JP3148817B2 - Plasticity control method of kneaded soil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the plasticity of a clay made of non-plastic particles such as alumina.

[0002]

2. Description of the Related Art
Extrusion molding is widely used as a method for molding fine ceramic materials such as alumina. In the case of ceramic materials, water is added to clay, which is itself plastic, to form a clay,
This is extruded, and the kneaded material generally has good plasticity so that the extrusion can be carried out smoothly.

However, in the case of the above-mentioned fine ceramic materials such as alumina, the primary particles themselves have substantially no plasticity (either having no plasticity or very poor plasticity). Extrusion cannot be performed favorably if it is only.

In the case of fine ceramic materials,
Plasticity is added to the clay by adding a binder or changing the type and amount of the binder, but ultimately the quality of the plasticity of the clay is determined empirically by touching the clay. The determination is made by measuring the rheological properties of the prepared clay.

[0005] However, for example, the binder which has the effect of improving the plasticity in the case of the A powder particles, has little effect in the case of the B powder particles, and thus has an influence on the plasticity of the clay. The decisive factor was unknown, and the fact was that, in the past, the only way to obtain the desired plasticity clay was through trial and error. However, in this case, a great deal of labor and time are required to finally obtain a clay having good plasticity.

[0006]

The invention of the present application has been made to solve such a problem. According to the method of claim 1, the particle-filled structure of the clay comprises a set of secondary particles that are aggregates of primary particles.
A gap containing water larger than the gap between the primary particles in the secondary particles between the secondary particles is set to 20 to 30 vol.
1%, and the particle filling structure is such that the interparticle gap between the primary particles in the secondary particles is 65% or less in volume ratio to the particle volume.

According to a second aspect of the present invention, the particle-filled structure of the kneaded material is formed such that a void-forming material that is insoluble in water, absorbs water, and deforms itself is interposed between primary particles. In the intervening portion, a void containing water larger than the inter-primary particle void in the non-intervening portion of the void forming material is formed between the primary particles at 20 to 30 vol% based on the kneaded soil, and the void interposing material is not interposed. It is characterized in that it has a particle-filled structure in which the space between primary particles in the site is 65% or less in volume ratio to the particle volume.

[0008]

The present inventor has paid attention to the particle filling structure of the clay as a factor influencing the plasticity of the clay. Examination of the packing structure revealed that there were many voids between the secondary particles, which were aggregates of the primary particles, larger than the voids between the primary particles.

On the other hand, water is added to an aggregate of primary particles (having a size of about 0.1 to several microns) of alumina which does not have plasticity itself to form a kneaded material, and the plasticity is determined based on the measurement of rheological properties. As a result, it was a material having low plasticity and could not be favorably molded by a molding technique such as the extrusion molding.

[0010] Therefore, an aggregating agent is added to the kneaded alumina made of the non-plastic particle powder to agglomerate the primary particles, and the secondary particles, which are the aggregates, are less than the voids between the primary particles in the secondary particles. It was confirmed that when many large voids were generated, the plasticity was increased, and molding by extrusion molding or the like became possible. The invention of claim 1 of the present application has been made based on such knowledge.

Here, the plasticity is enhanced by forming more voids between the secondary particles than the voids between the primary particles as described above because the large voids between the secondary particles are caused by the movement of the secondary particles, In other words, it works to increase the fluidity of the clay,
As a result, it is considered that the plasticity of the clay was enhanced.

In the present invention, it was also confirmed that the amount of the void was preferably in the range of 20 to 30% by volume based on the clay. The amount of the void having the above size is 20 vol%
If less, sufficient fluidity cannot be obtained, and conversely, 30
If the content exceeds vol%, the fluidity is increased, but the shape retention, which is called the stiffness of the clay, that is, the property of maintaining the shape is impaired, and the plasticity is rather reduced.

In the present invention, various techniques can be used as a technique for generating a gap between secondary particles larger than the gap between primary particles in the above range. For example, by adding a coagulant such as methylcellulose, starch or polyvinyl alcohol and controlling the amount of addition, or by performing a chemical treatment such as pH adjustment or surface ion substitution and controlling the treatment conditions. , And further, by performing a mechanical treatment such as pulverization to increase the specific surface area of the powder particles,
The generation and amount of voids can be controlled. In the present invention, the space between the primary particles in the secondary particles is set to 65% or less in terms of a volume ratio to the particle volume.

[0014] The shape retention of so-called koshi, which is called koshi, is
This is a factor that affects the plasticity as well as the fluidity. Thus, the shape retention is better when the voids between the primary particles are smaller.

In other words, the denser the primary particle packing structure, the better the shape retention. Thus, in the present invention, it has been found that the volume ratio of the primary interparticle space to the particle volume is preferably 65% or less. However, the lower limit is preferably set to 25% or more. This is because it is difficult to densely pack the particles so that the volume ratio is less than 25%.

[0016] By doing so, the flowability and the shape retention of the clay can be effectively enhanced, and the plasticity, which is a combined property thereof, can be further improved.

As a method of reducing the voids between the primary particles, the particle size distribution of the primary particles is broadened (widened),
It is possible to use a technique such that the filling structure can be finely packed, a mixture of coarse particles and fine particles is used as the powder, or the particle size of the primary particles is reduced.

As described above, clay as a ceramic material is a plastic particle in a state in which the clay particles themselves contain water. Therefore, in the case of a ceramic material (kneaded material), the clay itself has a certain degree of plasticity. ing.

However, in the case of a ceramic material composed of the above-described alumina alone, the constituent particles thereof are particles having substantially no plasticity. Therefore, in the case of a clay made of an aggregate of primary particles, the plasticity is extremely poor.

Here, when the present invention is applied to the kneaded material composed of such non-plastic particles, good plasticity can be imparted to the kneaded material, and it can be formed into a desired shape by extrusion molding or the like. Be able to process.

According to a second aspect of the present invention, a void-forming material is added instead of aggregating the primary particles to form secondary particles.
It is intended to control the particle filling structure, more specifically, the voids in the kneaded material by the interference action of the void forming material.

Curdlan, which is a kind of polysaccharide, forms voids containing water between primary particles in a kneaded alumina made of non-plastic particles, and deforms itself. It is known that they act to assist the relative movement of the primary particles, thereby improving the fluidity of the whole clay.

Therefore, the present inventors have proposed a method other than the card run.
A material that is insoluble and water-absorbing in the kneaded soil is added to the kneaded alumina made of non-plastic particles to be interposed between the primary particles, and large voids containing water between the primary particles (non-intervening water-absorbing material) Voids larger than primary interparticle voids at the site)
It was confirmed that the plasticity was increased when a large amount of was formed.

Further, it was confirmed for the first time that the range of 20 to 30% by volume based on the kneaded soil was appropriate as the amount of the void. The invention of claim 2 of the present application has been made based on such knowledge.

If the amount of the space is less than 20 vol%, sufficient fluidity cannot be obtained. Conversely, if it exceeds 30 vol%, the fluidity increases but the shape retention is impaired, and the plasticity is rather reduced. Let me do it.

[0026] In the invention of claim 2 of the present application, as a typical material for forming voids larger than the voids between the primary particles in the above range, a gel-like material which is insoluble in water, has water absorbency, and is itself deformed. Can be exemplified,
Other various materials can be used.

For example, agar or konjac, which is a water-absorbing polysaccharide insoluble in kneaded clay, or any other material that is insoluble in kneaded clay and has a property of being easily deformed by itself. The generation and amount of the space can be controlled by controlling the amount of addition.

Also in the second aspect of the present invention, the gap between the primary particles, more specifically, the gap between the primary particles in the non-intervening portion of the gap forming material should be 65% or less by volume ratio to the particle volume (however, a desirable lower limit). The value is 25%).

By doing so, the shape retention of the clay can be made good for the same reason as in the first aspect of the invention, and the plasticity can be made good.
In addition, the above-described method can be used as a method for reducing the gap between the primary particles.

[0030]

Next, embodiments of the present invention will be described in detail. Granular primary particles Alumina powder (primary particles having an average particle size of 0.3 μm) was mixed with 3 wt% of agar powder as an additive and mixed with water to prepare an alumina clay.

Examination of the particle filling structure of the kneaded material, specifically, the voids between the particles revealed the results shown in FIG. The measurement of the void was performed as follows.

That is, in a state of the clay containing water so that the structure does not change, the water in the clay is instantaneously frozen in liquid nitrogen and then kept at -5 ° C. in vacuum, Was sublimated and freeze-dried. The pore size distribution of the freeze-dried product was measured using a mercury intrusion porosimeter (Poresizer 9320 manufactured by Micromeritics).

In FIG. 1, (A) shows the size of the gap on the abscissa, and the total amount of the gap (total from the side of the larger gap to the smaller side of the gap) on the ordinate, and (B) Indicates its differential value.

As can be seen from the results, the alumina kneaded material obtained as described above has a structure in which the gap between the primary particles existing around the pore diameter of 0.1 μm in FIG. In addition, a considerable amount of voids larger than the voids between the primary particles are formed. From the observation of the freeze-dried product by a scanning electron microscope, it was found that the added agar powder was not melted in the clay and was interposed between the primary particles, and the agar powder acted as a void forming material (interference material), and the large void Was formed.

That is, there are roughly two types of voids in the above-mentioned alumina kneaded material, a void having a small pore diameter and a void having a large pore diameter, and the void having the smaller pore diameter is free of agar powder. It was confirmed that the voids between the primary particles at the site and the voids having the larger pore diameter were voids between the primary particles and the primary particles separated from each other by the agar powder at the agar powder intervening site.

Next, when the plasticity of the kneaded material was examined, the result shown in FIG. 5 was obtained. In FIG. 5, together with the plasticity of the alumina clay ((c) in the figure), the plasticity of the clay H clay which is conventionally considered to have good plasticity ((a) in the figure)
And the plasticity ((d) in the figure) of the clay of clay G which is considered to have poor plasticity.

The region between (a) and (d) is considered to be a region of good plasticity in which extrusion molding and the like can be carried out industrially. In this region, it can be said that the clay has good plasticity.

Incidentally, the particle packing structure of each of the clay H and the clay G, that is, the voids between the particles were examined by the same method as described above. there were.

As shown in FIGS. 2 and 3, in the case of the clay of clay H having excellent plasticity, the voids between the primary particles having a peak on the smaller pore diameter side in FIG. In the case of clay G having a large amount of larger voids but not so good plasticity, in the case of clay G having a peak on the side with a smaller pore diameter in FIG. You can see that the amount is not large.

The horizontal axis in FIG. 5 indicates the shape retention of the clay.
The vertical axis indicates the liquidity. However, specifically, the shape retention is shown as an apparent Young's modulus, and the fluidity on the vertical axis is shown as the work required in the stress increase range in the latter stage of deformation, and the smaller the value, the greater the fluidity . The plasticity of the kneaded soil is higher as the shape retention is higher and the flowability is higher.

Next, for the sake of comparison, a kneaded material obtained by mixing alumina powder and water without adding an additive to the above-mentioned granular alumina powder, that is, an aggregate of granular alumina primary particles, water and When the plasticity of the kneaded material consisting of was examined, it was as shown in FIG.

For confirmation, the voids in the kneaded material comprising the aggregate of the primary alumina particles and water were examined, and the results were as shown in FIG. As shown in FIG. 4, in the case of the kneaded material composed of aggregates of granular alumina primary particles and water, there are many voids between primary particles having a peak around 0.1 μm. It can be seen that there are few large voids.

That is, to the powder comprising the primary particles of such granular alumina, a material which is insoluble in water and has a water-absorbing property is added and interposed between the primary particles to form large voids between the primary particles. It can be understood from the comparison between FIG. 1 and FIG. 4 and the comparison between (c) and (e) of FIG.

Next, in order to examine how much large voids generated by the void-forming material (interference material) are required between the primary particles to obtain an appropriate kneaded material, the alumina obtained as described above was used. The amount of voids between the primary particles (voids between primary particles in the non-intervening portions of the void forming material) and the amount of large voids generated by the presence of the void forming material were calculated from FIG. When the relationship with the plasticity evaluation results was examined, the results shown in Table 1 were obtained.

[0045]

[Table 1]

The calculation of the void amount was performed as follows. That is, since the void distribution diagram (B) of the dried clay at 100 ° C. without the additive shows only a single peak at about 0.1 μm, this state indicates that the primary particles It is almost completely filled, and the voids in the kneaded material consist of voids between the almost completely filled primary particles, and it can be assumed that there is almost no void larger than that.

Accordingly, the upper limit of the pore diameter in the differential value curve of the pores of the dried body shown in FIG.
This corresponds to the upper limit pore diameter of the voids between primary particles in the kneaded material. Therefore, voids smaller than the upper limit void diameter of the voids between the primary particles are defined as voids between the primary particles in the non-intervening portions of the agar powder, and voids larger than the voids are defined as large voids generated by the agar powder. The amount of each of the divided voids was calculated.

The plasticity of the kneaded material which can be used for plastic molding such as extrusion molding is approximately 4 or less in terms of work showing fluidity and 0.15 or more in terms of apparent Young's modulus showing shape retention. Can be shown.

As shown in Table 1, the alumina clay was
If the gap larger than the gap between the primary particles is 20 to 30%, the work amount and the apparent Young's modulus fall within the above ranges. On the other hand, if the void is less than 20%, sufficient workability cannot be obtained because the work amount showing fluidity is in an appropriate range or more. Conversely, if it exceeds 30%, work amount decreases and fluidity increases. In addition, the apparent Young's modulus indicating the shape-retaining property is below the appropriate range, and the shape-retaining property is reduced, and the plasticity is rather reduced.

In the case of the clay H having excellent plasticity, the amount of voids (voids between aggregates of primary particles) larger than the voids between primary particles in a portion where primary particles are densely packed is also 20%.
It can be seen that the plasticity falls within the above-mentioned proper range when it is between 30% and 30%. On the other hand, in the case of clay G having a poor plasticity, the amount of voids larger than the voids between primary particles is 20 to
Even if it is between 30%, the shape retention falls outside the above range.

The reason is that the voids between the primary particles are present in a volume ratio of 80% or more with respect to the particle volume, and are larger than the above-mentioned clay of alumina and clay of clay H, that is, the filling between the primary particles is poor. For this reason, the shape retention is reduced.

Further, in the case of the clay obtained by mixing only the alumina powder and water, the voids larger than the voids between the primary particles are small, and the voids between the primary particles are 70% or more by volume ratio to the particle volume. Clay or clay H with agar added to alumina
Because of the large size compared to the kneaded clay, proper shape retention and fluidity are not obtained.

Therefore, the gap between the primary particles is 65% by volume.
If not less than 2 voids larger than between primary particles
Even if it is adjusted to be in the above range of 0 to 30%, it can be understood that since the filling of the primary particles is poor, the kneaded material having a good balance between the fluidity and the shape retention, that is, the appropriate kneaded material cannot be obtained. .

Incidentally, 1% by weight of methylcellulose as an aggregating agent was added to the above-mentioned granular primary alumina powder to form a kneaded soil with water, and the plasticity was examined.
(B) showed good plasticity as well.

As shown in Table 1, the particle filling structure of the clay when methylcellulose was added as the coagulant also showed that secondary particles (primary particles) larger than the voids between the primary particles as compared with the clay containing only alumina powder and water. It is understood that the plasticity falls within an appropriate range when the amount of the voids is large and the amount is between 20% and 30%, and the voids between the primary particles in the secondary particles formed by the flocculant have a volume ratio of Was 65% or less.

Although the embodiments of the present invention have been described in detail above, this is merely an example, and the present invention can be implemented in variously modified forms without departing from the gist thereof.

[Brief description of the drawings]

FIG. 1 is a diagram showing a void distribution of a kneaded material of granular alumina powder obtained in an example of the present invention.

FIG. 2 is a view showing a void distribution of a clay H clay.

FIG. 3 is a diagram showing a void distribution of a clay G clay.

FIG. 4 is a view showing a void distribution of a kneaded material of granular alumina powder alone without any additive and water.

FIG. 5 is a diagram showing the plasticity of each kneaded material having the void distribution shown in FIGS.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Saburo Sano 3-2-3, 15-24 Kita Chikusa, Chikusa-ku, Nagoya City, Aichi Prefecture (72) Inventor Takumi 2-109, Yachiyo-cho, Kita-ku, Nagoya City, Aichi Prefecture Yachiyo Dormitory 103 (72) Inventor Kenta Oguri 3-2, 103-1206, Sunadabashi, Higashi-ku, Nagoya-shi, Aichi (72) Inventor Shuji Kawai 2-3-2-22, Mizuho-cho, Handa-city, Aichi Prefecture, East Town Room 206 (72) Invention Person Yuji Nomura 2-1-1, Kinjo, Kita-ku, Nagoya-shi, Aichi, Co., Ltd. E-72 J. Misaki (56) References JP-A-2-97459 (JP, A) JP-A-1-238905 (JP, A) JP-A-63-274647 (JP, A) JP-A-4-337002 (JP, A) (58) Field surveyed (Int.Cl. ⁷⁾ , DB name) C04B 35/622-35/638 B28B 3/20 B28C 7/00

Claims (2)

(57) [Claims] Claims: 1. The particle-filled structure of a kneaded material comprises a collection of secondary particles, which are aggregates of primary particles.
A gap containing water larger than the gap between the primary particles in the secondary particles between the secondary particles is set to 20 to 30 vol.
1%, and having a particle-filled structure in which the voids between the primary particles in the secondary particles are 65% or less in volume ratio with respect to the particle volume. Control method. 2. A method for filling a particle of a kneaded material with a void-forming material which is insoluble in water, absorbs water, and deforms itself between primary particles. Between 20% and 30% by volume, based on the kneaded material, of voids containing water larger than the voids between the primary particles in the non-intervening portions of the void-forming material between the particles, and between the primary particles in the voids of the void-forming material. A method for controlling the plasticity of a kneaded material comprising non-plastic particles such as alumina, which has a particle-filled structure in which voids are 65% or less in volume ratio with respect to the particle volume.