JPH01119509A - Production of high purity fine mullite powder - Google Patents

Abstract

PURPOSE:To produce high purity fine mullite powder at a low cost by calcining a precursor of mullite obtd. by hydrolyzing a reaction product or mixture of halosilane with an aluminum compd. contg. oxygen. CONSTITUTION:A reaction product or mixture of halosilane such as tetrahalogenosilane with an aluminum compd. contg. oxygen such as Al(OH)3 in 1/4-1/3 ratio of Al/Si is hydrolyzed by adding >=4pts.wt. alcohol such as methanol per 1pt.wt. halosilane and water to obtain a precursor of mullite. This precursor is calcined at 1,000-1,500 deg.C in the air or in an inert gas to produce fine mullite powder of 0.1-1.0mum average particle size.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing high-purity fine mullite powder. Ceramics obtained from mullite have excellent mechanical properties at high temperatures. It is a useful material as a heat-resistant structural material. Recently, translucent ceramics and electronic ceramics such as IC substrates have been developed using mullite as a raw material, and highly pure and fine mullite powder is suitable as such a raw material. [Prior art] Mullite is a composite compound of aluminum and silicon.
Q, 03.2SiO2~2A Q 20. - Represented by a 5in2 composition formula. Mullite has a particularly small coefficient of thermal expansion among oxide ceramics, has a low density, and has excellent creep properties at high temperatures. Taking advantage of these points, research into heat-resistant structural materials is becoming more active. Generally, the ceramic sintered body is preferably made of a dense, fine, and uniform composition excluding porous materials. For this purpose, the finer the powder raw material and the higher the purity, the lower the sintering temperature, and the better the sintered body can be obtained, and there is a strong demand for high purity mullite fine powder. Conventional methods for producing mullite powder can be broadly divided into solid phase methods and wet methods. [In-phase method] (1) A method of firing a mixture of alumina powder and silica powder. (2) Kaolinite (A Q , O, ・SiO□・H,
A method of firing a mixture of O) and alumina. (3) A method of mixing and heating aluminum sulfate, sodium silicate, and sodium sulfate. [Wet method] (1) A method of producing mullite powder by hydrolyzing aluminum alkoxide and silicon alkoxide and further neutralizing them (Japanese Patent Publication No. 60-52083, J, ofAm,
Ceram, Soc, Vo155. Na1l 54
8-552) (2) A method of mixing and heating alumina sol and silica sol. [Problems to be solved by the invention] However, in the solid phase method, since solid raw materials are used, it takes a long time to mix them, and it is difficult to mix them uniformly, resulting in non-uniform products and not having a 100% mullite structure. It is impossible to do so. Furthermore, since the product particle size also depends on the particle size of the raw material solid, it is difficult to obtain a product with fine particles. Furthermore, when sodium silicate is used as a raw material, sodium and potassium tend to enter the product, resulting in problems such as the inability to obtain a high-purity product. The wet method is superior to the solid phase method, and high purity mullite powder can be obtained by using aluminum alkoxide and silicate alkoxide as raw materials.However, in this case, the raw materials are expensive and the hydrolysis reaction must be carried out strictly. It needs to be controlled and there is a manufacturing cost problem. Furthermore, methods using alumina sol and silica sol have problems with product purity and have the disadvantage that particles tend to aggregate during the manufacturing process. From this point of view, an object of the present invention is to provide a method for producing fine-particle, highly pure mullite powder at low cost. [Means for solving the problem] As a result of intensive research to develop a method for manufacturing fine, high-purity mullite powder at low cost, the present inventors discovered a reaction product of halosilane and an oxygen-containing aluminilla compound. The inventors have discovered that the objective can be achieved by adding alcohol and water to a mixture and hydrolyzing it to obtain a mullite precursor, and then firing the mullite precursor, and have completed the present invention. It was. The method of the present invention includes the steps of producing a mullite precursor;
The process consists of a process of firing the mullite precursor, and each of these processes will be explained in detail below. [Mullite Precursor Generation Step] The raw materials used in the present invention are a halosilane and an oxygen-containing aluminum compound. In this case, the halosilane has one or more halogen atoms and one or more silicon atoms in the molecule,
In some cases, those in which the halogen atom is substituted with an organic group are used.In the present invention, those represented by the following general formula are preferably used. R6S 1H4-<n4g) X@ (1
) In the above formula, R represents an organic group such as an alkyl group or an aryl group. In this case, the number of carbon atoms in the organic group is not particularly limited. X is a halogen atom, and includes chlorine, bromine, iodine, and fluorine. n is an integer of 0 to 3, and m is an integer of 0 to 4. Specific examples of the halosilane include tetrahalogenosilane, trihalogenosilane, dihalogenosilane,
Monohalogenosilane, monoalkyltrihalogenosilane, monoalkyldihalogenosilane, monoalkylmonohalogenosilane, monoaryltrihalogenosilane, monoaryldihalogenosilane, monoarylmonohalogenosilane, dialkyldihalogenosilane, dialkylmonohalogenosilane, Diaryldihalogenosilane, diarylmonohalogenosilane, trialkylmonohalogenosilane, triarylmonohalogenosilane, monoalkylmonoaryldihalogenosilane, dialkylmonoarylmonohalogenosilane, monoalkyldiarylmonohalogenosilane, etc. Examples include halogenodisilanes such as hexahalogenodisilane, pentahalogenodisilane, trihalogenodisilane, and dihalogenodisilane, and alkyl- and l- or aryl-substituted products thereof. As the oxygen-containing aluminum compound, one having an oxygen-containing group and/or a halogen that is reactive or hydrolyzable to the halosilane is used. In the present invention,
Those represented by the following general formula are used, and aluminum hydroxide is preferably used. XnA Q (OR), -n (n) In the above formula, R is H or an alkyl group, and X is a halogen atom, including chlorine, bromine, fluorine, and iodine. n represents an integer of 0 to 3. In this mullite precursor generation step, the halosilane and the oxygen-containing aluminum compound are brought into contact and reacted,
Or mix. The usage ratio of halosilane and aluminum compound is determined by the atomic ratio of aluminum to silicon (A Q /S
Preferably, i) is in the range of 174 to 173. Next, alcohol and water are added to this mixture or reactant for hydrolysis treatment. This hydrolysis treatment can preferably be carried out by adding alcohol to the mixture or reactant and then adding water dropwise. in this case,
Various alcohols can be used, such as aliphatic alcohols, alicyclic alcohols, aromatic alcohols, etc., but aliphatic alcohols generally include methanol, ethanol, propatool, butanol, pentanol, and hexanol. , heptatool, octatool, nonanol, decanol and isomers thereof, and lower alcohols are particularly preferably used. The amount of alcohol used is preferably 4 parts by weight or more, and more preferably 10 parts by weight or more, per 1 part by weight of the halosilane used. Through this hydrolysis treatment, hydrolyzable groups (halogen, alkoxide groups, etc.) in the mixture or reactants react with water and are converted into hydroxyl groups. The alcohol coexisting in the reaction system exhibits effects such as improving the dispersibility of the precipitate and controlling the hydrolysis reaction rate. The mixing or reaction of the halosilane and the oxygen-containing aluminum compound can be carried out either in the presence or absence of a solvent, but it is generally preferable to carry out the reaction in the presence of an organic solvent. Examples of such organic solvents include hydrocarbons such as aromatic hydrocarbons, aliphatic hydrocarbons, and alicyclic hydrocarbons, as well as halogenated hydrocarbons, aliphatic ethers, alicyclic ethers, and the like. In the mixing or reaction of the halosilane and the oxygen-containing aluminum compound and the hydrolysis treatment of the mixture or reactant, the reaction temperature and pressure are not particularly limited, but it is preferable to keep the temperature and pressure within a range in which the reaction system is liquid. . There are no particular restrictions on the atmosphere of the reaction system, and either air or inert gas atmosphere may be used. The mullite precursor obtained as described above is supplied to the next firing step after alcohol and solvent are separated by filtration and drying.

[Firing process]

In the present invention, the mullite precursor obtained as described above is fired at a temperature of 1000 to 1500° C. in air or in an inert gas. By this firing, mullite powder consisting of crystallized fine particles is obtained. Firing temperature is 10
If the temperature is lower than 00°C, crystallization will not proceed, and if it exceeds 1700°C, grain growth will be promoted, making it difficult to obtain fine crystal grains. According to the present invention, the average particle size within the membrane is 0.1 μ+1 to 1.
A mullite powder of 0 .mu.m, preferably 0.2 .mu.++-0.5 .mu.m can be obtained. [Effects] The present invention does not include a grinding and mixing process that is inefficient in energy efficiency, and relatively inexpensive raw materials can be used.
It can be implemented economically. Moreover, the mullite powder obtained by the present invention is fine and highly pure. Therefore, the mullite powder obtained by the present invention can be used as a heat-resistant structural material, and by taking advantage of its high purity, it can be used as an IC material.
It can be advantageously used as an electronic material such as a substrate. [Example] Next, the present invention will be explained in more detail with reference to Examples. Example 1 Silicon tetrachloride 0.087+aol and toluene 0.83 mo
1 into a flask, and 0.26 mo of aluminum hydroxide.
1 was added dropwise in the air at room temperature and stirred. At the same time as the addition, a yellow precipitate was generated due to the reaction. As a result of infrared absorption photometry, this precipitate was found to contain 5L-0 bonds, AQ-0 bonds,
It had a 5i-CQ bond. Furthermore, 1.7 mol of ethanol and 0.17 mol of pure water
The mixed solution was added dropwise to the yellow precipitate and stirred at room temperature for about 30 minutes to carry out hydrolysis treatment. The obtained precipitate was filtered using 5A filter paper and dried under reduced pressure in an oven at 100°C to obtain 25.0 g of a mullite precursor. Next, 2.0g of this precursor was placed in an alumina boat,
1,000°C x 3 hours each in an air atmosphere furnace
It was fired under the conditions of 300° C. for 3 hours and 1500° C. for 1 hour to crystallize it. (The heating rate is 10°C/min). As a result of X-ray diffraction analysis, the obtained fired products were all crystallized and were found to be mullite. In addition, as a result of SEX observation, the primary particle diameter of the obtained mullite powder was about 0.2 μm to 0.3 μm. Also,
As a result of impurity analysis, the purity of mullite was 99.9%. Example 2 Silicon trichloride 0.085+sol and toluene 0.81 mo
1 was placed in a flask, and 0.26 mol of aluminum hydroxide was added dropwise in the air with a water bath width of about 0°C, followed by stirring. A yellow precipitate was formed simultaneously with the dropwise addition. Furthermore, 1.7 mol of methanol and 0 mol of pure water were added to this precipitate.
．． 17 mol was added dropwise and hydrolyzed (all operations were carried out in a water bath at θ°C).
Filter/dry in the same manner as mullite precursor 24.7
I got g. Next, 2 g of this precursor was placed in an alumina boat and fired in an atmospheric furnace at 1300° C. for 1 hour. The obtained baked product is the result of X-ray diffraction analysis. It was crystallized and was mullite. Furthermore, as a result of SEM observation, the primary particles of the obtained mullite powder were 0.2μ.
It was about m. Example 3 0.087 mol of silicon tetrachloride was placed in a flask, and 0.35 mol of aluminum isopropoxide was added to 3 mol of toluene.
．． The solution was dissolved in 5 mol and gradually dropped into the flask. In this case, the reaction resulted in a precipitate. to this precipitate. Isopropatool 1, 7 mol and pure water 1, 7 mol
A mixed solution was added dropwise to carry out hydrolysis treatment. The precipitate was treated in the same manner as in Example 1 to obtain 22.4 g of mullite precursor.
I got it. Next, 2 g of this precursor was placed in an alumina boat and fired in a tubular furnace at 1300° C. for 3 hours in a nitrogen atmosphere. As a result of X-ray diffraction analysis, the obtained fired product was found to be crystallized and was mullite. Furthermore, as a result of SEM observation, the primary particle size of the obtained mullite powder was 0.2-0.3 μm.
It was about. Patent applicant Toa Fuel Industries Co., Ltd.

Claims (1)

[Claims] (1) Alcohol and water are added to a reaction product or a mixture of a halosilane and an oxygen-containing aluminum compound, and a mullite precursor is produced by hydrolysis, and then the mullite precursor is fired. A method for producing fine mullite powder.