Method of applying elastic end pieces to an absorbent product web and absorbent product produced thereby

Starting from an elastic material web and an absorbent product web, the method includes removing a first material piece from the elastic material web to provide a second material piece with an aperture and applying the first piece to a first portion of the absorbent product web. The second piece is supplied to a second application station and a section of the second piece is stretched and applied to a second portion of the absorbent product web. In this way an absorbent product with elastic waist portions is manufactured efficiently and with a minimum of waste.

FIELD OF THE INVENTION

The present invention relates to a method of applying elastic end pieces to end portions of an absorbent product web, said absorbent product web being used for producing an absorbent product for absorbing human exudate, such as a disposable diaper. In particular the invention relates to a method in which the elastic end piece at one end of the absorbent product has side flap members formed integrally therewith as a single strip, said side flap members allowing for releasable closure of an absorbent product around a user's waist.

The invention also relates to an absorbent product, which can be produced in accordance with the method of the invention.

BACKGROUND ART

Absorbent products such as disposable diapers typically have two end portions commonly termed waist portions. These each extend from one end edge of the absorbent product up to a central or crotch portion, and each of the portions may occupy about ⅓ of the length of the product.

Elastic material may be applied to absorbent product webs used for forming disposable absorbent diapers. Such elastic material may be applied in the rear waist portion and/or the front waist portion of the absorbent products which are to be produced from the absorbent product web.

WO-A-99/60967 discloses an elastically extensible waist region comprising a continuous belt together with side flaps which may be made elastic. The elasticity is provided by means of a layered structure consisting of a further elastic member, preferably laminated between layers of the absorbent product chassis. The elastic in the waist portion also extends continuously into an upper portion of the side flaps.

Elastic materials such as elastic laminates (i.e. a layer of elastic material laminated to at least one further non-elastic layer) are expensive compared to the majority of other materials in the product. Due to the high speed mass production techniques for absorbent products currently used, there is a constant effort to solve the problem of how to reduce not only the amount of material used but also the amount of waste of material.

The present invention seeks to overcome the above problems by a method of applying elastic material pieces to the waist portions of an absorbent product web, in both a cost-saving and efficient manner, whereby waste is also minimized.

SUMMARY

These and other objects are achieved by a method according to embodiments of the invention, in which end pieces formed from an elastic material web are applied to an absorbent product web in areas to be elastic or elasticated. In this regard a material web is considered to be an elastic material web in accordance with the invention if it can be elastically extended by more than 50% without substantial permanent strain, whereby substantial permanent strain is understood as being of the order of more than about 10 to 30% of the initial length at the first stretching.

An absorbent product web in accordance with embodiments of the invention should be understood to mean at least one, preferably continuous, web of top sheet or back sheet material which is passed along an absorbent product manufacturing line. When the elastic end pieces are applied to the absorbent product web in accordance with the method according to embodiments of the invention, the absorbent product web may comprise e.g. only the back sheet and/or top sheet material or it may comprise any number of additional elements added thereto during the course of production. For example, an absorbent product web may comprise a back sheet and/or top sheet together with an absorbent core and/or standing gathers, and/or leg elastics etc. Other items may also be added to comprise the absorbent product web. The application of the elastic end pieces to the absorbent product web in accordance with the invention may occur before, during or after the attachment of any items to the top and/or back sheet thereof.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

InFIG. 1, an absorbent product in the form of a disposable absorbent diaper produced by the method of the invention is shown in plan view with the top sheet2of said product uppermost. The back sheet6is hidden in the view shown, but is however generally co-extensive with the top sheet2, which has longitudinal side edges9and10extending longitudinally from end edge8(as shown in dotted lines underneath elastic end piece1) down to curved portion13,14of the top sheet and extending onward to end edge15.

An absorbent core, not shown for reasons of clarity, may be positioned between the top sheet2and the back sheet6of the absorbent product.

The product has two end portions, a first end portion5and a second end portion3, portions5and3being attached by means of a crotch portion4. Second end portion3can be a rear end portion intended to lie in contact with the rear waist region of a wearer during use, while first end portion5can be a front end portion intended to lie in contact with the front waist region of a wearer during use. The product may however be worn such that the first end portion5and the second end portion3are inverted.

There is also no exact dimension for each of these portions, although it is generally understood that the crotch portion is that portion which is approximately longitudinally and transversely centrally located in the product. The crotch portion can be displaced longitudinally towards the first end portion5.

The second end portion3can be provided with a continuous end piece1, formed from elastic material. The elastic material is preferably a laminate having nonwoven material forming each outer surface with an elastic lamina between these.

The elastic material of the end piece1is preferably formed to have elasticity only in the transverse direction (i.e. side-to-side inFIG. 1) and thereby substantially no elasticity in the longitudinal direction. This is of advantage for example in improving the fit of the absorbent product to the back of the wearer, since gathering of the rear part of the product in a longitudinal direction is easily prevented.

The end piece1(as will be explained further below) is one symmetrical half of a second material piece section61(seeFIG. 4), and overlies the other components of the absorbent product. In the embodiment shown, the end piece1overlies the combined top sheet2and back sheet6, the standing gathers (of which the inner edges16,17are depicted), the leg elastics18,19, as well as the absorbent core (not shown).

The end piece1of elastic material thus has a transverse end8extending from the outer edges20,21of respective side flaps22,23, whereby the side flaps22,23are to be understood as those portions of the continuous end piece1which extend beyond the longitudinal side edges9,10at the second end portion3.

The end piece1can be fixedly attached to the underlying elements of the absorbent product by means of adhesive or welding, or by any other suitable method.

In order to form a pocket cuff25in the absorbent article, to act as a barrier and containment pocket in particular for fecal matter, the end piece1is fixedly attached, while in a stretched condition, to the underlying components. However the attachment is preferably made only at locations which are longitudinally or laterally outside the dashed line24. The inner, rectangular cut-out edge26of the pocket cuff25up to the line24is thus unattached to the underlying components.

The elastic material end piece1is preferably hydrophobic in order to function so as to contain fluids within the pocket cuff25. However, it is undesirable to continue the elastic end piece1in the central part of the product4all the way down to the inner end edges27,28of the end piece1, since too great an area of the wearer may be juxtaposed to the hydrophobic layer and this may lead to leakage, especially when the wearer is lying on his/her back. Thus the rectangular cut-out indicated by edge26is provided in order to leave sufficient material remaining in the end piece1for forming the leg cut-outs29,30, but at the same time providing a recessed pocket cuff25which is less likely to result in leakage problems.

Releasable attachment means31,32, preferably of the mechanical fastening type such as hook-and-loop type fastening means (such as Velcro® for example) can be provided on the side flaps22,23. Such releasable attachments are well known to the skilled person and thus no further detailed description is provided here. These are adapted to releasably attach to complementary portions11,12provided on the back sheet6of the first end portion5of the product. The portions11and12cover the corner areas of the back sheet6and have inner margins shown with partly slanted dashed lines ending in shorter longitudinal sections just inside the edges of piece33. Such releasable attachment of the complementary releasable attachment means in the end portions may be made, in a manner known per se, after the absorbent product has been passed through the legs of a wearer in order to locate the crotch portion4in alignment with the user's crotch.

At the first end portion5, there is a further elastic end piece33in the form of a rectangular strip. Other shapes of strip are however also possible such as a half-oval shaped strip for example. This end piece33is placed, in the embodiment shown, on top of all the components in the first end region5, namely on top of the standing gathers and the top sheet in the first end region5.

The end piece33is one symmetrical half of a larger, rectangular, first material piece (to be described further below) and may be applied to the absorbent product web in a stretched or unstretched condition. When applied in a stretched condition, which is the preferred case, the piece33will function so as to provide an elasticated waist region. However, when applied in an unstretched condition, the piece33will still function to provide comfort-enhancing properties.

In the embodiment shown, the end pieces1and33have both been applied in a stretched condition and thus the dimensions of end piece33will substantially correspond to those of the rectangular cut-out denoted by line26when the amount of stretching of end piece1and end piece33at attachment is equal and when the underlying substrate (e.g. web56) presents the same stiffness resistance. In the unstretched condition of the end pieces, i.e. the relaxed condition, the dimensions of the end piece33will be substantially identical to that of the rectangular cut-out26(since end piece33is cut from end piece1, as explained below).

In the preferred embodiment described above, although the end piece33is placed above the top sheet2, the end piece33could also be attached to the back sheet6(e.g. on its outwardly facing side), or between the top sheet2and back sheet6.

The product of the invention formed for example as shown inFIG. 1thus has a first end portion5having an elastic end piece1, which can suitably be termed a first elastic end piece1, stretched and attached thereto. Similarly the second end portion3has a second elastic end piece33attached thereto, after having preferably been stretched. The first elastic end piece1includes an inner edge (i.e. an edge which is longitudinally inward in relation to the transversely extending end edges8,15at either longitudinal end of the product), the inner edge being formed by portions27,28. The cut-out26which is preferably rectangular, joins these portions27,28to form a recessed inner edge portion. Similarly, the second elastic end piece33is formed as a strip having dimensions equal to those of the cut-out26. As explained above, the dimensions of the second elastic end piece33will be the same as those of the cut-out26when both the first elastic end piece1and the second elastic end piece33are in an unstretched condition.

The method of applying elastic end pieces in the form of a first material piece44, and a second material piece section61, and of forming the final absorbent product with attached first and second elastic end pieces (such as end pieces1and33) will now be described with reference toFIGS. 2 to 5.

FIG. 2shows a schematic representation of the elements used in the method of the invention. Thus it will be understood that further, or different, components may be included than those described below. A product supply roll34containing an elastic material web37is depicted in the upper left corner. The elastic material web37preferably has elasticity only in the transverse direction. The web37is shown e.g. inFIG. 3, whereby the distance between the longitudinal side edges38and39of the web37is substantially constant and whereby the web has a generally longitudinal axis Y-Y midway between, and generally parallel to, the longitudinal side edges38,39.

The preferably continuous web37is unwound from supply roll34and fed around a first tensioning and/or guide and/or feed roller35, towards a cutting station40. The cutting station40may comprise for example a roller41fitted with a cutting and removal portion43, and a counter roller42. Counter roller42may have a surface which is able to bear against the cutting and removal portion43to allow cutting of the web37, or counter roller42may for example be provided with a recess47allowing the cutter43to engage therewith. Instead of a pair of rollers, other cutting devices may be used, such as a stamping cutter.

In cutting station40a first material piece44is removed from the web37. As shown, the piece44is removed from a location which is substantially centrally placed between the longitudinal side edges38,39of the web37.

The first material piece44is preferably rectangular, although other shapes are possible. The rectangular shape may also include rounded corners or slightly curved edges whilst still presenting a generally rectangular shape. From the first material piece44two equally sized second elastic end pieces33will be formed as explained below, such that the shape of the second elastic end pieces is determined by one substantially symmetrical half of the first material piece44.

The cutting device43also functions, in the embodiment shown inFIG. 2, as a removing device whereby the first material piece44is fed away from the cutting station40along a conveyor45. Conveyor45may for example be formed as a suction conveyor, whereby first material piece44would be held by means of suction to the conveyor45surface. Conveyor45is hereby shown passing around a further roller46, such as a guide roller.

Two further material pieces49,50located at respective longitudinal side edges38,39are also removed, preferably at cutting station40. The pieces49and50are removed for forming curved upper parts of leg cut-out portions29,30in the final product. The pieces49,50do not however need to be removed at cutting station40but instead may be removed upstream or downstream of station40by any suitable cutting device.

In the embodiment shown, the pieces49,50are removed at station40and fed, to e.g. a waste container, along a path48.

The first material pieces44are fed along conveyor45to a first application station55for application to an absorbent product web56.

By removal of first material piece44at cutting station40, the material web thus comprises an aperture51. The material web37exiting the cutting station40and containing the aperture51will be referred to as a second material piece54. The second material piece54is thus still in the form of a single web, but comprises an aperture51. The second material piece54may also contain the further apertures52,53, if already formed at that stage.

As will also be clear from the following, the aperture51corresponds to double the size of a cut out portion26in the first elastic end portion1described above.

An absorbent product web56, is fed by means (not shown) from left to right inFIG. 2. Absorbent product web56is fed through both a second application station57and a first application station55. Although the first application station55is shown downstream of the second application station57, it may equally be placed upstream thereof.

After exiting the cutting station40, the second material piece54is diverted by guide roller59to a third station58comprising a further cutting device63and a slip device62.

The purpose of the cutting device63is to cut the second material piece web transversely at successive locations60(see alsoFIG. 4) which are substantially midway across the aperture(s)51. The slip device62has the purpose of forming a separation in the direction of arrows “A” between the second material piece54and a second material piece section61cut from said second material piece54.

As will be apparent fromFIG. 4, the second material piece section61corresponds to two first elastic end pieces1(shown inFIG. 1) placed back-to-back across a line of symmetry B-B. The leg cut-outs29,30and rectangular cut-outs26thus comprise half of the apertures52,53and51respectively, while the cut-outs29′,30′ and26′ are half of the next set of apertures52′,53′, and51′.

From the condition shown inFIG. 4, the second material piece section61must then be stretched before being applied to the absorbent product web56. In order to do this, the second material piece section61is transferred to a stretching device64, which in the embodiment shown simultaneously rotates and stretches the section61before applying same to the absorbent product web in a stretched condition at the second application station57. Suitable means (not shown) are used for fixedly securing the section61in said stretched condition to the absorbent product web56. Such means may comprise adhesive application means, welding means such as an ultrasound welding device, or any other suitable device which can provide a fixed attachment of the section61to the absorbent product web56.

The section61comprises both a middle section and two end portions, whereby the end portions form side flaps22,23in the waist region. Since the elastic material of the side flaps does not need to be attached to any further underlying non-elastic material in the embodiment shown, an advantage in handling and reliability is obtained in the methods according to embodiments of the invention when attaching the elastic section61to the absorbent product web56only at its transverse central region. This is because the section61only needs to be stretched by an amount sufficient for providing elasticity in the waist band area, thus by an amount of typically between 25 and 75%. Therefore, even though the side flaps22,23may require to be extended by an amount between 100% and 200% or more (and in some cases even greater extensions of up to 300% or more), it is sufficient that just the section61is stretched, e.g. by between 25% and 75%, when being applied to the web56, resulting in relatively low forces acting to remove the elastic section61from the device64and from the absorbent web56after application and attachment. This method may be contrasted with prior art attempts at producing elasticated waist areas, in which elastic material in one piece is stretched by amounts up to or over 200%, over all of its length, and then applied to both a non-elastic waist region and non-elastic side flap regions in order to elasticate the side flaps to the required amount, even though the waist region need not be elasticated by the same amount.

FIG. 5shows a plan view of the absorbent product web56, whereby components such as standing gathers, leg elastics18,19etc., have not been shown so as to aid clarity of the Figure. One or more of these components may however be present.

The web56has two longitudinal side edges65and66. These longitudinal side edges correspond to, and will form, the longitudinal side edges9,10of the absorbent product shown inFIG. 1.

The first material piece44is applied, and fixedly attached, preferably in a stretched condition of between 25% and 75% elongation, to a first end portion67(e.g., the first, single, end portion5inFIG. 1) of the absorbent product web56. The first end portion67of the web56in the embodiment shown comprises the first or front waist end portions of two adjacent absorbent products. The material piece44is thus placed substantially symmetrically across a line of intended separation C-C. The reference numerals11,11′ and12,12′ are inserted to show, with respect toFIG. 1for example, where the complementary attachment portions11,12would be located on one side of line C-C.

Similarly, section61is applied, and fixedly attached in a stretched condition, to a second portion68of said absorbent product web56which second portion68is located at the second waist end portions (e.g., the second, single, end portion3inFIG. 1) of two adjacent absorbent products. The section61is attached symmetrically with respect to the intended line of separation D-D between two absorbent product second waist end portions.

The location of the attachment is such that an inner transverse end section of the second material section on either side of the line D-D will be unattached to the absorbent product web56over only a part of its longitudinal extent. This attachment is also shown clearly by means of line24inFIG. 1. In this way, a pocket cuff25will be suitably formed in each of the adjacent absorbent products.

The final absorbent products are produced by cutting all the way along the lines C-C and D-D through the absorbent product web56and the section61and the first material piece44. As the result of each single cut, two substantially identical elastic waist sections are formed, one on one product and one on the adjacent product. In this way, the end edges of the final product formed where lines C-C and D-D are located, will each be a substantially flush joint edge, one flush edge being formed between one half of the first material piece44and the underlying product web56and the other being formed between one half of the section61and the underlying product web56.

While in the presently preferred embodiments it has been described that the first material piece44and section61are attached to the absorbent product web56across adjacent waist end portions formed as a type of “dual” waist portion, in certain embodiments either the first material piece44and/or the second material piece61may be separated into two pieces before being applied to their respective ends. For example, if it is desired not to have the waist elastic piece33flush with the outer edge15of the first waist portion5, it may be suitable to split the piece44into two pieces at an earlier station before the first application station55and then apply these separate pieces to the absorbent product web56at a location respectively displaced from the lines C-C and D-D of intended separation.

Similarly, if the products are not be produced front/front and back/back as in the shown embodiments, it will be preferable to split each of the first-material piece44and the section61into two pieces for respective application to the appropriate part of the products. Nevertheless, certain advantages of the invention still apply since minimum wastage of the available elastic material occurs due to the use of material piece44taken from an area of the second material piece54in an area of the second material piece54where it would otherwise be removed and discarded.

The releasable fastening means31,32may be attached appropriately to the section61.

Further embodiments will be readily understood by the skilled person upon reading the aforegoing and are intended to be encompassed within the scope of the invention as defined by the appended claims.