JPH0832604B2 - Method for manufacturing ceramic molded body - Google Patents

Description

The present invention relates to a method for producing a ceramic molded body. More specifically, the present invention is a high-strength ceramics molding characterized in that a ceramics compact is impregnated with a specific silicon-containing polymer compound which is easily processable and has a silyl group in the side chain, and is then fired. A method of manufacturing a body.

[Problems to be Solved by Conventional Techniques and Inventions]

In recent years, the technological development of silicon-containing ceramics has been remarkable, and for example, silicon carbide (SiC), silicon nitride (S
i ₃ N _4), SiAlON, Si-Ti-CO Ceramics (Tyranno fibers, from Ube Industries), SiC-B ₄ C ceramic, Si ₃ N ₄ -
SiC composite ceramics are attracting attention as so-called fine ceramics.

Among these, especially SiC and Si ₃ N ₄ are in great demand, and their growth is expected in the future. In these ceramics, powder is generally applied under extremely high pressure (for example, 10
Since the molding method involves compression molding under high pressure (00 atm or more) and then sintering at high temperature, a large and expensive compression molding machine is required, or a complicated shape can be obtained due to compression molding. There were problems such as not being.

As a method of solving this, ceramic powder and easily processable polystyrene, a copolymer of styrene and butadiene,
A mixture of a lubricant such as stearic acid and a plasticizer such as diethyl phthalate, which is most likely to decompose and volatilize, in an appropriate ratio, a thermosetting resin added to the former, and a wax mixed with the thermosetting resin. Methods have been developed in which organic compounds such as those are mixed as additives, the mixture is injection molded, and then sintered (including de-additives or pre-sintering) at high temperatures.

The biggest problem in the current injection molding method is that the strength of the molded product is limited due to the generation of pores in the ceramics in the process of removing additives (resin).

Further, as an easily workable ceramic material, a method of forming a polymer compound containing silicon and firing it at a high temperature has been developed. Also in the thermal decomposition method of this polymer compound, a part of the polymer is decomposed and volatilized, so that the fine pores as described above are generated. SiC fiber, Si ₃
The production of N ₄ fibers is a specific example of this pyrolysis method.

On the other hand, various types of polymer compounds containing silicon have been known in the past, but the following examples are representative ones.

(A) Permethyl polysilane (B) Polysilastyrene (where X is 0.8 to 1.3,
Φ represents a phenyl group. same as below. ) (C) Polycarbosilane Polycarbosilane is a permethylpolysilane or various organosilicon compounds, for example, tetramethylsilane, dimethyldichlorosilane, which is obtained by thermal decomposition of dodecamethylcyclohexasilane, and has meltability, and
It is soluble in organic solvents such as benzene. Currently, there is SiC fiber (Nippon Carbon Co., Ltd., trademark "Nicalon") that is industrially manufactured by this thermal decomposition method. This fiber is
A dimethyldichlorosilane obtained by the direct method is used as a starting material and is produced according to the following formulas (A), (B) and (C). It is expected that the demand for reinforced materials will increase in the future (Chemistry Letters, 551 (1976), Japanese Patent Publication No. 57-
26527, JP-B 57-53892, JP-B-57-38548).

The problem with this method is that the manufacturing process is complicated, especially in the step (A), the removal of unreacted sodium is complicated because metal sodium is used in the solvent, and the fractionation of the polymer (low molecular weight) It is necessary to separate and remove polycarbosilane), it is necessary to carry out the reaction in the step (B) under high temperature and high pressure (400 ° C., 100 atm), and in addition, the total yield is low (particularly, (B ) And (C) step), and free carbon and silica contained in a considerable amount in the final product adversely affect the physical properties of the product.

An object of the present invention is to provide a method for producing a ceramics molded body having high strength as a molded product.

[Means for solving problems]

The present inventors have diligently made efforts to improve the strength of molded bodies of ceramics containing silicon produced by various methods, and have found that the use of a specific silicon-containing polymer compound is effective. Has been completed.

That is, the present invention, a ceramic molded body containing silicon, (In the formula, m is 0 or a positive integer of 1 to 20, n is 1, 2 or 3, R ¹ is hydrogen, an alkyl group, an aryl group or halogen, and R ² is an alkylene group or a phenylene group,
R ¹ and R ² may contain a functional group such as COOH, NH ₂ , Cl and OH. ) Is impregnated in a solution containing a silicon-containing polymer compound containing a repeating structural unit represented by
The present invention provides a method for producing a ceramic molded body, which comprises firing in a temperature range of 500 to 2500 ° C.

 Hereinafter, the present invention will be described in detail.

The silicon-containing polymer compound in the present invention is a carbon-based polymer containing a silyl group (SiH ₃ , Si ₂ H ₅ , Si ₃ H ₇ group) in its side chain, and has a general formula (I) Is a silicon-containing polymer compound containing a repeating structural unit represented by:

Further, m is 0 or a positive integer of 1 to 20, and the ceramic yield (Si weight in the fired body / silicon-containing polymer compound
From the viewpoint of Si weight (%), the smaller the value, the more preferable, and the most preferable value is 0.

R ¹ is hydrogen, an alkyl group or an aryl group, and is, for example, —H, —CH ₃ , —C ₂ H ₅ , iC ₃ H ₇ , —Φ (—Φ represents a phenyl group, the same applies hereinafter), — Φ‐C
H ₃ and —CH ₂ —Φ are listed, and those having a smaller number of carbon atoms are preferable, and hydrogen is most preferable.

R ² is an alkylene group or a phenylene group and is, for example, —CH ₂ —, CH _{2 2} , CH _{2 4} , —Φ (where —Φ— represents a phenylene group, the same applies hereinafter), —CH ₂
-Φ-, etc., but the smaller the carbon number is, the more preferable it is as in R ¹ . Note that R ¹ and R ² may include a functional group such as —COOH, —NH ₂ , —OH, and halogen.

Further, the silicon-containing polymer compound in the present invention may be a polymer composed of only the same kind of repeating structural units represented by the general formula (I), or may be a polymer represented by the general formula (I). It may be a polymer having different types of repeating structures. Of course, the stereoregularity of these polymers is not limited, and may have any stereostructure such as isotactic, syndioctactic and atactic.

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

Also, other vinyl-based polymer structures containing no repeating structural units and silicon, for example, ethylene, propylene, styrene, vinyl chloride, butene, isobutene, MMA.
It may be a copolymer composed of a repeating structural unit of vinyl origin such as Such copolymerization can be random, alternating,
It may be either a block or a graft. In this case, the structural unit part of the invention is at least 0.
It is preferably 1% by weight or more. The molecular weight of these copolymers is not particularly limited, but is usually 100 to 10,000,00.
0, preferably about 200 to 1,000,000, is desirable in terms of solubility in a solvent.

It is needless to say that the above-mentioned silicon-containing polymer compound used in the present invention is particularly desirable to have a high ceramic yield in view of the subject of the present invention. However, these ceramic yield, the ease of obtaining a monomer, and the production of a polymer. From the viewpoint of easiness and solvent solubility (workability), a particularly preferable specific example is a repeating structural unit. Examples thereof include silicon-containing polymer compounds containing one kind or two or more kinds and copolymers thereof.

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

For example, the method for polymerizing the silicon-containing α-olefin is not particularly limited, and various methods such as coordination anion polymerization, radical polymerization, and ionic polymerization can be adopted. That is, Ziegler-Natta type catalyst (titanium halide, alkoxy titanium, vanadium halide, magnesium oxyhalide, zirconium halide and other transition metal salts and alkylaluminum catalysts, these transition metal salts are magnesium halide , A catalyst composed of alkylaluminum supported on a carrier containing magnesium oxide, magnesium oxyhalide, silica, alumina, etc. as the main component), SiO ₂ -Al ₂ O
₃ catalyst supported the CrO _3, to adhere the MoO ₃ on gamma-Al ₂ O ₃
A catalyst reduced by LiAlH ₄ , NaH, H ₂ , CO, etc., Cp ₂ Zr (C
H ₃ ) ₂ or Cp ₂ TiCl ₂ (where Cp is cyclopentadienyl) and a polymerization method using a catalyst composed of an alkylaluminoxane (for example, JP-A-58-19309); metal oxide (Cr
_{O 3, SiO 2, Al 2} O 3 , etc.), hydrochloric acid _{(H 2 SO 4, H 3} PO 4, HClO 4,
HCl, etc.), Lewis acid (BF ₃ , AlCl ₃ , FeCl ₃ , SnCl _4, etc.) Cationic polymerization with a catalyst; alkali metal (L
i, Na, K, etc.), alkyl alkali (C ₂ H ₅ Na, sodium naphthalene, (C ₂ H ₅ ) ₃ Al, C ₄ H ₉ Li, C ₆ H ₅ Li, etc.), hydroxide (NaOH, KOH Etc.) A method of anionic polymerization with a catalyst; heat, light, radiation, electricity or hydrogen peroxide, ammonium persulfate, benzoyl peroxide, cumene peroxide, cyclohexane peroxide, di-t-butyl peroxide, t-butyl hydroper. Examples include a method of radical polymerization using a catalyst such as oxide, methyl ethyl ketone peroxide, and azobisisobutyronitrile.

The mode of polymerization is not particularly limited and may be either gas phase or liquid phase, and bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization and the like can be adopted. The reaction temperature and the reaction pressure vary depending on the polymerization mode and the reaction monomer, but the reaction temperature is 0 to 400.
C., preferably 20 to 200.degree. C., and the reaction pressure is preferably high pressure in equilibrium, and is normal pressure to 1000 atmospheric pressure. It is also possible to carry out the polymerization using a solvent such as benzene, toluene, xylene, pentane, dimethylformamide, chloroform and water. In addition, various additives such as a molecular weight modifier may be used. Further, in the case of copolymerization of silicon-containing α-olefin and α-olefin, the monomer composition and the polymerization mode are not particularly limited, and various modes such as random, alternating, block and graft can be adopted.

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

Among these, SiH ₄ is used as a raw material, and particularly, is a hydrosilylation reaction using a Group VIII metal as a catalyst, and the desired α-olefin can be easily obtained. The same applies to Si ₂ H ₆ and Si ₃ H ₆ . In recent years, the demand for SiH ₄ , Si ₂ H ₆ , and Si ₃ H ₈ for polysilicon and amorphous silicon has expanded, and they have been manufactured at low cost in large quantities. Is a new silicon raw material that is expected to progress. Therefore, the silicon-containing polymer compound containing a silyl group in the present invention is of great significance in that it can be easily and inexpensively produced by polymerizing a monomer obtained from a silicon hydride compound and an olefin. It can be said that there is.

Further, the silicon-containing polymer compound according to the present invention is different from the following polymers derived from alkylchlorosilane, The production can be carried out in a non-chlorine system, and the process is extremely simple without fear of corrosion. From the above, it is considered that the silicon-containing polymer compound according to the present invention can be manufactured more inexpensively in the future.

Further, the silicon-containing polymer compound used in the present invention is not only easy to polymerize, but the silyl groups present in the polymer compound are extremely stable and do not oxidize at room temperature even in the air at 150 ° C. It is only oxidized at high temperatures in the vicinity.

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

The ceramic molded body containing silicon, which is the base material to be impregnated with the silicon-containing polymer compound, is specifically, for example,
SiC, Si ₃ N ₄ , Sialon, Si-Ti-CO ceramics, S
iC-B ₄ C ceramics, Si ₃ N ₄ -SiC composite ceramics, mixed oxide ceramics containing SiO ₂ as a constituent component,
Furthermore, FRM (Fiber Ceramics Reinforced Metal), F
Examples include molded bodies such as RC (Fiber Ceramics Reinforced Ceramics), among which SiC, Si ₃ N ₄ , SiC-Si ₃ N ₄
Composite ceramics are the most suitable.

The method for producing these molded bodies is not particularly limited, and may be, for example, those obtained by compression-molding ordinary ceramic powder under high pressure as described above, but particularly those obtained by firing a silicon-containing polymer compound after molding, or Those obtained by adding additives and firing after processing by an injection molding method are preferable, and the effect of the present invention is great. The shape of the molded body is not particularly limited, and includes a fiber and a complexly processed product.

In the present invention, the method for impregnating the silicon-containing polymer compound into the ceramic compact is specifically, for example, immersing the ceramic compact in a solution in which the silicon-containing polymer compound according to the present invention is dissolved. The method of can be adopted as the simplest method. In this case, the solvent of the silicon-containing polymer compound is not particularly limited, and various solvents such as heptane, hexane, tetrahydrofuran, diglyme, dioxane, butyl ether, toluene, benzene and hexylamine can be used. Of course, when the silicon-containing polymer compound is liquid, a solvent is not always necessary. The temperature and time for impregnation are not particularly limited, but are preferably 0 to 200 ° C. and 1 to 100 hours, respectively.

The molded product impregnated with the silicon-containing polymer compound may be washed with a solvent or the like to remove excess surface polymer compound, if necessary.
It is dried and then calcined at an elevated temperature, preferably in the temperature range of 500-2500 ° C. The above-mentioned impregnation and firing operations can be carried out as many times as necessary.

According to the present invention, the pores or surfaces that were previously present in the ceramic molded body will be occupied by the SiC generated by the firing of the silicon-containing polymer compound, and this SiC is further the ceramic powder in the molded body. It is considered that the bulk density of the molded body is increased due to the formation of a bond with, and further the mechanical strength and sometimes the heat resistance of the molded body are improved.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

Example 1 100 g of vinylsilane and 1 g of AlBN (azobisisobutyronitrile) were placed in an autoclave and polymerized at 70 ° C. for 8 hours to obtain about 90 g of an oily silicon-containing polymer compound having an average molecular weight of about 2000.

40 g of a commercially available SiC powder having an average of about 300 mesh and 5 g of the above-mentioned silicon-containing polymer compound were kneaded, and then pressure-molded in a crucible shape. Next, the pressure-formed product was heated in a vacuum while gradually raising 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 3.12.

Furthermore, this crucible was filled with 50% oily polyvinylsilane.
Immerse in a benzene solution containing wt% concentration for 2 days at room temperature, then remove benzene, and then heat the crucible in vacuum while gradually increasing the temperature from room temperature to 1500 ° C, and then 1800 ° C. It was baked for 4 hours. The bulk density of the crucible obtained by repeating this operation three times was 3.15. The mechanical strength of this crucible is about 2 times that of the crucible obtained before treatment.
Also, when it was used for melting polycrystalline silicon, the life was greatly improved.

Example 2 An experiment was performed in the same manner as in Example 1 except that polyallylsilane was used instead of polyvinylsilane.

At this time, the mechanical strength of the crucible was about 1.5 times that of the crucible obtained before the treatment, and when it was used for melting polycrystalline silicon, the life was greatly improved.

Example 3 A silicon-containing polymer compound obtained by firing permethylpolysilane (manufactured by Shin Nisso Kako Co., Ltd., average molecular weight of about 2000) in an autoclave at 400 ° C. and 100 atm for 15 hours was spun by a melt spinning method. Then, a silicon-containing polymer compound fiber having a diameter of 10 μm was obtained. This fiber in vacuum (1 × 10 ^-3 mmHg) at 1000 ℃
Up to 1200 ° C. in an argon gas atmosphere, and then fired at that temperature for 2 hours to obtain SiC fibers.

The fiber is immersed in a benzene solution containing oily polyvinylsilane at a concentration of 50 wt% for 2 days at room temperature,
After that, benzene was removed, and then 1800 ° C in vacuum.
The temperature was gradually raised to 1,800 ° C., and further calcined at 1800 ° C. for 4 hours. This operation was repeated twice.

The strength of the fiber, which had a tensile strength of 1.5 GPa at 1200 ° C before the treatment, improved to 2.6 GPa after the treatment.

〔The invention's effect〕

The present invention provides a method for increasing the strength of a ceramic molded body, and is characterized by the silicon-containing polymer compound used. The silicon-containing polymer compound is easily available, and according to the present invention, SiC and Si ₃ N _{4 having} excellent strength can be obtained.
It is possible to manufacture various silicon-containing ceramic compacts including the above. The obtained molded product has a large bulk density and strength, and is particularly excellent in oxidation resistance and strength at high temperatures.

Claims (2)

[Claims] 1. A ceramic compact containing silicon, (In the formula, m is 0 or a positive integer of 1 to 20, n is 1, 2 or 3, R ¹ is hydrogen, an alkyl group, an aryl group or halogen, and R ² is an alkylene group or a phenylene group,
R ¹ and R ² may contain a functional group such as COOH, NH ₂ , Cl and OH. ) Impregnated in a solution containing a silicon-containing polymer compound containing a repeating structural unit represented by
A method for producing a ceramic molded body, which comprises firing in a temperature range of 500 to 2500 ° C. 2. The method according to claim 1, wherein the ceramic containing silicon comprises SiC, Si ₃ N ₄ or a mixture thereof.