Source: https://patents.google.com/patent/EP0929279B1/en
Timestamp: 2019-12-14 13:53:22
Document Index: 313994869

Matched Legal Cases: ['arts 4', 'art 105', 'art 106', 'art 107', 'art 105', 'art 107', 'art 106', 'art 106', 'art 106', 'art 205', 'art 206', 'art 207', 'art 205', 'arts 430', 'arts 530', 'arts 528', 'art 531', 'arts 530', 'art 628', 'art 629', 'arts 630', 'art 629', 'art 628', 'arts 728', 'arts 728']

EP0929279B1 - Absorbent bodies in absorbent articles having improved liquid acquisition properties - Google Patents
EP0929279B1
EP0929279B1 EP19970932086 EP97932086A EP0929279B1 EP 0929279 B1 EP0929279 B1 EP 0929279B1 EP 19970932086 EP19970932086 EP 19970932086 EP 97932086 A EP97932086 A EP 97932086A EP 0929279 B1 EP0929279 B1 EP 0929279B1
EP19970932086
EP0929279A1 (en
Urban Widlung
1996-06-28 Priority to SE9602579A priority Critical patent/SE511903C2/en
1996-06-28 Priority to SE9602579 priority
1999-07-21 Publication of EP0929279A1 publication Critical patent/EP0929279A1/en
2002-09-04 Publication of EP0929279B1 publication Critical patent/EP0929279B1/en
2003-06-04 First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=20403214&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=EP0929279(B1) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
241000193803 Therea Species 0 abstract claims description 4
238000009736 wetting Methods 0 claims description 52
229920003043 Cellulose fiber Polymers 0 claims description 19
230000000930 thermomechanical Effects 0 claims description 6
An absorbent article comprising a liquid-permeable casing sheet (1), a liquid-impermeable casing sheet (2) and an absorbent body (3) enclosed between the two casing sheets. The absorbent body (3) includes a liquid acquisition space (24) which consists of at least one cavity or one region of lower density than the density of an acquisition layer (19) located in said absorbent body (3) adjacent the space (24) and essentially in the same plane thereas. The acquisition layer (19) includes a material which when wetted increases in size in the thickness direction of the article (the z-direction). The article is mainly characterized in that the material in the acquisition layer (19) exhibits relatively low expansion in the plane of the article (the xy-direction) when wetted, such that the volume of the liquid-acquisition space (24) will increase by at least 100 %, preferably by at least 200 %, more preferably by at least 400 % and most preferably by 900 % when wetted.
The present invention relates to an absorbent article that includes a liquid-permeable outer casing sheet mounted on a first surface of the article, a liquid-impermeable outer casing sheet mounted on a second surface of the article, and an absorbent body enclosed between said two casing sheets, wherein the absorbent body includes a liquid-acquisition layer and, located essentially in the same plane thereas, a liquid-reception or liquid acquisition space comprising at least one cavity or at least one region of lower density than the acquisition layer that adjoins said space and wherein the liquid-acquisition layer includes a material which when wetted increases in size in a direction (z-direction) generally perpendicular to the first surface of the article.
One problem with hitherto known absorbent articles, such as diapers, pants-type diapers or trainers, incontinence guards, sanitary napkins and like articles, that are intended to repeatedly receive and absorb body fluid excreted by a user is that the rate at which liquid is able to penetrate into the article is greatly reduced at each renewed wetting occasion. This problem is particularly apparent in diapers and incontinence guards for children and adults, since the article must be capable of receiving and absorbing a relatively large volume of liquid excreted in the course of only a few seconds. It is therewith not unusual, particularly after a first wetting of the article, that liquid which is not immediately absorbed into the article will instead flow across the surface of said article and run past the edges thereof. Such body fluid leakages are, of course, highly undesirable because, among other things, they soil and stain clothes, bed linen and mattresses, sometimes destructively.
The reason why the body fluid acquisition rate decreases with repeated wettings of the article is because the absorbent body of the article becomes temporarily saturated with body fluid within a limited area around the point at which the surface of the article is first met by the body fluid, the so-called primary wetting point. As a rule, the absorbent articles include one or more layers of hydrophilic fibres, for instance cellulose fluff pulp, and often also a powerful absorbent hydrocolloidal material, so-called superabsorbents. Liquid transport in such material is relatively slow, since it is primarily dependent on capillary forces in those cavities present between fibres and particles in the absorbent body of the article. Liquid is transported within the hydrocolloidal materials by diffusion, which is a slower process than that generated by the capillary forces. Thus, the liquid will remain in the primary wetting region of the article for a relatively long period of time, and is then transported only gradually to surrounding parts of the absorbent body of said article.
U.S. 3,889,679 describes a diaper that has a plurality of circular holes disposed through the absorbent body of the diaper. However, since wetting of a diaper takes place within a limited region of the diaper, the primary wetting region, only those holes that are located nearest this region can be used to initially receive body liquid. These holes quickly fill with liquid, which is gradually drained by the surrounding absorbent material away from the holes by the suction effect generated by the capillary forces between the fibres in the absorbent material. This is a slow process, as before mentioned, and there is a considerable risk that liquid will still be left in the holes when liquid is discharged on the next wetting occasion. The absorbent material located nearest the primary wetting region of the diaper will gradually become saturated with body liquid and then lose essentially all ability to drain liquid from the holes. Another problem with this absorbent body is that it consists of a material which collapses when wetted and therewith essentially loses its three-dimensional structure. Consequently, the cavity space available in the absorbent body for acquisition of liquid is practically non-existent after a first wetting.
U.S. 4,560,372 describes an absorbent body that includes a resilient fibre layer and a layer of hydrophilic fibres that have been compressed, slit and then drawn apart to form openings. The absorbent body also includes 20-60% superabsorbent material. As a result of its high superabsorbent content, the material will swell in both the z-direction and in the xy-direction when wetted, i.e. the material will swell into the openings at the same time as it swells in the thickness direction of said material, wherewith the area of said openings are greatly reduced after wetting.
Prior publications WO 87/01914, U.S. 4,333,462, U.S. 4,333,463, U.S. 4,333,464, U.S. 4,413,996, EP 0,124,365, GB 2,156,681, U.S. 4,643,727 and EP 5,528,567 also describe similar products provided with liquid receiving and collecting cavities or basins.
Our earlier invention described in our copending PCT-application WO96/20670 concerns an absorbent article which includes a liquid-permeable outer sheet disposed on a first surface of the article, a liquid-impermeable outer sheet disposed on a second surface of the article, and an absorbent body which is enclosed between the two casing sheets and which includes a body liquid receiving space comprising at least one cavity or region of lower density than the density of a part of the absorbent body located adjacent the receiving space and extending generally in the same plane thereas, the article being characterized in that the receiving space is disposed in a storage layer in the absorbent body; and in that parts of the storage layer adjacent the receiving space include a material which, when wetted, increases in volume in a direction (z-direction) generally perpendicular to the first surface of the article, whereby the size of the receiving space also increases in said direction as a result of the article being wetted
There has been produced in accordance with the invention an article of the kind defined in the introduction that provides a solution to this problem. The inventive article is mainly characterized in that when wetted, the material present in the acquisition layer exhibits relatively low expansion in a direction (xy-direction) essentially parallel with the first surface of the article, such that the volume of the liquid-acquisition space will increase by at least 100%, preferably at least 200%, even more preferably 400% and most preferably at least 900% when the material of the acqusition layer is wetted to saturation with a 0.9%-NaCl solution.
Expansion of the material in the xy-direction will preferably not be greater than that which results in a decrease in the area of the liquid-acquisition space in the xy-direction by at most 25%, preferably at most 20% and most preferably at most 10% when the material is wetted.
There is preferably disposed between the liquid-permeable outer casing sheet and the acquisition layer a liquid transportation layer that includes a material capable of quickly accepting liquid and quickly releasing the liquid to the underlying layer. This transportation layer may be comprised of a lightly-compressed cellulose fluff layer of mechanical, thermomechanical, chemithermomechanical pulp (CTMP) cellulose fibres that have been chemically stiffened or cross-linked, a fibre mat or wadding of synthetic or natural fibres or an absorbent foam material.
Those cavities, regions of low density, channels or the like that together form the liquid-acquisition space of the article will preferably not have a dimension in the plane of the acquisition layer that exceeds 35 mm and preferably does not exceed 20 mm. By this is meant that the extension of each such cavity, region of low density, channel or the like will not accommodate within its area a circle having a diameter greater than 35 mm and preferably not greater than 20 mm anywhere in the plane of the acquisition layer. Because of the flexibility of the materials, it is difficult to avoid surrounding material layers from bulging in towards the liquid acquisition space with greater dimensions than those aforesaid, therewith reducing said space. Absorbent articles shape and curve in conformity with the wearer's body in use. The material layers that lie proximal to the wearer therewith tend to curve and bulge into the acquisition space. This bulging generally increases when the material in the casing sheet is wet, and is even more pronounced when the storage layer includes large cavities. Naturally, this bulging can be reduced by using a stiffer material layer nearest the storage layer. However, the extent of the acceptable stiffness of such a material layer is determined by the requirements placed on the shapability, flexibility and user comfort of the article. The smallest functional dimension of cavities or the like in the storage layer correspond approximately to the size of a water droplet. Consequently, the size of a cavity or some corresponding space in the acquisition layer should not be so small as to not enable a circle having a diameter of 3 mm or more to be enscribed inwardly of its boundary edges in the plane of the storage layer.
Figure 1 illustrates a diaper according to a first embodiment of the invention from above, showing an acquisition layer formed by separate material bodies;
Figure 2a is a sectional view of the diaper shown in Figure 1 taken on the line II-II, prior to wetting of the diaper;
Figure 2b is a sectional view of the diaper shown in Figure 1 taken on the line II-II, after wetting of the diaper;
Figure 3 illustrates a diaper according to a second embodiment of the invention from above, and shows an acquisition layer provided with longitudinally extending cavities or channels;
Figure 4a is a cross-sectional view of the diaper shown in Figure 3 taken on the line IV-IV, prior to wetting of the diaper;
Figure 4b is a cross-sectional view of the diaper shown in Figure 3 taken on the line IV-IV in Figure 3, after wetting of the diaper;
Figure 5 is a longitudinal sectional view of the diaper shown in Figure 3 taken on the line V-V, after wetting of the diaper;
Figure 6 illustrates a diaper having a net-forming storage layer from above;
Figure 7 illustrates an inventive acquisition layer having a plurality of through-penetrating holes;
Figure 8 illustrates an acquisition layer having centrally disposed openings alternating with overlapping material regions;
Figure 9 illustrates a web of material for producing an acquisition layer;
Figure 10 illustrates an acquisition layer having two rows of holes of mutually different sizes;
Figure 11 illustrates an acquisition layer having undulating, groove-like cavities;
Figures 12a and b are larger views of a hole and surrounding parts of a respective dry and wet sample of a first material; and
Figures 13a and b are enlarged views of a hole with surrounding parts of a respective dry and wet sample of a second material.
The diaper illustrated in Figures 1, 2a and 2b is seen form the side thereof that lies proximal to the wearer in use. The diaper is shown extended in a flat state and includes a first liquid-permeable casing sheet 1, e.g. made of non-woven material, perforated plastic film or net mounted on that side of the diaper which lies proximal to the wearer in use. A liquid-impermeable second casing sheet 2, comprised of plastic film, hydrophobous non-woven material or woven fabric, is placed on that side of the diaper which is intended to lie distal from the wearer in use. The two casing sheets 1, 2 enclose an absorbent body 3 and are mutually joined within parts 4 of the casing sheets 1, 2 that project out around the absorbent body 3.
An elastic device 12, 13 is mounted along each side edge 8, 9 of the diaper. The elastic devices 12, 13 are fastened to the diaper in a stretched state and function to draw the side edges 8, 9 of the diaper together when relaxed, such as to curve the diaper to a trough-like shape. This effect of the elastic devices 12, 13 is not apparent from Figure 1, however, since the diaper is shown in a flat state with the elastic devices 12, 13 stretched. The elastic devices 12, 13 function to hold the edges of the diaper leg-opening in tight abutment with the wearer's thighs. A further elastic device 14 is disposed along the rear waist edge 11 of the diaper, so as to bring the waist-opening defining edge in sealing abutment with the wearer's waist. Several different types of elastic devices 12-14 suitable to this end are known to the art, such as elastic threads, elastic bands, elastic non-woven, or like devices.
The absorbent body 3 includes a first layer, the transport layer 18 placed nearest inwardly of the liquid-permeable casing sheet 1. The transport layer 18 is conveniently comprised of a soft material that is able to quickly receive large volumes of liquid and which has relatively large pores or capillaries to this end. Examples of such materials are low-compressed cellulose fluff layers, in particular comprised of mechanical, thermomechanical or chemithermomechanical pulp (CTMP), chemical pulp comprised of chemically stiffened or cross-linked cellulose fibres, or fibre mats and wadding of other types of natural fibres or synthetic fibres. Mixtures of cellulose fluff pulp or other cellulose based fibres with different types of synthetic fibres may be used. Soft, perforated or open-cell foam material may also be used. The material will preferably have a low liquid dispersion ability, whereby the wet region of the layer will remain essentially restricted to the primary wetting region, even after repeated wetting of the material. The surface of the diaper that lies in contact with the wearer will therewith be felt to be dry and comfortable against the wearer's skin, even after being used for a relatively long time.
When the diaper is in use, the transport layer 18 functions to receive and transport body liquid further away from the liquid-permeable casing sheet 1 and will therefore preferably have large pores that offer the least possible resistance to the liquid flow. The transport layer 18 will also preferably be soft and comfortable against the wearer's body during the whole of its use. The properties of the material in the transport layer 18 will preferably not be changed appreciably after wetting. It is also desirable that the material has a certain resiliency, so that the material will strive to return to its original state after being compressed or wrinkled in use.
The transport layer 18 may also include a small quantity of so-called superabsorbents, i.e. material in the form of fibres, particles, granulates, films or the like which are able to absorb and bind body liquid chemically in a quantity corresponding to several times the intrinsic weight of the superabsorbent while forming hydrogel.
Disposed inwardly of the transport layer 18, as seen in a direction from the liquid-permeable casing sheet 1, is a second absorbent layer 19, hereinafter referred to as the acquisition layer, which is intended to quickly receive and collect relatively large volumes of body liquid. The acquisition layer 19 consists of a plurality of cylindrical bodies 20, each having one planar surface 21 in abutment with the transport layer 18 and its other planar surface 22 in abutment with a third absorbent layer, the storage layer 23, located inwardly of the acquisition layer 19, nearest the liquid-impermeable casing sheet 2. The cylindrical bodies 20 are disposed in mutual spaced relationship and leave therebetween a coherent cavity or space 24 in which body liquid discharged onto the diaper can be collected. The liquid-acquisition space 24 may alternatively be comprised of a space of lower density and weight per unit area than peripheral material parts, and include, e.g., a porous resilient material, such as fibre wadding, an absorbent foam or like material. Material may also extend from the transport layer 18 into the space 24.
As will be evident from the diaper shown in Figure 1, the main extension of the diaper lies in the xy-plane, the x-direction being defined by the transverse direction of the diaper and the y-direction being defined by the longitudinal direction of the diaper. The cylindrical bodies 20 are comprised of a material which when wetted with body liquid will expand heavily in the z-direction, i.e. in a direction perpendicular to the xy-plane, and only to a small extent in the xy-plane, such that the volume of the-liquid-acquisition space (24) will increase by at least 100%, preferably at least 200% and more preferably by at least 500% when the material is saturated with a 0.9%-NaCl solution. Expansion of the material in the xy-direction will preferably not be greater than an extent in which the area of the space 24 in said xy-direction decreases by at most 25%, preferably by at most 20% and most preferably by at most 10% when the material is wetted to saturation in accordance with the aforegoing. Expansion of the material in the z-direction will preferably be at least 100%, preferably at least 200% and most preferably at least 500% when wetted to saturation in accordance with the aforegoing.
Another suitable expanding material is compressed cellulose-fluff pulp (density at least 0.2 g/cm3) that has been admixed with a certain amount of superabsorbent material, although less than 20% by weight superabsorbent material. The admixture of superabsorbent will namely result in an increase in the extent to which the material swells in the xy-direction, i.e. the area of the spaces 24 will decrease. However, the material used in accordance with WO 94/10956 allows a greater amount of superabsorbent to be admixed with the material, since said material swells very substantially in the z-direction, which compensates for swelling in the xy-direction.
The aforedescribed materials are produced most often in the form of relatively thin webs that have a thickness of only some few millimetres. The cylindrical bodies may therewith be formed by one or more layers of such material.
The fourth layer 25 of the absorbent body, hereinafter referred to as the liquid-dispersion layer may, in accordance with a first alternative, comprise a material of high density and highly capable of dispersing, or spreading, liquid by capillaries. Suitable materials in this respect are compressed layers of cellulose fluff pulp, tissue, absorbent foam material, or dry-formed flash-dried cellulose fibres sheets according to WO 94/10956. The dispersion layer 25 is preferably superabsorbent-free, or contains only small quantities of superabsorbent. The layer will preferably have a smaller extension in the xy-plane of the diaper than the transport layer 18. The liquid dispersion layer will thereby be surrounded on all sides by a soft, body-friendly material of low liquid dispersing ability.
According to a second alternative, the liquid-dispersion layer 25 is comprised of a material that has a low resistance to liquid flow, so as to enable liquid to disperse, or spread, relatively freely along the layer. Suitable materials in this respect are a porous fibre mat or wadding of synthetic or natural fibres or an open-cell foam material.
The primary purpose of the dispersion layer 25 is to transport body liquid away from the diaper region that first receives body liquid, i.e. the primary wetting region. This results in better use of the absorbent material in the absorbent body 3. The dispersion layer 25 may either be disposed between the acquisition layer 19 and the storage layer 23 (shown with a dotted line in Figure 2a), or as described above between the storage layer 23 and the liquid-impermeable outer casing sheet 2.
As will be evident from Figure 2a, the liquid-acquisition layer 19 is comparatively thin prior to the diaper having absorbed body liquid. However, the cavity 24 formed between the cylindrical bodies 20 on the diaper shown in Figure 2a is sufficient to receive a first discharged liquid volume. The discharged body liquid hits the liquid-permeable casing sheet 1 of the diaper within a small limited region or area, the so-called primary wetting region.
Since the space 24 in the liquid-acquisition layer 19 is coherent between the cylindrical bodies, liquid that penetrates through the transportation layer 18 will flow-out over a relatively large area around the primary wetting region. Liquid is absorbed into the storage layer 23 and the dispersion layer 25 relatively slowly because of the compact structure of these layers, whereby a large part of the liquid is able to run on the surface of the layer 23 that faces towards the space 24 and therewith spread over a considerable area prior to being absorbed by the storage layer 23 or by the cylindrical bodies 20 in the acquisition layer 19. Thus, it is not only the cylindrical bodies 20 located nearest the primary wetting region that are wetted by the liquid and swell in the z-direction, but that such expansion will also be seen to occur at a distance from the wetting region. The liquid gradually spreads further out in the diaper by virtue of liquid transportation in the dispersion layer 25, for further storage in the storage layer 23.
The diaper illustrated in Figures 3-5 is principally of the same construction as the diaper in Figure 1, and includes an absorbent body 103 enclosed between a liquid-permeable casing sheet 101 and a liquid-impermeable casing sheet 102. The diaper has a front part 105, a rear part 106 and an intermediate crotch part 107 and includes two longitudinally extending side edges 108, 109, a front waist edge 110, and a rear waist edge 111. The diaper is essentially T-shaped with the cross member of the T forming the front diaper part 105 and the vertical member of the T increasing gradually in width from the diaper crotch part 107, over the rear part 106 and towards the rear waist edge 111.
Elastic devices 112, 113 are disposed along the side edges 108, 109 of the diaper in a V-shaped pattern, divergent from the front waist edge 110 towards the rear waist edge 111. A fastener tab 115, 116 is mounted on each side edge 108, 109, on the rear part 106, close to the rear waist edge 111, and a corresponding target area 117 is disposed on the outside of the liquid-impermeable casing sheet 102 at the front diaper part 106, close to the front waist edge 110.
The absorbent body 103 of the diaper includes a liquid transportation layer 118 of the same kind as that of the Figure 1 diaper and having the same format as the size of the diaper. A liquid-acquisition layer 119 having elongated liquid-acquisition spaces or channels 124 is disposed inwardly of the transportation layer 118. As evident from the Figure 3, the channels 124 may extend in the longitudinal direction of the article, or alternatively in its transverse direction. The channels 124 may either be comprised of cavities punched-out in the acquisition layer 119, or alternatively an acquisition layer 119 may be comprised of a plurality of longitudinally extending, or transversely extending, strips between which elongated liquid-acquisition spaces or channels 124 are located. The strips are fastened to a storage layer 123 or to a liquid dispersion layer 125 of a kind and shape corresponding to those of the diaper shown in Figure 1, e.g. by gluing or in some other way. As in Figure 2a Figure 4a shows the alternate positions of the liquid-dispersion layer 125. A dotted line indicates the position above the storage layer 123 and a continuous line shows the position below the storage layer 123. On Figures 4b and 5 only the second alternative is shown.
As will best be seen from Figure 4a, the channels 124 in the acquisition layer 119 are relatively shallow prior to wetting of the diaper. However, the volume of the channels 124 is sufficient for the diaper to receive a first liquid volume. The liquid penetrating into the diaper is able to run quickly away from the primary wetting region along the channels 124. The liquid from the channels 124 is then gradually absorbed by the acquisition layer 119, the storage layer 123 and the dispersion layer 125 respectively. Naturally, part of the liquid discharged onto the diaper and penetrating down through the transportation layer 118 will wet directly those parts of the acquisition layer 119 that are located in the primary wetting region of the diaper, these parts of said acquisition layer immediately beginning to swell in the z-direction of the diaper. Wetting of the acquisition layer 119 at a distance from the primary wetting region first takes place after a given time delay taken for the liquid to run out into the channels 124. Figure 5 shows how liquid is spread in the longitudinal direction of the diaper as a result of varying degrees of expansion of the acquisition layer 119 (shown in sections) in the z-direction of the diaper, depending on the distance from the primary wetting region. Figure 4b is a similar illustration showing dispersion of the liquid in the transverse direction of the diaper.
The diaper illustrated in Figure 6 has generally the same construction as the diapers shown in Figures 1-5 and includes an absorbent body 203 enclosed between a liquid-permeable casing sheet 201 and a liquid-impermeable casing sheet 202. The diaper has a generally hourglass shape and includes a front part 205, a rear part 206, an intermediate narrower crotch part 207, two longitudinally extending side edges 208, 209, a front waist edge 210, and a rear waist edge 211. The elastic devices 212, 213 are disposed along the longitudinally extending side edges 208, 209 of the diaper and along the rear waist edge 211. The diaper is fastened together in a pants-like shape with the aid of two fastener tabs 215, 216 disposed on the longitudinally extending side-edges 208, 209, close to the rear waist edge 211. The fastener tabs can be fastened onto a target area 217 on the front diaper part 205, close to the front waist edge 210.
The absorbent body 203 is comprised of two layers 219, 223. The absorbent layer 219, the acquisition layer 219, located nearest the liquid-permeable casing sheet 201 is comprised of a coarse-mesh, knitted, braided or woven net 226 of material that swells in the thickness direction of the diaper, i.e. in the z-direction, when wetted. The material may, e.g., be threads, bands or strips that include a superabsorbent, gel-forming material. Another conceivable material is threads or bands coated with a polymer mixture that will ferment when wet to form a stable foam on the bands or threads. Disposed beneath the acquisition layer 219, seen in a direction away from the liquid-permeable casing sheet 201, is a storage layer 223 of the same kind as that described with reference to the diapers shown in Figures 1-5. Naturally, the diaper illustrated in Figure 6 may also be provided with a soft, coarse-pore liquid-acquisition transportation layer between the liquid-permeable casing sheet 201 and the storage sheet 219, if so desired. Similarly, a liquid-dispersion layer may be disposed in a manner corresponding to that described with reference to Figures 1-5.
Figure 7 illustrates an alternative embodiment of a liquid-acquisition layer 319 comprised of a material that can swell in the z-direction. The acquisition layer 319 includes a plurality of through-penetrating circular holes or spaces 324 that function as liquid collecting reservoirs. The acquisition layer 319 is intended to be used as the sole absorption layer, or together with further absorption layers, such as liquid transportation layers, storage layers and/or dispersion layers in an absorbent article, such as a diaper, a sanitary napkin, an incontinence guard or like article. Because the acquisition layer swells in the z-direction, i.e. in its thickness direction. when wetted, the volume of the holes 324 will increase and therewith also their liquid accommodating capacity.
The highest proportion of cavities 324 in the acquisition layer 319 is located in the region that is intended to be placed in the primary wetting region of the absorbent article. Since the holes 324 are not mutually connected, liquid is unable to flow freely between the holes but is dispersed in the xy-plane of the acquisition layer 319 through capillary transportation in the absorbent material located between the holes 324. Consequently, there is no apparent reason for providing holes 324 at too far a distance from the primary wetting region.
Figure 8 illustrates a further embodiment of an acquisition layer 419 for use in absorbent articles. The acquisition layer according to Figure 8 is formed from a web of material that is cut into two pieces longitudinally along a sinusoidal curve 427, whereafter the two web halves 428, 429 have been offset relative to one another in the longitudinal direction of the web through a distance corresponding to one-half wave length. There is thus formed in the longitudinally extending centre part of the web holes 424 that alternate with overlapping web-parts 430. As in the earlier described embodiments, the acquisition layer 419 is comprised of a material which swells in the thickness direction of the material, i.e. in the z-direction, when wetted.
Shown in Figure 9 is an example of another web material provided with holes 524 and formed by first cutting the web 519 into two parts longitudinally in a curved pattern, whereafter the separated parts of the web have been offset longitudinally so as to produce a repetitive pattern of openings 524 and overlapping parts 530 in the web. The web 519 shown in Figure 9 has been cut longitudinally along two generally sinusoidal curves 527. Subsequent to offsetting the edge parts 528, 529 of the web in relation to its centre part 531, there are obtained two longitudinally extending rows of holes 524 with intermediate overlapping parts 530. Naturally, the principle can be used to provide any desired number of rows of openings in a web of material. In this regard, the number of hole rows is determined by the number of curve-shaped cuts made in the web.
The web 619 shown in Figure 10 has been cut longitudinally in the same way as the web 519 in Figure 9. One edge-part 628 of the web 619 has then been displaced longitudinally and transversely away from the longitudinal centre line 632 of the web 619. The other edge part 629 has been displaced both longitudinally and transversely in towards the longitudinal centre line 632 of the web 619. This enables the size of the holes 624', 624" and the size of the overlapping parts 630', 630" to be adjusted. The size of the holes 624" can be reduced, by displacing an edge part 629 towards the longitudinal centre line 632 of the web 619, while obtaining a larger overlap 630" between the web parts at the same time. the size of the hole 624' is increased in a corresponding manner, by displacing the edge part 628 of the web 619 away from the centre line 632.
Figure 11 illustrates the manner in which coherent, longitudinally extending openings can be obtained between parts of a material web 719 that has been cut apart along generally sinusoidal curves 727. The web parts 728, 729, 731 in Figure 11 are mutually displaced both in the longitudinal and in the transversal direction of the web 719, by moving the cut edge parts 728, 729 laterally away from the longitudinal centre line 732 of the web 719. The width of the coherent openings 724', 724" between two web parts is determined by the distance at which the web parts are separated. Figure 11 shows two examples of openings of mutually different widths 724', 724". Naturally, the web 719 may be provided with any number of coherent openings of the aforedescribed kind.
Varying sizes can be obtained with waves that have different amplitudes along the curve, e.g. such that the holes located in the wetting region will be larger than the holes located outside said region. Waves of varying wave lengths can also be chosen, wherewith a varying overlap is obtained between the holes at a given offset between the web parts.
Samples measuring 5 x 5 cm were punched from sample materials comprising:
The samples were weighed in a dry state and their thickness measured with a measurement tool of 45 x 45 mm at a pressure of 2.5N.
The samples were then removed from the basin and allowed to drip for about 30 seconds. whereafter the wet thickness was measured and the sample weighed.
The following results were obtained: Swellability in z-direction. Sample Dry weight g Wet weight g Dry thickness mm Wet thickness mm Increase % A 0.75 17.71 0.42 5.57 1226 B 1.17 32.50 0.96 8.51 786 C 2.30 77.57 8.96 22.19 148 D 1.19 37.27 5.18 12.21 136
Figures 12a and b illustrate a hole with surrounding parts of a dry and a wet sample piece of sample A respectively.
Figures 13a and b illustrate a hole with surrounding parts of a dry and a wet sample piece of sample C respectively.
A dry scale image was taken by placing a vernier caliper set at 10.0 mm on the dry sample, whereafter an image was taken in the image Grabber.
The following results were obtained: Change of hole area and hole volume when wetting. Sample Hole area dry mm2 Hole area wet mm2 Hole vol. dry mm3 Hole vol. wet mm3 Change hole vol. % A 7.53 7.31 3.16 40.71 1188 B 7.50 4.98 7.20 42.38 489 C 6.99 2.86 62.63 63.46 1 D 7.22 4.41 37.42 53.84 44
The results obtaind for the samples C and D show clearly that the requirement that the material of the acquisition layer shall increase in size in the z-direction is not enough to ensure a substantial increase of the volume of the liquid- acquisition space. In fact, the sample C having an increase in the z-direction of 148 % gives a volume increase of only 1 %. The sample D is only marginally better. Thus, the requirement of the present invention that the material of the acquisition layer also must show a relatively low expansion in the xy-direction when wetted is essential.
It will also be understood that the invention is not limited to the described shapes and sizes of holes, channels and swellable bodies, and that a number of further embodiments are conceivable. For instance, holes disposed in a liquid-acquisition layer may have any suitable form or size. It is, of course, also possible to combine holes and channels of different shapes and sizes in one and the same article. Swellable bodies disposed as "columns" in a coherent cavity may also vary in size and shape and are not restricted to the aforedescribed cylindrical bodies. As before mentioned, the liquid-acquisition cavities may also be comprised of a space whose density and weight per unit area are lower than the density and weight per unit area of the surrounding acquisition layer and may, for instance, include a porous, resilient material such as fibre wadding, an absorbent foam material or the like.
An absorbent article that includes a liquid-permeable outer casing sheet (1) disposed at a first surface on the article, a liquid-impermeable casing sheet (2) disposed at a second surface on the article, and an absorbent body (3) enclosed between the two casing sheets and including a liquid-acquisition layer (19) and, located essentially in the same plane thereas, a liquid-acquisition space (24) that comprises at least one cavity or at least one region of lower density than the liquid-acquisition layer (19) adjacent said space (24), and wherein the acquisition layer (19) includes a material which when wetted increases in size in a direction (z-direction) generally perpendicular to the first surface of said article, characterized in that the material in the acquisition layer (19) has, when wetted, relatively low expansion in a direction (xy-direction) generally parallel with the first surface of the article, such that the volume of the liquid-acquisition space (24) will increase by at least 100% when the material is wetted to saturation with a 0.9%-NaCl solution.
An absorbent article according to Claim 1, characterized in that the volume of the liquid-acquisition space (24) increases by at least 200%, preferably by at least 400% and most preferably by at least 900%.
An absorbent article according to Claim 1 or 2, characterized in that expansion of the material in the xy-direction is not greater than to result in a reduction of the area of the liquid-acquisition space (24) in the xy-direction by at most 25%, preferably at most 20% and most preferably at most 10% when wetted to saturation with a 0.9%-NaCl solution.
An absorbent article according to one or more of the preceding Claims, characterized in that the expansion of the material in the z-direction is at least 100%, preferably at least 200%, still more preferably at least 400% and most preferably at least 900% when wetted to saturation with a 0.9%-NaCl solution.
An absorbent article according to one or more of the preceding Claims, characterized in that a storage layer (23) is arranged in liquid communication with the acquisition layer (19) on that side of said acquisition layer lying proximal to the liquid-impermeable casing sheet (2).
An absorbent article according to Claim 5, characterized in that the storage layer (23) includes a material that has good liquid-retaining properties, such as cellulose fibres in combination with superabsorbent material, tissue laminates with superabsorbent material, or absorbent foam material.
An absorbent article according to Claim 5 or 6, characterized in that a liquid dispersion layer (25) is arranged in liquid communication with the acquisition layer (19), either between said acquisition layer and the storage layer (23) or between the storage layer and the liquid-impermeable casing sheet (2).
An absorbent article according to Claim 7, characterized in that the dispersion layer (18) includes a material that possesses good liquid dispersion properties, such as compressed cellulose pulp, a porous fibre mat or wadding of synthetic or natural fibres, or an open-cell foam material.
An absorbent article according to one or more of the preceding Claims, characterized by a liquid transportation layer (18) disposed between the liquid-permeable casing sheet (1) and the liquid-acquisition layer (19).
An absorbent article according to Claim 9, characterized in that the transportation layer (18) includes a material that is capable of quickly receiving liquid and releasing the liquid to underlying layers, and may consist, for instance, of a low-compressed cellulose-fluff layer of mechanical, thermomechanical or chemithermomechanical pulp (CTMP), chemically stiffened or cross-linked cellulose fibres, a fibre mat or wadding of synthetic or natural fibres, or an absorbent foam material.
An absorbent article according to one or more of the preceding Claims, characterized in that the liquid-acquisition space (24) is comprised of one or more holes that extend through at least parts of the thickness of the acquisition layer (19), or regions of lower density than the surrounding material (20, 125) in the acquisition layer (19).
An absorbent article according to one or more of Claims 1-10, characterized in that the acquisition layer (19) is comprised of at least two separate material bodies (20) that extend as pillar-like spacing devices generally perpendicularly between two further material layers (18, 23) in the article and define together with the material layers (18, 23) a coherent liquid-acquisition space (24) between the material layers (18, 23).
An absorbent article according to one or more of Claims 1-10, characterized in that the liquid-acquisition space (124) is comprised of at least one channel (124) that extends in the longitudinal direction of the article.
An absorbent article according to any one of Claims 1-10, characterized in that the acquisition layer (19) is formed by a material web that has been divided in the longitudinal direction of the web along an undulating curve that crosses at least two times a line extending in the longitudinal direction of the web; and in that the web parts are displaced relative to one another in the plane of the web, at least in the longitudinal direction of said web, whereby the web parts define therebetween said liquid-acquisition space (24) in the plane of the web.
An absorbent article according to Claim 14, characterized in that the material web is placed in the article with the undulating curve extending either in the longitudinal direction of the article or in the transverse direction thereof.
An absorbent article according to one or more of the preceding Claims, characterized in that the acquisition layer (19) is comprised of cellulose fibres of mechanical, thermomechanical, chemimechanical or chemithermomechanical pulp (CTMP) and/or chemical pulp fibres that have been chemically stiffened or cross-linked, said fibres having been formed into a web having a weight per unit area of 30-2000 g/m2, preferably 50-1500 g/m2 and more preferably 100-1000 g/m2, and compressed to a density of between 0.2-1.2 g/cm3, preferably 0.25-1.0 g/cm3 and most preferably 0.3-0.9 g/cm3.
An absorbent article according to Claim 16, characterized in that the cellulose fibres are comprised of flash-dried fibres that have been dry-formed into a web and incorporated in the article without defibration and fluff-forming.
An absorbent article according to one of Claims 16 or 17, characterized in that the acquisition layer (19) is comprised of an air-laid web of cellulose fibres that has been compressed into a dry-formed sheet that has a first density of between 0.2-1.2 g/cm3 and which has then been softened mechanically to a second density that is lower than the original density and therewith delaminated, such as to form a plurality of not fully separated thin fibre layers that have a density corresponding to the first density.
An absorbent article according to any one of the preceding Claims, characterized in that the acquisition layer (19) is comprised of a material layer having a first thickness and including resilient material, said material layer having been compressed perpendicular to a plane through the layer to a second thickness and bound in its compressed state with a binder that is dissolvable in body liquid, wherein said binding of the material layer ceases when the layer is wetted and the acquisition layer (19) returns at least partially to said first thickness.
An absorbent article according to Claim 19, characterized in that acquisition layer (19) is comprised of a compressed foam material that will expand in its thickness direction when wetted.
An absorbent article according to Claim 19, characterized in that the acquisition layer (19) is comprised of a compressed fibre layer that comprises at least partially fibres having a certain resiliency in a wet state.
An absorbent article according to one or more of the preceding Claims, characterized in that the proportion of the volume of said acquisition layer (19) that is comprised of the liquid-acquisition space (24) is greatest within the primary wetting region of the article, i.e. in the region of said article that is intended to be wetted first by body liquid.
EP19970932086 1996-06-28 1997-06-26 Absorbent bodies in absorbent articles having improved liquid acquisition properties Expired - Lifetime EP0929279B1 (en)
EP0929279A1 EP0929279A1 (en) 1999-07-21
EP0929279B1 true EP0929279B1 (en) 2002-09-04
EP19970932086 Expired - Lifetime EP0929279B1 (en) 1996-06-28 1997-06-26 Absorbent bodies in absorbent articles having improved liquid acquisition properties
DE (2) DE69715222D1 (en)
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2006-12-13 27O Opposition rejected
Expiry date: 20170625