JPS6127337B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel tempered glass container. In other words, the present invention relates to a novel tempered glass container having overlapping layers of a compressive stress layer formed by rapid cooling strengthening treatment and a compressive stress layer having a different ion exchange rate on its inner and outer surfaces. More specifically, the present invention relates to a tempered glass container whose impact resistance is particularly effectively increased against external forces such as contact and impact applied to the outer surface of the container. Conventional tempered glass containers are made by coating the outer surface of the glass container with organic substances such as metal oxides or synthetic resins, or a combination thereof.
Alternatively, there are those in which a compressive stress layer is applied to the surface of the glass container by ion exchange treatment, and there are those in which a synthetic resin coating is applied to the surface of the glass container. They have achieved certain effects in increasing their respective strengths, and are used in some markets. For example, tempered glass containers with a coating are designed to improve scratch resistance to prevent relative deterioration of internal pressure resistance, while ion-exchange tempered glass containers have slightly improved scratch resistance, some internal pressure resistance, and impact resistance. This is an attempt to increase the strength. However, these tempered glass containers are only intended to relatively prevent deterioration of various strengths of the tempered glass containers by coating.
In ion-exchange tempered glass containers, the compressive stress layer is thin, so that the scratch resistance, internal pressure resistance, and impact resistance are not sufficiently increased. On the other hand, a known glass strengthening method is the so-called rapid cooling strengthening method, which strengthens glass by rapidly cooling the glass surface and imparting a compressive stress layer, but the glass to which this method is applied is compared to flat glass etc. It is limited to simple shapes and uniform thickness. It is almost impossible to apply a uniform compressive stress layer to objects with complicated shapes or uneven wall thickness, such as glass containers, and due to the non-uniformity, it is difficult to apply a small amount of external force. There are still problems with its practicality, as there is a strong risk of inducing a self-destruction. Note that although Japanese Patent Publication No. 41-20096 discloses a glass product that combines rapid cooling strengthening and ion exchange strengthening, and a technology for manufacturing the same, it is essentially intended for plate glass, and is not applicable to glass containers. Although there is a description of the applicability of the method, it does not substantially disclose a technique for improving the strength of glass containers. In view of the current state of the prior art and in response to the insatiable demands of those skilled in the art, the inventors of the present invention have conducted extensive research to develop a new tempered glass container that has further increased strength compared to conventional tempered glass containers. developed. Glass containers, which are usually used for carbonated drinks and are called returnable bottles, are manufactured using common glass container forming techniques such as the blow-and-blow method and the press-and-blow method. The final contact between the outer surface and the mold is the final contact. In the following, the outer surface of the glass container is constantly exposed to contact with other objects during transportation on a conveyor, filling, and subsequent recycling, and is frequently subjected to external forces, and the external forces are large. Therefore, the scratches that occur on the outer surface of the container are relatively numerous and large. In comparison, the inner surface of the container is subjected to action during the cleaning process during filling or recycling, but this occurs less frequently and the external force is smaller than that on the outer surface. Therefore, there are fewer and smaller scratches on the inner surface. However, especially in glass containers with relatively thin glass walls called lightweight returnable bottles, when an external force such as an impact from the outside surface is applied, a particularly large tensile stress (FLEXURE) is applied to the inside surface of the container.
STRESS) occurs, and at the location where it occurs,
If the glass cannot withstand the stress, the glass container will break at that point. In contrast, for returnable bottles with a relatively large glass wall thickness, when an external impact force is applied from the outside surface, a FLEXURE STRESS is generated on the inside surface of the container, causing tension around the point of impact on the outside surface. If stress (HINGE STRESS) is mainly generated and the glass cannot withstand the stress at that point, the glass container will be destroyed, but due to the relatively large wall thickness, the so-called impact resistance strength is relatively large. The present inventor conducted a detailed analysis of the use of the returnable bottle, and determined the correlation between the magnitude of the external force applied to the inner and outer surfaces of the returnable bottle, the degree of damage caused by it, and the magnitude of the generated stress and its wall thickness. As a result of the above research, we found a causal relationship between increasing effective practical strength and maintaining that strength. An object of the present invention is to provide a tempered glass container which suppresses the occurrence of FLEXURE STRESS, which is caused by an external impact force particularly on the outer surface of the container, and advantageously increases impact resistance strength. Another object of the present invention is to provide a tempered glass container that has an advantageous combination of increased impact resistance and scratch resistance. Another object of the present invention is to provide a tempered glass container that effectively imparts the above-mentioned strengths and has sufficient strength for practical use as a lightweight returnable bottle. The configuration of the present invention that satisfactorily achieves the above object includes an overlapping layer of a first compressive stress layer applied by rapid cooling and a second compressive stress layer having a high ion exchange rate on its inner surface, and a layer formed by rapid cooling. The glass container has an overlapping layer of a first compressive stress layer having a low ion exchange rate and a third compressive stress layer having a low ion exchange rate on its outer surface. In the tempered glass container of the present invention, the first compressive stress layer imparted by the rapid cooling method cannot have a compressive stress value above a certain level due to the peculiarity or complexity of the shape of the glass container. In other words, the larger the stress value of the first compressive stress layer, the more it contributes to increasing the strength of the glass body, but for articles with complex shapes such as glass containers, the practical strength of the container is improved. For example, if the stress value exceeds a certain level, there is a risk of self-destruction, and this risk increases rapidly, and it becomes easily destroyed by a small amount of external force. As mentioned above, these problems are caused by unbalanced compressive stress due to the complexity of the shape of the glass used as a container and the non-uniformity of the wall thickness. Therefore, the stress value of the first compressive stress layer for the glass container cannot be set to 750 Kg/cm ² as previously proposed by the applicant in Japanese Patent Application No. 57181/1981 regarding the rapid cooling strengthening technology for glass containers. Should be avoided. On the other hand, when the stress value is less than 100 Kg/cm ² , it is difficult to achieve the desired synergistic increase in strength, so it is better to avoid it. The layer thickness of the first compressive stress layer is up to the glass thickness.
Up to 1/4 of the way, it reaches a certain depth from the glass surface. Normally, on each glass surface, the thickness of the first compressive stress layer is at least not less than 100 microns.
Since the thickness is substantially three times or more than the thickness of the compressive stress layer formed by the ion exchange treatment, it effectively prevents the elongation of scratches that would affect the deterioration of the container strength, especially the internal pressure resistance strength. On the other hand, the thickness of the compressive stress layer imparted by ion exchange rarely exceeds 100μ, and is substantially less than 30μ. However, since the compressive stress layer can be applied to a high value of approximately 5000 Kg/cm ² , it is possible to create FLEXURE STRESS in thin glass containers by applying this high stress compressive layer to the inner surface of the container. can be effectively suppressed. Therefore, in a thin glass container, it is possible to obtain high impact strength relative to the glass thickness. In the present invention, when the glass container whose average glass wall thickness in the container body is 2.5 mm or less is targeted, it is relatively advantageous in increasing the impact strength. In other words, the tensile stress (FLEXURE STRESS) generated on the inner surface of the container due to external forces such as impact
The thinner the average wall thickness of the body of the glass container, the greater the effect, and it acts particularly markedly in cases where the value is 2.5 mm or less. This FLEXURE
Suppressing the occurrence of STRESS is due to it. This will prevent breakage, or in other words, the impact strength will be effectively increased. Note that if the average wall thickness of the body is less than 1.0 mm, it will not be possible to sufficiently compensate for the decrease in strength due to the thin wall, and it will be difficult not only to increase the strength sufficiently but also to maintain the desired strength. These numerical limits were calculated from actual measurement data to determine whether or not it is possible to maintain sufficient practical strength, especially impact strength, based on the occurrence of FLEXURE STRESS. To be more specific about the tempered glass container of the present invention, the first compressive stress layer imparted by rapid cooling and the second and third compressive stress layers imparted by ion exchange overlap each other on the inner and outer surfaces of the container. A high stress value compression layer due to ion exchange on the inner surface is obtained by increasing the ion exchange rate, and a relatively low stress value compression layer on the outer surface is obtained by increasing the ion exchange rate. It can be obtained by The glass container applied to the present invention is usually made of soda lime silica glass, which has a softening point of about 725-730°C, a deformation point of about 635-640°C, an annealing point of about 550-555°C, and The strain point is within the range of approximately 510-515°C. In the first compressive stress layer obtained by rapid cooling, the stress value is set to 100 to 750 as described above.
In order to keep it within the range of Kg/cm ² , it is necessary to take into consideration the special shape of the glass container.
Effective in a temperature range of 200℃ by rapidly cooling the glass surface at approximately 10 to 30℃/sec and injecting air at room temperature (approximately 20℃) at a glass surface velocity of 10 to 60m/sec to cool the glass surface. can be obtained. Generally, the stress value of the compressive stress layer due to rapid cooling is determined by the viscosity coefficient and viscosity change rate of the glass, and these are all determined by the temperature of the glass before and after the rapid cooling process, the heat transfer coefficient, and the temperature of the cooling fluid.・It is determined by the correlation between speed and kinematic viscosity coefficient, and it has been empirically revealed that the cooling rate factor, which is determined by the glass temperature before and after treatment and the temperature and speed of the cooling fluid, has the most significant effect. ing. On the other hand, potassium salts are generally used as alkali salts for ion exchange of soda lime silica glass. Typically, one or a combination of two or more of potassium nitrate, potassium chloride, potassium sulfate, etc. can be employed. The method for applying the potassium salt to the glass container is not particularly limited, and may be a molten salt immersion method, a spray method, an aqueous solution immersion method, a spray method, or the like. The glass container is subjected to a heat treatment for ion exchange at a temperature within the range of 0 to 100°C below the strain point of ordinary glass while in contact with potassium salt. The compressive stress layer created by ion exchange is greatly affected by the amount of potassium salt attached to the glass surface, the heat treatment temperature, and the heat treatment time, and the stress value is particularly affected. Since it is extremely difficult to distinguish the heat treatment temperature and heat treatment time between the inner and outer surfaces of a glass container and control them individually, it is necessary to apply second and third compressive stress layers with different stress values to the inner and outer surfaces of the glass container. is realistically controlled by the amount of potassium salt deposited. In other words, the amount of potassium salt deposited is large on the inner surface of the glass container and comparatively less on the outer surface, and by applying ion exchange heat treatment after coating, the compressive stress layer on the inner surface of the glass container is larger than that on the outer surface. A second compressive stress layer having a stress value can be applied. More specifically, a stress layer can be efficiently applied by applying a concentrated potassium salt solution, such as a saturated solution, to the inner surface of the glass container and a diluted solution to the outer surface, followed by heat treatment. In addition, even if the amount of potassium salt attached to the outer surface is extremely small,
Within the scope of the present invention. The glass containers to be treated that are applied to the present invention are generally untreated, but in order to increase the practical strength of the container, especially the scratch resistance, a metal oxide coating is used. It is convenient to do so. In particular, in the tempered glass container of the present invention, the outer surface is a compressed layer with a relatively low stress value, so the scratch resistance is low. Note that the metal oxide film is usually applied as follows. That is, SnCl ₄ gas, SnCl ₂ (CH ₃ ) ₂ gas, etc. are applied to the high temperature outer surface of the glass container immediately after it comes out of the molding machine. Similarly, a metal oxide film can also be applied by using an organic compound such as titanium or zirconium. Furthermore, the glass container of the present invention can be provided with additional protection means on its outer surface to improve its scratch resistance compared to the general level, thereby further improving the practical strength properties of the final product. Another safeguard is
Formation of a protective film of an organic material having lubricity, elasticity, etc. on the outer surface of a glass container, such as fatty acids such as oleic acid, surfactants such as polyoxyethylene sorbitan monooleate, polyethylene, polyurethane, ionomer resins, etc. It is to coat the resin with an organic substance. Hereinafter, the present invention will be explained in more detail based on examples. Example: Glass container (capacity 250ml) at high temperature (approximately 680℃) immediately after coming out of the glass container molding machine (capacity 250ml) weight 98
g, body average wall thickness 1.7 mm) was treated with SnCl ₂ (CH ₃ ) ₂ gas to form a SnO ₂ film on its outer surface. Subsequently, online, the temperature of the container was adjusted to approximately 580°C on the outer surface of the center part of the body, and approximately 640°C on the inner surface of the body, and a rod-shaped nozzle was inserted into the inner surface of the container from the container mouth. 1.5Kg/cm ² of compressed air (temperature of approximately 20°C) was applied to the outer surface of the container through a nozzle roughly following the outer shape of the container, and 1.0Kg/cm ² of compressed air was applied to the container at approximately 120 RPM. It was sprayed for about 10 seconds while rotating to rapidly cool it down. Through this rapid cooling process, the outer surface of the container is heated to approximately 250°C and the inner surface to approximately 300°C.
The temperature dropped to ℃. At this stage, several of the glass containers were gradually cooled to room temperature, and the fractured surfaces of their bodies were measured using a Beretsk compensator, and a compressive stress value of approximately 360 kg/cm ² on average was observed on the inner and outer surfaces. . The thickness of the stress layer was approximately 170μ. In addition, a tensile stress value of approximately 160 Kg/cm ² was confirmed at the center of the cross section. After this rapid cooling process, the glass container was cooled to the above temperature, and then KNO ₃ and KCl were added to the inner surface of the glass container.
(KNO ₃ :KCl=6.2:3.8 weight ratio) mixed saturated aqueous solution, about 30% KNO ₃ aqueous solution on the outer surface,
The coating was applied by spraying for about 5 seconds each from Sonimist nozzles installed inside and outside the container. After drying, it was subjected to ion exchange treatment at about 480°C for 30 minutes in an electric furnace, cooled to room temperature, and residual alkali salts were washed away to obtain a tempered glass container. When the stress value of the outer surface compressed layer of this tempered glass container was measured using a surface stress meter, it was found that the average value was 1050 Kg/cm ² , and the thickness of the stress layer due to ion exchange was about 11 μm. Similarly, on the inner surface of the container, the average
The stress value was 1650 Kg/cm ² and the average layer thickness was 16 μ. The tensile stress at the center of the cross section due to the Beretsk compensator was approximately 133 Kg/cm ² . The glass composition of the glass container is as follows. ●Glass composition SiO ₂ 71.5% by weight Al ₂ O ₃ 2.5 CaO 10.9 Na ₂ O 12.7 K ₂ O 1.4 Others 1.0 Total 100.0 ●Softening point 727℃ ●Deformation point 637℃ ●Annealing point 554℃ ●Strain point 515℃ This implementation In the example, not a single glass container was broken during the process. The practical strength characteristics of the tempered glass container obtained in this example are compared with those of the untreated container and the comparative container, and are listed in Table 1. Note that each data is based on n=30 pieces.

[Table] As is clear from Table 1, the tempered glass container of the present invention has excellent practical strength in comparison with the untreated container and the comparative container. For example, especially in terms of impact strength, the "Example" container is found to have approximately 69% higher strength at 1 trip and approximately 127% higher strength at 10 trips compared to "Comparative Container 1." Moreover, compared to "Comparative Container 2", an increase in strength of about 10% after 1 trip and an increase of about 23% after 10 trips is observed. In addition, in terms of internal pressure resistance, the "Example" container has a relatively higher strength than the "Comparative container".
Also, in comparison with untreated containers, as the number of trips increases, the impact strength after tripping increases by about three times, and the internal pressure resistance strength also increases by about two times. In addition, "Comparison container 1" in Table 1 refers to a container that has the same shape as the "Example" container and was subjected to only the rapid cooling treatment under the same conditions as the "Example".
This is a tempered glass container that combines metal oxide coating and rapid cooling treatment. "Comparative Container 2" is a tempered glass container having the same shape as above and subjected to ion exchange treatment under the same conditions as in "Example", which is a combination of so-called metal oxide coating and ion exchange treatment.
Both "Comparison container 1", "Comparison container 2" and "Example"
This is an organic substance coated container coated with ionomer resin under the same conditions. The items and data in Table 1 were tested and measured using the following method. Internal pressure strength: In accordance with JIS S2302, the internal pressure value until the container breaks was measured using an internal pressure tester manufactured by AGR, and this was defined as the internal pressure strength. Impact strength: In accordance with JIS S2302, the impact value of the container up to breakage was measured using an impact tester manufactured by AGR, and this value was defined as the impact strength. Trip: In order to examine the degree of strength deterioration due to handling of the glass container during filling, etc., the container was damaged for 1 minute using a line simulator manufactured by AGR, and this was defined as 1 trip. As described in detail above, the present invention can be easily applied to conventional mass-produced glass containers, and aims to further increase practical strength, especially impact resistance, particularly for use as lightweight returnable bottles. It is possible,
Furthermore, even if the number of trips increases, there is almost no deterioration in the impact strength, which is noteworthy, and it is a significant contribution to this industry.

Claims (1)

[Claims] 1. An overlapping layer of a first compressive stress layer applied by rapid cooling and a second compressive stress layer with a high ion exchange rate on the inner surface, and a first compressive stress layer applied by rapid cooling. and a third compressive stress layer with a low ion exchange rate on its outer surface. 2. The tempered glass container according to claim 1, wherein the first compressive stress layer has a stress value of 100 to 750 Kg/cm ² . 3. The tempered glass container according to claim 1 or 2, wherein the body has an average wall thickness of 1.0 to 2.5 mm. 4. The tempered glass container according to claim 3, wherein the outer surface of the container is provided with a metal oxide coating and an organic protective coating.