JPH01103929A - Production of thermal shock resistant glass - Google Patents

Abstract

PURPOSE:To obtain glass having satisfactory strength and thermal shock resistance and well usable as the material of various daily necessaries such as cups by heat treating a powdery mixture of a volcanic glassy deposit as the principal starting material with specified m.p. reducing agents at a relatively low temp. CONSTITUTION:A powdery mixture consisting of 4-8wt.% LiO2 powder, 0.5-2wt.% Na2O powder and the balance volcanic glassy deposit powder or 3-5wt.% LiO2 powder, 10-13wt.% B2O3 powder and the balance volcanic glassy deposit powder is melted by heating to <=1,350 deg.C and subjected to strain relief treatment at 450-550 deg.C.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention makes effective use of volcanic glassy deposits represented by whitebait, which is naturally abundant but rarely used. The present invention relates to a method for obtaining glass having sufficient thermal shock resistance through treatment at low temperatures.

<Prior art> Examples of methods for producing glass using volcanic glassy deposits as raw materials are shown in, for example, Japanese Patent Publication No. 17338/1982 and Japanese Patent Application Laid-open No. 1915/1983. The former relates to a limited field of manufacturing methods for alkali-resistant glass, and the latter has a problem of poor production efficiency due to its high melting temperature of at least 1400°C.

<Problems to be Solved by the Invention> The present invention uses volcanic glassy deposits as the main raw material, and can be processed at relatively low temperatures to provide sufficient strength and thermal shock resistance as materials for various daily necessities such as pots. The purpose of this invention is to provide a method by which glass can be obtained.

Means for Solving the Problems> The above object of the present invention can be achieved by adopting the following means. That is, a mixed powder having a composition of 4 to 8% by weight of LiO2 powder, 0 to 2% by weight of NazO powder, and 0 to 2% by weight of NazO powder is heated and melted at a temperature of 1350°C or less, and then subjected to strain removal treatment at a temperature of 450 to 550°C. A method for producing thermal shock resistant glass (hereinafter referred to as the first invention), comprising 3 to 5 weight percent of L102 powder, 10 to 13 weight percent of B2O3 powder, and the balance consisting of volcanic glassy deposit powder. Mixed powder of composition 1
Melt by heating to a temperature of 350°C or less, then 450 to 55
This is a method for producing thermal shock resistant glass (hereinafter referred to as the second invention), characterized in that strain removal treatment is performed at a temperature of 0°C.

Effect> The volcanic glassy deposit has a composition as shown in Table 1 below, and is itself a very high melting point substance with a melting point of 1800° C. or higher. Therefore, this volcanic glassy deposit alone is not suitable as a raw material for glass, but if an appropriate amount of soda ash or the like, which has a melting point lowering effect, is mixed with it, the melting point can be lowered. However, even if the melting point is lowered by mixing soda ash or the like in this way, the resulting mixture has a very large coefficient of thermal expansion and cannot be used practically as glass.

However, by using LiO2 and Na2O or Li0z and B2O3 together as in the present invention, the melting point can be lowered and the coefficient of thermal expansion can also be kept low. That is, in the first invention, Li01 and NazO
Both B1O2 and NazO have the effect of lowering the melting point of volcanic glassy deposits, but LiO2 has a greater effect of reducing the coefficient of thermal expansion, so Nano is used as much as possible. The amount was kept at a small amount, ranging from 05% by weight, which is the minimum amount at which a decrease in the melting point appears, to 2% by weight, which is the limit at which the melting point decreases too much, the viscosity becomes too low, and the workability during manufacturing the product deteriorates.

Further, when L102 is less than 4% by weight, the melting point does not decrease much, and when it exceeds 8% by weight, the viscosity decreases too much, so the weight was 4 to 8 times higher.

In addition, in the second invention, LiO2 and B2O3 are used together, and since B2O3 used here lowers the melting point and also lowers the coefficient of thermal expansion, the effects of both are noticeable. Make sure to use 10% by weight or more,
If the amount is too large, the bending strength tends to decrease and the viscosity decreases too much, resulting in poor workability, so the amount is limited to 13% by weight. In addition, LiO2 is also related to the amount of B2O3, and in this second invention, 8203 is used in a relatively large amount, and the melting point decrease is considerably promoted by the B2O3, so the amount of LiO2 may be smaller than in the first invention. The content was set at 3 to 5% by weight, taking into consideration the melting point and viscosity that affects workability.

In both the first and second inventions, it is of course possible to use a well-known fining agent. Specifically, if a platinum container is used as the container for melting, In particular, it is not necessary to use a fining agent, but if an alumina container is used, the components of the alumina container will gradually dissolve and dissolve into the glass raw material during melting, which will cause the raw material to dissolve. As the melting point gradually increases, the viscosity increases and the bubbles generated in the glass raw material are difficult to remove and may remain in the final product. The amount of the agent used is 0.3% or less of the total weight.

By using the raw materials with the above-mentioned composition, the mixed powder that is the raw material of the present invention can be sufficiently melted at 1350 ° C, which is normally applied when manufacturing daily necessities such as pots on the market. The molten raw material was then heated to 450~5
If the strain is removed at 50°C and then slowly cooled, a glass with stable strength can be obtained.

<Example> Hereinafter, the present invention will be described in detail while showing examples thereof.

Shirasu (-
5mm) 90% by weight, LiO2 powder 8% by weight, Nan.

2% by weight of the powders were mixed to obtain a mixed powder. The composition of this mixed powder is also listed in Table 1.

The above mixed powder was placed in a platinum dish, heated and melted at 1350℃ for 1 hour in an electric furnace with an oxidizing atmosphere, then poured into water, taken out and dried, pulverized, placed in a platinum dish and heated again. It was melted in a furnace at 1350°C for 30 minutes. This molten material was injected into a carbon case with a lid that was housed in another electric furnace that had been previously maintained at 500°C. The carbon case was placed inside a steel container with a lid, and the surrounding area was filled with carbon powder.

It was kept in such a carbon case for 1 hour to remove strain and slowly cool. The obtained glass block was cut and subjected to RFF polishing (
SiC powder 3000#) L, 5 x 5 x 15
(mm) samples were prepared, and their thermal expansion coefficient, eK initiation temperature, transition point, and bending strength were measured. The measurement results were as shown in Table 2 below.

Using the mixed powder shown in Table 2 or Table 1 above, a prototype was made after melting in the same manner as described above, and after strain removal treatment, JI
A thermal shock resistance test was conducted in accordance with the method specified in S-32030. That is, heat the pot to 120±8℃ in an electric furnace.
After holding the glass for 30 minutes, it was placed in cold water, left for 1 minute, and then taken out.As a result, there were no cracks or breaks, and it was determined that the glass was suitable for use as heat-resistant glass for skylights. In addition, according to the JIS standard, 0
The coefficient of thermal expansion at temperatures between 300° C. and 300° C. is said to be 65×10 or less, but in this example, even a value of 88×10 was sufficient to pass the test as a heat-resistant glass for an overhead fire.

1-Same whitebait (-5mm) 84 as used in Example 1 above
87% by weight of LiO2 powder, 3.77% by weight of LiO2 powder, and 1136% by weight of B2O3 powder to obtain a mixed powder having the composition shown in Table 3 below.

The composition of the mixed powder in Example 2 is that the amount of B2O3 added is Na compared to the amount of Nano that Shirasu itself has.
In line with the fact that no: R103 = 1:5 has the smallest coefficient of thermal expansion of the entire mixture, the amount of Bzo3 was determined based on the premise that about 85% by weight of whitebait would be used of the total amount, so the amount of Bzo3 was determined as described above. This is a detailed quantity.

Such a mixed powder was melted and strain-removed in the same manner as described in Example 1 above, and then cut and polished (2000 #
) Samples of 5×5×15 (size n) were prepared, and various physical properties as shown in Table 4 below were measured.

In addition, using the mixed powder shown in Table 3 above, a prototype was made by melting it in the same manner as described above, and after strain removal treatment, it was rated according to the JIS standard.
A thermal shock resistance test was carried out in accordance with the method specified in JP-32030. That is, after holding the pot at 120±8°C in an electric furnace for 30 minutes, it was placed in cold water and held for 1 minute, and no abnormality was detected. Furthermore, after holding the glass at 150±10°C for 30 minutes for direct use, it was placed in cold water and left for 1 minute before being taken out. There were no cracks or breaks, and it was determined that the glass was suitable for use as heat-resistant glass for direct fire use.

As a reference for comparison with the glasses of Examples 1 and 2, the thermal expansion coefficients and bending strengths of commercially available glasses for pots and Pyrex glasses are shown in Table 5 below.

<Effects of the Invention> As described above, according to the present invention, it is possible to effectively utilize man-made glassy deposits, which are a type of unused resource that exists in large quantities in nature, and Instead of requiring extremely high temperatures for its purpose and/or melting, it can now be melted at a low temperature of 1,350°C, which is commonly used in the manufacture of ordinary glass daily necessities, greatly improving production efficiency. I can do it. The resulting glass is comparable to conventional products in terms of thermal expansion coefficient and strength, and has sufficient thermal shock resistance.

Patent applicant: Director of the Agency of Industrial Science and Technology (1 other person) Sub-Agent: Haru Yukichi

Claims (1)

[Claims] 1. LiO_2 powder 4-8% by weight, Na_2O powder 0.
A mixed powder having a composition of 5 to 2% by weight and the balance consisting of volcanic glassy deposit powder is heated and melted at a temperature of 1350°C or less, and then subjected to strain removal treatment at a temperature of 450 to 550°C. A method for producing thermal shock resistant glass. 2. LiO_2 powder 3-5% by weight, B_2O_3 powder 1
A mixed powder having a composition of 0 to 13% by weight and the balance consisting of volcanic glassy deposit powder is heated and melted at a temperature of 1350°C or less, and then subjected to strain removal treatment at a temperature of 450 to 550°C. A method for producing thermal shock resistant glass.