EP0032594A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method for producing silica glass
Assignee: Hitachi Ltd
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Filing: 1980-12-30
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Granted: —
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Expires: 2000-12-30
Abstract
Abstract A method for producing silica glass wherein a dry silica gel subjected to a water desorption treatment and a carbon removal treatment is heated and has its temperature raised in an atmosphere containing chlorine, to perform a hydroxyl group removal treatment, the resultant silica gel is thereafter heated to a temperature of approximately 1,000-1,100°C in an atmosphere containing at least 1 % of oxygen, to perform a chlorine removal treatment, and the resultant silica gel is further heated do a temperature of 1,050-1,300` C in He or in vacuum, to perform a sintering treatment. The silica glass thus produced forms quite no bubble even when heated to high temperatures of or above 1300° C. Therefore, it is easy of working and it is free from the lowering of transparency attributed to the bubble formation.
Inventors
- 👤 Kenzo Susa
- 👤 Iwao Matsuyama
- 👤 Shin Satoh
- 👤 Tsuneo Suganuma
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 18:04
CPC Classifications
C; C03; C03B; C03B19/00; C03B19/12; C03B37/00; C03B37/01; C03B37/012; C03B37/014; C03B37/016; C03C; C03C3/00; C03C3/04; C03C3/06; C03C2201/00; C03C2201/02; C03C2203/00; C03C2203/20; C03C2203/26; C03C2203/50; Y; Y10; Y10S; Y10S65/00; Y10S65/901
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
107 words
A method for producing silica glass characterized in that a dry silica gel subjected to a water desorption treatment and a carbon removal treatment is heated and has its temperature raised in an atmosphere containing chlorine, to perform a hydroxyl group removal treatment, that the resultant silica gel is thereafter heated to a temperature of approximately 1,000 °C - 1,100 °C in an atmosphere containing at least 1 % of oxygen, to perform a chlorine removal treatment, and that the resultant silica gel is further heated to a temperature of approximately 1,050 °C - approximately 1,300 °C in He or in vacuum, to perform a sintering treatment.
Claim 2
Independent Claim
107 words
A method for producing silica glass characterized in that a dry silica gel subjected to a water desorption treatment and a carbon removal treatment is heated and has its temperature raised in an atmosphere containing chlorine, to perform a hydroxyl group removal treatment, that the resultant silica gel is thereafter heated to a temperature of approximately 1,000 °C - 1,100 °C in an atmosphere containing at least 1 % of oxygen, to perform a chlorine removal treatment, and that the resultant silica gel is further heated to a temperature of approximately 1,050 °C - approximately 1,300 °C in He or in vacuum, to perform a sintering treatment.
Claim 3
Independent Claim
224 words
A method for producing silica glass characterized by comprising i) the step of heating a silica material made of a dry silica gel and raising. its temperature to approximately 250 °C, to perform a water desorption treatment, ii) the step of heating the silica material having undergone said water desorption treatment and raising its temperature to approximately 700 °C in an oxidizing atmosphere, to perform a carbon removal treatment, iii) the step of heating the silica material having undergone said carbon removal treatment and raising its temperature from approximately 700 °C to approximately 1,000 °C - approximately 1,050 °C in an atmosphere, containing at least 1 % of Cl 2 , to perform a hydroxyl group removal treatment, iv) the step of heating the silica material having undergone said hydroxyl group removal treatment to a temperature of approximately 1,000 °C - approximately 1,100 °C in an atmosphere containing at least 1 % of oxygen and holding said silica material at a predetermined temperature for at most 2 hours, to perform a chlorine removal treatment, and v) the step of heating the silica material having undergone said chlorine removal treatment to a temperature of approximately 1,050 °C - approximately 1,300 C in He or in vacuum and holding said silica material at a predetermined temperature for at most 1 hour, to perform a sintering treatment.
Claim 4
Independent Claim
224 words
A method for producing silica glass characterized by comprising i) the step of heating a silica material made of a dry silica gel and raising. its temperature to approximately 250 °C, to perform a water desorption treatment, ii) the step of heating the silica material having undergone said water desorption treatment and raising its temperature to approximately 700 °C in an oxidizing atmosphere, to perform a carbon removal treatment, iii) the step of heating the silica material having undergone said carbon removal treatment and raising its temperature from approximately 700 °C to approximately 1,000 °C - approximately 1,050 °C in an atmosphere, containing at least 1 % of Cl 2 , to perform a hydroxyl group removal treatment, iv) the step of heating the silica material having undergone said hydroxyl group removal treatment to a temperature of approximately 1,000 °C - approximately 1,100 °C in an atmosphere containing at least 1 % of oxygen and holding said silica material at a predetermined temperature for at most 2 hours, to perform a chlorine removal treatment, and v) the step of heating the silica material having undergone said chlorine removal treatment to a temperature of approximately 1,050 °C - approximately 1,300 C in He or in vacuum and holding said silica material at a predetermined temperature for at most 1 hour, to perform a sintering treatment.
Claim 5
Dependent Claim
26 words
A method for producing silica glass as defined in claim 2, characterized in that a temperature-raising rate in said step iii) is 30 - 100 °C/hr.
Claim 6
Dependent Claim
27 words
A method for producing silica glass as defined in claim 2, characterized in that a temperature raising rate in said step iii) is 50 - 60 °C/hr.
Claim 7
Dependent Claim
40 words
A method for producing silica glass as defined in claim 2, characterized in that said atmosphere in said step iii) is a mixed gas consisting of 5 - 50 % of C1 2 and the balance of 0 2 .
Claim 8
Dependent Claim
40 words
A method for producing silica glass as defined in claim 2, characterized in that in said step iii), a treatment of holding the silica material at a predetermined temperature for at most approximately 2 hours is performed at least once.
Claim 9
Dependent Claim
40 words
A method for producing silica glass as defined in claim 2, characterized in that in said step iv), the silica material is held at the predetermined temperature of approximately 1,000 °C - approximately 1,100 °C for 1 - 2 hours.
Claim 10
Dependent Claim
45 words
A method for producing silica glass as defined in claim 2, claim 3, claim 4, claim 5, claim 6 or claim 7, characterized in that said atmosphere in said step iv) is He containing at least 5 % of oxygen, or pure 0 2 .
Claim 11
Dependent Claim
51 words
A method for producing silica glass as defined in claim 2, claim 3, claim 4, claim 5; claim 6 or claim 7, characterized in that in said step v), the silica material has its temperature raised to the predetermined temperature at a temperature raising rate of 50 °C - 100 °C/hr.
Claim 12
Dependent Claim
42 words
A method for producing silica glass as defined in claim 2, characterized in that in said steps iii) and iv), the silica material is subjected to the next step without being exposed into an atmospheric air after end of said each step.
Claim 13
Dependent Claim
43 words
A method for producing silica glass as defined in claim 2, characterized in that in said steps ii), iii) and iv), the silica material is subjected to the next step without being exposed into an atmospheric air after end of said each step.
Claim 14
Dependent Claim
62 words
A method for producing silica glass as defined in claim 2, characterized in that in at least one of said steps i), ii), iii) and iv), a quantity of at least one gas constituting an exhaust gas is measured, a measured value of the gas quantity being fed back to a treatment condition in the step so as to control said step.
Claim 15
Dependent Claim
42 words
A method for producing silica glass as defined in claim 12, characterized in that in said step i), a quantity of H 2 0 in the exhaust gas is measured, a measured value thereof being used to control a temperature raising rate.
Claim 16
Dependent Claim
58 words
A method for producing silica glass as defined in claim 12, characterized in that in said step ii), a quantity of 0 2 , a quantity of HCOOH, a quantity of H 2 0 or a quantity of C0 2 in the exhaust gas is measured, a measured value thereof being used to control a temperature raising rate.
Claim 17
Dependent Claim
47 words
A method for producing silica glass as defined in claim 12, characterized in that in said step iii), a quantity of HOC1 or a quantity of HC1 in the exhaust gas is measured, said hydroxyl group removal treatment being ended when the measured gas has become unobserved.
Claim 18
Dependent Claim
43 words
A method for producing silica glass as defined in claim 12, characterized in that in said step iv), a quantity of C1 2 in the exhaust gas is measured, said chlorine removal treatment being ended when the C1 2 quantity has become unobserved.
References Cited (Backward Citations)
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