CA2084354C - Apparatus for changing both number and size of filaments - Google Patents

Abstract

A sealing plate upstream of a spinneret has cylindrical flow channels, at least some of which have a first diameter. Each of the flow channels corresponds in position to a bore in the spinneret plate. The number and denier of extruded filaments can be altered by simply changing the plate. The plate provides a seal by deflecting under the extrusion pressure.

Description

~2~%43S4 APPARATUS FOR CHANGING BOTH NUMBER
ANn SIZE OF FILAMENTS

FI~Tn OF THE INV~NTION

This invention relates generally to melt spinning filaments or fibers using a spinneret. More particularly, this invention relates to an apparatus for changing the number and size of filaments being spun from a single spinneret.

BACKGROUND OF THE INVENTION

Spinneret assemblies for sp; nn; ng synthetic filaments or fibers typically include an inlet block having an inlet port through which the material to be spun is introduced into the spinneret assembly and a chamber cont~;n;ng filtering material, a distribution plate, a distribution cavity, a metering plate and a spinneret plate. The metering plate includes a number of apertures having a compound shape, consisting of a capillary and a counterbore. The spinneret plate normally includes a corresponding number of bores having a compound shape consisting of a counterbore and a capillary or spinning orifice.
U.S. Patent No. 3,095,607 to Cobb describes a typical spinneret assembly. Other spinneret assemblies are described in U.S. Patent no. 3,028,627 to McCormick; U.S. Patent No.

2,883,261 to McGeorge; U.S. Patent No. 3,225,383 to Cobb; U.S.
Patent No. 3,289,249 CA 020843~4 1998-12-10 to Nakayama et al.; U.S. Patent No. 3,601,846 to Hudnall; U.S. Patent No. 3,659,988 to Walczak; and U.S. Patent No. 4,738,607 to Nakajima et al.
It is sometimes desirable to change the number of filaments or deniers of the filaments being spun from a single spinneret. Reasons for altering the filament count may 5 include product variations, keeping the total tow denier constant while çh~n~ing the individual filament denier, ch~n~ing q~l~nching characteristics and m~int~ining spinning speed at higher denier per filament where extruder capacity is limited. Also, mixed denier filaments produce unique product characteristics.
The traditional method for ch~nging filament count is to individually plug spinneret 1 0 capillaries using a soft metal bar of approximately the same diameter as the counterbore.
This method is time consuming, risks damage to the spinneret, and does not insure a leak-free seal.
The traditional method of generating mixed deniers is to make expensive, precision metering plates for each mixture.
1 5 Another known method for spinning a number of different filament counts from a single spinneret plate is described in U.S. Patent No. 3,336,633 to Curran. Curran employs metering plates having a number of apertures lower than the number of orifices in the spinneret plate. Since the compound shape of the apertures in the metering plate are normally precision drilled to provide a desired pressure drop, the metering plates are 20 relatively expensive to produce and m~int~ining a stockpile of metering plates to provide a variety of fiber counts may be cost-prohibitive.
U.S. Patent No. 2,980,492 to Jamieson et al. describes an apparatus for making mixed denier filaments. The apparatus requires two separate cavities within a single spin pack.
Each cavity corresponds to its own por~ion of the spin pack. This complicated arrangement allows polymer to be fed at two different feed rates, thereby making different denier filaments.

SUMMARY OF TIIE INVENTION
It is an object of the invention lo provide a simple and inexpensive apparatus for changing tbe filament count and denier mixture from a spinneret plate.
It is also an object of the invention to provide an apparatus which provides a good 10 seal of one or more capillaries of a spinneret plate without endangering the very expensive spinneret capiUaries.
It is a further object of this invention to economically change the deniers of individual filaments in a single yarn spun from the spinneret while avoiding the high cost and expense of purchasing new precision metering plates.
These objeclives and other advantages are achieved by providing a sealing plate upstream of the spinneret.
One aspect of the present invention involves a spinneret assembly including a spinneret plate with an upstream side and having a number of bores, each bore with one 20 or more tapered sections; and a sealing plate adjacent to the upstream side of the spinneret plate and forming an interface therewith. The sealing plate has non-compound cylindrical flow channels formed therein.
At least some of said flow channels have a first diameter and at least some of said flow channels have a second diameter which is smaller than the first diameter. Each ~ ~ .

CA 020843~4 1999-01-26 of said flow channels corresponds in position to a bore in the spinneret plate.
In another aspect of the invention, a spinneret assembly includes a spinneret plate ~ith an upstream side having a number of bores, each bore with one or more tapered sections; and a sealing plate positioned upstream from the spinneret plate. The sealing S plate has cylindrical flow channels which are fewer in nun-ber than the bores. Each of the flow channels corresponds in position to a bore in the spinneret plate.
Yet another aspect of the present invention involves a spinneret assembly for extruding polymeric material under pressure, including a spinneret plate having a number of bores and an upstream side; and upstream thereof, and next adjacent thereto, a sealing 10 plate made of a material and having flow channels therein and which sealingly deflects under spinning pressure. The deflection does not exceed the ultimate plastic limit of the sealing plate material. Each of the flow channels corresponds in position to a bore in said spinneret plate.
The present invention will now be described more fully with reference to the 15 accompanying drawings, in which illustrative embodiments of the invention are shown. This invention can, however, be embodied in many different forms and the invention should not be construed as being limited to the specific embodiments set forth herein. Rather, Applicants provide these embodiments so that this disclosure will be thorough and complete and will fully convey the intent of the invention to those skilled in the art.

208~35~
BRIEF DESCRIPI'ION OF THE DRAWINGS
FIG 1. is an exploded perspective view of the spinneret assembly in accordance with the invention.
FIG. 2 is a partial axial longitudinal section of an alternative embodiment of a 5 spinneret assembly in accordance with the invention.
FIG. 3 is a partial axial longitudinal section of another alternative embodiment of the present invention.
FIG. 4 is a partial cross-section of a modification of the embodiment of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 1, a spinneret assembly includes an inlet block 3 and a spinneret plate 4. The spinneret plate 4 includes a number of bores 5. The bores 5 may be of compound shape, having a relatively large counterbore 6 at the upstream side and a relatively small spinning orifice 7 through which the material being spun exits the spinneret plate 4.
Between the inlet block 3 and the spinneret plate 4 is sealing plate 10. Sealing plate 10 includes one or more flow channels 11, each of which is positioned to correspond with one of the bores 5 in the spinneret plate 4. The sealing plate 10 contains at least one less nOw channel 11 than the number of bores 5 in the spinneret plate 4. Thus, the sealing plate 10, will block at least one bore 5 of the spinneret plate 4, preventing the passage of the 20 material being spun, thereby changing the filament count from the spinneret. As seen in FIG. 1, there is no nOw channel corresponding to bore Sa in spinneret plate 4, thereby CA 020843~4 1998-12-10 ch~nging the fil~ment count from 5 to 4 from the illustrated spinneret. Surprisingly, as illustrated in the Examples below, the denier and number of filaments may be adjusted with the present invention.
Sealing plate lO can be manufactured from any suitable material, such as, for 5 example, mild steel, stainless steel, brass or alumimlm However, the material characteristics will dictate the a~plopl;ate thickness ofthe sealing plate. The thickness of the sealing plate must be such that the plate deflects to form a seal around the edge of the counterbore of the spinneret capillary. However, the sealing plate must not be so thin that the pressure above the seal generates a force great enough to exceed the ultimate plastic 10 limit of the material in the shearing zone generated at the edge of the counterbore. This could result in bursting of the sealing plate and loss of the seal. In the case where the sealing plate is also used to adjust the diameter of the filaments, the thickness and properties of the sealing plate must be further limited to prevent failure at the sealing plate aperture (metering hole) due to generation and propagation of a crack. This can be further 15 reduced by the method of aperture m~nllf~cture. For example, cleanly drilled, punched, etched or machined round holes are less likely to initiate cracks than non-round or jagged holes.
Sealing plate lO and flow channels can be formed by any suitable manufacturing technique such as, for example, die cutting, drilling, punching, stamping, etching, machining, 20 or molding. Any suitable means may be employed to align the various components of the spinneret assembly in precise registry with each other and to m~int~in the assembled spinneret assembly in a tight fitting relationship. For example, apertures (not shown) may CA 020843~4 1998-12-10 be formed in each component which, in the assembled spinneret assembly, provide thruways accommodating terminally threaded ~lignin~ bolts or rods (not shown) which receive locking nuts (not shown).
The overall dimensions of the spinneret plate 4 and the sealing plate 10 may vary considerably. In general, the spilmeret plate and the sealing plate will have the same or substantially the same planar dimensions. While in some instances spinneret plates may be as large as a few feet in length, typically, the planar dimensions range from about 1.0 to about 12 inches in length and about 1.0 to about 8.0 inches in width. The thickness of the spinneret and sealing plate may be the same or different. Preferably, however, the sealing 10 plate 10 will be substantially thinner than the spinneret plate 4. Typically, the thickness of spinneret plate 4 is between about .25 and about 1.5 inches, while the thickness of sealing plate 10 is preferably between about 0.003 and about 0.1 inches.
The location or pattern of the bores 5 in spinneret plate 4 and the corresponding flow channels 11 in sealing plate 10 may also vary considerably. Additionally, the 15 diameter of the bores 5 and the flow channels may vary, ranging, for example, between about 0.1 to about 0.3 inches in diameter. Preferably, the diameter of the flow channel 1 1 corresponds to the diameter of the counterbore 6 at the upstream side of spinneret plate 4.
Referring now to FIG. 2, in another embodiment of the invention, the spinneret assembly includes an inlet block 23, a metering plate 28, and a spinneret plate 24. Sealing 20 plate 30 is located between the metering plate 28 and the spinneret plate 24.The metering plate 28 has a number of apertures 29 bored therein. The number andlocation of the apertures 29 in the metering plate 28 correspond to the number and location CA 020843~4 1998-12-10 of bores 25 in the spinneret plate 24. The sealing plate 30 includes a number of flow channels 31 formed therein.
The flow channels 31 are positioned to correspond with the apertures 29 in the metering plate 28 and the bores 25 in the spinneret plate 24. The sealing plate 30 contains at least one less flow channel 31 than the number of apertures 29 and bores 26. Thus, the sealing plate 30 will prevent the passage of the material being spun from aperture 29a to bore 25a, thereby reducing the filament count from the spinneret.
The sealing plate may also contain apel lul es of different sizes as shown in FIG. 3.
FIG. 3 shows in cross-sectional elevation another embodiment of the spin pack of the 1 0 present invention. As shown, spinneret assembly 50 includes inlet block 52, plate 54, sealing plate 56 and spinneret plate 58.
Plate 54 has a number of apertures 60 bored therein. The number and location of apertures 60 correspond to the number and location of bores 62 in spinneret plate 58.
Sealing plate 56 includes a number of flow channels therein. Two sizes of flow 1 5 channels are shown. Larger channels 64 facilitate larger denier filaments when molten polymer passes therethrough to spinneret plate 58 and bores 62. Small channel 66 likewise facilitates small denier filaments. The larger channels may be as large as the opening diameter of the spinneret plate.
FIG. 4 is a partial cross-section of a modification of FIG. 3 wherein one spinneret bore 62a is sealed by sealing plate 56a.
As shown, when apertures are of different sizes, they may or may not be fewer innumber than bores 62. This causes differing flows to proceed to the spinneret capillaries.

2~84354 Th~e total flow through any component flow channel is determined by the total pressure drop. Orifices in a spinneret or a metering plate usually are identical so that uniform filament cross-section and denier per filament (DPF) can be achieved. With the sealing plate of the present invention having varying hole sizes in the plate, a unique yarn with S different filament deniers and geometries can be made using the normal spinneret or spinneret-metering plate combination.
While not wishing to be bound by theory, the foDowing may explain the operation of the present invention. At the top of the sealing plate (or metering plate if one is used), polymer pressure is generally equalized from channel to channel due to the rather free 10 lateral flow of polymer. This results in approximately the same pressure drop for different polymer paths from the sealing plate (or metering plate) top to the spinneret bottom face as governed by the following equation:

~P~ Pj~ Constan~

15 where ~Pj and ~Pj denote polymer pressure drops for two arbitrary polymer paths, and the subscript k denotes the Kth segment in an individual polymer path. Polymer pressure drop of a segment can be obtained from:

~Pi~ = ( 2 L,~ m~ AJ, ) ~ (2) where Lk, Ak Dhk are the segrnent length, area and hydraulic diameter respectively. ~kiS
the segment (orifice) shape factor. The polymer rheological pararneters, mk and nk, are based on the assumption that the polymer obeys the power law as defined by T = myn, where ~ is the average wall shear rate and ~ is the average wall shear rate. Qj is the 5 volumetric rate of polymer flow in that channel. Since a filament denier is proportional to the polymer flow rate of the channel it comes from, the denier ratio of two filarnents is equal to the ratio of corresponding polymer flow rates. If the power law parameters of a polymer (m and n) are known, the denier ratio of any two fil~mçnt~ can be calculated according to Equations l and 2 by using actual dimen~ions of the orifices (holes).
If polymer shear rates in different channels and segments are within a decade, the DPF ratio (R4pf) of an arbitrary filament to the smallest filament in the yarn can be estim~ted by the following simplified equation:

n ~ AJ: n L J~ Sn~+
R DPFn ~ 16 A2 ~ D3n~ 16 AS2kn~l where DPFj and DPFo are the deniers of an arbitrary and the smallest filament in the yarn and Dr is the diameter ratio of the ~bi~" hole to the smallest hold. Ls~ Ss~ and As are the 20 length ratio, area ratio and hydraulic diarneter ratio of a segment to the smallest hole in th sealing plate. An average value for n for the shear rate range should be determined.

It should be understood that the sealing plate may be positioned adja2c~to3tl~;eupstream face of the metering plate, or at any other position in the spinneret assembly provided that the sealing plate prevents the passage of the material to be spun into one or more particular spinneret bores, thereby changing the filament count.

A series of continuous filament yarns is made using nylon 6 polymer of 2.7 relative viscosity. The molten polymer is extruded through a spinneret with 102 trilobal-shaped orifices, each comprising three intersecting slots of 0.125 mm wide and 0.914 mm long.
Main operating conditions are: polymer temperature 270~C, polymer througbput 246g/min/spinneret, quench air flow rate 93.9 ft/min (28.6 m/min) and winding speed 650 m/min.
Three spinneret packs are made using the configuration demonstrated in FIG. 2 with 75, 60 and 49 open channels, respectively, in the sealing plates. The sealing plates are 0.003"
(0.076 mm) thick with 0.047" (1.19 mm) diameter holes. A control spin pack is also made using the same configuration but without a sealing plate. Although polymer throughputwas the same, yarns produced by these four spin packs are different in number of filaments, DPF and modification ratio (MR) as listed in TABLE 1.

Control Sample Identification A B C D
Yarn denier 3685 3647 3656 3654 Number of filaments 102 75 60 49 Denier per filament 36.1 48.6 60.9 74.6 Modification ratio 2.64 2.80 3.20 2.92 EXAMPLE 2 2~ 435 ~
A series of continuous filament yarns is made using nylon 6 polyrner of 2.7 relative viscosity. The molten polymer is extruded through a spinneret with 68 trilobal-shaped orifices which are identical to the orifices described in EXAMPLE 1. Main operating conditions are: polymer temperature 270~C, polyrner throughput 177 g/min/spinneret and winding speed 600 m/min. Three spinneret packs are made using the configuration demonstrated in FIG. 2 with 58, 52 and 46 open channels in the sealing plates. The sealing plates are 0.003" (0.076 mm) thick with 0.047" (1.19 mm) diameter holes. Another spin pack is also made using the same configuration but having 85 orifices in the spinneret and without a sealing plate. Quenching air flow rate was adjusted for each spin pack to get the same 3.0 modification ratio for all four yarns. Yarns produced by these four spin packs differ in number of filaments and DPF as listed in TABLE 2.

Control F G H
E
Yarn denier 1108 1133 1111 1119 Number of filaments 85 58 52 46 Denier per filament 13.0 19.5 21.4 24.3 l2 EXAMPLE 3 208~3S4 A continuous filament yarn is made using nylon 6 polymer of 2.7 relative viscosity.
The molten polymer is extruded through a spinneret with 102 trilobal-shaped orifices which are identical to the orifices described in EXAMPLE 1. The spinneret pack is made using S the configuration demonstrated in FIG. 3. The sealing plate is 0.400 mm thick. Holes in the sealing plate are in two different sizes as shown in FIG. 3 and with diameters of 3.175 mm and 0.350 mm respectively. Main operating conditions are: polyrner temperature 270~C, polymer throughput 287 g/min/spinneret, quench air flow rate 97.5 ft/min (29.7 mtmin) and winding speed 630 m/min. The whole yarn is 4154 denier. The resultant filament DPFs and 10 MRs are listed in TABLE 3.

Filament Size No. of Holes Hole Diameter DPF MR
or Filaments (mm) Large 17 3.175 100.2 3.01 Small 85 0.350 28.8 2.64 ~. , .. : . . ... ,.... . - . ~, . . . .

2~8435~

Two continuous filament yarns are made using nylon 6 polymer of 2.7 relative viscosity. The molten polymer is extruded through a spinneret with 68 trilobal-shaped orifices which are identical to the orifices described in EXAMPLE 1. Two spinneret packs 5 are made using the configuration demonstrated in FIG. 3. The sealing plates are 0.015"
(0.381 mm) thick. Holes in each sealing plate are ;D two different sizes. Main operating conditions are: polymer temperature 270~C, polymer throughput 177 g/min/spinneret, quench air flow rate 93.9 ft/min (28.6 m/min) and winding speed 600 m/min. Each yarn produced contains filaments with two different sizes. The hole sizes and filament properties 10 are listed in TABLE 4.

Sample No. Filament No. of Holes Hole Diameter DPF MR
Size or Filaments (mm) Il Large 14 1.588 53.8 3.37 Is Small 54 0.794 37.9 3.27 Jl Large 14 3.17S 57.4 3.27 Js Small 54 0.794 36.9 3.09 . , EXAMPLE 5 ~ 0 8 435 ~

A series of continuous filament yarns is made using nylon 6 polymer of 2.7 relative viscosity. The molten polymer is extruded through a spinneret with 68 tri~obal-shaped orifices which are identical to the orifices described in EXAMPLE 1. Three spinneret packs 5 are made using the configuration demonstrated in FIG. 3. The sealing plates are 0.020"
(0.508 mm) thick. Holes in each sealing plate are in two different sizes. Main operating conditions are polymer temperature 270~C, polymer throughput 177 g/min/spinneret, quench air flow rate 93.9 ft/min (28.6 m/min) and winding speed 600 m/min. Each yarn produced contains filaments with two different sizes. The hole sizes and filament properties are listed 10 in TABLE 5.

Sample No. Filament No. of Holes Hole Diameter DPF MR
Size or Fil~ments (mm) Kl Large 24 1.588 50.1 3.09 Ks Small 44 0.794 34.9 2.95 Ll Large 24 2.381 54.5 3.05 Ls Small 44 0.794 33.6 2.99 Ml Large 24 3.175 55.4 3.05 Ms Small 44 0.794 32.5 2.96 As will be appreciated by those skilled in the art, the cost of manufacturin~ u~e~ 4 of sealing plates for use in accordance with the present invention is significantly less than the cost of producing a corresponding number of metering plates or spinneret plates to effect various changes in filament count or denier mixtures. This is due primarily to the S ease and simplicity of forming the flow channels in the sealing plate of the invention compared to the difficulties encountered in forming the compound shape of the precision drilled apertures iD metering plates and spinneret plates.
The foregoing description is to be considered illustrative rather than restrictive of the invention, and those modifications which come within the meaning and range of equivalence 10 of the claims are to be included therein.

Claims (10)

1. A spinneret assembly comprising:
- a spinneret plate with an upstream side and having a number of bores, each bore with one or more tapered sections; and - a sealing plate adjacent to the upstream side of said spinneret plate and forming an interface therewith, said sealing plate having non-compound cylindrical flow channels formed therein, at least some of said flow channels having a first diameter and at least some of said flow channels having a second diameter, which is smaller than said first diameter and each of said flow channels corresponding in position to a bore in said spinneret plate.

2. The assembly of claim 1, wherein said flow channels are fewer in number than the number of bores in the spinneret plate.

3. The assembly of claim 1 wherein said sealing plate deflects and plastically deforms to form a seal under spinning pressure without reaching the ultimate plastic limit of the material from which the sealing plate was constructed.

4. The assembly of claim 3, wherein said sealing plate is formed from a material selected from:
- mild steel;
- stainless steel;
- brass; and - aluminum.

5. The assembly of claim 1, wherein said first diameter corresponds to the upstream diameter of said bores.

6. A spinneret assembly comprising:
- a spinneret plate with an upstream side having a number of bores, each bore with one or more tapered sections; and - a sealing plate positioned upstream from said spinneret plate, said sealing plate having non-compound cylindrical flow channels which are fewer in number than said bores and at least some of said flow channels having a first diameter, each of said flow channels corresponding in position to a bore in said spinneret plate.

7. The assembly of claim 6, wherein at least some of said flow channels have a second diameter which is smaller than said first diameter.

8. The assembly of claim 6, wherein said sealing plate deflects and plastically deforms to form a seal under spinning pressure without reaching the ultimate plastic limit of the material from which the sealing plate was constructed.

9. The assembly of claim 8, wherein said sealing plate is formed from a material selected from:
- mild steel;
- stainless steel;
- brass; and - aluminum.

10. The spinneret assembly of claim 6, wherein said first diameter corresponds to the upstream diameter of said bores.