JP2002037632A - Glass manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing glass suitable for recycling and controlling increase in quantity of antimony oxide in raw materials. SOLUTION: The glass is manufactured by melting glass cullet containing multivalent elements and having oxygen partial pressure 0.14 atmosphere or more at 1400 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing glass, particularly glass for a cathode ray tube.

[0002]

2. Description of the Related Art With respect to glass for a cathode ray tube, particularly, panel glass serving as a screen display portion of the cathode ray tube, it is required to reduce bubbles which cause deterioration in image quality. In order to solve this problem, conventionally, antimony oxide such as sodium antimonate (NaSbO ₃ ) has been added as a fining agent to the raw material.

[0003] Sb is, for example, the temperature of the molten glass is 15
When the temperature exceeds 00 ° C., the valence changes from pentavalent to trivalent (S
b ⁵⁺ → Sb ³⁺ ), and oxygen is released (O ² →→ O ₂ ↑) with the change in valence. This oxygen diffuses into the bubbles of the molten glass, increases the bubble diameter and promotes the floating of the bubbles, and as a result, reduces the bubbles in the molten glass.

[0004]

In recent years, there has been a strong social demand for recycling glass, that is, recycling used glass products as raw materials. When a used glass product is used as a raw material, the glass product is pulverized to an appropriate size and made into cullet.

When considering such recycling in the manufacture of panel glass, most of Sb in the cullet is Sb ³⁺ due to the change in valence, and there is a problem that Sb ⁵⁺ effective for reducing bubbles is small. Become. That is, when such a low Sb ⁵⁺ cullet is used, Sb ⁵⁺ having a foam reducing effect is substantially reduced, and the foam of the panel glass may increase.

As a solution to this problem, an increase in the amount of antimony oxide in the raw material can be considered. However, this may increase the Sb content of the panel glass, and may increase product defects due to Sb. It is considered that the product defect caused by the Sb is that Sb volatilized from the molten glass condenses on a low-temperature portion of the structure located above the molten glass, and the condensate drops into the molten glass.

[0007] An object of the present invention is to provide a method for producing glass that can recycle glass and suppress an increase in the amount of antimony oxide in the raw material.

[0008]

SUMMARY OF THE INVENTION The present invention is a method for producing glass by melting a raw material containing cullet,
The cullet contains a polyvalent element, and 14
Provided is a method for producing glass, wherein the oxygen partial pressure at 00 ° C. is 0.14 atm or more.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a method for producing glass of the present invention will be described. The glass produced according to the present invention contains a polyvalent element. The polyvalent element referred to in the present invention is an element having two or more valences, such as Sb (typical valence is trivalent, pentavalent) and Ce (typical valence is trivalent,
Tetravalent) and the like.

The glass is exemplified by glass for a cathode ray tube. Of the glass for cathode ray tubes, the panel glass is S
R ₂ O—R′O—SiO ₂ -based glass containing b and Ce, and the funnel glass is R ₂ O— containing Sb.
Is a R'O-PbO-SiO ₂ based glass (R: alkali metal, R ': alkaline earth metal). Typically, the content of Sb in panel glass in terms of Sb ₂ O ₃ is 0.3 to 0.4% in terms of mass percentage, and the content of Ce in terms of CeO ₂ is 0.3 to 0.35% in terms of mass. It is.

[0011] The cullet used as a raw material is a glass lump, and a typical size is 15 to 25 mm. The cullet has a more oxidized redox state than the conventionally used cullet. That is, the oxygen partial pressure P measured when the cullet was melted at 1400 ° C.
Is less than 0.13 atm for the cullet conventionally used for producing panel glass, funnel glass and the like, but is 0.14 atm or more for the cullet used in the present invention.

If P is less than 0.14 atm, the proportion of high-valent ions of the multivalent element in the cullet before melting becomes too small, so that oxygen release from the high-temperature molten glass described above for Sb hardly occurs. Foam reduction effect is reduced. P is preferably at least 0.20 atm, more preferably at least 0.25 atm.

The method for measuring P is not particularly limited. For example, P can be measured using a commercially available oxygen sensor using stabilized zirconia. P is measured by an Ir-stabilized zirconia-based oxygen sensor that measures an electromotive force with an Ir electrode based on the oxygen partial pressure of Ni-NiO and calculates an oxygen partial pressure from the electromotive force based on the Nernst equation. preferable.

[0014] Next, in the present invention, "containing a polyvalent element and having an oxygen partial pressure at 1400 ° C of 0.1
Preferred embodiments A to D of a method for producing a cullet having a pressure of 4 atm or more (hereinafter referred to as the cullet of the present invention) will be described. The cullet of the present invention contains a polyvalent element.
b or Ce is exemplified as a preferred polyvalent element.

In the embodiment A, the cullet of the present invention is obtained by heating a glass block containing a polyvalent element at 850 to 1300 ° C. in an oxygen-containing atmosphere having an oxygen concentration of 25% by volume or more.
It is manufactured by heating and cooling for more than a minute.

In the embodiment A, a glass lump containing a polyvalent element is heated, and the glass lump or the glass in a molten state in which the glass lump is melted (hereinafter, these are collectively referred to as a heated glass) are heated to an oxygen concentration. It is brought into contact with an oxygen-containing atmosphere (hereinafter referred to as a high oxygen atmosphere) having an oxygen concentration of 25% by volume or more and thus higher in oxygen concentration than air (oxygen concentration = 21% by volume) to increase the oxygen partial pressure of the heated glass. The heated glass having an increased oxygen partial pressure is cooled and pulverized into a cullet of a desired size. The cullet of a desired size may be formed by water granulation in which cooling and pulverization are performed simultaneously.

If the oxygen concentration is less than 25% by volume, the diffusion of oxygen from the oxygen-containing atmosphere into the glass becomes too small. Preferably at least 40% by volume, more preferably at least 50% by volume, particularly preferably at least 70% by volume, most preferably at least 9% by volume.
0 volume% or more.

When the heating temperature is lower than 850 ° C., the diffusion rate of oxygen from the oxygen-containing atmosphere becomes too low. In the case of panel glass, it is preferably at least 950 ° C., more preferably at least 1000 ° C., and in the case of funnel glass, it is preferably at least 900 ° C., more preferably at least 950 ° C.
° C or higher. If it exceeds 1300 ° C., the proportion of high valence ions of the polyvalent element becomes too small. Preferably 1250 ° C
Or less, more preferably 1200 ° C. or less.

If the heating time is less than 15 minutes, diffusion of oxygen from the oxygen-containing atmosphere to the heated glass is too small. Preferably, it is 30 minutes or more.

Next, the embodiment B will be described. In embodiment B, the cullet of the present invention contains a polyvalent element and contains
A glass lump having a viscosity of less than 10 ⁶ poise at 0 ° C. is placed in an oxygen-containing atmosphere having an oxygen concentration of 25% by volume or more in a temperature range from a temperature at which the viscosity of the glass lump becomes 10 ⁶ poise to 1300 ° C. or less. It is manufactured by heating and cooling for more than 15 minutes.

In the embodiment B, the temperature of the glass block is 1300 ° C.
Is different from embodiment A only in that the viscosity is limited to less than 10 ⁵ poise and that the lower limit of the heating temperature is a temperature (T ₅ ) at which the viscosity of the glass lump becomes 10 ⁵ poise. Only these different points will be described below. That is,
Heating temperature becomes insufficient sintering of the glass gob during heating is less than T _5, the oxygen concentration in the gap of the glass gob and glass gob is difficult to confine the oxygen-containing atmosphere is at least 25% by volume.

Next, the embodiment C will be described. In Embodiment C, the cullet of the present invention contains a polyvalent element,
A glass lump having a viscosity of less than 10 ⁵ poise at 300 ° C. is maintained in a range of T _{5 to} 1300 ° C. to form a molten glass, and an oxygen-containing gas having an oxygen concentration of 25% by volume or more is injected into the molten glass. And then cooled.

If the viscosity of the molten glass exceeds 10 ⁵ poise, it becomes difficult to inject the oxygen-containing gas. On the other hand, when the temperature of the molten glass exceeds 1300 ° C., the proportion of high-valent ions of the polyvalent element becomes too small. Preferably it is 1250 ° C or less, more preferably 1200 ° C or less.

When the oxygen concentration is less than 25% by volume, the diffusion of oxygen from the oxygen-containing gas into the molten glass is too small. It is preferably at least 40% by volume, more preferably at least 50% by volume, particularly preferably at least 70% by volume, most preferably at least 90% by volume. The time for injecting the oxygen-containing gas into the molten glass is preferably one hour or more.

Next, the embodiment D will be described. In the aspect D, the cullet of the present invention is obtained by mixing a mixture of 100 parts by mass of a glass lump containing a polyvalent element and 0.03 to ₅ parts by mass of an oxidizing agent having a decomposition temperature of 1300 ° C. or less with a temperature of T ₅ or more and 130 or more.
It is manufactured by heating to 0 ° C. or lower for 15 minutes or more and cooling.

The oxidizing agent referred to in the embodiment D is a substance which decomposes in an air atmosphere to release oxygen, and has a decomposition temperature T _D
However, assuming that the strain point of the glass block is T _S , it is not less than (T _S −100 ° C.) and not more than 1300 ° C. Panel glass (T
_{For S} = 470 ° C., T ₅ = 900 ° C.) and funnel glass (T _S = 450 ° C., T ₅ = 850 ° C.), NaN
O ₃ (T _D = 380 ° C.), KNO ₃ (T _D = 400 ° C.), B
a (NO ₃ ) ₂ (T _D = 600 ° C.), BaO ₂ (T _D = 84
0 ° C.), Al ₂ (SO ₄ ) ₃ (T _D = 770 ° C.), ZnSO
₄ (T _D = 740 ° C.), Zr (SO ₄ ) ₂ (T _D = 380
℃), MgSO ₄ (T _D = 1125 ° C.), CaSO ₄ (T _D
= 1200 ° C.), BaSO ₄ (T _D = 1200 ° C.) and the like.

In the embodiment D, at least a part of the oxygen released from the oxidizing agent at the time of heating the mixture is confined in the gap between the glass lump and the oxygen concentration in the gap is increased. When the amount of the oxidizing agent in the mixture is less than 0.03 parts by mass,
The effect of increasing the oxygen concentration in the gap is small. It is preferably at least 0.05 part by mass, more preferably at least 0.1 part by mass. If the amount of the oxidizing agent is more than 5 parts by mass, the amount of oxygen released from the oxidizing agent will be too large, and it will be difficult to confine oxygen in the gap between the glass blocks. 0.3 parts by mass or less when NaNO ₃ is used, and 0.1 part by mass when BaSO ₄ is used.
It is preferably 5 parts by mass or less.

[0028] The heating temperature is less than T _5, becomes insufficient sintering of the glass gob, comprising the oxygen released from the oxidizing agent is difficult to confine in the gap of the glass gob and glass gob.
If it exceeds 1300 ° C., the proportion of high valence ions of the polyvalent element becomes too small. Preferably it is 1250 ° C or less, more preferably 1200 ° C or less.

When the heating time is less than 15 minutes, the diffusion of oxygen trapped in the glass into the glass is too small. Preferably, it is 30 minutes or more. Aspect D may be performed in an air atmosphere, but is more preferably performed in a high oxygen atmosphere.

The size (maximum diameter) of the glass block used in the embodiments A to D is preferably 10 mm or less. If it exceeds 10 mm, the contact area between the glass lump and the high oxygen atmosphere becomes too small when the glass lump comes into contact with the high oxygen atmosphere until the glass lump becomes molten, and oxygen diffusion into the glass lump may be too small. . It is more preferably at most 5 mm, particularly preferably at most 0.5 mm.

[0031]

EXAMPLE A panel glass was recovered from a used CRT. This panel glass is expressed in terms of percentage by mass,
₂ : 61%, Al ₂ O ₃ : 2%, Na ₂ O + K ₂ O: 15
%, SrO + BaO + ZnO: 19%, ZrO ₂ : 0.
5%, Sb ₂ O ₃ : 0.3%, CeO ₂ : 0.45%, having a viscosity of 10 ⁵ poise, 10 ⁴ poise, 10 ³
Poise, the temperature to become 10 ² poise is 900 ℃, respectively
They were 1020 ° C, 1190 ° C and 1450 ° C.

First, the panel glass was pulverized into a glass lump. A group of glass lumps having a maximum size of 0.5 mm (glass lumps A) and a maximum size of 5 mm
(A glass lump B) was prepared.

A glass lump A (500 g) is placed in a platinum crucible and heated in an electric furnace (internal volume = 900 cm ³ ) in an oxygen-containing atmosphere having an oxygen concentration of 40% by volume, and heated to 1000 ° C. for 1 hour.
Hold for 5 minutes. The electric furnace was an electric furnace with a lid, and oxygen gas was supplied to the electric furnace at 1000 cm ³ / cm ² .
And the oxygen-containing atmosphere was formed.

Next, the temperature was lowered to 530 ° C. in 10 minutes, kept at that temperature for 1 hour, cooled to room temperature in 3 hours, and pulverized into cullet (cullet 1). P of caret 1 to I
r-stabilized zirconia oxygen sensor Rapidox
It was 0.30 atm as measured by (trade name, Heraeus Electronite).

A cullet was prepared in the same manner as the cullet 1 except that the heating temperature of the glass block was changed to 1200 ° C. instead of 1000 ° C. (cullet 2). P of cullet 2 was 0.25 atm.

A cullet was prepared in the same manner as the cullet 1 except that the glass block B was used instead of the glass block A (cullet 3). P of cullet 3 was 0.23 atm.

Further, a glass block B is used instead of the glass block A as the glass block, and the heating temperature of the glass block is set to 100.
A cullet was prepared in the same manner as cullet 1 except that the temperature was changed to 1200 ° C. instead of 0 ° C. (cullet 4). P of the cullet 4 was 0.20 atm. As described above, the P of the cullets 1 to 4 was 0.14 atm or more, whereas the P of the panel glass used for the production was 0.10 atm as a result of the measurement. .

Next, the size is 20 mm × 20 mm × 20
A cullet 1 mm (P = 0.30 atm) was prepared, heated in an air atmosphere, kept at 1550 ° C. for 1 hour, cooled, and the number of bubbles in the glass was counted. This was repeated twice, and the average value of the bubble number density was calculated to be 0.1 cells / g. On the other hand, when the same test was performed using the panel glass in which P was 0.10 atm, the average value of the bubble number density was 10 / g. That is, the average value of the bubble number density of the glass manufactured by the glass manufacturing method of the present invention was 1/100 of the average value of the bubble number density of the glass manufactured by the conventional manufacturing method.

[0039]

According to the present invention, a glass with few bubbles can be obtained without increasing the ratio of antimony oxide in the raw material even if the ratio of cullet in the raw material increases. Thereby, recycling of glass such as glass for a cathode ray tube can be promoted.

Continued on the front page F term (reference) 4G014 AB00 4G062 AA03 BB01 CC03 CC04 DA06 DB03 DC01 DD01 DE04 DF01 EA01 EB04 EC04 ED01 EE01 EF04 EG04 FA01 FB01 FC02 FD01 FE01 FF01 FG01 FH01 FJ01 FK01 H01H01 GB01 H01 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ04 JJ05 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM25 NN01 5C012 AA01 BB01

Claims (7)

[Claims] 1. A method for producing glass by melting a raw material containing cullet, wherein the cullet contains a polyvalent element and the cullet has an oxygen partial pressure at 1400 ° C. of 0.14 atm or more. A method for producing glass, comprising: 2. The cullet is produced by heating a glass lump containing a polyvalent element to 850 to 1300 ° C. for 15 minutes or more and cooling it in an oxygen-containing atmosphere having an oxygen concentration of 25% by volume or more. The method for producing glass according to claim 1, wherein 3. The cullet according to claim 1, wherein the cullet contains a polyvalent element.
A glass lump having a viscosity of less than 10 ⁵ poise at 0 ° C. is heated in an oxygen-containing atmosphere having an oxygen concentration of 25% by volume or more to a temperature at which the viscosity of the glass lump becomes 10 ⁵ poise or more.
The method for producing glass according to claim 1, wherein the glass is produced by heating at a temperature of 300 ° C or lower for 15 minutes or more and cooling. 4. The cullet according to claim 1, wherein the cullet contains a polyvalent element.
The glass gob viscosity is less than 10 ⁵ poise at 0 ° C., a temperature above the viscosity of the glass gob is 10 ⁵ poises 1
The glass according to claim 1, wherein the glass is produced by maintaining a temperature of 300 ° C. or lower to form a molten glass, injecting an oxygen-containing gas having an oxygen concentration of 25% by volume or more into the molten glass, and cooling the molten glass. Manufacturing method. 5. The cullet is a mixture of 100 parts by mass of a glass lump containing a polyvalent element and 0.03 to 5 parts by mass of an oxidizing agent having a decomposition temperature of 1300 ° C. or lower. 1 for temperatures above ⁵ poise and below 1300 ° C
The method for producing glass according to claim 1, wherein the glass is produced by heating and cooling for 5 minutes or more. 6. The method for producing a cullet according to claim 2, wherein the size of the glass lump is 10 mm or less. 7. The method for producing glass according to claim 1, wherein said polyvalent element is Sb or Ce.