JPH06135704A - Molding method for metal oxide molding by sol-gel method - Google Patents

Abstract

PURPOSE:To provide a molding method of metal oxide molding by which dimen sional stability can be obtd. for even a complicated sterical shape, by making use of a sol-gel method which is advantageous to obtain high-purity products. CONSTITUTION:A metal oxide molding is obtd. by a sol-gel method which comprises the steps of subjecting a metal alkoxide M(OR)n to hydrolysis and then to condensation polymn. to obtain a sol and/or gel (MOn/2)x; pulverizing and drying the obtd. soln and/or gel; adding a proper solvent to the intergranular spaces of the fine powder to give plasticity and to obtain a metal oxide plasticized body; and molding the metal oxide plastic body into a desired shape.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a metal alkoxide M.
According to the sol-gel method, using (OR) _n as a starting material, a sol and / or gel (MO _{n / 2} ) _x of the metal M is obtained by a sol-gel method to obtain an oxide molding of the metal M in a desired shape. The present invention relates to a method for molding a metal oxide molded body.

[0002]

2. Description of the Related Art A method of forming a glass or ceramic coating film of an oxide of a specific metal M on a substrate by using a sol-gel method is used for high value-added industrial products (eg, silicon semiconductor insulating film). The method will be described below.

When water is added to an alcohol solution of metal alkoxide M (OR) _n , hydrolysis and polycondensation occur. The outline of this process is expressed as follows. M (OR) _n + nH ₂ O → M (OH) _n + nROH formula M (OH) _n → (MO _{n / 2} ) _x + xn / H ₂ O formula The degree of polymerization of (MO _{n / 2} ) _x by the above reaction is When it is low, it is a so-called sol, and when the reaction progresses and the degree of polymerization increases, it loses fluidity and becomes a so-called gel.

Then, a gel film is formed on the substrate by a method such as dipping or pulling up the substrate at the sol stage. Next, a drying process for evaporating the residue such as water contained in the thin film coated on the substrate or a heat treatment for burning the residue is performed. A coating film having a desired film thickness is obtained by repeating this dipping / pulling-up and drying treatment or heat treatment. Next, high temperature heat treatment is performed for crystallization or the like.

Thus, the metal alkoxide M (OR)
A coating film formed by sol-gelation by hydrolysis and polycondensation of _n , coating, drying or heat treatment, and high temperature heat treatment has the following advantages.

Starting material metal alkoxide M (OR) _n
Since it is itself obtained by a chemical treatment such as distillation and purification, a high-purity product is obtained. Sol-gel formation by hydrolysis and polycondensation is also a pure chemical treatment in a solution state, and a highly pure and homogeneous sol and / or gel (MO _{n / 2} ) _x can be obtained. Moreover, since the treatment is performed at room temperature, the organic / inorganic composite material can be easily synthesized.

However, the biggest drawback of the sol-gel method is that large shrinkage and cracks occur during the process of drying or heat treatment or high temperature heat treatment. Therefore, the sol-gel method is utilized for industrial products in a form such as a thin film, a fiber, a bulk body, a porous body, etc. in which shrinkage or cracks are unlikely to occur, and even if they occur, shrinkage or cracks are not a problem. Limited to the ones.

[0008]

It is possible that a three-dimensional product such as a plate or a rod cannot be molded by the sol-gel method, but the polymer structure itself of the obtained sol and / or gel is porous. A large amount of residual substances such as water are taken in. Even if the residual material is poured into a mold and dried and then baked, the plate or rod shrinks greatly, and deformation or cracks occur during the shrinking process, resulting in poor dimensional stability and no product.

Therefore, as a method for ensuring the dimensional stability, it is possible to gradually and uniformly dry, but if it is attempted to uniformly and sufficiently dry the three-dimensional product,
Although it depends on the form of the product, it is necessary to remove the residue as much as possible over a long period of several months, which is not practical.

As described above, in the conventional sol-gel method, dimensional stability cannot be obtained even if a metal oxide molded body of a simple plate or rod is used, and a metal oxide having a complicated shape such as a blade shape is obtained. There is a problem that the sol-gel method cannot be applied to the molding of the molded body.

The present invention has been made in view of the above problems of the prior art, and its object is to make use of the advantage that a high purity product of the sol-gel method can be obtained, and to make it complicated. There is a need to provide a method for molding a metal oxide molded body by a sol-gel method that can secure dimensional stability even in a three-dimensional shape.

[0012]

In order to achieve the above object, a method of forming a metal oxide molded body by the sol-gel method in the present invention is a method of hydrolyzing a metal alkoxide M (OR) _n and a subsequent weight. A step of forming a sol and / or a gel (MO _{n / 2} ) _x by condensation, a step of pulverizing the sol and / or gel and drying, and adding a solvent between particles of the fine powder to impart plasticity And a forming step of forming the metal oxide plastic body into a desired shape.

[0013]

When the sol and / or gel (MO _{n / 2} ) _x is finely pulverized, the surface area is remarkably increased, and it is possible to dry in a short time to remove the residual substances such as water, and to completely remove the residual substances. It can also be removed. This pulverized (MO _{n / 2} ) _x is irreversible, and it is possible to fluidize the fine powder and impart plasticity by adding a solvent such as water to this and interposing a solvent between the particles. However, it is important to once make a metal oxide plastic body. The viscosity of the metal oxide plastic body can be freely adjusted by the amount of solvent added, and the molding method (injection, compression,
Adjust to a desired viscosity according to (extrusion, etc.). Further, this metal oxide molded body only contains a solvent between the particles, it can be easily removed by pressure, temperature, etc., easy to handle like ordinary fine ceramics and clay molding,
The shrinkage itself is equivalent to that in the molding of fine ceramics and clay.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a process diagram of the method of the present invention. First,
The concept of the method of the present invention will be described in detail with reference to FIG. 1, and then an experimental example will be described.

In FIG. 1, 1 is a sol-gelation step, 2 is
Is a pulverizing step, 3 is a plasticizing step, 4 is a molding step, and 5 is a firing step.

Step # in Sol-Gelization Process 1
1 represents a metal alkoxide M (OR) _n as a starting material. Here, M is a metal, R is a lower alkyl group,
O represents oxygen. This metal alkoxide M (OR) _n can be obtained by chemical treatment such as distillation purification if it is a metal capable of alkoxide reaction, and is generally selected from transition metals such as Si, Ti, Al, and alkaline earth metals. It can be appropriately selected. FIG. 2 is an element diagram showing a metal capable of this alkoxide reaction, and any metal marked with a circle can be used and its application range is wide. Lower alkyl group R
CH ₃ , C ₂ H ₅ , C ₃ H ₇ , and C ₄ H ₉ are generally used, but C _{1 to} C ₉ can be used.

The metal alkoxide M (OR) _n is not limited to one starting material, but may be M ′ (OR) _n , M ″.
A case where a mixture of (OR) _n , M ′ (OR ′) _{n and the} like is used as a starting material to obtain fine powder of a composite material such as (Si—O—Y—O ...) is also included.

Step # 2 is a step of preparing the above-mentioned metal alkoxide M (OR) _n with an alcohol solution. At this stage, if necessary, a stabilizing material is added as in step # 6. For example, in the case of a substance that is very easily hydrolyzed such as Zr or Al alkoxide, β-diketones and amines are added as stabilizers. These stabilizers replace the alkoxide group,
Suppresses hydrolysis and polycondensation rate of alkoxide.

Step # 3 is a step of adding pure water (H ₂ O). At this stage, if necessary, a catalyst is added as in step # 7. For example, in the case of a stable substance such as Si alkoxide, the hydrolysis of hydrochloric acid or ammonia is promoted. Step # 4 is a stirring step, which is a sol and / or gel having a uniform composition.

Step # 5 is a stage of sol and / or gelation by the hydrolysis process and the subsequent polycondensation process. The outline of the reaction is as shown by the above formula and formula, but the actual reaction mechanism is complicated and differs depending on the type of metal alkoxide and the reaction conditions. A sol is one in which colloidal particles are dispersed or dissolved in a liquid, and a gel is one in which a sol (colloidal solution) is solidified in a jelly form and loses fluidity. When the degree of polymerization is low, it becomes a sol, and when the reaction proceeds and the degree of polymerization becomes high, it becomes a gel. At this stage, if necessary, an organic polymer is added as in step # 8 to prolong the gel time and control the curing speed of the gel produced.

Next, the pulverizing step 2 will be described. Step # 11 is a stage of pulverization or fine powder. If it is in a gel state, the gel is crushed into a fine powder using a crusher such as a bladed mixer. If it is in a sol state, it is atomized with a nozzle and simultaneously dried in a vacuum to form a fine powder. Further, even if the sol and the gel are mixed, fine powder can be obtained. Further, the stabilizer of step # 14 can be mixed in if necessary.

Step # 12 is a drying step. The fine powder is put in a heating drying oven to be dried, or put in a vacuum drying oven to be dried. Since it is in the form of fine powder, the surface area is remarkably increased, and even if it is gradually dried in a heating drying oven or a vacuum drying oven, it can be almost completely dried in a few days at the maximum. At this drying stage, the fine particles undergo a large volume shrinkage, and the once-removed residue such as water is prevented from being taken into the fine powder again. By using a heating pulverizer, a vacuum pulverizer, or the like, it is possible to perform this drying step at the same time as the pulverization or fine powder step of Step # 11. Step # 13 is a stage of shaking that is inserted as needed. The size of the fine powder particles is selected by vibrating and sieving to obtain uniform fine powder particles having a predetermined particle size.

Next, the plasticizing step 3 will be described. Step # 21 is a stage of solvent addition. As a solvent,
Can be widely used with water, alcohols, hexane, dimethylformamide (DMF), etc. In short, it is not particularly limited as long as it can be provided between the fine powder particles to impart plasticity and can be easily removed by heating, pressurizing or the like. The amount of the solvent added depends on the molding method, that is, the viscosity range required for plasticity. Step # 22 is a step of kneading the plastic so as to have a uniform composition. A kneading mixer or the like is used.

Next, the molding step 4 will be described. Various molding methods such as injection, compression and extrusion molding can be applied. At the drying stage in the pulverization process, a large volume contraction is caused, and the plastic added with a solvent such as water has a much smaller water content than the sol / gel dried body, The dimensional stability in these moldings is not impaired.
FIG. 3 shows a molding example using the injection molding machine 10. Reference numeral 11 is a porous molding die, 12 is an external die, and 13 is a groove. Metal oxide plastic body 14 injected into the molding die 11
Is pressurized by injection pressure (hundreds of atmospheric pressure), the solvent such as water existing between the fine particles is extruded, and is discharged through the pores of the molding die 11 and the grooves 13 of the outer die 12 to form the metal oxide. The morphology of the material-plastic body does not collapse. When molding the metal oxide plastic body 14 with this injection molding machine 10,
The amount of the solvent added is preferably such that a metal oxide plastic body of 10 ² to 10 ⁶ poise can be obtained. Further, in compression molding, the viscosity of the plastic may be high, and when it is molded into a clay shape of 10 ⁵ poise or more, dehydration treatment at the time of molding becomes unnecessary.

Next, the firing step 5 will be described. Depending on the type of the formed metal (single or composite metal), various firings such as pressure heating and sintering or melting by heating alone are used. As for the heating temperature, an appropriate temperature range is selected according to the metal of the molded product.

[Experimental Example] As a starting material, Al (O- ⁱ⁾
A case where a rod-shaped ceramic is obtained by using C ₃ H ₇ ) ₃ will be described. To 1 mole of the _{^{Al (O- i C 3 H 7}} ) 3, p
100 mol of H2 water was added, and a small amount of a tertiary amine was added as a catalyst. And for stabilization, N of pH 2
1 mol of aOH was added and stirred for about 50 minutes to form a complete gel. Then, the gel is crushed into fine powder by a crusher with blades and then dried in a drying oven (100 degrees) for 6 hours,
Further, the dried fine powder was kneaded with a kneader for 10 minutes to homogenize. Then, as a solvent, 10 parts by weight of N, N-DMF is added to the fine powder and kneaded with a kneader for 30 minutes,
A clay-like plastic having a viscosity of about 3 × 10 ⁵ poise was obtained. This plastic is compressed in a mold to form a rod, which is then heated in a heating furnace to 1 degree Celsius.
It was fired at 200 degrees for 3 hours to obtain a rod-shaped ceramic having a diameter of 1 cm and a length of 12 cm. The shrinkage rate of the plastic material after firing was 10%, which was about the same as the shrinkage rate of ordinary fine ceramics when fired, and there was no bending.

[0027]

The method for molding a metal oxide molded body by the sol-gel method in the present invention comprises a step of pulverizing a sol and / or a gel and drying, and an appropriate solvent added between the particles of the fine powder. Including the step of making a metal oxide plastic body with plasticity, by expanding the surface area by pulverization, it is possible to completely dry the residue in a short time, and the amount of solvent added to this dried fine powder , A plastic with the desired viscosity is obtained,
Since various molding methods can be applied and a large volume shrinkage is caused in advance at the step of pulverization, the shrinkage after molding of the plastic can be minimized and dimensional stability A metal oxide molded article having excellent properties can be obtained. As a result, it is an epoch-making invention in which the applicable range of the sol-gel method can be expanded to include rods, plates, and three-dimensional molded bodies having complicated shapes.

[Brief description of drawings]

FIG. 1 is a process diagram of the method of the present invention.

FIG. 2 is an element diagram showing elements forming a metal alkoxide.

FIG. 3 is a diagram showing a molding example using an injection molding machine.

[Explanation of symbols]

 1 sol / gelation process 2 fine powdering process 3 plasticizing process 4 molding process

Claims (1)

[Claims] 1. A step of forming a sol and / or gel by hydrolysis of a metal alkoxide and subsequent polycondensation,
A step in which the sol and / or gel is pulverized and dried; a step in which a solvent is appropriately added between particles of the pulverized powder to obtain a plasticity-imparted metal oxide plastic body; A method for molding a metal oxide molded body by a sol-gel method, which comprises a molding step of molding into a desired shape.