IE43335B1 - Composite bicomponent polyamide filaments - Google Patents

Abstract

1478101 Knitting E I DU PONT DE NEMOURS & CO 30 July 1975 [31 July 1974 27 May 1975] 31932/75 Heading D1K [Also in Division B5] A drawn composite filament comprising a sheath of nylon 6,6, nylon 6; or nylon 6,12 and an eccentric core of a random copylener of nylon 6 and nylon 6,12, with the nylon 6 being present in a proportion which is greater than 25% but less than 45% by weight in the copolymer, is knitted into various garments. Ladies' stretch hose may be knitted using a single-feed knitting machine from these filaments. Two-ply yarns of these filaments may be knitted into pantyhose, or the legs only of pantyhose may be knitted from these filaments.

Description

This invention concerns improvements in and relating to filaments melt spun from synthetic, linear polyamides and, more particularly, to composite bicomponent polyamide filaments.

Nylon filaments and yarns have long been predominant in the women's hosiery market. In recent years, there has been a strong demand for so-called stretch hose which are much smaller than the- legs on which they are to be worn but which stretch sufficiently to fit the legs.

Crimpable filaments particularly suitable for such stretch hosiery have been disclosed in U.S. Patent Specification 3,399,108. This patent discloses crimpable composite nylon filaments consisting of two continuous, adherent, eccentric components, one component consisting essentially of a crystalline, fiber-forming homopolyamide, the other component consisting essentially of a nonisomorphic, fiberforming, random copolyamide containing at least 20% by weight of each of two polymer units. The components of the filament can be arranged in an eccentric sheath-core relationship or side-by-side. Example VI describes such filaments wherein 6-6 nylon polymer and 6-6/6-12 (50:50) nylon copolymer components are spun in a side-by-side relationship. It is stated that for optimum results, a 6-6/6-12 copolymer should contain 40 to 60% of the 6-6 units. It is also stated that, in addition to the copolymers exemplified, other crystallizable, nonisomorphic copolymers in which the 6-6 polymer units are replaced with other units including ε-caproamide may be employed. (In the above and following text, 6-12 refers to units of polyhexamethylene dodecanedioamide, 6-6 to units of polyhexamethylene adipamide, - 2 4333S and 6 to units of poly-c-caproamide).

Filaments of the compositions specifically disclosed in U.S. Patent Specification No. 3,399,108 have been used commercially to produce hosiery of good quality, pecause such precrimped filaments are able to redevelop crimp against tensions and restraints imposed by the stitches in a knit fabric, thus conferring stretchability on hosiery prepared from such a fabric. Nevertheless, a need for further improvements in the performance and appearance of today's stretch fabrics has been recognized.

In particular, there has been a need for improvements in the durability, fit, and fit retention of hose. There has also been a desire for higher levels of hosiery stretch than heretofore attainable, so as to achieve a reduction in the number of sizes required for the normal range of leg sizes.

The present invention provides an improvement in bicomponent nylon filaments of the type described in U.S. Patent Specification No. 3,399,108 by selection of a particular combination of components not specifically disclosed in U.S. Patent Specification No. 3,399,108.

According to one feature of the present invention there is provided a drawn nylon filament comprising two continuous, adherent; eccentric components, the first component being a sheath of polyhexamethylene dodecanedioamide, polyhexamethylene adipamide or poly-e-caproamide and the second component being a core of a random copolymer of hexamethylene dodecanedioamide units and ε-caproamide units, the copolymer containing more than 25 and less than 45% by weight ε-caproamide units.

The essence of the invention is the use of more than 25 and less than 45% by weight of 6 nylon units in the core copolymer, in combination with certain specific polyamides for the sheath.

As the amount of 6 nylon units in the core polymer increases, the tenacity decreases to unacceptable levels and as the amount of 6 nylon units decreases, so does the crimp elongation. Preferred proportions of 6 nylon units are 30 to 40% by weight, with about 35% by weight being especially suitable. Filaments having 30 to 70% by weight core polymer provide useful levels of crimp.

Although all three sheath species provide filaments having excellent stretch properties that are better than those of the prior art, we have found that filaments with a 6-12 sheath have the best crimp elongation and the best overall balance of properties and hose prepared therefrom have the best hosiery stretch. Filaments with a 6-6 sheath offer the advantage of the best (lowest) crimp shrinkage of the three species. Filaments with 6-6 or 6-nylon sheaths have an advantage of lower polymer cost than those with 6-12 sheaths. i Thus, while filaments with any of three sheath species have better properties than the prior art, those with the 6-12 sheath provide the most desirable properties but at somewhat higher cost.

Whilst the sheath will consist substantially of the specified polyamide and the core will consist substantially of the two specified copolymers, it will be appreciated that both the sheath and the core may contain minor amounts of other materials such as, for example, delusterants, antistats and other comonomers, without adversely affecting the properties of the filament.

The bicomponent filaments of the present invention are conveniently made by melt spinning the two components in an appropriate sheath/core relationship using the spinneret assembly shown in Figure 3 of U.S. Patent Specification No. 3,339,108 and are subsequently drawn. On emergence from the spinneret, the filaments are quenched. The filaments may then, if desired, be separated into yarns of one or more filaments, and either wound on an intermediate package before being drawn or advanced continuously to the draw zone.

The filaments have a continuous sheath of the selected polyamide which surrounds an eccentric core (which usually appears D-shaped in cross section) of the copolyamide. The sheath at its thinnest point is preferably as thin as possible while completely covering the core.

Xn the filaments exemplified herein, this radial thickness is about 1% of the filament diameter.

There is no need to precrimp the yarns of this invention before knitting, i.e., the as-drawn yarn can be knitted directly into a fabric. This is an important advantage. Surprisingly, tlie as-drawn yarn of the present invention provides significantly better hosiery stretch and recovery properties than the same yam even if precrimped (Table 14), which is itself better than the precrimxied yam of U.S. Specification 3,399,108 (although the term precrimping is not used therein, the heat relaxation step of that patent is a precrimping step.) Thus, the crimpable linear-polyamide bicomponent-filament yams of this invention can be made readily in a single coupled process beginning with melting of the components and ending With packaging of yarn ready for knitting or weaving.

Use of yarn that has not been precrimped is advantageous in a knitting operation and leads to more uniform crimp properties and fewer defects. Treatment of the woven or knit fabric with heat of the order of 100eC., as routinely used during customary fabric finishing, is sufficient to develop the crimp. Prior commercial crimpable filaments have not had sufficient differential shrinkage to develop adequate crimp for the first time against restraints present in fabrics and, accordingly, in the past it has been necessary to precrimp bicomponent filaments with heat setting at substantially zero tension in order - 5 43335 to substitute relatively stronger forces of heat-set, crystalline memory for weaker, skrinkage forces, as is the case in U.S. Specification 3,399,108. In contrast to the prior commerical filaments, the bicomponent filaments of the present invention have the ability to develop adequate crimp for the first time against fabric restaints. That the slow and costly precrimping step can be eliminated, while still developing more than adequate crimp by shrinkage in fabric form, results from the unexpectedly high shrinkage force of the copolymerie component.

The filaments of the invention may, however, be precrimped, if desired. Precrimping: can'be done for example by a sequence of steps as .enumerated ih U.S. Specification 3,399,108, comprising crimping with heat at low tension (sometimes termed heat relaxation), cooling, and stretching to remove crimp. In yet another modification, the filaments of the invention may also be subjected to a similar series of steps, but omitting the final stretching wherein crimp is removed.

As is well known in the spinning of bicomponent filaments, the magnitude of the difference in relative viscosities (ARV) between sheath and core polymers is selected to avoid bending of the extruded stream at the exit face of the spinneret. If ARV is either too large or too small, not only will bending occur but also the D-shape of the core will be undesirably distorted. When the filament is 50 to 60% by weight core and RV for each component is determined using the same solvent and polymer concentration, the RV of the sheath polymer is preferably from 2 to 8 units less than that of the core polymer. - 6 43335 While the 6-12//6-12/6, 6-6//6-12/6 and 6//6-12/6 nylon yarns disclosed herein (// separates sheath and core components and / separates polymer units in tlie copolymeric core) are especially well suited as hosiery leg yarns, their use is by no means so limited.

Welt yams in customary deniers and counts, and multifilament yams of usual textile deniers (e.g., 40 to 150 denier), are also readily prepared. Also, the filaments Of this invention may be cut to staple fibers (ordinarily from 3 to 10 denier per filament) and used alone or blended with other staple to prepare fabrics, which, on subsequent heat treatenent, become bulky when the staple fibers of this invention shrink and crimp.

Example I Three 6-12//6-12/6 bicomponent filaments according to the invention having varying amounts of 6 nylon units in the core were prepared and their properties were compared with a similar filament having an amount of 6 nylon units outside the invention, and also with filaments according to U.S. Patent 3,399,108 and with commercial bicomponent nylon filaments.

A 6-12 nylon homopolymar and four random copolymers of 6-12/6 nylon with 80/20, 70/30, 65/35, and 60/40 weight ratios, prepared ey conventional methods, delustered with 0.02% by weight of TiO2 in the final polymer (any customary amount of TiC>2 delustrant may be added, but all polymers exemplified herein contain 0.02S by weight based on the weight of the polymer), the RV of the homopolymer being 38.0 + 1.5 and that of the copolymers being 43 + 3 as measured on samples taken of each melt just before it enters the spinneret pack during extrusion of filaments, were spun as follows into bicomponent filaments having cross sections like those of filaments prepared in U.S. Specification 3,399,108 using a spinneret depicted in Figure 3 of that patent. The two flakes used for a given filament were separately melted using vacuum exhausted screw extruders. The two melts were fed by separate gear pumps at 260 + 3°C to the spinneret assembly at rates adjusted to provide a 40/60 Weight ratio of sheath (6-12) to core (6-12/6) .0 polymer, and the resulting filaments have a sheath thickness along the thinnest portion of the sheath which is about 1% of the filament diameter. Upon exiting from the spinneret, the filaments were quenched in a 60 inch (1.52 m.) chimney using cross flow air at 49 + 1°F. (9.5 + 0.5°C.). Before windup and after convergence to 3-filament yams, the yarns passed through a 75.6 inch (1.92 m.) long chamber containing saturated steam at atmospheric pressure. Windup of the undrawn yarn into packages was at 520 yd./min. (475.5 m./min.). The yarns ! were subsequently withdrawn from their packages and drawn at a draw ratio of 3.933X over an unheated draw pin located between the feed and draw rolls of a conventional drawtwister. The draw roll peripheral velocity was 385 yd./min (352 m./min.), and the ring-and-traveler ’ windup following drawing was at a spindle speed of 5689 rpm to provide 0.411 turns/inch (0.162 turns/cm.) of inserted twist.

Samples of each yarn of the invention were handled in three different ways between draw roll and - 8 windup. In the first, each drawn yarn was packaged immediately following drawing, without further heat treatment. Yarns so prepared are described as cold-drawn only and are identified by the code letter D (thus, D-30 identifies cold drawn only yarn containing 30% by weight 6 nylon units in the core).

The second and third types of handling immediately after drawing involved passing the drawn yarn through a 5.3 inch (14.7 cm.) long tube through which hot air was jetted cocurrently at 0.7 + 0.1 ft.^/nin. (19.8 + 2.3 liters/min.) to provide an exit-air temperature of 115 + 2’C. At the point of air entry, tlie tube is 0.08 in. (0.20 cm.) in diameter, increasing gradually to 0.20 in. (0.51 cm.) at a distance of 2.8 in. (7.1 cm.).

There the tube diameter increases abruptly to 0.25 in. (0.63 cm.) and remains constant for the last 3 in. (7.6 cm.) of tube length. Each yarn after exit from the tube passed in zig-zag fashion over 3 snub pins at a total contact angle of 390 + 15 degrees. In the second type of handling the yarn was immediately packaged under tension, as above described. These heat treated yarns are identified in the tables by code letter H. In the third type of handling, each yarn after snubbing was first wrapped round an additional roll operated at a peripheral velocity 40% less than that of the draw roll before packaging. Packaging tension was adjusted to just remove the crimp developed in the very low-tension region within and immediately following the heating. These precrimped yarns are identified by code letter P. They are yarns of the invention made by using the process described in U.S. Specification 3,399,108. •43335 D-20 Table I D-30 P-35 P-8o Denier (dtex) X5.5 (17.2) 15.6 (17.3) 15.7 (17.1) 15.8 (17.6) Tenacity (gm./den.) 5.7 5.3 8.6 4.7 CE (X) 3.8 13.0 23.6 38.9 CS (X) 15.3 16.6 15.8 16.0 Table 2 H-80 H-20 H-30 H-35 Denier (dtex) 17.3 (19.2) 17.6 (19.6) 18.5 (20.6) 18.3 (20.3) Tenacity fgm./den.) 5.1 4.6 3.7 3.3 CE (X) 3.9 16.0 23.7 23.0 CS (X) 6.8 6.8 6.1 ¢.5 P-2Q Tabled P-30 P-35 P-8o Denier (dtex) fit 20.0 (22.2) 20.0 (22.2) 19.6 (21.8) Tenacity (gra./den.) *« 3.8 2.9 2.4 CE (X) «« 87.5 38.9 35-0 CS (X) «Β 4.5 5.7 6.2 ·« was inoperable during preerimping due to insufficient shrinkage These results show that the cold drawn only yarns nave the highest tenacity, and that both heat treating and precriraping result in yarns having lower (better) crimp shrinkage.

Ladies' stretch hose were knitted with a plain jersey stitch using a single-feed circular knitting machine with 400 75-yauge knitting needles arranged in a circle about a cylinder which is 3.75 in, (9.52 cm.) in diameter. The welt and shadow welt are immaterial to the stretch and recovery tests to be performed, but they were knitted with 432 and 60 courses, respectively. The upper leg was knitted with 672 courses,' tapering began during the next 12 courses, and the lower leg comprised 516 courses. Then, the foot was knitted with 372 courses in the first of which a second yarn was inserted for a few stitches to serve as a heel mark.

In this and the remaining examples, tlie welt yarns used were commercially available stretch yarns of the false-twist-textured or bicomponent types. In knitting hose or pantyhose, two kinds of yarn are used, i.e., welt yarns and leg yarns. Welt yarns are normally 40-50 denier yarns with 6 to 13 filaments. They are used to knit the panty portion and toes of pantyhose and the welt, shadow welt, ana toes of regular hose. In these examples, only the legs of either type of garment were knitted from the yarns described in the examoles. The heel mark is simply a single end of another visible yarn knit in for a few stitches of one course. When changing from an area knit of welt yarn to one knit of leg yarn, or vice versa, the two yarns are plied for a portion of one course to fasten the areas together. All hose and pantyhose described herein were circular-knitted in a plain jersey stitch throughout.

After knitting, tlie greige hose (packed loosely in bags at 12 per bag) were first tumble-steamed in atmospheric steam for 15 minutes, then scoured conventionally at 99°C. for fifteen minutes, then rinsed in three 5-minute water rinses, and then spun dry in the spin cycle of a home laundering machine. The bags were made by doubling cheese clots (U.S.P. 11 or equivalent) and permanently closing three sides. When empty and flat, each bag is about 18 X 16 inches (45.7 X 40.6 cm.). The filled bags were tied snut at the fourth side. Still in bags, the hose were dyed in a conventional disperse dye bath at 60°C. for one hour and 15 minutes. After several short washings to remove excess dye solution, tlie hose were again spun dry. Drying was completed at room temperature with each, hose carefully laid flat on a table top.

Hosiery stretch (IIS) and hosiery recovery (HR) I were measured. In this determination, the applied load was a 2.27 kg. weight which was fastened to the toe and slowly lowered until tlie hose supported it without tensile shock.

Five to eight measurements were averaged to provide the hosiery stretch, hosiery recovery and cross stretch results reported in Table 4.

For purposes of comparison, filaments according to U.S.

Specification 3,399,108 were prepared. The yarns are 18-denier, 8 filaments, and each filament has 40% by weight sheath polymer and 60% by weight copolymer in an eccentric core. The sheath polymer is polyhexamethylene adiparuide (6-6) and the core polymer is a random copolymer of 50% by weight 6-6 units, 31.5% by weight hexamethylene sebacamide (6-10) units and 18.5% by weight hexamethylene dodecanedioamide (6-12) units. Relative viscosity (RV), measured on samples taken of the melt at a point just prior to entry into the spinning pack, is 50 for the sheath polymer and 63 for the core polymer. Upon extrusion, the filaments were quenched in a 60-inch (1.52 n.) long chinney using cross-flow air at 21.1aC. They were simultaneously converged to 8-filament yarns, each yarn being pulled from the chimney via feed rolls at 930 ypm. (850 m./min.).

From the feed rolls, each yarn passed to a first drav; roll operated at a peripheral velocity of 2457 ypm. (2247 m./min.) Thereafter, each yarn sequentially contacted opposite sides of a pair of draw pins heated to 200aC. while advancing to a pair of rolls having a peripheral velocity of 3150 ypm. (2880 m./min.) in a hot chest maintained at 145°C. Each yarn wrapped this pair of rolls several times and wa3 delivered therefrom to a precrimping jet having a supply pres2 sure of 29 psig. (2.04 kg./cm ) and supply temperature of 18b“C., and thence to a let-down roll having a peripheral speed of 2396 ypr.t. (2191 m./min.), a forwarding roll having a peripheral speed of 2749 ypm. (2514 m./min.), and then packaged on yarn tubes at a windup roll speed of 2736 ypm. (2502 m./min.). The 8-£ilament yarn has a denier of 18.3 (20.3 dtex), and a tenacity of 3.3 gm./den. (3.0 gm./dtex.) Table 5 shows the crimp elongation (CE*) and crimp skrinkage (CS*) of the yarn, and also the hosiery properties. Prior to this work, crimp elongation (CK) and crimp shrinkage (CS) had always been measured using - 13 43 335 the first variant of the crimp test measurements described under Definitions and Test Descriptions. It is to be noted that the CE values for yarns of this invention are much lower than previously obtained using precrimped bi5 component stretch yarns but that, in spite of low CE, the yarns of this invention yield hose of vastly superior stretch properties. In an attempt to obtain crimp elongation values correlating better with hosiery stretch properties, the modified (third) test precedure for CE* and “~-CS* was devised. - -The CE* value of Table 5 for prior art bicomponent yam is generally as great as tlie corresponding CE values of Table 1-3 for yams of this invention, but the IIS value of Table 5 is generally much smaller than found in Table 4 for yarns of this invention. While the reasons are not completely understood, experience has shown that CE* is not only a better predictor of ultimate hosiery stretch than CE, but also it is a far more reproducible property value.

Two additional yams for comparison were prepared from the same polymer of U.S. Specification 3,399,108 as described above, in a similar manner to that described, except that in one case treatment in the precrimping jet was omitted (thus giving yarns analogous to the H-serie3 yams of the invention), and in the other case both treatment in the hot-chest and precrimping jet were omitted (thus giving yarns analogous to the D-series yams of fcho invention) . Xn both cases the hosiery stretch values were poorer than those of the pracrimped prior art yarn shown in Table S, 4333S Further hose for comparison were knitted and finished identically from commercial 20-denier threebicomyonent-filament nylon hosiery yarn. The results showed that tiie hosiery stretch of hose knitted from yarns of the invention is better than that of hose knitted from the commerial yarn. Although hosiery stretch is a function of size (cross stretch), snail variations in cross-stretch have little effect on hosiery stretch and recovery, and the increase in hosiery stretch for hose from yarns of the invention over hose of commerical yarns is much larger than can be accounted for by small differences in size.

Table 4 Yarn Code llosiopy croarj stretch Hosiery Stretch (%) Hosiery Recovery Left (In./cm.) Ankle (in./cm.J D-20 13.3/34 9.8/25 184 79.7 D-30 12.7/32 9.3/24 271 «3.9 0-35 13.0/33 9.7/25 294 85.6 0-40 13.0/33 9.7/25 314 91.0 H-20 14.9/38 11.0/28 165 77.4 H-30 14.4/36 11.0/28 273 83.5 H-35 14.3/36 11.0/28 306 84.8 H-40 14.5/37 10.5/27 298 88.4 P-20 — -- -. P-30 14.1/36 10.9/28 236 65.8 P-35 13.7/35 10.5/27 228 65.4 P-40 14.7/37 10.6/27 222 73.0 CE* (X) 41.5 OS» (X) 3.9 Finished leg crossstretch, ln. (cn.) 13.81 (35.1) HS (X) 169 HR (X) 77.5 3335 Example 2 This example illustrates yams of the invention having a different homopolyanide sheath (6-6 nylon), and hosiery knitted from them, which otherwise are as described in Example 1. At the same time, additional 6-12//6-12/6 bicomponent-filament yarns were prepared in tlie same manner.

The polyhexamethylene adipamide (6-6 nylon) employed in forming the 6-6//6-12/6 filaments has an RV of 51.4 + 4.2 and was spun at a melt temperature of about 290°C.

In Tables 6 and 3, the listed properties are averages of 6 to 8 determinations. In Tables 7 and 9, the hosiery properties are averages for 4 hose, each knitted from a separate package of the indicated yarn type. Tlie out-of-hose properties were measured on yarn removed from hose after measurement of I1S and HR.

The filaments with 6-12/6 (50/50) cores (outside this invention) were difficult to prepare and nonuniform in denier. Interfilament sticking was frequent. Although hose prepared using these filaments have surprisingly high US' values, which is not predictable from tlie CE* values of the corresponding varus, the durability of the hose in use is poor. Statistical study of the breaking strengths of yarn out-of-hose (Table 7 and 9) reveals that breaking strength of each yarn decreases substantially linearly witn increasing weight percent of 6 nylon in the core of each filament. Above about 45% 6 nylon in the core, the yarns become too weak for adequate durability in use.

Use of 6-6 nylon as sheath polymer, rather than 6-12 nylon, yields slightly lower hosiery stretch and hosiery recovery values, but the diminishment is slight when compared to stretch properties attainable heretofore with known bioomponentfilament hosiery yarns. In both cases, the dependence of hosiery stretch on percent 6 nylon in the core is substantially the same. Below 25% 6 nylon in the core, stretch properties become inadequate Above 45% 6 nylon in the core, the yarns become not only difficult to handle in spinning but also inadequate in breaking strength.

Examples 1 and 2 show that filaments with cores containing either 20% or 50% by weight of 6 nylon units have been found unsuitable for present purposes. Filaments with cores containing 25% and 45% by weight of nylon, although more suitable, are outside the scope of the present invention.

Examples 1 and 2 further show that while the cold drawn only (D) yarns of the invention are better than heat treated (H) and precrlmped (P) yarns of the invention, all are better than the prior known yarns.

For adequate hosiery durability, it is desirable that the filaments have a tenacity at break greater than 5.0 gm/den.

Example 2 also shows, as can be seen from Table 6, that in the case of filaments having a 6-6 nylon sheath, for values greater than 5.0 gm./den., the core copolymer should contain less than 40% nylon units.

Table 6 6-6//6-12/6 Nylon Tarn Characterizations (Before Knitting) Yarn Denied Tenacity T(raZUen) Tenacity *jj(r,nZden) 5.8 $5»C. Water CS1 (2 ) dtex D-20 16.8 4.6 32-4 14.3 18.7 D-25 16.3 4.4 5.3 61.7 11.3 18.1 D-30 16.5 8.5 5.8 79.5 16.1 18.3 D-35 16.8 4.4 5.6 131.6 17.5 18.2 D-40 16.5 4.0 - 5.0 189.8 1H.1 18.3 D-85 16.8 3.a 4.» 124.3 13.2 IB.. D-50 16.5 3.6 4.4 56.7 18,0 18.3 H-20 17.2 8.5 6.1 28.8 8.8 19.1 H-25 17.4 4.1 5.8 39.6 10.0 19.3 H-30 17.8 4.0 5.3 54.H 9.8 19.3 H-35 17.5 4.0 5.8 77.7 11.1 19.4 H-40 17.8 3.7 4.9 91.8 10.6 19.3 H-85 17.3 3.5 4-5 100.1 12.0 19.2 H-50 17*0 3.3 4.2 41.0 9.0 18.9 Table 7 6-6ZZ6-12Z6 Nylon Hosiery Characterigatlona Hoolery Size Crose-stretch-in.(cm.) Hosiery Stretch Yam Out of Hose Yam iSE— ankle Ha(g) HHff) breaking Strength (gm) D-20 18.97(38.0) 11.87(29.1) 123*1 75.2 71.0 D-25 18.62(37.1) 11.25(28.6) 202« S 77.3 66.0 D-30 14.72(37.4) 11.16(28.3) 279.8 80.1 67.3 D-35 14.47(36.5) 11.22(28.5) 315.5 81.2 60.1 D-40 18.88(36.7) 11.28(28.7) 337.3 83.0 55.0 D-45 18.28(36.3) 10.87(27.6) 389.9 77.7 89.3 D-50 18.81(37.6) 11.19(28.8) 338.9 79.8 85.1 H-20 18.87(37.8) 10.59(26.9) 120.8 75.7 71.8 H-25 18.82(36.6) 10.33(26.2) 1B6.5 76.4 70.0 K-30 18.62(37.1) 10.87(26.6) 268.3 79.6 64.0 H-35 18.66(37.2) 10.72(27.2) 307.7 81.9 58.6 H-40 18.53(36.9) 10.56(26.8) 302.3 82.5 56.9 H-45 18.06(35.7) 10.12(25.7) 358.1 79.9 51.0 H-50 18.31(36.3) 10.31(26.2) 332.8 81.7 86.9 Tabic 8 6-12//C-12/6 Hylon Yarn Characterizations (Before Knitting? Yarn Denier Tenacity TCgm/den) Tenacity Tnfun/den) 95’C. Water dtex CE«(t) : 0-25 . 15.9 4.8 6.2 97.9 15.6 17.7 D-30 15.3 5.2 6.9 96.4 18.6 17.6 D-35 15.9 4.5 5.8 143.2 19.9 17.7 0-40 16.1 4.4 5.6 184.5 21.2 17.9 0-45 15.7 4.1 5-3 186.3 18.0 17.4 D-50 16.0 3.9 5.1 74.0 18.2 17.8 H-25 17.8 4.4 6.4 49.8 7.6 19.8 H-30 17.4 4.4 6.5 48.7 7.2 19.3 H-35 17.5 4.0 5.7 76.6 10.1 19.4 H-40 17.7 3.6 5.1 39.4 7.3 19.7 H-45 17.6 3.2 4.5 71.1 9.8 19.6 H-50 17.7 2.9 4.1 73.9 8.7 19.7 Table 9 6-12//6-12/6 Nylon Hosiery Characterizations - Hosiery Size Cros s-stre tch-in (cn. 5 Hosiery Stretch Yarn Out of Hose Yarn LCK Ankle asTO -ΗΗΠ7 Breaking Strengthlgm.) D-25 13.69(34.8) 10.50(26.7) 253.5 83.6 72.8 0-30 13.96(35.5) 10.67(27.1) 302.1 85.2 70.3 D-35 13.65(34.7) 10.47(26.6) 301.3 81.9 59.0 0-40 13.47(34.2) 10.25(26.0) 329.0 81.4 57.8 0-45 13.59(34.5) 10.28(26.1) 343.4 76.8 41.5 0-50 14.12(35.9) 10.62(27.0) 343.2 77.5 37.3 H-25 14.72(37.4) 10.72(27.2) 222.4 83.9 66.0 H-30 14.91(37.9) 10.96(27.8) 297.7 84.3 64.6 H-35 14.56(37.0) 10.66(27.1) 317.9 86.2 57.8 H-40 14.19(36.0) 10.41(26.4) 325.3 85.5 55.4 H-45 14.19(36.0) 10.25(26.0) 340.4 84.6 45.0 H-50 14.46(36.7) 10.67(27.1) 288.7 84.7 - Example 3 This example shows the effect of varying sheath core weight ratio. Samples J and K were prepared with a 6-12 sheath and a 6-12/6 core having 30% by weight 6 units as described for D-30 in Example 1 except for sheath/core weight ratio, which was varied by adjusting the flow rates of the tvzo melts into the spinneret assembly. Yam properties are reported in Table 10. sheath/core wgt. ratio Table 10 J K 45/55 35/65 Tenacity (gm./den.) 5.4 5.3 CE(%) 12.4 11.7 CS(%) 15.5 17.4 Denier (dtex) 15.6(17.3)15.5(17.2) Within the range investigated, sheath/core weight ratios have little effect on yarn properties. For hosiery filaments with the sheath at its thinnest point being about 1% of the filament diameter, maximum crimp frequency is obtained when the filament comprises about 50-60 percent by weight core polymer. Crimp frequency is not strongly dependent on percentage of core. Except at the lower extreme of the operable level for percentage of 6 nylon units in the core, filaments with 30-70% by weight core polymer can provide useful levels of crimp.

Example 4 This example compares 6//6-12/6 nylon yarns and hose with equivalently prepared 6-12//6-12/6 and 6-6//6-12/6 nylon yarns and hose. The RV's of the polymers, sampled just prior to entering the spinneret, were 4-3335 6-12/6 43 + 1.5 (65/35 weight ratio) 6-12 38.5 + 0.5 6 40.6 6-6 51.4 + 2.4 Melt temperatures were 260 + 3°C. for spinning fibers with 6-12 or 6 sheaths' and 287 + 3°C. for those with 6-6 sheaths. The appropriate two polymer flakes were separately melted in vacuum exhausted screw extruders and fed by separate meter pumps adjusted to provide 60% by volume of core polymer in each filament (which by calculation yields 58.7-59.0% by weight of core polymer) to a spinneret assembly indicated in Example 1. Monofilaments were spun, quenched, steam conditioned, and plied to 2-filament yarns just before windup of the undrawn yarns at 500 yd./ min. (457.2 m./min.). Cross-flow quenching air in a 60 in. (1.52 ra) long chimney was supplied at 49 + l’F. (9.4 + 0.5’C.). Steam conditioning was in a chamber 1.92 nt. long with saturated steam at atmospheric pressure.

The spun 2-filament yarns were subsequently drawn using an unheated draw pin located between feed and draw rolls. Draw ratio was 4.225X at a draw-roll speed of 590 yd./min. (540 m./min.). The drawn yarns were immediately packaged using a ring-and-traveler windup which inserted 0.335 turns of twist per inch (0.132 turns/cm,). Yarn properties obtained are shown in Table 11.

Hose were knitted and tested as described in Example 1 except that the load applied for HS and HR determinations was 2.77 kg. rather than 2.27 kg. The drawn-only yarns of Example 1 are nominally 16-denier, whereas the yarns of this example are nominally 20-denier.

The adjustment in load is proportional to the difference in yarn denier. Characterizations of the hose are presented in Table 12.

Except for the out-of-hose measured properties of Table 12, all recorded measurements are averages of samples from twelve yam packages for the 6 nylon sheath species and from six yam packages for the 6-6 and 6-12 nylon sheath species. Out-of-hose properties are measured for four hose of the 6 nylon sheath yarns and for two ) hose each of the yams witli 6-6 and 6-12 nylon Sheaths.

Table 11 Sheath Yarn Denier Tenacity (Ti (p,m,/den.) Broak Tenacity (T«) (gm./den.) CE CS dtex 6-12 21.5 4.8 6.3 194.6 21.3 23.9 6-6 22.2 4.3 5-5 143.8 16.3 24.7 6 22.2 5.4 6.5 147.6 21.3 24.7 Table 12 Hosiery Size Yarn Out of Hose Cross-stretch? In. (cm*) Hosiery Stretch Breaking Strength Sheath Leg Ankle IIS(S) nk(s) (Km.) 6-12 13.27(33.7) 10.27(26.1) 315.3 84.8 So.i 6-6 13.64(34.6) 10.77(27.4) 282.9 78.6 79.7 6 12.72(32.3) 9.88(25.1) 263.0 77.0 104.1' It is apparent from Tahle 12 tb^t, altho’ig*’ ; the hose of yarns with 6-12 nylon sheaths are superior, all three, species.provide excellent stretch properties.

Example 5 This example compares hose made from filaments * of the invention, with hose made from commercial biconponent - 22 _ ^3335 nylon filaments.

Additional cold drawn only* 2-filament yarns having a 6-12 nylon sheath and a 6-12/6 nylon core (70:30 weight ratio of 6-12 to 6) were prepared in a manner similar to that of Example 1.

The RV’s of the melted polymers were 36 and 42, respectively, and the weight ratio of sheath to core polymers was 40:60. Denier of the yarn was 23.4 (26 dtex).

A 30-denier 2-filament prior art control yarn was prepared by plying two 15-denier commercial bicomponent monofilaraents. The sheath is of 6-6 nylon forming 42% by weight, and the eccentric core is of 6-6/6-10/6-12 (50/31.5/18.5) forming the remaining 58% (6-10 identifies units of hexamethylene sebacanide). These monofilaments were prepared with precrimping substantially as described in Example VIII of U.S. Specification 3,3.99,108.

Properties measured for the test yarn and one ply of the control yarn are reported in Table 13.

Table 13 Test Control Tenacity (gm./den.) 5.6 4.6 (gm./dtex) 5.0 4.1 CE (%) 31.9 34.3 CS (%) 16.6 4.1 Ladies' medium-size, sheer, support pantyhose were circular-knitted to the same finished size from the two 2-filament yams. Finishing of the knit garments before wear comprised loose turnble-steaming at atmospheric pressure, conventional scouring and disperse dyeing and boarding on a medium board in a steam chest containing 220°F. (104.4°C.) saturated steam.

A panel of twenty women who normally wear sheer support hose wore the test pantyhose of this invention for five days. One pair failed before the end of the test, and one tester discontinued testing because of poor fit.

Of the remaining eighteen, sixteen found their pantyhose to fit well, and two rated their pantyhose too loose.

Twelve of the eighteen also rated their pantyhose as equivalent to or better than their usual support hose in terms of support provided.

A panel of nineteen of the above twenty women wore the control pantyhose for five days. There were two early failures, and three testers discontirted testing because of poor initial fit. Four of the fourteen who finished the test found their pantyhose to fit well, but . ten found they became too loose. Only five of the fourteen found the support provided equal to or better than that of their usual support hose.

Hosiery stretch (IIS) and hosiery recovery (HR) were measured for unworn pantyhose from the test yarn of this example (II D) and from an otherwise identical yarn (II P) which had been precrimped according to U.S. Specification 3,399,100. Pantyhose which had been worn for five days and which had been knit from the test yarn of this example (II D 5), from an otherwise identical but precrinped yarn (II P 5) and from the control yam (II C 5) were measured similarly. In these determinations, a 3.46 kg. load was applied at the foot-to-toe juncture. Average results for the two legs of each garment are reported in Table 14.

Table 14 HS, % HR, % II D 240 93 II P 184 84.4 II I) 5 277 94.3 II P 5 211 81.2 II C 5 171 87.3 Example 5 shows that hose made of yarns of the invention provide better fit than hose of commercial bicomponent nylon filaments. It also shows that as-drawn filaments of the invention provide better hosiery stretch than precrii.iped yarns of the invention, and that both of these provide better hosiery stretch than the precrimped commercial yarns.

Example 6 This example compares additional hose made from filaments of the invention with hose made from filaments according to U.S. Specification 3,399,108.

Additional yarns similar to those of Example 5, but having 8 filaments and a total denier of 15.6 (17.3 dtex), were prepared by a process wherein spinning, drawing and packaging were continuous but which was otherwise similar.

Averaged properties for this yarn, and for a control yarn as described below are reported in Table 15. Table 15 Test Control Tenacity (gm./den.) 6.0 3.7 (gm./dtex.) 5.4 3.3 CE (%) 6.3 29.0 CS (%) 11.6 4.4 Tiie control yarn is an 18.3-denier (20.3 dtex) 8-filament yarn prepared with precrimping as described in Example VIII of U.E. Specification 3,399,108. It has a 6-6 nylon sheath and a 6-6/6-10/6-12 (50/31.5/18.5) nylon core at a sheath/core weight ratio and eccentricity identical to the test yarn.

Pantyhose were knit using the above yarns for the leg portions. The panty portion is of commercial 50-denier 10-filament false-twist-textured 6-6 nylon yarn. Λ commercial 2-feed knitting machine producing a plain jersey stitch was used, and the number of courses and stitches per course are identical. In order to provide equal finished sizes for the legs from the two yarns, it is necessary to knit tho legs from the yarn of this invention with larger stitches, thus counterbalancing their higher shrinkage. The greige hose were dyed in a commercial disperse-dye bath, the control hose at 160°F. (71.1°C.) and the test hose at 210°F. (98.9°C.) for 45 minutes.

All hose were boarded on leg forms at 245°F. (118.3°C.) in a steam chest. The finished hose were of substantially equal size, as indicated by cross stretch measurements.

The hose from the test yams have a flatter appearance and are freer of visual defects than the control hose. A panel of twenty girls ranging in weight from 108 to 150 pounds (49 to 68 kg.) was selected to wear one pair of each type of hose for five days. Two of the testers found the panty portion of the tost hose to be too tight to wear. One pair of tiie control hose failed before completion of tiie test. The wearers rated each hose for fit. Results are reported in Table 16.

Table lfi Test Control Leg fit (initial/S-day)(initial/5-day) too tight 1/- -/- slightly tight -/- 1/- satisfactory 14/12 17/7 slightly loose 3/6 2/8 too loose -/- -/4 It is apparent that the test hose maintained their fit better than the control hose.

Crimp elongation (CE**) was measured on yarns removed from unworn hose (boarded at 118.3°C. for 45 min.), from hose worn for five days, and from two sets of hose identical in every way to the original unworn hose except for having been boarded in steam for 1 minute at 104.4 and 110.0°C., respectively. The values for CE** are reported in Table 17.

Table 17 CE**, Tests CE**, Control Boarded at 118.3°C. 99% 82% Worn 5 days 87% 73% Boarded at 110.0°C. 121% 82% Boarded at 104.4°C. 138% 77% It is apparent that lower boarding temperatures than used for tlie wear test hose yield even better stretch and that, for yarn removed from finished, hose, the test yarns are clearly improved over the control yarns. This improvement is completely unexpected in view of CE values obtained on the yarns before being knitted (Table 15). 335 DEFIHITIOHS AHD TEST DESCRIPTIONS 1. Relative Viscosity. Relative viscosity (RV) is the solution-to-solvent ratip of absolute viscosities at 25° + 0.05°C. For the 6-12 nylon and i> nylon reported herein, a 6.166 percent by weight solution of the polymer in a 50% formic acid (98%), 50% phenol solvent is used.

For the 6-6 nylon, the solvent is 90% by weight formic acid (10% water) and the polyner solution has 8.4% by weight polymer in the solvent. For the 6-12/G nylon core copolymer, either solvent can be used, but the values reported in these examples were obtained using formic acid/phenol. 2. Tensile Properties. These are calculated from measurements of a trace recorded on a stress-strain analyser. Sample length is ten inches (25.4 cm.) and elongation is at the rate of six in./min. (15.2 cm./min.). Before testing, packaged yarn is conditioned for at least 24 hours in a 72% RH, 25°C. atmosphere. Tenacity (T) is the load in grams at the point of failure divided by the denier of the packaged, conditioned yarn. Elongation (E) is the percent increase in length of the sample at the point of failure. Tenacity (Τβ) is the load in grams at the point of failure divided by denier at the point of failure. It is computed from: TQ = Td+E/100). 3. Crimp Properties. In the examples above, crimp properties were measured by three variants of the same general test method.

In the first variant, which has been for many years the standard form of this test, a 750 denier bundle of yarn is prepared by winding the requisite number of turns on a reel to yield a skein about 55 cm. long when suspended with a weight attached. The denier of the suspended skein will, of course, be twice that of the bundle, i.e,, 1500 denier. Initially, a 500 gm. weight is hung from the suspended skein. After one minute, length (a) of the skein is measured. The 500 gm. weight is then replaced with a 1.8 gm. weight to provide a tensile loading of 1.2 mg./den., i.e., a tension in excess of that usually experienced by the yarn in a knitted sheer fabric. The skein with the Weight attached is subjected to 100’C. steam at atmospheric pressure for two minutes, after which it is allowed to dry in air for ten minutes. Then, skein length (b) is measured. Finally, the 1.8 gm. weight is replaced by the 500 gi... weight and, after a one minute delay, skein length (c) is measured.

Crimp elongation (CL) is computed as CE(%) = 100(c-b)/b Crimp shrinkage (CS) is computed as CS('i) = 190(a-c)/a The second variant is used for yarn unraveled from finished hose. Crimp elongation (CE**) is determined by preparing a 45 meter skein having forty turns, allowing the skein to hang free for thirty seconds, hanging a 1.8 gram weight from the skein for about five minutes, recording its relaxed length L^, hanging a 300 gram weight on the skein, recording its extended lengtn L2 and computing CE** as 100(I^-L^)/Lp.

In the prior art, crimp elongation (CE) of a yarn lias been relied upon as an indication of stretch 13335 properties to be expected in knit hose. The higher the CE, tlie better is the anticipated stretch. Surprisingly, however, the yarns of this invention generally provide low Ch values, which do not predict their outstandingly improved stretch properties in hose. Accordingly, a modified test procedure (third variant) was developed which provides values of crinp properties which better correlate with the active stretch properties of hose.

In the third variant, a skein of yarn is formed from an integral number (n) of loops such that total skein denier (2nD, where D is denier of the yarn) is as close as possible to 2084. The suspended skein is 0.563 m. long Length Lo is measured and recorded for the skein suspended in air under a load of 695 gn. The heavy load is removed leaving only its aluminum support weighing 2.5 gn. The skein and attached support are suspended in water at 95°C. for one minute for crimp development. Due to water buoyancy, the support actually exerts only about 0.75 mg./den. of force on the skein during crimp development. Removed from the water, the skein dries in ambient air. Length L^ is then measured and recorded, the full 695 gm. load is reapplied, and extended length L2 is measured and recorded. CE* and CS* (the asterisk denoting this revised method) are computed as; CE* (%) = 100 (L2-L1)/L1 CS* {%) = 100 (lo-l2)/lo 4. Hosiery Properties. Hosiery stretch (IIS) and recovery (HR) are determined after suspending a leg portion of a pantyhose or hose from a clamp fastened at the weltto-leg juncture. First, initial length (Lo) is measured.

A load in grams of about 140D (where D is denier of a single leg yarn) is carefully applied to the toe and, after a minute, extended length (L^) is measured. Then, tiie load is removed suddenly and, after a minute, recovered length (L2) is measured. Hosiery lennths are measured from the clamp to the heel mar’; (the pantyhose of Example 5 have no heel mark and are measured to the toe juncture).

IIS (%) = 100 (Iq-Lo)/Lo HR {%) = 100 (L^L,)/(1^-1^) Tiie higher the IIS, the wider is tiie range of leg sizes a given hose can fit, i.e, fewer sizes of knit hose are required to fit the population of leg sizes. High values of HR indicate improved retention of fit.

Hosiery sizes are measured with a Hifonaco cross stretch tester (described in U.S. Specification 3,444,728). In Example 6 only, equivalent cross-stretch measurements are made using a Jones Tester (described in U.S. Specification 2,706,402). Cross-stretch as reported iierein is measured on finished, unboarded hose in the upper leg about four inches (10.2 cm.) below the shadow welt and at the ankle about two inches (5.1 cm.) above the heel mark. . dtex. The term dtex is an abbreviation for decitex, and is obtained by multiplying denier by 10/9. 6. precrimped. The term precrimped refers to yarn of one or more biconuonent filaments which has been drawn, crimped in a substantially tensionless state in a heated atmosphere and then stretched to remove the crimp before packaging. 7. as-drawn. The term as-drawn refers to yarn which has been drawn and packaged without precrimping.

Claims (32)

CLAIMS:

1. A drawn nylon filament comprising two continuous, adherent eccentric components, the first component being a sheath of polyhexamethylene dodecanedioamide, polyhexamethylene adipamide 5 or poly-e-caproamide and the second component being a core of a random copolymer of hexamethylene dodecandioamide units and e-capro amide units, the copolymer containing more than 25 and less than 45% by weight ε-oaproamide units.

2. A filament as claimed in claim 1 wherein the copolymer 10 contains from 30 to 40% by weight ε-caproamide units.

3. A filament as claimed in claim 2 wherein the copolymer contains about 35% by weight ε-caproamide units.

4. A filament as claimed in any of claims 1 to 3 wherein the core comprises from 30 to 70% by weight of the filament. 15

5. A filament as claimed in any of claims 1 to 4 comprising a sheath of polyhexamethylene dodecanedioamide.

6. A filament as claimed in any of claims 1 to 4 comprising a sheath of polyhexamethylene adipamide.

7. A filament as claimed in any of claims 1 to 4 comprising 20 a sheath of poly-ε-caproamide.

8. A filament as claimed in any of the preceding claims wherein the thickness of the sheath at its thinnest point is about 1% of the filament diameter.

9. A filament as claimed in any of the preceding claims in -5 crimped form.

10. A filament as claimed in any of the preceding claims having a tenacity at break greater than 5.0 gm/den.

11. A filament as claimed in claim 1 substantially as herein described. 10

12. A filament as claimed in claim 1 substantially as herein described in any of Examples 1 to 6.

13. A process for producing filaments as claimed in claim 1 wherein the two components are melt spun into filaments in an appropriate sheath/core relationship, the filaments subsequently -32being drawn.

14. A process as claimed in claim 13 wherein the filaments are drawn in the form of yarns to give yarns comprising at least one filament as claimed in claim 1.

15. A process as claimed in claim 13 or claim 14 wherein the filament or yarn is wound on an intermediate package prior to being drawn.

16. A process as claimed in claim 13 or claim 14 wherein the filament or yarn is advanced continuously to the drawing operation.

17. A process as claimed in any of claims 13 to 16 wherein the filament or yarn is subjected to a heating step to develop crimp.

18. A process for producing filaments as claimed in claim 1 or a yarn comprising at least one filament as claimed in claim 1 substantially as herein described.

19. A process for producing filaments as claimed in claim 1 or a yarn comprising at least one filament as claimed in claim 1 substantially as herein described in any of Examples 1 to 6.

20. A filament as claimed in claim 1 or a yarn comprising one or more filaments as claimed in claim 1 when prepared by a process as claimed in any of claims 13 to 19.

21. Yarns comprising two or more filaments as claimed in claim 1 when prepared by a process as claimed in any of claims 13 to 19.

22. A fabric comprising at least one filament as claimed in claim 1.

23. A fabric as claimed in claim 22' wharein the qr each filament as claimed in claim 1 is crimped.

24. A process for the preparation of a fabric as claimed in claim 22 which comprises knitting or weaving yarn comprising at least one filament as claimed in claim 1.

25. A process as claimed in claim 24 wherein the yarn is as claimed in claim 20 or claim 21. -33¢333 5

26. A process as claimed in claim 24 or claim 25 wherein the fabric is subsequently heated in order to develop crimp.

27. A fabric as claimed in claim 22 whenever prepared by a process as claimed in claim 24 or claim 25.

5. 28. A fabric as claimed in claim 23 whenever prepared by a process as claimed in claim 26.

29. A fabric as claimed in any of claims 22,23, 27 and 28 in the form of a knit garment.

30. A fabric as claimed in claim 22 substantially as herein 10 described.

31. A fabric as claimed in claim 22 substantially as herein described in any of Examples 1 to 6.

32. Staple fibers comprising portions of a filament as claimed in claim 1.