JP2021187724A - Method for degreasing molded body and method for manufacturing fired body - Google Patents

Abstract

To prevent a molded body from being damaged when degreased.SOLUTION: A method for degreasing a molded body according to at least one embodiment of this disclosure includes a step of degreasing the molded body at less than 600°C under a superheated steam-containing atmosphere, the molded body: being formed with a mixture of ceramic particles and a resin; and having a resin content of 20 vol.% or more and 50 vol.% or less.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a method for degreasing a molded product and a method for producing a fired product.

A fired ceramic body can be obtained by degreasing and firing a molded body obtained by molding a mixture of ceramic particles and a resin.
For example, Patent Document 1 discloses a method for producing a relatively dense ceramic fired body (see Patent Document 1).

Japanese Patent No. 5689325

As a fired ceramic body, a relatively porous molded body may be required, for example, breathability is required. However, in order to obtain a relatively porous fired body, the resin content is generally relatively high in the molded body obtained by molding a mixture of ceramic particles and a resin. Therefore, since the amount of gas derived from the resin is relatively large during degreasing, there is a risk of damage to the molded product.

At least one embodiment of the present disclosure is intended to suppress damage to the molded product during degreasing in view of the above circumstances.

(1) The method for degreasing a molded product according to at least one embodiment of the present disclosure is as follows.
A step of degreasing a molded product formed of a mixture of ceramic particles and a resin and having a resin content of 20% by volume or more and 50% by volume or less at a temperature of less than 600 ° C. in an atmosphere containing superheated steam.
To prepare for.

(2) The method for manufacturing a molded product according to at least one embodiment of the present disclosure is as follows.
The degreasing step of the method (1) above and
A step of firing the molded product at a temperature of 800 ° C. or higher after degreasing in the degreasing step is provided.

(3) The method for producing a fired body according to at least one embodiment of the present disclosure is as follows.
A step of degreasing a molded body formed of a mixture of ceramic particles and a resin and having a resin content of 20% by volume or more and 50% by volume or less in an atmosphere containing superheated steam.
A step of firing the molded product at a temperature of 800 ° C. or higher after degreasing in the degreasing step is provided.
The relative density of the molded product at the end of the firing step is 40% or more and less than 90%.

According to at least one embodiment of the present disclosure, a relatively porous ceramic molded product can be produced.

It is a figure which shows an example of the whole structure of the processing apparatus configured to be able to carry out the degreasing method of the molded body which concerns on some Embodiments, and the manufacturing method of the molded article which concerns on some Embodiments. This is an example of a flowchart showing a processing procedure when manufacturing a fired body using the processing apparatus shown in FIG. 1. It is a graph which shows the temperature condition in the degreasing step and the firing step which concerns on some embodiments.

Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure to this, and are merely explanatory examples. No.
For example, expressions that represent relative or absolute arrangements such as "in one direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" are exact. Not only does it represent such an arrangement, but it also represents a tolerance or a state of relative displacement at an angle or distance to the extent that the same function can be obtained.
For example, expressions such as "same", "equal", and "homogeneous" that indicate that things are in the same state not only represent exactly the same state, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
For example, the expression representing a shape such as a quadrangular shape or a cylindrical shape not only represents a shape such as a quadrangular shape or a cylindrical shape in a geometrically strict sense, but also an uneven portion or a chamfer within the range where the same effect can be obtained. It shall also represent the shape including the part and the like.
On the other hand, the expressions "equipped", "equipped", "equipped", "included", or "have" one component are not exclusive expressions excluding the existence of other components.

(About processing device 1)
FIG. 1 is a diagram showing an example of an overall configuration of a processing apparatus configured so that a method for degreasing a molded product according to some embodiments and a method for producing a molded product according to some embodiments can be carried out.
The processing device 1 shown in FIG. 1 includes a superheated steam generating device 3, a processing chamber 5, and a control device 7.

In some embodiments, the superheated steam generator 3 comprises a boiler 37 and an atmospheric gas supply unit 39.

In some embodiments, the boiler 37 is for generating superheated steam.
In some embodiments, the atmosphere gas supply unit 39 is for supplying the atmosphere adjusting gas in the processing chamber 5, which will be described later. In some embodiments, the atmospheric gas supply unit 39 is configured to be capable of supplying, for example, nitrogen gas to the treatment chamber 5.

In some embodiments, the treatment chamber 5 is a treatment chamber for degreasing and heat treating (baking) the molded body 10. The treatment chamber 5 includes a heater 51 for heating the molded body 10 arranged inside, an inlet opening 53 for introducing superheated steam and a gas for adjusting the atmosphere into the treatment chamber 5, as described later. It is provided with an exhaust port 55 for discharging superheated steam introduced into the processing chamber 5, gas for adjusting the atmosphere, gas generated in the processing chamber 5, and the like to the outside of the processing chamber 5. A deodorizing device (not shown) for adsorbing the gas generated by degreasing may be provided in the middle of the exhaust pipe 57 connected to the exhaust port 55.
Further, although not shown, a sensor (thermocouple) for measuring the temperature in the vicinity of the molded body 10 arranged inside is arranged in the processing chamber 5.

In some embodiments, the control device 7 is a control device for controlling each part of the processing device 1, and includes, for example, an arithmetic processing unit (CPU) 7a, a storage device (not shown), and the like.

In the processing apparatus 1 shown in FIG. 1, the superheated steam generated in the boiler 37 is supplied into the processing chamber 5 through the inlet opening 53 and discharged to the outside of the processing chamber 5 through the exhaust port 55 and the exhaust pipe 57. Will be done.
Further, in the processing apparatus 1 shown in FIG. 1, the atmosphere adjusting gas (atmosphere adjusting gas) from the atmosphere gas supply unit 39 is supplied into the processing chamber 5 through the inlet opening 53, and is supplied to the exhaust port 55 and the exhaust gas. It is discharged to the outside of the processing chamber 5 via the pipe 57.

(flowchart)
FIG. 2 is an example of a flowchart showing a processing procedure when the molded body 10 is manufactured by using the processing apparatus 1 shown in FIG.
The method for manufacturing a molded product according to some embodiments shown in FIG. 2 includes a slurry making step S10, a molding step S20, a degreasing step S30, and a firing step S40.

(Slurry creation step S10)
The slurry preparation step S10 according to some embodiments is a step of preparing a slurry which is a mixture of ceramic particles and a resin.
In the slurry preparation step S10 according to some embodiments, for example, silica particles are used as the ceramic particles. In the slurry preparation step S10 according to some embodiments, the particle size of the silica particles is, for example, an average diameter of 0.1 μm or more and 100 μm or less.
In the slurry preparation step S10 according to some embodiments, the ceramic particles and the resin are mixed by a general device and method generally used in the production of a ceramic slurry, such as a ball mill mixer or a stirrer.

In the slurry preparation step S10 according to some embodiments, for example, an acrylic resin, that is, a resin containing an acrylic acid ester copolymer or a methacrylic acid ester copolymer is used as the resin as the binder. In the slurry preparation step S10 according to some embodiments, the resin as the binder may be a photocurable resin. For example, as will be described later, when the molded body 10 (green body 10A) is molded from the slurry by irradiating light (for example, ultraviolet rays) in the molding step S20, a photocurable resin is used as the resin as the binder. ..
In the slurry preparation step S10 according to some embodiments, as the resin in the slurry, for example, a resin containing an ester group such as a glycerin fatty acid ester or a cellulose ester may be used in addition to the acrylic resin.

Since the side chain contains a relatively large amount of ester bonds that easily cause hydrolysis, the acrylic resin is more easily hydrolyzed than other types of resins.
Similarly, resins containing ester groups are more susceptible to hydrolysis than other types of resins.
Therefore, according to some embodiments, in the degreasing step S30 described later, the resin in the green body 10A is easily hydrolyzed by superheated steam, so that degreasing is easily performed.

In the slurry preparation step S10 according to some embodiments, the proportion of the acrylic resin in the slurry is 20% by volume or more and 50% by volume or less.
When the molded body 10 is, for example, a core for casting, the proportion of the acrylic resin in the slurry is 20% by volume or more and 40% by volume or less.
Further, when the molded body 10 is, for example, a base tube of SOFC (solid oxide fuel cell), the ratio of the resin (acrylic resin, glycerin fatty acid ester, cellulose ester, etc.) in the slurry is 10% by volume or more and 40 volumes. % Or less.

(Modeling step S20)
The modeling step S20 according to some embodiments is a step of modeling the molded body 10 (green body 10A) from the slurry prepared in the slurry making step S10.
In the molding step S20 according to some embodiments, when the molded body 10 is, for example, a core of a casting, a green body is used, for example, by using a stereolithography apparatus for laminating the photocurable resin while irradiating it with ultraviolet rays or the like to cure it. 10A may be modeled.
Further, in the modeling step S20 according to some embodiments, when the molded body 10 is, for example, a base tube of SOFC (solid oxide fuel cell), the green body 10A is molded by extrusion molding using an extrusion molding machine. You may.

(About the outline of degreasing step S30)
The degreasing step S30 according to some embodiments is a step of degreasing the green body 10A using, for example, the processing device 1 shown in FIG. Details of the degreasing step S30 according to some embodiments will be described in detail later.

(About the outline of firing step S40)
The firing step S40 according to some embodiments is a step of firing the degreased green body 10A using, for example, the processing device 1 shown in FIG. Details of the firing step S40 according to some embodiments will be described in detail later.

(Details of degreasing step S30)
Hereinafter, the details of the degreasing step S30 according to some embodiments will be described.
FIG. 3 is a graph showing the temperature conditions in the degreasing step S30 and the firing step S40 according to some embodiments.
In the degreasing step S30 according to some embodiments, the green body 10A is arranged in the processing chamber 5 of the processing apparatus 1, nitrogen gas is supplied from the atmosphere gas supply unit 39, and the atmosphere in the processing chamber 5 is regarded as a nitrogen gas atmosphere. do. Then, while supplying nitrogen gas from the atmosphere gas supply unit 39, the temperature of the green body 10A, more specifically, until the temperature detected by a sensor (not shown) arranged in the vicinity of the green body 10A reaches 150 ° C. The heater 51 raises the temperature at a heating rate of 75 ° C. per hour. In the following description, for convenience, the temperature detected by the above-mentioned sensor (not shown) is referred to as the temperature of the green body 10A or the temperature of the molded body 10.

In the degreasing step S30 according to some embodiments, when the temperature of the green body 10A reaches 150 ° C., the supply of nitrogen gas from the atmospheric gas supply unit 39 is stopped, and the superheated steam generated by the boiler 37 is stopped. The supply to the inside of the processing chamber 5 is started. The amount of superheated steam supplied is, for example, 5 kg per hour.
After that, in the degreasing step S30 according to some embodiments, the temperature of the green body 10A is raised by 10 ° C. per hour by the heater 51 while supplying superheated steam into the treatment chamber 5 until the temperature of the green body 10A reaches 430 ° C. The temperature rises at a rate.

In the degreasing step S30 according to some embodiments, after the temperature of the green body 10A reaches 430 ° C., the temperature of the green body 10A is maintained at 430 ° C. for 1 hour.
At the end of the degreasing step S30 according to some embodiments, the residual ratio of the resin remaining in the green body 10A (molded body 10) is 5 weights with respect to the weight of the green body 10A (molded body 10). % Or less.

When the green body 10A formed of a mixture of ceramic particles and a resin is degreased, the gas expands when the resin is decomposed and volatilized. Therefore, if the generation of gas is active, the molded body 10 (green body 10A) may be damaged.
For example, in the green body 10A formed of a mixture of ceramic particles and a resin in order to obtain a relatively porous molded body 10, if the resin content is relatively large, the amount of gas derived from the resin generated during degreasing. There is a risk that the molded body 10 (green body 10A) will be damaged during degreasing.
According to some embodiments, degreasing in an atmosphere containing superheated steam can promote hydrolysis of the resin contained in the green body 10A. This promotes the resin to volatilize as a substance having a relatively large molecular weight, so that the amount of gas generated can be suppressed. Further, by degreasing in an atmosphere containing superheated steam, degreasing is promoted by hydrolysis, so that the degreasing time can be shortened as compared with the case of degreasing in an atmosphere containing no superheated steam.

When the resin as the binder is a urethane-based resin or an epoxy-based resin that has been commonly used as a photocurable resin, it is heated to 430 ° C. in the atmosphere as shown by the broken line graph in FIG. In the case of degreasing, it took, for example, about 160 hours.
On the other hand, in some embodiments, as shown by the solid line graph in FIG. 3, it takes about 30 hours to heat up to 430 ° C.

In the degreasing step S30 according to some embodiments, the molded body 10 (green body 10A) is heated at a temperature rising rate of 3 ° C. or higher and 40 ° C. or lower per hour in a temperature range of at least 200 ° C. or higher. It is good to degreas.
As a result of diligent studies by the inventors, it was found that when the temperature rise rate exceeds 40 ° C. per hour when degreasing the green body 10A, gas generation becomes active and the green body 10A may be damaged. did. Further, when the temperature rising rate is lower than 3 ° C. per hour, the time required for degreasing becomes long, so that the productivity decreases.
Therefore, according to some embodiments, it is possible to suppress damage during degreasing while suppressing a decrease in productivity of the molded product 10.

(Details of firing step S40)
Hereinafter, the details of the firing step S40 according to some embodiments will be described.
As described above, in the degreasing step S30 according to some embodiments, the green body 10A is held at 430 ° C. for 1 hour, and then the firing step S40 according to some embodiments is carried out.
In the firing step S40 according to some embodiments, the supply of superheated steam to the treatment chamber 5 is stopped, and the temperature of the green body 10A is raised by 100 ° C. per hour by the heater 51 until the temperature of the green body 10A reaches 800 ° C. The temperature rises at a temperature rate. In the firing step S40 according to some embodiments, nitrogen gas is not supplied from the atmosphere gas supply unit 39.
When the molded body 10 is fired, if it is fired at a temperature of 800 ° C. or lower, the molded body 10 may not be sufficiently sintered and the strength of the molded body 10 may be insufficient.
According to some embodiments, the strength of the molded body 10 after firing, that is, the fired body 11 can be ensured.

In the firing step S40 according to some embodiments, the molded body 10 (green body 10A) may be fired while raising the temperature at a heating rate of 50 ° C. or higher and 400 ° C. or lower per hour.
As a result of diligent studies by the inventors, when the temperature rising rate exceeds 400 ° C. per hour when firing the molded body 10, the temperature difference inside the molded body 10 (green body 10A) causes the molded body 10 (green body 10A). It was found that 10A) may be deformed or cracked. Further, when the temperature rising rate is lower than 50 ° C. per hour, the time required for firing becomes long, so that the productivity decreases.
In some embodiments, as described above, most of the resin is decomposed and volatilized at the end of the degreasing step S30. Therefore, in the firing step S40 according to some embodiments, the rise is relatively high. Even if the temperature is raised at a temperature rate, there is no risk of damage to the molded body 10 (green body 10A).
According to some embodiments, productivity can be ensured while suppressing deformation and cracking of the molded body 10.

In the firing step S40 according to some embodiments, after the temperature of the molded body 10 reaches 800 ° C., the temperature of the molded body 10 is maintained at 800 ° C. for 1 hour. After that, the heating by the heater 51 is stopped, and the molded body 10 is cooled by natural cooling.
The residual ratio of the resin remaining in the fired body 11 obtained by performing the firing step S40 according to some embodiments is 1% by weight or less with respect to the weight of the fired body 11.

In the firing step S40 according to some embodiments, in order to stop the supply of superheated steam into the treatment chamber 5, for example, outside air (oxygen) is introduced into the treatment chamber 5 due to a leak through the exhaust port 55 and the exhaust pipe 57. It mixes inside and the oxygen partial pressure rises. However, in the firing step S40 according to some embodiments, since most of the resin is degreased, there is no problem even if the oxygen partial pressure is high, but rather the degreasing of the remaining resin is promoted and molding is performed. The oxygen partial pressure should be relatively high in order to suppress the formation of oxygen defects in the body 10. In the firing step S40 according to some embodiments, the oxygen partial pressure in the treatment chamber 5 is preferably ^10-3 atm or more, more preferably 0.1 atm or more.

In the fired body 11 obtained by performing the firing step S40 according to some embodiments, the residual ratio of the residual resin is 1% by weight or less with respect to the weight of the fired body 11.
Further, in the fired body 11 obtained by performing the firing step S40 according to some embodiments, the relative density of the fired body 11 is 40% or more and less than 90%. The relative density of the fired body 11 can be obtained, for example, by the so-called Archimedes method.
Therefore, according to some embodiments, the relatively porous fired body 11 can be efficiently manufactured while suppressing damage.

The present disclosure is not limited to the above-described embodiment, and includes a modification of the above-mentioned embodiment and a combination of these embodiments as appropriate.
In some of the above-described embodiments, for example, an acrylic resin or a resin containing an ester group was used as the resin. However, in some embodiments, the resin as the binder is not limited to the above-mentioned type of resin, and may be any resin that can be hydrolyzed by superheated steam.

The contents described in each of the above embodiments are grasped as follows, for example.
(1) The method for degreasing the molded body 10 according to at least one embodiment of the present disclosure is a molded body 10 formed of a mixture of ceramic particles and a resin and having a resin content of 20% by volume or more and 50% by volume or less. The step (solvent degreasing step S30) is provided in which (green body 10A) is degreased at a temperature of less than 600 ° C. in an atmosphere containing superheated steam.

According to the method (1) above, by degreasing in an atmosphere containing superheated steam, hydrolysis of the resin contained in the molded body 10 (green body 10A) can be promoted. This promotes the resin to volatilize as a substance having a relatively large molecular weight, so that the amount of gas generated can be suppressed. Further, by degreasing in an atmosphere containing superheated steam, degreasing is promoted by hydrolysis, so that the degreasing time can be shortened as compared with the case of degreasing in an atmosphere containing no superheated steam.

(2) In some embodiments, in the method (1) above, the resin may contain an acrylic resin.

Since the side chain contains a relatively large amount of ester bonds that easily cause hydrolysis, the acrylic resin is more easily hydrolyzed than other types of resins.
Therefore, according to the method (2) above, the resin in the molded body 10 (green body 10A) is easily hydrolyzed by superheated steam as compared with the case where the other type of resin is used, so that it is easy to degreasing. Become.

(3) In some embodiments, in the method (1) above, the resin may contain a resin containing an ester group.

As mentioned above, ester bonds are prone to hydrolysis. Therefore, the resin containing an ester group is more easily hydrolyzed than other types of resins.
Therefore, according to the method (3) above, the resin in the molded body 10 (green body 10A) is easily hydrolyzed by superheated steam as compared with the case where the other type of resin is used, so that it is easy to degreas. Become.

(4) In some embodiments, in any of the above methods (1) to (3), the step of degreasing (defatting step S30) is a step of degreasing the molded product per hour in a temperature range of at least 200 ° C. or higher. It is preferable to degreasing while raising the temperature at a heating rate of 3 ° C. or higher and 40 ° C. or lower.

As a result of diligent studies by the inventors, when the above-mentioned molded body 10 (green body 10A) is degreased, if the temperature rising rate exceeds 40 ° C. per hour, gas generation becomes active and the molded body may be damaged. It turned out that there is. Further, when the temperature rising rate is lower than 3 ° C. per hour, the time required for degreasing becomes long, so that the productivity decreases.
According to the method (4) above, it is possible to suppress damage during degreasing while suppressing a decrease in productivity of the molded product 10.

(5) In some embodiments, in any of the above methods (1) to (4), the residual ratio of the resin remaining in the molded product 10 at the end of the degreasing step (defatting step S30) is 5. It should be less than% by weight.

If the resin remains on the molded body 10 after degreasing, problems may occur depending on the use of the molded body 10. Therefore, it is preferable that the amount of resin remaining on the molded product 10 after degreasing is small. For example, if the molded body 10 is a core for casting or the like, no particular problem occurs if the residual ratio of the resin remaining in the molded body 10 after degreasing is 5% by weight or less with respect to the weight of the molded body after degreasing. ..
According to the method (5) above, it is possible to suppress defects caused by the resin remaining in the molded product after degreasing.

(6) The method for producing the molded product 10 according to at least one embodiment of the present disclosure includes a degreasing step (defatting step S30) and a degreasing step (defatting step) according to any one of the above (1) to (5). A step (baking step S40) of firing the molded product after degreasing in S30) at a temperature of 800 ° C. or higher is provided.

When firing the molded body at a temperature of 800 ° C. or lower, the molded body 10 may not be sufficiently sintered and the strength of the molded body may be insufficient.
According to the method (6) above, the strength of the molded body 10 (fired body 11) after firing can be secured.

(7) In some embodiments, in the method of (6) above, the step of firing (baking step S40) is to raise the temperature of the molded product 10 at a heating rate of 50 ° C. or higher and 400 ° C. or lower per hour. Bake.

As a result of diligent studies by the inventors, if the temperature rising rate exceeds 400 ° C. per hour when the molded product 10 is fired, the molded product 10 may be deformed or cracked due to the temperature difference inside the molded product 10. It turned out to be. Further, when the temperature rising rate is lower than 50 ° C. per hour, the time required for firing becomes long, so that the productivity decreases.
According to the method (7) above, productivity can be ensured while suppressing deformation and cracking of the molded body 10.

(8) The method for producing a molded product 10 according to at least one embodiment of the present disclosure is a molded product 10 formed of a mixture of ceramic particles and a resin and having a resin content of 20% by volume or more and 50% by volume or less. A step of degreasing (green body 10A) in an atmosphere containing superheated steam (degreasing step S30) and a step of firing the molded product 10 after degreasing in the degreasing step (degreasing step S30) at a temperature of 800 ° C. or higher (degreasing step S30). The firing step S40) is provided. The relative density of the fired body 11 at the end of the firing step (firing step S40) is 40% or more and less than 90%.

According to the method (8) above, by degreasing in an atmosphere containing superheated steam, hydrolysis of the resin contained in the molded product 10 (green body 10A) can be promoted. This promotes the resin to volatilize as a substance having a relatively large molecular weight, so that the amount of gas generated can be suppressed. Further, by degreasing in an atmosphere containing superheated steam, degreasing is promoted by hydrolysis, so that the degreasing time can be shortened as compared with the case of degreasing in an atmosphere containing no superheated steam.
According to the method (8) above, a relatively porous fired body 11 can be efficiently manufactured while suppressing damage.

1 Processing device 3 Superheated steam generator 5 Processing chamber 10 Molded body 10A Green body 11 Fired body

Claims (8)

A step of degreasing a molded product formed of a mixture of ceramic particles and a resin and having a resin content of 20% by volume or more and 50% by volume or less at a temperature of less than 600 ° C. in an atmosphere containing superheated steam.
A method for degreasing a molded product. The method for degreasing a molded product according to claim 1, wherein the resin contains an acrylic resin. The method for degreasing a molded product according to claim 1, wherein the resin contains a resin containing an ester group. The step of degreasing is according to any one of claims 1 to 3, wherein the molded body is degreased while raising the temperature at a heating rate of 3 ° C. or higher and 40 ° C. or lower per hour in a temperature range of at least 200 ° C. or higher. The method for degreasing a molded body according to the description. The method for degreasing a molded product according to any one of claims 1 to 4, wherein the residual ratio of the resin remaining in the molded product at the end of the step of degreasing is 5% by weight or less. The degreasing step according to any one of claims 1 to 5.
A method for producing a fired body, comprising: a step of firing the molded body at a temperature of 800 ° C. or higher after degreasing in the step of degreasing. The method for producing a fired body according to claim 6, wherein the firing step is to fire the molded body while raising the temperature at a heating rate of 50 ° C. or higher and 400 ° C. or lower per hour. A step of degreasing a molded body formed of a mixture of ceramic particles and a resin and having a resin content of 20% by volume or more and 50% by volume or less in an atmosphere containing superheated steam.
A step of firing the molded product at a temperature of 800 ° C. or higher after degreasing in the degreasing step is provided.
A method for producing a fired body, wherein the relative density of the molded body at the end of the firing step is 40% or more and less than 90%.

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