U.S. patent number 3,704,971 [Application Number 04/833,535] was granted by the patent office on 1972-12-05 for spinneret assembly.
This patent grant is currently assigned to E. I. du Pont de Nemours and Company. Invention is credited to Eugene M. Baird, John G. Ullman.
United States Patent |
3,704,971 |
Baird , et al. |
December 5, 1972 |
SPINNERET ASSEMBLY
Abstract
A spinneret assembly comprising sandwiched filter block,
distribution plates and a spinneret plate is designed to produce a
plurality of uniform sheath-core filaments with accurate regulation
of sheath thickness without overcrowding extrusion orifices. The
flow channels and passages are shaped and interconnected to provide
uniform pressure and distribution of the sheath and core polymers
across the plurality of extrusion orifices.
Inventors: |
Baird; Eugene M. (Martinsville,
VA), Ullman; John G. (Martinsville, VA) |
Assignee: |
E. I. du Pont de Nemours and
Company (Wilmington, DE)
|
Family
ID: |
25264677 |
Appl.
No.: |
04/833,535 |
Filed: |
June 16, 1969 |
Current U.S.
Class: |
425/197;
425/463 |
Current CPC
Class: |
D01D
5/34 (20130101) |
Current International
Class: |
D01D
5/34 (20060101); D01d 003/00 () |
Field of
Search: |
;18/8SL,8SM,8SC
;204/171,168 ;425/131,133,463 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Overholser; J. Spencer
Assistant Examiner: Safran; David S.
Claims
What is claimed is:
1. A spinneret for production of filaments in an eccentrically
disposed sheath core arrangement comprising a filter block, a
spinneret plate, and upper and lower distribution plates sandwiched
between said filter block and said spinneret plate, said filter
block having two separate filtration cavities on its upper face and
having two separate flow channels between said filter block and
said upper distribution plate, each being connected to a different
filtration cavity by a plurality of distribution passages, one flow
channel being connected to two upper recessed areas between the
upper and lower distribution plates, the other flow channel being
connected by holes in the upper distribution plate to two lower
recessed areas between the lower distribution plate and the
spinneret plate each of said upper recessed areas being connected
to a different lower recessed area by two rows of core meter holes
each of which terminates at the face of a cylindrical projection in
the lower recessed areas, said spinneret plate having four rows of
core spinneret passages coaxial with said core meter passages
connecting the lower surface of said spinneret plate with said
lower recessed areas, said spinneret plate additionally having
angular sheath spinneret passages connecting said lower recessed
areas with said core spinneret passages at junctions between the
upper and lower surfaces of said spinneret plate.
2. The spinneret of claim 1, said filter block having two separate
grooves on its lower surface which form said flow channels by the
junction of said filter block and said upper distribution
plate.
3. The spinneret of claim 1, said upper distribution plate having
two separate grooves on its upper surface which form said flow
channels by the junction of said filter block and said upper
distribution plate.
4. The spinneret of claim 1, said upper recessed areas being in the
upper surface of said lower distribution plate.
5. The spinneret of claim 1, said lower recessed areas being in the
lower surface of said lower distribution plate.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus for the production of
bicomponent filaments and, more particularly, to an improved
spinneret assembly for extrusion of sheathcore filaments.
2. Prior Art
Filaments consisting of two or more components are well known in
the art and are generally produced by extruding the different
components from the spinnerets in side-by-side relationship or in
an eccentrically disposed sheath-core arrangement. With the latter
type of filament, it has been found difficult to prevent variations
in the sheath thickness with the result that product uniformity was
less than desirable. U.S. Pat. No. 3,244,785 discloses a process
and apparatus which permits more accurate regulation of the sheath
thickness and thus produces a more uniform product. While few
problems are encountered with this arrangement when the number of
filaments extruded from a given spinneret is small, the extrusion
of larger numbers of filaments from a single spinneret inhibits
equal distribution of the two polymers to the spinneret plate
without undesirable crowding of the extrusion orifices.
SUMMARY OF THE INVENTION
The invention comprises sandwiched filter block, upper and lower
distribution plates and a spinneret plate. The filter block has two
separate filtration cavities in its upper face. One of the
filtration cavities is connected via passages in the filter block
and the upper distribution plate to recessed areas of the upper
surface of the lower distribution plate. The other filtration
cavity is connected by flow passages in the filter block and in the
upper and lower distribution plates to recessed areas of the lower
surface of the lower distribution plate. Said upper and lower
recessed areas are connected by core meter passages, each of which
terminates at the end of a cylindrical projection. These
projections protrude into the central portion of the lower recessed
areas and terminate in close proximity to the upper surface of the
spinneret plate. The spinneret plate has sheath-core spinneret
passages coaxial with the core meter passages which connect the
lower surface of the spinneret plate with the lower recessed areas.
The spinneret plate additionally has angular sheath spinneret
passages which connect the lower recessed areas with the
sheath-core spinneret passages at a junction between the upper and
lower surfaces of the spinneret plate.
The apparatus of this invention has the advantage of providing a
relatively simple arrangement for extruding a considerable number
of sheath-core filaments without undue crowding of the spinneret
orifices or enlargement of the spinneret assembly. Crowding is
obviously undesirable, since it leads to difficulties in proper
cooling of the freshly extruded filaments. Enlargement of the
assembly is expensive and otherwise undesirable due to space
limitations. The inventive juxtaposition of the various polymer
flow passages permits desirable spacing of a plurality of orifices
while meeting the spinneret requirements for sheath-core spinning
and without incurring other problems such as gel formation or
improper distribution of the molten polymers.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of the spinneret assembly of the instant
invention.
FIG. 2 is a view taken along line II -- II of FIG. 1, illustrating
the bottom surface of the filter block.
FIG. 3 is a view taken along line III -- III of FIG. 1,
illustrating the top portion of the upper distribution plate.
FIG. 4 is a view taken along line IV -- IV of FIG. 1, illustrating
the top portion of the lower distribution plate.
FIG. 5 is a view taken along line V -- V of FIG. 1, illustrating
the bottom portion of the lower distribution plate.
FIG. 6 is a view taken along line VI -- VI of FIG. 1, illustrating
the top surface of the spinneret plate.
FIG. 7 is an illustration, in an alternate embodiment, of the top
surface of the upper distribution plate.
FIG. 8 is an illustration, in an alternate embodiment, of the top
surface of the lower distribution plate.
FIG. 9 is an illustration, in an alternate embodiment, of the
bottom surface of the lower distribution plate.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, the spinneret assembly chosen for purposes of
illustration includes a filter block 10 having separate filtration
cavities 12,14 from which different viscous polymeric materials are
discharged through distribution passages 16,18. Material from
cavity 12 passes into groove 20 (see FIG. 2 for the vertical view)
in the bottom of the filter block which together with distribution
plate 30 forms a flow passage leading to holes 32 (FIG. 3) through
which holes the material passes into flow passages 46 and 48 (FIG.
4) and then into upper recessed areas 42, 44. Upper recessed areas
42,44 are closed to form flow channels by the junction of upper
distribution plate 30 and lower distribution plate 40. Flow
passages 46 and 48 are similarly formed. From recessed areas 42,44
the material passes through core meter holes 50 and then into
passages 72 in spinneret plate 70 to form the core of filaments
extruded from the spinneret. Meanwhile, another viscous material
from filtration cavity 14 passes through passages 18 into groove 22
in the bottom of the filter block which forms together with upper
distribution plate 30 a flow passage connecting to holes 34 in
plate 30 through which the material passes into holes 62,64 (FIG.
5), which are a continuation of holes 34, in the distribution plate
40, then into flow passages 58,60 which lead into lower recessed
areas 54,56. Part of the material in recessed areas 54,56 flows
around the core material being jetted from passages 50 and into
spinneret passages 72 to form a sheath-core column in passages 72
of spinneret plate 70. Additional material from recessed areas
54,56 passes into angled passages 74 in the spinneret plate and is
combined in substantially side-by-side relation with the
sheath-core column passing through passages 72.
In another embodiment of the invention, FIGS. 7,8,9 a different
arrangement of flow passages is employed between grooves 20,22 in
filter block 10 and upper and lower recessed areas 42,44,54,56.
Viscous material from groove 20 passes into grooves 33 in the upper
surface of upper distribution plate 30a and into flow holes 37
which communicated with upper recessed areas 42a,44a formed by the
junction of upper distribution plate 30a and lower distribution
plate 40a (either of the plates may be recessed to form areas
42a,44a). From recessed areas 42a,44a the material passes through
passages 50a into spinneret passages 72 as in FIG. 1. Material from
groove 22 passes through grooves 31 in upper plate 30a into flow
holes 35 in the upper plate, thence through flow holes 45 in the
lower plate into lower recessed areas 54a,56a. From recessed areas
54a,56a the viscous material flows around the core material being
jetted from passages 50a and into passages 72 and 74 of spinneret
plate 70 as in FIG. 1.
The spacing between cylindrical projections 52 and the top of
spinneret plate 70 is adjusted in relation to the pressure on the
polymers and the sizes of the flow passages to control the relative
amounts of sheath and core formed in holes 72. The width of
projection 52 relative to the diameter of hole 72 is also an
important design consideration in regulating the sheath-core
distribution in hole 72. The rate of polymer flow through holes 74
will, of course, depend on the diameter and length of the passage,
on the polymer viscosity and on the pressure in recessed areas
54,56.
At the juncture of passages 72 and 74 the polymers are combined in
an essentially side-by-side relationship and extruded through
spinning orifices 76. Formation of sheath-core filaments by first
forming a concentric sheath-core column of the polymer in one flow
passage and then combining this column with additional sheath
material from a second flow passage is disclosed in U.S. Pat. No.
3,244,785. Additional details relative to this procedure may be
found therein.
Wider spacing of the flow passages, especially passages 50 and
correspondingly passages 72, allows cylindrical projections 52 to
have a larger diameter. A projection 52 having a larger diameter
creates a longer flow path for the sheath polymer and consequently
induces a larger pressure drop across the face of a projection. The
result is a smaller percentage variation in sheath thickness when
spinning polymer pressure varies.
Recessed areas 42,44 and 54,56 may be tapered from either end
toward the center of the assembly to compensate for any temperature
gradients in the polymer from the inside to the outside of the
assembly as disclosed in U.S. Pat. No. 3,225,383. Suprisingly,
however, the spinneret assembly of this invention does not require
such tapering.
Grooves 20,22 may be formed by recesses in the filter block as
illustrated. However, alternatively they may be formed by
appropriate recesses in the top of upper distribution plate 30.
Similarly, the upper flow passages can be formed by appropriate
recesses in plate 30 rather than in the distribution plate 40 and
the lower flow passages by recesses in spinneret plate 70 rather
than in plate 40.
The spinneret assembly is, of course, provided with a suitable top
plate, and the various elements are bolted or otherwise fastened
together, for instance, as disclosed in U.S. Pat. No.
3,262,153.
Various modifications in the shape of the various passages and
areas for polymer flow will be apparent to those skilled in the
art.
* * * * *