JP6359916B2 - Manufacturing method of ceramic molded body - Google Patents

Description

  The present invention relates to a method of manufacturing a ceramic molded body that can be applied when manufacturing a ceramic sintered body used for, for example, a plug, a metal halide lamp, an electrostatic chuck, and a dome.

  Conventionally, ceramic parts made of a ceramic sintered body having high performance such as heat resistance and durability have been developed. These ceramic parts can be manufactured by sintering a ceramic molded body obtained by curing and drying a ceramic slurry.

  In recent years, for the purpose of improving the moldability of ceramics, ceramic powder, curable resins such as water-soluble epoxy resins, hardeners such as amine compounds, solvents such as water, etc. are mixed, defoamed and poured. A mold and a method of forming by curing are disclosed (see Patent Documents 1 and 2).

  In these Patent Documents 1 and 2, it is disclosed as a general theory that it is desirable to select a curable resin having a good affinity with a solvent, because bubbles are the cause of a decrease in strength. Yes. This is because if the affinity with the solvent is poor, the curable resin separates and segregates inside the molded body, which may cause defects such as pores during sintering.

JP 2009-234852 A JP 2007-136912 A

However, in the above-described prior art, there is no disclosure as to what characteristics are most suitable as a water-soluble epoxy resin when water is used as a solvent.
Specifically, for example, in each manufacturing process such as curing, drying, degreasing, and firing, there is no sufficient disclosure about a manufacturing method in which a molded body or the like is unlikely to crack.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a method for manufacturing a ceramic molded body in which cracks are unlikely to occur in the manufacturing process.

(1) In the present invention, as a first embodiment, a molded body is prepared using a mixture of at least an epoxy resin, a curing agent, water as a solvent, and ceramic powder, and then the molded body is heated to form the epoxy. in the method of manufacturing the ceramic formed body to form a ceramic green body by curing the resin, the total chlorine content of the epoxy resin is Ri der 4 wt% or less, a water ratio of the epoxy resin is 100%, the The water content in the mixture is 38 vol% to 44 vol% .

When the total chlorine content of the epoxy resin exceeds 4% by weight, cracks are likely to occur in the ceramic molded body, as will be apparent from experimental examples described later.
In other words, containing a large amount of chlorine indicates that there are many parts that are not epoxidized by the glycidyl etherification reaction, and the epoxy resin tends to be non-uniform and cracks are likely to occur in the ceramic molded body. it is conceivable that. In addition, since the portion where chlorine remains (the portion that is not glycidyl etherified) has low polarity, the water-solubility of the epoxy resin is low, so it is considered that cracks starting from insoluble matters are likely to occur.

Thus, in the first embodiment , since the total chlorine content of the epoxy resin is 4% by weight or less, there is an effect that cracks are hardly generated in the ceramic molded body.
That is, in the first aspect, for example, cracks are hardly generated in each molded body obtained in each step such as curing, drying, and degreasing, and as a result, cracks are generated in the ceramic sintered body obtained by firing the molded body. The effect is difficult.

Here, the epoxy resin is a water-soluble epoxy resin that dissolves in water, and the curing agent cures the epoxy resin.
Moreover, the ceramic molded body in the present invention means an unsintered ceramic molded body before sintering. That is, it is a concept including a ceramic molded body in each process such as curing, drying and degreasing (the same applies hereinafter).

In the first embodiment, since the water percentage of the epoxy resin is 100% (because all the epoxy resin is dissolved in water), cracks are generated in the ceramic molded body, as will be apparent from the experimental examples described later. hard.
That is, when the water percentage of the epoxy resin is less than 100%, the ceramic molded body is likely to crack. This is because when the water content is less than 100%, cracks starting from insoluble materials are likely to occur.
Usually, among products called water-soluble epoxy resins, there is a difference (superior or inferior) in water content, and those having a water content of 100% are suitable because cracks are unlikely to occur.
Here, the water solubility is a dissolution rate when 10 parts of epoxy resin is dissolved in 90 parts of water at room temperature (room temperature: 25 ° C.). That is, the ratio of the epoxy resin dissolved in water is the water solubility. Accordingly, when 10 parts of the epoxy resin is completely dissolved in 90 parts of water, the water solubility is 100%. (This water content is the same in the second embodiment)
Furthermore, in this 1st aspect, content (water content) of the water in the said mixture is 38 volume%-44 volume%.
As shown in an experimental example to be described later, when the water content is less than 38% by volume, the ceramic molded body is likely to crack. On the other hand, when the content of water exceeds 44% by volume, the curing of the resin does not proceed sufficiently, the strength decreases, and it is difficult to break during handling.
Therefore, the range described above is preferable because cracks are unlikely to occur and handling is easy.
(2) In the present invention, as a second embodiment, a molded body is prepared using a mixture of at least an epoxy resin, a curing agent, water as a solvent, and ceramic powder, and then the molded body is heated to form the epoxy. in the method of manufacturing the ceramic formed body to form a ceramic green body by curing the resin state, and are thixotropy index of 4 or more of the mixture, water rate of the epoxy resin is 100% of the water in said mixture Content is 38 volume%-44 volume%, It is characterized by the above-mentioned.

When the thixotropy index of the mixture is less than 4, cracks are likely to occur in the ceramic molded body, as is apparent from experimental examples described later.
That is, in the second aspect , since the thixotropic index of the mixture is 4 or more, there is an effect that cracks are hardly generated in the ceramic molded body.

Here, the thixotropic index is a viscosity ratio (viscosity at a shear rate of 1 s ⁻¹ / viscosity at a shear rate of 15 s ⁻¹ ) (the same applies hereinafter).
In addition, 30 or less can be employ | adopted as a thixotropy index of a mixture. This is because if the thixotropy index is too large, the liquid surface is difficult to flatten when the mixture is cast.

Further, in the second aspect, as in the first aspect, since the water content of the first epoxy resin is 100% (because all the epoxy resin is dissolved in water), as is clear from the experimental examples described later, Cracks are unlikely to occur in the ceramic molded body.
Furthermore, in this 2nd aspect, content of the water (water content) in the said mixture is 38 volume%-44 volume% similarly to the 1st aspect. Therefore, it is preferable because cracks are unlikely to occur and handling is easy.
(3) In the present invention, as a third aspect, the total chlorine content of the epoxy resin is 4% by weight or less.
In the third aspect, like the first aspect, the total chlorine content of the epoxy resin is 4% by weight or less, and, like the second aspect, the thixotropic index of the mixture is 4 or more, There is an effect that cracks are less likely to occur.

( 4 ) In the present invention, as a fourth aspect, the epoxy resin is an aliphatic glycidyl ether.
The fourth aspect exemplifies a suitable epoxy resin.

  Examples of the aliphatic glycidyl ether include bisphenol A type epoxy resin, bisphenol F type epoxy resin, promized bisphenol A type epoxy resin, promized bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin and the like. Can be adopted.

  In addition to the aliphatic glycidyl ether, for example, a glycidyl ester type epoxy resin, a glycidyl amine type epoxy resin, an aliphatic epoxy resin, an alicyclic epoxy resin, or the like can be adopted as the epoxy resin.

( 5 ) As a fifth aspect, the present invention is characterized in that the curing agent is a modified polyamide curing agent.
The fifth aspect exemplifies a suitable curing agent. This modified polyamide curing agent is suitable because it hardly affects the environment and the human body.

  As the modified polyamide curing agent, for example, one produced by the reaction of dimer acid and aliphatic polyamine can be used. The properties of the modified polyamide curing agent are determined by the type of polyamine, the ratio of amine to dimer acid, and the amount of the third modifying component. The third modifying component is, for example, an epoxy resin. By reacting this in advance, the compatibility of the modified polyamide with the epoxy resin is greatly improved.

  In addition to the modified polyamide curing agent, for example, primary, secondary, tertiary amine compounds, imidazole compounds, acid anhydrides, dicyandiamide, and the like can be employed as the curing agent.

( 6 ) As a sixth aspect, the present invention is characterized in that the first viscosity at room temperature when measured at a shear rate of 15 s ⁻¹ of the mixture is 4 Pa · s or less.

In the sixth aspect, since the first viscosity of the mixture is 4 Pa · s or less, there is an advantage that the flowability to the mold is good.
Here, room temperature indicates, for example, 25 ° C. (the same applies hereinafter).

In addition, 1 Pa * s is employable as a lower limit of 1st viscosity.
( 7 ) As a seventh aspect, the present invention is characterized in that the second viscosity at room temperature when measured at a shear rate of 1 s ⁻¹ of the mixture is 4 Pa · s or more.

In the seventh aspect, since the second viscosity of the mixture is 4 Pa · s or more, there is an advantage that it is difficult to settle after pouring into the mold.
In addition, as an upper limit of the second viscosity, 16 Pa · s can be adopted.

Here, the above-described configuration of the present invention will be further described.
-In the said 1st aspect, although the total chlorine content of the epoxy resin was 4 weight% or less, the method as described in Unexamined-Japanese-Patent No. 2011-207932 is mentioned, for example.

  The epoxy resin here is obtained by the reaction of an active hydrogen compound and epihalohydrin, and the total halogen content is 80 ppm by weight or less. This epoxy resin is purified by a sublimation method, a distillation method, a crystallization method, or an alkali washing method. As a result, a highly reliable epoxy resin free from the problem of halogen elution, which is useful as an electric or electronic material such as various insulating materials and laminated plates, can be obtained.

-The method for obtaining the chlorine content of an epoxy resin is defined in JIS K7243-3.
Specifically, the total chlorine amount consists of the total saponified organic chlorine amount such as 1,2-chlorohydrin, 1,3-chlorohydrin, 1-chloro-2-glycidyl ether and inorganic chlorine present in the epoxy resin. The evaluation principle is that a sample is dissolved with diethylene glycol monobutyl ether and saponified with a potassium hydroxide alcohol solution under heating to reflux to liberate organic chlorine. The total chlorine content is then measured by potentiometric measurement of a standard volumetric silver nitrate solution.

  -As a ceramic material of the said ceramic powder, an alumina, a zirconia, etc. are employable, for example (the following is same).

It is explanatory drawing which shows the state which pours a slurry into a casting mold and makes it harden | cure.

Hereinafter, embodiments of the present invention will be described.
[Embodiment]
a) First, the manufacturing method of the ceramic molded body of this embodiment is demonstrated.

In the present embodiment, a ceramic molded body was manufactured in the following steps, and then a ceramic sintered body was manufactured from the ceramic molded body.
<Dispersion mixing process>
First, 3.3 g (0 of dispersant): G-700 (manufactured by Kyoeisha Chemical Co., Ltd.) with respect to 660 g of alumina powder (AES-12, Sumitomo Chemical average particle size: 0.57 μm, BET specific surface area: 6.4 m ² / g) 0.5 wt%: outer wt%).

  Then, ion-exchanged water was added so that the final moisture amount was a predetermined moisture amount (for example, 38 volume% to 44 volume% of the entire slurry), and the mixture was placed in a pot together with cobblestones, rotated and mixed and dispersed. .

<Resin mixing process>
Next, 47.3 g of various epoxy resins (manufactured by Nagase ChemteX) were added to the alumina dispersion liquid dispersed and mixed in the dispersion mixing step, and mixed for 10 minutes.

  Further, a modified polyamide-based curing agent (TXH-694, amine number 172, viscosity 5 Pa · s, manufactured by T & K TOKA Co., Ltd.) is added in a stoichiometrically necessary amount, and further mixed for 2 minutes, and then vacuum-released for 2 minutes. Foam was done. This completes the slurry (mixture).

<Casting and curing process>
Next, the slurry was poured into a molding die (casting) 1 (made of metal coated with a fluororesin having a width of 5 mm) shown in FIG. 1 and sealed with an upper die 2 (made of polycarbonate).

Thereafter, the slurry (S) is heated and cured (80 ° C. × 100% RH × 5 h heating / cooling rate: 5 ° C./h), and then the upper mold 2 and the mold 1 are removed, and the cured wet body is removed. I took it out.
<Drying process>
Next, in order to remove moisture contained in the cured wet body, the cured wet body was dried under the following conditions to prepare a humidified dried body.

Under the following humidifying and drying conditions, the humidity was gradually lowered and drying was performed.
Humidification and drying conditions: 80 ° C. × 80% RH × 12 h → 80 ° C. × 60% RH × 12 h → 80 ° C. × 40% RH × 12 h
Temperature increase / decrease rate: 5 ° C / h
Humidity rate: 5% RH / h
<Degreasing process>
Next, the humidified dried body was degreased under the following degreasing conditions to produce a degreased body.

Degreasing conditions: 400 ° C x 2h
Temperature increase rate: 2.5 ° C / h
<Baking process>
Next, the degreased body was fired and sintered under the following firing conditions to produce a ceramic sintered body.

Firing conditions: 1600 ° C x 6h
Temperature increase rate: 25 ° C / h
The method for producing a ceramic molded body described above can suppress the occurrence of cracks in the ceramic molded body, as shown in the following experimental examples, and can easily produce an excellent ceramic product.

  In addition, there is an advantage that it is excellent in near net moldability and demoldability and is difficult to deform after molding. Furthermore, it is excellent in filling property to a fine mold, particularly a mold having a place having a width of 10 mm or less. In addition, since no organic solvent is used, there is an advantage that it is difficult to adversely affect the environment.

b) Next, an experimental example performed to confirm the effect of the method for producing a ceramic molded body of the present embodiment will be described.
In this experimental example (the following experimental examples 1 to 5), samples 1 to 9 and samples A to H were prepared by the manufacturing method of the embodiment described above using the materials shown in the following table and the like, and the characteristics shown in each table were obtained. Examined. Samples 1 to 9 are samples within the scope of the present invention, and samples A to H are samples outside the scope of the present invention.

  Specifically, the “(slurry) viscosity”, “(slurry) flowability”, “(demoldability of the cured wet body)”, “moldability”, “uniformity” of each sample is as follows. I examined "sex". The results are shown in Tables 1 to 5 below.

<Measurement method of viscosity>
The viscosity was measured at normal temperature (25 ° C.) at a shear rate of 1 s ⁻¹ and a shear rate of 15 s ⁻¹ . Note that the shear rate 1 s ⁻¹ corresponds to a state in which the casting is allowed to stand until the end and curing, and the shear rate 15 s ⁻¹ generally corresponds to the shear rate when casting.

Viscosity measuring device: Rheometer (Rheometric Scientific)
Viscosity evaluation method: Couette method Jig dimensions: Bob (φ25mm) / Cup (φ27mm)
Slurry input amount: 8ml
<Flowability evaluation method>
The flowability was evaluated by visually confirming whether the mold was filled with no gap after the slurry was filled in the mold and cured. The case where there was no gap or void was filled, and the case where it was not.

<Method for evaluating demoldability>
A cured wet body having the same dimensions was prepared using a mold having the following sample shape, and the case where it was able to be taken out from the mold without being deformed after curing was evaluated as x.

Sample shape: φ50mm x T (thickness) 10mm
<Formability evaluation method>
A sample of the humidified dried body having the following sample shape was prepared, and cracks and chipped edges were observed with the naked eye.

Sample shape: φ50mm x T (thickness) 10mm
<Evaluation method of uniformity>
If a difference in distribution or density occurs due to sedimentation of particles after casting, it is not preferable as a ceramic product. Therefore, it was evaluated whether there was a difference in particle distribution and density above and below the cured wet body. Particle distribution and density were evaluated by observing under a microscope. The case where there was no difference in the distribution and density of the particles was indicated by ○, and the case where the difference was observed was indicated by ×.

[Experimental Example 1]
In the method for producing a ceramic molded body according to the embodiment, each sample (Samples 1 to 4 and Sample A) in which the water content of the slurry was fixed at 39.6% by volume and the total chlorine content contained in the epoxy resin was changed. ) Was produced. And in each sample, the influence on the viscosity of the slurry, the demoldability of the cured wet body, and the moldability of the humidified dried body was evaluated. The results are shown in Table 1. Table 1 also shows the thixotropy index obtained from the viscosity ratio.

  All samples have a water solubility of 100%. Further, the total chlorine content of the epoxy resin was adjusted by changing the mixing ratio of EX1610 and EX521 in Table 2.

As apparent from Table 1, when the total chlorine content is more than 4% by weight (Sample A), the thixotropy index is low, and the demoldability and moldability are also poor. Therefore, the total chlorine content contained in the epoxy resin is desirably 4% by weight or less (Samples 1 to 4).

  Samples 1 to 4 having a thixotropy index as high as 4 or more are suitable for molding various ceramics. This is because it is possible to prevent sedimentation of particles having a large specific gravity or particles having a large particle size during curing, and is particularly preferable when molding an inorganic substance having a specific gravity difference.

[Experiment 2]
In the method for producing a ceramic molded body of the embodiment, an epoxy resin suitable for molding was evaluated with the moisture content being constant at 39.6% by volume. The epoxy resins used are shown in Table 2, and the evaluation results are shown in Table 3.

In addition, the product number of Table 2 is a product number of the epoxy resin made from Nagase ChemteX. Moreover, in this Table 2, the equivalent of the epoxy resin, the water content, and the viscosity were also displayed.

As is apparent from Tables 2 and 3, in the case of a glycidyl ether type epoxy resin (sample 5) having a total chlorine content of 4% by weight or less, a water content of 100%, and an aliphatic epoxy resin (sample 5), Excellent flowability, moldability, and uniformity, and good results without cracks were obtained. The density of the alumina after sintering was 3.9 g / cm ³ and the sinterability was good.

[Experiment 3]
With respect to the epoxy resin EX1610 (total chlorine content: 0.5 wt%) of Sample 5 for which good results were obtained in Experimental Example 2, the water content was changed and the viscosity, flowability, and moldability were evaluated. The results are shown in Table 4.

As can be seen from Table 4, samples (samples 7 and 8) having a water content in the range of 38% by volume to 44% by volume are excellent in flowability, moldability, and uniformity.

[Experimental Example 4]
For the epoxy resin EX521 (total chlorine content 6.4% by weight) used in Sample B of Experimental Example 2, the water content was changed and the viscosity, flowability and moldability were evaluated. The results are shown in Table 5 below.

As is apparent from Table 5, it can be seen that any of the samples (samples E to H) is not preferable in moldability. This is probably because the total chlorine content of the epoxy resin EX521 is high.

  Note that the present invention is not limited to the above-described embodiment and the like, and it is needless to say that the present invention can be implemented in various modes without departing from the present invention.

1 ... Mold 2 ... Upper mold S ... Slurry

Claims (7)

A molded body is prepared using a mixture of at least an epoxy resin, a curing agent, water as a solvent, and ceramic powder, and then the ceramic body is manufactured by heating the molded body to cure the epoxy resin. In the method for producing a ceramic molded body,
Ri total chlorine content of 4 wt% der less of the epoxy resin,
The water percentage of the epoxy resin is 100%,
Content of the said water in the said mixture is 38 volume%-44 volume%, The manufacturing method of the ceramic molded body characterized by the above-mentioned . A molded body is prepared using a mixture of at least an epoxy resin, a curing agent, water as a solvent, and ceramic powder, and then the ceramic body is manufactured by heating the molded body to cure the epoxy resin. In the method for producing a ceramic molded body,
Ri Der thixotropy index of 4 or more of the mixture,
The water percentage of the epoxy resin is 100%,
Content of the said water in the said mixture is 38 volume%-44 volume%, The manufacturing method of the ceramic molded body characterized by the above-mentioned .   The method for producing a ceramic molded body according to claim 2, wherein the total chlorine content of the epoxy resin is 4% by weight or less. The said epoxy resin is aliphatic glycidyl ether, The manufacturing method of the ceramic molded body of any one of Claims 1-3 characterized by the above-mentioned. The method for producing a ceramic molded body according to any one of claims 1 to 4 , wherein the curing agent is a modified polyamide curing agent. First viscosity at room temperature as measured at a shear rate 15s ^-1 of said mixture, of a ceramic molded body according to any one of claims 1 to 5, characterized in that less than 4 Pa · s Production method. Second viscosity at normal temperature when measured at a shear rate 1s ^-1 of said mixture, of a ceramic molded body according to any one of claims 1 to 6, characterized in that it is 4 Pa · s or higher Production method.