Crimped multifilament yarn

United States Patent Office 3,423,923

Patented Jan. 28, 1969

423 923

CRIMPED MULTIFILAMENT YARN Harold F. Hume, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware 5

No Drawing. Filed Oct. 29, 1965, Ser. No. 505,758

U.S. Cl. 57—140 4 Claims

Int. Cl. D02g 3/02; D04h 17/00; D05c 15/00

ABSTRACT OF THE DISCLOSURE

A yarn composed of multiple crimped filaments of at least two longitudinally extending adherent components, the crimp elongation of the yarn increasing by at least 10% of the original value when the yarn is wet and dried. This yarn is produced by simultaneously extruding at least two fiber-forming synthetic components to form a plurality of composite filaments, gathering and drawing the filaments to form a yarn, subjecting the yarn to heat treatment under low tension to partially ²⁰shrink the yarn and cooling the yarn to avoid removing the resulting crimp.

This invention relates to improved composite filaments 25 and to a process for their production.

Composite filaments are well known. Such filaments usually consist of at least two different longitudinally extending components which are usually arranged in an eccentric manner with respect to the filament axis so 30 that the differing shrinkage propensities of the components result in the formation of a crimped fiber when the filament is appropriately treated, e.g., with hot water; such filaments are produced by extruding the components in a side-by-side or sheath-core relationship. 35

In most cases, the composite filaments are maintained in the straight or substantially straight configuration until they are processed into a fabric, the fabric then being subjected to heat treatment to crimp the filaments and thereby produce a certain degree of bulkiness which en- 40 hances the covering power and aesthetics of the fabric. In some cases it has been found desirable to employ side-by-side composite filaments in which the components split apart in the fabric. Although the composite filament yarns of the prior art have contributed to improved fabric 45 aesthetic, further improvements, particularly in covering power and hand, are desired.

It has now been found that further improvements in fabric aesthetics may be obtained by the use of a novel composite filament yarn comprising crimped filaments 50 consisting of at least two longitudinally extending, adherent components selected from the group consisting of fiber-forming polyamides and polyesters and copolymers thereof, the filaments being characterized by a crimp diameter of 2 to 25 mils (0.05-0.64 mm.), a frequency 55 of 5-100 crimps/inch (2-40 crimps/cm.), a crimp elongation of 3 to 35%, the crimp elongation increasing by at least 10% of the original value when the yarn is wet and dried. The crimped yarn is then converted into a fabric and the fabric subjected to heat and moisture 60 to further shrink the filament components and thereby increase the bulkiness of the fabric.

The novel yarn of this invention may be prepared by a process comprising simultaneous extrusion of at least two different fiber-forming synthetic polymers selected 65 from the group consisting of polyamides and polyesters and copolymers thereof to form a plurality of composite filaments, each filament comprising at least two longitudinally extending, adherent components which differ in shrinkage potential; gathering and drawing the fila- 70 ments to form a yarn and subjecting the yarn to heat treatment under low tension, the time, temperature and degree of relaxation being adjusted to partially shrink the filament components thereby producing a spiral crimp in the filaments.

The filaments and yarns of this invention retain a certain amount of crimp under the tension employed in weaving and knitting the fabric so that the yarn is slightly bulky as woven into the fabric. This results in a greater degree of matrix freedom in the fabric so that when the filaments are further crimped by suitable treatment, the maximum bulking effect is obtained. These characteristics permit preparation of extremely uniform fabrics having unusual bulk, cover, appearance, handle and functional characteristics. Such fabrics are extremely desirable in various types of wearing apparel.

In one very desirable embodiment of this invention, the filament components are selected so that after developing additional crimp, the filaments split apart when subjected to vigorous agitation in hot aqueous solution. In this embodiment, components must, of course, lie in side-by-side arrangement.

It is important that the crimp dimensions and frequency fall within the previously specified limits in order that the yarn may process satisfactorily. Also, it is important that only part of the total shrinkage potential of the higher shrinking component of the filaments be developed prior to fabric preparation; otherwise, the maximum bulking effect cannot be had.

In order to produce a yarn which develops the desired type of crimp, the processing conditions must be adjusted carefully. The yarn must be given a relaxation treatment with sufficient heating to shrink the yam about 5 to 13%. Excess heating over and above that needed to shrink the yarn sufficiently to produce smooth running on the processing rollers should be avoided. Tension in this step should be below about 0.01 g.p.d. The tension in the relaxation step can be regulated by adjusting the temperature to which the yarn is heated prior to drawing, the relaxation temperature or the degree of relaxation. These variations must be adjusted to give the desired crimp. Also, the yarn should be allowed to cool before it is wound into a package to avoid loss of crimp.

The expression “relative viscosity,” as used herein, signifies the ratio of the flow time in a viscometer of a polymer solution relative to the flow time of the solvent by itself. Measurements of relative viscosities given in the examples were made with the following solution: 5.5 grams of polyamide in 50 ml. of 90% formic acid at 25° C., or 2.15 grams of polyester in 20 ml. of a 7/10 mixture of trichlorophenyl/phenol at 25° C.

The crimp elongation of the yarn is determined as follows: A 10,000 denier skein is prepared by winding the yarn under a tension of 0.1 g.p.d. on a yarn skeiner having a reel circumference of 112.5 cm. The length of the skein (a) under a load of 0.0015 g.p.d. and the length (b) under a load of 0.1 g.p.d. is measured. Crimp elongation is calculated from the equation

CE=100(ft-a)/a

The crimp elongation after wetting is determined by placing the skein, prepared as above, in an aqueous solution consisting of distilled water containing 0.01% Duponol ME (a fatty alcohol sulfate) at about 25° C. for 15 minutes. The skein is removed and placed on absorbent paper for a few minutes to remove excess water and allowed to air-dry. The crimp elongation is then determined as described above.

The following examples are intended to illustrate the invention. They are not intended to limit it in any manner.

Example 1

Using a spinneret assembly of the type described in Example I of British Patent 950,429, polyhexamethylene

3,423, 3 adipamide having a relative viscosity of 35 and polyethylene terephthalate having a relative viscosity of 29 are extruded in side-by-side relationship to form 34 composite filaments of round cross-section having a drawn denier of 98, the filaments consisting of 40% by weight 5 polyethylene terephthalate and 60% by weight poly hexamethylene adipamide. The filaments are air quenched, wound into a package in the conventional manner and then drawn 3.9 times their extruded length on a drawtwister. In drawing, the yarn is passed from a feed-roll ₁₀to and around an unheated draw-pin, with two passes around the pin, then to a stepped draw-roll where it passes three times around the larger diameter portion of the roll and an associated separator-roll, the yarn passing at about 600 yards per minute, in contact with a 3-inch hot 15 plate heated to 100° C. between the draw-roll and the separator-roll. The yarn is then given two passes around the smaller diameter portion of the draw-roll and around the separator-roll and contacts a 100° C. hot plate where it is permitted to retract 9% in length. The yarn, without 20 further heating after retraction, is then wound into a package under low tension. The yarn, when removed from the package, has a crimp elongation of 10%, a crimp diameter of 10 mils and a crimp frequency of 30 crimps per extended inch. When the yarn is wet and then 25 dried as described above, the crimp elongation increases to 15-20%.

Knitted tubing is prepared from the above yarn in the conventional manner. In finishing, the tubing is immersed in an aqueous scouring 'bath containing by weight 0.5% 30 of Duponol D (a fatty alcohol sulfate scouring agent) and 0.1% trisodium phosphate. The bath is then brought to a boil and boiled for about 15-30 minutes. After finishing, the tubing has a dry, crisp, cotton-like hand.

Woven fabric was also prepared from the above yarn 35 and finished as described above. After finishing these fabrics exhibited high bulk, high cover, and good uniformity.

Example 2

Polyhexamethylene adipamide having a relative vis- ⁴θ cosity of 46.9 and polyethylene terephthalate having a relative viscosity of 28.9 in the original polymer and 24.9 after extrusion are prepared in the conventional manner except that an antistatic agent is added to the 6-6 polymer during polymerization. The antistatic agent employed is 45 polyethylene oxide capped with nonyl phenol and containing about 30 ethoxy units.

This compound is added as a 30% aqueous solution to the stirred autoclave in sufficient amount to give 2.5% by weight based on the weight of the final polymer. The 50 polymers are melted separately in screw melters and the melts fed to the holes of a spinning assembly of the type shown in FIGURE 1 of U.S. Patent No. 3,095,607, in which the bottom plate is provided with 17 Y-shaped orifices. The two polymers are fed to the spinneret holes in 55 side-by-side relation in a ratio by weight of 40% polyamide and 60% polyester. The composite filaments have a trilobal cross-sectional shape of the type disclosed in FIGURE 11 of U.S. 2,939,201. The cross-section is characterized by a modification ratio of about 2.1. The poly- 60 amide portion of the cross-section is ribbon-shaped and the polyester portion bell-shaped. The filaments are airquenched in the conventional manner and wound into the package at a speed of 1200 y.p.m. The yarn is drawn on a modified drawtwister wherein the yarn, at about 300 65 yards per minute, is passed from the feed roll to a pair of driven rolls of the same diameter with a heating element situated between the two rolls. The yarn is given six passes around the roll and contacts the smooth surface of the heating element, which is heated to 116° C., 70 for about 3 inches on either side of the heater. The yarn is then given one wrap around a draw-pin and passed to a draw-roll and its associated separator-roll for seven passes. The yarn is drawn to a ratio of 3.45. The yarn is then passed to a roll of sufficiently smaller diameter 75 to permit the yarn to retract 7.5% in length. The yarn is given 6 passes around the roll and its associated separator-roll. A 4-inch long hot shoe is provided between this roll and the separator-roll to heat the yarn as it passes around the roll, the temperature of the hot shoe being 132° C. The yarn is then given 6 passes around another roll of the same diameter to permit it to cool and wound into a package in the conventional manner under a tension of 0.15 g.p.d. The final denier of the yarn is 92. When the yarn is removed from the package and examined, the crimp diameter is found to be 8 to 14 mils and the frequency 22 to 33 crimps/inch. The crimp elongation under a load of 0.0015 g.p.d. is 3.2%. Crimp elongation increases to 9.2% when the yarn is wet out and thereafter dried as previously described.

A broadcloth fabric is woven from the yam (without wetting) and finished as described in Example 1. The fabric is then napped to produce a surface fuzz. It is then subjected to a second scouring at the boil, the fabric being agitated in a relaxed state in a scouring bath containing 0.5% by weight of Duponol D for 30 minutes. The fabric is then dried in a relaxed condition at 250° F. and heat-set at 400° F. The resulting fabric has a very desirable cotton-like hand, while retaining the functional advantages of the synthetic fiber. The bulk and covering power of the fabric are substantially greater than that of a fabric prepared in an identical fashion except that the yarn is processed so that the filaments do not crimp prior to fabric preparation. Examination of the fabric indicates that the filaments have split apart to great extent during fabric finishing.

The yarns of this invention have the advantage that they possess a microcrimp which is at least partially retained under the tension imposed in weaving so that the individual yarn ends in the fabric are not held as tightly in place in the woven structure as is the case for straight yarns. As a result, the individual filaments are able to move in the structure somewhat more freely than is normally the case when additional crimping or splitting of the filaments occurs.

While the yarns of this invention are particularly suitable for preparation of woven fabrics, they may also be used to advantage in knitted fabrics. Continuous filament yarns may be employed or the filaments may be cut into staple lengths for utilization in fabrics or in other end uses such as in carpets.

In addition to the polymers exemplified, other suitable polyamides and polyester combinations may be utilized in carrying out this invention. Suitable polymer pairs for extrusion of multi-component filaments of this type include poly(hexamethylene adipamide) in combination with poly(p-xylylene azelamide), poly(2,5-dimethyl hexamethylene terephthalamide), the polymer prepared from 1,4-aminomethylcyclohexane and isophthalic acid, polymers prepared from bis(4-aminocyclohexyl)methane and azelaic, sebacic, undecanedioic, or dodecanedioic acids or copolymers from hexamethylene diamine and a mixture of terephthalic and isophthalic acids; or poly (ethylene terephthalate) in combination with copolymers prepared from hexamethylene diamine, adipic acid and caprolactam or copolymers prepared from ethylene glycol and a mixture of sebacic and terephthalic acids; or the copolymer of hexamethylene diamine and a mixture of isophthalic and terephthalic acids in combination with the copolymer from hexamethylene diamine and a mixture of adipic and terephthalic acids.

Preferably, the filaments are of non-round cross-secion, cross-sections of heart shape, cruciform shape, multilobal shape (Examples IV and V and the shield shapes of U.S. Patent No. 2,939,202) being superior to round cross-sections. Improvement in fabric luster and hand are realized by the use of such non-round cross-sectional shapes. The optimum shapes for this purpose appear to be the trilobal shapes disclosed and claimed in U.S. Patent No. 2,939,201, those having modification ratios

3,4: 5 of 1.8 to 3.0, tip radii of 0-0.5 and lobe angles of 0-60° being particularly desirable.

The yarns of this invention preferably contain a durable antistatic agent. The antistatic agent should be present in a concentration of at least 2% by weight of the filament and may be added to either or both of the polymeric compositions used in producing these yarns. Suitable antistatic agents include the high molecular weight poly(alkylene ethers), i.e., those in the molecular weight range of 1300 to 200,000. Use of such materials is taught in British Patent No. 963,320.

Many equivalent modifications will become apparent to those skilled in the art from a reading of the above without a departure from the inventive concept.