GB2142276A

GB2142276A - Absorbent materials

Info

Publication number: GB2142276A
Application number: GB08415607A
Authority: GB
Inventors: Alan Matthew Wraith
Original assignee: Smith and Nephew Associated Companies PLC
Current assignee: Smith and Nephew PLC
Priority date: 1983-06-28
Filing date: 1984-06-19
Publication date: 1985-01-16
Also published as: GB8415607D0; GB2142276B

Abstract

An absorbent material suitable for contact with the body which comprises an absorbent layer and a liquid pervious body facing layer of a thermoplastic polymer net heat bonded to a surface of the absorbent layer is characterised in that the net is a multi-layered composite net comprising a heat bonding layer of thermoplastic polymer and a substrate layer of a different thermoplastic polymer which has a melting temperature higher than that of the heat bonding layer. The net is bonded to the surface of the absorbent layer at a temperature at which the heat bonding layer melts but the substrate layer does not melt. Wound dressings comprising the absorbent material and method for the preparation thereof are described.

Description

SPECIFICATION Absorbent materials The present invention relates to absorbent materials, for contact with the body and processes for their preparation.

Absorbent materials are used in a wide range of body contacting products which are capable of absorbing body exudates. These absorbent products include wound dressings and sanitary pads such as sanitary towels, incontinence pads, maternity pads and the like. The absorbent material used in these products usually comprise an absorbent layer and a body facing layer which acts as a cover layer for the absorbent layer. Desirably these cover layers have openings which will allow the passage of body exudate to the absorbent layer but which will prevent contact of the absorbent layer with the body thus inhibiting transfer of the absorbent layer material to the body site. Apt known cover layers for use on absorbent pads comprise a net of thermoplastic polymer. Absorbent pads with with a cover layer of thermoplastic polymer net are disclosed in British Patents Nos. 970,123 and 1,142,323.British Patent No. 970,123 discloses a non-adhesive absorbent material, comprising an upper layer of pervious net made of thermoplastic polymer, for example a polyolefine and a backing layer of liquid impervious material which is joined to the net layer at the side edges of the pad. In such an arrangement the net cover layer is not held in intimate contact with absorbent layer which is necessary to get rapid penetration of the body exudate through the hydrophobic net cover layer. Furthermore relative movement between the net cover layer and the absorbent layer may cause the net cover layer to become creased or puckered when the pad is in contact with the body which may cause 'pooling' of the exudate on the surface of the pad or lead to irritation of the body contact area.It is therefore desirable that the net cover layer be attached to the surface of the absorbent layer so that it is in intimate contact therewith.

British Patent No. 1,142,323 discloses a surgical dressing comprising an absorbent pad with a non-adherent surface, a thermoplastic polymer net made by biaxially stressing a film having a regular pattern of embossments or cavities on at least one surface. British Patent No. 1,142,323 further discloses that the net may be adhered to the absorbent layer by heat sealing. Such an attachment of the net to the absorbent layer therefore avoids the problems associated with the absorbent pad of British Patent No. 970,123.It has been found, however, that in order to obtain adequate adhesion between the thermoplastic polymer net and the absorbent layer the heat bonding or sealing process has to be carried out either at a temperature which melts the polymer and causes the net to break up or sink into the absorbent layer or at a pressure which compacts the absorbent layer so that its softness and absorbency properties are reduced. The heat bonding of the thermoplastic polymer net layer to the absorbent layer is therefore difficult to achieve without affecting the structure of the net, so that it cannot effectively act as a cover layer, or the desirable softness and absorbent properties of the absorbent layer.An absorbent material suitable for contact with the body has now been found in which a thermoplastic polymer net layer has been heat bonded to an absorbent layer in a manner which overcomes these problems.

Accordingly the present invention provides an absorbent material suitable for contact with the body which comprises an absorbent layer and a liquid pervious body facing layer of thermoplastic polymer net heat bonded to a surface of the absorbent layer characterised in that the net is a multi-layered composite net comprising a heat bonding layer of a thermoplastic polymer and a substrate layer of a different thermoplastic polymer which has a melting temperature higher than that of the heat bonding layer, said net having been heat bonded to the surface of the absorbent layer at a temperature at which the heat bonding layer melts but the substrate layer does not melt.

The absorbent material of the invention is formed at a temperature at which the substrate layer of the composite multi-layered net does not melt. The net therefore will not break up or sink into the absorbent layer and thus retains its original structural form. Furthermore the molten nature of the heat bonding layer of the net at that temperature allows the absorbent material to be formed at a pressure which is sufficiently low to prevent the absorbent layer becoming compacted and losing its softness and absorbency properties.

The absorbent material of the invention formed in the manner described above thus comprises a body facing layer of net heat bonded to an absorbent layer in which the bonded net has a similar structural form to that of the original net and the absorbent layer has similar absorbent and softness properties to that of the original absorbent layer used to form the absorbent material.

The absorbent materials of the invention are especially suitable for use in wound dressings.

A wound dressing which comprises the absorbent material of the invention is thereffore a preferred aspect of the invention.

Preferably the wound dressing is sterile within a bacteria-proof pack.

A favoured wound dressing of the invention has a thickness of 1 to 20mm and consists of an intermediate absorbent layer between outer layers of composite multi-layered net heat bonded to the surfaces of the intermediate absorbent layer.

Preferably the wound dressing has a thick ness of 1.5 to 5mum.

Such wound dressings have desirable flexi bility and non-adherency characteristics. Furthermore these wound dressings have two surfaces suitable for contact with the body to eliminate the possibility of placing an unsuit able surface against the body.

The absorbent material of the invention, however, can consist of a body facing layer of composite multi-layered net heat bonded to a surface of the absorbent layer. Such an absor bent material can be used as an absorbent pad for a wound dressing for example a first aid dressing. The absorbent material can also be used as an absorbent pad or cover layer on a sanitary pad such as diapers, sanitary towels and incontinence pads.

Absorbent material of the invention having one or two outer layers of composite, multilayered net can also be used as a bandage.

The Composite multi-layered net used in the invention comprises a substrate layer and a heat bonding layer.

The heat bonding layer of the composite, multilayered net used to form the absorbent material of the invention will have a melting temperature which is sufficiently low to enable the net to be heat bonded to the absorbent layer without causing the net to break up and lose its structural form. The melting temperature of the heat bonding layer will usually be less than 150 C. The heat bonding layer can suitably have a melting temperature of 80 C to 150or and can desirably have a melting temperature of 110 C to 150 C. If the net is to be used as a wound facing layer on a wound dressing pad it is preferred that the melting temperature of the heat bonding layer is 135 C to 150 C. A net with a heat bonding layer having this preferred melting temperature range can be heat bonded to an absorbent layer to form a bond which will withstand a steam auto-clave sterilisation process which employs temperatures of up to 137 C.

The heat bonding layer of the composite, multi-layered net used to form the absorbent material of the invention will comprise a thermoplastic polymer having a melting temperature as herein before described. Suitable thermoplastic polymers for the heat bonding layers include ethylene vinyl acetate copolymers, saponified ethylene vinyl acetate copolymers, high density polyethylene, low and medium density polyethylene, linear low density polyethylene, copolyamides, copolyesters, ethylene ethyl acrylate copolymers and the alike and blends thereof.

Preferably the heat bonding layer comprises a polyethylene. Suitable polyethylenes have a melting temperature of 110 C to 140'C.

Such polyethylenes include low and medium density polyethylene made by the high pressure process, linear low density polyethylene and high density polyethylene. Preferred poly ethylenes are high density polyethylene and linear low density polyethylene. Apt high density polyethylenes are known as Solvay A3180 (melting temperature approximately 135 C, density 0.96, melt flow index 18) available from Solvay etCie S.A. and Vestolan A601 6F (melting temperature approximately 135 C density 0.96; melt flow index 7) available from Chemische Werke Huls A.G.Apt linear low density polyethylenes are known as MW 1210 (melting temperature approxi mately 125eC density 0.94; melt flow index 20) and MW 1350 (melting temperature approximately 115"C. density 0.92; melt flow under 20) available from CDF Chemie E.P.

The heat bonding layer can suitably be 5% to 30% by weight and preferably be 10% to 20% by weight of composite multi-layered net used in the invention.

The substrate layer of the composite multilayered net used to form the absorbent material of the invention will have a melting temperature which is sufficiently higher than that of heat bonding layer to prevent the substrate layer melting during the heat bonding of the net to the absorbent layer. The melting temperature of the substrate layer will be at least 5 C higher, desirably at least 10 C higher and preferably at least 30 C higher than that of the heat bonding layer. The melting temperature of the substrate layer will usually be above 80'C. The substrate layer can suitably have a melting temperature of 110 C to 250 C and preferably have a melting temperature of 135 C to 250 C.

The substrate layer of the composite multilayered net used to form the absorbent material of the invention will comprise a thermoplastic polymer having a melting temperature as hereinbefore described. Suitable thermoplastic polymers for the substrate layer include high density polyethylene, linear low density polyethylene, polypropylene, propylene-ethylene copolymers, polyamides, polyether amides, polyester amides, copolyamides, polyester, and copolyesters, polybutylene, polystyrene, polycarbonate and the like and blends thereof.

The substrate layer preferably comprises high density polyethylene or polypropylene.

Apt high density polyethylenes are those hereinbefore disclosed in relation to the heat bonding layer. Suitable polypropylenes include propylene homopolymers and copolymers of propylene with less than 10% by weight of ethylene which have a melting temperature of approximately 160 C to 170 C. Apt polyropylenes of this type are known as Profax 6524 (melting temperature of approximately 165 C, density 0.90, melt flow index 4) available from Hercules Inc. and Solvay HW609 (melting temperature of approximately 165 C, density 0.90 melt flow index 18) available from Solvay et Sie S.A.

A preferred composite multi-layered net for use in the absorbent material of the invention has a substrate layer which comprises poly propylene and a heat bonding layer which comprises high density polyethylene. Such a net can be heat bonded to an absorbent layer to form an absorbent material which will withstand steam autoclaving temperatures used for sterilising wound dressings. Another preferred composite multi-layered net has a sub strate layer which comprises a high density polyethylene and heat bonding layer of a linear low density polyethylene. Such a net can be heat bonded to an absorbent layer to form an absorbent material suitable for wound dressings which if necessary can be sterilised by methods other than steam autoclaving.A further preferred composite multi-layered net has a substrate layer which comprises an incompatible blend of high density poly ethy lene and polystyrene and heat bonding layer of linear low density polyethylene. Such a net can be heat bonded to an absorbent layer to form an absorbent material which has a soft body facing layer and which is highly suitable as a cover layer for sanitary pad products.

The composite, multi-layered net heat bonded to the absorbent layer forms the body facing layer of the absorbent material of the invention. Such a net will have apertures which will allow the passage of body exudate but will prevent contact of the absorbent layer with the body. Suitable composite multilayered nets have apertures with a maximum dimension of 0.05 to 4mm and preferably have apertures with a maximum dimension of 0.1 to 2.5mm. Such nets can suitable have a void area of 15% to 80% and preferably have a void area of 20% to 75% of the total area of the net.

The composite, multi-layered net used in the invention can suitably have a weight per unit area of 5 to 40g/m2 and preferably have a weight per unit area of 10 to 30g/m2.

The composite multi-layered net used in the invention can have various constructions. Favoured nets have a regular pattern of intersecting oriented strands and openings which provide the absorbent materials of the invention with a body facing layer having a similar regular pattern of apertures through which the body exudate can pass. Preferred regular nets are nets which have at least one set of parallel strands to provide if necessary reinforcement of the absorbent material. Such nets can have two or more sets of parallel strands which intersect to define openings of geometric shape which include shapes such as a square, rectangles, triangles, a rhombus, parallelograms and hexagons.

A preferred net of this type has a first set of parallel strands which intersect at 90 C with a second set of parallel strands to define square or rectangular openings. In such nets the first set of parallel strands may extend in the machine direction of the net and the second set of parallel strands may extend in a direction which is transverse to the machine direction to form a grid pattern net. Alternatively both sets of parallel strands may extend in directions which are at an angle to the machine direction to form a diamond pattern net.

Another preferred net has a first set of parallel strands and a transverse set of parallel strands which intersect at an angle of up to 60 C to the transverse direction. A preferred net with a substrate layer of an incompatible blend of polymers for example a blend of high density polyethylene and polystyrene can have fibrillated strands. Such a net will have a soft feel and will therefore provide the body facing layer of the absorbent material with a similar soft feel thus making the absorbent material highly suitable as a cover layer for absorbent pads such as diapers, sanitary towels and like sanitary pads.

A further preferred net has three sets of parallel strands which intersect to define triangles. Such nets exhibit a hexagonal pattern of strands and junctures. Apt nets of this type can have thicker junctures which are interconnected by thinner strands. Such nets are very flexible are therefore highly suitable when heat bonded to an absorbent material as a body facing layer on flexible wound-absorbent pads.

The regular pattern nets described above may have thicker strands or a higher density of strands in one direction than in another direction to provide directional reinforcement of the absorbent material.

The composite multi-layer nets used in the invention which comprise intersecting strands can suitably have 2 to 30 intersections per cm of strand and preferably 3 to 20 intersections per cm of strands in any one direction. In preferred nets of the invention which have a more than one set of parallel intersecting strands it is desirable that these nets have 2 to 30 intersections per cm of strand and preferably that these nets have 3 to 20 intersections per strand in the direction of any set of strands.

The composite multi-layered polymeric net used in the invention may be prepared by any one of a number of known techniques; see for example general methods of preparation described in British Patents Nos. 1,075 487. 1 427,281 and 1,427,282. In such methods of preparation the net is formed by stretching a composite multi-layer embossed sheet which has at least two layers of different polymeric resin. The multi-layer embossed sheet can be conveniently made by coextrusion or lamination of the different polymeric resin layers. A suitable method of forming a laminated multilayer embossed sheet comprises bringing a polymer film in contact with a molten film of a different polymer during the embossing stage for example by feeding the films into the nip of the embossing rollers.In general therefore such nets may be prepared by the lamination or coextrusion of at least two different synthetic, polymeric resin layers in a net form.

Preferred nets which have three sets of parallel intersecting strands which exhibit a hexagonal pattern of strands and junctures can be made from a composite multi-layered embossed sheet by the process disclosed in British Patent No. 1,055,963 for making single layer nets. Preferred net, which have a set of parallel strands which intersect with a transverse set of strands at an angle up to 60C to the transverse direction and which also have fibrillated strands, can be made from a composite multi-layer embossed sheet by the process disclosed in British Patent No.

1,548,865 for making the single layer net.

The absorbent layer for use in the absorbent material of the invention can be any of the absorbent layers used in body contacting pads providing that the layer is in a coherent form which will enable it to be heat bonded to the composite multi-layered net used in the invention. Such coherent absorbent layers include woven fabrics, knitted fabrics, non-woven fabrics and staple fibre batts and fleeces which have been lightly bonded by physical or chemical means.

Preferred coherent absorbent layers comprise a layer of staple fibres which have been lightly bonded by physical or chemical means and which are in a relatively uncompacted form so as to provide a soft layer. The absorbent layer preferably comprises water absorbent fibres which include cellulosic fibres such as cotton, viscose rayon and acetate rayon fibres. Such absorbent layers may advantageously contain blends of these water absorbent fibres with less water absorbent or hydrophobic fibres which includes polyester, polyamide, acrylic and polypropylene fibres.

The absorbent layer for use in the absorbent material of the invention can suitably have a weight per unit, area of 10 to 250g/m2.

The composition and weight per unit area of the absorbent layer of the absorbent material of the. invention can be adapted according to the intended use of the absorbent material. Suitable absorbent layers for an absorbent material which can be used as a cover layer for sanitary pads comprises a fleece having a weight per unit area of 10 to 30g/m2. An apt absorbent layer of this type is a carded fleece containing a blend of viscose rayon and cotton staple fibres having a weight per unit area of 12 to 20g/m2. Suitable absorbent layers for an absorbent material which can be used as an absorbent pad for wound dressings including first aid adhesive dressin#gs comprise a lightly bonded batt of fibres having a weight per unit area of 60 to 250g/m2 and preferably a weight per unit area of 90 to 150g/m2.Such absorbent layers preferably contain 50% to 95% by weight of cotton or viscose rayon fibres blended with a hydrophobic fibre such as polyester or acrylic fibres lightly bonded by heat, latex or other suitable chemical or mechantcal means. An apt absorbent layer of this type comprises a batt containing 90 to 95% by weight of cotton fibres and 5 to 10% by weight of polyester fibres lightly bonded by hot calendering having a weight per unit area of 100 to 120g/m2.

Another apt absorbent layer of this type is a batt containing 80% by weight of viscose fibres and 20% by weight of acrylic fibres lightly bonded by hot calendering having a weight of 85g/m2 and known as Lantor 1207 available from Lantor Limited.

The absorbent material of the invention can be formed by heat bonding a composite, multi-layered thermoplastic polymer net to an absorbent layer. Accordingly another aspect of the invention provides a process of making an absorbent material suitable for contact with the body which comprises heat bonding a thermoplastic polymer net to a surface of an absorbent layer to provide a liquid pervious body facing layer therefore characterised in that the net is a composite multi-layered net comprising a heat bonding layer of a thermoplastic polymer and a substrate layer of a different thermoplastic polymer which has a melting point higher than that of the heat bonding layer and the bonding of said net to the surface of the absorbent layer is carried out at a temperature at which the heat bonding layer melts-but the substrate layer does not melt.

The absorbent layer and the composite multi-layered net used in the process of the invention can be the same as those hereinbefore described in relation to the absorbent material of the invention.

The heat bonding process of the invention is carried out at the temperature at which the heat bonding layer melts but which is lower than that at which the substrate layer melts.

Such a process therefore has the advantage that the net can be heat bonded to the absorbent layer at a temperature which does not cause the net to break up or sink into the absorbent layer. Furthermore because of the molten nature of the heat bonding layer during the bonding process an excellent bond between the net and absorbent layer can be obtained under low bonding pressures which are sufficiently low to prevent the absorbent layer becoming compacted and losing its absorbency or softness properties.

In one aspect the process of the invention consists of heat bonding a layer of net to a surface of an absorbent layer. However in another aspect the process of the invention consists of heat bonding a layer of net to both surfaces of an absorbent layer to provide a liquid pervious facing layer suitable for contact with the body on both surfaces thereof.

The process of the invention is preferably carried out as a continuous process in which the absorbent layer and one or more net layers are fed between the nip of two heated rollers or belts. An apt apparatus comprises two heated belts. A favoured apparatus of this type is a fusion press reference M8 available from the Reliant Tooling Company. Using this apparatus the net and absorbent layers can be heat bonded at nip pressures of 0.35 to 1.4 kgf/cm2. It has been found that at these low nip pressures soft absorbent layers do not become compacted and lose their softness or absorbency properties.

The absorbent materials made by a continuous process of the invention can be shaped by any convenient method such as cutting or stamping to form the absorbent material of the invention into a shape suitable for use as a wound dressing pad, a sanitary pad, a cover layer for a sanitary pad or a bandage.

Favoured wound dressings of the invention preferably have a square or rectangular shape.

-Such wound dressings can suitably have a side dimension of 4cm to 30cm. Typical wound dressing sizes which have been found suitable are 5cm > < x 7.5cm,7.5cm, 1 cm X 7.5cm, 15cm X 7.5cm and 20cm X 7.5cm. Sterile wound dressings of the invention can be obtained by packaging the dressings in a bacteria-proof pack for example heat sealed pouches and sterilising the pack containing the dressing by any suitable sterilising method for example by an ethylene oxide sterilising method.

The invention will now be illustrated by reference to the following Examples.

Example 1 A composite multi-layer net (14g/m2) having a substrate layer (1 2g/m2) of high density polyethylene (density 0.96, melt flow index 7, melting temperature approximately 1 35 C) and a heat bonding layer (2g/m2) of linear low density polyethylene (density 0.94, melt flow index 18, melting temperature approximately 1 25 C) was bonded to an absorbent layer (85g/m2) consisting of a blend of 80% by weight of viscose fibres and 20% by weight of acrylic fibres, lightly bonded by hot calendering, by means of a fusion press (ref.

M8, Reliant Tooling Company). The heat bonding process was carried out at a temperature of approximately 1 25 C to 1 35 C, using a roller nip pressure of 0.35 to 1.4 kgf/cm2 and a speed of 15 metres/minute.

The net used in this example had a hexagonal pattern of thick bosses (100 to 150 ,um thick) each connected by six thinner strands to give approximately 10 intersections per cm in the direction of any strand.

The absorbent material formed by the process of this example was found to be suitable for use as an absorbent pad of first aid dressings.

Example 2 (Comparative Example) An absorbent material was made in the same manner as Example 1 using a single layer net of high density polyethylene instead of a composite multi-layered net. It was found that in order to obtain satisfactory bonding it was necessary to use a bonding temperature of 135 C to 138 C and a nip pressure of 2.8 to 4.9 kgf/cm2. The absorbent material formed by this example had a net cover which had sunk into the absorbent layer. The absorbent layer of this material had been compacted and had a 'harder feel' than that of the unbonded absorbent layer.

Example 3 An absorbent material was made in the same manner as Example 1 using a composite layer net (17g/m2) having a substrate layer (15g/m2) of polypropylene (melting temperature approximately 167 C, density 0.90, melt flow index 18)and heat bonding layer (2g/m2) of high density polyethylene (melting temperature approximately 135 C, density 0.96, melt flow index 18)which was heat bonded to both surfaces of an absorbent layer (110g/m2) consisting of a blend of cotton fibres (92.5% by weight) and bicomponent polyester fibres (7.5% by weight) lightly bonded by hot rolling. The heat bonding process was carried out at a temperature of 135 C to 140 C using a roller nip pressure of 0.35 to 1.4kgf/cm2 at a speed of 15 metres/minute.

The net used in this example had a square grid pattern of strands and openings and had 6 intersections per cm in the direction of both strands.

The absorbent material formed by this example had two outer net layers suitable for contact with the body and was found to be suitable for use as a wound dressing pad capable of withstanding a steam autoclaving sterilisation at 136 C. The material had a softness which was similar to that of the unbonded absorbent layer.

Example 4 A composite multi-layered net (10g/m2) having a substrate layer (9g/m2) incompatible blend of 92.5 parts by weight of high density polyethylene (density 0.96, melt flow index 7, melting temperature 135 C) and 7.5 parts by weight of high impact polystyrene (Styrene 485 available from Dow Chemicals) and a heat bonding layer 1 g/m2) of linear low density polyethylene (density 0.94, melt flow index 18, melting temperature approximately 125 C) was bonded to an absorbent layer consisting of a carded fleece (15g/m2) of viscose fibres in the same manner as Example 1.

The net used in this example had a parallel set of longitudinal strands (12 stands per cm) and a transverse set of diagonal parallel strands (16 strands per cm) which were partially fibrillated.

The absorbent material made by this example was found to be highly suitable for use as a cover layer for sanitary pads such as diapers, sanitary towels and incontinence pads.

Example 5 An absorbent material suitable for wound dressings was made in continuous process in which the composite multilayer net (40cm width) of Example 1 was heat bonded to both surfaces of a similar width absorbent layer (110g/m2) consisting of a blend of cotton fibres 192.5% by weight) and bicomponent polyester fibres (7.5% by weight), lightly bonded by hot rolling, by means of a fusion press (ref. Reliant Tooling Company).

The heat bonding process was carried out at a temperature of approximately 125 C to 135 C using a roller nip pressure of 0.35 to 1.4kgf/cm2 and a speed of 15 metres/mm.

The absorbent material sheet was then trimmed and slit in 7.5cm width strips. The strips of absorbent material were then fed into a packaging machine (Autowrap) where the strips were cut into dressing sizes (7.5m x 5cm) and sealed into bacteria-proof pouches.

The pouches were formed by edge heat sealing a Kraft paper (33g/m2) coated with polyethylene (12g/m2) to an uncoated Kraft paper (56g/m2). The pouches containing the dressings were then sterilized by ethylene oxide to form the sterile dressings of the invention.

The dressings had a thickness of 2 to 2.5mm.

Claims

1. An absorbent material suitable for contact with the body which comprises an absorbent layer and a liquid pervious body facing layer of a thermoplastic polymer net heat bonded to a surface of the absorbent layer characterised in that the net is a multi-layered composite net comprising a heat bonding layer of a thermoplastic polymer and a substrate layer of a different thermoplastic polymer which has a melting temperature higher than that of the heat bonding layer, said net having been heat bonded to the surface of the absorbent layer at a temperature at which the heat bonding layer melts but the substrate layer does not melt.

2. A wound dressing which comprises the absorbent material of claim 1.

3. A wound dressing as claimed in claim 2 which is sterile within a bacteria-proof pack.

4. A wound dressing as claimed in either of claims 1 or 2 which has a thickness of 1 to 20mm and consists of an intermediate absorbent layer between outer layers of composite multi-layered net heat bonded to the surfaces of the intermediate absorbent layer.

5. An absorbent material as claimed in claim 1 which consists of an absorbent layer and a layer of composite multi-alyered net heat bonded to a surface of the absorbent layer.

6. An absorbent material as claimed in either of claims 1 or 5 in which the substrate layer has a melting temperature of more than 80 C and the heat bonding layer has a melting temperature of less than 1 50'C and said substrate layer has a melting temperature which is at least 1 0 C higher than the melting point of said heat bonding layer.

7. An absorbent material as claimed in any of claims 1, 5 and 6 in which the substrate layer has a melting temperature of 1 35 C to 250 C and the heat bonding layer has a melting temperature of 1 1 0 C to 1 50 C.

8. An absorbent material-as claimed in any of claims 1 and 5 to 7 in which the heat bonding layer has a melting temperature of 1 35'C to 1 50 C.

9. An absorbent material as claimed in any of claims 1 and 6 to 8 in which the substrate layer comprises polypropylene and the heat bonding layer comprises polyethylene.

10. An absorbent material as-claimed in claim 9 in which the heat bonding layer comprises high density polyethylene.

11. An absorbent material as claimed in claim 9 in which the heat bonding layer comprises linear low density polyethylene.

12. An absorbent material as claimed in any of claims 1 and 5 to 7 in which the substrate layer comprises high density polyethylene.

13. An absorbent material as claimed in claim 12 in which the heat bonding layer comprises linear low density polyethylene.

14. An absorbent material as claimed in any of claims 1 and 5 to 13 in which the net has a weight per unit area of 10 to 30g/m2

15. An absorbent material as claimed in any of claims 1 and 5 to 14 in which the net comprises two or more sets of intersecting strands with 3 to 20 intersections per cm of strand in the direction of any set of strands.

16. An absorbent material as claimed in any of claims 1 and 5 to 15 in which the net comprises co-extruded polymer layers.

17. An absorbent material as claimed in any of claims 1 and 5 to 16 in which the heat bonding layer comprises 10% to 20% by weight of the net.

18. An absorbent material as claimed in any of claims 1 and 5 to 17 in which the absorbent layer has a weight per unit area of 60 to 250g/m2.

19. A process of making an absorbent material suitable for contact with the body which comprises heat bonding a thermoplastic polymer net to a surface of an absorbent layer to provide a liquid pervious body facing layer therefor characterised in that the netis a composite multi-layered net comprising a heat bonding layer of thermoplastic polymer and a substrate layer of a different thermoplastic polymer which has a melting point higher than that of the heat bonding layer and the bonding of said net to the surface of the absorbent layer is carried out at a temperature at which the heat bonding layer melts but the substrate layer does not melt.

20. A process of making an absorbent material as claimed in claim 19 in which the composite multi-layered net is bonded to both surfaces of an absorbent layer.