JPH0443866B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a method for producing a cristobalite porcelain base, which produces a porcelain product that has a wide range of uses as tableware porcelain and electrical porcelain, and has high mechanical strength. (Prior art) Porcelain has excellent whiteness and mechanical strength, so it is widely used in tableware, ornaments, and electrical products such as insulators. The main ingredients are Amakusa pottery stone and Izumiyama pottery stone, which have quartz and sericite as their main ingredients. There is a method in which the quartz component is transferred to cristobalite through a raw material processing step, followed by a molding step, drying, and firing step, thereby developing the mechanical strength unique to porcelain. In particular, when high-quality Amakusa pottery stone is used as a raw material for pottery stone, the quartz contained therein is fine, so the porosity of the finished porcelain product is reduced, making it dense, excellent in mechanical strength, and bright in color. We can provide quality porcelain. However, in recent years, high-quality Amakusa pottery stone has become depleted, and as an alternative raw material, silica sand (average particle size of about 700 μm), which is a quartz component, is used and wet-pulverized along with feldspar, pottery stone, clay, etc. It is proposed to produce porcelain blanks. (Problem to be solved by the invention) However, raw silica sand with an average particle size of about 700 μm,
Relatively hard non-plastic raw materials such as feldspar and pottery stone,
When wet-pulverizing low-hardness plastic raw materials such as clay at the same time, hard silica sand and feldspar, which are non-plastic raw materials, are difficult to crush, so the crushing efficiency of the entire blended raw material becomes poor, and homogeneous crushing is not possible, resulting in the formation of particles in the crushed raw material base. Coarse-grained quartz (grain size of approximately 30 μm or more) remains.
During the firing process, fine quartz melts and cristobalite crystallizes from the melt, but if the quartz is coarse-grained, it will remain in the porcelain as coarse-grained quartz even after sintering, and the porcelain itself will become This results in non-uniformity, which reduces the mechanical strength of the porcelain.
Furthermore, since the quartz remaining in the base material also reduces the transparency of the porcelain, this also has the disadvantage of causing a deterioration in the quality of the porcelain product. (Means for Solving the Problems) Therefore, in view of the above points, the present invention uses silica sand as a substitute raw material for high-quality pottery stone, which is being rapidly depleted, and also suppresses the residue of coarse quartz during the crushing process. , is a method for producing cristobalite porcelain with the aim of promoting the transition of quartz to cristobalite to obtain porcelain with strong mechanical strength.
The method is characterized in that silica sand classified into 1 is wet-pulverized together with plastic raw materials and non-plastic raw materials other than the silica sand of the porcelain base composition, and then clay is added and mixed. The present invention aims to compensate for the quartz content caused by the depletion of the raw material of pottery stone, which has traditionally been commonly used in cristobalite porcelain, with classified silica sand that has been classified to a specific grain size of silica sand that is produced in large quantities. It is most important to use silica sand classified to have a grain size of 100 μm or less and an average particle size of 5 to 35 μm.
The reason for setting the maximum particle size to 100 μm or less is that if coarse silica sand of 100 μm or more is present, it will not be finely crushed in the subsequent crushing process and will remain in the porcelain as quartz grains of 30 to 40 μm, resulting in a decrease in mechanical strength. This is not desirable as it may cause damage. In addition, the average grain size is limited to 5 to 35 μm. If it is less than 5 μm, a large amount of quartz will melt, making it impossible to obtain the high strength characteristic of cristobalite porcelain. On the other hand, if it exceeds 35 μm, the sinterability of the porcelain will decrease. However, the density decreases significantly and the mechanical strength decreases. Therefore, the maximum particle size and average particle size of classified silica sand are extremely important. (Example) First, the desired classified silica sand, which is obtained by dry-pulverizing silica sand and adjusting the particle size so that the maximum particle size and average particle size become the particle sizes listed in Table 1, and chinastone, feldspar, and other raw materials are used. The raw stone was mixed to have a base composition of , and wet-pulverized using a ball mill until the coarse particles with a particle size of 10 μm or more reached 25 to 29 wt% as described in Table 1: Base Particle Size to obtain a raw stone slurry. . Subsequently, clay was added to this raw stone slurry and mixed in a tank to adjust the base composition and base particle size as shown in Table 1, thereby producing cristobalite porcelain bases No. 5 to No. 11 of the present invention. On the other hand, as a conventional example, porcelain base A is the same as the previous example except that no classified silica sand is used at all, and pottery stone, feldspar, clay, and other raw materials are mixed to have the base composition shown in Table 1. Manufactured under the same conditions,
In addition, as a second conventional example, porcelain base B was manufactured under the same conditions as the previous example except that unclassified raw silica sand (average particle size of about 700 μm) was used instead of the classified silica sand of the previous example. . In addition, the silica sand of the present invention whose maximum particle size and average particle size are outside the numerical limit range of the present invention was prepared as a comparative example in the same manner as above, and Comparative Example No. 1 with a coarse particle size was prepared.
- No. 4 and Comparative Examples No. 12 to No. 15 with fine particle sizes were prepared, respectively. (Actions and Effects) As described above, the porcelain base produced by the method of the present invention, the porcelain base produced as a comparative example, and the porcelain base as an example were molded by a conventional method,
After drying, sintering at a heating rate of 10 to 20℃/hr, sintering temperature
1200~1250℃, holding time at sintering temperature 0.5~2hr,
The properties of the obtained porcelain (thermal expansion coefficient, amount of precipitated crystals, bending strength, residual quartz grain size) are shown in Table 1 together with the manufacturing conditions of the base material. In addition, in Table 1, the amount of precipitated crystals of porcelain is measured by X-ray diffraction quantitative method, and the bending strength is 12φ×
A 100 mm cylindrical specimen was measured using a three-point support bending test method, and the residual quartz grain size in the porcelain was measured using a scanning electron microscope.

【table】

[Table] As shown in this table, the porcelain obtained by sintering the base material manufactured by the manufacturing method of the present invention using classified silica sand classified to a specific particle size as _the SiO ₂ component is Compared to porcelain obtained by sintering base material B manufactured using unclassified raw silica sand (conventional example B), the bending strength is greater, and the quartz grain size remaining in the porcelain is also smaller, resulting in stronger strength. Excellent transparency. In addition, the strength and residual quartz grain size are not inferior to porcelain obtained from base A manufactured without using silica sand (conventional example A), and the SiO ₂ component of high-quality pottery stone, which is on the decline, can be used. The quality of porcelain can be maintained even if some of it is replaced with silica sand. Furthermore, it was confirmed that the products of the present invention were different from the comparative examples in terms of the quartz grain size remaining in the porcelain or the amount of cristobalite crystals precipitated in the porcelain, and as a result, they were superior in mechanical strength. As is clear from the above description, the present invention suppresses the residual coarse quartz in porcelain, promotes the transition of quartz to cristobalite, and provides high quality porcelain with excellent strength and transparency. As a method for manufacturing porcelain bases that can be used in a variety of ways, it eliminates the problems of the past and greatly contributes to the development of industry.

Claims (1)

[Claims] 1 The maximum particle size is 100μm or less and the average particle size is 5~
A method for producing a cristobalite porcelain base, characterized in that silica sand classified to 35 μm is wet-pulverized together with plastic raw materials and non-plastic raw materials other than the silica sand in the porcelain base composition, and then clay is added and mixed.