JP5586041B2 - Manufacturing method of ceramics - Google Patents

Description

  The present invention relates to a method for producing ceramics, and more particularly to a method for producing ceramics capable of greatly reducing the drying time of a molded body.

  Conventionally, ceramics are manufactured through the procedures of preparation, molding, drying, unglazing, glazing, main baking, and cooling of the substrate, but in the drying process of the molded product after forming the ceramic substrate, distortion of the molded product is required. In order to minimize the amount of water, the molded body is slowly dried, and in order to avoid explosion of the molded body that occurs when the temperature rises during firing, after confirming that the moisture content has decreased to about 5% by mass, The molded body had to be fired. Moreover, since it is necessary to determine drying conditions in consideration of the shape, size, etc. of ceramics, the present condition depends on the skill of each craftsman based on experience. Further, efforts are made to minimize defects such as distortion and cracking of ceramics by using any drying means and technology such as natural drying depending on the weather and forced drying using an energy source. Depending on the variety of ceramics, such as size and shape, and non-uniformity of the substrate thickness, it is necessary to proceed with the manufacturing process with great care, and the drying period may be several months. Generally, 70% or more of the total time required for the ceramic manufacturing process is spent in the drying process.

  Therefore, selecting a ceramic substrate in anticipation of shrinkage and stress that occurs during the drying / firing process in the manufacturing process is an important factor in determining product design. Relying on the skills of the current situation. In addition, in the dry construction method that can shorten the drying time, it is necessary to develop a product design that is forced to be pressurized and subjected to shape constraints.

  On the other hand, in the ceramic molding process, as one of the methods for imparting the shape, a method of filling granules or powder into a mold or rubber mold and molding by applying pressure is known. This is called a press molding method. Further, this molding method is classified into semi-dry press molding and dry press molding. Semi-dry press molding usually contains clay in the base powder and contains 10 to 15% of water to derive its plasticity. For this reason, the resulting molded article undergoes drying shrinkage. This forming method is inferior in dimensional accuracy but has a low base cost and has been conventionally used for forming low-voltage, low-frequency electric porcelains and wall tiles. On the other hand, dry press molding does not depend on plasticity by clay and is performed with the help of appropriate organic binders and lubricants, and is the most widely used ceramic molding method because of its high productivity. Yes. However, it has been difficult to produce a free shape by dry press molding.

JP 2007-045651 A JP 2006-327908 A Utility Model Registration No. 3078409

  By the way, it has been impossible with the current technology to fire the molded body before moisture is removed. This is because firing of the molded body containing moisture causes distortion, cracking, explosion, and the like. The causes are (1) stress on the molded body due to shrinkage that occurs in the drying process until firing, and (2) stress on the molded body due to firing in an insufficiently dried state. One can be considered. Therefore, in order to avoid these stresses, it is necessary to dry the molded body sufficiently, and since a period of one week to one month or more is usually required between molding and firing, the entire drying time is It was supposed to account for more than 70% of the time required. Note that the increase in the total number of hours for manufacturing ceramics results in an increase in delivery time and an increase in cost, leading to a decrease in competitiveness.

  On the other hand, problems such as distortion, cracks, explosions, and long-term production time are part of design education, model production, art work creation by experts, as well as emotional education, art education, and manufacturing education. In the field of art education in early childhood, elementary, middle and high school, lifelong learning education, etc., it is also a cause that hinders the use of ceramics such as ceramics. This is because, in any field, the produced works are unique and valuable and scarce, so the occurrence of cracks, explosions, etc. is fatal. The burden on the workers in these fields is large, and in many cases, in the field of education, there are many cases of abandoning efforts to make clay, which plays an important role in the development of emotion, expression and sense. Therefore, in order to reduce the burden of product management after production, a technique for avoiding distortion, cracks, explosions, etc., while reducing the manufacturing time of ceramics is required.

  Accordingly, an object of the present invention is to provide a ceramic manufacturing method capable of solving the above-described problems of the prior art and greatly reducing the drying time of a molded body while suppressing distortion, cracking, explosion, and the like. is there.

  As a result of intensive studies to achieve the above object, the present inventors have baked a molded body made of a ceramic body to which a volcanic glass foam has been added at a moisture content of 10 to 30% by mass, thereby forming the molded body. The inventors have found that the occurrence of distortion, cracks, explosions, and the like can be suppressed while drastically shortening the drying time, and have completed the present invention.

That is, the method for producing the ceramic of the present invention comprises:
Preparing a clay added with volcanic glass foam;
Molding the clay into a molded body;
A method for producing a ceramic, comprising: firing the molded body to obtain a sintered body,
The water content of the pre-fired molded body Ri 10-30% by mass,
The volcanic glass foam has a particle diameter of 5 mm or less,
The apparent bulk density of the volcanic glass foam is 0.04 to 0.6 g / ml .

  In the method for producing a ceramic of the present invention, the volcanic glass foam is preferably foamed pearlite, foamed pine stone, foamed obsidian, and foamed shirasu.

  In the ceramic manufacturing method of the present invention, the content of the volcanic glass foam in the ceramic substrate is preferably 1 to 40% by mass in terms of solid content.

  In the method for producing a ceramic of the present invention, it is preferable that the drying time until the molded body is fired is within 24 hours.

  According to the present invention, by firing a molded body made of a ceramic substrate to which a volcanic glass foam is added at a water content of 10 to 30% by mass, the drying time of the molded body can be greatly shortened, and distortion and cracking can be achieved. Further, it is possible to provide a method for producing ceramics capable of suppressing the occurrence of explosion or the like.

  Below, the manufacturing method of the ceramic of this invention is demonstrated in detail. In the production method of the present invention, first, a ceramic substrate to which a volcanic glass foam is added is prepared. Here, the ceramic substrate is prepared from a ceramic raw material. In addition, the ceramic raw material is not particularly limited, and any clay used in general ceramic products such as ceramics, tiles, bricks, tiles, and cements can be used. The clay is composed of various clay minerals such as kaolinite, allophane, montmorillonite, sericite, chlorite and moisture, and examples thereof include porcelain clay. Regardless of the type of clay, such as Seto, Shigaraki, Mashiko, or the type of clay, such as loess, red, white, etc. ) And the like are drastically reduced.

  In the production method of the present invention, for example, a ceramic substrate to which a volcanic glass foam is added can be prepared by blending and kneading a volcanic glass foam with the clay. Here, as a kneading method, for example, a method of mixing a volcanic glass foam into wet clay and kneading using a kneader or the like so as to be uniform may be employed, or manual kneading is employed. You can also Alternatively, the ceramic body can be prepared by mixing the clay and the volcanic glass foam in a powder state with uniform stirring and mixing, and then mixing the water.

  In the production method of the present invention, the volcanic glass foam can be produced by heating and foaming a crushed volcanic glass, and specific examples include foamed pearlite, foamed pine stone, foamed obsidian, and foamed shirasu. These volcanic glass foams may be used alone or in combination of two or more. In addition, volcanic glass is a generic term for objects in which acidic lava is rapidly cooled and solidified by contact with seawater, lake water or groundwater on the ground or underground to become glassy igneous rock. In general, when it becomes igneous rock, obsidian with 2% or less of bound water contained in igneous rock, pearlite with more than 2% and less than 5% by weight, 5% by weight The above is classified as pine sebite, and it becomes a volcanic glass with different properties and physical properties due to the difference in bound water content. In addition, when adding a volcanic glass foam to a ceramic raw material, mixing with the ceramic raw material can be facilitated and dust generation can be suppressed by adding the water to the volcanic glass foam so that it is lightly moistened. .

  The particle diameter of the volcanic glass foam is preferably 5 mm or less, and more preferably 1 mm or less. When the particle diameter of the volcanic glass foam exceeds 5 mm, workability may be deteriorated, and cracks may be caused. The particle diameter of the volcanic glass foam is measured by a dry sieve.

  Furthermore, the apparent bulk density of the volcanic glass foam is preferably in the range of 0.04 to 0.6 g / ml. If the apparent bulk density of the volcanic glass foam is within the above-specified range, it is possible to achieve further weight reduction of the ceramics to be manufactured while achieving the object of the present invention. If the apparent bulk density is less than 0.04 g / ml, the strength of the glass foam itself may be insufficient, and the foam structure may be destroyed when kneaded with clay. It becomes insufficient. The apparent bulk density of the volcanic glass foam can be measured by a unit volume mass measurement method based on JIS A5007.

  In the production method of the present invention, the content of the volcanic glass foam in the ceramic substrate containing the volcanic glass foam is preferably in the range of 1 to 40% by mass, and in the range of 5 to 30% by mass in terms of solid content. Further preferred. If the content of the above volcanic glass foam is in the range of 1 to 40% by mass in terms of solid content, the molded body with a predetermined amount of moisture remaining can be fired, thereby allowing drying time during the manufacturing process. Is significantly shortened, and further, the fuel cost for drying is greatly reduced. In addition, if the content of the volcanic glass foam in the solid content is less than 1% by mass, the improvement effect on productivity and cost may not be sufficiently obtained. May decrease. In addition to the moisture originally contained in the clay, additional moisture may be added to the ceramic substrate to improve the molding efficiency. Therefore, the volcanic glass foam is based on the solid content excluding the moisture. The content of is determined. Here, the solid content amount excluding the moisture is obtained from, for example, the sample amount after drying for 2 hours at 105 ° C.

  Next, in the manufacturing method of the present invention, the ceramic body to which the above-mentioned volcanic glass foam is added is formed into a formed body. In addition, in order to shape | mold this ceramic base, it does not restrict | limit in particular, A known method can be utilized. For example, molding methods such as roll molding, hand build molding, plate molding, mold molding and the like can be mentioned. Here, in the manufacturing method of this invention, it is required that the moisture content of the molded object before baking is the range of 10-30 mass%, and it is preferable that it is the range of 10-25 mass%. The molded body before firing is a molded body before shifting to the firing step. By adjusting the moisture content of the compact of the ceramic body containing the volcanic glass foam to a range of 10 to 30% by mass, the drying time can be greatly shortened, and further, cracking, distortion, and destruction (for example, , Explosion) and other problems do not occur. As a result, the productivity and manufacturing cost of ceramics are greatly improved. In addition, since distortion in the drying process and firing process is suppressed, the dimensions of the final product can be predicted almost accurately, thereby facilitating product design. In addition, according to the present invention, the drying time can be greatly shortened, so that there is no restriction on the shape of the molded body due to drying or the like, and creation of various product designs in the ceramics industry and the art and art world can be expected. become.

  Here, if the moisture content of the molded body before firing is less than 10% by mass, the drying time cannot be shortened, or the amount of moisture contained in the ceramic substrate is too low, and the workability is significantly reduced. On the other hand, if the moisture content of the green body before firing exceeds 30% by mass, it becomes extremely difficult to mold the ceramic body. Further, according to the production method of the present invention, it is possible to shift to the firing step without drying the formed body, but a drying step may be provided. In this case, after forming the ceramic base, The drying time until the molded body is fired is preferably within 24 hours, and more preferably within 5 hours.

  Next, in the manufacturing method of this invention, the said molded object is baked and it is set as a sintered compact. In addition, in order to bake a molded object, it does not restrict | limit in particular, A known method can be utilized. For example, a method of firing in a stepwise manner by a plurality of firing processes such as unbaking and main firing, a method of firing under temperature rising conditions, and the like can be given.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples. In addition, the description of the mass part used for clay and a volcanic glass foam means the mass part in the state except the water | moisture content.

<Brick shape>
In addition, the shape of a brick is a thick lump, and generally it is required for one month or more by natural drying for moisture to escape.
Example 1
Add 70 parts by mass of clay from Shigaraki to 30 parts by mass of volcanic glass foam (foamed pearlite, maximum particle size 1 mm, apparent bulk density 0.5 g / ml), and stir to disperse uniformly. 100 parts by mass of water was added to 25 parts by mass of water and kneaded to prepare a ceramic substrate (kneaded product). The kneaded product was formed into a lump with a substrate thickness of 6 cm, a width of 21 cm, and a depth of 10 cm, and left at 20 ° C. for 12 hours. The residual moisture in the molded body at this time was 18.5% by mass. The formed body was fired in an electric furnace under the conditions of temperatures of 1100 ° C., 1200 ° C. and 1300 ° C. (temperature increase rate: 100 ° C./hour) to obtain a sintered body. The above method was repeated to produce a plurality of sintered bodies, but in any case, no cracks / strains were observed, and there was no destruction during firing.

(Comparative Example 1-1)
A sintered body was produced in the same manner as in Example 1 except that 70 parts by mass of Shigaraki clay and 30 parts by mass of volcanic glass foam were changed to only 100 parts by mass of Shigaraki clay. Here, the residual moisture in the molded article when left (dried) at 20 ° C. for 12 hours was 18.5% by mass. The obtained sintered body had large cracks or fractures, and the shape could not be maintained.

(Comparative Example 1-2)
A sintered body was produced in the same manner as Comparative Example 1-1 except that the drying process at 20 ° C. for 12 hours was changed to a drying process at 20 ° C. for 20 days. Here, the residual moisture in the molded article when it was allowed to stand (dry) at 20 ° C. for 20 days was 5 mass%. However, as in Comparative Example 1-1, the obtained sintered body had large cracks or fractures, and the shape could not be maintained.

<Tile shape>
(Example 2)
Add 70 parts by mass of clay from Shigaraki to 30 parts by mass of volcanic glass foam (foamed pearlite, maximum particle size 1 mm, apparent bulk density 0.5 g / ml), and stir to disperse uniformly. 100 parts by mass of water was added to 25 parts by mass of water and kneaded to prepare a ceramic substrate (kneaded product). The kneaded product was formed into a lump with a substrate thickness of 1.5 cm, a width of 15 cm, and a depth of 15 cm, and left at 20 ° C. for 12 hours. The residual moisture in the molded body at this time was 18% by mass. The formed body was fired in an electric furnace under the conditions of temperatures of 1100 ° C., 1200 ° C. and 1300 ° C. (temperature increase rate: 100 ° C./hour) to obtain a sintered body. The above method was repeated to produce a plurality of sintered bodies, but in any case, no cracks / strains were observed, and there was no destruction during firing.

(Comparative Example 2)
A sintered body was produced in the same manner as in Example 2 except that 70 parts by mass of Shigaraki clay and 30 parts by mass of volcanic glass foam were changed to only 100 parts by mass of Shigaraki clay. Here, the residual moisture in the molded article when left (dried) at 20 ° C. for 12 hours was 18% by mass. Since the molded body exploded during firing, the obtained sintered body was a small lump having a diameter of 5 mm to 2 cm and was scattered throughout the kiln.

<Rocking molding>
(Example 3)
Add 8 parts by mass of volcanic glass foam (foamed pearlite, maximum particle size of 1 mm, apparent bulk density of 0.5 g / ml) to 60 parts by mass of red clay from Shigaraki and 40 parts by mass of clay from Mashiko. Then, 25 parts by mass of water was added to the total amount (108 parts by mass) and kneaded to prepare a ceramic substrate (kneaded product). The kneaded product was subjected to loft molding to produce a mug (molded body) having a base thickness of 0.5 cm, a height of 13 cm, and a diameter of 10 cm. The mug was cut at a high height and then left at 20 ° C. for 5 hours and placed in a kiln. The residual moisture in the mug at the time of putting in the kiln was 18% by mass. The mug was baked to a temperature of 1250 ° C. in 17.5 hours. The obtained sintered body was not observed to be cracked or distorted, and was not destroyed during firing.

(Comparative Example 3-1)
Sintered body in the same manner as in Example 3, except that 60 parts by weight of Shigaraki red clay, 40 parts by weight of Mashiko white clay, and 8 parts by weight of volcanic glass foam were changed to 108 parts by weight of Shigaraki red clay. Manufactured. Here, the residual moisture in the mug at the time of putting in the kiln was 18% by mass. The obtained sintered body was cracked and some distortion was observed.

(Comparative Example 3-2)
A sintered body was produced in the same manner as in Comparative Example 3-1, except that the drying process after cutting the high ridge was changed from 5 hours at 20 ° C to 4 days at 20 ° C. Here, the residual moisture in the mug at the time of putting in the kiln was 4% by mass. In addition, since a molded object was fully dried, the crack and distortion were not observed in the obtained sintered compact.

<Hand build molding>
Example 4
Add 6 parts by mass of volcanic glass foam (foamed pearlite, maximum particle diameter of 1 mm, apparent bulk density of 0.5 g / ml) to 100 parts by mass of red clay from Shigaraki, and knead to disperse uniformly. A ceramic substrate (kneaded material) was prepared by adding 25 parts by mass of water to (106 parts by mass) and kneading. The kneaded product was hand-build molded to produce a molded body with a base thickness of 0.8 cm, height of 90 cm, width of 50 cm, and depth of 45 cm. Dry at 20 ° C. for 24 hours. The water content in the molded body at this time was 22% by mass. The molded body was fired to 1250 ° C. in 30 hours. The obtained sintered body was not observed to be cracked or distorted, and was not destroyed during firing.

(Comparative Example 4-1)
A sintered body was produced in the same manner as in Example 4 except that 100 parts by mass of Shigaraki red clay and 6 parts by mass of volcanic glass foam were changed to only 106 parts by mass of Shigaraki red clay. Here, the moisture in the molded article when dried at 20 ° C. for 24 hours was 18% by mass. The obtained sintered body had large cracks and some strains were observed.

(Comparative Example 4-2)
A sintered body was produced in the same manner as in Comparative Example 4-1, except that the drying process at 20 ° C. for 24 hours was changed to a drying process at 20 ° C. for 21 days. Here, the moisture in the molded article when dried at 20 ° C. for 21 days was 4% by mass. However, some cracks were observed in the obtained sintered body.

<Plate-shaped molding with Ceraroller>
(Example 5)
Add 8 parts by mass of volcanic glass foam (foamed pearlite, maximum particle diameter of 1 mm, apparent bulk density of 0.5 g / ml) to 100 parts by mass of red clay from Mashiko, and knead to disperse uniformly. 25 parts by mass of water was added to (108 parts by mass) and kneaded to prepare a ceramic substrate (kneaded product). The kneaded product was formed into a plate shape with a Cera roller, and bonded and formed to produce a cylinder (molded body) having a base thickness of 2 cm and a height of 60 cm. When this was dried at 20 ° C. for 24 hours, the water content in the molded body was 22% by mass. The cylinder was fired to 1100 ° C. in 24 hours. The obtained sintered body was not observed to be cracked or distorted, and was not destroyed during firing.

(Comparative Example 5-1)
A sintered body was produced in the same manner as in Example 5 except that 100 parts by mass of Mashiko red clay and 8 parts by mass of volcanic glass foam were changed to only 108 parts by mass of Mashiko red clay. Here, the moisture in the molded article when dried at 20 ° C. for 24 hours was 22% by mass. The obtained sintered body had large cracks and was partially destroyed.

(Comparative Example 5-2)
A sintered body was produced in the same manner as in Comparative Example 5-1, except that the drying process at 20 ° C for 24 hours was changed to a drying process at 20 ° C for 16 days. Here, the moisture in the molded article when dried at 20 ° C. for 16 days was 7% by mass. However, the obtained sintered body was partially cracked and strain was also observed.

  In Examples 1 to 5, although the molded bodies having various shapes were produced, in any case, the molded bodies could be fired in a state of containing moisture of a certain value or more. Thereby, it turns out that the drying time of a molded object can be shortened significantly. Moreover, it turns out that it can be baked in the state which contained the water | moisture content of a fixed value or more, if only the volcanic glass foam was added, without being influenced by the production place and kind of a clay, or a shaping | molding method. Furthermore, the ceramic product can be reduced in weight by replacing part of the clay with a volcanic glass foam.

  The method for producing ceramics of the present invention can be used for a method for producing ceramic products such as ceramics, tiles, bricks, tiles, and cements.

Claims (4)

Preparing a clay added with volcanic glass foam;
Molding the clay into a molded body;
A method for producing a ceramic, comprising: firing the molded body to obtain a sintered body,
The water content of the pre-fired molded body Ri 10-30% by mass,
The volcanic glass foam has a particle diameter of 5 mm or less,
An apparent bulk density of the volcanic glass foam is 0.04 to 0.6 g / ml .   2. The method for producing ceramics according to claim 1, wherein the volcanic glass foam is at least one selected from the group consisting of foamed pearlite, foamed sebaceous rock, foamed obsidian, and foamed shirasu. Content of the volcanic glass foam in clay is 1-40 mass% in solid content, The manufacturing method of the ceramics of Claim 1 characterized by the above-mentioned.   2. The method for producing a ceramic according to claim 1, wherein a drying time until the compact is fired is within 24 hours.