US3574908A

US3574908A - Production of a nonwoven fleece of continuous filaments

Info

Publication number: US3574908A
Authority: US
Inventors: Helmut Werner; Hans Stapp
Original assignee: Glanzstoff AG
Current assignee: Glanzstoff AG
Priority date: 1968-01-02
Filing date: 1968-12-26
Publication date: 1971-04-13
Anticipated expiration: 1988-04-13
Also published as: BE724768A; CH487284A; DE1760471A1; GB1245437A; LU57476A1; NL6818773A; FR1600672A; NL57476C; US3723238A

Abstract

Process for the production of a nonwoven fleece from continuous filaments of a spun and stretched polymer yarn, especially a yarn composed of continuous hollow tubular polyethylene terephthalate filaments, wherein the yarn having permanently crimped filaments with an individual denier of about 0.5 to 20 denier is subjected to a temporary elongation within the range or region of the stress-strain curve which produces an elastic strain but under a load of at least 0.1 grams/denier, the permanent extension or set of the filaments being less than 4 percent, and then releasing the tension on the yarn whereby the crimped structure of the filaments is reformed and the yarn spreads out laterally. The resulting product is useful as a filler material in pillows, quilts, jackets and the like.

Description

United States te Inventors Helmut Werner Appl. No.

Filed Patented Assignee Priority PRODUCTION OF A NON-WOVEN FLEECE OF CONTINUOUS FILAMENTS 13 Claims, 3 Drawing Figs.

U.S. Cl 28/72, 28/ 72.3

Int. Cl D04h 13/00 Field of Search 28/72, 1,

INITIAL CRIMPE D YARN Primary Examiner-Louis K. Rimrodt Attorney-Johnston, Root, O'Keeffe, Keil Thompson &

Shurtleff ABSTRACT: Process for the production of a nonwoven fleece from continuous filaments of a spun and stretched polymer yarn, especially a yarn composed of continuous hollow tubular. polyethylene terephthalate filaments, wherein the yarn having permanently crimped filaments with an individual denier of about 0.5 to 20 denier is subjected to a temporary elongation within the range or region of the stress-strain curve which produces an elastic strain but under a load of at least 0.1 grams/denier, the permanent extension or set of the filaments being less than 4 percent, and then releasing the tension on the yarn whereby the crimped structure of the filaments is reformed and the yarn spreads out laterally. The resulting product is useful as a filler material in pillows, quilts, jackets and the like.

Patented A ril 13, 1971 2 Sheets-Sheet 1 mvwv'mus: HELMUT WE RNER H AN S STA P P BYE Patented April 13, 1971 2 Sheets-Sheet 3 FLEECE WEB FLEECE 'vsas IN VHN'IUKS. HELMUT WERNER. HANS STAPP ATT'YS PRODUCTlON OF A NON-WOVEN FLEECE F CONTINUOUS FILAMENTS Cushions, pillows and quilted articles, such as quilted blankets, anoraks and the like have been filled with nonwoven synthetic fibrous fleeces consisting of staple fibers and also with nonwoven fleeces which consist of endless or continuous filaments. Such fleeces of continuous filaments are preferably manufactured by spinning a synthetic fiber-forming polymer from multiapertured spinning heads so that the filaments, preferably after being drawn or stretched, are accumulated on a suitable base or support means. Texturizing or bulking of the filaments is usually carried out either by subjecting the filaments to a turbulent blowing or by applying an electrical field before collecting the filaments into a fleecelike web.

One object of the present invention is to provide a voluminous fleece or filler which can be used for filling cushions, pillows, or the like and which are nonwoven fibrous webs or planar structures, preferably made up in layers or in the form of a coil or roll..ln particular, it is an object of the invention to provide a process for the production of a nonwoven fleece composed of continuous fiber-forming thermoplastic filaments by using an initially spun and stretched yarn in which the filaments have already been given a permanent crimp, preferably by mechanical means'such as a conventional stuffing box. Yet another object of the invention is to provide a process for producing such a fleece which is easily carried out and which produce a novel effect in laterally spreading out the crimped filaments into a more useful nonwoven sheet or web of crimped continuous filaments. Other objects and advantages to the invention will become more apparent upon consideration of the following detailed description of the process of the invention and the product achieved thereby.

It has now been found in accordance with the invention, that a valuable improvement can be achieved in a process for the production of a nonwoven fleece from continuous filaments of a synthetic fiber-forming polymer if the initially spun and stretched yarn made of permanently crimped individual filaments having an individual titer of 0.5 to 20 and preferably about 3 to 8 denier and a crimping are number of from 50 to I50 and preferably about 65 to I20 arcs per l0 cm. is subjected to a temporary elongation sufficient to bring the individual filaments within the range of elastic strain under a load of at least about 0.l grams/denier, and the tension on the yarn is then partially or completely released but to an extent sufficient to reform the crimped structure of the individual filaments and to permit the yarn to spread out laterally. In general, the load producing the required elongation should amount to about 0.1 to l g./den., depending upon the particular synthetic filaments, i.e., after relaxation of the tension, should be less than 4 percent and preferably'less than 3 percent.

When it is desired to produce very bulky and voluminous nonwoven webs or fleeces, an extremely advantageous initial yarn is one composed of polyethylene terephthalate hollow tubular filaments which have a hollow volume of 10-30 percent, preferably 12-25 percent, with reference to the total volume of each individual filament, i.e., each filament preferably has a uniform annular cross section with the hollow central portion being not more than about 30 percent of the total cross-sectional area of the filament.

The expression range of elastic strain" should be understood throughout this specification and claims to mean that region of the stress-strain curve which extends up to a specific load value of the individual crimped filaments, this load value being that at which an identical but uncrimped yarn exhibits a permanent extension below 4 percent. This elastic elongation," i.e., that increment or region of elongation where the filament remains almost completely elastic except for a small amount of permanent extension. The optimum loading and with it the degree of elongation, varies for different types of polymer filaments, but may be readily determined by a few preliminary tests. This optimum effect is achieved for purposes of the present invention when the yarn or tow of crimped continuous filaments, after a temporary elongation, spreads apart to form a nonwoven fibrous web or fleece of maximum width. The maximum specific loading may be considered to be the load value at which the crimp of the yarn, after removal of load, still just reforms or springs back along the yarn. However, it is generally advisable to keep the load below this maximum loading value.

When using polyethylene terephthalate filaments, the temporary elongation is preferably carried out using such a load that the permanent extension or set produced in the yarn is less than 3 percent and most preferably less than 1.5 percent. However, the load must be at least Oil g./den.

With polyethylene terephthalate tubular filaments which have an individual filament titer of 0.5 to 20 den., preferably 3 to 8 den. and a crimping arc number of 60 to 150 per l0 cm., preferably to l50 per l0 cm., a load of 0.1 to l p/den. has been found satisfactory and produces adequate results; however, by using a load of about 0.5 to 0.8 g./den., extremely good results can be obtained. Continuous linear polyester filaments and particularly polyethylene filaments which have been spun in a conventional manner to provide a hollow tubular structure, e.g., with a hollow volume of l030 percent, preferably 12-25 percent, as defined above, may have a relatively wide range of crimping arc number, depending on the end use of the fleece. For example, as a fleece for filling cushions or pillows in the form of a coiled or layered web or the like, it is sufficient to provide a permanent crimping of these hollow tubular filaments of about 50 to l20 arcs per 10 cm., preferably about 65l00 arcs per 10 cm. When used as a voluminous fleece for filling quilted articles, e.g., in the form of a single sheet or web of fleece, these same are numbers are also quite suitable. Such crimping can be readily produced by conducting the initially spun and stretched hollow tubular filaments through a conventional stuffing box.

The process and products of the invention are not limited, however, to these initial polyester materials. If the nonwoven fibrous webs or fleeces are to be further processed in order to produce a lining material or insert of minimum thickness or a nonwoven textile fabric where the bulk or voluminosity of the web is less important, then yarns or tows made from polyamides, polypropylene or other synthetic fiber-forming polymers may also be used to great advantage. The chemical structure of the polymers being used, including stereoregulation, and any pretreatments to which the filaments have been subjected during their manufacture naturally have an effect on the process. Thus, for example, the spinning conditions, the nature and degree of the drawing for molecule orientation and the crimping to which the filaments have been subjected affect the final product. These factors must be considered whenselecting the process conditions and when trying toproduce certain properties in the final product.

However, the broad ranges recited herein are generally applicable to all such fiber-forming .polymers, and by following the specific elongation and relaxation steps defined herein while carefully controlling the amount of load during elongation to avoid exceeding the elastic limit, one can easily determine the optimum affect in terms of producing a maximum width or spreading apart of the fleece web or band.

One important influence on the process according to the invention is the degree of crimping, i.e., the number of crimping arcs per unit of length. It does not matter what kind of crimping is used or how the crimping has been obtained. For example, yarns crimped in a stuffing box, which exhibit a so-called two-dimensional crimp, are especially useful, but the process may also be applied very successfully to filaments which have a three-dimensional crimp. Such filaments or yarns are obtained, for example, by spinning two chemically or physically different polymers using special nozzles, to produce so-called-composite threads or filaments.

The individual filament titer or denier may vary within relatively wide limits and must ordinarily be chosen to suit the intended application or area of utility of the fleece. Likewise,

terephthalate the choice of initial filament materials depends on the end use of the fleece. Very good results are obtained using threads or filaments of all types which have an individual filament titer of 3 to 8 denier.

The spreading out or lateral separating effect is most strongly influenced by the degree of elongation which, according to the process of the invention, must take place in the region of elastic strain but under a load of at least 0.1 g./den. At the lower and upper limits of the region of elastic strain or the amount of loading, the spreading apart of the crimped filaments is usually only slight but a temporary elongation within such limits is still reasonably within the scope of the invention in terms of a distinguishing effect.

When the loading force tension of the elongation acts on a yarn of crimped filaments, the crimp first disappears" by becoming latent and the yarn as well as the individual filaments appear to be almost smooth before the filaments are subjected to the elongation or elastic strain. It is desirable, prior to the device which elongates the yarn within the region of elastic strain, to arrange an apparatus in which elongation may take place predominantly within the region of crimping elongation, i.e., simply to straighten out" the crimp. For example, conventional braking devices are suitable for this purpose.

The width of the nonwoven web or fleece which is produced depends, naturally, on the number of individual filaments of the yarn or two being used. This number of individual filaments, depending on the purpose for which the product is intended, may be for example between 3,000 and 30,000 or more.

The process is not limited to the use of any specific apparatus, although devices in which the elongation of the yarn is accomplished between triple or quadruple rollers, i.e., a series of draw rolls, have been found to be particularly suitable. Such devices must allow for the accurate adjustment and maintenance of the low degrees of tension which are necessary to provide a relatively low load. After the drawing step, the yarn maybe completely released of tension and taken off or accumulated in a tensionless condition. However, as a rule it is usually more convenient to guide the treated yarn, after the second set of draw rolls, over an additional takeoff device behind which a traversing device can be arranged.

The handling of the yarn between the second set of draw rolls and the takeofi' device may be varied within wide limits. Thus, for example, it is possible to release the tension in the treated yarn completely or only partially, so that the elastic strain and, where appropriate, the crimp, is able to relax or reform entirely or partially. In this situation, the spreading out effect is produced in the yarn in this relaxing zone, the extent of this effect depending on the lessening of the tension. The elongation of the yarn according to the invention may also be accomplished in two stages, e.g., if the peripheral velocities of three roller units are in sequence v v and v then one maintains relative speeds in which v v v applies. In such a case, it is desirable to effect the major proportion of the elongation in the first drawing zone. As soon as the yarn has left the last guide means, the complete spreading apart to form the nonwoven yarn structure of greater width takes place as already mentioned. At the same time, the crimping arcs again jump" back into position, i.e., the crimped structure simultaneously reappears.

In the accompanying drawings:

FIG. 1 is a partially schematic side elevational view of apparatus which is suitable for carrying out the process of the invention;

FIG. 2 is a perspective view of a coiled fleece web as one preferred type of nonwoven product obtained by the process of the invention; and

FIG. 3 is an enlarged perspective view of a small section of another type of nonwoven product obtained by the process of the invention.

The process of the invention will now be explained in detail by an example taken with reference to FIG. 1 of the accompanying drawing.

EXAMPLE Polyethylene terephthalate having a solution viscosity (1 of I .60, measured as a l percent solution of the polymer in mcresol at 25 C., is spun through a l-aperture nozzle or spinning head to produce a hollow tubular filament yarn. The yarn is drawn, i.e., stretched, in a conventional manner under an atmosphere of steam maintained at C. (draw ratio l:4. l and the stretched filaments are subsequently crimped in a stuffing box. The resulting yarn exhibits the following properties:

Strength 47.7 Rhm. (5.3 g./den.)

Elongation 45 percent Hollow volume approximately 12 percent Individual titer= 5.5 denier Crimping are number I00 arcs per 10 cm.

(The crimping are number is counted on a large number of filament lengths which have been loaded with a weight of 3 mg., the observed arcs being those variations considered to be any marked change in direction; i.e., a sine curve would correspond to two crimping arcs).

Referring now to FIG. I, this initial polyester crimped yarn is fed from a supply container 1, via a torsion bar brake 2 and the deflecting rods 3 and 4 to a set of three rollers 6. Arranged just before the latter is a yarn guide 5 which is particularly advantageous for the purpose of initially spreading out or positioning a large number of individual filaments into a web or band of minimum width. The peripheral velocity of the rollers of the set of three rollers 6 is 60 m/min. The yarn is elongated between the triple roller arrangement 6 and a second more rapidly rotating triple roller arrangement 7, by between 8 percent and I0 percent. The tension applied by this drawing operation corresponds to a loading of 0.75 g./den. After leaving the triple rollers 7, the yarn is then guided over two rods 8 to a pair of rollers 9, the peripheral velocity of which corresponds to that of the triple roller arrangement 7. Behind or after the pair of rollers 9, the yarn quickly spreads out with a complete release of tension to form a nonwoven fibrous web or fleece having a width of approximately 55 cm. and is deposited, by means of a simple traversing device 10 in a collecting carton-or box 11.

Instead of the receiving container I1 shown in FIG. I, it is also possible of course to use other collecting or takeup devices. Thus, for the manufacture of a filler for cushions, pillows or pads, the nonwoven fibrous web is wound loosely, e.g., on a reel or spindle either from the supply container shown or directly after leaving the takeoff rolls 9 as described. The nonwoven web or fleece may also be deposited in a number of relatively flat layers one above the other. The filling elements for cushions or the like, which are manufactured in this way and illustrated by way of example in FIG. 2 of the when the nonwoven fibrous fleeces are used in coiled form or as a number of layers, it is possible by inwardly folding the front or end portions of the nonwoven fibrous web to prevent any of the free filament ends from being disposed on the surface of the filler so that they cannot project through the covering or outer fabric of the filled article. However, even if such steps are not taken, any danger that the yarn or filament ends might project through the covering of a cushion or similar article is much less than when the filling material consists of staple fibers. FIG. 2 merely shows a cushion filling in the form of a wound or coiled web of the fleece.

When manufacturing quilted articles, it is possible,

depending on the desired result, to use thicker or thinner nonwoven fibrous webs. For quilts or sleeping bags, for example, a number of nonwoven yarn structures can be disposed in layers one above the other, whereas for protective and lightweight garments, thinner nonwoven fibrous webs are generally preferred. The filaments may all extend substantially in the same direction or they may form any desired angles with each other by cross laying. FIG. 3 shows a sector of a filler for a quilted article, in a highly enlarged perspective view, which has been formed by cross-laying of individual fleece bands or webs.

Further tests have shown that the procedure of the invention is also applicable to a wide variety of nonwoven fibrous webs or fleeces produced from other fiber-forming polymer or from mixtures of continuous thermoplastic crimped filaments. The nonwoven fleeces of the invention are especially distinguished by a substantially complete absence of broken or otherwise severely distorted filaments aside from the intentional permanent crimping which retains practically its original capacity for crimp contraction. At the same time, one achieves a much more voluminous fleece or web than could have been expected from the relatively mild processing conditions of the invention.

On the other hand, the fleece webs of the invention are also distinguished by a good coherence, and if desired they can be further impregnated with a bonding agent or otherwise bonded together to form a more rigid but highly flexible and porous fibrous structure.

We claim:

1. Process for the production of a nonwoven fleece from continuous filaments of a synthetic fiber-forming polymer which comprises: subjecting a spun and stretched yam made of permanently crimped individual filaments having an individual titer of 0.5 to denier and a crimping arc number of from 50 to 150 arcs per l0 cm. to a temporary elongation sufficient to bring the individual filaments within the range of their elastic strain under a load of at least 0.l grams/denier; and then releasing the tension on the yarn sufficiently to refonn the crimped structure of the individual filaments and to permit said yarn to spread out laterally.

2. A process as claimed in claim 1 wherein said yarn is made of polyethylene terephthalate filaments.

3. A process as claimed in claim 2 wherein the permanent extension produced by said elongation of the yarn within the range of elastic strain is less than 4 percent.

4. A process as claimed in claim 1 wherein the individual filament titer is between about 3 and 8 denier.

5. A process as claimed in claim 1 wherein the crimping are number is between about 65 and arcs per 10 cm.

6. A process as claimed in claim 1 wherein said yarn is made from hollow tubular filaments in which the hollow volume amounts to about 10 to 30 percent of the total volume of each individual filament.

7. A process as claim 6 wherein said hollow tubular filaments are polyethylene terephthalate filaments.

8. A process as claimed in claim 7 wherein the permanent extension produced by said elongation within the range of elastic strain is less than 3 percent.

9. A process as claimed in claim 1 wherein the yarn made from hollow tubular filaments of polyethylene terephthalate is subjected to elongation under a load of between about 0.1 and l g./den. and the hollow volume is about 10 to 30 percent of the total volume of each individual filament.

10. A process as claimed in claim 9 wherein the hollow volume is between about 12 and 25 percent of the total volume of each individual filament.

11. A process as claimed in claim 9 wherein said elongation of the yarn is carried out under a load of between about 0.5 and 0.8 g./den.

12. A process as claimed in claim 9 wherein said filaments have an individual titer of between about 3 and 8 denier.

13. A process as claimed in claim 12 wherein the permanent extension produced by said elongation of the yarn within the range of elastic strain is less than 1.5 percent.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. D t d 13,

Helmut Werner et al. Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, lines 68 and 69, "'elastic e1ongati0n" shoL read "elastic strain" is also sometimes referred to as the "elastic elongation" Signed and sealed this 17th day of August 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, Attesting Officer Commissioner of Paten

Claims

2. A process as claimed in claim 1 wherein said yarn is made of polyethylene terephthalate filaments.
3. A process as claimed in claim 2 wherein the permanent extension produced by said elongation of the yarn within the range of elastic strain is less than 4 percent.
4. A process as claimed in claim 1 wherein the individual filament titer is between about 3 and 8 denier.
5. A process as claimed in claim 1 wherein the crimping arc number is between about 65 and 120 arcs per 10 cm.
6. A process as claimed in claim 1 wherein said yarn is made from hollow tubular filaments in which the hollow volume amounts to about 10 to 30 percent of the total volume of each individual filament.
7. A process as claim 6 wherein said hollow tubular filaments are polyethylene terephthalate filaments.
8. A process as claimed in claim 7 wherein the permanent extension produced by said elongation within the range of elastic strain is less than 3 percent.
9. A process as claimed in claim 1 wherein the yarn made from hollow tubular filaments of polyethylene terephthalate is subjected to elongation under a load of between about 0.1 and 1 g./den. and the hollow volume is about 10 to 30 percent of the total volume of each individual filament.
10. A process as claimed in claim 9 wherein the hollow volume is between about 12 and 25 percent of the total volume of each individual filament.
11. A process as claimed in claim 9 wherein said elongation of the yarn is carried out under a load of between about 0.5 and 0.8 g./den.
12. A process as claimed in claim 9 wherein said filaments have an individual titer of between about 3 and 8 denier.
13. A process as claimed in claim 12 wherein the permanent extension produced by said elongation of the yarn within the range of elastic strain is less than 1.5 percent.