JP2003221223A - Silica - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica having not only a large pore volume and a large specific surface area but also a narrow pore size distribution as well as excellent physical properties such as heat resistance and waterproofness, capable of suppressing amounts of useless metal impurities. <P>SOLUTION: This silica has a most frequent pore diameter (D<SB>max</SB>) of ≤20 nm, and the chemical shift δ (ppm) of Q<SP>4</SP>peak in a solid Si-NMR satisfies the inequality (1): -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 excellent in heat resistance and water resistance and particularly suitable as a catalyst carrier and an adsorbent.

[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.

Here, "silica" refers to both silicic acid anhydride and hydrous silicic acid. For example, as silicic acid anhydride,
Quartz, tridymite, cristobalite, coesite,
Examples include stishov stone 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 oligomers, and formed with an organic substance as a template, for example, manufactured by Mobil Co. : MCM-41 type silica (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 the heat resistance and water resistance are not sufficient, so that it is not sufficient as a method for obtaining silica gel in a desired physical property range. is there.

The silica obtained by the former method (the method described in Patent Document 1) using an alkali silicate salt as a raw material usually contains sodium, calcium, magnesium, titanium, aluminum, zirconium, etc. derived from the raw material. It contains a large amount of impurities. 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 temperature. 2) The presence of these impurities promotes the hydrothermal reaction of silica gel in the presence of water, resulting in a decrease in pore diameter and pore volume. 3) These impurities decrease the sintering temperature, so heating silica gel containing these impurities promotes the decrease of the specific surface area. The impact can be mentioned. This effect is particularly strong in impurities containing an element belonging to an alkali metal or an alkaline earth metal. Furthermore, if titanium or aluminum is present as an impurity on the surface of silica gel or in a siloxane bond, the number of acid points increases, and silica gel itself may exhibit an undesired catalytic action when used as a catalyst carrier or adsorbent.

On the other hand, as a method for producing high-purity silica gel containing very few impurities, a method of purifying a gel obtained by neutralizing an alkali silicate salt or a method of hydrolyzing a silicon alkoxide is suitable. This is known as a technique well known to those skilled in the art, and in particular, in the latter method, since the starting material silicon alkoxide can be purified by distillation or the like, it is possible to obtain highly purified silica gel relatively easily.

The method using an alkoxide as a raw material is basically a hydrolysis / condensation step of hydrolyzing a silicon alkoxide in the presence of a catalyst and condensing the obtained silica hydrosol to form a silica hydrogel, And a physical property adjusting step of hydrothermally treating the obtained silica hydrogel.

In the above hydrolysis / condensation step,
Acids (sulfuric acid, hydrochloric acid or nitric acid) are usually used as catalysts. Further, it is said that an aging step is provided before the above-mentioned physical property adjusting step (hydrothermal treatment), and the aging step is intended to improve the physical properties such as the strength of silica gel. Such a method is called a sol-gel method and is well known to those skilled in the art. 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 compared with the above-mentioned respective conventional techniques, silica having a very sharp pore distribution can be produced. it 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.

[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 Mesostruc
tured Silica Vesicles Science ", 282, 1302 (1998)

[0012]

The macroscopic structure of silica is well known, and it is known that spherical particles of silica colloid have a close and continuous three-dimensional structure in which they are in close contact with each other. The structure has not been fully elucidated yet. Therefore, it has been desired to analyze the microscopic structure of such silica and find a novel silica having a well-balanced above-mentioned various physical properties among silicas having a conventionally unknown microscopic structure.

The present invention has been made in view of the above problems. That is, the object of the present invention is a silica having a novel microstructure that has not been known so far, and not only has a large pore volume and specific surface area, but also has a narrow pore distribution and suppresses the amount of unnecessary metal impurities. It is an object of the present invention to provide silica which can be obtained and is excellent in physical properties such as heat resistance and water resistance, that is, which has various desirable attributes in a well-balanced manner.

[0014]

Therefore, the present inventors have
As a result of diligent studies to solve the above problems, after the step of hydrolyzing and condensing the silicon alkoxide, the aging step is omitted and the physical property adjusting step is subsequently performed to obtain a specific structure characterized by solid-state Si-NMR. The present invention has been completed based on the finding that the silica having the above is obtained, which is excellent in heat resistance and hydrothermal resistance, and that fine pore control is possible.

That is, the gist of the present invention is silica having a mode diameter of pores (D _max ) of 20 nm or less, which is solid S.
The chemical shift of the Q ⁴ peak in i-NMR is represented by δ (pp
m), δ satisfies the following formula (I) −0.0705 × (D _max ) −110.36> δ ... (I).

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. (1) Characteristics of Silica of the Present Invention The silica of the present invention is hydrous silicic acid, and is SiO ₂ · nH ₂
It is represented by the rational formula of O. In the present invention, the effect is remarkable especially in “silica gel” and micellar template type silica among silica.

The silica of the present invention has a mode diameter (D) of pores.
_max ) is smaller than the usual one. The mode diameter (D _max ) is a characteristic that affects the adsorption and absorption of gas and liquid, and the smaller the mode diameter (D _max ) is, the higher the adsorption and absorption performance is. Therefore, among various characteristics, the mode diameter (D _max ) is an important physical property especially for silica used as a catalyst carrier or an adsorbent. Specifically, the preferred mode diameter (D _max ) of the silica of the present invention is usually 20 nm or less, preferably 17 nm or less, more preferably 15 nm.
It is the following. The lower limit is not particularly limited, but usually 2 nm
That is all.

The above-mentioned modal diameter (D _max ) is determined from the isothermal desorption curve measured by the BET method by adsorption and desorption of nitrogen gas.
P. Barrett, LG Joyner, PH Haklenda, J. Amer.
It is determined 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, in view of the three-dimensional structure of the silica of the present invention, in addition to the characteristics of the pore structure described above, it is preferable that the silica is amorphous, that is, no crystalline structure is recognized. . This means that when the silica of the present invention is analyzed by X-ray diffraction, substantially no crystalline peak is observed. In addition, in the present specification, non-amorphous silica refers to silica having at least one peak of a crystal structure at a position exceeding 6 Å (Å Units d-spacing) in an X-ray diffraction pattern. Amorphous silica is much more productive than crystalline silica.

In addition, the silica of the present invention is characterized in that its structure is less strained. Structural distortion of silica can be expressed by the value of Q ⁴ peak chemical shift in the solid Si-NMR measurement. Hereinafter, the relationship between the structural strain of silica and the chemical shift value of the Q ⁴ peak will be described in detail.

The silica of the present invention is represented by the above-mentioned rational formula. Structurally, O is bonded to each vertex of the tetrahedron of Si, and Si is further bonded to these O to form a net shape. Has a spread structure. And in the repeating unit of Si-O-Si-O-, a part of O is another member (for example, -O).
H, —OCH ₃ etc.), and when attention is paid to one Si, Si (Q ⁴ ) having four —OSi as shown in the following formula (A) and the following formula (B ), Si (Q ³ ) having three —OSi, etc. are present (in the following formulas (A) and (B), the above tetrahedral structure is ignored, and the net structure of Si—O is flat. Is represented). Then, in solid-state Si-NMR measurement, the peaks based on the respective Si described above are Q ⁴ peak, Q ³ peak, and
・ ・ It is called.

[0022]

[Chemical 1]

The greatest feature of the silica of the present invention is that the above-mentioned Q
^When the chemical shift of ⁴ peaks is δ (ppm), δ satisfies the following formula (I). −0.0705 × (D _max ) −110.36> δ (I) This fact means that the bond angle represented by two —OSi with respect to Si has little distortion.

The value δ of the Q ⁴ peak is usually larger than the value calculated based on the left side of the above formula (I).
Therefore, the silica of the present invention has a Q
The chemical shifts of the ^four peaks will have smaller values. This means that in the silica 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 less. 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).
It is preferably 0.05% or more, more preferably 0.1% or more, and particularly preferably 0.15% or more smaller than 6).

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 smaller value, specifically, -111.00.
It is preferably present in the range of from -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 Q ⁴ peak has the width as described above is that the bond angles represented by two —OSi usually have various values with respect to the observed Si.

Regarding the relation between the excellent heat resistance and water resistance of the silica of the present invention and the above-mentioned structural strain,
Although not always clear, it is estimated as follows. That is, silica is composed of aggregates of spherical particles of different sizes, but in a state where there is little structural distortion 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 strain of silica is less likely to appear.

Further, the silica of the present invention is a solid Si-NM.
The value of Q ⁴ / Q ³ measured by R is usually 1.3 or more, preferably 1.5 or more. Here, the value of Q ⁴ / Q ³ refers to S in which four —OSi are bonded to Si (Q ³ ) in which three —OSi are bonded among the above-mentioned silica repeating units.
It means a molar ratio of i (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, the higher the thermal stability of silica,
From this, it can be seen that the silica of the present invention is extremely excellent in thermal stability. On the other hand, crystalline micellar template silica often has a Q ⁴ / Q ³ value of less than 1.3 and is low in thermal stability, particularly in 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.

One feature of the silica of the present invention is that the pore volume and the specific surface area are in a range larger than usual values. Specifically, the value of the pore volume is usually 0.6 ml.
/ G or more, preferably 0.7 ml / g or more, and usually 1.6 ml / g or less. The value of the specific surface area is usually 200 m ² / g or more, preferably 300 m ² / g or more,
More preferably 400 m ² / g or more, particularly preferably 5
00m and ² / g or more and usually 1000 m ² / g or less, preferably 950 meters ² / g, more preferably 900 meters ²
/ G or less. The values of these pore volume and specific surface area are measured by the BET method by nitrogen gas adsorption / desorption.

Further, in the silica of the present invention, the total volume of pores in the range of ± 20% of the value of the most frequent diameter (D _max ) is usually 50% or more of the total volume of all pores, preferably Is 60
% Or more, more preferably 70% or more. This means that the diameter of the pores of the silica gel of the present invention is uniform in the pores near the mode diameter (D _max ).
In addition, centering on the value of the above-mentioned mode diameter (D _max ) ± 2
Although the upper limit of the total volume of pores in the range of 0% is not particularly limited, it is usually 90% or less of the total volume of pores.

In relation to such characteristics, the silica of the present invention has a differential pore volume ΔV / Δ (logd) in the mode diameter (D _max ) calculated by the above BJH method.
Is usually 2 ml / g or more, preferably 3 ml / g or more,
More preferably 5 ml / g or more, usually 20 ml / g
It is not more than g, preferably not more than 12 ml / g (in the above formula, d is the pore diameter (nm) and V is the nitrogen gas adsorption volume). Differential pore volume ΔV / Δ (log
Those in which d) falls within the above range have a mode diameter (D _max ).
It can be said that the absolute amount of pores aligned in the vicinity of is extremely large.

A further characteristic feature of the silica of the present invention is that it is known that its presence in silica affects the physical properties thereof. Alkali metals, alkaline earth metals, 3 of periodic table
The total content of metal elements (impurity elements) belonging to the group consisting of Group A, Group 4A and Group 5A, and transition metals is extremely low, and the purity is extremely high. Specifically, the total content of metal impurities is usually 100 ppm or less, preferably 50 ppm or less, more preferably 10 ppm or less,
It is particularly preferably 1 ppm or less. In particular, the total content of the elements belonging to the group consisting of alkali metals and alkaline earth metals, which has a great influence on the physical properties of silica gel, is usually 100 ppm or less, especially 50 ppm or less, and further 10
It is preferably ppm or less, and particularly preferably 1 ppm or less.
Such a small influence of impurities is one of the major factors by which the silica of the present invention can exhibit excellent properties such as high heat resistance and water resistance.

(2) Method for producing silica of the present invention Unlike the conventional sol-gel method, the silica of the present invention hydrolyzes a silicon alkoxide (hydrolysis step) and condenses the obtained silica hydrosol. The hydrolysis / condensation step for forming silica hydrogel, and the hydrolysis / condensation step
It is produced by a method including a condensation step and a physical property adjusting step of hydrothermally treating the silica hydrogel without aging.

The silicon alkoxide used as the raw material of the silica of the present invention is a lower one having 1 to 4 carbon atoms such as trimethoxysilane, tetramethoxysilane, triethoxysilane, tetraethoxysilane, tetrapropoxysilane and tetrabutoxysilane. Examples thereof include tri- or tetra-alkoxysilanes having an alkyl group or oligomers thereof, preferably tetramethoxysilane,
Tetraethoxysilane and oligomers thereof.
Since the above silicon alkoxide can be easily purified by distillation, it is suitable as a raw material for high-purity silica. The total content of metal elements (metal impurities) belonging to an alkali metal or an alkaline earth metal in a silicon alkoxide is usually 100 ppm or less, especially 50 ppm or less, and further 3
It is preferably 0 ppm or less, particularly preferably 10 ppm or less, and most preferably 1 ppm or less. The content of these metal impurities can be measured by the same method as a general method for measuring the content of impurities in silica.

In the present invention, first, in the hydrolysis / condensation step, the silicon alkoxide is hydrolyzed in the absence of a catalyst, and the obtained silica hydrosol is condensed to form a silica hydrogel.

The hydrolysis of silicon alkoxide is usually 2 mol or more, preferably 3 mol or more, particularly preferably 4 mol or more, usually 20 mol or less, preferably 10 mol or less, particularly preferably 1 mol of silicon alkoxide. Perform using less than 8 moles of water. Hydrolysis of silicon alkoxide produces silica hydrosol of silica doped with the target foreign element and alcohol, and the produced silica hydrosol is sequentially condensed to form silica hydrogel. The temperature during hydrolysis is usually room temperature or higher, preferably 3
0 ° C or higher, preferably 40 ° C or higher, more preferably 50 ° C or higher, usually 100 ° C or lower, preferably 90 ° C or lower, particularly preferably 80 ° C or lower, further preferably 70
It is below ℃. This hydrolysis reaction can be carried out at a higher temperature by maintaining the liquid phase under pressure.

Further, the hydrolysis may be carried out in the presence of a solvent such as alcohols which is compatible with water, if necessary. Specifically, lower alcohols having 1 to 3 carbon atoms, dimethylformamide, dimethylsulfoxide, acetone, tetrahydrofuran, methylcerolube, ethylcerolub, methylethylketone, other organic solvents that can be arbitrarily mixed with water, can be used, Among them, those which do not show strong acidity or basicity are preferable because they can form a uniform silica hydrogel.

When these solvents are not used, the stirring speed during hydrolysis is particularly important for the production of the silica of the present invention. That is, since the silicon alkoxide and the water for hydrolysis are separated at the initial stage, they are 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) is usually 3 depending on the shape of the stirring blade, the number of the stirring blades, the contact area with the liquid, and the like.
It is 0 rpm or more, preferably 50 rpm or more.

If this stirring speed is generally too fast, the droplets generated in the tank may block various gas lines,
In addition, it may adhere to the inner wall of the reactor to deteriorate heat conduction, which may affect temperature control, which is important for physical property 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 200
It is preferably 0 rpm or less, and more preferably 1000 rpm or less.

In the present invention, as a method of stirring the separated two liquid phases (aqueous phase and silicon alkoxide phase), any stirring method can be used as long as it is a method of promoting the reaction. Among these, examples of the device for further mixing the two 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 in which the liquid flows vertically. : A stirrer having a stirrer blade provided with the axis of rotation substantially parallel to the interface between the two liquid phases and stirring the two 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 of the stirring blade and the length of the stirring blade are arbitrary, and examples of the stirring blade include a propeller type, a flat blade type, a flat blade type with an angle, a flat blade type with a pitch, a flat blade disk turbine type, a curved blade type, and a Faudler type. , Bull margin type, anchor type, ribbon type and the like.

The width of the blades, the number of blades, the inclination angle, 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 rotating shaft is provided above the liquid level in the reaction vessel and a stirring blade is provided at the tip end portion of the shaft extended from this rotating shaft is preferably used from the viewpoint of stirring efficiency and equipment maintenance.

If the above stirring speed conditions are not satisfied, it will be difficult to obtain the silica 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.

Crystalline silica 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 silica, Silica easily contains a crystal structure. 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 of hydrolysis 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, an acid,
Hydrolysis can be promoted by adding an alkali, a salt or 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 hydrolysis reaction of the above-mentioned silicon alkoxide, the silicon alkoxide is hydrolyzed to generate a silicate, but subsequently a condensation reaction of the silicate occurs, the viscosity of the reaction solution increases, and finally the gel is converted into a silica hydrogel. Become.

Next, in the present invention, as a physical property adjusting step, hydrothermal treatment is immediately performed without substantially aging so that the hardness of the silica hydrogel produced by the above hydrolysis does not increase. Hydrolysis of silicon alkoxide produces a soft silica hydrogel, which is stable aged or dried, and a method of hydrothermal treatment further hydrolyzes the hydrogel, which finally controls the pore characteristics. It is difficult to produce silica having the physical properties defined by the invention.

Immediately performing hydrothermal treatment on the hydrogel of silica produced by hydrolysis without substantially aging means that the soft state immediately after the hydrogel of silica is maintained is maintained. ,next,
It means to be 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, it may be considered that a large amount of silica hydrogel produced is once stored in a silo or the like and then subjected to hydrothermal treatment. 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 at the time of standing is as low as possible, for example, 50 ° C. or less, preferably 35 ° C. or less, particularly 30 ° C. or less. Further, as another method for preventing the aging substantially from occurring, 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 hydrothermal treatment without substantially aging the silica hydrogel and the reason why this effect is obtained, the following can be considered. That is, when the silica hydrogel is aged, -Si-OS
It is considered that a macroscopic network structure by i-bond 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. Therefore, in the present invention, it is important to perform hydrothermal treatment without aging the silica hydrogel. 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.

It is not preferable to add an acid, an alkali, a salt or the like to the hydrolysis reaction system of the silicon alkoxide, or to make the temperature of the hydrolysis reaction too strict, since the aging of the hydrogel proceeds. 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 as described in Examples below can be referred to. That is,
By subjecting a hydrogel in a soft state having a breaking stress of usually 6 MPa or less, preferably 3 MPa or less, more preferably 2 MPa or less to hydrothermal treatment, silica having a physical property range defined in the present invention can be obtained.

The condition of the hydrothermal treatment may be either a liquid state or a gas state, and may be diluted with a solvent or another gas. However, liquid water is preferably added to a silica hydrogel to form a slurry. As a state. The amount of water used is usually 0.1 with respect to the silica hydrogel.
It is more than 1 times by weight, preferably not less than 1 times by weight, more preferably not more than 10 times by weight, preferably not more than 5 times by weight, particularly preferably not more than 3 times by weight. The temperature of hydrothermal treatment is usually 40 ° C. or higher, preferably 5
0 or higher, usually 250 ° C or lower, preferably 200 ° C
It is the following. The hydrothermal treatment time is usually 0.1 hour or longer, preferably 1 hour or longer, and usually 100 hours or shorter, preferably 10 hours or shorter.

The water used for the hydrothermal treatment may contain lower alcohols, methanol, ethanol, propanol, dimethylformamide (DMF), dimethylsulfoxide (DMSO), other organic solvents and the like. Further, this hydrothermal treatment method is also applied to a material in which silica is formed in a film or layer form on a substrate such as particles, a substrate, or a tube for the purpose of producing a membrane reactor or the like. It is also possible to perform hydrothermal treatment by changing the temperature conditions using a reactor for hydrolysis reaction, but the optimum conditions are usually different between the hydrolysis reaction and the subsequent hydrothermal treatment. Obtaining the silica of the present invention is generally difficult.

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 will be difficult to obtain the silica of the present invention. For example, if the temperature of the hydrothermal treatment is too high, the pore diameter and pore volume of silica become too large, and the pore distribution also widens. Conversely, if the temperature of the hydrothermal treatment is too low, the silica produced will be
The degree of cross-linking is low, the thermal stability is poor, the pore distribution does not have a peak, and the Q ⁴ / Q ³ value in the solid-state Si-NMR is extremely small.

When the hydrothermal treatment is carried out in ammonia water, the same effect can be obtained at a lower temperature than when it is carried out in pure water. Further, when hydrothermal treatment is carried out in ammonia water, the silica gel finally obtained generally becomes hydrophobic as compared with the case of treatment in pure water, but usually 30 ° C. or higher, preferably 40 ° C. or higher, and usually 250 ℃ or less, preferably 2
When the hydrothermal treatment is performed at a relatively high temperature of 00 ° C. or lower, the hydrophobicity becomes particularly high. The ammonia concentration in the ammonia water here is preferably 0.001% or more, particularly preferably 0.005% or more, or preferably 10% or less, particularly preferably 5% or less.

The hydrothermally treated silica hydrogel is usually 40 ° C. or higher, preferably 60 ° C. or higher, and usually 200 ° C. or higher.
Drying is performed at a temperature of not higher than 0.degree. 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. If necessary, when the carbon content derived from the raw material silicon alkoxide is contained, it is usually 400 to 600.
It can be removed by firing at ℃. Further, in order to control the surface condition, firing may be performed at a temperature of up to 900 ° C. Furthermore, the silica of the present invention finally obtained is obtained by pulverizing and classifying as required.

(3) Uses of Silica of the Present Invention The silica of the present invention can be used for any purpose other than conventional uses of silica. 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.), waste water / waste oil treatment agents, odor treatment agents, gas 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 of the present invention has a large pore volume and specific surface area as compared with conventional silica having an equivalent pore diameter, so that it has a high adsorption / absorption capacity and enables precise pore control. Is. Therefore, among the various applications described above, particularly excellent heat resistance and hydrothermal resistance are required, controlled pore characteristics, and preferably used in a field requiring little change in physical properties over a long period of time. it can.

Further, the silica of the present invention is preferably used also in a field where a particle size of 50 μm or less is required and finely controlled pore characteristics and stable physical properties are required.
Generally, when the average particle size of silica is 50 μm or less, the outer surface area per unit weight increases and various substances can be adsorbed / absorbed at the grain boundaries, which further improves the adsorption / absorption performance. Get higher That is, by reducing the particle size of the silica of the present invention, high pore volume, high specific surface area, sharp pore distribution already possessed by the silica of the present invention,
By developing various characteristics such as high purity and little change in physical properties,
Further, it is possible to use silica having excellent adsorption / absorption properties.

When the silica of the present invention is used in such a field, the average particle size may be adjusted according to the value required in the field, but is usually 50 μm or less, preferably 30 μm.
The following is particularly preferably used as 5 μm or less. The lower limit is not particularly limited, but is preferably 0.1 μm or more. There are various applications of silica having such a small particle size, such as various adsorbents, fillers for resins, ink absorbents for inkjet paper, anti-blocking agents for films, filter aids for beverages, and various catalyst carriers. . For example, the silica of the present invention having an average particle size of 5 μm or less is useful as an absorbent for inkjet paper because it has a high ink absorption rate and high oil absorption performance.

On the other hand, the silica of the present invention is preferable even if the average particle size is increased. By increasing the average particle size, the silica of the present invention has features such as the above-mentioned high specific surface area, high pore volume, sharp pore distribution, high purity and little change in physical properties, and characteristics peculiar to large particles. It will be extremely useful in the fields where both are required. For example, silica having a large average particle size reduces the scattering of light and can be used as a glass body for optical applications.

Specifically, the silica of the present invention is 500 μm
It is also preferably used in a field where a particle size of m or more is required and finely controlled pore characteristics and stable physical properties are required. When the silica of the present invention is used in such a field, the average particle size may be adjusted according to the value required in the field, but is usually 500 μm or more, preferably 5 mm or more. The upper limit is not particularly limited, but is preferably 5 cm or less. For example, since the silica of the present invention having an average particle size of 500 μm or more has controlled nanopores, optically useful dyes, metals, photocatalysts, photochromic compounds, and other optical functionalities are utilized by utilizing the pores. The material can be supported in a certain size according to the pore diameter and is useful as a functional optical material. In general, it is difficult to produce particles having a large average particle diameter without causing coarse cracks, but the silica of the present invention has a homogeneous structure and undergoes coarse cracks even by a treatment involving volume change such as hydrothermal treatment. It is possible to obtain a product having a controlled pore characteristic and a relatively large average particle size.

[0068]

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.

[A] Hardness measurement of silica hydrogel 6 with silicon alkoxide in a 5 L separable flask.
After reacting with a molar amount of water and the temperature of the reaction solution reached the boiling point of the alcohol produced by the reaction, the reaction solution was extracted from the flask, and the extracted reaction solution was put into a 50 cc glass screw tube at a certain amount (at the liquid depth). 20 mm), sealed and kept in a water bath controlled at a substantially constant temperature, and the puncture strength was measured by a digital force gauge (manufactured by A & D Co., Ltd., model:
AD-4935). A probe (a round bar made of stainless steel and having a diameter of 5 mm) is attached to the measuring instrument,
The hydrogel retained in the container is crushed by being pushed slowly into the hydrogel. The breaking stress was defined as the maximum stress value shown until the hydrogel was compressed and broken.

The measurement results are shown in FIG. Note that FIG. 1 is a graph in which the common logarithm of the aging time of silica hydrogel is plotted on the horizontal axis and the fracture stress is plotted on the vertical axis. From FIG. 1, it can be seen that the fracture stress increases with the aging time and that the aging rate depends on the temperature. [B] Example / Comparative Example Group I

(1) Silica analysis method 1-1) Pore volume, specific surface area, differential pore volume: The BET nitrogen adsorption isotherm was measured by AS-1 manufactured by Kantachrome Co., and the pore volume and specific surface area were measured. I asked. Specifically, the pore volume adopts a value when the relative pressure P / P ₀ = 0.98, and the specific surface area is 3 of P / P ₀ = 0.1, 0.2, 0.3.
It was calculated using the BET multipoint method from the nitrogen adsorption amount at each point. 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 The measurement was performed using RAD-RB apparatus manufactured by Rigaku Denki Co., Ltd. with CuKα as a radiation source. The divergence slit was 1/2 deg, the scattering slit was 1/2 deg, and the light receiving slit was 0.15 mm.

1-3) Content of Metal Impurities Hydrofluoric acid was added to 2.5 g of the sample to heat it to dry it, and then water was added to make 50 ml. Using this aqueous solution I
CP emission analysis was performed. In addition, sodium and potassium were analyzed by the flame flame method.

1-4) Solid-state Si-NMR measurement Solid-state NMR apparatus manufactured by Bruker ("MSL300")
And a resonance frequency of 59.2 MHz (7.
05 Tesla), using a 7 mm sample tube, C
P / MAS (Cross Polarization / Magic Angle Spinn
ing) was measured under the conditions of the probe. Specific measurement conditions are shown in Table 1 below.

[0075]

[Table 1]

The analysis of the measurement data (determination of Q ⁴ and Q ³ peak positions) is carried out by a method of extracting each peak by dividing the peaks. Specifically, waveform separation analysis using a Gaussian function is performed. For this analysis, Thermo Galatec (Ther
mogalatic) waveform processing software "GRAMS38"
6 "can be used. Using the peak areas of Q ⁴ and Q ³ thus obtained by peak division, the ratio (Q ⁴
/ Q ³⁾ was determined.

1-5) Thermal stability test of silica in water Pure water was added to a sample to prepare a 40 wt% slurry.
About 40 ml of the slurry prepared above was placed in a stainless steel micro bomb having a volume of 60 ml, sealed, and immersed in an oil bath at 280 ± 1 ° C. for 3 days. A part of the slurry was extracted from the micro bomb and filtered through 5A filter paper. The filter cake was vacuum dried at 100 ° C. for 5 hours, and then the specific surface area of the remaining sample was measured.

(2) Production and Evaluation of Silica Examples I-1 to I-3: A 5 L separable flask (with a jacket) made of glass and equipped with a water-cooled condenser open to the atmosphere was charged with 1000 g of pure water. I prepared it. While stirring at a stirring speed such that the stirring blade tip speed was 2.5 m / s, 1400 g of tetramethoxysilane 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). 450g of this hydrogel and 450g of pure water
Was charged into a 1 L glass autoclave, and Example I-
130 ° C. × 3 Hr for Example 1, 150 ° C. × 3 Hr for Example I-2, and 200 ° C. for Example I-3
Hydrothermal treatment was carried out under the condition of × 3Hr. After hydrothermal treatment for a predetermined time, No. The silica was filtered with 5A filter paper, and the obtained silica was dried under reduced pressure at 100 ° C. to a constant weight without washing with water to obtain silica of Examples I-1 to I-3.

Example I-4: A hydrogel was produced under the same conditions as in Examples I-1 to I-3 above. 450 g of the obtained hydrogel and 450 g of 0.56% ammonia water were charged into a 1 L autoclave, and hydrothermal treatment was carried out under the condition of 60 ° C. × 3 Hr. After hydrothermal treatment for a predetermined time, No. The silica obtained by filtering with 5A filter paper is washed with 100% water.
It was dried under reduced pressure at 0 ° C. until a constant weight was obtained to obtain silica of Example I-4.

Example I-5: 6 liters of SUS316
Silica was obtained in the same manner as in Example I-1 except that the autoclave was used and hydrothermal treatment was performed under the conditions of 160 ° C. × 3 Hr. The average particle size of the obtained silica was 331 μm. This silica, 100AFG made by Hosokawa Micron
When jet milling was carried out for 26 minutes using a mold pulverizer, the average particle diameter of silica was 5.3 μm. The conditions for crushing and classification at this time are as follows. Pulverizing air volume: 0.72 m ³ / min Air pressure: 0.59 MPa Nozzle diameter * Number: φ1.9 mm * 3 classifier type: 50 ATP rotation speed: 17800 rpm Dust collection cloth: Bag filter processing capacity: 0.97 kg / h

Example I-6: Opening 600 μm (μ
The procedure of Example I-2 was repeated, except that the nylon net of m) was changed to a nylon net having an opening of 5 mm. The average particle size of the obtained silica was 2.8 mm (= 2800 μm).

Various physical properties of the obtained silicas of Examples I-1 to I-6 are shown in Tables 2 and 4 (however, since there is no measured value of the chemical shift of the Q ⁴ peak in Example I-6. Only shown in Table 2). No crystallinity peak appears in the powder X-ray diffraction pattern of any of the silicas, and no peak on the low angle side (2θ ≦ 5 deg) due to the periodic structure is recognized. In addition, as for the impurity metal content rate of the silica of Examples I-1 to I-6, for any of the silica of Examples I-1 to I-6,
Sodium was 0.2 ppm, potassium was 0.1 ppm, calcium was 0.2 ppm, and other metals were not detected.

Further, in FIG. 2, the most frequent pore diameter (D _max ) and the chemical shift of the Q ⁴ peak of silica of Examples I-1 to I-5 and Comparative Examples I-1 to I-6 described later are shown. The graph showing the correlation with the value (δ) is shown. As can be seen in Figure 2,
For any of the silicas of Examples I-1 to I-5, solid S
The value of the chemical shift of the Q ⁴ peak of i-NMR (the value plotted as series 1 in the graph of FIG. 2) is the left side of the above formula (I) (−0.0705 × (D _max ) −110.
36), which was in a smaller region than the value calculated (value represented by a black line segment in the graph of FIG. 2).

The silica having an average particle size of 5.3 μm obtained in Example I-5 has a sharp pore size distribution and a high distribution even though the particle size is small, as is clear from the above-mentioned physical properties. Since it has a pore volume, it is apparent that it has excellent moisture absorption performance and has a humidity control function for various materials. And this silica can be conveniently used as a filler of various films for which the smoothness of the surface is maintained and antiblocking property is required, for example.

The large particle size silica having an average particle size of more than 500 μm obtained in Example I-6 has a pressure loss when used by being packed in a column for use as a catalyst carrier or an adsorbent. It is very preferable because it can be greatly reduced. further,
Since the silica obtained in Example I-6 has few impurities and high purity, deterioration over time can be suppressed and the life as a catalyst carrier or the like can be extended. Further, since this silica has a high purity and a sharp pore distribution, it has the ability to adsorb and remove only the target compound with high selectivity, and it can also be suitably used in the fields of food and medicine. I can.

The following silicas were prepared as Comparative Examples I-1 to I-6. Comparative Example I-1: Silica CARIACT G-3 for catalyst carrier manufactured by Fuji Silysia Chemical Ltd. was used. Comparative Example I-2: Cariact G-6, a silica for catalyst carrier manufactured by Fuji Silysia Chemical Ltd., was used. Comparative Example I-3: Cariact G-10 (Lot No. 703091), a silica for catalyst carrier manufactured by Fuji Silysia Chemical Ltd., was used. Comparative Example I-4: Silica for catalyst carrier manufactured by Fuji Silysia Chemical Ltd. CARIACT G-10 (Lot No. C-OO0901)
4) was used. Comparative example I-5: Silica CARIACT Q-15 for catalyst carrier manufactured by Fuji Silysia Chemical Ltd. was used. Comparative Example I-6: Mizusuka Chemical Co., Ltd. Mizukaso
rb C-1 was used.

Physical properties of the silicas of Comparative Examples I-1 to I-6 described above are shown in Tables 3 and 4 below. With respect to all of the silicas of Comparative Examples I-1 to I-6, no crystalline peak appeared in the powder X-ray diffraction pattern, and no peak on the low angle side due to the periodic structure was observed. Furthermore, when the impurity metal contents were measured, the results were as shown in the table below.
The silicas of I-2 to I-6 contained more impurities than the silicas of Examples I-1 to I-6. Further, as is clear from FIG. 2, for all of the silicas of Comparative Examples I-1 to I-6, the chemical shift values of the Q ⁴ peak of solid Si-NMR (in the graph of FIG. 2, plotted as series 2). Value)
Is in a larger region than the value calculated from the left side of the above formula (I) (the value indicated by the black line segment in the graph of FIG. 2), the structure is similar to that of Example I-1. It seems that the strain is larger than that of the silica of ~ I-5 and the physical properties are likely to change.

Further, Examples I-1 to I-6 and Comparative Example I-1
Tables 2 and 3 show the results of measuring the specific surface area of the silica of Nos. 1 to 6 as a sample and conducting a thermal stability test in water under the above conditions. The silicas of Examples I-1 to I-6 are the same as Comparative Example I.
Compared with the silicas of -1 to I-6, the reduction of the specific surface area was small and the hydrothermal stability was excellent.

[0089]

[Table 2]

[0090]

[Table 3]

[0091]

[Table 4]

[C] Example / Comparative Example Group II: (1) Silica Analysis Method: The same conditions as in Example / Comparative Example Group I were used. Furthermore, the heat resistance test of silica was conducted as follows. Heat resistance test of silica: 5g of sample was placed in a quartz beaker,
1000 at 200 ° C / hour in an electric furnace in an air atmosphere
After raising the temperature to 0 ° C. and holding for 1 hour, the beaker was immediately taken out to room temperature and allowed to cool. The specific surface area of this sample was measured by the BET method.

(2) Production and evaluation of silica: Example II-1: In a 5 L separable flask (with a jacket) equipped with a water-cooled condenser open to the atmosphere at the top,
1000 g of pure water was charged. Stirring blade tip speed 2.5m /
Tetramethoxysilane 140
0 g was charged over 1 minute. The water / tetramethoxysilane molar ratio is about 6. Hot water at 50 ° C was passed through the jacket of the separable flask. Then, stirring was continued and the temperature of the contents was kept at 60 to 70 ° C to prevent runaway. Continue to wear a jacket for about 0.5 hours
The sol produced by passing warm water at ℃ was gelled. The hardness of the obtained gel was 1.5 MPa.

Then, the gel was immediately taken out, and the gel was crushed through a nylon net having an opening of 600 microns,
A powdery wet gel (silica hydrogel) was obtained. 450 g of this hydrogel and 450 g of pure water were charged into a 1 L glass autoclave and subjected to hydrothermal treatment at 130 ° C. for 3 hours. After that, No. Filter with 5A filter paper,
The filter cake was dried under reduced pressure at 100 ° C. to a constant weight without washing with water. The measurement result of the metal impurity concentration of the obtained silica is sodium 0.2 ppm, potassium 0.1 ppm,
At 0.2 ppm calcium no magnesium, aluminum, titanium or zirconium was detected. Table 5 shows other physical properties.

Example II-2: Silica was obtained in the same manner as in Example II-1, except that the charging time of tetramethoxysilane was changed to 3 minutes. Table 5 shows the results of measurement of physical properties.

Comparative Example II-1: Silica was obtained in the same manner as in Example II-1, except that the charging time of tetramethoxysilane was changed to 30 minutes. Table 5 shows the results of measurement of physical properties.

Comparative Examples II-2 and II-3 For comparison between the silica of the present invention and ordinary commercially available silica, an ordinary silica of "CARIACT G series" for catalyst support manufactured by Fuji Silysia Chemical Ltd. was used. "G-
3 "and" G-6 "(crushed) were used as Comparative Examples II-2 and II-3, respectively. In addition, the measurement result of the metal impurity concentration of commercially available silica (“G-6”) is as follows: sodium 170 ppm, magnesium 31 ppm, aluminum 15 ppm, potassium 23 ppm, calcium 16
0ppm, 260ppm titanium, 44pp zirconium
It was m. Table 5 shows other physical properties.

[0098]

[Table 5]

[0099]

INDUSTRIAL APPLICABILITY Since the novel silica of the present invention has a smaller mode diameter (D _max ) than conventional silica, it has excellent adsorption and absorption performances, and is extremely excellent in productivity. Furthermore, since the structure has little distortion, it is also excellent in heat resistance and water resistance.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between each aging time and the fracture stress of the hydrogel when the hydrogel of silica is aged at each temperature of 35 ° C., 45 ° C. and 55 ° C.

FIG. 2 is a graph showing the correlation between the most frequent pore size (D _max ) and the chemical shift value (δ) of the Q ⁴ peak for the silica of Examples and Comparative Examples of the present invention.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuya Funayama             1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa             Within Mitsubishi Chemical Corporation F-term (reference) 4G072 AA26 AA27 DD08 DD09 GG01                       HH30 JJ11 MM01 PP17 RR05                       RR19 TT01 TT08 TT09 UU11                       UU17

Claims (17)

[Claims] 1. A silica having a mode diameter (D _max ) of pores of 20 nm or less, which has a chemical shift δ of Q ⁴ peak in solid-state Si-NMR.
(Ppm) satisfies the following formula (I): silica. −0.0705 × (D _max ) −110.36> δ (I) 2. The silica according to claim 1, wherein the chemical shift δ of the Q ⁴ peak is in the range of -111.00 to -112.00 ppm. 3. Silica according to claim 1 or 2, characterized in that the pore volume is between 0.6 and 1.6 ml / g. 4. The silica according to claim 3, wherein the pore volume is 0.7 to 1.6 ml / g. 5. Silica according to claim 1, characterized in that it has a specific surface area of 200 to 1000 m ² / g. 6. The silica according to claim 5, wherein the specific surface area is 300 to 900 m ² / g. 7. The total volume of pores having a diameter within a range of D _max ± 20% is 50% or more of the total volume of all pores, and the total volume is 50% or more. The silica according to item 1. 8. The silica according to claim 7, wherein the total volume of pores having a diameter within D _max ± 20% is 60% or more of the total volume of all the pores. 9. The silica according to claim 1, wherein the total content of metal impurities is 100 ppm or less. 10. The silica according to claim 1, wherein the total content of elements belonging to the group consisting of alkali metals and alkaline earth metals is 100 ppm or less. 11. Silica according to any one of claims 1 to 10, characterized in that the differential pore volume at the modal diameter (D _max ) is 2 to 20 ml / g. 12. Q ⁴ / in solid-state Si-NMR measurement
The value of the Q ³ peak is 1.3 or more,
Silica according to any one of claims 1 to 11. 13. The silica according to claim 1, wherein the average particle size is 50 μm or less. 14. The silica according to claim 1, wherein the silica has an average particle diameter of 500 μm or more. 15. The method according to claim 1, wherein the silicon alkoxide is produced through a step of hydrolyzing a silicon alkoxide.
The silica according to any one of 4 above. 16. A hydrolysis / condensation step of hydrolyzing a silicon alkoxide and condensing the obtained silica hydrosol to form a silica hydrogel, and the hydrolysis / condensation step.
The silica according to claim 15, which is produced by a method comprising a condensation step and a physical property adjusting step of hydrothermally treating the silica hydrogel without aging. 17. The silica according to claim 16, wherein the hydrolysis / condensation step is carried out in the absence of a catalyst.