JP6721892B2 - Raw material composition for wet molding - Google Patents

Description

The present invention relates to a binder for wet molding.

When producing a sintered body such as ceramics, a molding step, a drying step, and a firing step are often sequentially performed.

Among them, in the molding step, a molded body is produced from the raw material composition containing the raw material powder and the binder. In addition, in the molding step, a method in which the raw material composition contains a liquid and is molded in a wet state is particularly referred to as a “wet molding method”. The “wet molding method” includes, for example, a casting molding method, a tape molding method, and an extrusion molding method.

The drying step is carried out to dry the molded body produced by such a wet molding method.

It has been observed that cracks and cracks often occur in the molded body during this drying step.

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

For example, Patent Document 1 describes a method of preventing cracks in a molded body by adjusting humidity in the environment in a drying process. Further, Patent Document 2 describes a method of using a drying device capable of irradiating the honeycomb molded body with microwaves at a predetermined angle when the honeycomb molded 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 or cracks in the molded body in the drying step (hereinafter referred to as "dry cracking").

However, the conventional measures against dry cracks have a problem that a special and complicated device is required, resulting in an increase in processing cost and/or a complicated process.

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

Further, the method described in Patent Document 2 requires a special drying device capable of adjusting the microwave irradiation angle in the step of drying the molded body.

As described above, the conventional measures against dry cracking cannot be said to be sufficient, and there is still a demand for a simpler and lower-cost drying process capable of preventing cracks and cracks in the molded body.

The present invention has been made in view of such a background, and in the present invention, in the drying step, without using a special and/or expensive apparatus, or performing a complicated procedure, An object of the present invention is to provide a binder for wet molding which can significantly suppress dry cracking of a molded body.

In the present invention, a raw material composition for wet molding,
The raw material composition includes a raw material powder and a binder,
The raw material powder contains two different types of ceramic powder,
The binder is
water and,
A nanocellulose fiber having a diameter of 1 nm to 10 nm and a length of 0.1 μm to 10 μm,
An organic component (excluding the nanocellulose fiber),
Containing
A raw material composition is provided in which the ratio L/R is in the range of 2 to 100, where L is the total length of the nanocellulose fiber and R is the average particle diameter of the raw material powder .

In the present invention, in the drying step, it is possible to significantly suppress the dry cracking of the molded body without using a special and/or expensive apparatus or performing a complicated procedure. A binder for molding can be provided.

FIG. 3 is a diagram schematically showing an example of a microstructure of a molded body produced using the binder according to the embodiment of the present invention. FIG. 3 is a diagram showing an example of a scanning electron microscope (SEM) image of the nanocellulose fiber used in Example 1. FIG. 3 is a diagram showing an example of a scanning electron microscope (SEM) image of a fractured surface of a molded body in Example 1.

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

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

Among them, in the cast molding method, the 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 component in the raw material composition remains on the surface portion inside the mold, and a molded body can be obtained. As the mold, a water absorbing mold (water absorbing type) or a non-water absorbing mold (non-water absorbing type) 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, the raw material composition (also referred to as “slurry”) is usually spread on the surface of a horizontal non-water-absorbent sheet in a thin and uniform state. When the raw material composition is dried, the solid component in the raw material composition remains in a tape form on the surface of the sheet, and a molded body can be obtained.

Further, in the extrusion molding method, a raw material composition (also referred to as “paste” or “kneaded clay”) is filled in a container having a die having a specific structure. Moreover, a molded product having a predetermined shape can be obtained by extruding the raw material composition from the die.

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

Here, the raw material powder is a powdery substance that is the basis of the above-mentioned sintered body.

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

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

The other additive is a general term for substances added in the molding step for imparting functions other than the binding property imparted by the binder, such as dispersibility, wettability, and plasticity.

An embodiment of the present invention will be described below.

In one embodiment of the invention,
A binder for wet molding,
water and,
A nanocellulose fiber having 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,
An organic component (excluding the nanocellulose fiber),
There is provided a binder containing

As described above, it often becomes a problem that cracks or cracks are generated in the molded body in the drying step of the molded body. In addition, various measures have been proposed to deal with the problem of dry cracking. However, in the conventional measures against dry cracking, it is necessary to use a special and/or expensive device or perform a complicated procedure 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 or more and 100 nm or less and a length of 0.1 μm or more and 500 μm or less. When a molded body is produced using a binder containing such "fine" nanocellulose fibers, the nanocellulose fibers can be sufficiently dispersed between (gap) of the particles of the raw material powder. ..

Further, the nanocellulose fiber has a relatively large aspect ratio (ratio of total length/diameter). For this reason, the nanocellulose fiber is easily entangled with the particles, thereby exerting the effect of holding the particles together. In other words, the nanocellulose fibers are three-dimensionally dispersed in the molded body in a random orientation, and the particles of the raw material powder are entangled with these nanocellulose fibers. As a result, the "cohesion" between the particles is strengthened.

In the present application, the term “diameter” is used when expressing the dimension of the cross section 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 "elliptical", the term "diameter" means the dimension of the major axis. In addition, when the cross-sectional shape of the nanocellulose fiber is any other shape, the term “diameter” means the maximum dimension.

FIG. 1 schematically shows an example of a microstructure of a molded body produced by using the binder according to the embodiment of the present invention.

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

Further, the molded body 10 has the nanocellulose fiber 40 included in the binder according to the embodiment of the present invention. The nanocellulose fiber 40 has entered the gaps between the particles 20, and is dispersed in the molded body 10 in a state of being entangled with the particles 20.

Note that in FIG. 1, in order to clarify the morphology of the molded body 10 and to emphasize the characteristics of the nanocellulose fiber 40, the nanocellulose fiber 40 does not overlap with the particles 20 (that is, along the contour of the particles 20). It is drawn. However, in reality, the nanocellulose fibers 40 are three-dimensionally randomly dispersed in the molded body 10, and when viewed from the direction of FIG. Overlapping with 20.

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

In the molded body 10 including the nanocellulose fiber 40 as described above, the particles 20 are unlikely to come apart during drying, and the distance between adjacent particles 20 (that is, the gap between the particles 20) falls within a predetermined range. Can be maintained.

As a result, when a raw material composition containing a binder according to an embodiment of the present invention is used to produce a molded body, it is 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 according to one embodiment of the present invention (hereinafter, referred to as “first binder”) having the above-described characteristics 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 methods for dealing with dry cracks require special and expensive equipment and/or a complicated drying process.

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

It should be noted that this does not mean that the conventional drying process is not applied to the molded body containing the first binder. That is, when the molded body containing the first binder is dried, in addition to natural drying, a conventional two-step drying process described in Patent Document 1 or the use of the drying device described in Patent Document 2 is used. The person skilled in the art will of course understand that it is also possible to apply a drying process.

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

(Nanocellulose fiber)
As mentioned 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, 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, more preferably in the range of 1 μm to 50 μm.

When the diameter of the nanocellulose fiber is less than 1 nm, the strength of the nanocellulose fiber is weak and it is difficult to improve the strength of the molded body. Further, if the diameter of the nanocellulose fiber is larger than 100 nm, the sintering of the raw material powder is hindered by the large voids after the nanocellulose fiber is burnt in the firing step of the molded body.

If the total length of the nanocellulose fiber is less than 0.1 μm, the nanocellulose fiber cannot be sufficiently entangled with the particles of the raw material powder. On the other hand, when the total length of the nanocellulose fibers exceeds 500 μm, the nanocellulose fibers are aggregated, and in the subsequent firing step of the molded body, the raw powder is sintered due to the large voids after the aggregated nanocellulose fibers are burned. May be disturbed.

The nanocellulose fiber may be an aggregate of a plurality of nanocellulose fibers. 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. Each nanocellulose fiber forming 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 based on 100 parts by weight of the total solid content of the first binder. In this case, the nanocellulose fibers are densely dispersed in the molded body, and the effect of holding the particles together is further enhanced.

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

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

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

The nanocellulose fiber is thermally decomposed and burned when heated to about 600° C. or higher. Therefore, when firing the molded body composed of the raw material composition containing the first binder, a firing temperature exceeding 600° C. may be selected.

The sintered body obtained by firing such a molded body is characterized by relatively few defects. This is because the nanocellulose fibers contained in the molded body are fine, and even if the nanocellulose fibers disappear during firing, large voids that hinder sintering are unlikely to occur.

(Organic component)
Examples of the organic component include polyvinyl alcohol, methyl cellulose, polyvinyl butyral, and/or emulsion-based substances. Examples of emulsion-based substances include alkyl acrylates, urethane-based emulsions, acrylic-based emulsions, vinyl acetate-based emulsions, and waxes.

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

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. Further, in the extrusion molding method, the organic component preferably contains at least polyvinyl alcohol and/or methyl cellulose 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 0.01 to 40 parts by weight.

(Aspects of using the binder according to one embodiment of the present invention)
Next, a possible usage mode of the binder according to the embodiment of the present invention (herein referred to as “second binder”) will be described. In addition, here, in particular, the case where the second binder is used for the molded body produced by the above-described casting molding method and the molded body is subjected to the firing treatment will be described.

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

Next, the second binder is mixed with the raw material powder, the liquid, and the 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 them, 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 oxides. Metal oxides such as niobium, molybdenum oxide, tantalum oxide, tungsten oxide, barium titanate and 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 sialon.

Further, as the metal, 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.

Further, examples of the alloy include iron alloy, copper alloy, aluminum alloy, nickel alloy and the like.

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 size R of the raw material powder is not particularly limited. For example, the average particle size R of the raw material powder may be in the range of 0.1 μm to 10 μm. In addition, as described above, the ratio L/R of the total length L of the nanocellulose fiber and the average particle diameter R 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 absorbing type or a water absorbing type. Then, 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 device and/or a complicated drying process are required.

On the other hand, the second binder and further the second raw material composition contain the nanocellulose fiber as described above. Therefore, when the second raw material composition is dried, the occurrence of dry cracks is significantly suppressed.

Next, the dried molded body is removed from the mold. Further, this molded body is fired under predetermined conditions.

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

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

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

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

In this case, first, 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-mentioned material group, for example. Further, the additive may be selected from the above-mentioned material group, for example.

Next, the third raw material composition is filled in a container having a specific shape. Further, the raw material composition is extruded from a die having a predetermined structure, whereby a molded product having a desired shape 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 are required.

On the other hand, the third binder and further the third raw material composition contain the nanocellulose fiber as described above. Therefore, when the third raw material composition is dried, the occurrence of dry cracks is significantly suppressed.

Next, the dried molded body is fired under predetermined conditions. As mentioned above, the firing is carried out at temperatures above 600°C. After firing, the raw material powder is sintered to obtain a sintered body.

The nanocellulose fiber contained in the molded body has a fine morphology. Therefore, even if the nanocellulose fiber disappears during firing, large voids are unlikely to occur in the sintered body.

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

The possible usage of the binder according to the embodiment of the present invention has been described above.

However, these are merely examples and the binder according to one embodiment of the 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 cast 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. In this case as well, it is possible to obtain 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.

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. As the nanocellulose fiber, the nanocellulose fiber in (RHEOCRYSTA: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used. This nanocellulose fiber has a diameter of 10 nm and a total length of about 10,000 nm.

FIG. 2 shows a scanning electron microscope (SEM) image of the used nanocellulose fiber.

Next, 12.5 parts by weight of the prepared binder was 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 to prepare a raw material composition. The thing (slurry) was prepared.

The slurry was poured into a non-water absorbent dish-shaped container and dried by natural drying. After drying, the obtained molded body was observed, and it was found that no dry cracking occurred.

In addition, the molded body was cracked and the fracture surface was observed.

FIG. 3 shows a scanning electron microscope (SEM) image of the fractured surface of the molded body.

From FIG. 3, it can be seen that the nanocellulose fibers exist in a three-dimensional, random orientation between the particles. Further, it can be seen that the nanocellulose fiber is dispersed so as to be entangled with the particles, whereby the adjacent particles are connected to each other.

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 found in the sintered body.

(Comparative Example 1)
A slurry containing a binder was prepared in the same manner as in Example 1 to prepare a molded body. In this 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 in the same manner as in Example 1 to prepare 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-absorbent gypsum mold, the mold was made to absorb water to obtain a molded body. This molded body was placed in a dryer at 70° C. and dried.

When the obtained molded product was observed after drying, no dry cracks were observed.

(Comparative example 2)
A slurry containing a binder was prepared in the same manner as in Example 2 to prepare a molded body. In addition, in this Comparative Example 2, nanocellulose fiber was not 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 in Example 1 was used.

Next, 20 parts by weight of the prepared binder was 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 to prepare a raw material composition ( Slurry) was prepared.

The slurry was thinly spread on a non-water absorbent sheet for tape molding. Then, the slurry was dried by natural drying. After drying, the obtained molded body was observed and found to have no dry cracks.

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 found in the sintered body.

(Comparative example 3)
A slurry containing a binder was prepared in the same manner as in Example 3 to prepare a molded body. In addition, in this Comparative Example 3, the nanocellulose fiber was not added to the binder. That is, 14.2 parts by weight of water and 5.8 parts by weight of 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 parts 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 in Example 1 was used.

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

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

When the obtained molded product was observed after drying, no dry cracks were observed.

(Comparative Example 4)
By the same method as in Example 4, an alumina kneaded material containing a binder was prepared and a molded body was produced. In addition, in this 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 methyl cellulose (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 parts 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 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), and water 20 By weight, 1.4 parts by weight of a water-soluble acrylic acid-based dispersant were mixed to prepare a raw material composition (slurry).

After injecting this slurry into a non-water-absorbing dish-shaped container, the dish-shaped container was placed in a dryer at 80° C. for drying. After observing the obtained molded body after the drying step, it was found that no dry cracks occurred.

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

(Comparative example 5)
A slurry containing a binder was prepared in the same manner as in Example 5 to prepare a molded body. In addition, in this Comparative Example 5, nanocellulose fiber was not 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 raw material composition for wet molding, comprising:
The raw material composition includes a raw material powder and a binder,
The raw material powder contains two different types of ceramic powder,
The binder is
water and,
A nanocellulose fiber having a diameter of 1 nm to 10 nm and a length of 0.1 μm to 10 μm,
An organic component (excluding the nanocellulose fiber),
Containing
A raw material composition in which the ratio L/R is in the range of 2 to 100, where L is the total length of the nanocellulose fiber and R is the average particle diameter of the raw material powder . The raw material composition according to claim 1, wherein the content of the nanocellulose fiber is 0.1 parts by weight or more based on 100 parts by weight of the total solid content in the binder. The raw material composition according to claim 1, wherein the organic component contains at least one of a urethane emulsion and an acrylic emulsion. The raw material composition according to claim 1, wherein the organic component includes at least one of polyvinyl alcohol and methyl cellulose.