Appeal No. 1998-2300
Application No. 08/366,762
BACKGROUND
The invention is directed to a method for the preparation of vitrified silica glass
particles. The vitrified silica glass particles are suitable for use as base material of
transparent fused silica glass bodies. Claim 1 which is representative of the invention is
reproduced below:
1. A method for the preparation of poreless vitrified silica glass particles which
comprises the successive steps of:
(a) admixing finely divided silica particles having a specific surface area in the
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range from 1 m /g to 400 m /g with water to form a uniform mixture of the
silica particles and water, wherein the amount of water is in the range from 100
to 200 parts by weight per 100 parts by weight of the silica particles;
(b) dehydrating and drying the mixture of the silica particles and water to give
a porous caked mass of the silica particles;
(c) disintegrating the porous caked mass of the silica particles to give porous
silica particles;
(d) heating the porous silica particles at a temperature in the range from
o o
800 C to 1300 C for a length of time in the range from 5 hours to 100 hours in
an atmosphere of chlorine or thionyl chloride to give semi-sintered silica
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particles having a bulk density in the range from 0.6 to 0.9 g/cm ; and
(e) heating the semi-sintered silica particles at a temperature in the range
o o
from 1450 C to 1550 C for a length of time of at least 10 minutes.
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