Patent Application
20050147798
The present invention relates to a topsheet for absorbent articles such as disposable diapers, sanitary napkins, and incontinence pads.
Topsheets that have been used in absorbent articles, such as disposable diapers and sanitary napkins, include nonwoven fabrics prepared by various methods, perforated nonwoven fabrics, and perforated films of organic resins such as polyethylene.
Characteristics primarily required of absorbent articles include absorption characteristics relating to absorbing performance and surface characteristics for giving no adverse influences to the wearer's skin, such as an itch and a rash.
Conventional topsheets have satisfied the requirements for the absorption characteristics to some extent in letting low-viscosity waste liquids pass through and be absorbed quickly by an absorbent member lying under the topsheet but still leave room for improvement on the properties of making high-viscosity waste matter pass through and be absorbed. With respect to the surface characteristics for having no adverse influences on the skin, further improvements have been desired for alleviating skin irritation.
Skin troubles by absorbent articles are assumed attributed to the following causes. An absorbent article, while worn, creates an internal environment in which the skin is apt to be hydrated and swollen because of temperature and humidity rises, adhesion and remaining of the waste, e.g., urine or blood, and the like. The skin in such a condition is readily susceptible to physical irritation, i.e., the friction of the topsheet against the skin, and chemical irritation, namely, percutaneous absorption of irritants such as urine, soft stools or blood, resulting in skin troubles. It seems that the physical irritation is largely dependent on the surface characteristics of the topsheet with which the wearer's skin is in direct contact, and the chemical irritation is ascribable chiefly to high-viscosity waste that is less absorbable and likely to remain on the topsheet.
Under these circumstances, studies have been made to develop a topsheet for absorbent articles which feels soft.
JP-W-10-502000 (unexamined published international patent application) discloses a topsheet having a large number of protrusions extending along its longitudinal direction to have a wavy profile. The protrusions extending in the longitudinal direction contribute to soft feel but fail to retain their shape, being easily collapsed under the pressure while worn. More specifically, because the protrusions have a protuberant mountain-like profile, sticking out from the base (fixed part between adjacent projections), they have poor resistance against compression. As the protrusions are collapsed more and more, the contact area between the protrusions and the skin increases considerably. Therefore, they are not expected to suppress discomfort (overhydration) or skin troubles such as a rash. In addition, the protrusions having such a profile have limited conformability to the movement of the wearer's body. Due to the increase in contact area with the skin and the limited conformability, it is very likely that the topsheet causes friction on the skin, resulting in a failure to maintain the advantage of the wavy unevenness, i.e., soft feel, as designed.
JP-A-11-347062 discloses a topsheet having unevenness made by heat embossing. However, the top of the bosses are in a flat film form, the flat tops are hard and ruin the softness of the whole sheet.
Hence, the topsheets of related art do not have such protrusions that are flexible and deformable as would follow the body movement. A topsheet which securely prevents an itch, a rash, etc. while giving a wearer comfort of softness has not yet been provided.
An object of the present invention is to provide a topsheet for an absorbent article which maintains a macroscopic surface profile capable of making irritating body waste such as urine, soft tools and blood, particularly high-viscosity waste be absorbed quickly by an absorbent member without allowing the waste to remain on the surface thereof and yet which feels soft and gives little frictional irritation to the skin, hardly causing skin troubles, such as an itch and a rash.
The present invention accomplishes the above object by providing a topsheet for an absorbent article which has an uneven profile formed on a surface thereof to be brought into contact with a wearer's skin, the uneven profile being flexibly deformable in conformity to the contour of the wearer's body and to the wearer's movement, and depressions of the uneven profile being capable of trapping high-viscosity excreta thereby separating the high-viscosity excreta from the wearer's skin while an absorbent article having the topsheet is worn.
The present invention will be more particularly described with reference to the accompanying drawings, in which:
The present invention will be described in greater detail with reference to its preferred embodiments.
As shown in
The uneven profile according to this embodiment is made up of a large number of parallel folds 3 formed of an unevenness-forming sheet 4 and joined to a base sheet 2. More specifically, an unevenness-forming sheet 4 is gathered into a great number of parallel folds 3 and joined to the base sheet 2 at the bases of the folds 3 in linear contact. As far as this embodiment is concerned, the unevenness-forming sheet 4 before being folded will be referred to as a folding sheet 4, while after being folded will be referred to as a folded sheet 4. The sanitary napkin comprises the topsheet 1 as a liquid-permeable sheet, a liquid-impermeable backsheet 5, and a liquid-retentive absorbent member 6 interposed between the topsheet 1 and the backsheet 5. The topsheet 1 is disposed with the longitudinal direction of the folds 3 agreeing with the longitudinal direction of the sanitary napkin.
The topsheet for absorbent articles according to the present invention is flexibly deformable in conformity to the contour of a wearer's body and to wearer's movement while in contact with the wearer's skin as a topsheet of an absorbent article. Further, the depressions of the uneven profile are capable of trapping high-viscosity excreta thereby separating the high-viscosity excreta from the wearer's skin.
A topsheet simply having an uneven profile on its surface on the wearer's side without flexible deformability to the contour or movement of a wearer's body will cause frictional irritation against the skin (physical irritation), not only giving a wearer discomfort but also causing skin troubles such as an itch and a rash.
If the depressions of an uneven profile are incapable of trapping high-viscosity excreta, contacts between high-viscosity excreta and the skin are not broken, and chemical irritation is given to the skin, which can cause skin troubles.
Even though the depressions of an uneven profile are capable of trapping high-viscosity excreta, if they are incapable of separating the trapped high-viscosity excreta from the wearer's skin, the high-viscosity excreta once trapped would leak when the topsheet is compressed under a strong force.
The expression “capable of separating high-viscosity excreta from the skin” is intended to mean that the topsheet traps high-viscosity excreta in its depressions which hardly come into contact with the skin without allowing the high-viscosity excreta to remain on at least the parts in contact with the skin (i.e., the tops of the unevenness) and also accelerates migration of the excreta to an absorbent member. The term “high-viscosity excreta” as used herein is intended to include liquid waste having a low viscosity of about 5 to 30 cps to solid waste having too high viscosities to be measured with a viscometer. As described later, a viscous liquid having a viscosity of 10,000 to 30,000 cps was used for evaluating the performance of a topsheet.
In order for the topsheet of the present invention to satisfy the above-mentioned requirements, the profile of the unevenness formed on the surface that comes in contact with a wearer's skin (hereinafter referred to as a surface profile) is preferably such that the height H measured from the top 31 to the base 32 (see
If the height H is less than 0.5 mm, the size of the high-viscosity excreta-trapping space formed by the unevenness (the space between adjacent folds 3 and 3 in this embodiment) is insufficient, and it is difficult to quickly put high-viscosity excreta discharged on the topsheet into a state kept off the skin. If the height H exceeds 15 mm, the topsheet 1 hardly maintains the surface profile, resulting in impairment of flexibility and difficulty in trapping high-viscosity excreta in the depressions. The height H from the top 31 to the base 32 is obtained by subtracting the thickness of the topsheet at the base 32 (denoted as B in
Means for making the uneven profile of the topsheet capable of flexible deformation in conformity to the contour and the movement of a wearer's body include fulfillment of the following conditions (1) and (2) (hereinafter inclusively referred to as conditions for flexibility).
The pressure imposed on an absorbent article, for example, a sanitary napkin while worn seems to vary widely because, for one thing, the part of a wearer's body to which the absorbent article is applied has a complicatedly curved contour, which changes greatly with wearer's movement and, for another, the style of wearing a sanitary napkin, i.e., the kind of panties and whether a girdle is used, varies among wearers depending on the length of their period and the amount of menstrual blood. In such a situation, a pressure change of Δ2.5 gf/cm2 and application of a 20 gf/cm2 load are within ranges that are typically and/or commonly encountered.
With the maximum thickness change for a load change of Δ2.5 gf/cm2 ranging from 0.3 to 5 mm, the topsheet is smoothly deformed with no resistance against pressure by the skin, causing little frictional irritation to the skin. As a result, the topsheet feels comfortable and effectively prevents development of skin troubles.
If the maximum thickness change for a load change of Δ2.5 gf/cm2 is less than 0.3 mm, conformability of the topsheet to the body's movement is poor and may give excessive frictional irritation to the skin. If the maximum thickness change is more than 5 mm, the topsheet tends to be too soft to maintain the surface profile, failing to trap high-viscosity excreta in the depressions.
A topsheet having a higher compressive deformation percentage under 20 gf/cm2 load (CΔL20) comes into contact with the skin more softly. From considerations particularly for the vulva, which is depressed, the topsheet which is deformable softly under a pressure no higher than 20 gf/cm2 would cause little irritation. If the compressive deformation percentage CΔL20 is less than 50%, the topsheet has high resistance to the skin. If it is more than 90%, it is likely that the topsheet is too soft to maintain its surface profile, failing to trap high-viscosity excreta in the depressions.
It is not the entire area of the topsheet but only the tops 31 of the surface profile and their vicinities that come into contact with the skin. Therefore, the contact area with the skin is remarkably reduced. Further, spaces S of prescribed configuration formed among protrusions or in the folds (in the folds in the embodiment shown in
It is preferred for at least part of the topsheet that is brought into contact with the excreting part of a wearer's body to fulfill at least one of the following conditions (3) and (4) (hereinafter referred to as conditions for shape retention) in order that the uneven profile may be deformed softly in conformity to the contour and the movement of the body and that high-viscosity excreta may be trapped satisfactorily in the depressions of the uneven profile.
The compressive deformation percentage CΔL2.5 being within the above range, the protrusions of the uneven profile hardly collapse in the initial stage of compression, i.e., under a low applied pressure. As a result, the high-viscosity excreta trapping performance is improved, and high-viscosity excreta can be separated from the skin.
With the compressive deformation percentage CΔL5 falling within the above range, the high-viscosity excreta trapping performance is improved further. Fulfillment of the condition (4) is also effective in reducing skin irritation by friction.
It is still preferred for the topsheet to satisfy the following condition (5) in order that the uneven profile may be deformed flexibly in conformity to the contour and the movement of a wearer's body and that high-viscosity excreta trapped in the depressions of the uneven profile may be separated from the skin more securely.
The compressive recovery LR2.5/L2.5 being in the above range means particularly excellent conformability of the surface profile to the movement of a wearer's body. Fulfillment of the condition (5) promises satisfactory retention of the surface structure capable of trapping high-viscosity excreta and flexible deformability for reduction of skin irritation while the absorbent article is used.
The topsheet of the present invention which shows the maximum thickness change with a load change of Δ2.5 gf/cm2 at the very start of compression, i.e., when the load imposed rises from zero to 2.5 gf/cm2, can be seen as capable of achieving the object of reducing friction against the skin, one of the objects contemplated in the present invention. However, from the viewpoint of fulfillment of the above-mentioned conditions for shape retention, it is desirable that the maximum thickness change with a load change of Δ2.5 gf/cm2 should occur while the load is increased from 2.5 gf/cm2 up to 20 gf/cm2.
The above-described compression characteristics, i.e., a thickness change for a load change Δ2.5 gf/cm2, the maximum of thickness changes, compressive deformation percentages under 2.5 gf/cm2, 5 gf/cm2 and 20 gf/cm2 (CΔL2.5, CΔL5, and CΔL20), and a recovery from compressive deformation (DΔLR2.5/L2.5=LR2.5/L2.5×100) are measured as follows.
Measurement of Compression Characteristics:
The compression characteristics can be measured with a compression tester KES-FB3, supplied by Katotec. The tester has a disk indenter having a compressing area of 2 cm2. The disk indenter is vertically moved to give a compression-recovery load to such a sample as fabric or film to obtain a compression load-compressive deformation hysteresis loop for the compression-recovery cycle, which furnishes compression data, such as the sample thickness, the compression work done, the recovery properties and the like.
In carrying out the measurement on the topsheet, a 2.5 cm-side square cut out of the topsheet is set on KES-FB3. The disk indenter is moved down at a speed of 0.02 mm/sec to apply a compression load up to 20 gf/cm2, at which time the manual return switch is pushed to switch the downward movement to an upward movement. The disk indenter is lifted until the load decreases to zero. Thus, a hysteresis loop for the compression-recovery cycle is obtained.
A thickness reduction for every load increase by 2.5 gf/cm2 is obtained from the hysteresis loop. The thickness reduction (mm) in the load range in which the test piece has undergone the greatest thickness change is taken as the maximum thickness change for a load change Δ2.5 gf/cm2.
Further, the thicknesses L0, L2.5, L5 and L20 at 0.5 gf/cm2, 2.5 gf/cm2, 5 gf/cm2 and 20 gf/cm2, respectively, in the compression step are read from the hysteresis loop to calculate the compressive deformation percentages CΔL2.5, CΔL5 and CΔL20 at the respective loads.
The compressive deformation recovery (DΔLR2.5/L2.5) is calculated from the thickness L2.5 at 2.5 gf/cm2 in the compression step and the thickness LR2.5 at 2.5 gf/cm2 in the recovery step according to the equation: DΔLR2.5/L2.5=LR2.5/L2.5×100.
The topsheet of the present invention preferably has the following configuration so as to satisfy the conditions (1) to (5). Joints 7 between the folded sheet 4 and the base sheet 2 each have a width WI (see
While the folded sheet 4 is joined to the base sheet 2 via an adhesive applied on the base sheet 2 in parallel with the folds 3 at a prescribed interval in the embodiment shown in
It is preferred for each fold 3 formed of the folding sheet 4 to have an Ω-shaped cross-sectional contour (profile) in its width direction as shown in
Since the individual folds to have a Ω-shaped contour in the width direction this provides a structure in which the expanded part of the upper half is supported by the narrowed part of the lower half, which is ready to meet the conditions for shape retention.
For forming folds having a particularly favorable Ω-shaped transverse section, it is desirable for the folding sheet 4 to have a bulk softness of 5 to 40 cN, particularly 15 to 30 cN. The “bulk softness” as referred to herein is measured as follows.
Measurement of Bulk Softness:
A 30 mm wide and 150 mm long test piece cut out of a sample sheet is looped with the shorter sides overlapped. The upper and lower ends of the overlap are stapled in parallel with the circumferential direction with No. 10-1M staples available from Max Co., Ltd. to make a cylindrical specimen having a diameter of 45 mm and a height of 30 mm. The cylindrical specimen is set upright on a Tensilon compression tester RTA-100, supplied by Orientec K.K., and compressed in its axial direction by a disk having a diameter of 70 mm or more at a speed of 10 mm/min. The maximum load applied in the compression is read. The initial position of the compressing disk is higher than the height of the specimen (30 mm). The measurement was made on five specimens for each sample sheet to obtain an average.
The folding sheet 4 has two bulk softness values, one in the direction which agrees with the longitudinal direction of the folds 3 of the folded sheet 4, and the other in the direction which agrees with the width direction of the folds 3. It is preferred for the folding sheet 4 to have its bulk softness in the direction agreeing with the width direction of the folds 3 range within the above range. The bulk softness in the direction agreeing with the width direction of the folds 3 is measured by preparing a cylindrical specimen whose circumferential direction agrees with the longitudinal direction of the folds 3.
Materials of the folding sheet 4 used in the topsheet 1 according to the present embodiment include nonwoven fabric made of single or conjugate fiber of polyethylene, polypropylene, polyester, etc.; perforated and thereby liquid-permeable film of polyethylene, etc.; and composites of nonwoven fabric and a film.
The base sheet 2 can be of any material that is commonly employed in general absorbent articles with no particular restriction.
It is preferred that the surface unevenness be formed on at least the area corresponding to the excreting part of a wearer's body, particularly over the total area of the topsheet disposed on the absorbent member. Because the uneven surface profile is effective in preventing leaks of body fluids flowing on the surface of the topsheet, in another embodiment there is disposed the uneven surface profile in the area corresponding to the whole peripheral portion of the absorbent member.
The unevenness of the topsheet may be made up of a great number of protrusions having a nipple-like shape or any other shapes.
Another embodiment of the topsheet according to the present invention will be described by referring to
The topsheet 1′ shown in
The uneven sheet 4′ is nonwoven fabric, and the base sheet 2 is a fiber web having been thermally shrunken. As shown in
As shown in
The topsheet 1′ according to the embodiment shown in
The protrusions 3′ preferably have a height H (the distance from the top 31 to the base 32 (A-B), wherein A is measured under a load of 0.5 gf/cm2) is 0.5 to 15 mm, particularly 0.5 to 7 mm as measured under a load of 0.5 gf/cm2. The joints 7 preferably have a width W1 of 0.1 to 10 mm, particularly 0.5 to 5 mm. The interval W2 between adjacent joints 7 is preferably 0.5 to 20 mm, still preferably 0.5 to 10 mm.
The above-described surface unevenness having a continuous wavy profile achieves a high compressive deformation percentage. It provides a soft texture as well as a good fit because of flexible deformability in conformity to a wearer's movement. In particular, the continuous smaller protrusions 34 protruding from the depressed borders actively bear a part in deformation and/or recovery. Further, the continuous protrusions 3′ which are further outward over the smaller protrusions 34 have such a structure as easily retains their height even under pressure, thereby securing spaces for entrapping high-viscosity excreta. Thus, the topsheet 1′ is capable of softly following the movement of a wearer's body and trapping high-viscosity excreta.
The unevenness-forming sheet 4 used in this embodiment may be replaced with a fiber web to make a topsheet having protrusions filled with fibers. Joining of the unevenness-forming sheet 4 and the base sheet 2 by thermal embossing can be replaced with joining with an adhesive.
Where a fiber web is used as an unevenness-forming sheet 4, each joint 7 between the unevenness-forming sheet 4 and the base sheet 2 preferably has a width W1 of 0.1 to 10 mm, particularly 0.5 to 5 mm. The interval W2 between adjacent joints 7 is preferably 0.5 to 20 mm, still preferably 0.5 to 10 mm. The minimum distance between adjacent protrusions 3′ is preferably 0 to 5 mm, particularly 0 to 3 mm, as measured under no load applied.
The uneven sheet 4′ may have a large number of slits of prescribed length.
The absorbent articles to which the topsheet of the present invention is applicable include not only sanitary napkins but panty liners, disposable diapers, incontinence pads, and so forth.
The present invention will now be illustrated in greater detail with reference to Examples. Unless otherwise noted, all the percents and ratios are given by weight.
Preparation of Sample G:
A topsheet having the configuration of
Compression characteristics of the resulting topsheet, designated sample G, are shown in Table 1 below.
Preparation of Sample H:
A nonwoven fabric sheet (spun-bond nonwoven) made of polypropylene fiber and having a basis weight of 12 g/m2, an initial thickness (at 0.5 gf/cm2) of 0.15 mm, and a bulk softness of 3.7 cN in the MD and 3.3 cN in the CD was used as an unevenness-forming sheet 4. Crimping fibers capable of crimping in a helix (CPP fiber, available from Daiwabo Co., Ltd.; 2.2 dtex×51 mm) were fabricated by carding into a web having a basis weight of 35 g/m2, which was used as a base sheet 2.
The unevenness-forming sheet 4 and the base sheet 2 were heat-sealed together by thermal embossing at 220° C. using an embossing plate having standing pins (diameter: 1.5 mm) in a regularly repeated pattern. As shown in
The resulting embossed laminate was allowed to stand in a hot drier at 130° C. for at least 10 minutes to make the base sheet 2 shrink in the horizontal direction to obtain a topsheet 1′ having the configuration shown in
The resulting topsheet 1′ had a great number of protrusions 3′ in both the MD and the CD, each protrusion 3′ having a height H (the distance from the top 31 to the base 32 (A-B), wherein A is measured under a load of 0.5 gf/cm2) of 1.5 mm. The compression characteristics of the topsheet 1′, designated sample H, are shown in Table 1.
For comparison, compression characteristics of samples A to F shown below were measured. The results obtained are shown in Table 1. Samples A to C are perforated polyethylene films typically available in the market as a topsheet of absorbent articles. Samples D and E are commercially available topsheets comprising nonwoven fabric. Samples B, C and E had an almost flat surface.
Sample A:
A perforated film topsheet used in a sanitary napkin Laurier Dry Up Mesh Regular, available from Kao Corp. (sales name: Laurier DR-h-114)
Sample B:
A perforated film topsheet used in a sanitary napkin Whisper Regular, available from the Procter & Gamble Co. (sales name: Whisper Ca5-a)
Sample C:
A perforated film topsheet used in a sanitary napkin Elis Sarasara Silk Regular, available from Daio Paper Corp. (sales name: Elis SS-R2)
Sample D:
A perforated nonwoven fabric topsheet used in a sanitary napkin Laurier Yawaraka Mesh Slim, available from Kao Corp. (sales name: Laurier UN-f-114)
Sample E:
A topsheet (Cotton Fuwafuwa Sheet) used in a sanitary napkin Sofy Bodyfit (for medium to long-time use), available from Uni-Charm Corp. (sales name: Sofy aon).
The topsheet was sampled as joined to nonwoven fabric which is disposed under the topsheet and perforated together with the topsheet.
Sample F:
A nonwoven fabric sheet (spun-bond nonwoven) made of polypropylene fiber and having a basis weight of 12 g/m2, an initial thickness (at 0.5 gf/cm2) of 0.15 mm, and a bulk softness of 3.7 cN in the MD and 3.3 cN in the CD was used as a base sheet. A hot-melt adhesive was applied to the base sheet in 3 mm wide stripes along the longitudinal direction (MD) at an interval of 7 mm (pitch 10 mm) in the CD. Separately, the same nonwoven fabric sheet was pressed onto a plate having a large number of grooves of prescribed depth at a prescribed pitch so as to set the sheet with as many projections as the grooves having a height of 5 mm at a pitch of 10 mm. The adhesive-applied side of the base sheet was attached thereto to prepare a topsheet having longitudinally extending projections.
The resulting topsheet, designated sample F, had an initial thickness (at 0.5 gf/cm2) of 5.2 mm. The projections had a height (from the base to the top of the projections) of 5.0 mm. The width of the joints between the two sheets was 3 mm in the CD. Each projection had a semicircular profile, the width of which in the CD gradually decreased from the base toward the top.
High-viscosity liquid-trapping performance:
The performance of samples A to H in trapping a high-viscosity liquid in their depressions was evaluated by the following test, in which the amount of a residual high-viscosity liquid was measured. The results obtained are shown in Table 1.
A diaper-like or sanitary napkin-like structure was fabricated from each of samples A to H as a topsheet, an intermediate absorbent sheet made of 200 g/m2 of pulp and 40 g/m2 of an absorbent polymer, and a waterproof backsheet. One gram of a 5% aqueous solution of carboxymethyl cellulose sodium salt as a high-viscosity liquid was poured into the structure from the topsheet side, and the structure was applied to the crotch of a human body model. The position at which the liquid had been poured corresponded to the excreting part of the model. The model with the structure fitted on was moved in a walking mode for 1 minute. The structure was removed from the model, and a stack of 10 sheets of absorbent paper was put on the area of the topsheet where the liquid had been absorbed. A load of 10 gf/cm2 was put thereon for 10 seconds, and the amount of the liquid absorbed by the absorbent paper was taken as a residual amount of the liquid.
Evaluation of texture (softness):
A panel of 20 members touched samples A to H by hand, gave them scores according to the softness, and rated the texture on an A-to-D scale.
D: The average score given by the 20 members is lower than −0.5.
A: The average score given by the 20 members is higher than +0.5.
B: The average score given by the 20 members is from 0 to +0.5.
C: The average score given by the 20 members is from −0.5 to 0.
D: The average score given by the 20 members is lower than −0.5.
The topsheet for absorbent articles according to the present invention maintains a macroscopic surface structure capable of making irritating body waste such as urine, soft tools and blood, particularly high-viscosity waste be absorbed quickly without allowing the waste to remain on the surface thereof and yet which feels soft and gives little frictional irritation to the skin, hardly causing skin troubles, such as an itch and a rash.
While the invention has been described in detail and with reference to specific examples thereof, it will be apparent that various modifications can be made therein. Such modifications are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications, as would be obvious in the art, are intended to be included within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2000-289364 | Sep 2000 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09956950 | Sep 2001 | US |
| Child | 11071103 | Mar 2005 | US |
