JPH0417904B2 - - Google Patents

Description

[Detailed description of the invention]

Technical Field The present invention relates to a lead-free frit composition for coloring glass, specifically an improved frit composition that does not contain harmful lead components, has particularly excellent alkali resistance, and is suitable for coloring, displaying, etc. glass containers for storing food and drink products, etc. The invention relates to a lead-free frit composition. BACKGROUND TECHNOLOGY Traditionally, lead borosilicate frit has been used in glass enamel for labels and decoration of glass products such as bottles and tumblers due to its surface gloss and chemical resistance. As the toxicity of certain lead has become an issue, there has been a demand for a lead-free type of frit that does not contain lead components, and various research and development efforts have been made on such a lead-free frit. However, the lead-free frits of various compositions that have been developed generally still have room for improvement in the fusing temperature, expansion coefficient, and chemical resistance, which are the basic characteristics required for frits. Alkali resistance) is insufficient, and even if it is excellent, it cannot be said to be fully applicable to applications that are repeatedly washed with alkaline water, such as bottle labels. It's hard to match Fritz. OBJECTS OF THE INVENTION An object of the present invention is to provide a lead-free frit composition that has excellent alkali resistance and is particularly suitable for bottle labels. Structure of the Invention The above object is achieved by a composition having the following composition. SiO ₂ 45-50% by weight B ₂ O ₃ 8-12 ZnO 20-25 Total of two or more selected from K ₂ O, Na ₂ O and Li ₂ O 5-10 CaO 3-6 ZrO ₂ 1-5 〃 Fluorine 1-4 〃 As a result of intensive research, the present inventors found that the composition having the above composition does not contain harmful lead components and has strong alkali resistance. Therefore, the composition of the present invention is extremely effective as a lead-free frit that is comparable to or even superior to conventional lead borosilicate frits, particularly for labels on bottles and the like. Of course, the above composition can be fired at a firing temperature of 640°C or lower, which is required for frits.
It has a linear expansion coefficient of approximately 85×10 ^-7 /°C or less. The reason why the composition of the present invention has such excellent properties is still not clear, but in order to improve the alkali resistance, it is possible to improve the alkali resistance.
The main contributions are the appropriate increase in the amount of SiO ₂ and the combination of ZrO ₂ and CaO components in specified amounts, and by increasing the amount of SiO ₂ mentioned above, an appropriate expansion coefficient can be given, and the fusion caused by these modified components is The increase in the deposition temperature is caused by the _three components of B ₂ O and K ₂ O.
This is thought to be due to the fact that it can be suppressed suitably by appropriately increasing the amounts of alkaline components such as and ZnO components and adding a fluorine component. In any case, a frit having the above composition has not been known in the past, and the present inventors have also discovered for the first time that such a composition exhibits significantly improved alkali resistance and other properties. It is essential that the composition of the present invention has the above-mentioned specific composition, and if any one component is out of the above-mentioned range, it will be difficult to achieve the desired effects of the present invention. That is, if the SiO ₂ component, which is one of the most important components in the composition of the present invention, is below the above range, the effect of improving alkali resistance, which is the most important feature, will be reduced. On the other hand, if the SiO ₂ component exceeds the above range, the fusion temperature will rise too much and a large amount of B ₂ O ₃ , ZnO, etc. will be required to suppress it.
Blending a large amount of these components has the disadvantage of lowering chemical resistance and causing frit crystallization, and in addition, the amount of other components to be blended is reduced. Further, K ₂ O and other alkaline components mainly contribute to lowering the fusion temperature, but if they exceed 10% by weight, the coefficient of expansion becomes too large, which may cause cracks in the base glass. ZrO ₂ and CaO play an auxiliary role in improving alkali resistance, but at 4% by weight ZrO ₂
If it exceeds , the fusion temperature will be too high and CaO will be 6
If it exceeds % by weight, there is a drawback that the expansion coefficient becomes too high. Furthermore, although fluorine can lower the fusing temperature, if it exceeds 4% by weight, it has the disadvantage of making the glass cloudy. The frit according to the present invention is produced by mixing the components having the above-mentioned composition in the form of commonly used oxides, salts, fluorides, etc., melting the mixture at about 1200 to 1800°C, and quenching the melt in water. A frit powder is prepared by wet-pulverizing the resulting granular frit using a ball mill or the like, and then drying and sieving the slurry. The frit powder thus obtained is used as a paste or ink in the same way as ordinary glass coloring frits of this type. That is, the above-mentioned frit powder is mixed with a suitable heat-resistant inorganic pigment such as titanium white, cobalt blue, chrome green, iron brown, etc., and then kneaded with an organic vehicle such as ordinary screen oil to form a paste enamel. Or it is kneaded with wax etc. to make thermoplastic enamel. The application of such enamels to glass products is also carried out according to known methods. For example, it is printed on bottles etc. according to the usual screen printing method, and then the maximum temperature of about
It is fired at 620-640℃. Thus, by using the frit of the present invention, a colored film having excellent alkali resistance and sufficient surface gloss is formed. Examples Examples of the present invention will be described below. Example 1 Each oxide, a salt serving as an oxide, and a fluoride were mixed to have the following composition. SiO ₂ 46.0% by weight B ₂ O ₃ 12.0 ZrO ₂ 3.0 Li ₂ O 2.0 Na ₂ O 6.0 ZnO 24.0 CaO 5.0 F 2.0% by weight The above mixture was placed in a crucible and heated and melted at 1250°C. The melt was poured into water to obtain granular frit, which was wet-pulverized in a ball mill, and the resulting slurry was dried and loosened with a sieve to obtain a frit powder of the present invention. 90 parts by weight of the obtained powder was mixed with 10 parts by weight of titanium white, and screen oil (manufactured by Okuno Pharmaceutical Co., Ltd. #
1068) to paste it. This paste was printed on a glass plate by screen printing and baked at 680°C to form a baked film. The physical properties of the baked film thus obtained were tested as follows. <Alkali resistance test> As alkali resistance test liquid, NaOH 9% by weight,
Using a solution consisting of 1% by weight Na ₃ PO ₄ 12H ₂ O and 90% by weight water, the sample was immersed in the solution at 88±1°C for 24 hours to determine the amount of film thickness reduction and weight loss in the baked film part of the sample. The amount was measured, and the alkali resistance was evaluated based on these values. <Expansion coefficient and presence or absence of cracks> In addition to measuring the linear expansion coefficient of the sample baked film,
The presence or absence of cracks was visually observed. The results are shown in Table 1 below. For comparison, Table 1 shows a lead borosilicate frit (commercial product, bottle enamel, Z-728 (white color) manufactured by Okuno Pharmaceutical Industries, Ltd.) with the following composition, which has conventionally been widely used as this kind of frit for glass coloring. )) The results of the same test were also listed. <Lead borosilicate frit composition> SiO ₂ 36% by weight B ₂ O ₃ 3 〃 PbO 48 〃 ZrO ₂ 6 〃 TiO ₂ 2 〃 Li ₂ O 3 〃 Na ₂ O 2% by weight

【table】

[Table] From Table 1 above, the frit of the present invention has excellent alkali resistance, which is almost equivalent to that of lead borosilicate frit, and the firing temperature and expansion coefficient are appropriate, so there is no risk of cracking. That is clear. In addition, pastes were obtained in the same manner using cobalt blue, chrome green, and iron brown instead of titanium white in the above method, and after screen printing, the pastes were baked at 630°C to obtain printed and fired films. .
As a result of the same test, the obtained films were found to be almost equally excellent in alkali resistance and other properties. This shows that the lead-free glass coloring frit of the present invention is very useful as a bottle label.

Claims (1)

[Claims] 1 _SiO2 45-50% by weight, _{B2O3 8-12} % by weight,
ZnO20 to 25% by weight, two or more selected from K ₂ O, Na ₂ O and Li ₂ O in total of 5 to 10% by weight, CaO3 to
A lead-free frit composition for coloring glass, characterized in that it has a composition consisting of 6% by weight, 1 to 5% by weight of ZrO ₂ and 1 to 4% by weight of fluorine.