JPH01294575A - Production of ceramic molded article - Google Patents

Abstract

PURPOSE:To increase bulk density and strength and improve oxidation resistance at high temperature, etc., by baking a mixture of silicon-containing polymeric compound containing repeating structural unit expressed by the general formula and powder of SiC or Si3N4 at fixed temperature. CONSTITUTION:A silicon-containing polymeric compound having repeating structural unit expressed by the general formula (with a proviso that, m; 0 or 1-10 positive integer, n; 1, 2 or 3, R1: hydrogen, alkyl group or aryl group, R2: alkylene group or phenylene group) is prepared. Said compound is mixed with SiC powder or Si3N4 powder and molded. Next, said molded material is baked at a temperature; 500-2500 deg.C.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a method for producing a ceramic molded body from a mixture of a specific silicon-containing polymer compound that is easy to process and contains a silyl group in its side chain, and SiC or 5isNa powder. Relating to a method of manufacturing.

(Prior art and problems to be solved by the invention) In recent years, the state of technological development of silicon-containing ceramics has been remarkable. For example, silicon carbide (SiC), silicon nitride (
SiJ4), Sialon, Si-Ti-C-O ceramics (Tirano Fiber, Ube Industries), SiCBJC
5tsNa-SiC composite ceramics and the like are attracting attention as so-called fine ceramics.

Among these, demand for SiC and 5izN4 is especially large, and demand is expected to increase in the future.

These ceramics require a large and expensive compression molding machine because the molding method used is to mix powder into -S, compression mold it under high pressure (for example, over 1000 atmospheres), and then sinter it at high temperature. There were problems in that it was difficult to obtain products with complicated shapes because of compression molding. To solve this problem, ceramic powder is mixed with additives such as easily processable organic compounds, the mixture is injection molded, and then sintered at high temperature (including removal of additives or pre-sintering).
A method has been developed to do so. The main organic additives announced in the past are polystyrene, copolymers of styrene and butadiene, lubricants such as stearic acid, and plasticizers such as diethyl phthalate, which are most prone to decomposition, in appropriate proportions. Those that are mixed with thermosetting resin (phenol resin), those that are mixed with wax to thermosetting resin (phenol resin, epoxy resin, coumaron indene resin, etc.), and those that are mixed with monoolefin polymer. These include mixtures of ethylene glycol and compositions mainly composed of sublimable substances such as naphthalene.

The biggest problem with the current injection molding method is the removal of additives (
There is a limit to the strength of the molded product due to the formation of pores in the ceramic during the resin process.

An object of the present invention is to provide a method for manufacturing a ceramic molded article having high strength.

(Means and effects for solving the problem) The present inventors have made earnest efforts to improve the method of molding such ceramics, particularly to develop additives for injection molding methods, and have used specific organosilicon compounds as additives. The present inventors have discovered that the object of the present invention can be achieved by doing so, and have completed the present invention.

That is, the present invention has the following formula: General formula (1) % formula % (However, m is O or a positive integer from 1 to 10, and n is 1.
2 or 3, R9 represents hydrogen, an alkyl group or an aryl group, R2 represents an alkylene group or a phenylene group) and SiC powder or 5rsNa powder are mixed. , the mixture is molded, and then 500 to 250
This is a method for producing a sintered carbon compound body, which is characterized by firing at a temperature range of 0°C.

The present invention will be explained in detail below.

The silicon-containing polymer compound used as an additive in the present invention includes silyl groups (SiHs, 5ixHs,
5SiJy group), and is a silicon-containing polymer compound containing a repeating structural unit represented by the general formula (1).

The degree of polymerization of the polymer compound represented by formula (1) is 3 or more, preferably 10 or more, and more preferably 50 or more. Further, n is O or a positive integer from 1 to 10, and from the viewpoint of ceramic yield (St weight in the fired body/St type weight in the silicon-containing polymer compound χ)), the smaller the better,
Most preferred is O.

R1 is hydrogen, an alkyl group, or an aryl group, such as -■, -CHff, -CJs, 1-CJ71. Φ
(-Φ represents a phenyl group as mentioned above, the same applies hereinafter), -Φ-CHff, -C8! −Φ etc. are mentioned,
The smaller the number of carbon atoms, the more preferable it is, and hydrogen is the most preferable.
R2 is an alkylene group or a phenylene group, such as -CHl-, iCHzh, +CHt+a, -Φ
-1-CH! -Φ- etc., but as with R1, the smaller the number of carbon atoms, the more preferable.The above R1, R, is -COOH
, -NH*.

It may contain functional groups such as -OH and halogen.

Further, the silicon-containing polymer compound in the present invention may be a polymer consisting only of the same type of repeating structural units represented by the -i formula (1), or may be a polymer consisting only of the same type of repeating structural units represented by the -M formula (1). Of course, there are no restrictions on the stereoregularity of these polymers, and they may have any stereostructure, such as isotactic, syndiotactic, actic, etc. .

This molecular weight is not particularly limited, but is usually 100 to 10.
000,000, preferably 200 to 1,000,0
00 is desirable in terms of moldability, solubility in solvents, etc.

In addition, the repeating structural unit and other vinyl polymer structures that do not contain silicon, such as ethylene, propylene, styrene, vinyl chloride, butene, isobutyne, HMA
It may be a copolymer consisting of vinyl-derived repeating structural units such as, etc., and such copolymerization may be random, alternating, block, or graft, etc.
In this case, the portion of the structural unit of the invention is at least 0.1
The molecular weight of these copolymers, which is preferably at least % by weight, is not particularly limited, but is usually 100 to 10.0.
00,000, preferably 200 to 1,000,00
A value of about 0 is desirable in terms of moldability and solubility in solvents.

Needless to say, it is particularly desirable for the silicon-containing polymer compound used in the present invention to be easily processable and to have a high ceramic yield for the purpose of the present invention. Ease of manufacturing, meltability, and solvent solubility (processability) of the polymer
As a particularly preferable specific example, 5IHs 5iJsC1,C as a repeating structural unit
Examples include silicon-containing polymer compounds containing one or more types of HtCHzSiH3 iHi and copolymers thereof.

As the silicon-containing polymer compound used in the present invention, those mentioned above are used, but the manufacturing method or polymerization method thereof is not particularly defined, and those manufactured by various methods can be suitably used.

For example, an α-olefin having a silyl group is treated with a Ziegler-Natta type catalyst (
Transition metal salts such as titanium halides, vanadium halides, zirconium halides, and alkyl aluminum)
Coordination anion polymerization method, metal oxide (Cr
y,,SfO,,AI! (h etc.), hydrogen acid (HgSO4
, HsPOa, HCl0a, IC1, etc.), cationic polymerization using a Lewis acid (BFz, AlCl5, FeC15,5nCI, etc.) catalyst, alkali metal (
Li.

Na, K, etc.), alkyl alkali (CJJa.

(CJs)sAl, CJ5Li, etc.), hydroxides (N
aOH, OH, etc.) method of anionic polymerization using a catalyst, method of radical polymerization using a peroxide as an initiator,
Various methods such as Naturally, the polymerization can be carried out in either the gas phase or the liquid phase, and either in a solvent or without a solvent (bulk polymerization).

Furthermore, in these polymerizations, the molecular weight of the polymer can be easily adjusted by coexisting hydrogen or the like.

The α-olefin containing a silyl group, which is a monomer for polymerization, can be produced by various methods, and the present invention is not particularly limited thereto, but for example, a method as shown in the following formula can be adopted.

-) IcI HSiCIs + CIHzG-(CHz) --C
H-CHt -1→600 °C -I+2 SiH4+CI=CII HtStC
H-C)lx ■H2S1CCHz), 19
+cTocL ■ Of these, ■, ■, ■, ■ are S
iH4 is used as a raw material, and in particular, (1) and (2) are hydrosilylation reactions using group (2) metals as catalysts, and the desired α-olefin can be easily obtained. 5ilH6,
The same applies to the case of 5izHt. Cover, 5i) I4.
In recent years, demand for 5iJa and 5iJs for use in polysilicon and amorphous silicon has expanded, and they have become manufactured cheaply and in large quantities, and are new silicon raw materials that are expected to continue to grow in this trend. Therefore, the silicon-containing polymer compound containing silyl groups in the present invention has great significance in that it can be easily and inexpensively produced by polymerizing a silicon hydride compound and a monomer obtained from an olefin. It can be said that there is.

The use of a silicon-containing polymer as an additive for injection molding of ceramics according to the present invention is disclosed in Japanese Patent Application Laid-Open No. 52-40509.
, Journal of Organometallic Chemistry
icChemistry) 300 (1986) 32
7-346, the polymer according to that report is obtained by using alkylchlorosilane as a raw material through a complicated process including reaction with sodium metal1, for example, it is a polymer having the following repeating structural units. 6 Compared to this, the polymers of the present invention can be manufactured using a non-chlorine system, and there is no fear of corrosion, and the process is extremely simple. It is thought that it will be possible to manufacture it even more cheaply in the future.

Furthermore, the silicon-containing polymer compound used in the present invention is not only easy to polymerize, but also has good processability (melt flowability,
Solvent solubility) can also be easily changed by controlling its molecular weight and stereoregularity. Furthermore, the silyl groups present in the silicon-containing polymer compound used in the present invention are extremely stable, and are not oxidized even in air at room temperature, but are only oxidized at a high temperature of around 150°C.

Next, a method for manufacturing a ceramic molded body according to the present invention will be described.

The manufacturing process essentially consists of the first step of mixing and kneading SiC or SiJ powder and the silicon-containing polymer compound (1) as an additive, the second step of molding the mixture, and the sintering of the molded body ( The third step includes removing additives or pre-sintering.

The first step is to mix the ceramic powder and the silicon-containing polymer compound (1). It is also possible to use additives (thermoplastic resin, plasticizer, lubricant, auxiliary agent, etc.) at the same time. The amount of the silicon-containing polymer compound (1) to be added varies depending on its type, other additives used simultaneously, and the subsequent molding method, but is preferably 0.01 wt% to 200 wt%, more preferably 0.1 wt% to 200 wt%. It is 50wt%. If the amount added is too small, it will be difficult to obtain a SiC sintered body,
On the other hand, if the amount added is too large, the bulk specific gravity decreases, the strength decreases, and the oxidation resistance at high temperatures decreases.

The second step is to mold the mixture, which can be done by various methods such as mechanical pressing, isostatic pressing, slurry casting, doctor blading, extrusion, injection molding, and hot pressing. , either method can be adopted.

Among these, the injection molding method makes the most of the effects of the present invention.

Further, in the hot press method and the isostatic press method, sintering, which will be described later, is performed simultaneously.

The third step is a step of sintering the compact, and if necessary, it is necessary to perform additive removal (degreasing, binder removal, dewaxing) and preliminary sintering as a preliminary step.

The temperature in this case is usually in the range of room temperature to 500°C. Final sintering is carried out at a temperature range of 500 to 2500°C.

As mentioned above, the sintered body of the present invention has a higher bulk specific gravity (and higher strength and excellent oxidation resistance at high temperatures) at the same additive amount than when using an additive that does not contain silicon. The silicon-containing polymer used in the present invention has been disclosed in Japanese Patent Application No. 62-15929 and Japanese Patent Application No. 62-159.
As disclosed in No. 2-31514, the ceramic yield is high. This is thought to be because SiC remains as SiC during the firing and sintering stages, and this remaining SiC further forms bonds with SiC powder.

According to the present invention, impurities (alumina, silica, boron,
A high-purity SiC self-sintered body can be obtained with almost no remaining silicon, iron, free carbon, Si3Nm, etc.

(Example) Hereinafter, the present invention will be explained by examples.

Example 1 100 g of vinylsilane and 1 g of AIBN (azobisisobutyronitrile) were placed in an autoclave and heated to 70°C.
Polymerized for 8 hours to form an oil with an average molecular weight of 2000.
About 90 g of silicon-containing polymer (1) was obtained.

After mixing 40 g of commercially available SiC powder with an average size of about 300 meshes and 5 g of the above polymer (1), the zero-order press-formed product was pressure-molded into a crucible shape and heated at 1500° from room temperature in a vacuum.
The mixture was heated while gradually increasing the temperature to C, and further baked at 1800 C for 4 hours.

The bulk specific gravity of the obtained crucible was 3.12. When this crucible was used to melt polycrystalline silicon, it was found that
Compared to an IC crucible, the life span was greatly improved, and the amount of impurities in the single crystal obtained by pulling was extremely small.

Example 2 40 g of the same SiC powder used in Example 1 was mixed with 6 g of silicon-containing polymer (1) and 25 g of polystyrene, and then heated and molded into a rod shape at 150° C. in nitrogen. The temperature was gradually raised from room temperature to 600''C under reduced pressure, and then fired at 1700°C for 5 hours in an argon atmosphere.

The bulk specific gravity of the obtained sintered body was 3.04. When this rod-shaped sintered compact was used as a heating element, it was sufficiently durable for practical use and had a longer life than a conventional SiC heating element.

Example 3 200 g of vinylsilane was polymerized at 70° C. for 3 hours using a titanium trichloride type catalyst for olefin polymerization to obtain 110 g of powdered polyvinylsilane (II).

After mixing 10 g of polyvinylsilane ([) with 40 g of the same SiC powder used in Example 1, 200Xg/cd
It was molded into a rod shape under pressure. 170 from room temperature under reduced pressure
The temperature was gradually raised to 0''C, and then fired at 01700C for 5 hours in an argon atmosphere.

The bulk specific gravity of the obtained sintered body was 3.04. When this rod-shaped sintered body was used as a heating element, it was sufficiently durable for practical use and had a longer lifespan than a conventional StC heating element.

Example 4 200 g of allylsilane was polymerized at 70'C for 3 hours using a titanium trichloride type catalyst for olefin polymerization to obtain 150 g of powdered polyallylsilane.

After mixing 40 g of the same SiC powder used in Example 1 and 6 g of the above polymer, the mixture was heated and molded into a crucible shape in nitrogen.
Next, the molded product was heated in a vacuum while gradually increasing the temperature from room temperature to 1500°C, and further baked at 1800'C for 4 hours.

The bulk specific gravity of the obtained crucible was 3.09. When this crucible was used to melt polycrystalline silicon, it was found that
Compared to the iC crucible, the life span was greatly improved, and the amount of impurities in the single crystal obtained by pulling was extremely small.

Example 5 The silicon-containing polymer (1) Log used in Example 1 and 40 g of commercially available 5isL powder having an average of 400 meshes were mixed and then heated and molded into a plate at 150° C. in nitrogen.

The molded product was gradually heated in vacuum from room temperature to 1500°C, and further baked at 1800°C for 4 hours.

The bulk specific gravity of the obtained sintered body was 3.02. The impact fracture strength of this sintered body was about three times that of the case where polystyrene was used instead of the silicon-containing polymer (1) (bulk specific gravity: 2.94).

(Effects of the Invention) The present invention provides a method for manufacturing a ceramic molded body, and the present invention is characterized by the organosilicon compound used as an additive. A sintered ceramic molded body can be obtained. This has a higher bulk density and greater strength than conventional silicon-free organic additives, and is particularly excellent in oxidation resistance and strength at high temperatures.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (2)

[Claims] (1) General formula (1) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, m is 0 or a positive integer from 1 to 10, n is 1,
2 or 3, R_1 represents hydrogen, an alkyl group or an aryl group, R_2 represents an alkylene group or a phenylene group) and SiC powder or Si_3N_4 powder are mixed. , the mixture is molded and then 500 to 2
A method for producing a ceramic molded body, characterized by firing in a temperature range of 500°C. (2) The method according to claim 1, wherein the silicon-containing polymer compound is a polymer of vinylsilane or allylsilane.