JP2668495B2 - Method for producing silicon-based powder material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing a silicon-based powder material.

[0002]

2. Description of the Prior Art Generally, metal alkoxides rapidly undergo hydrolysis-polycondensation upon contact with water to produce a polymer or a powdery substance, but alkoxysilanes are exceptionally slow in hydrolysis. Therefore, the so-called "sol-
It is usefully used as a material for the low temperature synthesis process of ceramics and glass by the "gel method" [Sakuka Sakuo, "Sol-gel method science", Acne Jofusha (1988)]. In addition, it is possible to give the condensate in the form of a bulk, a thin film, a fiber, or the like, due to the slow hydrolysis property of the alkoxysilane.

The hydrolysis-polycondensation method in the so-called "sol-gel method" is carried out by mixing water with an alcohol solution of alkoxysilane, and an acidic catalyst (hydrochloric acid, sulfuric acid, etc.) is used as a catalyst. Is used.
This method is very useful for producing ceramics, glass, etc., but has a problem that an ultrafine and porous silicon-based powder substance cannot be obtained. That is, since the hydrolysis rate of alkoxysilane is slow, particles which are reaction products are gradually formed, and as a result, the obtained particles become large, and the particles have a packed structure, so that the bulk specific gravity also becomes large. Because.

In order to obtain an ultrafine and porous silicon-based powder substance, it is considered to increase the hydrolysis rate of alkoxysilane. That is, if the hydrolysis-polycondensation can be performed in a short time, the condensation is completed while containing a solvent such as water or alcohol, so that it is expected that an ultrafine and porous silicon-based powder material can be obtained. It The present invention and the like have previously found that by using hydrofluoric acid as a catalyst, a hydrolysis-polycondensation reaction of an alkoxysilane occurs in a very short time, and a suitable silicon-based powder material can be obtained. (JP-A-62-166887).

[0005]

However, hydrofluoric acid is a very effective acid catalyst, but when considering mass production due to industrialization, etc., its toxicity and danger make it
There is a drawback that operability and safety are serious problems.

With other acid catalysts such as hydrochloric acid, sulfuric acid and trifluoromethanesulfonic acid, the hydrolysis-polycondensation time can be shortened to some extent by increasing the amount of the catalyst, but the reduction is still insufficient. However, an ultrafine and porous silicon-based powder material cannot be obtained. Moreover, it is very difficult to remove a large amount of these acid catalysts after the reaction, and these catalysts are not so excellent in operability and safety.

Accordingly, an object of the present invention is to provide a method for producing an ultrafine and porous silicon-based powder substance which is excellent in operability and safety and can be produced in a short time.

[0008]

According to the present invention, there is provided a method for producing a silicon-based powder substance by carrying out hydrolysis-polycondensation of an alkoxysilane in the presence of a fluoride salt compound.

[0009]

In other words, the present invention is distinguished by the use of a fluoride compound as a catalyst for the hydrolysis-polycondensation reaction of alkoxysilane. This fluorinated salt compound exhibits a catalytic action equivalent to that of the hydrofluoric acid described above, and completes the hydrolysis-polycondensation reaction of the alkoxysilane extremely quickly. Therefore, it becomes possible to obtain an ultrafine and porous silicon-based powder material. Moreover, since this fluoride salt compound is less dangerous than conventional hydrofluoric acid, hydrochloric acid, sulfuric acid, etc., it is remarkably excellent in operability and safety.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Alkoxysilane In the present invention, alkoxysilane as a reaction raw material is
A silane compound having at least one hydrolyzable alkoxy group in the molecule, for example, the following general formula (1): (OR ¹ ) _X Si (R ² ) _4-X (1) In the formula, X is , R is an integer of 1 to 4, and R ¹ and R ² are monovalent hydrocarbon groups. In the formula, examples of the monovalent hydrocarbon groups R ¹ and R ² include an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group and an octyl group, a cyclohexyl group and the like. The cycloalkyl group, aryl group such as phenyl group, aralkyl group such as benzyl group, phenylethyl group and the like can be exemplified, and in these groups, some or all of the hydrogen atoms thereof are substituted with a halogen atom. May be. In the present invention, those generally preferred as these groups R ¹ and R ² are alkyl groups having 4 or less carbon atoms, and phenyl groups.

Typical alkoxysilanes used in the present invention are as follows. In the formula below, Ph represents a phenyl group.

Those having 3 or 4 alkoxy groups (X); Si (OCH ₃ ) ₄ , Si (OC ₂ H ₅ ) ₄ ,
Si (OC ₃ H ₇ ) ₄ , Si (OC ₄ H ₉ ) ₄ , CH ₃
Si (OCH ₃ ) ₃ , CH ₃ Si (OC ₂ H ₅ ) ₃ , C
H ₃ Si (OC ₃ H ₇ ) ₃ , CH ₃ Si (OC ₄ H ₉ )
₃ , C ₂ H ₅ Si (OCH ₃ ) ₃ , C ₂ H ₅ Si (OC
_{2 H 5) 3, C 2} H 5 Si (OC 3 H 7) 3, C 2 H 5
Si (OC ₄ H ₉ ) ₃ , C ₃ H ₇ Si (OCH ₃ ) ₃ ,
C ₃ H ₇ Si (OC ₂ H ₅ ) ₃ , C ₃ H ₇ Si (OC _{3
H 7) 3, C 3 H} 7 Si (OC 4 H 9) 3, C 4 H 9 S
i (OCH ₃ ) ₃ , C ₄ H ₉ Si (OC ₂ H ₅ ) ₃ , C
₄ H ₉ Si (OC ₃ H ₇ ) ₃ , C ₄ H ₉ Si (OC ₄ H
₉ ) ₃ , PhSi (OCH ₃ ) ₃ , PhSi (OC ₂ H
₅ ) ₃ , PhSi (OC ₃ H ₇ ) ₃ , PhSi (OC ₄
H ₉ ) ₃

The number of alkoxy groups (X) is 2;
(CH ₃ ) ₂ Si (OCH ₃ ) ₂ , (CH ₃ ) ₂ Si
(OC ₂ H ₅ ) ₂ , (CH ₃ ) ₂ Si (OC
_{3 H 7) 2, (CH} 3) 2 Si (OC 4 H 9) 2, (C
_{2 H 5) 2 Si (OCH} 3) 2, (C 2 H 5) 2 Si
(OC ₂ H ₅ ) ₂ , (C ₂ H ₅ ) ₂ Si (OC ₃ H ₇ )
₂ , (C ₂ H ₅ ) ₂ Si (OC ₄ H ₉ ) ₂ , (C
_{3 H 7) 2 Si (OCH} 3) 2, (C 3 H 7) 2 Si
(OC ₂ H ₅ ) ₂ , (C ₃ H ₇ ) ₂ Si (OC ₃ H ₇ )
₂ , (C ₃ H ₇ ) ₂ Si (OC ₄ H ₉ ) ₂ , (C
_{4 H 9) 2 Si (OCH} 3) 2, (C 4 H 9) 2 Si
(OC ₂ H ₅ ) ₂ , (C ₄ H ₉ ) ₂ Si (OC ₃ H ₇ )
₂ , (C ₄ H ₉ ) ₂ Si (OC ₄ H ₉ ) ₂ , (Ph) ₂
Si (OCH ₃ ) ₂ , (Ph) ₂ Si (OC
_{2 H 5) 2, (Ph} ) 2 Si (OC 3 H 7) 2, (P
h) ₂ Si (OC ₄ H ₉ ) ₂

The number of alkoxy groups (X) is 1;
(CH ₃ ) ₃ SiOCH ₃ , (CH ₃ ) ₃ SiOC ₂ H
₅ , (CH ₃ ) ₃ SiOC ₃ H ₇ , (CH ₃ ) ₃ SiO
C ₄ H ₉ , (C ₂ H ₅ ) ₃ SiOCH ₃ , (C ₂ H ₅ )
₃ SiOC ₂ H ₅ , (C ₂ H ₅ ) ₃ SiOC ₃ H ₇ ,
(C ₂ H ₅ ) ₃ SiOC ₄ H ₉ , (C ₃ H ₇ ) ₃ SiO
CH ₃ , (C ₃ H ₇ ) ₃ SiOC ₂ H ₅ , (C ₃ H ₇ )
₃ SiOC ₃ H ₇ , (C ₃ H ₇ ) ₃ SiOC ₄ H ₉ ,
(C ₄ H ₉ ) ₃ SiOCH ₃ , (C ₄ H ₉ ) ₃ SiOC
_{2 H 5, (C 4 H} 9) 3 SiOC 3 H 7, (C 4 H 9)
₃ SiOC ₄ H ₉ , (Ph) ₃ SiOCH ₃ , (Ph)
₃ SiOC ₂ H ₅ , (Ph) ₃ SiOC ₃ H ₇ , (P
h) ₃ SiOC ₄ H ₉

The above alkoxysilane is hydrolyzed
As long as the polycondensation reaction product is a solid, it can be used alone or in combination of two or more. For example, when an alkoxysilane having three or four alkoxy groups is used, the alkoxy group may be added in an amount of 30% by weight or less to 1 to 30% by weight.
Two alkoxysilanes can be used together.
If the amount of the alkoxysilane used in combination is more than 30% by weight, the resulting hydrolysis-polycondensation reaction product becomes a liquid or oily substance, and it becomes difficult to obtain the intended solid powdery substance.

Catalyst The catalyst used to promote the hydrolysis-polycondensation reaction of the alkoxysilane is a fluoride salt compound.
For example, fluorine-containing salt compounds of Group I elements such as LiF, NaF, KF, RbF, and CsF, BeF ₂ , MgF ₂ , Ca
Group II element fluorine-containing salt compounds such as F ₂ , SrF ₂ and BaF ₂ , BF ₃ , AlF ₃ , GaF ₃ , InF ₃ , Tl
A fluorine-containing salt compound of a Group III element such as F ₃ , CuF ₂ ,
ZnF ₂ , SnF ₂ , PdF ₂ , SbF ₃ , CrF ₃ ,
Fluorine-containing salt compound such as _{YF 3, LaF 3, CeF 3} ,
PrF ₃ , NdF ₃ , SmF ₃ , EuF ₃ , GdF ₃ ,
Lanthanoid fluorine-containing salt compounds such as TbF ₃ , DyF ₃ , HoF ₃ and ErF ₃ , (CH ₃ ) ₄ N · F,
(CH ₃ CH ₂ ) ₄ NF, (CH ₃ CH ₂ CH ₂ ) ₄
N · F, can be used in _{(CH 3 CH 2 CH 2 CH} 2) 4 quaternary ammonium salts such as N · F, and alone or in combination of these hydrates. Among these, NaF, KF, (CH ₃ CH ₂ CH ₂ CH ₂ ) ₄ in consideration of cost, water solubility, operability and safety.
N · F and the like are particularly suitable.

Such a catalyst has a molar ratio of Si: F of 1.0:
It is used in an amount such that it ranges from 0.001 to 1.0: 2.0, especially from 1.0: 0.01 to 1.0: 0.1. When the amount of the catalyst is less than the above range, it does not act effectively as a catalyst, the hydrolysis-polycondensation reaction of the alkoxysilane requires a long time, and the resulting powdery substance has ultrafineness, porosity, etc. Tend to be unsatisfactory in. Further, if the catalyst is used in a larger amount than the above range, the pot yield will be reduced and the cost will be increased.

Hydrolysis-Polycondensation Reaction The hydrolysis- polycondensation reaction of alkoxysilane is carried out by mixing the alkoxysilane and water in the presence of the above-mentioned catalyst, and the reaction effectively proceeds at room temperature. In some cases, heating may be performed appropriately.

In the reaction, an organic solvent such as alcohol, ether, ester or ketone may be appropriately used. The alcohol-based organic solvent is preferably methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol or the like, and the ether-based organic solvent is preferably dimethyl ether, diethyl ether, dipropyl ether or the like, and ester-based. As the organic solvent, methyl acetate, ethyl acetate and the like are preferable, and as the ketone-based organic solvent, acetone, methyl ethyl ketone and the like are suitably used. In general, the amount of the organic solvent to be used is preferably not more than 500% by weight, particularly preferably not more than 150% by weight based on the alkoxysilane.

The amount of water mixed with the alkoxysilane for the hydrolysis-polycondensation reaction is such that the molar ratio of the alkoxy groups of the alkoxysilane to the water is in the range of 1: 0.5 to 1:50. It is preferable that If the amount of water used is less than the above range, the amount of organic residues remaining without hydrolysis increases, and it becomes difficult to obtain a porous powdery substance. On the other hand, if the amount of water used is larger than the above range, the pot yield is reduced, which is economically disadvantageous.

Generally, mixing alkoxysilane and water
(a) adding water to the stirred alkoxysilane solution,
(b) An alkoxysilane solution is added to water under stirring, and the like.

The catalyst (fluoride compound) is preferably added to the reaction system in a state where it is dissolved in water or a suitable organic solvent. Further, this catalyst may be added in advance to the alkoxysilane or water used for hydrolysis, or may be added after mixing water and the alkoxysilane solution.

It is also possible to partially hydrolyze the alkoxysilane in advance using an aqueous solution containing a suitable acid catalyst or base catalyst before carrying out the above-mentioned hydrolysis-polycondensation reaction.

Formation of Powder Material By the hydrolysis-polycondensation reaction described above, Si--O--Si
Although a silicon compound having a bond is produced, this condensation reaction product is separated from the solution by a method such as filtration, and water and an organic solvent are removed by volatile drying,
The target powdery substance can be obtained. Alternatively, the reaction product may be directly taken out of the reaction system in the form of a powder using a device such as a spray dryer or a vacuum dryer.

Powder substance Since the silicon-based powder substance thus obtained has a small bulk specific gravity and is a porous and ultrafine solid, it is used as a packing material for columns or a solid for supporting various enzymes, metal compounds and the like. It is useful and can be used as a bioreactor, an immobilized enzyme, an immobilized catalyst, a carrier for recovering metals, and the like. It is also useful as a material for new ceramics.

Example 1 61 g (400 mmol) of tetramethoxysilane and 68 g (1,500 mmol) of ethanol were placed in a 500 ml reactor equipped with a stirrer, a thermometer and a condenser, and mixed by stirring. 30 g of water in which 0.23 g (4 mmol) of KF was dissolved (1,680 m
mol) and was added dropwise. After completion of the addition, the mixture was stirred at room temperature for 3 minutes.
The reaction solution that was colorless and transparent changed to a white gel. This was filtered off with a Buchner funnel, washed with distilled water and subsequently with acetone, and then dried at 120 ° C. and 15 mmHg × using a vacuum dryer.
After treatment for 2 hours and removal of the solvent, 24.0 g of a silicon-based powder substance was obtained. The bulk specific gravity of the obtained silicon-based powder material was 0.30 g / cm ³ , and the specific surface area was 790 m ² / g.

Example 2 A reaction was performed in the same manner as in Example 1 except that 0.17 g (4 mmol) of NaF was used instead of KF. The reaction solution changed into a white gel in 5 minutes after the dropwise addition of the NaF aqueous solution was completed. Therefore, the same process as in Example 1 was performed. As a result, 23.1
g of silicon-based powder substance was obtained. This silicon powder material had a bulk specific gravity of 0.40 g / cm ³ and a specific surface area of 702 m ² / g.

Example 3 A reaction was conducted in the same manner as in Example 1 except that NH ₄ F 0.15 g (4 mmol) was used instead of KF. The reaction solution became a white gel after 8 minutes from the dropwise addition of the NH ₄ F aqueous solution. However, the same process as in Example 1 was performed. As a result, 23.0 g of a silicon-based powder material was obtained. This silicon-based powder had a bulk specific gravity of 0.41 g / cm ³ and a specific surface area of 690 m ² / g.

Example 4 A reaction was performed in the same manner as in Example 1 except that 0.20 g (2 mmol) of CuF ₂ was used instead of KF. The reaction solution changed to a white gel in 10 minutes after the dropping of the CuF ₂ aqueous solution was completed. Therefore, the same process as in Example 1 was performed. As a result, 23.0 g of a silicon-based powder material was obtained. This silicon powder material had a bulk specific gravity of 0.39 g / cm ³ and a specific surface area of 715 m ² / g.

Example 5 (CH ₃ CH ₂ CH ₂ CH ₂ ) ₄ NF instead of KF
When the reaction was performed in the same manner as in Example 1 except that the amount was 1.05 g (4 mmol), the reaction liquid changed to a white gel 3 minutes after the completion of the dropwise addition of the (CH ₃ CH ₂ CH ₂ CH ₂ ) ₄ NF aqueous solution. Processed as in Example 1. As a result, 23.0 g of a silicon-based powder material was obtained. This silicon powder material had a bulk specific gravity of 0.32 g / cm ³ and a specific surface area of 778 m ² / g.

Example 6 A reaction was performed in the same manner as in Example 1 except that KF was changed to 0.46 g (40 mmol). The reaction solution changed into a white gel 3 minutes after the dropping of the KF aqueous solution was completed. Processed as in 1. As a result, 24.0 g of a silicon-based powder material was obtained. This silicon-based powder material had a bulk specific gravity of 0.28 g / cm ³ and a specific surface area of 802 m ² / g.

Example 7 When a reaction was performed in the same manner as in Example 1 except that ethanol was not added and a solvent was not used, a white gel was formed in the reaction solution in 1 minute. Therefore, the same treatment as in Example 1 was performed. . As a result, 24.0 g of a silicon-based powder material was obtained. This silicon-based powder substance has a bulk specific gravity of 0.27 g / cm ³ and a specific surface area of 837 m ² / g.
Met.

Example 8 0.2 g (4 mmol) of KF, 30 g (1,680 mmol) of water, and 68 g (1,500 mmol) of ethanol were placed in a 500 ml reactor equipped with a stirrer, a thermometer and a condenser, and tetra- When 61 g (400 mmol) of methoxysilane was added dropwise and the mixture was stirred at room temperature for 4 minutes after the completion of the addition, the colorless and transparent reaction liquid changed to a white gel. Thereafter, the same treatment as in Example 1 was performed to obtain 23.6 g of a silicon-based powder material. This silicon-based powder material had a bulk specific gravity of 0.36 g / cm ³ and a specific surface area of 727 m ² / g.

Example 9 The reaction was carried out in the same manner as in Example 1 except that water was changed to 120 g (6,670 mmol). The reaction liquid changed to a white gel 15 minutes after the completion of dropping the KF aqueous solution. Processed as in 1. As a result, 23.0 g of a silicon-based powder material was obtained.
This silicon powder material has a bulk specific gravity of 0.38 g / cm ³ and a specific surface area of
It was 711 m ² / g.

Example 10 Instead of tetramethoxysilane, tetraethoxysilane
When the reaction was carried out in the same manner as in Example 1 except that 84 g (400 mmol) was used, the reaction solution changed to a white gel in 9 minutes, so the same treatment as in Example 1 was carried out. As a result, 23.
1 g of silicon-based powder substance was obtained. This silicon-based powder material had a bulk specific gravity of 0.31 g / cm ³ and a specific surface area of 785 m ² / g.

Example 11 In place of tetramethoxysilane, 55 g (400 mmol) of methyltrimethoxysilane was used, and the amount of water added was 23
When the reaction was carried out in the same manner as in Example 1 except that the amount was changed to g (1,280 mmol), the reaction solution turned into a white gel in 7 minutes. Thereafter, the same processing as in Example 1 was performed. As a result, 26.2 g of a silicon-based powder material was obtained. This silicon-based powder substance has a bulk specific gravity of 0.
It was 38 g / cm ³ and the specific surface area was 707 m ² / g.

Example 12 Instead of tetramethoxysilane, 79.2 g (400 mmol) of phenyltrimethoxysilane were used, and the amount of water added was 23
When the reaction was carried out in the same manner as in Example 1 except that the amount was changed to g (1,280 mmol), the reaction solution turned into a white gel in 20 minutes. Thereafter, the same processing as in Example 1 was performed. As a result, 51.8 g of a silicon-based powder material was obtained. This silicon-based powder substance has a bulk specific gravity
It was 0.40 g / cm ³ and the specific surface area was 699 m ² / g.

Comparative Example 1 61 g (400 mmol) of tetramethoxysilane and 68 g (1,680 mmol) of ethanol were placed in a 500 ml reactor equipped with a stirrer, a thermometer and a condenser and mixed with stirring. To this, 30 g of a 5% hydrochloric acid aqueous solution was added dropwise, and after 40 days at room temperature after the completion of the addition, the reaction liquid, which was colorless and transparent, changed into a white gel. Therefore, the same treatment as in Example 1 was performed. As a result, 22.1 g of a silicon-based powder material was obtained. This silicon powder material has a bulk specific gravity of 1.10 g / c.
m ³ and the specific surface area were 157 m ² / g.

Comparative Example 2 When a reaction was carried out in the same manner as in Comparative Example 1 except that 45 g of 33% hydrochloric acid aqueous solution was used instead of 5% hydrochloric acid aqueous solution, it changed into a white gel after 10 hours. Then, the same treatment as in Example 1 was carried out to obtain 23.0 g of a silicon-based powder substance. This silicon-based powder substance has a bulk specific gravity of 0.96 g / cm ³ and a specific surface area of 180 m ^2.
/ G.

[0040]

EFFECTS OF THE INVENTION According to the present invention, the hydrolysis-polycondensation time of the alkoxysilane compound is significantly reduced by using a fluoride salt compound as a catalyst. It is possible to synthesize a porous silicon-based powder material having a small specific gravity. Also, operability and safety are remarkably improved as compared with other acidic catalysts (hydrochloric acid, sulfuric acid, hydrofluoric acid, etc.).

Claims (1)

(57) [Claims] 1. A method for producing a silicon-based powder material by carrying out hydrolysis-polycondensation of an alkoxysilane in the presence of a fluoride salt compound.