JPH01145317A - Production of spherical fine particle of silica - Google Patents

Abstract

PURPOSE:To obtain high-purity spherical fine particles of silica suitable as an additive for coating compound, having controlled average particle diameter, true specific gravity, etc., by blending specific two silane compounds in a given ratio, hydrolyzing and condensing in an organic solution containing water and an ammonium ion as a catalyst. CONSTITUTION:(A) A hydrolyzable and condensable silane compound (e.g. tetramethoxysilane) shown by formula I (X is alkoxy, acyloxy, hydroxyl or H) is blended with (B) a silane compound (derivative) (e.g., methyltrimethoxysilane) shown by formula II (R<2> is alkyl, aryl or unsaturated aliphatic residue; m is 1-3) in the ratio of the component B to total silane compounds of 0.0017-1 calculated as equivalent ratio of Si atom. The blend is hydrolyzed and condensed in an organic solution (e.g., methanol) containing NH3 ion as a catalyst and water in an amount exceeding hydrolysis equivalent. Consequently, high-purity spherical fine particles of silica shown by formula III (R<1> is average composition of organic group containing carbon atom directly bonded to silicon atom; n is 0.005-1), 0.05-20mum average particle diameter, 1-1.5 standard deviation of particle diameter and 1.2-2.1 true specific gravity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing fine silica particles. Specifically, the present invention relates to a method for producing highly pure, true 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 particle diameter of 0.02 to 0.1 μm obtained by thermal decomposition of silicon halide, and 1 to 5 μm obtained by a sodium silicate wet method.
There are pulverized silica made from aggregates of m, and silica made from crushed natural silica melted into spherules, but both have irregular particle shapes, and even if they are close to spherical, the particle size distribution is extremely wide. be.

Fine silica particles with perfectly spherical particles and a sharp particle size distribution include silica with an average particle diameter of up to about 0.1 μm produced from an aqueous sodium silicate solution by an ion exchange method, and a hydrous ammoniacal alcohol solution containing tetraalkoxysilane. The average particle size produced by hydrolysis in
Silica down to 0 μm (STOBER et al. Journal of Colloid Interface Science Vol. 26,
62-69 (1968), JP-A-62-72514
Publications, etc.). However, the true specific gravity of silica fine particles expressed as SiO2 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 above-mentioned conventional method, which is manufactured by various manufacturing methods, The true specific gravity of known silica fine particles is at least 2.05 or more, and in many cases greater than 2.10, and it has not been possible to obtain silica fine particles having a true specific gravity of any value of 2.10 or less.

Conventionally, there has been no known specific example of a method for producing highly purified true 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 organic silicon oxide powder containing an organic group and having an average particle diameter of 1 μm or less, using a silane compound having an organic group and a hydrolyzable group, and a hydrolyzable group. 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 true spherical fine particles with a sharp particle size distribution of arbitrary particle size and arbitrary true specific gravity value could not be obtained with the above-mentioned specific method. 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 has the following features:
The average compositional formula is R1nSiO4-n (wherein, R1 represents the average composition of an organic group having a carbon atom directly bonded to a silicon atom, and n represents a number in the range of 0.005 to 1, respectively). A method for producing silica fine particles represented by the formula: a silane compound (A) represented by the general formula SiX4 which can be hydrolyzed and condensed; and a silane compound (A) represented by the general formula R2m 31 X4
-l [However, in the general formula, 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; , at least one group selected from the group consisting of aryl groups and unsaturated aliphatic residues, and m represents an integer in the range of 1 to 3, respectively. ] or their derivatives are mixed so that the ratio of the silane compound (B) and/or its derivative to the total number of silane compounds is in the range of 0.0017 to 1 expressed as the ratio of the number of equivalents of silicon atoms, and at least as a catalyst. Hydrolyzed and condensed in an organic solution containing ammonium ions and water in excess of the amount of water that can be hydrolyzed.The average particle diameter is 0.05.
~20 μm, the standard deviation value of the particle diameter 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. It is something.

Silica in the present invention is defined as a silicon oxygen compound in which silicon atoms mainly form a three-dimensional network through bonds with oxygen atoms, and the average compositional formula is R1nS.
It is expressed as iO, and 0 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, W(X) derived from raw materials, etc. may be bonded to silicon atoms, but these groups are not included in the composition formula. shall not be included.

X of the silane compound (A) represented by the general formula 5iXa, which is one of the fine particle raw materials, is an alkoxy group, an acyloxy group,
The four X's may be different from each other and are at least one group selected from the group consisting of a hydroxyl group and a hydrogen atom. Specific examples of the silane compound (A) include tetramethoxysilane,
Tetraethoxysilane, tetraisopropoxysilane,
Examples include tetrabutoxysilane, tetrapentoxysilane, dimethoxyjethoxysilane, tetraacetoxysilane, trimethoxysilane, triethoxysilane, and jetoxysilane. Another fine particle raw material is a silane compound (B) represented by the general formula R2m 3i At least one group selected from the group consisting of groups does not necessarily have to be a hydrophobic group. X is the same group as in the silane compound (A), m is an integer in the range of 1 to 3, and m R2
and (4-m) X may be different from each other.

Specific examples of the silane compound (B) include methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, octyltriethoxysilane, and phenyltrimethoxysilane. , trimethoxyvinylsilane, chloromethyltrimethoxysilane, mercaptomethyltrimethoxysilane, 3.
3.3-trifluoropropyltrimethoxysilane, 3
-Aminopropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, allyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-(2-aminoethylaminopropyl)trimethoxysilane, dimethoxymethylsilane , jetoxymethylsilane, methyltriacetoxysilane, ethyltriacetoxysilane, triacetoxyvinylsilane, diacetoxymethylsilane, dimethoxydimethylsilane, dimethoxydimethylsilane, jetoxydimethylsilane, jetoxydiethylsilane, dimethyldibutoxysilane, dimethoxydiphenyl Silane, chloromethyljethoxysilane, jetoxymethylvinylsilane, jetoxymethylphenylsilane, dimethoxymethyl-3,3,3-1
-Lifluoropropylsilane, dimethylethoxysilane, diethylsilane, diacetoxydimethylsilane, diacetoxydiphenylsilane, diacetoxymethylvinylsilane, methoxytrimethylsilane, ethoxytrimethylsilane, acetoxytrimethylsilane, acetoxytriethylsilane, trimethylsilanol, etc. . 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. - For example, compounds in which some of the hydrolyzable groups (X) of 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, or these silanes It is a low condensate obtained by partially hydrolyzing a compound or a chelate compound.

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.

Silane compounds (A) and silane compounds (B')
The usage ratio of silane compounds (B) to all silane compounds expressed as a molar ratio per silicon atom (hereinafter abbreviated as addition ratio) is in the range of 0.0017 to 1. There is a need. 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. - Hydrolysis in an organic solution,
It is preferable that the fine particles produced by condensation be monodispersed without agglomerated particles, but if the above addition ratio becomes large, agglomeration may easily occur, so it is preferable that the addition ratio is 0.0017 to 0.2. preferable. Further, within this 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, but the addition ratio of silane compounds (B) is 0.0,
When there are many such as 5 or more, syn compounds (A) and (
B) may be added intermittently. However, when the addition ratio is less than 0.05, the silane compounds (B) are added after hydrolyzing and condensing only the silane compounds (A) as a raw material to form true spherical silica particles. The true specific gravity cannot be controlled using the method of using as a coupling agent. It is necessary that an organic group derived from the silane compound (B) be present at least inside the fine particles.

It is preferable to add the silane compounds (A) and silane compounds (B) to a final concentration of 2 mol/l or less in the organic solution, since aggregation of the produced 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 methanol, ethanol, isopropanol,
Alcohols such as 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; ) Paraffins, 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. Here, the water of today's world is a silane compound (in the case of A>, Si X4 +2H20
→Si 02 +4HX, in the case of silane compound (B), -m R2mSiX + 2 820 -m →R2m SiO4-m ” (4m) Multiply the theoretical water calculated as HX by the respective addition amount (mol) and add If the amount does not exceed the equivalent amount, uniform particles will not be obtained.The preferred amount of water is in a molar ratio of 1.5 to 50 with respect to the total amount of the silane compound, and the amount exceeds 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 shape, particle size, and dispersion state of the particles, so they must be controlled within the above range, but the amount depends on the type, concentration, and concentration of the raw material silane compound. It changes depending on the situation.

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
This is carried out by stirring at a temperature in the range of 100°C, preferably in the range of 0 to 70°C, for 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. Further, there are no restrictions on the number and position of the addition ports, stirring, mixing method, etc., and 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 is expressed as R1n SiO, and the true specific gravity is It is possible to produce silica fine particles that can vary arbitrarily.

By selecting more preferable conditions, fine particles with less aggregation can be produced. However, in the above average compositional formula, R1 represents the average composition of an organic group having a carbon atom directly bonded to a silicon atom, and is derived from at least one organic group (R2) of the silane compound (B), n represents O, [a number in the range of 5 to 1;

(Effects of the Invention) As mentioned 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, makes it possible for the first time to increase the average particle size. Standard deviation value of 0.05-20 μm 1 particle size is 1.0
〜1.5, and the true specific gravity of the particles is 1.20 to 2.
．． It was possible to produce highly pure spherical silica fine particles whose purity was arbitrarily controlled within a range of 10. High purity true spherical fine particles of any particle size with a sharp particle size distribution can be used as a filler,
It can enhance the functionality of polymers, paints, inks, toners, adsorbents, catalysts, ceramics, etc. used as surface treatment agents, molded objects, etc. Furthermore, arbitrary control of true specific gravity allows control of the hardness of fine particles. In addition, when the fine particles are used by being dispersed in a solvent, polymer, etc., they can exhibit effects on dispersibility, anti-sedimentation properties, 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.

In addition, the shape, average particle diameter, standard deviation value,
Crystallinity, amount of bound organic groups, true specific gravity, and specific surface area were analyzed by the following methods.

・Particle shape Judgment was made by observation with an electron microscope at a magnification of 50,000 times.

- Average particle diameter and standard deviation value The particle diameter of 300 arbitrary particles in an electron microscope photographed image with a magnification of 50,000 times was actually measured and determined from the following formula.

Σ Volatile components such as water are completely removed to obtain a fine 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 a Shimadzu autobicmeter 1320.

・Bound organic group amount (measurement of n) Accurately weigh 5 g of the powder sample obtained by the method described above and obtain 0.0
Add to 250 - 5 N aqueous NaOH solution and stir at room temperature for 1
Continue stirring for 0 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 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 R2m SiX4-m used as the raw material. R1 was determined from the average carbon number of R2, and n■ when the average composition of the fine particles was expressed as R1n Si 2 O was determined. Moreover, on the other hand, the bonding of Kenichi 8i-C in the particles was also confirmed by FT-IR.

Example 1 Into a 30-inch glass reactor equipped with a stirrer, a dropping port, and a thermometer, 1.4 liters of methanol and 1.0 liters of a 28% aqueous ammonia solution were added.
After adding 5 kg, ammonia gas was further blown into the tank.
26 Ky was absorbed and mixed to adjust the ammonia concentration. The mixed solution was adjusted to 10°C±0.5°C, and while stirring, 1.0% tetramethoxysilane was added as the silane compound (A).
A mixture of 22 Kff and 0.79 Ky of phenyltrimethoxysilane as the silane compound (8) was mixed with methanol 2
A solution diluted to Jl was dripped from the dripping port over 7 hours,
After dropping, the internal temperature was raised to 50° C. and stirred for 5 hours, followed by aging and hydrolysis to produce an organic (methanolic) solution suspension of silica fine particles (a). At this time, the concentration of each raw material with respect to the total amount of the final solution was 0.5% for tetramethoxysilane.
40 mol/i, phenyltrimethoxysilane 0.20 mol/i, water 3.0 mol/1, ammonia 2.0 mol/i
Met. In addition, the silicon remaining in the clear organic solution from which the particles were separated from the suspension after repulsion 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 in the form of particles. . Table 1 shows the reaction conditions and particle analysis results. Further, the fine particles were added to 25
Even after firing at 0°C, there was no change in particle shape, average particle diameter, standard deviation value, crystallinity, etc.

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 reactions were carried out six times by changing the organic solvent from methanol to ethanol.

First, in the first step, a solution prepared by diluting 1,130 g of tetraethoxysilane as the silane compound (A> and 63 g of 3-aminopropyltriethoxysilane as the silane compound (B) in 2.71 g of ethanol and 2.2 g of 28% aqueous ammonia 20℃ in a mixture of .310g and 147g of ethanol.
was added to the solution while adjusting the wetness and hydrolyzed to obtain a suspension of silica fine particles (BL) having an average particle diameter of 1.53 μm.

Next, in the second stage, 3.41 of the suspension was diluted with the same amount of ammonia water ethanol mixture as in the first stage, and the same amount of silane compounds (A> and (B) as in the first stage were added. ) was added and hydrolyzed in the same manner as in the first step to obtain an average particle size of 2.9.
A suspension of 3 μm silica fine particles (b2) was obtained. Similarly, fine silica particles (b3) with an average particle diameter of 5.62 μm
) was obtained. Table showing the analysis results of each particle.
1 and Table 2.

Examples 3 to 6 In Example 1, the solvent was ethanol, methyltrimethoxysilane was used as the silane compound (B), and the amounts of the silane compounds (A) and (B) were as shown in Table 1. The same procedure as in Example 1 was carried out except that suspensions of silica fine particles (C) to (f>) having different true specific gravity were produced. The results are shown in Tables 1 and 2.

Comparative Example 1 A suspension of fine silica particles (gl) 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. Further, methyltrimethoxysilane was added to the suspension in an amount of 5 mol % based on tetramethoxysilane to produce a suspension of silica fine particles (g2) in which the silica fine particles (ql) were subjected to a coupling treatment. The results are shown in Table-1 and Table-2.

Example 7 In Example 1, 48 (average) tetraethoxysilane derivatives of the silane compound (A>) and the silane compound (
A suspension of silica fine particles (h) was prepared in the same manner as in Example 1 using dimethoxydimethylsilane as B). The results are shown in Table-1 and Table-2.

Example 8 Using the same reactor as in Example 1, cyclohexane 221
, polyethylene glycol nonylphenyl ether (average number of added moles of ethylene oxide: 6; hereinafter referred to as NP.>0.97 Kg, 28% aqueous ammonia 0.49 Kg
and 0.37 Ky of water were mixed to form a uniform microemulsion of aqueous ammonia in cyclohexane. The temperature of the emulsion was adjusted to 35°C, and while stirring, a mixture of 1.257 g of tetraethoxysilane and 0.16 Ky of diacetoxydimethylsilane was added over 2 hours, and the mixture was stirred at the same temperature for 70 hours to complete the reaction. An organic (cyclohexane) solution suspension of silica fine particles (i) was prepared.The results are shown in Tables 1 and 2.

Example 9 A suspension of silica fine particles (j) was produced in the same manner as in Example 8, except that jetoxymethylsilane was used instead of diacetoxydimethylsilane. The results are shown in Table-1 and Table-2.

Claims (1)

[Claims] (1) The average compositional formula is R^1nSiO_4_-_n (where R^1 indicates the average composition of organic groups having carbon atoms directly bonded to silicon atoms, and n is a number in the range of 0.005 to 1. ) is a method for producing silica fine particles represented by the general formula SiX_ which can be hydrolyzed and condensed.
A silane compound (A) represented by 4, and the general formula R^
A silane compound (B
) [However, in the general formula, X is an alkoxy group, an acyloxy group,
at least one group selected from the group consisting of a hydroxyl group and a hydrogen atom; R^2 is at least one group selected from the group consisting of an optionally substituted alkyl group, an aryl group, and an unsaturated aliphatic residue; each represents an integer in the range of 1 to 3. ] or their derivatives, the ratio of the silane compound (B) and/or its derivatives to the total silane compounds is 0.0, expressed as the ratio of the number of equivalents of silicon atoms.
017 to 1 and hydrolyzed and condensed in an organic solution containing at least ammonium ions as a catalyst and water exceeding the hydrolytic equivalent; Standard deviation value of particle size is 1
．． In the range of 0 to 1.5, the true specific gravity of the particles is 1.20
A method for producing highly pure spherical silica fine particles controlled within the range of ~2.10.