IE52399B1 - Absorbent products - Google Patents

Abstract

Absorbent articles e.g. wound dressing, napkins, sanitary pads, comprise absorbent material wholly or partly faced with perforated cellular plastics film, the perforations having been made by electrical discharges, specifically which pit and oxidise the side of the film facing the absorbent material. Pref. the film is stretched polyolefin film e.g. polyethylene of wt. 10 to 100 gms. per sq.m., and with closed cells forming up to 14% of its vol. The film permeability is improved by spark discharge perforation.

Description

The present invention relates to absorbent products of the kind comprising absorbent material and a porous facing material, for example, plasters and bandages, surgical wound dressings, female sanitary protection products, baby napkins, e.g. disposable napkins and incontinence products.

According to the present invention there is provided an absorbent product comprising an absorbent material at least partially faced by a cellular plastics film having perforations which have been produced by passing electrical discharges therethrough. In one aspect of the invention, the absorbent material is entirely embraced by said cellular plastics film. In another aspect of the present invention, one face of the absorbent material is covered by said cell15 ular plastics film and another face is optionally covered by a backing sheet.

A suitable cellular plastics film is described in British Patent Specification No. 1556614 and is a thermoplastic polymeric film in which voids or cells are generated by one or more of a variety of means including i) the use of physical or chemical blowing agents; ii) the physical deformation of materials containing additives other than blowing agents which cause the material to be void-containing on physical deformation, which additives may, for example, be inorganic or organic fillers or pigments and iii) the leaching out of soluble additives.

Preferably the film is as described and claimed in British Patent Specification No. 1525224. This is a stretched polyolefin film having a substantially uniform cellular structure and formed from a composition comprising a crystal35 line linear polyolefin, which film has at least the following characteristics :1) it comprises no more than 14% by volume of the film of closed cells; 2) it has an apparent density which is 90 to 20% of the density of the non-cellular unstretched composition; 3) it has a cell factor equal to or less than +0.65, which factor may be zero or negative; 4) it contains from 0 to 25% by weight based on the polyolefin of a filler and/or pigment; ) it has a thickness of up to 0.011 (0.028 cm); 6) it comprises cells with dimensions such that the average cell volume is no greater than 10 cc; 7) it has been stretched in the plane of the film by an amount corresponding to a stretch ratio of at least 1.1:1 in one direction or in two substantially mutually perpendicular directions.

The mode of calculation of the percentage volume of closed cells, the apparent density, the cell factor, film thickness and average cell volume are described in British Patent Specification No. 1525224.

The film is preferably a foamed high density polyethylene film having a weight range of 10 to 100, preferably 10 to 50 g/m and preferably containing from 10 to 80 per7 forations /cm . Foamed high density polyethylene film sold under the name Aerowrap (Trade Mark) B.X.L. Plastics Limited having a weight of about 12 or 16 g/m and 40 perforations 2 /cm has been found particularly useful. The foam cell structure reduces the springiness of the film so that it folds and retains the folds well in the machine make up of the absorbent products.

The perforations may be made by the discharge method disclosed in German Offenlegungsschrift No. 2552919. This produces a spread of sizes for the perforations due to the cellular nature of the film. The range of sizes is normally between approximately 100 microns in diameter and 800 microns with preferably at least 30% of the perforations having sizes between 300 microns and 600 microns. The spark discharge perforations are preferentially formed at the voids and thin walled cells of the foam structure and thereby the perforations are neatly formed with a minimum of thermal degradation or melt displacement and with melt-smooth edges which 2399 are virtually inconspicuous and non-abrasive as they contain a minimum of displaced plastics material. The small smooth edged perforations gives good drainage of fluids into the absorbent material, whilst providing good encapsulation of the absorbent material. It has.been found that this material has non-adherent wound release properties, allows the passage of blood and water through the perforations, is soft, smooth, flexible and non-abrasive, conforms wells and is not harsh or rigid in contact with the skin or wounds and is strong With good resistance to tear initiation and propagation. Also compared to previously used materials, the relative freedom from surface roughness, large holes, and perforations containing polymer webs, reduces the chance of amalgamation of the dressing to a scab or developing wound repair tissue.

It is also believed that the electrical discharge method of perforation assists in providing the permeability properties of the cellular plastics film required in absorbent products and its effect is somewhat similar to the corona electrical discharge process used to promote ink adhesion on plastics films which are to be printed. The effect of the electrical discharge is that one side of the film is lightly pitted and oxidized by the discharge and ionisation, and that surface tension is modified and the contact angle reduced. Drops of water, for example, applied to such side of the film will spread and hence penetrate the film more easily than on the other side on which water remains as discrete drops.

Accordingly the cellular film enhances passage of liquid in the direction towards the untreated side of the film. When the film is used in products, such as baby napkins, where a large 'volume of liquid needs to be rapidly distributed and absorbed over a large area, it is preferred that the pitted and oxidized side of the film be exposed to the liquid to be absorbed.

Thus an absorbent incontinence product in accordance with the present invention comprises a layer of absorbent material covered on one face by a perforated cellular plastics film, having perforations produced by passing electrical dis5 charges therethrough, wherein one side of the perforated film is pitted and oxidised by the electrical discharges and the pitted and oxidised side of the film faces away from the said absorbent material.

However when the film is used in wound dressings, it is preferred that the untreated side of the film be exposed to the blood or wound exudate to be absorbed. The blood or 2399 wound exudate is generally small in volume and more viscous and moves more slowly through the perforations.

However on meeting the pitted and oxidized side of the film, the blood or wound exudate is assisted to disperse and becomes more uniformly distributed in the absorbent. It is also known that the untreated side of the film has lower adhesion to, and better releases from the wound repair tissue.

The following Figs. 1 to 9 illustrate a number of absorbent products according to the present invention in which the perforations in the perforated cellular film have been produced by electrical discharges.

In the drawings, the same reference numerals indicate the same or similar parts.

Fig. 1 shows a cross-section through an adhesive plaster or bandage; Fig. 2 is a plan view of Fig. 1; Figs. 3 t'o 6 show cross-sections of various surgical wound dressings; Figs 7 and 8 show cross-sections of female sanitary protection products; and Fig. 9 shows a cross-section of a baby napkin.

Referring to Figs. 1 and 2 there is shown an adhesive plaster or bandage comprising a backing sheet 3 having a layer of pressure sensitive adhesive 4 thereon. A layer, such as a pad, of absorbent material 2 is entirely embraced by a perforated cellular plastics film 1. In use, the plaster is placed over the wound with the perforated film 1 in contact with the wound.

Preferably the cellular plastics film is of the foamed type such as described and claimed in British Patent Specification No. 1525224 or described in British Patent Specification No. 1556614, and is preferably a foamed high density polyethylene film having a weight range of 10 to 100, preferably 10 to 50, g/m and preferably containing 2 from 10 to 80 perforations /cm . Foamed high density polyethylene film sold under the trade name Aerowrap by B.X.L, Plastics Limited having a weight of about 12 or 16 g/m and 40 perforations /cm has been found particularly useful.

Referring to Figs. 3 to 6 there are shown various surgical wound dressings. In Fig. 3, a pad of absorbent material 2 (such as cotton or rayon fibres) is embraced by a sheet of perforated cellular plastics film 1 having its ends joined by adhesive 6. Within absorbent material 2 are two layers of semi-repellent tissue 5. In Fig. 4, absorbent material 2 is covered on one face by a perforated portion 1 and on the other face by a non-perforated portion or backing sheet portion 7 of a sheet of plastics film. Again the ends of plastics film are joined by adhesive 6 and within absorbent material 2 are two layers of semi-repellent tissue 5.

In Figs. 5 and 6 perforated plastics film is mounted over one face of absorbent material 2 by lines of adhesive 8.

The absorbent material 2 may be foam (as in Fig. 5) or needle-loomed or felted cotton or rayon (as in Fig. 6). In use, the wound dressings described in Figs. 3 to 6 are placed on the wound with the perforated cellular film in contact with the wound.

In Fig. 7, the pad of absorbent material 2, such as woodpulp, is partially embraced by a plastics film 10 for retaining absorbed fluid. The absorbent material 2 and plastics film 10 is wholly embraced by a layer of tissue 9 which in turn is embraced by a perforated plastics film 1.

The ends of the tissue and the ends of the film 1 overlap as shown and are secured by known means. An attachment layer of pressure sensitive adhesive 11 is secured to the underside of the perforated plastics film 1 and a layer of silicone coated release paper 12 protects the adhesive before use.

In Fig. 8, a layer pad of absorbent material 2, such as woodpulp is wholly embraced by a layer of tissue 9. The tissue layer 9 is covered on one face by a perforated portion of plastics film 1, and on the opposite face by a nonperforated portion, or backing sheet portion 7 of said film 1. An attachment layer strip of pressure sensitive adhesive 11 is secured to the underside of the backing sheet portion 7, and a layer of silicone release paper 12 protects the ad52399 hesive before use. In use the female sanitary protection products of Figs. 7 and 8 are secured to panties by means of adhesive 11.

In Fig. 9, a pad of absorbent material 2, such as woodpulp, is wholly embraced by tissue 9 which in turn is embraced by perforated plastics film 1. The perforated plastics film 1 is attached to a non-perforated plastics backing sheet 14 by means of adhesive 13.

As mentioned hereinbefore, the electrical discharge method of perforation enhances passage of liquid in the direction towards the untreated side of the film. This property is essential in films used as nappy liners. Accordingly the invention also comprehends the use, as a nappy liner, of electrical discharge perforated cellular film (par15 ticularly as claimed and described in British Patents Specification Nos. 1525224 or 1556614). In use, the nappy liner is inserted between the baby's body and the nappy.

As indicated in the opening paragraph of the present description, the present invention includes the use of electrical discharge perforated plastics film (particularly as claimed and described in British Patents Specification Nos. 1515224 or 1556614) in incontinence products, these being absorbent products in accordance with the invention as defined in the second paragraph of the present description.

Claims (22)

1. An absorbent product comprising an absorbent material at least partially faced by a cellular plastics film having perforations which have been produced by passing electrical discharges therethrough.

2. An absorbent product according to claim 1 wherein said.absorbent material is entirely embraced by said cellular plastics film.

3. An absorbent product according to claim 1 wherein one face of said absorbent material is covered by said cellular plastics film and another face is optionally covered by a backing sheet.

4. An absorbent product according to claim 1 or 2 comprising a backing sheet having a layer of pressure sensitive adhesive thereon, and a layer of absorbent material entirely embraced by a perforated cellular plastics film on said pressure sensitive adhesive.

5. An absorbent product according to claim 1 or 2 comprising a layer of absorbent material embraced by a sheet of perforated cellular plastics film, said absorbent material having therein two layers of semi-repellent tissue.

6. An absorbent product according to claim 1 or 3 comprising a layer of absorbent material covered on one face by a perforated portion and on the other face by a nonperforated portion of a sheet of cellular plastics film, said absorbent material having therein two layers of semirepellent tissue.

7. An absorbent product according to claim 1 or 3 comprising a layer of absorbent material having a perforated cellular plastics film mounted on one face thereof by lines of adhesive.

8. An absorbent product according to claim 1 or 2 comprising a layer of absorbent material, a plastics film partially embracing said absorbent material for retaining absorbed fluid, a sheet of tissue entirely embracing said absorbent material and plastics film, a sheet of perforated cellular plastics film entirely embracing said tissue, and an attachment layer of pressure sensitive adhesive on said perforated plastics film.

9. An absorbent product according to claim 1 or 3 comprising a layer of absorbent material, a sheet of tissue entirely embracing said absorbent material, said tissue 5 being covered on one face by a perforated portion of a sheet of cellular plastics film, and an attachment layer of pressure sensitive adhesive on said non-perforated portion of said plastics film.

10. An absorbent product according to any preceding 10 claim wherein said plastics film is a polyolefin film.

11. An absorbent product according to claim 10 wherein said polyolefin film is a polyethylene film.

12. An absorbent product according to any preceding claim wherein said plastics film is of the foamed type. 15

13. An absorbent product according to any preceding claim wherein said film is a stretched polyolefin film having a substantially uniform cellular structure and formed from a composition comprising a crystalline linear polyolefin, which film has at least the following 20 characteristics: 1. it comprises no more than 14% by volume of the film of closed cells; 2. it has an apparent density .which is 90 to 20% of the density of the non-cellular 25 unstretched composition; 3. it has a cell factor equal to or less than +0.65, which factor may be zero or negative; 4. it contains from 0 to 25% by weight based on the polyolefin of a filler and/or pigment; 30 5. it has a thickness of up to O.ll (0.028 cm); 6. it comprises cells with dimensions such that the average cell volume is no greater than 10 -4 cc; 7. it has been stretched in the plane of the film by an amount corresponding to a stretch ratio of at least 1.1:1 in one direction or in two substantially mutually perpendicular directions. 58399

14. An absorbent product according to any preceding claim wherein said film has a weight range of lo to 100 g/m .

15. An absorbent product according to claim 14 wherein said film has a weight range of 10 to 50 g/m .

16. An absorbent product according to any preceding claim wherein said film contains from 10 to 80 perforations /cm .

17. An absorbent product according to any preceding claim wherein said film has a weight of about 16 g/m and 40 2 perforations /cm .

18. An absorbent product according to any preceding claim wherein said absorbent material is formed from cotton or rayon fibres, foam, needle-loomed or felted cotton or rayon, or woodpulp.

19. An absorbent product according to any preceding claim wherein one side of the perforated film is pitted and oxidized by the electrical discharges, and the pitted and oxidized side of the film faces said absorbent material.

20. An absorbent product substantially as hereinbefore described with reference to and as shown in Figures 1 and 2 or Figures 3, 4, 5, 6, 7 or 8 of the accompanying drawings.

21. An absorbent incontinence product according to claim 1 or 3 comprising a layer of absorbent material covered on one face by said perforated cellular plastics film wherein one side of the perforated film is pitted and oxidized by the electrical discharges and the pitted and oxidized side of the film faces away from the said absorbent material.

22. When used to at least partially face an absorbent product comprising a nappy, a nappy liner formed from cellular plastics film having perforations which have been produced by passing electrical discharges therethrough.