JPH02191705A - Fine hole of spinning nozzle - Google Patents

Abstract

PURPOSE: To provide a spinneret having uniformity along the length of and between the capillaries by making specified capillaries on a metal plate having upper and lower surfaces connected with a path. CONSTITUTION: Capillaries are machined after machining a countersinking 20 having a flat inlet face 30 on a spinneret metal plate 10. The ratio a capillary length 14a to a slot width 18a is >=1.5 preferably >=2 and the side wall of the capillary slot is tapered in a direction of a lower surface 28 with included angle A about >=3 deg. preferably about 3 deg. to about 20 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION The present invention relates to spinneret pores, and more particularly to spinneret pores having a length to width ratio greater than two.

To summarize the invention, a spinneret made from a hardened metal plate has a plurality of slot-shaped pores exiting the face of the spinneret. The pore walls taper towards the face of the spinneret;
and each pore has a length-to-width ratio greater than about 2.

The most common method of making spinneret sheath 11 passages is to countersink a partial hole through a plate and then complete the hole by punching out the remaining thickness. Among the known methods for forming pores, countersinking and punching methods are generally recognized as being the least expensive, most flexible in the shapes formed, and providing the most uniform pores. .

The production of spinneret pores by drilling and electrical discharge machining (EDM) is also known. Both of these methods are relatively slow (and therefore expensive) and have poorer hole-to-hole uniformity than the countersinking method. Six-to-one uniformity is important in obtaining the filament-to-filament uniformity required for high quality spun yarns.

Additionally, drilling is more fragile than punching, so
Their use is generally limited to the formation of large holes.

The pore portion of the passageway was limited to either a short length or a relatively large diameter by the physical characteristics of the punch, drill, or other tool used to form the passageway. Due to the short pore length, insufficient molecular orientation is transferred to the filament during spinning or extrusion of the filament, when done by prior art methods, causing the cross-sectional shape to vary considerably from the designed shape of the hole. In particular, in hollow filament spinning, short pores significantly reduce the amount of structural support to internal elements or obstructions in the passageway that creates the hollow inner portion of the filament.

This is done to remove nicks or other small imperfections.
Limit the number of times the spinneret is lapped or polished. Furthermore, failure to impart sufficient orientation to the hollow filaments during spinning or extrusion results in the formation of a large number of undesired open or split filaments instead of the desired true hollow filaments.

The ideal spinneret has perfect pore-to-pore uniformity with uniformity along the length of the pores.

Each pore has a length to width ratio of at least 1.5, and preferably 2 or more, for proper molecular orientation during spinning. The holes are as small as practical for accurate metering of the polymer flow, and the pore walls are straight for the same reason. The spinneret is made from hard metal for long life. Additionally, the spinneret can be used at low pressures (e.g., 14.00
(lower than 0 kPa). Unfortunately, the requirements for good metering (small straight side holes with large length-to-width dimensions) conflict with low pressure operation.

SUMMARY OF THE INVENTION The present invention significantly reduces pressure drop through the pores by tapering the pores in the direction of polymer flow through the spinneret. More specifically, the spinneret includes a metal plate having upper and lower surfaces connected by a passageway. The passageway is larger than 1.5, preferably
Exit the lower surface of the plate at a pore length having a length-to-width ratio greater than 2 and with an included angle of greater than about 3 degrees, preferably from 3 to about 20 degrees. , having sidewalls that taper toward the lower surface of the plate. The plate 1 preferably has a hardness greater than +50 Brinell.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the present invention produces a large number of multi-slot type spinneret pores, it will be described below with reference to one particular type. However, it is understood that the invention is not limited to the particular types of pores shown.

Figure 1 is a plan view of a portion of the exit face of a spinneret plate 10 having one multi-slot type spinneret hole 12.

Typically, the finished spinneret plate will have a few to many pores identical to those shown.

As is clear, the "spinneret pore" defined herein is
It is a complex arrangement of slot-type openings that provide extrusion of a single filament. Pore 12 generally includes four circumferential slot-type openings 14 surrounding an inner subarea. Inside the common intersection, four straight slot-type openings I8
extend radially, each connecting to a peripheral opening 14 at the center. A peripheral spinneret plate 10 and an intervening air outlet 16 separate the peripheral openings. Preferably, the circumferential width of the air outlet 16 is less than the radial width of each opening 14.

For example, during extrusion of molten polymer through the pores 12, four T-shaped streams are formed immediately downstream of the exit face of the spinneret plate IO. Adjacent ends of the T-shaped stream then coalesce to form a cohesive filament with four continuously extending uniform voids. Air outlet 16 allows air to enter the void prior to coalescence, thus preventing collapse of the filament due to internal vacuum.

In FIG. 2, the peripheral opening 14 is shown at an exit face 28 leading to a tapered countersink 22 that is machined at the same time. Similarly, i
A radial aperture I8 with a counterbore 26 is shown. The spinneret plate 10 is typically much thicker than the thickness between the pore entrance 30 and exit face 28. Prior to machining the pores, a large counterbore 20 with a flat entrance surface 30 is machined into the plate 10 at each location where a spinneret full pore is to be formed. The ratio of the pore length 14a to the pore slot width 18a is preferably greater than 2, and the sidewalls of the pore slot are preferably beveled in the range of about 3 to about 20 degrees. At angle A, the lower surface 28 of spinneret plate lO
tapered in the direction of

By scaling the desired spinneret pores, slots 14 and 18 are preferably approximately 0.05 Qmm to 0.
- M (18a) of 130 mm and approximately 0
-40 mm to 1-0 mm length (14a). Slot opening 14 is preferably equal to slot opening 18.

The pores were drilled with a laser beam (150 Watt pulsed Nd YAG laser by LASAG), followed by an Extrude Hone Corporation
ion), Ilwyn, PA, by polishing the inside of the hole using fluid machining equipment.

The spinneret pores shown in FIGS. 1 and 2 illustrate a variety of composite pores using the principles of the present invention.

The main features and aspects of the invention are as follows.

1. A spinneret comprising a metal plate having upper and lower surfaces connected by a passageway, the passageway exiting the lower surface at a pore length, the pore length being 1.
A spinneret having a sidewall having a length-to-width ratio greater than 5 and tapering in the direction of the lower surface at an included angle greater than about 3 degrees.

2. The spinneret according to 1 above, wherein the metal plate has a hardness greater than 150 Brinell.

3. The spinneret according to item I or 2 above, wherein the groove angle is about 3 to about 20 degrees.

4. The spinneret according to 1, 2 or 3 above, wherein the length-to-width ratio of the pore length is greater than 2.

5. The spinneret according to 1 or 2 above, wherein the pore length is slot-shaped.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the outlet surface of the spinneret plate, and FIG. 2 is a cross-sectional view taken along line 2--2 in FIG. 1.

Claims (1)

[Claims] 1. A spinneret comprising a metal plate having upper and lower surfaces connected by a passageway, the passageway exiting the lower surface at a pore length, the pore length being 1.
A spinneret characterized by having a sidewall having a length-to-width ratio greater than 5 and tapering in the direction of the lower surface at an included angle greater than about 3 degrees.