Patent Application
20080249496
The present invention relates to an absorbent article for positioning in an undergarment to absorb body exudates and to a method of manufacturing such absorbent articles. Generally, these kinds of absorbent articles are known, e.g., as feminine hygiene or femcare products, in particular sanitary napkins, or adult incontinence products.
EP 0 988 808 A1 discloses a hook fastening material for mechanical fastening systems of the hook and loop type. This hook fastening material comprises different prongs to allow for an effective engagement with a variety of various loop materials. The engaging means of the prongs may vary in shape, material composition or dimensions. The hook fastening material disclosed in EP 0 988 808 A1 may be used to affix a disposable absorbent article to an undergarment of a wearer.
WO 99/03369 discloses a finger grip for a mechanical fastener system, wherein the hook elements in the finger grip area are treated to become non-functional to allow for a convenient grip. This fastening system is used for disposable articles such as diapers, incontinence garments, and the like.
U.S. 6,210,389 B1 also discloses a fastener system with a lift region. A first fastener component includes an engagement substrate having an appointed lift region, and a plurality of engagement members which are operably attached to extend away form the engagement substrate. The lift region is disposed along at least a longitudinally extending, outboard edge of the engagement substrate, and the lift region contains a plurality of engagement members which have been substantially deactivated. WO 97/32556 relates to a mechanical fastening system with a grip tab. The fastening system includes a hook base layer which has an appointed fastening region and an appointed grip region. The fastening region has a plurality of hook elements which are integrally formed with the base layer and extend away from a base plane of the hook base layer. The hook elements are configured to operably engage a selected, cooperating loop material. The grip region has a relatively lower density of the hook elements per unit area, as compared to the fastening region.
U.S. Pat. No. 6,276,032 B1 relates to a fastening system to be applied on a diaper where the fastening tab comprises stems and hooks. The height of the stems and hooks may vary in order to provide fastening systems having a desired combination of comfort, ease of fastening, strong securement and ease of unfastening. The article disclosed in U.S. Pat. No. 6,276,032 B1 comprises a fastening system of male and female fasteners.
U.S. Pat. No. 5,300,058 A relates to a sanitary napkin comprising oriented hooks with a different orientation in different quadrants of the napkin. This construction is said to provide a sanitary napkin that can be more securely affixed to the undergarment of a wearer.
It is an object of the present invention to provide an absorbent article for positioning in an undergarment to absorb body exudates, wherein the article can be securely attached to the undergarment and minimizes potential damage to the undergarment due to the positioning means. This object is achieved with the absorbent article as defined in the claims.
According to the present invention, the absorbent article for positioning in an undergarment to absorb body exudates, e.g., a sanitary napkin, comprises a main portion having a liquid-permeable body side sheet, a liquid-impermeable garment side sheet opposite to the body side sheet, and a liquid-absorbent core between the body side sheet and the garment side sheet. The article has an outer edge defining the shape of the article and a center area. The liquid-impermeable garment side sheet comprises at least two regions of fastening elements with different engagement characteristics, i.e. engageability. A first region with higher engageability is located at the center area of the article, and at least one further region with lower engageability is located between the center area and the outer edge.
The center area of the absorbent article can generally be considered to be the area around the geometrical center of the article and does not necessarily extend to the center so that, e.g., a ring-shaped region around the center can also constitute the center area. The center area preferably covers at least 50%, more preferably at least 60%, most preferably at least 75% of the total area of the article.
The engageability of the fastening elements with an undergarment may be determined and defined by using standard undergarment materials. Generally, the term “engageability” as used herein relates to the ability of the absorbent article to be mechanically attached to an undergarment, wherein a higher engageability particularly refers to higher peel strength, higher dynamic shear strength and/or higher dynamic friction.
Although the region(s) with lower engageability may be provided only at distinct sections between the center area and the edge of the article, it is preferred that the fastening elements with lower engageability are present at least at opposing transverse, i.e. short, edges of the article. The region(s) with lower engageability may, however, also be provided along the whole edge or contour line of the article, i.e. the further region(s) preferably extends completely along the circumference of the article.
According to a preferred embodiment at least two regions of fastening elements with different engageability are provided on the absorbent article, i.e. the first region and the at least one further region are provided with mechanical fastening elements which have different engageability. It is also within the scope of the present invention that the engageability characteristics of the fastening elements change gradually, e.g., from the edge towards the center area of the article so that the fastening elements have incrementally or continuously increasing engageability. In accordance with the invention it is also contemplated that the at least one further region comprises a region without mechanical fastening elements. Such a region may be provided, for example, at the transverse edges of the article.
The engageability of the fastening elements can be varied by various methods. For example, the fastening elements of the at least one further region may have lower average height than the fastening elements of the first region. Generally, the difference in height between the fastening elements of the at least one further region and the fastening elements of the first region may be at least 10 percent, preferably at least 20 percent, and more preferably at least 50 percent, based on the height of the fastening elements of the first region. For instance, the difference in height between the fastening elements of the at least one further region and the fastening elements of the first region may be at least 50 μm, preferably at least 80 μm. Preferably, the height of the fastening elements in the at least one further region may be in the range of between 30-400 μm, preferably 75-300 μm, more preferably 150-250 μm, and the height of the fastening elements in the first region may be in the range of between 50-500 μm, preferably 100-350 μm, more preferably 200-300 μm.
Alternatively, or in addition to varying heights of the fastening elements in the various regions, fastening elements of different types may be provided in the first and further regions. For example, the fastening elements of the first region may be provided in the form of hook-type or mushroom-type fastening elements and the fastening element of the at least one further region may be stems with smaller hook heads or mushroom heads or eventually without heads. It would also be possible to provide the fastening elements of the at least one further region in the form of mushroom-type hooks with a generally circular cap and in the first region mushroom-type hooks with a generally elliptical cap to increase their engageability. More generally, the size and/or shape of the heads of the male fastening elements may be varied so as to provide a suitable engageability.
Another possibility of varying the engageability characteristics of the fastening elements in the first and further regions is to alter the density of the fastening elements. For example, the fastening elements of the at least one further region may be provided with a lower density per unit area than the fastening elements of the first region. The density of the fastening elements may generally be in the range from about 30 to 2500 hooks per square centimeter. Preferably, the hook density is in the range from about 150 to 500 hooks per square centimeter, more preferably in the range from about 200 to 300 hooks per square centimeter.
Another option in order to vary the engageability of the fastening elements is to change the cross-sectional area of stems of the fastening elements. With stems of the fastening elements in the at least one further region having a smaller cross-sectional area than the fastening elements of the first region a lower engageability in the at least one further region than in the first region can be achieved. The material properties of the fastening elements may also be varied, e.g., more flexible material may be used for the fastening elements in the at least one further region and stiffer material in the first region. Combinations of the above-mentioned methods for varying the engageability are also contemplated.
Furthermore, the mechanical fastening elements in at least one of the first and further regions may be provided with an adhesive. Preferably, the adhesive is provided in a pattern of varying tackiness. For example, the hook and/or stem can be coated with an adhesive as taught, e.g., in U.S. Pat. No. 6,489,003, U.S. Pat. No. 6,428,525, U.S. Pat. No. 6,402,730, U.S. Pat. No. 6,393,673, and U.S. Pat. No. 4,959,265. Alternatively and preferably, the adhesive may be provided between the stems and/or hooks as disclosed, e.g., in U.S. Pat. No. 5,053,028 and U.S. Pat. No. 5,019,065.
The absorbent articles of the present invention typically have an elongated shape, e.g. generally oval or elliptical, triangular, hourglass or keyhole shape. Advantageously, the main body of the article may comprise at each of its two opposite longitudinal edges flaps that are adapted to be folded over the opposite side of the undergarment. Each of these flaps may comprise a first region with fastening elements of higher engageability located at the center area of the flap and at least one further region with fastening elements of lower engageability located between the center area and the edge of the flap. Typically, the at least one further region of the flaps comprises the same or similar fastening elements as the at least one further region of the main body, and the first region of the flaps comprises the same or similar fastening elements as the first region of the main body.
Generally, the engageability of the fastening elements of the at least one further region with the undergarment may be at least 20%, preferably at least 35% and more preferably at least 50% lower than the engageability of the fastening elements of the first region.
With the absorbent article according to the present invention, which has particularly at its edge areas a lower engageability, damage to the undergarment can be effectively minimized. It is believed that this positive effect is due to the lower engageability, particularly lower peel resistance, of at least one further region which is located between the center area and the edge of the absorbent article. While the peel resistance of the fastening elements in this at least one further region is rather small, the shear strength and friction of the fastening elements of the at least one further region are preferably still adequate and sufficient so as to assist in positioning and securely holding the absorbent article in the undergarment.
The invention also relates to a method of manufacturing an absorbent article for positioning in an undergarment to absorb body exudates. This method comprising the steps of providing a main portion having a liquid-permeable body side sheet, a liquid-impermeable garment side sheet opposite to said body side sheet, and a liquid-absorbent core between said body side sheet and said garment side sheet, and providing on said liquid-impermeable garment side sheet at least two regions of fastening elements with different engageability. A first region with higher engageability is located at a center area of the article, and at least one further region with lower engageability is located between the center area and an outer edge of the article.
The regions with fastening elements of different engageability may be provided particularly by joining or laminating a separate hook carrier web to a given garment side sheet of the sanitary napkin. This lamination can be done by the use of an adhesive, application of thermal and/or sonic means. Alternatively, these regions may be integrally provided on the napkin.
Preferably, the first region and the at least one further region are provided with mechanical fastening elements by means of a micro-replication process. For example, micro-replicated stems may be provided from a master belt, master drum, master screen, or any other form. The master belt, drum or screen is typically formed as a negative with differences in height, diameter, shape, density in registry to build the corresponding web with stems of the various regions. For instance, the master belt, drum or screen may be provided with openings or cavities by use of drilling, etching, laser erosion, punching or similar electrical, mechanical or chemical processing.
In accordance with a preferred method, the mechanical fastening elements are provided by first forming a plurality of stems on a substrate web, and then capping the stems in the first region so as to form mushroom-type mechanical fastening elements. The stems in the first region are preferably provided with a larger height than the stems in the at least one further region. It is preferred that at least some of the fastening elements of the at least one further region located generally at the edge of the article remain uncapped. Accordingly, the substrate web and the stems are produced from the same material. Alternatively, the substrate web may be different in chemistry to the stems. Suitable substrate webs may be paper, nonwoven, all film type constructions, scrim, etc.
Another manufacturing technique suitable for the absorbent article of the present invention is polymeric printing as disclosed, e.g., in US 2001/0018110 A1, US 2001/0016245 A1, US 2004/0180186 A1, US 2004/0178544 A1.
In the following preferred embodiments of the absorbent article according to the invention will be described with reference to the drawings, in which:
a is a cross-sectional view along line a-a of
a is a photo of a standard testing fabric which has been engaged with and removed from the absorbent article of the present invention several times;
b is a photo of a standard testing fabric that has been engaged with and removed from a conventional absorbent article several times; and
Absorbent articles, e.g., sanitary napkins, may have quite different shapes, and the specific size and shape of the first and further regions with different engageability generally depends on the shape of the absorbent article so as to optimize both the secure holding of the article in an undergarment and preventing damage to the undergarment.
In
In the embodiments illustrated in
The width w of the at least one further region 10 around the circumference according to the embodiments of
As already mentioned above, the first region 12 is generally located in the center area 8 of the article 2. In other words, the first region 12 is preferably delimited or surrounded by the at least one further region 10. The first region 12 does, however, not necessarily extend to the center, i.e., the first region can also be provide as ring-shaped strip around the center.
In the embodiment shown in
The embodiment shown in
In
In order to achieve the different engageability in the first region and the at least one further region several techniques can be used. For example, the fastening elements of the at least one further region 10 may have a lower average height than the fastening elements of the first region 12. According to a specific example, the fastening elements in the at least one further region 10 may have a height of 30 to 400 μm, preferably 75 to 300 μm, more preferably 150 to 250 μm, whereas the fastening elements in the first region 12 may have a height of 50 to 500 μm, preferably 100 to 350 μm, and more preferably 200 to 300 μm.
The engageability of the fastening elements in the various regions may also be varied by using different types of fastening elements in these regions. For example, the fastening elements of the at least one further region 10 may be provided in the form of stems substantially or completely without heads, while the fastening elements of the first region 12 may be provided in the form of stems with heads, e.g., as hook-type fastening elements, and/or mushroom-type fastening elements. This may be particularly advantageous from a manufacturing point of view since hook-type or mushroom-type fastening elements may be formed from stems by a capping process so that initially the whole fastener, including the first and further regions, can be made from the same precursor material, i.e. a backing with upstanding stems. The different regions are then formed in a final capping process in which only the stems of the first region are capped to form heads, e.g., mushroom-type hooks. Suitable methods for producing mechanical fastening elements in this way are disclosed, e.g., in U.S. Pat. No. 5,077,870. Regarding manufacturing techniques as well as hook configurations, sizes and densities further reference is made to WO 94/23610, U.S. Pat. No. 5,607,635, U.S. Pat. No. 4,894,060, U.S. Pat. No. 5,679,302, U.S. Pat. No. 5,620,769, U.S. Pat. No. 4,794,028, WO 94/04839, U.S. Pat. No. 4,984,339 and U.S. Pat. No. 5,781,969.
The hook density on the backing is preferably from 30 to 2500 hooks/cm2, and more preferably from about 150 to 500 hooks/cm2. The stem diameter and/or stem width adjacent the heads of the hooks is preferably from 0.05 to 0.45 mm, and more preferably from about 0.127 to 0.279 mm. The hook head may be circular, elliptical, rectangular, square, hexagonal. For example, a circular disc-like head projects radially past the stem on each side preferably by an average of about 0.013 to 0.254 mm, and more preferably by an average of about 0.025 to 0.127 mm.
To have both good flexibility and strength, the backing of the mushroom-type hook strip preferably may be from 0.025 to 0.512 mm thick, and more preferably from 0.064 to 0.254 mm thick, especially when the hook strip is made of polypropylene or a copolymer of polypropylene and polyethylene. For some uses, a stiffer backing could be used, or the backing can be coated with a layer of pressure sensitive adhesive on its surfaces opposite the hooks by which the backing could be adhered to a substrate so that the backing could then rely on the strength of the substrate to help anchor the hooks.
It is also possible to use both different types of fastening elements and different heights of the fastening elements in the first and the further regions.
Furthermore, different engageability characteristics can be achieved with differently shaped heads or caps of hook-type fastening elements. For example, with rather oval or elliptical heads a higher engageability can be achieved relative to many fabrics, compared with circular heads.
Another possibility is to alter the density of the fastening elements. For example, a lower density of fastening elements per unit area in the at least one further region leads to a lower engageability than with more densely packed fastening elements in the first region.
Another option is to use fastening elements with a smaller stem diameter, i.e. smaller cross-sectional area, in the at least one further region than the fastening elements of the first region. This makes the fastening elements of the at least one further region more flexible than those of the first region which may vary engageability.
It is also possible to combine several or all of these measures in order to adapt the engageability of the fastening elements to the specific requirements in the first and at least one further regions.
It is also within the scope of the invention to provide more than two regions of different engageability. For example, the at least one further region may comprise a second region and a third region, wherein the third region of the absorbent article may be completely free of fastening elements. Such a third region may be provided, for example, at a portion or along the outermost edge of the article, particularly at the transverse (i.e. curved outermost edges of the absorbent article 2) as shown in
Alternatively, in the embodiments of
Furthermore, the at least one further region 10 and/or the first region 12 of the main body as well as the at least one further region 18 and/or the first region 20 of the flaps 14 may be at least partially provided with an adhesive. The adhesive may be applied in the form of a pattern of varying tackiness. This may also assist in properly positioning the absorbent article in an undergarment.
Generally, the engageability of the at least one further 10 region should be at least 20%, preferably at least 35%, and more preferably at least 50% lower than the engageability of the fastening elements of the first region 12. In particular, it has been found that the peel strength of the fastening elements is primarily responsible for damages to the undergarment upon repeated removal therefrom. It is therefore preferred that the peel strength of the fastening element of the first region 12 is at least two times, preferably at least five times, and more preferably at least 10 times the peel strength of the at least one further region 10. The shear strength of the fastening elements of the at least one further region may be lower, generally the same or higher than the shear strength of the fastening elements of the first region. A higher shear strength of the fastening elements of the at least one further region advantageously contributes in positioning and fixing the absorbent article 2, however, without at the same time causing damage to the undergarment upon removal of the article from the undergarment.
In connection with
As can also be seen in
Alternatively, it is also feasible to form a web of upstanding stems with the same height and perform the capping process with an eccentric or engraved capping roll so that only the stems of the first region 12 will be capped.
The capping process is schematically illustrated in
In
In
In order to demonstrate the advantageous effects of absorbent articles with lower engageability and higher engageability at appropriate regions of the article several tests have been conducted.
The 90° peel strength was measured according to ASTM D 5170-91 using a roll down weight of 5000 g. Instead of removing the hook from the fabric just once as described in the above test method this was done twice prior to testing. The tested hook area was 25.4 mm×15 mm, wherein the 25.4 mm was used as the peel front. The maximum peel force in N/25.4 mm is reported in Table 1 below for several test fabrics.
Hook and fabric material was cut out in a width of 1 inch (25.4 mm). The hook strip was placed onto the fabric and pushed down by a flat steel plate for a period of two seconds. The steel plate was carefully removed and the test specimen was rolled down with a 5 kg roller with 5 cycles. This initial closure was opened by hand and again fastened and opened using the same procedure as described. After the third fastening of the hook into the fabric using 5 cycles of a 5 kg roll down weight the test specimen was positioned into the clamps of the tensile tester being 1 inch (25.4 mm) apart. The testing speed was set to 300 mm/min and the peal, force was recorded along a travel distance of the clamps of 50 mm.
The dynamic shear strength was tested according to ASTM D 5169-91, using a roll down weight of 5000 g. Instead of removing the hook patch from the fabric just once as described in the above test method this was done twice prior to testing. The test area was 25.4 mm×40 mm. The maximum shear force is reported in Table 2 in N/25.4mm for several test fabrics.
Hook and fabric material was cut out in a width of 1 inch (25.4 mm) having a length of about 4 inch. The hook strip was aligned and placed onto the fabric with an overlap of 40 mm. The test specimen was pushed down by a flat steel plate for a period of two seconds. The steel plate was carefully removed and the test specimen was rolled down with a 5 kg roller with 5 cycles. This initial closure was opened by hand with a peel mode and again fastened and opened using the same procedure as described. After the third fastening of the hook into the fabric using 5 cycles of a 5 kg roll down weight the test specimen was positioned into the clamps of the tensile tester being 75 mm apart. The testing speed was set to 300 mm/min and the peak force was recorded.
The dynamic friction of the first region and the further region was tested on a polypropylene spunbond nonwoven according to DIN 53375.
The fabric (size about 50 mm×200 mm) was adhered by using a double coated adhesive tape to the sample table. The male component was cut into a pieces of 25.4×25.4 mm. One piece of 25.4×25.4 mm was adhered with the help of a double coated tape in the geometric center of the slide with a weight of 200 g. The 200 g slide with the male hook patch was positioned onto the fabric so that the male component was in contact with the fabric. The horizontal thread to move the slide is positioned behind a 90° turn into the clamp of the tensile tester. The testing speed was 100 mm/min and the dynamic friction was recorded.
The following test fabrics were used as typical examples for undergarment materials in order to test the 90° peel strength, dynamic shear strength and friction of the fastening elements used in accordance with the invention:
1. Nylon 6.6 (ECE) S/361 standard testing fabric with the designation M.0361, supplied by Testex Prüftextilien, Bad Münstereifel, Germany
2. Polyester fabric (ECE) S/777 standard testing fabric with the designation M.0777, supplied by Testex Prüftextilien, Bad Münstereifel, Germany
3. Cotton standard testing fabric with the designation M.0460, Lot 540, supplied by Testex Prüftextilien, Bad Münstereifel, Germany
4. Typical cotton underwear, bought in a warehouse
5. Typical undergarment made out of 96% polyamide and 4% elasthan, bought in a warehouse
6. Polypropylene spunbond with a weight of 40 g/m2 for friction testing.
1. A mushroom-type hook web which is commercially available under the trade designation 3M Microreplicated Hook CS-600 from 3M Company, St. Paul, Minn., USA. The hook cap (head) geometry is elliptical with the large diameter in cross direction, wherein cross direction means a direction perpendicular to the direction in which the hook itself is manufactured. The density of the hooks is 248 hooks/cm2. This type of hook web is described in more detail in U.S. Pat. No. 6,000,106, particularly in connection with FIG. 9 thereof, and U.S. Pat. No. 6,132,660, particularly FIG. 6B thereof.
2. A web with stems, i.e., without heads or caps, extending substantially perpendicular from the surface thereof. This material is a precursor web of the CS-600 material mentioned in item 1 above.
From Table 1 it follows that the peel strength of the CS-600 hook material is considerably higher than that of the stems only, independently from the test fabric used. This means that if stems were used in critical regions of the absorbent article, e.g., the edge region, the fabric of the undergarment would not be damaged because the fasteners would substantially not tear out any fibers. This can be seen, upon a comparison of
As can be taken from Table 2, the stems as fastening elements of lower engageability provide a lower shear resistance compared to the CS-600 fastening material used in the second region of higher engageability. This means that the stems, while providing substantially no peel resistance with the test fabrics, provides a at least some sheer resistance assisting in the attachment of the absorbent article to the undergarment.
Furthermore, the region with fastening elements of lower engageability also assists in holding the absorbent article on the undergarment due to its higher friction vis-à-vis a region completely free of fastening elements. This can be taken from Table 3 below where the dynamic friction is shown for a precursor web of the CS-600 material, i.e. stems only, on the test fabric M.0460 and on a polypropylene spunbond. For comparison, the same film without stems (here the backside of the same film was used) was tested for dynamic friction with the same test fabrics.
As can be seen from Table 3, the stem side has much higher dynamic friction forces than the backside of the film, i.e. a film without fastening elements. Thus, the fastening elements of lower engageability still contribute to the fixation of the absorbent article to the undergarment.
| Number | Date | Country | Kind |
|---|---|---|---|
| 05006036.7 | Mar 2005 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2006/009152 | 3/14/2006 | WO | 00 | 6/11/2008 |
