WO1998052505A1

WO1998052505A1 - An absorbent multilayer material and a method and arrangement for its manufacture

Info

Publication number: WO1998052505A1
Application number: PCT/SE1998/000898
Authority: WO
Inventors: Ulf Johannison
Original assignee: Mölnlycke Health Care Ab
Priority date: 1997-05-20
Filing date: 1998-05-14
Publication date: 1998-11-26
Also published as: SE510799C2; SE9701869D0; SE9701869L

Abstract

The present invention relates to an absorbent multilayer material (9) that includes a perforated layer (4') of hydrophobic material and at least one layer (5') of absorbent material. According to the invention, mutually sequential rows of depressions (13) are disposed over that side of the multilayer material (9) which includes the hydrophobic layer (4'), wherein the depressions have the form of hammock-like parts of the hydrophobic layer that penetrate down into the layer of absorbent material (5') so as to form openings (14) perpendicular to the plane of the hydrophobic layer, wherein the hammock-like parts are fastened to the absorbent layer over the major part of their respective surfaces, and the absorbent layer is compressed within the region of each depression. The invention also relates to a method and to an arrangement for producing such material.

Description

AN ABSORBENT MULTILAYER MATERIAL AND A METHOD AND ARRANGEMENT

FOR ITS MANUFACTURE

The present invention relates to an absorbent multilayer material and also to a method and to an arrangement for its manufacture .

With the intention of preventing wound dressings from adhering to a wound, the dressings are normally constructed of a layer of material that can only adhere lightly to the wound, or sore, and an overlying layer of absorbent material. The layer of the dressing that lies against the wound is often comprised of a perforated plastic film. The surface sheet of absorbent articles, such as sanitary napkins or diapers, will also often include a perforated plastic layer which is intended to lie proximal to the wearer's body in use. In order for such articles to function effectively, it is essential that the dressing and such surface layers are constructed to achieve effective transportation of discharged fluid or liq- uid into the absorbent layer, through the openings in the plastic film.

The object of the present invention is to provide an absorbent multilayer material which is composed of one or more absorbent layers, or sheets, fastened to a layer of hydrophobic material that has good fluid or liquid transportation and absorption properties and with which there is little danger of any part of the absorbent layer coming into contact with the wound or with the wearer's skin.

This object is achieved by means of an absorbent multilayer material that includes a perforated layer, or sheet, of hydrophobic material and at least one layer, or sheet, of absorbent material. The inventive material is characterised in that mutually sequential rows of depressions are disposed over that side of the material which lies above that side of said material which includes said hydrophobic layer, wherein said depressions have the form of hammock-like parts of the hydrophobic layer that penetrate down into the absorbent layer so as to form openings at right angles to the plane of the hydrophobic layer, and wherein the hammock-like parts are fastened to the absorbent layer over the major part of their surfaces; and in that the absorbent layer is compressed in the region of each depression. Because the openings in the multilayer material are perpendicular when the articles in which the multilayer materials included are placed in position, there is little danger of fibre ends or the like in the absorbent layer and present in said openings coming into contact with the surface of the wound or with the skin, while the compressed parts of the absorbent layer assist in transporting fluid quickly away from the openings.

In a preferred embodiment, the hydrophobic layer or sheet is comprised of plastic film and the absorbent layer, or sheet, is comprised of nonwoven material that includes absorbent fibres .

According to one variant, the absorbent multilayer material includes several layers of nonwoven material, of which at least those layers that are not in contact with the hydrophobic layer include melt fibres.

In another embodiment, the absorbent layer is comprised of absorbent foam. The invention also relates to a method of producing an ab^¬ sorbent multilayer material. The method is characterised by the steps of combining a layer of weldable hydrophobic material with at least one layer of absorbent material; passing the combined layers through the nip defined between an ultra- sound horn and an anvil roll with the layer of weldable mate- rial in abutment with the anvil roller, said roller having disposed in mutually sequential rows about its circumference discrete projections that have curved outwardly facing surfaces and vertical side surfaces and said rows extending essentially in an axial direction; and setting the distance between the ultrasound horn and the anvil roller so that the weldable material will be cut along the curved edges located between the outside and the vertical sides of each projection whilst simultaneously deforming the combined layers in the region of each projection so as to form rows of depressions and so as to fasten the weldable layer to the layer of absorbent material within the major part of the region of each proj ection.

In one preferred embodiment, several layers that include absorbent fibres are combined with the layer of weldable material, wherein at least those layers that do not lie against the layer of weldable material also include melt fibres .

The invention also relates to arrangement for producing an absorbent multilayer material that has a perforated side. The arrangement is characterised by means for combining at least two webs of material, means for passing the combined webs through the nip defined between an ultrasound horn and an anvil roll that includes around its circumference mutually sequential rows of discrete projections that have curved outwardly facing surfaces and vertical side surfaces, said rows extending essentially in an axial direction, and means for cutting individual pieces of material from said combined web subsequent to its passage past the ultrasound horn.

In one preferred embodiment of the invention, the vertical sides of said projections have a segmental shape. The invention will now be described in more detail with reference to the accompanying Figures, in which

Fig. 1 is a schematic illustration of an arrangement for producing wound dressings, or pads, in accordance with one preferred embodiment of the invention;

Fig. 2 illustrates part of an anvil roll included in the arrangement shown in Fig. 1;

Fig. 3 is a schematic illustration of a wound dressing or pad manufactured by means of the arrangement shown in Fig. 1;

Fig. 4 is a sectioned view taken on the line IV-IV in Fig. 3; and

Fig. 5 is a sectioned view taken on the line V-V in Fig. 3.

Fig. 1 illustrates schematically an inventive arrangement for manufacturing wound dressings or pads. The arrangement includes an anvil roll 1 and an ultrasound horn 2 included in a typical ultrasound welding unit positioned above the periphery of the anvil roll and movable in a radial direction so as to enable a mean distance to be set between the periphery of the anvil roll and said horn 2. Although not shown, the arrangement also includes means for drawing a web of material 3 through the nip defined between the roll 1 and the horn 2. The web 3 is comprised of two webs of material, i.e. a web 4 of plastic film and a web 5 of absorbent material, said webs being taken from respective storage reels 6 and 7. The plastic film 4 may consist of polyethylene and the web 5 may consist of nonwoven material that includes absorbent fibres, such as viscose or cellulose fibres. An appropriate material in this regard is a spun laced polypropylene-viscose nonwoven material. The two webs 4 and 5 are fastened to one another as they pass the horn 2 and the resultant combined web 3 is passed to a cutter 8 which cuts or punches-out individual pads 9 from the web 3.

Fig. 2 shows part of the anvil roll 1 in larger scale. As will be seen from Fig. 2, the periphery of the roll 1 includes rows of projections 10 that have curved outwardly facing surfaces 11 and vertical sides 12. By "outwardly facing surfaces" is meant the outer peripheral sides 11 of the projections 10, and by "vertical sides" is meant that the mutually opposing circle-segment shaped sides 12 of each projection are plane parallel with the plane of the paper in Fig. 1.

As the combined webs 4 and 5 pass the horn 2, the horn will press the webs 4, 5 against the periphery of the anvil roll as the horn moves up and down. It has been found that the plastic film that lies closest to the anvil roll 1 is cut by the opposing edges of the projections and that those web parts that lie outside these edges are then pressed down between said projections. At the same time, the side of the plastic layer that faces towards the web 5 will melt over the major part of the sides 12 of the projections 10. This re^¬ sults in compression of the nonwoven material 5 in those parts of the material that lie between the outer sides of the projections and the horn. This compression remains when the individual dressings or pads are cut from the combined web 3. It has been found that an anvil roll that includes projections which have curved outer sides produces a larger fastening area between those parts of the plastic film that have been depressed by the projections and the underlying absorbent material than an anvil roll where the outwardly facing surface of respective projections is straight. Figs. 3-5 illustrate a wound pad or dressing produced in accordance with the described method. The Figures show the dressing with that side of the dressing that lies against a wound when the pad is applied facing upwards. The dressing is comprised of a layer 4' of plastic film and a nonwoven layer 5' and includes mutually parallel rows of depressions 13 in the plastic layer and the underlying nonwoven layer. The depressions 13 have a hammock-like configuration in the plas- tic layer, as will best be seen from Fig. 5, and openings 14 perpendicular to the plane of the dressing are formed by the mutually separated cut surfaces of the plastic layer. The nonwoven material is compressed in the region of each depressions, as evident from Figs. 4 and 5. The layers 4' and 5' are also welded together within a greater part of the region of each depression.

Fluid, or liquid, absorbed in the absorbent material around the openings 14 will be quickly transported away therefrom, as a result of the smaller capillaries in the compressed parts of the absorbent layer 5'. In addition to favourable fluid transportation in the pad 9, there is also less risk of the openings 14 becoming blocked with solidified wound fluid than in the case of a dressing that lacks such compressed parts.

The dressing may conveniently be provided with a backing sheet of hydrophobic nonwoven material, such as polypropylene, for instance.

The wound dressing 9 can be sterilised by beta, steam or gas sterilising processes.

The described method can be used advantageously for the manu- facture of liquid-permeable outer sheets for absorbent arti- cles such as sanitary napkins or diapers. In respect of such outer sheets, it is important that discharged liquid can be transported quickly away from the skin in order for the napkin or diaper to give the impression of being dry and also in order to reduce the risk of discharged liquid flowing along the surface of the plastic film.

It will be understood that the described and illustrated embodiment can be modified within the scope of the present invention. For instance, the wound dressing may include more than one layer of absorbent material, although the outer layers must contain melt fibres, such as polypropylene or polyester fibres. Materials other than nonwoven material can be used, such as absorbent foam material, for instance. Fur- ther ore, the rows of projections may conveniently extend obliquely to the axial direction of the anvil roll. The statement in Claim 5 to the effect that the rows of projections extend "essentially in an axial direction" will be understood to include rows that define an angle of up to 45° with said axial direction. The projections may have a curved shape different to that shown in the Figures. It will there^¬ fore be understood that the invention is restricted solely by the contents of the following Claims.

Claims

1. An absorbent multilayer material (9) comprising a perforated layer (4') of hydrophobic material and at least one layer (5') of absorbent material, characterised by mutually sequential rows of depressions (13) disposed over one side of the material (9) that includes the hydrophobic layer (4'), wherein said depressions have the form of hammock-like parts of said hydrophobic layer that penetrate down into the layer of absorbent material (5') such as to form openings (14) which are perpendicular to the plane of said hydrophobic layer, and wherein said hammock-like parts are fastened to the absorbent layer over the major part of their respective surfaces; and is further characterised in that the absorbent layer is compressed in the region of each depression.

2. An absorbent multilayer material according to Claim 1, characterised in that the hydrophobic layer (4') is com^┬¼ prised of plastic film and the absorbent layer (5') is com- prised of a nonwoven material that includes absorbent fibres.

3. An absorbent multilayer material according to Claim 2 or Claim 3, characterised in that the material includes several layers of nonwoven material, of which at least those layers which are not in contact with the hydrophobic layer include melt fibres.

4. An absorbent multilayer material according to Claim 1, characterised in that the absorbent layer is comprised of absorbent foam.

5. A method of producing an absorbent multilayer material, characterised by combining a layer (4) of weldable material with at least one layer (5) of absorbent material and passing the combined layers through the nip between an ultrasound horn (2) and an anvil roll (1) with the layer of weldable material (4) lying against said anvil roll, wherein said anvil roll is provided around its circumference with mutually sequential rows of discrete projections (10) having

5 curved outwardly facing surfaces (11) and vertical side surfaces (12), and wherein said rows extend essentially in an axial direction, and wherein said method is further characterised by setting the distance between the ultrasound horn and the anvil roll so that the weldable material will be cut w along the curved edges between the outwardly facing side surface (11) and the vertical side surfaces (12) of each projection while, at the same time, the combined layers (4, 5) are deformed within the region of each projection such as to form rows of depressions and such as to fasten the weld-

15 able layer (4) to the layer of absorbent material (5) within the major part of the region of each projection (10) .

6. A method according to Claim 5, characterised by combining several layers that include absorbent fibres to-

20 gether with said layer of weldable material, of which layers at least those layers that have no contact with the layer of weldable material also include melt fibres.

7. An arrangement for producing an absorbent multilayer 25 material that has one perforated side, characterised by means for combining at least two webs of material (4, 5) , means for passing the combined webs through the nip between an ultrasound horn (2) of an ultrasound welding unit and an anvil roll (1) that has circumferentially disposed sequential rows 30 of discrete projections (10) that have curved outwardly facing surfaces (11) and vertical side surfaces (12), said rows extending essentially in an axial direction, and by means (8) for cutting individual pieces from the web (3) subsequent to said web passing the ultrasound horn.

35

8. An arrangement according to Claim 7, characterised in that the vertical side surfaces (12) of the projections (10) have a circle-segmental shape.

9. An arrangement according to Claim 8, characterised in that the vertical side surfaces (12) of the projections (10) have a semi-circular shape.