NON-ROUND SOLUTION SPUN SPANDEX FILAMENTS AND METHODS AND DEVICES FOR PRODUCTION THEREOF

Field of Invention

[0001] The present disclosure relates to non-round or shaped solution spun spandex filaments as well as methods and devices for production of these non-round or shaped solution spun spandex filaments.

Background

[0002] Spandex, also referred to as elastane, is a synthetic fiber of segmented polyurethane with extraordinary elasticity as well as strength and durability which exceeds natural rubber.

[0003] Spandex fibers may be produced by any of four different methods including melt extrusion, reaction spinning, solution dry spinning, and solution wet spinning. All of these methods begin with the initial step of reacting monomers to produce a prepolymer. Once formed, the prepolymer is further reacted by various means and drawn out to make the fibers. The solution dry spurning method is used to produce over 90% of the world's spandex fibers.

[0004] In the dry spinning method, the prepolymer is produced by mixing a macroglycol with a diisocyanate monomer. The two compounds are mixed in a reaction vessel typically at a ratio of glycol to diisocyanate of 1 :2 to produce the prepolymer. The prepolymer is diluted with solvent and then further reacted with an equal amount of diamine in a reaction known as chain extension reaction to form a spinning solution. Additional solvent is typically added during the chain extension reaction. Various additives can be added to the spandex polymer solution to improve the appearance, performance and quality in manufacture, storage, processing and use of the fiber.

[0005] An apparatus for dry spinning spandex filament is described in U.S. Patent 3,094,374, In general a dry-spinning process comprises extruding a solvent-containing solution of a spandex polymer through a spinneret having a plurality of orifices into a spinning cell to form a plurality of separate filaments. Often lubricating oil, e.g. silicone oil or a blend of mineral oil and silicone oil will be applied before winding onto a package to reduce tackiness and improve package delivery in customer processing. Finally the spandex threads are collected onto a spool.

[0006] Various configurations for spinnerets have been described. Some spinnerets used commercially for producing coalesced spandex filaments of low decitex have two coaxial rings of grouped circular orifices wherein the outer ring has a greater number of groups than the inner rings and each group of grouped orifices is usually 3, 4, 5 or 6. See, for example, U.S. Patent 4,679,998

[0007] U.S. Patent 5,002,474 discloses a spinneret with two coaxial rings of grouped circular orifices wherein the number of orifice groups in the inner ring and outer ring are equal. Dry spinning spandex filaments with this spinneret is suggested to significantly decrease the number of band defects

[0008] EP0182615 discloses a spinneret with an outer ling and inner ring of grouped circular orifices characterized in that the distance between orifices in each group in the outer ring is less than the distance between orifices in each group of the inner ring.

[0009] GB 1,112,938 discloses a spinneret for producing dry spun fibers with non-circular sections with a number of groups of orifices arranged at intervals of from about 4 to about 12 mm with each group being composed of 2 to 6 circular orifices having a diameter of from 0.01 to 1 mm and being spaced at a distance from one another of 1 to 5mm. It is taught to be essential that the distance between two adjacent orifices of each orifice group should not be less than one millimeter.

[0010] CN201236230Y discloses a double-channel compound spinneret for producing double- cross parallel compound fiber. The spinneret has a cross-shaped micro pore and a spinneret guide hole formed with double channels, where two guide holes are asymmetric and inclined.

[0011] CN201053043 Y discloses a compound spinneret plate for producing paratactic peanut- shaped elastic fiber. The spinneret millipores are connected beneath spinneret lead holes that are oblique symmetrical and not connected together.

[0012] CN201793822U discloses a spinning head for manufacturing polyurethane fiber having a spinneret plate with multiple processing holes that are provided with inlet groove and capillary hole connected with inlet groove. In this disclosure, the capillary cross-section is rectangular.

[0013] CN103911677A discloses a spinneret plate for preparing a dumbbell fiber. A spinneret plate main body is provided with dumbbell spinneret micro-pore and formed with polygon- shaped spinneret micro hole, and geometrical image provided with a rectangular middle part.

[0014] CN103911677A discloses abarbell shaped capillary and spinneret design for PET spinning. [0015] CN201971936U describes a triangular capillary for spandex production to enhance drying.

[0016] KR2013064641 A discloses spinneret plates for preparing peanut shaped fibers comprising two holes or capillaries positioned adjacently or connected via a narrow slot.

Embodiments are disclosed wherein connected holes are positioned 0.13 to 0.25 mm apart from their centers and adjacent holes are positioned 0.11 to 0.40 mm apart from their centers.

[0017] EP1673495B1 and WO2005035842A1 disclose wet-spun, flat multifilament elastomeric yarns, preferably of polyurethane, obtained by passing yarn over rotating shaping cylinder having peripheral shaping channels.

[0018] Alternative methods for producing spandex fibers with non-circular sections of dog bone or lobe shape are disclosed in EP2337884B1, JP7197318A, JP53139847A, JP11124728A, DE1288235B, US6639041B2, US3840630A and CN104294439A.

Summary of the Invention

[0019| An aspect of the present invention relates to non-round or shaped solution spun spandex filaments.

[0020] Another aspect of the present invention relates to a spinneret for producing non-round or shaped solution spun spandex filaments.

[0021] Another aspect of the present invention relates to a method for producing non-round or shaped solution spun spandex filaments.

Brief Description of the Figures

[0022] FIG. 1 A is a diagram of a nonlimiting embodiment of a spinneret used in production of non-round or shaped solution spun spandex filaments. In this nonlimiting embodiment, the holes or capillaries of the spinneret are spaced 0.023 inches apart from their centers.

[0023] FIG. IB is a cross-sectional view of a non-round or shaped solution spun spandex filament produced with the spinneret of FIG. 1 A.

[0024] FIG. 2A is a diagram of a nonlimiting embodiment of a spinneret used in production of non-round or shaped solution spun spandex filaments. In this nonlimiting embodiment, the holes or capillaries of the spinneret are spaced 0.0150 inches apart from their centers and are connected via a narrow slot 0.0030 inches wide. [0025] FIG. 2B is a cross-sectional view of a non-round or shaped solution spun spandex filament produced with the spinneret of FIG. 2 A.

[0026] FIG. 3 A is a diagram of a spinneret used in production of solution spun spandex filaments. In this embodiment, the holes or capillaries of the spinneret are spaced 0.050 inches apart from their centers.

[0027] FIG. 3B is a cross-sectional view of a solution spun spandex filament produced with the spinneret of FIG. 3 A.

[0028] FIG. 4 A is a diagram of a nonlimiting embodiment of a spinneret used in production of a non-round or shaped solution spun spandex filaments. In this nonhmiting embodiment, there are three holes or capillaries in the spinneret spaced 0.0289 inches from the center of the cluster connected via a rectangular slot 0.055 inches wide

[0029] FIG. 4B is a cross-sectional view of a non-round or shaped solution spun spandex filament produced with the spinneret of FIG. 4 A.

[0030] FIG. 5 A is a diagram of a nonlimiting embodiment of a spinneret used in production of a coalesced spandex threadline comprised of three non-round filaments. In this nonhmiting embodiment, there are three pairs of holes or capillaries where the spacing between holes or capillaries within a pair is 0.023 inches and the spacing between the centerlines of the pairs is 0.529 inches.

[0031] FIG. 5B is a cross-sectional view of a non-round or shaped solution spun spandex filament produced with the spinneret of FIG. 5 A.

[0032] FIG. 6 is a diagram of a nonlimiting embodiment of a spinneret used in production of a non-round or shaped solution spun spandex filaments. In this nonlimiting embodiment, there are three holes or capillaries in the spinneret with the individual holes located at the vertices of an equilateral triangle with sides of 0.023 inches.

Detailed Description of the Invention

[0033] The inventors herein have now found that non-round or shaped solution spun spandex filaments such as, but not limited to, dogbone or peanut-shaped filaments, provide more surface area and thinner films that can promote drying.

[0034] Provided by this disclosure is non-round or shaped solution spun spandex filaments as well as methods and devices for their production. [0035] The term "spandex", as used herein, has its usual definition, a long-chain synthetic polymer that comprises at least 85% by weight segmented polyurethane.

[0036] By "non-round or shaped solution spun spandex filaments" as used herein, it is meant to be inclusive of multilobal filaments such as, but not limited to, dogbone, peanut-shaped or bilobal filaments as well as filaments with 3, 4, 5 or 6 or more lobes. Lobes may be similar in size or varied in size depending upon the application.

[0037] FIGs. 1 A, 2 A, 4 A, 5 A and 6 depict nomimiting embodiments of spinnerets useful in production of the non-round or shaped solution spun spandex filaments. As shown therein, the spinnerets may comprise two or more holes, also referred to herein interchangeably as capillaries. In one nonlimiting embodiment, the holes or capillaries are between 0.009 and 0.025 inches in diameter. The holes or capillaries may be separated as depicted in FIG. 1A and 5A or connected as depicted in FIG. 2A and 4A via narrow rectangular slots. In one nonlimiting embodiment, the narrow rectangular slot is between 0.0025 and 0.006 wide. In one nonlimiting embodiment, the narrow rectangular slot is 0.0055 inches in width. As shown by comparison of FIG. IB to FIG. 3B, spacing of these holes or capillaries may be critical to desired formation of the non-round or shaped solution spun spandex filament. Spacing, as measured from the centers of the holes or capillaries is preferably less than 0.05 inches, less than 0.04 inches, less than 0.038 inches, less than 0.035 inches, less than 0.030 inches, or less than 0.025 inches, and greater than 0.016 inches, or greater than 0.018 inches, when separated. Spacing, as measured from the centers of the holes or capillaries is less than 0.05 inches, less than 0.04 inches, less than 0.038 inches, less than 0.035 inches, less than 0.03 inches, less than 0.025 inches, or less than 0.020 inches and greater than 0.01 inches, or equal to 0.015 inches apart, when connected.

[0038] FIG. 6 shows a spinneret with a plate comprising three holes or capillaries. In this nonlimiting embodiment, the holes are between 0.009 to 0.015 inches in diameter and oriented in an equilateral triangular configuration. These holes are juxtaposed to form a cluster. In one nonlimiting embodiment, the holes may be connected via rectangular slots radiating from the center of the capillary cluster to each of the capillaries as shown in Figure 4A. In one nonlimiting embodiment, the rectangular slot is 0.0030 inches in width. In one nonlimiting embodiment, the holes or capillaries are connected via rectangular slots radiating from the center of the capillary cluster to each of the holes capillaries less than 0.0300 inches from the center point, the slot being 0.055 inches wide. These plates are useful in accordance with the present invention to form non-round or tri-Iobal shaped solution spun spandex filament by solution dry spinning.

[0039] Accordingly, an aspect of the present invention relates to a non-round or shaped solution spun spandex filament produced by solution dry spinning using a spinneret with a plate comprising two or more closely spaced grouped holes or capillaries.

[0040] In one nonlimiting embodiment, the non-round or shaped solution spun spandex filaments are produced by solution dry spinning using a spinneret with a plate comprising two or more holes or capillaries spaced less than 0.05 inches apart and greater than 0.016 inches, more preferably greater than 0.018 inches, apart. In one nonlimiting embodiment, the non-round or shaped solution spun spandex filaments are produced by solution dry spinning using a spinneret with a plate comprising two or more holes or capillaries spaced less than 0.025 inches apart and greater than 0.016 inches, more preferably greater than 0.018 inches, apart. In one nonlimiting embodiment, the non-round or shaped solution spun spandex filaments are produced by solution dry spinning using a spinneret with a plate comprising two or more holes or capillaries spaced less than 0.05 inches apart and greater than 0.01 inches apart, wherein the holes or capillaries are connected via a narrow rectangular slot 0.0030 inches wide. In one nonlimiting embodiment, the holes or capillaries are between 0.009 to about 0.0230 inches in diameter.

[0041] In one nonlimiting embodiment, a non-round or tri-lobal shaped solution spun spandex filament is produced by solution dry spinning form using a spinneret with a plate comprising three holes or capillaries. In this nonlimiting embodiment, the holes are between 0.009 to 0.015 inches in diameter and oriented in an equilateral triangular configuration. These holes are juxtaposed to form a cluster. In one nonlimiting embodiment, the holes may be connected via rectangular slots radiating from the center of the capillary cluster to each of the capillaries as shown in Figure 4A. In one nonlimiting embodiment, the rectangular slot is 0.0030 inches in width. In one nonlimiting embodiment, the holes or capillaries are connected via rectangular slots radiating from the center of the capillary cluster to each of the holes capillaries less than 0.0300 inches from the center point, the slot being 0.055 inches wide.

[0042] Another aspect of the present invention relates to spinnerets for production of non-round or shaped solution spun spandex filaments.

[0043] In one nonlimiting embodiment, the spinneret comprises a plate with two or more holes or capillaries closely spaced less than 0.05 inches apart and greater than 0.016 inches, more preferably greater than 0.018 inches, apart. In one nonlimiting embodiment, the spinneret comprises a plate with two or more holes or capillaries closely spaced less than 0.025 inches apart and greater than 0.016 inches, more preferably greater than 0.018 inches, apart.

[0044] In one nonlimiting embodiment, the spinneret comprises a plate with two or more holes or capillaries closely spaced less than 0.05 inches apart and greater than 0.01 inches apart, wherein the holes or capillaries are connected via a narrow rectangular slot 0.0030 inches wide. In one nonlimiting embodiment, the two or more holes or capillaries on the spinneret are spaced less than 0.020 inches apart. In one nonlimiting embodiment, the two or more holes or capillaries on the spinneret are spaced 0.015 inches apart.

[0045] In one nonlimiting embodiment, each capillary or hole is between 0.009 to 0.025 inches in diameter.

[0046] In one nonlimiting embodiment, the spinneret comprises a plate comprising three holes or capillaries. In this nonlimiting embodiment, the holes are between 0.009 to 0.015 inches in diameter and oriented in an equilateral triangular configuration. These holes are juxtaposed to form a cluster. In one nonlimiting embodiment, the holes may be connected via rectangular slots radiating from the center of the capillary cluster to each of the capillaries as shown in Figure 4A. In one nonlimiting embodiment, the rectangular slot is 0.0030 inches in width. In one

nonlimiting embodiment, the holes or capillaries are connected via rectangular slots radiating from the center of the capillary cluster to each of the holes capillaries less than 0.0300 inches from the center point, the slot being 0.055 inches wide.

[0047] In these embodiments, the spinneret may comprise multiple groups of these closely spaced holes or capillaries for production of multiple threadlines containing one or more non- round filaments.

[0048] The spinneret may be made from a variety of materials suitable for the manufacture of spandex spinnerets. A nonlimiting example is 317 stainless steel.

[0049] As will be understood by the skilled artisan upon reading this disclosure, the dimensions and shape of the spinneret as well as the number of closely spaced holes or capillaries can be selected to be compatible with the geometry of the spin cell, such as round or rectangular, and the number of filaments desired.

[0050] Another aspect of the present invention relates to a method for producing non-round or shaped solution spun spandex filaments. In the solution dry spinning method, the spandex polymer is made by a two-step process. In the first step, an isocyanate-terminated urethane prepolymer is formed by reacting a polymeric glycol with a diisocyanate. Typically, the molar ratio of the diisocyanate to the glycol is controlled in a range of 1.50 to 2.50. If desired, catalyst can be used to assist the reaction in this prepolymerization step. In the second step, the urethane prepolymer is dissolved in a solvent such as N,N-dimethylacetamide (DMAc) and is chain extended with a short chain diamine or a mixture of diamines to form the spandex solution. Various additives can be added to the spandex polymer solution to improve the appearance, performance and quality in manufacture, storage, processing and use of the fiber. In this method, the polymer spinning solution is pumped into a spinning cell where it is converted into fibers by forcing the polymer solution through a spinneret comprising a plate with two or more closely spaced holes or capillaries.

[0051] In one nonlimiting embodiment, the spinneret comprises a plate with two or more holes or capillaries closely spaced less than 0.05 inches apart and greater than greater than 0.016 inches, more preferably greater than 0.018 inches, apart. In one nonlimiting embodiment, the spinneret comprises a plate with two or more holes or capillaries closely spaced less than 0.025 inches apart and greater than 0.016 inches, more preferably greater than 0.018 inches, apart.

[0052] In one nonlimiting embodiment, the spinneret comprises a plate with two or more holes or capillaries closely spaced less than 0.05 inches apart and greater than 0.01 inches apart, wherein the holes or capillaries are connected via a narrow rectangular slot 0.0030 inches wide. In one nonlimiting embodiment, the two or more holes or capillaries on the spinneret are spaced less than 0.020 inches apart. In one nonlimiting embodiment, the two or more holes or capillaries on the spinneret are spaced 0.015 inches apart.

[0053] In one nonhmiting embodiment, the spinneret comprises a plate comprising three holes or capillaries. In this nonlimiting embodiment, the holes are between 0.009 to 0.015 inches in diameter and oriented in a equilateral triangular configuration. These holes are juxtaposed to form a cluster. In one nonlimiting embodiment, the holes may be connected via rectangular slots radiating from the center of the capillary cluster to each of the capillaries as shown in Figure 4A. In one nonlimiting embodiment, the rectangular slot is 0.0030 inches in width. In one

nonlimiting embodiment, the holes or capillaries are connected via rectangular slots radiating from the center of the capillary cluster to each of the holes capillaries less than 0.0300 inches from the center point, the slot being 0.055 inches wide. [0054] In any of these embodiments, the spinneret may comprise multiple groups of the closely spaced holes or capillaries within a single spinning cell to produce multiple threadlines containing one or more non-round filaments.

[0055] As the closely spaced, adjacent filaments exit the spinneret they fuse to form a non-round or shaped solution spun spandex filament. Preferred is that the fusing of the filaments occur in a region where the solvent concentration is sufficient to form a fully fused filament. A number of the fused filaments may be coalesced further down the cell by means of a false twist jet located below the cell exit to provide a final product of the desired thickness. The twist action of the false jet propagates up the cell to a location where the filaments are somewhat dry, but are sufficiently tacky to adhere and form a coalesced threadline comprised of multiple non-round filaments. After exiting the spin cell, the spandex threadline may be treated with a finish to improve threadline lubricity and reduce tack on the package.

[0056] The following section provides further illustration of the non-round or shaped solution spun spandex filaments of the present invention as well as the spinnerets and methods for their production. These working examples are illustrative only and are not intended to lirnit the scope of the invention in any way.

EXAMPLES

Example 1: Production of 22/1 862 W non-round or dogbone-shaped filament

[0057] A 22 dtex mono-filament dogbone spandex produced in accordance with the present invention using a spinneret as depicted in FIG. 2A was evaluated.

[0058] The spin process was found to run with an acceptable break level. The cross-section of the resultant spandex threadline is shown in FIG. 2B. The strength and elastic properties of the spandex threadlines were measured in accordance with the general method of ASTM D 2731-72. Three filaments, a 2-inch (5-cm) gauge length and a 0-300% elongation cycle were used for each of the measurements. The samples were cycled five times at a constant elongation rate of 50 centimeters per minute. Load power, the stress on the spandex during initial extension, was measured on the first cycle at 200% extension and is reported as centinewtown (cN) per threadline. Unload power is the stress at an extension of 200% for the fifth unload cycle and is also reported in centinewton (cN). Percent elongation at break and tenacity were measured on a sixth extension cycle. Table 1 shows the physical properties for the 22 dtex mono-fil dogbone spandex samples.

Table 1: Physical properties of 22 dtex mono-fil dogbone shape threadline

Example 2: Production of 44 dtex 3-fil spandex

[0059] Samples of a 44 dtex 3-fil spandex were produced via conventional spandex dry spinning process using a spinneret as depicted in FIG. 5A. The break level during spinning was acceptable. The cross-section of the resultant threadline is shown in FIG, 5B. Physical properties of the spandex are shown in Table 2.

Table 2: Physical properties of 44 dtex 3-filament coalesced non-round, dogbone shape threadline

Example 3: Production of a series of 22 dtex mono-fil spandex fibers

[0060] A series of 22 dtex mono-fil spandex fibers were produced at constant spinning conditions using a spinneret with round holes or capillaries, a spinneret with holes or capillaries as shown in FIG. 2A and a spinneret with holes or capillaries as shown in FIG. 4A at identical spinning conditions. Each of the fibers was analyzed for residual solvent. Results of the analysis are shown in Table 3.

[0061] DMAc in spandex yarn is determined by extraction in a solvent and the DMAc in the extract analyzed by gas chromatography with a flame ionization detector. The solvents used may be a polar organic solvent such as methanol or water.

[0062] The analysis method is as follows: (1) place 2 ± 0.2 g of spandex yarn in a vial with sealable cap and add 50 mL of solvent; (2) place the sample vial in a heating block or oven and heat to approximately 60°C for at least 15 minutes; (3) place an aliquot of the solvent in a GC vial for analysis; (4) analyze the sample solution by GC-FID; and (5) determine the DMAc concentration in solution relative to a known standard or standard calibration curve.

[0063] DMAc concentration in yarn was determined using the following calculation:

DMAc concentration in spandex yarn, wt. % = DMAc concentration in solvent (μg/mL) * 50 mL solvent * dilution factor *100% Weight of Yarn extracted (g) * 1,000,000 (μg/g) where dilution factor = 4 for a 1:4 dilution or 1 for no dilution

Table 3: Residual solvent level of spandex produced from various capillary shapes