WO1995016423A2

WO1995016423A2 - Tampon with cover

Info

Publication number: WO1995016423A2
Application number: PCT/IB1995/000008
Authority: WO
Inventors: Stephen Kenneth Williams
Original assignee: Kimberly-Clark Limited
Priority date: 1993-12-17
Filing date: 1994-12-16
Publication date: 1995-06-22
Also published as: GB2284765A; DE4481414B4; AU1249695A; GB2284765B; WO1995016423A3; GB9325829D0; CA2138196A1; DE4481414T1; FR2713918A1; FR2713918B1; DE19581398T1; ZA9410020B

Abstract

A tampon for female hygiene or medical use comprising a pledget formed by a spirally wound absorbent ribbon (1) and a cover web (2) extending around the outer circumference of the pledget. The cover web (2) is secured to the pledget by one end thereof extending into and being embedded in at least an outer part of the pledget spiral winding. The outer end of the cover web (2) extends beyond the outer free end of the absorbent ribbon (1) and is bonded to an underlying intermediate section of the cover web. A withdrawal string is looped around both the absorbent ribbon and the cover web before widing.

Description

Tampon with cover

This invention relates to a tampon for female hygiene or for medical or surgical use, for example.

More particularly, the invention relates to an improved tampon of the type provided with a fluid permeable cover web which web enhances the structural integrity of the tampon, prevents fibres from being detached during the use of the tampon, and permits fluid to enter the tampon whilst tending to restrain fluid from flowing from the tampon.

Tampons of this general type are known in which the tampon core or "pledget" is formed of a spirally wound ribbon composed of non-woven natural and/or synthetic fibres, the ribbon having a width corresponding approximately to the length of the finished tampon. A withdrawal string is wound up with the pledget. To the outer surface of the pledget is secured a cover web which may wholly or partially consist of a plastic material. The assembly of spirally wound absorbent ribbon and outer cover web is compressed generally radially to give the final form of the tampon.

Tampons of this type and machines and processes for producing them are known, for example, from US 4,222,381, US 4,859,273 and US 4,863,450.

In tampons of this type it is desirable that the cover is firmly mounted to the pledget so that it does not become detached in use and that it remains in good face to face contact with the outer surface of the pledget to promote good intake of fluid across the interface between cover and pledget.

As disclosed in US Patent Specification 4,222,381, the cover web is substantially wider than the absorbent ribbon such that when the ribbon has been rolled up, the cover edges extend beyond the longitudinal edges of the pledget, the cover then being secured by folding the edges of the cover web back into the axial space formed centrally in the pledget before the assembly is pressed to give the final form of the tampon. Thus, the fixing of the cover web relies primarily on the folding of its edges into the longitudinal edges of the pledget.

However, a drawback with this arrangement is that the cover may be insufficiently tightly and securely mounted to the pledget and, moreover, the insertion of the folding of the edges of the web back into the longitudinal end faces of the pledget complicates the manufacturing process.

US Patent Specification No. 4,863,450 discloses a tampon which is intended to overcome these drawbacks. In this arrangement, a bicomponent, thermoplastic cover web is continuously bonded along its entire length to the portion of the non-woven ribbon which, when wound, forms the outer surface of the pledget. Thus, before the tampon is pressed into its final form, the pledget is provided with a continuously bonded outer cover which extends around its outer circumference. This arrangement therefore relies on continuous sealing of the cover web to the ribbon to maintain intimate contact therebetween and enhance structural integrity.

The arrangement of US 4,863,450 suffers however from the disadvantage that the continuous sealing between the cover web and the ribbon extending around the outer circumference of the tampon unavoidably creates zones or points where absorption of fluids into the tampon will be diminished. Moreover, since the cover web is secured only to the outer circumference of the pledget, there remains the possibility that withdrawal of the complete tampon assembly is not achieved by means of the withdrawal string which is looped around part of the absorbent ribbon adjacent the central axis of the tampon. The withdrawal force is applied at a position which is significantly spaced inwardly from the cover web. It is an object of the invention to provide a tampon in which these drawbacks of the prior art may be overcome.

Viewed from a first aspect the invention provides a tampon comprising a pledget formed by a spirally wound absorbent ribbon, and a cover web extending around the outer circumference of the pledget, the cover web being secured to the pledget by one end thereof extending into and being embedded in at least an outer part of the pledget spiral winding and the other end thereof extending beyond the outer free end of the absorbent ribbon and being bonded to an underlying intermediate section of the cover web.

Viewed from a second aspect the invention provides a method of forming a tampon in which a cover web is laid against a length of absorbent ribbon, with a free end of the cover web projecting beyond a corresponding free end of the absorbent ribbon, spirally winding the absorbent ribbon to form a pledget with a substantial part of the cover web entrapped in the spiral winding and with the cover web extending around the outer circumference of the pledget, and bonding said free end of the cover web to an underlying, intermediate section of cover web. In accordance with the invention, the cover web is anchored at one end within the spiral winding of at least the outer part of the pledget and, at the other end, by bonding of an end portion of the cover web extending beyond the end of the ribbon to an underlying cover web section. In this way, a secure structure for the tampon is provided, with the cover web maintained ^n face to face contact with the absorbent ribbon, without the need for continuous bonding of the cover web to the ribbon around the outer circumference of the pledget and without significantly complicating the manufacturing process.

It is envisaged that the anchoring of the internal

SUBSTITUTESHEET(RULE26. - 4 - end of the cover web within the pledget might be achieved solely by a sufficient length of cover web being entrapped within the spirally wound ribbon of the pledget. However, in a preferred form of the invention the cover web is, adjacent its internal end, tacked or firmly bonded to the absorbent ribbon in order to fix it in position during winding and to enhance the strength of the cover mounting. Thus, the method in accordance with the invention preferably includes bonding or otherwise tacking the cover web to the absorbent ribbon only in the region of the end of the cover web which is embedded in the pledget when wound.

The length of cover web which is embedded into the spirally wound pledget may vary and will depend partly on the extent of internal bonding between the free end of the cover web and absorbent ribbon within the pledget as discussed above. However, for reasons of not impairing the absorbent characteristics of the tampon it is desirable that the areal extent of any such bonding should be minimised and, further, that the bonding be provided towards the axis of the assembled pledget rather than adjacent its outer circumference. Accordingly, it is desirable for the internal end of the cover web to extend a substantial distance into the spirally wound pledget. It is therefore preferred that the cover web extends internally beneath at least a major part of the outer winding of the absorbent ribbon and, most preferably but not essentially, the cover web is wound internally through more than 360* so that its internal end, which is optionally bonded to the underlying ribbon, is separated from the outer surface of the pledget by at least two overlying layers of absorbent ribbon.

It will be appreciated that the depth to which the cover web is wound into the pledget can be predetermined by selecting appropriate relative lengths of cover web and ribbon and by an appropriate degree of overlap therebetween prior to winding. The absolute lengths will depend on the desired size and type of the tampon. However, it is preferred that the ratio of cover web length to absorbent ribbon length is between 0.5 and 1, preferably between 0.6 and 0.9, and most preferably between 0.7 and 0.8. These relative lengths allow for substantial embedding of one end of the cover web within the pledget and a sufficient overhang of cover web beyond the outer end of the absorbent ribbon to provide secure web to web bonding.

A further significant advantage of the invention is that since the cover web extends into the spiral windings of the pledget, the effectiveness of the interconnection between a withdrawal string for the tampon and the cover member may be improved. Thus, in a preferred embodiment, the tampon includes a withdrawal string which is positively interconnected with a part of the cover member embedded within the pledget. In a preferred embodiment, this is achieved by looping the withdrawal string around a part of the cover web as well as around the absorbent ribbon. We have found that this capturing of cover web and absorbent ribbon by the string maintains security of the cover and ensures consistent withdrawal of the complete tampon assembly. This aspect of the invention represents in itself a new departure from the prior art.

Accordingly, viewed from a third aspect, the invention provides a tampon comprising a pledget formed from a wound ribbon of absorbent material, a cover web and a withdrawal string, wherein at least a part of the cover web is embedded in the pledget, and wherein the withdrawal string positively engages both a portion of absorbent ribbon and a portion of cover web inside the outer circumference of the pledget. This positive engagement is preferably achieved by the withdrawal string being looped around so as to trap said cover web and ribbon portions. A fourth aspect of the invention provides a method of forming a tampon which comprises laying a length of cover web against a length of absorbent ribbon so that they at least partly overlap one another, looping a withdrawal string around the overlapping web and ribbon, and winding the web and ribbon together to form a pledget with said string emerging from one end thereof. The process steps of the different aspects of the invention described above take place before the pledget is hydraulically compressed to form the final tampon form. As is traditional, such compressing can take place by means of a suitable die press. Thus, the "softwound" pledget is formed into a "hardwound" pledget. This is then transferred, as is also traditional, to a heat setting station, which in the preferred embodiment does not provide sufficient heat to bond the cover web to the outer surface of the absorbent ribbon. During heat setting, the tip of the tampon may be shaped into a hemispherical dome by a noser-cap, as is also traditional.

A continuous manufacturing process preferably comprises means for cutting the absorbent ribbon into appropriate lengths by means of a serrated roller, and thereafter applying lengths of cover web to the top surface of the ribbon. These two components are then preferably "tacked" together by means of a heated pressure roller which gives a limited area of thermal bonding adjacent the cover web's leading edge. Thereafter, a loop of withdrawal string is applied around the cover web and ribbon, and is preferably knotted. Winding preferably takes place in a revolving vacuum mandrel which is at 90* to the machine index direction. Such a mandrel is well known in the art and will not be described further. The overhanging outer free end part of the cover web is preferably heat sealed to the underlying web portion e.g. by means of a heated shoe which preferably applies sufficient heat to weld the layers of cover material together but not sufficient to weld the two ply cover web portion thus formed to the underlying ribbon material .

The absorbent ribbon may be made from a blend of non-woven cellulosic fibres. The cover material is preferably formed of polyester fibres with an addition of polyester binder material . Such a material is known as powder-bonded-carded web (PBCW) and may be further treated with a surfactant. However, those skilled in the art will appreciate that the cover web and absorbent ribbon materials may vary.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is a schematic plan view of the initial placement of cover web, absorbent ribbon and withdrawal string during assembly;

Figures 2a and 2b are, respectively, side and end elevations of the softwound pledget; Figure 3 is a perspective view of the softwound pledget; and

Figure 4 is a perspective view of the hardwound pledget after pressing.

Referring firstly to Figure 1, the tampon is formed from three parts which are a length of absorbent fibre ribbon 1, a length of liquid-permeable cover web 2, and a withdrawal string 3.

In a specific example, the absorbent ribbon is formed of a blend of cellulosic fibres. The rayon stock is hypochlorite bleached fibre with 26.1 denier weight and 31 mm staple length. A 0.15% application of glycerine is made to the rayon with respect to the initial weight of fibres. The cotton fibres are also hypochlorite bleached and have a 12 mm target staple length. The target fibre blend ratio is 85% rayon and 15% cotton.

The absorbent ribbon is manufactured from this blend of fibres by a known carding process. Depending on the desired absorbency for the finished tampons, basis weight of the carded ribbon is varied. Ribbon weights of 127 gsm, 170 gsm and 230 gsm are targeted to meet regular, super and super-plus FDA absorbency standards, respectively. The carding process is controlled to produce ribbon in a 50 mm width for regular absorbency tampons. Super and super-plus absorbency tampon ribbon is made to be 55 mm wide. During the pledget-making process, the ribbon is cut into approximately 300 mm lengths.

The cover material is formed from 100% polyester fibres and a 20% addition of modified polyester binder material with respect to initial fibre weight. This combination of fibres and binder material is manufactured to a target weight of 18 gsm. This material is known as a powder-bonded-carded web (PBCW) and is further treated with a 6% addition of Cetiol surfactant with respect to the untreated web weight. The PBCW is made in continuous rolls of wound web with a 48 mm width, i.e. slightly narrower than the absorbent ribbon. As the tampons are made, pieces of cover web are cut from the roll in about 230 mm lengths.

The tampon string 3 is a 10/4 thread made from 100% cotton fibres. Before use in tampon manufacture, the string is dyed and treated with anti-wicking agent.

The tampon assembly method will now be described with reference to the drawings. In practice, each assembly step would take place at a separate processing station.

The lengths of absorbent ribbon, which may be formed by conventional means, are cut from a continuous feed and proceed on a conveyor (not shown) to a cover- attachment station. The length of PBCW cover web as described above is positioned on top of the ribbon piece. As illustrated in Figure 1, the cover is placed in such a way that the major part of the cover's length is superimposed on the ribbon, with a small overhang, for example in the order of 30 mm, extending past the downstream end of the absorbent material . The precise amount of the overhang may vary. This combination of ribbon and cover is passed to a heat-sealing roll (whose construction is conventional and will not be described further) which creates a single block-weld illustrated at 4 in Figure 1 between the web and the ribbon. In a preferred form, the weld area is approximately 30 mm along the longitudinal direction of the ribbon and 50 mm across its width. The weld is placed at the extreme upstream end of the cover material, such that the remaining 200 mm length of cover web is not bound to the absorbent ribbon. The welding occurs by contact of a heat-sealing roll on the web and absorbent ribbon, the temperature of the roll being controlled to a range between 250 and 260^βC for a time that may vary between 0.1 and 0.2 seconds . This high temperature reactivates the modified polyester powder binder in the cover web such that the binder adheres to fibres from the absorbent ribbon creating a direct bond.

A piece of string is then looped around the width of the web and absorbent ribbon, the string preferably being placed such that it is at least 30 mm behind, but not more than 70 mm behind the front edge of the cover web. A knot is tied which joins the two ends of the string. Placement of the string in this way aids in maintaining integrity of the cover web and absorbent ribbon during winding.

The assembly of Figure 1 is then wound about itself beginning from the leading, uncovered end of the absorbent ribbon. A softwound pledget as shown in Figures 2a, 2b and 3 is therefore formed in which the outermost circumference of absorbent ribbon is completely encircled by the cover web. The leading end of the cover web which is bonded to the absorbent ribbon - 10 - is positioned in the interior of the spirally wound pledget, as shown in Figure 2b. Further, the overhanging length of cover web which extends past the downstream end of the absorbent ribbon is positioned so that it winds about the outer circumference of the pledget, and overlies an intermediate portion of cover material on the outer circumference. This double layer of web 5 is then bonded by a heated shoe to create a continuous cylinder of cover material around the outer circumference of the softwound pledget. This shoe makes contact with the outermost layer of cover material, applying heat and pressure. The temperature of the shoe is controlled to between 250 and 260"C. Whilst this forms a weld between the layers of web material, there is not sufficient heat applied to cause bonding between the web and the underlying absorbent ribbon.

As shown in Figure 3, the withdrawal string emerges from the withdrawal end of the tampon and is looped around both the absorbent ribbon and cover web so as to ensure that integrity of the tampon is maintained during withdrawal.

The tampon is then compressed by a traditional arrangement of convex and concave dies, and is heat-set at a temperature between 90 and 100*C and domed shaped at one end to form the hardwound pledget shown in Figure 4. It should be noted that the heat setting is effective to gain dimensional uniformity and does not supply sufficient heat to bond the cover web to the absorbent material. Thus, the present invention provides a tampon whose structural integrity and performance may be improved compared with known tampons and which may be manufactured without substantially increasing the complexity of known manufacturing processes.

Claims

1. A tampon comprising a pledget formed by a spirally wound absorbent ribbon, and a cover web extending around the outer circumference of the pledget, the cover web being secured to the pledget by one end thereof extending into and being embedded in at least an outer part of the pledget spiral winding and the other end thereof extending beyond the outer free end of the absorbent ribbon and being bonded to an underlying intermediate section of the cover web.

2. A tampon according to claim 1 in which the cover web is bonded adjacent its internal end to the absorbent ribbon.

3. A tampon according to claim 2 in which the bonding of the cover web to the absorbent ribbon is provided towards the axis of the pledget.

4. A tampon according to claim 2 or 3 which the areal extent of the bonding of the cover web to the absorbent ribbon is minimised.

5. A tampon according to any preceding claim in which the cover web extends internally beneath at least a major part of the outer winding of the absorbent ribbon.

6. A tampon according to claim 5 in which the cover web is wound internally through more than 360°.

7. A tampon according to any preceding claim including a withdrawal string which is positively interconnected with a part of the cover member embedded within the pledget.

8. A tampon according to claim 7 in which the withdrawal string is looped around a part of the cover web as well as around the absorbent ribbon.

9. A tampon according to any preceding claim in which the ratio of cover web length to absorbent ribbon length is between 0.5 and 1.

10. A tampon according to claim 9 in which the ratio of cover web length to absorbent ribbon length is between

0.6 and 0.9.

11. A tampon according to claim 10 in which the ratio of cover web length to absorbent ribbon length is between 0.7 and 0.8.

12. A tampon according to any preceding claim in which the absorbent ribbon is made from a blend of non-woven cellulosic fibres.

13. A tampon according to claim 12 in which the cover web is made from polyester fibres with an addition of polyester binder material.

14. A tampon according to claim 13 in which the cover web is made from powder-bonded-carded-web.

15. A tampon according to claim 14 in which the powder- bonded-carded-web is further treated with a surfactant.

16. A method of forming a tampon which comprises laying a cover web against a length of absorbent ribbon, with a free end of the cover web projecting beyond a corresponding free end of the absorbent ribbon, spirally winding the absorbent ribbon to form a pledget with a substantial part of the cover web entrapped in the spiral winding and with the cover web extending around the outer circumference of the pledget, and bonding said free end of the cover web to an underlying, intermediate section of cover web.

17. A method according to claim 16 which includes bonding or otherwise tacking the cover web to the absorbent ribbon only in the region of the end of the cover web which is embedded in the pledget when wound.

18. A method according to claim 16 or 17 which includes cutting the absorbent ribbon into appropriate lengths by means of a serrated roller, and applying lengths of cover web to the top surface of the ribbon.

19. A method according to any of claims 16 to 18 which includes looping a withdrawal string around the cover web and absorbent ribbon before winding to form the pledget.

20. A method according to claim 19 which includes knotting the withdrawal string.

21. A method according to any of claims 16 to 20 which includes compressing the formed pledget.

22. A method according to claim 21 which includes shaping the tip of the tampon into a hemispherical dome.

23. A tampon comprising a pledget formed from a wound ribbon of absorbent material, a cover web and a withdrawal string, wherein at least a part of the cover web is embedded in the pledget, and wherein the withdrawal string positively engages both, a portion of absorbent ribbon and a portion of cover web inside the outer circumference of the pledget.

24. A tampon according to claim 23 in which the withdrawal string is looped around so as to trap the cover web and ribbon portions to positively engage therewith.

25. A method of forming a tampon which comprises laying a length of cover web against a length of absorbent ribbon so that they at least partly overlap one another, looping a withdrawal string around the overlapping web and ribbon, and winding the web and ribbon together to form a pledget with said string emerging from one end thereof.

26. A method according to claim 25 which further comprises cutting the absorbent ribbon into appropriate lengths by means of a serrated roller, and applying lengths of cover web to the top surface of the ribbon.

27. A method according to claim 25 or 26 in which the ribbon and cover web are bonded together adjacent the leading edge of the cover web.

28. A method according to claim 25, 26 or 27 which includes knotting the withdrawal string.

29. A method according to any of claims 25 to 28 which includes heat sealing the overhanging outer free end of the cover web to the underlying web portion.

30. A method according to any of claims 25 to 29 which further comprises compressing the formed pledget.

31. A method according to claim 30 which includes shaping the tip of the tampon into a hemispherical dome.

32. A tampon substantially as hereinbefore described with reference to the accompanying drawings.

33. A method of forming a tampon substantially as hereinbefore described with reference to the accompanying drawings.