JP6740942B2 - Molded body manufacturing method, porous sintered body manufacturing method - Google Patents

Description

The present invention is directed to a method for producing a molded body which is cured by irradiating a molding slurry containing an inorganic raw material powder, an ultraviolet curable resin and a solvent with ultraviolet rays, and a porous calcination for firing the molded body obtained by the manufacturing method. The present invention relates to a method for producing a bound body.

The ceramic product is obtained, for example, by drying and curing a mixture containing ceramic powder, a curable resin, and a solvent to obtain a molded body, and then firing the molded body. Since the resin component disappears during firing, a ceramic product made of, for example, a porous sintered body can be obtained. Further, the metal product can be similarly produced by using, for example, a mixture containing a metal powder, a curable resin, and a solvent.

For example, Patent Document 1 proposes a method of obtaining a molded product by using a thermosetting resin such as urethane resin or epoxy resin as the curable resin. In the method for producing a molded body using a thermosetting resin, curing by a polymerization reaction such as urethane reaction and epoxy reaction is used.

However, polymerization and curing using a thermosetting resin requires a long curing time of several minutes to several hours. Therefore, improvement is desired from the viewpoint of productivity. On the other hand, there is an attempt to use an ultraviolet curable resin as the curable resin, and Patent Document 1 also discloses a curing method by light.

The ultraviolet curable resin is composed of a liquid monomer such as acrylate and an initiator. By irradiating the ultraviolet curable resin with ultraviolet rays, the initiator instantly turns into a radical, and the radical reacts with a liquid monomer to initiate a polymerization reaction to polymerize and cure. Therefore, high-speed curing on the order of several seconds is possible.

JP, 2007-136912, A

However, when a mixture containing an inorganic raw material powder such as ceramic powder or metal powder is irradiated with ultraviolet rays, ultraviolet rays are reflected and scattered on the surface of the inorganic raw material powder. Therefore, the curing occurs near the irradiation surface where the ultraviolet rays reach, but the ultraviolet rays do not reach the inside sufficiently and the curing becomes insufficient. This is because the curing of the ultraviolet curable resin occurs at high speed due to the generation of radicals within the range where the ultraviolet rays reach. As a result, there is a problem that a molded body having a desired thickness cannot be obtained and a sintered body having a large thickness cannot be manufactured.

Further, by reducing the particle size of the inorganic raw material powder such as ceramic powder or metal powder, it is possible to suppress the reflection of ultraviolet rays and increase the penetration depth of ultraviolet rays. It is also considered that the ultraviolet curing depth is improved by reducing the particle size of the ultraviolet curable resin in the mixture. However, in this case, the pore characteristics and the like of the porous sintered body obtained after firing change from those desired. That is, there is a problem in that design changes are forced and desired products cannot be obtained.

Due to the above problems, the method for producing a molded body and a sintered body of an inorganic raw material powder using an ultraviolet curable resin has not been actually realized.

The present invention has been made in view of such problems, there is no need to change the design, it is possible to manufacture a product having good productivity and a large thickness, and a method for manufacturing a porous sintered body. Is to provide.

According to one aspect of the present invention, ultraviolet rays (4) are applied to a molding slurry (3) containing an inorganic raw material powder (31), an ultraviolet curable resin (32) and a solvent (33) in a molding die (2). In the method for producing a molded body (1) in which the molding slurry is cured by irradiation,
The ultraviolet curable resin contains a radically polymerizable polymerizable material (321) and a polymerization initiator (322),
The molding slurry is in a method for producing a molded body, which contains 900 parts by mass or less of the solvent with respect to 100 parts by mass of the ultraviolet curable resin.

Another aspect of the present invention is a method for producing a porous sintered body, in which the molded body obtained by the above production method is fired.

In the method for producing a molded body, ultraviolet rays are applied to a molding slurry containing an inorganic raw material powder such as ceramic powder or metal powder, an ultraviolet curable resin and a solvent. That is, the forming slurry containing the predetermined amount of the solvent is irradiated with ultraviolet rays. Therefore, the ultraviolet transmission depth is improved, and the ultraviolet rays reach the inside from the irradiation surface sufficiently. As a result, the inside of the molded body can be sufficiently cured. Therefore, it is possible to avoid the design change of the molded body produced by the ultraviolet irradiation. That is, for example, the thickness from the irradiation surface of ultraviolet rays can be increased, and a molded body having a large thickness and volume can be manufactured.

Further, when the molding slurry containing the solvent is irradiated with ultraviolet rays, the radicals generated by the irradiation of ultraviolet rays have a long life and diffuse in the solvent. Therefore, even if ultraviolet rays are reflected and scattered on the surface of the inorganic raw material powder, the generated radicals diffuse to the inside. Therefore, even if the ultraviolet rays do not reach directly, the curing reaction occurs even inside the molding slurry. As a result, the inside of the molded body can be sufficiently cured. Therefore, it is possible to avoid the design change of the molded body produced by the irradiation of the ultraviolet rays, and for example, it becomes possible to manufacture a molded body having a large thickness and volume.

Further, as described above, since the radicals in the solvent can be cured to the inside, it is not necessary to reduce the particle size of the inorganic raw material powder in order to suppress reflection or scattering on the surface of the inorganic raw material powder. .. From this point of view, it is possible to obtain a desired molded body without changing the design of the molded body.

Further, the ultraviolet curable resin can be cured in a short time by irradiation with ultraviolet rays. Therefore, a molded product can be manufactured with high productivity.

Further, a porous sintered body can be obtained by firing the molded body obtained by the above manufacturing method. As described above, since the molded body can be cured without reducing the particle size of the inorganic raw material powder, it is possible to obtain a porous sintered body having desired characteristics without changing the pore characteristics. That is, the desired porous sintered body can be obtained without the need for design changes.

As described above, according to the above aspect, it is possible to provide a method for manufacturing a molded body and a method for manufacturing a porous sintered body, which enables production of a product with good productivity and a large thickness without the need for design change. it can.
The reference numerals in parentheses described in the claims and the means for solving the problems indicate the corresponding relationship with the specific means described in the embodiments described later, and limit the technical scope of the present invention. Not a thing.

(A) Partial cross-sectional view of a molding slurry irradiated with ultraviolet rays, (b) Partial cross-sectional view of a molded body after curing, and (c) Part of a porous sintered body after sintering in Embodiment 1. Sectional view. FIG. 3 is a diagram showing an ultraviolet wavelength range in which the transmittance of a typical solvent is 100% and a wavelength range in which the transmittance is 50% or more and less than 100% in the first embodiment. FIG. 3A is an image diagram in which ultraviolet rays permeate the inside of the forming slurry, and FIG. 3B is an image diagram in which radicals diffuse in the forming slurry in the first embodiment. FIG. 3 is a diagram showing a process in which water radicalizes and reacts with a monomer in the first embodiment. FIG. 3 is an explanatory view showing a step of irradiating ultraviolet rays while applying vibration to the molding slurry in the first embodiment. FIG. 3A is a partial cross-sectional view of a dried body irradiated with ultraviolet rays and a partial cross-sectional view of a molded body after curing in Comparative Example 1. FIG. Explanatory drawing which shows the measuring apparatus of the ultraviolet penetration depth in Experimental example 1. Explanatory drawing which shows the relationship between the solvent fraction of a shaping|molding slurry and ultraviolet penetration depth in Experimental example 1. FIG. 6 is an explanatory diagram showing the relationship between bond dissociation energy and radical diffusion depth in Experimental Example 2. FIG. 6 is a side view of the gas sensor element according to the second embodiment. XI-XI line arrow sectional drawing. FIG. 6 is an explanatory view showing a series of steps for forming a molded body, which will become a porous protective layer after firing, on a gas sensor element in the second embodiment.

(Embodiment 1)
An embodiment relating to a method for manufacturing a molded body and a porous sintered body will be described with reference to FIGS. 1 to 5. In the following description, ultraviolet rays will be appropriately referred to as “UV”.

As illustrated in FIG. 1A, first, a molding slurry 3 containing an inorganic raw material powder 31, a UV curable resin 32, and a solvent 33 is prepared. Then, the molding slurry 3 is irradiated with UV4 in the molding die to fabricate the molding 1 illustrated in FIG. 1B. Next, the molded body 1 is dried and fired to produce the porous sintered body 5 illustrated in FIG. 1(c).

The molding slurry 3 is obtained by mixing at least the inorganic raw material powder 31, the UV curable resin 32, and the solvent 33.

The inorganic raw material powder 31 is not particularly limited, and various ceramic powders, metal powders and the like can be used. Alumina such as α-alumina and θ-alumina can be used as the ceramic powder. In addition, fine ceramics such as zirconia, silicon carbide and aluminum nitride, ceramics, refractories, cement, glass and the like can be used. As the metal powder, for example, iron, copper, aluminum, cobalt, nickel, phosphorus or the like can be used.

The UV curable resin 32 contains a polymerizable raw material 321 and a polymerization initiator 322. The polymerizable raw material 321 is a monomer, an oligomer or the like. The polymerizable raw material may be radically polymerizable or cationically polymerizable, but in order to obtain the above radical diffusion effect, it is preferably radically polymerizable.

The material of the UV curable resin 32 is not particularly limited, and examples thereof include (meth)acrylate-based and unsaturated polyester-based materials. A (meth)acrylate type is preferable from the viewpoint of excellent curability. The (meth)acrylate may be monofunctional or polyfunctional. Further, it may be an acrylate monomer which is a polymerizable monomer, or a polymerizable oligomer such as urethane acrylate, polyester acrylate, epoxy acrylate, and acrylic acrylate. The (meth)acrylate is a concept including both acrylate and methacrylate. It is also possible to use a cationically polymerizable epoxy-based UV curable resin 32.

Next, the curing reaction in the case where the UV curable resin 32 contains the radically polymerizable polymerizable raw material 321 and the polymerization initiator 322 will be described. As illustrated in FIG. 1A, when the molding slurry 3 is irradiated with UV4, the polymerization initiator 322 is radicalized. The "radicalized polymerization initiator" is hereinafter appropriately referred to as "initiator radical". Then, the initiator radical 322 causes the polymerization reaction of the polymerizable raw material 321 composed of a monomer, an oligomer, etc. to proceed and cure. Thus, as illustrated in FIG. 1B, the molded body 1 containing the cured product 11 of the UV curable resin and the inorganic raw material powder 31 is obtained.

As the polymerization initiator 322, a compound that is converted into a radical by UV irradiation is used. As the polymerization initiator 322, a generally available one can be used. Various UV curable resins that are commercially available as a composition containing the polymerizable raw material 321 and the polymerization initiator 322 can be used, and the polymerizable raw material 321 and the polymerization initiator 322 are used in an arbitrary combination. You can also

As the solvent 33, one having a high UV transmittance is preferable, and specifically, a solvent having a higher UV transmittance than the UV curable resin is preferable. UV transmittances of representative solvents are shown in FIG. The UV transmittance can be known from literature values and the like. When the UV transmittance of the solvent 33 is higher than that of the UV curable resin, for example, UV 4 can penetrate from the UV irradiation surface 300 to the inside, as illustrated in FIG. 3A. Therefore, the molding slurry can be hardened from the irradiation surface 300 to the inside. Note that, in FIGS. 3A and 3B, the inorganic raw material powder in the molding slurry is omitted for convenience of description.

The wavelength of UV4 with which the molding slurry 3 is irradiated is determined according to the type of the polymerization initiator 322, for example. Specifically, the UV wavelength can be determined according to the wavelength required for activation of the polymerization initiator 322. Therefore, the solvent 33 having a high transmittance in the UV wavelength range necessary for activation of the polymerization initiator 322 can be selected based on the type of the polymerization initiator 322. Activation of the polymerization initiator 322 means radicalization in the case of radical polymerization.

For example, UV in the wavelength range of 250 to 350 nm is necessary for radicalization of "IRGACURE 1173" manufactured by BASF, which is a polymerization initiator 322 used in Experimental Example 1 described later. It can be seen that as the solvent 33 having a high transmittance in this wavelength range, water, hexane, methanol, ethanol and the like are preferable among those exemplified in FIG. This is because these solvents 33 have a 100% UV transmittance in the wavelength range of 250 to 350 nm required for radicalization of the polymerization initiator 322. Therefore, the combination of the solvent 33 and the polymerization initiator 322 is determined so that the wavelength region required for radicalization of the polymerization initiator 322 and the wavelength region in which the UV transmittance of the solvent 33 is 100% overlap. Preferably.

Further, the solvent 33 preferably has good compatibility with the UV curable resin 32. The compatibility can be determined from the viewpoint that the UV curable resin 32 and the solvent 33 do not separate when mixed. The compatibility can be determined to be good when there is no separation visually.

For example, in the radicalization of "IRGACURE 1173", which is a polymerization initiator 322 manufactured by BASF, used in Experimental Example 1 described later, from the viewpoint of UV transmittance, as described above, water, hexane, methanol, ethanol, etc. Is preferred. Among these, water, methanol, and ethanol have good compatibility with “polyethylene glycol #600 diacrylate” manufactured by Shin Nakamura Chemical Co., Ltd., which is the acrylate-based UV curable resin 32 used in Experimental Example 1. As a result, the effect of improving the ultraviolet penetration depth and the effect of prolonging the life of radicals become more remarkable. On the other hand, hexane has poor compatibility. Therefore, in the case of the acrylate-based UV curable resin 32, it is preferable to use at least one of water and alcohol as the solvent 33. The alcohol is preferably a lower alcohol having 6 or less carbon atoms.

As the solvent 33, it is preferable to use a solvent having a bond dissociation energy higher than that of the polymerizable raw material 321 of the UV curable resin 32. In this case, the life of radicals can be extended in the solvent 33. Therefore, for example, the initiator radicals 322 can exist longer in the solvent 33, and the initiator radicals 322 can diffuse more inward from the irradiation surface 300, as illustrated in FIG. 3B. .. That is, since the diffusion depth of radicals can be improved, it is possible to cure the UV irradiation surface 300 to the inside. The bond dissociation energy of each substance can be known from literature values and the like.

As the solvent 33, it is preferable to use one having a bond dissociation energy of 300 kJ/mol or more. In this case, the diffusion depth of radicals can be further improved. From the viewpoint of further increasing the diffusion depth, the bond dissociation energy of the solvent is more preferably 400 kJ/mol or more, further preferably 450 kJ/mol or more.

The solvent 33 preferably contains at least water. In this case, the molding slurry 3 can be cured further from the irradiation surface 300 to the inside. There are three possible reasons for this. The first reason is that water has a wide wavelength range in which the UV transmittance is 100% as illustrated in FIG. 2 and can sufficiently transmit UV in the UV wavelength range. The second reason is that the bond dissociation energy of water is as high as 497 kJ/mol, and the initiator radicals can have a longer life and can be diffused. The third reason is that, as illustrated in FIG. 4, a water molecule reacts with an initiator radical to generate a hydroxy radical, the hydroxy radical is stabilized and diffused in a solvent, and a polymerizable raw material such as a monomer is generated. Because it can react with.

The content of the solvent 33 in the molding slurry 3 is preferably 900 parts by mass or less based on 100 parts by mass of the ultraviolet curable resin. If the amount of solvent exceeds 900 parts by mass, the molding slurry may not be cured.

When the content of the solvent per 100 parts by mass of the ultraviolet curable resin exceeds 0 parts by mass, the curing depth is increased as compared with the case where the content of the solvent is 0 due to the effect of improving the penetration depth of ultraviolet rays and the effect of radical diffusion. Can be improved. From the viewpoint of reliably obtaining the effect of adding the solvent, the content of the solvent is preferably 10 parts by mass or more with respect to 100 parts by mass of the ultraviolet curable resin. Further, from the viewpoint of further enhancing the effect of improving the UV penetration depth, the content of the solvent relative to 100 parts by mass of the ultraviolet curable resin is preferably 50 parts by mass or more, and more preferably 100 parts by mass or more. ..

The amount of the inorganic raw material powder 31 in the molding slurry 3 can be adjusted arbitrarily. From the viewpoint of improving the dispersibility in the molding slurry 3, the content of the inorganic raw material powder 31 in the molding slurry is preferably 70% by mass or less, more preferably 50% by mass or less, It is more preferably 30% by mass or less.

The molding slurry 3 can be hardened in the molding die 2 such as a mold. The mold 2 is preferably capable of transmitting UV4. The mold 2 is preferably made of quartz glass or sapphire from the viewpoint that the transmittance of UV4 is high and the molding slurry 3 is easily cured. The cavity of the mold 2 can be formed in any shape. Therefore, the molded body 1 having an arbitrary shape can be manufactured.

As the light source used for UV irradiation, for example, a mercury xenon lamp, a pressure mercury lamp, a constant pressure mercury lamp, a light emitting diode (that is, an LED), or the like can be used. The light source is not limited to these and can be used regardless of the type.

Irradiation of the molding slurry 3 with UV4 may be from one direction, but is preferably from multiple directions. In this case, since ultraviolet rays are transmitted from each irradiation surface 300, even the molded body 1 having a larger volume can be cured to the inside. For example, in the bottomed square tube-shaped mold 2, UV4 can be irradiated from four side surfaces and the lower surface.

During UV irradiation, it is preferable to apply vibration to the molding slurry 3. In this case, since the molding slurry 3 can be made to flow, the diffusion of radicals can be further promoted. Therefore, the molding slurry 3 can be hardened further to the inside.

As illustrated in FIG. 5, vibration to the molding slurry 3 can be applied by the vibration generator 7. The vibration can be applied by ultrasonic waves, for example. In this case, for example, an ultrasonic oscillator can be used as the vibration generator 7. Although the vibration is applied from one direction in the example of FIG. 5, it may be applied from multiple directions. In applying the vibration, the molding die 2 may be vibrated or the molding slurry 3 may be vibrated directly.

After obtaining the molded body 1 illustrated in FIG. 1B, the molded body 1 can be dried and fired, for example. The firing temperature is determined, for example, according to the sintering temperature of the inorganic raw material powder 31. By the firing, the inorganic raw material powder 31 is sintered and the cured product 11 of the UV curable resin disappears. As a result, as illustrated in FIG. 1C, the porous sintered body 5 having a large number of pores 52 inside can be obtained.

When the inorganic raw material powder 31 is a ceramic powder, it is possible to obtain the porous sintered body 5 made of porous ceramics after firing the molded body 1. When the inorganic raw material powder 31 is a metal powder, the porous sintered body 5 made of a porous metal can be obtained after firing the molded body 1.

In the present embodiment, as illustrated in FIGS. 1A and 1B, the molding slurry 3 is cured by irradiation with UV4. Therefore, high speed curing becomes possible. For example, it can be cured at a sufficiently high speed as compared with the case of using a thermosetting resin. Therefore, the productivity of the molded body 1 and the porous sintered body 5 is improved.

As illustrated in FIG. 1A, in the present embodiment, the forming slurry 3 containing the solvent 33 is irradiated with UV4. Therefore, as illustrated in FIG. 1A and FIG. 3A, the UV transmission depth is improved. That is, UV4 sufficiently reaches from the irradiation surface 300 to the inside.

As a result, the inside of the molded body 1 can be sufficiently cured as illustrated in FIG. Therefore, it is possible to avoid a design change of the molded body 1 produced by UV irradiation. That is, for example, the thickness from the UV4 irradiation surface 300 can be increased, and the molded body 1 having a large thickness and volume can be manufactured.

Further, as illustrated in FIG. 3B, the initiator radical 322 generated by the irradiation of UV4 has a long life in the solvent and diffuses. When the solvent 33 is water, it is considered that not only the initiator radicals 322 but also hydroxyl radicals are generated and the hydroxyl radicals have a long life and diffuse in the solvent 33, as illustrated in FIG. 4.

Therefore, even if UV is reflected and scattered on the surface of the inorganic raw material powder 31, the generated radicals 322 diffuse to the inside. Therefore, even if UV4 does not reach directly, the curing reaction occurs inside the molding slurry 3. As a result, the inside of the molded body 1 can be sufficiently cured.

In addition, as described above, since the radicals in the solvent 33 can be cured to the inside as well, it is necessary to reduce the particle size of the inorganic raw material powder 31 in order to suppress reflection and scattering on the surface of the inorganic raw material powder. Nor. From this point of view, the desired molded body 1 can be obtained without the need to change the design of the molded body 1.

Further, the porous sintered body 5 can be obtained by firing the molded body 1 obtained by the above manufacturing method. As described above, the molded body 1 can be hardened without reducing the particle diameter of the inorganic raw material powder 31, so that the porous sintered body 5 having desired characteristics can be obtained without changing the pore characteristics. .. That is, the desired porous sintered body 5 can be obtained without the need for design changes.

As described above, according to the above aspect, there is provided a method for producing the molded body 1 and a method for producing the porous sintered body 5, which enable production of a product having good productivity and a large thickness, without requiring a design change. be able to. In addition, among the reference numerals used in each of the embodiments after the present embodiment, the same reference numerals as those used in the above-mentioned embodiments represent the same components and the like as those in the above-mentioned embodiments, unless otherwise specified.

(Comparative form 1)
In this embodiment, the molding slurry is dried and then cured to produce a molded body. Specifically, first, similarly to Embodiment 1, a molding slurry containing an inorganic raw material powder, a UV curable resin, and a solvent is prepared.

The molding slurry is then dried and the solvent evaporated. As a result, the dried body 90 is obtained as illustrated in FIG. The dried body 90 has the inorganic raw material powder 31 and the UV curable resin 32, and contains substantially no solvent.

Next, as illustrated in FIG. 6A, the dried body 90 is irradiated with UV4 to cure the UV curable resin 32. Thereby, the molded body 9 can be obtained as illustrated in FIG.

When the dried body 90 obtained by drying the molding slurry is irradiated with UV4 as in this embodiment, UV4 is reflected and scattered on the surface of the inorganic raw material powder 31 as illustrated in FIG. 6A. Therefore, the UV transmission depth is significantly reduced. As a result, as illustrated in FIGS. 6A and 6B, a cured product 91 is generated in the vicinity of the irradiation surface 900 where UV4 reaches, but UV does not reach inside and curing does not occur. This is because the curing of the UV curable resin 32 occurs at high speed due to the generation of radicals within the range where UV4 reaches.

As a result, as illustrated in FIG. 6B, curing occurs only near the surface, and the molded body 9 having a desired thickness cannot be obtained. Even if such a molded body 9 is fired, a sintered body having a large thickness and a large volume cannot be manufactured.

(Experimental example 1)
This example is an example for comparatively examining the type and amount of the solvent for the molding slurry from the viewpoint of the UV transmission depth. First, a molding slurry was prepared as follows.

First, θ-alumina having an average particle diameter of 20 μm is used as the inorganic raw material powder 31, polyethylene glycol #600 diacrylate manufactured by Shin Nakamura Chemical Co., which is a UV monomer, is used as the polymerizable raw material 321, and Irgacure 1173 manufactured by BASF is used as the polymerization initiator 322. did. Next, the inorganic raw material powder 31 and the UV curable resin 32 composed of the polymerizable raw material 321 and the polymerization initiator 322 were added to the solvent and mixed to prepare the molding slurry 3.

The amount of the inorganic raw material powder 31 in the total amount of 100 parts by mass of the solvent 33, the inorganic raw material powder 31, and the UV curable resin 32 is 30 parts by mass, and the compounding ratio of the solvent 33 and the UV curable resin 32 is changed to be plural. Molding slurry 3 of was prepared. As the solvent 33, as shown in FIG. 2, water, methanol, and ethanol, which have high transmittance in the wavelength region necessary for radicalization of Irgacure 1173 and have good compatibility with the UV curable resin 32, were used.

Next, the UV transmission depth of each molding slurry 3 was measured. The UV transmission depth was measured as follows. First, as illustrated in FIG. 7, a bottomed square tubular mold 2 was prepared. The mold 2 is made of quartz glass. An illuminometer 29 was installed on the bottom surface 22 of the mold 2. Each of the molding slurries 3 was filled in the molding die 2, and UV4 was irradiated from the opening 21 on the upper surface of the molding die 2 toward the bottom surface 22. A mercury-xenon lamp was used as the UV4 light source. The irradiation intensity I ₀ from the light source is 400 mJ/cm ² . By illumination meter 29 measures the UV transmitted intensity I, was calculated based on the UV transmissive intensity ratio I _r in the formula (I) below. The depth of the molding slurry 3 from the irradiation surface 300 when I _r =5% was defined as the UV transmission depth of the molding slurry 3.
I _r =100×I/I ₀ (I)

The UV transmission depth of each molding slurry 3 is shown in FIG. In FIG. 8, the vertical axis represents the UV transmission depth, and the horizontal axis represents the solvent fraction in the molding slurry 3. The molding slurry 3 contains the solvent 33, the UV curable resin 32, and the inorganic raw material powder 31 as described above, and the content of the inorganic raw material powder is 30 wt %. Therefore, the value obtained by subtracting the total of the solvent fraction on the horizontal axis of FIG. 8 and the content of the inorganic raw material powder 31 of 30 wt% from 100 wt% is the content of the UV curable resin 32.

Further, for comparison of the respective molding slurries, the UV transmission depth was also measured for a mixture of an inorganic raw material powder containing no solvent and a UV curable resin. The result is shown in FIG. The content of the inorganic raw material powder in the mixture is 30 wt% and the content of the UV curable resin is 70 wt%.

As is known from FIG. 8, the UV penetration depth is improved as compared with the case where the solvent fraction is 0 regardless of which solvent 33 is used. In addition, the UV penetration depth is improved as the solvent fraction is increased regardless of which solvent 33 is used.

It should be noted that the solvent fraction of 63 wt% is the curing limit of the molding slurry 3, and if it exceeds this, curing cannot be performed. The content of the UV curable resin 32 at a solvent fraction of 63 wt% is 7 wt %. Therefore, from the viewpoint of the curing limit of the molding slurry 3, the content of the solvent is preferably 900 parts by mass or less with respect to 100 parts by mass of the UV curable resin.

As described above, according to this example, it is understood that the UV penetration depth is improved by using the solvent 33. Further, although increasing the content of the solvent 33 also improves the UV transmission depth, it is understood that the upper limit or less is preferable from the viewpoint of the curing limit of the solvent slurry 3.

(Experimental example 2)
This example is an example in which the types of solvents for the molding slurry are compared and examined from the viewpoint of the diffusion depth of radicals. Also, the actual cure depth is measured. Also in this example, water, methanol, and ethanol are used as the solvent as in Experimental Example 1.

First, a molding slurry was prepared in the same manner as in Experimental Example 1 using each solvent. The amount of the solvent was set to 63 wt% at which the UV transmission depth became maximum in Experimental Example 1. Then, in the same manner as in Experimental Example 1, each molding slurry was irradiated with UV in the molding die to cure the molding slurry. Next, the cured molded body was taken out from the molding die, and the thickness in the irradiation direction was measured by a laser thickness meter. This thickness was defined as the curing depth. Further, the UV transmission depth of each molding slurry was determined in the same manner as in Experimental Example 1.

The diffusion depth is a value obtained by subtracting the UV transmission depth from the curing depth. FIG. 9 shows the relationship between the bond dissociation energy of the solvent of each molding slurry and the diffusion depth. The bond dissociation energy can be known from literature values. Table 1 shows bond dissociation energies of water, methanol, and ethanol. In Table 1, the bond dissociation energy of the monomer CH ₂ CHCOR is also shown for reference.

As is known from Table 1 and FIG. 9, the diffusion depth is largest when water having the highest bond dissociation energy is used as the solvent. Also, when methanol and ethanol were used as the solvent, the diffusion depth was increased as compared with the case where no solvent was used.

In FIG. 9, when the diffusion depths of water, methanol, and ethanol are compared, the diffusion depth of water significantly increases as compared with the rate of increase in bond dissociation energy. This is considered to be caused by the generation and diffusion of hydroxy radicals as described above in the first embodiment. Generation and diffusion of hydroxy radicals were also confirmed by verification using a fluorescent reagent that reacts with hydroxy radicals and exhibits strong fluorescence. Therefore, when water is used as the solvent, it is considered that the hydroxy radical also plays a role in the polymerization reaction and the diffusion depth increases.

Further, the curing depth when irradiated with UV having a wavelength of 350 nm at an irradiation dose of 400 mJ/cm ² was 0.75 mm when 63% by mass of water was used and 0.4 mm when no solvent was used. Therefore, it can be seen that the curing depth increases by using the solvent.

Further, the curing depth can be increased by increasing the irradiation amount. For example, the cure depth, which was 0.75 mm at a dose of 400 mJ/cm ² , increases to 1.4 mm at a dose of 6000 mJ/cm ² . Furthermore, it has been confirmed that the curing depth can be increased in a shorter time by changing the light source.

As described above, according to this example, it is understood that the diffusion depth of radicals is increased by using the solvent. From the effect of improving the UV transmission depth in Experimental Example 1 and the effect of increasing the radical diffusion depth in Experimental Example 2, it can be seen that the curing depth from the UV irradiation surface actually increases.

(Embodiment 2)
In this embodiment, an embodiment in which the method for manufacturing the molded body and the porous sintered body of Embodiment 1 is applied to a gas sensor element will be described. Specifically, it is applied to the formation of a porous protective layer that covers the tip side of the gas sensor element.

As illustrated in FIGS. 10 and 11, the gas sensor element 6 has an element body 60, a porous protective layer 61, and an insulator 62. The gas sensor element 6 is long, and the long direction is called the axial direction X. Of the two ends in the axial direction, the end exposed to the measurement gas such as exhaust gas to be measured is called the tip 68, and the opposite end is called the base 69. Note that in FIG. 11, the insulators are omitted for convenience of drawing.

Although not shown, the element body 60 has a solid electrolyte body, an electrode layer, an alumina layer, a heater layer, and the like. The element body 60 in the present embodiment is, for example, a laminated type in which a solid electrolyte body, an electrode layer, an alumina layer, a heater layer, etc. are laminated together. The element body may be a cup type having a bottomed cylindrical solid electrolyte body, electrode layers formed on the outer and inner surfaces thereof, and a heater inserted in the solid electrolyte body.

An insulator 62 is formed in the central portion of the element body 60 in the axial direction X. The insulator 62 is made of ceramics such as alumina. The insulator 62 is a tubular body that inserts and holds the element body 60 inside. The tip 68 side and the base end 69 side of the element body 60 in the axial direction X are exposed from the insulator 62.

The tip 68 of the element body 60 is covered with the porous protective layer 61. The porous protective layer 61 is a porous film made of alumina. The thickness of the porous protective layer 61 is, for example, 0.2 to 0.6 mm.

A method of forming the porous protective layer 61 will be described with reference to FIG. First, the molding slurry 2 is filled in the molding die 2. The same molding slurry as used in Experimental Example 1 was used. The solvent is, for example, water, and the amount of the solvent is, for example, 63 wt %. The mold 2 is made of quartz glass, for example.

Next, the tip side of the element body 60 inserted through the insulator 62 is immersed in the molding slurry 3. Next, the molding slurry 3 is irradiated with UV from the outside of the bottomed square tubular molding die 2. UV can be emitted from, for example, five sides of the side surface and the bottom surface of the molding die 2. The irradiation time in this case is, for example, 1 to 4 seconds. This UV irradiation cures the molding slurry 3 to form a molded body 1 made of a cured product of the molding slurry 3.

Next, the element body 60 having the molded body 1 formed at its tip is taken out from the molding die by releasing. Then, the molded body 1 is fired. By firing, the cured resin disappears and alumina is sintered. In this way, the porous protective layer 61 made of the porous sintered body 5 can be formed. Then, the gas sensor element 6 illustrated in FIGS. 10 and 11 can be obtained.

In this embodiment, the embodiment in which alumina is used as the inorganic raw material powder and applied to the porous protective layer of the gas sensor element has been described. Besides, it is also possible to apply to the adsorption core of the heat pump by using, for example, a metal powder as the inorganic raw material powder. The present invention is not limited to the above-described embodiments, but can be applied to various embodiments without departing from the spirit of the invention.

DESCRIPTION OF SYMBOLS 1 Molded body 2 Molding die 3 Molding slurry 31 Inorganic raw material powder 32 UV curable resin 33 Solvent 4 UV ray 5 Porous sintered body

Claims (11)

In the molding die (2), the molding slurry (3) containing the inorganic raw material powder (31), the ultraviolet curable resin (32) and the solvent (33) is irradiated with ultraviolet rays (4), whereby the molding is performed. In the method for producing a molded body (1) for curing a slurry,
The ultraviolet curable resin contains a radically polymerizable polymerizable material (321) and a polymerization initiator (322),
The method for producing a molded body, wherein the molding slurry contains 900 parts by mass or less of the solvent with respect to 100 parts by mass of the ultraviolet curable resin. The method for producing a molded article according to claim 1, wherein a solvent having a bond dissociation energy higher than that of the polymerizable raw material (321) of the ultraviolet curable resin is used as the solvent. The method for producing a molded article according to claim 1, wherein a solvent having a bond dissociation energy of 300 kJ/mol or more is used as the solvent. The method for producing a molded body according to claim 1, wherein the solvent contains at least one of water and alcohol. The method for producing a molded article according to claim 1, wherein the solvent contains at least water. The method for producing a molded article according to any one of claims 1 to 5, wherein the ultraviolet rays are irradiated while applying vibration to the molding die. The method for producing a molded article according to claim 1, wherein the ultraviolet rays are irradiated from multiple directions into the molding die. The method for producing a molded body according to any one of claims 1 to 7, wherein the inorganic raw material powder comprises at least one of ceramic powder and metal powder. The method for producing a molded body according to any one of claims 1 to 8, wherein the molding die is made of quartz glass or sapphire. A method for producing a porous sintered body (5), which comprises drying and firing a molded body obtained by the method according to any one of claims 1 to 9. The method for producing a porous sintered body according to claim 10, wherein the porous sintered body is a protective layer (61) formed on the surface of the gas sensor element (6).

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