JP2003238142A - Silica particulate agglomerate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica particulate agglomerate which is low in crushing strength, has a high specific surface area, a high pore volume and a sharp pore distribution, is excellent in heat resistance, water resistance and physical stability or the like, is low in production cost, and is excellent in productivity. <P>SOLUTION: This particulate agglomerate comprises a silica which has a highly frequent pore diameter (D<SB>max</SB>) of smaller than 20 nm, a crushing strength of 100 N or lower and a chemical shift δ (ppm) of Q<SP>4</SP>peak in a solid Si-NMR satisfying the formula: -0.0705×(D<SB>max</SB>)-110.36>δ. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel silica fine particle aggregate having excellent heat resistance and water resistance.

[0002]

2. Description of the Related Art Silica has been widely used as a desiccant for a long time, but recently its use is expanding to catalyst carriers, separating agents, adsorbents, etc. Performance requirements are also diversifying. The performance of silica is determined by physical properties such as surface area, pore size, pore volume, and pore size distribution of silica, and these physical properties are greatly influenced by the production conditions of silica.

"Silica" refers to both silicic anhydride and hydrous silicic acid. Examples of silicic acid anhydride include quartz, tridymite, cristobalite, coesite, stishovite, and quartz glass. And, as the hydrous silicic acid, obtained by gelling and drying silica hydrosol, in addition to so-called amorphous "silica gel", colloidal silica, silicate oligomer, and formed by using an organic substance as a template, for example, manufactured by Mobil Co. Examples thereof include silica of a type such as MCM-41 (so-called micelle template type silica) and the like. Further, examples of the raw material of “silica gel” include water glass and alkoxysilanes.

The most commonly used method for producing silica gel is to hydrolyze an alkaline silicate salt such as sodium silicate with a mineral acid and gelate the resulting silica hydrosol to dry it. In order to improve the performance of silica gel, many proposals have been made regarding the details of this manufacturing method.

For example, in Patent Document 1, silica hydrosol produced by the reaction of an aqueous alkali silicate solution and a mineral acid is gelated and treated with an acid solution having a pH of 2.5 or less,
After washing with water, there has been proposed a method for producing silica gel having a narrow pore distribution by adjusting the pH to 4 to 9 in an aqueous solution having a buffering effect and performing hydrothermal treatment. In addition, Patent Document 2
Proposes a method in which the silica hydrogel is dried by batch fluidized drying, followed by hydrothermal treatment.

According to these production methods, the performance of the obtained silica gel is certainly changed, and silica gel having a sharper pore distribution can be produced. But,
The pore volume, specific surface area and average pore diameter of the obtained silica gel cannot be sufficiently changed, and heat resistance and water resistance are not sufficient, so that it is not sufficient as a method for obtaining silica in a desired physical property range. is there.

The silica obtained from the alkali silicate as a raw material by the former method usually contains a considerable amount of impurities such as sodium, calcium and magnesium derived from the raw material. The presence of impurities in silica has a great influence on the performance of silica even if the total content thereof is a trace amount of several hundred ppm. For example, 1) the presence of these impurities promotes the crystallization of silica gel at high temperatures, and 2) the presence of these impurities promotes the hydrothermal reaction of silica gel in the presence of water, and Expansion of volume,
3) These impurities lower the sintering temperature, resulting in a decrease in the specific surface area and an increase in the pore distribution. Therefore, heating silica gel containing these impurities promotes a decrease in the specific surface area. Can be mentioned. This effect is particularly strong in impurities containing an element belonging to an alkali metal or an alkaline earth metal.

On the other hand, as a method for producing high-purity silica gel having extremely few impurities, a method of purifying a gel obtained by neutralizing an alkali silicate salt and a method of hydrolyzing a silicon alkoxide are known. In particular, in the latter method, since the silicon alkoxide can be purified by distillation or the like, it is possible to obtain silica gel of high purity relatively easily. However, silica gel obtained from a silicon alkoxide by the sol-gel method generally has a small average pore diameter and a wide pore distribution. Moreover, even if hydrothermal treatment is applied to this silica gel, there is almost no report of noticeable improvement in performance.

On the other hand, Non-Patent Document 1 discloses that an electrically neutral
After forming a supramolecular structure consisting of hydrogen bonds between the gemini surfactant and the silica precursor, the gemini surfactant is removed to obtain heat resistance (1000 ° C) and water resistance (1
It is described that a mesoporous molecular sieve having a temperature of 00 ° C. for 150 hours or more) is produced. This is a kind of so-called micellar template silica that forms pores using an organic template, and is capable of producing silica having a very sharp pore distribution compared to the above-mentioned respective conventional techniques. You can However, in this production method, there is a problem that the water resistance of the obtained silica is not sufficient, the production process is complicated, and the productivity is poor.

[0010]

[Patent Document 1] Japanese Patent Laid-Open No. 62-113713

[Patent Document 2] Japanese Unexamined Patent Publication No. 9-30809

[Non-Patent Document 1] Kim et al., Ultrastable Mesostruct
ured Silica Vesicles Science, 282, 1302 (1998)

[0011]

When silica is used for various purposes, the particle size,
It often controls various factors such as particle shape, hardness, agglomeration state, and particle size distribution to provide additional performance. In particular, a silica agglomerate of fine particles is useful in any of the various applications described above. Among them, a low-strength agglomerate of a fine particle is, for example, a certain amount before use such as during charging or transportation. It is preferably used in applications where it is desirable to maintain the shape and disintegrate into fine particles when used.

For example, when silica is used as a carrier for an olefin polymerization catalyst, it is known that the polyolefin polymerized on the surface of the catalyst supported on the silica particles grows while the silica particles are disintegrated. It is desirable to use low-strength silica particles as the polymerization catalyst carrier. Further, when silica is used for applications such as anti-blocking agents for films and matting agents for coatings, fine powdery silica is preferably used, but dust is not generated at the time of preparation, bulk specific gravity is large, and the composition is large. Since it is required to be easy, it may be provided in the form of a fine particle aggregate. Furthermore, when silica is used as an additive to foods, oral pharmaceutical carriers, synthetic detergents, etc., the form before use is granulated to suppress powdering and facilitate handling, and at the time of use, it is immediately atomized into water. It is desirable to disperse them into

In addition, when handling silica fine particle related products, for the purpose of automation of supply and packaging, improvement of accuracy, conversion from weight to quantity, and improvement of packaging materials,
The shape of the fine particle aggregate may be required. These applications are just a few examples, and silica fine particle aggregates have been used for various applications from the past, but recently, in each application, the pore distribution is sharper and even after the aggregating step. Materials having stable physical properties such as pore characteristics have been desired.

The term "silica fine particle agglomerate" as used herein means that agglomerates of silica primary particles having a particle size of 0.1 to 10 μm are agglomerated to form an agglomerate having a particle size of 5 times the primary particle size or more. The following methods are mentioned as a method for producing such silica fine particle aggregates. Silica obtained by a conventionally known method is finely pulverized, and if necessary, an inorganic or organic binder component is added to aggregate. The reaction conditions at the time of silica synthesis are manipulated to directly obtain silica in the state of aggregated particles.

The above method is the most frequently used method for obtaining agglomerates of powder, and silica obtained by a conventionally known method is subjected to a wet or dry pulverization method.
It is pulverized into fine powder (primary particles) having a size of μm or less, and processed into an aggregate shape by a known granulation method. As the porous silica material obtained by a conventionally known method, as described above, water glass is used as a raw material, those whose pores are controlled by hydrothermal treatment, and those whose silicon alkoxide is a raw material and whose pores are controlled by hydrothermal treatment, water. It is known that glass or silicon alkoxide is used as a silica source, pores are formed by using an organic template such as a surfactant, and only the template is removed by washing or firing (micelle template silica). Although it can be made into an aggregate by the above method, the physical properties of the obtained silica fine powder aggregate are basically the physical properties of the raw silica before being made into an aggregate, so that a sharp pore distribution is obtained. It was not possible to obtain a silica fine powder agglomerate having the following properties and excellent physical property stability. Further, the physical properties of the raw material silica are likely to change in each step of pulverization and agglomeration, and it has been difficult to obtain a fine powder agglomerate in which the pore characteristics of the raw material are sufficiently utilized.

On the other hand, as an example of the above method, when the water glass is neutralized with sulfuric acid to obtain silica hydrogel, the pH value is 7
A method for producing silica, which is so-called precipitated silica, in which gelation occurs in an alkaline region of 10 to 10. The silica obtained by this method generally has a very small specific surface area and pore volume, and the pore distribution often does not have a sharp peak. In addition, since the degree of freedom in controlling the aggregation state is low, it is difficult to control the particle size and crushing strength of the aggregate.

As described above, the crushing strength is controlled to be low, the high specific surface area and the high pore volume have a sharp pore distribution, the stability of physical properties is excellent, the manufacturing cost is low, and the productivity is low. Also, there has been a demand for a silica fine powder agglomerate which is excellent, that is, which has various physical properties in good balance.

The present invention has been made in view of the above problems. That is, the object of the present invention is low crushing strength, high specific surface area and high pore volume, has a sharp pore distribution, excellent heat resistance, water resistance, stability of physical properties, etc. It is to provide a novel silica fine particle aggregate that is low and excellent in productivity.

[0019]

Therefore, the present inventors have
As a result of intensive studies to solve the above problems, the crushing strength is controlled to be low, and it is possible to successfully produce a silica fine particle aggregate having less distortion in the structure, which satisfies various physical properties in a well-balanced manner, The present invention has been completed by finding that it can be effectively solved.

That is, the gist of the present invention is a fine particle agglomerate made of silica having a mode diameter (D _max ) of pores of less than 20 nm, and having a crushing strength of 100 N or less, and
The chemical shift of the Q ⁴ peak in solid-state Si-NMR is δ
(Ppm), δ satisfies the following formula (I) −0.0705 × (D _max ) −110.36> δ ... (I), and relates to a silica fine particle aggregate. .

Further, the silica fine particle aggregate is
(A) the pore volume is 0.6 to 1.6 ml / g,
(B) has a specific surface area of 200 to 1000 m ² / g,
(C) diameter the total volume of pores in the range of D _{m ax} ± 20%, at least 50% of the total volume of all the pores, is at 100ppm or less total content of (d) metal impurities This is a preferable feature.

In the present invention, "silica" refers to both silicic acid anhydride and hydrous silicic acid, as described above. In the present invention, among silica, hydrous silicic acid, particularly in so-called "silica gel" and micellar template type silica,
The effect is remarkable.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The silica fine particle aggregate of the present invention is characterized by being formed by agglomeration of silica fine particles (primary particles). The primary particles preferably have a particle size of about 0.1 to 10 μm, and the silica fine particle aggregate of the present invention constituted by the primary particles preferably has a particle size of 5 times or more the particle size of the primary particles. .

Further, the silica fine particle aggregate of the present invention is characterized in that the crushing strength thereof is as low as 100 N or less. Here, the crushing strength is one measure showing the strength of the fine particle aggregate. For applications requiring high strength, this value generally needs to be 15 kgf (about 147 N) or more. Considering this, the crush strength is 100
Aggregates of the present invention that are N or less are particles having relatively low strength. If the crushing strength is less than 30 N, the particles may be broken at the time of charging and it is difficult to use as a molded product. When the value is as low as about 10 N, it is barely possible to keep the particle shape. However, these numerical values are for reference only, and the crush strength suitable for each application is different.

In the silica fine particle aggregate of the present invention, the mode diameter of pores (D _max ) is less than 20 nm. That is, the mode diameter (D _max ) is a characteristic relating to adsorption and absorption of gas or liquid, and the smaller the mode diameter (D _max ) is, the higher the adsorption and absorption performance is. Therefore, among the various characteristics, the most frequent diameter (D _max ) is an important physical property especially for silica fine particle aggregates used as catalyst carriers and adsorbents. The most preferred mode diameter (D _max ) of the silica of the present invention is 17 nm or less, more preferably 15 nm or less. The lower limit is not particularly limited, but is usually 2 nm or more.

The above-mentioned modal diameter (D _max ) is determined from the isothermal desorption curve measured by the BET method by nitrogen gas adsorption / desorption according to E.
P. Barrett, LG Joyner, PH Haklenda, J. Amer.
It is obtained by plotting a pore distribution curve calculated by the BJH method described in Chem. Soc., Vol. 73, 373 (1951). Here, the pore distribution curve refers to the differential pore volume, that is, the differential nitrogen gas adsorption amount (ΔV / Δ (logd)) with respect to the pore diameter d (nm). The above V represents the nitrogen gas adsorption volume.

Further, the silica fine particle aggregate of the present invention comprises:
Looking at the three-dimensional structure of silica constituting this, it is preferable that it is amorphous, that is, no crystalline structure is recognized. This means that the silica fine particle aggregate of the present invention is
It means that substantially no crystalline peak is observed when analyzed by line diffraction. In the present specification, crystalline silica refers to a silica that exhibits at least one peak of a crystal structure at a position exceeding 6 angstroms (Å Units d-spacing) in an X-ray diffraction pattern. An example of such a silica material is micellar template silica that forms pores using an organic template. The fine particle aggregate made of amorphous silica is extremely excellent in productivity as compared with the fine particle aggregate made of crystalline silica.

In addition, the silica fine particle aggregate of the present invention comprises:
It is characterized in that the structure of silica constituting this has little distortion. Here, the structural distortion of silica is due to solid Si-
It can be represented by the value of the chemical shift of the Q ⁴ peak in the NMR measurement. Hereinafter, the relationship between the structural strain of silica and the value of the chemical shift of the Q ⁴ peak will be described in detail.

The silica constituting the silica fine particle aggregate of the present invention is a hydrate of amorphous silicic acid, and is composed of SiO ₂ .nH ₂
It is represented by the rational formula of O, but structurally, it has a structure in which O is bonded to each vertex of a tetrahedron of Si, and Si is further bonded to these O to spread in a net shape. And Si-O
In some of the repeating units of —Si—O—, some of O is substituted with another member (eg, —H, —CH ₃ etc.), and when one Si is focused, the following formula (A) , Si (Q ⁴ ) having ⁴ —OSi, and Si (Q ³ ) having 3 —OSi as shown in the following formula (B).
Etc. (in the following formulas (A) and (B), the above tetrahedral structure is ignored, and the Si—O net structure is represented in a plane). Then, in the solid-state Si-NMR measurement, the above-mentioned peaks based on each Si are Q ⁴ peaks,
Q ³ peak, called a ....

[0030]

[Chemical 1]

The feature of the silica fine particle agglomerate of the present invention is that when the chemical shift of the Q ⁴ peak is δ (ppm), δ is represented by the following formula (I) −0.0705 × (D _max ) −110. .36> δ ... (I). δ satisfies the above formula (I), that is, the value of δ is smaller than the value represented by the left side of the above formula (I) (−0.0705 × (D _max ) −110.36) (more negative). Existing on the side) means that the bond angle represented by two —OSi with respect to Si has little distortion.

The chemical shift value δ of the above Q ⁴ peak
Is usually larger than the value calculated based on the left side of the above formula (I). Therefore, the silica fine particle aggregate of the present invention has a smaller value of the chemical shift of the Q ⁴ peak than the conventional silica fine particle aggregate. This means that in the silica fine particle aggregate of the present invention, the chemical shift exists in a high magnetic field, and the above-mentioned bond angle is more uniform and the strain is small. In the present invention, the chemical shift δ of the Q ⁴ peak of silica is preferably a value (−0.0705 × (D _max ) -110.3 calculated based on the left side of the formula (I).
The value is smaller than 6) by 0.05% or more, more preferably 0.1% or more, and particularly preferably 0.15% or more.

The chemical shift value δ of the Q ⁴ peak is −106.00 to −11 for ordinary silica.
Although observed in the range of 3.00 ppm, the silica of the present invention has a larger value, specifically, -111.00 to
It is preferably present in the range of -112.00 ppm. This also means that in the silica of the present invention, the above bond angle is more uniform and the strain is small. In addition,
The reason why the chemical shift value δ of the Q ⁴ peak has the above-described width is that two −O atoms are usually observed with respect to the observed Si.
This is because the bond angle represented by Si has various values.

The relationship between the excellent heat resistance and water resistance of the silica fine particle agglomerate of the present invention and the above-mentioned structural strain is not necessarily clear, but is presumed as follows. That is, silica is composed of aggregates of spherical particles of different sizes, but in the state where the structural distortion is small as described above, a high degree of microstructural homogeneity of the entire spherical particles is maintained. Therefore, as a result, it is considered that excellent heat resistance and water resistance are exhibited. In addition, since the peak of Q ³ or less is limited in the spread of the Si—O net structure, structural distortion of silica is difficult to appear.

Further, in relation to the above characteristics, the silica fine particle aggregate of the present invention has a Q ⁴ by solid-state Si-NMR measurement.
The value of / Q ³ is usually 1.3 or more, preferably 1.5 or more. Here, the value of Q ⁴ / Q ³ refers to the Si (Q ³ ) having three —OSi bonded to the Si having four —OSi bonded among the repeating units of silica described above.
It means the molar ratio of (Q ⁴ ). The upper limit value is not particularly limited, but is usually 10 or less. It is generally known that the higher this value is, the higher the thermal stability of silica is. From this, it is understood that the silica fine particle aggregate of the present invention is extremely excellent in thermal stability. The crystalline micelle template silica often has a Q ⁴ / Q ³ value of less than 1.3,
Low thermal stability, especially hydrothermal stability.

The chemical shift of Q ⁴ peak and Q ⁴
The value of / Q ³ can be calculated based on the result of solid-state Si-NMR measurement performed by the method described later in the description of the examples. The analysis of the measurement data (determination of the peak position) is performed by a method of dividing and extracting each peak by, for example, waveform separation analysis using a Gaussian function.

In addition to the above characteristics, the silica fine particle aggregate of the present invention preferably has a pore volume and a specific surface area in a range larger than usual. Specifically, the value of the pore volume is usually in the range of 0.6 to 1.6 ml / g, and in particular, 0.
In the range of 8 to 1.6 ml / g, and the value of specific surface area is
Usually in the range of 200 to 1000 m ² / g, especially 300 to
Range of 900m ² / g, it is particularly preferable to present in a range of 400~900m ² / g. The values of these pore volume and specific surface area are measured by the BET method by nitrogen gas adsorption / desorption.

In the silica fine particle agglomerate of the present invention, the total volume of pores in the range of ± 20% of the value of the mode diameter (D _max ) is usually 50% of the total volume of all pores. Above all, it is preferably 60% or more. Further, the total volume of pores within the range of ± 20% centering on the value of the above-mentioned mode diameter (D _max ) is usually 90% or less of the total pore volume.
This means that the diameter of the pores of the silica fine particle aggregate of the present invention is uniform in the pores near the mode diameter (D _max ).

In relation to such characteristics, the silica fine particle aggregate of the present invention has a differential pore volume ΔV / Δ (log in the mode diameter (D _max ) calculated by the above BJH method.
d) is usually 2 to 20 ml / g, especially 3 to 12 ml / g
Is preferred. In the above equation, d is the pore diameter (nm), and V is the nitrogen gas adsorption volume. Those differential pore volume [Delta] V / delta that (logd) is included in the range, the absolute amount of pores are aligned in the vicinity of the modal diameter (D _{ma x)} is said to be extremely high.

The silica fine particle aggregate of the present invention preferably has a very low impurity content and an extremely high purity. Specifically, alkali metals, alkaline earth metals, groups 13 and 14 and 1 of the periodic table, which are known to affect the physical properties of silica, are known.
The total content of metal elements (metal impurities) belonging to the group consisting of Group 5 and transition metals is usually 500 ppm or less, particularly 100 ppm or less, further 50 ppm, and particularly 10 p.
It is preferably pm or less. In particular, the total content of elements belonging to the group consisting of alkali metals and alkaline earth metals, which has a particularly large effect on the physical properties of silica, is 1
00ppm or less, 50ppm or less, further 30p
It is preferably pm or less, and particularly preferably 10 ppm or less.
The fact that the influence of impurities is small is one of the major factors by which the silica fine particle aggregate of the present invention can exhibit excellent properties such as high heat resistance and water resistance.

Unlike the conventional sol-gel method, the silica fine particle aggregate of the present invention forms a silica hydrogel through a condensation step of condensing the obtained silica hydrosol with a hydrolysis step of hydrolyzing a silicon alkoxide. After the hydrolysis / condensation step, and subsequent to the hydrolysis / condensation step, a hydrothermal treatment without aging the silica hydrogel is performed to obtain a raw material silica having a desired physical property range, and the obtained raw material silica is finely divided. It can be manufactured by a method including both a pulverizing process to form primary particles and a fine pulverizing / granulating process of granulating the primary particles into an aggregate form.

The silicon alkoxide used as the material for the silica fine particle aggregate of the present invention includes trimethoxysilane, tetramethoxysilane, triethoxysilane, tetraethoxysilane, tetrapropoxysilane,
Examples thereof include tri- or tetraalkoxysilanes having a lower alkyl group having 1 to 4 carbon atoms such as tetrabutoxysilane, and oligomers thereof, but tetramethoxysilane, tetraethoxysilane and oligomers thereof are preferable. Since the above silicon alkoxides can be easily purified by distillation, they are suitable as a raw material for high-purity silica. The total content of metal impurities in the silicon alkoxide is usually 100 ppm or less, preferably 50 ppm or less, more preferably 30 ppm or less, and particularly preferably 10 ppm or less. The content of these metal impurities can be measured by the same method as the general method for measuring the content of impurities in silica.

The hydrolysis of silicon alkoxide is usually 2 to 20 mol per mol of silicon alkoxide.
It is preferably carried out using 3 to 10 mol, particularly preferably 4 to 8 mol of water. Hydrolysis of the silicon alkoxide produces a hydrogel of silica doped with the target foreign element and an alcohol. The temperature during the hydrolysis is usually 30 ° C. or higher, preferably 40 ° C. or higher, more preferably 50 ° C. or higher, and usually 100 ° C. or lower, preferably 90 ° C. or lower, and particularly preferably 80 ° C. or lower, further preferably Is 70 ° C. or lower. This hydrolysis reaction can be carried out at a higher temperature by maintaining the liquid phase under pressure.

Further, at the time of hydrolysis, a solvent such as alcohols which is compatible with water may be added if necessary.
Specifically, lower alcohols having 1 to 3 carbon atoms, dimethylformamide, dimethylsulfoxide, acetone, tetrahydrofuran, methylcerolrub, ethylcerolrub,
Methyl ethyl ketone and other organic solvents that can be arbitrarily mixed with water can be optionally used, but among them, those which do not exhibit strong acidity or basicity are preferable from the reason that a uniform silica hydrogel can be produced.

When these solvents are not used, the stirring speed at the time of hydrolysis is particularly important for the production of the silica fine particle aggregate of the present invention. That is, since the silicon alkoxide and the water for hydrolysis are separated in the initial stage,
The mixture is emulsified by stirring to accelerate the reaction.

At this time, it is important to perform sufficient stirring. For example, when a stirring device having a stirring blade on the rotating shaft is used, the stirring speed (the number of rotations of the rotating shaft) usually depends on the shape of the stirring blade, the number of sheets, the contact area with the liquid, etc. 30 rpm or more, preferably 50 rpm or more.

Further, if the stirring speed is generally too fast, the droplets generated in the tank may block various gas lines, or may adhere to the inner wall of the reactor to deteriorate heat conduction, thereby controlling physical properties. It may affect important temperature control. Further, the adhered substance on the inner wall may be peeled off and mixed into the product to deteriorate the quality. For this reason, the stirring speed is preferably 2000 rpm or less, and more preferably 1000 rpm or less.

In the present invention, the stirring method of the separated two liquid phases (aqueous phase and silicon alkoxide phase) may be any stirring method as long as it is a method of promoting the reaction. Among these, examples of an apparatus for further mixing the two liquid phases include the following.

A device having a stirring blade in which the rotary shaft is inserted perpendicularly or at a slight angle to the liquid surface and the liquid flows vertically. : A stirrer having a stirring blade provided with a rotation axis direction substantially parallel to an interface between the two liquid phases and stirring the two liquid phases.

The rotation speed of the stirring blade when using the above-mentioned device is the peripheral speed of the stirring blade (the speed of the stirring blade tip).
, 0.05-10 m / s, especially 0.1-5 m / s,
Further, it is preferably 0.1 to 3 m / s.

The shape and length of the stirring blade are arbitrary, and examples of the stirring blade include propeller type, flat blade type, angled flat blade type, pitched flat blade type, flat blade disc turbine type, curved blade type, Examples include the Faudler type and the bull margin type.

The width of the blades, the number of blades, the angle of inclination, etc. are determined by
It may be appropriately selected according to the size and the target stirring power. For example, the ratio (b / D) of the blade width (blade length in the rotation axis direction) to the inner diameter of the reactor (the longest diameter of the liquid phase surface forming a plane perpendicular to the rotation axis direction) is 0.05 to 0.2,
A preferable example is a stirrer having an inclination angle (θ) of 90 ° ± 10 ° and 3 to 10 blades.

Above all, a structure in which the above-mentioned rotary shaft is provided above the liquid level in the reaction vessel and a stirring blade is provided at the tip of the shaft extended from this rotary shaft is suitable from the viewpoint of stirring efficiency and equipment maintenance. used.

If the stirring conditions are not satisfied, it will be difficult to obtain the silica fine particle aggregate of the present invention. In addition, it is preferable to stop the stirring in order to form a uniform hydrogel after alcohol is generated by the hydrolysis and the liquid becomes a uniform liquid and the heat generation is stopped.

Silica having crystallinity tends to have poor thermal stability in water, and when the silicon alkoxide is hydrolyzed in the presence of a template such as a surfactant used to form pores in the gel, The gel easily becomes crystalline. Therefore, in the present invention, it is preferable to hydrolyze in the absence of a template such as a surfactant, that is, under the condition that they do not exist in an amount sufficient to exert the function as a template.

The reaction time depends on the composition of the reaction solution (the kind of silicon alkoxide and the molar ratio with water) and the reaction temperature, and since the time until gelation differs, it is not generally specified. As a catalyst in the reaction system, acid, alkali,
Hydrolysis can be promoted by adding salts and the like. However, the use of such additives is not preferred in the production of the silica of the present invention, as it will cause aging of the produced hydrogel, as will be described later.

In the above hydrolysis reaction of the silicon alkoxide, the silicon alkoxide is hydrolyzed to produce a silicate, but subsequently, the condensation reaction of the silicate occurs, the viscosity of the reaction solution increases, and finally the gelation occurs. It becomes silica hydrogel. In order to produce the silica fine particle aggregate of the present invention, it is important to perform hydrothermal treatment immediately without substantially aging so that the hardness of the hydrogel of silica produced by the above hydrolysis does not increase. is there. When hydrolyzing a silicon alkoxide, a soft silica hydrogel is produced, but by the method of subjecting this hydrogel to stable aging or drying, and further subjecting it to hydrothermal treatment, the pore characteristics are finally controlled. It is difficult to produce silica having the physical property range defined by.

Immediately performing hydrothermal treatment on the silica hydrogel produced by hydrolysis as described above, without substantially aging, means that the soft state immediately after the silica hydrogel is produced is maintained, and It means that it is subjected to hydrothermal treatment.

Specifically, it is preferable that the hydrothermal treatment is generally performed within 10 hours from the time when the silica hydrogel is formed, and within 8 hours, more preferably within 6 hours, and particularly within 4 hours. Hydrothermal treatment is preferred.

In an industrial plant or the like, a large amount of produced silica hydrogel is temporarily stored in a silo or the like,
It may be possible that hydrothermal treatment is performed thereafter. In such a case, in the silica hydrogel, the time from the production of the silica hydrogel to the hydrothermal treatment, that is, the so-called standing time may exceed the above range. In such a case, the liquid component in, for example, the silica hydrogel may not be dried during the standing in the silo so that the aging does not substantially occur.

Specifically, for example, the inside of the silo may be sealed or the humidity may be adjusted. Further, the silica hydrogel may be left standing while the silica hydrogel is immersed in water or another solvent.

It is preferable that the temperature during standing is as low as possible, for example, 50 ° C. or lower, especially 35 ° C. or lower,
In particular, it is preferable to stand at 30 ° C. or lower. Further, as another method of preventing aging substantially, there is a method of preparing the silica hydrogel by controlling the raw material composition in advance so that the silica concentration in the silica hydrogel becomes low.

Considering the effect obtained by the hydrothermal treatment without substantially aging the silica hydrogel and the reason why this effect is obtained, the following can be considered.

First, when the silica hydrogel is aged,
It is considered that a macroscopic network structure of —Si—O—Si— bonds is formed in the entire silica hydrogel. Since this network structure is present in the entire silica hydrogel, it is considered that this network structure becomes an obstacle during hydrothermal treatment, making it difficult to form mesoporous materials. Further, the silica hydrogel obtained by controlling the raw material composition in advance so that the silica concentration in the silica hydrogel becomes low can suppress the progress of crosslinking in the silica hydrogel that occurs during standing. Therefore, it is considered that the silica hydrogel does not age.

Therefore, in the present invention, it is important to carry out hydrothermal treatment without aging the silica hydrogel.

It is not preferable to add an acid, alkali, salt or the like to the hydrolysis reaction system of the silicon alkoxide, or to make the temperature of the hydrolysis reaction too strict, as this will accelerate the aging of the hydrogel. Further, in the post-treatment after the hydrolysis, washing, drying, leaving and the like should not take more temperature and time than necessary.

As a means for specifically confirming the aging state of the hydrogel, the hardness of the hydrogel measured by the method described in the below-mentioned examples can be referred to. That is,
By hydrothermally treating a hydrogel having a breaking stress of usually 6 MPa or less, preferably 3 MPa or less, more preferably 2 MPa or less, a silica fine particle aggregate having a physical property range defined by the present invention can be obtained.

As the condition of this hydrothermal treatment, the state of water may be liquid or gas, and may be diluted with a solvent or another gas, but liquid water is preferably used. The silica hydrogel is usually 0.1 to 10 times by weight, preferably 0.5 to 5 times by weight, particularly preferably 1 times.
~ 3 times by weight of water is added to form a slurry, usually 40 ~ 2
At a temperature of 50 ° C., preferably 50 to 200 ° C., usually 0.
It is carried out for 1 to 100 hours, preferably 1 to 10 hours.
Water used for hydrothermal treatment includes lower alcohols, methanol, ethanol, propanol, dimethylformamide (DMF), dimethylsulfoxide (DMSO),
Other organic solvents and the like may be included. It is also possible to carry out hydrothermal treatment by changing the temperature conditions using a hydrolysis reaction reactor, but the optimum conditions are usually different between the hydrolysis reaction and the subsequent hydrothermal treatment. Therefore, it is generally difficult to obtain the silica fine particle aggregate of the present invention.

When the temperature is raised under the above hydrothermal treatment conditions, the pore diameter and pore volume of the obtained silica tend to increase. The hydrothermal treatment temperature is 100 to 200 ° C.
It is preferably in the range of. Further, with the treatment time, the specific surface area of the obtained silica tends to gradually decrease after reaching the maximum once. Based on the above tendency, it is necessary to appropriately select the conditions according to the desired physical property values, but hydrothermal treatment is for the purpose of changing the physical properties of silica, and therefore, it is usually higher temperature conditions than the above hydrolysis reaction conditions. Preferably.

If the temperature and time of hydrothermal treatment are set outside the above ranges, it becomes difficult to obtain the silica fine particle aggregate of the present invention. For example, if the temperature of the hydrothermal treatment is too high, the pore size and pore volume of silica gel become too large, and the pore distribution also widens. On the other hand, if the temperature of the hydrothermal treatment is too low, the resulting silica has a low degree of crosslinking, poor thermal stability, no peak appears in the pore distribution, and Q ⁴ / S in solid Si-NMR described above. Q ³ value may become extremely small.

In particular, during the hydrothermal treatment, it is preferable to make the temperature rising rate fast so that the temperature in the reaction system reaches the target temperature within 5 hours. Specifically, it is filled in a tank and treated. In this case, the average heating rate from the start of heating to reaching the target temperature is 0.1 to 100 ° C./min, especially 0.1 to 30.
C./min, preferably 0.2 to 10.degree. C./min. A temperature raising method using a heat exchanger or the like, a method of charging hot water prepared in advance, and the like are also preferable because the temperature raising rate can be shortened. Further, if the temperature raising rate is within the above range, the temperature may be raised stepwise. When it takes a long time for the temperature in the reaction system to reach the target temperature, the aging of the silica hydrogel may proceed during the temperature rise, and the microstructural homogeneity may be deteriorated. The temperature rising time to reach the above target temperature is preferably within 4 hours, more preferably within 3 hours. The water used for the hydrothermal treatment can be preheated to shorten the temperature raising time.

When the hydrothermal treatment is performed in ammonia water, the same effect can be obtained at a lower temperature than that in pure water. Further, when hydrothermal treatment is performed in ammonia water, the silica finally obtained generally becomes hydrophobic as compared with the case of treatment in pure water, but it is usually 30 to 250 ° C., preferably 40 to 200 ° C. When hydrothermally treated at high temperature,
Especially, the hydrophobicity becomes high. The ammonia concentration in the ammonia water here is preferably 0.001 to 10%, and particularly preferably 0.005 to 5%.

The hydrothermally treated silica hydrogel is usually dried at 40 to 200 ° C, preferably 60 to 120 ° C. The drying method is not particularly limited, and may be a batch type or a continuous type, and can be dried under normal pressure or reduced pressure. However, when the crushing step of the next step is a wet method, the drying may be omitted in some cases. If necessary, when the carbon content derived from the raw material silicon alkoxide is contained, it can be usually removed by firing at 400 to 600 ° C. Further, in order to control the surface condition, firing may be performed at a temperature of up to 900 ° C. Thus, silica (raw material silica), which is a raw material for the silica fine particle aggregate of the present invention, is obtained.

Any known apparatus or instrument may be used as a method for finely pulverizing the raw material silica, but in order to obtain fine powder (fine silica particles) of 10 μm or less, a ball mill (rolling mill, vibrating ball mill, planetary mill) is used. Mill, etc.), stirring mill (tower type crusher, stirring tank type mill, flow tube type mill, annular (annular) mill, etc.), high speed rotary fine pulverizer (screen mill, turbo type mill, centrifugal classification type mill), jet Devices and instruments such as a crusher (circulation jet mill, collision type mill, fluidized bed jet mill), shear mill (decompressor, ong mill), colloid mill, mortar and the like can be used. Among these, a ball mill and a stirring mill are more preferable for obtaining ultrafine particles of 2 μm or less. The state during pulverization includes a wet method and a dry method, both of which can be selected, but the wet method is more preferable for obtaining ultrafine particles.
In the case of the wet method, as the dispersion medium to be used, any of organic solvents such as water and alcohol may be used, or a mixed solvent of two or more kinds may be used, and the dispersion medium may be selected depending on the purpose. Also,
In the case of the wet method, drying may be performed as necessary before starting the granulation step of the next step. It is not preferable to continue applying unnecessarily strong pressure or shearing force for a long time during fine pulverization, because the pore characteristics of the raw material silica may be impaired.

The silica fine particles (primary particles) obtained by fine pulverization are granulated by a known method to form an aggregate (for example, spherical). When silica has a primary particle diameter of 2 μm or less, agglomerated particles can be obtained by simply drying this as a water slurry without adding a binder. Is often required. Any binder can be used as the binder as long as it does not significantly impair the characteristics of the silica fine particle aggregate of the present invention or the primary silica particles constituting the aggregate. For example, as water-soluble substances, sugar, dextrose, corn syrup, gelatin, carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), other water-soluble polymers, water glass, and hydrolyzed silicon alkoxide, wet grinding (Silica) slurry, silica sol, colloidal silica (these can also be used in a solvent system) and the like. Further, when used by being dissolved in a solvent, various waxes, lacquers, silacs, oil-soluble polymers and the like can be used. Among these, as the binder, a high-purity silica slurry, silica sol, or the like is preferable because it does not impair the characteristics of the silica fine particle aggregate of the present invention.

When silica slurry, silica sol or the like is used, the dispersion medium may be any one such as water or an organic solvent. Of these, water and hydrophilic organic solvents are preferable, and water is particularly preferable.

The size (particle diameter) and shape of the silica fine particles present in the dispersion medium are arbitrary. Among them, it is preferable to use one having a particle size smaller than the primary silica particle diameter in the silica fine particle aggregate of the present invention, to maintain the pore characteristics of the silica fine particle aggregate of the present invention, and the binder property (bond the primary particles to each other in the silica fine particle aggregate. It is preferable from the standpoint of maintaining the characteristics of wearing). Further, the silica fine particles in this binder are preferably porous silica.

The size of the silica fine particles present in the dispersion medium is, for example, 1 nm to 1 μm. Above all,
The silica fine particles having a particle diameter of 0.1 μm or less are 0.1 to 0.1% with respect to the total silica fine particles in the silica slurry or silica sol.
It is preferable to adjust the concentration of the slurry or sol to be 50% by weight.

The amount of the silica fine particles contained in the silica slurry or silica sol used as the binder is arbitrary, but, for example, when aggregates of silica fine particles are formed, the amount of the silica particles derived from the binder is based on all the silica fine particles constituting the aggregate. It is preferable to adjust the slurry or silica sol so that the amount of silica fine particles is usually 0.1 to 50% by weight, and particularly 0.5 to 10% by weight.

The amount of binder used may be appropriately selected depending on the intended use of the silica fine particle aggregate. If the amount of the binder is too large, the pore characteristics of the silica fine particle aggregate of the present invention may be impaired. Conversely, if the amount is too small, the strength of the silica fine particle aggregate may be too small for the desired use. There is.

Further, when the binder is used, it is preferable to use the minimum amount, and to use a high-purity binder containing a small amount of metal impurities that induces a change in the physical properties of the raw material silica.

Any known method may be used as the method for granulating the silica fine particles. Typical methods are rolling method, fluidized bed method, stirring method, crushing method, compression method, extrusion method,
An injection method and the like can be mentioned. Among these, in order to obtain a silica fine particle aggregate of low strength and controlled pore characteristics of the present invention, attention is paid to the kind and amount of binder used, the selection of the purity, and unnecessary when granulating silica fine particles. It is important not to apply pressure. Further, the obtained fine particle agglomerates are crushed and classified as required to finally obtain the intended silica fine particle agglomerates of the present invention.

The silica fine particle aggregate of the present invention may have voids, that is, voids between the primary particles in the silica fine particle aggregate formed by the primary particles, in addition to the pores of the silica fine particles as the primary particles. Characterize. The method for measuring such voids is arbitrary, but may be determined by, for example, the mercury intrusion method.

The presence of these voids promotes the diffusion of the adsorbed substance or the reaction substance in the silica fine particle aggregate when the silica fine particle aggregate of the present invention is used as an adsorbent, a catalyst or a catalyst carrier. And because of this void,
Since the outer surface area of the primary particles (fine particles of silica) becomes relatively large, diffusion of adsorbents and reactants into the pores of the primary particles is promoted, and, for example, effects such as an increase in adsorption amount and an increase in catalytic reaction rate are achieved. Can be expected.

The voids in the silica fine particle aggregate of the present invention are preferably uniformly present in the silica fine particle aggregate. The volume of the voids in the silica fine particle aggregate of the present invention is arbitrary, but is usually 0.01 to 200%, and particularly 0.1 to 100% with respect to the pore volume of the primary particles measured by nitrogen gas adsorption. It is preferable.

The silica fine particle agglomerate of the present invention can be used for any purpose other than the conventional use of silica fine particle agglomerates. Among them, the conventional uses include the following.

For example, in the field of application used for manufacturing and treating products in industrial facilities, various catalysts and catalyst carriers (acid-base catalysts, photocatalysts, precious metal catalysts, etc.), wastewater / waste oil treatment agents, odor treatment agents, gas, etc. Examples of applications include separating agents, industrial desiccants, bioreactors, bioseparators, membrane reactors, and the like. Examples of building materials include humidity control agents, soundproofing / sound absorbing materials, refractories, and heat insulating materials. In the air conditioning field, desiccant air conditioner humidity control agents,
Examples include heat storage agents for heat pumps. In the application field of paints / inks, examples include matting agents, viscosity adjusting agents, chromaticity adjusting agents, anti-settling agents, antifoaming agents, ink strike-through preventing agents, stamping foils, and wallpaper. In the application field of additives for resins, anti-blocking agents for films (polyolefin films, etc.), plate-out prevention agents, reinforcing agents for silicone resins, reinforcing agents for rubber (for tires / general rubber, etc.), fluidity improvers, Powder resin anti-caking agent, printability improving agent, matting agent for synthetic leather and coating film, adhesive / adhesive tape filler, translucency adjusting agent, anti-glare adjusting agent, porous polymer sheet Applications include fillers for use. In the field of papermaking applications, thermal paper fillers (such as dust adhesion preventives), ink jet paper image improving fillers (ink absorbing agents, etc.), diazo photosensitive paper fillers (photosensitive density improving agents, etc.), tracing papers. Examples thereof include writability improvers, coated paper fillers (writability, ink absorbability, antiblocking property improvers, etc.), electrostatic recording fillers, and the like. In the field of food applications, filter aids for beer, hanging agents for fermented products such as soy sauce, sake, and wine, stabilizers for various fermented beverages (removal of turbidity factor protein and yeast, etc.), food additives, powdered food products, etc. Applications include anti-caking agents. In the field of medicines and agricultural chemicals, tableting aids for medicines, crushing aids, dispersion / pharmaceutical carriers (dispersion / sustained release / improved delivery, etc.), pesticide carriers (oil pesticide carrier / hydrated dispersibility improved, sustained release)・ Improvement of delivery property, etc., pharmaceutical additives (anti-caking agent, graininess improving agent, etc.), agricultural chemical additives (anti-caking agent, anti-settling agent, etc.) and the like. In the field of separation materials,
Examples thereof include packing materials for chromatography, separating agents, fullerene separating agents, adsorbents (proteins, dyes, odors, etc.), dehumidifying agents, and the like. In the field of agriculture, feed additives and fertilizer additives can be mentioned. As other uses, in the field of daily life, humidity control agents, desiccants, cosmetic additives, antibacterial agents, deodorant / deodorant / fragrance agents, detergent additives (surfactant powdering, etc.), abrasives (toothpaste) Etc.), powder fire extinguishing agents (powder graininess improving agents, anti-caking agents, etc.), antifoaming agents, battery separators and the like.

In particular, the silica fine particle agglomerate of the present invention is required to have controlled pore characteristics among these applications, and it is required that the physical properties of the aggregate should be small over a long period of time. It can be preferably used in applications where it is desirable to maintain a certain shape before use and to disintegrate into fine particles during use.

Specifically, for example, when silica is used as a carrier for an olefin polymerization catalyst, it is known that the polyolefin polymerized on the surface of the catalyst supported on the silica particles grows while the silica particles are disintegrated. Therefore, it is desirable to use low-strength silica particles as the olefin polymerization catalyst carrier. Further, when silica is used for applications such as anti-blocking agents for films and matting agents for coatings, fine powdery silica is preferably used, but dust is not generated at the time of preparation, bulk specific gravity is large, and the composition is large. Since it is required to be easy, it may be provided in the form of a fine particle aggregate. Furthermore, when silica is used as an additive to foods, oral pharmaceutical carriers, synthetic detergents, etc., the form before use is granulated to suppress powdering and facilitate handling, and at the time of use, it is immediately atomized into water. It is desirable to disperse them into Therefore,
In these applications, the silica fine particle pseudo-aggregate of the present invention can be particularly preferably used.

The silica fine particle aggregate of the present invention may have any shape such as a granular shape, a granular shape or a spherical shape, but the spherical shape is preferable because the following advantages can be obtained.・ High packing density during transportation and preparation. In a process such as slurry formation, the time required for slurry formation (the time required for uniform dispersion in a solvent such as water) is constant. This effect is particularly remarkable when the particle sizes are made uniform. -Part of the particles is less likely to collapse due to friction, minute pressure, etc., compared to amorphous particles, and is easy to handle. In particular, when used as an olefin polymerization catalyst carrier, the shape of the obtained polymer is similar to the shape of carrier silica, and thus the spherical shape is preferable to the amorphous shape.

[0091]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

(1) Silica analysis method 1-1) Pore volume, specific surface area: AS manufactured by Cantachrome
The BET nitrogen adsorption isotherm was measured at -1, and the pore volume and specific surface area were determined. Specifically, the pore volume is the relative pressure P / P _0.
= 0.98, the specific surface area is P / P ₀ =
BET from the nitrogen adsorption amount of 0.1, 0.2, 0.3
It was calculated using the multipoint method. In addition, the BJH method was used to determine the pore distribution curve and the differential pore volume at the mode diameter (D _max ). The distance between the measured relative pressure points was 0.025.

1-2) Powder X-ray diffraction: RA manufactured by Rigaku Denki Co., Ltd.
The measurement was performed using a D-RB device and CuKα as a radiation source. Divergence slit 1/2 deg, scattering slit 1/2
deg, the light receiving slit was 0.15 mm.

1-3) Content of metal impurities: Sample 2.5
Hydrofluoric acid was added to g to heat the mixture to dry it, and then water was added to make 50 ml. ICP emission spectrometry was performed using this aqueous solution. In addition, sodium and potassium were analyzed by the flame flame method.

1-4) Solid-state Si-NMR measurement: Bruk
The solid-state NMR device (“MSL300”) manufactured by er Co., Ltd. is used, and a sample tube with a resonance frequency of 59.2 MHz (7.05 Tesla) and 7 mm is used.
The measurement was performed under the condition of S (Cross Polarization / Magic Angle Spinning) probe. Table 1 below shows specific measurement conditions.
Shown in.

[0096]

[Table 1]

The analysis of the measurement data (determination of Q ⁴ peak position) is performed by a method of extracting each peak by dividing the peak. Specifically, waveform separation analysis using a Gaussian function is performed. For this analysis, Thermo Galatec (Thermo
Galatic) waveform processing software "GRAMS386"
Can be used.

1-5) Particle size distribution measurement: L manufactured by Seishin Enterprise
The particle size distribution and average particle size were measured using an MS-30 device (dispersion medium: water).

1-6) Crushing strength measurement: Fujisawa
Company hardness meter (Kiya type digital hardness meter KHT-20N
The crush strength was measured using a mold.

1-7) Particle size distribution measurement: L manufactured by Seishin Enterprise
The particle size distribution and average particle size were measured using an MS-30 device (dispersion medium: water).

(2) Production and Evaluation of Silica [Example 1] Production of raw material silica: 1000 g of pure water was put in a 5 L separable flask (with a jacket) made of glass and having a water-cooled condenser open to the atmosphere. Was charged. As for the stirring speed, while stirring so that the tip speed of the stirring blade becomes 2.5 m / s, tetramethoxysilane 1
400 g was charged over 3 minutes. The water / tetramethoxysilane molar ratio is about 6. Hot water at 50 ° C was passed through the jacket of the separable flask. The stirring was continued, and when the contents reached the boiling point, the stirring was stopped. Subsequently, warm water of 50 ° C. was passed through the jacket for about 0.5 hours to gelate the sol produced. Then, the gel was immediately taken out, and the gel was crushed through a nylon net having an opening of 600 microns to obtain a powdery wet gel (silica hydrogel). 450 g of this hydrogel and 450 g of pure water were charged into a 1 L glass autoclave,
Hydrothermal treatment was carried out under the conditions of 150 ° C. and 3 hours. After hydrothermal treatment for a predetermined time, No. The silica thus obtained was filtered with 5A filter paper and dried under reduced pressure at 100 ° C. to a constant weight without washing with water to obtain a raw material silica of Example 1. Various physical properties of the raw material silica of Example 1 are shown in Table 2 below.

Finely pulverized: The raw material silica of Example 1 (average particle size 30 μm) was supplied at a feed rate of 20 kg / hr using a vertical screw feeder, and STJ-200 manufactured by Seishin Enterprise Co., Ltd.
Type jet mill, pushing pressure 7kg / c
Preliminary pulverization was performed at m ² and a pulverization pressure of 7 kg / cm ^{2 to} obtain particles having an average particle size of 3 μm. The particles were collected with a filter cloth, and 500 g of the particles was charged into a 2 L polyethylene container together with 2 mm of 0.5 mm zirconia balls and 1 L of water (dispersion medium), and finely pulverized by a rolling ball mill at 100 rpm for 200 hours. Zirconia beads were removed from the obtained slurry, and the remaining silica fine particles (primary particles) were subjected to the granulation step as the slurry. The average particle size of silica fine particles is 0.2
It was 6 μm. The particles having a particle size of 0.1 μm or less accounted for 10% of the whole.

Granulation: 100 g of the jet mill pulverized silica obtained by the above method was placed in a rotating dish (rotation number: 30 rpm) kept at 60 ° C. The ball-milled silica slurry (silica concentration:
200 g (10% by weight) was gradually added using a spray and the rotation was continued.

After visually confirming particles of several mm, the particle size was further increased by 1
The rotation was continued for 5 minutes and then stopped. The obtained silica powder was classified, and particles of about 2 to 4 mm were collected to obtain silica fine particle aggregates.

Evaluation: Physical properties of the silica fine particle aggregate of Example 1 are shown in Table 3. In the powder X-ray diffraction pattern, no peak on the low angle side (2θ ≦ 5 deg) due to the periodic structure is observed. Further, the chemical shift value of the Q ⁴ peak of solid-state Si-NMR is represented by the above formula (I) (−0.0705 × (D
_It was smaller than the value calculated from the left side of ( _max ) −110.36> δ) (existing in a more negative region). The pore distribution curve was very sharp, and the deterioration of the pore characteristics was small even during the fine pulverization / granulation process. As the metal impurities, only the inclusion of zirconia and aluminum in the fine pulverization and granulation steps was recognized, and the total content thereof was extremely low at 2.3 ppm, and the purity was high. Since the value of the crush strength was 100 N or less, it is considered that the silica fine particle aggregate of Example 1 can be suitably used, for example, as a carrier for an olefin polymerization catalyst.

Example 2 To the slurry of the ball-milled silica obtained in Example 1, the jet-milled silica similarly obtained in Example 1 was added in an amount 3 times the dry weight of silica in the slurry. In addition, a slurry was prepared again.
Using this silica slurry as a material, a disk atomizer type spray dryer is used, and granulation is carried out under the conditions of contact method cocurrent flow, hot air inlet temperature 200 ° C., hot air outlet temperature 95 ° C., disk rotation speed 10000 rpm, and slurry concentration 34 wt%. As a result, semi-transparent spherical aggregate particles having a particle diameter of 45 to 150 μm (silica fine particle aggregate of Example 2)
Got

The silica thus obtained is obtained by passing through a spray dryer, a pipe and a cyclone in this order at the time of molding. When the silica of the present invention obtained through this series of devices was observed with an optical microscope, a few crushed particles were observed. This is because, for example, when this silica is used as a carrier for an olefin polymerization catalyst, a screw of an extrusion molding machine or an injection molding machine used when molding a polymer obtained by polymerization, or a container through which the polymer passes. It shows that the damage such as abrasion is small, and it is obvious that it is suitable for industrial production.

Moreover, it is easily predicted that the pore characteristics shown in the table have a favorable effect on the polymerization activity and the polymerization degree distribution of the olefin. The silica of the present invention is preferable because it can be easily ground with fingers and its strength is not too high.

[Comparative Example 1] Silica gel CARIAC manufactured by Fuji Silysia was used as raw material silica (raw material silica of Comparative Example 1).
An experiment was conducted under the same conditions as in Example 1 except that TG-6 (10 μm product) was used. The obtained aggregated particles (silica fine particle aggregates of Comparative Example 1) were semitransparent and spherical aggregated particles having an average primary particle diameter of 0.23 μm and an aggregated particle diameter of 45 to 150 μm.

Table 2 shows the physical properties of the raw material silica of Comparative Example 1, and Table 3 shows the physical properties of the silica fine particle aggregate of Comparative Example 1. In the powder X-ray diffraction diagram, the low angle side (2θ ≦ 5 due to the periodic structure is shown.
No deg) peak was observed. The pore distribution curve is not as sharp as that of the silica fine particle agglomerate of Example 1, and the degree of deterioration of the pore characteristics is slightly larger than that of the silica fine particle agglomerate of Example 1 even in the fine pulverization and granulation steps. It was The content of metal impurities is very high as compared with the silica fine particle aggregate of Example 1, and it is considered that the heat resistance and water resistance of silica are lower than those of Example 1. Also,
The value of the chemical shift of the Q ⁴ peak of solid-state Si-NMR is larger (existing in the more positive region) than the value calculated from the left side of the above formula (I), and its structure is shown in Example 1. Compared with the silica fine particle agglomerate, the strain is large and the physical properties are likely to change.

[0111]

[Table 2]

[0112]

[Table 3]

[0113]

The novel silica fine particle pseudo-collection of the present invention is
Not only large pore volume and specific surface area but also low crushing strength, sharp pore distribution, excellent heat resistance, water resistance, stability of physical properties, etc., and low manufacturing cost and productivity. Are better.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4G072 AA27 AA28 BB01 BB05 CC10                       GG01 GG03 HH30 JJ11 MM01                       MM26 RR12 TT05 TT08 TT09                       TT19 UU11 UU12 UU17

Claims (9)

[Claims] 1. An aggregate of fine particles of silica having a mode diameter (D _max ) of pores of less than 20 nm, having a crushing strength of 100 N or less, and having a Q ⁴ peak in solid Si-NMR measurement. When the chemical shift value is δ (ppm), δ satisfies the following formula (I) −0.0705 × (D _max ) −110.36> δ ... (I), Silica fine particle aggregate. 2. (a) Pore volume of 0.6-1.6 ml /
g, and (b) the specific surface area is 200 to 1000 m ² / g.
And (c) the total volume of pores having a diameter within the range of D _max ± 20% is 50% or more of the total volume of all pores,
(D) The total content of metal impurities is 100 ppm or less, and the silica fine particle aggregate according to claim 1. 3. The silica fine particle aggregate according to claim 1 or 2, which has a pore volume of 0.8 to 1.6 ml / g. 4. The silica fine particle aggregate according to claim 1, which has a specific surface area of 300 to 900 m ² / g. 5. The silica fine particle aggregate according to any one of claims 1 to 4, wherein the mode diameter (D _max ) of the pores is 2 nm or more. 6. The total volume of pores having a diameter within D _max ± 20% is 60% or more of the total volume of all pores, wherein the total volume is 60% or more. The silica fine particle aggregate described. 7. The silica fine particle aggregate according to claim 1, wherein a differential pore volume at a mode diameter (D _max ) is 2 to 20 ml / g. 8. Q ⁴ / Q ³ in solid-state Si-NMR measurement
The silica fine particle aggregate according to any one of claims 1 to 7, which has a peak value of 1.3 or more. 9. The method according to claim 1, wherein the silica gel obtained through the step of hydrolyzing a silicon alkoxide is manufactured through a step of pulverizing, then aggregating and granulating. The silica fine particle aggregate according to item 1.