JPS632906B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for treating the surface layer of soda-lime glass, and in particular, it is possible to improve both the mechanical strength and chemical durability of the glass by performing ion exchange and dealkalization of the glass in a single heat treatment step. Regarding possible surface treatment methods. One effective method to improve the mechanical strength of conventional soda-lime glass is to replace the sodium ions on the glass surface with potassium ions having a larger ionic radius at temperatures below the strain point of the glass. An ion exchange method is used to form a compressive stress layer on glass.
This ion exchange method greatly contributes to reducing the weight of glass and saving resources. However, this ion exchange method merely replaces the sodium ions on the glass surface with potassium ions of a different type, and it has not been possible to improve the chemical durability (chemical resistance, water resistance, etc.) of the glass surface. That is, the alkaline components on the surface of soda-lime glass react with various chemical components and have a harmful effect on the glass products and their contents. For example, when used as a glass bottle for liquid pharmaceuticals, etc., it is filled with an aqueous solution with a pH range from weakly acidic to weakly alkaline and heated for sterilization.
Alternatively, it may be stored for a long period of time, but during this process, thin pieces of glass called flakes may come off from the glass surface due to alkaline components eluting from the glass surface. . Furthermore, when bottles are used for these liquid medicines, there is a risk that the alkaline components in the glass will elute into the internal solution and react with each other, altering the quality of the contents. There are strict regulations in place. As a means for suppressing the amount of alkali elution in order to improve the chemical durability of the glass surface, treatment by a dealkalization reaction using ammonium chloride or sulfur dioxide gas is effective and common. However, dealkalization treatment removes alkaline components from the glass surface, and is generally considered to be incompatible with the strengthening of glass by ion exchange methods, which presupposes the presence of alkali ions on the glass surface. In other words, the glass bottles currently used for liquid pharmaceuticals are dealkalized with ammonium chloride or sulfur dioxide gas to reduce the amount of alkaline elution. When performing ion exchange treatment, there is a problem with the amount of alkali eluted after ion exchange, and a sufficient dealkalization effect cannot be expected. Furthermore, if a strong dealkalization treatment is applied to the surface of tempered glass that has undergone ion exchange, the compressive stress layer obtained by ion exchange will be removed, resulting in the glass losing its function as a tempered glass. Improving the mechanical strength of glass is based on the desire to make glass products lighter.However, when viewed in this way, ion-exchanged tempered glass has poor chemical durability, so the glass products are The fields in which it is used are naturally limited, and on the other hand, in fields where chemical durability is required, it is not possible to strengthen glass products and further reduce their weight. Therefore, as a result of repeated efforts, the inventor of the present invention has found that even in reactions such as ion exchange and dealkalization, which have elements that cancel each other's effects, the thickness of the surface treatment layer by ion exchange and the degree of dealkalization can be controlled and adjusted. The experiment showed that there is a range in which both the mechanical strength and chemical durability of glass can be improved by doing so. However, when ion exchange and dealkalization treatment are combined individually, there is a processing difficulty in that the degree of dealkalization must be controlled and adjusted depending on the thickness of the surface treatment layer due to ion exchange. In addition, two or more steps were required to carry out the ion exchange treatment and the dealkalization treatment, which was uneconomical in terms of cost. In view of these problems, the present inventors conducted further research and improvement, and discovered that there is an effective and appropriate method for performing ion exchange and dealkalization of the glass surface layer in a single heat treatment process. . According to this method, during one heat treatment, a three-step reaction of dealkalization → ion exchange → dealkalization occurs sequentially using a chemical that is mainly composed of potassium salt and reacts with the alkaline component of the glass surface layer. By tightening, it is possible to obtain mechanical strength and chemical durability that are comparable to those obtained by each treatment alone. The present invention aims to propose a new method that is capable of further strengthening the glass surface layer, centering on this composite surface treatment step. That is, the present invention involves the step of applying a compound such as tin or titanium to a hot bottle immediately after manufacture to form an oxide film of these metals on the bottle surface; Once using potassium thiocyanate, which exchanges sodium ions in the glass surface layer with potassium ions in a temperature range and causes a dealkalization reaction in the glass surface layer over the temperature range from a temperature lower than the temperature at which the ion exchange occurs. a step of simultaneously performing the formation of a compressive stress layer by ion exchange of the glass surface layer and dealkalization treatment through a heat treatment step;
The present invention relates to a method for treating a surface layer of soda-lime glass, which comprises a step of closely applying a coating agent for improving lubricity or preventing scratches on the appropriately cooled and cleaned glass surface. Examples will be described in detail below along with experimental examples. First, a composite surface treatment process, which is the main process of the present invention, in which the formation of a compressive stress layer by ion exchange of the glass surface layer and dealkalization treatment are performed simultaneously will be explained. Since this method causes two reactions, ion exchange and dealkalization, in one heat treatment step, an agent that causes ion exchange and dealkalization reactions in the temperature range of the heat treatment step is used. That is, since the ion exchange in this invention is the exchange of sodium ions and potassium ions at a temperature below the strain point of the glass, thiocyanic acid is mainly composed of potassium salts that meet the above conditions, and reacts with the alkali components on the glass surface in the temperature range. Potassium is used. First, in order to improve adhesion to the glass surface, a soda-lime glass bottle at a temperature higher than room temperature is immersed in an aqueous solution of potassium thiocyanate that has been heated for the same purpose. When the liquid has sufficiently spread throughout the bottle, the bottle is taken up, dried with air, and then transferred to a heat treatment furnace at a temperature that will not damage the bottle, and the temperature is gradually raised. Ion exchange between sodium ions in glass and potassium ions, which have a larger ionic radius, is generally considered to be at its lowest limit when the glass temperature is around 300 to 350°C. On the other hand, potassium thiocyanate begins to decompose at temperatures below 300°C and generates hydrogen sulfide. This hydrogen sulfide reacts with oxygen in the air, producing water and sulfur dioxide gas. The sulfur dioxide gas generated at this time reacts with the sodium ions in the glass, resulting in a dealkalization effect. Then, as the temperature rises, this dealkalization reaction and the ion exchange between the potassium ions of potassium thiocyanate and the sodium ions in the glass maintain an equivalent balance between potassium ions and thiocyanate ions.
It is presumed that these processes will proceed in a manner that is correlated with each other.
Then, the temperature is maintained at 400 to 450°C for about 1 hour, and then the cooling stage begins. When the temperature of the glass reaches around 300°C, the ion exchange capacity approaches its limit, and then the dealkalization reaction plays the role of removing the sodium ions that had been pushed to the surface layer by ion exchange. After this heat treatment, the bottle was washed and the washing solution was examined, and the presence of thiocyanate ions was found, indicating that potassium thiocyanate was decomposed even during the cooling stage. The above heat treatment process is illustrated in FIG. 1. In the heat treatment step in this method, it is necessary to set the heat treatment temperature and time. In ion exchange, below the strain point of glass and above 300℃, the
It can be carried out for 30 minutes to 1 hour, but temperature has an especially important influence in order to simultaneously produce chemical durability in relation to the characteristics of the chemicals used. Next, Table 1 shows the results of investigating the relationship between treatment temperature and strength while keeping the treatment time constant (1 hour). The strength test shown below is based on the JIS S2303 mechanical impact test. In addition, the bottles used in the following experimental examples had SiO ₂ :72.5% by weight;
_Al2O3 : 2.0%, _{Fe2O3 :} 0.045%, _CaO : 10.7%,
For each test, 10 bottles of the same shape, same size, and same model number with a content of 100 ml _and a weight of 110 g were used with the composition of MgO: 0.2%, Na ₂ O: 13.5%, and K 2 O: 1.0%. The average value was taken.

[Table] As is clear from Table 1, as the treatment temperature increases, the strength increases, and a slight increase in strength is observed from 400 to 450°C, and the maximum strength is reached at about 450°C. Next, we conducted an experiment on the relationship between treatment time and strength at a constant treatment temperature (450°C), and the results are shown in Table 2.

[Table] As is clear from the above table, the strength of the glass increases rapidly with time until the treatment time is 30 minutes, but after 30 minutes the strength increases only slightly. Furthermore, the results of an investigation on the amount of alkali elution are shown as an experimental example regarding chemical durability. Tests were conducted on bottles similar to those described above using two methods, including the alkali elution test method in the test method for glass containers for injections of the Japanese Pharmacopoeia, and the average value was calculated. (Table 3)
This study investigated the relationship between the treatment temperature and the amount of alkali elution while keeping the treatment time constant (1 hour).

[Table] According to the above experiment, the amount of alkali elution is extremely small at 300 to 450°C, and increases rapidly at 500°C. As mentioned above, when the treatment temperature is 500℃ or higher, the amount of alkali elution increases (Table 3), and even if the treatment time is kept at approximately 450℃ for more than 30 minutes, the strength increases only slightly (Table 3). 2) I learned something. Then, the processing temperature is 450℃ and the time is about 30 minutes.
What about the relationship with the solution concentration of potassium thiocyanate under the 60 minute condition? (Table 4)
shows the relationship between the solution concentration of potassium thiocyanate and the amount of alkali elution.

[Table] As shown, the amount of alkali elution is very small when the solution concentration is 30% or more, and as the concentration decreases to 30% or less, the amount of alkali elution tends to increase. As can be seen from the experimental examples mentioned above, temperature,
Regarding time and concentration, if we choose treatment conditions that are excellent in both mechanical strength and chemical durability from the viewpoint of economic efficiency and stability, when potassium thiocyanate is used, the maximum solution concentration is 30%. Processing temperature
It can be said that the optimum treatment conditions are 400 to 450°C and 30 to 60 minutes. Next, a mechanical impact test (JIS
S2303), internal pressure test (JIS S2302), thermal shock test (JIS S2304), and alkali elution amount test (two methods of alkali elution test method in the glass container test method for injections of the Japanese Pharmacopoeia): 10 or more each. Table 5 shows the results of tests conducted using the above-described method.

[Table] As mentioned above, this composite surface treatment process improves the mechanical strength and chemical durability of the glass surface by performing ion exchange and dealkalization on the glass surface in one heat treatment process. It is possible to improve both. In the present invention, prior to this complex surface treatment process, compounds such as tin and titanium are applied to hot bottles immediately after production in a bottle making machine to form an oxide film of these metals on the bottle surface. The present invention proposes to combine this process with the process of closely applying a coating agent to improve slipperiness or prevent scratches on the appropriately cooled and cleaned glass surface after the composite surface treatment process. be. That is, the surface of heated soda lime glass is treated with one or more of compounds such as tin, titanium, zirconium, etc. to thermally decompose these compounds and form a film of these oxides on the glass surface. Increasing the impact strength of bottles is known as so-called hot-end coating, but by applying the above-mentioned combined surface treatment of ion exchange and dealkalization to bottles that have undergone such a treatment process, excellent results can be achieved. This makes it possible to obtain a glass surface layer that has both good mechanical strength and chemical durability. The metal compounds used in this step include metal halides such as stannic chloride and titanium tetrachloride, dimethyltin dichloride, ethyltin tribromide, dibutyltin dibromide, dioctyltin dibromide, etc. Alkyltin halide compounds, alkyltin compounds, alkyltitanates,
Alkyl zirconate salts and the like are known, and these can be dissolved or colloidized with a solvent,
It is applied to the glass surface by spray or steam. Furthermore, after the above-mentioned composite surface treatment process of ion exchange and dealkalization treatment, a coating agent such as paraffin type or fatty acid with good slip properties or a plastic film is closely applied to the appropriately cooled and cleaned glass surface. further improves the lubricity or abrasion resistance of the glass surface. The process of improving the lubricity of glass surfaces using coating agents such as paraffin and fatty acids with good lubricity is generally called cold-end coating treatment. In this case, the lubricity of the coating agent prevents scratches caused by bottles rubbing against each other, smoothing the flow of the production line, and greatly improving the efficiency of subsequent packaging and transportation. It is. In this way, a composite surface treatment is performed by forming a metal oxide film such as tin or titanium on the bottle surface, and simultaneously forming a compressive stress layer through ion exchange of the glass surface layer and dealkalization treatment. Then, applying a coating agent to improve lubricity or prevent scratches is an extremely excellent method for improving both the mechanical strength and chemical durability of the surface layer of this type of soda-lime glass. It is recommended. As described above, the present invention proposes an extremely effective method that can improve both the mechanical strength and chemical durability of the surface layer of glass, thereby expanding the uses of tempered glass. It meets recent demands for stronger and lighter glass products used in the medical and chemical fields, including pharmaceuticals, and has made it possible to dramatically expand the field of glass manufacturing.

[Brief explanation of the drawing]

FIG. 1 is a temperature-time curve showing a heat treatment process in an embodiment of the present invention.

Claims (1)

[Claims] 1 A process of applying compounds such as tin and titanium to the hot bottle immediately after production to form an oxide film of these metals on the bottle surface; Next, the glass surface is heated in a temperature range of about 350°C or higher and below the strain point of the glass. In a single heat treatment step, potassium thiocyanate is used to exchange sodium ions in the layer for potassium ions and to cause a dealkalization reaction in the glass surface layer over a temperature range from below the temperature at which the ion exchange takes place. Then, a process of forming a compressive stress layer by ion exchange on the glass surface layer and dealkalization treatment is carried out at the same time; after that, a coating agent is applied to the appropriately cooled and cleaned glass surface to improve lubricity or prevent scratches. A method for treating a surface layer of soda-lime glass, comprising the steps of: