JPS6127336B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel tempered glass container. More specifically, the present invention relates to a novel tempered glass container having compressive stress layers formed by rapid cooling strengthening treatment and compressive stress layers having different ion exchange rates on the inner and outer surfaces thereof.
More specifically, the container has a protective means that effectively increases the damage resistance against relatively large external forces such as contact impact on the outer surface of the container and the internal pressure resistance against increased pressure inside the container. Concerning efficiency-strengthened glass containers. 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, or by applying ion exchange treatment to the surface of the glass container to form a compressive stress layer. There are those that are coated with synthetic resin and those that are coated with synthetic resin. They have achieved considerable effectiveness in increasing the strength of each type, and are also used in some markets. For example, tempered glass containers with coatings are designed to improve scratch resistance to prevent deterioration of internal pressure resistance, while ion-exchange tempered glass containers have improved scratch resistance and simply increase internal pressure resistance. This is an attempt to increase impact strength. However, in these tempered glass containers, coatings are only used to prevent relative strength deterioration, and ion-exchange tempered glass containers have a low compressive stress layer, so it is especially important to reduce scratch resistance. However, the reinforcement of various strengths has not been sufficiently increased, such as limited reinforcement. 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 actually a sheet. It is limited to those with a relatively simple shape and uniform thickness. It is almost impossible to apply a uniform compressive stress layer to objects with complex shapes and uneven wall thickness, such as glass containers, and due to this non-uniformity, self-destruction may occur due to the addition of a small amount of external force. Since there is a risk of inducing Furthermore, Japanese Patent Publication No. 41-20096 discloses a technology for a glass product that combines rapid cooling strengthening and ion exchange strengthening, and a method for manufacturing the same, but it is essentially aimed at sheet glass, and is not applicable to glass containers. The technology for improving practical strength has not been disclosed yet. In view of the current state of the prior art and in response to the insatiable demands of those skilled in the art, the inventor of the present invention has conducted intensive research and has discovered a new tempered glass container that has further increased strength compared to conventional tempered glass containers. Ta. Glass containers called returnable bottles, which are normally used for carbonated beverages, are manufactured using common glass container forming techniques such as the blow-and-blow method and the press-and-blow method. The final step is the contact between the outer surface of the container and the outer mold. In the following, the outer surface of the glass container is constantly exposed to contact with other objects during transportation on a conveyor, filling, etc. and subsequent recycling use, and the outer surface of the glass container is exposed to a large amount of external force. . In contrast, the inner surface of the container is only slightly affected during the cleaning process during filling or recycling.
Compared to that on the outer surface, the frequency is lower and the external force is also smaller. In the external force that the glass container receives, the present invention
There is a large difference between its outer and inner surfaces,
By eliminating the destructive factors that occur from frequent and strong external forces on the external surface, most of the destruction that occurs on the external surface can be prevented, and appropriate protection measures are sufficient for less frequent and weak external forces. It is based on knowledge and various data and analysis results that match it. A first object of the present invention is to provide a tempered glass container which has both increased strength due to the large stress value of the ion-exchange compressive stress layer and increased strength due to the large layer thickness of the quenched compressive stress layer. A second object of the present invention is to provide a tempered glass container that is particularly effective in increasing scratch resistance and internal pressure resistance. A third object of the present invention is to provide a tempered glass container that has sufficient strength for practical use as a lightweight "returnable bottle." The structure of the present invention that satisfactorily achieves the above object includes a first compressive stress layer applied to the inner and outer surfaces by rapid cooling, a second compressive stress layer having a high ion exchange rate on the outer surface, and a second compressive stress layer with a high ion exchange rate on the inner surface. The glass container has third compressive stress layers each having a low ion exchange rate, one on top of the other. More specifically, an overlapping layer of a first compressive stress layer imparted by rapid cooling and a second compressive stress layer having a relatively large stress value imparted by ion exchange is applied to the outer surface thereof, and then by rapid cooling. The glass container has, on its inner surface, an overlapping layer of a first compressive stress layer applied by ion exchange and a third compressive stress layer having a relatively small stress value applied by ion exchange. 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, as the stress value of the first compressive stress layer increases, it contributes to increasing the strength of the glass itself, but it cannot improve the strength of the container for products with complex shapes such as glass containers. For example, if the stress value exceeds a certain level, there is a risk of self-destruction, and the rate of self-destruction increases rapidly, and it becomes easy to break due to a small amount of external force. As described above, these problems are caused by the unbalanced stress layer due to the complicated shape of the glass used as a container and the non-uniform thickness of the glass. Therefore, the stress value of the first compressive stress layer for the glass container should be 750 Kg/cm ² or more, as previously proposed by the applicant in Japanese Patent Application No. 57181/1981 regarding 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. Typically, on each glass surface, the thickness of the first compressive stress layer is at least not less than 100 microns. Since it is substantially three times or more thicker than the thickness of the compressive stress layer formed by the ion exchange treatment, it is possible to effectively prevent scratches from elongating, which would affect the deterioration of the container strength. However, since the compressive stress value is small, it is not possible to sufficiently prevent the occurrence of even minute scratches due to small external forces, and as it is, it is difficult to maintain sufficient and desired practical strength as a tempered glass container for a long period of time. On the other hand, the thickness of the compressive stress layer imparted by ion exchange hardly exceeds 100μ, and is substantially 30μ or less. Therefore, since it is considerably weaker than the first compressive stress layer, that layer is easily penetrated, and once a flaw occurs that penetrates that layer, it is no longer possible to prevent the flaw from elongating. This has the disadvantage that it does not contribute to maintaining strength in any way. On the other hand, since the compressive stress value can be raised to a high value of approximately 5000Kg/cm ² ,
It has the advantage of high resistance to prevent scratches. The present invention provides a first compressive stress layer applied by a rapid cooling method and a second and third compressive stress layer applied by an ion exchange method, each of which compensates for each other's shortcomings and effectively brings out the advantages of each. At the very least, it is a tempered glass container that is organically bonded. More specifically, in a glass container, a first compressive stress layer imparted by rapid cooling and second and third compressive stress layers imparted by ion exchange overlap and exist on the inner and outer surfaces of the container, respectively. , the ion-exchanged second compressive stress layer on the outer surface is
The ion-exchange rate is increased to have a large compressive stress value, and the ion-exchanged third compressive stress layer on the inner surface has a relatively small ion-exchange rate to have a relatively small compressive stress value. In the tempered glass container of the present invention, since the overlapping compressive stress layer on the outer surface has a large stress value, it can sufficiently suppress the generation of tensile stress on the outer surface caused by an increase in the internal pressure of the container. It contributes to an increase in internal pressure strength, and because the surface hardness increases, it contributes to an increase in scratch resistance.Thereby, it reduces the surface microscopic scratches that cause strength deterioration, and indirectly leads to an increase in various strengths. It creates a synergistic effect of being Although the stress value of the overlapping compressive stress layer on the inner surface is relatively small, the external force applied to the inner surface of the container is small and infrequent, so it does not directly cause damage to the container. More specifically about the overlapping compressive stress layers on the outer and outer surfaces of the tempered glass container of the present invention, the overlapping compressive stress layers on the outer surface of the glass container, which improve the internal pressure resistance strength, are effective as a protection measure against elongation of the depth of scratches. A first compressive stress layer caused by the cooling method and a second compressive stress layer with a large stress value due to ion exchange, which is effective as a protection measure against microscopic surface scratches, are integrated and overlap, and the overlapped compressive stress layer on the inner surface of the glass container is formed. The layer includes a first compressive stress layer due to rapid cooling applied opposite to a first compressive stress layer due to rapid cooling of the outer surface, and a third compressive stress layer having a stress value smaller than that of the outer surface due to ion exchange. Existing as one and overlapping,
The integral overlapping compressive stress layers on the inner and outer surfaces balance each other and exist in a stable state. 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 , the temperature must be approximately 10 to 30℃/ses within the temperature range of 0 to 200℃ below the deformation point of glass.
This can be advantageously obtained by cooling the glass surface by injecting air at room temperature (approximately 20°C) at a cooling rate of 10 to 60 m/ses and a glass surface velocity of 10 to 60 m/s. in general,
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, which both depend on the temperature of the glass before and after the rapid cooling process,
It is determined by the correlation between the heat transfer coefficient, the temperature and velocity of the cooling fluid, and the kinematic viscosity coefficient, and the most significant influence is the cooling rate factor, which is determined by the temperature of the glass before and after treatment and the temperature and velocity of the cooling fluid. This has been demonstrated empirically. On the other hand, potassium salts are generally used as alkaline 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 alkali 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 heat treatment for ion exchange while in contact with an alkali salt, usually at a temperature within the range of 0 to 100°C below the strain point of the glass.
The compressive stress layer caused by ion exchange is greatly affected by the amount of alkali salt that contributes to ion exchange attached to the glass surface, heat treatment temperature, and heat treatment time.
In particular, the influence on stress values is large. heat treatment temperature,
The heat treatment time is determined by distinguishing between the inner and outer surfaces of the glass container.
Since it is extremely difficult to control them individually, the second, inner and outer surfaces of the glass container with different stress values
It is practical to control the application of the third compressive stress layer by the amount of alkali salt deposited. In other words, the amount of alkali salt attached to the outer surface of the glass container is large;
By applying a small amount to the inner surface and subjecting it to ion exchange heat treatment, it is possible to provide the outer surface of the glass container with a second compressive stress layer having a stress value greater than the compressive stress value on the inner surface. in particular,
A stress layer can be efficiently applied by applying a concentrated alkaline salt solution, such as a saturated solution, to the outer surface of a glass container and a diluted solution to the inner surface, followed by ion exchange heat treatment. Alternatively, the tempered glass container of the present invention can also be produced by immersing a glass container whose inner surface is coated with a saturated solution in a molten alkaline salt bath and subjecting its outer surface to ion exchange treatment. Note that cases where the amount of potassium salt adhering to the inner surface of the container is extremely small are also included within the scope of the present invention. The glass containers to be treated to be applied to the present invention are generally untreated, but in order to further improve the practical strength of the container, it is preferable to use one coated with a metal oxide coating. Metal oxide coatings are typically applied as follows. That is, SnCl ₄ gas, Sncl ₂ (CH ₃ ) ₂ gas, etc. are applied to the high-temperature glass container immediately after it comes out of the molding machine. Alternatively, a metal oxide film can be applied in a similar manner by applying an organic compound such as titanium or zirconium. Further, additional protective means can be added to the outer surface of the glass container of the present invention to further improve the scratch resistance and further improve the practical strength characteristics of the final product. Another protective means is the formation of an organic protective film that imparts lubricity to the outer surface of the glass container, and includes fatty acids such as oleic acid, surfactants such as polyoxyethylene sorbitan monooleate, polyethylene polyurethane, and ionomers. Coating with organic substances such as resin or other resins. Hereinafter, the present invention will be explained in more detail based on examples. Example: A glass container (capacity 272 ml, weight 160
g) 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 of the body and approximately 640°C on the inner surface, and a rod-shaped nozzle was inserted into the inner surface of the container from the mouth of the container, and the temperature was adjusted to 1.5Kg/cm ² compressed air (temperature: approx. 20°C) for about 10 seconds, and compressed air (temperature: ^approx .
°C) were simultaneously injected while rotating the container at approximately 120 RPM to perform a rapid cooling process. This rapid cooling process lowered the temperature of the outer surface of the container to approximately 300°C and the inner surface to approximately 350°C. At this stage, several of the glass containers were gradually cooled to room temperature, and the broken surfaces of their bodies were measured at several locations with a Beretsk compensator.
Compressive stress values of Kg/cm ² were observed. A tensile stress value of approximately 190 Kg/cm ² was confirmed at the center of the cross section. It was also confirmed that the thickness of the stress layer was approximately 210μ. After this rapid cooling process, a mixed saturated aqueous solution of KNO ₃ and KCl (KNO ₃ :KCl=6.2:3.8 weight ratio) was applied to the outer surface of the glass container, and 30% of the mixture was applied to the inner surface of the glass container.
The KNO ₃ aqueous solution was applied by spraying from each Sonimist nozzle for about 5 seconds each. and,
After drying, it was subjected to ion exchange heat treatment at about 480°C for 25 minutes in an electric furnace, and after cooling to room temperature, residual alkali salts were washed away to obtain a tempered glass container. When the external surface pressure second compressive stress value of this tempered glass container was measured using a surface stress meter, it was found that the average was 1920 Kg/cm ² and the thickness of this stress layer was about 17 μm. Similarly, the third compressive stress value on the inner surface is the average
The weight was 1200Kg/cm ² and the layer thickness was 13μ. The tensile stress value at the center of the cross section measured by the Beretsk compensator was approximately 140 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 ℃ ●Change point 637 ℃ ●Annealing point 554 ℃ ●Strain point 515 ℃ Main In the examples, not a single glass container was broken during the process. The practical strength characteristics of the tempered glass container obtained in this example are listed in Table 1 in comparison with those of the untreated container and the comparative container. Note that each data is based on n = 30 pieces.

[Table] As is clear from Table 1, it can be seen that 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 internal pressure resistance, the "Example" container has about 12% higher strength after 1 trip and about 50% higher strength after 10 trips compared to "Comparative Container 1." Moreover, compared to "Comparative Container 2", an increase in strength of about 95% after 1 trip and an increase of about 180% after 10 trips is observed. In addition, the “Example” container is also a “Comparative container” in terms of impact strength.
The strength is relatively increased compared to . Also, in comparison with the untreated container, the internal pressure resistance strength after tripping is more than twice as high, and the impact strength is almost twice as high. In addition, "Comparison container 1" in Table 1 refers to a container that has the same shape as the "Example" container, is subjected to the quenching treatment under the same conditions as the "Example", and is a combination of metal oxide coating and quenching treatment. "Comparative Container 2" is a tempered glass container having the same container shape as above and subjected to ion exchange treatment under the same conditions as "Example", which is a combination of so-called metal oxide coating and ion exchange treatment. It is a tempered glass container. The items listed in Table 1 were tested in the following manner. 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 was determined as the internal pressure strength. Impact resistance 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 the impact strength was determined. Trip: In order to examine the degree of strength deterioration due to handling of the glass container during filling, etc., the container was scratched for 1 minute using a line simulator manufactured by AGR, and this was defined as 1 trip. As described above in detail, the present invention can be easily applied to conventional mass-produced glass containers, and can provide even higher practical strength, especially internal pressure resistance, suitable for use as lightweight returnable bottles. Moreover, it is noteworthy that even if the number of trips increases, the deterioration of the internal pressure strength is extremely small.Furthermore, the strengthening method is not particularly complicated, and the overall manufacturing process can be shortened. The fact that it has now become possible and even lower costs has made a huge contribution to this industry.

Claims (1)

[Scope of Claims] 1. 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 is formed on the outer surface of the first compressive stress layer applied by rapid cooling.
A tempered glass container having an overlapping layer of a compressive stress layer and a third compressive stress layer having a low ion exchange rate on its inner 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. A tempered glass container according to claim 1 or 2, wherein the outer surface of the container is provided with a metal oxide coating. 4. The tempered glass container according to claim 2 or 3, wherein an organic protective coating is provided on the outer surface of the container. 5. In a soda lime silica glass container whose inner and outer surfaces are given a compressive stress value in the range of 100 to 750 kg/cm ² by rapid cooling, a large amount of potassium salt is applied to the outer surface and a small amount of potassium salt is applied to the inner surface. 1. A method for producing a tempered glass container, which comprises adhering the container to the glass container and subjecting the container to heat treatment for ion exchange.