Plastic and nonmetallic article shaping or treating: processes – Vacuum treatment of work
Reexamination Certificate
1999-08-05
2001-06-19
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Vacuum treatment of work
C264S205000, C264S211120, C264S211170, C425S072200, C425S377000, C425S378200, C425S382200, C425S464000
Reexamination Certificate
active
06248273
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to dry spinning spandex yarns and, more particularly, it relates to a rectangular spinning cell for dry spinning spandex.
2. Description of the Background Art
One method of making spandex is to dry-spin it from a solvent which is evaporated from the threadline by a hot, inert gas. As disclosed in U.S. Pat. Nos. 3,737,508, 4,431,602, 4,679,998 and 4,804,511, this method generally employs an upright heated tube (spin cell), spinnerets at the top end of the tube through which the solution is introduced into the spin cell, a hot inert gas which evaporates the solvent as it contacts the threadlines in the tube, and removal of the spandex filaments from the bottom of the spin cell.
Research Disclosure No. 34866, April 1993, describes a variety of apparatus configurations for dry-spinning synthetic fibers including spandex.
FIGS. 10
a
through
10
f
depict different spinneret hole arrangements including circular and uniform linear capillary arrays.
FIGS. 1 through 9
depict different capillary arrangements for introducing the gas into the cell.
James et al., U.S. Pat. No. 5,387,387, disclose advantages of a uniform, linear array of spinneret capillary groups over a circular arrangement for dry spinning spandex. In this method, a hot, inert gas is distributed about the spinnerets and flows down the spin cell cocurrently with the threadlines. The spinnerets can be arranged in one row or more than one row and each row can be staggered within each linear configuration as illustrated in
FIGS. 2 and 3
of the '387 patent. However, with cocurrent feed of the hot, inert gas, the gas penetration into the filament bundles is poor, and solvent is not effectively removed from the filament bundles. Such deficiencies produce filaments having non-uniform physical properties such as tenacity and load power. The filaments closer to the gas feed have properties which differ from those of the filaments further from the gas feed.
The highly regular, uniform arrangements disclosed in the prior art make spandex which is unsatisfactorily nonuniform along its length, and a practical arrangement is still desired.
SUMMARY OF THE INVENTION
The spinning cell of this invention for dry-spinning spandex comprises:
(A) a substantially rectangular, adiabatically controlled shaft;
(B) a top plenum in a wall of the shaft for providing a cross-flow of hot inert gas; and
(C) a substantially rectangular bar containing groups of spinneret capillaries mounted atop the shaft and having short axis, a long axis, and a nonuniform array of spinneret capillary groups in which a first row and a second row of capillary groups are in staggered relationship to each other, the first row being closer to the top plenum than the second row, wherein the capillary groups in each row deviate from a uniform linear arrangement in that:
(i) the first row comprises two more capillary groups than the second row;
(ii) the second row is divided into two segments by omitting one capillary group therein adjacent to the short axis of the bar;
(iii) at least two of the capillary groups at each end of the first row are offset toward the long axis of the bar;
(iv) at least one capillary group at each end of the second row is offset toward the long axis of the bar; and
(v) at least one capillary group at each end of the first row is offset toward the short axis of the bar.
The method of this invention for dry-spinning spandex comprising the steps of:
(a) pumping a heated solution containing polyurethane through a nonuniform array of spinneret capillary groups in a substantially rectangular bar to extrude filaments;
(b) contacting the extruded filaments with a cross-flow of hot, inert gas introduced through a top plenum into an upper portion of an adiabatically controlled, substantially rectangular shaft;
(c) removing the filaments through an exit guide at the bottom of the shaft; and
(d) winding the spandex on cores to form packages;
wherein the bar contains groups of spinneret capillaries and is mounted atop the shaft and has a short axis, a long axis, and a nonuniform array of spinneret capillary groups in which a first row and a second row of capillary groups are in staggered relationship to each other, the first row being closer to the top plenum than the second row, wherein the capillary groups in each row deviate from a uniform linear arrangement in that:
(i) the first row comprises two more capillary groups than the second row;
(ii) the second row is divided into two segments by omitting one capillary group therein adjacent to the short axis of the bar;
(iii) at least two of the capillary groups at each end of the first row are offset toward the long axis of the bar;
(iv) at least one capillary group at each end of the second row is offset toward the long axis of the bar; and
(v) at least one capillary group at each end of the first row is offset toward the short axis of the bar.
REFERENCES:
patent: 3737508 (1973-06-01), Weir
patent: 3847522 (1974-11-01), Heckrotte et al.
patent: 4283364 (1981-08-01), Capps et al.
patent: 4431602 (1984-02-01), Behrens et al.
patent: 4679998 (1987-07-01), Dreibelbis et al.
patent: 4804511 (1989-02-01), Pieper et al.
patent: 5387387 (1995-02-01), Alexander et al.
Benin Joshua
Caldwell Gary L.
Goldman George W.
Huffer Charles S.
Jin Gang
E. I. Du Pont de Nemours and Company
Frank George A.
Tentoni Leo B.
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