EP0850037A1

EP0850037A1 - Composite nonwoven material, fabrication process and application to absorbent hygienic articles

Info

Publication number: EP0850037A1
Application number: EP96930220A
Authority: EP
Inventors: Jean-Pierre Koczab
Original assignee: Avgol Ltd; SCA Molnlycke AB; Molnlycke Vafveri AB
Current assignee: Avgol Ltd
Priority date: 1995-09-15
Filing date: 1996-09-06
Publication date: 1998-07-01
Also published as: FR2738845B1; US6204210B1; FR2738845A1; WO1997009952A1; AU6934596A; JP2001503336A

Abstract

Material characterized by an improved body fluid through-piercing time and an improved rewetting resistance. The composite nonwoven material (1) is comprised of two external layers (2, 3) consisting of body fluid permeable nonwoven material, between which is arranged a synthetic fiber lap (4) which is permeable to body fluids, at least the external layers (2, 3) being assembled between each other by thermal fusion according to a pattern forming a network of points, and further comprising a central area of perforations. Application to webs of surfaces for absorbent hygienic articles.

Description

Composite nonwoven material, its manufacturing process and its application to any absorbent hygiene article.

The present invention relates to a composite nonwoven material which when used as a surface veil or in addition to the surface veil as a strip in the crotch area, above the absorbent pad in an absorbent hygiene article, such as a diaper or an incontinence pad, improves the speed of passage of urine through this nonwoven material towards the absorbent pad while limiting the flow of urine to the skin. user (rewetting), which provides better insulation of the skin of the absorbent cushion of the hygiene article.

Generally absorbent hygiene articles, such as diapers and incontinence pads, include an outer layer or sheet of material impermeable to bodily fluids, such as urine, and an inner surface layer or veil permeable to body fluids, between which is placed a cushion or mattress of absorbent material.

This veil of surface permeable to bodily fluids aims to isolate the skin from the moistened absorbent cushion. Consequently, the surface veil must have a suitable degree of softness, and must ensure rapid passage of the urine towards the absorbent pad while forming an obstacle to the return of urine to the skin of the user.

Document FR-A-2 588 285 describes a multilayer nonwoven fabric having at least two layers of nonwoven web, one of the layers being formed of fibers of bilobed cross section and

SUBSTITUTE SHEET (RULE 26) the other layer being formed of three-lobed cross-section fibers.

Each layer of veil is preferably obtained by the spun bonded technique and the two layers of veil are combined to form the multilayer nonwoven by thermal bonding in compacted and discontinuous zones.

Document WO 87/07117 describes an absorbent hygiene article comprising an absorbent body surrounded by an envelope. This envelope or surface veil consists of two layers of nonwoven material. The first layer of nonwoven material, in contact with the skin of the user, consists of a thin layer of fibrous fabric bonded to the spinning and of a hydrophobic material, and the second layer in contact with the absorbent body is a hydrophobic fibrous layer of fusion bonded fiber fabric, similar in construction to the first layer. These two layers of surface veil are not linked together in the zone intended to come into contact with the body of the user.

WO 88/05269 relates to a surface veil for a disposable absorbent article composed of at least two layers of nonwoven which may be identical or different and which are joined by lines of adhesive forming an open pattern.

Document FR-A-2 698 385 describes a composite nonwoven material comprising at least one layer composed of a nonwoven permeable to body fluids, and on this first layer, a web of carded type fibers, permeable to fluids bodily, the web of carded type fibers being linked to the first layer by a switch. This composite nonwoven material can be used as a surface fleece in an absorbent hygiene article. The present invention therefore aims to provide a composite nonwoven material having a desired degree of softness, as well as a speed of passage through liquids and an improved rewetting resistance, compared to the prior nonwovens described above. and used heretofore to form the surface veils of absorbent hygiene articles. The present invention also aims to provide an absorbent hygienic article such as diapers and incontinence pads preferably comprising a formed surface veil of such a composite nonwoven material, the manufacturing cost of which is reduced due to the characteristics of said composite nonwoven material. The present invention also aims to provide a method of manufacturing such a composite nonwoven material. According to the present invention there is provided a composite nonwoven material comprising two outer layers of a nonwoven permeable to body fluids between which is disposed a sheet of synthetic fibers permeable to body fluids, characterized in that at least the outer layers are joined together by thermofusion according to a pattern forming a network of points and that they also comprise a perforated central zone. Advantageously, the two outer layers of nonwoven are constituted by natural or synthetic textile fibers chosen from cellulose, viscose, polyester, polyethylene, polypropylene, nylon or ethylene-propylene copolymer fibers. Also advantageously, the intermediate ply is of the carded type or with unbound continuous filaments, consisting of synthetic textile fibers of polyester, polyethylene, polypropylene, nylon or ethylene-propylene copolymers.

The outer layers and the intermediate layer can advantageously have a grammage of between 5 and

15 m / m ² for the first and between 5 and 30 g / m ² for the tablecloth. In addition, the upper external nonwoven layer has a longitudinal hydrophilic central zone, delimited by continuous weld lines formed between at least the two external layers, forming barriers to the transverse diffusion of body fluids.

Another object of the present invention is constituted by an absorbent hygienic article, such as a diaper, which comprises an outer layer impermeable to bodily fluids, an absorbent pad permeable to bodily fluids which is attached to this outer layer and a surface veil permeable to bodily fluids covering the absorbent cushion and fixed to the external layer, the surface veil consisting of the composite material according to the invention described above, the upper external layer of the nonwoven provided with a hydrophilic central zone constituting the layer intended to be in contact first with bodily fluids therefore with the body of the user.

The invention also relates to an absorbent hygiene article comprising an outer layer impermeable to body fluids, an absorbent pad permeable to body fluids and attached to the outer layer, and having two opposite widened end portions and a crotch area more narrow, a strip of crotch area permeable to body fluids, of width similar to the crotch area of the cushion and of length similar to the cushion, and a veil of surface permeable to bodily fluids and attached to the outer layer, the strip of crotch zone being made of the composite nonwoven material according to the invention, the upper outer layer of nonwoven provided with a hydrophilic central zone being oriented so as to be in contact first with body fluids or immediately after the surface veil. Advantageously, the crotch zone strip is disposed between the absorbent pad and the surface veil.

The invention also provides a method of manufacturing a composite nonwoven material, which comprises the steps of:

- unroll simultaneously a sheet of synthetic fibers permeable to body fluids and two sheets of nonwoven permeable to body fluids,

- insert the ply of synthetic fibers between the two non-woven plies,

supplying the assembly to a calendering device allowing a regular connection by points between at least the nonwoven plies by thermofusion,

- supply the composite strip obtained by a perforation device in order to obtain a perforated central zone.

Advantageously, the method comprises the step consisting in supplying the composite strip to a welding device making it possible on the one hand to produce a first pair of continuous weld lines symmetrical with respect to the longitudinal central axis of the strip, between at least the two layers of nonwoven, near each longitudinal edge of said strip and on the other hand a second pair of continuous weld lines also symmetrical with respect to the axis longitudinal median of the strip, the transverse spacing of which is less than that of the first pair and which thus delimits a hydrophilic longitudinal central zone on the upper face of said composite nonwoven material. Advantageously, the calendering, perforating and welding devices can be of the ultrasonic type.

In addition, the perforated central zone may be continuous or discontinuous and have a width less than that of the hydrophilic central zone of the upper outer layer of nonwoven. The following description refers to the appended figures which represent respectively: FIG. 1: a partial top view of the composite nonwoven material according to the invention, FIG. 2: a schematic sectional view of the composite nonwoven material according to invention, before the calendering and welding steps, FIG. 3: a top view, partially cut away, of an absorbent hygiene article, such as a diaper comprising a surface veil made of the composite material according to the invention. invention, and Figure 4: a sectional view taken along line IV-IV of Figure 3.

Referring to Figures 1 and 2, there is shown the composite nonwoven material 1 according to the invention.

This material comprises first and second external layers 2, 3 of nonwoven permeable to bodily fluids, such as urine, between which is inserted a sheet of synthetic fibers 4 permeable to bodily fluids, the whole being joined by thermofusion. at least the outer layers together.

Can be used for the outer layers 2, 3 in nonwoven, all types of conventional nonwovens, for example, natural or synthetic textile fibers, such as cellulose fibers, viscose, polyester, polyethylene, polypropylene, nylon or ethylene-propylene copolymers. These external layers of nonwoven may consist of a nonwoven fabricated by any conventional process such as, for example, spun bonded, thermal bonding, chemical bonding, blowing air connection, spinning lacing. Preferably these layers have a basis weight between 5 and 15 g / m ² . The upper outer layer 3 has a hydrophilic central zone 5 while the lower outer layer 2 can be hydrophilic or hydrophobic.

The ply of synthetic fibers 4, permeable to fluids, is of the carded type or made up of unbound continuous filaments, and can be made up of synthetic textile fibers such as polyester, polyethylene, polypropylene, nylon, or copolymers of ethylene-propylene. Polyester fibers are particularly recommended for their resilience and good fluid transport characteristics. In general, the ply 4 has a grammage of between 5 and 30 g / m ² and the denier of the fibers of this ply is generally between 3 and 13. We will describe the process for manufacturing such a composite material according to the invention.

The cohesion of the composite nonwoven material 1 is obtained by subjecting all of the layers 2, 3 and of the ply 4, after having superimposed them and brought into contact, with a hot calendering operation so as to obtain the joining by thermofusion of at least the outer layers 2, 3 in a pattern forming a network of dots.

It is obvious that depending on the nature of the fibers chosen for layers 2 and 3, if the intermediate ply 4 is made of polyester fibers, there will be no fusion of the fibers of layers 2 and 3 with the fibers of polyester, taking into account the significant differences in the melting temperatures of these polymers. This is the case in the preferred embodiment where the layers 2 and 3 are constituted by polypropylene fibers and have a grammage of 10 g / m ² , the sheet 4 of polyester fibers also having a grammage of 10 g / m ² . However, it is possible to envisage the use of fibers having identical or fairly close melting points for the layers and the sheet so as to obtain a fusion between the three.

The calendering device used is of the ultrasonic type (with a sonotrode and an anvil), the rotary anvil of which bears relief patterns intended to form the hot-melt points which may by way of example of embodiment be of cylindrical shape, with a diameter of 1 mm and arranged so as to form a stitch mesh in staggered rows with a distance between two successive points in a row of 7 mm. However other types of mesh are possible.

The advantage of such a calendering device is its flexibility of use.

In addition, other devices than ultrasound can be used, such as heated calendering cylinders. The next step in the manufacturing process is the perforation of the composite material; it is carried out by passing through a second ultrasonic device of higher power.

The shape of the anvil knobs used for this operation depends on the size desired for the perforations. In a suitable embodiment, the perforations have a diameter of 1 to 2 mm and the distance between two successive perforations is 10 mm.

As shown in FIG. 1, the perforation zone 6 is centered on the median longitudinal axis XX ′ of the composite material and is located inside the hydrophilic central zone 5 of the outer layer 3. This perforation zone can have for example a width of 40 mm and a length of 100 mm, when it is discontinuous, as is the case in FIG. 1. In this case, the pitch of this zone 6 must correspond to the manufacturing pitch of a layer - pants so as to be able to incorporate this material on the production line as a surface veil of diapers and center the perforation zone in the crotch zone of the diaper, which receives the urine.

Finally, the last stages of the production of the composite material are the welding operations by passage also in ultrasonic devices.

They comprise a first weld assembly which makes it possible to produce two first continuous longitudinal weld lines 7, at least between the external layers 2 and 3, symmetrical with respect to the axis XX ', and arranged near the longitudinal edges 8 of the composite strip 1. Preferably these weld lines 7 may be sinusoidal and spaced from the longitudinal edges 8 by about 5 mm. They thus form barriers to the transverse migration of bodily fluids absorbed by the composite material 1 used as the surface veil of a diaper.

A second weld assembly makes it possible to produce two second continuous longitudinal weld lines 9, at least between the outer layers 2 and 3, also symmetrical with respect to the median axis XX '. The distance between these two lines 9 can be for example 90 mm for a composite material 1 of 330 mm in width; these weld lines 9 delimit the hydrophilic central zone 5 of the composite material 1 and have the main function of forming a first tight barrier to the transverse diffusion of body fluids such as urine when said composite material 1 is used as a surface veil in diapers.

The second welding set can also be adapted to form, in addition to continuous lines, discontinuous decorative welding patterns 10, which can take shapes as diverse as those of flowers, birds, or various geometric shapes (ovals, circles, etc. .).

Referring to Figures 3 and 4, there is shown an absorbent hygiene article 1 1, such as a diaper, comprising an outer layer 12 of a flexible material impermeable to bodily fluids such as urine, on which is fixed an absorbent cushion 13 permeable to bodily fluids of dimension smaller than the outer layer. The absorbent pad 13 is fixed to the waterproof layer 12 by any conventional means such as by gluing. On this absorbent cushion

13 is disposed a surface veil 14 permeable to bodily fluids of dimension similar to that of the outer layer 12. The surface veil 14 is bonded around the periphery of the absorbent pad 13 to the outer layer 12 by any means such as by bonding. As is well known in the art, the outer layer 12, the absorbent pad 13 and the surface veil 14 are in the form of an hourglass comprising two relatively large opposite end portions joined by a crotch portion or area more narrow. As shown in Figures 3 and 4, the surface veil consists of the composite nonwoven material 1 shown in FIGS. 1 and 2, and which comprises two external layers of nonwoven 2 and 3 and an intermediate layer of synthetic fibers 4. As shown in the figures, the upper outer layer 3 provided with a hydrophilic central zone 9 and a perforation zone

6 constitutes the innermost layer of the veil intended to come into contact with the body of the user of the hygiene article 11.

A hygiene article according to the invention is thus produced which has improved properties of softness, speed of crossing of body fluids and barrier to rewetting. When used in addition to a conventional surface veil, the composite material according to the invention is preferably used in the form of a crotch zone strip having a width similar to that of the crotch zone of the absorbent cushion and a length similar to that of this cushion. In this embodiment, which is not illustrated in the figures of the present patent application, the crotch zone strip made of the composite material according to the invention is preferably placed between the conventional surface veil and the absorbent pad, so that the upper outer layer 3 of nonwoven comes into direct contact with the surface veil.

There was thus produced according to the invention a particularly useful and economical nonwoven composite material in the manufacture of surface veils for absorbent hygiene articles.

Claims

1. Composite nonwoven material comprising two external layers (2, 3) of a nonwoven permeable to bodily fluids between which is disposed a sheet of synthetic fibers (4) permeable to bodily fluids, characterized in that at least the external layers (2, 3) are joined together by hot-melt in a pattern forming a network of dots and that they also comprise a perforated central zone (6).

2. composite nonwoven material according to claim 1, characterized in that the external nonwoven layers (2, 3) are constituted by natural or synthetic textile fibers chosen from cellulose, viscose, polyester, polyethylene fibers, polypropylene, nylon or ethylene-propylene copolymer.

3. composite nonwoven material according to claim 1, characterized in that the intermediate ply of synthetic fibers (4) is of the carded type or with unbound continuous filaments.

4. composite nonwoven material according to any one of claims 1 to 3, characterized in that the intermediate ply of synthetic fibers (4) consists of synthetic textile fibers chosen from polyester, polyethylene, polypropylene, nylon or ethylene-propylene copolymer.

5. Composite nonwoven material according to any one of claims 1 and 2, characterized in that the external nonwoven layers (2, 3) have a basis weight between 5 and 15 g / m ² .

6. composite nonwoven material according to any one of claims 1, 3 and 4, characterized in that the intermediate ply of synthetic fibers (4) has a basis weight between 5 and 30 g / m ² .

7. composite nonwoven material according to any one of the preceding claims, characterized in that the upper external layer (3) of nonwoven comprises a hydrophilic longitudinal central zone (5), delimited by continuous weld lines (9 ) produced between at least the two outer layers (2, 3) forming barriers to the transverse diffusion of body fluids.

8. Absorbent hygiene article (1 1) comprising an outer layer impermeable to bodily fluids (12), an absorbent pad permeable to bodily fluids (13) and attached to the outer layer, and a surface veil permeable to bodily fluids ( 14) covering the absorbent pad and fixed to the outer layer, characterized in that the surface veil (14) consists of a composite nonwoven material according to any one of the preceding claims, the upper outer layer (3) of nonwoven provided with a hydrophilic central zone constituting the layer intended to be in contact first with bodily fluids therefore with the body of the user.

9. Absorbent hygiene article comprising an outer layer impermeable to bodily fluids (12), an absorbent pad permeable to bodily fluids (13) and attached to the outer layer, and having two opposite widened end portions and a zone of narrower crotch, a band of crotch area permeable to body fluids, of width similar to the crotch area of the cushion and of length similar to the cushion, and a surface veil permeable to body fluids (14), and attached to the outer layer (12), characterized in that the crotch zone strip consists of the composite nonwoven material according to any one of claims 1 to 7, the upper outer layer (3) of nonwoven provided with 'a hydrophilic central zone being oriented so as to be in contact first with bodily fluids or immediately after the surface veil (14).

10. absorbent hygiene article according to claim 9, characterized in that the crotch zone strip is disposed between the absorbent pad (13) and the surface web (14).

1 1. A method of manufacturing a composite nonwoven material, characterized in that it comprises the steps consisting in: - simultaneously unrolling a sheet of synthetic fibers permeable to body fluids (4) and two sheets of permeable nonwoven to bodily fluids (2, 3).

- insert the ply of synthetic fibers (4) between the two nonwoven plies (2, 3), - supply the assembly to a calendering device allowing a regular point bond between at least the nonwoven plies by thermofusion,

- supply the composite strip obtained to a perforation device in order to obtain a perforated central zone (6).

12. A method of manufacturing a composite nonwoven material according to claim 1 1, characterized in that it further comprises the step consisting in:

- then supply the composite strip to a welding device making it possible, on the one hand, to produce a first pair of continuous weld lines (7) symmetrical with respect to the longitudinal central axis (XX ') of the strip between at least the two nonwoven plies near each longitudinal edge of said strip, and on the other hand a second pair of continuous weld lines (9) also symmetrical with respect to the longitudinal median axis (XX ') of the strip, of which the transverse spacing is less than that of the first pair, and which thus delimits a hydrophilic longitudinal central zone (5) on the upper face of said composite nonwoven material.

13. A method of manufacturing a composite nonwoven material according to any one of claims 1 1 and 12, characterized in that the calendering, perforating and welding devices are of the ultrasonic type.

14. A method of manufacturing a composite nonwoven material according to any one of claims 1 1 to 13, characterized in that the perforated central zone (6) can be continuous or discontinuous and has a width less than that of the hydrophilic central zone (5) of the upper nonwoven outer layer.