JP5531280B2 - Manufacturing method of inorganic material molded body and manufacturing method of inorganic material sintered body - Google Patents

Description

  The present invention relates to a method for producing an inorganic material molded body and a method for producing an inorganic material sintered body. Specifically, a method for producing an inorganic material molded body obtained by removing an organic substance necessary for the expression of good moldability to a predetermined amount or less without undergoing combustion / decomposition of the organic substance by heating, and inorganic The present invention relates to a method for manufacturing a sintered material.

  Inorganic materials such as ceramics are used in various applications such as structural materials and electrical / electronic materials because they are superior in mechanical / thermal / electromagnetic properties compared to metals and plastics. In the manufacturing process, the raw material particles are generally formed into a desired shape, and the formed body is heated to be densified (sintered).

  As a method for producing such a molded body, for example, an aggregate particle (ceramic powder, etc.), a dispersion medium (water, etc.), an organic binder, etc. are mixed and kneaded to obtain a clay, and the clay is extruded. A manufacturing method is disclosed in which a molded body is obtained by the above method, and a ceramic sintered body is obtained by drying and firing the molded body (extrusion molding method: see, for example, Patent Document 1).

  Also, aggregate particles (ceramic powder, etc.), dispersion medium (water, etc.), organic binder, etc. are mixed to obtain a slurry, and the slurry is poured into a water-absorbing mold made of a porous material, and the slurry is dried. Then, a manufacturing method for obtaining a ceramic sintered body by firing is disclosed (casting molding method: see, for example, Non-Patent Document 1).

  Furthermore, aggregate particles (ceramic powder, etc.), dispersion medium (water, etc.), gelling agent (monomer, prepolymer, etc.), etc. are mixed to obtain a slurry, and the slurry is poured into a mold and heated. A manufacturing method is disclosed in which a gelling agent is gelled by addition of a polymerization initiator or the like to solidify a slurry, and then degreased to obtain an inorganic material molded body (gel casting method: see, for example, Patent Document 2) ).

Japanese Patent No. 3227039 JP 2002-179468 A

Edited by the Ceramic Society of Japan, Ceramics Engineering Handbook, 2nd edition, Gihodo Publishing, 2002, p. 176-178

  The extrusion molding method has an advantage that a rod-shaped, hollow, thin plate, and honeycomb-shaped molded body can be continuously produced. However, in order to ensure good moldability and shape retention after molding, it is necessary to add a large amount of organic binder such as 10 to 20 parts by mass with respect to 100 parts by mass of the aggregate particles. Due to this large amount of organic binder, during firing, i) carbon dioxide and harmful gases are generated by burning the organic binder, causing global warming and air pollution. Ii) When the organic binder burns There are still various problems such as cracks (defects) in the sintered body, yield decrease, iii) burning time is increased by burning the organic binder, and still sufficient It was not satisfactory.

  As for the casting molding method and gel casting method, in order to ensure good moldability and shape retention after molding, a large amount of organic binder or gelation such as 3 to 17 parts by mass with respect to 100 parts by mass of aggregate particles. It was necessary to add an agent. In other words, these methods also cause problems such as global warming and air pollution because carbon dioxide and harmful gases are generated by the combustion of organic substances in the molded body, and are still sufficiently satisfactory. It wasn't.

  In developing the manufacturing method of the inorganic material molded body of the present invention, the present inventors ensure both good moldability and shape retention after molding unless a large amount of organic matter is added in the conventional method. We examined the causes that could not be done.

  As a result, moldability is due to fluidity between inorganic material particles, shape retention is due to bonding between inorganic material particles, and plasticizers that provide moldability and organic binders that provide shape retention are different substances. For this reason, it has been found that both good moldability and shape retention after molding cannot be secured unless a large amount of organic substance is added.

  The present invention was made in order to solve the problems of the background art as described above, and in addition to ensuring good moldability and shape retention, an organic substance added for ensuring moldability was added. The present invention provides a method for producing an inorganic material molded body that can be removed without degreasing by heating and subjecting a molded body having a low organic binder content to firing, and a method for producing an inorganic material sintered body.

  As a result of intensive studies, the present inventors have secured shape retention by a technique in which inorganic material particles that are aggregate particles are bonded to each other by a covalent bond via a bridging atomic group containing an organic atomic group. Thus, it is conceived that the plasticizer necessary for ensuring good moldability is eluted in a solvent after molding, so that the plasticizer can be removed without thermal decomposition while maintaining the shape of the molded body. Was completed. Specifically, this invention provides the manufacturing method of the following inorganic material molded object, and the manufacturing method of an inorganic material sintered compact.

[1] A method for producing an inorganic material molded body comprising inorganic material particles and a bridging atomic group composed of an organic atomic group as constituent elements, wherein the inorganic material particles have a structure in which the respective inorganic material particles are bonded to each other by the bridging atomic group. There,
First step: Inorganic material particles having organic functional groups having binding functional groups chemically modified on the surface are used as the inorganic material particles, and the binding property of the surface of the inorganic material particles in response to an external stimulus is used as a crosslinking agent. Using a stimulus-responsive cross-linking agent having two or more functional groups (stimulus-responsive functional groups) that cause a binding reaction with a functional group, a mixture containing the inorganic material particles and the stimulus-responsive cross-linking agent is used as a plasticizer. To obtain a molded body precursor by molding into a desired shape,
Second step: Applying the external stimulus to the molded body precursor, and bonding the inorganic material particles to each other using a binding reaction between the functional group and the stimulus-responsive crosslinking agent. By forming a bridging atomic group, an inorganic material molded body is obtained,
Third step: By immersing and holding the inorganic material molded body in a solvent, only the plasticizer is eluted and removed while maintaining the shape of the molded body, and the organic substances contained in the molded body are reduced.
The manufacturing method of the inorganic material molded object characterized by consisting of a process.

[2] In addition to the inorganic material particles, inorganic material particles whose surface is chemically modified with an organic atomic group containing a stimulus-responsive functional group are used, and in addition to the stimulus-responsive cross-linking agent, two or more binding functional groups are included. Using polyfunctional organic compounds,
The production method according to [1], wherein the bridging atomic group that bonds the inorganic material particles to each other is formed using a binding reaction between the stimulus-responsive functional group and the binding functional group.

[3] In addition to the inorganic material particles, inorganic material particles in which both the organic atomic group having the stimulus-responsive functional group and the organic atomic group having a binding functional group are chemically modified on the surface are used.
The production method according to [1], wherein the modification atomic groups are bonded to each other without using a crosslinking agent, and the crosslinking atomic groups are bonded to each other between the inorganic material particles.

[4] By light irradiation, a binding reaction between the phenyl azide group (—C ₆ H ₄ —N ₃ ) as the stimulus-responsive functional group and the amino group (—NH ₂ ) as the binding functional group is performed. The production method according to [1], [2] or [3], wherein the method proceeds to form a phenylhydrazo group (—C ₆ H ₄ —NHNH—).

[5] By the microwave irradiation, a binding reaction between the amino group (—NH ₂ ) as the stimulus-responsive functional group and the carboxyl group (—COOH) as the stimulus-responsive functional group is allowed to proceed, and the imide The production method according to [1], [2] or [3], wherein a bond (—N (CO—) ₂ ) is formed.

[6] By a microwave irradiation, a binding reaction between the carbodiimide group (—N═C═N—) as the stimulus-responsive functional group and the amino group (—NH ₂ ) as the binding functional group is performed. The production method according to [1], [2], or [3], wherein the process proceeds to form a guanidine structure ((—NH) ₂ C═NH—).

[7] By microwave irradiation, the carbodiimide group (—N═C═N—) as the stimulus-responsive functional group and the carboxyl group (—COOH) as the binding functional group proceed. The carbamoylamide structure (—NHC (O—C (═O) —) = N—) is formed, and the production method according to the above [1], [2] or [3].

[8] By the microwave irradiation, the binding reaction between the carbodiimide group (—N═C═N—) as the stimulus-responsive functional group and the hydroxyl group (—OH) as the binding functional group is advanced. The process according to [1], [2] or [3], wherein an isourea structure (—NHC (O—) ═N—) is formed.

[9] Utilizing a binding reaction between the amino group (—NH ₂ ) as the stimulus-responsive functional group and the carboxyl group (—COOH) as the stimulus-responsive functional group by heating at 300 ° C. or lower. The production method according to [1], [2] or [3] above, wherein an amide bond (—NHCO—) is formed.

[10] Bonding between the carbodiimide group (—N═C═N—) as the stimulus-responsive functional group and the amino group (—NH ₂ ) as the binding functional group by heating at 300 ° C. or less The production method according to [1], [2] or [3], wherein the reaction is allowed to proceed to form a guanidine structure ((—NH) ₂ C═NH—).

[11] By heating at 300 ° C. or lower, the binding reaction between the carbodiimide group (—N═C═N—) as the stimulus-responsive functional group and the carboxyl group (—COOH) as the binding functional group To produce a carbamoylamide structure (—NHC (O—C (═O) —) = N—). The production method according to the above [1], [2] or [3].

[12] A bonding reaction between the carbodiimide group (—N═C═N—) as the stimulus-responsive functional group and the hydroxyl group (—OH) as the binding functional group proceeds, and an isourea structure (— NHC (O-) = N-) is formed, The manufacturing method as described in said [1], [2] or [3].

[13] An inorganic material molded body in which an inorganic material molded body is obtained by the production method according to any one of [1] to [12], and the plasticizer eluted in the solvent is used again for the production of a new molded body. Manufacturing method.

[14] An inorganic material sintered body obtained by obtaining the inorganic material molded body by the manufacturing method according to any one of [1] to [13], and firing the inorganic material molded body to obtain an inorganic material sintered body. Production method.

  In addition to being able to ensure good moldability and shape retention after molding, the method for producing an inorganic material molded body according to the present invention removes organic substances added to ensure moldability without degreasing by heating. It is possible to produce an advantageous effect as compared with the conventional production method, in which a molded body having a small organic binder content can be subjected to firing.

It is IR chart which shows the result of having analyzed the silica molded object precursor 1, the silica molded object precursor 2, and the silica molded object by infrared spectroscopy. It is a thermal analysis chart which shows the result of having thermally analyzed the silica molded object precursor 1 and the silica molded object.

  The best mode for carrying out the method for producing an inorganic material molded body of the present invention will be specifically described below. However, the present invention provides an inorganic material molded body based on the idea that each of the inorganic material particles to be aggregate particles is bonded to each other by a bridging atomic group containing an organic atomic group, and then the plasticizer is eluted and removed into a solvent. The method includes a wide range of manufacturing methods and should not be construed as limited to the embodiments described below.

  The method for producing an inorganic material molded body of the present invention comprises, as constituent elements, inorganic material particles that become aggregate particles, a bridging atomic group that includes an organic atomic group, and a plasticizer that includes the organic atomic group. This is a method for obtaining an inorganic material molded body in which a plasticizer is contained in a structure in which are bonded to each other by a bridging atomic group, and removing the plasticizer by elution into a solvent.

[1] First Step The first step of the production method of the present invention includes inorganic material particles each having a binding responsive functional group and a binding functional group that cause a binding reaction in response to an external stimulus, and a crosslinking agent. This is a molded body precursor manufacturing process in which a mixture is molded into a desired shape using a plasticizer to obtain a molded body precursor.

  Aggregate particles are particles that are the main constituents of a molded body. When an inorganic material molded body is manufactured, inorganic material particles made of an inorganic material are used. In the production method of the present invention, it is necessary to use inorganic material particles whose surface is modified with a modified atomic group containing an organic atomic group and having a stimulus-responsive functional group or a binding functional group. “Organic atomic group” means an atomic group containing a carbon atom as a constituent atom, and the other structure is not particularly limited.

  The “stimulus responsive functional group” means a functional group that causes a binding reaction with another binding functional group in response to an external stimulus. By utilizing the bonding reaction between the stimulus-responsive functional group and another binding functional group, it is possible to form a bridging atomic group that bonds the inorganic material particles to each other.

  “External stimulus” means physical or chemical stimulus supplied from the external environment, such as thermal stimulus (heating), light stimulus (light irradiation), electrical stimulus (voltage application), magnetic stimulus, etc. Examples include physical stimulation, chemical stimulation such as pH change (addition of acid / alkali) and moisture change. Since the production method of the present invention is intended to obtain a molded body under mild conditions in the pre-stage of firing at a high temperature, a binding reaction with other functional groups by an external stimulus that meets such conditions. It is desirable to be induced. Examples of such external stimuli include light irradiation, microwave irradiation, ultrasonic irradiation, heating at low temperature, and room temperature plasma.

As the stimulus-responsive functional group, a phenylazide group (—C ₆ H ₄ —N ₃ ) that causes a binding reaction with an amino group (—NH ₂ ) by light irradiation to form a hydrazo bond (—NHNH—). ) And the like. In addition to stimuli-responsive functional groups such as a phenyl azide group, a binding reaction is caused by the action of one functional group, as well as those that cause a binding reaction by the interaction of two functional groups. It is. For example, when a combination of an amino group (—NH ₂ ) and a carboxyl group (—COOH) is used as a stimulus-responsive functional group, a binding reaction is induced between the two functional groups by microwave irradiation, and an imide bond (—N (CO−) ₂ ) can be formed, and an amide bond (—NHCO—) can be formed by heating at 300 ° C. or lower. In addition, the stimuli-responsive functional group is caused to undergo a binding reaction with an amino group (—NH ₂ ), a carboxyl group (—COOH), or a hydroxyl group (—OH) by microwave irradiation or heating at 300 ° C. or less, Forms guanidine structure ((—NH) ₂ C═NH—), carbamoylamide structure (—NHC (O—C (═O) —) = N—), isourea structure (—NHC (O —) = N—) Carbodiimide group (—N═C═N—) and the like.

  As the “inorganic material particles”, those made of an inorganic material having a binding site (hydroxyl group or the like) capable of forming a covalent bond with a modified atomic group are preferably used. For example, the “inorganic material particle” is made of an oxide ceramic having a surface hydroxyl group. Particles can be suitably used. Also, particles made of non-oxide ceramics or metals can be used as “inorganic material particles” because oxide ceramics are inevitably formed on the surface by air oxidation (surface oxide film). That is, in the production method of the present invention, it is preferable to use inorganic material particles made of at least one inorganic material selected from the group of oxide ceramics, non-oxide ceramics, and metals.

  Examples of the oxide ceramic include metal oxides such as barrier, ceria, zinc oxide, germanium oxide, indium oxide, tin oxide, and antimony oxide, in addition to general-purpose ceramics such as silica, alumina, zirconia, and titania. These oxide ceramics have a surface hydroxyl group to be a binding site, and are preferable in that chemical modification of the modifying atomic group is easy. Examples of non-oxide ceramics include silicon carbide and silicon nitride. Examples of metals include silicon, aluminum, zirconium, titanium, barium, cerium, zinc, germanium, indium, tin, and antimony.

  The average particle diameter of the “inorganic material particles” is preferably in the range of 1 nm to 50 μm, and more preferably in the range of 10 to 500 nm. If it is less than the above range, the specific surface area of the inorganic material particles becomes excessive, and the proportion of the modified atomic group per unit mass of the inorganic material particles may be too large. In such a case, there is a possibility that an inorganic material molded body having a small organic content, which is the object of the present invention, may not be obtained, which is not preferable. On the other hand, if the above range is exceeded, the activity of the surface of the inorganic material particles may be reduced and it may be difficult to form a bond with the modifying atomic group, and when the slurry is made, the inorganic material particles are likely to settle, Handling may be difficult. In the present specification, the term “average particle size” refers to an X-ray transmission type particle size distribution measuring apparatus (for example, trade name: Cedi, which uses the Stokes liquid phase precipitation method as a measurement principle and performs detection by the X-ray transmission method. It means the value of 50% particle diameter measured by Graph 5000-02 type, manufactured by Shimadzu Corporation.

  The method for chemically modifying the modifying atomic group is not particularly limited, and a conventionally known chemical modification method can be used. Examples thereof include a method of fixing organic molecules with a coupling agent, a method of fixing organic molecules by an autoclave method, a method using surface modification by corona discharge, a method using surface modification by ozone, and the like. Among them, it is preferable to use a method of fixing organic molecules with a coupling agent because it is possible to easily form a strong bond.

  As the coupling agent, for example, a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, a chromium coupling agent, or the like can be used.

  Examples of the chemical modification method using a silane coupling agent include the following methods.

  First, a silanol residue acts on the inorganic material particles by causing a silane coupling agent to act on the inorganic material particles and causing a condensation reaction between the inorganic material particles and the silane coupling agent. Silanol-bonded inorganic material particles having a structure bonded by covalent bonds are obtained.

For example, as shown in the following general formula (1), a silane coupling agent (II) is allowed to act on the inorganic material particles (I), and the surface hydroxyl groups (OH) of the inorganic material particles (I) and the silane system By causing a condensation reaction with the hydrolyzable functional groups (Hy ₁ , Hy ₂ , Hy ₃ ) of the coupling agent (II), silanol residues are bonded to the inorganic material particles by covalent bonds. Silanol-bound inorganic material particles (III) having the above structure are obtained.

_{However, Hy 1, Hy 2, Hy} 3: hydrolyzable functional group, A: an organic atomic group, Re _1: reactive functional groups, Pi: inorganic material particles

Examples of the hydrolyzable functional group (Hy ₁ , Hy ₂ , Hy ₃ ) include an alkoxy group (RO-: R is an alkyl group). Each functional group may be the same functional group or a different functional group. In the case of an alkoxy group, it is hydrolyzed by the presence of water to produce a silanol group (—SiO—), and the silanol group is adsorbed on the surface hydroxyl group of the inorganic material particles by a hydrogen bond. By heating this at a high temperature, silanol groups and surface hydroxyl groups undergo dehydration condensation, and silanol residues are bonded to the inorganic material particles by covalent bonds.

Next, a modified atomic group is formed by causing an organic compound having a stimulus-responsive functional group to act on the silanol-bound inorganic material particles and causing a bond-forming reaction between the silanol-bound inorganic material particles and the organic compound. Forming stimuli-responsive inorganic material particles. Alternatively, a reactive functional group Re _1, may be used as the binding functional group that binds to stimuli-sensitive functional group bridging group.

In addition to the above method, a silane coupling agent having a stimulus-responsive functional group is allowed to act on the inorganic material particles, so that the surface hydroxyl group of the inorganic material particles and the hydrolyzable functional group of the silane coupling agent A method of obtaining a stimuli-responsive inorganic material particle by forming a modified atomic group by causing a condensation reaction in (1) may be adopted.

  In the production method of the present invention, a mixture containing inorganic material particles, a bridging atomic group, and a plasticizer is molded into a desired shape to obtain a molded body precursor. It is necessary for inorganic material particles to be aggregate particles to include inorganic material particles that have been surface-modified with a modified atomic group containing a stimuli-responsive functional group or a binding functional group. There is no need to be inorganic material particles. Further, the form of the mixture may be a dry powder form, or a clay or slurry to which a dispersion medium is added. Examples of the dispersion medium include water or a mixed solvent of water and an organic solvent such as alcohol, and water is particularly preferably used.

  In the production method of the present invention, a substance that becomes a plasticizer is mixed in addition to the inorganic material particles and the bridging atomic group for the purpose of improving moldability (plasticity) during molding. The amount of the plasticizer added at this time is not particularly limited, but can be added within a range of 40 parts by mass or less with respect to 100 parts by mass of the aggregate particles. If the above range is exceeded, the slurry becomes excessively viscous when it is made into a slurry, which makes it difficult to handle and may cause problems due to a large amount of organic substances. On the other hand, when the amount of the plasticizer is too small, the effect of improving plasticity is small, and the effect of improving moldability may not be sufficiently obtained. Considering this, the amount of plasticizer added is more preferably in the range of 1 to 20 parts by mass.

  As the plasticizer, for example, polyethylene glycol, polyvinyl alcohol, methyl cellulose, glycerol, glycerin, phthalic acid ester, sucrose acetate isobutyrate, dibutyl phthalate, diisodecyl phthalate, or the like can be preferably used.

  There is no restriction | limiting in particular about the method of shaping | molding, What is necessary is just to select suitably from conventionally well-known shaping | molding methods according to the form of a mixture. For example, uniaxial press, isotropic press, cast molding, centrifugal molding, extrusion molding, electrophoresis method, filtration method, magnetic field press, sheet molding, tape molding, etc. are preferred methods in which aggregate particles are filled in a dense state. Can be used. In this way, a molded body of a mixture containing inorganic material particles is obtained. In the present specification, this molded body is referred to as “molded body precursor 1”. This is because the above-mentioned molded body has not yet formed a bridging atomic group, and the removal of the plasticizer by elution has not been completed, and can be regarded as a precursor of the inorganic material molded body of the present invention.

[2] Second Step In the second step of the production method of the present invention, an external stimulus is applied to the molded body precursor 1, and a binding reaction between the stimulus-responsive functional group and the binding functional group is utilized. This is a step of forming a bridging atomic group for bonding inorganic material particles to each other.

  Specifically, an external stimulus suitable for the type of stimulus-responsive functional group is applied to the molded body precursor 1 produced as described above. For example, when the stimulus-responsive functional group is a carbodiimide group and the binding reaction proceeds with an amino group, microwaves with a frequency of 2450 MHz are irradiated for 1 second to 60 minutes. Thereby, a binding reaction proceeds between both functional groups, and a guanidine structure is formed. That is, a structure in which each of the inorganic material particles is bonded to each other by a bridging atomic group including a guanidine structure is obtained. In the case of microwaves, when the governments of each country have determined frequencies that can be used industrially, it is necessary to select the frequencies to be used in accordance with the frequencies. At present, in Japan, frequencies of 433.92 MHz, 2450 MHz, 5800 MHz, and 24.125 GHz can be used, and an appropriate frequency may be appropriately selected from these frequencies. In other countries, frequencies other than these frequencies (for example, 915 MHz (US), 896 MHz (UK), 2375 MHz (Eastern Europe / Russia), etc.) may be used.

  Further, for example, when the stimulus-responsive functional group is a carbodiimide group and the binding reaction proceeds with an amino group, the functional group may be heated at a relatively low temperature of 300 ° C. or lower for 1 minute to 30 days. Thereby, a binding reaction proceeds between both functional groups, and a guanidine structure is formed. That is, a structure in which each of the inorganic material particles is bonded to each other by a bridging atomic group including a guanidine structure is obtained.

  As a mode of bond formation, for example, as a raw material, an inorganic material particle in which the above-mentioned stimulation-responsive functional group containing the stimulation-responsive functional group is chemically modified on at least a part of the aggregate particle, and a stimulation-responsive functional group are used. Two types of modified inorganic material particles, a modified inorganic material particle having a modified functional group having a binding functional group capable of forming a bond between them and chemically modified, are used as a stimulus-responsive functional group and a binding functional group. A modification may be used in which the modification atomic groups of the inorganic material particles are bonded to each other by using a bonding reaction between the two, and a crosslinked atomic group that bonds the inorganic material particles to each other is formed.

  In this way, a molded body of a mixture containing inorganic material particles having a structure in which each of the inorganic material particles is bonded to each other by a bridging atomic group is obtained. In the present specification, this molded body is referred to as “molded body”. This will be referred to as “precursor 2”. This is because the removal of the plasticizer by elution has not been completed yet, and the above-described molded body can be regarded as a precursor of the inorganic material molded body of the present invention.

[3] Third Step In the third step of the production method of the present invention, only the plasticizer is eluted and removed while the shape of the molded body precursor 2 is maintained by immersing and holding the molded body precursor 2 in a solvent. This is a step of reducing organic substances contained in the interior.

  Examples of the solvent for elution of the plasticizer include an organic solvent such as water and alcohol, or a mixed solvent of water and an organic solvent such as alcohol. For the selection of the solvent, a solvent that is suitable in consideration of the fact that the plasticizer is dissolved in the solvent and that the bridging atomic group bonding the inorganic material particles is stable in the solvent is used.

  Although the immersion / holding time in the solvent is not particularly limited, it is usually sufficient to select a time during which the plasticizer is sufficiently eluted in the range of 10 minutes to 30 days. The temperature during immersion / holding in the solvent may be selected from the range of 1 ° C. to 300 ° C., and the range of normal temperature to 50 ° C. is particularly suitable.

  The inorganic material molded body obtained as described above may be used as it is, or may be used after drying under appropriate conditions. The drying method is not particularly limited, and conventionally known drying methods such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying and the like can be used.

  It is also possible to obtain an inorganic material molded body by the method for manufacturing an inorganic material molded body of the present invention, and to use the plasticizer eluted in the solvent for a new method of manufacturing an inorganic material molded body again. One. Not only can the amount of plasticizer be saved, but there is also the advantage that the amount of plasticizer released into the environment can be reduced and does not cause environmental pollution.

  In addition, it is one of the preferable forms of this invention to obtain an inorganic material molded object by the manufacturing method of the inorganic material molded object of this invention, and to calcine the inorganic material molded object and to obtain an inorganic material sintered compact. The inorganic material molded body obtained as described above is obtained by bonding aggregate particles made of an inorganic material to each other by covalent bonding via a bridging atomic group containing an organic atomic group. In addition to high shape retention, the plasticizer is eluted and removed, so the organic content is very low. Therefore, when this inorganic material molded body is fired, a high-quality inorganic material sintered body having high mechanical strength and few defects (voids and cracks) due to organic substances can be obtained. In addition, there is an advantage that the firing time can be shortened, carbon dioxide and harmful gas are hardly generated, and it does not cause global warming or air pollution.

  In this case, the removal of the organic matter can be further promoted by performing an operation (degreasing / calcination) for burning and removing the organic matter in the inorganic material molded body before firing or in the temperature raising process of firing. Is preferable. Since the combustion temperature of the organic substance is about 200 to 300 ° C., the calcining temperature may be about 200 to 1000 ° C. The calcining time is not particularly limited, but is usually about 10 to 100 hours.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, since the following examples show only some embodiments of the present invention, the present invention should not be construed as being limited to these examples.

Example 1
By using silica particles as inorganic material particles and chemically modifying a modified atomic group having an amino group (—NH ₂ ) as a binding functional group on the silica particle, the modified atomic group is bonded to the silica particle. Bonding silica particles having a structure bonded by covalent bonds were obtained.

First, as shown in the following formula (2), 3-aminopropyltriethoxysilane (II-a: NH ₂ C ₃ H ₆ Si (II-a), which is a silane coupling agent, is applied to the silica particles (Ia). OC ₂ H _{5) 3)} reacted to give a silanol-bonded silica particles (III-a).

  Specifically, 1.0 g of 3-aminopropyltriethoxysilane was dissolved in 100 ml of pure water to prepare an aqueous solution of a silane coupling agent, and an average particle diameter of 270 nm obtained by a sol-gel method was obtained in the aqueous solution. After dispersing 5.0 g of the silica particles and stirring for 1 hour, 3-aminopropyltriethoxysilane was adsorbed on the surface of the silica particles, and free 3-aminopropyltriethoxysilane was removed by centrifugal washing. Silanol-bonded silica particles having a structure in which silanol residues are covalently bonded to the silica particles by causing a condensation reaction between the silica particles and 3-aminopropyltriethoxysilane by heating and drying at ° C. Got.

  Next, a molded body precursor 1 composed of an organic compound having a molecular weight of about 2000 (water-soluble carbodiimide) having a structure in which an oxyethylene structure and a carbodiimide group are linked at a ratio of 10: 1, the silanol-bonded silica particles, and polyvinyl alcohol. Got.

  Specifically, 5 g of an 11% by mass polyvinyl alcohol aqueous solution and 2.5 g of the silanol-bonded silica particles (used as the bindable silica particles here) are added to 15 ml of water, stirred, and 11% by weight water-soluble. A carbodiimide aqueous solution (5 ml) was dissolved to form a slurry, and this slurry was cast into a cylindrical shape having an outer diameter of 20.0 mmφ and a thickness of 3.0 mm to obtain a molded body precursor 1.

Next, as shown in the following formula (3), the carbodiimide group in the water-soluble carbodiimide is allowed to act as a stimulus-responsive functional group on the silanol-bonded inorganic material particles (III-a) to obtain a molded body precursor 2. It was.

Specifically, the molded body precursor 1 was heated to 105 ° C. in the atmosphere, held for 24 hours, and then cooled to room temperature to obtain a molded body precursor 2. Each of the molded body precursor 1 and the molded body precursor 2 was analyzed by infrared spectroscopy. As shown in the IR chart of FIG. 1, the molded body precursor 1 has an absorption peak (2120 / cm ⁻¹⁾ due to the carbodiimide structure. ) Was observed, however, it was shown that the strength of the absorption peak was reduced in the molded body precursor 2 and the carbodiimide structure was converted to a guanidine structure by the reaction. Moreover, the absorption peak (1750 / cm ^<-1 >) by polyvinyl alcohol was observed by any of the molded object precursor 1 and the molded object precursor 2. FIG.

The molded body precursor 2 was immersed in water at room temperature and held for 7 days to elute polyvinyl alcohol to obtain an inorganic material molded body. When the inorganic material molded body was dried and analyzed by infrared spectroscopy, the absorption peak (1750 / cm ⁻¹ ) due to polyvinyl alcohol disappeared as shown in the IR chart of FIG. That is, this inorganic material molded body includes inorganic material particles made of silica and a bridging atomic group having a guanidine structure as constituent elements, and the bridging atomic group has a structure in which silica particles are bonded to each other. And the polyvinyl alcohol which existed at the time of molding was removed by elution.

(Comparative Example 1)
A silica molded body precursor 2 was obtained in the same manner as in Example 1 except that the same amount of polyvinyl alcohol was added without using a water-soluble carbodiimide containing a carbodiimide group as a stimulus-responsive functional group. .

(Evaluation)
The silica molded body precursor 2 of Example 1 and the silica molded body precursor 2 of Comparative Example 1 were immersed in water. As a result, the structure of the silica molded body precursor 2 of Comparative Example 1 was easily disintegrated in water, and the water became cloudy. For this reason, it was impossible to elute and remove the organic substance while maintaining the shape of the molded body.

  Furthermore, the molded body precursor 1 produced in Example 1 and the inorganic material molded body were subjected to thermal analysis, and the amount of organic matter was measured. As shown in the thermal analysis chart of FIG. 2, desorption of adsorbed water occurred at temperatures up to about 200 ° C., and it was recognized that decomposition / desorption of organic substances occurred at a temperature range of 200 ° C. to 800 ° C. . The organic substance content of the molded body precursor 1 calculated from the analysis results is about 4.5% by mass, the organic substance content of the inorganic material molded body is 2.5% by mass, and the organic substance by elution of polyvinyl alcohol. Weight loss was observed.

  The method for producing an inorganic material molded body of the present invention is suitably used for the production of various molded articles of ceramics and metals that are used in various applications such as structural materials and electrical / electronic materials.

Claims (14)

A method for producing an inorganic material molded body comprising inorganic material particles and a bridging atomic group consisting of organic atomic groups as constituent elements, each of the inorganic material particles having a structure in which each of the inorganic material particles is bonded to each other by the bridging atomic group,
First step: Inorganic material particles having organic functional groups having binding functional groups chemically modified on the surface are used as the inorganic material particles, and the binding property of the surface of the inorganic material particles in response to an external stimulus is used as a crosslinking agent. Using a stimulus-responsive cross-linking agent having two or more functional groups (stimulus-responsive functional groups) that cause a binding reaction with a functional group, a mixture containing the inorganic material particles and the stimulus-responsive cross-linking agent is used as a plasticizer. To obtain a molded body precursor by molding into a desired shape,
Second step: Applying the external stimulus to the molded body precursor, and bonding the inorganic material particles to each other using a binding reaction between the functional group and the stimulus-responsive crosslinking agent. By forming a bridging atomic group, an inorganic material molded body is obtained,
Third step: By immersing and holding the inorganic material molded body in a solvent, only the plasticizer is eluted and removed while maintaining the shape of the molded body, and the organic substances contained in the molded body are reduced.
The manufacturing method of the inorganic material molded object characterized by consisting of a process. In addition to the inorganic material particles, the inorganic material particles whose surface is chemically modified with an organic atomic group containing a stimulus-responsive functional group are used, and in addition to the stimulus-responsive cross-linking agent, the polyfunctionality having two or more binding functional groups. Using organic compounds,
The manufacturing method according to claim 1, wherein the bridging atomic group that bonds the inorganic material particles to each other is formed using a binding reaction between the stimulus-responsive functional group and the binding functional group. In addition to the inorganic material particles, using inorganic material particles in which both the organic atomic group having the stimulus-responsive functional group and the organic atomic group having a binding functional group are chemically modified on the surface,
The manufacturing method according to claim 1, wherein the modifying atomic groups are bonded to each other without using a crosslinking agent, and the crosslinked atomic groups are bonded to each other between the inorganic material particles. By light irradiation, a binding reaction between the phenyl azide group (—C ₆ H ₄ —N ₃ ) as the stimulus-responsive functional group and the amino group (—NH ₂ ) as the binding functional group proceeds, to form a phenyl hydrazo group _{(-C 6} H 4 -NHNH-), the method according to claim 1, 2 or 3. By microwave irradiation, a binding reaction between the amino group (—NH ₂ ) as the stimulus-responsive functional group and the carboxyl group (—COOH) as the stimulus-responsive functional group is allowed to proceed, and an imide bond (— The manufacturing method of Claim 1, 2, or 3 which forms N (CO-) ₂ ). By the microwave irradiation, the binding reaction between the carbodiimide group (—N═C═N—) as the stimulus-responsive functional group and the amino group (—NH ₂ ) as the binding functional group proceeds, to form the guanidine structure _{((-NH) 2 C = NH-} ), the method according to claim 1, 2 or 3.   By irradiating with microwaves, the carbodiimide group (—N═C═N—) as the stimulus-responsive functional group and the carboxyl group (—COOH) as the binding functional group are allowed to proceed, and carbamoyl The manufacturing method of Claim 1, 2, or 3 which forms an amide structure (-NHC (OC (= O)-) = N-).   By the microwave irradiation, the bonding reaction between the carbodiimide group (—N═C═N—) as the stimuli-responsive functional group and the hydroxyl group (—OH) as the binding functional group proceeds, and an isourea structure The production method according to claim 1, wherein (—NHC (O—) ═N—) is formed. By heating at 300 ° C. or less, an amide bond is obtained by utilizing a bonding reaction between the amino group (—NH ₂ ) as the stimulus-responsive functional group and the carboxyl group (—COOH) as the stimulus-responsive functional group. The manufacturing method of Claim 1, 2, or 3 which forms (-NHCO-). By heating at 300 ° C. or lower, the binding reaction between the carbodiimide group (—N═C═N—) as the stimulus-responsive functional group and the amino group (—NH ₂ ) as the binding functional group proceeds. The guanidine structure ((—NH) ₂ C═NH—) is formed to form the guanidine structure.   By heating at 300 ° C. or lower, the binding reaction between the carbodiimide group (—N═C═N—) as the stimulus-responsive functional group and the carboxyl group (—COOH) as the binding functional group is allowed to proceed. The carbamoylamide structure (-NHC (OC (= O)-) = N-) is formed, The manufacturing method of Claim 1, 2, or 3.   A bonding reaction between the carbodiimide group (—N═C═N—) as the stimulus-responsive functional group and the hydroxyl group (—OH) as the binding functional group is allowed to proceed, and an isourea structure (—NHC (O The production method according to claim 1, 2 or 3, wherein-) = N-) is formed. An inorganic material molded body is obtained by the production method according to any one of claims 1 to 12,
A method for producing an inorganic material molded body, wherein a plasticizer eluted in a solvent is used again for the production of a new molded body. An inorganic material molded body is obtained by the production method according to any one of claims 1 to 13,
A method for producing an inorganic material sintered body, wherein the inorganic material molded body is fired to obtain an inorganic material sintered body.