JP5371418B2 - Method for producing inorganic molded body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of cheaply and easily producing an inorganic molded article exhibiting sufficiently low heat capacity and heat conductivity, sufficient strength, and excellent resistance to an alkaline gas when it is used as a furnace material. <P>SOLUTION: The method of producing an inorganic molded article includes: the process of preparing a slurry having a wet volume of 300 mL/20 g or greater by adding alumina fibers and alumina particles into a solvent so that the mass ratio of the alumina particles relative to the aggregate amount of the alumina fiber and the alumina particles falls in a range of 30 to 70 mass%, further adding an inorganic binder, starch as an organic binder, and a polymeric flocculant thereinto, and mixing and agitating the mixture; the process of subjecting the slurry to the dehydration molding process or the paper-making process to obtain a wet molded article; and the process of drying the wet molded article. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for producing an inorganic molded body.

  Conventionally, firing in an industrial furnace has been performed to heat-treat electronic components, battery electrode materials, and the like.

  In addition, furnace materials (heat insulating materials) provided inside industrial furnaces are required to have low heat capacity and thermal conductivity, and by using such furnace materials, heat energy during heating can be used efficiently. In addition, the tact time is shortened to improve production efficiency.

  However, in recent years, depending on the member to be fired, alkali gas such as lithium gas or sodium gas may be generated from the object to be fired, and this alkali gas erodes the furnace material provided inside the industrial furnace, Phenomena such as peeling, cracking, and dropping off can occur, so that furnace materials are easily worn out.

In order to suppress the wear of the furnace material, a furnace material having a high content ratio of alumina excellent in corrosion resistance has been proposed (for example, see Patent Document 1), but a material having sufficient alkali resistance is reported. Was not.
JP 2007-70769 A

  As a furnace material having high corrosion resistance against alkali gas, one that suppresses permeation of alkali gas by densifying high-purity alumina having high crystallinity can be considered.

  However, as a result of studies by the present inventors, it has been found that the furnace material made of alumina having a high purity and a high density is very expensive, and the furnace material peels off when reacted with an alkali gas. .

  Further, as a result of studies by the present inventors, a conventional inorganic molded body formed by binding alumina fibers with an inorganic binder has an inorganic binder on the surface of the skeleton portion made of alumina fibers as shown in FIG. It has an internal structure that aggregates and adheres in the form of particles or whiskers, and since the inorganic binder component is susceptible to erosion by alkali gas, even through the use of highly corrosion-resistant alumina fibers, It turned out to be susceptible to erosion.

  Under such circumstances, the present invention, when used as a furnace material, produces an inorganic molded body having low heat capacity and low thermal conductivity, sufficient strength, and high resistance to alkali gas at low cost and in a simple manner. It is intended to provide a method.

  In order to solve the above technical problems, the present inventors have conducted intensive studies. As a method for producing an inorganic molded body, alumina fibers and alumina particles are produced by adding alumina to the total amount of alumina fibers and alumina particles. While adding to a solvent so that the mass ratio of particles is 30 to 70% by mass, an inorganic binder, starch as an organic binder, and a polymer flocculant are added to the solvent and mixed and stirred. By the method including a step of obtaining a slurry having a wet volume of 300 mL / 20 g or more, a step of obtaining a wet molded body by dehydrating or papermaking the slurry, and a step of drying the wet molded body. The inventors have found that the present invention can be solved, and have completed the present invention.

That is, the present invention
(1) A method for producing an inorganic molded body,
Alumina fibers and alumina particles are added to the solvent so that the mass ratio of the alumina particles to the total amount of the alumina fibers and alumina particles is 30 to 70% by mass, and the titania sol is removed from the solvent. Adding an inorganic binder, starch as an organic binder, and a polymer flocculant, and mixing and stirring to obtain a slurry having a wet volume of 300 mL / 20 g to 800 mL / 20 g ;
A step of dehydrating or paper-making the slurry to obtain a wet molded body;
A method for producing an inorganic molded body comprising the step of drying the wet molded body,
(2) When the total amount of alumina fibers and alumina particles contained in the slurry is 100 parts by mass, the slurry contains 1 to 8 parts by mass of starch and 0.2 to 4 parts by mass of the polymer flocculant. A method for producing an inorganic molded body according to (1) above, comprising:
(3) When the total amount of alumina fibers and alumina particles contained in the slurry is 100 parts by mass, the slurry has an alumina content ratio of 30 to 70 mass% with an alumina content ratio of 80 mass% or more. Part, an alumina particle 30-70 mass part, and the manufacturing method of the inorganic molded object as described in said (1) or (2) containing the inorganic binder 3-15 mass part except a titania sol ,
(4) The manufacturing method of the inorganic molded object in any one of said (1)-(3) whose average particle diameter of the said alumina particle is 5-100 micrometers,
(5) The manufacturing method of the inorganic molded object in any one of said (1)-(4) whose bulk density of the obtained inorganic molded object is 100-200 kg / m < ³ >,
(6) The method for producing an inorganic molded body according to any one of the above (1) to (5), wherein the ventilation resistance of the obtained inorganic molded body by ASTM C522 is 6 × 10 ⁵ Pa · S / m ² or less, And (7) The manufacturing method of the inorganic molded object in any one of said (1)-(6) whose alumina content rate in the inorganic molded object obtained is 80 mass% or more.

  According to the present invention, as a raw material of the inorganic molded body, a predetermined amount of alumina particles that are alkali-resistant gas components are used and alumina fiber that is a skeleton-forming component is used, and these raw materials are added to a solvent to form a slurry. Sometimes, by using starch and a polymer flocculant, which are organic binders, in addition to an inorganic binder, a bulky slurry having a wet volume of 300 mL / 20 g or more is obtained, and a wet molded body obtained from this slurry is dried. In addition, it is possible to obtain an inorganic molded body obtained by forming a film-like part independently of a skeleton part composed of alumina fiber having a low bulk density and low airflow resistance as well as low corrosion resistance and an inorganic fiber having high corrosion resistance. .

  For this reason, according to the present invention, the heat capacity and the thermal conductivity are sufficiently low, and the structure has a skeleton part that easily diffuses alkali gas inside and has high resistance to alkali gas. It is possible to provide a method for producing an inorganic molded body having a sufficient strength at low cost and in a simple manner while reducing the erosion of alkali gas in the portion and the inside and suppressing the occurrence of peeling and cracking.

  In the method for producing an inorganic molded body of the present invention, alumina fibers and alumina particles are added to a solvent so that the mass ratio of the alumina particles to the total amount of the alumina fibers and the alumina particles is 30 to 70% by mass. In addition, an inorganic binder, starch as an organic binder, and a polymer flocculant are added to the solvent, and mixed and stirred to obtain a slurry having a wet volume of 300 mL / 20 g or more, and The method includes a step of obtaining a wet molded body by dehydrating or paper-making the slurry, and a step of drying the wet molded body.

  In the present application, the alumina fiber means a metal oxide fiber containing alumina as a main component, and may contain components such as silica and zirconia in addition to alumina as long as alumina is a main component.

  The alumina content in the alumina fiber is preferably 80% by mass or more, and more preferably 90% by mass or more. When the content of alumina is 80% by mass or more, the alkali resistance is improved and the alkali gas is less likely to be eroded.

  Further, when the crystallinity of α-alumina contained in the alumina fiber is 50% or more, the alkali resistance is improved. However, the fiber with higher crystallinity becomes brittle, and the fiber is easily broken when mixed and stirred at the time of slurry formation. Since the wet volume of the material becomes small, the resulting molded product can be easily densified. On the other hand, when the crystallinity of α-alumina contained in the alumina fiber is 10% or less, the alkali resistance is slightly lowered, and the molded product obtained is slightly shrunk when heated to a temperature of 1300 ° C. or more. Since it becomes difficult to break, the wet volume of the slurry is increased, and the resulting molded product is easily reduced in density. For this reason, it is preferable that the crystallinity of the alumina fiber is appropriately selected according to the characteristics of the molded product to be obtained. Specifically, the alumina fiber is composed of 30 to 70% by mass of highly crystalline alumina fiber having a crystallinity of 50% or more and 70 to 30% by mass of low crystal alumina fiber having a crystallinity of 10% or less. Or may be composed of 40 to 60% by mass of highly crystalline alumina fibers having a crystallinity of 50% or more and 60 to 40% by mass of low crystalline alumina fibers having a crystallinity of 10% or less. Good.

  The alumina fiber preferably has an average length of 100 to 100,000 μm, more preferably 1,000 to 80,000 μm, and still more preferably 3,000 to 50,000 μm.

  In the present application, the alumina fiber means one having an aspect ratio (aspect ratio) of 25 or more.

  The alumina fiber is considered to function as a skeleton-forming component in the obtained inorganic molded body.

  The alumina particles are preferably made of α-alumina having high crystallinity, and alkali resistance can be improved by using alumina particles made of α-alumina.

  The average particle diameter of the alumina particles is preferably 5 to 100 μm, more preferably 10 to 90 μm, and further preferably 30 to 80 μm. Here, for example, the primary particles having an average particle diameter of 2 to 10 μm may be aggregated to form secondary particles having an average particle diameter of about 40 to 80 μm. Since these alumina particles have a large specific surface area and the alumina particles themselves are bulky, the bulk density of the resulting inorganic molded body can be easily lowered, and the alkali resistance can be further improved.

  When the average particle diameter of the alumina particles is less than 5 μm, the specific surface area of the alumina particles increases, and it easily reacts with the alkali component, and the alkali resistance is easily lowered, and the density of the obtained molded body is increased. In addition, as the average particle size is larger, the density and ventilation resistivity of the obtained inorganic molded body are reduced and the alkali resistance is easily improved. When the average particle size exceeds 100 μm, the resulting inorganic molded product has a rough feeling. And the particles easily fall off.

  In addition, in this application, an average particle diameter means the value measured with the laser diffraction type particle size distribution measuring apparatus.

  In the method of the present invention, the alumina particles are added to the solvent so that the mass ratio of the alumina particles to the total amount of the alumina fibers and the alumina particles is 30 to 70% by mass when forming the slurry. The mass ratio is preferably 35 to 65% by mass, and more preferably 40 to 60% by mass. Thus, in the method of the present invention, the amount of alumina particles decreases as the amount of added alumina fibers increases, and in this sense, the alumina fibers and alumina particles are in a complementary relationship. When the alumina particles have a mass ratio of less than 30% by mass, deformation of the molded body is likely to increase when the alumina fiber, which is a skeleton-forming component of the obtained inorganic molded body, is eroded by alkali gas, and cracks are generated. It becomes easy to do. Further, when the mass ratio of the alumina particles exceeds 70 mass%, the content ratio of the alumina fibers as the skeleton-forming component becomes small, and peeling easily occurs when the obtained inorganic molded body is eroded by alkali gas. Become.

  In the method of the present invention, when the total amount of alumina fibers and alumina particles contained in the slurry is 100 parts by mass, the slurry contains 30 to 70 masses of alumina fibers having an alumina content of 80 mass% or more. Part and 30 to 70 parts by mass of alumina particles are preferable.

  When the total amount of alumina fiber and alumina particles is 100 parts by mass, the content of the alumina fiber is preferably 30 to 70 parts by mass, more preferably 35 to 65 parts by mass, and further 40 to 60 parts by mass. preferable. Moreover, when the total amount of alumina fiber and alumina particles is 100 parts by mass, the content of the alumina particles is preferably 30 to 70 parts by mass, more preferably 35 to 65 parts by mass, and 40 to 60 parts by mass. Further preferred.

  In the method of the present invention, in order to form a slurry, the alumina fiber and alumina particles are added to a solvent, and further, an inorganic binder, starch as an organic binder, and polymer aggregation are added to the solvent. Add the agent.

  The inorganic binder is not particularly limited, and examples thereof include colloidal silica such as anionic colloidal silica and cationic colloidal silica, fumed silica, zirconia sol, titania sol, alumina sol, bentonite, and the like. Of the inorganic binders, colloidal silica is preferred.

  The inorganic binder may be added to the solvent in the form of a solid, or may be added in the form of a suspension or a solution.

  In the method of the present invention, when the total amount of alumina fibers and alumina particles contained in the slurry is 100 parts by mass, the slurry preferably contains 3 to 15 parts by mass of an inorganic binder. More preferably, it contains 5 parts by mass, and even more preferably 5-11 parts by mass. When the total amount of the alumina fibers and alumina particles contained in the slurry is 100 parts by mass, if the content of the inorganic binder is less than 3 parts by mass, the binding force as the binder tends to be reduced, 15 When the amount exceeds mass parts, the alkali resistance of the obtained inorganic molded body tends to be lowered.

  Moreover, it does not restrict | limit especially as starch which is an organic binder, For example, cationic starch, anionic starch, amphoteric starch etc. other than normal raw material starch can be mentioned.

  Examples of the raw material starch include natural polysaccharides such as potato starch, tapioca starch, and corn starch, and hydrolysates thereof.

  Cationic starch is obtained by introducing a cationic group into raw starch, and is a positively charged starch by introducing a primary, secondary or tertiary alkylamine or quaternary ammonium salt into the raw starch molecule. Can be mentioned.

  Anionic starch is obtained by introducing an anionic group into raw material starch, and examples thereof include those in which a phosphoric acid group, a sulfonic acid group, a carboxyl group or the like is introduced into the raw material starch molecule.

  Amphoteric starch is a material in which a cationic group and an anionic group are introduced into raw starch and both functional groups are contained in the starch molecule. Examples of the cationic group and the anionic group are the same as those described above. be able to.

  Examples of the polymer flocculant that is an organic binder include those composed of polymers such as polyacrylamide polymers, amide polymers, polyacrylic ester polymers, polyacrylic ether polymers, and the like. Of the polymer flocculants, those composed of polyacrylamide polymers are preferred.

  Moreover, as an organic binder, you may use a pulp, a suitable emulsion, etc. with the said starch and a polymer flocculent as needed.

  In the method of the present invention, the kind and amount of the organic binder added to the solvent to form a floc having a desired size are adjusted according to the charge amount of the inorganic binder, the nature of the charge, the size of the alumina particles used, and the like. You can optimize.

The organic binder may be added to the solvent in the form of a solid, or may be added in the form of a suspension or a solution.
In the method of the present invention, starch and polymer aggregates are used as an organic binder together with an inorganic binder, thereby promoting floc formation and obtaining a bulky slurry having a wet volume of 300 mL / 20 g or more as will be described later. It makes it possible.

  In the method of the present invention, when the total amount of alumina fibers and alumina particles contained in the slurry is 100 parts by mass, the slurry contains 1 to 8 parts by mass of starch and 0.2 to It is preferable that 4 mass parts is included. When the total amount of alumina fibers and alumina particles contained in the slurry is 100 parts by mass, the slurry more preferably contains 2 to 7 parts by mass of starch, and further contains 3 to 6 parts by mass. preferable. Moreover, when the total amount of the alumina fibers and the alumina particles contained in the slurry is 100 parts by mass, the slurry more preferably contains 0.5 to 3 parts by mass of a polymer flocculant. More preferably, 2.5 parts by mass are included.

  By setting the starch content in the slurry to 1 to 8 parts by mass when the total amount of the alumina fibers and alumina particles is 100 parts by mass, the inorganic binder is effectively fixed to the alumina fibers and the alumina particles. It becomes possible. Moreover, when the total amount of the alumina fiber and the alumina particles is 100 parts by mass, the polymer flocculant content in the slurry is 0.2 to 4 parts by mass, so that the material can be effectively used in the slurry. Aggregates to form floc.

  Moreover, when the total amount of the alumina fiber and the alumina particles contained in the slurry is 100 parts by mass, the slurry preferably contains 3 to 12 parts by mass of the organic binder in a total amount of 4 to 10 parts by mass. More preferably, it is more preferably 5 to 8 parts by mass. When the organic binder content in the slurry is less than 3 parts by mass when the total amount of alumina fibers and alumina particles is 100 parts by mass, any of the fixing action, agglomeration action of the inorganic binder, and the bending strength of the molded article If the content exceeds 12 parts by weight, a large amount of organic decomposition gas is generated when the resulting inorganic molded body is heated.

  When starch is used alone as the organic binder, it becomes easy to fix the inorganic binder, and it becomes easy to give bending strength to the resulting inorganic molded body, but the floc forming action is reduced due to the small agglomeration action of the slurry. For this reason, the resulting inorganic molded body is oriented in the stacking direction, so that sufficient ventilation resistance cannot be imparted and alkali resistance is reduced. In addition, when a polymer flocculant is used alone as the organic binder, the floc forming action of the slurry is large, and it becomes easy to give sufficient ventilation resistance by reducing the orientation of the obtained molded body. A sufficient strength cannot be ensured after the body is fired. For this reason, if an attempt is made to develop the strength after firing equivalent to that when starch is used, a large amount of an inorganic binder is required, which also reduces the alkali resistance.

  On the other hand, in the method of the present invention, by using both the starch and the polymer flocculant as the organic binder, the inorganic binder is obtained as a fixing material when combined with the alumina fibers and the alumina particles. Inorganic molding obtained by forming a bulky slurry with a wet volume of 300 mL / 20 g or more by functioning to agglomerate materials in the slurry and form flocs while giving sufficient bending strength to the resulting inorganic molded body The body can have a low density and bulky structure to provide sufficient ventilation resistance.

  Further, in the method of the present invention, using colloidal silica as the inorganic binder and using starch as the organic binder, as described later, the inorganic molded body contains alumina fibers, alumina particles, and an inorganic binder. An inorganic binder whose inner structure is formed so as to connect the alumina fibers near the intersection of the alumina fibers and the skeleton formed by dispersing the alumina fibers in an irregular direction. What is comprised by the film-like part containing this can be obtained.

  In order to produce an inorganic molded body in which the skeleton part and the film-like part are formed, it is preferable that colloidal silica, which is an inorganic binder, and starch have opposite charges. For example, it is preferable to combine colloidal silica having an anionic charge when the starch has a cationic charge, and when the starch has an anionic charge, the cationic charge It is preferable to combine colloidal silica having The optimum amount of colloidal silica and starch can be determined by combining them so that the zeta potential becomes the isoelectric point.

  In the method of the present invention, the solvent used in forming the slurry is not particularly limited, and examples thereof include water and a polar organic solvent.

  Examples of water include distilled water, ion-exchanged water, tap water, ground water, and industrial water. Examples of polar organic solvents include monovalent alcohols such as ethanol and propanol, and divalents such as ethylene glycol. Can be mentioned. Among these, as the solvent, water is preferable in that the working environment is not deteriorated and there is no burden on the environment.

  The total solid content concentration contained in the slurry is preferably 0.1 to 10% by mass, more preferably 0.3 to 8% by mass, and further preferably 0.5 to 3% by mass. preferable. If the concentration of all added components contained in the slurry is less than 0.1% by mass, the amount of water to be removed in the dehydration molding process becomes too large, so that the production efficiency tends to decrease. It becomes difficult to uniformly disperse the solid content in the slurry.

  In the method of the present invention, a slurry having a wet volume of 300 mL / 20 g or more can be obtained by sequentially adding the above components to a solvent, mixing and stirring. The wet volume is suitably 300 to 800 mL / 20 g, more preferably 300 to 700 mL / 20 g.

When the wet volume of the slurry is 300 mL / 20 g or more, an inorganic molded body having a bulky structure that has a sufficiently low bulk density and can diffuse alkali gas to the inside can be obtained.
As described above, a slurry having a wet volume of 300 mL / 20 g or more can be obtained by adding starch and polymer aggregates as an organic binder together with an inorganic binder during the formation of the slurry.

In the present application, the wet volume means a value calculated by the following procedures (1) to (10).
(1) A total of 20 g of alumina fibers and alumina particles is weighed with a scale having an accuracy of two decimal places or more.
(2) Put the material weighed in (1) into a 2L beaker.
(3) Charge ion-exchanged water adjusted so that the total amount becomes 1 L into a beaker. Here, the total amount is an amount obtained by adding the total amount of the inorganic binder and the organic binder added in the following (5) to the total amount of the above-mentioned alumina fiber, alumina particles, and ion-exchanged water.
(4) Stir for 2 minutes so that ion-exchanged water, alumina fibers and alumina particles are uniform. Stirring uses a propeller-type stirring blade, and the rotation speed is 1100 rpm.
(5) Subsequently, stirring is performed while adding an inorganic binder and starch and a polymer flocculant as the organic binder, respectively. The order in which the materials are charged is not particularly limited, but the materials to be charged are one by one and stirred for 1 minute each time one material is charged.
(6) A raw material additive solution is obtained by adding and stirring all the materials.
(7) After the stirring is stopped, the raw material additive solution obtained in (6) is transferred to a 1 L graduated cylinder.
(8) Close the mouth of the graduated cylinder with your hands and stir it upside down taking care not to leak water. This is repeated a total of 10 times.
(9) Let stand at room temperature, and visually measure the sedimentation volume after 15 minutes.
(10) The volume (mL / 20 g) per 20 g of slurry obtained by allowing to stand for 15 minutes is defined as the wet volume.

  In the method of the present invention, the slurry is subjected to dehydration molding or papermaking to obtain a wet molded body.

  As a dehydration molding method, a known method can be adopted, and is not particularly limited. However, a suction dehydration molding method in which slurry is poured into a mold having a net installed at the bottom and a solvent is sucked, or pressure dehydration molding. The law can be mentioned.

  In the present application, a solvent other than water may be used as the solvent used in forming the slurry, but the solvent is also referred to as dehydration molding, including the case where the solvent other than water is removed.

  As a papermaking method, a known method can be adopted, and is not particularly limited. However, a flow-on method in which a slurry is poured from a flow box onto a belt-like porous carrier, a Hatschek-type papermaking method, or a long-net type papermaking method. For example, the slurry can be continuously made.

  In the method of the present invention, when the slurry produced in a stirring tank or the like is transported to a mold or a storage tank for dehydration molding or papermaking, a molding die or a storage tank is disposed below the stirring tank. For example, the slurry is preferably transferred by its own weight. By transferring the slurry by its own weight, the slurry can be transferred without reducing the wet volume of the slurry. Conventionally, a pump or the like has generally been used for the conveyance of such a slurry, but the inorganic fiber is sheared by the stirring force of the pump, and the wet volume may be reduced in some cases.

  As the wet molded body, those having a shape similar to the inorganic molded body to be obtained are suitable, and examples thereof include a board shape, a sheet shape, and a block shape. Here, in the production process, in order to keep the bulk density as a quality within a certain range, the wet molded body may be pressed as necessary. However, in the present invention, as much as possible in order to realize a low bulk density. It is preferable not to press.

  The wet molded body thus obtained is then dried.

  The drying treatment can be performed with a known dryer, and the drying temperature is preferably 40 to 180 ° C, more preferably 60 to 150 ° C, and further preferably 80 to 120 ° C. The drying time is preferably 6 to 48 hours, more preferably 8 to 40 hours, and further preferably 10 to 36 hours.

  In the method of the present invention, the dried product of the wet molded body may be further baked.

  The firing treatment can be performed with a known heating furnace, and the firing temperature is not particularly limited, but is preferably 800 ° C. or higher, and more preferably 800 to 1600 ° C. Moreover, when using the dried processed material of the said wet molded object as a heat insulating material or a refractory material, you may carry out a baking process by heating a heating furnace to predetermined temperature at the time of use.

  In the method of the present invention, an inorganic molded body can be obtained simply and at low cost in this way.

  The obtained inorganic molded body preferably has, for example, a board shape, a sheet shape, or a block shape.

  The inorganic molded body obtained by the method of the present invention has an alumina particle content of 30 to 70 mass% with respect to the total amount of alumina fibers and alumina particles. As the inorganic molded body obtained by the method of the present invention, the content of the alumina particles is more preferably from 35 to 65% by mass, and more preferably from 40 to 60% by mass.

  Moreover, the inorganic molded body obtained by the method of the present invention is 30 to 70 parts by mass of alumina fibers when the total amount of alumina fibers and alumina particles having an alumina content of 80% by mass or more is 100 parts by mass. And it is preferable that 30-70 mass parts of alumina particles and 3-15 mass parts of inorganic binders are included. When the total amount of alumina fibers and alumina particles is 100 parts by mass, the content of the alumina fibers is more preferably 35 to 65 parts by mass, and still more preferably 40 to 60 parts by mass. Moreover, when the total amount of the alumina fiber and the alumina particles is 100 parts by mass, the content of the alumina particles is more preferably 35 to 65 parts by mass, and further preferably 40 to 60 parts by mass. Furthermore, when the total amount of alumina fibers and alumina particles is 100 parts by mass, the content of the inorganic binder is more preferably 4 to 12 parts by mass, and further preferably 5 to 11 parts by mass.

  Examples of the alumina fibers, alumina particles, and inorganic binder include the same ones as described above.

According to the method of the present invention, an inorganic molded body having a bulk density of 100 to 200 kg / m ³ can be obtained, but the inorganic molded body having a bulk density of 100 to 195 kg / m ³ is more suitable. An inorganic molded body of 100 to 190 kg / m ³ is more suitable.

When the bulk density exceeds 200 kg / m ³ , the strength of the obtained inorganic molded body increases, but the airflow resistance increases, the surface portion is easily eroded, and the molded body surface portion is easily peeled off. In addition, when the bulk density is less than 100 kg / m ³ , the ventilation resistance is lowered and the diffusibility of the alkali gas is improved, but the strength of the molded body is reduced, and when the molded body is used as a furnace material, Deformation can occur.

In addition, according to the method of the present invention, an inorganic molded body having an airflow resistance of 6 × 10 ⁵ Pa · S / m ² or less according to ASTM C522 can be obtained, but the airflow resistivity is 1 × 10 ³ to An inorganic molded body of 6 × 10 ⁵ Pa · S / m ² is more suitable, and an inorganic molded body of 1 × 10 ³ to 1 × 10 ⁵ Pa · S / m ² is more suitable.

When the ventilation resistivity is 6 × 10 ⁵ Pa · S / m ² or less, an alkali gas easily diffuses into the molded body, and erosion to the surface of the molded body is reduced. However, if the airflow resistance exceeds 6 × 10 ⁵ Pa · S / m ² , alkali gas tends to stay on the surface of the inorganic molded body, and peeling and cracking are likely to occur on the surface of the molded body. Become. Moreover, in order to maintain the performance as a heat insulating material such as strength while reducing the thermal conductivity of the inorganic molded body, it is preferable that the ventilation resistance is 1 × 10 ³ Pa · S / m ² or more.

  Furthermore, according to the method of the present invention, an inorganic molded body having an alumina content ratio of 80% by mass or more can be obtained, but an inorganic molded body having an alumina content ratio of 81% by mass or more is more suitable. An inorganic molded body having a mass% or more is more suitable.

  When the alumina content is 80% by mass or more, the alkali resistance of the obtained inorganic molded body can be improved.

  Further, according to the method of the present invention, the inorganic molded body includes alumina fibers, alumina particles, and an inorganic binder, and the internal structure is formed by dispersing the alumina fibers in an irregular direction. In the vicinity of the intersection between the skeletal part and the alumina fibers, a film-like part containing an inorganic binder formed so as to connect the alumina fibers can be obtained.

As shown in FIG. 1, a conventional inorganic molded body formed by binding alumina fibers with an inorganic binder is a particulate portion or a whisker-like shape formed by agglomerating inorganic binders on the surface of a skeleton portion 1 made of alumina fibers. As shown in FIG. 2, the inorganic molded body obtained by the method of the present invention has an internal structure that forms part 2 so as to connect skeleton part 1 made of alumina fiber in the vicinity of the intersection of alumina fiber. It has an internal structure in which an inorganic binder forms the film-like part 3.
In the present application, the skeleton means a fibrous portion made of alumina fibers as shown in FIG. 2, and the film-like portion means an intersection of two alumina fibers as shown in FIG. As a base point, it means a thin film-like portion that is widened so as to connect both of the alumina fibers. As shown in FIG. 2, the membrane-like portion has a web-like shape, but three or more alumina fibers intersect in a complicated manner, and a plurality of membrane-like portions are formed between the alumina fibers. In some cases, various shapes such as a polygonal shape are formed by connecting them.

  The proportion of alumina present in the entire skeleton and film-like part is preferably 60% by mass or more and less than 90% by mass, more preferably 70 to 88% by mass, and 75 to 85% by mass. Further preferred. Moreover, it is preferable that the abundance ratio of the alumina in the skeleton part where the film-like part is not formed is 90 to 99% by mass, more preferably 90 to 98% by mass, and 90 to 97% by mass. More preferably it is.

  In the present application, the abundance ratio of alumina occupying the entire skeleton part and film-like part and the abundance ratio of alumina in the skeleton part mean values measured by a scanning electron microscope with an energy dispersive X-ray analyzer. .

  In the conventional inorganic molded body shown in FIG. 1, an inorganic binder component that easily reacts with an alkali gas adheres to the entire skeleton portion made of alumina fibers. For this reason, the conventional inorganic molded body shown in FIG. 1 is liable to be deteriorated through the inorganic binder even when an alumina fiber having high corrosion resistance is used, and the alkali gas resistance is lowered. In contrast, the inorganic molded body having a skeleton part and a film-like part obtained by the method of the present invention is watered so that the binder component gathers in the vicinity of the intersection of the alumina fibers and connects the skeleton parts made of alumina fibers. It is thought that the alkali gas resistance can be improved while taking advantage of the characteristics of the alumina fiber having high corrosion resistance because the film-like portion having a shape such as a shape is formed.

  In the method of the present invention, the inorganic molded body having the skeleton portion and the film-like portion can be suitably produced by using colloidal silica as the inorganic binder while using starch as the organic binder as described above. In the process of drying the wet molded product obtained by dehydrating the slurry, the starch swollen in the aqueous solution gathers near the intersection of the alumina fibers by capillary action together with the inorganic binder fixed on the starch. It is considered that a film-like part is formed by the evaporation of moisture from starch and an inorganic binder.

  As a method for evaluating alkali resistance of an inorganic molded body obtained by the method of the present invention, for example, a plate-shaped test piece having a thickness of 25 mm made of the obtained inorganic molded body is formed, and the molar ratio of lithium to cobalt is 1: 1. In a state where the test piece is arranged so as to cover a crucible made of alumina having a diameter of 42 mm and a height of 35 mm containing 10 g of lithium cobaltate, heating at 1100 ° C. for 8 hours is performed as one cycle. When the treatment is repeated for a plurality of cycles, it can be carried out by visually confirming the presence or absence of cracks, peeling or erosion in the test piece.

  According to the method of the present invention, it is possible to obtain an inorganic molded body in which cracks, peeling or erosion are not visually recognized even if the above treatment is repeated twice. An inorganic molded body in which peeling or erosion is not visually recognized is more suitable, and an inorganic molded body in which cracks, separation or erosion is not visually recognized in the test piece even when the above treatment is repeated four or more times is more suitable.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by the following examples.
Example 1
An inorganic molded body according to Example 1 was produced by the method described below.
(1) Slurry preparation process In water, alumina fiber ("B97N5" manufactured by Denki Kagaku Kogyo Co., Ltd., alumina content rate 97 mass%, silica content rate 3 mass%, α-alumina content rate 50-59% in alumina) ) 70 parts by mass, 30 parts by mass of alumina particles (“A11” manufactured by Nippon Light Metal Co., Ltd., having an average particle size of 50 μm), colloidal silica as an inorganic binder (“Silica Doll 30” manufactured by Nippon Kagaku Kogyo Co., Ltd.), 30% by mass % Suspension, solid content average particle size 15 nm, pH 10.0) in terms of solid content, 8 parts by mass, starch (manufactured by Nissho Chemical Co., Ltd., “Petrosize J”) and polymer flocculant 3 parts by mass of a certain polyacrylamide (“Polystron 311” manufactured by Arakawa Chemical Industries, Ltd., cationic, nonvolatile content 10 mass%, pH 4.2 to 4.8, viscosity 500 to 1500 cps) was added. Further, so that the slurry concentration became 2 mass%, the addition of water and stirred to prepare a slurry.
It was 700 mL / 20g when the wet volume of the obtained slurry was measured.

(2) Wet molded body preparation process The slurry obtained as described above was dehydrated and molded by a suction dehydration molding method in which the slurry was poured into a mold having a net installed at the bottom and the solvent was sucked. A wet molded body having a board shape similar to the inorganic molded body was obtained.

(3) Drying step The wet molded body obtained in (2) was dried at 110 ° C. for 36 hours with a dryer, so that the bulk density was 100 kg / m ³ , the alumina content was 89% by mass, and the thickness was 25 mm. A board-shaped inorganic molded body was obtained.

  When the obtained inorganic molded body was measured using a scanning electron microscope with an energy dispersive X-ray analyzer (JED-2300 manufactured by JEOL Ltd.), as shown in FIG. 2, alumina fibers were dispersed in an irregular direction. Having a microstructure composed of a film-like part containing an inorganic binder, formed so as to connect the alumina fibers in the vicinity of the intersection of the alumina fibers and the skeleton formed by It turns out that.

In addition, the obtained inorganic molded body was measured for air permeability resistivity, bending strength, and alkali resistance by the following methods. The results are shown in Table 1.
<Measurement of ventilation resistance>
The ventilation resistivity was measured by a method based on ASTM C522.
<Bending strength>
The bending strength of a flat specimen having a length of 150 mm, a width of 50 mm, and a thickness of 25 mm made of the inorganic molded body was applied at a head speed of 10 mm / min using a three-point bending strength tester, and the breaking load was Measured and calculated by the following formula.
Bending strength (MPa) = {3 × maximum load (N) × distance between lower fulcrums (mm)} / {2 × width (mm) × (thickness (mm)) ² }
Further, the bending strength of the post-fired test piece obtained by firing the test piece at 1300 ° C. for 24 hours was also measured.
<Measurement of alkali resistance>
A flat test piece having a length of 80 mm, a width of 80 mm, and a thickness of 25 mm made of the inorganic molded body was formed.
In a state where the test piece was placed so as to cover a crucible made of alumina having a diameter of 42 mm and a height of 35 mm containing 10 g of lithium cobaltate having a molar ratio of lithium to cobalt of 1: 1, the temperature was 1100 ° C. The above-described treatment was repeated for a plurality of cycles, with the time heating treatment being one cycle, and the presence or absence of cracks, peeling or erosion on the surface of the test piece was visually confirmed.
In this test, every time the heat treatment is performed once, lithium cobalt oxide is replaced with a new one.

(Example 2 to Example 33)
As shown in Tables 1 to 5, the addition amount of each component is changed, or mullite fiber ("Maftech" manufactured by Mitsubishi Plastics, Inc., alumina content ratio 72 mass%, silica content ratio 28 mass%, as alumina fiber, Alumina particles having an α-alumina content of 0 to 59% in the alumina) or alumina particles having different average particle diameters (average particle diameters of 120 μm, 100 μm, 60 μm, 30 μm, 15 μm, 5 μm, and 3 μm, respectively) An inorganic molded body was produced in the same manner as in Example 1 except that the above was used.

  When each obtained inorganic molded body was measured using a scanning electron microscope with an energy dispersive X-ray analyzer (JED-2300, manufactured by JEOL Ltd.), as shown in FIG. In the vicinity of the intersection between the skeletal part formed by dispersion and the alumina fibers, it has a microstructure formed by a film-like part containing an inorganic binder formed so as to connect the alumina fibers. It turned out to be a thing.

  Tables 1 to 5 show the wet volume of the slurry at the time of manufacturing the inorganic molded body in each of the obtained inorganic molded bodies. Moreover, the result of having measured ventilation resistance, bending strength, and alkali resistance with the method similar to Example 1 with the bulk density and alumina content rate in the obtained inorganic molded object in Table 1-Table 5 is shown.

  In addition, about the result of Example 3, while describing in Table 1, also in Table 2, Table 3, and Table 4, the physical property by the difference in colloidal silica addition amount, starch addition amount, and polymer flocculant addition amount, respectively, etc. In order to compare the differences, the same content is repeated. Further, the results of Example 16 are described in Table 3, and the same contents are also described in Table 4 in order to compare differences in physical properties and the like due to differences in the amount of the polymer flocculant added. Further, the results of Example 25 are described in Table 4, and are also repeated in Table 5 in order to compare differences in physical properties and the like due to differences in the average particle diameter of alumina particles.

(Comparative Examples 1 to 7)
As shown in Tables 1 to 5, the addition amount of each component is changed, or mullite fiber ("Maftech" manufactured by Mitsubishi Plastics, Inc., alumina content ratio 72 mass%, silica content ratio 28 mass%, as alumina fiber, Α-alumina content in the alumina is 0 to 59%), silica particles (“fused silica” manufactured by Kinsei Matec Co., Ltd. having an average particle size of 60 μm) are used instead of alumina particles, starch or high A comparative inorganic molded body was produced in the same manner as in Example 1 except that the molecular flocculant was not used.

  Tables 1, 3 and 4 show the wet volume of the slurry at the time of production in each comparative inorganic molded body obtained. Tables 1, 3 and 4 show the results of measuring the air permeability, bending strength and alkali resistance in the same manner as in Example 1 together with the bulk density and alumina content in the obtained comparative inorganic molded bodies. Indicates.

  By comparing Examples 1 to 33 and Comparative Examples 1 to 7, the inorganic molded body obtained by the method of the present invention has a low bulk density and low airflow resistance, and thus diffuses alkali gas therein. Since the film-like part containing an inorganic binder that is easily eroded by alkali gas is formed separately from the skeleton part made of alkaline fibers and contains alumina having alkali resistance, the surface part is eroded by alkali gas. It can be seen that the formation of an inorganic molded body having a sufficient bending strength can be produced inexpensively and easily while the occurrence of peeling and cracks can be suppressed.

  Further, from the results obtained in Examples 1 to 33, the inorganic molded body obtained by the method of the present invention is independent of the skeleton part in which the inorganic binder that is easily eroded by the alkali gas is made of alumina fibers. It can be seen that the formation of the film-like portion reduces the erosion of the alumina fiber by the alkali gas not only on the surface but also on the inside.

  According to the present invention, an inorganic molded body having a sufficiently low heat capacity and thermal conductivity when used as a furnace material and having sufficient strength and high resistance to alkali gas can be produced inexpensively and easily. .

It is a figure which shows the internal structure of the conventional inorganic molded object. It is a figure which shows the internal structure of the inorganic structure obtained by the method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Skeletal part 2 Particulate or whisker-like part 3 Film-like part

Claims (7)

A method for producing an inorganic molded body, comprising:
Alumina fibers and alumina particles are added to the solvent so that the mass ratio of the alumina particles to the total amount of the alumina fibers and alumina particles is 30 to 70% by mass, and the titania sol is removed from the solvent. Adding an inorganic binder, starch as an organic binder, and a polymer flocculant, and mixing and stirring to obtain a slurry having a wet volume of 300 mL / 20 g to 800 mL / 20 g ;
A step of dehydrating or paper-making the slurry to obtain a wet molded body;
And a step of drying the wet molded body.   When the total amount of alumina fibers and alumina particles contained in the slurry is 100 parts by mass, the slurry contains 1 to 8 parts by mass of starch and 0.2 to 4 parts by mass of a polymer flocculant. The manufacturing method of the inorganic molded object of Claim 1. When the total amount of alumina fibers and alumina particles contained in the slurry is 100 parts by mass, the slurry contains 30 to 70 parts by mass of alumina fibers having an alumina content of 80% by mass or more, and alumina. The manufacturing method of the inorganic molded object of Claim 1 or Claim 2 containing 3-15 mass parts of inorganic binder except particle | grains 30-70 mass part and titania sol .   The average particle diameter of the said alumina particle is 5-100 micrometers, The manufacturing method of the inorganic molded object in any one of Claims 1-3. The bulk density of the obtained inorganic molded object is 100-200 kg / m < ³ >, The manufacturing method of the inorganic molded object in any one of Claims 1-4. The manufacturing method of the inorganic molded object in any one of Claims 1-5 whose ventilation resistance by ASTM C522 of the obtained inorganic molded object is 6 * 10 < ⁵ > Pa * S / m < ² > or less.   The manufacturing method of the inorganic molded object in any one of Claims 1-6 whose alumina content rate in the inorganic molded object obtained is 80 mass% or more.

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