JP6195524B2 - Hydrophobic silica powder and method for producing the same - Google Patents

Description

  The present invention relates to a hydrophobic silica powder and a method for producing the same.

  Conventionally, hydrophobic silica powder has been used in various technical fields. For example, hydrophobic silica powder is used as a toner external additive for the purpose of improving the fluidity of printer toner, stabilizing charging characteristics or adjusting charging properties. When used as an external toner additive, it has high hydrophobicity in order to reduce the change in charge amount due to humidity. In addition, if the toner surface can be uniformly coated, it improves the fluidity of the toner, so that there is less aggregation and high dispersibility. Hydrophobic silica powder having

  When producing such hydrophobic silica powder, as a raw material, silica obtained by applying a gas phase method (flame hydrolysis method or flame combustion method) to a silicon compound (generally referred to as fumed silica), Widely used. Examples of conventional methods relating to this include those described in Patent Documents 1 to 3. In addition, a method for obtaining a hydrophobic silica powder using an aqueous silica sol as a raw material has been proposed (for example, Patent Document 4).

JP 2004-67475 A International Publication No. 2004/060803 Pamphlet JP 2011-236089 A JP 2006-169096 A

  However, the hydrophobic silica powder obtained by the conventional methods described in Patent Documents 1 to 4 has room for improvement in dispersibility. The hydrophobic silica powder is preferably adjusted to a desired charge amount.

  An object of the present invention is to solve the above problems. That is, an object of the present invention is to provide a hydrophobic silica powder excellent in dispersibility and a method for producing the same. Furthermore, a hydrophobic silica powder adjusted to a desired charge amount and a method for producing the same can be provided.

The inventor has intensively studied to solve the above-mentioned problems, and has completed the present invention.
The present invention includes the following (1) to (5).
(1) Prepared using sodium silicate as a raw material,
The average particle diameter (D2) measured by the dynamic light scattering method when dispersed in an organic solvent is in the range of 0.02 to 0.3 μm, and the frequency of the particle size distribution in the same range is 95% or more. Hydrophobic silica powder having a standard deviation of 0.10 μm or less.
(2) The hydrophobic silica powder according to (1) above, which is an aggregate of particles having at least one shape selected from the group consisting of spherical and confetti.
(3) Subsequent to Step 1 to Step 2, Step 3 to Step 4 are repeated 1 to 6 times, and the hydrophobic silica powder according to the above (1) or (2) A method for producing the obtained hydrophobic silica powder.
Step 1: Sodium silicate is used as a raw material, the average particle diameter (D1) is in the range of 0.02 to 0.3 μm, the frequency of the particle size distribution in the same range is 95% or more, and the standard deviation is 0.10 μm. A step of performing decation treatment and deanion treatment on a silica sol in which silica fine particles are dispersed.
Step 2: Following the previous step, the silica sol is spray-dried to obtain a dried silica powder product.
Step 3: Following the previous step, a step of adding a silane compound or a silane compound and a silane coupling agent to the dried silica powder in the presence of water and mixing to obtain a hydrophobized silica powder.
Step 4: A step of pulverizing the hydrophobized silica powder following the previous step.
(4) Following step 1 to step 2, step 3 to step 4 are repeated 1 to 6 times, and then step 3 is performed again. Method for producing hydrophobic silica powder.
(5) The step 1 is a step of subjecting the silica sol to decation treatment and deanion treatment, adding polyaluminum chloride, mixing, and further deionization treatment,
The method for producing a hydrophobic silica powder according to the above (3) or (4), wherein the steps 3 to 4 are repeated 1 to 3 times.

  ADVANTAGE OF THE INVENTION According to this invention, the hydrophobic silica powder excellent in a dispersibility and its manufacturing method can be provided. Moreover, according to the preferable aspect of this invention, the hydrophobic silica powder further adjusted to the desired charge amount and its manufacturing method can be provided.

The present invention will be described.
The present invention is prepared using sodium silicate as a raw material, and the average particle size (D2) measured by a dynamic light scattering method when dispersed in an organic solvent is in the range of 0.02 to 0.3 μm, and It is a hydrophobic silica powder having a frequency of particle size distribution in the same range of 95% or more and a standard deviation of 0.10 μm or less.
Hereinafter, such hydrophobic silica powder is also referred to as “silica powder of the present invention”.

In addition, the present invention is characterized in that following the steps 1 to 2, the steps 3 to 4 are repeated 1 to 6 times to obtain the silica powder of the present invention. It is a manufacturing method.
Step 1: Sodium silicate is used as a raw material, the average particle diameter (D1) is in the range of 0.02 to 0.3 μm, the frequency of the particle size distribution in the same range is 95% or more, and the standard deviation is 0.10 μm. A step of performing decation treatment and deanion treatment on a silica sol in which silica fine particles are dispersed.
Step 2: Following the previous step, the silica sol is spray-dried to obtain a dried silica powder product.
Step 3: Following the previous step, a step of adding a silane compound or a silane compound and a silane coupling agent to the dried silica powder in the presence of water and mixing to obtain a hydrophobized silica powder.
Step 4: A step of pulverizing the hydrophobized silica powder following the previous step.
Hereinafter, such a method for producing a hydrophobic silica powder is also referred to as “the production method of the present invention”.

<Production method of the present invention>
Steps 1 to 4 included in the production method of the present invention will be described.

<Step 1>
In step 1 included in the production method of the present invention, first, a specific silica sol is prepared. This silica sol is prepared using sodium silicate as a raw material. In addition, silica fine particles having an average particle diameter (D1) in the range of 0.02 to 0.3 μm and a frequency of particle size distribution in the same range of 95% or more and a standard deviation of 0.10 μm or less are dispersed. It is what.

  Such a silica sol can be obtained by the method described in Japanese Patent Application Laid-Open No. 63-045114 by the applicant of the present application or the silica particles having a relatively small particle size used as seed particles described in Japanese Patent Application Laid-Open No. 63-64911. It can obtain by the manufacturing method of the dispersion liquid.

  In addition, such a silica sol is obtained by removing an acidic silicate solution by removing a cation component using a cation exchange resin or the like for an aqueous sodium silicate solution obtained by dissolving cullet. The seed liquid, another part is used as a feed liquid, the seed liquid is adjusted to be alkaline (for example, pH is 11 to 12), more preferably maintained at about 80 to 90 ° C., and here, preferably 1 to 20 ° C. The above feed liquid can be gradually added.

  The silica sol used in step 1 is obtained, for example, by the method as described above, and is obtained by dispersing silica fine particles in water.

  Here, the average particle diameter (D1) of the silica fine particles is in the range of 0.02 to 0.3 μm, but is preferably 0.03 μm or more. Moreover, it is preferable that it is 0.2 micrometer or less, and it is more preferable that it is 0.16 micrometer or less.

  The frequency (volume basis) in the particle size distribution of the silica fine particles is 95% (volume%) or more within the range of 0.02 to 0.3 μm. The frequency within this range is preferably 98% or more, and more preferably substantially 100%.

  The frequency (volume basis) in the particle size distribution of the silica fine particles has a standard deviation (SD) of 0.10 μm or less, and preferably 0.07 μm or less.

The average particle diameter (D1) of the silica fine particles and the frequency of the particle size distribution mean values obtained by measuring the particle size distribution by the following method.
First, pure water is added to a silica sol in which silica fine particles are dispersed to adjust the mass concentration of the silica fine particles to 1% by mass and dispersed with ultrasonic waves for 10 minutes. Then, conventionally known dynamic light scattering particles The particle size distribution is measured with a diameter measuring device (for example, Microtrack, manufactured by Nikkiso Co., Ltd.). The measurement conditions are: particle refractive index: 1.45, density: 2.2 g / cm ³ , solvent refractive index: 1.333, measurement time: 60 seconds. Then, the particle size distribution (volume basis) is measured, and the average particle diameter (median diameter, μm) and frequency (volume%) are read from the particle size distribution.
In Examples and Comparative Examples described later, the average particle diameter (D1) of silica fine particles and the frequency of particle size distribution were measured by such methods.

The specific surface area of the silica fine particles is not particularly limited, but is preferably 140 m ² / g or less, and more preferably 110 m ² / g or less. This is because a hydrophobic silica powder having more excellent dispersibility can be obtained.

In the present invention, the specific surface area is a value determined by BET one-point measurement by a continuous flow method. This measurement method will be specifically described. First, 50 ml of silica sol was adjusted to pH 3.5 with HNO ₃ , 40 ml of 1-propanol was added, and the sample dried at 110 ° C. for 16 hours was pulverized in a mortar and then baked at 500 ° C. for 1 hour in a muffle furnace. Use a sample for measurement. Then, 0.5 g of the sample is placed in a measurement cell, degassed for 20 minutes at 300 ° C. in a mixed gas stream of 30% by volume of nitrogen / 70% by volume of helium, and then the sample is liquid nitrogen in the mixed gas stream. Maintain temperature and allow nitrogen to equilibrate to sample. Next, the sample temperature is gradually raised to room temperature while flowing the mixed gas, the amount of nitrogen desorbed during that time is detected, and the specific surface area is calculated using a calibration curve prepared in advance. Such a BET specific surface area can be measured using a known BET type powder specific surface area measuring device (for example, model number Multisorb 12 manufactured by Yuasa Ionics).

The average particle diameter (D0) calculated from the specific surface area of the silica fine particles is preferably in the range of 0.02 to 0.3 μm. The average particle diameter (D0) is preferably 0.02 μm or more. Further, it is preferably 0.2 μm or less, more preferably 0.16 μm or less, and further preferably 0.12 μm or less.
Here, the average particle diameter (D0) is calculated from 6000 / (2.2 × SA). SA means a specific surface area and means a value measured by the BET one-point method described above.

The shape of the silica fine particles is preferably at least one shape selected from the group consisting of a spherical shape and a confetti shape.
Here, the spherical silica fine particles mean those having a minor axis / major axis ratio in the range of 0.8 to 1.2 which can be read from an image enlarged 250,000 to 500,000 times using a scanning electron microscope. Shall.
The confetti-like silica fine particles are formed by forming a plurality of ridge-like projections on the surface of the spherical silica fine particles, and the shape thereof is generally similar to that of confetti. The range of the surface on which such a plurality of hook-shaped protrusions are formed is defined by the surface roughness, and specifically, is defined in Japanese Patent Application Laid-Open No. 2008-169102 by the applicant of the present application. A method for producing such a confetti-like silica sol is also described in the publication.

  The concentration (solid content concentration) of the silica fine particles contained in the silica sol is not particularly limited, but is preferably 5 to 50% by mass, and more preferably 10 to 40% by mass.

  The pH of the silica sol is not particularly limited, but is preferably 8 to 11, and more preferably 9 to 10.5.

  The silica sol can contain conventionally known stabilizers such as HCl and NaOH.

In step 1, the silica sol as described above is subjected to decation treatment and deanion treatment.
The order of performing the decation treatment and the deanion treatment is not particularly limited, but it is preferable to perform the deanion treatment after the silica sol is subjected to the decation treatment.

  The decation treatment is not particularly limited as long as it can remove at least a part (preferably almost all) of the cation component contained in the silica sol, and for example, a conventionally known treatment can be applied. The decation treatment is preferably a cation exchange treatment. Examples of the cation exchange treatment include a treatment in which a cation exchange resin and silica sol are brought into contact with each other.

  The deanion treatment is not particularly limited as long as it can remove at least a part (preferably almost all) of the anion component contained in the silica sol, and for example, a conventionally known treatment can be applied. The deanion treatment is preferably an anion exchange treatment. Examples of the anion exchange treatment include a treatment in which an anion exchange resin and silica sol are brought into contact with each other.

  The silica sol after the decation treatment and deanion treatment obtained as described above can be subjected to the next step 2. The silica sol after the above treatment is further treated with It is preferable that aluminum chloride is added and mixed, and further subjected to deanion treatment (preferably anion exchange treatment). This is because when such a treatment is performed, the amount of negative charges increases and a hydrophobic silica powder excellent in dispersibility can be obtained.

The polyaluminum chloride mixed with the silica sol after the above decation treatment and deanion treatment may be in the form of powder or in a state where the powder is dispersed in a liquid.
The silica sol and polyaluminum chloride may be mixed by a conventionally known method. For example, after adding polyaluminum chloride to the silica sol, it can be mixed by stirring using a stirrer or the like.

  The mixing ratio of the silica sol and polyaluminum chloride is not particularly limited, but the ratio (percentage) of the alumina-equivalent mass of polyaluminum chloride as a solid to the mass of silica fine particles contained in the silica sol (that is, in the polyaluminum chloride) Alumina / silica fine particles × 100), preferably 0.01 to 4.0% by mass, and more preferably 0.1 to 2.0% by mass.

  The subsequent deanion treatment may be the same as the deanion treatment performed on the silica sol described above.

<Process 2>
In step 2, the silica sol after the treatment in step 1 is spray-dried to obtain a dried silica powder product.

  The spray drying is a method in which silica sol is sprayed into a chamber from a nozzle, is brought into contact with hot air in the chamber, and is dried instantaneously. Since the drying time is short, the spray drying method is suitable for the case of using a relatively heat-sensitive material. Further, since it can be continuously mass-produced, a silica powder dry product can be obtained at a low cost.

  Each condition for spray drying can be appropriately adjusted in consideration of the particle diameter of the obtained dried silica powder product. For example, it is performed by spraying in a hot air stream at a rate of 1 to 3 liters / minute. Here, the nozzle spray pressure is preferably 0.2 to 0.6 MPa. At this time, the temperature of the hot air is such that the inlet temperature is preferably in the range of 70 to 400 ° C, more preferably 100 to 300 ° C, and further preferably 220 to 240 ° C, and the outlet temperature is preferably in the range of 40 to 60 ° C. Adjust as shown in The silica sol is preferably adjusted in advance so that the solid content concentration is 1 to 50% by mass, preferably 5 to 30% by mass, and then spray-dried using a spray dryer.

  Here, when the outlet temperature is 40 to 60 ° C. (preferably 50 to 60 ° C.), an appropriate amount of moisture remains in the obtained silica powder dry product, and the process of adjusting the moisture amount to an appropriate range in the next step is omitted. This is preferable.

<Step 3>
In Step 3, the silica powder dried product obtained in Step 2 is added with a silane compound or a silane compound and a silane coupling agent in the presence of moisture (that is, only a silane compound is added, or a silane compound and a silane coupling agent are added). To obtain a hydrophobized silica powder.

As the silane compound, a disilazane compound is preferable. For example, 1,1,1,3,3,3-hexamethyldisilazane, 1,3-Bis (chloromethyl) tetramethyldisilazane, 1,3-Bis (3,3,3-trifluoropropyl)- 1,1,3,3-tetramethyldisilazane, 1,3-diphenyltetramethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, heptamethyldisilazane, 1,1 , 3,3-tetramethyldisilazane and the like.
However, the silane compound of the present invention does not include a silane coupling agent described later.

The disilazane compound is preferably 1,1,1,3,3,3-hexamethyldisilazane (bis (trimethylsilyl) amine, hereinafter also referred to as “HMDS”). HMDS usually exists as a colorless and transparent liquid.
The amount of silane compound (preferably HMDS) added to the silica powder dry product is not particularly limited, but is preferably 0.5 to 100 parts by mass with respect to 100 parts by mass (dry base) of the silica powder dry product, It is more preferable that it is 4-60 mass parts.

Moreover, although a silane coupling agent can be added to a silica powder dry product with said silane compound, a silane coupling agent does not need to be added. In the present invention, the silane coupling agent is used as a charge control agent for hydrophobic silica powder.
The silane coupling agent has a general formula of YSiX ₃ or Y ₂ SiX ₂ , where X is a hydrolyzable substituent such as an alkoxy group and reacts with an inorganic substance, Y is a vinyl group that easily reacts with an organic substance, Examples thereof include an epoxy group and an amino group. For example, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidyl Sidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldi Ethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3 -Aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-amino Propyltrimethoxysilane, N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane carbonate, Tris- (trimethoxysilylpropyl) isocyanurate, 3-ureidopropyltriethoxysilane, 3-mercapto Examples include propylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, and 3-isocyanatopropyltriethoxysilane. In particular, when it is desired to obtain a positively charged hydrophobic silica powder, an aminosilane coupling agent such as 3-aminopropyltrimethoxysilane is preferably used.

  When the silane coupling agent is added together with the silane compound, the addition amount of the silane coupling agent to the dried silica powder product is not particularly limited, but is 0.5 mass with respect to 100 parts by mass (dry base) of the dried silica powder product. Part or less, preferably 0.05 part by weight or less.

  When the silane compound (preferably HMDS) or the silane compound and the silane coupling agent are added to the dried silica powder product, the moisture of the dried silica powder product is previously contained. That is, a silane compound, or a silane compound and a silane coupling agent are added to a dried silica powder in the presence of moisture. As described above, when an appropriate amount of moisture remains in the dried silica powder product obtained in step 2, the silane processed product, or the silane compound and the silane coupling agent are added to the dried silica powder product in that state. Although it may be added, when the moisture content of the dried silica powder obtained in Step 2 is insufficient, water is added for adjustment. Specifically, when the moisture content of the dried silica powder product is 1 to 30% by mass, the moisture content may be an appropriate amount. The water content is preferably 5 to 25% by mass, and more preferably 10 to 20% by mass.

  When a silane compound (preferably HMDS) or a silane compound and a silane coupling agent are added to a silica powder dry product and mixed, the silica powder dry product and the silane compound (preferably Preferably promote contact with HMDS) or silane coupling agents.

  When adding a silane compound (preferably HMDS) or a silane compound and a silane coupling agent to a silica powder dry product, a predetermined amount of the silane compound (preferably HMDS) or the silane compound and the silane coupling agent is divided into a plurality of times. It is preferable to add to the dried silica powder. Specifically, it is preferable to add in about 5 times. That is, a desired amount of a silane compound (preferably HMDS), or a silane compound and a silane coupling agent are added to a dried silica powder product, followed by stirring, and then again a predetermined amount of the silane compound (preferably HMDS), or It is preferable to repeat the operation of adding and stirring the silane compound and the silane coupling agent. This is because contact between the dried silica powder and the silane compound (preferably HMDS) or the silane coupling agent can be further promoted, and the degree of hydrophobicity in the resulting hydrophobic silica powder tends to increase.

  It is preferable to add a silane compound (preferably HMDS), or a silane compound and a silane coupling agent to the dried silica powder product, and after mixing, a drying treatment is preferably performed. For example, the drying treatment is preferably performed at a temperature of about 100 to 200 ° C. (preferably 130 to 160 ° C.) for about 1 to 5 hours. This is because the degree of hydrophobicity in the resulting hydrophobic silica powder tends to increase. Moreover, it is because an excess silane compound or a silane coupling agent, by-product methanol, and ammonia can be removed.

  When adding a silane coupling agent to a silica powder dry product, it is preferable to carry out before adding the silane compound mentioned above. If it is added after the silane compound (preferably HMDS) is added, it is affected by the steric hindrance of the silane compound, and a predetermined amount of the silane coupling agent cannot be applied to the powder, and the charge amount of the powder cannot be controlled. is there.

<Step 4>
In step 4, the hydrophobized silica powder obtained in step 3 is pulverized.
For the pulverization, it is preferable to use a high-speed swirling pulverizer (jet mill) that injects high-pressure gas (air or the like) into the mill to pulverize the raw material.

In the production method of the present invention, after performing Step 1 and Step 2 as described above, Step 3 to Step 4 are repeated 1 to 6 times. For example, when the average particle diameter (D2) and particle size distribution of the hydrophobic silica powder obtained after performing Step 1, Step 2, Step 3 and Step 4 are not desired, Step 3 and Step 4 are performed again. It can be done iteratively. That is, Step 3 and Step 4 are set as one set, and this set can be repeated. Therefore, after performing Step 4, it is preferable to perform an operation of measuring the particle size distribution of the obtained hydrophobic silica powder to confirm whether the average particle size (D2) or the particle size distribution is within a desired range. .
In addition, after performing step 1, step 2, step 3 and step 4, when the set of step 3 and step 4 is performed once, the number of iterations is counted as two.
In addition, following Step 1 to Step 2, it is preferable to repeat Step 3 to Step 4 once to 6 times and then perform Step 3 again.
The number of repetitions is 1 to 6 times. However, in the case where the polyaluminum chloride is added, mixed, and further subjected to anion exchange treatment in the step 1 as described above, The number of repetitions is preferably 1 to 3 times. The reason for this is that the present inventors believe that the coating of silica particles with polyaluminum chloride increases the negative charge amount of the hydrophobic silica powder and makes it difficult to reaggregate due to repulsion of the particles during crushing. Yes.

  The silica powder of the present invention can be obtained by such a production method of the present invention. However, if the silica powder of this invention is adjusted by using sodium silicate as a raw material, the manufacturing method will not be limited.

<Silica powder of the present invention>
The silica powder of the present invention has an average particle diameter (D2) measured by a dynamic light scattering method when dispersed in an organic solvent in a range of 0.02 to 0.3 μm, and a particle size distribution in the same range. Is a hydrophobic silica powder having a frequency of 95% or more and a standard deviation of 0.10 μm or less.

  The average particle diameter (D2) of the silica powder of the present invention is in the range of 0.02 to 0.3 μm, but preferably 0.03 μm or more. Moreover, it is preferable that it is 0.2 micrometer or less, and it is more preferable that it is 0.16 micrometer or less.

  The frequency (volume basis) in the particle size distribution of the silica powder of the present invention is 95% (volume%) or more within the range of 0.02 to 0.3 μm. The frequency within this range is preferably 98% or more, and more preferably substantially 100%.

  The frequency (volume basis) in the particle size distribution of the silica powder of the present invention has a standard deviation (SD) of 0.10 μm or less, preferably 0.07 μm or less.

The average particle diameter (D2) and the frequency of the particle size distribution of the silica powder of the present invention mean values obtained by measuring the particle size distribution by the following method.
First, 0.3 g of the measurement powder was weighed, diluted to 1% with 30 g of methanol, and dispersed with ultrasonic waves for 10 minutes, and then a conventionally known dynamic light scattering particle size measuring device (for example, manufactured by Nikkiso Co., Ltd., Measure the particle size distribution with Microtrac). The measurement conditions are a particle refractive index of 1.45, a density of 2.2 g / cm ³ , a solvent refractive index of 1.329, and a measurement time of 60 seconds. Then, the particle size distribution (volume basis) is measured, the average particle diameter (median diameter, μm) is calculated from the particle size distribution, and the frequency (volume%) within the above range is read.
In Examples and Comparative Examples described later, the average particle diameter (D2) and the frequency of particle size distribution of the silica powder (hydrophobic silica powder) of the present invention were measured by such methods.

The specific surface area of the silica powder of the present invention is not particularly limited, but is preferably 7 m ² / g or more, and more preferably 18 m ² / g or more. Further, it is preferably 128m ² / g or less, and more preferably less 110m ² / g.

  The specific surface area of the silica powder of the present invention means a value obtained by measurement by the BET one-point method described above.

The shape of the silica powder of the present invention is not particularly limited, but is preferably at least one shape selected from the group consisting of a spherical shape and a confetti shape. The definition of the spherical shape and the confetti shape is the same as in the case of the silica fine particles described above.
When the silica powder of the present invention is in the shape of confetti, when the silica powder of the present invention is used as an external toner additive, the silica powder of the present invention is difficult to fall off from the toner surface due to the anchor effect, and the fluidity and durability are improved. The printing performance is preferably improved.

  The silica powder of the present invention exhibits hydrophobicity. The degree is preferably 40 to 70%, more preferably 45 to 65%, and even more preferably 49 to 62%, obtained by the hydrophobicity evaluation method described below.

The hydrophobicity evaluation method will be described.
First, after adding 50.0 ml of pure water to a glass container, a rotor is put and 0.5 g of measurement powder is added. And methanol is dripped at the surface of the pure water in the glass container while stirring at a rotational speed of 600 rpm, and the amount of methanol at the time when all the powder floating on the liquid is dispersed is confirmed. Calculate hydrophobicity.
Formula 1: Hydrophobicity (%) = Methanol amount (ml) ÷ (Pure water amount (ml) + Methanol amount (ml)) × 100
In Examples and Comparative Examples described later, the degree of hydrophobicity of the silica powder (hydrophobic silica powder) of the present invention was measured by such a method.

  The electrostatic charge of the silica powder of the present invention can be negative. As described above, when polyaluminum chloride is added and mixed in Step 1 and further anion exchange treatment is performed, the electrostatic charge amount becomes smaller. Specifically, it can be −1.0 to −5.0 nC / g (preferably about −3.0 to −5.0 nC / g).

  Moreover, in the above-mentioned process 3, when a silane coupling agent is added to the silica powder dry product together with the silane compound, the electrostatic charge amount increases. Specifically, it can be +1.0 to +5.0 nC / g (preferably about +3.0 to +5.0 nC / g).

Here, the electrostatic charge amount of the silica powder of the present invention means a value obtained by measurement by the Faraday gauge method using 1 g of the measurement sample.
In Examples and Comparative Examples described later, the electrostatic charge amount of the silica powder (hydrophobic silica powder) of the present invention was measured by such a method.

The ratio of the average particle diameter (D2) to the average particle diameter (D1) (D2 / D1) is approximately 1.2 or less, preferably 1.1 or less, more preferably 0.8 to 1. .1, more preferably 0.9 to 1.0.
The ratio of the average particle diameter (D2) to the average particle diameter (D0) (D2 / D0) is generally 1.8 or less, preferably 1.5 or less, more preferably 1.4. Hereinafter, more preferably 0.9 to 1.3, and still more preferably 1.0 to 1.2. If D2 / D0 is smaller than this range, the primary particles may be broken. Conversely, if D2 / D0 is larger than this range, the primary particles are not in the state of primary particles but are present as aggregates. Conceivable.
Therefore, it is considered that the silica powder (hydrophobic silica powder) of the present invention is dispersed in a single particle state (monodispersed state) in an organic solvent (methanol).
When such a silica powder of the present invention is used as a toner external additive, the silica powder adheres to the toner surface in the form of single particles, so that it is easy to design fluidity and charge amount, and individual externally added toner Is uniform, so that the printing performance is excellent, which is preferable.

On the other hand, it is considered that the conventional product is not monodispersed. For example, with respect to the silica powder described in Patent Document 4 as Example 1 to Example 5, values corresponding to the average particle diameter (D0) and the average particle diameter (D2) in the present invention were obtained, and these ratios (D2 / D0) was calculated to be 1.7 to 5.5. Accordingly, it is considered that the silica powder is not monodispersed but exists as an aggregate, and this aggregate is dispersed in a solvent.
When silica powder that exists as such an aggregate is used as an external additive for the toner, the silica powder becomes difficult to adhere uniformly, for example, because large aggregates are buried in the toner surface, resulting in poor fluidity and charge amount. It becomes uniform and leads to deterioration of the performance of the toner itself, and the printing performance is deteriorated.
In addition, since the operation described in Patent Document 4 requires an operation for removing the organic solvent, it is not preferable in that the manufacturing cost increases.

Thus, the silica powder of the present invention has a small average particle size, a very sharp particle size distribution, and high dispersibility (monodispersed and not agglomerated).
As described above, the silica powder of the present invention can be preferably used as an external toner additive, and can also be preferably used as a film or a coating material.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

The measurement method and evaluation method of physical properties in the following examples and comparative examples will be described.
The specific surface area was measured by the method described above using a model number Multisorb 12 manufactured by Yuasa Ionics as a measuring device. Moreover, the average particle diameter (D0) was calculated | required from the specific surface area by the above-mentioned method.
The average particle diameter (D1) and frequency of the silica fine particles (silica sol) and the average particle diameter (D2) and frequency of the hydrophobic silica powder are manufactured by Nikkiso Co., Ltd. as a dynamic light scattering particle diameter measuring device. It was measured by the method described above.
The hydrophobicity of the hydrophobic silica powder was evaluated by the method described above, and the value was calculated.
The electrostatic charge amount of the hydrophobic silica powder was measured by the above-described method using KQ-1400 manufactured by Kasuga Electric Co., Ltd.

<Example 1> Method for producing spherical 120 nm hydrophobic silica powder Step A: 5.4 L of cation exchange resin is added to 20 kg of spherical 120 nm silica sol (manufactured by JGC Catalysts & Chemicals, Spiral Slurry (registered trademark), SS-120). After performing cation exchange for 30 minutes, 0.36 L of anion exchange resin was added to the cation exchange product obtained by separating the resin, and the mixture was stirred for 30 minutes to separate the resin. Obtained.
Process B: 2.2 kg of an anion exchange product is sprayed with a NIRO spray device under the conditions of a slurry flow rate of 2 L / Hr, a nozzle spray pressure of 0.4 MPa, and an inlet temperature of 220 to 240 ° C. 8 g was obtained. The moisture content of the dried silica powder product is considered to be 10 to 20% by mass.
Step C: 100 g of the obtained dried silica powder was put into a high-speed mixer, and after 10 minutes of mixer grinding, 1.8 g of HMDS (hexamethyldisilazane) was added, and surface treatment was performed by mixer grinding. Was repeated for a total of 5 times, followed by drying at 150 ° C. for 3 hours to obtain 107 g of a surface-treated product. This operation was carried out twice to obtain a total of 210 g of surface treated products.
Step D: 134 g of the surface-treated product is pulverized with Nanojet Mizer NJ-50, manufactured by Aisin Nano Technologies, at a throughput of 2 g / min, an indentation pressure of 1.5 MPa, and a pulverization pressure of 0.4 MPa. Obtained.

  The average particle size (D2) of the obtained pulverized product by a dynamic light scattering particle size measuring device was 0.16 μm, and showed one peak at a frequency of 100%. The standard deviation (SD) was 0.019. In addition, the average particle diameter (D1) by the dynamic light scattering particle diameter measuring apparatus of the starting material was 0.16 μm, the frequency was 100%, and the ratio of D2 / D1 was 1.0. The hydrophobicity was 60%, and the electrostatic charge amount was -1.2 nC / g.

<Example 2> Method for producing spherical 80 nm hydrophobic silica powder Step A: Add 2.5 kg of pure water to 2.5 kg of spherical 80 nm silica sol (manufactured by JGC Catalysts & Chemicals, Cataloid (registered trademark), SI-80P) and add 20 After adding the cation exchange resin 0.6L and performing cation exchange for 30 minutes, the anion exchange resin 0.13L was added to the cation exchange product obtained by separating the resin for 30 minutes. The mixture was stirred and the resin was separated to obtain 4.9 kg of an anion exchange product.
Step B: 4.7 kg of anion exchange product is sprayed with a NIRO spray device under the conditions of a slurry flow rate of 2 L / Hr, a nozzle spray pressure of 0.4 MPa, and an inlet temperature of 220 to 240 ° C. to obtain 686 g of a dried silica powder product. Obtained.
Step C: 100 g of the obtained dried silica powder was put into a high-speed mixer, and after 10 minutes of mixer grinding, 3.5 g of HMDS (hexamethyldisilazane) was added and surface treatment was performed by mixer grinding. Was repeated for a total of 5 times, followed by drying at 150 ° C. for 3 hours to obtain 91.2 g of a surface-treated product.
Step D: 28 g of the surface-treated product was pulverized with Nanojet Mizer NJ-50, manufactured by Aisin Nano Technologies, at a throughput of 2 g / min, an indentation pressure of 1.5 MPa, and a pulverization pressure of 0.4 MPa. 5 g was obtained.
Step E: The average particle size (D2) of the pulverized product by a dynamic light scattering particle size measuring device is 0.16 μm, the peak frequency of 0.11 μm is 84%, and the frequency of the peak of 0.35 μm is 16%. Therefore, 19 g of this pulverized product was put into a high-speed mixer, and after 10 minutes of mixer pulverization, 0.7 g of HMDS (hexamethyldisilazane) was added, resurface treatment was performed by mixer pulverization, and this operation totaled 5 After repeating several times, it was dried at 150 ° C. for 3 hours to obtain 16.4 g of a resurface-treated product.

  The average particle size (D2) of the obtained resurface-treated product by a dynamic light scattering particle size measuring device was 0.12 μm and showed one peak at a frequency of 100%. The standard deviation (SD) was 0.026. In addition, the average particle diameter (D1) by the dynamic light scattering particle diameter measuring apparatus of the starting material was 0.12 μm, the frequency was 100%, and the ratio D2 / D1 was 1.0. The hydrophobicity was 60%, and the electrostatic charge amount was -1.0 nC / g.

<Example 3> Method for producing spherical 45 nm hydrophobic silica powder Steps A and B were carried out in the same manner as in Example 2 using a spherical 45 nm silica sol (manufactured by JGC Catalysts and Chemicals, Cataloid (registered trademark), SI-45P). Then, Step C was performed in the same manner except that 6.3 g of HMDS was added to 100 g of the dried silica powder, and then Steps D and E were further performed, followed by Steps D and E.

  (D2) of the obtained resurface-treated product by a dynamic light scattering particle size measuring apparatus showed one peak of 0.06 μm and a frequency of 100%. The standard deviation (SD) was 0.040. In addition, the average particle diameter (D1) by the dynamic light scattering particle diameter measuring apparatus of the starting material was 0.06 μm, the frequency was 100%, and the ratio of D2 / D1 was 1.0. The hydrophobicity was 62%, and the electrostatic charge amount was -0.8 nC / g.

<Example 4> Method for producing spherical 25 nm hydrophobic silica powder Steps A and B were carried out in the same manner as in Example 2 using a spherical 25 nm silica sol (manufactured by JGC Catalysts & Chemicals, Cataloid (registered trademark), SI-50). Step C was performed in the same manner except that 11.3 g of HMDS was added to 100 g of the dried silica powder product. Thereafter, Steps D and E were performed, and Steps D and E were further repeated three times.

  The average particle diameter (D2) of the obtained resurface-treated product by a dynamic light scattering particle diameter measuring apparatus was 0.03 μm, and showed one peak at a frequency of 100%. The standard deviation (SD) was 0.055. In addition, the average particle diameter (D1) by the dynamic light scattering particle diameter measuring apparatus of the starting material was 0.03 μm, the frequency was 100%, and the ratio of D2 / D1 was 1.0. The hydrophobicity was 61%, and the electrostatic charge amount was -0.7 nC / g.

<Example 5> Production method of confetti sugar-like 80 nm hydrophobic silica powder Step A and B in the same manner as in Example 2 using confetti sugar-like 80 nm silica sol (manufactured by JGC Catalysts & Chemicals, Cataloid (registered trademark), CO-80A). Step C was performed in the same manner except that 4.7 g of HMDS was added to 100 g of the dried silica powder, and then Steps D and E were performed.

  (D2) of the obtained resurface-treated product by a dynamic light scattering particle size measuring apparatus showed one peak of 0.12 μm and a frequency of 100%. The standard deviation (SD) was 0.020. In addition, the average particle diameter (D1) by the dynamic light scattering particle diameter measuring apparatus of the starting material was 0.13 μm, the frequency was 100%, and the ratio of D2 / D1 was 0.9. The hydrophobicity was 58%, and the electrostatic charge amount was -0.2 nC / g.

<Example 6> Method for producing spherical 45 nm hydrophobic silica powder (polyaluminum chloride)
Step A: Spherical 45 nm silica sol (manufactured by JGC Catalysts & Chemicals, Cataloid (registered trademark), SI-45P) 1.5 kg with pure water 1.5% diluted to 20%, added cation exchange resin 0.34 L After 30 minutes of cation exchange, 0.078 L of anion exchange resin was added to the cation exchange product obtained by separating the resin, and the mixture was stirred for 30 minutes to separate the resin. .8 kg was obtained.
Step A1: After adding 10.14 g of polyaluminum chloride (manufactured by Taki Chemical Co., Ltd .; 23.55%) to 2.6 kg of anion exchange product and stirring for 10 minutes, it is diluted to 5% with addition of pure water. After adding 0.13 L of ion exchange resin and stirring for 30 minutes, the resin was separated to obtain 8.56 kg of anion exchange product.
Step B: 8.56 kg of the anion exchange product obtained in Step A1 is sprayed with a NIRO spray device under conditions of a slurry flow rate of 2 L / Hr, a nozzle spray pressure of 0.4 MPa, and an inlet temperature of 220 to 240 ° C. 280.1 g of a dry powder product was obtained.
Step C: 100 g of the obtained dried silica powder was put into a high-speed mixer, pulverized for 10 minutes, 6.3 g of HMDS (hexamethyldisilazane) was added, surface treatment was performed by pulverizing the mixer, and this operation was performed. Was repeated for a total of 5 times and then dried at 150 degrees for 3 hours to obtain 95.2 g of a surface-treated product.
Step D: 70 g of the surface-treated product was pulverized with Nanojet Mizer NJ-50, manufactured by Aisin Nano Technologies, at a throughput of 2 g / min, an indentation pressure of 1.5 MPa, and a pulverization pressure of 0.2 MPa. 5 g was obtained.
Step E: The average particle size (D2) of the pulverized product by a dynamic light scattering particle size measuring device is 0.22 μm, the peak frequency of 0.08 μm is 91%, and the peak frequency of 1.4 μm is 9%. Therefore, 60 g of this pulverized product was put into a high-speed mixer, and after 10 minutes of mixer pulverization, 3.8 g of HMDS (hexamethyldisilazane) was added, resurface treatment was performed by mixer pulverization, and this operation totaled 5 After repeating several times, it was dried at 150 ° C. for 3 hours to obtain 57 g of a resurface-treated product.

  The average particle diameter (D2) of the obtained resurface-treated product by a dynamic light scattering particle diameter measuring apparatus was 0.06 μm, and showed one peak at a frequency of 100%. The standard deviation (SD) was 0.042. In addition, the average particle diameter (D1) by the dynamic light scattering particle diameter measuring apparatus of the starting material was 0.06 μm, the frequency was 100%, and the ratio of D2 / D1 was 1.0. The hydrophobicity was 49%, and the electrostatic charge amount was -3.5 nC / g.

<Example 7> Method for producing spherical 80 nm hydrophobic silica powder Step C: Steps A and B similar to those in Example 2 were performed, and 100 g of the obtained dried silica powder product was put into a high-speed mixer and subjected to mixer grinding for 10 minutes. Then, 0.3 g of 3-aminopropyltrimethoxysilane was added, surface treatment was performed by mixer pulverization, and this operation was repeated a total of 5 times. Thereafter, 3.5 g of HMDS (hexamethyldisilazane) was further added, and surface treatment was performed by mixer pulverization in the same manner as in Example 2. This operation was repeated 5 times in total and dried at 150 ° C. for 3 hours, and 98.4 g of the surface-treated product. Got. This operation was performed three times to obtain a total of 288 g of surface-treated products.
Step D: 280 g of the surface-treated product was pulverized with Nanojet Mizer NJ-50, manufactured by Aisin Nano Technologies, at a throughput of 2 g / min, an indentation pressure of 1.5 MPa, and a pulverization pressure of 0.4 MPa. Obtained.
Step E: After putting 100 g of the pulverized product of Step D into a high-speed mixer, performing mixer pulverization for 10 minutes, adding 0.7 g of HMDS (hexamethyldisilazane), performing resurface treatment by mixer pulverization, and performing this operation. After repeating 5 times in total, it was dried at 150 ° C. for 3 hours to obtain 95.0 g of a resurface-treated product.

  The average particle diameter (D2) of the obtained resurface-treated product by a dynamic light scattering particle diameter measuring device was 0.13 μm, and showed one peak at a frequency of 100%. The standard deviation (SD) was 0.045. In addition, the average particle diameter (D1) by the dynamic light scattering particle diameter measuring apparatus of the starting material was 0.12 μm, the frequency was 100%, and the ratio of D2 / D1 was 1.1. The hydrophobicity was 47%, and the electrostatic charge amount was +3.0 nC / g.

<Comparative Example 1> Method for producing spherical 120 nm hydrophobic silica powder Step A: 5.4 L of cation exchange resin was added to 20 kg of spherical 120 nm silica sol (manufactured by JGC Catalysts & Chemicals, Sprular Slurry (registered trademark), SS-120). After performing cation exchange for 30 minutes, 0.36 L of anion exchange resin was added to the cation exchange product obtained by separating the resin, and the mixture was stirred for 30 minutes to separate the resin. Obtained.
Process B: 2.2 kg of an anion exchange product is sprayed with a NIRO spray device under the conditions of a slurry flow rate of 2 L / Hr, a nozzle spray pressure of 0.4 MPa, and an inlet temperature of 220 to 240 ° C. 8 g was obtained.
Step C: 100 g of the obtained dried silica powder was put into a high-speed mixer, and after 10 minutes of mixer grinding, 1.8 g of HMDS (hexamethyldisilazane) was added, and surface treatment was performed by mixer grinding. Was repeated for a total of 5 times, followed by drying at 150 ° C. for 3 hours to obtain 107 g of a surface-treated product. This operation was carried out twice to obtain a total of 210 g of surface-treated products.

  The average particle diameter (D2) of the obtained surface-treated product by a dynamic light scattering particle size measuring apparatus is 0.34 μm, the peak frequency of 0.19 μm is 86%, and the frequency of 1.1 μm peak is 14%. there were. The standard deviation (SD) was 1.526.

<Comparative Example 2> Method for producing spherical 80 nm hydrophobic silica powder Step A: Spherical 80 nm silica sol (manufactured by JGC Catalysts & Chemicals, Cataloid (registered trademark), SI-80P) 2.5 kg with pure water 2.5 kg and 20 After adding the cation exchange resin 0.6L and performing cation exchange for 30 minutes, the anion exchange resin 0.13L was added to the cation exchange product obtained by separating the resin for 30 minutes. The mixture was stirred and the resin was separated to obtain 4.9 kg of an anion exchange product.
Step B: 4.7 kg of anion exchange product is sprayed with a NIRO spray device under conditions of a slurry flow rate of 2 L / Hr, a nozzle spray pressure of 0.4 MPa, and an inlet temperature of 220 to 240 ° C. to obtain 686 g of a dried silica powder product. It was.
Step C: 100 g of the obtained dried silica powder was put into a high-speed mixer, and after 10 minutes of mixer grinding, 3.5 g of HMDS (hexamethyldisilazane) was added and surface treatment was performed by mixer grinding. Was repeated for a total of 5 times, followed by drying at 150 ° C. for 3 hours to obtain 91.2 g of a surface-treated product.
Step D: 28 g of the surface-treated product was pulverized with Nanojet Mizer NJ-50, manufactured by Aisin Nano Technologies, at a throughput of 2 g / min, an indentation pressure of 1.5 MPa, and a pulverization pressure of 0.4 MPa. 5 g was obtained.

  The average particle size (D2) of the obtained pulverized product by a dynamic light scattering particle size measuring device was 0.15 μm, the peak frequency of 0.12 μm was 90%, and the frequency of 0.38 μm peak was 10%. It was. The standard deviation (SD) was 0.109.

<Comparative Example 3> Method for producing spherical 45 nm hydrophobic silica powder Steps A and B were carried out in the same manner as in Comparative Example 2 using a spherical 45 nm silica sol (manufactured by JGC Catalysts & Chemicals, Cataloid (registered trademark), SI-45P). Step C was performed in the same manner except that 6.3 g of HMDS was added to 100 g of the dried silica powder.
Step D: 28 g of the surface-treated product was pulverized with Nanojet Mizer NJ-50, manufactured by Aisin Nano Technologies, at a throughput of 2 g / min, an indentation pressure of 1.5 MPa, and a pulverization pressure of 0.4 MPa. 3 g was obtained.

  The average particle diameter (D2) of the obtained pulverized product by a dynamic light scattering particle size measuring apparatus is 0.32 μm, the frequency of 0.08 μm peak is 72%, and the frequency of 0.32 μm peak is 7%. The frequency of the 1.07 μm peak was 21%. The standard deviation (SD) was 0.408.

  The starting materials, process characteristics, and product characteristics in Examples 1 to 7 and Comparative Examples 1 to 3 are summarized in Table 1.

Claims (3)

Subsequent to Step 1 to Step 2, Step 3 to Step 4 are repeated 1 to 6 times, and the average particle diameter measured by a dynamic light scattering method when dispersed in methanol Hydrophobic silica in which (D2) is in the range of 0.02 to 0.3 μm, and a hydrophobic silica powder having a frequency of particle size distribution in the same range of 95% or more and a standard deviation of 0.10 μm or less is obtained. Powder manufacturing method.
Step 1: The average particle diameter (D1) measured by the dynamic light scattering method when prepared using sodium silicate as a raw material and dispersed in water is in the range of 0.02 to 0.3 μm, and the same range A step of decation treatment and deanion treatment of silica sol in which silica fine particles having a particle size distribution frequency of 95% or more and a standard deviation of 0.10 μm or less are dispersed.
Step 2: Following the previous step, the silica sol is spray-dried to obtain a dried silica powder product.
Step 3: Following the previous step, a step of adding a silane compound or a silane compound and a silane coupling agent to the dried silica powder in the presence of water and mixing to obtain a hydrophobized silica powder.
Step 4: A step of pulverizing the hydrophobized silica powder following the previous step. Following the steps 1 to 2, after the step 3 step 4 was carried out repeated 6 times once again, and performs step 3, a hydrophobic silica powder according to claim 1 Manufacturing method. The step 1 is a step of subjecting the silica sol to decation treatment and deanion treatment, adding polyaluminum chloride, mixing, and further deionization treatment,
The method for producing a hydrophobic silica powder according to claim 1 or 2 , wherein the steps 3 to 4 are repeated 1 to 3 times.