GB2473227A

GB2473227A - Absorbent article having an encapsulated adhesive

Info

Publication number: GB2473227A
Application number: GB0915372A
Authority: GB
Inventors: Carolyn Berland
Original assignee: SCA Hygiene Products AB
Current assignee: Essity Hygiene and Health AB
Priority date: 2009-09-03
Filing date: 2009-09-03
Publication date: 2011-03-09
Also published as: GB0915372D0

Abstract

The invention provides an absorbent article 10 with a garment-facing surface 20, which comprises a first adhesive 30 and capsules 40 of a second adhesive 50. The first adhesive 30 has a tack of less than 1.5N and may be a pressure-sensitive hot melt adhesive which may be printed, coated or sprayed onto the absorbent article 10. The first adhesive 30 and encapsulated adhesive 40 may occupy different spatial regions (see fig 4). The capsules 40 rupture upon application of a 15N or more force. The capsules may have an irregular 3D form or may be micelles. The capsules may also contain a fragranced perfume or lotion which is released upon capsule rupture.

Description

INTELLECTUAL

. .... PROPERTY OFFICE Application No. GBO9 15372.7 RTM Date:8 January 2010 The following terms are registered trademarks and should be read as such wherever they occur in this document: Dispomelt 3M Post-it Pluronic

BASF

Intellectual Property Office is an operating name of the Patent Office www.ipo.gov.uk

ABSORBENT ARTICLE WITH IMPROVED ADHERENCE

TECHNICAL FIELD

The present invention provides an absorbent article. The garment-facing surface of the article comprises a first adhesive, and capsules of a second adhesive. The combination of the first adhesive and the second adhesive provide good adhesion of the absorbent article to the underwear of the wearer.

BACKGROUND OF THE INVENTION

Certain absorbent articles, such as sanitary napkins, panty liners and incontinence guards for male and female use, are adhered to the garment (i.e. the underwear) of a wearer to keep them correctly positioned during use. The adhesive properties of such absorbent articles must be sufficient to allow simple and easy application of the article in the wearer's garment, to maintain the article in a correct position under the forces experienced during wear, and yet to release the article from the garment readily after use.

Adhesive which binds too strongly to garments tends to damage the absorbent article and/or the garment to which it is adhered. Adhesive which binds too weakly will not hold the absorbent article sufficiently US 4720417 teaches microencapsulated materials on a sanitary article, US 5591.146 discloses a sanitary napkin having adhesive with perfume-carrying release agents.

US5514122 presents a feminine hygiene pad which is provided with a linerless microsphere pressure-sensitive adhesive attachment region for attaching the pad to an undergarment.

Numerous efforts have been made to balance the adhesive properties of absorbent articles to achieve sufficient adhesion during wear yet to release the article from the underwear without damage to the article or the underwear. In addition, it would be useful to provide an article which adheres sufficiently during initial application, but which can also adjust to movement and/or forces experienced during wear, so that a sufficient level of adhesive is maintained between the absorbent article and the underwear of the wearer.

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SUMMARY OF THE INVENTION

The invention provides an absorbent article. The absorbent article comprises a garment-facing surface. The garment-facing surface comprises a. a first adhesive, said first adhesive being such that the Initial Tack as defined herein is less than 1.5N per product, b. capsules of a second adhesive, said capsules being arranged so as to rupture upon application of a Shear Force of at least 15N per product and release said second adhesive.

Suitably, the first adhesive is a pressure-sensitive hot melt (PSHM) adhesive. The first adhesive may be coated (e.g. slot-coated, roll-coated), printed or sprayed onto the garment-facing surface.

The first adhesive and the capsules of the second adhesive suitably occupy separate. and distinct regions of the garment-facing surface. Typically, the first adhesive occupies a region of the garment-facing surface which is located adjacent the front edge of the article.

The capsules of a second adhesive suitably occupy a region of the garment-facing surface which is located within 3cm, preferably within 2cm, preferably within 1cm of the periphery of said garment-facing surface.

Suitably, the capsules have an irregular three-dimensional form. The capsules may comprise micelles. The capsules may additionally comprise a fragrance, lotion, dye, or a combination thereof, which is also released upon rupture of said capsules.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to the appended schematic figures, in which: Figure 1 shows an embodiment of the invention, seen from the garment-facing surface, Figure 2 shows an embodiment of the invention, seen from the garment-facing surface, Figure 3 shows an embodiment of the invention, seen from the garment-facing surface.

Figure 4 shows an embodiment of the invention, seen from the garment-facing surface.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Figures 1-4 shows an absorbent article 10 according to the invention. Absorbent articles are meant to be worn against the body in the genital region of a wearer to absorb bodily exudates such as urine, blood and/or faeces.

The illustrated absorbent article is in the form of a sanitary napkin, but the invention equally applies to all absorbent articles 10 which are intended to be adhered to the underwear of the wearer via the garment-facing surface 20 of the article 10. Adherence to the underwear typically takes place on the inside of the underwear, but absorbent articles may have flaps or so-called wings" which fold around the edges of the underwear and can adhere to the outside of the underwear, Examples of absorbent articles 10 relevant to the present invention are sanitary napkins, panty liners and male or female incontinence guards.

Figures 1-2 and 4 shows a sanitary napkin, while Figure 3 shows and absorbent article 10 in the form of a male incontinence guard. Sanitary napkins have longitudinal (L) and transverse (T) extensions as shown, and are symmetric about a longitudinal centre line.

They may also be symmetric about a transverse centre line, although this is less common.

Sanitary napkins have a variety of shapes in the L-T plane, including oval, "dog-bone", "race-track" and "mermaid". Certain sanitary napkins may be triangular. Male incontinence guards are substantially triangular, being wider at the front edge than at the rear edge. Sanitary napkins are usually planar, which allows for easier transport and packaging, but may even have a three-dimensional form, provided e.g. by extra components or elastics in certain regions. The absorbent article 10 has a middle region 13 and front 11 and rear 12 regions, said middle region 13 being located between said front 11 and rear 12 regions in the longitudinal direction. A typical absorbent article may have an extension in the longitudinal direction L of between circa 200 and 300cm, and an extension in the transverse direction T of between circa 50 and 90cm.

The absorbent article 10 shown in Figures 1-4 comprises a liquid-permeable topsheet 14, a liquid-impermeable backsheet 15 and an absorbent core 16 located therebetween.

However, not all absorbent articles comprise all of these components. Certain small panty liners do not comprise an absorbent core 16 as such, but instead comprise additional layers of material, e.g. nonwoven material, in the certain regions thereof.

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Certain sanitary napkins do not comprise a traditional combination of fluff pulp and superabsorbent material, but instead comprise foam material or NW laminate material.

Additionally, certain absorbent articles do not comprise separate topsheets 14 or backsheets 15. Absorbent articles according to the invention may also comprise one or more elastic members (not shown) which are arranged so that the article adopts the appropriate form when in use.

The topsheet 14 of the article 10 is the layer which lies in contact with the wearer's body when the article is in use. As such, it should be soft, non-irritating and comfortable against the skin, and bodily fluid should be able to pass through it without hindrance. The topsheet 14 can consist of a nonwoven material, e.g. spunborid, meltblown, carded, hydroentangled, wetlaid etc. Suitable rionwoven materials can be composed of natural fibers, such as woodpulp or cotton fibres, manmade fibres, such as polyester, polyethylene, po'ypropylene, viscose etc. or from a mixture of natural and manmade fibres. The topsheet may further be composed of tow fibres, which may be bonded to each other in a bonding pattern, as e.g. disclosed in ER-A-i 05 818. Further examples of materials suitable for topsheets are porous foams, apertured plastic films etc. Combinations or laminates of the above products are also possible in the topsheet 14.

The topsheet 14 may be different in different parts of the absorbent article 10. The topsheet 14 is preferably extensible (it can be stretched without significant elastic forces being present which return it to its original dimensions).

The backsheet 15 of the article 10 is the layer which lies furthest from the wearer's body when the article is in use. To protect the wearer's garments from soiling, it should be liquid-impermeable, but is desirably gas-permeable (i.e. breathable) to allow air and vapour to pass in and out of the article so that the warm, damp conditions which can arise in an article are reduced. Typically, the backsheet 15 is of a liquid impervious material, such as a thin plastic film, e.g. a polyethylene or polypropylene film, a nonwoven material coated with a liquid impervious material, a hydrophobic nonwoveri material, which resists liquid penetration or a laminate comprising plastic films and nonwoven materials.

Examples of breathable backsheet materials are porous polymeric films, nonwoven laminates from spunbond and meitbiown layers, laminates from porous polymeric films and nonwovens. The backsheet 15 may also comprise foam material, alone or in combination with one or more of the above-mentioned materials. The backsheet 15 is preferably extensible. The backsheet 15 may be different in different parts of the absorbent article 10.

The absorbent core 16 of the article 10 acts to receive and contain liquid and other bodily exudates and can be of any conventional kind. As such, it typically comprises absorbent material. Examples of commonly-occurring absorbent materials are cellulosic fluff pulp, tissue layers, highly-absorbent polymers (so called superabsorbents),. absorbent foam materials, absorbent nonwoven materials or the like. It is common to combine cellulosic fluff pulp with superabsorbents in an absorbent body. It is also common to have absorbent cores comprising layers of different material with different properties with respect to liquid receiving capacity, liquid distribution capacity and storage capacity. The thin absorbent cores, which are common in for example baby diapers and incontinence guards, often comprise a compressed mixed or layered structure of celiulosic fluff pulp and superabsorbent. The size and absorbent capacity of the absorbent core 31 may be varied to be suited for different uses such as for infants or for incontinent adults.

The absorbent core 16 may comprise one or more layers which are designed to improve the handling of bodily waste. Such layers are designed to receive a large amount of liquid in a short space of time and distribute it evenly across the absorbent core 16. They may include so-called transfer, distribution, surge or acquisition layers, and are usually located between the topsheet 14 and the absorbent core 16. So-called all-in-one" absorbent cores comprise substantially the same material throughout the core, but at least one property (e.g. density or porosity) of the material varies within said core.

The topsheet 14 and backsheet 15 generally have a similar extension in the plane of the article, while the absorbent core 16 has an extension which is somewhat smaller. The topsheet 14 and backsheet 15 are joined to one another around the periphery of the absorbent core 16, so that the core 16 is enclosed within the envelope formed by the topsheet 14 and the backsheet 15. The absorbent core 16 is at least located in the middle region 13 of the article 10, and may also extend somewhat into the front 11 and rear 12 regions. The topsheet 14 and backsheet 15 may be joined to one another by any means common in the art, e.g. ultrasonic welding, thermal welding or gluing.

The absorbent article 10 according to the invention comprises a garment-facing surface 20, being that surface of the article 10 which makes contact with the underwear of the wearer. The garment-facing surface 20 is typically the backsheet 15, although additional layers may be present between the liquid-impermeable backsheet 15 and the garment-facing surface 20.

As shown in Figures 1-4, the garment-facing surface 20 comprises a first adhesive 30.

The first adhesive 30 provides good initial attachment of the article 10 to the underwear of the wearer. The first adhesive 30 could be coated in a continuous layer throughout one or more portions of the garment-facing surface 20 e.g. one stripe or several stripes in the longitudinal, transversal, diagonal or any other direction, dots and/or in any other suitable pattern. The first adhesive 30 is suitable coated (e.g. slot-coated, roll-coated), printed or sprayed (e.g. spiral-sprayed) onto the garment-facing surface 20. The first adhesive 30 may occupy any region of the garment-facing surface 20, but preferably occupies a region of the garment-facing surface 20 which is located at least adjacent the front edge of the article 10. Suitably, the first adhesive 30 is present in an amount of between 5 and 80 grams per square meter (gsrn), suitably between 10 and 40 gsm. The first adhesive 30 may cover substantially the entire garment-facing surface, but preferably only occupies a portion thereof, e.g. at most 70%, preferably at most 50%, more preferably at most 30% of the surface area of the garment-facing surface. The first adhesive 30 is suitably a pressure-sensitive hot melt (PSHM) adhesive. Adhesives that may be used as the first adhesive according to the present invention are e.g. FULLER hotmelt Lunamelt� PS364/li ZP, NATIONAL hotmelt Dispomelt 8638 (Duro-Tak H1538) andlor 3M Post it, see more information in US 3691140. Another suitable first adhesive is e.g. FULLER hotmelt NW1OS3.

The first adhesive 3D is such that the Initial Tack as defined herein is less than 1.5N per product.

As well as the first adhesive 30, the absorbent article 10 also comprises capsules 40 of a second adhesive 50. The term capsules' is used to define that the second adhesive 50 is present in small individual amounts, each amount being surrounded by (i.e. encapsulated by) another material. Any of the adhesives which are suitable for the first adhesive 30, above, may also be suitable for use as the second adhesives 50.

The material which makes up the walls of the capsules 40 of the invention (i.e. which surrounds the second adhesive 50) may comprise any such material which is compatible with the second adhesive 50 and which forms stable capsules 40. Examples of suitable materials include polysaccharides (e,g. carageenan, starch, cellulose, chitosan), proteins (e.g. gelatine, collagen, keratin), synthetic polymers (e.g. polyolefins, polyethers (e.g. thos of the Pluronic brand sold by BASF), polyesters, polyacrylates, poiyurethanes, polyurea, formaldehyde/urea polymers) or mixtures and copolymers thereof.

A common method for the formation of capsules 40 is to dissolve the second adhesive 50 in a solvent together with the material which makes up the walls of the capsules 40.

Optional additional ingredients may be added, e.g. surfactants, to provide the appropriate capsule-forming properties (e.g. surface tension). The mixture is then dried, to provide capsules. Further details of how capsules may be produced are provided in US 4,720,417 and US 5,591,146.

The capsules 40 may be applied in any conventional manner, such as those set out for the first adhesive 30 above. The amount of capsules may be adjusted so as to lie between 1 and 120 grams per square meter (gsm), suitably between 5 and 60 gsm. The capsules 40 of second adhesive 50 may occupy substantially the entire garment-facing surface of the article 10, but preferably only occupies a portion thereof, e.g. at most 70%, preferably at most 50%, more preferably at most 30% of the surface area of the garment-facing surface. The capsules 40 of second adhesive 50 suitably occupy a region of the garment-facing surface 20 which is located near the periphery of the garment-facing surface 20. By the phrase near the periphery" of the garment-facing surface is meant a region which is located within 3cm, preferably within 2cm, preferably within 1cm of the periphery of said garment-facing surface 20.

The capsules 40 themselves may be sufficiently adhesive that they can be applied to the garment-facing surface 20 of the article 10 and adhere thereto. For example, they may be applied to the garment-facing surface before they are completely dried or solidified.

Alternatively or additionally, additional adhesive may be used to adhere the capsules 40 to the garment-facing surface. Any of the above-mentioned adhesives may be used for this purpose. Additionally, if the first adhesive 30 and the capsules 40 are applied in the same region of the garment-facing surface 20, as shown in Figures 1-3, the first adhesive may be used to secure the capsules 40 to the garment-facing surface 20.

The capsules 40 are arranged so as to rupture upon application of a Shear Force as measured herein of at least 15N per product. The second adhesive 50 is thus released.

The capsules 40 may have an irregular three-dimensional form. This way, only a small portion of the surface area of the capsules 40 is attached to the garment-facing surface 20, while a large, irregular surface area is provided for contact with the underwear. The irregular three-dimensional form provides areas of weakness in the capsule 40, thus increasing its tendency to rupture upon the appiication of a shear force.

The capsules 40 may also comprise micelles. Micelles comprise aggregates of surfactant molecules surrounding the second adhesive 50. Micelles can be formed of any commercially-available surfactant.

The capsules 40 may additionafly comprise a fragrance, lotion, dye, or a combination thereof, which is also released upon rupture of said capsules 40. Suitable examples of methods and means to encapsulate perfumes are found in e.g. US 5,591,146 or US 4,720,417.

The first adhesive 30 is suitably covered before use by one or more release papers, which serve to protect this adhesive 30 from dust and dirt, but which are designed to be released from the first adhesive 30, freeing it to attach to the underwear. The capsules 40 of the second adhesive 50 may also be covered before use by one or more release papers. Suitable release papers for use in connection with the present invention will be known to the skilled person.

The absorbent article 10 according to the present invention initially adheres only tightly to the underwear of the wearer, by means of the first adhesive 30, which is the only adhesive which is exposed to the underwear. Subsequent movement of the article and/or the wearer may generate shear forces between the absorbent article 10 and the underwear, causing the article to lift from the underwear in one or more regions.

However, due to the specific construction of the article 10 described herein, such shear forces also cause the capsules 40 of the second adhesive 50 to rupture. The second adhesive 50 is then released from said capsules 40, particutarly in those regions in which shear forces are present (i.e. those areas in which second adhesive 50 is most required).

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This helps to maintain the absorbent article 40 in good adhesive contact with the underwear.

in addition, by placement of the second adhesive 50 in capsules 40, the amount of S adhesive which makes contact with the underwear of the wearer can be reduced, thus reducing the chances of adhesive remaining on the underwear after use, and/or the underwear being damaged by too much strong adhesive.

The first adhesive 30 and the capsules 40 of the second adhesive 50 may, occupy overlapping regions of the garment-facing surface 20, as shown in Figures 1-3. However, it is preferred that the first adhesive 30 and the capsules 40 of the second adhesive 50 occupy separate and distinct regions of the garment-facing surface 20 (see e.g. Figure 4).

For example, the first adhesive 30 may extend in the longitudinal direction of the garment-facing surface 20 in the region of the longitudinal centre line (e.g. one or more strips of first adhesive centered about the longitudinal centre line), while the capsules 40 of second adhesive 50 occupy a region of the garment-facing surface 20 which is located near the periphery of the garment-facing surface 20. By the phrase near the periphery" of the garment-facing surface is meant a region which is located within 3cm, preferably within 2cm, preferably within 1cm of the periphery of said garment-facing surface 20. This embodiment, exemplified by Figure 4, provides particularly good adhesion of an absorbent article 10, as it is usually the periphery of the article 10 which tends to loosen from the underwear during use. Placement of the capsules 40 of second adhesive 50 near the periphery of the garment-facing surface 20 means that additional adhesive is provided where it is most needed.

The present invention should not be considered as being limited by the above description and the appended Figures. instead, features described above may be combined by the skilled person, yet still remain within the scope of the claims. In particular. the areas occupied by the first 30 and second 50 adhesives may be varied e.g. according to the particular adhesive properties required at various areas of the garment-facing surface, the nature of the absorbent article 10, the nature of the underwear (e.g. string-type, full panty, boxer shorts), and even the wearer (adult/youth, male/female). The full scope of the invention is defined by the appended claims.

DESCRIPTION OF TEST METHODS

Initial Tack This method is meant for the determination of the adhesion between self-adhesive glue and panty material after application (initial tack).

Apparatus -Tensile tester with plotter and integrator, pulling speed 500mm/minute -Clamps, width 60mm, for the tensile tester -Reeling apparatus, speed l500mmlminute -Press roller 0.25kg, 25mm width, diameter 95mm, used when testing 1 glue string.

-Press roller 0.6kg, 60mm width, diameter 95mm, used when testing whole glue picture -Panty material; cotton style no. 460 and satin 100% polyester, quality 229, colour Marine 0548, Formula No, 080206.

-Slide calliper, accuracy + 0.05mm.

Sample Preparation -Wash the polyester fabric in washing machine three times at 4000, and the cotton fabric once at 60°C.

-Punch out samples of cotton and polyester, large enough for covering the glued area, e.g. 25 x 200 mm when testing one glue string and 60 x 200 mm when testing whole glue picture.

-Punch the fabric with the long side in the direction of the material -Determine the surface weight of the glue -Determine the width of the glue strings, accuract at least 0.5mm (more exact if possible).

-Remove the absorbent core when testing sanitary towels -Cut out the glue strings but let the release paper remain.

Initial Tack -Place the polyester with the dull side towards the glue -Locate the inside of the cotton fabric and place it towards the glue -Place the cloth and the glue together in the reeling apparatus, at 1 SDOmm/min and one cycle".

-Testing shall be performed approximately 60 seconds after the pressing/merging of cloth and glue.

Procedure -Caflbrate the tensile tester o Distance between clamps 50mm and for wings 25mm o Pulling speed 500mm/mm o Extension: 140mm (for glue on wings, adjusted to the length of the glue string) o Tested glue length. 70mm (for glue on wings, adjusted to the length of the glue string) -Separate the strip and fold the carrier material about 2cm with the glue inside -Fasten the strip of cotton panty material in the upper clamp and the carrier material in the lower clamp. Ensure that the panty material and the carrier is material are aligned straight in the clamps and that the sample is stretched when you start the test.

-Start the test and note the behaviour of the sample during the test, e.g. break of carrier material.

-The Initial Tack is stated as the mean value for the forces needed for separating the glue-coated carrier material from the panty material.

Shear Force is measured according to ASTM D4501

Claims

ICLAIMS1. An absorbent article (10), said absorbent article (10) comprising a carment-facing surface (20), said garment-facing surface (20) comprising a a first adhesive (30), said first adhesive (30) being such that the initial Tack as defined herein is less than 1.5N per product, b. capsules (40) of a second adhesive (50), said capsules being arranged so as to rupture upon application of a Shear Force of at least 1 5N per product and release said second adhesive (50).
2. An absorbent article (10) according to claim 1, wherein the first adhesive (30) is a pressure-sensitive hot melt (PSHM) adhesive.
3. An absorbent article (10) according to any of the preceding claims, wherein the first adhesive (30) is coated (e.g. slot-coated, roll-coated), printed or sprayed onto the garment-facing surface (20).
4. An absorbent article (10) according to any of the preceding claims, wherein the first adhesive (30) and the capsules (40) of the second adhesive (50) occupy separate and distinct regions of the garment-facing surface (20).
5. An absorbent article (10) according to any of the preceding claims, wherein the first adhesive (30) occupies a region of the carment-facing surface (20) which is located adjacent the front edge of the article (10)
6. An absorbent article (10) according to any of the preceding claims, wherein the capsules (40) of a second adhesive (50) occupy a region of the garment-facing surface (20) which is located within 3cm, preferably within 2cm, preferably within 1cm of the periphery of said garment-facing surface (20).
7. Ar absorbent article (10) according to any of the preceding claims, wherein the caosules (40) have an irregular three-dimensional form.
8. An absorbent article (10) accordin to any of the oreceding claims wherein the capsuies (40) comprise miceUes.I9. An absorbent article (10) according to any of the preceding cairns, wherein the capsules (40) additionally comprise a fragrance, lotion, dye, or a combination thereof, which is also released upon rupture of said capsues (40).10. An absorbent article substantially as hereinbefore described with reference to the accompanying drawings.