxide represented by the following general formula (1) or a partial hydrolysis-condensation product thereof or a combination thereof. In the method of surface treatment with a hydrophobizing agent, the surface treatment is performed by supplying an inert gas and the hydrophobizing agent into the reaction vessel in a state where the hydrophilic sol-gel silica particles are placed in the reaction vessel. A dry surface treatment performed by flowing particles, wherein a linear velocity per cross-sectional area of the reaction vessel of the inert gas supplied into the reaction vessel is set in a range of 1 to 12 m / s, and the surface treatment The bulk density of the hydrophilic sol-gel particles at the time is in the range of 0.6 to 0.9 times the bulk density of the hydrophilic sol-gel silica particles when left in the reaction vessel And a hydrophobic sol-gel silica powder having a hydrophobic surface is obtained by setting the bulk density of the hydrophilic sol-gel silica particles during the surface treatment in the reaction vessel in the range of 150 to 300 g / L. This is a surface treatment method for hydrophilic sol-gel silica particles.
Si (OR ¹ ) ₄ (1)
(However, R1 is the same or different C1-C4 alkyl group.)

  A second aspect of the present invention is the surface treatment method of the first aspect of the invention, wherein the hydrophilic sol-gel silica particles before the surface treatment have an average primary particle diameter in the range of 50 to 300 nm. is there.

  A third aspect of the present invention is a hydrophobic sol-gel silica powder surface-treated according to the invention of the first or second aspect, having a loss on drying of 0.8% by mass or less, and a hydrophobization rate of 70 to 100 %, And the content of carbon contained in the organic solvent extract is 0.001 to 0.03% by mass per unit area.

  A fourth aspect of the present invention is a toner external additive for developing electrostatic images obtained from the hydrophobic sol-gel silica powder of the third aspect of the present invention.

  According to the first aspect of the present invention, when the hydrophilic sol-gel silica particles are surface-treated with a hydrophobizing agent, the linear velocity per cross-sectional area of the reaction vessel of the inert gas supplied into the reaction vessel is set to 1. The bulk density of the hydrophilic sol-gel particles at the time of the surface treatment is set in the range of ˜12 m / s, and the bulk density of the hydrophilic sol-gel silica particles when left in the reaction vessel is 0.6 to 0. By setting the range of 9 times and setting the bulk density of the hydrophilic sol-gel silica particles during the surface treatment in the reaction vessel in the range of 150 to 300 g / L, the silica particles are sufficiently dispersed in the reaction vessel. Hydrophobic sol-gel silica with high hydrophobicity, low loss on drying, and moderate carbon content, which can react well with hydrophobizing agents without making silica particle aggregates Powder Obtained.

  According to the second aspect of the present invention, since the average primary particle diameter of the hydrophilic sol-gel silica particles before the surface treatment is in the range of 50 to 300 nm, the smaller particle diameter is utilized by taking advantage of the characteristics of the large particle diameter. A spacer effect for preventing the toner external additive from being embedded in the toner can be exhibited.

  According to the third aspect of the present invention, since the loss on drying is in the above range, when it is used as an external toner additive, it prevents moisture before the surface treatment or generation of volatile components of the organic solvent due to the surface treatment. The charge applied to the toner can be stabilized. In addition, since the hydrophobization rate is in the above range, sufficient environmental stability with the same charge can be obtained and silica particles can flow smoothly, and the carbon content (carbon amount) contained in the organic solvent extract can be measured in units. Since it is in the above range per area, surface treatment for hydrophobizing with organic substances is sufficiently performed, toner charging stability and toner dispersibility are improved, and toner aggregation can be prevented.

  The fourth aspect of the present invention is a toner external additive for developing an electrostatic charge image obtained from the hydrophobic sol-gel silica powder of the third aspect of the present invention, so that the charging stability of the toner and the dispersibility of the toner are improved. It is possible to prevent further toner aggregation and the like.

It is a schematic sectional drawing of the 1st reaction container used for the dry surface treatment of this invention. It is a schematic sectional drawing of the 2nd reaction container used for the dry surface treatment of this invention. It is a SEM photograph (10,000 times) at the time of mixing the hydrophobic sol-gel silica powder (Example 2) which performed the dry surface treatment of this invention, and a toner. It is a SEM photograph (10,000 times) when the hydrophobic sol-gel silica powder (Comparative Example 2) subjected to the dry surface treatment of the present invention and the toner are mixed.

The present invention is a surface treatment method for obtaining a hydrophobic sol-gel silica powder by uniformly and sufficiently imparting a hydrophobizing agent to hydrophilic sol-gel silica particles having a predetermined particle size in a reaction vessel by dry surface treatment.
The dry surface treatment of the present invention is a surface treatment performed without immersing or suspending the hydrophilic sol-gel silica particles to be hydrophobized in a liquid, and the hydrophilic sol-gel silica particles are treated with a hydrophobizing agent under flow or stirring. The surface treatment to be sprayed or the hydrophobizing agent vapor is introduced under flow or stirring of the hydrophilic sol-gel silica particles. At this time, after adding a hydrophobizing agent, it may be heated as necessary. You may supply not only 1 type but 2 or more types of hydrophobizing agents. When two or more types of hydrophobizing agents are supplied, two or more types of hydrophobizing agents may be reacted simultaneously or sequentially.

  In order to perform the above dry surface treatment uniformly and satisfactorily, the shape of the reaction vessel for dry surface treatment is preferably a cylindrical or substantially spherical shape installed vertically, and hydrophilic sol-gel silica particles It is necessary to have a means for fluidizing. Moreover, it is preferable to equip the heating means for reaction promotion suitably. A dry surface treatment method using a cylindrical reaction vessel as shown in FIG. 1 as a first embodiment of the present invention, and a spherical reaction vessel as shown in FIG. 2 as a second embodiment of the present invention. The dry surface treatment method used will be described below.

<First Embodiment>
First, the hydrophilic sol-gel silica particles to be hydrophobized are obtained by hydrolysis and condensation of a silicon alkoxide represented by the following general formula (1) or a partial hydrolysis-condensation product thereof or a combination thereof.
Si (OR ¹ ) ₄ (1)
(Wherein, R ¹ is the same or different alkyl group of 1 to 4 carbon atoms.)
In the general formula (1), R1 is a monovalent hydrocarbon group having 1 to 4 carbon atoms, particularly preferably 1 to 2. Examples of the monovalent hydrocarbon group represented by R1 include a methyl group, an ethyl group, a propyl group, a butyl group, and a phenyl group, preferably a methyl group, an ethyl group, a propyl group, and a butyl group, and particularly preferably Examples thereof include a methyl group and an ethyl group. Examples of the tetrafunctional silane compound represented by the general formula (1) include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, tetraphenoxysilane, and the like. Methoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, particularly preferably tetramethoxysilane and tetraethoxysilane. Examples of the partial hydrolysis-condensation product of the tetrafunctional silane compound represented by the general formula (1) include methyl silicate and ethyl silicate.

  Among the hydrophilic sol-gel silica particles obtained by the above method, hydrophilic sol-gel silica particles having an average primary particle diameter in the range of 50 to 300 nm are preferable. When the average primary particle size is less than 50 nm, the surface-treated hydrophobic sol-gel silica powder particles become smaller, so that there is a problem that the spacer effect is substantially reduced or the toner is easily embedded in the toner, whereas it exceeds 300 nm. In such a case, there is a problem in that separation from the toner surface is likely to occur, and as a result, a large problem is often caused in image characteristics such as insufficient image characteristics or white spots in an image. As a result, if the average primary particle diameter is out of the range, the toner is not suitable as an external additive for the toner. Further, the average primary particle diameter is preferably 80 to 180 nm. This is because the above problems can be further reduced.

Next, surface treatment for hydrophobizing the prepared hydrophilic sol-gel silica particles 14 is performed by the reaction vessel 1 of the fluidized bed shown in FIG.
As shown in FIG. 1, a fluidized bed reaction vessel 1 includes a cylindrical tube body 2 having both ends closed and extending in the vertical direction, and hydrophilic sol-gel silica particles 14 connected to the center of the side surface of the tube body 2. A raw material introduction tube 3 to be introduced into the main body 2, a rectifying plate 4 provided near the lower end in the cylindrical main body 2 and receiving the hydrophilic sol-gel silica particles 14, a hydrophobizing agent and an inert gas connected to the bottom wall 2 a of the cylindrical main body 2 And an introduction pipe 5 for introducing gas from the introduction pipe 5 into the cylinder main body 2.

As the hydrophobizing agent, an organosilicon compound is used. There are no particular restrictions on the organosilicon diameter compound, but general examples include alkylsilazane compounds such as hexamethyldisilazane, dimethyldimethoxysilane, diethyldiethoxysilane, trimethylmethoxysilane, methyltrimethoxysilane, and butyltrimethoxy. Alkyl alkoxysilane compounds such as silane, chlorosilane compounds such as dimethyldichlorosilane and trimethylchlorosilane, silicone oil, silicone varnish, and the like can be used. These hydrophobizing agents may be used alone or in a combination of two or more.
Examples of the inert gas include helium, nitrogen, and argon as general examples. When industrially used, nitrogen gas is preferred from the viewpoint of cost.

  The rectifying plate 4 is formed in a porous or net-like shape having many pores smaller than the particle diameter of the hydrophilic sol-gel silica particles 14 and rectifies the inert gas vertically upward. Further, a lower take-out pipe 6 is connected to a position slightly higher than the rectifying plate 4 on the side surface of the cylinder main body 2, and a height of the side face of the cylinder main body 2 is located between the raw material introduction pipe 3 and the lower take-out pipe 6. Thus, the upper take-out pipe 7 is connected.

  The lower take-out pipe 6 is provided with a manual valve 8 for opening and closing the pipe, and the upper take-out pipe 7 is provided with a flow rate adjusting valve 9 for adjusting the flow rate of the hydrophobic sol-gel silica powder passing through the pipe. Further, the lower take-out pipe 6 and the upper take-out pipe 7 merge to form a collective take-out pipe 10. Further, a bag filter 11 for preventing the hydrophilic sol-gel silica particles 14 from being discharged together with the exhaust gas is provided on the upper portion of the cylinder body 2, and an exhaust pipe for discharging the exhaust gas is provided on the upper wall 2b of the cylinder body 2. 12 is connected. With the manual valve 8 and the flow rate adjusting valve 9 closed, a predetermined amount of hydrophilic sol-gel silica particles 14 having an average primary particle diameter in the range of 50 to 300 nm are supplied from the raw material introduction tube 3 to the cylinder body 2. A hydrophobizing agent and an inert gas are introduced into the cylinder body 2.

Here, the linear velocity V per cross-sectional area of the reaction vessel of the inert gas sent to the reaction vessel 1 of the fluidized bed is set in the range of 1 to 12 m / s. When the linear velocity is less than 1 m / s, there is a problem that it is difficult to obtain a sufficient stirring effect due to the inert gas of the particles or powder. On the other hand, when the linear velocity exceeds 12 m / s, the particles or powder is scattered. However, there is a problem that uniform surface treatment is not performed. The linear velocity V (m / s) per cross-sectional area of the reaction bed 1 of the fluidized bed of the inert gas depends on the flow rate Q (m ³ / s) of the inert gas to be introduced and the cylinder body 2 of the reaction vessel 1 of the fluidized bed. The ratio Q / S with the cross-sectional area S (m ² ) of the inner wall can be calculated. The flow rate Q (m3 / s) of the inert gas can be controlled by installing a gas flow controller (not shown) between the introduction pipe 5 and an inert gas tank (not shown). .

Hydrophilic sol-gel silica particles 14 are supplied into the fluidized bed reaction vessel 1 having such a configuration through the introduction tube 3. In a state where the hydrophilic sol-gel silica particles 14 are put in the reaction vessel 1 of a fluidized bed, the linear velocity V is set to 1 to 12 m / s, and the inert gas rectified vertically by the rectifying plate 4 is used as a hydrophobizing agent. Supply with. The reaction vessel is preferably heated to 150 to 400 ° C. by a heating means (not shown). Thereby, while the hydrophilic sol-gel silica particles 14 form a fluidized state in the reaction vessel 1 of the fluidized bed, each silica particle reacts with the hydrophobizing agent to be hydrophobized.
At this time, in the present invention, the bulk density of the hydrophilic sol-gel silica particles during surface treatment, that is, the fluidized hydrophilic sol-gel silica particles in the fluidized bed reaction vessel 1 is set to 0.6 to 0 as the bulk density of the hydrophilic sol-gel silica particles. .9 times, preferably 0.7 to 0.9 times, and the flow rate of the inert gas is controlled to adjust the bulk density of the hydrophilic sol-gel silica particles flowing in the reaction vessel to 150 to It is set in the range of 300 g / L, preferably in the range of 200 to 300 g / L.

At this time, when the surface treatment is performed, the bulk density of the powder is 0.6 to 0.9 times the bulk density at the time of standing. On the other hand, when the ratio exceeds 0.9, uniform surface treatment cannot be performed, and as a result, sufficient hydrophobicity cannot be obtained. Further, the bulk density of the hydrophilic sol-gel silica particles that are flowing in the reaction vessel is in the range of 150 to 300 g / L. If the bulk density is less than 150 g / L, there is a problem that powder scattering occurs during the surface treatment. On the other hand, if it exceeds 300 g / L, there is a problem that the cohesive force of the powder is too strong, and in any case, uniform surface treatment is difficult to be performed. The bulk density of the powder can be calculated from the weight charged with the powder and the volume occupied by the charged powder in the reaction vessel.
At this time, the bulk density of the hydrophilic sol-gel silica particles 14 when left in the fluidized bed reaction vessel 1 is constant in the hollow bottom and side wall inner diameter of the fluidized bed reaction vessel 1. The height of the fluid state of the silica particles is measured from the horizontal height. In addition, since the upper surface of the silica particles in the fluidized state does not necessarily become flat, the height of the fluidized surface ascertained from the wall surface in the reaction vessel 1 of the fluidized bed is measured a plurality of times, and the bulk density is calculated from the average thereof. taking measurement.

  Thus, according to the first embodiment of the present invention, the bulk density of the hydrophilic sol-gel silica particles 14 when standing in the fluidized bed reaction vessel 1 and the fluidized bed in the reaction vessel 1 are flowing. By setting the range of the bulk density of the hydrophilic sol-gel silica particles 14 based on the linear velocity of the inert gas flow, the silica particles that are surface-treated and hydrophobized by the hydrophobizing agent are well isolated in a fluidized state. As a result, the hydrophobizing agent reacts sufficiently and uniformly with the hydrophilic sol-gel silica particles 14, and the hydrophilic sol-gel silica particles 14 become hydrophobic sol-gel silica powders whose particle surfaces are well modified. The hydrophobic sol-gel silica powder can be discharged from the fluidized bed reaction vessel 1 by opening the manual valve 8.

<Second Embodiment>
In the second embodiment, the same powder as the hydrophilic sol-gel silica particles 14 prepared in the first embodiment is subjected to a surface treatment using the reaction vessel 15 shown in FIG.
As shown in FIG. 2, the reaction vessel 15 has a spherical four-necked flask with first to fourth short tubes 15 a to 15 d connected to the upper part. The stirrer shaft 16a of the stirrer 16 is rotatably inserted into the first short tube 15a of the four-necked flask, the thermometer 17 is inserted into the second short tube 15b, and the third short tube 15c is further hydrophobic. An introduction pipe 18 for introducing an inert gas into the agent is inserted. A stirring blade 16b is attached to the lower end of the stirring shaft 16a. After the hydrophilic sol-gel silica particles 14 are put into the four-necked flask, the hydrophilic sol-gel silica particles 14 are stirred by the stirrer 16 and at the same time, the hydrophobizing agent and the inert gas are introduced from the introduction pipe 18. At this time, the flow rate of the inert gas is adjusted so as to keep the temperature of the hydrophilic sol-gel silica particles 14 at 120 to 350 ° C. while watching the thermometer 17 and to adjust the bulk density of the silica particles described later. Further, the inert gas after the hydrophilic sol-gel silica particles 14 are hydrophobized is discharged from the fourth short tube 15d. The fourth short tube 15d is preferably provided with a filter (not shown) for preventing the hydrophilic sol-gel silica particles 14 from being discharged together with the inert gas.

In the second embodiment, a predetermined amount of hydrophilic sol-gel silica particles 14 having the same average primary particle diameter as in the first embodiment are introduced into a four-necked flask that is a spherical reaction vessel, and these four Hydrophobizing agent is added to the mouth flask while flowing the inert gas, and the hydrophilic sol-gel silica particles 14 are hydrophobized by the surface treatment method of the present invention by flowing the hydrophilic sol-gel silica particles 14 for a predetermined time. it can.

  In the second embodiment, the shape of the reaction vessel is different from the shape of the reaction vessel (FIG. 1) of the first embodiment, but basically the hydrophilic sol-gel silica particles 14 of the hydrophobizing agent as in the first embodiment. The surface treatment method is performed in the same manner. In the first embodiment, the flow of the hydrophilic sol-gel silica particles 14 is created by supplying an inert gas, whereas in the second embodiment, the above-described operation is performed by rotating the stirring blade 16b together with the supply of the inert gas. Creating a flow. For this reason, in order to set the bulk density within the range of the present invention, the supply amount of the inert gas and the rotation speed of the stirring blade are controlled. Since the upper central portion of the fluid state of the hydrophilic sol-gel silica particles 14 is depressed downward along the stirring shaft 16a of the stirring blade 16b, the bulk density of the silica particles during the flow can be understood from the wall surface in the reaction vessel 15. It is calculated by calculating from the height of the convex portion and the average height of the flow portion concave portion of the stirring shaft 16a in the central portion. Moreover, in 2nd Embodiment, the cross-sectional area of the flask which is a reaction container when calculating | requiring the linear velocity of an inert gas is taken as the cross-sectional area equivalent to the maximum diameter of a flask.

  Furthermore, in the first embodiment or the second embodiment, the hydrophobizing agent may be reacted with the hydrophilic sol-gel silica particles while being sprayed or vaporized and heated while maintaining the fluid state. At this time, water, amine, and other catalysts may be used. Also in this case, it is desirable to carry out in an inert gas atmosphere such as nitrogen. Alternatively, a hydrophobizing agent is dissolved in a solvent, mixed and dispersed with hydrophilic sol-gel silica particles, and then subjected to a heat treatment as necessary to obtain a hydrophobic sol-gel silica powder by adopting the dry method as described above. You can also. In this case, the heat treatment conditions are not particularly limited, but generally, a heating temperature of 120 to 350 ° C. and a heating time of about 10 to 200 minutes are employed. If the heating temperature is less than 120 ° C, sufficient surface treatment of the organosilicon compound is not performed and high hydrophobicity cannot be obtained. On the other hand, if the heating temperature exceeds 350 ° C, the organosilicon compound may partially decompose. Because there is.

Next, the characteristics of the hydrophobized silica powder obtained by the present invention will be described.
First, the loss on drying of the hydrophobized silica powder obtained in the present invention is preferably 0.8% by mass or less. This loss on drying is measured from the change in weight before heating after heating at 105 ° C. for 2 hours. If the weight loss after drying exceeds 0.8% by mass, water and solvent during the surface treatment for hydrophobization remain in the hydrophobic silica powder, and charge stability or external toner additives When used as, there is a problem such as emission of volatilization and individual components, which is not preferable. The loss on drying is preferably 0.6% by mass or less. This is because the above problems are further prevented.

  The hydrophobicity of the hydrophobic silica powder obtained in the present invention is preferably in the range of 70 to 100%. This hydrophobicity is related to the stability of the charge, and if the hydrophobicity is less than 70%, there is a problem that sufficient environmental stability of the charge and fluidity of the silica particles cannot be obtained during the surface treatment, In order to exceed 95%, enormous energy and time are required for the hydrophobization treatment. The hydrophobicity is preferably in the range of 95 to 100%. This is because the above problems are further prevented.

Furthermore, the carbon content contained in the organic solvent extract of the hydrophobic silica powder obtained in the present invention is preferably in the range of 0.001 to 0.03% by mass / m ² per unit area. When the amount of carbon is less than 0.001% by mass / m ² per unit area, sufficient surface treatment with an organic substance is not performed, and there is a problem that generally charging stability and dispersibility tend to be insufficient. If it exceeds mass% / m ² , the organic content is too high, and on the contrary, aggregation or the like will occur and sufficient dispersibility may not be obtained in many cases. As a result, this hydrophobic silica powder is applied as an external additive for toner. However, there is a problem that sufficient image quality cannot be obtained, which is not preferable.

<Toner for electrostatic charge development>
Next, an electrostatic charge developing toner using a hydrophobic sol-gel silica powder as an external additive of the toner will be described.
The toner generally contains a small amount of a pigment, a charge control agent, and other external additives in addition to a thermoplastic resin (toner base resin), but in the present invention, the hydrophobic sol-gel silica powder of the present invention is blended. As long as the other components are used, the other components may be the same as those in the past, and may be either magnetic or non-magnetic one-component toner or two-component toner. Further, either negatively chargeable toner or positively chargeable toner may be used, and either monochrome or color may be used. There are no particular restrictions on the toner composition and its production method, and known compositions and methods may be employed.

  In the production of the electrostatic charge developing toner of the present invention, the amount of the hydrophobic sol-gel silica powder of the present invention added as an external additive of the electrostatic charge developing toner is such that a desired characteristic improving effect can be obtained. Although there is no particular limitation as long as it is present, it is preferable that 0.1 to 8.0% by mass of the hydrophobic sol-gel silica powder of the present invention is contained in the toner for electrostatic charge development. If the content of the hydrophobic sol-gel silica powder is less than 0.1% by mass, there is a problem that the effect of improving the durability and the stabilizing effect such as charging property cannot be sufficiently obtained by adding the hydrophobic sol-gel silica powder of the present invention. On the other hand, if the content of the hydrophobic sol-gel silica powder exceeds 8.0% by mass, the surface of the toner is completely covered and a large amount of excessive silica particles are still present, which may cause contamination in the apparatus such as the reaction vessel. This is because there is a possible defect.

  Furthermore, in the production of the electrostatic charge developing toner of the present invention, the hydrophobic sol-gel silica powder of the present invention as an external additive is not limited to being used alone, but may be used with other metal oxide powders depending on the purpose. You may use together. For example, the hydrophobic sol-gel silica powder of the present invention can be used in combination with dry silica particles surface modified by other methods, dry titanium particles surface modified or dry alumina particles surface modified.

Next, examples of the present invention will be described in detail together with comparative examples. In the following examples and comparative examples, nitrogen was used as an inert gas.
<Example 1>
In Example 1, the surface treatment was performed under the treatment conditions shown in Table 1 using a reaction vessel 15 of a four-necked flask having a volume of 3 L as shown in FIG. More specifically, 700 mL of methanol, 40 mL of ion-exchanged water, and 50 g of 28 mass% ammonia water were placed in a 3 L four-necked flask equipped with a dropping funnel (2), a stirrer, and a thermometer. While stirring the resulting solution at 35 ° C., 1590 g of tetraethoxysilane and 420 g of diluted ammonia water having a concentration of 5% by mass were added simultaneously, and tetraethoxysilane was added dropwise over 5 hours and diluted ammonia water over 4 hours. After completion of the dropwise addition, stirring was further continued for 2 minutes. Next, the solvent was distilled off under reduced pressure while heating the reaction solution to 70 ° C. with an evaporator to obtain a crude sol-gel silica powder. Next, the crude sol-gel silica powder was heat treated at 800 ° C. for 3 hours to obtain 450 g of hydrophilic sol-gel silica particles.
Next, the hydrophilic sol-gel silica particles were hydrophobized. Table 1 shows the characteristics of the hydrophilic sol-gel silica particles and the surface treatment conditions of the hydrophilic sol-gel silica particles.
The “hydrophobizing agent charge amount (parts)” shown in Table 1 is the mass part of the hydrophobizing agent added to the reaction vessel when the mass part of the hydrophilic sol-gel silica particles is 100. Specifically, Put 300 g of the above hydrophilic sol-gel silica particles into a 3 L four-necked flask and introduce 50 g of hexamethyldisilazane (hereinafter referred to as HMDS) as a hydrophobizing agent into the four-necked flask together with nitrogen gas in a nitrogen gas atmosphere. Then, the reaction mixture was heated to 250 ° C. and heated for 2 hours while setting the linear velocity of nitrogen gas to 8.7 (m / s) and stirring at a stirring speed of 800 (rpm). Thus, a hydrophobic sol-gel silica powder was obtained, and the powder characteristic results of the obtained silica powder are shown in Table 2.

<Examples 2, 4, and 5>
In Examples 2, 4, and 5, the surface treatment was performed under the treatment conditions shown in Table 1 using the reaction vessel 15 shown in FIG. In Examples 2, 4, and 5, a commercially available hydrophilic sol-gel silica powder having an average primary particle size of 110 nm (silica manufactured by Company A) was used in place of the hydrophilic sol-gel silica particles of Example 1, and as an inert gas. This silica powder was hydrophobized under the surface treatment conditions shown in Table 1 using nitrogen gas and further using a hydrophobizing agent shown in Table 1. Table 2 shows the powder characteristic results of the obtained hydrophobic sol-gel silica powder. FIG. 3 shows an SEM observation image obtained when the hydrophobic sol-gel silica powder obtained in Example 2 and the toner are mixed. In Examples 2, 4, and 5, the same operation as in Example 1 was performed while changing the rotation speed of stirring and the linear velocity of nitrogen gas during the hydrophobization treatment of the hydrophilic sol-gel silica powder. However, in Example 5, the bulk density was increased by consolidating the powder of the hydrophilic sol-gel silica particles A in advance. In this way, hydrophobic sol-gel silica powders of Examples 2, 4, and 5 were obtained. Table 2 shows the powder characteristic results of the obtained silica powder.

<Example 3>
In Example 3, the surface treatment was performed under the treatment conditions shown in Table 1 using a reaction vessel 1 having a volume of 10 L as shown in FIG. More specifically, 500 g of a commercially available hydrophilic sol-gel silica powder (silica manufactured by Company A) having an average primary particle size of 110 nm was introduced from the raw material introduction tube 3. The introduced silica powder was held on the current plate 4. 75 g of the hydrophobizing agent shown in Table 1 was introduced into the reaction vessel 1 together with nitrogen gas from the gas introduction pipe 5 formed on the bottom wall 2a of the reaction vessel 1. This nitrogen gas is used as a carrier gas for the hydrophobizing agent and also as a fluidizing gas for the silica powder. When the hydrophobizing agent conveyed by nitrogen gas contacted the silica powder, the surface of the silica powder was hydrophobized by a chemical reaction. Next, nitrogen gas was introduced into the reaction vessel 1 and held at 180 ° C. for 1 hour, and then the oxide powder was taken out from the lower take-out pipe 6 by opening the manual valve 8. In this way, a hydrophobic sol-gel silica powder of Example 3 was obtained. Table 2 shows the powder characteristic results of the obtained silica powder.

<Example 6>
In Example 6, surface treatment was performed under the treatment conditions shown in Table 1 using the reaction vessel 1 shown in FIG. However, instead of the hydrophilic sol-gel silica particles of Example 3, in Example 6, a commercially available hydrophilic sol-gel silica powder (silica manufactured by B company) having an average primary particle size of 75 nm was used.

<Example 7>
In Example 7, surface treatment was performed under the treatment conditions shown in Table 1 using the reaction vessel 15 shown in FIG. In Example 7, a commercially available hydrophilic sol-gel silica powder (silica manufactured by B company) having an average primary particle size of 220 nm was used. Further, the silica particles were hydrophobized using the hydrophobizing agent shown in Table 1 under the surface treatment conditions shown in Table 1. Table 2 shows the powder characteristic results of the obtained silica powder. In Example 7, in the hydrophobization treatment of the hydrophilic sol-gel silica powder, the surface treatment was carried out under the surface treatment conditions shown in Table 1 using the reaction vessel 15 shown in FIG. 2 while changing the rotation speed of stirring and the linear velocity of nitrogen gas. Went.

<Comparative Example 1>
In Comparative Example 1, the surface treatment was performed under the treatment conditions shown in Table 1 using the reaction vessel 15 shown in FIG. That is, the hydrophilic sol-gel silica particles produced by the same method as in Example 1 were subjected to a hydrophobic treatment. At this time, the rotation speed of stirring and the linear velocity of nitrogen gas were changed. Other surface treatment conditions were the same as in Example 1. Table 2 shows the powder characteristic results of the obtained silica powder.

<Comparative Examples 2, 4, 5>
In Comparative Examples 2, 4, and 5, the surface treatment was performed under the treatment conditions shown in Table 1 using the reaction vessel 15 shown in FIG. In Comparative Examples 2, 4 and 5, commercially available hydrophilic sol-gel silica particles used in Examples 2, 4 and 5 were used, respectively. Further, the silica particles were hydrophobized using the hydrophobizing agent shown in Table 1 under the surface treatment conditions shown in Table 1. Table 2 shows the powder characteristic results of the obtained silica powder. In Examples 2 to 5, during the hydrophobization treatment of the hydrophilic sol-gel silica particles, the stirring rotation speed and the linear velocity of nitrogen gas were changed. Other conditions were the same as those in Examples 2 to 5.
Further, FIG. 4 shows the SEM observation result (10,000 times) obtained by mixing the hydrophobic sol-gel silica powder obtained under the condition of Comparative Example 2 and the toner. Silica aggregates that were not dispersed in the center of FIG. 4 were observed.

<Comparative Example 3>
In Comparative Example 3, the surface treatment was performed under the treatment conditions shown in Table 1 using the reaction vessel 1 shown in FIG. However, in Comparative Example 3, commercially available hydrophilic sol-gel silica particles used in Examples 2, 4 and 5 were used. .

<Comparative Example 6>
In Comparative Example 6, the surface treatment was performed under the treatment conditions shown in Table 1 using the reaction vessel 15 shown in FIG. However, in Comparative Example 6, commercially available hydrophilic sol-gel particles (silica manufactured by Company A) having an average primary particle size of 100 nm were used in place of the hydrophilic sol-gel silica particles of Example 1. The silica particles were hydrophobized using the hydrophobizing agent shown in Table 1 under the surface treatment conditions shown in Table 1.

<Comparative Example 7>
In Comparative Example 7, as in Example 3, the reaction vessel 1 shown in FIG. However, instead of the hydrophilic sol-gel silica particles of Example 3, in Comparative Example 7, commercially available hydrophilic sol-gel particles (silica manufactured by Company A) having an average primary particle size of 30 nm were used. The silica particles were hydrophobized using the hydrophobizing agent shown in Table 1 under the surface treatment conditions shown in Table 1.

<Comparative Example 8>
In Comparative Example 8, surface treatment was performed under the treatment conditions shown in Table 1 using the reaction vessel 15 shown in FIG. However, instead of the hydrophilic sol-gel silica particles of Example 1, commercially available hydrophilic sol-gel particles (silica manufactured by Company A) having an average primary particle size of 500 nm were used. Further, the silica particles were hydrophobized using the hydrophobizing agent shown in Table 1 under the surface treatment conditions shown in Table 1. Table 2 shows the powder characteristic results of the obtained silica powder. In Comparative Examples 8 and 9, during the hydrophobization treatment of the hydrophilic sol-gel silica particles, the stirring rotation speed and the linear velocity of nitrogen gas were changed.

<Comparative Example 9>
In Comparative Example 9, as in Example 3, the reaction vessel 1 shown in FIG. However, instead of the hydrophilic sol-gel silica particles of Example 3, in Comparative Example 9, commercially available hydrophilic sol-gel particles (silica manufactured by Company A) having an average primary particle diameter of 500 nm were used. The silica particles were hydrophobized using the hydrophobizing agent shown in Table 1 under the surface treatment conditions shown in Table 1.

  The average primary particle diameter, bulk density ratio, hydrophobizing agent charge, hydrophobicity, loss on drying and carbon content in Tables 1 and 2 are as follows.

The “average primary particle size” was taken with a transmission electron microscope (300,000 times) for silica particles of less than 110 nm, and with a scanning electron microscope (50,000 times) for silica particles of 110 nm or more. About the silica particle in the photograph figure, it is the value which measured the particle diameter of 50 or more at random, and took the average.
The “bulk density ratio” is the ratio Y / X of the bulk density X at the time of standing to the bulk density Y at the time of surface treatment.
The “stirring rotational speed (rpm)” is the rotational speed of the motor that drives the stirrer.
“Hydrophobic” refers to a sample of 1 g of hydrophobic sol-gel silica powder, weighed in a 200 mL separatory funnel, added 100 mL of pure water, capped, and shaken with a tumbler mixer at a stirring speed of 90 rpm for 10 minutes. Let stand for 10 minutes after shaking. After standing, after removing 20-30 mL of the lower layer from the funnel, the lower layer mixed solution is dispensed into a 10 mm quartz cell, subjected to a colorimeter using pure water as a blank, and light transmittance at a wavelength of 500 nm (%) Is the hydrophobic rate (%).
“Weight loss” measures the weight of a sufficiently dried weighing bottle (weight: A), samples the surface-modified silica powder into the weighing bottle, and measures the weight (weight: B). Dry at 105 ° C. for 2 hours using a constant temperature dryer. After completion of drying, the product is transferred to a desiccator, allowed to cool for 15 minutes, and the weight after cooling is measured (weight: C). Then, the moisture (mass%) is measured by the following formula, and the weight loss is reduced (mass%).
Moisture (mass%) = {(BC) / (BA)} × 100

  “Carbon amount” is a carbon content contained in an organic solvent extract, and is measured as follows using a carbon analyzer (SUMIGRAPH NC-22, manufactured by Sumika Chemical Analysis Co., Ltd.). A boat containing a standard sample and a measurement sample for which weighing has been completed is set in the apparatus, and measurement is started. The measurement data processing program automatically calculates the final result. At that time, the automatically calculated carbon value is evaluated. When measuring the amount of carbon, the sample surface-treated in advance was measured with a sample subjected to Soxhlet extraction. In Soxhlet extraction, the solvent used for extraction is distilled each time it is heated, and is received at the portion where the sample is placed.As the amount of the distilled solvent increases, all of the solvent accumulated by the Siphon principle exceeds the required amount. The operation returns to the flask, and the sample is extracted from the sample in the meantime.

Further, electrostatic charge developing toners obtained from the hydrophobic sol-gel powders of Examples and Comparative Examples were evaluated. This evaluation is based on SEM observation and toner evaluation.
In SEM observation, evaluation of silica dispersibility on the toner surface was evaluated. Using a commercially available negatively charged polyester toner base powder (manufactured by Sinnar) manufactured by a polymerization method, this toner was mixed with the surface-modified silica powder shown in Examples and Comparative Examples at a weight ratio of 97: 3, and Henschel After premixing for 1 minute at 600 rpm with a mold mixer, a sample for evaluation of dispersibility was prepared by mixing for 3 minutes at 3000 rpm, and observed with a SEM at a magnification of 10,000 times. The observation results were evaluated as “excellent”, “possible”, and “impossible” in order of good dispersibility.

Toner evaluation was evaluated by a printing test. Using 3 parts by weight of a toner made of a commercially available negatively charged polyester toner base powder (manufactured by Sinnar) manufactured by a polymerization method, this toner was used with the surface-modified silica powder shown in Examples and Comparative Examples and a weight of 97: 3. The mixture was mixed at a ratio, premixed at 600 rpm for 1 minute with a Henschel mixer, and then mixed at 3000 rpm for 3 minutes. Further, this mixed powder and 97 parts by weight of ferrite for carrier (FL100: manufactured by Powdertech) are mixed to prepare a two-component developer, and this developer is put into a two-component developer equipped with an organic photoreceptor, A printing test of 20,000 sheets was performed. At this time, toner adhesion to the photoconductor can be detected as white spots in all solid images, and photoconductor wear can be detected as image disturbance. The degree of white spots is divided into stages of 10 or more / cm ² , 4 to 9 / cm ² , 1 to 3 / cm ² , and 0 / cm ² . “No”, “Good”, “Yes”, and “No” were evaluated in the order in which they could be evaluated comprehensively when there was no image, no large image disturbance, and no image disturbance.

<Comprehensive evaluation>
By subjecting the hydrophilic sol-gel silica particles to a dry surface treatment under the conditions of a predetermined inert gas linear velocity and / or stirring rotation speed, the hydrophilic sol-gel silica particles have a high hydrophobicity and a low loss on drying, and contain an appropriate carbon content. A hydrophobic surface-treated hydrophobic sol-gel silica powder could be obtained. A hydrophobic sol-gel silica powder containing a high hydrophobicity and an appropriate amount of carbon had good dispersibility when mixed with a toner, and it was possible to obtain a toner external additive having no image distortion in a printing test.

  The hydrophobic sol-gel silica powder obtained by the surface treatment of the hydrophilic sol-silica particles of the present invention is used as an external additive for toners for developing electrostatic images and added to toners of copying machines, printers, facsimiles, plate making systems and the like. The

Claims (4)

In the method of surface-treating hydrophilic sol-gel silica particles obtained by hydrolyzing and condensing silicon alkoxide represented by the following general formula (1) or a partial hydrolysis-condensation product thereof or a combination thereof with a hydrophobizing agent ,
The surface treatment is a dry surface treatment in which the hydrophilic sol-gel silica particles are flowed by supplying an inert gas and the hydrophobizing agent into the reaction vessel while the hydrophilic sol-gel silica particles are placed in a reaction vessel. There,
A linear velocity per cross-sectional area of the reaction vessel of the inert gas supplied into the reaction vessel is set in a range of 1 to 12 m / s, and a bulk density of the hydrophilic sol-gel particles during the surface treatment is set in the reaction. The bulk density of the hydrophilic sol-gel silica particles during the surface treatment in the reaction container is set in a range of 0.6 to 0.9 times the bulk density of the hydrophilic sol-gel silica particles when left in the container. A surface treatment method for hydrophilic sol-gel silica particles, characterized in that a hydrophobic sol-gel silica powder whose surface has been hydrophobized is obtained by setting the amount to 150 to 300 g / L.
Si (OR ¹ ) ₄ (1)
(However, R1 is the same or different C1-C4 alkyl group.)   The surface treatment method according to claim 1, wherein an average primary particle diameter of the hydrophilic sol-gel silica particles before the surface treatment is in a range of 50 to 300 nm.   Loss on drying is 0.8% by mass or less, hydrophobicity is in the range of 70 to 100%, and carbon content in the organic solvent extract is 0.001 to 0.03% by mass per unit area. Item 3. A hydrophobic sol-gel silica powder surface-treated by the method according to Item 1 or 2.   A toner external additive for developing an electrostatic charge image obtained from the hydrophobic sol-gel silica powder according to claim 3.