JPH0432022B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a glaze composition for glazed cement products used in glazed cement products such as roof tiles, architectural exterior panels, and the like. (Conventional technology) When cement products are heated to a high temperature of 650°C or higher, Ca(OH) ₂ generated by hydration decomposes into CaO and H ₂ O, resulting in a significant decrease in strength. Lead-based or phosphoric acid-based frits, which can be baked at low temperatures below 650°C, have been used. However, such frits that can be fired at low temperatures have poor weather resistance and chemical resistance, and therefore have problems such as loss of gloss within a short period of time when used outdoors. In order to solve such conventional problems, the present inventors have published Japanese Patent Publications No. 48464/1986 and Japanese Patent Publication No. 57-48464.
As shown in Publication No. 55674, the company first invented a method for manufacturing cement products that exhibits little strength deterioration even when fired at temperatures of 650 to 900 degrees Celsius. Frits used for cement have been reused, and when glazed on the surface of cement, there are still problems such as the coefficient of thermal expansion not matching and poor weather resistance and gloss.
A desirable glazed cement product was not obtained. (Problems to be solved by the invention) The present invention solves these conventional problems,
By making various improvements to the composition of the frit, it was completed with the aim of creating a glaze composition for glazed cement products that has excellent weather resistance, chemical resistance, and gloss, as well as excellent compatibility with cement. (Means for Solving the Problems) The present invention is a glaze composition for glazing and firing the surface of a cement molded article formed into an arbitrary shape, the composition of which is in mol%, SiO ₂ 50 to 65%,
_{Al2O3 0} ~7%, _B2O3 18~26%, MO3~15% ( _M
is Ca, Mg, Zn, Ba, Sr), _R2O6 ~12% (R is
Li, Na, K), and ZrO ₂ in a range of 0 to 10%. As mentioned above, the present invention is based on the invention disclosed in Japanese Patent Publication No. 56-48464 and Japanese Patent Publication No. 57-55674. With these two inventions, it has been revealed that cement products with excellent mechanical strength can be obtained even after firing. In the present invention, the composition of the frit used for glazing is limited to the above-mentioned special range in order to maximize compatibility with cement.
The characteristics of this frit composition are that the amounts of SiO ₂ and Al ₂ O ₃ were adjusted so that it can be baked at 650 to 900°C, where the cement product has the highest mechanical strength, and that the coefficient of thermal expansion of the cement and the temperature of the frit In order to match the coefficient of thermal expansion and increase weather resistance and chemical resistance, the R ₂ O content is set low, while B ₂ O ₃ and MO
In addition to increasing the component to prevent a decrease in meltability due to a decrease in the R ₂ O component, and setting the B ₂ O ₃ component to the optimal range to increase the gloss of the glazed surface.
It is possible to obtain either a transparent frit or a milky white frit depending on the amount of ZrO ₂ .
Next, the reason for limiting the numerical values of each component will be explained. SiO ₂ forms the framework of the frit and accounts for 50%
(mol%, the same applies hereinafter), the weather resistance and acid resistance will be insufficient as a glaze for cement products;
If it exceeds 65%, the melting point will be too high and it will be unsuitable for glazing cement products. Al ₂ O ₃ is a component that contributes to weather resistance and acid resistance like SiO ₂ , but at 7%
If the temperature exceeds 100%, the melting point will rise and it will become unsuitable for glazing cement products. B ₂ O ₃ acts as a flux for creating frit, and if it is less than 18%, the gloss will be poor, and if it exceeds 26%, the acid resistance and weather resistance will be significantly reduced. R ₂ O (R is Li, Na, K) also acts as a flux for making frits, but if it is less than 6%, the temperature required for firing becomes too high, making it difficult to use as a frit for cement. If it exceeds 12%, acid resistance and weather resistance will deteriorate, and the coefficient of thermal expansion will not match that of cement.
MO (M is Ca, Mg, Zn, Ba, Sr) is B ₂ O ₃ and
It supplements the effect of the R ₂ O component, but if it is less than 3%, the firing temperature will become too high and it is unsuitable for use in cement, and if it exceeds 15%, it will also result in deterioration of weather resistance and acid resistance. Among these MO components, Ca is an important component for increasing weather resistance and acid resistance, and especially in transparent frits containing less than 3% ZrO ₂ as described below, Ca is an essential component. ZrO ₂ is a component to improve acid resistance and weather resistance, and is also an important component as a nucleating agent that determines whether the frit will be transparent or milky white.
As mentioned above, a transparent frit is obtained when ZrO ₂ is 0 to 3%, and in this case Ca is an essential component. Also, when ZrO ₂ is 3 to 10%, a milky white frit is produced, but when ZrO ₂ is 10%
If it exceeds this, the melting point will rise too much and it will be impossible to bake it into cement. The preferable ranges of each component in the case of forming a transparent frit are SiO ₂ 50-65%, Al ₂ O ₃ 0-5%,
_B2O3 18~26%, MO3~12%, _{R2O6 ~} 12%,
ZrO ₂ 0-3%, the most preferred range is SiO ₂ 55
~63%, _{Al2O3 1.4} ~3.5%, _{B2O3 21} ~26%, MO5
~8%, _R2O6 ~12%, and ZrO2 ₀ ~2%. In addition, the preferable ranges of each component in the case of producing a milky white frit are SiO ₂ 50-60%, Al ₂ O ₃ 0-7%, B ₂ O ₃ 18-60%.
26%, MO5~15%, _R2O6 ~12%, _ZrO2 3~10%
It is. A frit having such a composition is ground into a slip using a pot mill in a conventional manner, and pigments, clay, CMC, etc. are added as necessary. This slip is glazed onto the surface of the cement molded product by any method such as spraying or dipping, and then dried. The glazed cement moldings are then fired at 650-900°C for 5-60 minutes. This firing simultaneously bakes the applied glaze and allows the unhydrated portions within the cement particles to be sufficiently hydrated and hardened by curing after firing, contributing to improving the mechanical strength of the product. The composition of the frit of the present invention is determined so that it can be baked at a temperature of 650 to 900 degrees Celsius, where the mechanical strength of the cement molded product is at its maximum, so if the baking temperature is outside this range, baking will not only be difficult but also impossible. , the mechanical strength of the cement product will also be reduced. After firing in this manner, the fired product is cured under conditions where the necessary amount of water can be sufficiently supplied, and is sufficiently hydrated and hardened to become a finished product. (Example) Next, examples of the present invention will be shown separately for cases where ZrO ₂ is 0 to 3% and cases where ZrO ₂ is 3 to 10%. Example 1 A cement mixture obtained by kneading a mixture of 100 parts of cement, 200 parts of crushed andesite of 8 mesh under, and 50 parts of water was pressed to 50 kg using a 500 ton hydraulic press.
A cement molded product was obtained by pressure dehydration molding under conditions of f/cm ² or more and a holding time of 30 seconds or more. On the other hand, transparent frits of Examples shown as No. 1 to No. 10 in Table 1 were prepared, and each frit was placed in a pot mill with 100 parts of frit, 5 parts of frog's eye clay, 2 to 10 parts of pigment, and 50 parts of water. and crushed to 4 to 5 g/200 mesh/50 c.c. to form a slip. Each slip was glazed onto the cement molded article by a spray method, dried, and then fired for 40 minutes at the firing temperature listed in Table 1. The fired product was immersed in water for one day and then steam-cured for 12 hours at 40°C and 100% temperature, resulting in a fully hydrated and hardened finished product. The glazed surface of each test piece was visually observed to evaluate its gloss, and it was immersed in 10% sulfuric acid at room temperature for 24 hours, and its acid resistance was evaluated based on the change in gloss. The results are shown in Table 1. Example 2 A milky white frit having the composition shown as No. 1 to No. 10 in Table 2 was prepared, and glazed on a cement molded product prepared in the same manner as in Example 1. The gloss and acid resistance were evaluated. The second result is
Shown in the table. In both Examples 1 and 2, the linear thermal expansion coefficient of the frit is in the range of 6 to 7 × 10 ^-6 /°C, which is 6.7 × the linear thermal expansion coefficient of the cement product.
It showed a value close to 10 ^-6 /℃. (Effects of the Invention) As is clear from the above description, the present invention provides a cement molded product with a glazed surface that has excellent weather resistance, chemical resistance, and gloss, and is also excellent in compatibility with cement in terms of expansion resistance. As a glaze composition for glazed cement products, it can be widely applied to the production of unconventional roof tiles, exterior panels for buildings, etc., making an extremely large contribution to the development of industry. be.

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Claims (1)

[Claims] 1. A glaze composition for glazing and firing the surface of a cement molded article formed into an arbitrary shape,
Its composition is in mol%, _SiO2 50~65%, _{Al2O3 0} ~
7%, _B2O3 18-26%, MO3-15% (M _is Ca,
Mg, Zn, Ba, Sr), _R2O6 ~12% (R is Li, Na,
K), a glaze composition for glazed cement products, characterized in that the ZrO ₂ content is in the range of 0 to 10%.