Method for processing glass in forming fibers

The disclosure embraces a method of and apparatus for processing heat-softened mineral material, such as glass, wherein streams of glass flowing from orifices in depending projections of a stream feeder are conditioned for attenuation through the use of metal fin shields for conveying heat away from the streams of glass, the method and apparatus involving the utilization of a moving gas environment between rows of the depending projections at the floor of the stream feeder and above the fin shields to eliminate or minimize the accumulation of compounds of the glass volatiles on the fin shields and to reduce the tendency of the glass to flood the stream flow region of the feeder.

The invention relates to the establishment of an environment at the stream 
flow region of a stream feeder involving the continuous delivery of gas in 
relatively small amounts to improve the fiber-forming operation by 
reducing or minimizing the accumulation or build-up of condensed products 
or compounds from volatiles emitted from the glass and minimizing the 
tendency for the glass to flood over the stream flow region of a feeder. 
Heretofore textile glass compositions have usually included boron and 
fluorine compounds. The fluorine in the glass tends to minimize the 
deposition or accumulation of compounds from volatiles emitted from the 
glass on the metal members or fin shields conventionally employed for 
conducting heat away from the glass streams to render the glass streams of 
a viscosity suitable for attenuation to fibers. 
By reason of environmental restrictions pertaining to air pollution and 
contamination, glass compositions for forming textile fibers or filaments 
are being employed wherein the glass compositions contain boron but little 
or no fluorine. In employing such fluorine-free glass compositions for 
forming streams of glass for attenuation to fibers, the major chemical 
species in the high temperature environment at the stream flow region is 
boric oxide. 
The vapor pressure of boric oxide B.sub.2 O.sub.3 decreases very rapidly 
with temperature so that the boric oxide condenses on the fin shields 
resulting in a comparatively rapid buildup of solid boric oxide on the fin 
shields. This condition necessates frequent cleaning of the fin shield 
assembly to remove the accumulated condensation products from the metal 
fin shields or members. 
In the absence of a substance such as a fluoride to reduce the vapor 
pressure of boric oxide B.sub.2 O.sub.3, the beads of glass formed at the 
orifice projections during start-up tend to be large in diameter and 
comparatively short due to the lower viscosity and surface tension of the 
glass surface. Such beads of glass contact one another and the metal fin 
shields causing flooding of the glass over the stream feeder floor 
surface. 
The present invention embraces a method involving supplying a gas in the 
region above the metal fin shields or members adjacent a glass stream 
feeder promoting volatilization of boron compounds from the glass and 
thereby reducing or substantially eliminating condensation of the boron 
compounds on the fin shields or members. 
An object of the invention resides in a method of establishing an 
environment at the orificed projections on the floor of a glass stream 
feeder from which flow glass streams for attenuation to fibers including 
directing streams of gas of low velocities above metal fin shields or 
members adjacent the glass streams to reduce or minimize the condensation 
of volatiles from the glass on the metal fin shields or members. 
Another object of the invention resides in a method of establishing and 
maintaining an environment at the stream flow region of a feeder having 
depending orificed projections through which flow streams of glass 
associated with fin shield members conveying heat away from the glass 
streams to render the glass streams suitable for attenuation, the 
environment including directing streams of gas between rows of the 
depending projections and above the fin shield members, the gas reacting 
with volatiles emitted from the glass to reduce or minimize condensation 
of the volatiles on the fin shield members. 
Another object of the invention resides in a method of processing 
heat-softened glass including flowing streams of glass from orificed 
projections depending from a stream feeder with which is associated fin 
shield members for conducting heat away from glass streams flowing from 
the projections, and flowing streams of a gas, such as water vapor or a 
mixture of air and hydrogen fluoride, above the fin shield members in 
relatively small amounts for reducing or substantially eliminating 
condensation of volatiles from the glass streams on the fin shield members 
and effecting at the formation at start-up of longer beads of glass of 
reduced lateral dimension to reduce the tendency for the glass to flood at 
the stream feeder. 
Another object of the invention resides in the use of a glass stream feeder 
having rows of orificed depending projections through which flow streams 
of glass for attenuation to fibers in association with means for supplying 
streams of gas between rows of the depending projections and above the fin 
shield members effective to reduce the condensation of volatiles emitted 
from the glass on the fin shields.

While the method and apparatus of the invention provide a gaseous 
environment having particular utility in processing glass for forming 
fibers, it is to be understood that the method and apparatus may be 
utilized in the processing of other fiber-forming mineral materials. 
Referring to the drawings in detail and initially to FIG. 1, there is 
illustrated a stream feeder or bushing 10 adapted to contain heat-softened 
mineral material, such as glass. In the embodiment illustrated, the stream 
feeder 10 is connected with a forehearth 12 which conveys molten glass 
from a melting furnace (not shown) into the stream feeder. If desired, 
heat-softened glass may be supplied to the stream feeder from a melter in 
which pieces or marbles of prerefined glass are reduced to a molten 
condition. 
The stream feeder 10 is fashioned of a metal or alloy capable of 
withstanding the high temperatures of molten glass, such as an alloy of 
platinum and rhodium. The feeder 10 is provided at its ends with terminal 
lugs 14 for connection with current supply conductors (not shown) for 
passing electric current thorugh the feeder to maintain the glass at the 
desired temperature and viscosity for flowing streams of glass from the 
feeder. 
The floor 16 of the feeder 10, usually referred to as a tip section, is 
formed with transverse rows of depending hollow projections or tips 18 
providing passages or orifices 20 through which flow streams 21 of molten 
glass from the feeder. The glass streams immediately below the projections 
18 are in the form of cones 22 of glass. 
The glass streams 21 are attenuated into continuous fibers or filaments 24 
by winding a strand of the fibers or filaments into a package. In the 
arrangement illustrated in FIG. 1, the continuous fibers or filaments are 
converged to form a multifilament strand 26 through the medium of a 
gathering device or shoe 28. The strand is wound into a package 30 upon a 
collector or forming tube 32 mounted upon a mandrel 33 rotated by a 
suitable motor (not shown) contained in a housing 35 of a winding machine 
of conventional construction. 
As is conventional in winding textile fibers or filaments into a package, 
the strand is traversed lengthwise of the collector 32 to build the 
package of superposed layers of strand by a rotatable and reciprocable 
traverse means 37. The traverse means 37 may be of the character 
illustrated in the U.S. Pat. No. 2,391,870 to Beach which engages and 
oscillates the strand to effect a crossing of successive convolutions of 
the strand on the collector in a conventional manner. A lubricant, size or 
other coating material may be applied to the filaments by engaging them 
with a roll applicator 39 mounted by a receptacle 40 containing the size 
or coating material. 
Disposed adjacent and lengthwise of the stream feeder 10 is a header and 
fin shield assembly 42. The assembly 42 is inclusive of a tubular header 
44 having an inlet tube 45 and an outlet tube 46, the header accommodating 
a circulating heat-absorbing or heat-trasnferring medium, such as water. 
Welded or otherwise joined with the header is plurality of 
heat-transferring metal members, fins or fin shields 48. 
It is preferred that the fins or members 48 in operating position are 
disposed with the upper edge 50 of each fin or member at a level slightly 
above the extremities of the tips or projections 18 as shown in FIGS. 2 
and 3. Heat from the glass streams is transferred to the metal members or 
fins 48 and the circulating cooling medium or fluid in the header 44 
conveys away the heat from the glass streams. Such arrangement is of 
conventional character and functions to convey sufficient heat away from 
the glass streams to render the glass of the streams at a proper viscosity 
to facilitate attenuation of the streams to fibers or filaments. 
Textile glass compositions have heretofore included such constituents as 
boron and fluorine. The environment above the fin shields at the region of 
the feeder floor in prior fiber-forming operations is nearly quiescent or 
stagnant, the environment being composed of air, volatiles from the glass 
and their reaction products. If both boron and fluorine are present in the 
glass, both volatilize from the surface of the molten glass of the streams 
and the major chemical species present in the environment is boron 
fluoride from the reaction of the fluoride with boric oxide vapor. 
This reaction reduces the vapor pressure of the boric oxide in the 
environment and accelerates its vaporization from the glass surface. The 
greater the depletion of the glass surface of boron by volatilization, the 
greater the viscosity and surface tension of the glass surface enhancing 
the stability of the cones of glass. The beads of glass forming at the 
tips of the orificed projections during start-up tend to be longer and 
thinner reducing the tendency for the beads to contact or hang up on the 
fin shields and cause flooding at the stream flow region of the feeder. 
By reasons of environmental restrictions, textile glass compositions are 
being used having little or no fluorine in the compositions. If only boron 
is present in the glass, with little or no fluorine, the major chemical 
species in the stream flow environment is boric oxide B.sub.2 O.sub.3. The 
equilibrium vapor pressure is low at the feeder tip temperatures so that 
volatilization from the glass very rapidly reaches equilibrium in the 
relatively quiescent or stagnant environment, and surface volatilization 
becomes very slow. 
Hence, in the absence of a substance such as fluoride to reduce the vapor 
pressure of the gaseous boric oxide, the beads of glass formed at the tips 
of the orificed projections during start-up tend to be large in diameter 
and substantially shorter due to the lower viscosity and surface tension 
of the glass surface. The vapor pressure of the gaseous boric oxide 
decreases very rapidly with decreased temperature so that solid boric 
oxide B.sub.2 O.sub.3 condenses on the fin shields or metal members 
resulting in a comparatively rapid build-up of boron compounds on the fin 
shields or metal members. The fiber-forming operation must be interrupted 
frequently to clean the fin shields. The invention is inclusive of a 
method and arrangement providing a gaseous environment between rows of 
depending projections on the stream feeder and above the metal members or 
fin shields, the environment being effective to eliminate or greatly 
reduce the accumulation on the fin shields or solids from the volatiles 
emitted from the glass and promote the formation of longer and thinner 
beads of glass during start-up to thereby reduce the tendency of flooding 
of glass over the stream flow area of the feeder. 
The method includes the supplying or delivery of streams of gas of low 
volume and at low velocities between rows of the depending projections and 
above the fin shields providing continuous movement of the gas between the 
rows of projections for eliminating the stagnant air environment at such 
regions, the gas effecting reactions with the volatiles emanating from the 
glass to attain the above-mentioned results of preventing fin shield 
build-up and modifying the configuration of the beads of glass formed 
during start-up. 
As shown in FIGS. 1, 3 and 4, manifold means comprising manifolds 55 and 
55' are respectively disposed at each side of the stream feeder 10. Welded 
or otherwise secured to the manifold 55 are tubes or nozzles 57 for 
delivering streams of gas from the manifold 55. As shown in FIGS. 2, 3 and 
4, each tube or nozzle 57 is disposed above and in lengthwise parallel 
relation with the adjacent fin shield 48. 
The streams of gas from the tubes or nozzles 57 are directed above and 
lengthwise of the adjacent fin shields or metal members 48 and between 
transverse rows of orificed projections 18 depending from the feeder floor 
or tip section of the stream feeder 10. 
As shown in FIGS. 2, 3 and 4, each tube or nozzle 57' connected with the 
manifold 55' is disposed above and in lengthwise parallel relation with 
the adjacent fin shield 48. The streams of gas from the tubes or nozzle 
57' are directed above and lengthwise of the adjacent fin shields or metal 
members 48 and between transverse rows of orificed projections 18 
depending from the feeder floor or tip section of the stream feeder 10. 
As shown in FIGS. 3 and 4, the tubes or nozzles 57 and the tubes or nozzles 
57' are in aligned relation transversely of the feeder so that the gas 
streams directed or delivered from the nozzles impinge one another. 
Through this arrangement the gas streams, moving between rows of 
projections and above and in lengthwise parallel relation with the fin 
shields or metal members 48, provide a continuously moving gaseous 
environment between rows of depending projections 18 thus obtaining a more 
uniform reaction of the gas with the volatiles from the glass. 
With reference to FIG. 4, the manifold means 55 and 55' are joined by tee 
fittings 60 and 60'. The tee 60 is connected by tubular means with a valve 
or valve means 63, the valve 63 being connected by a pipe or tube 64 with 
the gas supply. The tee 60' is connected by tubular means with a valve or 
valve means 63', the valve 63' being connected by a pipe or tube 64' with 
the gas supply. The valves 63 and 63' regulate or control the flow of gas 
to the manifold means 55 and 55'. 
It is found that a gas such as water vapor or steam at a temperature of 
above 250.degree. F. or more provides a gas environment above the fin 
shields or metal members 48 and between rows of depending projections 18 
on the stream feeder floor which is effective to attain the chemical 
reactions with volatiles emitted from a glass having boron therein but 
little or no fluorine to greatly reduce or minimize the accumulation or 
build-up of solids or condensation products on the fin shields or metal 
members 48 and to render the glass beads formed during start-up longer and 
thinner to reduce the tendency of flooding of the glass over the feeder 
floor or tip section. 
If boron is present in the glass with little or no fluorine, the major 
chemical species in the environment is boric oxide. The water vapor or 
steam reacts with the boric oxide B.sub.2 O.sub.3 as a gas to form a gas 
HBO.sub.2, meta-boric acid, but this is an equilibrium reaction with the 
amount of boric oxide as a gas converted to a gaseous meta-boric acid 
increasing as the square root of the water vapor or steam concentration. 
The equilibrium vapor pressure of the gas HBO.sub.2 with HBO.sub.2 as a 
solid is several orders of magnitude greater than than of the gas B.sub.2 
O.sub.3 with the solid B.sub.2 O.sub.3. As the temperature is reduced the 
meta-boric acid HBO.sub.2 as a gas further reacts with the steam or water 
vapor to form H.sub.3 BO.sub.3, ortho-boric acid in gas form which has a 
relatively high vapor pressure at all temperatures above 250.degree. F. 
Therefore, the H.sub.3 BO.sub.3 remains in gas form in the environment and 
eliminates or reduces the condensation of boric oxide on the metal members 
or fin shields 48 and promotes the formation of longer and thin beads of 
glass at the ends of the orificed projections 18 during start-up. 
The velocity of the water vapor or steam delivered from the nozzles 57 and 
57' is comparatively low, the maximum velocity, being about 170 
centimeters per second. The volume of steam or water vapor of the streams 
delivered from the nozzles 57 and 57' is comparatively low. As an example, 
with a stream feeder floor section or bushing having 816 orificed 
projections or tips, the range of volume of water vapor or steam is from 
500 to 3000 cubic centimeters per minute, or from 0.62 to 3.7 cubic 
centimeters per minute for each tip or projection. 
The preferred volume of steam is 2.45 cubic centimeters per minute for each 
projection or tip, which is equivalent to 2000 cubic centimeters per 
minute for a stream feeder section or bushing having 816 orificed 
projections or tips. 
Another gas that may be used as a gaseous environment above the fin shields 
48 and between rows of orificed projections 18 to eliminate or minimize 
build-up of compounds on the fin shields or metal members and promote the 
formation of long thin beads of glass at start-up is a mixture of hydrogen 
fluoride and air in a ratio of one part hydrogen fluoride to about ten 
parts of air by volume. 
The amount of hydrogen fluoride in the air and hydrogen fluoride mixture is 
about 0.075 cubic centimeters per minute for each orificed projection or 
tip 18. With this gas the reaction between boric oxide B.sub.2 O.sub.3 in 
gas form and hydrogen fluoride HF in gas form results in the formation of 
boron fluoride BF.sub.3 in gas form which remains in gas form and thus 
eliminates the deposition of boron compounds on the fin shields or metal 
members 48 and promotes the formation of longer and thinner beads of glass 
at the orificed projections during start-up. The amount of hydrogen 
fluoride employed in the gaseous environment is well within the amount 
allowed by the present environmental restrictions. 
FIG. 5 illustrates schematically the configurations of glass forming at the 
exits of the orificed projections 18 during start-up operations. IN the 
use of a glass composition containing little or no fluorine and without 
the gas environment of the invention, the beads of glass illustrated at 68 
in broken lines are short and of comparatively large diameters. This form 
of bead configuration promotes the tendency for the beads to contact one 
another and contact the metal members or fin shields causing the glass to 
flood across the floor of the stream feeder or bushign. 
With the use of the gas environment of the invention above the fin shields 
and between rows of depending orificed projections, the beads formed of a 
glass composition having little or no fluorine are longer and of lesser 
diameter, such beads being indicated at 70. Beads of the latter character 
drop freely with no tendency to contact or hang up on the fins and cause 
flooding of the feeder floor. 
It is found that a further advantage results from the use of the gas 
environment of the invention. The cones of glass 22 at the exits of the 
orificed projections 18 during attenuating operations are shorter and more 
stable than cones of glass in the absence of the gas environment. 
It is important that the metal members or fin shields 48 are operated at a 
temperature above the condensation temperature of the compounds or 
materials formed as a result of the addition of the gas. Otherwise those 
reaction products would have a tendency to accumulate on the fin shields. 
With the water vapor injection system, for example, the fin shields or 
metal members 48 should be operated above 250.degree. F. 
Furthermore the gas is delivered above the level of the terminal of the 
depending projections and between rows of depending projections and 
oriented also so as to not directly impinge the floor or tip section 16 of 
the feeder 10. And since the volume and velocity of the gas is so 
relatively low it is believed there is no significant increase in the 
amount of heat transferred from the feeder or the fibers being formed. 
Therefore, the electrical power consumed by the feeder by the fiber 
forming process will not be significantly increased. It is believed to be, 
at maximum, less than a 1% increase in power consumed by the feeder 10. 
The use of the invention in forming glass fibers particularly from glass 
compositions containing little or no fluorine enables the fiber-forming 
operation to be continued without interruption for much longer periods of 
time before it becomes necessary to clean the fin shields. 
It is apparent that, within the scope of the invention, modifications and 
different arrangements may be made other than as herein disclosed, and the 
present disclosure is illustrative merely, the invention comprehending all 
variations thereof.