# Patent

## Title
Absorbent structure for absorbent articles

## Abstract

Absorbent structures for diapers are provided, comprising, immobilized onto a supporting sheet, an absorbent layer with absorbent material containing superabsorbent polymer particles and therein, in the front region, a first and a second substantially longitudinal channel, each being free of said superabsorbent polymeric particles, for improved fit and/or performance throughout the use thereof.

## Background
CROSS REFERENCE TO RELATED APPLICATION
This application claims the benefit of U.S. Provisional Application Ser. No. 61/495,404, filed Jun. 10, 2011, which is herein incorporated by reference in its entirety.


FIELD
The present disclosure relates to an absorbent structure for absorbent articles such as diapers comprising an absorbent layer with absorbent material containing superabsorbent polymer particles and therein, in the front region, a first and a second substantially longitudinal channel, each being free of said superabsorbent polymeric particles, for improved fit and/or performance throughout the use thereof.
BACKGROUND
Disposable absorbent articles for receiving and retaining bodily discharges such as urine or feces are well known in the art. Examples of these include disposable diapers, training pants and adult incontinence articles. Typically, disposable diapers comprise a liquid pervious topsheet that faces the wearer's body, a liquid impervious backsheet that faces the wearer's clothing and an absorbent core interposed between the liquid pervious topsheet and the backsheet.
Since their introduction into the market place, disposable diapers have continued to improve regarding comfort, fit and functionalities.
An important component of disposable absorbent articles is the absorbent core/absorbent structure. The absorbent core/structure typically includes superabsorbent polymer material, such as hydrogel-forming polymer material, also referred to as absorbent gelling material, AGM, or super-absorbent polymer, SAP. This superabsorbent polymer material ensures that large amounts of bodily fluids, e.g. urine, can be absorbed by the absorbent article during its use and be locked away, thus providing low rewet and good skin dryness.
Traditionally, the superabsorbent polymer material is incorporated into the absorbent core structure with pulp, i.e. cellulose fibres. However, over the past years, significant effort has been spent to make thinner absorbent core structures which can still acquire and store large quantities of discharged body fluids, in particular urine. Hereto, it has been proposed to reduce or eliminate these cellulose fibres from the absorbent core structures.
In some instances, to maintain the mechanical stability of the absorbent core structures, small quantities of thermoplastic adhesive material, such as fibrous thermoplastic adhesive material, may for example be added to stabilize the absorbent polymer material. Resultantly, absorbent structures having the required permeability/porosity, reduced gel-blocking, and that form stable structures in use or transport, are provided.
However, it was found that some absorbent core structures with reduced cellulose fibre levels, whilst very thin when not loaded with bodily fluids, may have an increased stiffness when partially loaded or fully loaded, especially in those regions which comprise most of the absorbent capacity of the absorbent article, such as the front region and crotch region of the diaper. Increased stiffness is not desirable since it reduces the absorbent article's ability to conform to the body of the wearer once worn. Therefore there is still a need for absorbent articles having an increased flexibility during the whole use of the article which deliver in particular a better fit in the wet state (at equal absorbing and containing performances).
The inventors have found that by providing specific channels that are free of superabsorbent polymer particles or free of superabsorbent polymer material in front region of the absorbent core/structure, diapers of increased flexibility at equal performances are provided.
SUMMARY
The disclosure relates to an absorbent structure (17) for a diaper, comprising a supporting sheet (16) and an absorbent layer (50) of absorbent material, comprising at least a superabsorbent polymer material and optionally a cellulosic material, said absorbent layer (50) being supported by and immobilized on said supporting sheet (16); and said absorbent layer (50) having a transverse dimension and an average width W, a longitudinal dimension and average length L, and a height dimension;
and said absorbent layer (50) having first and second longitudinally extending side portions one on either side of the longitudinal axis; and said absorbent layer (50) having a front region, back region and therein between a crotch region, each arranged sequentially in said longitudinal dimension;
whereby said absorbent layer (50) has at least a first substantially longitudinally extending channel (26) and a second substantially longitudinally extending channel (26) that are substantially free of said superabsorbent polymer material and extending through the height of said absorbent layer (50), said first channel (26) being present in said first side portion's front region only and said second channel (26) being present in said second side portion's front region only, and each channel (26) has an average width W′ that is least 4% of the average width W of said absorbent layer (50), or for example W′ is at least 7% of W and/or for example and up to 25% of W, and/or for example at least 5 mm and for example up to 25 mm; optionally, said channels (26) do not extend up to any of the longitudinal side edges or a transverse front edge of said absorbent layer (50).
Said absorbent layer (50) may comprise one or more further channels (26′; 26′′) that are substantially free of superabsorbent polymer material, extending substantially in the longitudinal dimension, each further channel (26′; 26′′) have an average width W′′ of at least 4% W, for example present in at least the crotch region of said absorbent layer (50).
Said channels (26; 26′) are semi permanent or permanent, being immobilized on said supporting sheet (16). Said immobilization may be done by folding (undulating) said supporting sheet (16) into said first and second channels (26), or part thereof, and optional into said further channel(s) (26′′26′′) or part thereof, e.g. said supporting sheet (16) may have undulations into said channels (26) or part thereof. Alternatively, or in addition, the absorbent structure (17) may comprise one or more adhesive materials to immobilize said absorbent material onto said supporting sheet (16). For example, said one or more adhesive materials may include a first adhesive material (40) that is applied to said absorbent layer (50) once on said supporting sheet (16) and/or a second adhesive material (60) applied onto said supporting sheet (16), or part thereof, prior to depositing said absorbent material (formation of said absorbent layer (50)) thereon.
The disclosure also relates to an absorbent core comprising the absorbent structure (17) of the disclosure, as described herein (this being referred to as the first absorbent structure (17)) and comprising a further material present adjacent said absorbent layer (50); said further material being for example selected from: i) a further supporting sheet (16), ii) an acquisition material layer; iii) a second absorbent structure, comprising a second supporting sheet (16; 16′) and a second absorbent layer (50; 50′), whereby said second absorbent layer (50; 50′) and said absorbent layer (50) of the first structure are sandwiched between said supporting sheet (16) of the first structure and said second supporting sheet (16), optionally said second absorbent structure being as in any preceding claim. The second absorbent structure may be an absorbent structure (17) of the disclosure too; then, for example, said channels (26) of said second absorbent structure (17) may be substantially identical to said channels (26) of said first absorbent structure (17) and substantially completely overlapping therewith. The second absorbent structure may also be an absorbent structure (15) without channels, but for example comprising a supporting sheet (16′) and an absorbent layer (50′) with absorbent material as described herein, and optionally adhesive, as described herein.
The supporting sheet (16) of the first absorbent structure (17) and/or said second supporting sheet (16′) may fold (undulate) into said channels (26), or part thereof, and then one or both said supporting sheets (16; 16′) may comprise one or more adhesive material(s) (applied to said supporting sheet (16) or sheets, and/or to said absorbent layer (50)) and whereby said supporting sheets (16;16′) are adhered to one another in said channels (26) by said adhesive material (and the same may apply for any further channels (26′′26′′) if present) and/or by pressure bonding, or bonding by said adhesive to aid absorbent layer in said channels.
In some embodiments herein, a pressure is applied selectively (e.g. with a pressure means, such as a roll, with raised portions corresponding to said channels (26)), to the supporting sheet (16) material portion that correspond to said channels (26), to further fold (e.g. form undulations) said supporting sheet (16) into said channels (26), optionally said absorbent layer (50) and/or said supporting sheet (16) comprising one or more adhesive material and said pressure aids to bond said supporting sheet (16) into said channels (26)
In some embodiments, the front transverse edge zone (G) does not comprise any channels, and that this zone (G) has at least an average longitudinal dimension of from 5% to 15%, or to 10%. If there are channels (26) in the back region of the article, it may also be in some embodiments, that the back transverse edge zone (F) does not comprise any channels, and that this zone (F) has for example at least an average longitudinal dimension of from 5% to 15%, or to 10%.
In some embodiment, such as shown in FIG. 5, an acquisition material (70) may be present on said absorbent core (7) or absorbent structure (17) and be present in said channels, i.e. on said supporting sheet (16) or further supporting sheet (16′), that folds (undulates) into said channels (26).
The absorbent structure (17) or absorbent core of the disclosure has an improved fit even when having absorbed already bodily fluids, e.g. urine; the disclosure also relates to an absorbent article, such as a diaper comprising the absorbent structure (17) or absorbent core (7) as described herein.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view of a diaper core in accordance with one non-limiting embodiment.
FIG. 2A is a perspective view of an absorbent structure core in accordance with one non-limiting embodiment.
FIG. 2B is a perspective view of a further absorbent structure that can be combined with an absorbent structure core in accordance with one non-limiting embodiment.
FIG. 2C is a perspective view of an alternative absorbent structure core in accordance with one non-limiting embodiment.
FIG. 2D is a perspective view of an alternative absorbent structure core in accordance with one non-limiting embodiment.
FIGS. 3, 4 and 5 are cross sectional views of alternative absorbent cores core in accordance with non-limiting embodiments.
FIG. 6 is a schematic view of the formation of an absorbent core in accordance with one non-limiting embodiment, combining two absorbent structures core in accordance with one non-limiting embodiment.



DETAILED DESCRIPTION
Definitions
“Absorbent article” refers to a device that absorbs and contains body exudates, and, more specifically, refers to devices that are placed against or in proximity to the body of the wearer to absorb and contain the various exudates discharged from the body. Absorbent articles may include adult and infant diapers, including pants, such as infant training pants and adult incontinence undergarments, and feminine hygiene products, such as sanitary napkins and panty-liners and adult in continent pads, and breast pads, care mats, bibs, wound dressing products, and the like. Absorbent articles may further include floor cleaning articles, food industry articles, and the like. As used herein, the term “body fluids” or “body exudates” includes, but is not limited to, urine, blood, vaginal discharges, breast milk, sweat and fecal matter.
As used herein “diapers” refers to devices which are intended to be placed against the skin of a wearer to absorb and contain the various exudates discharged from the body. Diapers are generally worn by infants and incontinent persons about the lower torso so as to encircle the waist and legs of the wearer. Examples of diapers include infant or adult diapers and pant-like diapers such as training pants. “Training pant”, as used herein, refers to disposable garments having a waist opening and leg openings designed for infant or adult wearers. A pant may be placed in position on the wearer by inserting the wearer's legs into the leg openings and sliding the pant into position about a wearer's lower torso. A pant may be preformed by any suitable technique including, but not limited to, joining together portions of the article using refastenable and/or non-refastenable bonds (e.g., seam, weld, adhesive, cohesive bond, fastener, etc.). A pant may be preformed anywhere along the circumference of the article (e.g., side fastened, front waist fastened).
“Disposable” is used herein to describe articles that are generally not intended to be laundered or otherwise restored or reused (i.e., they are intended to be discarded after a single use and, may be recycled, composted or otherwise disposed of in an environmentally compatible manner).
As used herein “absorbent structure (17)” refers to a three dimensional structure useful to absorb and contain liquids, such as urine. The absorbent structure (17) may be the absorbent core of an absorbent article or may be only part of the absorbent core of an absorbent article, i.e. an absorbent component of the absorbent core, as will be further described herein.
“Superabsorbent polymer material” as used herein refers to substantially water-insoluble polymer material that can absorb at least 10 times (and typically at least 15 times or at least 20 times) its weight of a 0.9% saline solution in de-mineralized water as measured using the Centrifuge Retention Capacity test (Edana 441.2-01).
“Nonwoven material” as used herein refers to a manufactured web of directionally or randomly orientated fibers, excluding paper and products which are woven, knitted, tufted, stitch-bonded incorporating binding yarns or filaments, or felted by wet-milling, whether or not additionally needled. Nonwoven materials and processes for making them are known in the art. Generally, processes for making nonwoven materials comprise laying fibers onto a forming surface, which may comprise spunlaying, meltblowing, carding, airlaying, wetlaying, coform and combinations thereof. The fibers may be of natural or man-made origin and may be staple fibers or continuous filaments or be formed in situ.
Absorbent Structure (17)
The absorbent structure (17) herein comprises a supporting sheet (16) with an absorbent layer (50) of absorbent material. The absorbent material comprises at least a superabsorbent polymer material and optionally a cellulosic material, such as a cellulose, e.g. pulp, or modified cellulose.
The absorbent structure (17) may comprise further components such as one or more adhesive material(s) (40; 40′; 60) further described below. The absorbent layer (50) is three dimensional and comprises a first substantially longitudinal channel (26) and a second substantially longitudinal channel (26) that are substantially free of said superabsorbent polymer material. Other materials may be present in said channels (26), as further described below.
The absorbent structure (17) and the absorbent layer (50) each have a longitudinal dimension and average length L, e.g. extending in the longitudinal dimension of the structure, absorbent layer (and absorbent article) and a transverse dimension and average width W, e.g. extending in the transverse dimension. The absorbent structure (17) and the absorbent layer (50) each have a front region, being in use towards the front of the user, back region, being in use towards the back of the user, and therein between a crotch region, each extending the full transverse width of the structure/layer, and each having 1⁄3 of the average length of the structure/layer.
The absorbent structure (17) and the absorbent layer (50) each possess a central longitudinal axis, a central transverse axis perpendicular to said central longitudinal axis; said absorbent layer (50) and said absorbent structure (17) have each a pair of opposing longitudinal side edges (18) extending in the longitudinal dimension of the absorbent layer/structure and a pair of opposing transverse edges (19), e.g. front transverse edge being in use towards the front of a user (wearer), and a back transverse edge being in use towards the back of a user. The longitudinal side edges (18) and/or transverse edges (19) of the absorbent structure (17) or absorbent layer (50) may be parallel respectively to the central longitudinal axis and/or central transverse axis respectively or one or more may be curvilinear, and for instance provide for a narrower transverse dimension in the crotch region. Typically the longitudinal side edges are mirror images of one another in the longitudinal X-axis.
The central longitudinal X-axis of the absorbent layer (50) delimits first and second longitudinal portions of the absorbent layer (50), respectively, referred herein as longitudinal portions. Each of said longitudinal portions is thus present in said front region, crotch region and back region, and hence, there is a first longitudinal portion's front region, and a second longitudinal portion's front region etc. In some embodiments herein, said longitudinal portions of the absorbent layer (50) are mirror images of one another in the longitudinal axis of the layer.
The absorbent layer (50) comprises at least a first channel (26) and second channel (26) that are substantially free of (e.g. free of) said superabsorbent polymer particles, said channels (26) extending through the thickness (height) of the absorbent layer (50). (It should be understood that, accidentally, a small, negligible amount of superabsorbent polymer particles may be present in the channel, which does not contribute to the overall functionality). When the absorbent layer (50) comprises cellulosic or cellulose, optionally, said first and second channels (26) are also free of such cellulosic/cellulose material.
The first and second channels (26) are present in only said front region of the absorbent layer (50) (e.g. and of the absorbent structure (17)). Typically, the first channel (26) of the absorbent layer (50) is present in the front region of said first longitudinal portion and a second channel (26) is present in the front region of said second longitudinal region. The channels (26) act as folding lines in the absorbent structure (17); the channels (26) provide a comfortable and superior fit. This is for example shown in FIG. 2A and FIG. 6.
The first and second channel (26) each extend substantially longitudinally, which means typically that each channel (26) extends more in the longitudinal dimension than in the transverse dimension, and typically at least twice as much in the longitudinal dimension than in the transverse dimension.
Thus, this includes channels (26) that are completely longitudinal and parallel to the longitudinal direction of said absorbent layer (50) (i.e. paralleled to said X-axis); and this includes channels (26) that may be curve, provided the radius of curvature is typically at least equal to W; and this includes channels (26) that are straight but under an angle of (e.g. from 5°) up to 30°, or for example up to 20°, or up to 10°.
Each of said first and second channels (26) has an average width W′ that is least 4% of the average width W of said absorbent layer (50), or for example W′ is at least 7% of W; and/or for example and up to 25% of W, or up to 15% of W; and/or for example at least 5 mm; and for example up to 25 mm, or for example up to 15 mm.
Each of said first and second channels (26) has an average length L′ which may for example be up to 30% of the average length L of said absorbent layer (50), or for example L′ is up to 25% of L, or up to 20% of L, and/or L′ is for example at least 5% of L, or at least 10% of L ; and/or for example and up to 25% of W, or up to 15% of W; and/or L′ is for example at least 10 mm, or at least 20 mm.
The channels (26) may typically be so-called “permanent” channels (26). By permanent, it is meant that the integrity of the channels (26) is at least partially maintained both in the dry state and in the wet state, including during friction by the wearer thereon. The Wet Channel Integrity Test described below can be used to test if channels are permanent following wet saturation and to what extent.
Wet Channel Integrity Test
This test is designed to check the integrity of a channel following wet saturation. The test can be performed directly on a absorbent structure or on a absorbent core containing the absorbent structure.

    
    
        1. The length (in millimeters) of the channel is measured in the dry state (if the channel is not straight, the curvilinear length through the middle of the channel is measured).
        2. The absorbent structure or core is then immersed in 5 liters of synthetic urine “Saline”, with a concentration of 9.00 g NaCl per 1000 ml solution prepared by dissolving the appropriate amount of sodium chloride in distilled water. The temperature of the solution must be 20+/−5° C.
        3. After 1 minute in the saline, the absorbent structure or core is removed and held vertically by one end for 5 seconds to drain, then extended flat on a horizontal surface with the garment-facing side down, if this side is recognizable. If the absorbent structure or core comprises stretch elements, the absorbent structure or core is pulled taut in both X and Y dimensions so that no contraction is observed. The extremes/edges of the absorbent structure or core are fixed to the horizontal surface, so that no contraction can happen.
        4. The absorbent structure or core is covered with a suitably weighted rigid plate, with dimensions as follows: length equal to the extended length of the absorbent structure or core, and width equal to the maximum absorbent structure or core width in the cross direction.
        5. A pressure of 18.0 kPa is applied for 30 seconds over the area of the rigid plate above mentioned. Pressure is calculated on the basis of overall area encompassed by the rigid plate. Pressure is achieved by placing additional weights in the geometric center of the rigid plate, such that the combined weight of the rigid plate and the additional weights result in a pressure of 18.0 kPa over the total area of the rigid plate.
        6. After 30 seconds, the additional weights and the rigid plate are removed.
        7. Immediately afterwards, the cumulative length of the portions of the channel which remained intact is measured (in millimeters; if the channel is not straight, the curvilinear length through the middle of the channel is measured). If no portions of the channel remained intact then the channel is not permanent.
        8. The percentage of integrity of the permanent channel is calculated by dividing the cumulative length of the portions of the channel which remained intact by the length of the channel in the dry state, and then multiplying the quotient by 100.
    
    


Advantageously, a permanent channel according to the disclosure has a percentage of integrity of at least 20%, or 30%, or 40%, or 50%, or 60, or 70%, or 80%, or 90% following this test.
Permanent channels (26) are for example obtained by immobilizing the absorbent material on the supporting sheet (16), such as by applying one or more adhesive materials (e.g. first material (40;40′)) for example over the absorbent material/over the absorbent layer (50) (on the surface opposite to the surface that is on the supporting sheet (16)), after said absorbent material is deposited onto said supporting sheet (16), for example in the form of fibrous adhesive (adhesive fibers); and/or for example by applying an adhesive material (e.g. second adhesive (60)) onto said supporting material, prior to forming said absorbent layer (50) thereof, and/or by undulating the supporting sheet (16) into said channels (26) or part thereof, as further described herein below.
The absorbent cores (7) of the disclosure may comprise in particular permanent channels formed by bonding of the first supporting sheet (16) and second supporting sheet (16′) through the channels. Typically, glue may be used to bond both supporting sheets throughout the channel, but it is possible to bond via other known means, for example ultrasonic bonding, or heat bonding. The supporting layers can be continuously bonded or intermittently bonded along the channels.
Thus, an adhesive material (e.g. second (60)) may be present between said supporting sheet (16) and said absorbent layer (50). In addition, or alternatively, the absorbent structure (17) may comprise an adhesive (40; 40′) deposited over said absorbent material/absorbent layer (50), e.g. after said absorbent material is deposited on said supporting sheet (16). This is for example shown in FIGS. 3, 4 and 5.
In any such case, the absorbent material is thereby immobilized on the supporting sheet (16) and/or the folded portions supporting sheet (16), i.e. said undulations thereof, are thereby fixed into said channels (26) or part thereof, to ensure the channels (26) are maintained (at least partially) during use. For example, an adhesive material (60) may be applied to the supporting sheet (16) uniformly, or in a pattern, for example by spraying or slot coating or other techniques know in the art. For example, the adhesive material (60) may be applied on those portions of the supporting sheet (16) that are to receive to the absorbent material; then, it helps to immobilize the absorbent material thereon. Alternatively, an adhesive material (60) may be applied only on those portions of the supporting sheet (16) that are to be adjacent said channels (26), or undulating into said channels (26), to ensure the supporting sheet (16) is adhered into said channels (26) to said absorbent material or to a further material, as described herein after. This is for example shown in FIGS. 4 and 5.
The first and second channels (26) may be mirror images of one another with respect to the central longitudinal axis (X-axis) of the absorbent layer (50)/structure (17).
In some embodiment, there is no channel (26) that coincides with said longitudinal axis of said absorbent layer (50). The channels (26) may be spaced apart from one another over their whole longitudinal dimension. The smallest spacing distance D may for example be at least 5% of average the transverse dimension of the layer, or for example at least 10%, or at least 15%; or for example may for example at least 5 mm, or for example at least 8 mm.
Furthermore, in order to reduce the risk of fluid leakages, the longitudinal main channels (26) typically do not extend up to any of the transverse and/or longitudinal edges of the absorbent layer (50). For example, the smallest distance between a channel (26) and the nearest longitudinal edge of the absorbent layer (50) corresponds to at least 5% of the average transverse dimension W of the layer, or to at least 10%. In some embodiments, the distance is for example at least 10 mm. For example, the smallest distance between a channel (26) and the nearest transverse edge of the absorbent layer (50) corresponds to at least 5% of the average longitudinal dimension L of the layer, or to at least 10%. In some embodiments, the distance is for example at least 10 mm.
In addition to the above-described first and second channels (26) present in the front region only, the absorbent layer (50) (and hence absorbent structure (17)) may comprise further channels (26′; 26′′), referred herein as “further channels (26′; 26′′)”, that are substantially longitudinally and substantially free of superabsorbent polymer material. The above description of the first and second channel (26) may equally apply to any of said further channels (26′; 26′′). However, in some embodiments, the further channels (26′; 26′′) are longer than said first and second channel, for example from 40% to 90% or to 80% or to 60% of L.
For example the front region of the absorbent layer (50) may comprise one or more further channels (26′; 26′′), in addition to the first and second channels (26), and/or the central (crotch) region may comprise such one or more further channels (26′ 26′′), that may optionally extend into said front and/or back region; and/or the back region may comprise one or more of such further channels (26′; 26′′).
In some embodiments, the absorbent structure (17) comprises at least one further channel (26′) in at least said central (crotch) region, optionally extending into said front and/or back region; or for example two such further channels (26′) may be present, one on either side of the longitudinal axis, and for example, they may be mirror images of one another in said axis of the absorbent layer (50). Indeed, the inventors observed that such further channels (26) provide for fast liquid acquisition which reduces risk of leakages. The channels (26; 26′), in particular when immobilized/permanent channels, avoid saturation of the absorbent layer (50) in the region of fluid discharge (such saturation increases the risk of leakages). This is for example shown in FIGS. 2C and 2D.
Furthermore, the inventors surprisingly, and in contrast to what would be expected, found that whilst decreasing the overall amount of superabsorbent polymer material in the absorbent structure (17) (by providing channels (26) free of such material), the fluid handling properties of the absorbent structure (17), or diaper, are improved.
In some embodiments, the front region comprises said first and second channel (26) and two further channels (26′; 26′′) one on either side of the longitudinal axis; and/or for example one further channel being parallel to the first channel (26) and a second further channel (26) parallel to said second channel.
To avoid liquid-transport to the transverse edges (19), the absorbent structure (17) and layer is typically free of completely or substantially transverse channels (26).
In some embodiments, the smallest transverse distance D between said two channels (26) is at least 5% of W, at least 10% W.
The first and second channels (26), and optionally further channels (26′; 26′′), may be positioned in said absorbent layer (50) such that there is a central longitudinal strip with a certain minimum width (D; D′), coinciding with said longitudinal axis, which is free of any channels (26); said absorbent material is optionally substantially continuously present in said strip. For example, said strip may have a minimum width (D; D′) of at least 5% of W, or at least 10% of W, and/or for example at least 5 mm, or at least 10 mm or at least 15 mm, and/or even up to 40 mm. In some embodiments, adjacent each first and second channel, and optionally adjacent said further channel(s) (26′; 26′′), said absorbent material is substantially continuously present.
In some embodiments, the front transverse edge zone (G) does not comprise any channels, and that this zone (G) has at least an average longitudinal dimension of from 5% to 15%, or to 10%. If there are channels (26) in the back region of the article, it may also be in some embodiments, that the back transverse edge zone (F) does not comprise any channels, and that this zone (F) has for example at least an average longitudinal dimension of from 5% to 15%, or to 10%.
In some embodiments, in said central longitudinal strip between said first and second channels (26) the average basis weight of absorbent material, or of said superabsorbent polymer material, is at least 350, and for example up to 1000 grams per m2, or for example from 450 grams per m2, and for example up to 750 grams per m2.
The absorbent structure (17) typically comprises a further material (e.g. a further material layer) to cover the absorbent layer (50), herein referred to as further material. This may herein be referred to as absorbent core (7). This is for example shown in FIGS. 3, 4, and 5 and 6.
The further material may comprise, on the surface to be placed adjacent said absorbent layer (50) of the absorbent structure (17), a further adhesive material (40′).
This further material may be a further absorbent structure (17), with a second absorbent material layer and a second supporting sheet (16), so that both absorbent layers (50;50′) are sandwiched between said supporting sheets (16); this may be a further absorbent structure (17) of the disclosure, with two or more channels (26) as described herein. The channels (26) of the first absorbent structure (17) and second absorbent structure (17) may then coincide and overlap with one another, e.g. completely or for example coincide only partially and overlap only partially, or they may even not coincide and not overlap one another. In some embodiments they are about identical to one another and the channels (26) of one structure substantially completely coincide and overlap the channels (26) of another structure. This is for example shown in FIG. 6.
In some embodiments, the further material is a part of the supporting sheet (16), which is folded over the absorbent layer (50) and then sealed along the peripheral edges, to enclose the absorbent layer (50).
In some embodiments, the absorbent structure (17) is covered with a further supporting sheet (16), or a further absorbent structure not having channels, as for example shown in FIGS. 3, 4 and 5.
In some embodiments the further material may be an acquisition material layer, or acquisition sheet, for example sealed to said supporting sheet (16). In some embodiment, such as shown in FIG. 5, an acquisition material (70) may be present on said absorbent core (7) or absorbent structure (17) and be present in said channels, e.g. on said supporting sheet (16) or further supporting sheet (16′), that folds (undulates) into said channels (26).
In any of these cases, the folded supporting sheet (16) or said two supporting sheets (16) can then be sealed to one another along the peripheral edges, to enclose the absorbent layer(s) (50).
In any of these cases the supporting sheet (16) or acquisition layer/sheet may fold into (i.e. undulate into) said channels (26) or part thereof. It may be adhered to the supporting sheet (16) of the absorbent structure (17) of the disclosure in said channels (26), e.g. by an adhesive material, as described herein.
In some embodiments the absorbent structure (17) comprises such a further material overlaying said absorbent layer (50), and a pressure means is applied selectively to said supporting sheet (16) or to said further material, in those parts that coincide with said channels (26), to pressurize said supporting sheet (16) and/or said further material into said channels (26), to aid formulation of said undulations and/or to aid adhering of the further material and said supporting sheet (16) to one another in said channels (26), if an adhesive material is present as described herein.
The pressure means may be a pressure roll with raised portions that have substantially the size, shape, pattern of said channels (26), that can coincide (i.e.: mate) with said parts of the supporting sheet (16) or further material coinciding with said channels (26).
In some embodiments, second supporting sheet (16) may be wider than the absorbent layer (50)/structure to enable the second supporting sheet (16) to fold into the channels (26) and thereby may adhere to the first supporting sheet (16).
In embodiments wherein the absorbent core (7) comprises two (or more) absorbent structures (17) comprising the channels (26), described herein, it may be that one or two, or more, or all, of the channels (26) of one absorbent structure (17) substantially superpose the channels (26) of the adjacent absorbent structure (17). The resulting absorbent core (7) is a laminate of absorbent structures with channels (26), wherein the channels (26) extend substantially through the thickness of the absorbent layers (50).
In addition or alternatively, it may be that one or two, or more, or all, channels (26) of one absorbent structure (17) do not superpose the channels (26) of the adjacent absorbent structure (17); they may for example be complementary with the channels (26) of the adjacent structure. By complementary it is meant that the channels (26) of the second absorbent structure (17) form an extension of the channels (26) of the first absorbent structure (17).
In some embodiments, the absorbent core (7) may comprise two or more absorbent structures, one of which being the structure (17) of the disclosure, and one being a absorbent structure (15) with a supporting sheet (16′) with thereon an absorbent layer (50) (with superabsorbent polymer material) without channels (26), such as for example shown in FIG. 2B, and FIGS. 3, 4 and 5. Such a second absorbent structure (15) may have any of the supporting sheets, absorbent material and adhesive materials as described herein.
Absorbent Material
The absorbent layer comprises absorbent material that comprises superabsorbent polymer material (e.g. particles), optionally combined with cellulosic material (including for example cellulose, comminuted wood pulp in the form of fibers). If the further material described herein above comprises an absorbent material, the following is also applicable thereto.
In some embodiment, the absorbent material may comprise at least 60%, or at least 70% by weight of superabsorbent polymer material, and at the most 40% or at the most 30% of cellulosic material.
In some other embodiments, the absorbent layer (50) comprises absorbent material that consists substantially of absorbent polymer material, e.g. particles, e.g. less than 5% by weight (of the absorbent material) of cellulosic material is present; and said absorbent layer (50)/absorbent structure (17), may be free of cellulosic material.
Typically, the superabsorbent polymer material is in the form of particles. Suitable for use in the absorbent layer (50) can comprise any superabsorbent polymer particles known from superabsorbent literature, for example such as described in Modern Superabsorbent Polymer Technology, F. L. Buchholz, A. T. Graham, Wiley 1998. The absorbent polymer particles may be spherical, spherical-like or irregular shaped particles, such as Vienna-sausage shaped particles, or ellipsoid shaped particles of the kind typically obtained from inverse phase suspension polymerizations. The particles can also be optionally agglomerated at least to some extent to form larger irregular particles.
In some embodiments herein, the absorbent material as a whole and/or said particulate superabsorbent polymer material at least, has a high sorption capacity, e.g. having a CRC of for example at least 20 g/g, or at 30 g/g. Upper limits may for example be up to 150 g/g, or up to 100 g/g.
In some embodiments herein, the absorbent material comprising or consisting of superabsorbent polymer particles that are formed from polyacrylic acid polymers/polyacrylate polymers, for example having a neutralization degree of from 60% to 90%, or about 75%, having for example sodium counter ions.
The superabsorbent polymer may be polyacrylates and polyacrylic acid polymers that are internally and/or surface cross-linked. Suitable material are described in the PCT Patent Application WO 07/047598 or for example WO 07/046052 or for example WO2009/155265 and WO2009/155264. In some embodiments, suitable superabsorbent polymer particles may be obtained by current state of the art production processes as is more particularly as described in WO 2006/083584. The superabsorbent polymers may be internally cross-linked, i.e. the polymerization is carried out in the presence of compounds having two or more polymerizable groups which can be free-radically copolymerized into the polymer network. Useful crosslinkers include for example ethylene glycol dimethacrylate, diethylene glycol diacrylate, allyl methacrylate, trimethylolpropane triacrylate, triallylamine, tetraallyloxyethane as described in EP-A 530 438, di- and triacrylates as described in EP-A 547 847, EP-A 559 476, EP-A 632 068, WO 93/21237, WO 03/104299, WO 03/104300, WO 03/104301 and in DE-A 103 31 450, mixed acrylates which, as well as acrylate groups, include further ethylenically unsaturated groups, as described in DE-A 103 31 456 and DE-A 103 55 401, or crosslinker mixtures as described for example in DE-A 195 43 368, DE-A 196 46 484, WO 90/15830 and WO 02/32962 as well as cross-linkers described in WO2009/155265. The superabsorbent polymer particles may be externally surface cross-linked, or: post cross-linked). Useful post-crosslinkers include compounds including two or more groups capable of forming covalent bonds with the carboxylate groups of the polymers. Useful compounds include for example alkoxysilyl compounds, polyaziridines, polyamines, polyamidoamines, di- or polyglycidyl compounds as described in EP-A 083 022, EP-A 543 303 and EP-A 937 736, polyhydric alcohols as described in DE-C 33 14 019, cyclic carbonates as described in DE-A 40 20 780, 2-oxazolidone and its derivatives, such as N-(2-hydroxyethyl)-2-oxazolidone as described in DE-A 198 07 502, bis- and poly-2-oxazolidones as described in DE-A 198 07 992, 2-oxotetrahydro-1,3-oxazine and its derivatives as described in DE-A 198 54 573, N-acyl-2-oxazolidones as described in DE-A 198 54 574, cyclic ureas as described in DE-A 102 04 937, bicyclic amide acetals as described in DE-A 103 34 584, oxetane and cyclic ureas as described in EP-A 1 199 327 and morpholine-2,3-dione and its derivatives as described in WO 03/031482.
The superabsorbent polymers or particles thereof may have surface modifications, such as being coated or partially coated with a coating agent. Examples of coated absorbent polymer particles are disclosed in WO2009/155265. The coating agent may be such that it renders the absorbent polymer particles more hydrophilic. For example, it may be hydrophilic (i>e. fumed) silica, such as Aerosils. The coating agent may be a polymer, such as an elastic polymer or a film-forming polymer or an elastic film-forming polymer, which forms an elastomeric (elastic) film coating on the particle. The coating may be a homogeneous and/or uniform coating on the surface of the absorbent polymer particles. The coating agent may be applied at a level of from 0.1% to 5%.
The superabsorbent polymer particles may have a particle sizes in the range from 45 μm to 4000 μm, more specifically a particle size distribution within the range of from 45 μm to about 2000 μm, or from about 100 μm to about 1000 or to 850 μm. The particle size distribution of a material in particulate form can be determined as it is known in the art, for example by means of dry sieve analysis (EDANA 420.02 “Particle Size distribution).
In some embodiments herein, the superabsorbent material is in the form of particles with a mass medium particle size up to 2 mm, or between 50 microns and 2 mm or to 1 mm, or from 100 or 200 or 300 or 400 or 500 μm, or to 1000 or to 800 or to 700 μm; as can for example be measured by the method set out in for example EP-A-0691133. In some embodiments of the disclosure, the superabsorbent polymer material is in the form of particles whereof at least 80% by weight are particles of a size between 50 μm and 1200 μm and having a mass median particle size between any of the range combinations above. In addition, or in another embodiment of the disclosure, said particles are essentially spherical. In yet another or additional embodiment of the disclosure the superabsorbent polymer material has a relatively narrow range of particle sizes, e.g. with the majority (e.g. at least 80% or at least 90% or even at least 95% by weight) of particles having a particle size between 50 μm and 1000 μm, between 100 μm and 800 μm, between 200 μm and 600 μm.
Supporting Sheet
The absorbent structure (17) herein comprises a supporting sheet (16) on which said absorbent material is supported and immobilized. If a further material is present in the absorbent core, and this is or includes a supporting sheet (16′), the following is also applicable thereto.
The supporting sheet may be an individual sheet or a web material that is subsequently divided in to individual absorbent structures, in particular paper, films, wovens or nonwovens, or laminate of any of these.
In some embodiments herein, the supporting sheet is a nonwoven, e.g. a nonwoven web, such as a carded nonwoven, spunbond nonwoven or meltblown nonwoven, and including nonwoven laminates of any of these.
The fibers may be of natural or man-made origin and may be staple or continuous filaments or be formed in situ. Commercially available fibers have diameters ranging typically from less than about 0.001 mm to more than about 0.2 mm and they come in several different forms: short fibers (known as staple, or chopped), continuous single fibers (filaments or monofilaments), untwisted bundles of continuous filaments (tow), and twisted bundles of continuous filaments (yarn). The fibers may be bicomponent fibers, for example having a sheet-core arrangement, e.g. with different polymers forming the sheet and the core. Nonwoven fabrics can be formed by many processes such as meltblowing, spunbonding, solvent spinning, electrospinning, and carding. The basis weight of nonwoven fabrics is usually expressed in grams per square meter (gsm).
The nonwoven herein may be made of hydrophilic fibers; “Hydrophilic” describes fibers or surfaces of fibers, which are wettable by aqueous fluids (e.g. aqueous body fluids) deposited on these fibers. Hydrophilicity and wettability are typically defined in terms of contact angle and the strike through time of the fluids, for example through a nonwoven fabric. This is discussed in detail in the American Chemical Society publication entitled “Contact angle, wettability and adhesion”, edited by Robert F. Gould (Copyright 1964). A fiber or surface of a fiber is said to be wetted by a fluid (i.e. hydrophilic) when either the contact angle between the fluid and the fiber, or its surface, is less than 90°, or when the fluid tends to spread spontaneously across the surface of the fiber, both conditions are normally co-existing. Conversely, a fiber or surface of the fiber is considered to be hydrophobic if the contact angle is greater than 90° and the fluid does not spread spontaneously across the surface of the fiber.
The supporting sheet (16) herein may be air-permeable. Films useful herein may therefore comprise micro pores. Nonwovens herein may for example be air permeable. The supporting sheet (16) may have for example an air-permeability of from 40 or from 50, to 300 or to 200 m3/(m2×min), as determined by EDANA method 140-1-99 (125 Pa, 38.3 cm2). The supporting sheet (16) may alternatively have a lower air-permeability, e.g. being non-air-permeable, to for example be better detained on a moving surface comprising vacuum.
In some executions, the supporting sheet (16) is a nonwoven laminate material, a nonwoven laminate web, for example of the SMS or SMMS type.
In order to form easily said undulations, the supporting sheet (16) may have a basis weight that is less than 60 gsm, or for example than 50 gsm, for example from 5 gsm to 40 gsm, or to 30 gsm.
The supporting sheet (16) may have a CD-extensibility or a MD-extensibility.
In one of the embodiment herein, the supporting sheet (16) has undulations that fold (undulate) into said first and second channels (26), and optionally in to said further channel(s) (26′: 26′′), of part thereof. For example the undulations may extend over about the full longitudinal dimension of the channel; they may for example extend to complete average height of the absorbent layer (50)/channel, or for example only up to 75% thereof, or up to 50% of the average height of the absorbent layer (50)/channel. This aids immobilization of the absorbent material adjacent said channels (26) and said channels (26) of said layers.
Adhesive Material
The absorbent structure, and/or a further absorbent structure if present, may comprise one or more adhesive material (40; 60; 40′). Any suitable adhesive can be used for this, for example so-called hotmelt adhesives used. For example, a sprayable hot melt adhesives, such as H.B. Fuller Co. (St. Paul, Minn.) Product No. HL-1620-B, can be used, or for example HB Fuller's HL1358LO.
Immobilization may be achieved by applying a thermoplastic adhesive material (40;60;40′) which holds and immobilizes the absorbent material on the supporting sheet (16). The thermoplastic adhesive material may also be present in said channels (26) and on said supporting sheet (16) present in said channel, e.g. undulation(s). This may be herein referred to as a first adhesive material (40).
The thermoplastic adhesive material may not only help in immobilizing the absorbent polymer particles on the supporting sheet (16) but it may also helps in maintaining the integrity of the channels (26) in the absorbent structure (17)/absorbent core (7) during storage and/or during use of the disposable article. The thermoplastic adhesive material may help to avoid that a significant amount of material migrates into the channels (26). Furthermore, when the thermoplastic adhesive material is applied over the absorbent layer (50) including the channels (26), it may thereby help to adhere the supporting sheet (16) of the absorbent structure (17) to a further material, as will be described in further details below.
In some embodiments, the thermoplastic adhesive material may be applied as a fibrous layer forming a fibrous network that immobilizes the absorbent material on the supporting sheet (16). The thermoplastic adhesive fibrous layer may be partially in contact with the supporting sheet (16) of the absorbent structure (17).
The thermoplastic adhesive material may allow for such swelling, without breaking and without imparting too many compressive forces, which would restrain the absorbent polymer particles from swelling.
Thermoplastic adhesive materials suitable for use in the present disclosure includes hot melt adhesives comprising at least a thermoplastic polymer in combination with a plasticizer and other thermoplastic diluents such as tackifying resins and additives such as antioxidants. Exemplary suitable hot melt adhesive materials are described in EP 1447067 A2. In some embodiments, the thermoplastic polymer has a molecular weight (Mw) of more than 10,000 and a glass transition temperature (Tg) below room temperature or −6° C.>Tg<16° C. In certain embodiments, the concentrations of the polymer in a hot melt are in the range of about 20 to about 40% by weight. In certain embodiments, thermoplastic polymers may be water insensitive. Exemplary polymers are (styrenic) block copolymers including A-B-A triblock structures, A-B diblock structures and (A-B)n radial block copolymer structures wherein the A blocks are non-elastomeric polymer blocks, typically comprising polystyrene, and the B blocks are unsaturated conjugated diene or (partly) hydrogenated versions of such. The B block is typically isoprene, butadiene, ethylene/butylene (hydrogenated butadiene), ethylene/propylene (hydrogenated isoprene), and mixtures thereof.
Other suitable thermoplastic polymers that may be employed are metallocene polyolefins, which are ethylene polymers prepared using single-site or metallocene catalysts. Therein, at least one comonomer can be polymerized with ethylene to make a copolymer, terpolymer or higher order polymer. Also applicable are amorphous polyolefins or amorphous polyalphaolefins (APAO) which are homopolymers, copolymers or terpolymers of C2 to C8 alpha olefins.
The thermoplastic adhesive material applied over or on the absorbent layer (40; 40′) is generally present in the form of fibres, i.e. the adhesive can be fiberized. In some embodiments, the thermoplastic adhesive material forms a fibrous network over the absorbent polymer particles. Typically, the fibres can have an average thickness from about 1 μm to about 100 μm, or from about 25 μm to about 75 μm, and an average length from about 5 mm to about 50 cm. In particular the layer of hot melt adhesive material can be provided such as to comprise a net-like structure. In certain embodiments the thermoplastic adhesive material is applied at an amount of from 0.5 to 30 g/m2, or from 1 to 15 g/m2, or from 1 and 10 g/m2 or even from 1.5 and 5 g/m2 per supporting sheet (16).
A typical parameter for an adhesive suitable for use in the present disclosure can be a loss angle tan Delta at 60° C. of below the value of 1, or below the value of 0.5. The loss angle tan Delta at 60° C. is correlated with the liquid character of an adhesive at elevated ambient temperatures. The lower tan Delta, the more an adhesive behaves like a solid rather than a liquid, i.e. the lower its tendency to flow or to migrate and the lower the tendency of an adhesive superstructure as described herein to deteriorate or even to collapse over time. This value is hence particularly important if the absorbent article is used in a hot climate.
It may be beneficial, e.g. for process reasons and/or performance reasons, that the thermoplastic adhesive material has a viscosity of between 800 and 4000 mPa·s, or from 1000 mPa·s or 1200 mPa·s or from 1600 mPa·s to 3200 mPa·s or to 3000 mPa·s or to 2800 mPa·s or to 2500 mPa·s, at 175° C., as measurable by ASTM D3236-88, using spindle 27, 20 pmp, 20 minutes preheating at the temperature, and stirring for 10 min.
The thermoplastic adhesive material may have a softening point of between 60° C. and 150° C., or between 75° C. and 135° C., or between 90° C. and 130° C., or between 100° C. and 115° C., as can be determined with ASTM E28-99 (Herzog method; using glycerine).
In one embodiment herein, the thermoplastic adhesive component may be hydrophilic, having a contact angle of less than 90°, or less than 80° or less than 75° or less than 70°, as measurable with ASTM D 5725-99.
Absorbent Articles and Diapers (1)
The absorbent structure (17) or absorbent core (7) herein may be useful in an absorbent article, for example such as a diaper (1), as for example shown in FIG. 1, including fastenable diapers and (refastenable) training pants, for infants or for adults; or such as incontinence undergarments and the like.
The article, e.g. diaper (1), may comprise in addition to the absorbent structure (17) or absorbent core (7) herein, a topsheet and backsheet, and for example one or more side flaps or cuffs. The topsheet or cuffs or side flaps may comprise a skin care composition or lotion or powder, known in the art, panels, including those described in U.S. Pat. Nos. 5,607,760; 5,609,587; 5,635,191; 5,643,588.
Diapers (1) herein may comprise a topsheet, facing the wearer in use, for example a nonwoven sheet, and/or an apertured sheet, including apertured formed films, as known in the art, and a backsheet.
The backsheet may be liquid impervious, as known in the art. In some embodiments, the liquid impervious backsheet comprises a thin plastic film such as a thermoplastic film having a thickness of about 0.01 mm to about 0.05 mm. Suitable backsheet materials comprise typically breathable material, which permit vapors to escape from the diaper (1) while still preventing exudates from passing through the backsheet. Suitable backsheet films include those manufactured by Tredegar Industries Inc. of Terre Haute, Ind. and sold under the trade names X15306, X10962 and X10964.
The backsheet, or any portion thereof, may be elastically extendable in one or more directions. The backsheet may be attached or joined to a topsheet, the absorbent structure (17) or absorbent core (7), or any other element of the diaper (1) by any attachment means known in the art.
Diapers herein may comprise leg cuffs and/or barrier cuffs (10); the article then typically has a pair of opposing side flaps and/or leg and/or barrier cuffs, each of a pair being positioned adjacent one longitudinal side of the absorbent core (7) or structure (17), and extending longitudinally along said structure or core, and typically being mirror images of one another in the Y-axis (in MD) of the article; if leg cuffs and barrier cuffs are present, then each leg cuffs is typically positioned outwardly from a barrier cuff. The cuffs may be extending longitudinally along at least 70% of the length of the article. The cuff(s) may have a free longitudinal edge that can be positioned out of the X-Y plane (longitudinal/transverse directions) of the article, i.e. in z-direction. The side flaps or cuffs of a pair may be mirror images of one another in the Y-axis (longitudinal axis; MD axis) of the article. The cuffs may comprise elastic material (11).
The diapers herein may comprise a waistband, or for example a front waistband and back waist band, which may comprise elastic material. The diaper (1) may comprise fasteners (8) and landing zone therefor (9).
The diaper (1) may comprise side panels, or so-called ear panels. The diaper (1) may comprise fastening means, to fasten the front and back, e.g. the front and back waistband. Fastening systems may comprise fastening tabs and landing zones, wherein the fastening tabs are attached or joined to the back region of the diaper (1) and the landing zones are part of the front region of the diaper (1).
The absorbent structure may be combined with, and the absorbent core (7) and absorbent article, (e.g. diaper (1)) may comprise, an acquisition layer/acquisition material layer (70), or system thereof this may comprise chemically cross-linked cellulosic fibers. Such cross-linked cellulosic fibers may have desirable absorbency properties. Exemplary chemically cross-linked cellulosic fibers are disclosed in U.S. Pat. No. 5,137,537. In certain embodiments, the chemically cross-linked cellulosic fibers are cross-linked with between about 0.5 mole % and about 10.0 mole % of a C2 to C9 polycarboxylic cross-linking agent or between about 1.5 mole % and about 6.0 mole % of a C2 to C9 polycarboxylic cross-linking agent based on glucose unit. Citric acid is an exemplary cross-linking agent. In other embodiments, polyacrylic acids may be used. Further, according to certain embodiments, the cross-linked cellulosic fibers have a water retention value of about 25 to about 60, or about 28 to about 50, or about 30 to about 45. A method for determining water retention value is disclosed in U.S. Pat. No. 5,137,537. According to certain embodiments, the cross-linked cellulosic fibers may be crimped, twisted, or curled, or a combination thereof including crimped, twisted, and curled.
In a certain embodiment, one or both of the upper and lower acquisition layers may comprise a non-woven, which may be hydrophilic. Further, according to a certain embodiment, one or both of the upper and lower acquisition layers may comprise the chemically cross-linked cellulosic fibers, which may or may not form part of a nonwoven material. According to an exemplary embodiment, the upper acquisition layer may comprise a nonwoven, without the cross-linked cellulosic fibers, and the lower acquisition layer may comprise the chemically cross-linked cellulosic fibers. Further, according to an embodiment, the lower acquisition layer may comprise the chemically cross-linked cellulosic fibers mixed with other fibers such as natural or synthetic polymeric fibers. According to exemplary embodiments, such other natural or synthetic polymeric fibers may include high surface area fibers, thermoplastic binding fibers, polyethylene fibers, polypropylene fibers, PET fibers, rayon fibers, lyocell fibers, and mixtures thereof. Suitable non-woven materials for the upper and lower acquisition layers include, but are not limited to SMS material, comprising a spunbonded, a melt-blown and a further spunbonded layer. In certain embodiments, permanently hydrophilic non-wovens, and in particular, nonwovens with durably hydrophilic coatings are desirable. Another suitable embodiment comprises a SMMS-structure. In certain embodiments, the non-wovens are porous.
The diaper (1) may include a sub-layer disposed between the topsheet and the absorbent layer (17) or absorbent core (7), capable of accepting, and distributing and/or immobilizing bodily exudates. Suitable sublayers include acquisition layers, surge layers and or fecal material storage layers, as known in the art. Suitable materials for use as the sub-layer may include large cell open foams, macro-porous compression resistant non woven highlofts, large size particulate forms of open and closed cell foams (macro and/or microporous), highloft non-wovens, polyolefin, polystyrene, polyurethane foams or particles, structures comprising a multiplicity of vertically oriented, looped, strands of fibers, or apertured formed films, as described above with respect to the genital coversheet. (As used herein, the term “microporous” refers to materials that are capable of transporting fluids by capillary action, but having a mean pore size of more than 50 microns. The term “macroporous” refers to materials having pores too large to effect capillary transport of fluid, generally having pores greater than about 0.5 mm (mean) in diameter and more specifically, having pores greater than about 1.0 mm (mean) in diameter, but typically less than 10 mm or even less than 6 mm (mean).
Processes for assembling the diaper (1) include conventional techniques known in the art for constructing and configuring disposable absorbent articles. For example, the backsheet and/or the topsheet can be joined to the absorbent structure (17) or absorbent core (7) or to each other by a uniform continuous layer of adhesive, a patterned layer of adhesive, or an array of separate lines, spirals, or spots of adhesive. Adhesives which have been found to be satisfactory are manufactured by H. B. Fuller Company of St. Paul, Minn. under the designation HL-1258 or H-2031. While the topsheet, the backsheet, and the absorbent core (7) may be assembled in a variety of well-known configurations, some diaper (1) configurations are described generally in U.S. Pat. No. 5,554,145 entitled “Absorbent Article With Multiple Zone Structural Elastic-Like Film Web Extensible Waist Feature” issued to Roe et al. on Sep. 10, 1996; U.S. Pat. No. 5,569,234 entitled “Disposable Pull-On Pant” issued to Buell et al. on Oct. 29, 1996; and U.S. Pat. No. 6,004,306 entitled “Absorbent Article With Multi-Directional Extensible Side Panels” issued to Robles et al. on Dec. 21, 1999.
Method of Making the Absorbent Structure
The absorbent structure herein may be made by any method comprising the step of depositing absorbent material onto a supporting sheet (16), for example by pacing first said supporting sheet (16) onto raised portions in the shape and dimensions of said channels (26) to be produced and then depositing said absorbent material thereon; thereby, the absorbent material does not remain onto said raised portions, but only on the remaining portions of the supporting sheet (16).
In some embodiments, the absorbent structure (17) with the absorbent layer (50) with therein two or more channels (26) with substantially no absorbent material is for example obtainable by a method comprising the steps of:

    
    
        a) providing a feeder for feeding said absorbent material to a first moving endless surface, such as a hopper;
        b) providing a transfer means for transferring a supporting sheet (16) to a second moving endless surface;
        c) providing a first moving endless surface, having one or more absorbent layer (50)-forming reservoirs with a longitudinal dimension and averaged length, a perpendicular transverse dimension and average width, and, perpendicular to both, a depth dimension and average depth, and a void volume for receiving said absorbent material therein, said reservoir(s) comprising in the front region thereof one or more substantially longitudinally extending raised strips, not having a void volume, for example each having an average width W of at least 4% or at least 5% of the average width of the reservoir, and an average length L of at least 5% and at the most 30% of the average longitudinal dimension of the reservoir; said reservoir(s) being for transferring said absorbent material to said second moving endless surface adjacent and in proximity thereto
        d) providing a second moving surface, having an outer shell that has one or more air permeable or partially air permeable receptacles with for receiving said supporting sheet (16) thereon or therein, with a receiving area and with one or more substantially longitudinally extending mating strips that may be air impermeable, and having each an average width of for example W′ of at least 2.5 mm, from 0.5×W to 1.2×W, an average length of for example L′ being from about 0.8×L to 1.2×L;
    
    


whereby said air-permeable outer shell is connected to one or more secondary vacuum systems for facilitating retention of supporting sheet (16) and/or said absorbent material thereon, and
whereby, in a meeting point, said first moving endless surface and said outer shell are at least partially adjacent to one another and in close proximity of one another during transfer of said absorbent material and such that each mating strip is substantially completely adjacent and in close proximity to a raised strip during transfer of said absorbent material;

    
    
        d) feeding with said feeder an absorbent material to said first moving endless surface, in at least said reservoir(s) thereof;
        e) optionally, removing any absorbent material on said raised strips (s);
        f) simultaneously, transferring said supporting sheet (16) to said second moving endless surface, onto or into said receptacle(s);
        g) selectively transferring in said meeting point, said absorbent material with said first moving endless surface only to said part of the supporting sheet (16) that is on or in said receiving area of said receptacle.
    
    


Said reservoir(s) may be formed by of a multitude of grooves and/or cavities with a void volume, for receiving said absorbent material therein. In some embodiments, the average width W of (each) strip may be at least 6 mm, or for example at least 7 mm, and/or at least at least 7%, or for example at least 10% of the average width of the respective reservoir.
Said grooves and/or cavities may each for example have a maximum dimension in transverse direction which is at least 3 mm, and whereby the shortest distance between directly neighboring cavities and/or grooves in substantially transverse dimension, is less than 5 mm. Cavities and/or grooves that are directly adjacent a raised strip may have a volume that is more than the volume of one or more, or all of their neighboring cavities or grooves, that are not directly adjacent said strip or another strip (thus further removed from a strip).
Said first moving endless surface's reservoir may be at least partially air permeable and said first moving endless surface may have a cylindrical surface with said reservoirs, rotatably moving around a stator, comprising a vacuum chamber; said second moving surface's outershell may be cylindrical, rotatably moving around a stator, comprising a secondary vacuum chamber connected to said secondary vacuum system.
The method may be to produce an absorbent core (7) that comprises two or more of the above described absorbent structures; for example two such layers, superposed on one another such that the absorbent material of a first layer and the absorbent material of the other second layer are adjacent one another and sandwiched between the supporting sheet (16) of the first layer and the supporting sheet (16) of the second layer.
The method may comprise the addition a step i):
i) 1) applying an adhesive material (i.e. a first adhesive material (40)) to said absorbent structure (17) produced in step g); and/or
i) 2) applying an adhesive material (i.e. a second adhesive material (60)) to said supporting sheet (16;16′), prior or step f, or simultaneously therewith, but in any event prior to step h).
Step i) 1) may involve spraying said first adhesive material in the form of fibers onto said absorbent layer, or part thereof, for example substantially continuously, so it is also present in said channels (26).
Step i) 2) may involve slot coating or spray-coating the supporting sheet (16; 16′), either continuously, or for example in a pattern corresponding to the channel pattern (26).
The method may involve the provision of a pressure means, such as a pressure roll, that can apply pressure onto the absorbent structure (17), and typically an absorbent structure (17) whereby the absorbent material is sandwiched between the supporting sheet (16) a further material; the pressure may be applied onto said supporting sheet (16) or on any of the further material/layer that placed over the absorbent layer (50), as described above in this section. This pressure application may be done to selectively apply pressure only onto the channels (26) of the absorbent structure (17), e.g. on the portions of the supporting sheet (16) that correspond to the channels (26), and that thus not comprise (on the opposed surface) absorbent material, to avoid compaction of said absorbent material itself. Thus, the pressure means that has a raised pressuring pattern corresponding to said pattern of the raised strip(s) and/or of said mating strip(s), in some corresponding to the pattern of the mating strip(s).
The method may comprise the step of applying an adhesive material (e.g. a second adhesive material 60)) onto the supporting sheet (16) or part thereof prior to deposition of the absorbent material/formation of said absorbent layer (50), and/or applying an adhesive material (40;40′) onto said absorbent layer (50), after deposition. Formation thereof on said supporting sheet (16).
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”
Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

## Claims

1. An absorbent structure for an absorbent article, comprising a longitudinal axis, a supporting sheet and an absorbent layer of absorbent material, comprising a superabsorbent polymer material and a cellulosic material, said absorbent layer being supported by and immobilized on said supporting sheet; and said absorbent layer having a transverse dimension and an average width W, a longitudinal dimension and average length L, and a height dimension;
and said absorbent layer having a first longitudinally extending side portion on one side of said longitudinal axis and a second longitudinally extending side portions on the other side of the longitudinal axis; and said absorbent layer having a front region, back region and therein between a crotch region, each arranged sequentially in said longitudinal dimension;
wherein said absorbent layer has at least a first continuous, substantially longitudinally extending channel and a second continuous, substantially longitudinally extending channel that are substantially free of said superabsorbent polymer material and extending through the height of said absorbent layer, said first channel being present in said first side portion's front region only and said second channel being present in said second side portion's front region only, and each channel having an average width W′ that is least about 4% of the average width W of said absorbent layer and an average length L′ that is up to 25% of the average length L of said absorbent layer and at least 10 mm; and
wherein said supporting sheet folds into said first and second channels.

2. The absorbent structure of claim 1, wherein said absorbent layer has longitudinal side edges and a transverse front edge and a transverse back edge, and said channels do not extend up to any of the longitudinal side edges or a transverse front edge of said absorbent layer.

3. The absorbent structure of claim 1, wherein said W′ is from about 7% to about 25% of W.

4. The absorbent structure of claim 1, wherein said absorbent layer comprises one or more further channels that are substantially free of superabsorbent polymer material, extending substantially in the longitudinal dimension, each further channel having an average width W′′ of at least about 4% W.

5. The absorbent structure of claim 4, wherein said one or more further channels are present in at least the crotch region of said absorbent layer.

6. The absorbent structure of claim 1, further comprising one or more adhesive materials to immobilize said absorbent material onto said supporting sheet.

7. The absorbent structure of claim 6, wherein said one or more adhesive materials includes a first adhesive material that is applied to said absorbent layer or part thereof once supported by said supporting sheet, said adhesive being a thermoplastic fibrous adhesive material.

8. The absorbent structure of claim 6, wherein said one or more adhesive material include a second adhesive material present between said supporting sheet and said absorbent layer.

9. The absorbent structure of claim 1, wherein said absorbent material consists substantially of said superabsorbent polymer material, being in the form of particles.

10. The absorbent structure of claim 1, further comprising a material present adjacent said absorbent layer, selected from the group consisting of: i) a further supporting sheet, ii) an acquisition material layer; iii) a second absorbent structure, comprising a second supporting sheet and a second absorbent layer, wherein said second absorbent layer and said absorbent layer of the first structure are sandwiched between said supporting sheet of the first structure and said second supporting sheet.

11. The absorbent structure of claim 10, comprising the second absorbent structure, wherein the second absorbent structure comprises channels and wherein said channels of said second absorbent structure are substantially identical to said channels of said first absorbent structure and substantially completely overlapping therewith.

12. The absorbent structure of claim 10, comprising the second absorbent structure, wherein said supporting sheet of the first structure and/ or said second supporting sheet folds into said channels, or part thereof, and wherein one or both said supporting sheets comprise an adhesive material and wherein said supporting sheets are adhered to one another or to said absorbent layer in said channels by pressure bonding or by an adhesive material.

13. The absorbent structure of claim 10, wherein a pressure is applied selectively to the supporting sheet material portion that correspond to said channels, to further fold said supporting sheet into said channels, wherein said absorbent layer and/ or said supporting sheet comprising one or more adhesive material and said pressure aids to bond said supporting sheet into said channels.

14. The absorbent structure of claim 1, the absorbent article preferably being a diaper.