AU713528B2

AU713528B2 - Stretchable nonwoven fabric and method for making it

Info

Publication number: AU713528B2
Application number: AU40491/95A
Authority: AU
Inventors: Tsutomu Kido; Hisashi Takai
Original assignee: Unicharm Corp
Current assignee: Unicharm Corp
Priority date: 1994-12-28
Filing date: 1995-12-18
Publication date: 1999-12-02
Anticipated expiration: 2015-12-18
Also published as: AU4049195A; JP3217630B2; KR960023377A; KR0139436B1; TW285691B; JPH08188950A; SA96160549B1

Description

i

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Uni-Charm Corporation Actual Inventor(s): Hisashi Takai Tsutomu Kido Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: STRETCHABLE NONWOVEN FABRIC AND METHOD FOR MAKING IT Our Ref 436182 POF Code: 1647/76530 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1-

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STRETCHABLE NONWOVEN FABRIC AND METHOD FOR MAKING IT The present invention relates to a stretchable nonwoven fabric and, more particularly, to a stretchable nonwoven fabric suitable for surface materials for sanitary articles such as disposable diapers and menstruation pads and a method for making it.

o Techniques by which a desired stretchability is given to a nonwoven fabric are well known. For example, it is well known to intertwine elastomeric stretch yarns such as urethane yarns and thereby to form a stretch nonwoven fabric.

It is also well known to thermally treat a web composed of heat crimpable fibers and thereby to obtain a stretch nonwoven fabric. In addition, it is also well known to bond stretch members integrally to a nonwoven fabric and thereby to obtain a stretch composite nonwoven fabric. In these well known techniques, the fibrous web is subjected to a needle punch treatment or a high pressure water jet treatment to achieve a desired mechanical intertwinement of the fibers or the fibers are intermittently welded together if the fibers are of heat-sealable nature. Sometimes, hot melt adhesive or heat-sealing technique is employed to bond the stretch members to the nonwoven fabric.

However, the nonwoven fabric employing the elastomeric stretch yarns is unsuitable for undergarments or sanitary articles destined to be put in direct contact with a wearer's skin, since the elastomeric stretch members inevitably deteriorate the touch. The nonwoven fabric composed of heat crimped fibers is disadvantageous with respect to a material cost, since its elastic coefficient for stretching can be improved only by increasing a thermally crimpable fiber content of relatively high unit price to achieve a high fiber density. The nonwoven fabric having the stretch members bonded thereto is accompanied by disadvantages that the gathers are inevitably formed as the members contract, such gathers sometimes obstruct the articles to be smoothly worn and bonding of the stretch members to the nonwoven fabric often deteriorates the touch of the nonwoven fabric.

Accordingly, it would be desirable to solve the above-mentioned problems by subjecting a laminate including upper and lower fibrous webs and 0:00 OO0e elastic stretch members disposed therebetween to a high pressure water jet 00:6 treatment to form a nonwoven fabric.

~According to one aspect of the present invention, there is provided a nonwoven fabric including a first fibrous layer, a second fibrous layer and a 000 0 20 plurality of fibrous elastic stretch members disposed between these two layers and substantially parallel extending in a desired direction so that constituent fibers of said first and second fibrous layers are mechanically intertwined to hold said fibrous elastic stretch members within a tissue of said nonwoven fabric, and wherein said nonwoven fabric has at least one of an upper surface and a 25 lower surface thereof bulging along said fibrous elastic stretch member in a striped pattern.

S. iOS 00S 000 S 0 0: 0 pa40491 95 25/02/99 Preferably, the elastic stretch members include elastic stretch yarns or an elastic stretch netty sheet and the elastic stretch yarns may be core spun yarn having elastic yarns as their cores. The constituent fibers of the first and second fibrous layers are substantially of a non-stretchable nature and these fibrous layers may have a plurality of gathers formed in the desired direction.

The constituent fibers of at least one of the first and second fibrous layers may be in crimped state.

According to a second aspect of the present invention, there is provided a method for making stretch nonwoven fabric at least including steps of: continuously feeding first and second fibrous webs destined to form upper and lower layers of the stretch nonwoven fabric; continuously feeding with a tension a plurality of fibrous elastic stretch members extending substantially parallel in a desired direction so as to be disposed between said first and second fibrous webs; laminating said first and second fibrous webs with said elastic stretch members extending therebetween followed by jetting high pressure water from orifices onto the upper surface of the laminate and thereby see mechanically intertwining constituent fibers of said first and second fibrous webs 20 to form a nonwoven fabric; relieving said tension of said elastic stretch members after said 0 nonwoven fabric has been obtained; drying said nonwoven fabric; and thereby obtaining said nonwoven fabric having at least one of an 25 upper surface and a lower surface bulging along said fibrous elastic stretch members in a striped pattern.

pa40491 95 26/02/99 Preferably, any one of the first and second fibrous webs includes heat crimpable fibers and further including a step of heat treating the nonwoven fabric to thermally crimp the fibers. The elastic stretch members may include core spun yarns having elastic yarns as their cores.

The nonwoven fabric is stretchable longitudinally of the elastic stretch members. The elastic coefficient for stretching of the nonwoven fabric depends on the particular type of the stretch members employed. For example, elastic stretch yarns of high elastic coefficient 0000* *0 *00* O* 0 0***000 0g

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S*o *0 *0 0 pa40491 95 25/02/99 may be employed or the number of elastic stretch yarns may be increased to improved the elastic coefficient for stretching. The inventive nonwoven fabric presents an improved feel and improved drapability, since it is formed by mechanically intertwining the constituent fibers.

According to the inventive method for making such a nonwoven fabric, the technique of subjecting the fibrous webs to the high pressure water jet treatment, which is well known itself, is adopted to obtain the nonwoven fabric.

For the fibrous web of non-stretchable nature, the elastic stretch yarns are fed with a tension and, after the water jet treatment, the elastic stretch yarns are relaxed so that the elastic stretch yarns contract to provide the stretch nonwoven fabric having the gathers formed thereon. For the fibrous web of heat crimpable nature, the nonwoven fabric having the gathers may be heat crimped to remove the gathers. When the core spun yarns having elastic yarns as their cores are employed, the constituent fibers of the fibrous webs can be intertwined together and the elastic stretch yarns can be reliably held within a tissue of the nonwoven fabric thus obtained.

e BRIEF DESCRIPTION OF THE DRAWINGS Si..

20 Fig 1 shows a nonwoven fabric according to the invention in a •perspective view; iO C

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CS C pa40491 95 26/02/99 -6- Fig. 2 shows a part of the nonwoven fabric shown by Fig. 1 in an enlarged scale; Fig. 3 shows various patterns in which elastic stretch yarns are arranged in plan views through respectively; and Fig. 4 is a diagram schematically illustrating steps for making the nonwoven fabric.

A stretch nonwoven fabric as well as of a method for making it will be better understood from the following description made in reference with the accompanying drawings.

DETAILED DESCRIPTION OF A PREFERRED

EMBODIMENT

Figs. 1 and 2 show nonwoven fabric 1 in a perspective view and in fragmentary scale-enlarged perspective view, respectively. The nonwoven l4* fabric 1 composed of a fibrous web 2 including staple fibers 5 mechanically intertwined in the form of a nonwoven fabric and a plurality of elastic stretch yarns 3 extending substantially parallel in one direction. The fibrous web 2 has upper and lower surfaces 6, 7 and a plurality of gathers 8 formed transversely of 20 the direction in which the stretch yarns 3 extend. The fibrous web 2 includes a layer of stable fibers 5A concentrated in upper half and a layer of staple fibers concentrated in lower half of the fibrous web 2 in the direction of its thickness as viewed in a cross-section of the fibrous web 2, 0 0 0. i @66000 7 wherein not only the staple fibers 5A as well as the staple fibers 5B are mechanically intertwined with themselves, respectively, but also the staple fibers 5A are mechanically intertwined with the staple fibers 5B. The stretch yarns 3 are disposed between the upper and lower surfaces 6, 7 and densely covered with the staple fibers 5A, 5B so that the stretch yarns 3 can not easily slip off from the interior of the fibrous web 2. The individual stretch yarns 3 may be *ga.

composed of a single element yarn extending substantially parallel to one another and spaced from one another by a desired distance. However, the individual yarns 3 may be a. a bundles of plural element yarns. Such stretch yarns 3 are u h s r t c a n r shown as in their relaxed state and being longitudinally stretchable until the gathers 8 are flattened. It should be understood that the stretch yarns 3 used here are potentially stretchable beyond such limitation. Referring to Fig. 2, a diameter of each stretch yarn 3 may be larger or smaller than a substantial thickness of the fibrous web 2 and, in any case, the nonwoven fabric 1 may have its upper surface 6 and/or lower surface 7 bulging along the stretch yarns 3 in a striped pattern.

Fig. 3 is a plan view of the nonwoven fabric 1 on which the stretch yarns 3 are arranged in various patterns.

-8- Referring to Fig. 3, corresponds to the pattern of the stretch yarns on the nonwoven fabric 1 shown by Fig. 1. (B) shows a pattern in which two sets of the stretch yarns 3 obliquely extend in two different directions and intersect each other. The nonwoven fabric 1 including the stretch yarns 3 arranged in this pattern is stretchable vertically as well as transversely as viewed in this figure. It should be understood that, in this case, a stretch net may be used in the place of the stretch yarns. is different from (A) in that the stretch yarns 3 extend transversely as viewed in this figure.

The staple fibers 5A, 5B used in the nonwoven fabric 1 may be either of a common type or of types different from each other selected from a group consisting of natural fibers, semisynthetic fibers and synthetic fibers of various types. While, for the fibrous web 2 composed of such fibers and being non-stretchable, the fibrous web 2 may be formed with gathers as shown by Figs. 1 and 2 to provide the nonwoven fabric 1 with a desired stretchability, such formation of the gathers is not always necessary for the fibrous web 2 composed, for example, of crimped synthetic fibers and being already stretchable. The nonwoven fabric 1 of the latter type has an elongation percentage depending i 9 on a stretchability of the crimped fibers. Elastomeric yarn or stretch fiber such as OPELON yarn, spun yarn C81 of UNITIKA CO., LTD., or core spun yarn having elastic yarn as its core, is used as the stretch yarn 3. When the spun yarn such as the C81 or core spun yarn is used as the stretch yarn 3, the spun yarn is sufficiently intertwined with the constituent fibers of the fibrous web 2 to maintain the *.Soo stretch yarn 3 and the fibrous web 2 in their states integrated as the nonwoven fabric 1 even after the nonwoven foe fabric 1 has been repeatedly stretched and contracted.

'00:*0 In the nonwoven fabric i, the constituent fibers eo maintain their flexibility to improve the touch and the drapability, since these fibers are mechanically intertwined without help of adhesive and/or welding. Accordingly, the nonwoven fabric 1 is suitable for surface materials of skincontacting disposable undergarments and sanitary articles such as disposable diapers and menstruation pads.

Fig. 4 is a diagram schematically illustrating the method for making the nonwoven fabric i. According to this method, a first fibrous web 51 and a second fibrous web 52 fed by respective web formers (not shown) are laminated by a nip defined between a pair of first rolls 50 with a plurality of elastic stretch yarns 53 fed under a tension substantially 1 _Ijljr__ Llij l~~~__=iP~~IIIII1~1 parallel to one another so as to be disposed between the two webs 51, 52. A laminate 54 obtained in this manner is then guided to a high pressure water jet system 55 as disclosed, for example, by Japanese Laid-Open Patent Application No.

Sho57-161151. The system 55 includes a group of nonporous supports 56 in the form of rolls and a group of nozzles 57 arranged above the respective supports 56, each of the r nozzles 57 is associated with a water guide pipe provided at

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its lower end with a plurality of fine orifices through which high pressure water streams may be jetted onto the associated support 56. Specifically, the high pressure water streams S 58 are jetted from the nozzles 57 onto the laminate 54 guided along the supports 56 so as to intertwine the constituent fibers of the first and second fibrous webs 51, 52 and simultaneously to entangle these fibers around the stretch yarns 53. Such laminate 54 is then fed with the stretch yarns 53 being stretched or relaxed onto a dryer 60 in the form of a drum and, if necessary, pressed by a top felt 61 against a peripheral surface of the drum. After dried by the dryer, the laminate 54 is peeled by a doctor blade 62 off from the drum surface to obtain a nonwoven fabric 71 which is then rolled up with the stretch yarns 53 being relaxed. In the nonwoven fabric 71, the first and second webs 51, 52 of If 11 which the constituent fibers are intertwined together form the nonwoven fabric 71 corresponding to the fibrous web 2 shown by Fig. 2 and the stretch yarns 53 are covered with the constituent fibers of the nonwoven fabric 71 and extend substantially parallel to one another longitudinally of the 0 nonwoven fabric 71. Such nonwoven fabric 71 is cut into a desired size to obtain the nonwoven fabric 1 shown by Fig. 1.

S.e[ Fibers used for the first and second webs 51, 52 may be of any type, for example, continuous filaments, so far as they can be intertwined together under the effect of the high pressure water streams 58. The web also may be of any configuration, for example, a web composed of merely carded fibers or a nonwoven fabric composed of intertwined or bonded fibers, so far as the constituent fibers can be rearranged by the high pressure water streams 58. When the fibrous web 2 obtained from these fibers is of nonstretchable nature, the nonwoven fabric 71 including the stretch yarns 53 being relaxed will form the gathers 8 as shown by Fig. i. When the fibrous web 2 composed of heat crimpable composite fibers passes the dryer 60 where it is heated at a desired temperature with the stretch yarns 53 being relaxed so as to obtain the crimped nonwoven fabric 71, the gathers 8 will disappear as the nonwoven fabric 71 is crimped.

12 If the stretch yarns 53 are rubber yarns each having a smooth surface, they will be covered but not intertwined with the first and second fibrous webs. The stretch yarns 53 each having a rough surface, on the contrary, facilitate the constituent fibers of these webs to be mechanically caught by goofs* the respective stretch yarns 53 and do not readily slip off from the nonwoven fabric 71 even after the nonwoven fabric 71 *too •s has been repeatedly stretched and contracted. If the core spun yarns including elastic yarns as their cores are used as the stretch yarns 53, the constituent fibers of the first and second webs 51, 52 will be intertwined with these core spun S" yarns, reliably holding the stretch yarns 53 within the tissue of the nonwoven fabric 71 and keeping them against slipping off from the tissue of the nonwoven fabric 71.

Additionally, a stretch netty sheet may be used in the place of the stretch yarns 53 and the individual stretch yarns 53 may include a plurality of fine element yarns.

The inventive nonwoven fabric is effective to improve the touch and the stretchable drapability, since the constituent fibers of the webs are mechanically intertwined together and the elastic stretch yarns are covered with these fibers so as to be held within the tissue of the nonwoven fabric. The elastic coefficient of the nonwoven fabric can i i 13 be easily and economically adjusted to a desired value by appropriately selecting an elastic coefficient for stretching of the nonwoven fabric and the number of elastic stretch yarns to be used. Heat crimpable fibers may be used as the constituent fibers of the webs to obtain the nonwoven fabric having no gather thereon.

Core spun yarns having elastic yarns as their cores may be employed as the elastic stretch yarns to improve its durability, since such core spun yarns do not readily slip off from the nonwoven fabric.

Claims

1. A nonwoven fabric including a first fibrous layer, a second fibrous layer and a plurality of fibrous elastic stretch members disposed between these two layers and substantially parallel extending in a desired direction so that constituent fibers of said first and second fibrous layers are mechanically intertwined to hold said fibrous elastic stretch members within a tissue of said nonwoven fabric, and wherein said nonwoven fabric has at least one of an upper surface and a lower surface thereof bulging along said fibrous elastic stretch member in a striped pattern.

2. A nonwoven fabric according to claim 1, wherein the respective constituent fibers of said first and second fibrous layers are substantially identical to each other.

3. A nonwoven fabric according to claim 1 or claim 2, wherein said elastic stretch members are elastic stretch yarns. *oo A nonwoven fabric according to claim 3, wherein said elastic stretch ••"yarns are core spun yarns having elastic yarns as their cores.

5. A nonwoven fabric according to claim 1 or claim 2, wherein each pair of adjacent elastic stretch members are connected to each other for form a netty 20 configuration as a whole.

6. A nonwoven fabric according to any one of claims 1 to 5, wherein the constituent fibers of said first and second fibrous layers are substantially non-stretchable and the respective fibrous layers have gathers formed in said desired direction. S: 25 7. A nonwoven fabric according to any one of claims 1 to 6, wherein the constituent fibers of at least one of said first and second fibrous layers are in a crimped state.

8. A method for making stretch nonwoven fabric at least including steps of: continuously feeding first and second fibrous webs destined to form upper and lower layers of the stretch nonwoven fabric; continuously feeding with a tension a plurality of fibrous elastic stretch members extending substantially parallel in a desired direction so as to be disposed between said first and second fibrous webs; pa40491 95 25/02/99 I "I' laminating said first and second fibrous webs with said elastic stretch members extending therebetween followed by jetting high pressure water from orifices onto upper surface of the laminate and thereby mechanically intertwining constituent fibers of said first and second fibrous webs to form a nonwoven fabric; relieving said tension of said elastic stretch members after said nonwoven fabric has been obtained; drying said nonwoven fabric; and thereby obtaining said nonwoven fabric having at least one of an upper surface and a lower surface bulging along said fibrous elastic stretch members in a striped pattern.

9. A method according to claim 8, wherein any one of said first and second fibrous webs includes heat crimpable fibers and further including a step of thermally treating said nonwoven fabric to thermally crimp said fibers after said tension of said elastic stretch members has been relieved.

10. A method according to claim 8 or 9, wherein said elastic stretch members include core spun yarns having elastic yarns as their cores.

11. A nonwoven fabric according to any one of the embodiments 20 substantially as herein described and illustrated with reference to the accompanying drawings.

12. A method for making a stretch nonwoven fabric according to any one of the embodiments substantially as herein described and illustrated with reference to the accompanying drawings. a$ 'a a a a CS *O a a S. S DATED: 25 FEBRUARY 1999 S PHILLIPS ORMONDE FITZPATRICK Attorneys For: UNI-CHARM CORPORATION pa40491 95 26/02/99