JPH0555798B2 - - Google Patents

Description

[Detailed description of the invention]

A. Field of Industrial Application of the Invention The present invention relates to an underlay material used when firing pottery such as ceramics and ceramics. Conventional technology and its problems Conventionally, when firing pottery, molded products and shelf boards or molded products tend to stick together due to dripping of glaze, which is a major cause of defective products. To solve this problem, methods such as spreading alumina or cordierite powder or applying or scattering alumina paste mixed with a small amount of clay have been used, but methods that spread powder cause the powder to scatter. It has drawbacks such as spoiling the appearance of the pottery and making cleaning after firing difficult.On the other hand, the method of applying alumina paste has to be applied thinly and evenly, otherwise the coating layer may crack or the pottery may become deformed. There are disadvantages such as being time consuming and requiring skill. There is also a method of fixing molded ceramic products with triangular points and polishing only the contact areas, but this method also has the disadvantage of leaving traces of the triangular points and poor workability. That's what I'm doing. Furthermore, a method was also used in which a placing plate called tool clay or senbei, which had a shrinkage rate similar to that of pottery, was prepared in advance using china clay similar to that used for pottery, and then coated with alumina or the like on top of it to serve as an underlay material for pottery. However, it has the major disadvantage of being extremely time-consuming and inefficient. The present invention aims to solve the above-mentioned problems, and is an underlay material used when firing pottery, comprising:
This was achieved as a result of intensive study to obtain a sheet-like product that does not stick to the pottery even if the glaze drips down, can be easily removed from the pottery after firing, is inexpensive and disposable. B. Structure and operation of the invention The structure of the present invention is a sheet used as an underlay material during the firing of pottery, etc., the main components of which are heat-resistant inorganic powder, heat-resistant inorganic fiber, and clay mineral made by a wet paper-making method. The initial tensile strength of the sheet is 0.5 kg/15 mm width or more, the air permeability is 5 seconds/100 c.c. or more, and the folding strength after firing treatment of the sheet is is 10~500g/
It is 50mm wide and has a shrinkage rate of 10% due to the firing process.
The gist of the present invention is an underlay material for firing, which is characterized by the following. Means to solve the problem The main components of the sheet-like material are a mixture of heat-resistant inorganic powder, heat-resistant inorganic fiber, and clay mineral,
We finished these into single hybrid layer sheets with various physical properties using a wet paper-making method, and determined the appropriate range of physical properties through experiments.As a result, we found that the sheet with the following physical property conditions was the most suitable. I discovered that it is something. First of all, the major requirement for this sheet is that the glaze does not penetrate at high temperatures. This requires making the sheet denser and increasing its air permeability, and as a result of experiments, the air permeability was increased to 5.
They learned that by limiting the temperature to 100 c.c./sec or more, it was possible to prevent the glaze from penetrating at high temperatures. It goes without saying that if the air permeability is smaller than this value, the glaze will penetrate and the object of the present invention cannot be achieved, and the preferred value is 10 seconds/100 c.c. or more. . Next, as for strength, the initial strength of this sheet is high to a certain extent, and after firing, the strength is low enough that even if the sheet and the pottery stick together, it can be easily removed, and it can be broken into powder for easy cleaning. It is required to have sufficient strength to prevent damage. As a physical property that satisfies this requirement, as a result of an experiment, the initial tensile strength of this sheet is 0.5Kg/15mm.
It is necessary that the folding strength of the sheet after baking treatment is 10 to 500 g/50 mm width. If the initial tensile strength is less than this value, the handling becomes difficult and it cannot be used. On the other hand, if the folding strength after firing is less than the above lower limit, it will break into pieces and become difficult to clean; If it sticks to the pottery, it becomes difficult to remove and may damage the pottery itself. The desirable range of this folding strength is 20 to 200 g/
It is about 50mm wide. In addition, this folding strength means that the sample is 50mm wide x
Cut into 100mm long pieces and place on measuring stand (height 10mm)
50mm from above), and 50mm from this stand.
This is the value measured by placing a load on the center of the x50mm section and measuring the load when this sheet folds. Since this folding strength is the value after firing, in the present invention, the measurement was performed on a product heat-treated at 1300° C. for 1 hour. In addition, the sheet must not curl, roll up, or wave at high temperatures, and will not adhere to the pottery.To do this, the sheet must have a low shrinkage rate during the firing process.
As a result of experiments, it was determined that a shrinkage rate of 10% or less was a necessary condition. In other words, if the shrinkage rate of this sheet exceeds 10%, it will curl or wave during firing, and the sheet will turn over and adhere to the pottery. The underlay material of the present invention is required to satisfy the above-mentioned conditions, but also has a low organic component content, does not melt or vitrify during firing and adhere to the shelf board, and has smoothness and flexibility. This is what is required. If this organic component is too large, carbide remains and has an adverse effect, so it is desirable that the content of the organic component is 5% or less. In addition, when removing the sheet after firing or when taking out the sheet with the baked goods still attached, it is required that the sheet does not adhere to the shelf board to the extent that this removal work is not hindered. It is necessary to use a material that does not vitrify or melt at the maximum temperature of 1300°C. Furthermore, it is desirable that the shrinkage rates of the sheet and the pottery are similar; even if the difference is large, the surface of the sheet should be smooth and slippery, and the sheet should be flexible enough not to interfere with stable shrinkage of the pottery. Therefore, appropriate smoothness and flexibility are required. This flexibility also brings about good results in the manufacture, storage, and transportation of the sheet, and also provides the effect that it will not bend or crack when placing pottery on it. These problems, such as low organic content, high melting point or softening point, smoothness and flexibility, can be solved mainly by changing the constituent materials. The material was selected. The main materials of the underlay material of the present invention are heat-resistant inorganic powder,
It is a mixture of heat-resistant inorganic fibers and clay minerals using a wet papermaking method, and is naturally a single layer consisting of a mixture of these fibers, which will be specifically explained below. As a heat-resistant inorganic powder, the melting point or softening point is
A material having a temperature of 1300° C. or higher, preferably 1500° C. or higher, and having fire resistance such as alumina, silica, mullite, silicon carbide, zirconia, or zircon can be suitably used. However, if it contains low melting point substances such as sodium oxide, potassium oxide, boron oxide, etc., it will stick to the shelf board, so it is necessary to select a material that does not contain these substances. The content of this inorganic powder is preferably 50 to 90%; if it is less than 50%, the pores will become large and the glaze will easily penetrate, while if the content exceeds 90%, the entire sheet will become brittle and easily break. This is a major disadvantage in manufacturing, as it falls off during papermaking, resulting in poor yields, and attempts to prevent this falling off require time for watering, and it also becomes difficult to handle in terms of strength. The heat-resistant inorganic fibers used in the present invention preferably have a melting point or softening point of 1300°C or higher, preferably 1500°C or higher, such as silica/alumina fibers, alumina fibers, silicon carbide fibers, and ceramic fibers. It can be used. The content of this inorganic fiber is desirably 5 to 45%; if it is less than 5%, the sheet becomes brittle and easily folds, and shrinks greatly during firing, making it difficult to manufacture. On the other hand, this content
If it exceeds 45%, the porosity increases and the air permeability decreases, making it easier for the glaze to penetrate. Moreover, if this content is high, it is generally disadvantageous in terms of cost. Clay minerals in the present invention include, for example, sepiolite, attapulgite, montmorillonite, and swellable fluorine mica, and those having the ability to form a film upon dehydration are preferably used. The content of this clay mineral is preferably 5 to 30%; if it is less than 5%, the strength will be low and it will be difficult to handle, while if the content is more than 30%, the sheet will shrink significantly during firing, and At the same time, the sheet becomes brittle and its water resistance deteriorates, making it difficult to manufacture. Note that if natural clay minerals containing impurities are used, they will tend to adhere to the shelf board, so care must be taken. The underlay material of the present invention can be used at normal firing temperatures of 800 to 1,300°C, but if necessary, it can be designed to withstand firing temperatures of 1,300°C or higher, such as when firing ceramics. Of course, it is also possible to use special glazes at temperatures below 800°C. Further, the basis weight of the underlay material of the present invention is preferably 50 g/m ² or more from the viewpoint of tensile strength and air permeability, and 500 g/m ² or less from the viewpoint of flexibility and folding strength. be. Example Using alumina powder with a particle size of 5μ as the heat-resistant inorganic powder, using ceramic fiber as the heat-resistant inorganic fiber, and using sepiolite as the clay mineral,
Underlay materials with three mixing ratios as shown in Table 1 were made into a single mixed layer by a wet papermaking method.

[Table] In this case, after mixing 2 parts by weight of acrylic adhesive with these raw materials and adding a small amount of coagulant,
Paper is made and dried using a box-shaped hand-paper machine, and each piece is given a basis weight.
It was manufactured to be a sheet of 200g/m ² . This test No. 1 is a comparative example in which the amount of ceramic fiber blended is too small; on the other hand, test No.
No. 3 is a comparative example in which the amount of alumina powder is small. In other words, Test No. 2 is an example corresponding to the present invention. The initial physical properties of these sheets were as shown in Table 2.

[Table] Next, these sheets were fired at 1250℃ for 3 hours,
When the bending strength and the shrinkage rate due to firing were measured, the results shown in Table 3 were obtained.

[Table] From these tables, it is determined that Test No. 1 cannot be used because the shrinkage rate is too high, and Test No. 3 has low air permeability and can easily pass through the glaze. Actually, I placed the above three types of sheets on a shelf board, and placed an unglazed plate covered with clay ash glaze on top of it.
When we conducted an experiment to perform firing at 1250℃, Test No.
1 had a large shrinkage rate and the edges rolled up and stuck to the plate, which not only significantly damaged the appearance of the pottery, but also
Cracks appeared in the sheet and glaze adhered to the shelf board in some areas. In Test No. 3, the glaze penetrated through the sheet to the shelf board, and the pottery and shelf board were completely bonded together. However, the sheet in Test No. 2 that was used as an underlay material slightly adhered to the pottery, but did not stick to the shelf board, and the entire sheet could be easily taken out from the shelf board, and the sheet attached to the pottery was removed. Damaged and excluded;
When I sanded it with sandpaper, I was able to get a very nice finish. C. Effects of the Invention As explained above in detail, the present invention is a sheet whose main components are heat-resistant inorganic powder, heat-resistant inorganic fiber, and clay mineral, and which has a low organic content and moderate density. This underlay material for firing is made so that the glaze does not penetrate through it, and in terms of strength, the initial tensile strength is increased to a certain extent, and the folding strength after firing is limited to a predetermined range. Therefore, even if the glaze drips onto this underlay material, it will not stick to the shelf board, and even if it does stick to the pottery, it can be easily removed, and since it breaks into pieces of a certain size rather than powder, it is easy to clean. It becomes very easy. In addition, the underlay material of the present invention has a low shrinkage rate and does not curl or wave during firing, so it does not have a negative effect on the pottery.It also has excellent smoothness and flexibility, and the sheet itself is easy to handle. Because it has cushioning properties when placing pottery on it, it will not bend or crack, and it will not prevent the pottery from shrinking. As described above, the underlayment material of the present invention revolutionizes the conventional pottery firing method, exhibits simple and efficient workability, and is extremely effective in obtaining stable quality of pottery products.

Claims (1)

[Scope of Claims] 1. A sheet used as an underlay material when baking pottery, etc., the main components of which are heat-resistant inorganic powder, heat-resistant inorganic fiber, and clay mineral blended using a wet papermaking method. , the initial tensile strength of the sheet is 0.5 kg/15 mm width or more, the air permeability is 5 seconds/100 c.c. or more, and the folding strength of the sheet after firing is 10 to 500 g/ An underlay material for firing, which has a width of 50 mm and has a shrinkage rate of 10% or less due to the firing treatment. 2 The content of heat-resistant inorganic powder is 50 to 90%, the content of heat-resistant inorganic fiber is 5 to 45%, and the content of clay mineral is 5 to 30% in the formulation by wet papermaking method. The underlay material for firing according to item 1.