JP4831779B2 - Inorganic substance powder molded body manufacturing method, inorganic substance powder sintered body and manufacturing method thereof - Google Patents

Description

The present invention relates to a method for producing a high-density inorganic substance powder compact, and a low shrinkage inorganic substance powder sintered article obtained by firing (sintering) the inorganic substance powder compact obtained thereby, and It relates to the manufacturing method.

  Inorganic materials such as ceramics are used in various applications including structural materials, electrical / electronic materials and the like because they are superior in mechanical / thermal / electromagnetic properties as compared to metals and plastics. In order to manufacture products / members made of inorganic materials such as ceramics, it is common to heat and densify (sinter) a molded body obtained by molding a raw material powder into a desired shape. .

  In the case of molding powders (inorganic substance powders) of ceramics and metals, it is common practice to add a polymer molding aid such as a binder to these powders in order to improve moldability. For this reason, the inorganic substance powder molded body obtained by molding the inorganic substance powder contains inorganic substance powder, solvent, molding aid (binder) and the like. Here, in order to improve the fluidity of the molding material and maintain the shape of the resulting molded body (enhance the shape retention), the plasticity, fluidity, In addition, good shape retention is required. For example, when manufacturing a honeycomb-shaped formed body used for manufacturing a honeycomb structure such as a catalyst carrier for exhaust gas purification or a diesel particulate filter, the partition wall of the honeycomb structure is thinned (25 to 100 μm). Accordingly, high fluidity of the kneaded clay during extrusion molding and high shape retention of the molded body after extrusion molding are required.

  In order to prepare a dough with good fluidity, various additives such as a solvent, polycarboxylic acid-based, maleic acid-based, polyethylene glycol-based, or acrylic ether copolymer may be added to the raw material powder simultaneously with the binder addition. It is known (see, for example, Patent Document 1). The kneaded clay is produced using a kneader such as a kneader. However, it is difficult to control the fluidity and shape retention of the resulting kneaded clay because there are strong empirical factors regarding the selection and addition amount of additives. is there.

  In recent years, as a technique for improving the fluidity of the kneaded clay and the shape retention of the molded body, wax, oleic acid, and an ethylene / vinyl acetate copolymer are added to the raw material powder without using water as a solvent. An example of producing soil has been reported (for example, see Patent Document 2). However, since it is a system with many organic components, there is an aspect in which the amount of carbon dioxide discharged when heated and degreased after molding increases.

  In addition, the particle filling structure of the dough is composed of secondary particles that are aggregates of primary particles, and by containing 20 to 30 vol% of insoluble substances such as agar and konjac, the dough fluidity and the compact Attempts have been made to improve the shape retention (see, for example, Patent Document 3). However, when aggregates such as secondary particles are present in the molded body, density unevenness is likely to occur, and the strength of the molded body may be reduced due to pores formed due to the aggregates. Moreover, since shrinkage at the time of drying or firing increases, warping or cracking may easily occur in the molded body or sintered body.

  By the way, a molded body made of ceramic powder is produced by, for example, molding a clay obtained by mixing and kneading ceramic powder, a dispersion medium such as water, and an organic binder by a method such as an extrusion molding method. (For example, see Patent Document 4). In addition, a ceramic sintered compact can be obtained by drying and baking the molded object (extruded molded object) obtained by such a method.

  In general, the extrusion method is a method of obtaining an extruded product having a desired cross-sectional shape by kneading the dough in a reduced pressure space to remove the air contained therein and then extruding it through a die. This extrusion molding method is a method suitable for mass production of rod-shaped, hollow, thin plate-shaped, rectangular parallelepiped (block) -shaped, tubular, and honeycomb-shaped molded bodies.

  However, when carrying out extrusion molding, in order to ensure the fluidity of the kneaded clay and the shape retention of the compact, a large amount of organic material such as 10 to 20 parts by mass with respect to 100 parts by mass of the inorganic substance powder such as ceramic powder. It is necessary to add a binder. When a large amount of organic binder is used in this way, (1) the amount of carbon dioxide discharged during degreasing and firing increases, and (2) the sintered body obtained due to thermal stress generated during combustion of the organic binder. Defects such as cracks are likely to occur, and (3) due to uneven density of the molded body due to aggregation of inorganic substance powder contained in the dough, warpage and cracks are likely to occur in the obtained sintered body. It sometimes happened.

JP 2007-137693 A JP 2002-265790 A JP 11-92233 A Japanese Patent No. 3227039

The present invention has been made in view of such problems of the prior art, and the object is to form a high-density inorganic powder that has a uniform thickness and extremely low warpage and distortion. It is providing the manufacturing method of the inorganic substance powder molded object which obtains a body. Another object of the present invention is to provide a low shrinkage inorganic substance sintered body having a uniform thickness and extremely low warpage and distortion, and a method for producing the same.

  As a result of diligent study to achieve the above-mentioned problems, the inventors of the present invention formed a clay obtained by using a slurry containing an inorganic substance powder partially coated with a surface modifier, The present inventors have found that the above problems can be achieved and have completed the present invention.

That is, according to the present invention, a method of manufacturing a indicates to free machine material powder molded body, the inorganic material powder sintered body, and a manufacturing method of an inorganic substance powder sintered body is provided below.

[ 1 ] A preliminary step for calculating in advance a minimum amount of a surface modifier necessary for completely coating the surface of the inorganic substance powder, the inorganic substance powder, and the surface modifier in an amount less than the minimum amount A first step of coating the surface of the inorganic substance powder with the surface modifier at a coverage of 15 to 70%, and following the first step, a molding aid and a solvent are added. obtaining a second step Ru obtain slurry was added, and a third step of obtaining a kneaded soil removing at least a portion of the liquid component from the slurry, the inorganic substance powder molded body by molding the kneaded soil A method for producing an inorganic substance powder compact.

[ 2 ] When the solid phase obtained by centrifuging the mixture containing the inorganic substance powder, the surface modifier, the molding aid, and the solvent is burned, it is caused by disappearance of the molding aid. The manufacturing method of the inorganic substance powder compact | molding | casting as described in said [ 1 ] whose mass decreasing rate to perform is 0.05-0.4 mass%.

[ 3 ] The inorganic substance according to [ 1 ] or [ 2] , wherein the proportion of the molding aid contained in the dough is 0.1 to 20% by mass with respect to 100% by mass of the inorganic substance powder. A method for producing a powder compact.

[ 4 ] An inorganic substance powder sintered body obtained by firing the inorganic substance powder molded body obtained by the method for producing an inorganic substance powder molded body according to any one of [1] to [ 3 ].

[ 5 ] The inorganic substance powder sintered body according to [ 4 ], wherein the proportion of the inorganic substance powder contained in the dough is 50% by volume or more and the shrinkage ratio is 19% or less.

[ 6 ] The inorganic substance powder sintered body according to [ 4 ] or [ 5 ], wherein the proportion of the inorganic substance powder contained in the clay is 50% by volume or more and the relative density is 95% or more. .

[ 7 ] including firing the inorganic substance powder compact obtained by the method for producing an inorganic substance powder compact according to any one of [1] to [ 3 ] to obtain an inorganic substance powder sintered body. Manufacturing method of inorganic substance powder sintered body.

  According to the method for producing an inorganic substance powder molded body of the present invention, it is possible to produce an inorganic substance powder molded body having a uniform thickness and extremely low warpage and distortion and a high density.

  The inorganic powder sintered body of the present invention has the effects that the wall thickness is uniform, warpage and distortion are extremely small, and the shrinkage rate is low.

  According to the method for producing an inorganic substance powder sintered body of the present invention, it is possible to produce an inorganic substance powder sintered body having a uniform wall thickness, extremely low warpage and distortion, and low shrinkage.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below, but the present invention is not limited to the following embodiment, and is based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention. It should be understood that modifications and improvements as appropriate to the following embodiments also fall within the scope of the present invention.

1. Inorganic substance powder compact and manufacturing method thereof:
The inorganic substance powder molded body of the present invention comprises an inorganic substance powder, a surface modifier, a molding aid, and a solvent, and a slurry in which a part of the surface of the inorganic substance powder is coated with the surface modifier. A clay obtained by removing at least a part of the liquid component is formed. The details will be described below.

(Inorganic substance powder)
The inorganic substance powder is a powder made of an inorganic substance and is a raw material powder constituting the inorganic substance powder compact. Examples of inorganic substances include various oxides and non-oxides such as carbides and nitrides. Specific examples of the inorganic substance include alumina, silica, zirconia, zinc oxide, aluminum nitride, boron nitride, silicon carbide, barium titanate, and titanium dioxide. The inorganic substance powder may be a mixed powder of a plurality of types of inorganic substance powders.

(Surface modifier)
The surface modifier is a component that adsorbs or chemically reacts with the surface (particle surface) of the inorganic substance powder, and can coat (or modify) at least a part of the surface of the inorganic substance powder. Specific examples of the surface modifier include polyacrylate, polymethacrylate, polyamide resin, polyethylene resin, polypropylene resin, polyolefin resin, polystyrene resin, alkoxide resin, and the like.

(Molding aid)
The molding aid is a so-called binder that functions to hold the inorganic substance powder in a certain shape, and usually a polymer resin can be used. Specific examples of the molding aid include thermoplastic resins such as methyl cellulose, polyvinyl alcohol, polyvinyl butyl resin, and vinyl acetate resin. Although the kind of shaping | molding adjuvant is not specifically limited, It is preferable to select and use the shaping | molding adjuvant with low affinity with the surface modifier used simultaneously. Thereby, the lubricity of inorganic substance powder can be increased.

  The affinity between the surface modifier and the molding aid can be determined as follows.

  [1] The amount of the surface modifier necessary for completely covering the surface (particle surface) of the inorganic substance powder is determined. Specifically, the slurry before the addition of the molding aid is separated into a solid phase and a liquid phase by centrifugation. At this time, the surface modifier not adsorbed on the particle surface is separated into the liquid phase, and the surface modifier adsorbed on the particle surface is separated into the solid phase. A solid phase (solid phase powder) separated by centrifugation is placed in a thermal analyzer and heated. Thereby, the surface modifier adsorb | sucked to the particle | grain surface lose | disappears, and the mass reduction amount accompanying loss | disappearance is measured. The measured mass loss is proportional to the amount of surface modifier added until the surface modifier completely coats the particle surface. However, when the particle surface is completely coated with the surface modifier, the excessively added surface modifier is not adsorbed on the particle surface but separated into a liquid phase. That is, the maximum value of mass loss measured by thermal analysis corresponds to the amount of surface modifier required to completely coat the particle surface.

  [2] A sample is obtained by adding a predetermined amount of molding aid to the slurry before adding the molding aid, which is obtained in the above [1] and contains the surface modifying agent in an amount necessary to completely coat the particle surface. . The obtained sample is separated into a solid phase and a liquid phase by centrifugation. At this time, the surface modifier and molding aid not adsorbed on the particle surface are separated into a liquid phase, and the surface modifier and molding aid adsorbed on the particle surface are separated into a solid phase. The solid phase powder separated by the centrifugal separation is placed in a thermal analyzer and heated, whereby the surface modifier and the molding aid adsorbed on the particle surface disappear. That is, the mass reduction amount measured at this time corresponds to the amount of the surface modifier and the molding aid adsorbed on the particle surface.

  [3] When the amount of the surface modifier required to completely coat the particle surface obtained in [1] and the mass reduction obtained in [2] are the same, the molding aid is a particle. It is not bridge | crosslinked between, but is isolate | separated into the liquid phase. That is, the surface modifier completely covers the particle surface, so that it can be interpreted that there is no place where the molding aid crosslinks to the particle surface, and the affinity between the surface modifier and the molding aid is low. Can be determined. On the other hand, when the amount of mass reduction determined in [2] is larger than the amount of the surface modifier required to completely coat the particle surface determined in [1], the surface modification is performed. It can be assumed that the molding aid is cross-linked between the surfaces of the agent, and it can be determined that the affinity between the surface modifier and the molding aid is high.

  In the present invention, in accordance with the above method ([1] to [3]), a solid phase obtained by centrifuging a mixture containing an inorganic substance powder, a surface modifier, a molding aid, and a solvent. Is burned, the mass reduction rate due to the disappearance of the molding aid is preferably 0.05 to 0.4% by mass, more preferably 0.08 to 0.38% by mass. . That the mass reduction rate is within the above numerical range means that the affinity between the surface modifier and the molding aid is low. Therefore, it is preferable to use a surface modifier and a molding aid that satisfy the above numerical range because the lubricity of the inorganic substance powder can be further increased.

  The proportion of the molding aid contained in the kneaded clay is preferably 0.1 to 20% by mass, and more preferably 0.2 to 10% by mass with respect to 100% by mass of the inorganic substance powder. When the content of the molding aid is within the above range, the dough exhibits high fluidity while maintaining good shape retention. As a result, warping and distortion are extremely small, and high-density molding is achieved. The body can be manufactured. Moreover, when such a high-density molded body is fired, an inorganic substance powder sintered body having a small shrinkage rate, extremely small warpage and distortion, and a uniform thickness can be produced.

  Molding of a molded body obtained as the shape retention of the kneaded material is reduced when the content of the molding aid contained in the kneaded material is less than 0.1% by mass with respect to 100% by mass of the inorganic substance powder. Tend to decrease. On the other hand, if it exceeds 20% by mass, the density of the molded body tends to decrease, and the density of the sintered body obtained by firing the molded body tends to decrease or the shrinkage rate tends to increase. In addition, the amount of carbon dioxide generated with the removal of the molding aid by firing (combustion) tends to increase.

(solvent)
As the solvent, an aqueous solvent is usually used. Specific examples of the solvent include water such as distilled water, alcohol such as ethanol, acetone, toluene, hexane, and benzene. Two or more of these solvents can be used in combination. However, considering the influence of the waste liquid on the environment, it is particularly preferable to use water.

(slurry)
The slurry is a liquid (slurry) raw material mixture containing an inorganic substance powder, a surface modifier, a molding aid, and a solvent. The ratio of the inorganic substance powder contained in the slurry is usually 1 to 50% by volume with respect to the whole slurry.

(Kneaded clay)
Kneaded clay is a clay-like forming raw material that can be produced by removing at least a part of a liquid component mainly composed of a solvent from a slurry according to a conventional method and kneading using a kneader such as a kneader. The ratio of the inorganic substance powder contained in the dough is usually 20 to 65% by volume with respect to the entire dough.

(Inorganic substance powder compact)
The inorganic powder molded body of the present embodiment can be produced by forming a dough into a desired shape by a molding method such as extrusion using a die, and drying and calcining as necessary. it can. In the case of calcining, the calcining temperature is usually about 500 to 1000 ° C., and the calcining time is usually about 1 to 4 hours.

  Since the slurry for preparing the dough used to form the inorganic substance powder compact contains the inorganic substance powder and the surface modifier, a part of the surface of the inorganic substance powder is surface modified. It is coated with an agent. That is, by covering a part of the surface of the inorganic substance powder with the surface modifier, the surface modifier itself functions as a dispersant in the slurry production stage, so that the dispersibility of the inorganic substance powder is improved. Conceivable. Therefore, the inorganic substance powder contained in the obtained dough becomes difficult to form aggregates, and it is possible to obtain an inorganic substance powder molded body having high density and extremely low warpage and distortion. Furthermore, by firing such an inorganic substance powder compact, it is possible to produce an inorganic substance powder sintered body that has a low shrinkage, extremely small warpage and distortion, and a uniform thickness.

  The surface of the inorganic substance powder to be coated with the surface modifier is a part but not all. That is, it is presumed that the affinity between the molding aid and the (partially coated) inorganic substance powder is controlled by partially coating the surface of the inorganic particle powder with the surface modifier. For this reason, it is considered that the coating part of the inorganic substance powder contributes to the improvement of the fluidity of the dough by the lubrication of the molding aid. On the other hand, the uncovered part of the inorganic substance powder (exposed part) is considered that the molding aid bridges adjacent inorganic substance powders and contributes to maintaining good shape retention of the dough. It is done.

  The coverage of the surface of the inorganic substance powder by the surface modifier is preferably from 5 to 90%, more preferably from 10 to 80%, and more preferably from 15 to 70%, as a percentage of the surface area of the inorganic substance powder. It is particularly preferred. If the coverage is within the above numerical range, the dough will also exhibit high fluidity while maintaining good shape retention, and as a result, warp and distortion are extremely small, producing a high-density molded body. can do. Moreover, when such a high-density molded body is fired, an inorganic substance powder sintered body having a small shrinkage rate, extremely small warpage and distortion, and a uniform thickness can be produced.

  Note that if the coverage is less than 5%, the fluidity of the dough becomes poor, and thus the density of the obtained inorganic substance powder compact tends to be low, and warping or the like tends to occur. On the other hand, if the coverage is more than 90%, the shape retention of the kneaded clay becomes poor, and molding may be difficult.

  As a preliminary step for preparing the slurry, first, an inorganic substance powder, a surface modifier, and a solvent are mixed, and a molding aid containing an inorganic substance powder partially coated with the surface modifier is added. It is preferable to prepare a pre-slurry and then add the molding aid to the prepared slurry before the addition of the molding aid to obtain a slurry. As described above, before adding the molding aid, the inorganic material powder is previously brought into contact with the surface modifier, and a part of the surface of the inorganic material powder is coated with the surface modifier, so that the clay can be removed. Furthermore, higher fluidity is exhibited while maintaining good shape retention. In addition, the inorganic substance powder contained in the obtained dough becomes more difficult to form aggregates, and it becomes possible to produce an inorganic substance powder molded body having a higher density and extremely low warpage and distortion. In addition, there is no restriction | limiting in particular about the method of reducing a liquid component from a slurry, For example, methods, such as vacuum pressure reduction, evaporation in the air, a filter press, can be mentioned.

  The kneaded material used for producing the inorganic substance powder molded body of the present embodiment has high fluidity while maintaining shape retention, so that the inorganic substance powder easily flows during molding and is in a stable state. Inorganic powders are easily arranged. For this reason, the inorganic substance powder molded body of this embodiment has a relative density of usually 54% or more, preferably 55% or more when the proportion of the inorganic substance powder contained in the dough is 50% by volume or more. is there.

2. Inorganic substance powder sintered body and manufacturing method thereof:
The inorganic powder sintered body of the present invention is obtained by firing the above-mentioned inorganic powder compact. For this reason, the inorganic substance powder sintered body of the present invention has a small shrinkage rate, extremely small warpage and distortion, and a uniform thickness.

  As described above, the inorganic substance powder compact used for producing the inorganic substance powder sintered body of the present embodiment was produced using a dough having high fluidity while maintaining shape retention. Is. For this reason, in the inorganic substance powder molded body, the inorganic substance powder easily flows during molding, and the inorganic substance powder is arranged in a stable state. Therefore, the inorganic powder sintered body of the present embodiment has a very low shrinkage because the shrinkage that occurs during the sintering is mostly due to grain growth (sintering). Therefore, when the proportion of the inorganic substance powder contained in the dough is 50% by volume or more, the shrinkage rate of the inorganic substance powder molded body of the present embodiment is usually 20% or less, preferably 19% or less. is there.

  Moreover, even if the surface of the inorganic substance powder is partially covered with the surface modifier, the relative density of the obtained inorganic substance powder sintered body is not significantly affected. This is an inorganic substance powder molded body used for producing the inorganic substance powder sintered body of the present embodiment was produced using a kneaded material having high fluidity while maintaining shape retention. It is presumed that there is. Therefore, the inorganic material powder sintered body of the present embodiment has a sufficiently high relative density. Specifically, when the proportion of the inorganic substance powder contained in the dough is 50% by volume or more, the relative density is usually 95% or more, preferably 97% or more.

  In addition, when manufacturing the inorganic substance powder sintered compact of this embodiment, the calcination temperature is about 1400-1600 degreeC normally. The firing time is usually about 1 to 5 hours.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

Example 1
Alumina powder having an average particle diameter of 570 nm, distilled water, and polyacrylic acid ammonium salt (PAA) were mixed to obtain a slurry before addition of a molding aid. In addition, the alumina concentration of the slurry before forming auxiliary agent addition was 15 volume% with respect to the whole slurry before forming auxiliary agent addition. Moreover, the PAA content ratio of the slurry before the molding aid was added was 0.12% by mass with respect to the alumina powder. A methylcellulose aqueous solution was added and mixed to the obtained slurry before the addition of the molding aid to obtain a slurry. In addition, the methylcellulose content rate of the slurry was 2 mass% with respect to the alumina powder. Moreover, the alumina concentration of the slurry was 10% by volume with respect to the whole slurry.

  While removing a part of liquid component from the obtained slurry, it was molded into a cylindrical shape having an outer diameter of 10 mm and a wall thickness of 2 mm using a vacuum kneader to obtain a kneaded clay as a primary molded body. The alumina concentration of the obtained dough was 49.1-54.3 volume%. The dough was dried at room temperature for 24 hours, then placed in an electric furnace, heated to 800 ° C. at a heating rate of 100 ° C./hour, calcined at 800 ° C. for 2 hours, and then cooled at a rate of 100 ° C./hour. The molded body was obtained by cooling to room temperature over time.

  The obtained molded body was again put in an electric furnace, heated to 1550 ° C. at a heating rate of 100 ° C./hour, then fired at 1550 ° C. for 2 hours, and then cooled to room temperature at a cooling rate of 100 ° C./hour. Thus, a sintered body was obtained.

(Comparative Example 1)
A molded body and a sintered body were obtained by the same method as in Example 1 except that PAA was not added during the preparation of the slurry before the addition of the molding aid.

(Comparative Example 2)
In preparing the slurry before the addition of the molding aid, the dough was prepared by the same method as in Example 1 except that the PAA content in the slurry before the addition of the molding aid was 0.4% by mass with respect to the alumina powder. Was made. Although it tried to shape | mold the produced kneading degree using a vacuum kneader similarly to Example 1, a kneaded material was not able to be extruded from a cylindrical die with an outer diameter of φ10 mm and a wall thickness of 2 mm. And a sintered body could not be obtained.

[Measurement of coverage]:
The slurry before the addition of the molding aid was separated into a solid phase and a liquid phase by centrifugation. The PAA not adsorbed on the surface of the alumina powder is separated into the liquid phase, and the PAA adsorbed on the surface of the alumina powder is separated into the solid phase. The separated solid phase (powder) is placed in a thermal analyzer and heated to eliminate PAA adsorbed on the surface of the alumina powder, and coated from the mass loss (PAA adsorption rate) that accompanies the disappearance of PAA The rate was measured and calculated. Table 1 shows the measured and calculated coverage. FIG. 1 is a graph showing the adsorption ratio of PAA.

  As shown in FIG. 1, in Comparative Example 2, although the PAA content was 0.4% by mass, the PAA adsorption rate measured by a thermal analyzer was 0.2% by mass. That is, if the content ratio of PAA is 0.2% by mass or more with respect to the alumina powder, it is estimated that the surface of the alumina powder is entirely covered with PAA and the coverage is 100%. On the other hand, in Example 1, the adsorption ratio of PAA measured by a thermal analyzer was 0.12% by mass. From the above, in Example 1, Comparative Example 1, and Comparative Example 2, the surface coverage of the alumina powder by PAA was calculated to be 60%, 0%, and 100%, respectively, as shown in Table 1. can do.

[Measurement of adsorption ratio of methylcellulose (molding aid)]:
The slurry obtained in Example 1, Comparative Example 1 and Comparative Example 2 was separated into a solid phase and a liquid phase by centrifugation. Note that PAA and methylcellulose not adsorbed on the surface of the alumina powder are separated into a liquid phase, and PAA and methylcellulose adsorbed on the surface of the alumina powder are separated into a solid phase. The separated solid phase (powder) was placed in a thermal analyzer and heated, and the PAA and methylcellulose adsorbed on the surface of the alumina powder were eliminated, and the mass loss accompanying the disappearance of PAA and methylcellulose was measured. The ratio (adsorption ratio) in which methyl cellulose is cross-linked between adjacent alumina powders is the amount of mass decrease due to the disappearance of PAA obtained from the loss of PAA and methyl cellulose due to the disappearance of PAA. It can be obtained by reducing. The results are shown in Table 1 and FIG.

  As shown in Table 1 and FIG. 2, the proportion (crosslinking rate) of methylcellulose as a molding aid adsorbed to the alumina powder is 0.43 mass% in Comparative Example 1, whereas in Example 1, It was 0.21 mass%. This can be presumed to be because, in Example 1, PAA partially covered the surface of the alumina powder, so that the portion where methylcellulose adsorbs to the surface of the alumina powder decreased. In Comparative Example 2, it is clear that methylcellulose is not adsorbed on the alumina powder (the alumina powder is not cross-linked). It can be presumed that this is because there is no portion where methylcellulose is adsorbed on the surface of the alumina powder because the coverage by PAA is 100%. From the above results, it can be seen that the affinity between PAA and methylcellulose is low.

[Appearance of inorganic substance powder compact]:
FIG. 3 is a photograph showing a state in which the molded bodies produced in Example 1 and Comparative Example 1 are viewed from the side. FIG. 4 is a photograph showing a state where the molded bodies produced in Example 1 and Comparative Example 1 are viewed obliquely from above. As shown in FIGS. 3 and 4, the shape of the molded body manufactured in Example 1 is straight and no defects such as warpage and distortion are observed, whereas the molded body manufactured in Comparative Example 1 is warped. It is clear that distortion is observed.

[Relative density of inorganic substance powder compact]:
Measured by Archimedes method. More specifically, after measuring the dry mass (W _g ), the produced molded body was immersed in water. The air contained in the molded body was removed by reducing the pressure for 30 minutes under vacuum, and the mass of the molded body in water (W _i ) and the wet mass (W _d ) were measured. From the measured dry mass (W _g ), underwater mass (W _i ), and wet mass (W _d ), and the density of water at the water temperature at the time of measurement (D _w ), the density of the molded body is expressed by the following formula (1). Calculated. Further, as represented by the following formula (2), the relative density was calculated by dividing the calculated density by the true density. The results are shown in Table 2 and FIG.
Density (g / cm ³ ) = W _g × D _w / (W _d −W _i ) (1)
Relative density (%) = (density / true density) × 100 (2)

  As shown in Table 2 and FIG. 5, in Example 1, when the alumina concentration of the kneaded clay was 50% by volume or more, the relative density of the obtained molded body was 55% or more. Moreover, when the clay with an alumina concentration of 53.3% by volume was used, the relative density of the compact reached 56.9%. On the other hand, in Comparative Example 1, even when the alumina concentration of the kneaded clay was 53.3% by volume, the relative density of the obtained molded body was only 53.7%. This is presumably because the dough used in Comparative Example 1 has poor fluidity, and the alumina powder behaved in an aggregated state during molding, so that the alumina powder was not arranged in a stable state.

[Appearance of inorganic powder sintered body]:
FIG. 6 is a photograph showing a state in which the sintered bodies produced in Example 1 and Comparative Example 1 are viewed from the side. As shown in FIG. 6, the shape of the sintered body produced in Example 1 is straight and no defects such as warpage and distortion are observed, whereas the sintered body produced in Comparative Example 1 has warpage and distortion. It is clear that distortion is observed.

  7A to 7C are photographs showing cut surfaces of the sintered body produced in Example 1, and FIGS. 8A to 8C are photographs showing cut surfaces of the sintered body produced in Comparative Example 1. FIG. The “water content” in the figure is the content ratio of water contained in the dough. As shown in FIGS. 7A to 7C, the thickness (wall thickness) of the sintered body produced in Example 1 was uniform regardless of the moisture content of the used clay. On the other hand, as shown in FIGS. 8A to 8C, the thickness (wall thickness) of the sintered body produced in Comparative Example 1 does not depend on the moisture content of the used clay and is not uniform. there were. This is presumed to be because the alumina powder was not arranged in a stable state because the fluidity of the dough was poor and the alumina powder behaved in an aggregated state during molding.

[Relative density of inorganic powder sintered body]:
Measured by Archimedes method. More specifically, after measuring the dry mass (W _g ), the manufactured sintered body was immersed in water. The air contained in the sintered body was removed under reduced pressure under vacuum for 30 minutes, and the mass of the sintered body in water (W _i ) and the wet mass (W _d ) were measured. From the measured dry mass (W _g ), underwater mass (W _i ), and wet mass (W _d ), and the density of water at the water temperature at the time of measurement (D _w ), the density of the sintered body according to the following formula (3) Was calculated. Further, as represented by the following formula (4), the relative density was calculated by dividing the calculated density by the true density. The results are shown in Table 2 and FIG.
Density (g / cm ³ ) = W _g × D _w / (W _d −W _i ) (3)
Relative density (%) = (density / true density) × 100 (4)

  As shown in Table 2 and FIG. 9, in Example 1, when the alumina concentration of the kneaded clay was 50% by volume or more, the relative density of the obtained sintered body was 95% or more. This is because the fluidity of the alumina powder was improved by coating the surface with PAA having a low affinity with methylcellulose, and thus the clay showed high fluidity while maintaining its shape retention. It is presumed that the alumina powder easily flows during molding, and the alumina powder was arranged in a stable state. Also in Comparative Example 1, when the alumina concentration of the kneaded clay was 50% by volume or more, the relative density of the obtained sintered body was 95% or more. This is presumed to be due to the fact that the alumina powder was baked and hardened with sintering by sintering, while the fluidity of the dough was poor. From the above results, it was found that a sufficiently high density sintered body can be produced even when the surface of the alumina powder is partially coated with PAA.

[Shrinkage ratio of sintered powder of inorganic substance]
It calculated according to the following formula (5) from the outer diameter (mm) of the sintered body and the diameter φ (10 mm) of the die used at the time of extrusion molding. The results are shown in Table 2 and FIG.
Shrinkage rate (%) = {(diameter of base (mm) −outer shape of sintered body (mm)) / diameter of base (mm)} × 100 (5)

  As shown in Table 2 and FIG. 9, in Example 1, when the alumina concentration of the kneaded clay was 50% by volume or more, the shrinkage ratio of the obtained sintered body was 19% or less. This is because the dough has good shape retention and fluidity, so the alumina powder is arranged in a stable state, density unevenness is reduced, and shrinkage that occurs during sintering is accompanied by sintering (grain growth) Is presumed to be due to the majority. On the other hand, in Comparative Example 1, it is clear that the shrinkage rate is 20% or more when the alumina concentration of the kneaded clay is 50% by volume or more. This is because the fluidity of the kneaded clay used in Comparative Example 1 was poor, and the alumina powder behaved in the state of aggregates during molding, which caused shrinkage to fill the pores of the aggregates during sintering. It is estimated that.

  The inorganic substance powder sintered body of the present invention has a uniform thickness, extremely small warpage and distortion, and a low shrinkage, and is suitable as a thin-walled member or a honeycomb structure.

It is a graph which shows the adsorption | suction ratio of PAA. It is a graph which shows the adsorption | suction ratio of methylcellulose. It is a photograph which shows the state which looked at the molded object manufactured in Example 1 and Comparative Example 1 from the side. It is a photograph which shows the state which looked at the molded object manufactured in Example 1 and Comparative Example 1 from diagonally upward. It is the graph which plotted the relative density of the molded object with respect to the alumina density | concentration of kneaded clay. It is a photograph which shows the state which looked at the molded object manufactured in Example 1 and Comparative Example 1 from the side. 2 is a photograph showing a cut surface of the sintered body produced in Example 1. FIG. 2 is a photograph showing a cut surface of the sintered body produced in Example 1. FIG. 2 is a photograph showing a cut surface of the sintered body produced in Example 1. FIG. 4 is a photograph showing a cut surface of a sintered body produced in Comparative Example 1. 4 is a photograph showing a cut surface of a sintered body produced in Comparative Example 1. 4 is a photograph showing a cut surface of a sintered body produced in Comparative Example 1. It is the graph which plotted the relative density of the sintered compact with respect to the alumina density | concentration of kneaded clay. It is the graph which plotted the shrinkage | contraction rate of the sintered compact with respect to the alumina density | concentration of kneaded clay.

Claims (7)

A preliminary step of calculating in advance the minimum amount of surface modifier required to completely cover the surface of the inorganic substance powder ;
First, the surface of the inorganic substance powder is coated with the surface modifier at a coverage of 15 to 70% by mixing the inorganic substance powder and the surface modifier in an amount less than the minimum amount. Process,
Following the first step, a second step Ru obtain a slurry by adding a molding aid and a solvent,
A third step of obtaining a dough by removing at least part of the liquid component from the slurry ;
A fourth step of obtaining the inorganic substance powder compact by molding the kneaded clay , and a method for producing the inorganic substance powder compact. When the solid phase obtained by centrifuging the mixture containing the inorganic substance powder, the surface modifier, the molding aid, and the solvent is burned,
The method for producing an inorganic substance powder molded body according to claim 1 , wherein a mass reduction rate due to disappearance of the molding aid is 0.05 to 0.4 mass%. The method for producing an inorganic substance powder molded body according to claim 1 or 2 , wherein the proportion of the molding aid contained in the kneaded clay is 0.1 to 20 mass% with respect to 100 mass% of the inorganic substance powder. . The inorganic substance powder sintered compact obtained by baking the said inorganic substance powder molded object obtained by the manufacturing method of the inorganic substance powder molded object as described in any one of Claims 1-3 . The inorganic substance powder sintered body according to claim 4 , wherein the proportion of the inorganic substance powder contained in the kneaded clay is 50% by volume or more and the shrinkage ratio is 19% or less. The inorganic substance powder sintered body according to claim 4 or 5 , wherein a ratio of the inorganic substance powder contained in the clay is 50% by volume or more and a relative density thereof is 95% or more. An inorganic substance powder firing comprising firing the inorganic substance powder compact obtained by the method for producing an inorganic substance powder compact according to any one of claims 1 to 3 to obtain an inorganic substance powder sintered body. A method for producing a knot.