WO1999045874A1 - Absorbent article with extensible flaps comprising microporous film - Google Patents

Absorbent article with extensible flaps comprising microporous film

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Publication number
WO1999045874A1
WO1999045874A1 PCT/US1998/004673 US9804673W WO1999045874A1 WO 1999045874 A1 WO1999045874 A1 WO 1999045874A1 US 9804673 W US9804673 W US 9804673W WO 1999045874 A1 WO1999045874 A1 WO 1999045874A1
Authority
WO
Grant status
Application
Patent type
Prior art keywords
strain
microporous film
extensibility
absorbent article
flaps
Prior art date
Application number
PCT/US1998/004673
Other languages
French (fr)
Inventor
John Glasgow Burns, Jr.
Chiun-Hsien Chang
Masashi Kishida
Original Assignee
The Procter & Gamble Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

Links

Classifications

    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, E.G. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00Bandages or dressings; Absorbent pads
    • A61F13/15Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/51Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the outer layers
    • A61F13/514Backsheet, i.e. the impermeable cover or layer furthest from the skin
    • A61F13/51456Backsheet, i.e. the impermeable cover or layer furthest from the skin characterised by its properties
    • A61F13/51464Backsheet, i.e. the impermeable cover or layer furthest from the skin characterised by its properties being stretchable or elastomeric
    • A61F13/51466Backsheet, i.e. the impermeable cover or layer furthest from the skin characterised by its properties being stretchable or elastomeric providing stretchability without the use of elastic material
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, E.G. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00Bandages or dressings; Absorbent pads
    • A61F13/15Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/45Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the shape
    • A61F13/47Sanitary towels, incontinence pads or napkins
    • A61F13/476Sanitary towels, incontinence pads or napkins characterised by encircling the crotch region of the undergarment
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, E.G. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00Bandages or dressings; Absorbent pads
    • A61F13/15Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/51Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the outer layers
    • A61F13/514Backsheet, i.e. the impermeable cover or layer furthest from the skin
    • A61F13/51456Backsheet, i.e. the impermeable cover or layer furthest from the skin characterised by its properties
    • A61F13/51458Backsheet, i.e. the impermeable cover or layer furthest from the skin characterised by its properties being air-pervious or breathable
    • A61F13/51462Backsheet, i.e. the impermeable cover or layer furthest from the skin characterised by its properties being air-pervious or breathable being defined by a value or parameter

Abstract

An absorbent article with flaps having extensibility is disclosed. The absorbent article comprises a topsheet, a backsheet and an absorbent core therebetween. The backsheet comprises a breathable microporous film. The breathable microporous film is made by stretching a mixture of a thermoplastic resin and inorganic fillers at least in one direction. The flaps comprise a composite sheet including a flap topsheet and an extension of the breathable microporous film. At least a part of the flaps is imparted a predetermined extensibility by being subjected to a plastic strain to obtain the predetermined extensibility such that Z number specified by equation (I) is 3.0 or above, wherein MS: average composite sheet material strain at break; AS: average applied strain to the composite sheet to obtain the predetermined extensibility; N: neck down prevention coefficient, σMS: standard deviation of composite sheet material strain at break; σAS: standard deviation of applied strain.

Description

ABSORBENT ARTICLE WITH EXTENSIBLE PLAPS COMPRESING

MICROPOROUS FILM

FIELD

The present invention relates to an absorbent article comprising a microporous film having extensibility. The present invention further relates to an absorbent article with flaps which comprise a microporous film having extensibility.

BACKGROUND

A microporous film having breathability is well known and used for various consumer products such as packaging film and absorbent articles. There are prior art which are directed to improvement of such a microporous film, such as U.S. Patent 4,923,650 published on May 8, 1990, JP Patent publication 93/230252-A published on September 7, 1993, JP Patent publication 96/225680- A published on September 3, 1996, JP Patent publication 94/62794-B published on August 17, 1994, JP Patent publication 95/231913-A published on September 5, 1995, JP Patent publication 96/300436-A published on November 19, 1996, JP Patent publication 96/300498-A published on November 19, 1996, JP Patent publication 96/300499-A published on November 19, 1996, JP Patent publication 96/300500-A published on November 19, 1996, and JP Patent publication 87/167332-A published on July 23, 1987. The microporous film described in the prior art worked quite well as a backsheet of an absorbent article which requires breathability and liquid impermeability. There are also prior art which are directed to a process for making a microporous film and the microporous film made by the process, such as U.S. Patent 4,116,892 published on September 26, 1978, U.S. Patent 4,153,751 published on May 8, 1979, and U.S. Patent 4,289,831 published on September 15, 1981. These prior art disclose processes using a process of stretching a material to make a microporous film. However, none of the prior art discloses a microporous film having extensibility or a process to make a microporous film having extensibility so that a part of a microporous film is extensible. These prior art are directed to a technology to make non-microporous film microporous, but not a technology to make a microporous film extensible. Absorbent articles such as a sanitary napkin having a portion of extensibility are disclosed in prior art, such as PCT publication WO 97/12576 published on April 10, 1997, PCT publication WO 96/12462 published on May 1 , 1996, U.S. Patent 5,389.094 published on February 14, 1995 and U.S. Patent 5,704,930 published on January 6, 1998. In these disclosures, the flaps of the sanitary napkin are provided extensibility for relieving the stresses that develop in the flaps when the flaps are folded down and under a wearer's undergarment. The extensibility can be provided by a number of different processes. For example, the extensibility on the flaps can be provided by mechanically straining, corrugating, "ring-rolling", heating and deforming, subjecting portions of the flaps to compression between mating plates, and the like. These processes include the process of applying a strain to a material to mechanically and permanently deform the material. Extensibility on the material is provided by remaining permanent deformation on the material. Therefore, a degree of extensibility is determined by a degree of an applied strain. The more extensibility requires, the higher strain is applied to the material.

As described above, microporous films are commonly used for a breathable backsheet of an absorbent article. Microporous films typically comprise a blend of a thermoplastic polymer and an inorganic filler such as calcium carbonate. The blend undergoes pore formation upon stretching as the inorganic filler separates from the polymer due to stress concentration. The formation of micropores permits the film to be breathable allowing the passage of vapor through the micropores while retarding the passage of liquid. While microporous films have good breathability, microporous films have lower "strain at break" than an ordinary non-microporous film. Therefore, if microporous films are subjected to high strain beyond the strain at break of the microporous film to obtain extensibility of the microporous film, such high strain causes many visible pin holes in the area where the strain is applied.

Based on the foregoing, there is a need for an absorbent article comprising a microporous film having extensibility. In addition, there is a need for an absorbent article with flaps which comprise the microporous film having breathability and extensibility while being lesser visible pin holes. None of the existing art provides all of the advantages and benefits of the present invention.

SUMMARY

The present invention relates to an absorbent article with flaps having extensibility. The absorbent article comprises a topsheet, a backsheet and an absorbent core therebetween. The backsheet comprises a breathable microporous film. The breathable microporous film is made by stretching a mixture of a thermoplastic resin and inorganic fillers at least in one direction. The flaps comprise a composite sheet including a flap topsheet and an extension of the breathable microporous film. At least a part of the flaps is imparted a predetermined extensibility by being subjected to a plastic strain to obtain the predetermined extensibility such that Z number specified by a following equation is 3.0 or above.

N • MS - AS

Z= wherein

MS : average composite sheet material strain at break AS : average applied strain to the composite sheet to obtain the predetermined extensibility N : neck down prevention coefficient σMS : standard deviation of composite sheet material strain at break σAS : standard deviation of applied strain

The present invention further relates to an absorbent article having extensibility. The absorbent article comprises a topsheet, a backsheet and an absorbent core therebetween. The backsheet comprises a breathable microporous film. The breathable microporous film is made by stretching a mixture of a thermoplastic resin and inorganic fillers at least in one direction. At least a part of the microporous film is imparted a predetermined extensibility by being subjected to a plastic strain to obtain the predetermined extensibility such that Z number specified by a following equation is 3.0 or above.

N • MS - AS

Z= wherein MS : average microporous film material strain at break

AS : average applied strain to the microporous film to obtain the predetermined extensibility N : neck down prevention coefficient σMS : standard deviation of microporous film material strain at break σAS : standard deviation of applies strain

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a preferred sanitary napkin embodiment of the present invention.

FIG. 2 is a lateral cross-sectional view taken along line 2-2 of Figure 1 through the comer region of the flaps of the sanitary napkin.

FIG. 3 is a fragmentary enlarged cross-sectional view of a part of the absorbent core and a part of the backsheet of the sanitary napkin.

FIG. 4 is a side elevational view of the ring rolling unit used for making the sanitary napkin.

FIG. 5 is a front elevational view of the ring rolling unit used for making the sanitary napkin. FIG. 6 is a fragmentary enlarged cross sectional view of the tooth engagement of the ring rolling unit shown in FIG. 5. FIG. 7 is a graph showing a relationship between strain distribution for the applied strain (AS) to obtain a predetermined extensibility and strain distribution for the material strain at break (MS).

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of a sanitary napkin 20 of the present invention is shown in FIG. 1. As shown in FIG. 1, the sanitary napkin 20 basically comprises an absorbent means (or "main body portion") 22, and two flaps 24. The sanitary napkin 20 has two surfaces, a body-contacting surface or "body surface" 20A and a garment surface 20B. The sanitary napkin 20 is shown in FIG. 1 as viewed from its body surface 20A. The body surface 20A is intended to be worn adjacent to the wearer's body. The garment surface 20B is intended to be placed adjacent to the wearer's undergarments when the sanitary napkin 20 is worn. The sanitary napkin 20 has two centerlines, a principal longitudinal centerline L and a principal transverse centerline T.

FIG. 1 shows that the main body portion 22 of the sanitary napkin 20 comprises the portion of the sanitary napkin without the flaps 24. The main body portion 22 has two spaced apart longitudinal edges 26, two spaced apart transverse or end edges (or "ends") 28, which together form the periphery 30 of the main body portion. The main body portion 22 of the sanitary napkin 20 can be of any thickness, including relatively thick, intermediate thickness, relatively thin, or even very thin (or "ultra thin"). An "ultra-thin" sanitary napkin 20 as described in U.S. Patents 4,950,264 and 5,009,653 issued to Osborn preferably has a caliper of less than about 3 millimeters. The embodiment of the sanitary napkin 20 shown in the drawings is intended to be an example of a sanitary napkin of an intermediate thickness. The main body portion 22 of the sanitary napkin 20 may also be relatively flexible, so that it is comfortable for the wearer. It should be understood that the sanitary napkin shown is merely one embodiment, and that the present invention is not limited to absorbent articles of the type or having the specific configurations shown in the drawings.

FIG. 2 shows the individual components of the main body portion 22 of the sanitary napkin 20 of the present invention. The main body portion 22 of the sanitary napkin 20 preferably comprises at least three primary components. These include a liquid pervious topsheet 38 typically provided by a liquid permeable substrate of fibrous such as nonwoven or film like structure such as apertured formed films, a liquid impervious backsheet 40 preferably provided by a liquid impermeable, but breathable substrate, and an absorbent core 42 positioned between the topsheet 38 and the backsheet 40. The backsheet 40 comprises two layers; a first layer comprising a gas permeable apertured formed film layer 40A and a second layer comprising a breathable microporous film layer 40B.

The topsheet, the backsheet, and the absorbent core may be assembled in a variety of configurations known in the art (including layered or "sandwich" configurations and wrapped or "tube" configurations). FIGS. 1 and 2 show a preferred embodiment of the sanitary napkin 20 assembled in a sandwich construction in which the topsheet 38 and the breathable microporous film 40B have length and width dimensions generally larger than those of the absorbent core 42. The topsheet 38 and the breathable microporous film 40B extend beyond the edges of the absorbent core 42 to form portions of the periphery 30. The apertured formed film 40A of the backsheet has the approximately same shape as the absorbent core 42 to cover at least the region where the absorbent core 42 lies as shown in FIG. 2. Alternatively, it may have a little bigger shape than the absorbent core 42, or may have the same shape as the main body portion 22 of the sanitary napkin 20. In any case, preferably, the apertured formed film 40A does not extend into the flaps 24 as shown in FIG. 2. Alternatively, the apertured formed film 40A may extend into the flaps 24 so that the apertured formed film constitutes a part of the flaps 24.

The topsheet 38 is preferably joined to the body-facing side of the absorbent core 42 and the backsheet 40 (i.e., the apertured formed film 40A) is preferably joined to the garment-facing side of the absorbent core 42. The topsheet 38 and the apertured formed film 40A can be joined to the absorbent core 42 in any suitable manner known in the art for this purpose, such as by an open pattern of adhesives. The portions of the topsheet 38 and the breathable microporous film 40B that extend beyond the edges of the absorbent core are preferably also joined to each other. The topsheet 38 and the breathable microporous film 40B can be joined in any suitable manner known in the art for this purpose. Preferably, in the embodiment shown, these portions of the topsheet 38 and the breathable microporous film 40B are joined using adhesives over substantially the entire portions that extend beyond the edges of the absorbent core 42, and a crimp seal at the end edges 28 of the main body portion where the topsheet 38 and backsheet 40 are densified by the application of pressure or heat and pressure.

The sanitary napkin 20 shown in FIGS. 1 and 2 also comprises a pair of flaps 24 that are joined to the main body portion 22 along a juncture, such as lines of juncture 52. The flaps 24 extend laterally outward beyond the longitudinal side edges 26 of the main body portion 22 from their proximal edges to their distal edges (or "free end"). The flaps 24 comprise a flap topsheet 44 and a flap backsheet 46. In the embodiment shown in FIGS. 1 and 2, the flaps 24 are integral with the main body portion 22, that is, the flap topsheet 44 and the flap backsheet 46 comprise integral extensions of the topsheet 38 and the breathable microporous film 40B, respectively. In the preferred embodiment, the apertured formed film 40A does not extend into the flaps 24.

The extensions of the topsheet 38 and the breathable microporous film 40B of the flaps 24 (i.e., the flap topsheet 44 and the flap backsheet 46) may be joined any suitable method, such as adhesive attachment, ultrasonic attachment, heat attachment or the like. In the preferred embodiment, the extensions of the topsheet 38 and the breathable microporous film 40B are joined by applying adhesive to substantially all the region of the flaps 24. The topsheet 38 is preferably compliant, of feeling, and non-irritating to the wearer's skin. Further, the topsheet 38 is fluid pervious, permitting fluid to readily penetrate through its thickness. A suitable topsheet 38 may be manufactured from a wide range of materials such as woven and nonwoven materials; polymeric materials such as apertured formed thermoplastic films, apertured plastic films, and hydroformed thermoplastic films; porous foams; reticulated thermoplastic films; and thermoplastic scrims. Suitable woven and nonwoven materials can be comprised of natural fibers (e.g., wood or cotton fibers), synthetic fibers (e.g., polymeric fibers such as polyester, polypropylene, or polyethylene fibers); or from a combination of natural and synthetic fibers. A preferred topsheet comprises an apertured formed film. In the embodiment, apertured formed films are preferably used for the topsheet because they are pervious to body exudates and yet non-absorbent and have a reduced tendency to allow fluids to pass back through and rewet the wearer's skin. Thus, the surface of the formed film which is in contact with the body remains dry, thereby reducing body soiling and creating a more comfortable feel for the wearer. Suitable apertured formed films are described in U.S. Patent No. 3,929,135 issued to Thompson, on December 30, 1975; U.S. Patent No. 4,324,246 issued to Mullane et al., on April 13, 1982; U.S. Patent No. 4,342,314 issued to Radel, et al., on August 3, 1982; U.S. Patent No. 4,463,045, issued to Ahr, et al., on July 31 , 1984 and U.S. Pat . No. 5,006,394 issued to Baird, on April 9, 1991.

The backsheet 40 is preferably impervious to liquid and pervious to vapor. The primary role of the backsheet 40 is to prevent the extrudes absorbed and contained in the absorbent core 42 from wetting articles that contact the absorbent product such as underpants, pants, pajamas and undergarments. In addition however, the backsheet 40 also permits the transfer of both vapor and air through it and thus allows the circulation of air into and out of the backsheet 40.

In the embodiment shown in Fig. 2, the backsheet 40 comprises two layers; a first layer comprising a gas permeable apertured formed film layer 40A and a second layer comprising a breathable microporous film layer 40B. The first layer 40A is typically located adjacent to the absorbent core 42 and subsequent layers of the backsheet are typically located further away from the absorbent core 42. The backsheet 40 may comprise additional layers. All of the layers of the backsheet 40 can be substantially in intimate and direct contact with one another.

As shown in FIG. 3 which shows an enlarged cross sectional view of the backsheet 40 with a part of the absorbent core 42, the first layer of the apertured formed film 40A comprises a layer having discrete apertures 41A which extend beyond the horizontal plane of the garment facing surface of the layer towards the absorbent core 42 thereby forming protuberances 41 B. Each protuberance 41 B has an orifice located at its terminating end. Preferably the protuberances 41 B have a funnel or conical shape, similar to those described in US 3,929,135. The apertures located within the plane of the layer and the orifices located at the terminating end of protuberances themselves maybe circular or non circular. In any case the cross sectional dimension or area of the orifice at the termination of the protuberance is smaller than the cross sectional dimension or area of the aperture located within the plane of the layer. The first layer 40A of the backsheet 40 may be made of any material known in the art, but is preferably manufactured from commonly available polymeric materials. The first layer 40A may also comprise any type of formed films which may be used for a topsheet as described above.

The second layer 40B of the backsheet 40 may comprise a breathable microporous film composed of a thermoplastic resin and inorganic fillers dispersed in the thermoplastic resin. Suitable thermoplastic polymers include polyolefins such as polyethylenes, including liner low density polyethylene (LLDPE), low density polyethylene (LDPE), ultra low density polyethylene (ULDPE), high density polyethylene (HDPE), or polypropylene and blends thereof with the above and other materials. Examples of other suitable thermoplastic polymers which may also be used include, but are not limited to, polyester, polyurethanes, compostable or biodegradable polymers, thermoplastic elastomers, and metallocene catalyst-based polymers (e.g., INSITE® available from Dow Chemical Company and Exxact® available from Exxon). The inorganic material or filler is selected from the group consisting of calcium carbonate, clay and titanium dioxide, with the preferred inorganic filler being calcium carbonate. The inorganic filler may be coated with a fatty acid ester to obtain higher loadings in the polymer. The inorganic filler and the thermoplastic polymer are blended together to form a homogeneous mixture in a suitable mixing extruder, or in a separate preliminary compounding step. The mixture is then cast or blown into a film. The obtained film is stretched at least in one direction to impart breathability on the substantially entire area of the film. The step of stretching a film to impart breathability may be done at a different place prior to manufacturing process of absorbent articles. Alternatively, the step of stretching may be done at the same place, i.e., same manufacturing process, prior to assembling a breathable microporous film with other elements of absorbent articles. In any case, the film is imparted breathability on the substantially entire area of the film before the resulting breathable microporous film is assembled with other elements of absorbent articles.

The absorbent core 42 may be any absorbent means which is generally compressible, conformable, resilient, non-irritating to the wearer's skin and capable of absorbing and containing body exudates. The absorbent core 42 may be manufactured from a wide variety of fluid absorbent materials commonly used in disposable sanitary napkins, and other disposable absorbent articles. Examples of suitable absorbent materials include comminuted wood pulp (which is generally referred to as airfelt), creped cellulose wadding, modified cross- linked cellulose fibers (such as those described in U.S. Patent No. 5,217,445 issued to Young, et al., on June 8, 1993), capillary channel fibers (that is, fibers having intra-fiber capillary channels such as those described in U.S. Patent No. 5,200,248 issued to Thompson, et al., on April 6, 1993), absorbent foams (such as those described in U.S. Patent No. 5,260,345 issued to DesMarais, et al., on November 9, 1993 and U.S. Patent No. 5,268,244 issued to DesMarais, et al., on December 7, 1993), thermally bonded airlay materials (such as those material described in U.S. Patent No. 5,607,414 issued to Richards, et al., on March 4, 1997), hydrogel-forming polymer gelling agents (such as those material described in U.S. Patent No. 4,673,402 issued to Weisman, et al., on June 16, 1987 and U.S. Patent No. 4,935,022 issued to Lash et al., on June 19, 1990), absorbent sponges, synthetic staple fibers, polymeric fibers, peat moss, or any equivalent materials or combinations of materials. Further, the absorbent core 42 may comprise a first portion and a second portion, the first portion comprising the following components: (a) an optional primary fluid distribution layer preferably together with a secondary optional fluid distribution layer; (b) a fluid storage layer; and the second portion comprising (c) an optional fibrous layer underlying the storage layer; and (d) other optional components. Such a structure is disclosed in PCT publication WO 97/24096 published on July 10, 1997 and WO 97/24095 published on July 10, 1997.

The sanitary napkin 20 shown in FIG. 1 preferably has zones of extensibility (or "zone of differential extensibility") 56 for relieving the stresses on the flaps 24 when they are folded around a panty crotch. The zone of extensibility 56 provides a portion of the sanitary napkin 20 which is capable of extending (and are preferably capable of extending a greater amount than surrounding portions of the sanitary napkin 20). Additionally, the sanitary napkin 20 may have a hinge 54 between the main body portion 22 and at least a portion of the flaps 24. The hinge 54 provides a region of the sanitary napkin 20 with increased flexibility to create preferred bending axes for the flaps 24 to bend or fold about. The hinge 54 may be imparted extensibility. These are further described in PCT publication WO 97/12576 published on April 10, 1997.

The zones of extensibility 56 and hinge 54 can, for instance, be formed by a process which has been described as pre-corrugating (or "ring rolling"). The zones of extensibility 56 and hinge 54 are provided by at least partly, mechanically straining a base material. Suitable methods for ring rolling are described in U.S. Patent 4,107,364 issued to Sisson on August 15, I978, U.S. Patent 4,834,741 issued to Sabee on May 30, I989, U.S. Patent 5,143,679 issued to Gerald M. Weber, et al. on September 1 , I992, U.S. Patent 5,156,793 issued to Kenneth B. Buell, et al. on October 20, I992, and U.S. Patent 5,167,897 issued to Gerald M. Weber, et al. on December 1 , I992. Alternatively, the zones of extensibility 56 and hinge 54 are provided by forming a strainable network in the region along the juncture 52 of the flaps 24 with the main body portion 22 by mechanically straining a base material. This technology is further described in allowed U.S. Patent Application Serial No. 08/203,087 filed in the name of Chappell, et al. on February 28, 1994 (PCT Publication No. WO 95/03765, published February 9, 1995).

A base material into which extensibility is imparted comprises a single layer of material or laminate of materials, at least one of which is a breathable microporous film. Preferably, in the embodiment, the base material (composite sheet) that has extensibility therein comprises a laminate formed by an extension of the topsheet 38 and the breathable microporous film 40B.

Referring to FIGS. 4 and 5, there is shown a ring rolling unit 100 used to form the zone of extensibility 56 as well as the hinge 54. The ring rolling unit 100 includes intermeshing rolls 101 and 102. The rolls 101 , 102 include a plurality of intermeshing teeth 103, 104 respectively on the surfaces of the rolls along the circumferential direction of the rolls 101 , 102. In one embodiment, the teeth in this embodiment preferably have a height of 3.175 mm, and are evenly spaced with the centerlines of the teeth spaced apart at 1.9 mm pitches. The entire shape of each toothed regions of the rolls 101 and 102 is generally the same as the entire shape of the zone of extensibility 56 and the hinge 54 of the sanitary napkin 20 shown in FIG. 1. The rolls 101, 102 are arranged so that the teeth 103 and 104 engage to each other as shown in FIG. 6. The engagement of the teeth 103 and 104 is determined based on desired extensibility. The tooth engagement of 2.11 mm, 2.26 mm and 2.31 mm is preferably used to obtain extensibility of 75 %, 80 % and 85 %.

The base material 110 positioned between the rolls 101 and 102 is subjected to a strain (applied strain). The term "applied strain" refers to a strain applied to a material by a process in the direction of extensibility to obtain a residual strain for a predetermined extensibility which will be imparted on the material. The applied strain is described by a strain distribution and its standard deviation of the strain distribution. When the base material 110 is subjected to the applied strain, a portion 110A of the base material 110 between the ridge 103 A of the tooth 103 and the ridge 104A of the tooth 104 is mechanically strained by the applied strain and incrementally and plastically deforms so that a residual strain remains on the base material 110, while portions 110B of the base material 110 on the ridge 103A and 104A are not strained or strained only a little. Since the base material 110 tends to be strained only at the portion 110A between the ridges on the teeth next to each other and the applied strain is not necessarily applied constantly (the applied strain may be sometimes bigger than a desired applied strain or may be smaller than a desired applied strain), the portion 110A of the base material 110 may be strained exceeding a material strain at break of the base material 110. When this occurs, the base material 110 ruptures. The term "material strain at break" refers to a strain at which a material breaks or ruptures. Extensibility of. the zone of extensibility 56 may be from about 50 % to about 100 %. Preferably, extensibility of the zone of extensibility 56 may be from about 65 % to about 90 %. In order to obtain a residual strain for extensibility of, e.g., 75% on the base material, the base material must be strained beyond the residual strain. In one example, the base material comprising an apertured formed film which is marketed as Code No. X-15507 by Tredegar Film Products and a polyethylene film which is marketed as Code No. DH-215 Sofflex Blue 240 by Clopay Plastic Products Company needs to be strained up to 210 % to obtain residual strain for extensibility of 75 % on the base material. In this example, since the polyethylene film is non-microporous film, the base material is capable of being strained up to 210 % without rupturing or creating many visible pin holes. However, the base material comprising a breathable microporous film may not be capable of such high strain without rupturing or many visible pin holes created because a breathable microporous film is weaker against a strain to obtain a residual strain for extensibility than a non-microporous film and easy to rupture. This is because the breathable microporous film undergoes the "second time" strain for obtaining a residual strain (the "first time strain is applied when stretching a film for imparting breathability). Thus, a breathable microporous film has lower strain at break than a non-microporous film.

Therefore, the relationship between the applied strain to obtain a predetermined extensibility and the material strain at break must be carefully considered to avoid rupturing or many visible pin holes created especially when a microporous film is used for a base material into which extensibility is imparted.

FIG. 6 shows a relationship between strain distribution for an applied strain (AS) to obtain a residual strain for a predetermined extensibility and strain distribution for a material strain at break (MS). The applied strain and the material strain at break can be measured by the method described below. The applied strain (AS) and the material strain (MS) is descibed by a Gauss curve with standard deviations of σMS and σAS. When both curves overlaps in the area X as shown in FIG. 7, there is a possibility that the applied strain exceeds the material strain at break. When this occurs, the material ruptures or breaks (or visible pin holes created). Therefore, the less the overlapping area X, the less rupturing or the visible pin holes created occurs.

"Z" number specified by a following equation is preferably 3.0 or above when a microporous film is used for a part of a base material which has extensibility therein. More preferably, Z number is 3.5 or above. Z number refers to a number of standard deviation between material strain at break and applied strain to obtain a residual strain for extensibility.

N « • MS - AS σc

N • MS - AS

/ 2 2 v GAS ÷ CJMS wherein

MS : average composite sheet material strain at break

AS : average applied strain to the composite sheet to obtain the predetermined extensibility N : neck down prevention coefficient, which is a coefficient to calibrate possible neck down on the material perpendicular to the direction where the "applied strain" is applied on the material σc : combined standard deviation of σMS and σAS, which is described by the following equation using σAS and σMS σc = σAS 2 + σMS 2 σMS : standard deviation of composite sheet material strain at break σAS : standard deviation of applied strain

If the base material comprises only a microporous film, then the above

"composite sheet" may be read as "microporous film".

When the material strain at break and the applied strain satisfy the above equation, rupturing of the base film is extremely reduced and visible pin holes created are reduced to the level at which the consumers do not see products as defect.

Measurement method for applied strain (AS)

The samples used for this measurement are polyethylene film which have grids pattern on surface of film and grids pattern is drawn parallel to and perpendicular to the direction of extensibility which is applied by a process. Grid interval length is preferably 1/20 or less of intermeshing teeth pitch. Samples have suitable width to cover the entire shape of each intermeshing teeth 103 and 104. Preferably, the sample is the same as microporous film (evaluated film). In the case where the sample material for this test is different from evaluated film, selected sample material properties are similar to the evaluated material.

The sample is stretched throughout the ring rolling unit 100 at each required strain rate and each required strain to obtain a residual strain for a predetermined extensibility on the sample. The sample stretched indicates visible strain distribution with a grid pattern transformation. Visible strain distribution on the sample surface of the surface is photographed. Each grid length on the photography parallel to the direction of extensibility which is applied by the ring rolling unit 100 is measured by a steel ruler. Measurement of each grid length is conducted in stretched area. Each grid strain is calculated by the length change from the original grid interval length. Applied strain by the process can be obtained from each grid strain.

Measurement method for material strain (MS)

The tensile test is used for measurement of material strain by measuring force versus percent elongation properties and percent available stretch of material. The tests are performed on an Instron Model 4301 , available from Instron Corporation, which is interfaced to a IBM 330 computer. All essential parameters needed for measuring are input in the MTS software (Testworks 3.07) for each test. Also, all data collection , data analysis and gathering are done using the MTS software. The sample used for this test are 1 inch wide and 4 inches long with the long axis of the sample cut parallel to the direction of extensibility of the sample which is applied by a process. The sample is cut with a sharp exact knife or some suitably sharp cutting device design to cut a precise 1 inch wide sample. The sample is cut so that an area representative of the symmetry of the overall pattern of the deformed region is represented. There will be cases (due to variations in either the size of the deformed portion) in which it will be necessary to cut either larger or smaller samples than is suggested herein. In this case, it is very important to note (along with any data reported) the size of the sample, which area of the deformed region it was taken from and preferabley include a schematic of representative area used for the sample. Ten samples of a given material are tested.

The grips of the Instron consist of air actuated grips designed to concentrate the entire gripping force along a single line perpendicular to the direction of testing stress having one flat surface and an opposing face from which protrudes a half round to minimize slippage of the sample. The distance between the lines of gripping force should be 2 inches as measured by a steel ruler held beside the grips. This distance will be referred to from hereon as the "gauge length". The sample is mounted in the grips with its long axis perpendicular to the direction of applied percent elongation. The crosshead speed is set to 20 inch/min. The crosshead elongates the sample until the sample breaks at which point the crosshead stops and returns to its original position (0% elongation ).

The percent available stretch is the point at which there is an inflection in the force - elongation curve, beyond which point there is rapid increase in the amount of force required to elongate the sample further. The average of the percent available stretch for ten samples are recorded.

Calculation for neck down prevention coefficient

The tensile test is used for a preparation for calculation of neck down prevention coefficient by measuring force versus percent elongation properties and percent available stretch of material. The tests are performed on an Instron Model 4301 , available from Instron Corporation, which is interfaced to a IBM 330 computer. Essential parameters needed for measuring are input in the MTS software(Testworks 3.07) for each test. The sample used for this test are 1 inch wide and 4 inches long with the long axis of the sample cut parallel to the direction of extensibility of the sample which is applied by a process. The sample is cut with a sharp exact knife or some suitably sharp cutting device design to cut a precise 1 inch wide sample. The sample is cut so that an area representative of the symmetry of the overall pattern of the deformed region is represented. There will be cases (due to variations in either the size of the deformed portion) in which it will be necessary to cut either larger or smaller samples than is suggested herein. In this case, it is very important to note (along with any data reported) the size of the sample, which area of the deformed region it was taken from and preferably include a schematic of representative area used for the sample. Ten samples of a given material are tested.

The grips of the Instron consist of air actuated grips designed to concentrate the entire gripping force along a single line perpendicular to the direction of testing stress having one flat surface and an opposing face from which protrudes a half round to minimize slippage of the sample. The distance between the lines of gripping force should be 2 inches as measured by a steel ruler held beside the grips. This distance will be referred to from hereon as the "gauge length". The sample is mounted in the grips with its long axis perpendicular to the direction of applied percent elongation. The crosshead speed is set to 20 inch/min. The crosshead elongates the sample until required percent elongation at which point the crosshead stops, and returns to its original position (0% elongation ) with manual operation.

Neck down is defined as the absolute change in width of a sample due to stretching. Material is necked down at applied percent elongation. Applied percent elongation is set in MTS software and MTS software calculates movement distance to achieve required percent elongation with percent available stretch. The percent available stretch is the point at which there is an inflection in the force - elongation curve, beyond which point there is rapid increase in the amount of force required to elongate the sample further. In the case where the sample is stretched perpendicular to the direction of applied percent elongation to prevent (recover) neck down, material breaks at lower strain (material strain at break recovered neck down) than material strain (MS) that is measured by the above method for material strain (MS). In order to measure material strain at break recovered neck down, the material is stretched in the direction perpendicular to applied percent elongation to recover neck down at applied percent strain. Recovering neck down is done by paper clip so that the paper clip stretch the narrowest point in the width direction of the sample. When the sample breaks upon stretching for recovery, applied percent elongation is recorded as material strain at break recovered neck down. The measurement for material strain at break recovered neck down is preferably done under the same conditions (such as temperature) as the actual process for obtaining extensibility on the absorbent article.

Neck down prevention coefficient is calculated by the following formula,

Neck down prevention coefficient (N) material strain at break recovered neck down average material strain

EXAMPLES

The following examples further describe and demonstrate the preferred embodiments within the scope of the present invention. The examples are given solely for the purpose of illustration, and are not to be construed as limitations of the present invention since many thereof are possible without departing from its spirit and scope.

(Example 1)

A topsheet is an apertured formed film as Code No. X-15507 obtainable from Tredegar Film Products. An absorbent core is the absorbent core used in "Whisper Ultra Slim" manufactured by Procter & Gamble. A backsheet is a breathable microporous film as Code No. PG-OI obtainable from Mitsui Chemical. The breathable microporous film has average material strain at break of 563.9 % with standard deviation 25.3. Neck down prevention coefficient is 0.6749. Flaps of the sanitary napkins are made of the extensions of the apertured formed film and the microporous film. The apertured formed film and the microporous film constituting the flaps are joined by an adhesive (Nitta Findley Co., Ltd.; code No. H-4031). The sample is processed by the process described in FIGS. 4 - 6 under the condition of average applied strain of 210 % with standard deviation of 48.3 to obtain 75 % extensibility on the flaps. In this example, Z number is 3.1.

(Example 2)

The breathable microporous film has average material strain at break of

579 % with standard deviation 17.3. Neck down prevention coefficient is 0.6646. The sample is processed under the condition of average applied strain of 219 % with standard deviation of 50.4 to obtain 80 % extensibility on the flaps. In this example, Z number is 3.3. The other structures are the same as the Example 1.

(Example 3) The breathable microporous film has average material strain at break of

580 % with standard deviation 18.2. Neck down prevention coefficient is 0.6516. The sample is processed under the condition of average applied strain of 232 % with standard deviation of 53.4 to obtain 85 % extensibility on the flaps. In this example, Z number is 3.0. The other structures are the same as the Example 1.

(Example 4)

The breathable microporous film has average material strain at break of

584 % with standard deviation 16.5. Neck down prevention coefficient is 0.6749.

The sample is processed under the condition of average applied strain of 210 % with standard deviation of 48.3 to obtain 75 % extensibility on the flaps. In this example, Z number is 3.6. The other structures are the same as the Example 1.

(Example 5)

The breathable microporous film has average material strain at break of 577.4 % with standard deviation 14.8. Neck down prevention coefficient is 0.6516. The sample is processed under the condition of average applied strain of 232 % with standard deviation of 53.4 to obtain 85 % extensibility on the flaps. In this example, Z number is 3.0. The other structures are the same as the Example 1. (Example 6)

The breathable microporous film has average material strain at break of 627.6 % with standard deviation 21.9. Neck down prevention coefficient is 0.6749. The sample is processed under the condition of average applied strain of 210 % with standard deviation of 48.3 to obtain 75 % extensibility on the flaps. In this example, Z number is 4.0. The other structures are the same as the Example 1.

All example provides a product with significantly reduced frequency of occurrence of pin holes.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention.

Claims

What is claimed is:
1. An absorbent article with flaps having extensibility, the absorbent article comprising a topsheet, a backsheet and an absorbent core therebetween, the backsheet comprising a breathable microporous film, the breathable microporous film made by stretching a mixture of a thermoplastic resin and inorganic fillers at least in one direction, wherein
the flaps comprise a composite sheet including a flap topsheet and an extension of the breathable microporous film, and
at least a part of the flaps is imparted a predetermined extensibility by being subjected to a plastic strain to obtain the predetermined extensibility such that Z number specified by a following equation is 3.0 or above.
N ΓÇó MS - AS
wherein
MS : average composite sheet material strain at break
AS : average applied strain to the composite sheet to obtain the predetermined extensibility N : neck down prevention coefficient σMS : standard deviation of composite sheet material strain at break σAS : standard deviation of applied strain
2. The absorbent article of Claim 1 wherein the Z number is 3.5 or above.
3. The absorbent article of Claim 1 wherein the flap topsheet comprises an extension of the topsheet of the absorbent article.
4. The absorbent article of Claim 2 wherein the topsheet comprises an apertured formed film.
5. The absorbent article of Claim 1 wherein the flap topsheet and the flap backsheet are joined to each other by applying adhesive.
6. The absorbent article of Claim 1 wherein the backsheet comprises the breathable microporous film and an apertured formed film, wherein the apertured formed film does not extends into the flaps.
7. The absorbent article of Claim 1 wherein the predetermined extensibility is from about 50 % to about 100 %.
8. The absorbent article of Claim 7 wherein the predetermined extensibility is from about 65 % to about 90 %.
9. An absorbent article having extensibility, the absorbent article comprising a topsheet, a backsheet and an absorbent core therebetween, the backsheet comprising a breathable microporous film, the breathable microporous film made by stretching a mixture of a thermoplastic resin and inorganic fillers at least in one direction, wherein
at least a part of the microporous film is imparted a predetermined extensibility by being subjected to a plastic strain to obtain the predetermined extensibility such that Z number specified by a following equation is 3.0 or above.
N ΓÇó MS - AS Z= wherein
MS : average microporous film material strain at break AS : average applied strain to the microporous film to obtain the predetermined extensibility N : neck down prevention coefficient σMS : standard deviation of microporous film material strain at break σAS : standard deviation of applied strain
10. The absorbent article of Claim 9 wherein the Z number is 3.5 or above.
PCT/US1998/004673 1998-03-10 1998-03-10 Absorbent article with extensible flaps comprising microporous film WO1999045874A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US1998/004673 WO1999045874A1 (en) 1998-03-10 1998-03-10 Absorbent article with extensible flaps comprising microporous film

Applications Claiming Priority (11)

Application Number Priority Date Filing Date Title
PCT/US1998/004673 WO1999045874A1 (en) 1998-03-10 1998-03-10 Absorbent article with extensible flaps comprising microporous film
DE1998612718 DE69812718D1 (en) 1998-03-10 1998-10-29 An absorbent article having a microporous movie
ES98955201T ES2191975T3 (en) 1998-03-10 1998-10-29 absorbent article comprising a microporous film.
CA 2322455 CA2322455C (en) 1998-03-10 1998-10-29 Absorbent article comprising microporous film
DE1998612718 DE69812718T2 (en) 1998-03-10 1998-10-29 An absorbent article having a microporous film
US09623814 US6328723B1 (en) 1998-03-10 1998-10-29 Absorbent article comprising microporous film
PCT/US1998/023029 WO1999045871A1 (en) 1998-03-10 1998-10-29 Absorbent article comprising microporous film
JP2000535287A JP4509379B2 (en) 1998-03-10 1998-10-29 Absorber with a microporous film
EP19980955201 EP1061879B1 (en) 1998-03-10 1998-10-29 Absorbent article comprising microporous film
CN 98813839 CN1243523C (en) 1998-03-10 1998-10-29 Absorbent article comprising microporous film
KR20007009978A KR100489858B1 (en) 1998-03-10 1998-10-29 Absorbent article comprising microporous film

Publications (1)

Publication Number Publication Date
WO1999045874A1 true true WO1999045874A1 (en) 1999-09-16

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ID=22266556

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1998/004673 WO1999045874A1 (en) 1998-03-10 1998-03-10 Absorbent article with extensible flaps comprising microporous film

Country Status (1)

Country Link
WO (1) WO1999045874A1 (en)

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4116892A (en) 1975-03-31 1978-09-26 Biax-Fiberfilm Corporation Process for stretching incremental portions of an orientable thermoplastic substrate and product thereof
US4153751A (en) 1975-03-31 1979-05-08 Biax-Fiberfilm Corporation Process for stretching an impregnated film of material and the microporous product produced thereby
US4923650A (en) 1988-07-27 1990-05-08 Hercules Incorporated Breathable microporous film and methods for making it
WO1995003023A2 (en) * 1993-07-22 1995-02-02 The Procter & Gamble Company Absorbent articles having fixed length undergarment covering components that automatically wrap the sides of undergarments
WO1995008311A1 (en) * 1993-09-20 1995-03-30 The Procter & Gamble Company Absorbent articles having undergarment covering components with patterned regions of extensibility
WO1996012462A1 (en) 1994-10-20 1996-05-02 The Procter & Gamble Company High speed mechanical straining process to provide extensibility to laminates for use in disposable absorbent articles
WO1997012576A1 (en) 1995-10-06 1997-04-10 The Procter & Gamble Company Absorbent article having flaps with a deformed hinge and zones of extensibility

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4116892A (en) 1975-03-31 1978-09-26 Biax-Fiberfilm Corporation Process for stretching incremental portions of an orientable thermoplastic substrate and product thereof
US4153751A (en) 1975-03-31 1979-05-08 Biax-Fiberfilm Corporation Process for stretching an impregnated film of material and the microporous product produced thereby
US4923650A (en) 1988-07-27 1990-05-08 Hercules Incorporated Breathable microporous film and methods for making it
WO1995003023A2 (en) * 1993-07-22 1995-02-02 The Procter & Gamble Company Absorbent articles having fixed length undergarment covering components that automatically wrap the sides of undergarments
WO1995008311A1 (en) * 1993-09-20 1995-03-30 The Procter & Gamble Company Absorbent articles having undergarment covering components with patterned regions of extensibility
WO1996012462A1 (en) 1994-10-20 1996-05-02 The Procter & Gamble Company High speed mechanical straining process to provide extensibility to laminates for use in disposable absorbent articles
WO1997012576A1 (en) 1995-10-06 1997-04-10 The Procter & Gamble Company Absorbent article having flaps with a deformed hinge and zones of extensibility

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