JP2018065727A - Binder for wet molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a binder for wet molding, which can significantly suppress season check of a molded article, without using special and/or expensive apparatus or executing complex treatment.SOLUTION: There is provided a binder for wet molding including water, nano cellulose fiber with a diameter of 1 nm or more and 100 nm or less and a length of 0.1 μm or more and 500 μm or less, and an organic component (excluding the nano cellulose fiber).SELECTED DRAWING: Figure 3

Description

  The present invention relates to a binder for wet molding.

  For example, when a sintered body such as ceramics is manufactured, a forming step, a drying step, and a firing step are often performed sequentially.

  Among these, in the molding step, a molded body is produced from the raw material composition containing the raw material powder and the binder. In the molding step, the method in which the raw material composition contains a liquid and is molded in a wet state is particularly referred to as “wet molding method”. Examples of the “wet molding method” include a cast molding method, a tape molding method, and an extrusion molding method.

  A drying process is implemented in order to dry the molded object produced with such a wet-molding method.

  In this drying process, it is often observed that cracks and cracks occur in the molded body.

  Therefore, various measures have been proposed in order to suppress the occurrence of cracks and cracks in the molded body in the drying process.

  For example, Patent Document 1 describes a method for preventing cracks in a molded body by adjusting the humidity in the environment in the drying process. Patent Document 2 describes a method of using a drying apparatus capable of irradiating the honeycomb formed body with a microwave at a predetermined angle when the honeycomb formed body is dried.

JP-A-7-109166 JP 2011-207113 A

  As described above, various measures have been proposed in order to suppress the occurrence of cracks and cracks in the molded body in the drying step (hereinafter referred to as “dry cracking”).

  However, conventional countermeasures against dry cracking require a special and complicated device, which increases the processing cost and / or makes the process complicated.

  For example, in the method described in Patent Document 1, two stages of drying, a primary drying process and a secondary drying process, in which the temperature and humidity are controlled when a molded body molded by the slip casting method is dried. It is necessary to carry out the process.

  In addition, the method described in Patent Document 2 requires a special drying apparatus that can adjust the microwave irradiation angle in the drying step of the molded body.

  As described above, the conventional measures against dry cracking are still not sufficient, and there is still a demand for a more simple and low-cost drying process that can prevent cracking and cracking of the molded body.

  The present invention has been made in view of such a background, and in the present invention, a special and / or expensive apparatus is used in the drying process, or complicated procedures are not performed. It aims at providing the binder for wet molding which can suppress the dry crack of a molded object significantly.

In the present invention,
A binder for wet molding,
water and,
A nanocellulose fiber having a diameter of 1 nm to 100 nm and a length of 0.1 μm to 500 μm;
An organic component (excluding the nanocellulose fiber);
There is provided a binder containing

  In the present invention, a wet process capable of significantly suppressing dry cracking of a molded body without using a special and / or expensive apparatus or carrying out complicated treatments in the drying process. A molding binder can be provided.

It is the figure which showed typically an example of the microstructure of the molded object produced using the binder by one Embodiment of this invention. 1 is a diagram showing an example of a scanning electron microscope (SEM) image of a nanocellulose fiber used in Example 1. FIG. 2 is a diagram showing an example of a scanning electron microscope (SEM) image of a fracture surface of a molded body in Example 1. FIG.

  First, terms used in the present application will be described.

  In the present application, the “molded body” means one produced by molding a “raw material composition” using various molding methods. In particular, in the present application, a wet molding method is used as the molding method. The wet molding method includes a casting molding method, a tape molding method, an extrusion molding method, and the like.

  Among these, in the casting method, a raw material composition (also referred to as “slurry”) is poured into a mold having a desired shape. When the raw material composition is dried, the solid components in the raw material composition remain on the surface portion inside the mold, and a molded body can be obtained. As the mold, a water-absorbing mold (water-absorbing mold) or a non-water-absorbing mold (non-water-absorbing mold) is used. When the water absorption type is used, the liquid component in the raw material composition is absorbed by the water absorption type. Therefore, in this case, the molded body can be dried relatively quickly.

  On the other hand, in the tape molding method, a raw material composition (also referred to as “slurry”) is usually spread thinly and uniformly on the surface of a horizontal non-water-absorbent sheet. When the raw material composition is dried, a solid component in the raw material composition remains in a tape shape on the sheet surface, and a molded body can be obtained.

  In the extrusion molding method, a raw material composition (also referred to as “paste” or “soil”) is filled into a container having a die having a specific structure. Moreover, the molded object of a predetermined shape can be obtained by extruding this raw material composition from the die.

  In the present application, the “raw material composition” means an object to be processed which is processed by the wet molding method as described above. The “raw material composition” usually contains a raw material powder, a liquid, a binder, and other additives.

  Here, the raw material powder is a powdery substance that is the element of the sintered body.

  The liquid is added in order to perform molding in a wet state in the above-described wet molding method, and is, for example, water and / or an organic solvent.

  The binder is a substance that is added in order to develop the strength of the molded body and maintain a desired shape in the molding process, and has binding properties.

  The other additive is a general term for substances to be added in the molding process in order to impart functions other than the binding property imparted by the above-described binder, such as dispersibility, wettability, and plasticity.

  Hereinafter, an embodiment of the present invention will be described.

In one embodiment of the invention,
A binder for wet molding,
water and,
A nanocellulose fiber having a diameter of 1 nm to 100 nm and a length of 0.1 μm to 500 μm;
An organic component (excluding the nanocellulose fiber);
There is provided a binder containing

  As described above, in the drying process of the molded body, it is often a problem that the molded body is cracked or cracked. Various measures have been proposed to deal with the problem of dry cracking. However, with conventional countermeasures against dry cracking, it is necessary to use a special and / or expensive apparatus or to perform complicated measures in the drying process.

  On the other hand, in one embodiment of the present invention, a binder containing water, nanocellulose fibers, and an organic component is used when preparing a raw material composition for wet molding.

  Here, the nanocellulose fiber has a diameter of 1 nm to 100 nm and a length of 0.1 μm to 500 μm. When a molded body is produced using a binder containing such “fine” nanocellulose fibers, the nanocellulose fibers can be sufficiently dispersed between the particles of the raw material powder (in the gaps). .

  In addition, the nanocellulose fiber has a relatively large aspect ratio (total length / diameter ratio). For this reason, the nanocellulose fiber is easily entangled with the particles, thereby exhibiting an effect of connecting the particles. In other words, the nanocellulose fibers are three-dimensionally dispersed in a molded body in a random orientation, and the raw material powder particles are entangled with these nanocellulose fibers. As a result, “bundling” between particles is strengthened.

  In the present application, the term “diameter” is used to represent the cross-sectional dimension of the nanocellulose fiber. However, this does not necessarily mean that the cross-sectional shape of the nanocellulose fiber is limited to a “circle”. For example, when the cross-sectional shape of the nanocellulose fiber is “ellipse”, the term “diameter” means the dimension of the major axis. In addition, when the cross-sectional shape of the nanocellulose fiber is another shape, the term “diameter” means the maximum dimension.

  In FIG. 1, an example of the microstructure of the molded object produced using the binder by one Embodiment of this invention is typically shown.

  As shown in FIG. 1, the molded body 10 has raw material powder particles 20, and a liquid 30 exists in a gap between these particles. The liquid 30 may include other additives contained in the raw material composition in addition to water and organic components contained in the binder according to an embodiment of the present invention.

  Moreover, the molded object 10 has the nano cellulose fiber 40 contained in the binder by one Embodiment of this invention. The nanocellulose fibers 40 enter the gaps between the particles 20 and are dispersed in the molded body 10 in an entangled state with the particles 20.

  In FIG. 1, in order to clarify the form of the molded body 10 and emphasize the characteristics of the nanocellulose fiber 40, the nanocellulose fiber 40 is not overlapped with the particle 20 (that is, along the outline of the particle 20). It is drawn. However, in actuality, the nanocellulose fibers 40 are three-dimensionally randomly dispersed in the molded body 10, and when viewed from the direction of FIG. 20 and overlap.

  Further, in FIG. 1, the nanocellulose fibers 40 are drawn so as not to overlap each other. In practice, however, some nanocellulose fibers 40 intersect each other when viewed from the direction of FIG.

  In the molded body 10 including such nanocellulose fibers 40, the particles 20 are not easily separated even during drying, and the distance between adjacent particles 20 (that is, the gap between the particles 20) is within a predetermined range. Can be maintained.

  As a result, when a molded body is produced using the raw material composition containing the binder according to one embodiment of the present invention, it becomes possible to significantly suppress or avoid dry cracking of the molded body in the drying step. .

(Binder according to one embodiment of the present invention)
Next, the binder (hereinafter referred to as “first binder”) according to an embodiment of the present invention having the above-described features will be described in more detail.

(First binder)
The first binder has water, nanocellulose fibers dispersed in the water, and other organic components.

  As described above, the conventional method for dealing with dry cracking requires a special and expensive apparatus and / or a complicated drying process.

  However, the first binder includes nanocellulose fibers. Therefore, due to the above-described effect, when a molded body is produced from the raw material composition containing the first binder and dried, the dry cracking of the molded body can be significantly suppressed.

  It should be noted that this does not mean that the application of the conventional drying process is excluded from the molded body containing the first binder. That is, when drying the molded body containing the first binder, in addition to natural drying, various conventional methods such as the two-stage drying process described in Patent Document 1 or the use of a drying apparatus described in Patent Document 2 are used. One skilled in the art will understand that a drying process can also be applied.

  Hereinafter, each component contained in the first binder will be described.

(Nanocellulose fiber)
As described above, the nanocellulose fiber contained in the binder has a diameter in the range of 1 nm to 100 nm and a length in the range of 0.1 μm to 500 μm.

  The diameter of the nanocellulose fiber is preferably in the range of 1 nm to 10 nm, and more preferably in the range of 3 nm to 4 nm. On the other hand, the length of the nanocellulose fiber is preferably in the range of 0.5 μm to 100 μm, and more preferably in the range of 1 μm to 50 μm.

  If the diameter of the nanocellulose fiber is less than 1 nm, it is difficult to improve the strength of the molded article because the strength of the nanocellulose fiber is weak. On the other hand, if the diameter of the nanocellulose fiber is larger than 100 nm, sintering of the raw material powder is hindered by the large voids after the nanocellulose fiber is burned out in the firing step of the molded body.

  In addition, when the total length of the nanocellulose fiber is less than 0.1 μm, the nanocellulose fiber cannot be sufficiently entangled with the raw material powder particles. On the other hand, when the total length of the nanocellulose fiber exceeds 500 μm, the nanocellulose fiber is agglomerated, and in the subsequent firing step of the molded body, the raw powder is sintered by the large voids after the agglomerated nanocellulose fiber is burned out. May be disturbed.

  The nanocellulose fiber may be an aggregate of a plurality of nanocellulose fibers. This aggregate may have a diameter in the range of 1 nm to 100 nm and a length in the range of 0.1 μm to 500 μm. Each nanocellulose fiber constituting the aggregate may have a diameter in the range of 1 nm to 100 nm and a length in the range of 0.1 μm to 500 μm.

  The content of the nanocellulose fiber contained in the first binder is preferably 0.1 parts by weight or more with respect to a total of 100 parts by weight of the solid content of the first binder. In this case, the nanocellulose fiber is densely dispersed in the molded body, and the effect of connecting the particles is further enhanced.

  Note that the appropriate amount of nanocellulose fibers contained in the first binder also varies depending on the molding process of the molded body. For example, in the tape molding method, in order to suppress dripping of the raw material composition, it is necessary to increase the viscosity of the raw material composition, and it is preferable to set the addition amount of the nanocellulose fiber relatively high.

  However, if the amount of nanocellulose fiber added is excessive, the viscosity of the raw material composition becomes too high, and it may be difficult to remove bubbles. Therefore, it is preferable to adjust the addition amount of the nanocellulose fiber in consideration of workability.

  The ratio L / R is preferably in the range of 2 to 100, more preferably in the range of 5 to 50, where L is the total length of the nanocellulose fiber and R is the average particle diameter of the raw material powder. preferable. When the ratio L / R is within this range, the nanocellulose fiber and the particles are more strongly entangled, and the problem of dry cracking can be further reduced.

  Nanocellulose fibers thermally decompose and burn out when heated to about 600 ° C. or higher. Therefore, when the molded body composed of the raw material composition containing the first binder is fired, a firing temperature exceeding 600 ° C. may be selected.

  A sintered body obtained by firing such a molded body is characterized by relatively few defects. This is because the nanocellulose fiber contained in the molded body is fine, and even if the nanocellulose fiber disappears during firing, a large void that inhibits sintering is unlikely to occur.

(Organic component)
Examples of the organic component include polyvinyl alcohol, methyl cellulose, polyvinyl butyral, and / or an emulsion-based substance. Examples of the emulsion substance include acrylic acid alkyl ester, urethane emulsion, acrylic emulsion, vinyl acetate emulsion, and wax.

  The kind and amount of the organic component contained in the first binder are not particularly limited, and these are appropriately selected according to the molding process of the molded body.

  For example, in the tape molding method, the organic component contains at least an emulsion-based substance in order to increase the viscosity of the raw material composition. In the extrusion molding method, the organic component preferably contains at least polyvinyl alcohol and / or methylcellulose in order to further increase the viscosity of the raw material composition.

  The amount of the organic component (solid content) contained in the first binder is approximately in the range of 0.01 to 40 parts by weight.

(Usage of the binder according to one embodiment of the present invention)
Next, an assumed mode of use of the binder according to an embodiment of the present invention (herein referred to as “second binder”) will be described. Here, in particular, a case will be described in which the second binder is used in a molded body produced by the above-described casting method, and this molded body is further fired.

  In this case, first, a nanocellulose fiber and an organic component are added and mixed in water to prepare a second binder. The organic component may include, for example, at least one of alkyl acrylate ester, urethane emulsion, acrylic emulsion, and vinyl acetate emulsion.

  Next, the second binder is mixed with the raw material powder, liquid, and additive to prepare a raw material composition (hereinafter referred to as “second raw material composition”).

  The raw material powder is not particularly limited. The raw material powder may be, for example, ceramics (metal oxide, metal nitride, metal carbide, or composite oxide), metal, alloy, or the like.

  Among these, ceramics include aluminum oxide, magnesium oxide, silicon oxide, calcium oxide, titanium oxide, vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide, copper oxide, zinc oxide, yttrium oxide, zirconium oxide, and oxide. Metal oxides such as niobium, molybdenum oxide, tantalum oxide, tungsten oxide, barium titanate, strontium titanate, aluminum nitride, silicon nitride, boron nitride, titanium nitride, vanadium nitride, chromium nitride, zirconium nitride, niobium nitride, tantalum nitride , Silicon carbide, titanium carbide, vanadium carbide, zirconium carbide, niobium carbide, molybdenum carbide, tantalum carbide, tungsten carbide, mullite, spinel, diopside, cordierite, forsterite, and silica Such as Ron can be exemplified.

  The metals include aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, yttrium, zirconium, niobium, molybdenum, silver, indium, hafnium, tantalum, tungsten, rhenium, Examples include osmium, iridium, platinum, gold, thallium, and lead.

  Furthermore, examples of the alloy include an iron alloy, a copper alloy, an aluminum alloy, and a nickel alloy.

  The raw material powder may be only one kind of material (single powder) or a mixed powder of two or more kinds of materials.

  The average particle diameter R of the raw material powder is not particularly limited. For example, the average particle diameter R of the raw material powder may be in the range of 0.1 μm to 10 μm. As described above, the ratio L / R of the total length L and the average particle diameter R of the nanocellulose fiber is preferably in the range of 2 to 100.

  On the other hand, examples of other additives include a dispersant, a lubricant, and a plasticizer.

  Next, the second raw material composition is poured into a mold having a desired shape. As described above, the mold may be a non-water absorption type or a water absorption type. Thereafter, when the second raw material composition is dried, the solid component in the second raw material composition remains on the surface of the mold, and a molded body can be obtained.

  Here, when the conventional raw material composition is used, the above-mentioned problem of dry cracking may occur. In order to avoid this, a special and expensive apparatus and / or a complicated drying process is required.

  On the other hand, the second binder and further the second raw material composition contain nanocellulose fibers as described above. For this reason, when the 2nd raw material composition dries, generation | occurrence | production of a dry crack is suppressed significantly.

  Next, the dried molded body is removed from the mold. Moreover, this molded object is baked on predetermined conditions.

  As described above, since the decomposition temperature of the nanocellulose fiber is about 600 ° C., the firing is performed at a temperature exceeding this. After firing, the raw material powder can be sintered to obtain a sintered body.

  The nanocellulose fiber contained in the molded body has a fine form. For this reason, even if this nanocellulose fiber disappears during firing, large voids that inhibit sintering are unlikely to occur in the sintered body.

  Therefore, with such a method, a sintered body with few defects can be manufactured.

(Another usage of the binder according to one embodiment of the invention)
Next, an assumed mode of use of the binder according to an embodiment of the present invention (herein referred to as “third binder”) will be described. Here, in particular, a case will be described in which the third binder is used in a molded body produced by the above-described extrusion molding method, and this molded body is further subjected to a firing treatment.

  In this case, first, a nanocellulose fiber and an organic component are added and mixed in water to prepare a third binder. The organic component may include, for example, at least one of polyvinyl alcohol, methyl cellulose, and polyvinyl butyral.

  Next, the third binder is mixed with the raw material powder and the additive to prepare a raw material composition (hereinafter referred to as “third raw material composition”).

  The raw material powder may be selected from the above-described material group, for example. Moreover, an additive may be selected from the above-mentioned material group, for example.

  Next, the third raw material composition is filled into a container having a specific shape. In addition, the raw material composition is extruded from a die having a predetermined structure, whereby a molded body having a desired form can be obtained.

  Next, this molded body is dried.

  Here, when the conventional raw material composition is used, the above-mentioned problem of dry cracking may occur. In order to avoid this, a special and expensive device and / or complicated processing is required.

  In contrast, the third binder and further the third raw material composition contain nanocellulose fibers as described above. For this reason, when the 3rd raw material composition dries, generation | occurrence | production of a dry crack is suppressed significantly.

  Next, the dried molded body is fired under predetermined conditions. As described above, the firing is performed at a temperature exceeding 600 ° C. After firing, the raw material powder can be sintered to obtain a sintered body.

  The nanocellulose fiber contained in the molded body has a fine form. For this reason, even if this nanocellulose fiber disappears during firing, large voids are hardly generated in the sintered body.

  Therefore, with such a method, a sintered body with few defects can be manufactured.

  In the above, the assumed usage aspect of the binder by one Embodiment of this invention was demonstrated.

  However, these are merely examples, and the binder according to one embodiment of the present invention may be used in other ways.

  For example, in the above example, the raw material composition containing the binder according to one embodiment of the present invention was molded into a molded body by a casting molding method or an extrusion molding method.

  However, separately from this, the raw material composition containing the binder according to one embodiment of the present invention may be molded into a molded body using a tape molding method. Also in this case, the same effects as those described above, that is, the effect of suppressing dry cracking and the effect of suppressing defects in the sintered body can be obtained.

  Examples of the present invention will be described below.

Example 1
First, 12.1 parts by weight of water, 0.2 parts by weight of nanocellulose fiber, and 0.2 parts by weight of polyvinyl alcohol (solid content) were mixed to prepare a binder. The nanocellulose fiber (RHEOCRYSTA: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used as the nanocellulose fiber. The nanocellulose fiber has a diameter of 10 nm and a total length of about 10,000 nm.

  In FIG. 2, the scanning electron microscope (SEM) image of the used nano cellulose fiber was shown.

  Next, 12.5 parts by weight of the prepared binder is mixed with 100 parts by weight of alumina powder (center particle size 0.6 μm), 15 parts by weight of water, and 1 part by weight of a water-soluble acrylic acid-based dispersant. A product (slurry) was prepared.

  This slurry was poured into a non-water-absorbing dish-like container and dried by natural drying. When the obtained molded body was observed after drying, it was found that dry cracking did not occur.

  Moreover, the molded body was broken and the fracture surface was observed.

  In FIG. 3, the scanning electron microscope (SEM) image of the fracture surface of a molded object is shown.

  From FIG. 3, it can be seen that nanocellulose fibers are present between particles in a three-dimensional, random orientation. Moreover, it turns out that the nano cellulose fiber is disperse | distributed so that it may get entangled with particle | grains, and it has become the state by which adjacent particles were connected by this.

  Next, this molded body was held in the atmosphere at 1600 ° C. for 2 hours to perform a firing treatment. After firing, a dense sintered body having a relative density of 95% or more was obtained. No cracks were observed in the sintered body.

(Comparative Example 1)
A slurry containing a binder was prepared by the same method as in Example 1 to produce a molded body. In Comparative Example 1, no nanocellulose fiber was added to the binder. That is, 12.1 parts by weight of water and 0.4 parts by weight of polyvinyl alcohol (solid content) were mixed to prepare a binder.

  As a result, dry cracking occurred in the molded body in the drying process of the molded body.

(Example 2)
A slurry containing a binder was prepared by the same method as in Example 1 to produce a molded body. However, in Example 2, a water-absorbing gypsum mold was used as the mold. After the slurry was poured into a water-absorbing gypsum mold, the molded body was obtained by allowing the mold to absorb water. This molded body was placed in a dryer at 70 ° C. and dried.

  Observation of the resulting molded product after drying revealed no dry cracking.

(Comparative Example 2)
A slurry containing a binder was prepared by the same method as in Example 2 to produce a molded body. In Comparative Example 2, no nanocellulose fiber was added to the binder. That is, 12.1 parts by weight of water and 0.4 parts by weight of polyvinyl alcohol (solid content) were mixed to prepare a binder.

  As a result, dry cracking occurred in the molded body in the drying process of the molded body.

(Example 3)
First, 14.2 parts by weight of water, 0.2 parts by weight of nanocellulose fiber, and 5.6 parts by weight of urethane emulsion (solid content) were mixed to prepare a binder. The same nanocellulose fiber as that used in Example 1 was used.

  Next, 20 parts by weight of the prepared binder is mixed with 100 parts by weight of alumina powder (center particle size 0.6 μm), 20 parts by weight of water, and 1 part by weight of a water-soluble acrylic acid-based dispersant. Slurry) was prepared.

  This slurry was thinly drawn on a non-water-absorbent sheet for tape molding. Thereafter, the slurry was dried by natural drying. When the obtained molded body was observed after drying, it was found that dry cracking did not occur.

  Next, this molded body was held in the atmosphere at 1600 ° C. for 2 hours to perform a firing treatment. After firing, a dense sheet-like sintered body having a thickness of 0.5 mm and a relative density of 95% or more was obtained. No cracks were observed in the sintered body.

(Comparative Example 3)
A slurry containing a binder was prepared by the same method as in Example 3 to produce a molded body. In Comparative Example 3, no nanocellulose fiber was added to the binder. That is, 14.2 parts by weight of water and 5.8 parts by weight of a urethane emulsion (solid content) were mixed to prepare a binder.

  As a result, dry cracking occurred in the molded body in the drying process of the molded body.

Example 4
First, 9.8 parts by weight of water, 0.2 part by weight of nanocellulose fiber, and 2 parts by weight of methylcellulose (solid content) were mixed to prepare a binder. The same nanocellulose fiber as that used in Example 1 was used.

  Next, 100 parts by weight of alumina powder (center particle size 0.6 μm) and 17 parts by weight of water were mixed with 12 parts by weight of the prepared binder to prepare a raw material composition (alumina clay).

  This alumina clay was filled into a mold having a base having a diameter of 3 mm at the bottom. Moreover, the alumina clay was extruded from the die using a universal testing machine. As a result, a noodle-shaped shaped body having a diameter of 3 mm was continuously extruded. Thereafter, the molded body was placed in a dryer at 70 ° C. and dried.

  Observation of the resulting molded product after drying revealed no dry cracking.

(Comparative Example 4)
By the same method as in Example 4, an alumina clay containing a binder was prepared, and a molded body was produced. In Comparative Example 4, no nanocellulose fiber was added to the binder. That is, 9.8 parts by weight of water and 2.2 parts by weight of methylcellulose (solid content) were mixed to prepare a binder.

  As a result, dry cracking occurred in the molded body in the drying process of the molded body.

(Example 5)
First, 16.8 parts by weight of water, 0.2 part by weight of nanocellulose fiber, and 9 parts by weight of urethane emulsion (solid content) were mixed to prepare a binder. The same nanocellulose fiber as that used in Example 1 was used.

  Next, to 26 parts by weight of the prepared binder, 90 parts by weight of silicon nitride powder (center particle size 1.1 μm), 5 parts by weight of yttrium oxide powder, 5 parts by weight of alumina powder (center particle size 0.8 μm), water 20 A raw material composition (slurry) was prepared by mixing 1.4 parts by weight of a water-soluble acrylic acid-based dispersant.

  After this slurry was poured into a non-water-absorbing dish-like container, the dish-like container was placed in a dryer at 80 ° C. and dried. When the obtained molded body was observed after the drying step, it was found that no dry cracking occurred.

  Next, this molded body was held at 1800 ° C. for 6 hours in a nitrogen gas atmosphere at a pressure of 0.9 MPa and subjected to a firing treatment. After firing, a dense sintered body having a relative density of 95% or more was obtained. No cracks were observed in the sintered body.

(Comparative Example 5)
A slurry containing a binder was prepared by the same method as in Example 5 to produce a molded body. In Comparative Example 5, no nanocellulose fiber was added to the binder. That is, 16.8 parts by weight of water and 9.2 parts by weight of a urethane emulsion (solid content) were mixed to prepare a binder.

  As a result, dry cracking occurred in the molded body in the drying process of the molded body.

10 Molded body 20 Particles 30 Liquid 40 Nanocellulose fiber

Claims (4)

A binder for wet molding,
water and,
A nanocellulose fiber having a diameter of 1 nm to 100 nm and a length of 0.1 μm to 500 μm;
An organic component (excluding the nanocellulose fiber);
Containing a binder.   2. The binder according to claim 1, wherein the content of the nanocellulose fiber is 0.1 parts by weight or more with respect to 100 parts by weight of the total solid content in the binder.   The binder according to claim 1, wherein the organic component includes at least one of a urethane emulsion and an acrylic emulsion.   The binder according to any one of claims 1 to 3, wherein the organic component includes at least one of polyvinyl alcohol and methylcellulose.