IE42890B1 - Improvements in or relating to disposable diapers - Google Patents

Abstract

1513055 Diapers J T McCULLINS 28 June 1976 [2 July 1975] 28151/75 Heading A5R A disposable diaper comprises a moisture impervious backing sheet 2, Fig. 4, a mass of absorbent material 3, a porous top sheet 6, edge portions of which are secured to said backing sheet, and sealing strips 10 attached to longitudinal marginal portions of the top sheet 6, said sealing strips, in use, encircling the infant's legs, thereby reducing leakage of liquid. In Fig. 4 the backing sheet 2 is wider than the top sheet 6 and its edges are turned over the edges of the top sheet and over the sealing strips; in Fig. 7 (not shown) the backing sheet (22) and the top sheet (26) are of the same width and additional strips (29) of moisture impervious material are secured over the edges of the top sheet and the backing sheet and over the sealing strips. The diaper may be folded inwardly along fold lines 12, Fig. 1, and outwardly along fold lines 13 to form a box-pleated configuration which is maintained by means of spots of adhesive 11 located between the fold lines 12 and midway between the ends 8 and 9 of the diaper. The absorbent material 3, which may comprise cellulose fibres impregnated with a quaternary ammonium salt and surrounded by absorbent cellulosic sheets 4, 5, Fig. 4, is confined to the area between the outer fold lines 13. The sealing strips 10 may be made of resilient foamed materials such as polyurethanes or natural or synthetic rubber foams, or may comprise lengths of twisted cellulose sheet. The backing sheet 2 may be made of polyethylene, polyethylene terephthalate or plasticised polyvinyl chloride and the top sheet 6 may be a non-woven cellulose sheet impregnated with a hydrophobic resin; the edge portions of the sheets 2 and 6 may be secured together by means of an emulsion adhesive or by heat-sealing. The diaper is secured in position by adhesive fastening tabs (14), Fig. 2 (not shown) attached to the backing sheet 2.

Description

This invention relates to disposable diapers.

A variety of disposable diapers is commercially available comprising a sture impervious backing sheet, a pad of absorbent material on the backing et and a top sheet overlying the pad of absorbent material, edge portions of ch are secured to the backing sheet. Such diapers may be supplied in a ded condition with a box pleated configuration obtained by folding about gitudinally extending fold lines. Typical of such diapers is that described British Patent Specification No. 1,011, 888.

The box pleated configuration is maintained by spots of adhesive lied to the top sheet within the pleat, these spots of adhesive being itioned approximately midway between the ends of the diaper. For use the ends of diaper are spread out somewhat and the infant is placed with its buttocks on the per so that one end of the diaper lies at about Its waist level and the other is drawn up between its legs. Opposite ends of the diaper are brought ether on each side and secured by self-adhesive tabs provided for the purpose, se may be secured by one end to the backing sheet with a free end whose adherent face is protected by a tab of release paper. The box pleated configuration is - 2 42890 maintained in the crotch region by means of the spots of adhesive and provides channels for urine and/or semi-liquid excreta.

After use the top sheet can be peeled away from the backing sheet and the top sheet and pad of absorbent material flushed away down a toilet, the backing sheet being disposed of in a waste bin.

Such disposable diapers are very convenient to use particularly when it is desired to travel with a young baby or to take a young baby on holiday. However their use is not without disadvantages. More particularly, although the pad of absorbent material may have a considerable capacity for liquid absorption, leakage may occur around the edges of the diaper where this contacts the legs, leading to undesirable wetting and/or soiling of the child's outer garments.

Such leakage may occur in particular when the infant is restless and turning.

The present invention accordingly seeks to provide an improved disposable diaper in which the above-mentioned disadvantage is substantially obviated and the danger of leakage minimised.

According to the present invention there is provided a disposable diaper comprising a moisture impervious backing sheet of length greater than its width, a mass of absorbent material on said backing sheet, a porous top sheet of length greater than its width overlying said mass, edge portions of said top sheet being secured to said backing sheet, and a strip of material applied to each longitudinal marginal portion of said top sheet so as to form a raised bead therealong, each said strip being overlaid by a layer of moisture impervious material arranged to cover the corresponding edge of the top sheet and prevent escape of liquid from the diaper via said strip or via said corresponding edge of said top sheet.

Preferably said backing sheet has a longitudinally extending central zone and longitudinally extending marginal portions, said diaper being folded into a box-pleated configuration by inward folding about a first pair of fold lines extending longitudinally of said backing sheet within said central zone and by outward folding about a second pair of fold lines at the junctions between - 3 lid central zone and said marginal portions, and said strips extending ingitudinally of said diaper on the top of each of the outwardly folded parts ! said diaper corresponding to said marginal portions.

In a particularly preferred form said mass of absorbent material is sposed on said central zone of said backing sheet so as to lie wholly within iid second pair of fold lines.

The strips may comprise strips of a resilient foamed material, such ; a polyurethane or natural or synthetic rubber foam. Alternatively the strips y each comprise a length of cellulose sheet twisted upon itself. In any event ie strips are covered by a moisture impervious layer in order to prevent or nimize the escape of liquid from the diaper after application to an infant due to eking via the strips or the edges of the top sheet. Thus in one form of aper according to the invehtion the backing sheet is wider than the top sheet id longitudinal edge portions of the backing sheet are folded over the top sheet ong each edge thereof so as to overlie the strips and form the superjacent isture impervious layer. Alternatively a separate strip of moisture impervious eet material may be applied along each marginal portion of the top sheet so as overlie the strips. In the case where the top sheet and backing sheet are of bstantially the same width each such separate strip is folded over the edge of e diaper and secured by heat sealing or by means of a suitable adhesive to the eking sheet.

The mass of absorbent material preferably comprises cellulosic fibres, ich may have been treated with a biocidally effective amount of a quarternary monium salt such as a benzalkonium chloride. A sheet of absorbent material y be interposed between said mass and said backing sheet and/or between said ss and said top sheet. The mass may be sandwiched between a pair of sheets of sorbent material.

In order that the invention may be clearly understood and readily rried into effect some preferred embodiments thereof will now be described by / of example only with reference to the accompanying drawings, in which:- 4 42890 Figures 1 and 2 show top and bottom views respectively of a disposable diaper according to the invention in unfolded state; Figure 3 is a view of the diaper of Figure 1 when folded into a boxpleated configuration; Figures 4 and 5 are semi-diagrammatic cross-sectional views on the lines IV-IV and V-V respectively of Figure 3; Figure 6 is a perspective view showing the diaper as though applied to an infant; and Figure 7 is a cross-section similar to that of Figure 4 through a modified form of diaper.

Referring to the drawings a diaper 1 comprises a water impervious backing sheet 2 on which is a pad 3 of cellulosic fibres impregnated with a quaternary ammonium salt. Pad 3 is sandwiched between absorbent sheets 4 and 5, as can be seen from Figure 1, is slightly shorter than backing sheet 2 and slightly less than two-thirds of its width. Overlying pad 3 and backing sheet 2 is a top sheet 6. Strips 10 of resilient foamed material are adhered to longitudinal marginal portions of the top sheet 6. Backing sheet 2 is somewhat wider than top sheet 6 and its edges are turned over the edges of top sheet 6 and over strips 10 to form turned over portions 7, the strips 10 producing beads or ridges 17 along each longitudinal edge of diaper 1.

Backing sheet 2 is made of a moisture-impervious material such as polyethylene, polyethylene terephthalate or plasticised polyvinyl chloride and may be impregnated with a natural or synthetic perfume such as rose, lavender, bouquet or jasmine. It may be pigmented with a white, pink, blue, yellow or other coloured pigment. Turned over portions 7 of backing sheet 2 prevent escape ot liquid from the interior of the diaper by wicking through the strips 10 or top sheet 6 when the diaper is properly applied to an infant.

Pad 3 may be made by the process described in my British Patent Specification No. 1,513,056. The quaternary ammonium salt may be, for example a benzalkonium chloride such as benzyl trimethyl ammonium chloride. - 5 >0 Preferably the cellulose fibres of pad 3 are impregnated with a mixture quaternary ammonium salts sold under the trade name Bardoc 20 as a solution isopropyl alcohol.

The sheets 4 and 6 are preferably cellulose sheets and may be of fferent weights per unit area.

Top sheet 6 is preferably hydrophobic in nature but must be porous to l low passage of urine. Preferably it is a non-woven cellulose sheet impregnated th a hydrophobic resin, e.g. a pine resin based ethylene oxide condensate :h as that sold by Hercules Powder Company or a silicone resin. The preferred i-woven cellulose sheet is made from long haired wood cellulose fibres.

Top sheet 6 is secured along its edges and at the ends 8 and 9 of the jper 1 to backing sheet 2 by means of an adhesive or by heat sealing. Suitable lesives include conventional polyvinyl chloride adhesives e.g. emulsion lesives based on polyvinyl chloride, vinyl chloride/vinyl acetate copolymers or lyl chloride/vinylidene chloride copolymers. Such adhesives are conventionally isticised with a plasticiser such as di-ji-butyl phthalate and may contain tween about 40% and about 60% by weight of solids. A suitable emulsion is > of those sold under the trade name Corvic by Imperial Chemical Industries nited (the word Corvic is a Registered Trade Mark). These adhesives can be )lied by transfer roller and have the desired property of fast tack. They are ;o organic solvent-free which is advantageous from the point of view of safety •ing manufacture.

Suitable resilient foamed materials for forming strips 10 include ixible polyurethane and sponge rubber materials, for example a polyester/ yether type of flexible polyurethane in strip form such as that used for lught excluder strips. Natural or synthetic rubber foam strips may be used, ise strips 10 are adhered to top sheet 6 by means of one of the above-mentioned ilsion adhesives or using a natural rubber latex adhesive. Although the ustrated strips are approximately square in section other cross sections of •ip, e.g. rectangular or semi-circular can be used. Typical dimensions for - 6 43890 the strip are, for example in the case of a rectangular section foam strip, from about J to about Γ' wide and from about J to about J high.

During manufacture of the diaper 1 two spots of adhesive 11 are applied to a central portion of top sheet 6. Suitable adhesives include the emulsion r adhesives mentioned above as well as adhesives of the organosol type, for example a mixture of polyvinyl chloride, a silicone resin and a plasticiser.

After application of spots 11 the diaper is folded inwardly about a first pair of longitudinal fold lines 12 and outwardly about a second pair of longitudinal fold lines 13 so as to form a box-pleated configuration. The spots of adhesive 11 which are disposed approximately midway between the ends 8 and 9 of the diaper serve to maintain the box-pleated configuration of the diaper.

Fold lines 13 divide backing sheet 2 into a central longitudinal zone and two longitudinally extending marginal portions, while fold lines 12 lie within the central longitudinally extending zone.

The backing sheet 2 has applied thereto near the end 8 a pair of fastening tabs 14 (see Figure 2). These are shown in more detail in Figure 5. Each tab 14 consists of a length of pressure sensitive tape 15, the adhesive side of which is protected at one end by a length 16 of release paper. The tape 15 is folded so that its sticky side is outwards and applied to the backing sheet 2 near one edge thereof. Tape 15 is long enough to project past the edge of the diaper when the release paper 16 is removed and the tape 15 allowed to unfold.

Diaper 1 may be folded for packing purposes about a transverse line approximately intermediate the ends 8 and 9 so that the backing sheet 2 is on the outside.

In use the diaper 1 is placed backing sheet 2 side down on a suitable flat surface and the box pleat splayed out ready to receive the infant. The buttocks of the infant are placed on the diaper approximately midway between its ends and the free end drawn up between its legs. The lengths 16 or release paper are torn off and the tape 15 is pressed into contact with the backing sheet adjacent a corner at the other end of the diaper. It is convenient to place the diaper so - 7 at the end 8 is at the back of the infant. This facilitates fastening of the as 14. The initial box pleated configuration forces the diaper 1 to take up a ipe somewhat as shovm in Figure 6.

The ridges formed by sealing strips 10 bear against the infant's legs d serve to inhibit leakage of urine and semi-liquid excreta in the crotch region am the interior of the diaper. It is not necessary that the ridges bear with / great pressure against the infant's legs; indeed any great pressure would tend result in undesirably reduced blood circulation. The purpose of the ridges 17 not to produce a tight seal but merely a seal that is sufficient to prevent cape of liquid when the infant first discharges urine. This extends the sidence time of the urine with the diaper and allows the cellulosic material pad 3 to absorb all liquids and semi-solids substantially completely.

In other diapers of similar construction but lacking sealing strips 10 is extension of the liquid retention time is not present and when urine is oduced in quantities it leaks from the diaper within a few seconds because of e lack of a seal in the crotch region and not because the cellulosic pads do t have the required absorptive capacity.

In place of the foam strips 10 there may be used twisted lengths of llulose sheet.

If desired, prior to the application of each strip 10 the diaper can draped or folded in the region where each foam strip 10 is to be applied so to form a channel to receive the strip 10.

In this case the adhesive may extend somewhat up the side faces of the am strips which are then placed in the channels. The portions 7 are thereafter rned over onto the strip 10 so as to cover the strips or form beads or ridges 17 the same way as described in relation to Figures 1 to 6.

In Figure 7 there is shovm a modified form of diaper 21. This consists a backing sheet 22, a pad of cellulose fibres 23 sandwiched between two layers of llulose sheet 24 and 25. Overlying the cellulose sheet 24 is a hydrophobic rous top sheet 26. In this case backing sheet 22 and top sheet 26 are the same - 8 42890 width. As with diaper 1 the box pleated configuration is held in place by adhesive spots 27. Foam strips 28 are adhered along the exposed faces of top sheet 26 and a further strip 29 of moisture impervious material (e.g. polyethylene, polyethylene terephthalate or plasticised polyvinyl chloride sheet) overlies and is adhered to strip 28 along each edge of the diaper so as to form a sealing ridge 30. The edge 31 is folded over the edge of the diaper and is adhered to the backing sheet 22. The diaper is otherwise similar to diaper 1.

According to the manufacturers' literature Bardoc 20 has the formulationϊΧ by weight Octyl decyl dimethyl ammonium chloride 25 Di octyl dimethyl ammonium chloride 12.5 Di decyl dimethyl ammonium chloride 12.5 Isopropanol 30 Water 20 The backing sheet 2 or 22 can be, for example, a polyethylene sheet, which may be smooth or embossed (so as to improve its drape and feel), having a thickness of approximately 0.001 inch. An alternative material is polyethylene terephthalate sheet of thickness about 0.0005 inches.

Pad 3 or 23 may be a batt formed of loosely compacted short cellulose fibres, such as wood pulp fibres, or cotton linters, or mixtures thereof, which are primarily held together by inter-fibre bonds requiring no added adhesive, as is known in the art. Briefly, this batt is a low bulk density coherent web of loosely compacted cellulose fibres, preferably, comminuted wood pulp fibres, in the form of so-called “fluff.

The term short fibres, as used herein, refers to fibres less than J inch in length, in contrast to long fibres, or textile length fibres, which are longer than J inch in length, and generally are between J and 2J inches in - 9 ngth. The former are substantially less costly than the latter. The assification of fibres by length may be carried out by the Clark Classification ocedure described in the test manual of the Technical Association of Pulp and per Industry (TAPPI-T233 SU64).

Preferably the pad 3 or 23 comprises a batt formed from loosely mpacted comminuted cellulose fibres, substantially all of which have a length less than 1 mm, and preferably less than about 0.6 mm.

If desired the side of the batt adjacent to the backing sheet 2 or 22 y be densified by a slight moistening of that surface of the batt followed by the plication of pressure thereto.

The top sheet 6 or 26 may be made up of a mixture of fibres consisting edominantly of inexpensive short cellulose fibres such as wood pulp fibres or tton 1 inters, in amounts of about 75% to about 98%, the balance being textile ngth fibres such as rayon. In such material, the short fibres are in uniform mixture with 2% to 25% by weight of textile length fibres, such as 1.5 denier yon fibres uniformly cut to 1J inch length. The short and long fibres are rtdomly and substantially uniformly dispersed and bonded with a bonding agent ch as a self-crossed-1inking emulsion. The material of the top sheet 6 or may also be treated with a wetting agent to partially counteract the water pellency of the bonding agent and bring the sheet to the desired degree Of liability.

Sheet materials for use as top sheet 6 or 26 preferably have fabric ights in the range of 1 to 5 oz per square yard and densities, less than 0.15 ams per cc, generally in the range between 0.05 and 0.10 grams per cc. The y strength, for a fabric for use as top sheet 6 or 26 and having a weight of out 1.5 oz per square yard, is preferably at least 0.15 pounds per inch of dth in the machine direction and at least 0.10 pounds per inch of width in the oss direction. Such fabrics have good elongation, loft, softness and drape aracteri sties. - 10 42890 The top sheet 6 or 26 may also be an apertured non-woven fabric formed, for example as a foraminous structure wherein groups or groupings of fibres have been rearranged from a fibrous non-woven starting web into positions surrounding less dense fabric portions by passage of a fluid through the starting material.

The fibres within the groupings are mechanically interlocked and may be arranged into various patterns, as is well understood by those skilled in the art. A suitable binder may be utilized to help retain the fibres in their rearranged locations, as is also well understood by those skilled in the art. The fabric can be made of naturally occuring fibres, synthetic fibres or blends thereof.

Typical material for top sheet 6 or 26 made of a polyester material may have a weight of | oz. per square yard.

It should also be understood that the top sheet 6 or 26 may be formed of nonapertured (but porous) material such as a non-woven isotropic web, sponge, or the like. In all of the aforementioned top sheet materials, the materials should preferably be relatively hydrophobic so as to retard wicking within the top sheet 6 or 26.

Claims (23)

1. A disposable diaper comprising a moisture impervious backing sheet of length greater than its width, a mass of absorbent material on said backing sheet, a porous top sheet of length greater than its width overlying said mass, edge portions of said top sheet being secured to said backing sheet, and a strip of material applied to each longitudinal marginal portion of said top sheet so as to form a raised bead therealong, each said strip being overlaid by a layer of moisture impervious material arranged to cover the corresponding edge of the top sheet and prevent escape of liquid from the diaper via said strip or via said corresponding edge of said top sheet.

2. A disposable diaper according to Claim 1, in which said backing sheet has a longitudinally extending central zone and longitudinally extending marginal portions, said diaper being folded into a box-pleated configuration by inward folding about a first pair of fold lines extending longitudinally of said backing - 11 ieet within said central zone and outward folding about a second pair of fold ines at the junctions between said central zone and said marginal portions, and tid strips extending longitudinally of said diaper on the top of each of the itwardly folded parts of said diaper corresponding to said marginal portions.

A disposable diaper according to Claim 2 in which areas of adhesive e applied to the top sheet within said second pair of fold lines to maintain id box-pleated configuration by mutual adherence of portions of said top sheet e to another.

A disposable diaper according to Claim 3, in which said areas of hesive are located approximately midway between the shorter edges of the top eet.

A disposable diaper according to any one of Claims 2 to 4, in which id mass of absorbent material is disposed on said central zone of said backing aet so as to lie wholly within said second pair of fold lines,

A disposable diaper according to any one of Claims 1 to 5, in which id backing sheet comprises a sheet of polyethylene or plasticised polyvinyl loride.

A disposable diaper according to any one of Claims 1 to 6, in which id mass of absorbent material comprises a pad of absorbent fibres.

A disposable diaper according to Claim 7, in which said absorbent ires comprise cellulose fibres.

A disposable diaper according to Claim 8, in which said cellulose ires have been treated with a biocidally effective amount of a quaternary ionium compound.

A disposable diaper according to any one of Claims 1 to 9, in which a et of absorbent material in interposed between said mass and said backing sheet.

A disposable diaper according to any one of Claims 1 to 10, in which heet of absorbent material is interposed between said mass and said top sheet.

A disposable diaper according to Claims 10 and 11, in which said mass of orbent material is sandwiched between a pair of sheets of absorbent material. - 12 42890

13. A disposable diaper according to any one of Claims 1 to 12, in which said top sheet comprises a sheet of porous hydrophobic material.

14. A disposable diaper according to Claim 3, in which said top sheet comprises a non-woven cellulosic sheet which has been impregnated with a hydrophobic resin.

15. A disposable diaper according to any one of Claims 1 to 14, in which said strips comprise strips of a resilient foamed material.

16. A disposable diaper according to Claim 15, in which said resilient foamed material comprises a polyurethane or natural or synthetic rubber foam.

17. A disposable diaper according to any one of Claims 1 to 14, in which said strips comprise lengths of twisted cellulose sheet.

18. A disposable diaper according to any one of Claims 1 to 17 ; in which said strips are adhered to the top sheet.

19. A disposable diaper according to any cne of Claims 1 tc 18, in which said backing sheet is wider than said top sheet and is folded over said top sheet along each longitudinal edge thereof and over the corresponding strip to form the corresponding over-lying layer of moisture impervious material.

20. A disposable diaper according to any one of Claims 1 to 18, in which each said strip is overlaid by a separate strip of moisture impervious material which extends around the adjacent edge of said top sheet and is secured to said backing sheet,

21. A disposable diaper according to any one of Claims 1 to 20, in which said edge portions of said top sheet are secured to said backing sheet by means of an emulsion adhesive.

22. A disposable diaper according to any one of Claims 1 to 20, in which said edge portions of said top sheet are secured to said backing sheet by means of heat sealing.

23. A disposable diaper according to any one of Claims 1 to 22, in which fastening tabs are provided adjacent each edge of said diaper on said backing sheet adjacent one end thereof. - 13 90 A disposable diaper constructed and arranged substantially as herein cribed with particular reference to the accompanying drawings.