Note: Descriptions are shown in the official language in which they were submitted.
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BICOMPONENT GLASS AND POLYMER FIBERS
MADE BY ~OTARY PROCESS
TECHNICAI~ FIEL,D
S This invention relates in general to the m~nllfacture of fibers, and
specifically to a method for m~nllfslrturing bicomponent glass and polymer fibers by a
modified rotary process.
BACKGl~OUND
Bicomponent polymer fibers have previously been made by a textile
10 process for use in products such as fabrics and hosiery. In this process, two molten
polymers are supplied to a stationary spinneret having holes from which fibers are pulled
or drawn. The polymers are usually combined to form fibers having a core of one
polymer and a surrounding sheath of the other polymer.
The textile process usually makes relatively large diameter bicomponent
15 fibers. For certain applications, there are advantages to using smaller diameter fibers.
Also, the textile process is limited to the use of components having similar melting points,
so that the lower melting component does not therm:~lly degrade when exposed to the
higher melting component.
Bicomponent glass f1bers have been made by a modified rotary process.
20 Two different types of molten glass are supplied to a rotating spinner having an orificed
peripheral wall. The two types of molten glass are centrifuged through the orifices to
form bicomponent glass fibers. The fibers are particularly useful in insulation products.
The m~mlf~c.ture of glass fibers is a different field from the m~nllf~ ture of
polymer fibers. The two materials have different physical properties such as different
25 viscosities, and usually the softening point of the glass is different from the melting point
of the polymer. The technologies for making the fibers are also different.
It has not previously been known to produce bicomponent fibers by
combining glass and polymers. ~uch fibers would provide advantages associated with
both bicomponent glass fibers and bicomponent polymer fibers, and would have
30 properties and uses not provided by either fiber. Accordingly, it would be desirable to
provide a process for mak.ing bicomponent glass and polymer fibers.
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DISC~OSU~U~ OF n~VENTION
This invention relates to a method for making multicomponent fibers~ and
particularly bicomponent fibers. The bicomponent fibers are forrned from glass and a
thermoplastic m~t~ri~l, preferably a polymer. In the method, molten glass and molten
5 thermoplastic m~t.ori7~1 are supplied to a rotating spinner having an orificed peripheral
wall. Preferably the t~ dl~lre at which the glass viscosity is 1000 poise is from about
200~C to about 495~C, and the melting point of the therrnoplastic material is from about
200~C to about 345~C. The coefficient of thermal expansion of the thermoplastic
material is preferably higher than that of the glass by an amount greater than about 10
10 ppm/~C. The molten glass and molten thermoplastic material are centrifuged through the
orifices as molten bicomponent streams of glass and thermoplastic material. Then the
streams are cooled to make bicomponent fibers of glass and therrnoplastic material.
The bicomponent fibers of glass and thermoplastic material produced by
the method arc novel and provide advantages associated with both bicomponent glass
15 fibers and bicomponent polymer fibers. They also have properties and uses not provided
by either of the previously known fibers.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is a sehem~tic view in elevation of apparatus for carrving out the
rotary method of the invention for m~king bicomponent fibers of glass and polymer.
Fig. 2 is a cross-sectional view in elevation of a spinner by which
bicomponent fibers of glass and polymer can be produced according to the invention.
Fig. 3 is a schematic view in perspective of a portion of the spinner of Fig.
2.
Fig. 4 is a sçhem~tic view in elevation of the spinner of Fig. 2, taken along
25 line 4-4 of Fig. 2.
Fig. 5 is a plan view of a portion of a second embodiment of a spinner for
making bicomponent fibers of glass and polymer.
Fig. 6 is a cross-sectional view in elevation of a third embodiment of a , .
spinner for making bicomponent fibers of glass and polymer.
Fig. 7 is a cross-sectional view in elevation of the orifice of the spinner of
Fig. 6.
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Fig. 8 is a s~h.em~tic cross-sectional view of a bicomponent fiber of glass
and polymer produced according to the invention.
Fig. ~ is a s~hem~tic cross-sectional view of a bicomponent fiber of glass
,~ and polymer in which differing viscosities of the glass and polymer enables the lower
S viscosity polymer to flow partially around the higher viscosity glass.
l~ig. 10 is a schematic cross-sectional view of a bicomponent fiber of glass
and polymer in which the differing viscosities ena~les the lower viscosity polymer to
nearly enclose the higher viscosity glass.
Fig. 11 is a schematic cross-sectional view of a bicomponent fiber of glass
10 and polymer in which the lower viscosity polymer flows all the way around the higher
viscosity glass to enclose the glass and form a cl~d-lin~.
Fig. 12 is a srh~m~tic cross-sectional view of a tricomponent fiber formed
of glass and two different polymers.
BEST MODE FO~ CARRYING OUT THE INVENTIQN
Fig. 1 illustrates a rotary fiber forming process for m~kin~v insulation
products from bicomponent fibers of glass and polymer in accordance with this invention.
It is understood, however, that different fabrication processes can be used with the fibers
to make textiles, filtration products, and other products. ~uch processes include stitching,
neetllin~, hydro-entanglement, and encapsulation. It is also understood that
20 multicomponent fibers other than bicomponent fibers are included in the invention, and
that the fibers can be formed from other thermoplastic materials such as asphalt in
addition to polymers.
In the illustrated process, molten glass and molten polymer are supplied to
spinners 10. The molten glass is supplied from any suitable source such as furnace 11
25 and forehearth 13. The molten polymer is supplied from any suitable source. For
example, hopper 12 cont~inin~ polymer granules can be connected to extruder 14 where
the polymer is melted and then supplied to the spinners. As will be described below, the
spinners produce veils 16 of bicomponent fibers of glass and polymer. The fibers are
directed downwardly by any means, such as by annular blower 18. As the fibers are
30 blown downwardly, they are ~tt~nn~tecl and cooled. The fibers are collected as a wool
pack 20 on any suitable surface, such as conveyor 22. A partial vacuum, not shown, can
be positioned beneath the conveyor to facilitate fiber collection.
CA 02246283 1998-08-13
W O97/33841 PCT~US97103012The wool pack of bicomponent fibers of glass and polymer may then
optionally be passed through a station for further processing, such as oven 24. While
passing through the oven, the wool pack is preferably shaped by top conveyor ~6 and
bottom conveyor 28, and by edge guides (not shown). The wool pack exits the oven as
S insulation product 30.
As shown in Fig. 2, each spinner 10 includes a peripheral wall 32 and a
bottom wall 34. The spinner is rotated on any suitable means, such as spindle 36, as is
known in the art. The rotation of the spinner centrifuges molten glass and molten
polymer through orifices in the peripheral wall to form bicomponent fibers 38 of glass
10 and polymer, in a manner described in greater detail below. The spinner preferably
rotates at a speed from about 1200 rpm to about 3000 rpm. Spinners of various diameters
can be used, and the rotation rates adjusted to give the desired radial acceleration at the
inner surface of the peripheral wall. The spinner diameter is preferably from about 20
centimeters to about ~ 00 centimeters. The radial acceleration (velocity2/radius) at the
15 inner surface of the peripheral wall is preferably from about 4,500 meters/second2 to
about 14,000 meters/second2, and more preferably from about 6,000 meters/second2 to
about 9,000 meters/second2.
Annular blower 18 is positioned to direct the fibers downwardly for
collection on the conveyor as shown in Fig. 1. Optionally the annular blower can use
20 in~ ce~l air 40 to further ~tt~n~l~te the fibers.
Preferably the interior of the spinner is heated by any heating means (not
shown) such as by blowing in hot air or other gas. The temperature of the sprnner is
preferably from about 1 50~C to about 450~C but can vary depending on the type of glass
and polymer.
A heating means such as annular hot air supply 42 can optionally be
positioned outside the spinner to heat either the spinner or the fibers, to facilitate the fiber
~tten~ tion and m:~intzlin the temperature of the spinner at the level for o~Lilllulll
centrifugation of the glass and polymer. .,
The interior of the spinner is supplied with separate streams of molten
30 glass and molten polymer, a first stream cont~ining glass and a second stream Cont~ining
polymer. If desired, the streams of molten glass and molten polymer can be supplied by
injection under pressure. The molten glass in the first stream drops from a first delivery
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tube 44 directly onto the bottom wall and flows outwardly due to the centrifugal force
toward the peripheral wall to form a head of glass indicated as "A" in Fig. 2. The molten
polymer, delivered via a second delivery tube 46, is positioned closer to the peripheral
., wall than the first stream, and molten polymer is intercepted by annular horizontal flange
5 48 before it can reach the bottom wall. Thus, a build-up or head of molten polymer,
indicated as "B" in Fig. 2, is formed above the horizontal flange as shown. It is
understood that the molten glass and molten polymer could also be supplied so that the
molten glass is intercepted by the annular horizontal flange and the molten polymer drops
to the bottom wall.
As shown in ~ig. 3, the spinner is adapted with a vertical interior wall 50
which is generally circumferential and positioned radially inwardly from the peripheral
wall 32. A series of vertical baffles 52, positioned between the peripheral wall and the
vertical interior wall, divide that space into a series of generally vertically-aligned
cc,lllpal .ll,ents 54 which run substantially the entire height of the peripheral wall. It can
15 be seen that the horizontal flange, vertical interior wall, and vertical baffles together
comprise a divider for directing the molten glass "A" and molten polymer "B" into
alternate adjacent con~l."ents so that every other com~alLlnent contains molten glass
"A" while the rem~inin~ coll~al kllents contain molten polymer "B".
The peripheral wall is adapted with orifices 56 which are positioned
20 adjacent the radially outward end of the vertical baffle. Each orifice has a width greater
than the width of the vertical baffle, thereby enabling a flow of both molten glass "A" and
molten polymer "B" to emerge from the orifice as a single bicomponent fiber of glass and
polymer. As can be seen in Fig. 3, each compartment 54 runs the entire height of the
peripheral wall 32 with orifices along the entire vertical baffle separating the25 co~ ~lrllents. Preferably, the peripheral wall has from about 200 to about 5,000 orifices,
depending on the spinner diameter and other process parameters.
As shown in Fig. 4, the orifices 56 are in the shape of slots, although other
shapes of orifices can be used. The molten glass "A" usually has a higher viscosity than
the molten polymer "B" at the temperature of the peripheral wall. Consequently, an
30 orifice perfectly centered about the vertical baffle would be expected to emit a higher
throughput of the lower viscosity polymer than the throughput of the higher viscosity
glass. One method to counteract this tendency and to balance the throughputs of the
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molten glass and molten polymer, is to increase the height of the head of molten glass "A"
relative to the height of the head of molten polymer "B". Another method to balance the
throughputs of the molten glass and molten polymer is to position the slot orifice so that it
is offset from the centerline of the vertical baffle 52. As shown in Fig. 4, the orifice will
S have a smaller end 58 which will restrict the flow of the lower viscosity polymer "B", and
a larger end 60 which will enable a comparable flow or throughput of the higher viscosity
glass "A". Another method to balance the throughputs of the molten glass and molten
polymer is to restrict the flow of polymer into the alternate compartments cont~ininp the
low viscosity polymer, thereby partially starving the holes so that the throughputs of
10 molten glass and molten polymer are roughly equivalent. The orifice can also be centered
about the vertical baffle when the molten glass and molten polymer have similar
viscosities or when different throughputs are desirable.
Fig. S illustrates a portion of a second embodiment of the spinner. Like
the first embodiment shown in Fig. 4, the spinner is adapted with vertical baffles 62
15 exten~1ing between a vertical interior wall 64 and the peripheral wall 66 to form
compartments 68. The peripheral wall is adapted with rows of orifices 70 which are
positioned adjacent the radial outward end of the vertical baffle. The orifices are in the
shape of a "V", with one end or leg leading into a compal ~lllent cont~inin~ molten glass
"A" and one leg leading into a compartment cont~ining molten polymer "B". The flows
20 of both molten glass "A" and molten polymer "B" join and emerge from the orifice as a
single bicomponent fiber of glass and polymer.
Fig. 6 illustrates a third embodiment of the spinner. The spinner 72
includes a peripheral wall 74 and a bottom wall 76. The bottom wall slants upwardly as it
approaches the peripheral wall. The interior of the spinner is supplied with separate
25 streams of molten glass and molten polymer. The molten glass in the first stream drops
from a first delivery tube 78 directly onto the bottom wall and flows outwardly and
upwardly due to centrifugal force toward the peripheral wall to form a head of molten
glass indicated as "A" in Fig. 6. The molten polymer, delivered via a second delivery
tube 80, is positioned closer to the peripheral wall than the first stream, and the molten
30 polymer is intercepted by annular horizontal flange 82 before it can reach the bottom wall.
Thus, a build-up or head of molten polymer, indicated as "B" in Fig. 6, is formed above
the horizontal flange as shown.
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The peripheral wall is adapted with a row of orifices 84 around its
circumference, the orifices being positioned adjacent the radially outward end of the
horizontal flange. As can be seen in Fig. 7, each orifice is in the shape of a "Y", with one
arm leading to the molten glass "A", the other arrn leading to the molten polymer "B", and
5 the base leading to the exterior of the peripheral wall. The flows of both molten glass and
~ molten polymer join and emerge ~rom the orifice as a single bicomponent fiber 86 of
glass and polymer.
Other spinner configurations can also be used to supply streams of molten
glass and molten polymer to the spinner orifices.
The bicomponent fibers of this invention can be formed from many
different kinds of glass and thermoplastic material. Usually the softening point of glass is
significantly higher than the melting point of a thermoplastic material. Under ordinary
circumstances, if molten thermoplastic material is exposed to the higher temperature of
molten glass, there is a problem of thermal degradation of the thermoplastic material. It is
15 believed that the bicomponent fibers formed by the rotary process of this invention
substantially avoid thermal degradation of the thermoplastic material. The molten
bicomponent streams are formed, centrifuged and cooled so rapidly that the molten
thermoplastic material is exposed to the higher temperature of the molten glass for only a
fraction of a second. The spinner can be provided with an inert atmosphere or insulating
20 material between the molten glass and the molten thermoplastic material to further avoid
any signif1cant thermal degradation.
Generally, however, the bicomponent fibers of this invention are formed
from a low softening glass and a high melting thermoplastic material so that the two
components have similar fiber forming temperatures. For purposes of this invention, the
25 glass will be characterized by the temperature at which its viscosity is 1000 poise, as
measured according to ASTM C965. The thermoplastic material will be characterized by
its melting point as determined using DSC (Differential Scannin~ Calorimetry). It is
understood that use of the term "melting point" does not strictly apply to some classes of
thermoplastic materials, specifically amorphous materials. In such cases, the term
30 "melting point" means the temperature at which the material softens and is easily
flowable so that it can be fiberized, as known to persons skilled in the art.
CA 02246283 1998-08-13
WO 97/33841 PCTAUS97/03012Preferably the temperature at which the viscosity of the glass is 1000 poise
is within about 200~C of the melting point of the thermoplastic material~ more preferably
within about 1 50~C, and most preferably within about 1 00~C. The temperature at which
the viscosity of the glass is 1000 poise is less than about 600~C, preferably less than about
5 550~C, more preferably less than about 500~C, more preferably from about 200~C to
about 495~C, and most preferably from about 260~C to about 445~C. The melting point
ofthe thermoplastic material is above about 140~C, preferably from about 200~C to about
345~C, and more preferably from about 260~C to about 345~C. The glass and
thermoplastic material can be modifled to adjust these temperatures.
Preferred low softening glasses are high-borate glasses and high-phosphate
glasses. The term "high-borate glass" means that the glass composition has a B2O3
content greater than about 8% by weight of the total glass composition. A particularly
preferred high-borate glass has a composition by weight percent of from about 0% to
about 10% SiO2, from about 0% to about 8% Al2O3, from about 70% to about 92% PbO,
15 and from about 8% to about 25% B2O3. The temperature at which the viscosity of a high-
borate glass is 1000 poise is usually from about 300~C to about 500~C. Some examples
of the compositions by weight% of suitable high-borate glasses, and the temperature at
which their viscosity is 1000 poise, are shown below in Table I:
Table I
B2O3 9 7 19.6 9.6 18.6 10 9.9
SiO2 0.8 0.6 10.4 5 5
PbO 89.5 79.8 80 74.6 82 80.2
Al2O3 6.8 3
AlF3 4.9
T (~C) 427 494 538 497 431 399
The term "high-phosphate glass" means that the glass composition has a
P2O5 content greater than about 20% by weight of the total glass composition. A
particularly ~-c;r~llcd high-phosphate glass has a composition by weight percent of from
about 50% to about 80% P2Os, from about 10% to about 30% Na2O and K2O, from about
0% to about 30% PbO, from about 0% to about 7% Al2O3, and from about 0% to about 7
15% other oxides such as ZnO, MgO, CaO, SnO and BaO. The temperature at which the
viscosity of a high-phosphate glass is 1000 poise is usually from about 200~C to about
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500~C. Some examples of the compositions by weight% of suitable high-phosphate
gl~çs, and the temperature at which their viscosity is 1000 poise, are shown below in
Table II:
Table II
P2O561.2 71.8 59.2 27.4 26 19
Na2O6.5
K2O 9.8 19.6 19
ZnO 4.3 2.1 4.1
PbO11.6 11.3 10.7 7.2 9.3
AlF36.6 6.5 6.4
SnO 37.8 30.8 25.8
S~2 24 35.9 45.9
T(~C)530 499 492 289 247 179
If desired or necessary, additives such as fluorides or other halides,
15 th~ m oxide or alkali oxides can be added to the glass to lower the tRmperature at which
its viscosity is 1000 poise. A preferred low softening glass cont~ining fluorine is
disclosed in U.S. ~at. No. 4,379,070 to Fick, and in Phys. & Chem. Glasses, Vol. 70, pp.
49-55, 1988. Other low softening ~ sçs, and mixtures of glasses, can also be used.
The thermoplastic material used for forming the mul~icomponent fibers
20 can be selected from a w;de variety of suitable thermoplastic materials known for use in
m~king fibers. Preferred high melting thermoplastic materials are selected from the
following polymers: poly(phenylene sulfide) ("PPS"), poly(ethylene terephthz~ e)("PET"), poly(butylene terephth~l~qte) ("PBT"), polycarbonate, polyamide, and mixtures
thereof. Polyolefins and asphalt are also suitable but less preferred because they are
25 somewhat lower melting or so~~rPning. Other high melting thermoplastic materials,
amorphous thermoplastic materials, and mixtures of thermoplastic materials, can also be
used.
An advantage of the rotary process of this invention is that the viscosities
of the molten glass and molten thermoplastic material are not required to be close to one
30 another. The two viscosities can be significantly different and the process still forms
suitable multicomponent fibers. Usually the viscosity of molten glass is higher than the
viscosity of a molten thermoplastic material. In a specific embodiment of this invention,
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the viscosity of the glass, at the temperature of the peripheral wall of the spinner, is higher
than that of the thermoplastic material by a factor within the range of from about 5 to
about 1000, and usually from about 50 to about 500.
The bicomponent fibers of this invention have a very irregular, curvilinear
5 nature due to the difference in therrnal expansion coeff1cients of the glass and
thermoplastic material. Such a curvilinear nature is particularly advantageous for giving
the fibers excellent insulating properties when they are used in in~ ting materials or
textiles. As the fiber cools, the thermoplastic material contracts at a faster rate than the
glass. The result is stress upon the fiber, and to relieve the stress, the fiber must bend into
l O a curve. Preferably the coefficient of thermal expansion of the thermoplastic material is
higher than that of the glass by an amount greater than about 10 ppm/~C, more preferably
greater than about 30 ppm~~C, more preferably greater than about 50 pprn/~C, and most
preferably greater than about 70 ppm~~C. Usually the glass has a coefficient of thermal
expansion from about 5 ppm~~C to about 30 ppm/~C, while the thermoplastic material is a
15 polymer having a coefficient of thermal expansion from about 80 ppm/~C to about 120
ppm/~C.
The bicomponent fibers made by the rotary process of this invention can
be formed having a smaller diameter than bicomponent fibers made by a textile process.
This advantage is provided because the rotary process uses centrifugal force to attenuate
20 the fibers instead of relying on the mechanical ~tten~l~tion of the textile process.
Preferably the bicomponent fibers have an average outside diameter of from about 2
microns to about 50 microns, and more preferably from about 5 microns to about 40
microns.
Each of the bicomponent fibers of the present invention is composed of
25 glass and thermoplastic mzltPri~l. If one were to make a cross-section of an ideal
bicomponent fiber, one half of the fiber would be glass and the other half would be
thermoplastic m~tPri~l In reality, a wide range of proportions of the amounts of glass and
thermoplastic material may exist in the fibers, or perhaps even over the length of an
individual fiber. The pcrcentage of glass may vary within the range of from about 5% to
30 about 9S% by volume of the total fiber, with the remainder being thermoplastic mzltPri~
In general, a group of fibers such as a wool pack will have many different combinations
of percentages of glass and thermoplastic material, including a small fraction of fibers that
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are single component. The pl~r~llc;d composition of the bicomponent fibers will differ
depending on the application. For some applications, preferably the bicomponent fibers
comprise, by volume, from about 40% to about 60% glass and from about 40% to about
60% thermoplastic material.
Cross-section photographs of fibers can be obtained by mounting a bundle
of fibers in epoxy with the fibers oriented in parallel as much as possible. The epoxy plug
is then cross-sectioned and polished. The polished sample surface is then coated with a
thin carbon layer to provide a conductive sample for analysis by ~c~nnin~ electron
microscopy (SEM). The sample is then ç~ ned on the SEM using a backscattered-
10 electron detector, which displays variations in average atomic number as a variation in the
gray scale. For exarnple, this analysis reveals the presence of glass and polymer by a
darker and lighter region on the cross-section of the fiber, and shows the interface of the
glass and polymer.
As shown in Fig. 8, if the glass/polymer ratio is 50:50, the interface 88
15 between the glass 90 and the polymer 92 passes through the center 94 of the fiber cross-
section. As shown in Fig. 9, where the molten polymer has a lower viscosity than the
molten glass, the polymer 92 can somewhat bend around or wrap around the glass 90 so
that the interface 88 becomes curved. This requires that the bicomponent glass and
polymer fiber stream em~n~tin~ from the spinner be m~inf~ined at a temperature
20 sufficient to enable the low viscosity molten polymer to flow around the higher viscosity
molten glass. Adjustments in the spinner operating parameters, such as hot air flow rate,
blower ples~ule, and polymer or glass temperature, may be necessary to achieve the
desired wrap of the low viscosity polymer.
As shown in Fig. 10, the lower viscosity polymer 92 has flowed almost all
25 the way around the higher viscosity glass 90. One way to quantify the extent to which the
lower viscosity polymer flows around the higher viscosity glass is to measure the angle of
wrap, such as the angle alpha shown in Fig. 10. In some cases the lower viscosity
- polymer flows around the higher viscosity glass to forrn an angle alpha of at least 270
degrees, i.e., the lower viscosity polymer flows around the higher viscosity glass to an
30 extent that at least 270 degrees of the circumferential surface 96 of the bicomponent glass
and polymer fiber is made up of the polymer.
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As shown in Fig. 11, under certain conditions the polymer 92 can flow all
the way around the glass 90 so that the polymer encloses the glass to form a clz~ ing In
that case, the entire circurnferential surface 96 (360 degrees~ of the bicomponent glass and
polymer fiber is the polymer.
The method of the invention is not limited to bicomponent fibers, but
rather includes other multicomponent fibers of glass and thermoplastic material such as
the tricomponent fiber illustrated in Fig. 12. To form this tricomponent fiber, separate
strearns of first and second molten polymers 97 and 98 and molten glass 99 are supplied
to a rotating spinner having an orificed peripheral wall. The first and second molten
10 polymers and molten glass are m~int~ined separate until combined in the orifices. One
method is to use a spinner having a single row of orifices like in Fig. 6, but where the area
above the annular hori~ontal flange 82 is separated into alternate compartments like in
Fig. 5. Thus, two streams could be fed into each orifice from above the flange while a
third stream is fed into each orifice from below the flange. Other spinner structures can
15 also be used. The first and second molten polymers and molten glass are centrifuged
through the orifices as a molten tricomponent stream, and the tricomponent stream is
m~in~ined at a temperature sufficient to enable one of the lower viscosity polymers 97 to
flow around at least the molten glass 99. Upon cooling of the tricomponent stream, a
tricomponent fiber is forrned. Another method to form a tricomponent fiber is to form a
20 molten bicomponent stream of glass and a blend of two polymers, where the polymers
have different physical properties so that they separate from one another upon cooling to
form fibers. The multicomponent fibers can also include more than three components.
The above descriptions and comparisons of the physical properties of glass and
thermoplastic material apply to each of the materials of a multicomponent fiber.2~ Bicomponent fibers in accordance with this invention include fibers in
which the glass and the thermoplastic material are disposed in side by side relation with
one another. The rotary Ll~d~d~llS described above usually forms such side by side
bicomponent fibers. The bicomponent fibers of this invention also include fibers in
which one of the glass and the thermoplastic material forms a core, while the other forms
30 a sheath surrounding the core. The rotary apparatus can be specially constructed by
methods known in the art to form sheath and core bicomponent fibers. In general, such
apparatus feeds one molten component through orifices which form a sheath, and feeds
CA 02246283 1998-08-13
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the other molten component into the interior of the sheath to form a core. Combinations
of different kinds of fibers can also be formed. The multicomponent fibers of the
invention can also be shaped fibers, produced by shaping the orifice so that fibers are
formed having a non-circular cross section. Methods of m~mlf~cturing shaped fibers are
5 disclosed in U.S. Patent Nos. 4,636,234 and 4,666,485 to Huey et al.
Bicomponent fibers of glass and polymer of this invention could be formed
according to the following example. The glass used to make the fibers is a high-borate
glass. The temperature at which the glass has a viscosity of 1000 poise is about 399~C.
The glass has a coefficient of thermal expansion of about 10 ppm/~C. The polymer used
10 to make the fibers is poly(phenylene sulfide). The polymer has a melting point of about
2~5~C and a coefficient of thermal expansion of about 100 ppm/~C. Separate streams of
molten glass and molten polymer are supplied to the spinner illustrated in Figs. 2 and 3
having a temperature of about 360~C at the peripheral wall. At this temperature, the
viscosity of the glass is about 5,600 poise and the viscosity of the polymer is about 3,000
15 poise. The spinner has a diameter of about 38 cm and is rotated to provide a radial
acceleration of about 7,600 meters/second2. The spinner peripheral wall is adapted with
350 orifices. Bicomponent streams of molten glass and molten polymer are centrifuged
through the orifices. The streams are cooled to make bicomponent glass and polymer
fibers which are collected as a wool pack. The average outside diameter of the fibers is
20 about 25 microns.
The principle and mode of operation of this invention have been explained
and illustrated in its preferred embodiment. However, it must be understood that this
invention may be practiced otherwise than as specif1cally explained and illustrated
without departing from its spirit or scope.
INDUSTRIAL APPLICABILITY
The multicomponent fibers of this invention are useful in many
applications including apparel products, thermal and acoustical insulation products,
- filtration products, and as binders in composite materials.
