PULPLESS ABSORBENT CORE AND METHOD OF CORE FORMING

Abstract

A pulpless core is provided with flexibility for superabsorbent expansion by using elastic strands stretched and coupled to a nonwoven layer, and then relaxed partially to create receiving valleys (puckers) and the puckers are provided with superabsorbent polymer, and then a layer of nonwoven or acquisition film can be coupled on top of nonwoven/elastic/sap carrier layers to create an absorbent core laminate.

Claims

1. A method of forming an absorbent core, the method comprising: providing a first material layer; coupling elastic strands to the first material layer at a first tension to form an elastic and material layer combination; performing a first tension let-off to partially relax the elastic strands to a second tension that is less than the first tension, wherein the partial relaxing of the elastic strands to the second tension deforms the first material layer to form a plurality of valleys in the first material layer; applying a superabsorbent polymer material onto the first material layer; and securing a second material layer to the elastic and material layer combination to capture the superabsorbent polymer material in the plurality of valleys.

2. The method of claim 1 performing a second tension let-off to partially relax the elastic strands to a third tension that is less than the first tension and the second tension, wherein the partial relaxing of the elastic strands to the third tension creates a continuous web of superabsorbent polymer material in the absorbent core.

3. The method of claim 1 wherein the superabsorbent polymer material is applied when the first material layer is moving in a machine direction.

4. The method of claim 1 wherein coupling the elastic strands to the first material layer and securing the second material layer to the elastic and material layer combination comprises adhering the elastic strands to the first material layer and adhering the second material layer to the elastic and material layer combination, with a pattern of adhesive on the second material layer matching a pattern of the elastic strands on the first material layer.

5. The method of claim 1 wherein applying the superabsorbent polymer material onto the first material layer comprises applying the superabsorbent polymer material in a plurality of lanes defined by adjacent pairs of elastic strands.

6. The method of claim 5 wherein the plurality of lanes of the superabsorbent polymer material are applied intermittently to form gaps in the superabsorbent polymer material extending in the machine direction.

7. The method of claim 1 further comprising urging the second material layer into contact with the elastic and material layer combination via a ridged nip wheel, the ridged nip wheel including wheel peaks and wheel valleys, wherein the superabsorbent polymer material migrates into the wheel valleys as the second material layer is pressed into contact with the elastic and material layer combination.

8. The method of claim 1 wherein coupling the elastic strands to the first material layer comprises one of: coupling elastic strands to the first material layer such that the elastic strands are parallelly aligned and spaced apart in the machine direction; coupling elastic strands to the first material layer such that the elastic strands are parallelly aligned and spaced apart in a cross-machine direction; or coupling elastic strands to the first material layer such that the elastic strands are in a curved pattern and oriented generally in the machine direction.

9. A stretchable absorbent core formed by a process comprising: providing a first material layer; coupling elastic strands under tension to the first material layer to form an elastic and material layer combination; performing a first tension let-off to partially relax the elastic strands, wherein the partial relaxing of the elastic strands deforms the first material layer to form a plurality of valleys in the first material layer; applying a superabsorbent polymer material onto the first material layer; and securing a second material layer to the elastic and material layer combination to capture the superabsorbent polymer material in the plurality of valleys

10. The stretchable absorbent core of claim 9 formed by a process comprising performing a second tension let-off to further relax the elastic strands to a lower tension, wherein the further relaxing of the elastic strands to the lower tension creates a continuous web of superabsorbent polymer material in the absorbent core.

11. The stretchable absorbent core of claim 9 formed by a process comprising adhering the elastic strands to the first material layer and adhering the second material layer to the elastic and material layer combination, with a pattern of adhesive on the second material layer matching a pattern of the elastic strands on the first material layer.

12. The stretchable absorbent core of claim 9 formed by a process comprising applying the superabsorbent polymer material in a plurality of lanes defined by adjacent pairs of elastic strands.

13. The stretchable absorbent core of claim 13 wherein the plurality of lanes of the superabsorbent polymer material are applied intermittently to form gaps in the superabsorbent polymer material extending in the machine direction.

14. The stretchable absorbent core of claim 9 formed by a process comprising urging the second material layer into contact with the elastic and material layer combination via a ridged nip wheel, the ridged nip wheel including wheel peaks and wheel valleys, wherein the superabsorbent polymer material migrates into the wheel valleys as the second material layer is pressed into contact with the elastic and material layer combination.

15. The stretchable absorbent core of claim 9 formed by a process comprising one of: coupling elastic strands to the first material layer such that the elastic strands are parallelly aligned and spaced apart in the machine direction; coupling elastic strands to the first material layer such that the elastic strands are parallelly aligned and spaced apart in a cross-machine direction; or coupling elastic strands to the first material layer such that the elastic strands are in a curved pattern and oriented generally in the machine direction.

16. A stretchable absorbent core comprising: a first material layer; a series of elastic strand members coupled to the first material layer at a partially tensioned state that deforms the first material layer to form a plurality of valleys therein; a second material layer coupled to the elongated elastic strand members and over the first material layer; and a superabsorbent polymer material positioned in the plurality of valleys and between the first material layer and the second material layer, so as to be captured in the plurality of valleys.

17. The stretchable absorbent core of claim 16 wherein the series of elastic strand members comprise elongated, linear elastic strands.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIGS. 1a and 1b are in process top and side views respectively, of a core forming process of the present invention, with a first nonwoven web receiving a plurality of elastic strands under tension;

[0031] FIGS. 2a and 2b are in process top and side views respectively, showing a first tension let off of the elastic strands, to create peaks and valleys in the nonwoven;

[0032] FIGS. 3a and 3b are in process top and side views respectively, showing a SAP distribution system applying SAP laid into the created peaks and valleys in the nonwoven;

[0033] FIGS. 4a and 4b are in process top and side views respectively, showing a second nonwoven layer applied over the elastic strands and SAP filled peaks and valleys in the first nonwoven layer;

[0034] FIG. 5 is a side view of the second nonwoven layer applied over the elastic strands and SAP filled peaks and valleys in the first nonwoven layer, showing a second tension let off of the elastic strands to create a continuous web of absorbent core material;

[0035] FIG. 6 is a first alternate embodiment of an elastic strand deposition pattern onto the first nonwoven layer;

[0036] FIG. 7 is a second alternate embodiment of an elastic strand deposition pattern onto the first nonwoven layer;

[0037] FIG. 8 is a cross sectional view of the second nonwoven layer applied over the elastic strands and SAP filled peaks and valleys in the first nonwoven layer, showing a second tension let off of the elastic strands, in an in use condition, for instance shaped as an absorbent core would be when a diaper is worn by a user;

[0038] FIG. 9 is a top view of the second nonwoven layer applied over the elastic strands and SAP filled peaks and valleys in the first nonwoven layer, showing a second tension let off of the elastic strands to create a continuous web of absorbent core material, the absorbent core rotated and placed on a receiver running web;

[0039] FIG. 10 is a top view of a portion of a system for producing an absorbent core;

[0040] FIG. 11 is a side view of the portion of the system shown in FIG. 10;

[0041] FIG. 12 is a side view of other portions of the system for producing an absorbent core shown in FIG. 10;

[0042] FIG. 13a is bottom view of a system for applying adhesive to a top nonwoven layer for use in creating an absorbent core;

[0043] FIG. 13b is a bottom view of an alternate system for applying adhesive to a top nonwoven layer for use in creating an absorbent core;

[0044] FIG. 13c is a top view of a SAP distribution system applying SAP in a preferred embodiment of SAP lanes to a base nonwoven layer coupled to elastic strands;

[0045] FIG. 13d is a top view of a SAP distribution system applying SAP in a second preferred embodiment of intermittent SAP lanes to a base nonwoven layer coupled to elastic strands;

[0046] FIG. 14 is a side view of a roller/nip combination coupling a top nonwoven layer to elastic strands carried by a base nonwoven layer, the base nonwoven layer carrying SAP material;

[0047] FIG. 15 is a cross sectional view of a top nonwoven layer coupled to elastic strands carried by a base nonwoven layer, the base nonwoven layer carrying SAP material to form an absorbent core laminate;

[0048] FIG. 16 is a side view of a system for winding a top nonwoven layer coupled to elastic strands carried by a base nonwoven layer, the base nonwoven layer carrying SAP material to form an absorbent core laminate;

[0049] FIG. 17 is a side view of a system for stacking a top nonwoven layer coupled to elastic strands carried by a base nonwoven layer, the base nonwoven layer carrying SAP material to form an absorbent core laminate;

[0050] FIG. 18 is a perspective view of an absorbent core laminate.

DETAILED DESCRIPTION

[0051] Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention.

[0052] In a preferred embodiment, creation of an absorbent core is accomplished by using two layers of nonwoven material 12 and 20, sandwiching SAP 16 and elastic strands 14 between the two layers of nonwoven material 12 and 20. However, in place of one or both of the nonwoven material layers 12 and 20, other materials can be used, such as woven materials, elastic materials, or any other useful material. The invention is not limited to use of nonwoven material layers in creating the laminate.

[0053] Referring now to FIGS. 1a and 1b, in process top and side views respectively, of a core forming process of the present invention are shown. A first nonwoven web 12 receives a plurality of elastic strands 14 under tension.

[0054] Referring now to FIGS. 2a and 2b, a first tension let off of the elastic strands 14 is allowed, to create peaks and valleys (or puckers) 22 in the nonwoven 12. Referring now to FIGS. 3a and 3b, a SAP distribution system 19 applies SAP laid 16 into the created peaks and valleys 22 in the nonwoven 12. The created peaks and valleys 22 act as pockets to carry the SAP 16. SAP 16 can be laid continuously (not shown) or discontinuously as shown. The SAP 16 delivery methods can be vibratory, by dimple drum, timed delivery, or any other methods known in the art. Additionally, the coordination between the SAP 16 deposition and the timing and orientation of joining nonwoven layer 20 can vary between in a vertical SAP 16 drop into a gap between vertically running web 20 and combined web 12/16 through nips, or the SAP 16 can be deposited onto horizontally machine direction running web 12/16 so that the pockets 22 can be collecting SAP 16 prior to horizontal machine direction running web 20.

[0055] The dimensions of the puckers 22 are adjustable with different spacing or number of strands of elastic 14. It may be desirable to vary the spacing and pucker size to allow higher or lower concentrations of SAP 16 in some sections of the diaper. The level of stretch in the strands 14 and the amount of relaxation before SAP 16 deposition can also change the pucker 22 dimensions.

[0056] In a preferred embodiment, SAP 16 can be deposited on nonwoven layer 12 while web 12 is moving horizontally in the machine direction, and when the second nonwoven layer 20 is applied and coupled, the combined pulpless core web can move downstream in any desired fashion.

[0057] Referring to FIGS. 4a and 4b, a second nonwoven 20 layer is applied over the elastic strands 14 and SAP 16 filled peaks and valleys 22 in the first nonwoven layer 12. As shown in FIG. 5, an alternate second tension let off of the elastic strands 14 create a continuous web of absorbent core material. The continuous web of absorbent core can then be processed as desired, for instance cut and placed onto a diaper chassis as individual cores, or rotated cut and placed as shown in FIG. 9 onto a running carrier web 24 which itself can be further processed as desired. The second nonwoven layer 20 could alternatively be a layer of acquisition/distribution film (an ADL layer). Describing an intended diaper from the outside, one preferred embodiment is a nonwoven layer, a poly layer, a nonwoven with lycra (core wrap) layer, SAP, an additional nonwoven (top core wrap), an acquisition/distribution layer, and a topsheet layer.

[0058] Referring still to FIGS. 4a and 4b, SAP is shown deposited in areas where the elastic strands 14 reside, but outer channels of elastics 14 can be created that either do or do not contain SAP 16, as desired.

[0059] FIGS. 6 and 7 show first and second alternate embodiments of elastic strand 14 deposition patterns onto the first nonwoven layer 12. In FIG. 6, the deposition is in the cross machine direction, and in FIG. 7, the deposition is in a curved fashion generally in the machine direction. The elastics 14 can be curved using curved or flared elastic deposition patterns as a method of tuning the absorption performance, and also to improve the fit and appearance of the final diaper product. The elastic deposition also provides control over the direction of elasticity of the core.

[0060] Referring to FIG. 8, a cross sectional view of the second nonwoven 20 layer applied over the elastic strands 14 and SAP 16 filled peaks and valleys 22 in the first nonwoven layer 12, shows a second tension let off of the elastic strands 14, in an in use condition, for instance shaped as an absorbent core would be when a diaper is worn by a user. It is evident that the rugosities of the present invention desirably inhibit migration of SAP, for instance used beneficially in adult incontinent products. This feature could also increase the soft feel of the product, but in the current art, a thick ADL is needed to provide the soft feature of the product. The peaks and valleys or pockets 22 formed by the present invention minimized the tendency for the SAP 16 to accumulate through gravity to crotch area, the lowest portion of the core as shown. The elastic strands and its lamination with nonwoven in the middle of the core can better immobilize the SAP on its wet stage.

[0061] The present invention may permit lower performance, less expensive, elastics to be used because the elastics and the cores formed thereby can hold a shape at body temperature. Less costly variations become possible e.g. lower decitex Spandex, plastomers or high copolymer olefins that are semi elastic. In place of or in addition to traditional elastics 14 as shown, ribbons, or films slit into ribbons or ribbonlike elements can be used in order to access these less costly technologies. The present invention can also use ultrasonic bonding to couple the layers (selecting Polypropylene as a blend component for example), or ultrasonic bonding can be used to trap elastic strands.

[0062] The entire crotch area can be provided with elasticity, and when combined with a front and back stretch panel, results in an overall diaper product which provides elastic from end to end of the diaper product if desired.

[0063] An additional embodiment (not shown), is that several layers of the absorbent core can be used. For instance, each layer might be designed for a different level of absorbency, or have different directional zones in it.

[0064] Additionally, a leg cuff could be built with into the core concept by stretching the outer strands of elastics 14 to a higher draw ratio than the central strands 14, and then when the product is allowed to spring back these strands of Lycra will raise up to make a bowl or boat shape without requiring a special apparatus and additional materials.

[0065] Referring now to FIG. 10, a top view (and in FIG. 11, a side view) of a portion of a system for producing an absorbent core laminate 12/14/16/20 is shown. Adhesive applicator or applicators 32 apply adhesive preferably to elastic strands 14 (or to nonwoven layer 12) and adhesive strands 14 are brought into contact with nonwoven layer 12 by passing the strands 14 and nonwoven layer 12 over a roller 30. Alternatively (not shown), a thermally compatible elastic 14 in strand or ribbon form can be used and ultrasonically bonded where desired.

[0066] Referring now to FIG. 12, after the elastic 14 is coupled to the base nonwoven 12, base nonwoven 12 is preferably slightly de-tensioned between roller 30 and roller 38/nip 40 combination to accommodate receipt of SAP 16 by the base nonwoven 12 by creating a slight furrow for SAP 16.

[0067] Draw ratios of elastic 14 can be varied. A larger draw ratio could reduce SAP 16 level per unit of nonwoven 12/elastic 14, but when relaxed, the SAP 16 can be contained in a relatively small area to achieve a high effective concentration of SAP. On the other hand, a smaller draw ratio will increase SAP level per unit of nonwoven 12/elastic 14. In this case, a higher SAP doping rate is used to achieve a high effective concentration of SAP. Higher draw ratio may desirably give a softer feel to the composite and when lower draw ratio can also reduce the cost of manufacturing. By changing the draw ratio, the performance and cost balance can be easily adjusted.

[0068] A SAP distribution system 34 applies SAP 16 to the base nonwoven 12. Incoming top nonwoven layer 20 receives adhesive from adhesive distribution system 36, and top nonwoven layer 20 is brought into contact with the base nonwoven 12 and elastic strand 14 combination at roller 38/nip 40 combination to create an absorbent core laminate 12/14/16/20 which is passed downstream for further processing as desired, for example cutting/placing, stacking, or rolling.

[0069] Referring now to FIG. 13a, a bottom view of adhesive applicator 36 is shown, applying adhesive 43 in a pattern to the bottom of top nonwoven layer 20. As shown in FIG. 13a, the pattern can be substantially continuous across desired areas of top nonwoven layer 20, or as shown in FIG. 13b, adhesive 43 can be applied in a striped pattern to top nonwoven 20. It may be desirable to apply adhesive 43 in a striped pattern to correlate to the spacing of elastic strands 14 carried by base nonwoven 12. As the spacing and orientation of elastic strands 14 carried by base nonwoven 12 can vary in spacing, orientation and laydown pattern, so too can the pattern of adhesive 43 applied to top nonwoven 20.

[0070] Referring now to FIG. 13c, a top view of a SAP distribution system 34 applying SAP 16 in a preferred embodiment of SAP 16 lanes to a base nonwoven layer 12 coupled to elastic strands 14 is shown. SAP 16 is received from a source such as a fed hopper as shown in FIG. 12, and passed to void spaces 44 in the SAP distribution system 34 to allow SAP 16 to be applied to the base nonwoven 12. A preferred SAP 16 laydown pattern is lanes or stripes as depicted in FIG. 13c, and as shown in FIG. 13d, these lanes can be intermittent SAP 16 lanes. Intermittent SAP 16 distribution is accomplished for example by interrupting the inbound flow of SAP 16, or by removing intermittently portions of the flow of SAP 16.

[0071] By forming puckers, channels or lanes in the core with SAP 16, retention, acquisition and distribution of liquid is assisted. In an alternative embodiment, alternating patterns or divergent patters of channels or lanes of SAP can be created by heavy and light SAP 16 distribution levels. This also enhances the distribution performance of the core and allows for the performance to be tailored according to the desired usage. In this manner, elastic strand 14 spacing can be alternated with heavy SAP 16 lanes adjacent to light SAP 16 lanes that can channel the liquid in a desired pattern.

[0072] The present invention allows for use of a thinner ADL layer because the contracted core is corrugated and can store liquid. The ADL layer can be allowed to contract with the absorbent core laminate 12/14/16/20 and the result is a fully elastic core in zones where elastification is desired.

[0073] For a higher dosage of SAP 16, larger (or longer) void spaces 44 and feed rate can be used. Likewise, for a lower dosage of SAP 16, smaller void spaces 44 and feed rates can be used.

[0074] Referring now to FIG. 14, once SAP 16 has been applied to the base nonwoven layer 12, and adhesive 43 has been applied in a pattern to the bottom of top nonwoven layer 20, the materials of the absorbent core laminate 12/14/16/20 are brought together by nip wheel 38 urging the top nonwoven 20 carrying adhesive 43 against elastic strands 14. Base nonwoven 12 is carried by ridged nip wheel 40. In a preferred embodiment, peaks 46 of the ridged nip wheel 40 carry base nonwoven 12 and elastic strands 14, and the elastic strands 14 carried by base nonwoven 12 are urged into contact with top nonwoven 20. Valleys 42 of the ridged nip wheel 40 allow SAP 16 a position to migrate during compression of the materials of the absorbent core laminate 12/14/16/20 and coupling of the top nonwoven 20 to elastic strands 14. SAP 16 accumulates in the valleys 42. As shown in FIG. 15, an absorbent core laminate 12/14/16/20 is formed, with SAP 16 remaining captured in pockets, to create an absorbent core laminate 12/14/16/20 as shown in FIG. 18.

[0075] After creation of the absorbent core laminate 12/14/16/20, laminate is passed downstream for further processing as desired. This can include winding to create a roll 50 of absorbent core laminate 12/14/16/20 as shown in FIG. 16, cutting and stacking of absorbent core laminate 12/14/16/20 as shown in FIG. 17. Referring to FIG. 17 in particular, is a side view of a system for stacking a top nonwoven layer coupled to elastic strands carried by a base nonwoven layer, the base nonwoven layer carrying SAP material to form an absorbent core laminate is shown. A stack 52 of discrete absorbent core laminate 12/14/16/20 pieces can be assembled for packaging.

[0076] Preferably, absorbent core laminate 12/14/16/20 is cut and placed, and this cutting and placing can take any fashion such as traditional cores are variably placed in disposable product construction. For instance, the formed absorbent core laminate 12/14/16/20 can be situated adjacent to an acquisition/distribution (ADL) layer (not shown).

[0077] The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.