PARTICLE ENTRAINED AIR-PERMEABLE STRUCTURES

Abstract

A method is provided, for dissipating and entrapping super absorbent polymer particles (11, 12, 13, 14) within air-permeable, non-woven structures (100), for use in the construction of absorbent articles (600). The method comprises the steps of: (i) of constructing an air-permeable, non-woven structure (100) comprising at least first (1), second (2) and third (3) layers of non-woven fabric, each said layer having void spaces of differing size defined therein; (ii) dispersing absorbent particles (11, 12, 13, 4) onto an external surface (10) of the highest numbered layer of said air-permeable, non-woven structure (100) formed in step (i); and (iii) dissipating the dispersed absorbent particles (11, 12, 13, 14) within the air-permeable, non-woven structure (100) by applying an external energy source acting upon the absorbent particles (11, 12, 13, 14) in a direction substantially normal to the plane of the external surface (10) of the air-permeable, non-woven structure (100).

Claims

1. A method for dissipating and entrapping absorbent particles within air permeable structures, for use in the construction of absorbent articles, said method comprising the steps of: constructing an air-permeable, non-woven structure comprising at least first, second and third layers of non-woven fabric, each said numbered layer (n) being bonded, manufactured onto or otherwise joined to each subsequently numbered layer (n+1), and wherein fibres in each said layer are arranged so as to define void spaces therebetween of pre-determined size, corresponding to a given absorbent particle size distribution range; and wherein the void spaces in each said numbered layer (n), are of smaller size than the void spaces in each subsequently numbered layer (n+1); (ii) dispersing, by controllable mechanical means, absorbent particles onto an external surface of the highest numbered layer of said air-permeable, non-woven structure formed in step (i), said absorbent particles having a pre-determined particle size distribution range; (iii) dissipating said dispersed absorbent particles within the air-permeable, non-woven structure by applying an external energy source acting upon the absorbent particles in a direction substantially normal to the plane of the external surface of the air-permeable, non-woven structure.

2. A method as claimed in claim 1, wherein the external energy source in step (iii) is a low frequency vibration source generating a frequency in the range of between 10 Hz and 200 Hz, and an amplitude in the range of between 0.1 mm and 5 mm.

3. A method as claimed in claim 1, wherein the external energy source in step (iii) is an alternating electric field generating a frequency in the range of between 10 Hz and 200 Hz and a voltage in the range of between 5 kV and 50 kV.

4. A method as claimed in claim 1, wherein the external energy source in step (iii) generates a vacuum pressure of at least 1×10.sup.5 Nm.sup.−2 applied from below the first said layer of the air-permeable, non-woven structure.

5. A method as claimed in claim 1, wherein the external energy source in step (iii) is an ultra-sonic vibration source generating a frequency in the range of between 10 kHz and 50 kHz, and an amplitude in the range of between 5 microns (μm) and 500 microns (μm).

6. A method as claimed in any of the preceding claims wherein the highest numbered layer of the air-permeable, non-woven structure comprises bi-component fibres, each said component having differing thermal expansion properties.

7. A method as claimed in any of the preceding claims wherein each layer of the air-permeable, non-woven structure, with the exception of the first said layer, comprises bi-component fibres, each said component having differing thermal expansion properties.

8. A method as claimed in any of the preceding claims, wherein at least one of the layers of the air-permeable, non-woven structure comprises a blend of at least two different fibre types having differing thermal expansion properties.

9. A method as claimed in any of claims 6 to 8, further comprising the step, after the dissipation step (iii), of: (iv) subjecting at least one layer of the air-permeable, non-woven structure to an external heat source, and subsequently effecting or allowing cooling of said at least one layer, so as to entrap said absorbent particles within said air-permeable, non-woven structure.

10. A method as claimed in claim 9 when dependent upon claim 6, wherein in step (iv), the highest numbered layer of the air-permeable, non-woven structure is subjected to an external heat source, such that said components in said bi-component fibres expand upon heating and contract upon cooling at differential rates, causing said fibres to curl or crimp, thereby entrapping said absorbent particles within said highest numbered layer.

11. A method as claimed in claim 9 when dependent upon claim 7, wherein in step (iv), all of the layers of the air-permeable, non-woven structure are subjected to an external heat source, such that said components in said bi-component fibres expand upon heating and contract upon cooling at differential rates, causing the fibres to curl or crimp, thereby entrapping said absorbent particles within said air-permeable, non-woven structure.

12. A method as claimed in claim 9 when dependent upon claim 8, wherein in step (iv), all of the layers of the air-permeable, non-woven structure are subjected to an external heat source, such that the fibres having the lowest melting temperature soften and become tacky so as to adhere to adjacent absorbent particles thereby entrapping said absorbent particles within said air-permeable, non-woven structure.

13. A method as claimed in any of the preceding claims, further comprising the step of: (v) welding, bonding or otherwise attaching a further layer to the external surface of the highest numbered layer of said air-permeable, non-woven structure incorporating said dissipated absorbent particles.

14. A method as claimed in claim 13, wherein said further layer is a layer of non-woven fabric.

15. A method as claimed in claim 13, wherein said further layer is a polymer film.

16. A method as claimed in any of the preceding claims wherein the absorbent particles are organic.

17. A method as claimed in any of claims 1 to 15, wherein the absorbent particles comprise sodium polyacrylate or a polymer blend incorporating sodium polyacrylate.

18. A method as claimed in any of the preceding claims, wherein the air-permeable, non-woven structure is compostable in accordance with EN 13432 and or ASTM D6400.

19. A method as claimed in any of the preceding claims, wherein the absorbent particles are hydrophilic.

20. A method as claimed in any of the preceding claims wherein the resulting air-permeable, non-woven structure and absorbent particle matrix is further consolidated by the application of heat and/or pressure.

21. A method as claimed in any of the preceding claims wherein the resulting air-permeable, non-woven structure and absorbent particle matrix is subjected to a heated through air process to consolidate the fibres by partial melting and simultaneously to attach said partially melted fibres to said incorporated absorbent particles, thereby to prevent diffusion of the particles from the air-permeable structure.

22. A method as claimed in any of the preceding claims wherein, in step (ii) the dispersion of the absorbent particles is made across the entire surface of said air-permeable, non-woven structure.

23. A method as claimed in any of claims 1 to 21 wherein, in step (ii) the dispersion of the absorbent particles is made across selected specific areas of the surface of said air-permeable, non-woven structure.

24. A method as claimed in claim 23, further comprising the step, after at least the dispersion (ii) and dissipation (iii) steps, of cutting or otherwise extracting said selected specific areas from the surrounding air permeable substrate.

25. A method as claimed in claim 24, further comprising the subsequent step of welding or sealing the edges of said extracted selected specific areas on a line on or within 30 millimetres of the cut line.

Description

[0067] In order that the present invention may be fully understood, preferred embodiments thereof will now be described in detail, though only by way of example, with reference to the accompanying drawings in which:

[0068] FIG. 1 is a cross-sectional view of an air-permeable, non-woven structure as formed in step (i) of the method of the present invention;

[0069] FIG. 2 is a cross-sectional view of the air-permeable, non-woven structure of FIG. 1, having absorbent particles dispersed thereon, as per step (ii) of the method of the present invention;

[0070] FIG. 3 is a cross-sectional view of the air-permeable, non-woven structure of FIG. 2, following dissipation of the absorbent particles, as per step (iii) of the method of the present invention;

[0071] FIG. 4 is a cross-sectional view of the air-permeable, non-woven structure of FIG. 3, following consolidation of the absorbent particle and non-woven matrix, as per step (iv) of the method of the present invention;

[0072] FIG. 5 is a top view of an absorbent particle and non-woven matrix having absorbent particles arranged in a pre-determined pattern;

[0073] FIG. 6 is a top view of an absorbent article, having been cut from the matrix of FIG. 5;

[0074] FIG. 7 is an illustration of a process layout for performing steps (ii) and (iii) of a first embodiment of the method of the present invention;

[0075] FIG. 8 is an illustration of a process layout for performing steps (ii) and (iii) of a second embodiment of the method of the present invention;

[0076] FIG. 9 is an illustration of a process layout for performing steps (ii) and (iii) of a third embodiment of the method of the present invention; and

[0077] FIG. 10 is an illustration of a process layout for performing steps (ii) and (iii) of a fourth embodiment of the method of the present invention.

[0078] Referring first to FIG. 1, there is shown an air-permeable, non-woven structure, generally indicated 100, as formed in step (i) of the method of the present invention. A first layer 1 comprised of non-woven fibres is bonded, manufactured onto or otherwise attached to a second layer 2 at interface 6; a third layer 3 is bonded, manufactured onto or otherwise attached to the second layer 2 at interface 7; a fourth layer 4 is bonded, manufactured onto or otherwise attached to the third layer 3 at interface 8; and a fifth layer 5 is bonded, manufactured onto or otherwise attached to the fourth layer 4 at interface 9. The surface 10 of the fifth layer 5 in this embodiment is the uppermost surface. The fifth layer 5 comprises bi-component fibres in which the two components have differential melting temperatures.

[0079] Referring now to FIG. 2, there is shown the air-permeable, non-woven structure described above with reference to FIG. 1, now generally indicated 200. Absorbent particles 11, 12, 13 and 14 of varying particle sizes, have been dispersed onto the uppermost surface 10 of the fifth layer 5, as per step (ii) of the method of the present invention. Due to the relatively open structure of the surface of the fifth layer 5, some of the particles 11, 12, 13 and 14 have passed into the subsequent layers 2, 3, 4 and 5. Some of the absorbent particles have thus come to rest in layers where the void space within that specific layer allows free passage of the absorbent particles. Other particles 11, 12, 13 and 14 have come to rest partially above and partially below the surface of the fifth layer 5 such that absorbent particles 11 are prevented from passing into the fourth layer 4 at interface 9 due to the restrictive spaces between the fibres that constitute the fourth layer 4; whilst absorbent particles 12 are prevented from passing into the third layer 3 at interface 8 due to the restrictive spaces between the fibres that constitute the third layer 3; absorbent particles 13 are prevented from passing into the second layer 2 at interface 7 due to the restrictive spaces between the fibres that constitute the second layer 2; whilst the restrictive void spaces between the fibres that constitute the first layer 1 are too small to allow the passage of any of the absorbent particles, irrespective of their size.

[0080] Referring now to FIG. 3, there is shown the air-permeable, non-woven structure described above with reference to FIGS. 1 and 2, now generally indicated 300. The structure 300, and the dispersed absorbent particles 11, 12, 13 and 14 have now been exposed to a particle dissipation process as per step (iii) of the method of the present invention. The absorbent particles 11, 12, 13 and 14 have been de-agglomerated and as a result of the effect of the dissipation process have become located substantially below the uppermost surface 10 of the fifth layer 5 and have become substantially dispersed throughout the structure according to both the void space size within each of the individual layers 2, 3, 4 and 5 and the specific particle size distribution profile of the absorbent being dispersed. Particles 11, 12, 13 and 14 have come to rest substantially below the surface of the fifth layer 5; absorbent particles 11 are prevented from passing into the fourth layer 4 at interface 9 due to the restrictive spaces between the fibres that constitute the fourth layer 4; absorbent particles 12 are prevented from passing into the third layer 3 at interface 8 due to the restrictive spaces between the fibres that constitute the third layer 3; absorbent particles 13 are prevented from passing into the second layer 2 at interface 7 due to the restrictive spaces between the fibres that constitute the second layer 2; whilst the restrictive void spaces between the fibres that constitute layer 1 are too small to allow the passage of any of the absorbent particles, irrespective of their size.

[0081] Referring now to FIG. 4, there is shown the air-permeable, non-woven structure described above with reference to FIGS. 1 to 3, now generally indicated 400, following the performance of a consolidation process, as per optional step (iv) of the method of the present invention. The consolidation process has been applied to the uppermost (fifth) layer 5 such that now dissipated particles 11, 12, 13 and 14 are prevented from exiting the air-permeable structure via the uppermost (fifth) layer 5 due to the consolidation of fibres in region 15 of the fifth layer 5.

[0082] Referring now to FIG. 5, there is shown an absorbent particle and non-woven matrix, generally indicated 500, emerging from method step (iv), as described above with reference to FIG. 4. In this embodiment, the uppermost surface 10 of the fifth layer 5 has had absorbent particles dispersed upon it in a pre-determined pattern or shape 16. Following exposure to a suitable dissipation process (iii) followed by consolidation (iv) of the particles, an portion 18 of the matrix 500 may be cut or otherwise extracted from the air permeable non-woven matrix 500 along path 17, such that the path of the cut line 17 is larger in size than the pre-determined pattern or shape 16.

[0083] Referring now to FIG. 6, there is shown an absorbent article generally indicated 600, following cutting or otherwise extracting the portion 18 of the particle and non-woven matrix 500 along path 17, as described above with reference to FIG. 5.

[0084] Referring now to FIG. 7, there is shown a process layout 700 for performing steps (ii) and (iii) of a first embodiment of the method of the present invention. Absorbent particles 11, 12, 13 and 14 are dispersed, as per step (ii), onto the surface of an air-permeable, non-woven structure 21, comprising layers 1, 2, 3, 4 and 5, by means of a controlled scattering device 19. The non-woven structure 21 is moved in the direction of arrow 23 across a base plate 24 whilst simultaneously a substantially vertically applied ultra-sonic force is applied, as per step (iii), at the interface 26 of an ultra-sonic device 22 causing the particles 11, 12, 13 and 14 to become entrained within the non-woven layers 25.

[0085] Referring now to FIG. 8, there is shown a process layout 800 for performing steps (ii) and (iii) of a second embodiment of the method of the present invention. Absorbent particles 11, 12, 13 and 14 are dispersed, as per step (ii) onto the surface of an air-permeable, non-woven structure 21, comprising layers 1, 2, 3, 4 and 5 by means of a controlled scattering device 19. The non-woven layer 21 is moved in the direction of arrow 23 across a base plate 24 whilst simultaneously a substantially vertically applied low frequency vibration in the range of 10 Hz to 200 Hz is applied, as per step (iii), at the interface 27 of a low frequency vibration device 28 causing the particles 11, 12, 13 and 14 to become entrained within the non-woven layers 25.

[0086] Referring now to FIG. 9, there is shown a process layout 900 for performing steps (ii) and (iii) of a third embodiment of the method of the present invention. Absorbent particles 11, 12, 13 and 14 are dispersed, as per step (ii), onto the surface of an air-permeable, non-woven structure 21, comprising layers 1, 2, 3, 4 and 5, by means of a controlled scattering device 19. The non-woven structure 21 is moved in the direction of arrow 23 across a perforated plate or membrane 30 whilst simultaneously a substantially vertically applied vacuum force 29 is applied, as per step (iii), from beneath the perforated plate or membrane 30 causing the particles 11, 12, 13 and 14 to become entrained within the non-woven layers 25.

[0087] Referring finally to FIG. 10, there is shown a process layout 1000 for performing steps (ii) and (iii) of a fourth embodiment of the method of the present invention. Absorbent particles 11, 12, 13 and 14 are dispersed, as per step (ii) onto the surface of an air-permeable, non-woven an air-permeable, layers 1, 2, 3, 4 and 5, by means of a controlled scattering device 19. The non-woven structure 21 is moved in the direction of arrow 23 between an upper electrode device 31 and a lower electrode device 32, each electrode device having a dielectric plate 33 and 34 located between said electrode devices 31 and 32 and the target particles 11, 12, 13 and 14 together with the non-woven structure 21. The upper electrode device 31 is connected to a high voltage, alternating current generator via cable 37 whilst the lower electrode device 32 is connected to earth 35. As the dispersed powder 11, 12, 13 and 14 is transported into the zone 36 between the two dielectric plates 33 and 34, the energy field generated between the upper electrode 31 and lower electrode 32 causes the powder to become excited and vibrate in a plane substantially normal to the plane of the dielectric plates 33 and 34 and become dissipated, as per step (iii), within the non-woven layers 25.

[0088] The method according to the present invention will now be further described by way of the following examples:

Example 1

[0089] A non-woven fabric structure was manufactured comprising five individual layers of varying void space dimensions between individual and groups of fibres. Each of the four lower layers were manufactured using a blend of polypropylene, polyethylene and polyester fibres in the ratio of 20%, 40% and 40% respectively.

[0090] The construction of the entire non-woven structure was such that the lowermost layer or first layer (ADL) would not permit the entry into or passage through of any Super Absorbent Polymer (SAP) particles of less than 10 μm in minimum diameter. Effectively, this layer was manufactured to act as a physical barrier to the passage of any of the SAP to be processed within this entire example.

[0091] The next layer or second layer was manufactured to permit the entry of SAP particles in the range of 10 μm to 150 μm but not to allow the entry of or passage through of SAP particles of particle size greater than 150 μm.

[0092] The next or third layer was manufactured to permit the entry of SAP particles in the range 10 μm to 400 μm but not to permit the entry of or passage through of SAP of particle size greater than 400 μm.

[0093] The next or fourth layer was manufactured to permit the entry of SAP particles in the range 10 μm to 600 μm but not to permit the entry or passage through of SAP of particle size greater than 600 μm.

[0094] The next or fifth layer was manufactured to permit the entry of SAP particles in the range 10 μm and above. The uppermost layer of the non-woven structure was manufactured from bi-component fibres in a side by side configuration from polyester and polyethylene.

[0095] The method of manufacture of the non-woven substrate as a whole was a combination of conventional random carding, air through and needle punch processes.

[0096] A sodium polyacrylate SAP of particle size distribution ranging between 40 μm to 850 μm commercially manufactured by a market leader in the hygiene materials supply market was mechanically dispersed onto the uppermost surface of the aforesaid high loft non-woven fabric at an areal dispersion rate of 325 gsm (gm.sup.−2) which in practice would equate to an amount of 13 g in a typical infant diaper core.

[0097] The SAP and non-woven fabric structure was then subjected to an external vibrating energy source of frequency 50 Hz and amplitude 1.5 mm to dissipate the SAP particles within the structure of the non-woven. The particles were caused to come to rest within the structure in a gradient manner according to the specific PSD of the SAP particles and the void space at a given location within the non-woven fabric structure.

[0098] Following the dissipation process, the uppermost layer of the non-woven fabric structure was then subjected to an external heat source provided by infra-red heating lamps, to cause the bi-component fibres in the uppermost layer of the structure to crimp as a result of differential expansion of each component of the bi-component fibres.

[0099] The entire non-woven fabric structure and SAP matrix was then allowed to cool. After cooling it was found that the SAP was fully contained within the non-woven structure.

Example 2

[0100] A non-woven fabric structure was manufactured comprising five individual layers of varying void space dimensions between individual and groups of fibres. Each of the four lower layers were manufactured using a blend of polypropylene, polyethylene and polyester fibres in the ratio of 20%, 40% and 40% respectively.

[0101] The construction of the non-woven structure was such that the lowermost layer or first layer (ADL) would not permit the entry into or passage through of any Super Absorbent Polymer particles (SAP) of less than 10 μm in minimum diameter. Effectively, this layer was manufactured to act as a physical barrier to the passage of any of the SAP to be processed within this example.

[0102] The next layer or second layer was manufactured to permit the entry of SAP particles in the range of 10 μm to 150 μm but not to allow the entry of or passage through of SAP of particle size greater than 150 μm.

[0103] The next or third layer was manufactured to permit the entry of SAP particles in the range 10 μm to 400 μm but not to permit the entry of or passage through of SAP of particle size greater than 400 μm.

[0104] The next or fourth layer was manufactured to permit the entry of SAP particles in the range 10 μm to 600 μm but not to permit the entry or passage through of SAP of particle size greater than 600 μm.

[0105] The next or fifth layer was manufactured to permit the entry of SAP particles in the range 10 μm and above. The uppermost layer of the non-woven structure was manufactured from bi-component fibres in a side by side configuration from polyester and polyethylene.

[0106] The method of manufacture of the non-woven substrate as a whole was a combination of conventional random carding, air through and needle punch processes.

[0107] A sodium polyacrylate SAP of particle size distribution ranging between 40 μm to 850 μm commercially manufactured by a market leader in the hygiene materials supply market was mechanically dispersed onto the uppermost surface of the aforesaid high loft non-woven fabric at an areal dispersion rate of 325 gsm (gm.sup.−2) which in practice would equate to an amount of 13 g in a typical infant diaper core.

[0108] The SAP and non-woven fabric structure was then subjected to an alternating voltage energy field (AVEF) of 25 kV and of frequency 50 Hz between two opposed electrode plates placed 10 mm apart along their longitudinal axis to excite the SAP particles such that the particles were made to vibrate in a direction normal to the opposed surfaces of the electrode plates, the vibration energy being sufficient to dissipate the SAP within the non-woven fabric structure such that no SAP remained on the uppermost surface of the non-woven fabric structure.

[0109] Following the dissipation process the entire non-woven structure and SAP matrix was subject to an air-through heating process such that the lower melting temperature component of the bi-component fibres that constitute the uppermost layer of the structure became soft and tacky such as to bond to adjacent individual and groups of fibres thereby entrapping the SAP dissipated within the uppermost layer and creating a physical barrier to those SAP particles dissipated within the adjacent and lower layer from passing out through the uppermost layer upon the entire matrix being subjected to agitation.

[0110] Upon cooling, the lower melting temperature component of the bi-component fibres in the uppermost layer of the structure retained their solid state now bonded to adjacent individual and groups of fibres.

Example 3

[0111] A non-woven fabric structure was manufactured comprising five individual layers of varying void space dimensions between individual and groups of fibres. Each of the four lower layers were manufactured using a blend of polypropylene, polyethylene and polyester fibres in the ratio of 20%, 40% and 40% respectively.

[0112] The construction of the entire non-woven structure was such that the lower most layer or first layer (ADL) would not permit the entry into or passage through of any Super Absorbent Polymer particles (SAP) of less than 10 μm in minimum diameter. Effectively, this layer was manufactured to act as a physical barrier to the passage of any of the SAP to be processed within this example.

[0113] The next layer or second layer was manufactured to permit the entry into of SAP particles in the range of 10 μm to 150 μm but not to allow the entry of or passage through of SAP of particle size greater than 150 μm.

[0114] The next or third layer was manufactured to permit the entry of SAP particles in the range 10 μm to 400 μm but not to permit the entry of or passage through of SAP of particle size greater than 400 μm.

[0115] The next or fourth layer was manufactured to permit the entry of SAP particles in the range 10 μm to 600 μm but not to permit the entry or passage through of SAP of particle size greater than 600 μm.

[0116] The next or fifth layer was manufactured to permit the entry of SAP particles in the range 10 μm and above. The uppermost layer of the non-woven structure was manufactured from bi-component fibres in a side by side configuration from polyester and polyethylene.

[0117] The method of manufacture of the non-woven substrate as a whole was a combination of conventional random carding, air through and needle punch processes.

[0118] A sodium polyacrylate SAP of particle size distribution ranging between 40 μm to 850 μm commercially manufactured by a market leader in the hygiene materials supply market was mechanically dispersed onto the uppermost surface of the aforesaid high loft non-woven fabric structure at an areal dispersion rate of 325 gsm (gm.sup.−2) which in practice would equate to an amount of 13 g in a typical infant diaper core.

[0119] The SAP and non-woven fabric structure was then subjected to a vacuum, applied from below the lowermost surface of the structure of greater than 1 bar in pressure such that the SAP particles dispersed upon the uppermost layer of the structure were drawn into the structure with the SAP particles coming to rest within a specific given layer dependent upon the given diameter of the SAP particle in question.

[0120] Following the dissipation process as a result of the applied vacuum, a sixth layer of spun bonded polypropylene non-woven fabric of areal weight of 8 gsm (gm.sup.−2) was then attached to the uppermost surface of the SAP and non-woven fabric matrix by means of intermittent ultra-sonic welding such that the SAP particles now dissipated within the non-woven fabric structure were prohibited from egress via the uppermost layer of the structure.

Example 4

[0121] A non-woven fabric structure was manufactured comprising five individual layers of varying void space dimensions between individual and groups of fibres. Each of the four lower layers were manufactured using a blend of polypropylene, polyethylene and polyester fibres in the ratio of 20%, 40% and 40% respectively.

[0122] The construction of the entire non-woven structure was such that the lower most layer or first layer (ADL) would not permit the entry into or passage through of any Super Absorbent Polymer particles (SAP) of less than 10 μm in minimum diameter. Effectively, this layer was manufactured to act as a physical barrier to the passage of any of the SAP to be processed within this example.

[0123] The next layer or second layer was manufactured to permit the entry into of SAP particles in the range of 10 μm to 150 μm but would not allow the entry of or passage through of SAP of particle size greater than 150 μm.

[0124] The next or third layer was manufactured to permit the entry of SAP particles in the range 10 μm to 400 μm but would not permit the entry of or passage through of SAP of particle size greater than 400 μm.

[0125] The next or fourth layer was manufactured to permit the entry of SAP particles in the range 10 μm to 600 μm but would not permit the entry or passage through of SAP of particle size greater than 600 μm.

[0126] The next or fifth layer was manufactured to permit the entry of SAP particles in the range 10 μm and above. The uppermost layer of the non-woven structure was manufactured from bi-component fibres in a side by side configuration from polyester and polyethylene.

[0127] The method of manufacture of the non-woven substrate as a whole was a combination of conventional random carding, air through and needle punch processes.

[0128] A sodium polyacrylate SAP of particle size distribution ranging between 40 μm to 850 μm commercially manufactured by a market leader in the hygiene materials supply market was mechanically dispersed onto the uppermost surface of the aforesaid high loft non-woven fabric structure at an areal dispersion rate of 325 gsm (gm.sup.−2) which in practice would equate to an amount of 13 g in a typical infant diaper core.

[0129] The SAP and non-woven fabric structure was then subjected to an external vibrating energy source of frequency 50 Hz and amplitude 1.5 mm to dissipate the SAP particles within the structure of the non-woven. The particles were caused to come to rest within the substrate in a gradient manner according to the specific PSD of the SAP particles and the void space at a given location within the cross-section of the entire non-woven fabric structure.

[0130] Following the dissipation process, a polyethylene film, coated on one surface with a heat sensitive adhesive based on polyurethane chemistry, was bonded onto the uppermost surface of the uppermost layer such that the SAP particles now dissipated within the non-woven fabric structure were prohibited from egress via the uppermost layer of the substrate.

Example 5

[0131] A non-woven fabric structure was manufactured comprising five individual layers of varying void space dimensions between individual and groups of fibres. Each of the four lower layers were manufactured using a blend of polypropylene, polyethylene and polyester fibres in the ratio of 20%, 40% and 40% respectively.

[0132] The construction of the entire non-woven structure was such that the lowermost layer or first layer (ADL) would not permit the entry into or passage through of any Super Absorbent Polymer particles (SAP) of less than 10 μm in minimum diameter. Effectively, this layer was manufactured to act as a physical barrier to the passage of any of the SAP to be processed within this example.

[0133] The next layer or second layer was manufactured to permit the entry into of SAP particles in the range of 10 μm to 150 μm but not to allow the entry of or passage through of SAP of particle size greater than 150 μm.

[0134] The next or third layer was manufactured to permit the entry of SAP particles in the range 10 μm to 400 μm but not to permit the entry of or passage through of SAP of particle size greater than 400 μm.

[0135] The next or fourth layer was manufactured to permit the entry of SAP particles in the range 10 μm to 600 μm but not to permit the entry or passage through of SAP of particle size greater than 600 μm.

[0136] The next or fifth layer was manufactured to permit the entry of SAP particles in the range 10 μm and above. The uppermost layer of the non-woven structure was manufactured from bi-component fibres in a side by side configuration from polyester and polyethylene.

[0137] The method of manufacture of the non-woven substrate as a whole was a combination of conventional random carding, air through and needle punch processes. A sodium polyacrylate Super Absorbent Polymer (SAP) of particle size distribution ranging between 40 μm to 850 μm commercially manufactured by a market leader in the hygiene materials supply market was mechanically dispersed onto the uppermost surface of the aforesaid high loft non-woven fabric at an areal dispersion rate of 325 gsm (gm.sup.−2) which in practice would equate to an amount of 13 g in a typical infant diaper core.

[0138] The SAP, now dispersed onto the uppermost surface of the non-woven fabric, was then subjected to an ultra-sonic energy source of 15 kHz and with an amplitude of 90 microns via a suitably engineered sonotrode to excite the SAP particles such that the particles were made to vibrate in a direction normal to surface of the non-woven fabric structure, the vibration energy being sufficient to dissipate the SAP within the non-woven fabric structure such that no SAP remained on the uppermost surface of the non-woven fabric structure.

[0139] Following the dissipation process the non-woven structure and SAP matrix was subject to an external heating process such that the lower melting temperature component of the bi-component fibres that constitute the uppermost layer of the structure became soft and tacky such as to bond to adjacent individual and groups of fibres thereby entrapping the SAP dissipated within the uppermost layer and creating a physical barrier to those SAP particles dissipated within the adjacent and lower layers from passing out through the uppermost layer upon the entire matrix being subjected to agitation.

[0140] Upon cooling, the lower melting temperature component of the bi-component fibres in the uppermost layer of the structure retained its solid state now bonded to adjacent individual and groups of fibres.