IL131269A - Diaper and process for making the same - Google Patents

Abstract

An improved diaper (10), which comprises: (a) a back sheet (11) impermeable to liquids; (b) a liquid-absorbing material (12), superimposed to the back sheet; (c) a top sheet (13) sealed to the back sheet; and (d) two double-barrier flaps (14) extending longitudinally on the top sheet, each having a longitudinal central strip (21) attached to the top sheet and two longitudinal wings extending on the two sides of said central strip. 283 ו' בניסן התשס" ד - March 28, 2004

Description

131269/2 iQ ri τνοτ y>!?nm l wia ΊΊΦΌ IMPROVED DIAPER AND PROCESS FOR MAKING THE SAME 131269/2 -1- Field of the Invention This invention relates to an improved diaper structure having a particularly efficient body excrement barrier, and to a continuous process for its manufacture.

Background of the Invention Many diaper structures are disclosed in the art. In many cases, they comprise a back sheet, that is liquid impermeable, and a top sheet connected thereto which is liquid permeable, and a liquid-absorbing material interposed between said two sheets. Typically, said diapers comprise a crotch section and two wider terminal sections, which are directed from the crotch upwards to protect the front and the back of the user's body when the diaper is placed on the body. In addition, in some cases, two barrier flaps are provided on the top sheet, which extend longitudinally from one end of the diaper to the other, which serve to trap liquid in the central part of the diaper and force it to pass through the top sheet into the absorbent material.

Thus, USP 4,704,116 discloses an absorbent diaper which comprises a pair of wedged sections together defining a waist opening; a crotch section disposed between said waist section and a pair of elasticized leg openings separated by said crotch section; a back sheet; a liquid impervious body side liner attached to said back sheet; an absorbent body disposed 7256/99 between said liner and said back sheet; and first and second elasticized fluid impervious flaps, attached to or formed from said liner and spaced inwardly from said elasticized leg opening, respectively, defining a waist containment pocket.

USP 5,562,650 discloses an absorbent article which includes a back sheet layer and an absorbent retention portion superimposed on the back sheet layer. A management portion is located adjacent the body side surface of the retention portion, and is constructed to temporarily hold received liquid and release the liquid to the retention portion. A pair of barrier flaps are connected to laterally opposed, longitudinally extended regions of the top sheet layer. The top sheet layer is operably sealed to said barrier flaps and the back sheet layer at a securement section with a strip of adhesive to substantially block a leakage of liquid through said securement section.

USP 5,678,026 discloses an absorbent article having a main body portion, a pair of flaps joined to the main body portion, and a unitary release material joined to a portion of each of the flaps, such that the unitary release material superimposes the flap when the flap is folded along the fold line.

USP 5,601,544 discloses a child's training pant, which includes a pant body having a waist opening and a pair of leg openings and an elasticized shaped absorbent composite having elasticized absorbent side portions. 7256/99 -3- Elasticized side flaps are formed from a liquid impermeable material situated between the absorbent composite and the pant body.

EP-A 605 287 discloses a disposable absorbent product including liquid permeable cover layer, an absorbent core and a liquid impervious layer for preventing body excrement entrapped in the absorbent core contacting the wearer's undergarment and skin, and further including a secondary liquid contained in the containment structure for intercepting body excrement leaking past the side edges of the absorbent product, which is mounted underneath the liquid impervious layer.

The diapers of the prior art, even when they provide barrier flaps for retaining liquid on the top sheet and forcing it to seep through the top sheet into the absorbent material, are so structured that the barrier flaps are not as efficient in preventing liquids from spilling to the sides of the diaper, as would be desirable. Further, the structures of the prior art diapers are relatively complicated and no method of manufacture, particularly method of continuous manufacture, is disclosed in the prior art that would permit to make the diapers economically and with high throughput.

It is therefore a purpose of this invention to overcome the inadequacies of the prior art structures and provide a better body excrement barrier superimposed to the top sheet securely to prevent liquid from spilling to the sides of the central portion of the diaper. 7256/99 It is another purpose of this invention to provide body excrement barrier means, extending longitudinally of the diaper, that have increased liquid retaining properties from the center of the diaper to the sides.

It is a still further purpose of the invention to provide the better body excrement barrier even during motion of the user, with a double barrier system, that enables to distribute sealing pressure on the user's body for comfort feeling.

It is a further purpose of this invention to provide a method of manufacture of the diaper, that is simple and economical and provides high throughput.

It is a still further purpose of the invention to provide such a method which can be, and preferably is, carried out continuously, and can be automatically controlled.

Other purposes and advantages of the invention will appear as the description proceeds.

Summary of the Invention For a better understanding of the invention, the precise meanings of certain terms used in the following description should be kept in mind.

The terms "top sheet" and "back sheet" designate respectively the sheet that is close to and the sheet that is spaced from the wearer's skin, when 7256/99 the diaper is used. When the diaper is spread out in flat configuration before being adapted to the wearer's body, the top sheet is on the top and the back sheet is on the bottom. The term "crotch section" designates the central section of the diaper which covers the crotch when the diaper is worn. Correspondingly, when the diaper is worn, it includes, besides the said crotch section, two sections extending substantially vertically, a front section which is placed on the front of the wearer's body and a rear section which is placed on the rear of the wearer's body. The expressions "front waist section" and "back waist section" refer to the configuration of the diaper when it is spread out. It is assumed that it is so spread out that the back waist section is on the top and the front waist section is on the bottom, and it is so illustrated. The surface of the diaper that is in contact the wearer's body when the diaper is worn is called the "inside" of the diaper and the opposite surface is called the "outside".

The directions parallel to the said edges of the diaper will be called the "transverse", and the directions perpendicular to the edges will be called "longitudinal". It will be appreciated that the longitudinal dimension of the diaper is longer than the transverse dimension. It will also be appreciated that the transverse dimension in the crotch portion is variable, and shorter than at the edges of the diaper.

The improved diaper according to the invention comprises: a) a back sheet impermeable to liquids; b) a liquid-absorbing material, superimposed to the back sheet; c) a top sheet sealed to the back sheet; 7256/99 -6- d) two double -barrier flaps extending longitudinally on the top sheet, each having a longitudinal central strip attached to the top sheet and two longitudinal wings extending on the two sides of said central strip; and e) for each wing of each barrier flap, an elastic strand connected with the wing and being substantially stretched out when the diaper is in its distended configuration, each of said strands being preferably held in a folded-over edge of the corresponding wing.

The liquid-absorbent material, generally in the form of a layer, is superimposed to the back sheet in such a way as to leave exposed longitudinal and transverse margins for connection of the top sheet to the back sheet. The top sheet is of liquid-permeable material, which may be wider than the back sheet or have the same width, and is sealed to said back sheet longitudinally along the aforesaid exposed longitudinal margins and transversely along the aforesaid exposed transverse margins of said back sheet. The two wings of each barrier flap may be symmetric or different from one another, and particularly of different heights. Each of them preferably has a folded-over longitudinal edge, which is longitudinally connected to the body of the wing to form a cavity for housing the elastic strands, and may have an unconnected side margin beyond the longitudinal connections to said wing body. The edge of each wing may be folded inwards, viz. towards the other wings of the same flap, or outwards. Each barrier flap extends longitudinally over the entire length of the diaper, is attached along a central strip to the top sheet, and may be attached to said top sheet at its end over its entire width, or 7256/99 -7- otherwise. As is customary in this kind of diaper, the top sheet is cut back at its sides in its central portion to form a crotch section of the diaper, which is only slightly wider than the back sheet. The liquid absorbent material layer is also narrower in correspondence of the crotch section of the diaper.

The connections, particularly sealing connections, between the various components of the diaper according to the invention can be effected in any way that is convenient and adapted to the materials used. It can be effected by welding, such as by heat or microwave or ultrasonic welding, or by means of an adhesive, or by sewing.

The top sheet is made of a hydrophilic textile fabric, made from natural, artificial or synthetic fibers of different sizes and finishes, chosen, preferably but not exclusively, from among woven, knitted or non-woven fabrics. The back sheet is hydrophobic and is constituted by a film of gas and/or liquid impermeable plastic material, such as e.g. polyethylene, or by a laminate of such a plastic film and textile material. The liquid-absorbent material, enclosed between the top sheet and the back sheet, is preferably chosen from among hydrophilic fibers, particularly natural fibers, such as e.g. cellulose, or artificial or synthetic fibers, or artificial or synthetic, non-fibrous, absorbing materials, such as e.g. sodium polyacrylate salts The elastic strands may be of any material that has the desired elastic properties, preferably chosen from among elastic synthetic polymeric fibers, such as Lycra™, or natural or synthetic rubbers. 7256/99 -8- The double-barrier flaps can be made of any suitable material, chosen preferably from among the same material of which the top sheet or the back sheet is made. The known purpose of barrier flaps is to retain any body excrement that is deposited over the top sheet in a excrement-retaining space, formed between said flaps particularly in the crotch section of the diaper, and cause it to seep through said top sheet and be absorbed by the liquid-absorbent material. The fact that the diapers of the invention have two double-barrier flaps, each formed with two wings, creates two additional excrement-retaining spaces between the two flaps of each wing, thereby increasing the efficiency and reliability of the diaper regarding sealing security and comfort.

The dimensions of the diaper depend on the use for which it is intended. The diaper according to the invention can be used for children or for adults, and its dimensions will be determined accordingly.

The invention also comprises a preferably continuous process for making a diaper having the structure hereinbefore defined, which comprises: I - advancing a back sheet; II — depositing on the back sheet, at predetermined positions, a piece of liquid-absorbent material, having a predetermined shape and leaving the longitudinal and the transverse margins of the back sheet exposed; III - forming a top sheet assembly, by 1 - advancing a top sheet; 2 - generating two flaps; 7256/99 3 - advancing said flaps; 4 - juxtaposing two elastic strands to the underside of each flap at a predetermined distance from its edges; 5 - folding the wings over the elastic strands and sealing them to enclose the strands; 6 - attaching the flaps to the top sheet along central strips thereof; and 7 - attaching the flaps to the top sheet at their ends; IV — advancing the top sheet assembly and bringing it into contact with the back sheet; V — sealing the top sheet to the back sheet along the exposed margins thereof; VI — the advancing motions under I, III and IV being preferably continuous and controlled as to speed and direction, so that the back sheet, the top sheet and the components of the top sheet assembly be maintained in the desired mutual registration, viz. in the predetermined positioned relationship both longitudinally and transversely; VII - transversely sealing the top sheet to the back sheet at predetermined intervals; and VIII — cutting the resulting assembly to the desired diaper shape.

The attachment of the various components of the diaper to one another may be continuous or intermittent. Particularly, the attachment of the flaps to the top sheet at their ends may be intermittent. 131269/2 -10- Brief Description of the Drawings In the drawings: - Fig. 1 is a front view of a distended diaper; - Fig. 2 is a transverse cross-section of the diaper of Fig. 1, taken along plane II-II of Fig. 1, a detail of which is shown at an enlarged scale as detail "A"; - Fig. 3 is a longitudinal cross-section of the diaper of Fig. 1, taken along its plane of symmetry III-III; - Figs. 4a, 4b, 4c and 4d are schematic perspective illustrations fragmentarily illustrating the top sheet and the barrier flaps in an intermediate stage of manufacture of the diaper; and - Fig. 5 is a flow sheet of the process of manufacture of the diaper according to an embodiment of the invention.

Detailed Description of Preferred Embodiments Referring now to Figs. 1 to 3, numeral 10 generally designates a diaper according to an embodiment of the invention, which comprises a back sheet 11, a layer of liquid-absorbent material 12, having a predetermined shape, a top sheet 13, and two barrier flaps 14, each including two elastic strands 15. The top sheet 13 is cut off at the sides in the central portion of the diaper, to determine a central crotch portion of the diaper, generally indicated at 17. It is seen that the absorbent material 12 is so shaped as to leave exposed margins 18 and 19 of the back sheet at its sides and at its longitudinal ends, respectively. The top sheet is connected to the back sheet in correspondence of said exposed margins. 7256/99 -11- The connection is effected by any suitable means, and in this particular embodiment it is assumed that it is done by adhesive, but other systems such as ultrasonic bonding can be employed. The transverse strips 20 formed by the connected top sheet and back sheet form the waist ends of the diaper, when it is worn.

The flaps 14 are longitudinally connected to the top sheet 13 along longitudinal strips indicated at 21. At both sides of said strip, each flap has a wing 23. Each wing 23 is folded over on itself on both sides of the central strip 21, and is sealed longitudinally at 25, so as to enclose an elastic strand 15. The edge portion 27 of each flap can be left free, or the bond to the body of the wing 23 may not be longitudinally localized, as shown in the detail A of Fig. 3, but extend to said edge portion as well, whether the bond is effected thermally or with adhesive or with ultrasound.

Figs. 4a to 4d show various embodiments of barrier flaps in an intermediate stage of manufacture, viz. before their edge portions are sealed at 25 or over the whole edge portions 27, and before the flaps are flattened against the top sheet and connected thereto along strips 20. The embodiment of Fig. 4a gives rise to the wings shown in Figs. 1-3. The wings are initially bent to form hook-like margins directed outwards, viz. each wing is folded away from the other wing. An elastic strand, or a plurality of such strands, is inserted into each hook-like margin, and then the hook-like margins are sealed, as in Figs. 1-3. In Fig. 4b, the wings 30-31 of each double-barrier flap have different heights. The inner wing, 7256/99 -12- viz. the one that is directed towards the other wing and therefore overlaps the absorbent material 12, is shorter than the other, outer wing. In this way, a two-stage barrier to liquid is formed, the first barrier stage being created by the lower wing of the flap and the second being created by the higher wing of the flap. Figs. 4c and 4d correspond to Figs. 4a and 4b, except that the hook portions of flaps 23' and 30-31' are directed inwards, viz. for each wing towards the other wing of the same flap.

During the manufacture of the diaper, the elastic strands 15 are fed in stretched condition in suitable, separate lengths, onto the flap wings. When the flaps are connected at their ends to the top sheet, and through it to the back sheet, said strands are maintained in their stretched condition. However, when the last step of the process is carried out, viz. the continuous structure of back sheet and top sheet assembly, created by the process, is cut transversely to define individual diapers, the strands become free to contract, and therefore, when the diaper is worn, they bring the barrier flaps to a corrugated configuration.

Fig. 5 is a flowsheet of the process of manufacturing the diaper according to an embodiment of the invention. The back sheet and top sheet are supplied in the form of rolls and are advanced longitudinally. The liquid-absorbent material, which has been preformed in layers having the desired shape, as shown in Fig. 1, are deposited on the back sheet, as said sheet advances, at distances corresponding to the length of the diaper. 7256/99 -13- The flaps are provided in flat configuration in roll form and are advanced parallel to the top sheet with the same speed. They pass through a forming device, constituted, for instance, by two cylinders suitably profiled and heated, which bend each flap to form the wings as shown in Figs. 4a-4d. Elastic strands, having the desired length are introduced into the hook-like portions of the wings of the barrier flaps. Thereafter, the flaps pass through rollers which flatten the hook-like portions and seal them, as shown at 25 (see Fig. 2).

Thereafter, the flaps are brought into contact with the top sheet and are applied to it and sealed, e.g., by suitable sealing rollers, along their central strips 25 and are flattened against the top sheet. The top sheet assembly is thus created.

The top sheet assembly is brought into contact with the back sheet and sealed thereto along the exposed longitudinal margins of this latter. Then, the top sheet assembly, the back sheet and the flaps are sealed transversely at the end of each diaper. Finally, each diaper is cut out of the continuous assembly thus created, while the side cuts that are required to form the crotch portion of the diaper are created.

Although embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried out with many modifications, variations and adaptations, without exceeding the scope of the claims. 131269/3 -14 -

Claims (30)

1. An improved diaper, which comprises: a) a back sheet impermeable to liquids; b) a liquid-absorbing material, superimposed to the back sheet; c) a top sheet sealed to the back sheet; and d) two double-barrier flaps extending longitudinally on the top sheet, each having a longitudinal central strip attached to the top sheet and two longitudinal wings extending on both sides of said central strip.

2. The diaper according to claim 1, further comprising, for each wing of each barrier flap, an elastic strand connected with the wing and being substantially stretched out when the diaper is in its distended configuration

3. The diaper according to claim 2, wherein each of the elastic strands is held in a folded-over edge of the corresponding wing.

4. The diaper according to claim 1, wherein the liquid-absorbent material is in the form of a layer and is superimposed to the back sheet such a way as to leave exposed longitudinal and transverse margins.

5. The diaper according to claim 1, wherein the top sheet is of liquid-permeable material. 131269/2 - 15-

6. The diaper according to claim 4, wherein the top sheet is wider than the back sheet, and is sealed to said back sheet longitudinally along the exposed longitudinal margins and transversely along the exposed transverse margins of said back sheet.

7. The diaper according to claim 1, wherein the two wings of each barrier flap are symmetric.

8. The diaper according to claim 1, wherein the two wings of each barrier flap have different heights.

9. The diaper according to claim 2, wherein the wings of the barrier flaps have folded-over longitudinal edges, which are connected to one another to house the elastic strands.

10. The diaper according to claim 1, wherein the wings of the barrier flaps have unconnected side margins.

11. The diaper according to claim 1, wherein the wings of the barrier flaps are bent inwards, for each wing towards the other wing of the same flap.

12. The diaper according to claim 1, wherein the wings of the barrier flaps are bent outwards, for each wing away from the other wing of the same flap. 131269/2 -16-

13. The diaper according to claim 1, wherein the barrier flaps extend longitudinally over the entire length of the diaper and are attached at their ends to the top sheet

14. The diaper according to claim 1, wherein the connections between the components of the diaper are effected by means chosen from the group consisting of welding, such as by heat or microwave welding or sonication, adhesives and sewing.

15. The diaper according to claim 14, wherein the connections between the components of the diaper are effected by means chosen from the group consisting of heat welding, microwave welding and sonication.

16. The diaper according to claim 1, wherein the top sheet is made of a hydrophilic textile fabric.

17. The diaper according to claim 16, wherein the hydrophilic textile fabric is chosen from among woven, knitted or non-woven fabrics, made from fibers chosen from among natural, artificial or synthetic fibers.

18. The diaper according to claim 1, wherein the back sheet is hydrophobic and is chosen from among films of gas and/or liquid impermeable plastic material or laminates of such a plastic film and textile material.

19. The diaper according to claim 18, wherein the impermeable plastic material is polyethylene. 131269/2 -17-

20. The diaper according to claim 1, wherein the liquid-absorbent material, enclosed between the top sheet and the back sheet, is preferably chosen from among hydrophilic fibers or artificial or synthetic, non- fibrous, absorbing materials.

21. The diaper according to claim 20, wherein the hydrophilic fibers are chosen from among natural, artificial or synthetic fibers.

22. The diaper according to claim 21, wherein the hydrophilic fibers are cellulose fibers.

23. The diaper according to claim 20, wherein the liquid-absorbent material is a sodium polyacrylate salt.

24. The diaper according to claim 20, wherein the elastic strands are chosen from among elastic synthetic polymeric fibers or natural or synthetic rubbers.

25. The diaper according to claim 1, wherein the barrier flaps are made of the same material as the top sheet.

26. The diaper according to claim 1, wherein the barrier flaps are made of a material chosen from among the same material of which the top sheet or the back sheet is made. 131269/2 -18-

27. A process for making a diaper according to claim 1, which comprises: I - advancing a back sheet; II - depositing on the back sheet, at predetermined positions, a piece of liquid-absorbent material, having a predetermined shape and leaving the longitudinal and the transverse margins of the back sheet exposed; III - forming a top sheet assembly, by 1 - advancing a top sheet; 2 - advancing two flaps; 3 - forming in each flap a central strip and two wings; 4 - juxtaposing two elastic strands to the underside of each flap at a predetermined distance from its edges; 5 — folding the wings over the elastic strands and sealing them to enclose the strands; and 6 - attaching the flaps to the top sheet along the central strips thereof; IV — advancing the top sheet assembly and bringing it into contact with the back sheet; V - sealing the top sheet to the back sheet along the exposed margins thereof; VI - transversely sealing the top sheet to the back sheet at predetermined intervals; and VTI - cutting the resulting assembly to the desired diaper shape.

28. The process according to claim 27, wherein the advancing motions under I, III and IV are continuous and have the same speed.

29. A diaper, substantially as described and illustrated. 131269/2 -19-

30. A process for making a diaper, substantially as described illustrated.