Note: Descriptions are shown in the official language in which they were submitted.
1~768~
This invention relates to a process for spinning glass
fibers. More particularly, this invention relates to an improved
process for spinning glass fibers using a flat nozzle plate which
is made of a material showing almost no wetting with molten glass
and has a large number of orifices per unit area therein.
Heretofore various apparatuses for producing glass
fibers have been proposed. A typical example of the apparatuses
is a spinning furnace having a flat spinneret made of a platinum- :
rhodium alloy. Said spinneret is a flat plate made of a plati-
num-rhodium alloy and has such a simple structure as having a
few orifices with 1.5 - 3 mm in diameter therein. But the
platinum-rhodium alloy has a defect in that a contact angle of
it to molten glass is very small, i.e. wetting with molten glass ~ ;
is great. A spinneret made of a platinum-gold-rhodium alloy, ,~
which has been developed later, has a larger contact angle to
molten glass than the platinum-rhodium alloy spinneret and thus
wetting with molten glass is not so great. But it is inevitable
in the case of using either the platinum-rhodium alloy or the
platinum-gold-rhodium alloy that, if pitches between each
orifice become narrower, once one of the filaments passing
through an orifice is cut, molten glass bead would be formed on
the exit hole of the orifice and spread over the surface of the
orifice widely so as to cut other filaments passing through the
adjacent orifices, and this phenomenon would proceed succes-
sively until all the filaments are cut and the under surface of
the spinneret would be covered with the molten glass delivered ;
from the orifices. Once such a phenomenon takes place, it is
very difficult to separate into each filament, that is, to
recover the state in which molten glass passing through one
30 orifice forms an independent stream of filament without being -
combined with other molten glass passing through another
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orifice. Particularly if pitches between each orifice are less
than 5 mm, it is completely impossible even for a skilled
worker to separate into individual filaments so as to form each
independent stream from each orifice according to the conven-
tional process.
In order to improve such defects as mentioned above, a
process for using tip nozzles has been developed. According to
said process, since the area which can be wetted with molten
glass from one nozzle is limited to the bottom of a tip, molten
glass from one nozzle is enforced to form an independent stream
without combined with molten glass from another nozzle.
Therefore separation of filaments can easily be carried out even
if nozzles are placed closely. Thus it is possible to make more
nozzles per unit area than thè flat spinnerets mentioned above
and to increase the productivity remarkably. But the tip
nozzle has, on the other hand, the following defects. The side
wall of each tip nozzle needs some thickness and then there are
concave parts among tips, and if one tip is placed very closely
to another tip, molten glass would intrude into the concave
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` 20 parts, which gives bad influence on the effect of the tip nozzle.
Further in order to increase the productivity, it is necessary
to attach cooling apparatus to places between the two tips. By
the reasons mentioned above, there is, as a matter of course,
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limitation to the number of nozzles per unit area. If too many '
tip nozzles are perforated in a nozzle plate, the shape of the
nozzle plate should be enlarged and about 2000 holes seem to be
the practical upper limit of the number of nozzles in the plate
due to deformation of the plate. In addition, since the nozzle
plate i5 made of an expensive platinum-rhodium or platinum-gold-
rhodium alloy, the amount of used noble metals may increase with
an increase of the number of nozzles, which results in an in- ;
crease in equipment investment and cost for the product.
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Other processes are disclosed in, e.g. K.L. Leowenstein
"The Manufactural Technology of Continuous Glass Fibers"
Elserier Scientific Publication Co., N.Y., 1973, but they are ;
insufficient in the above-mentioned points.
It is an object of the present invention to provide an
improved process for spinning glass fibers stably with excellent
productivity by using a special nozzle plate having a large
number of orifices per unit area, easily finding the end of
individual filament, and overcoming the defects of the known
processes.
The present invention provides a process for spinning
glass fibers by drawing individual filament from each orifice in
a nozzle plate attached to a melting furnace, characterized by
using a nozzle plate made of a material having a contact angle
of 60 or more to molten glass and containing a large number of
orifices per unit area so that molten glass effluent from the
orifices may form combined beads, drawing gradually the combined
molten glass beads on the under surface of the nozzle plate so
as to separate the molten glass into individual filament from
each orifice and finding the end of individual filament.
According to the process of the present invention, since
the special nozzle plate having a large number of orifices per ;;
unit area ia used, the productivity of the nozzle plate per unit ;~
area is about 10 to 80 times as much as the conventional methods
and glass fibers can be produced stably and continuously unlike
the conventional methods. -
In the present process, glass is melted down in a con-
ventional melting furnace such as a bushing, a glass melting
tank, or the like. At the bottom of the bushing, a special flat
nozzle plate is attached. The nozzle plate must be made of a
material having a contact angle of 60 or more to molten glass,
preferably 90 or more.
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Contact angle of the material to molten glass is
measured as follows. A little glass bead (0.1 to 0.2 g) is
placed on a flat plate made of the material whose angle is to be
measured, and the plate and the glass bead are put into a furnace
in which the plate is placed horizontal, and kept for one hour
at a constant temperature, e.g. 1100 to 1200C. Then they are
taken out and quenched. Subsequently, they are photographed
from the exactly lateral direction. Then the contact angle is
measured using a conventional method. It is known that the `
contact angle measured by this quenching method is almost equal
to the contact angle at high temperatures.
In the present invention, when a contact angle to molten
glass is 90 or more, it is defined that the material has non-
wetting property, and when a contact angle is 60 or more and
less than 90, the material has little wetting property.
The materials having a contact angle of 90 or more to
molten glass are particularly preferable to make a nozzle plate
in the present invention. Examples of such materials are ~ `
graphite (150 measured at 1100C) or boron nitride (130 measured `
at 1100C). The materials having a contact angle of 60 or more
and less than 90 to molten glass can be used for making a
nozzle plate, if the spinning operation conditions, for instance
speed, temperature, rate of molten glass delivery, viscosity,
etc. are changed. Examples of such materials are a platinum-
rhodium-gold alloy, a gold-palladium alloy, and the like.
The flat nozzle plate made of such materials as men- `
tioned above has a large number of orifices per unit area so that
the molten glass effluent from the orifices may form combined
molten glass beads. More concretely, pitches between each ori-
fice are 5 mm or less, preferably from 0.5 to 2.5 mm. Since the
diameter of an orifice is usually from 0.3 to 2.0 mm, the
1~76810
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number of orifices per unit area in the nozzle plate is prefer-
ably 25 to 200 per square centimeter. Since the number of
orifices per unit area in a conventional flat nozzle plate made
of a platinum-rhodium alloy is about 2.4 per square centimeter,
the value of 25 - 200 is 10 to 80 times as many as the conven-
tional value. Thus the yield of glass fibers per unit area of
the nozzle plate can increase up to 10 to 80 times as much as
that which can be obtained in the conventional method.
The process of the present invention using such a special
nozzle plate is explained in more detail below.
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Combination of two or more streams of molten glass
effluent from orifices in a nozzle plate is generally due to
wetting property between the molten glass and the nozzle plate,
that is, each stream of molten glass effluent from an orifice
spreads outwards from the periphery of the orifice to combine
with each other. Therefore, in order to prevent the combination
of two or more streams of molten glass on the under surface of a
nozzle plate, it is necessary to allow a considerable distance
between two or more orifices so that each molten glass bead ;
formed from a stream of molten glass naturally effluent from an
orifice should not be combined together. But even though the
~- conditions as mentioned above are satisfied, it has been impos-
sible even for a skilled worker to separate the combined molten '
glass beads into each independent stream of filament from each
orifice and to find the end of individual filament, so far as
employing the conventional spinning process wherein each filament
is drawn from each orifice.
On the contrary, according to the present process, the
combined molten glass beads can easily be separated into indi-
vidual filament and the end of individual filament can easily be
found, since the nozzle plate is made of a material having non-
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wetting or little wetting property, and the combined molten glass
beads are drawn gradually from the under surface of the nozzle
plate.
In the case of spinning glass fibers using a nozzle
plate made of the material having a con-tact angle of 90 or more
to molten glass, i.e. having non-wetting property, and pitches
between each orifice being 5 mm or less, the following procedure
can be employed. Since the n~ber of orifices per unit area is
very large, and molten glass wets itself easily, each molten glass
bead effluent from the orifices spreads on the under surface of
the nozzle plate and eventually all beads combine with each other
to cover the whole area of the surface. Since the nozzle plate
has non-wetting property against molten glass, when the molten
glass blanketing the under surface of the plate with increased
viscosity is drawn downwards at a greater speed than the effluent
speed of the molten glass from the melting furnace, the molten
glass spreading over the whole surface of the nozzle plate is
pulled back to each periphery of orifice and easily separated
into individual filament. The greater the viscosity of molten ;
,.
glass blanketing the under surface of the nozzle plate becomes,
the easier the separation into individual filament becomes due
to an increase in amount of the molten glass drawn downwards
and influence of the tensile force. Thus the end of individual
filament can easily be found.
In the case of spinning glass fibers using a nozzle plate
made of the material having a contact angle of 60 - 90 to
molten glass, i.e. having little wetting property, and pitches
between each orifice being 5 mm or less, the separation of the
combined molten glass beads into individual filament can easily
be attained in the same manner as mentioned above, i.e. drawing
downwards gradually the molten glass effluent from the orifices
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and increasing the viscosity of the combined beads blanketing
the under surface of the nozzle. If separation into individual
filament is attained insufficièntly, an air stream is blown to
the combined molten glass beads blanketing the under surface of
the nozzle plate to cool and increase the viscosity of molten
glass. Thus the end of individual filament can easily be found.
When the separation into individual filament is attained and
stable windup of filaments begins~ air blowing is stopped. In-
asmuch as tensile force applied to filaments has a sufficient
influence on each periphery of meniscus formed under each
orifice, the influence of surface tension to cut the filaments
and to make glass beads decreases, and the stability of meniscus
shaped under the orifices can be maintained.
A nozzle plate made of graphite or boron nitride is by
far superior to conventional ones in wetting and can be used for
spinning glass fibers easily to obtain excellent products. A
nozzle plate made of a platinum-rhodium-gold alloy having a con-
tact angle of 60 or more to molten glass is very excellent in
strength, durability, oxidation resistance, and the like and
20 can be used for stable spinning of glass fibers for a long i
period. On the other hand, the nozzle plate made of graphite or
boron nitride is slightly inferior to that made of the above
mentioned alloy in durability, but since the former has non-
wetting property, it has many advantages, particularly an easy `-
operation and low cost.
The following examples will serve further to illustrate
the present invention.
Example 1
A nozzle plate made of graphite and having 87 orifices
of 1.0 mm in diameter, the number of orifices per square centi-
meter being 29, was attached to the bottom of a conventional
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bushing. As glass, E-glass was used for spinning. From each
orifice, molten glass was delivered at the rate of 0.3 g/min.
Each molten glass bead naturally effluent from each orifice was
combined together and blanketed the under surface of the nozzle
plate while increasing the viscosity of the molten glass. Then
the molten glass blanketing the surface was drawn downwards at
a greater speed than the effluent speed of the molten glass from
the bushing. The combined molten glass beads were separated into
-` individual rilaments, and the ends of individual filaments could
easily be found. The filaments were wound up at a speed of
; 1000 m/min. Glass filament with a diameter of 13 microns was -~
obtained. Spinning temperature was 1120C. The contact angle
; between the molten glass and the graphite was 150 at 1100C.
Using a nozzle plate made of graphite and having 400
orifices of 1.0 mm in diameter, the number of orifices per square
centimeter being 36, and using the same manner as mentioned above,
glass filaments having the same fineness were obtained at a
windup speed of 500 m/min.
Example 2 ;
Using a nozzle plate made of boron nitride instead of
graphite, the procedure of Example 1 was repeated to obtain the
same results as Example 1. The contact angle between the molten
glass and the boron nitride was 130 at 1100C. ;
Example 3
Nozzle plates made of the platinum-rhodium-gold alloy
(composition: Pt 85.5% by weight, Rh 9.5% by weight and Au 5%
by weight) and having o~ifices of 1.3 mm in diameter, the numbers
of orifices being as shown in Table 1 ware used. Each nozzle
plate was attached to the bottom of a conventional bushing and
spinning of glass fibers was carried out using E-glass as used
in Example 1. From each orifice, molten glass was delivered
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e.g. at the rate of about 0.6 y/min. Each molten glass bead
naturally effluent from each orifice was combined together and
blanketed the under surface of the nozzle plate. Then the
molten glass blanketing the surface was drawn downwards at a
greater speed than the effluent speed of the molten glass from
the orifices. The combined molten glass beads were separated
into individual filaments and the ends of individual filaments
could easily be found. The filaments were wound up at speeds of
- 1000 - 3000 m/min as shown in Table 1. Thus glass filaments
with diameiers of 6 - 10 microns were obtained as shown in
~ Table 1.
- Table 1
Run No. of No. of Windup Spinning Fineness
No. orifices orific2es speed temp. (microns)
per cm (m/min) (C)
1 100 29 3000 116010
2 400 36 3000 116010
3 800 45 2000 1150 8
4 2000 45 1000 1140 6
The contact angle between the molten glass and the
platinum-rhodium-gold alloy was 76 at 1200C. When an air
stream of 10 - 50 l./min was blown to the combined molten glass
beads blanketing the surface of the nozzle plate for cooling
during the end of individual filament being found, the separa-
tion of the molten glass into individual filaments emerging from
each orifice could be attained more easily comparing with the
case of blowing no air. The air stream was blown in the direc-
tion of the orifices suitable for cooling meniscuses of the
molten glass emerging from the orifices. The air blowing was
stopped after stable windup of the filaments began.
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Example 4
Using a nozzle plate made of the gold-palladium alloy
(composition: Au 80% by weight and Pd 20% by weight), glass
fibers were spun in the same manner as Example 3 Run Nos. 1, 2
and 3. Almost the same results as in Example 3 Run Nos. 1, 2
and 3 were obtained. Since heat resistance of the gold-palladium
alloy is inferior to that of the platinum-rhodium-gold alloy
` used in Example 3, the former has a disadvantage in useful life.
The contact angle between the molten glass and the gold-palladium
10 alloy was 82 at 1200C.
Referential Example
A platinum-rhodium alloy which has widely been used for
making a nozzle plate has a contact angle of 32 at 1200C to
molten glass. Using a nozzle plate made of the platinum-
rhodium alloy, spinning of glass fibers was tried in the same
manner as Example 3 Run No. 2. Since the platinum-rhodium alloy
has wetting property to molten glass, separation of the filaments
was very difficult and stable spinning of glass fibers could not
be attained.
As is clear from the above examples, it is not only pos-
sible to spin glass fibers stably but also easy to produce very
fine glass fibers since the finding of the end of individual
filament is very easy according to the present process. It is
also possible to increase production of glass fibers up to 10
to 80 times as much as the conventional process if a nozzle plate
of the same area as used in the conventional process is used.
Further it is possible to produce directly the strands composed
of remarkably increased number of the filaments without employing
: conventional processes of warp beaming, doubling and the like.
According to the present process, glass fibers can be produced
;; in large scale and economically.
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