JPH054325B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing silica fine particles. Specifically, the present invention relates to a method for producing highly pure spherical silica fine particles having a specified composition, physical properties, etc. and a controlled true specific gravity. The fine particles are industrially valuable as fillers for various resin molded products, surface treatment agents, paints, inks, and other additives. (Prior art) Silica fine particles have conventionally been produced using fumed silica with an average primary fine particle diameter of 0.02 to 0.1 μm obtained by thermal decomposition of silicon halide, crushed silica in the form of aggregates of 1 to 5 μm obtained by wet sodium silicate method, and crushed natural silica. There are silicas whose bodies are fused and spheroidized, but all of them have irregular particle shapes, and even if they are close to spherical, the particle size distribution is extremely wide. Silica fine particles, which are perfectly spherical and have a sharp particle size distribution, are produced from an aqueous sodium silicate solution by an ion exchange method, etc.
Silica of up to about 0.1 μm, silica with an average particle size of up to 10 μm produced by hydrolyzing tetraalkoxysilane in a water-containing ammoniacal alcohol solution (STO¨BER et al. Journal of Colloid Interface Science Vol. 26, 62-69
(1968), Japanese Unexamined Patent Publication No. 62-72514, etc.).
However, the true specific gravity of silica fine particles expressed as SiO ₂ is originally influenced by the manufacturing method and particle size of the fine particles, but in the case of particles with a particle size of 0.05 μm or more, the true specific gravity of silica fine particles expressed as SiO 2 is The true specific gravity of conventionally known silica fine particles is at least
2.05 or more, often greater than 2.10, true specific gravity
It was not possible to obtain silica fine particles having an arbitrary value of 2.10 or less. Conventionally, there has been no known specific example of a method for producing highly pure spherical silica fine particles having an arbitrary average particle diameter, a sharp particle size distribution, and an arbitrarily controlled true specific gravity. By the way, JP-A No. 61-243828 describes a method for producing organosilicon oxide powder containing an organic group and having an average particle diameter of 1 μm or less. A method is disclosed for hydrolyzing a silane compound containing only silane compounds in an organic solution. However, this publication specifically discloses production using a halogenated silane compound whose hydrolyzable group is a halogen as a raw material for the purpose of producing hydrophobized fine particles by reducing the amount of silanol groups in the produced particles. However, the shape and size distribution of the particles are not clear. Furthermore, the possibility of controlling the true specific gravity of particles is not clear, and judging from specific examples, it seems impossible. The present inventors conducted a detailed study on the method described in the above-mentioned known literature, and found that the above-mentioned specific method did not yield true spherical fine particles having any desired true specific gravity value without sharpening the particle size distribution of any particle size. Problems were found, such as that halogen derived from the raw material remained in the process, making it difficult to obtain highly pure fine particles, and that there were problems with equipment due to the use of halides. (Problems to be Solved by the Invention) The present invention provides an industrially advantageous method for producing highly pure silica particles in which the shape, particle size distribution, true specific gravity, etc. of silica particles are arbitrarily controlled within specified ranges. It is something to do. (Means and effects for solving the problems) The present invention provides that the average compositional formula is

[Formula] (where, R ¹ represents the average composition of organic groups having carbon atoms directly bonded to silicon atoms, and n is 0.005 to 1
Each number represents a range of numbers. ) A method for producing silica fine particles represented by: a silane compound (A) represented by the general formula SiX ₄ that can be hydrolyzed and condensed;
and a silane compound (B) represented by the general formula R ² _n SiY _4-n [wherein X and Y are at least one group selected from the group consisting of an alkoxy group, an acyloxy group, a hydroxyl group, and a hydrogen atom, R ² represents at least one group selected from the group consisting of an alkyl group, an aryl group, and an unsaturated aliphatic residue which may have a substituent, and m represents an integer in the range of 1 to 3, respectively. ] or their derivatives as silane compounds.
The ratio of (B) and/or its derivatives to the total silane compounds is expressed as the ratio of the number of equivalents of silicon atoms.
0.0017 to 1, and hydrolyzed and condensed in an organic solution containing at least ammonium ions as a catalyst and water exceeding the hydrolysis equivalent; The present invention relates to a method for producing highly pure spherical silica fine particles in which the standard deviation value of the particles is in the range of 1.0 to 1.5 and the true specific gravity of the particles is controlled in the range of 1.20 to 2.10. In the present invention, silica is defined as a silicon oxygen compound in which silicon atoms constitute a three-dimensional network mainly through bonds with oxygen atoms, and the average compositional formula is

It is expressed as [Formula], and n is in the range of 0.005 to 1. However, in the method for producing silica fine particles of the present invention, in addition to hydrocarbon groups, hydroxyl groups, groups (X) and (Y) derived from raw materials are added to silicon atoms.
etc. may be bonded, but these groups shall not be included in the composition formula. In the silane compound (A) represented by the general formula SiX ₄ , which is one of the fine particle raw materials, X is at least one group selected from the group consisting of an alkoxy group, an acyloxy group, a hydroxyl group, and a hydrogen atom, and the four Xs are different. You can leave it there. Specific examples of the silane compound (A) include:
Tetramethoxysilane, Tetraethoxysilane,
Examples include tetraisopropoxysilane, tetrabutoxysilane, tetrapentoxysilane, dimethoxydiethoxysilane, tetraacetoxysilane, trimethoxysilane, triethoxysilane, and diethoxysilane. Another fine particle raw material is a silane compound represented by the general formula R ² _n SiY _4-n.
(B) in the general formula, R ² may have a substituent,
It is at least one group selected from the group consisting of an alkyl group, an aryl group, and an unsaturated aliphatic residue, and does not necessarily have to be a hydrophobic group. Y is a silane compound
In the same group as in (A), m represents an integer in the range of 1 to 3, and m R ² and (4-m) Y may be different from each other. Specific examples of the silane compound (B) include methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, octyltriethoxysilane, and phenyltrimethoxysilane. Silane, trimethoxyvinylsilane, chloromethyltrimethoxysilane, mercaptomethyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, allyl Triethoxysilane, 3
- methacryloxypropyltrimethoxysilane,
3-(2-aminoethylaminopropyl)trimethoxysilane, dimethoxymethylsilane, diethoxymethylsilane, methyltriacetoxysilane, ethyltriacetoxysilane, triacetoxyvinylsilane, diacetoxymethylsilane, dimethoxydimethylsilane, dimethoxydimethylsilane, Diethoxydimethylsilane, diethoxydiethylsilane, dimethyldibutoxysilane, dimethoxydiphenylsilane, chloromethyldiethoxysilane, diethoxymethylvinylsilane, diethoxymethylphenylsilane, dimethoxymethyl-3,3,3-trifluoropropyl Examples include silane, dimethylethoxysilane, diethylsilane, diacetoxydimethylsilane, diacetoxydiphenylsilane, diacetoxymethylvinylsilane, methoxytrimethylsilane, ethoxytrimethylsilane, acetoxytrimethylsilane, acetoxytriethylsilane, and trimethylsilanol. The silane compounds (A) and (B) are not limited to those exemplified. Considering the ease of obtaining raw materials for industrial production, a silane compound containing an alkoxy group as X is preferred. Further, as silane compounds that can be used as raw materials for fine particles, there are derivatives of the above-mentioned silane compounds. As an example, a compound in which some of the hydrolyzable groups (X) and (Y) of the silane compounds (A) and (B) are substituted with a group capable of forming a chelate compound, such as a carboxyl group or a β-dicarbonyl group, Alternatively, it is a low condensate obtained by partially hydrolyzing these silane compounds or chelate compounds. The above-mentioned raw material silane compound (A) and/or its derivatives (hereinafter referred to as silane compounds (A)) and (B) and/or its derivatives (hereinafter referred to as silane compounds (B)) are at least catalysts. It is added to an organic solution containing ammonium ions and water in an amount exceeding the hydrolysis equivalent, and is hydrolyzed and condensed to form true spherical silica fine particles. The usage ratio of silane compounds (A) and silane compounds (B) is the addition ratio (hereinafter referred to as addition ratio), which is the ratio of silane compounds (B) to all silane compounds expressed as a molar ratio per silicon atom. ) must be in the range of 0.0017 to 1. When it is less than 0.0017, the effect of lowering the true specific gravity of fine particles is weak, and when it exceeds 1, true spherical fine particles are not produced. On the other hand, fine particles produced by hydrolysis and condensation in an organic solution are preferably monodispersed without agglomerated particles, but if the above addition ratio becomes large, aggregation may easily occur.
The addition ratio is preferably 0.0017 to 0.2. or,
In that range, the true specific gravity of the generated fine particles changes greatly. When adding silane compounds (A) and (B) to an organic solution, it is preferable to mix them and add them as a homogeneous solution. Silane compound (A) in many cases
and (B) may be added intermittently. However, if the addition ratio is less than 0.05, silane compounds (A) are hydrolyzed and condensed as raw materials to form true spherical silica fine particles, and then silane compounds (B) are added, so-called coupling of (B). The true specific gravity cannot be controlled by chemical methods. It is necessary that an organic group derived from the silane compound (B) be present at least inside the fine particles. The total amount of silane compounds (A) and silane compounds (B) added is 2 mol/min as the final concentration in the organic solution.
The following is preferable because agglomeration of generated particles can be prevented. The organic solution refers to a solution in which water and ammonium ions are completely dissolved in an organic solvent capable of dissolving the raw material silane compound, or a solution in which water and ammonium ions are uniformly dispersed as micelles in the organic solvent. Specific examples of organic solvents include alcohols such as methanol, ethanol, isopropanol, n-butanol, t-butanol, pentanol, ethylene glycol, propylene glycol, and 1,4-butanediol; ketones such as acetone and methyl ethyl ketone; Esters such as ethyl acetate, isooctane, (cyclo)paraffins after cyclohexane, ethers such as dioxane and diethyl ether, aromatic compounds such as benzene and toluene, etc. can be used singly or in mixtures. In the case of organic solvents that are incompatible with water and ammonia, a surfactant may be added to them to form uniform micelles. The amount of water present in the organic solution exceeds the equivalent amount required for hydrolysis of the raw material silane compound. In the case of the silane compound (A), the equivalent amount of water is SiX ₄ +2H ₂ O→SiO ₂ +4HX, and in the case of the silane compound (B), Defined as the amount added by multiplying the theoretical water calculated as the respective addition amount (mol). If the amount does not exceed the equivalent amount, uniform particles will not be obtained. The preferred amount of water is 1.5 to 50 molar ratio to the total amount of silane compound.
The amount should be within the range and exceed the equivalent amount. The amount of ammonium ions serving as a catalyst is preferably in a molar ratio of 1 to 30 with respect to the total amount of silane compounds. Ammonium ions can be added as ammonia gas or aqueous ammonia, but other compounds that can generate ammonium ions in an organic solution can also be added. The amounts of water and ammonium ions present in the organic solution affect the particle shape, particle size, and dispersion state, so they must be controlled within the above range, but depending on the type and concentration of the raw material silane compound, etc. It changes over time. Hydrolysis and condensation can be carried out, for example, by adding the above-mentioned raw material silane compound or its organic solvent solution to the above-mentioned organic solution, and heating the mixture at a temperature in the range of 0 to 100°C, preferably 0 to 70°C.
This is carried out by stirring at a temperature ranging from 30 minutes to 100 hours. During hydrolysis and condensation, the raw material silane compound may be added in portions or continuously, and the same applies to water and ammonium ions. Furthermore, the number and position of those addition ports, stirring, mixing method, etc.
There are no restrictions on the specific manufacturing method. If the raw material silane compound is hydrolyzed and condensed in an organic solution under appropriate conditions in this way, an average composition with a spherical shape and a very sharp particle size distribution can be obtained.

It is possible to produce silica fine particles represented by the following formula and whose true specific gravity can be arbitrarily changed. By selecting more preferable conditions, fine particles with less aggregation can be produced. however,
In the above average compositional formula, R ¹ represents the average composition of an organic group having a carbon atom directly bonded to a silicon atom, and at least one or more organic groups (R ² ) of the silane compound (B)
, where n represents a number in the range of 0.005 to 1. (Effects of the Invention) As described above, the method for producing silica fine particles containing organic groups of the present invention, which is characterized by hydrolysis and condensation using specified raw materials and under specified conditions, enables the production of average particles for the first time. It is possible to produce highly pure true spherical silica fine particles with diameters in the range of 0.05 to 20 μm, standard deviation of particle diameter in the range of 1.0 to 1.5, and true specific gravity of the particles arbitrarily controlled in the range of 1.20 to 2.10. did it. Highly pure spherical fine particles with a sharp particle size distribution of any size can be used as fillers, surface treatment agents, molded products, etc., and have functions such as polymers, paints, inks, toners, adsorbents, catalysts, ceramics, etc. In addition, arbitrary control of true specific gravity makes it possible to control the hardness of the fine particles, and improves the dispersibility when the fine particles are used by dispersing them in a solvent, polymer, etc.
It can be effective in preventing sedimentation, etc. Furthermore, according to the production method of the present invention, it is possible to produce fine particles in which the balance between the amount of organic groups and silanol groups in the fine particles is arbitrarily selected. If a reactive material is used as a material, it is possible to graft a substance capable of bonding with a reactive organic group after micronization. (Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples, but the scope of the present invention is not limited by the Examples. The shape, average particle diameter, standard deviation value, crystallinity, amount of bound organic groups, true specific gravity, and specific surface area of the silica fine particles were analyzed by the following methods. - Particle shape Determined by electron microscope observation at 50,000x magnification. - Average particle size and standard deviation value The particle size of 300 arbitrary particles in an image taken with an electron microscope at a magnification of 50,000 times was actually measured and determined using the following formula. ・Crystallinity of fine particles A part of the suspension of organic solution of silica fine particles obtained by hydrolysis and condensation is vacuum-dried at 100℃ for one day and night to completely remove volatile components such as solvent and water and to form fine particles. Obtain a powder sample. The crystallinity of the fine particles of the powder sample was evaluated by X-ray diffraction analysis. In addition, a powder produced by separating particles from a suspension and then drying or firing was evaluated in the same manner. - Specific surface area The specific surface area of the powder sample obtained by the method described above was measured by the BET method. - True specific gravity The true specific gravity of the powder sample obtained by the method described above was measured using an autopycnometer 1320 manufactured by Shimadzu. - Amount of bound organic groups (measurement of n) Accurately weigh approximately 5 g of the powder sample obtained by the method described above, add it to 250 ml of 0.05N NaOH aqueous solution, and add it to 250 ml of 0.05N NaOH aqueous solution,
Continue stirring for 10 hours. As a result, all the hydrolyzable groups in the fine particles are hydrolyzed and extracted into an aqueous solution. The fine particles in the suspension were separated by ultracentrifugation, washed repeatedly with water, and then dried at 200°C for 5 hours. The total carbon content was measured by elemental analysis, and the total carbon content was determined from the R ² mSiY used as the raw material. _n-4
Calculate R ¹ from the average carbon number of R ² and calculate the average composition of the fine particles.

When expressed as [Formula], n was calculated. Ma On the other hand, FT-IR was used to detect particles in particles.

The bond of [Formula]C was also confirmed. Example 1 After adding 1.5 kg of methanol 14 and 28% ammonia aqueous solution to a 30 glass reactor equipped with a stirrer, a dropping port, and a thermometer, ammonia gas was further blown in to absorb 0.26 kg and mix to reduce the ammonia concentration. It was adjusted. Adjust the mixture to 10°C ± 0.5°C,
While stirring, a solution prepared by diluting a mixture of 1.22 kg of tetramethoxysilane as the silane compound (A) and 0.79 kg of phenyltrimethoxysilane as the silane compound (B) in 2 methanol was added dropwise from the dropping port over 1 hour. Raise the internal temperature to 50℃ and continue stirring for 5 hours to mature and hydrolyze the silica fine particles.
An organic (methanolic) solution suspension of (a) was prepared. The concentrations of each raw material based on the total amount of the final solution at this time were 0.40 mol/tetramethoxysilane, 0.20 mol/phenyltrimethoxysilane, 3.0 mol/water, and 2.0 mol/mol ammonia. In addition,
After the reaction, the particles were separated from the suspension and the silicon remaining in the clear organic solution was measured by atomic absorption spectrometry, and it was found to be less than 10 ppm, confirming that the raw material silane compound was almost completely converted into particles. Table 1 shows the reaction conditions and particle analysis results. Furthermore, even after the fine particles were fired at 250°C, there was no change in the shape, average particle diameter, standard deviation value, crystallinity, etc. of the particles. Table 2 shows the surface area, true specific gravity, and amount of bound organic groups after firing. Example 2 Using the same apparatus as in Example 1, the following reaction was carried out by changing the organic solvent from methanol to ethanol. First, in the first step, a solution of 1130 g of tetraethoxysilane as the silane compound (A) and 63 g of 3-aminopropyltriethoxysilane as the silane compound (B) diluted in 2.7 ethanol was mixed with 2310 g of 28% aqueous ammonia and 14 ml of ethanol. 20℃ inside
was added to the solution while controlling the temperature and hydrolyzed to obtain a suspension of silica fine particles (b ₁ ) having an average particle diameter of 1.53 μm. Then, as a second stage, 3.4 of the suspension
Add the same amount of silane compounds (A) and (B) as in the first step to a suspension diluted with the same amount of ammonia water ethanol mixture as in the first step, and perform hydrolysis in the same manner as in the first step. A suspension of silica fine particles (b ₂ ) with an average particle diameter of 2.93 μm was obtained. Similarly, the average particle diameter
A suspension of 5.62 μm silica fine particles (b ₃ ) was obtained.
Table 1 and Table 2 show the analysis results of each particle.
Shown below. Examples 3 to 6 In Example 1, ethanol was used as the organic solvent and methyltrimethoxysilane was used as the silane compound (B), and the amounts of the silane compounds (A) and (B) added are shown in Table-1.
The same procedure as in Example 1 was carried out except that the procedure was as shown in , to produce suspensions of silica fine particles (c) to (f) having different true specific gravity. The results are shown in Table-1 and Table-2. Comparative Example 1 A suspension of fine silica particles (g ₁ ) containing no organic group inside the particles was produced in the same manner as in Example 2 except that methyltrimethoxysilane was not used in Example 3. Furthermore, 5 mol% of methyltrimethoxysilane based on tetramethoxysilane was added to the suspension.
A suspension of fine silica particles (g ₂ ) was produced by adding and coupling the fine silica particles (g ₁ ). The results are shown in Table-1 and Table-2. Example 7 Silica fine particles were prepared in the same manner as in Example 1, except that a tetramer (average) of tetraethoxysilane, which is a derivative of the silane compound (A), and dimethoxydimethylsilane were used as the silane compound (B). (h)
A suspension was prepared. The results are shown in Table-1 and Table-2. Example 8 Using the same reactor as in Example 1, 22 cyclohexane, 0.97 kg of polyethylene glycol nonyl phenyl ether (average number of added moles of ethylene oxide: 6; hereinafter referred to as NP), 0.49 kg of 28% aqueous ammonia, and 0.37 kg of water. Kg was mixed to form a homogeneous aqueous ammonia microemulsion in cyclohexane. The temperature of the emulsion was adjusted to 35°C, and while stirring, a mixture of 1.25 kg of tetraethoxysilane and 0.16 kg of diacetoxydimethylsilane was added over 2 hours, and stirring was continued at the same temperature for 70 hours to complete the reaction. ) was prepared as an organic (cyclohexane) solution suspension. The results are shown in Table-1 and Table-2. Example 9 A suspension of silica fine particles (j) was produced in the same manner as in Example 8, except that diethoxymethylsilane was used instead of diacetoxydimethylsilane. The results are shown in Table-1 and Table-2.

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Claims (1)

[Claims] 1. The average compositional formula is [Formula] (where R ¹ represents the average composition of organic groups having a carbon atom directly bonded to a silicon atom, and n is a number in the range of 0.005 to 1, respectively. ) A method for producing silica fine particles represented by the general formula capable of hydrolysis and condensation.
A silane compound (A) represented by SiX ₄ and a silane compound (B) represented by the general formula R ² mSiY _4-n [However, in the general formula, X and Y are composed of an alkoxy group, an acyloxy group, a hydroxyl group, and a hydrogen atom. ^R2 is at least one group selected from the group consisting of an alkyl group that may have a substituent, an aryl group, and an unsaturated aliphatic residue; m is in the range of 1 to 3; Each represents an integer. ]
or their derivatives, the ratio of the silane compound (B) and/or its derivative to the total silane compound is 0.0017 to 0.0017, expressed as the ratio of the number of equivalents of silicon atoms.
1, and hydrolyzed and condensed in an organic solution containing at least ammonium ions as a catalyst and water exceeding the hydrolysis equivalent, with an average particle size of 0.05 to 20 μm, and a standard particle size. A method for producing highly pure true spherical silica fine particles in which the deviation value is in the range of 1.0 to 1.5 and the true specific gravity of the particles is controlled in the range of 1.20 to 2.10.