U.S. patent number 3,920,362 [Application Number 05/440,983] was granted by the patent office on 1975-11-18 for filament forming apparatus with sweep fluid channel surrounding spinning needle.
This patent grant is currently assigned to Albert L. Jeffers. Invention is credited to Rexford H. Bradt.
United States Patent |
3,920,362 |
Bradt |
November 18, 1975 |
Filament forming apparatus with sweep fluid channel surrounding
spinning needle
Abstract
A congealable synthetic material, for example, a melted
thermoplastic, is formed into a filament by causing its removal in
a fine stream from the tip of a pointed solid element to the
surface of which the congealable material is fed at a controlled
rate. The removal of the congealable material from the point of the
pointed element is effected by directing a stream of fluid along
the element toward the point while the fluid attenuates the
withdrawn filament before it congeals. After leaving the point of
the element, the material of the filament congeals, or is
congealed, to form a dimensionally stable fiber or filament.
Inventors: |
Bradt; Rexford H. (Claypool,
IN) |
Assignee: |
Jeffers; Albert L. (Fort Wayne,
IN)
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Family
ID: |
26972496 |
Appl.
No.: |
05/440,983 |
Filed: |
February 11, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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301611 |
Oct 27, 1972 |
|
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96305 |
Dec 9, 1970 |
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Current U.S.
Class: |
425/72.2;
264/164; 425/7; 65/506; 65/524 |
Current CPC
Class: |
D01D
5/18 (20130101); D01D 5/00 (20130101) |
Current International
Class: |
D01D
5/00 (20060101); D01D 5/18 (20060101); D01D
005/02 (); D01D 005/18 () |
Field of
Search: |
;425/7,72 ;264/164,167
;65/7,14 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Baldwin; Robert D.
Attorney, Agent or Firm: Jeffers; Albert L. Rickert; Roger
M.
Parent Case Text
RELATED APPLICATION
The present application is a division of my co-pending application,
Ser. No. 301,611, filed Oct. 27, 1972 entitled APPARATUS AND
PROCESS FOR FORMING AND USING PLASTIC FIBERS, now abandoned, which
application was a continuation-in-part of my copending application
Ser. No. 96,305, filed Dec. 9, 1970 and now abandoned.
Claims
What is claimed is:
1. An apparatus for making filaments of uniform diameter and free
of beaded ends from a congealable liquid material comprising, in
combination, a spinning element in the shape of an elongated needle
having a longitudinal axis and an outer surface facing outwardly
away from said axis and tapering inwardly in one axial direction of
said spinning element to a spinning point, nozzle means for
supplying congealable liquid material to substantially the entire
outer surface of said spinning element at a region thereof which is
axially spaced from said spinning point, wall means substantially
surrounding the spinning element in radially spaced relation
thereto and forming a channel surrounding and extending axially of
said spinning element for the flow of sweep fluid in one axial
direction along said spinning element and on beyond the spinning
point in said one axial direction so that fluid impelled in said
axial direction within the channel will cause the liquid material
to flow around the spinning element to the spinning point, whereby
the fluid will draw the liquid material from the spinning point as
a filament and will convey the filament away from the spinning
point while attenuating the filament.
2. An apparatus according to claim 1 wherein the wall means
includes at least one additional fluid passage adjacent the channel
and having a discharge orifice positioned to discharge fluid
against the filament being formed.
3. An apparatus according to claim 1 in which support means is
provided for mounting the spinning element within said nozzle
means.
4. An apparatus according to claim 3 wherein the spinning element
has a diameter less than that of the orifice of the nozzle and
extends forwardly through and beyond the orifice of the nozzle.
5. An apparatus according to claim 1 including an annular series of
nozzle means having fluid discharge orifices disposed around the
axis of the spinning point so that fluid flowing from the discharge
orifices will cause a twist to be imparted to the filament
formed.
6. An apparatus according to claim 1 including at least one
additional said spinning element and wall means in spaced relation,
each said spinning element having liquid material and sweep fluid
supplied thereto whereby a plurality of filaments are formed
simultaneously.
7. An apparatus according to claim 6 in which said spinning
elements are disposed in coplanar aligned relation.
Description
BACKGROUND OF THE INVENTION
Continuous synthetic fibers, or filaments, such as have been used
in the textile industry have commonly been produced in one of two
different ways. In one way a normally viscous material, such as a
modified cellulose, for example, is forced through a spinneret and
the emerging discrete streams are chemically treated to congeal the
material and thereby form it into continuous filaments. In the
other way, a thermoplastic resin is liquified, as by melting or
dissolving it in an appropriate solvent, and forcing it through a
spinneret, and the emerging discrete streams congeal on cooling to
form filaments. The latter method also has been used to form
continuous filaments of glass adapted for various uses.
There are several disadvantages inherent in these methods.
Production rates are limited, and the fine openings in the
spinneret have a tendency to clog or plug up with material, thereby
requiring either a new spinneret or a great deal of effort to
correct the situation. It is also very difficult to make
discontinuous, or short, fibers with any high degree of
uniformity.
Inorganic "wools" for uses as heat insulation have been produced by
treating a stream of molten slag, glass, or the like with a
high-velocity stream of air or gas which shatters the molten
material into fine fibers. Fibers so produced lack uniformity and
frequently are characterized by beaded ends rendering them
unsuitable for certain uses. Glass wool has also been produced by
feeding a glass rod into a high velocity, turbulent gas flame which
both melts the glass and shatters the melt into fibers. Fibers
produced in these ways have wide variations in size and
lengths.
It has further been proposed to create continuous fibers or
filaments by drawing them under tension from points on the
uninterrrupted surface of molten baths of glass. Such a method is
disclosed in U.S. Pat. No. 2,235,352 to Bates. According to the
Bates disclosure, the locations on the bath surface from which the
fibers are drawn are determined initially by use of a horizontally
extending element the upper edge of which is serrated in effect.
This element is first immersed in the bath to submerge the
serrations and then raised to bring the serrations above the glass
level. Once the drawing of filaments from the serrrations has
started, the serrrated element is lowered beneath the bath surface
and tension in the filaments continues to draw them from the bath.
One drawback to this method is that the size and length of the
fibers cannot be closely controlled, as they are formed from an
excess pool of material, not a metered feed.
It is, therefore, an object of this invention to provide an
apparatus by which liquid congealable materials can be formed into
fibers with a high degree of uniformity in length and cross-section
and under conditions capable of control with precision and of
providing high production rates .
SUMMARY OF THE INVENTION
This invention relates to the production of filaments or fibers by
causing congealable liquid material to leave the tip of a pointed
element to the outer surface of which the liquid is supplied and to
products of various types made from such fibers or filaments. The
liquid material may be either a molten thermoplastic; a solution of
suitable material; or a normally liquid material such as a modified
cellulose; or an incompletely polymerized plastic convertible by
heat and further polymerization into a stronger thermoplastic or
into a thermoset. After leaving the point, the fibers are congealed
by subjecting them to an atmosphere with the appropriate congealing
properties. The thermoplastic may be congealed simply by cooling;
the dissolved material by evaporation of the solvent; the modified
cellulose by heat or chemical treatment; and the incompletely
polymerized plastic by a sprayed catalytic fog.
In preferred forms of my invention the congealable material is
supplied in flowable form and at a controlled rate to a pointed
element, hereinafter called a "spin-off-point" while a stream of
fluid, preferably gaseous, sweeps the material to the tip of the
point and therefrom as a fine stream congeable into a fiber or
filament. The fluid stream also attenuates the drawn off filament
before it congeals. The fibers may be continuous or discontinuous.
The length of the discontinuous fibers as well as the tapering of
their end portions may be controlled by regulating the supply of
liquid material to the spin-off point. By pulsing or controlled
starving of the liquid feed, discontinuous fibers of a specific
length may be formed.
By the use of supplemental streams of fluid or gas playing on the
congealing or fully congealed filament, various effects may be
produced. If the supplemental fluid stream flows in the same
direction as the sweep fluid, tension can be introduced into the
congealing filament to stretch orient it and promote its congealing
in a straight form. If the supplemental fluid stream flows in the
opposite direction and strikes the forming filament at an
appropriate point, crimping in the finished filament will result.
Depending on its composition or temperature supplemental fluid may
effect or modify congealing of the liquid material into solid
form.
A thread-like or yarn-like product may be produced from a
congealable liquid by an apparatus comprising a circular rotatable
head fitted with a plurality of spin-off points located about its
periphery and all pointed in the same circumferential direction. As
the head is rotated, centrifugal forces feed the liquid to the
points, and tangentially blown sweep fluid, flowing in the same
circumferential direction as the spin-off points are pointing,
sweeps discontinuous incipent fibers therefrom, and the congealed
fibers become combined and intertwisted by the swirling fluid to
form a continuous thread, yarn, or the like.
Filaments may be felted or otherwise agglomerated to produce bats,
sheets, or the like in a wide variety of sizes and characteristics.
In materials so formed, the degree of cohesion holding the
individual fibers in place can be controlled by controlling the
extent to which filaments have congealed before being brought into
contact with other filaments. If cohesion in the felted sheet is to
be avoided, complete congealing of the fibers before disposition
may be effected by treatment with a gas or fog containing a release
agent.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings illustrate the invention. In such
drawings:
FIG. 1 is a vertical section showing fiber spinning apparatus for
producing and twisting fibers;
FIG. 2 is a section on the line 2--2 of FIG. 1;
FIG. 3 is a sectional view on an enlarged scale illustrating a
detail of construction;
FIG. 4 is a sectional view of a device for forming single
filaments;
FIG. 5 is a section on the line 5--5 of FIG. 4;
FIG. 6 is a front elevation of an apparatus containing a circular
array of spin-off points;
FIG. 7 is a section on the line 7--7 of FIG. 6;
FIG. 8 is a front elevation of an apparatus with a linear array of
spin-off points;
FIG. 9 is a section on the line 9--9 of FIG. 8.
FIG. 10 is a fragmental section showing apparatus for making fibers
from a rod of meltable material;
FIG. 11 is a side elevational depicting apparatus for intertwisting
into a thread or yarn fibers formed therein;
FIG. 12 is a diagrammatic showing of a system for felting fibers
into a sheet or bat;
FIG. 13 is a representation, partially diagrammatic, of a system
for producing a faced bat;
FIG. 14 is a diagrammatic showing of apparatus for producing
multi-layered material;
FIG. 15 is an axial section showing an embodiment in which
filaments are spun from an annular series of spin-off points;
and
FIG. 16 is a cross-section on the line 16--16 of FIG. 15.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1 through 3 illustrate apparatus for forming short fibers and
combining them into a thread or the like. Such apparatus comprises
a casing 10 having a conical wall 12 provided at its apex with an
opening 14. A hollow shaft 16 extends through the upper wall of the
casing 10 and supports therein a circular hollow head 18. The
peripheral wall of the head 18 is provided with a series of radial
holes 19 (FIG. 3) each of which has in its outer end a screw
threadedly mounted discharge fitting 20. Each of the fittings 20
carries a tangentially projecting spin-off point 26 to which the
congealable material is supplied at a region spaced from the point
via a passage 22 from the hole 19. The fittings 20 are so oriented
about the axes of the holes 19 that the points 26 all project in
the same circumferential direction, which is opposite to the
direction of head rotation, indicated by arrow 18a in FIG. 2.
Fluid, such as air, or other gas, is supplied to the casing 10
through a tangential inlet conduit 24 in about the plane of the
head 18 and so arranged that the gas introduced through it will
swirl in the casing in a direction opposite to that in which the
head 18 rotates. The swirling gas acts on liquid emerging from each
passage 22 to cause the liquid to flow along the surface of the
respective fittings 20 to the points 26 and to be carried therefrom
as fine streams each of which, when congealed, will constitute a
fiber.
The rate at which the congealable liquid is supplied to the extreme
tip of the spin-off point is low enough that the fibers produced
are discontinuous as explained below, and short relative to the
size of the head 18. The fibers from the several points become
entrained in the swirling gas, which acts to combine and intertwist
the fibers into a continuous thread that can be withdrawn from the
casing through the opening 14.
An arrangement for forming a single filament in accordance with my
invention is shown in FIGS. 4 and 5. In this structure a nozzle 28
is fitted interiorly with a point support 30 in which is mounted a
spin-off point in the form of a solid needle-like member 32. The
member 32 has a diameter less than that of the orifice of the
nozzle 28 and extends forwardly through and beyond such orifice. A
plurality of grooves 36 (FIG. 5) in the periphery of the support 30
permit congealable liquid material to flow past the support to the
nozzle orifice and thence along the outer surface of the spin-off
point 32 to the pointed tip end 38 thereof.
The nozzle 28 and the projecting spin-off point extend from the
rear into a converging gas-passage 42 through which fluid, gas, for
example, flows from a supply conduit 43 to sweep liquid material on
the spin-off point to and off the tip 38 as a fine stream which, on
congealing, will become a filament. If the feed of liquid to the
spin-off point is adequate, the filament can be continuous, but at
lower feed rates, the sweep fluid passing through passage 42 may
intermittently sweep the tip 38 of the spin-off point clean, thus
interrupting filament-generation and causing the production of
discontinuous fibers.
As shown in FIG. 4, the body 46 in which sweep fluid passage 42 is
formed contains a plurality of additional fluid passages disposed
in forwardly converging relation around the passage 42, and
terminating at their forward ends in discharge orifices 48 directed
to discharge jets of fluid obliquely against the filament or aginst
the fine liquid stream that is to congeal into a filament or fiber.
The function performed by the jets from the orifices 48 depends
upon several factors. If the congealable material is melted
thermoplastic, jets having a temperature below the melting point of
the material will further congeal and create tension in the
congealing material to provide some stretch orientation and
overcome any tendency of the still soft filament to contract as a
result of its plastic memory. Further, the jets from the orifices
48 may contain catalysts or reagents necessary to effect chemical
congealing of the liquid material leaving the spin-off point.
Whatever material is used, if the jets do not participate in the
congealing or setting of the filament, they still can be used to
stretch, stabilize and refine the material.
By using an annular series of nozzles 48 so oriented that the jet
from each has a tangential velocity-component about the axis of the
spin-off point, a twist will be imparted to the filament formed.
Such twist imparts to the filament an appearance somewhat different
from that of an untwisted filament. A similar series of similarly
disposed nozzles about the axis of an annular series of spin-off
points such as shown in FIGS. 6 and 7, and below described, will
cause the several filaments respectively propelled from the points
to be intertwisted as they are formed. Twisting effects, either on
a single filament, or on a group of parallel filaments, can also be
produced by an annular series of orifices such as shown in FIG. 4
and progressively pulsing the gas discharged from successive
nozzles.
An apparatus comprising a series of spin-off points arranged in a
circle is shown in FIGS. 6 and 7. The spin-off points 54 are
located respectively in axially extending grooves 56 formed in the
circumferential surface of a cylindrical member 58. Each groove 56
is open at its front and rear ends, and the spin-off points project
forwardly beyond the front ends of the grooves. The member 58 is
snugly received in a central opening in an internal annular flange
60 in a hollow, cylindrical body 62. Surrounding the member 58 in
rear of flange 60 is an annular plenum chamber 63 to which fluid
under pressure is supplied through a conduit 64 and from which the
fluid escapes in the axial direction through the grooves 56. The
liquid material to be spun is supplied to the grooves near their
rear ends through passages 66 in the member 58 and is carried by
the escaping fluid to the tips of the spinning points.
The fiber formation in this case is like that hereinbefore
described in that the congealable material, under the control of
the sweeping action of the fluid supplied from chamber 63, encases
the tip and sweeps the film of congealable material along the outer
surface thereof and off the point to propel forwardly off each
spin-off point a fine, congealable stream.
A second multiple spin-off point arrangement, in which the several
spin-off points are disposed in a common plane, is shown in FIGS. 8
and 9. The body comprises three portions 72, 74 and 76 to
facilitate the provision of the necessary internal cavities. Each
of the spin-off points is the outer end portion of a solid member
78 fitted in a screw 80 which is received in the rear body portion
76. Congealable material is supplied from pipe 82 into supply
chamber 84 which is common to all the spin-off point members in the
apparatus Fowardly of this supply chamber 84, and separated
therefrom by a wall 85, is a chamber 86 which is supplied with
pressurized sweep fluid through a pipe 88. The members 78 extend
through holes of larger diameter in the wall 85 and across the
chamber 86, their front ends, which constitute the spin-off points
proper, projecting into nozzles 89 provided on body portion 72. The
length and diameter of the fibers produced are affected by the
longitudinal position and the general form of the spin-off points
78.
A variation upon my spin-off filament apparatus is shown in FIG.
10. A rod 90 of a thermoplastic material with a pointed conical end
92 is positioned within a chamber 94 with its pointed end entering
an outlet nozzle 95. Fluid entering the chamber 94 via inlet pipe
96 is hot enough to melt the material on the surface of the rod,
and, as the fluid flows along such surface and exits through nozzle
95, it causes the melted material to flow on the as yet unmelted
core to the point thereof from which it leaves as a fine stream 97
congealable into a filament upon cooling. The point 92 is
self-rejuvenating as long as the rod is steadily fed into the hot
sweep fluid at an appropriate rate. The longitudinal position of
the tip 92, the velocity of sweep fluid and the temperature thereof
determine the length and diameter of the filament to be swept. As
long as the feed of the unmelted rod 90 is balanced against the
amount of material being swept from the point 92, continuous fibers
may be formed at a below turbulent sweep fluid speed which permits
a high degree of uniformity in the fiber's diameter. Discontinuous
fibers may be produced by intermittently interrupting the feed of
the rod or pulsing the sweep fluid. If the rod 90 is of a
thermoplastic resin it may be formed by an extruder and fed
directly therefrom and thereby into chamber 94 through a suitable
guide channel.
Apparatus for producing a thread or yarn from discontinuous fibers
formed from spin-off points is shown in FIG. 11. Typically, melted
thermoplastic or other congealable material is placed in a hopper
98 and fed by an extruder 100 to a fiber forming device 104, which
may be of the general type shown in FIGS. 6-7 and 8-9. Fluid under
pressure supplied to this device 104 through intake 106 sweeps the
spin-off points 108 of device 104 to form discontinuous incipient
fibers delivered to a plenum chamber 110. The chamber 110 is
supplied with fluid of the proper temperature and pressure through
inlet pipe 112 to partially cool the incipient fibers. This is done
to control the amount of cohesion between the respective fibers in
the twisted thread or yarn to be formed.
The suspension of semi-cooled fibers then enters tangentially into
an inverted conical chamber 114 generally of the form used in dust
separators of the so called "cyclone" type. Fluid escapes from the
chamber 114 through outlet conduit 116, and a whirlpool of fluid
rotating at high speeds exists within the apparatus.
In the chamber 114, the fibers are twisted together into a
thread-like or yarn-like form 118 which is pulled from the lower
end 120 of the chamber 114 by a pair of pulling rollers 122 driven
by drive means 126. A set of tension rollers 124, driven at a
greater speed than the pulling rollers 122, applies tension to the
thread for stretch orienting its fibers, before it is taken up on
take-up roller 128. This orientation of the fibers after twisting
is effective because the fiber's high degree of uniformity promotes
uniform distribution of the tensile stress among the several
fibers. By stretching the thread after twisting instead of before,
a helical set is given the individual fibers which enhances
uniformity in the tensile stress on each. This overcomes the
disadvantage of conventional non-uniformly loaded threads wherein
many fibers may break before others assume any tensile loading at
all.
The felting system depicted in FIG. 12 may incorporate, as
indicated at 134, any of the spin-off point devices shown in FIGS.
1 through 9, using a molten thermoplastic 131 as the filament
material. An annular accelerating ring or collar 130 may surround
the filament or filaments emerging from the device 134 to discharge
fluid against those filaments in a direction such as to stretch
them and assure their impingement upon a rotating and reciprocating
drum 136. As this drum 136 is moved axially back and forth, as
shown by the arrows, it is slowly rotated, steadily or
incrementally, as the impinging fibers form a mat or sheet on its
surface. The fineness of the fibers produced, along with the speed
with which the drum rotates and reciprocates, determine the nature
of the felted material produced.
The surface of drum 136 can also be used to impart a texture or
design to the formed sheet. For example, if a screen mesh
constitutes or is placed on the surface of the drum 136 the
resultant sheet will have a screen mesh texture. The use of any
other embossed base will likewise cause the sheet to have a
corresponding appearance. By first coating the drum 136 with a
jellied vinyl plastic and impinging the hot fibers thereon, a
reinforced web-backed vinyl sheet can be produced in a one step,
single machine operation.
A variation of this apparatus is shown in FIG. 13. Here, two
rotating drums 138 and 140 feed two strips or sheets 142 and 144 of
fabric, for example, in parallel spaced relation as a layer of hot
felted filaments formed by a spin-off point apparatus 146 is
deposited between them. This sandwiched hot layer of thermoplastic
fibers adheres to and bonds together the two fabrics 142 and 144
and can provide a permanent insulating layer between them.
In another felting apparatus, shown in FIG. 14, a conveyor belt 148
driven by a drive means 150 on rollers 152 and 154 can be used as
the impinging target or to carry an impinging target. This target,
as above, may be of any material or may have any surface texture
which is desired to impart to the felted sheet to be formed. Head
support 156 carries two spin-off heads 158 and 160 on guide member
162 extending transversely of belt 148. Conveyor belt 148 is moved
in the direction shown and the head support 156 is moved back and
forth on its guide 162 to deposit the filaments across the belt. In
the absence of any auxiliary fluid jet, or jets, serving to deflect
laterally the filaments discharged from a spin-off head, such
filaments will be deposited in generally parallel relationship. The
angle between those generally parallel filaments and the direction
in which the belt 152 moves is largely determined by the
orientation of the head relative to the path of belt movement, but
will be influenced to an extent by the relation between the speed
of belt movement and the speed of movement of the support 156. By
depositing on a layer of filaments oriented in one direction a
second layer in which the filaments are oriented in another
direction an appearance simulating that of a woven fabric can be
created. Where a plurality of heads are used variations in
appearance can be created by supplying the heads with materials of
different colors. In felted sheets simulating fabrics in appearance
successively deposited layers of filaments will be bonded together
either by the cohesiveness of still soft filaments or by an
adhesive sprayed on or otherwise applied.
FIGS. 15 and 16 illustrate a spin-off head which, like those of
FIGS. 6-7 and 8-9, simultaneously produces a plurality of filaments
or fibers. This head comprises a hollow circular casing 160 which
tapers at its front end to a nozzle-like portion 162. Mounted
axially within the nozzle 162 is a tubular sleeve 164 of smaller
diameter than the nozzle and providing an annular opening 166. At
its front end, the sleeve 164 is serrated to provide an annular
series of spin-off points 168 and at its rear end it terminates in
a funnel-like flange 170. On the axis of the head and spaced
rearwardly from the rear end of flange 170 is the outlet of a
conduit 172 through which is supplied the material to be spun.
Axially between the flange 170 and the outlet of conduit 172, the
interior of casing 160 communicates with a tangentially discharging
conduit 174 for sweep fluids, such as air or gas.
In operation of the device shown in FIGS. 15 and 16, fluid such as
air, or other gas, entering the casing 160 tangentially swirls
therein and escapes from the casing through the sleeve 164 and
annular opening 166 thereby sweeping the spin-off points 168. The
stream 176 of more or less viscous material emerging from conduit
172 does not atomize or otherwise break up and, caught in the
swirling air, impinges upon the inner surface of the sleeve 164 to
be swept forwardly to the spin-off points 168 and therefrom by the
fluid escaping from the sleeve and around it through opening
166.
In any of the various forms of spin-off point devices above
described the parameters obtaining will depend upon the type of
congealable material employed and upon the type of filaments or
fibers desired. Temperatures at and adjacent the spin-off points
are to be controlled so as to insure that the material to be spun
is of appropriate viscosity for spinning but not high enough to
damage the material. For example, in spinning fibers or filaments
from polypropylene, the material is ordinarily supplied to the
spin-off device at a temperature from about 400.degree. to about
600.degree.F. Sweep fluid, air, or such other gas, ordinarily would
have a temperature about that of the material or somewhat higher,
although in some cases using thermoplastics supplied at relatively
high temperature, it may be advisable that the sweep fluid be
substantially cooler than the material to be spun. With
thermoplastics, temperatures of course affect viscosities; the
spinning of fine filaments requires lower viscosities than does the
spinning of coarser filaments.
Ambient temperatures beyond the spin-off points may be of
importance. With thermoplastics, if the incipient filaments are
allowed to cool slowly while not maintained under tension, plastic
memory may cause them to contract, or snap back, into pretzel-like
snarls. This may be prevented, even in the absence of tension, by
quick cooling produced, for example, by a cooling fog or mist. In
some instances, as when the spun material is of a character such
that its congealing requires heat-curing or drying, ambient
temperatures may be higher than spinning temperature as referred to
here may be simply the temperature of the space into which the
sweep fluid carries spun fibers or the temperature of auxiliary
fluid discharged against filaments after they have left the
spin-off points. Ambient temperatures may also be significant in
felting operations and other situations where the incipient
filaments are deposited on other filaments, for in such situations
temperature can determine the extent to which successively
deposited filaments cohere. Coherence, or its absence, between
successively deposited fibers may also be controlled by spraying
the fibers with a liquid adhesive or with a release agent.
Sweep fluid velocities and nature of flow thereof can effect the
filaments produced. Laminar flow of sweep fluid promotes the
formation of straight filaments, while turbulent flow tends to
produce crimped filaments. Crimped filaments can also be produced
if the sweep fluid decelerates too rapidly before the filaments
have set. Velocity of sweep fluid at a spin-off point affects the
diameter of filament produced. For instance, raising from about 12
psi to about 25 psi the pressure of sweep fluid supply when air or
gas is used, and thereby increasing the velocity of the sweep fluid
at the spin-off has reduced filament diameter from 0.010-0.015 inch
to 0.0005-0.001inch.
It has been pointed out above that the relation between sweep fluid
velocity and the rate at which the spin-off point receives the
congealable material affects the length of fibers or filaments
produced. Specifically, the sweep fluid velocity can be made high
enough that it intermittently strips the spin-off point completely
and so terminates continuing lengthening of the filament being
produced. As the feed of liquid material to the spin-off point
continues, filament generation will resume when enough of the
liquid has accumulated on the point. The length of the
discontinuous fibers produced in this manner decreases as the
velocity of the sweep fluid increases without a related increase in
the rate of liquid supply. The fibers are especially well suited to
being spun into thread, as they taper toward their ends. The
tapered ends of fibers contribute to imparting a smooth feel to a
felted sheet, yarn, or fabric.
Although the above description of illustrated embodiments all
contemplate the use of air or other gas as the spinning fluid,
there are cases in which the spinning can be performed by a liquid.
For example, where the congealable material is a modified cellulose
the spinning fluid could be a liquid of the type used in the
production of rayon to congeal the liquid streams emerging from a
conventional spinneret.
Instead of sweeping the congealable material from a spin-off point
with a fiber spinning fluid, the material can, if adequately
viscous, be pulled from the tip of the spin-off point by a reel or
like device. It will of course be understood that, in this method,
the material leaving this spin-off point must be substantially
congealed by the time it reaches the reel. Owing to its viscosity,
the liquid material on the point will be drawn to the tip of the
point to replace that pulled from the tip by the reel. The relation
between the speed of the reel and the rate at which material is
supplied to the point determines the size of the filament
produced.
In every example given above, the spinning element is solid to the
extent that it has an outwardly facing surface which tapers in to a
point at one axial end of the element and from which point the
liquid, or flowable, material is drawn to form a filament and which
filament is then attenuated and caused to congeal. The fluid which
sweeps the material along the spinning element to the point end
thereof and which draws the material off the spinning point as a
filament and conveys it away from the point while attenuating the
filament is usually a gas, air, for example.
As has been mentioned above, the method and apparatus of the
present invention is applicable to a variety of synthetic
materials. Among the materials, which can be softened, or liquified
by heat and which congeal upon cooling are polypropylene,
polyethylene, certain of the polyvinylchlorides and polyamids.
Among the materials which are rendered flowable by a solvent and
which congeal by evaporation of the solvent therefrom are the
acrylics and certain polyvinylchlorides.
An example of the material which congeals by catalytic action is a
polyester resin or a viscose in which the spinning is preceded by
an acid bath and wherein the sweep air, or the air which impinges
on the filament after it is attenuated, contains an acidic
precipitant.
An example of a material which congeals by chemical action supplied
to the material in the sweep fluid, or in fluid or air impinging on
the filament is phenol-formaldehyde. In this case, an acidic vapor
is employed to effect the congealing which could, for example, be
hydrochloric acid. Alternatively, a fog consisting of or containing
evaporated phosphoric acid could be employed. At least some of the
resorcinol formaldehyde resins also fall in this
classification.
In every case, fine nozzles to form filaments are eliminated, as
well as the known problems attendant thereto. Filaments of
controlled uniform diameter free of beaded ends are formed at a
rapid rate and can be individually twisted, twisted together in
groups, matted, or otherwise processed.
Modifications may be made within the scope of the appended
claims.
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