JP2001163633A - Method for recycling glass product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recycling glass products which is capable of eliminating the treatment of secondary wastes, such as sludge, and surely removing the carbon coating films formed on glass in removing the carbon coating films on the glass surfaces. SOLUTION: This method for recycling the glass of the glass products made unnecessary as raw materials by disassembling the glass products and removing the carbon coating films on the glass surfaces consists in applying an aqueous oxidizing agent solution dissolved with an oxidizing agent to the glass, then heating the glass and removing the carbon coating films.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recycling glass as a raw material, and more particularly to a method for removing a carbon coating film formed on a glass surface and reusing it as cullet.

[0002]

2. Description of the Related Art To reduce the amount of waste, prevent environmental pollution due to harmful components, and recycle resources, dismantle glass products.
There is a demand for reusing as much useful material as possible as a resource, minimizing the amount of waste, and preventing environmental pollution. Particularly, among television components, a cathode ray tube occupies a large volume, and a method of disassembling the tube and recycling the glass as a raw material has already been proposed.

For example, in a glass used for a cathode ray tube, a funnel glass has a carbon coating film formed on its inner surface by water glass, and a panel glass serving as an image display portion of the cathode ray tube. Some of them have a carbon coating film formed thereon. The carbon in these carbon coatings remains as a foreign substance in the obtained glass product or impairs the melting characteristics of the raw material when the glass product is recycled and used as a raw material for a new glass product. Therefore, it is necessary to peel off and remove the glass from the glass before reusing it as a glass raw material.

Conventionally, as a method of peeling and removing a carbon coating film of a glass article for a cathode ray tube, a hydrofluoric acid treatment method of immersing glass in an aqueous hydrofluoric acid solution and stirring and mixing to remove the carbon coating film, Alkaline boiling method to remove carbon film by immersing glass in aqueous solution and boiling, stirring and mixing method to knead glass in mixer and remove carbon film by collision of glass, aluminum oxide powder or glass There is a blast method in which a carbon coating film is removed by blasting beads.

[0005]

However, these conventional methods have the following problems.

In the hydrofluoric acid treatment method, it is necessary to treat sludge generated in the solution. Moreover, when applied to recycling of funnel glass for cathode ray tubes containing a large amount of lead oxide, lead oxide, which is a harmful substance, is mixed into the sludge due to glass erosion of hydrofluoric acid. Also requires a processing step. There are also problems such as the necessity of special treatment equipment by using hydrofluoric acid and expensive equipment for filtration of used solutions and wastewater treatment.

As in the case of the hydrofluoric acid treatment method, the alkali boiling method has a problem that sludge generated in a solution and a strong alkali sludge must be treated, and when applied to a funnel glass, the sludge is oxidized as described above. There is a problem that a removal process for removing lead is required, and a special treatment facility and a drainage facility are required like the hydrofluoric acid treatment facility because the glass is boiled with a strong alkaline solution.

In the stirring and mixing method, fine glass powder is generated by collision of glass pieces, and these fine glass powder are mixed with the removed carbon coating film. Further, in the device for stirring and mixing the glass pieces, there is a problem that the high hardness of the glass easily causes wear and breakage of the internal structure of the device and shortens the life of the device. Further, when applied to funnel glass, a step of removing lead oxide from these glass fine powders is required.

In the blast method, it is necessary to treat a used blast material generated as waste, and when applied to funnel glass, a step of removing lead oxide from the used blast material is required. .

As described above, in the conventional method, there is a problem that it is necessary to treat secondary waste such as sludge and used processing material, which leads to a decrease in efficiency due to an increase in the number of steps and a reduction in facility cost and cost. There is a problem that increases.

Accordingly, an object of the present invention is to remove the carbon coating film on the glass surface by eliminating the need to treat secondary waste such as sludge, and to reliably remove the carbon coating film formed on the glass. The purpose is to provide a way to recycle products.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems and objects, and disassembles glass products that are no longer needed, removes a carbon coating film on the glass surface, and uses the glass as a raw material. In a method of recycling as, after applying an oxidizing agent aqueous solution in which the oxidizing agent is dissolved to the glass,
A glass recycling method characterized by removing the carbon coating by heating.

Further, the present invention is characterized in that the oxidizing agent is a nitrate.

Further, in the present invention, the glass product is a glass article for a cathode ray tube.

In the present invention, an oxidizing agent refers to a substance that provides an oxygen atom to another substance.

[0016]

According to the present invention, an oxidizing agent solution in which an oxidizing agent is dissolved is applied to glass, and then heated, whereby the oxidizing agent is thermally decomposed to generate oxygen. Combines to form carbon dioxide. Thereby, the carbon coating film formed on the glass evaporates as carbon dioxide and is removed from the glass surface.

In the present invention, oxidizing agents such as nitrates, sulfates, permanganic acid, chromic acid, chloric acid, hypochlorous acid, bromic acid, iodic acid, salts thereof, concentrated sulfuric acid, peroxide, etc. One or more of oxides and the like can be used, but nitrates are more preferable from the viewpoint of melting point and handleability. Nitrate has a melting point as low as 600 ° C. or less as compared with other oxidizing agents, and is particularly excellent in energy efficiency, economy and workability during heating. Nitrates
As the temperature rises, oxygen is released to generate nitrite, which is further reacted and thermally decomposed into alkali oxide, oxygen, and nitrogen oxide. Oxygen generated by the thermal decomposition of nitrate oxidizes carbon in the carbon coating to generate carbon dioxide, thereby removing the carbon coating on the glass surface,
The alkali oxide forms a reaction layer by melting the surface of the glass body as the base. In addition, for example, in the case of a funnel glass for a cathode ray tube, the alkali oxide is an additive in a carbon coating film, that is, silicon oxide as a water glass component used at the time of forming the carbon coating film and a glass body as a base. The surface is melted to form a reaction layer.

Examples of such a nitrate include alkali metal salts, alkaline earth metal salts, ammonium salts, and transition metal salts of nitric acid. Examples thereof include sodium nitrate, potassium nitrate, lithium nitrate, ammonium nitrate, calcium nitrate, and nitrate. Aluminum, strontium nitrate, magnesium nitrate, barium nitrate, manganese nitrate, iron nitrate, copper nitrate, silver nitrate and the like can be used.

When a glass material for a cathode ray tube is reused as a glass raw material, it is required that the glass characteristics such as transmittance and dielectric constant, and the discharge characteristics when the cathode ray tube is operated are not deteriorated. In addition, in a funnel glass containing a large amount of lead oxide for the purpose of shielding X-rays among CRT glass articles, lead oxide, which is a harmful substance in the glass, is volatilized in a high-temperature atmosphere of 1000 ° C. or higher, Such high temperature heating must be avoided. Therefore, in the case of glass articles for cathode ray tubes, sodium nitrate and potassium nitrate which do not affect the glass properties and electrical properties after reuse and are easily decomposed at low temperatures are particularly preferable.

When sodium nitrate or potassium nitrate is used as an oxidizing agent to remove the carbon coating film formed on the surface of the funnel glass for a cathode ray tube, the concentration of the aqueous solution of sodium nitrate is considered in view of the processing efficiency and the working efficiency. Is 30 to 50% by mass, the coating amount on the glass surface is 10 to 15 g / cm ^{2 in} terms of the amount of the oxidizing agent, the heating temperature of the glass after coating is 600 to 650 ° C., and the heating time is 15
-30 minutes is more preferred.

As a heating method, an electric furnace heated by a winding heater, a baking furnace using fuel or electricity, or a batch heating furnace for individually heating glass coated with an oxidizing agent aqueous solution may be used. It can also be used for a continuous firing furnace or the like incorporating a spraying device. In the heating step, a special temperature schedule is not required, and the heating may be performed in a predetermined temperature atmosphere for a certain time.

With respect to the method of applying the oxidizing agent aqueous solution, it is possible to apply by spraying or brushing, or by immersing the glass itself in the oxidizing agent aqueous solution.
For example, in the case of a funnel glass for a cathode ray tube, the coating amount of the oxidizing agent aqueous solution required per unit area of the carbon coating film formed on the inner surface may be small, and the glass shape is curved, In the case of a dilute aqueous solution, a liquid flow along a curved surface is likely to occur, and it is difficult to uniformly apply the solution on the glass surface. Therefore, spray application of a high-concentration aqueous solution is preferable.

The application of the oxidizing agent aqueous solution to the glass on which the carbon coating film is formed may be performed after the glass is crushed or may be applied as it is without crushing. In order to apply uniformly and easily on the carbon coating film, it is preferable that the glass is crushed to a size of about 20 to 50 mm square before the application.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

Example 1 In recycling a funnel glass for a CRT having a carbon coating formed on the inner surface, a 17-inch funnel glass for a CRT was removed by removing the carbon coating formed on the surface of the funnel glass. A glass piece having a size of 25 mm square was crushed, and a 10% by mass aqueous solution of sodium nitrate was spray-coated on the glass surface on which the carbon coating film was formed.
Each of the furnaces was set at an ambient temperature of 550 ° C., 550 ° C., 600 ° C., and 650 ° C., and subjected to heat treatment to remove the carbon coating on the glass surface.

(Example 2) A 30% by mass aqueous solution of sodium nitrate was spray-coated on a glass piece having the same type and the same dimensions as in Example 1 on the glass surface on which the carbon coating film was formed. The carbon coating film on the glass surface was removed by putting into each heating furnace set to the atmosphere temperature of the same conditions and performing a heat treatment.

Example 3 A 50% by mass aqueous solution of sodium nitrate was spray-coated on a glass piece having the same type and the same dimensions as in Example 1 on the glass surface on which the carbon coating film was formed. The carbon coating film on the glass surface was removed by putting into each heating furnace set to the atmosphere temperature of the same conditions and performing a heat treatment.

Example 4 A 10% by mass aqueous solution of potassium nitrate was spray-coated on a glass piece having the same type and the same dimensions as in Example 1 on the glass surface on which the carbon coating film was formed. The carbon coating film on the glass surface was removed by putting into each heating furnace set to the atmospheric temperature of the condition and performing a heat treatment.

Example 5 A 30% by mass aqueous solution of potassium nitrate was spray-coated on a glass piece having the same type and the same dimensions as in Example 1 on the glass surface on which the carbon coating film was formed. The carbon coating film on the glass surface was removed by putting into each heating furnace set to the atmospheric temperature of the condition and performing a heat treatment.

(Example 6) A 50% by mass aqueous solution of potassium nitrate was spray-coated on a glass piece having a carbon coating on a glass piece having the same type and the same dimensions as in Example 1, and then the same as in Example 1. The carbon coating film on the glass surface was removed by putting into each heating furnace set to the atmospheric temperature of the condition and performing a heat treatment.

In each of Examples 1 to 6, 10 pieces of glass were placed in a heating furnace at each ambient temperature, and the processing time required until the carbon coating was completely removed from the surface of each piece of glass was shown in Table 1. Shown in Confirmation that the carbon coating was completely removed was made by visual inspection. Also,
Table 2 shows the results of component analysis in which the surface of the glass piece after the carbon coating was completely removed according to Example 1 was analyzed using an electron beam microanalyzer.

[0032]

[Table 1]

[0033]

[Table 2]

In the present embodiment, the carbon coating film formed on the funnel glass for a cathode ray tube is coated with a 10% aqueous solution of sodium nitrate or potassium nitrate and then treated for 60 to 120 minutes, and 30 to 90 minutes with a 30% aqueous solution.
In a 50% aqueous solution for 15 to 60 minutes, it was confirmed that the carbon coating film formed on the surface of the glass piece could be effectively oxidized and removed.

Further, on the surface of each glass piece treated in this embodiment, only the components of the water glass used in forming the carbon coating and the components of the funnel glass itself were detected. The carbon component was 0. This indicates that the carbon coating was completely removed from the surface of each glass piece.

The components remaining after the removal of the carbon coating film do not hinder the reuse of such a funnel glass piece as a glass material.

As described above, a water glass component and a funnel glass component were detected on the surface of the glass piece after the treatment, but these components were melted and solidified at the time of the heat treatment to form on the glass surface. It is fixed in a thin layer. These glass pieces were immersed in pure water and boiled for 10 minutes to conduct a water solubility test. As a result, it was found that the glass pieces had no water solubility. This indicates that the glass pieces treated according to the present invention have no risk of elution of glass components and the like and have environmental safety during storage and handling as cullet.

[0038]

As described above, the present invention eliminates the need for treatment of secondary waste such as sludge and removes the carbon coating formed on the glass when removing the carbon coating on the glass surface. This has an excellent effect that it can be surely removed and the efficiency and economy in the recycling operation can be significantly improved.

Claims (3)

[Claims] In a method of dismantling an unnecessary glass product, removing a carbon coating film on a glass surface, and recycling the glass as a raw material, an oxidizing agent aqueous solution in which an oxidizing agent is dissolved is applied to the glass. Thereafter, the method is heated to remove the carbon coating film. 2. The method for recycling glass according to claim 1, wherein the oxidizing agent is a nitrate. 3. The method for recycling glass according to claim 2, wherein the glass product is a glass article for a cathode ray tube.