WO2013097879A1

WO2013097879A1 - Method of applying structural elements to an absorbent article

Info

Publication number: WO2013097879A1
Application number: PCT/EP2011/006598
Authority: WO
Inventors: Angelica Burvall; Solgun Drevik
Original assignee: Sca Hygiene Products Ab
Priority date: 2011-12-29
Filing date: 2011-12-29
Publication date: 2013-07-04

Abstract

A method of applying structural elements to an absorbent article, the article having a longitudinal direction and a transverse direction, side edges extending in the longitudinal direction and end edges extending in the transverse direction, said absorbent article comprising a topsheet and a backsheet, the backsheet having a body facing surface and a garment facing surface, and a mechanical fastening material secured to the garment facing surface of the backsheet. The method comprises the steps of applying an expandable ink on at least a part of the garment facing surface, and activating the expandable ink at least partly, whereby three-dimensional structural elements are obtained thereon.

Description

Method of applying structural elements to an absorbent article TECHNICAL FIELD

The present invention pertains to a method of applying structural elements to the garment facing surface of an absorbent article and to an absorbent article comprising such structural elements.

BACKGROUND ART

Absorbent articles such as panty liners, sanitary napkins and incontinence pads are typically held in place by adhesives, e.g. in the form of a double sided tape or a hot melt adhesive applied on the garment facing surface of the backsheet of the article. The adhesive holds the absorbent article in place by adhering it to the crotch part of the user^'s underwear. Mechanical fasteners such as hook fasteners may be used instead of adhesives as disclosed in US 5,778,457. The use of mechanical fasteners has the advantage that no release paper is needed as is the case with the adhesives. The use of hook fasteners on absorbent articles have however been limited due to the hook carrier material being stiff causing discomfort for the wearer and irritation of the skin.

US 20030009144 A1 discloses a mechanical fastener having a cloth-like carrier material. US 20070098953 A1 discloses a mechanical fastener in the form of a foam having a plurality of free-standing struts. Prior art solutions may alleviate the roughness problem of mechanical fasteners to some degree. However, there is still a need for a cost-effective and simple solution making it possible to use even rough and less expensive mechanical fasteners on absorbent articles.

SUMMARY OF THE INVENTION

The present invention relates to a method of applying structural elements to an absorbent article according to claim 1. The article have a body facing surface and a garment facing surface, a longitudinal direction and a transverse direction, side edges extending in the longitudinal direction and end edges extending in the transverse direction, said absorbent article comprising a topsheet and a backsheet, the backsheet having a body facing surface and a garment facing surface, and a mechanical fastening material secured to the garment facing surface of the backsheet. The method comprises applying an expandable ink on at least a part of the garment facing surface of the absorbent article, and activating the expandable ink at least partly, whereby three-dimensional structural elements are obtained thereon.

The invention further concerns an absorbent article, the article having a body facing surface and a garment facing surface, a longitudinal direction and a transverse direction, side edges extending in the longitudinal direction and end edges extending in the transverse direction, comprising a topsheet and a backsheet, the backsheet having a body facing surface and a garment facing surface and a mechanical fastening material secured to the garment facing surface of the backsheet. Structural elements of expandable ink has further been applied to at least a part of the garment facing surface of the absorbent article and have subsequently been activated at least partly to form three-dimensional structural elements thereon.

In addition, the invention concerns the use of an expandable ink to provide expanded three-dimensional structural elements on the garment facing surface of an absorbent article, the article having a body facing surface and a garment facing surface, a longitudinal direction and a transverse direction, side edges extending in the longitudinal direction and end edges extending in the transverse direction, the absorbent article comprising a topsheet and a backsheet, the backsheet having a body facing surface and a garment facing surface and a mechanical fastening material secured to the garment facing surface of the backsheet. The method according to the invention makes it possible to provide soft structural elements on at least a part of the garment facing surface of the absorbent article in a simple, fast and cost-effective way. The application and the activation of the

expandable ink allows forming of very precise lines, patterns and dots making it possible to provide a soft texture where needed, such as on or near rough edges of the mechanical fastening material.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1-18 illustrates mechanical fastener material and expanded ink applied on the garment facing surface of an absorbent article. Figures 19 and 20 illustrate two different embodiments of the structural elements of figure 7, seen in cross-section taken along the line in the figure.

DETAILED DESCRIPTION OF THE INVENTION

According to the method of the present invention structural elements are applied on at least a part of the garment facing surface of an absorbent article, the article having a body facing surface and a garment facing surface, a longitudinal direction and a transverse direction, side edges extending in the longitudinal direction and end edges extending in the transverse direction, the absorbent article comprising a top sheet and a back sheet and a mechanical fastening material secured to the garment facing surface of the backsheet, and may, if desired, also comprise an absorbent core arranged between the top sheet and the back sheet. The absorbent article may be a personal hygiene article such as a sanitary napkin, a panty liner, a male or female incontinence article. The expandable ink is activated at least partly so as to be transformed into three-dimensional structural elements protruding from the garment facing surface, as a result of the activation. The absorbent article of the invention will be described in more detail below.

The expandable ink preferably comprises a polymer, a solvent and a blowing agent or expandable microspheres. The ink may be a standard formulation known to the skilled man in the art, comprising a polymer, a solvent, binders, thickeners, pigments and a blowing agent or expandable microspheres comprising a propellant. The ink may be applied by a printing technique, e.g. by screen printing, flexoprint, ink jet printing, rotary screen printing or gravure. Application by flexoprint is an

advantageous printing method, due to its stability, and insensitivity to dust or particles in the ink. It may also be preferable to combine inks of different colours.

The amount of expandable ink applied will depend on the composition of the ink, on the desired pattern and/or on the desired height of the structural elements after activation of the ink. The amount of ink needed may vary also depending on the surface absorbency and the thickness of the material. The skilled person can find out the amounts required to achieve the desired surface by routine experiments. The height of the three dimensional structures of expanded ink may be of the same height or preferably higher than the mechanical fastening material. The three-dimensional structural elements may have a height of 0.1-15 mm, preferably 0.5-5 mm.

After application of the ink on the absorbent article, any solvents will evaporate. An optional drying step may be performed after the application of the ink. As said above, the expandable ink is activated at least partly in order to obtain the desired effect. The activation and the drying may be performed in one single process step. During activation, components of the ink swell up due to the action of blowing agent or microspheres, so that the applied ink is transformed into three-dimensional structural elements, which protrude from the garment facing surface of the absorbent article.

The activation may be carried out by exposing the expandable ink to heat, preferably by means of infra-red radiation, hot air, or microwaves. These heating methods allow flexible and versatile heating, which will provide for effective activation of the expandable ink. Alternatively, the ink may be brought into contact with a heated surface, such as a calendering roll The activation temperature depends on the amount of ink applied and of the type of ink used, and is typically 80 till 180°C, preferably 100-180°C. If the expandable ink is of a type that can be activated by UV radiation, the activation may instead be performed by means of UV radiation, which may be advantageous in particular when heat-sensitive materials are used in the absorbent article.

The steps of printing and activation can be incorporated as inline steps in a process of manufacturing absorbent articles, or the surface may be printed and activated offline. It is also possible to print the surface before or during assembly of the

components of the absorbent article and to activate the expandable ink in a later stage in the process. The printing may be a continuous print or a synchronized print. There is no need to take the location of the mechanical fastening material into account when printing on the garment facing surface of the absorbent article when printing continuously. The location of the mechanical fastening material may be taken into account when activating the ink. The method of the invention may be performed in an apparatus where equipment for carrying out the steps of application of expandable ink and activation of the ink is arranged such that absorbent article blanks can be fed through each step in a line production, e.g. by arranging discrete absorbent article blanks on a conveyor belt, passing each step of the method. The ink may be applied in different steps. Thus, different types of ink may be applied and activated in different steps.

The expandable ink may be activated so as to obtain expansion only in selected areas, while leaving other areas unexpanded. Thereby, patterns of printed ink can be formed in which some pattern elements are two-dimensional and some pattern elements are three-dimensional allowing for expansion only where needed. This can be done by masking areas which are not to be activated, or by directing heat or UV radiation only to areas which are to be activated, e.g. by using a directed beam. Hot calendering may also be used for this purpose. By activating the ink in selected areas only, creation of different protruding patterns from the mechanical fastening material on the garment facing surface of absorbent articles can be accomplished, without having to modify the pattern in which the ink is applied. The expandable ink may be applied in selected areas as desired and where needed, and in any desired pattern. The present method allows very accurate patterns of structural elements, and fine lines, dots, zigzagged patterns, chequered, waves, flower patterns etc to be formed. The expandable ink may be applied on at least a part of a side edge of the

mechanical fastening material, such as in order to smooth a sharp edge. The expandable ink may also be applied in close proximity to the material and still achieve the same effect. The expandable ink may also be applied along at least one of the longitudinal side edges and/or the transverse side edges of a mechanical fastening material having a square or rectangular circumference or any other shape. Further, the expandable ink may substantially cover the side edge around the whole circumference of the mechanical fastening material. Thus, by applying expandable ink on at least a part of the garment facing surface of an absorbent article means herein, that the expandable ink may be applied to the garment facing surface of the backsheet and/or the mechanical fastening material secured to the garment facing surface of the backsheet.

As indicated above, the final pattern of structural elements on the garment facing surface of the backsheet may be obtained by printing the desired pattern of expandable ink or by activating printed expandable ink in a desired pattern, or a combination thereof. Depending on the location and structure of the structural elements applied in this way, various advantageous functional effects can be obtained. Examples of patterns of expandable ink, giving rise to structural elements with different functions are given herein but should not be limited thereto. These patterns can be used individually, but can of course advantageously be combined to achieve the desired characteristics of the absorbent article.

The term mechanical fastening material as used herein refers to a mechanical fastening material for fastening of the absorbent article inside a supporting pant garment, such as a pair of underpants, and may be a hook material, a material having friction elements thereon such as lamellar and scale structures, or other similar materials and combinations thereof. The mechanical fastening material has a first and second surface, wherein hooks, lamellae and scales etc protrude from the second surface. The mechanical fastening material may be secured to the garment facing side of the backsheet by an adhesive, the adhesive being applied on the first surface of the mechanical fastening material. The material may also be secured by other means such as welding.

The mechanical fastening material may cover substantially the whole backsheet or may cover only a part of it depending on the desired fastening properties. When the mechanical fastening material covers substantially the whole backsheet, the mechanical fastening material may have properties normally assigned to a backsheet material as stated herein. The mechanical fastening material may be in the form of longitudinally extending bands, transverse bands, dots, circles, curves, stars, etc. arranged on the garment-facing surface of the backsheet. The number of mechanical fasteners is at least one, but there may be a number of the same or different mechanical fasteners. The mechanical fastening material may be of thermoplastic polymers, preferably selected from polyesters, polyamides, and polyolefins such as polyethylenes and polypropylenes or a mixture of any of these.

A hook material comprises a hook carrier layer having a first and second surface and a plurality of hooks protruding from and secured to the second surface of the carrier layer. The hooks may be of any shape such as mushroom shape, T-shape, l-shape or L-shape. The hooks may be adapted to interact with synthetic and/or cotton textile materials. Expandable ink may be applied on at least a part of the carrier layer or on at least a part of both carrier layer and the hooks protruding therefrom.

An absorbent product will generally be described below. An absorbent product according to the invention comprises a topsheet, facing the wearer during use, and a backsheet, facing the garment during use, and may further comprise a core therebetween. The topsheet and the backsheet of the absorbent article is connected to each other in an edge joint which in case a core is present will be formed around the periphery of the absorbent core. The edge joint may be formed in any suitable manner as known in the art such as by means of adhesive, ultrasonic bonding, thermobonding, stitching, etc. Alternative covering arrangements such as wrapped- around covers are also conceivable within the scope of the invention.

The topsheet may consist of any material which is suitable for the purpose, i.e. be soft and liquid pervious. Examples of commonly found topsheet materials are nonwoven materials, perforated plastic films, plastic or textile mesh, and fluid permeable foam layers. Laminates consisting of two or more topsheet materials are also commonly employed, as are top sheets consisting of different materials within different parts of the fluid permeable wearer-facing surface.

The backsheet is fluid impermeable. The backsheet is commonly constituted by a thin, flexible, fluid-impermeable plastic film, but fluid-impermeable nonwoven materials, fluid impermeable foams and fluid impermeable laminates are also contemplated within the scope of the invention. The backsheet may preferably be breathable, implying that air and vapor may pass through the backsheet. Furthermore, the backsheet may have an outer, garment-facing surface of a textile material such as nonwoven.

An absorbent core may be made up of any suitable absorbent or fluid uptake material as known in the art, such as one or more layers of cellulose fluff pulp, foam, fibre waddings, etc. The absorbent core may contain fibers or particles of highly absorbent polymer material, commonly known as superabsorbents, which are materials having the ability to absorb and retain large quantities of fluid upon formation of a hydrogel. The superabsorbents may be mixed with cellulose fluff pulp and/or may be arranged in pockets or layers in the absorbent core. The fibres may be pulp fibres and the superabsorbent material may be polyacrylate-based particles. An absorbent structure may comprise 0-60% superabsorbents and 40-100% pulp fibres.

The absorbent article may further incorporate components for improving the

properties of the absorbent core. Some examples of such components are binder fibers, fluid-dispersing materials, wetness indicators, fluid acquisition materials, etc., as known in the art.

The absorbent article typically, in case of a pad or a sanitary napkin, has an

elongate, generally rectangular shape when fully extended in all directions. In this context, a generally rectangular shape is intended to encompass also that, for instance, the corners of the absorbent article may be rounded, or that the edges of the absorbent article may not be completely linear. Accordingly, any suitable shape may be used for the absorbent article, such as hourglass shape, trapezoidal shape, triangular shape an oval shape, etc., The shape of the article of the invention may be symmetrical about a transverse center line through the article, or may be

asymmetrical with end portions having differing shapes and/or differing sizes.

The absorbent article may have two longitudinal side edges having equal length and extending generally in the same direction as a longitudinal center line through the absorbent article. Front and rear end edges typically extend transversely to the longitudinal center line at the ends of the absorbent article. The rear end edge is intended to be orientated rearwards during use of the absorbent article, and the front end edge is intended to be facing forwards towards the abdomen of the wearer. The absorbent article may have a front end portion, a rear end portion and a crotch portion located intermediate the end portions, the crotch portion being a portion, which is intended to be placed against the crotch of a wearer during use of the article and to constitute the main acquisition area for body fluid that reaches the absorbent article.

An absorbent article having an absorbent core may have a core being homogeneous in structure or may have a layered structure such as absorbent laminates of the same or different materials. The absorbent layers may have uniform thickness or may vary in thickness in different parts of the layers. Similarly, the basis weight and composition may vary within the absorbent layers. By way of example, an absorbent layer may comprise a mixture of absorbent and/or non-absorbent fibres and superabsorbent material, wherein the ratio of superabsorbent material to fibres may vary in the layer.

An absorbent layer may have any suitable shape, such as an hourglass shape with widened end portions and a narrow portion in the crotch portion, or a rectangular shape. The invention will now be described by means of example referring to Figures 1-20. The absorbent article 2 comprises a body facing surface 10 and a garment facing surface 1 , a longitudinal direction and a transverse direction, side edges 13 extending in the longitudinal direction and end edges 14 extending in the transverse direction. Figures 1- 8 discloses the garment facing surface 1 of absorbent articles 2 wherein mechanical fastening material 3 has been applied to the garment facing surface 5 of the backsheet material 6. The mechanical fastening material 3 is configured in different ways and covers different parts of the backsheet 6 and differently sized areas, numbers of mechanical fasteners etc. Figure 1 discloses a mechanical fastening material 3 covering substantially the whole garment facing surface 5 of the backsheet 6. Expandable ink 4 has been applied around the circumference of the mechanical fastening material 3. In figures 2-9 expandable ink 4 has been applied substantially around the whole circumference of the mechanical fastening material 3. The expandable ink 4 may be applied on the mechanical fastening material 3 only, the backsheet 6 only or on both mechanical fastening material 3 and backsheet 6.

Figures 10-18 exemplifies different ways of applying and expanding the expandable ink 4. Figure 10 discloses small squares of expandable ink 4 applied on or near a rectangular mechanical fastening material 3. Figure 11 discloses winding ornaments of expandable ink 4 applied on or near the mechanical fastening material 3. Figures 12 and 15 disclose flower ornaments of expandable ink 4 applied on or near the mechanical fastening material 3. Figure 13 discloses checked patterns of expandable ink 4 applied on or near the mechanical fastening material 3. Figures 14 and 16 disclose lace like patterns of expandable ink 4 applied around the circumference of mechanical fastening material 3. Figure 17 discloses larger areas of expandable ink 4 applied on or near the mechanical fastening material 3 and wherein the expandable ink 4 has been expanded only in selected areas. Figure 18 discloses circular patterns of expandable 4 ink applied around the mechanical fastening material 3 and the ink 4 being expanded in selected areas only.

Figures 19 and 20 exemplify different locations for the expandable ink 4 on the absorbent article 2. Figures 19 and 20, respectively, discloses a cross-section taken along the line of figure 7 and discloses an absorbent artcle 2 comprising a body facing surface 10 and a garment facing surface 1 , a topsheet 11 and a backsheet 6, the backsheet 6 having a body facing surface 12 and a garment facing surface 5, and a mechanical fastening material 3 secured to the garment facing surface 5 of the backsheet 6. Expandable ink 4 is applied on the garment facing surface 1 of the absorbent article 2. Figure 20 discloses expandable ink 4 applied on the garment facing surface 1 of the absorbent article 2, such as on the garment facing surface 5 of the backsheet 6 and on the mechanical fastening material 3. The mechanical fastening material 3 is here exemplified with a hook material 7 and the expandable ink is applied on both carrier material 8 and hooks 9.

Claims

1. A method of applying structural elements to an absorbent article (2), the article (2) having a body facing surface (10) and a garment facing surface (1), a longitudinal direction and a transverse direction, side edges (13) extending in the longitudinal direction and end edges (14) extending in the transverse direction, said absorbent article (2) comprising a topsheet (11) and a backsheet (6), the backsheet (6) having a body facing surface (12) and a garment facing surface (5), and a mechanical fastening material (3) secured to the garment facing surface (5) of the backsheet (6), characterized in that it comprises:

-applying an expandable ink (4) on at least a part of the garment facing surface (1) of the absorbent article (2), and

-activating the expandable ink (4) at least partly, whereby three-dimensional structural elements are obtained thereon.

2. Method according to claim 1 , wherein the ink is applied by a printing technique.

3. Method according to claim 1 or 2, wherein the expandable ink is applied as a continuous print.

4. Method according to any one of claims 1-3, wherein the mechanical fastening material has side edges and wherein expandable ink is applied along at least one of the longitudinal side edges and/or the transverse side edges of the material.

5. Method according to any one of claims 1-4, wherein the expandable ink is substantially covering the side edge around the circumference of the mechanical fastening material.

6. Method according to any one of claims 1-5, wherein the expandable ink is applied as a synchronized print.

7. Method according to any one of claims 1-6, wherein the mechanical fastening material is selected from hook material, a material having friction elements thereon or a combination thereof.

8. Method according to any one of claims 1-7, wherein the mechanical fastening material is a hook material comprising a hook carrier layer and a plurality of hooks secured to the carrier layer and wherein the expandable ink is applied on at least a part of the carrier layer.

9. Method according to any of claims 1-8, wherein the expandable ink is activated by means selected from infra-red radiation, UV radiation, hot air, microwaves, or by a hot calendering.

10. The method of any one of the previous claims, wherein the expandable ink comprises a polymer, a solvent and a blowing agent or expandable microspheres.

1 . The method of any one of the previous claims, wherein the absorbent article is selected from: a sanitary napkin; a panty liner; a male or female incontinence article.

12. An absorbent article (2), the article (2) having a body facing surface (10) and a garment facing surface (1), a longitudinal direction and a transverse direction, side edges (13) extending in the longitudinal direction and end edges (14) extending in the transverse direction, comprising a topsheet (11) and a backsheet (6), the backsheet (6) having a body facing surface (12) and a garment facing surface (5) and a mechanical fastening material (3) secured to the garment facing surface (5) of the backsheet (6), characterised in that structural elements of expandable ink (4) has been applied to the at least a part of the garment facing surface (1) of the absorbent article (2) and has been subsequently activated at least partly to form three-dimensional structural elements thereon.

13. The absorbent article of claim 12, wherein the three-dimensional structural elements have a height of 0.1-15 mm, preferably 0.5-5 mm.

14. Use of an expandable ink (4) to provide expanded three-dimensional structural elements on the garment facing surface (1) of an absorbent article (2), the absorbent article (2) having a body facing surface (10) and a garment facing surface (1), a longitudinal direction and a transverse direction, side edges (13) extending in the longitudinal direction and end edges (14) extending in the transverse direction, comprising a topsheet (11) and a backsheet (6), the backsheet (6) having a body facing surface (12) and a garment facing surface (5) and a mechanical fastening material (3) secured to the garment facing surface (5) of the backsheet (6).