Patent Description:
The invention has been developed in particular in view of its application in the field of absorbent sanitary articles, such as, for example, diapers, training pants, absorbent sanitary products for incontinent adults, etc..

The present invention also relates to methods for producing an elastic film and to a method for producing elastic laminates, in particular for absorbent sanitary articles.

An absorbent sanitary article typically includes several elastic elements, such as elastic waist bands, elastic leg cuffs, elastic side panels, etc..

A traditional method for manufacturing elastic elements for absorbent sanitary articles consists in providing a plurality of elastic wires which are unwound from respective reels and supplied parallel to each other and longitudinally stretched in a machine direction. The plurality of parallel elastic wires is enclosed and fixed between two non-woven webs. Fixing the elastic wires between the non-woven webs may be carried out by glue or by a pattern of spot welds, e.g. as disclosed in <CIT>. A problem of this method it the high complexity of the devices for unwinding and feeding a very high number of elastic wires with controlled longitudinal tension. In case of break of one of the elastic wires the whole line for manufacturing absorbent sanitary article has to be stopped to replace or repair the broken wire.

Another method for manufacturing elastic elements for absorbent sanitary articles consists in providing a continuous elastic film unwound from a reel and stretched in a longitudinal o in transverse direction, which is enclosed between two webs of non-woven material and is fixed thereto by a pattern of glue spots or spot welds. One of the drawback of this method is that there are problems when the width of the elastic film is small. Reels of continuous elastic films should have a minimum width of <NUM> in order to ensure stability of the reel. Elastic films having a width lower than <NUM> should be wound in spool rolls, which complicate the unwinding devices.

<CIT> discloses an elastic film having activated and non-activated zones formed during an activation process. The activated zones allow the film to expand without generating excessive tensional forces. The film has M-polypropylene or M-polyethlyene skin layers and a core layer having an elastomeric polyurethane, ethylene copolymer such as ethylene vinyl acetate, an ethylene/propylene copolymer elastomer or ethylene/propylene/diene terpolymer elastomer. The activation process allows the skin layers to behave more like the core layer.

<CIT> discloses a method for producing a film with areas of different elastic extensibility, wherein a coextruded film with an elastic film layer and at least one non-elastic film layer is provided, wherein the non-elastic film layer is at least partially destroyed by a laser radiation.

<CIT> discloses microtextured elastomeric laminates comprising at least one elastomeric layer and at least one thin skin layer, prepared by coextrusion of the layers followed by stretching the laminate past the elastic limit of the skin layers in predetermined regions of the laminate and then allowing the laminate to recover in these regions.

<CIT> discloses an elastic film material intended for e.g. diapers, comprising parallel MD elastic ribbons bonded to an extensible nonwoven sheet. The ribbons may also be bonded to a second non-woven sheet on their opposite second surface.

<CIT> discloses an elastic film material for e.g. diapers, comprising elastic ribbons laminated on each side with an elastomeric meltblown layer.

<CIT> discloses an elastic film material for e.g. absorbent hygiene articles, comprising parallel elastic strands which are bonded to an elastic meltblown non-woven layer on a first surface and to a facing layer on an opposite second surface.

The object of the present invention is to overcome the problems of the prior art.

According to the invention, this object is achieved by an elastic film according to claims <NUM> or <NUM>.

According to other aspects, the invention relates to a method for producing an elastic laminate having the features of claim <NUM> and to a method for producing an elastic film having the features of claims <NUM> or <NUM>.

The claims form an integral part of the technical disclosure provided here in relation to the invention.

The present invention will now be described with reference to the attached drawings, provided purely by way of non-limiting example, wherein:.

It should be appreciated that the attached drawings are schematic and not to scale with respect to real products. Various figures may not be represented in the same scale. Also, in various figures some elements may not be shown to better show other elements.

With reference to <FIG>, an elastic film according to a first embodiment of the present invention is indicated by the reference number <NUM>.

The elastic film <NUM> comprises a plurality of parallel elastic ribbons <NUM> elongated in a longitudinal direction and spaced apart from each other in a transverse direction Y orthogonal to the longitudinal direction.

The elastic ribbons <NUM> are coated on two opposite surfaces by first and second skin layers <NUM>, <NUM>. The first skin layer <NUM> is continuous in the transverse direction Y and joins the elastic ribbons <NUM> to each other. The second skin layer <NUM> is discontinuous in the transverse direction Y and coats the surfaces of the elastic ribbons <NUM> opposite to the first skin layer <NUM>.

The first skin layer <NUM> may have a plurality of parallel longitudinal break lines <NUM>, each of which extends between each pair of adjacent elastic ribbons <NUM>.

With reference to <FIG>, the elastic film <NUM> of <FIG> may be produced by extruding a transversely continuous flat elastic element <NUM> of elastic material and applying first and second transverse continuous skin layers <NUM>, <NUM> on opposite surfaces of the transversely continuous flat elastic element <NUM>. The first and second transversely continuous skin layers <NUM>, <NUM> may be co-extruded with the transversely continuous flat elastic element <NUM>.

Then, the transversely continuous flat elastic element <NUM> and the second skin layer <NUM> are cut longitudinally, e.g. by rotating knives, so as to divide the continuous elastic core <NUM> in a plurality of parallel elastic ribbons <NUM>. The longitudinal break lines <NUM> on the first skin layer <NUM> may be formed simultaneously with the longitudinal cuts that form the parallel elastic ribbons <NUM>.

With reference to <FIG>, in a second embodiment of the present invention the elastic film <NUM> comprises a plurality of parallel elastic ribbons <NUM> elongated in a longitudinal direction and spaced apart from each other in a transverse direction Y orthogonal to the longitudinal direction. The elastic ribbons <NUM> are coated on two opposite surfaces by first and second skin layers <NUM>, <NUM> which are both continuous in the transverse direction Y and both join the elastic ribbons <NUM> to each other.

In a possible embodiment, the spacing in the transverse direction Y between the parallel elastic ribbons <NUM> may be variable.

In a possible embodiment, at least two parallel elastic ribbons <NUM> may be different from each other e.g. they may be made of different materials and/or they may have different shapes.

The elastic film <NUM> of <FIG> may be produced by extruding a plurality of separate parallel elastic ribbons <NUM> of elastic material and applying first and second transversely continuous skin layers <NUM>, <NUM> on opposite surfaces of the parallel elastic ribbons <NUM>. The first and second transversely continuous skin layers <NUM>, <NUM> may be co-extruded with the parallel elastic ribbons <NUM>.

Longitudinal spacers elements <NUM> of non-elastic filling material, e.g. wax, may be provided between each pair of adjacent elastic ribbons <NUM>. The longitudinal spacers elements <NUM> may be co-extruded together with the separate parallel elastic ribbons <NUM> and the first and second transversely continuous skin layers <NUM>, <NUM>.

In the embodiment of <FIG> both the first and the second skin layers <NUM>, <NUM> may have a plurality of parallel longitudinal break lines <NUM>, formed for instance by cutting knives, each of which extends between each pair of adjacent elastic ribbons <NUM>.

The elastic ribbons <NUM> may be made of a material selected among: styrene block copolymer, elastic polyolefin, thermoplastic urethane. The elastic ribbons may have an elastic elongation comprised between <NUM> and <NUM>%.

The skin layers <NUM>, <NUM> may be made of a material selected among: low density polyethylene (LDPE), low density polypropylene (LDPP), and elastic polyolefin added with thermoplastic materials.

In the embodiment of <FIG> the parallel elastic ribbons <NUM> may be coated on only one surface by only one skin layer <NUM> continuous in the transverse direction Y, which joins the parallel elastic ribbons <NUM> to each other. The embodiment of <FIG> is cheap but may be difficult to handle because the uncoated surfaces of the elastic ribbons <NUM> may be sticky.

In the embodiment of <FIG> the parallel elastic ribbons <NUM> are coated on two opposite surfaces by first and second skin layers <NUM>, <NUM>, so as to increase the stability and to facilitate wounding of the film <NUM> in reels.

In the embodiment of <FIG> the first skin layer <NUM> is continuous in the transverse direction Y and joins the elastic ribbons <NUM> to each other, and the second skin layer <NUM> is discontinuous in the transverse direction Y and coats the surfaces of the elastic ribbons <NUM> opposite to the first skin layer <NUM>.

In the embodiment of <FIG> the first and second skin layers <NUM>, <NUM> are both continuous in the transverse direction and both join the elastic ribbons <NUM> to each other, and empty spaces may extend between the elastic ribbons <NUM>.

In the embodiment of <FIG> non-elastic filling elements <NUM>, which may be integrally formed with the skin layers <NUM>, <NUM>, may fill the spaces between each pair of adjacent elastic ribbons <NUM>.

In the embodiment of <FIG> in the spaces between each pair of adjacent elastic ribbons <NUM> the first and second skin layers <NUM>, <NUM> may be calendered by a ring roller so as to form weakened portions <NUM> in the spaces between the adjacent elastic ribbons <NUM>. In a possible embodiment the weakened portions <NUM> may be coextruded with the skin layers <NUM>, <NUM>.

The elastic film <NUM> may be used for producing an elastic laminate, in particular in machines for manufacturing absorbent sanitary articles.

The elastic film <NUM> with an indefinite extension in the longitudinal direction is wound in a reel, which is arranged in an unwinding device which unwinds the elastic film <NUM> from the reel and feeds the elastic film <NUM> in a machine direction parallel to the longitudinal extension of the elastic film <NUM>.

In a first step the elastic ribbons <NUM> are detached from each other.

In a possible embodiment, detaching from each other the elastic ribbons <NUM> may be carried out by breaking the longitudinal portions of the at least one skin layer <NUM>, <NUM> which join to each other the parallel elastic ribbons <NUM>.

With reference to <FIG>, breaking the longitudinal portions of the at least one skin layer <NUM>, <NUM> which join to each other the parallel elastic ribbons <NUM> may be carried out by passing the elastic film <NUM> between two mutually meshing toothed wheels <NUM>. During the passage of the elastic film <NUM> between the mutually meshing toothed wheels <NUM> the elastic ribbons <NUM> are stretched longitudinally. The longitudinal extension of the elastic ribbons <NUM> generates a transverse compression thereof, which breaks the longitudinal portions of the at least one skin layer <NUM>, <NUM> which join to each other the parallel elastic ribbons <NUM>. Breaking the longitudinal portions of the at least one skin layer <NUM>, <NUM> may be facilitated by the longitudinal break lines <NUM>.

With reference to <FIG>, in another possible embodiment, detaching from each other the elastic ribbons <NUM> may be carried out by cutting the longitudinal portions of the at least one skin layer <NUM>, <NUM> which join to each other the parallel elastic ribbons <NUM>, e.g. by a longitudinal cutting device <NUM> comprising a plurality of parallel cutting disks <NUM> cooperating with an anvil roller <NUM>.

With reference to <FIG>, in another possible embodiment, detaching from each other the elastic ribbons <NUM> may be carried out by fusing, e.g. by a plurality of laser nozzles <NUM> the longitudinal portions of the at least one skin layer <NUM>, <NUM> which join to each other the parallel elastic ribbons <NUM>.

After detaching from each other the elastic ribbons <NUM>, the elastic film <NUM> is converted into a plurality of separate elastic ribbons <NUM> which move in a machine direction MD parallel to the longitudinal axes of the elastic ribbons <NUM>.

With reference to <FIG>, the separate elastic ribbons <NUM> are then spaced from each other in the transverse direction Y as the move in the machine direction MD.

The spaced apart elastic ribbons <NUM> are stretched in the machine direction MD, either before or after spacing the elastic ribbons <NUM> from each other in the transverse direction Y. As shown in <FIG>, the elastic ribbons <NUM> are enclosed between two opposite non-woven webs <NUM>, while longitudinally stretched in the machine direction MD. The elastic ribbons <NUM> longitudinally stretched in the machine direction MD are fixed to the two opposite non-woven webs <NUM> to form a continuous elastic laminate <NUM>.

The elastic ribbons <NUM> may be fixed to the two opposite non-woven webs <NUM> by a pattern of glue spots or spot welds <NUM>. In a possible embodiment the longitudinally tensioned elastic ribbons <NUM> are fixed in discrete points to the two non-woven webs <NUM> by welds forming mechanical anchoring points, as disclosed in <CIT> and <CIT>.

An elastic film <NUM> according to the present invention has considerable advantages in machines for manufacturing absorbent sanitary articles. As compared to machines where the elastic laminates are formed starting from many elastic wires unwound from respective reels, the elastic film according to the present invention requires only one unwinding device, instead of the large number of unwinding devices associated to the respective wires. As compared to elastic laminates produced starting from elastic films, the present invention has no limitations on the width of the elastic laminates and provides elastic laminates which have a far greater permeability to air (breathability) than elastic laminates produced using elastic films of the prior art.

Claim 1:
An elastic film (<NUM>) comprising a plurality of parallel elastic ribbons (<NUM>) elongated in a longitudinal direction (MD) and spaced apart from each other in a transverse direction (Y) orthogonal to said longitudinal direction (MD), wherein said plurality of parallel elastic ribbons (<NUM>) are coated on two opposite surfaces by first and second skin layers (<NUM>, <NUM>) wherein said first skin layer (<NUM>) is continuous in said transverse direction (Y) and joins said elastic ribbons (<NUM>) to each other, and wherein the second skin layer (<NUM>) is discontinuous in said transverse direction (Y) and coats surfaces of said elastic ribbons (<NUM>) opposite to said first skin layer (<NUM>).